THE DIFFERENTIATION OF THE COMPETITIVE ATHLETE WITH PHYSIOLOGIC CARDIAC REMODELING FROM THE ATHLETE WITH CARDIOMYOPATHY

There are currently 5 million active high school, collegiate, professional, and master athletes in the United States. Regular intense exercise by these athletes can promote structural, electrical and functional remodeling of the heart, which is termed the "athlete's heart." In addition, regular intense exercise can lead to pathological adaptions that promote or worsen cardiac disease. Many of the athletes in the United States seek medical care. Consequently, physicians must be aware of the normal cardiac anatomy and physiology of the athlete, the differentiation of the normal athlete heart from the athlete with cardiomyopathy, and the contemporary care of the athlete with a cardiomyopathy. In athletes with persistent cardiovascular symptoms, investigations should include a detailed history and physical examination, an ECG, a transthoracic echocardiogram, and in athletes in whom the diagnosis is uncertain, a maximal exercise stress test or a continuous ECG recording, and cardiac magnetic resonance imaging or a cardiac computed tomography angiography when definition of the coronary anatomy or characterization of the aorta and the aortic great vessels is indicated. This article discusses the differentiation of the normal athlete with physiologic cardiac remodeling from the athlete with hypertrophic, dilated or arrhythmogenic ventricular cardiomyopathy (ACM). The ECG changes in trained athletes that are considered normal, borderline, or abnormal are listed. In addition, the normal echocardiographic measurements for athletes who consistently participate in endurance, power, combined or heterogeneous sports are enumerated and discussed. Algorithms are listed that are useful in the diagnosis of trained athletes with borderline or abnormal echocardiographic measurements suggestive of cardiomyopathies along with the major and minor criteria for the diagnosis of ACM in athletes. Thereafter, the treatment of athletes with hypertrophic, dilated, and arrhythmogenic right ventricular cardiomyopathies are reviewed. The distinction between physiologic changes and pathologic changes in the hearts of athletes has important therapeutic and prognostic implications. Failure by the physician to correctly diagnose an athlete with hypertrophic cardiomyopathy, dilated cardiomyopathy, or ACM, can lead to the sudden cardiac arrest and death of the athlete during training or sports competition. In contrast, an incorrect diagnosis by a physician of cardiac pathology in a normal athlete can lead to an unnecessary restriction of athlete training and competition with resultant significant emotional, psychological, financial, and long-term health consequences in the athlete.

The diagnosis and treatment of women with recurrent cardiac ischemia and normal coronary arteries

Cardiac disease is the leading cause of death in women. Among women with recurrent chest pain, abnormal electrocardiograms, and/or stress tests who undergo coronary angiography, as many as 50% have normal or <50% coronary artery obstructive disease. Pharmacologic stress assessment of coronary artery flow reserve in these women frequently demonstrates an inability to increase blood flow to >2.5 times normal flow. Contributory factors include abnormal epicardial or microvascular reactivity, microvascular remodeling or rarefaction, autonomic dysfunction, or coronary plaque rupture/erosion. Assessment is necessary of serum biomarkers and coronary artery flow reserve, fractional flow reserve, microvascular resistance, and epicardial/microvascular spasm. Aggressive treatment of women with positive tests is necessary because these women have an increased incidence of recurrent chest pain, repeated hospitalizations and coronary angiograms, and cardiac death.

Particulate Matter Air Pollution is a Significant Risk Factor for Cardiovascular Disease

Air pollution is responsible worldwide for 9-12 million deaths annually. The major contributor to air pollution is particulate matter ≤2.5 µg per cubic meter of air (PM2.5) from vehicles, industrial emissions, and wildfire smoke. United States ambient air standards recommend annual average PM2.5 concentrations of ≤12 μg/m³ while European standards allow an average annual PM2.5 concentration of ≤20 μg/m3. However, significant PM2.5 cardiovascular and pulmonary health risks exist below these concentrations. Chronic PM2.5 exposure significantly increases major cardiovascular and pulmonary event risks in Americans by 8 to more than 20% for each 10-μg/m3 increase in PM2.5. PM2.5-induced increases in lipid peroxidation, induction of vascular inflammation and endothelial cell injury initiate and propagate respiratory diseases, coronary and carotid atherosclerosis. PM2.5 can cause atherosclerotic vascular plaque rupture and myocardial infarction and stroke by activating metalloproteinases. This article discusses PM2.5 effects on the cardiovascular and pulmonary systems, specific PM2.5 pathophysiologic mechanisms contributing to cardiopulmonary disease, and preventive measures to limit the cardiovascular and pulmonary effects of PM2.5.

The epidemiology, mechanisms, diagnosis and treatment of cardiovascular disease in adult patients with HIV

More than 1.2 million people in the United States have Human Immunodeficiency Virus (HIV) infections but 13% of these people are unaware of their HIV infection. Current combination antiretroviral therapy (ART) does not cure HIV infection but rather suppresses the infection with the virus persisting indefinitely in latent reservoirs in the body. As a consequence of ART, HIV infection has changed from a fatal disease in the past to a chronic disease today. Currently in the United States, more than 45% of HIV+ individuals are greater than 50 years of age and 25% will be greater than 65 years of age by 2030. Atherosclerotic cardiovascular disease (CVD), including myocardial infarction, stroke, and cardiomyopathy, is now the major cause of death in HIV+ individuals. Novel risk factors, including chronic immune activation and inflammation in the body, antiretroviral therapy, and traditional CVD risk factors, such as tobacco and illicit drug use, hyperlipidemia, the metabolic syndrome, diabetes mellitus, hypertension, and chronic renal disease, contribute to cardiovascular atherosclerosis. This article discusses the complex interactions involving HIV infection, the novel and traditional risk factors for CVD, and the antiretroviral HIV therapies which can contribute to CVD in HIV-infected people. In addition, the treatment of HIV+ patients with acute myocardial infarction, stroke, and cardiomyopathy/heart failure are discussed. Current recommended ART and their major side effects are summarized in table format. All medical personnel must be aware of the increasing incidence of CVD on the morbidity and mortality in HIV infected patients and must be watchful for the presence of CVD in their patients with HIV.

Cardiovascular complications of COVID-19 severe acute respiratory syndrome

603,711,760 confirmed cases of COVID-19 have been reported throughout the world and 6,484,136 individuals have died from complications of COVID-19 as of September 7, 2022. Significantly, the Omicron variant has produced the largest number of COVID-19 associated hospitalizations since the beginning of the pandemic. Cardiac injury occurs in ≥20% of the hospitalized patients with COVID-19 and is associated with cardiac dysrhythmias in 17 to 44%, cardiac injury with increases in blood troponin in 22 to 40%, myocarditis in 2 to 7%, heart failure in 4 to 21%, and thromboembolic events in 15 to 39%. Risk factors for cardiac complications include age >70 years, male sex, BMI ≥30 kg/m², diabetes, pre-existing cardiovascular disease, and moderate to severe pneumonia at hospital presentation. Patients with prior cardiovascular disease who contract COVID-19 and experience a significant increase in their blood troponin concentration are at risk for mortality rates as high as 69%. This review focuses on the prevalence, the pathophysiologic mechanisms of CoV-2 injury to the cardiovascular system and the current recommended treatments in hospitalized patients with COVID-19 in order that medical personnel can decrease the morbidity and mortality of patients with COVID-19 and effectively treat patients with Covid and post Covid syndrome.

Handheld ultrasound is an adjunct to the physical examination in the diagnosis of cardiopulmonary disease

Handheld 2D ultrasound devices (HUDs) have become available as an adjunct to physical examinations, visualizing the heart and lungs in real time and facilitating prompt patient diagnosis and treatment of cardiopulmonar.y disorders. These devices provide simple and rapid bedside alternatives to repetitive chest x-rays, standard ultrasound examinations and thoracic CT scans. Two currently available HUDs are described. This paper discusses the use of HUDs in the diagnosis of patients with pericardial effusion and tamponade, ventricular dilation, aortic and mitral regurgitation, cardiogenic pulmonary edema, viral and bacterial pneumonia, pleural effusion and pneumothorax. The use of a HUD by physicians increases clinical diagnostic accuracy, adds quantitative information about cardiopulmonary disease severity and guides the use of medications and interventions.

Tricuspid valve regurgitation: current diagnosis and treatment

Tricuspid regurgitation (TR) is present in 1.6 million individuals in the United States and 3.0 million people in Europe. Functional TR, the most common form of TR, is caused by cardiomyopathies, LV valve disease, or pulmonary disease. The five-year survival with severe TR and HFrEF is 34%. Echocardiography can assess the TR etiology/severity, measure RA and RV size and function, estimate pulmonary pressure, and characterize LV disease. Management includes diuretics, ACE inhibitors, and aldosterone antagonists. Surgical annuloplasty or valve replacement should be considered in patients with progressive RV dilatation without severe LV dysfunction and pulmonary hypertension. Transcatheter repair/replacement is possible in patients with a LVEF <40%, dilated annuli, and impaired RV function. The diagnosis and treatment of TR, including coaptation, annuloplasty devices and prosthetic valves, success rates, morbidity/mortality, and trials are discussed. Transcatheter tricuspid valve repair/replacement is an emerging therapy for high-risk patients with TR who would otherwise have a dismal clinical prognosis.

Obesity and obesity-induced inflammatory disease contribute to atherosclerosis: a review of the pathophysiology and treatment of obesity

Two billion people worldwide older than 18 years of age, or approximately 30% of the world population, are overweight or obese. In addition, more than 43 million children under the age of 5 are overweight or obese. Among the population in the United States aged 20 and greater, 32.8 percent are overweight and 39.8 percent are obese. Blacks in the United States have the highest age-adjusted prevalence of obesity (49.6%), followed by Hispanics (44.8%), whites (42.2%) and Asians (17.4%). The impact of being overweight or obese on the US economy exceeds $1.7 trillion dollars, which is equivalent to approximately eight percent of the nation's gross domestic product. Obesity causes chronic inflammation that contributes to atherosclerosis and causes >3.4 million deaths/year. The pathophysiologic mechanisms in obesity that contribute to inflammation and atherosclerosis include activation of adipokines/cytokines and increases in aldosterone in the circulation. The adipokines leptin, resistin, IL-6, and monocyte chemoattractant protein activate and chemoattract monocytes/macrophages into adipose tissue that promote visceral adipose and systemic tissue inflammation, oxidative stress, abnormal lipid metabolism, insulin resistance, endothelial dysfunction, and hypercoagulability that contribute to atherosclerosis. In addition in obesity, the adipokines/cytokines IL-1β, IL-18, and TNF are activated and cause endothelial cell dysfunction and hyperpermeability of vascular endothelial junctions. Increased aldosterone in the circulation not only expands the blood volume but also promotes platelet aggregation, vascular endothelial dysfunction, thrombosis, and fibrosis. In order to reduce obesity and obesity-induced inflammation, therapies including diet, medications, and bariatric surgery are discussed that should be considered in patients with BMIs>35-40 kg/m2 if diet and lifestyle interventions fail to achieve weight loss. In addition, antihypertensive therapy, plasma lipid reduction and glucose lowering therapy should be prescribed in obese patients with hypertension, a 10-year CVD risk >7.5%, or prediabetes or diabetes.

The current diagnosis and treatment of high-risk patients with chronic primary and secondary mitral valve regurgitation

Mitral valve regurgitation (MR) is due primarily to either primary degeneration of the mitral valve with Barlow's or fibroelastic disease or is secondary to ischemic or nonischemic cardiomyopathies. Echocardiography is essential to assess MR etiology and severity, the remodeling of cardiac chambers and to characterize longitudinal chamber changes to determine optimal therapies. Surgery is recommended for severe primary MR if persistent symptoms are present or if left ventricle dysfunction is present with an EF <60% or a left ventricle end-systolic diameter ≥40 mm. For secondary MR, therapy of heart failure with vasodilators and diuretics improves forward cardiac output. Coronary artery bypass grafts (CABG) or percutaneous coronary intervention (PCI) should be considered for severe MR due to ischemia. This review summarizes the pathophysiology, the characteristics, the management and the different interventions for high risk patients with chronic primary and secondary MR.

The current diagnosis and treatment of patients with aortic valve stenosis

Aortic valve stenosis (AS) is the third most frequent cardiovascular abnormality after coronary artery disease and hypertension. A bicuspid aortic valve is the most common cause for AS until seventh decade and calcific valve degeneration is responsible thereafter. In symptomatic patients, The risk of death increases from ≤1%/year to 2%/month. An echo valve area ≤1 cm², peak transaortic velocity ≥4 m/s, mean valve gradient ≥40 mmHg and/or computerized tomography valve calcium score >2000 Agatston units (AU) for males or more than 1200 AU for females indicate severe AS. AS stages and management are discussed. Valve replacement is based on surgical risk, valve durability/hemodynamics, need for anticoagulation and patient preferences. EuroSCORE ≥20%, Society of Thoracic Surgeons Predicted Risk of Mortality ≥8% and co-morbidities indicate high surgical risk. Surgery is recommended for low-intermediate risk patients. Transcatheter aortic valve implantation is an alternative in older patients at low, intermediate, high or prohibitive risk. Transaortic valve implantation/replacement trials are summarized.

Cardiovascular Exosomes and MicroRNAs in Cardiovascular Physiology and Pathophysiology

Cardiac exosomes mediate cell-to-cell communication, stimulate or inhibit the activities of target cells, and affect myocardial hypertrophy, injury and infarction, ventricular remodeling, angiogenesis, and atherosclerosis. The exosomes that are released in the heart from cardiomyocytes, vascular cells, fibroblasts, and resident stem cells are hypoimmunogenic, are physiologically more stable than cardiac cells, can circulate in the body, and are able to cross the blood-brain barrier. Exosomes utilize three mechanisms for cellular communication: (1) internalization by cells, (2) direct fusion to the cell membrane, and (3) receptor-ligand interactions. Cardiac exosomes transmit proteins, mRNA, and microRNAs to other cells during both physiological and pathological process. Cardiac-specific exosome miRNAs can regulate the expression of sarcomeric genes, ion channel genes, autophagy, anti-apoptotic and anti-fibrotic activity, and angiogenesis. This review discusses the role of exosomes and microRNAs in normal myocardium, myocardial injury and infarction, atherosclerosis, and the importance of circulating microRNAs as biomarkers of cardiac disease. Graphical Abstract.

Diagnosis and treatment of adults with congenital heart disease

Approximately 50 million adults worldwide have known congenital heart disease (CHD). Among the most common types of CHD defects in adults are atrial septal defects and ventricular septal defects followed by complex congenital heart lesions such as tetralogy of Fallot. Adults with CHDs are more likely to have hypertension, cerebral vascular disease, diabetes and chronic kidney disease than age-matched controls without CHD. Moreover, by the age of 50, adults with CHD are at a greater than 10% risk of experiencing cardiac dysrhythmias and approximately 4% experience sudden death. Consequently, adults with CHD require healthcare that is two- to four-times greater than adults without CHD. This paper discusses the diagnosis and treatment of adults with atrial septal defects, ventricular septal defects and tetralogy of Fallot.

Diagnosis and treatment of heart failure with preserved left ventricular ejection fraction

Nearly six million people in United States have heart failure. Fifty percent of these people have normal left ventricular (LV) systolic heart function but abnormal diastolic function due to increased LV myocardial stiffness. Most commonly, these patients are elderly women with hypertension, ischemic heart disease, atrial fibrillation, obesity, diabetes mellitus, renal disease, or obstructive lung disease. The annual mortality rate of these patients is 8%-12% per year. The diagnosis is based on the history, physical examination, laboratory data, echocardiography, and, when necessary, by cardiac catheterization. Patients with obesity, hypertension, atrial fibrillation, and volume overload require weight reduction, an exercise program, aggressive control of blood pressure and heart rate, and diuretics. Miniature devices inserted into patients for pulmonary artery pressure monitoring provide early warning of increased pulmonary pressure and congestion. If significant coronary heart disease is present, coronary revascularization should be considered.

Recognition and treatment of ischemic heart diseases in women

Heart disease is the leading cause of death among women in the industrialized world. However, women after myocardial infarctions (MIs) are less likely to receive preventive medications or revascularization and as many as 47% experience heart failure, stroke or die within 5 years. Premenopausal women with MIs frequently have coronary plaque erosions or dissections. Women under 50 years with angina and nonobstructive epicardial coronary artery disease often have coronary microvascular dysfunction (CMD) with reductions in coronary flow reserve that may require nontraditional therapies. In women with coronary artery disease treated with stents, the 3-year incidence of recurrent MI or death is 9.2%. Coronary bypass surgery operative mortality averages 4.6% for women compared with 2.4% in men. Addition of internal mammary artery and radial artery coronary grafts in women does not increase operative survival but improves 5-year outcome to greater than 80%.

Type-2 diabetes mellitus and cardiovascular disease

The global prevalence of diabetes has risen in adults from 4.7% in 1980 to 8.5% in 2014. 90–95% of adults with diabetes have Type 2 diabetes (T2D). This paper focuses on the diagnosis and treatment of T2D patients who have or are at risk for cardiovascular disease. Hyperglycemia, insulin resistance and excess fatty acids increase oxidative stress, disrupt protein kinase C signaling and increase advanced glycation end-products that result in vascular inflammation, vasoconstriction, thrombosis and atherogenesis. Intensive T2D treatment produces a ≥10% risk reduction in major macrovascular and microvascular events. Glucose-lowering therapies must be individualized. Metformin is an optimal drug for monotherapy. If hemoglobin A1c is not at goal, a sodium-glucose cotransporter-2 inhibitor or a dipeptidyl peptidase-4 inhibitor should be considered for therapy with metformin. Coronary angioplasty/stenting is recommended for diabetic patients with acute myocardial infarctions. Coronary artery bypass grafting is recommended for symptomatic diabetic patients with multivessel disease.

Current status of stem cells in cardiac repair

One out of every two men and one out of every three women greater than the age of 40 will experience an acute myocardial infarction (AMI) at some time during their lifetime. As more patients survive their AMIs, the incidence of congestive heart failure (CHF) is increasing. 6 million people in the USA have ischemic cardiomyopathies and CHF. The search for new and innovative treatments for patients with AMI and CHF has led to investigations and use of human embryonic stem cells, cardiac stem/progenitor cells, bone marrow-derived mononuclear cells and mesenchymal stem cells for treatment of these heart conditions. This paper reviews current investigations with human embryonic, cardiac, bone marrow and mesenchymal stem cells, and also stem cell paracrine factors and exosomes.

Cardio-oncology: cardiovascular complications of cancer therapy

This paper focuses on three classes of commonly used anticancer drugs, which can cause cardiotoxicity: anthracyclines, monoclonal antibodies exemplified by trastuzumab and tyrosine kinase inhibitors. Anthracyclines can induce cardiomyocyte necrosis and fibrosis. Trastuzumab can cause cardiac stunning. The tyrosine kinase inhibitors can increase systemic arterial pressure and impair myocyte contractility. In addition, radiation therapy to the mediastinum or left chest can exacerbate the cardiotoxicity of these anticancer drugs and can also cause accelerated atherosclerosis, myocardial infarction, heart failure and arrhythmias. Left ventricular ejection fraction measurements are most commonly used to assess cardiac function in patients who receive chemo- or radiation-therapy. However, echocardiographic determinations of global longitudinal strain are more sensitive for detection of early left ventricular systolic dysfunction. Information on patient-risk stratification and monitoring is presented and guidelines for the medical treatment of cardiac dysfunction due to cancer therapies are summarized.

Therapeutic angiogenesis: angiogenic growth factors for ischemic heart disease

Stem cells encode vascular endothelial growth factors (VEGFs), fibroblastic growth factors (FGFs), stem cell factor, stromal cell-derived factor, platelet growth factor and angiopoietin that can contribute to myocardial vascularization. VEGFs and FGFs are the most investigated growth factors. VEGFs regulate angiogenesis and vasculogenesis. FGFs stimulate vessel cell proliferation and differentiation and are regulators of endothelial cell migration, proliferation and survival. Clinical trials of VEGF or FGF for myocardial angiogenesis have produced disparate results. The efficacy of therapeutic angiogenesis can be improved by: (1) identifying the most optimal patients; (2) increased knowledge of angiogenic factor pharmacokinetics and proper dose; (3) prolonging contact of angiogenic factors with the myocardium; (4) increasing the efficiency of VEGF or FGF gene transduction; and (5) utilizing PET or MRI to measure myocardial perfusion and perfusion reserve.

Chitosan hydrogels significantly limit left ventricular infarction and remodeling and preserve myocardial contractility

BACKGROUND

Left ventricular myocardial infarctions (MIs) consist of a central area of myocardial necrosis that is surrounded by areas of myocardial injury and ischemia. We hypothesized that chitosan hydrogels, when injected around the perimeter of MIs in rats, could decrease left ventricle (LV) wall stress by the Law of LaPlace, and therefore myocardial oxygen requirements, and prevent the ischemic and injured myocardium from becoming necrotic. In this manner, chitosan gels could limit LV infraction size and LV remodeling. Chitosan hydrogels are liquid at 25°C but gel at 37°C.

METHODS

Seventy Sprague-Dawley rats with ligation of the left coronary artery were treated with either Dulbecco's Modified Eagle Medium (DMEM) or chitosan hydrogel in DMEM, which was injected around the infarct perimeter. Echocardiograms were obtained before MI and at 2, 4, 8, 12, and 16 wk after MI. Hearts from randomly selected rats were harvested at baseline and at the time of echocardiography for determinations of LV infarct size, remodeling, and histopathology.

RESULTS

Infarct sizes as a percentage of the total ventricular myocardium in the DMEM group averaged 17% versus 14% in the chitosan group at 4 wk (P < 0.05), 18% versus 14% at 8 wk (P < 0.01), 19% versus 14% at 12 wk (P < 0.001), and 20% versus 14% at 16 wk (P < 0.001). Injection of chitosan into the infarctions produced LV wall thicknesses in the MI border zones that averaged 0.66 cm at 4 wk, which were greater than the LV wall thicknesses in the border zones of rats treated with DMEM, which averaged 0.33 cm (P < 0.01). Arteriole densities in the MI border zones were 160/mm(2) in the chitosan group but only 92/mm(2) in the DMEM rats (P < 0.01). The left ventricular end-diastolic diameters (LVEDs) in the rats averaged 0.73 cm before MI. After MI, LVED increased in the DMEM rats to 0.84 cm at 2 wk, then 0.89 cm at 4 wk, 0.89 cm at 8 wk, 0.89 m at 12 wk, and 0.87 cm at 16 wk. In contrast, LVED in the chitosan rats were on average 19% smaller in comparison with the DMEM rats (P < 0.05) and did not significantly change in comparison with their baseline LVEDs. Left ventricular ejection fraction (LVEF) in the rats averaged 83% before infarctions. In the infarction + DMEM group, the LVEFs significantly decreased after MI and averaged 59.7% at 2 wk, 52.5% at 4 wk, 46.1% at 8 wk, 52.4% at 12 wk, and 53.6% at 16 wk (P < 0.05). In the infarction + chitosan-treated rats, the LVEFs were greater and averaged 67.8% at 2 wk (P < 0.02), 68.9% (P < 0.02) at 4 wk, 69% (P < 0.003) at 8 wk, 65.2% at 12 wk (P < 0.05), and 67% at 16 wk (P < 0.05).

CONCLUSIONS

Chitosan gel can increase LV myocardial wall thickness, decrease infarct size and LV remodeling, and preserve LV contractility.

Recent advances in the diagnosis and treatment of acute myocardial infarction

The Third Universal Definition of Myocardial Infarction (MI) requires cardiac myocyte necrosis with an increase and/or a decrease in a patient’s plasma of cardiac troponin (cTn) with at least one cTn measurement greater than the 99^th percentile of the upper normal reference limit during: (1) symptoms of myocardial ischemia; (2) new significant electrocardiogram (ECG) ST-segment/T-wave changes or left bundle branch block; (3) the development of pathological ECG Q waves; (4) new loss of viable myocardium or regional wall motion abnormality identified by an imaging procedure; or (5) identification of intracoronary thrombus by angiography or autopsy. Myocardial infarction, when diagnosed, is now classified into five types. Detection of a rise and a fall of troponin are essential to the diagnosis of acute MI. However, high sensitivity troponin assays can increase the sensitivity but decrease the specificity of MI diagnosis. The ECG remains a cornerstone in the diagnosis of MI and should be frequently repeated, especially if the initial ECG is not diagnostic of MI.

There have been significant advances in adjunctive pharmacotherapy, procedural techniques and stent technology in the treatment of patients with MIs. The routine use of antiplatelet agents such as clopidogrel, prasugrel or ticagrelor, in addition to aspirin, reduces patient morbidity and mortality. Percutaneous coronary intervention (PCI) in a timely manner is the primary treatment of patients with acute ST segment elevation MI. Drug eluting coronary stents are safe and beneficial with primary coronary intervention. Treatment with direct thrombin inhibitors during PCI is non-inferior to unfractionated heparin and glycoprotein IIb/IIIa receptor antagonists and is associated with a significant reduction in bleeding. The intra-coronary use of a glycoprotein IIb/IIIa antagonist can reduce infarct size. Pre- and post-conditioning techniques can provide additional cardioprotection. However, the incidence and mortality due to MI continues to be high despite all these recent advances. The initial ten year experience with autologous human bone marrow mononuclear cells (BMCs) in patients with MI showed modest but significant increases in left ventricular (LV) ejection fraction, decreases in LV end-systolic volume and reductions in MI size. These studies established that the intramyocardial or intracoronary administration of stem cells is safe. However, many of these studies consisted of small numbers of patients who were not randomized to BMCs or placebo. The recent LateTime, Time, and Swiss Multicenter Trials in patients with MI did not demonstrate significant improvement in patient LV ejection fraction with BMCs in comparison with placebo. Possible explanations include the early use of PCI in these patients, heterogeneous BMC populations which died prematurely from patients with chronic ischemic disease, red blood cell contamination which decreases BMC renewal, and heparin which decreases BMC migration. In contrast, cardiac stem cells from the right atrial appendage and ventricular septum and apex in the SCIPIO and CADUCEUS Trials appear to reduce patient MI size and increase viable myocardium. Additional clinical studies with cardiac stem cells are in progress.

Stem cells for cardiac repair: problems and possibilities

Ischemic heart disease is a major cause of death throughout the world. In order to limit myocardial damage and possibly generate new myocardium, stem cells are currently being injected into patients with ischemic heart disease. Three major patient investigations, The LateTIME, the TIME and the Swiss Myocardial Infarction trials, have recently addressed the questions of whether progenitor cells from unfractionated bone marrow mononuclear cells limit myocardial damage and what the optimal time to inject these cells after acute myocardial infarctions (AMIs) is. In each of these trials, there were no significant differences between treated and control patients when bone marrow cells were administered 5-7 days or 2-3 weeks after AMIs. Nevertheless, these investigations provide important information regarding clinical trial designs. Patients with AMIs in these trials were treated with percutaneous coronary intervention within a median of 4-5 h after the onset of chest pain. Thereafter, all patients received guideline-guided optimal medical therapy. Consequently, the sizes of AMIs were significantly limited. In patients with small AMIs and near-normal left ventricular ejection fractions, progenitor cells are least effective. However, these trials do question whether autologous bone marrow mononuclear cells are the optimal cells for myocardial repair owing to low numbers of progenitor cells in bone marrow aspirates and the significant variability in potency and efficacy of these cells in patients with chronic multisystem diseases. In contrast, the SCIPIO and the CAUDUCEUS trials examined cardiac progenitor cells in patients with ischemic cardiomyopathies. These trials reported over 1-2 years that cardiac progenitor cells produced significant improvements in left ventricular contractility due to 12-24 g decreases in myocardial scars and 18-23 g increases in viable myocardial muscle. However, caution must be exercised in the interpretation of these studies due to the small numbers of highly selected patients and intra- and inter-observer variability in infarct size measurements. Anatomical and histological examinations of large numbers of patients treated with these cells are necessary to confirm significant generation of myocytes and decreases in infarct size and fibrosis.

Human umbilical cord blood mononuclear cell-conditioned media inhibits hypoxic-induced apoptosis in human coronary artery endothelial cells and cardiac myocytes by activation of the survival protein Akt

We have previously demonstrated in acute myocardial infarctions that human umbilical cord blood mononuclear cells (HUCBCs), which contain hematopoietic, endothelial, and mesenchymal stem cells, reduce acute myocardial infarction size by ≥50% and preserve LV contractility. We hypothesize that the beneficial effects of HUCBCs are due to secretion of biologically active factors that activate in cardiac endothelial cells and myocytes the cell survival protein Akt. We determined by protein microarrays the growth factors and anti-inflammatory cytokines secreted by HUCBCs into culture media during 12 h of hypoxia (1% O2). We then determined by Western blots the effects of cell-free media from hypoxic-conditioned HUCBCs (HUCM) on activation of the cell survival protein Akt in human coronary artery endothelial cells and cardiac myocytes in culture during 24 h of 1% O2. We also determined in separate experiments endothelial cell and myocyte apoptosis by caspase-3 and Annexin V. In the present experiments, HUCBCs secreted multiple growth factors, anti-inflammatory cytokines, and inhibitors of metalloproteinase during normoxia and hypoxia. Human cord blood cells increased the concentration in culture media of angiopoietin, hepatocyte growth factor, interleukin-4, insulin-like growth factor, placental growth factor, vascular endothelial cell growth factor, angiogenin, and stem cell factor by 100 to >10,000% during 12 h of 1% O2 (p<0.001). HUCM, which contained these biological factors, significantly increased Akt phosphorylation/activation in coronary artery endothelial cells and cardiac myocytes subjected to 24 h of 1% O2 by more than 60% (p<0.05) and increased the antiapoptotic protein Bcl-2 expression by 34-50% in comparison with endothelial cells and myocytes treated without HUCM in 1% O2(p<0.05). HUCM also significantly decreased caspase-3 activity and decreased hypoxic endothelial cell and cardiac myocyte apoptosis by more than 40% in comparison with cells cultured without HUCM (p<0.05). Inhibition of Akt activation in endothelial cells and myocytes by the sensitive and specific antagonist API-1 during 24 h of hypoxia nearly completely prevented the beneficial effects of HUCM on inhibiting caspase-3 activity and apoptosis. We conclude that HUCBCs secrete biologically active factors during hypoxia that activate survival proteins in endothelial cells and myocytes that significantly limit apoptosis.

Human umbilical cord blood mononuclear cells activate the survival protein Akt in cardiac myocytes and endothelial cells that limits apoptosis and necrosis during hypoxia

We have previously reported that human umbilical cord blood mononuclear cells (HUCBC), which contain hematopoietic, mesenchymal, and endothelial stem cells, can significantly reduce acute myocardial infarction size. To determine the mechanism whereby HUCBC increase myocyte and vascular endothelial cell survival, we treated cardiac myocytes and coronary artery endothelial cells in separate experiments with HUCBC plus culture media or culture media alone and subjected the cells to 24 h of hypoxia or normoxia. We then determined in myocytes and endothelial cells activation of the cell survival protein Akt by Western blots. We also determined in these cells apoptosis by annexin V staining and necrosis by propidium iodide staining. Thereafter, we inhibited with API, a specific and sensitive Akt inhibitor, Akt activation in myocytes and endothelial cells cultured with HUCBC during hypoxia and determined cell apoptosis and necrosis. In cells cultured without HUCBC, hypoxia only slightly activated Akt. Moreover, hypoxia increased myocyte apoptosis by ≥ 226% and necrosis by 58% in comparison with myocytes in normoxia. Hypoxic treatment of endothelial cells without HUCBC increased apoptosis by 94% and necrosis by 59%. In contrast, hypoxia did not significantly affect HUCBC. Moreover, in myocyte + HUCBC cultures in hypoxia, HUCBC induced a ≥ 135% increase in myocyte phospho-Akt. Akt activation decreased myocyte apoptosis by 76% and necrosis by 35%. In endothelial cells, HUCBC increased phospho-Akt by 116%. HUCBC also decreased endothelial cell apoptosis by 58% and necrosis by 42%. Inhibition of Akt with API in myocytes and endothelial cells cultured with HUCBC during hypoxia nearly totally prevented the HUCBC-induced decrease in apoptosis and necrosis. We conclude that HUCBC can significantly decrease hypoxia-induced myocyte and endothelial cell apoptosis and necrosis by activating Akt in these cells and in this manner HUCBC can limit myocardial ischemia and injury.

Stem Cells in Cardiac Repair – Recent Developments and Future Directions

Myocardial infarction (MI) is the leading cause of death among people in the industrialised world and will, according to the World Health Organization (WHO), become the leading cause of death in the world in 2020. For the treatment of patients with MIs and ischaemic cardiomyopathies, remarkable medical advances have been made during the second half of the 20th Century that have increased patient survival. As a consequence, patients with heart disease are living longer and the incidence of congestive heart failure in patients is significantly increasing. New treatments for patients with acute MI and ischaemic cardiomyopathies are needed. In this regard, the next major advance in the treatment of patients with cardiac disease promises to be stem cells and stem cell products. Currently, basic research scientists and clinicians worldwide are investigating human embryonic stem cells, skeletal stem cells (myoblasts), adult bone marrow stem cells, cardiac stem cells and human umbilical cord stem cells for the treatment of patients with MIs and ischaemic cardiomyopathies. This review highlights the recent developments and the future directions of each of these stem cells in the treatment of patients with heart disease.

Stem cells in cardiac repair

Myocardial infarction is the leading cause of death among people in industrialized nations. Although the heart has some ability to regenerate after infarction, myocardial restoration is inadequate. Consequently, investigators are currently exploring the use of human embryonic stem cells (hESCs), skeletal myoblasts and adult bone marrow stem cells to limit infarct size. hESCs are pluripotent cells that can regenerate myocardium in infarcted hearts, attenuate heart remodeling and contribute to left ventricle (LV) systolic force development. Since hESCs can form heart teratomas, investigators are differentiating hESCs toward cardiac progenitor cells prior to transplantation into hearts. Large quantities of hESCs cardiac progenitor cells, however, must be generated, immune rejection must be prevented and grafts must survive over the long term to significantly improve myocardial performance. Transplanted autologous skeletal myoblasts can survive in infarcted myocardium in small numbers, proliferate, differentiate into skeletal myofibers and increase the LV ejection fraction. These cells, however, do not form electromechanical connections with host cardiomyocytes. Consequently, electrical re-entry can occur and cause cardiac arrhythmias. Autologous bone marrow mononuclear cells contain hematopoietic and mesenchymal stem cells. In several meta-analyses, patients with coronary disease who received autologous bone marrow cells by intracoronary injection show significant 3.7% (range: 1.9-5.4%) increases in LV ejection fraction, decreases in LV end-systolic volume of -4.8 ml (range: -1.4 to -8.2 ml) and reductions in infarct size of 5.5% (-1.9 to -9.1%), without experiencing arrhythmias. Bone marrow cells appear to release biologically active factors that limit myocardial damage. Unfortunately, bone marrow cells from patients with chronic diseases propagate poorly and can die prematurely. Substantial challenges must be addressed and resolved to advance the use of stem cells in cardiac repair including identifying the optimal stem cell(s) that permit transplantation without requirements for host immune suppression; timing of stem cell transplantation that maximizes chemoattraction of stem cells to infarcts; and determining the optimal technique for injecting stem cells for cardiac repair. Techniques must be developed to enhance survival and propagation of stem cells in the myocardium. These studies will require close cooperation and interaction of scientists and clinicians. Cell-based cardiac repair in the 21st century will offer new hope for millions of patients worldwide with myocardial infarctions who, otherwise, would suffer from the relentless progression of heart disease to heart failure and death.

Human umbilical cord blood mononuclear cells decrease fibrosis and increase cardiac function in cardiomyopathy

AIMS

We investigated whether human umbilical cord blood mononuclear cells (HUCBC) can limit progressive cardiomyopathy in TO2 hamsters.

MATERIALS & METHODS

A total of 22 TO2 1-month-old hamsters were treated with intramyocardial HUCBC, 4 x 10(6) in Isolyte, and 23 TO2 1-month-old hamsters were treated with intramyocardial Isolyte. A total of 16 1-month-old F1B hamsters served as controls and received intramyocardial Isolyte. Echocardiograms were performed on all hamsters prior to and monthly after treatment for 6 months. Heart tissues were then stained with hematoxylin and eosin, Masson's Trichrome and human leukocyte antibody.

RESULTS

In F1B hamsters, left ventricular fractional shortening (FS) and ejection fractions (EF) did not significantly decrease over 6 months. By contrast, in Isolyte-treated TO2 hamsters, FS decreased from 56.2 +/- 1.0% to 19.7 +/- 3.2% and EF decreased from 89.5 +/- 1.4% to 44.9 +/- 5.9% at 6 months (both p < 0.0001). The FS and EF in HUCBC-treated TO2 hamsters also progressively decreased over 6 months but the changes were more gradual, especially during the first month after HUCBC treatment when FS was 52.0 +/- 1.5% and EF was 89.5 +/- 1.4%, which was not significantly different from the FS and EF in the F1B hamsters. Moreover, in the HUCBC-treated hamsters, the FS and EF were 20-30% greater than FS and EF in Isolyte TO2 hamsters at 3 and 5 months (p < 0.01). In Isolyte-treated TO2 hamsters at 6-7 months, fibrosis involved 30.0 +/- 5.0% of left ventricle and 35.0 +/- 5.0% of septum. By contrast, in HUCBC-treated hamsters, fibrosis involved only 6.5 +/- 2.3% of the left ventricle and 6.3 +/- 1.8% of septum (p < 0.05). The average number of blood vessels per myocardial microscopic field in HUCBC-treated hearts was 53.5 +/- 0.8 versus 46.2 +/- 3.0 in Isolyte-treated TO2 hearts (p < 0.05).

CONCLUSION

HUCBC, when given as a single intramyocardial injection, can limit fibrosis and increase heart function over the short term in TO2 hamsters with cardiomyopathy.

Human cord blood mononuclear cells decrease cytokines and inflammatory cells in acute myocardial infarction

We investigated whether human umbilical cord blood mononuclear cells (HUCBC), which contain hematopoietic and mesenchymal progenitor cells, can limit myocardial cytokine expression and inflammatory cell infiltration in acute myocardial infarction. We permanently ligated the left coronary artery of rats and injected into the myocardium either Isolyte or 4 x 10(6) HUCBC in Isolyte and measured myocardial cytokines with antibody arrays at 2, 6, 12, 24, and 72 hours after infarction. We then measured with flow cytometry myocardial macrophages, neutrophils and lymphocytes at 12, 24, and 72 hours after infarctions in rats treated with either intramyocardial Isolyte or 4 x 10(6) HUCBC. In the Isolyte-treated hearts, between 2 and 12 hours after myocardial infarction, tumor necrosis factor-alpha increased from 6.7 +/- 0.9% to 52.3 +/- 4.7%, monocyte chemoattract protein increased from 9.5 +/- 1.2% to 39.8 +/- 2.1%, fractalkine increased from 11 +/- 1.5% to 28.1 +/- 1.3%, ciliary neurotrophic factor increased from 12.1 +/- 0.02% to 25.9 +/- 1.1%, macrophage inflammatory protein increased from 10.3 +/- 1.5% to 23.9.0 +/- 1.4%, interferon-gamma increased from 8.7 +/- 0.4% to 26.0 +/- 1.6%, interleukin-1beta increased from 6.1 +/- 0.04% to 19.0 +/- 1.2%, and IL-4 increased from 5.9 +/- 0.03% to 15 +/- 1.5% (all p < 0.001 compared with controls). The concentrations of fractalkine remained significantly increased at 72 hours after acute infarction. In contrast, the myocardial concentrations of these cytokines did not significantly change in HUCBC treated hearts at 2, 6, 12, 24, or 72 hours after infarction. The percentage of neutrophils increased from 0.04 +/- 0.2%/50,000 heart cells in the controls to 5.3 +/- 1.2%/50,000 heart cells 12 hours after infarction in Isolyte-treated hearts but averaged only 1.3 +/- 0.7%/50,000 heart cells in HUCBC treated hearts (p < 0.02). Thereafter, the percentages of neutrophils rapidly decreased at 24 and at 72 hours after infarction and averaged 0.6 +/- 0.2%/50,000 heart cells at 72 hours after infarction in Isolyte-treated hearts in contrast to 0.2 +/- 0.1%/50,000 cells in HUCBC hearts (p < 0.05). Moreover, the percentages of neutrophils at 24 and 72 hours in HUCBC hearts were not significantly different from controls. At 24 hours post infarction, the percentage of CD3 and CD4 lymphocytes were 10.7 +/- 1.4% and 6.3 +/- 1.1%/50,000 cells in Isolyte hearts in comparison with only 4.9 +/- 0.8% and 2.9 +/- 0.5% in HUCBC hearts (p < 0.005 for Isolyte versus HUCBC). The percentage of CD11b macrophages was 2.8 +/- 0.3% in Isolyte hearts and 1.9 +/- 0.2% in HUCBC treated hearts (p < 0.05). At 72 hours after infarction, the percentage of CD3 and CD4 lymphocytes averaged 8.0 +/- 1.1% and 5.1 +/- 0.8%/50,000 heart cells in Isolyte hearts in comparison with only 4.1 +/- 0.5% and 2.3 +/- 0.4%/50,000 heart cells in the HUCBC treated infarctions (p < 0.005). Left ventricular infarct sizes in Isolyte-treated hearts at 72 hours post infarction averaged 15.7 +/- 1.4% of the left ventricular muscle area in contrast to HUCBC treated infarctions that averaged 6.9 +/- 1.4% of the left ventricular muscle area (p < 0.02). Moreover in rats followed for 2 months post infarction, the LV ejection fractions decreased to 65.4 +/- 1.9% and 69.1 +/- 1.9% at 1 and 2 months after infarction in Isolyte-treated hearts and were significantly different from HUCBC treated hearts that averaged 72.1 +/- 1.3% and 75.7 +/- 1.4% (both p < 0.02). The present experiments suggest that an important mechanism whereby HUCBC limit infarct size and improve left ventricular ejection fraction is by significantly limiting inflammatory cytokines and inflammatory cells in infarcted myocardium.

Human cord blood cells and myocardial infarction: effect of dose and route of administration on infarct size

There is no consensus regarding the optimal dose of stem cells or the optimal route of administration for the treatment of acute myocardial infarction. Bone marrow cells, containing hematopoietic and mesenchymal stem cells, in doses of 0.5 x 10(6) to >30 x 10(6) have been directly injected into the myocardium or into coronary arteries or infused intravenously in subjects with myocardial infarctions to reduce infarct size and improve heart function. Therefore, we determined the specific effects of different doses of human umbilical cord blood mononuclear cells (HUCBC), which contain hematopoietic and mesenchymal stem cells, on infarct size. In order to determine the optimal technique for stem cell administration, HUCBC were injected directly into the myocardium (IM), or into the LV cavity with the ascending aorta transiently clamped to facilitate coronary artery perfusion (IA), or injected intravenously (IV) in rats 1-2 h after the left anterior coronary artery was permanently ligated. Immune suppressive therapy was not given to any rat. One month later, the infarct size in control rat hearts treated with only Isolyte averaged 23.7 +/- 1.7% of the LV muscle area. Intramyocardial injection of HUCBC reduced the infarct size by 71% with 0.5 x 10(6) HUCBC and by 93% with 4 x 10(6) HUCBC in comparison with the controls (p < 0.001). Intracoronary injection reduced the infarction size by 47% with 0.5 x 10(6) HUCBC and by 80% with 4 x 10(6) HUCBC (p < 0.001), and IV HUCBC reduced infarct size by 51% with 0.5 x 10(6) and by 75-77% with 16-32 million HUCBC (p < 0.001) in comparison with control hearts. With 4 x 10(6) HUCBC, infarction size was 65% smaller with IM HUCBC than with IA HUCBC and 78% smaller than with IV HUCBC (p < 0.05). Nevertheless, IM, IA, and IV HUCBC all produced significant reductions in infarct size in comparison with Isolyte-treated infarcted hearts without requirements for host immune suppression. The present experiments demonstrate that the optimal dose of HUCBC for reduction of infarct size in the rat is 4 x 10(6) IM, 4 x 10(6) IA, and 16 x 10(6) IV, and that the IM injection of HUCBC is the most effective technique for reduction in infarct size.

Human umbilical cord blood progenitor cells are attracted to infarcted myocardium and significantly reduce myocardial infarction size

We are investigating the effects of human umbilical cord blood mononuclear progenitor cells (HUCBC) for the treatment of acute myocardial infarction because human cord blood is a readily available and an abundant source of primitive cells that may be beneficial in myocardial repair. However, there is currently no scientific consensus on precisely when to inject stem/progenitor cells for the optimal treatment of acute myocardial infarction. We used an in vitro assay to determine the attraction of infarcted rat myocardium at 1, 2, 2.5, 3, 6, 12, 24, 48, and 96 h after left anterior descending coronary artery (LAD) occlusion from 45 rats for HUCBC in order to determine the optimal time to transplant HUCBC after myocardial infarction. Our assay is based on the migration of fluorescent DAPI-labeled HUCBC from wells in an upper chamber of a modified Boyden apparatus through a semiporous polycarbonate membrane into wells in a lower chamber that contain either normal or infarcted myocardium. DAPI-labeled HUCBC (100,000) were placed in each of the separate wells above the membrane that corresponded to normal or infarct homogenate in the lower wells. The greatest HUCBC migration to infarcted myocardium occurred at 2 h and 24 h after LAD occlusion in comparison with normal controls. A total of 76,331 +/- 3384 HUCBC migrated to infarcted myocardium at 2 h and 69,911 +/- 2732 at 24 h after LAD occlusion (both p < 0.001) and significantly exceeded HUCBC migration to normal heart homogenate. The HUCBC migration remained greatest at 2 and 24 h after LAD occlusion when the number of migrated cells was adjusted for the size of each myocardial infarction. Injection of 106 HUCBC in saline into infarcted myocardium of non immunosuppressed rats within 2 h (n=10) or at 24 h (n=5) after LAD occlusion resulted in infarction sizes 1 month later of 6.4 +/- 0.01% and 8.4 +/- 0.02% of the total left ventricular muscle area, respectively, in comparison with infarction sizes of 24.5 +/- 0.02% (n=10) in infarcted rat hearts treated with only saline (p < 0.005). Acute myocardial infarction in rats treated with only saline increased the myocardial concentration of tumor necrosis factor-alpha (TNF-alpha) from 6.9 +/- 0.8% to 51.3 +/- 4.6%, monocyte/macrophage chemoattractant protein (MCP-1) from 10.5 +/- 1.1% to 39.2 +/- 2.0%, monocyte inflammatory protein (MIP) from 10.6 +/- 1.6% to 23.1 +/- 1.5%, and interferon-gamma (INF-gamma) from 8.9 +/- 0.3% to 25.0 +/- 1.7% between 2 and 12 h after coronary occlusion in comparison with known controls (all p < 0.001). In contrast, the myocardial concentrations of these cytokines in rat hearts treated with HUCBC did not significantly change from the controls at 2, 6, 12, and 24 h after coronary occlusion. The present investigations suggest that infarcted myocardium significantly attracts HUCBC, that HUCBC can substantially reduce myocardial infarction size, and that HUCBC can limit the expression of TNF-alpha, MCP-1, MIP, and INF-gamma in acutely infarcted myocardium.

Mechanisms of vasoactive intestinal peptide-elicited coronary vasodilation in the isolated perfused rat heart

The present study investigated the potential role of vasoactive intestinal peptide (VIP) receptors, VPAC1 and VPAC2, in VIP-elicited coronary vasodilation of the isolated perfused rat heart. Additional studies determined the role of ATP-sensitive (K(ATP)) and voltage-gated K(+) (K(V)) channels in the VIP-elicited coronary vasodilation. Both the selective VPAC1 agonist, K15,R16,L27VIPl-7GRF8-27, and the selective VPAC2 agonist, RO25-1553, decreased coronary vascular resistance (CVR) in a dose-dependent manner, with EC(50) values of 1.67x10(-9)M and 7.11x10(-9)M, respectively (VPAC1 vs VPAC2 agonist, P<0.05). K15,R16,L27VIP1-7GRF8-27 and RO25-1553 maximally reduced CVR by -42+/-4% and -39+/-6% at 1x10(-8) and 3x10(-8)M, respectively. VIP at 1x10(-10)M decreased CVR by -14+/-2% in the absence (vehicle), by -11+/-3% in the presence of the nonselective VIP receptor antagonist VIP10-28 (1x10(-7)M; P>0.05 vs. vehicle) and by only -4+/-2% in the presence of the selective VPAC2 receptor antagonist PACAP6-38 (1x10(-7)M; P<0.05 vs. vehicle). In additional studies, VIP at 1x10(-10)M decreased CVR by -22+/-1% in the absence (control) and by only -10+/-2% in the presence of the nonselective K(+) channel blocker tetrabutylammonium (3x10(-4)M; P<0.05 vs. control). VIP reduced CVR by -4+/-1% in the presence of the K(ATP) channel blocker glibenclamide (3x10(-6)M; P<0.05 vs control) and by -28+/-2% in the presence of the K(V) channel blocker 4-aminopyridine (3x10(-4)M; P>0.05 vs control). Thus, selective VPAC1 and VPAC2 receptor activation in the coronary circulation produces vasodilation and the VIP-elicited coronary vasodilation involves activation of VPAC2 receptors and K(ATP) but not K(V) channels. In addition, VIP10-28 does not effectively block coronary vascular VIP receptors.

Cocaine activates calcium/calmodulin kinase II and causes cardiomyocyte hypertrophy

Cardiac hypertrophy occurs in as many as 47% of normotensive individuals who chronically use cocaine. We investigated the effects of cocaine, in concentrations commonly found in chronic cocaine users, on calcium/calmodulin kinase (CaMK), and whether cocaine can activate CaMK, increase cardiac myocyte protein expression, and cause cardiac hypertrophy in this manner. In series I to III, 0 (control) or cocaine in concentrations of 10 to 10 mol/L was added to cultured adult rat cardiac ventricular myocytes to determine by Western blots and by P incorporation the optimal treatment time and the optimal dose for CaMK activation. In series I, cocaine, 10 mol/L, increased myocyte CaMKII translocation from myocyte soluble to particulate fractions by > or =73 +/- 9% (P < 0.01) in comparison with controls but did not cause the translocation of CaMKI or CaMKIV. In series II and III, cocaine treatment of myocytes for 15 minutes increased maximal CaMKII activity by 86.5 +/- 13.3% (P < 0.001) and a cocaine dose of 5 x 10 mol/L increased CaMKII activity by 169.5 +/- 18.1% (P < 0.001). In series IV we measured by silver staining beta-myosin heavy chain protein (beta-MHC) expression in myocytes before and after cocaine and also CaMK inhibition with KN-62 (1-[N,O-bis-(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine). In these experiments, cocaine, 5x10 mol/L, increased myocyte protein concentration by 29.2 +/- 2.8%, and beta-MHC by 93.2 +/- 8.8% (P < 0.001). In series V and VI, cocaine effects on calcium currents (ICa) and intracellular Ca ([Ca]i) were determined before and after CaMK inhibition with KN-62 in rat myocytes. Cocaine, 10 mol/L, enhanced ICa peak amplitude in a voltage-dependent manner (by 173.9 +/- 14.9% at -20 mV and by 38.4 +/- 6.9% at 0 mV P < 0.01). Cocaine, 10 to 10 mol/L, in series VI promoted Ca transients from myocyte sarcoplasmic reticulum and increased [Ca]i to 607 +/- 141 x 10 mol/L (P < 0.05). KN-62 decreased cocaine-induced myocyte protein expression by 76.6%, and beta-MHC by 66.2% (P < 0.01) and significantly decreased cocaine-induced Ca transients and [Ca]i. We conclude that CaMKII activation is an important mechanism whereby cocaine can cause myocyte hypertrophy.

Human umbilical cord blood mononuclear cells for the treatment of acute myocardial infarction

Cell transplantation is a new treatment to improve cardiac function in hearts that have been damaged by myocardial infarction. We have investigated the use of human umbilical cord blood mononuclear progenitor cells (HUCBC) for the treatment of acute myocardial infarction. The control group consisted of 24 normal rats with no interventions. The infarct + vehicle group consisted of 33 rats that underwent left anterior descending coronary artery (LAD) ligation and after 1 h were given Isolyte in the border of the infarction. The infarct + HUCBC group consisted of 38 rats that underwent LAD ligation and after 1 h were given 10(6) HUCBC in Isolyte directly into the infarct border. Immunosuppression was not given to any rat. Measurements of left ventricular (LV) ejection fraction, LV pressure, dP/dt, and infarct size were determined at baseline and 1, 2, 3, and 4 months. The ejection fraction in the controls decreased from 88+/-3% to 78+/-4% at 4 months (p = 0.03) as a result of normal aging. Following infarction in the infarct + vehicle group, the ejection fraction decreased from 87+/-4% to 51+/-3% between 1 and 4 months (p < 0.01). In contrast, the ejection fraction of the infarcted + HUCBC-treated rat hearts decreased from 87+/-4% to 63+/-3% at 1 month, but progressively increased to 69+/-6% at 3 and 4 months, which was different from infarct + vehicle group rats (p < 0.02) but similar to the controls. At 4 months, anteroseptal wall thickening in infarct + HUCBC group was 57.9+/-11.6%, which was nearly identical to the control anteroseptal thickening of 59.2+/-8.9%, but was significantly greater than the infarct + vehicle group, which was 27.8+/-7% (p < 0.02). dP/dt(max) increased by 130% in controls with 5.0 microg of phenylephrine (PE)/min (p < 0.001). In the infarct + vehicle group, dP/dt(max) increased by 91% with PE (p = 0.01). In contrast, in the infarct + HUCBC group, dP/dt(max) increased with PE by 182% (p < 0.001), which was significantly greater than the increase in dP/dt(max) in the infarct + vehicle group (p = 0.03) and similar to the increase in the controls. Infarct sizes in the infarct + HUCBC group were smaller than the infarct + vehicle group and averaged 3.0+/-2.8% for the infarct + HUCBC group versus 22.1+/-5.6% for infarct + vehicle group at 3 months (p < 0.01); at 4 months they averaged 9.2+/-2.0% for infarct + HUCBC group versus 40.0+/-9.2% for the infarct + vehicle group (p < 0.001). The present experiments demonstrate that HUCBC substantially reduce infarction size in rats without requirements for immunosuppression. As a consequence, LV function measurements, determined by LV ejection fraction, wall thickening, and dP/dt, are significantly greater than the same measurements in rats with untreated infarctions.

Coronary vascular effects of vasoactive intestinal peptide in the isolated perfused rat heart

The potency and mechanism of action of vasoactive intestinal peptide (VIP) for producing coronary vasodilation was investigated in the isolated perfused heart of the rat. VIP reduced coronary vascular resistance in a dose-dependent manner, starting at 1 x 10(-10) M, and maximally reduced coronary vascular resistance by 49% at 1 x 10(-8) M. The potency of VIP for reducing coronary vascular resistance (EC50=3.02 x 10(-10) M) was considerably greater than that of adenosine (EC50=6.17 x 10(-8) M) and sodium nitroprusside (EC50=2.45 x 10(-6) M). The vasodilatory action of VIP was more easily observed after increasing vascular tone by perfusion of the hearts with a modified physiological solution containing reduced concentrations of potassium (3.2 mM) and calcium (1.2 mM). Under these conditions, VIP maximally reduced coronary resistance by 54% at 7 x 10(-9) M. The potency of VIP for reducing coronary resistance in these hearts, however, decreased 16-fold (EC50=4.90 x 10(-9) M) while that of SNP remained unaltered (EC50=3.39 x 10(-6) M), compared with hearts perfused with higher levels of potassium (5.9 mM) and calcium (2.5 mM). The vasodilatory effect of VIP occurred without a significant change in heart rate, myocardial contractility or oxygen consumption. In additional studies, the dose-dependent effect of VIP on cyclic nucleotide release from the heart was determined by infusing VIP into the coronary circulation in a cumulative fashion to produce final concentrations between 1 x 10(-11) and 1 x 10(-9) M. VIP increased cyclic AMP at 1 x 10(-9) M but did not increase cyclic GMP. Studies using RT-PCR and immunohistochemistry clearly demonstrated the presence of two VIP receptor subtypes, VPAC1 and VPAC2, in the arteries and arterioles of the heart. In conclusion, VIP is a potent vasodilator in the coronary circulation of the rat and the role of VIP in the control of coronary vascular resistance depends on the circulating levels of potassium and calcium. This vasodilatory effect involves binding to specific coronary cell surface receptors, VPAC1 and/or VPAC2, and is dependent on cyclic AMP only during maximal vasodilation.

Cocaine produces cardiac hypertrophy by protein kinase C dependent mechanisms

BACKGROUND

Chronic cocaine users can have as much as a 69% increase in left ventricular muscle mass without associated increases in arterial blood pressure, heart rate, renin, aldosterone, or cortisol. We determined whether cocaine directly increases cardiomyocyte protein content and whether protein kinase C is important in this process.

METHODS AND RESULTS

Adult rat cardiomyocytes were isolated and grown in cultures. In Series I experiments, cocaine, 10(-8) to 10(-6) M, or vehicle, in the absence or presence of phentolamine or metoprolol, was added to each culture and the cells were subsequently harvested. In Series II, cocaine, 10(-6) M, cocaine, 10(-6) M, plus bisindolylmaleimide, 10(-6) M, a protein kinase C inhibitor, or vehicle were added to each culture and the cells subsequently harvested. We determined the total protein content, the content of alpha-myosin and fetal beta-myosin heavy-chain protein, and the presence of protein kinase C isoforms in the cardiomyocyte soluble and particulate fractions. Protein kinase C translocation from the soluble to particulate fraction is indicative of activation. In Series III, we determined the cocaine effects on ERK, SAPK/JNK, and p38. In Series I, cocaine, 10(-8) to 10(-6) M, dose-dependently increased myocyte protein content by as much as 28%+/-2% (P<.001) and fetal beta-myosin heavy-chain protein content by 80%+/-2% (P<.001). Neither phentolamine nor metoprolol inhibited this process. In Series II, we determined that ventricular myocytes contain alpha (alpha), beta (beta), delta (delta), epsilon (epsilon), and zeta (zeta) protein kinase C isoforms. Cocaine, 10(-6) M, caused a 45+/-5% increase (P<.001) in protein kinase Calpha in the particulate fraction. The addition of a protein kinase C inhibitor to the myocyte cultures prevented the cocaine-induced translocation of protein kinase Calpha and limited the increase in beta-myosin heavy-chain protein content by >75% (P<.001). However, cocaine did not increase the phosphorylation of ERK, SAPK/JNK or p38 in Series III.

CONCLUSIONS

Cocaine increases adult cardiomyocyte protein content by protein kinase Calpha-dependent mechanisms, and this process can contribute to the cardiac hypertrophy and cardiomyopathy that results from chronic cocaine use.

Atrial myxoma: case report and a review of the literature

Atrial myxomas are the most common benign primary tumor of the heart and occur in as many as 3 in 1000 patients. These tumors are a major cause of patient morbidity and mortality. Although the majority of atrial myxomas occur in the left atrium, 3 separate familial myxoma syndromes can result in multiple myxomas in atypical locations. Approximately 50% of patients with myxomas may experience symptoms due to central or peripheral embolism or intracardiac obstruction, but 10% of patients may be completely asymptomatic. Screening for myxomas should involve a thorough history and physical examination and a transthoracic and/or transesophageal echocardiogram. Transthoracic echocardiography is approximately 95% sensitive for the detection of cardiac myxomas, and transesophageal echocardiography approaches 100% sensitivity. Though the majority of atrial myxomas are sporadic, it is imperative that first-degree relatives of patients with documented myxomas undergo screening for occult myxomas. Surgical removal of the myxoma is the treatment of choice and usually curative; however, myxoma recurrence does occur and is most frequently associated with a familial syndrome.

Acute and chronic aortic dissection

Each year acute aortic dissection is diagnosed in 2,000 individuals in the United States. Acute aortic dissection is no longer a catastrophic event because this problem can be rapidly diagnosed with current medical technology, and therefore promptly treated with medication and surgery. Consequently, patients with aortic dissection can survive for 10 to 20 or more years after the initial event. However, there is considerable current debate regarding the most optimal technique(s) for the diagnosis of aortic dissection. Moreover, little information is available on the best methods for the long-term assessment and treatment of patients who have been successfully treated for acute aortic dissection. This report reviews the current techniques that are available for the diagnosis of aortic dissection and discusses the important issues regarding the acute and long-term treatment of patients with this problem.

Vasoactive intestinal peptide: cardiovascular effects

Vasoactive intestinal peptide (VIP) is present in the peripheral and the central nervous systems where it functions as a nonadrenergic, noncholinergic neurotransmitter or neuromodulator. Significant concentrations of VIP are present in the gastrointestinal tract, heart, lungs, thyroid, kidney, urinary bladder, genital organs and the brain. On a molar basis, VIP is 50-100 times more potent than acetylcholine as a vasodilator. VIP release in the body is stimulated by high frequency (10-20 Hz) nerve stimulation and by cholinergic agonists, serotonin, dopaminergic agonists, prostaglandins (PGE, PGD), and nerve growth factor. The VIP peptide combines with its receptor and dose-dependently activates adenylyl cyclase. The vasodilatory effect of VIP in different vascular tissues or species also may be due to increases in nitric oxide, cyclic GMP, and other signaling agents. In the heart, VIP immunoreactive nerve fibers are present not only in the epicardial coronary arteries and veins, but also the sinoatrial node, atrium, interatrial septum, atrioventricular node, intracardiac ganglia, and ventricles (right ventricle >> left ventricle). In the coronary arterial walls, VIP may contribute to the regulation of normal coronary vasomotor tone. In research animals and in humans, VIP, administered into the coronary artery or intravenously, increases the epicardial coronary artery cross-sectional area, decreases coronary vascular resistance, and significantly increases coronary artery blood flow. High frequency parasympathetic (vagal) nerve stimulation also releases endogenous VIP in the coronary vessels and heart and significantly increases coronary artery blood flow. In addition, the release of VIP in the heart is increased during coronary artery occlusion and during reperfusion where VIP may promote local blood flow and may have a free-radical scavenging effect. VIP also has a primary positive inotropic effect on cardiac muscle that is enhanced by its ability to facilitate ventricular-vascular coupling by reducing mean arterial pressure by 10-15%. In concentrations of 10(-8)-10(-5) mol, VIP augments developed isometric force and increases atrial and ventricular contractility. The presence of VIP-immunoreactive nerve fibers in and around the sinus and the atrioventricular nodes of mammals strongly suggests that this peptide can affect the heart rate. In this regard, endogenously released or exogenous VIP can significantly increase the heart rate and has a more potent effect on heart rate than does norepinephrine. The presence and significant cardiovascular effects of VIP in the heart suggests that this peptide is important in the regulation of coronary blood flow, cardiac contraction, and heart rate. Current investigations are defining the physiological role of VIP in the regulation of cardiovascular function.

Cocaine increases beta-myosin heavy-chain protein expression in cardiac myocytes

BACKGROUND

As many as 47% of chronic cocaine users develop cardiac ventricular hypertrophy. The presence and degree of cocaine-induced ventricular hypertrophy is not correlated with the use of other substances of abuse such as alcohol or cigarettes. Moreover, this hypertrophy occurs in individuals without sustained increases in arterial blood pressure or heart rate, or increases in the plasma concentration of renin, aldosterone, norepinephrine, or cortisol. Therefore, we investigated whether cocaine, in concentrations commonly found in cocaine users, has any direct effects on the protein content in cardiac ventricular myocytes. We compared the effects of cocaine with norepinephrine, which increases the total protein content, especially beta-myosin heavy-chain contractile protein (beta-MHC), in cardiac ventricular myocytes.

METHODS

Experiments were performed on 30-day-old rat ventricular myocytes suspended in culture media and cultured in flasks. In 12 suspension-culture experiments, cocaine or norepinephrine, in doses of 0 (control) or 10(-6) mol/L was added to each culture and the cells were harvested on day 5. In 16 flask-culture experiments, cocaine or norepinephrine was added to each culture on day 7 in doses of 0 (control-vehicle), 10(-7), or 10(-6) mol/L and the cells were harvested on day 10. The total protein content and the myosin protein expression of the myocytes in each culture were determined. Juvenile and adult rat cardiac myosin protein is predominately alpha-myosin heavy-chain protein (alpha-MHC), whereas beta-MHC occurs primarily in fetal rat hearts.

RESULTS

In the suspension-culture experiments, cocaine, 10(-6) mol/L, increased the cardiomyocyte total protein concentration by 29% +/- 2% (P <.001) and the beta-MHC expression by 81% +/- 10% (P <.01) in comparison with the control myocytes. Cocaine slightly decreased cardiomyocyte alpha-MHC. Norepinephrine increased the total protein concentration by 21% +/- 3% (P <.001) and the beta-MHC expression by 59% +/- 10% (P <.01), but did not increase alpha-MHC expression. In the flask-culture experiments, cocaine, 10(-6) mol/L, maximally increased the total protein concentration by 28% (P <.001), the protein/cell ratio by 57% +/- 10% (P <.01), and the beta-MHC expression by 85% +/- 8% (P <.01). Cocaine slightly decreased alpha-MHC. Norepinephrine, 10(-6) mol/L, maximally increased the total protein concentration by 35%, the protein/cell ratio by 63% +/- 9% (P <.01), and the expression of beta-MHC by 78% +/- 11% (P <. 01). Norepinephrine did not increase alpha-MHC expression. In 18 separate flask-culture experiments, cocaine, 10(-6) mol/L, was added to the cardiomyocyte cultures after the addition of phentolamine (n = 9), in concentrations of 10(-7) to 10(-5) mol/L, or metoprolol (n = 9), in concentrations of 10(-7) to 10(-5) mol/L. Neither phentolamine nor metoprolol inhibited the cocaine-induced increase in cardiomyocyte total protein content or the expression of beta-MHC.

CONCLUSION

Cocaine, similar to norepinephrine, significantly increases the total protein content and the expression of beta-MHC in cardiac ventricular myocytes. In this manner, cocaine may cause cardiac ventricular hypertrophy. This process is not inhibited by alpha- or beta-adrenergic receptor blockade.

Coronary artery blood flow: physiologic and pathophysiologic regulation

Acute myocardial ischemia, which results from a significant imbalance between myocardial oxygen demands and myocardial oxygen supply, occurs in as many as six million persons with atherosclerotic coronary artery disease in the United States. Accordingly, a clear understanding of the physiologic and pathophysiologic factors that influence coronary artery blood flow is important to the clinician and provides the basis for the judicious use of medications for the treatment of patients with atherosclerotic coronary artery disease. This review discusses the endothelial, metabolic, myogenic, and neurohumoral mechanisms of coronary blood flow regulation and the interaction of the different mechanisms in the regulation of coronary blood flow. The importance of nitric oxide in coronary blood flow regulation is emphasized. We also discuss the common clinical problems of hyperlipidemia and coronary atherosclerosis, coronary artery spasm, and systemic arterial hypertension that result in coronary artery endothelial dysfunction, the impaired production and increased inactivation of nitric oxide, and impairment in coronary blood flow regulation. This information is important to clinicians because more than forty million people in the United States have atherosclerotic or hypertensive heart disease and therefore are at risk for significant myocardial complications due to impairment of coronary blood flow regulation.

Vagal nerve stimulation releases vasoactive intestinal peptide which significantly increases coronary artery blood flow

OBJECTIVE

To determine the effects of vasoactive intestinal peptide (VIP), released endogenously from cardiac vagal nerves, on coronary artery blood flow (CBF).

METHODS

We determined the effects of vagal nerve stimulation (VNS) at frequencies of 10, 15, 20, and 30 Hz on left circumflex coronary artery (LCx) blood flow. The increases in CBF during VNS were compared with the increases in CBF produced by exogenous VIP and also nitroglycerin (NTG). In 18 anesthetized open chest mongrel dogs, we blocked the muscarinic and beta-adrenergic receptors with atropine and propranolol. We controlled heart rate and aortic pressure by right atrial pacing and an arterial reservoir. CBF was measured in the LCx with a Doppler flow probe. A 25 gauge catheter was placed in the proximal LCx to inject the VIP receptor antagonist [4Cl-D-Phe6Leu17]VIP, VIP, NTG, or vehicle. CBF, aortic and ventricular pressures, ventricular contractility (+dp/dt(max)) and relaxation (-dp/dt(min)) and the EKG were measured.

RESULTS

VNS (0.5 ms, 20 V, 5 min.) at 20 Hz maximally increased CBF by 62 +/- 14% at 5 min from 71 +/- 10 to 115 +/- 19 ml/min (p < 0.01). VNS at 10, 15, and 30 Hz increased CBF by 6 +/- 1%, 24 +/- 5%, and 24 +/- 7%, respectively (all p < 0.05 vs control). Following 20 Hz VNS, CBF returned toward the baseline over 30 min. Aortic and left ventricular (LV) pressures, LV +dp/dt(max) and LV-dp/dt(min) did not significantly change. After the direct administration of [4Cl-D-Phe6Leu17]VIP into the LCx, VNS increased CBF by only 10 +/- 4% (p = NS). Exogenous VIP, in doses of 9.0 x 10(-11) to 2.1 x 10(-9) mol, increased CBF by 106 +/- 17% to 169 +/- 17% (all p < 0.01 vs control). NTG, in doses of 2.2 x 10(-8) to 1.7 x 10(-7) mol, increased CBF by 101 +/- 15% to 169 +/- 20% (all p < 0.01 vs control). These increases in CBF persisted during the 1 to 2 min injection period and returned to the baseline within 5 min. Neither VIP nor NTG significantly changed the heart rate, aortic or LV pressures, LV +dp/dt(max) or LV -dp/dt(min). VNS at 20 Hz, exogenous VIP, 9.0 x 10(-11) mol, and exogenous NTG, 2.2 x 10(-8) to 4.4 x 10(-8) mol, produced equivalent increases in CBF by analysis of variance determination.

CONCLUSION

The present experiments suggest that VNS releases VIP which directly dilates coronary arteries and significantly increases coronary artery blood flow.

Vagal nerve stimulation during muscarinic and beta-adrenergic blockade causes significant coronary artery dilation

Vasoactive intestinal peptide (VIP) is present in post-ganglionic vagal nerve fibers in the coronary arteries and right ventricle but no significant amounts are found in the left ventricle. We determined the effects of VIP, released endogenously from cardiac vagal nerves, on the circumflex mean coronary artery pressure and on right and left ventricular (RV and LV) contractility (dP/dtmax) and relaxation (dP/dtmin). In 20 anesthetized, open chest mongrel dogs, the cervical vagus nerves and cardiac sympathetic ansa subclaviae were isolated and transected. Electrodes were applied to the cardiac segments of the right and left vagus nerves for subsequent stimulation. The muscarinic and beta-adrenergic receptors were blocked with atropine and propranolol, respectively. The heart rate was controlled by either producing atrioventricular node block in 10 dogs and pacing the ventricles (series 1) or by right atrial pacing in 10 separate dogs (series 2). Coronary artery blood flow was controlled by perfusing the circumflex coronary artery in each dog with femoral arterial blood at a controlled flow rate. Coronary artery pressure, ventricular and aortic pressures and dP/dt were continuously measured. Experiments were performed prior to and after the administration of [4Cl-D-Phe6,Leu17]VIP, a sensitive and selective VIP antagonist. Vagal nerve stimulation at 20 Hz (0.5 ms, 20 V) for 5 min significantly decreased the circumflex mean coronary artery pressure by 17% from the control value of 95+/-2 mmHg in series 1 and by 13% from the control value of 109+/-2 mmHg in series 2 (both p < 0.005). Aortic, LV and RV systolic and end-diastolic pressures, LV dP/dtmax and dP/dtmin, and the EKG did not change. In contrast, RV dP/dtmax and dP/dtmin increased by 22% (p < 0.04) and 23% (p < 0.02), respectively, in series 1 and by 26% (p < 0.02) and 33% (p < 0.01), respectively, in series 2. The VIP antagonist, [4Cl-D-Phe6,Leu17]VIP, directly injected into the left circumflex coronary artery, had no effect on coronary, aortic or ventricular pressures, ventricular dP/dt or the EKG. However, 20 Hz vagal stimulation in the presence of the VIP antagonist did not decrease circumflex mean coronary artery pressure. In addition, vagal stimulation, in the presence of the VIP antagonist, had no effect on LV pressures or dP/dt but increased RV dP/dtmax and dP/dtmin. RV dP/dtmax increased by 16% (p < 0.01) and RV dP/dtmin increased by 22% (p < 0.04), respectively, in series 1 and by 27 and 24%, respectively, in series 2 (both p < 0.01). Vagal nerve stimulation during muscarinic and beta-adrenergic blockade releases VIP or a 'VIP-like' substance that significantly decreases circumflex coronary artery vascular resistance and increases RV dP/dtmax and dP/dtmin.

Pseudoaneurysm of the thoracic aorta presenting as purulent pericarditis and pericardial effusion

Report of a case of a mycotic pseudoaneurysm of the ascending thoracic aorta occurring in the absence of surgical or blunt trauma in a patient who presented with purulent pericarditis. Surgical pericardial drainage was required, which revealed Staphlococcal aureus. Subsequent transesophageal echocardiogram demonstrated a 4 cm x 4 cm pseudoaneurysm of the posterior wall of the aorta above the sinotubular junction. The patient refused surgical correction of the aortic pseudoaneurysm and was successfully managed with antibiotic therapy.

Cocaine: pathophysiology and clinical toxicology

PURPOSE

To review the medical complications of cocaine abuse and the mechanisms of action of cocaine that contribute to medical complications.

DATA SOURCES

Pertinent articles identified through a MEDLINE search of the English-language literature from 1985 to 1996 and through a manual search of bibliographies of all identified articles.

STUDY SELECTION

All articles describing complications of cocaine use including case reports, small reported series, and review articles.

DATA SYNTHESIS

A qualitative description of reported complications.

RESULTS

Since the introduction of freebase and crack cocaine, multiple medical complications have been observed, and all major body organ systems have been affected. Cocaine can cause acute strokes, myocardial infarction, cardiac dysrhythmias, pulmonary edema, rhabdomyolysis, and acute renal failure.

CONCLUSION

Adverse reactions to cocaine should be considered in the differential diagnosis of acute ischemic events that occur in young adults. General awareness of the significant complications of cocaine will facilitate early diagnosis and prompt treatment.

Right ventricular obstruction caused by epicardial defibrillator patches

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Vagal nerve stimulation increases right ventricular contraction and relaxation and heart rate

OBJECTIVE

To determine the effects of vasoactive intestinal peptide, released from the right and left vagal nerves, on ventricular contraction, relaxation, and heart rate.

METHODS

The muscarinic and beta-adrenergic receptors were blocked with atropine and propranolol, and afterload was controlled in 48 anesthetized, open-chest mongrel dogs. Experiments were performed in the absence (Series 1, 10 dogs) and in the presence (Series 2, 22 dogs) of a controlled heart rate and prior to and after the administration of a sensitive and selective vasoactive intestinal peptide antagonist (Series 3, 16 dogs).

RESULTS

Right ventricular contraction (+dp/dtmax), relaxation (-dp/dtmin) and heart rate increased significantly during 20 Hz vagal nerve stimulation for 5 min. Vagal nerve stimulation in Series 1 increased right ventricular +dp/dtmax by 28% from a control value of 480 +/- 11 (P < 0.001) and right ventricular -dp/dtmin by 23% from a control value of 341 +/- 11 (P < 0.002). Left ventricular +dp/dtmax and -dp/dtmin increased slightly but not significantly. Vagal nerve stimulation also increased the heart rate by 29% from a control value of 149 +/- 2 (P < 0.001). During controlled heart rate in Series 2, vagal nerve stimulation at 20 Hz consistently increased right ventricular +dp/dtmax and -dp/dtmin comparable to Series 1 experiments but did not increase left ventricular +dp/dtmax or -dp/dtmin. Injection of the vasoactive intestinal peptide antagonist [4Cl-DPhe6, Leu17]VIP into the right coronary artery of 16 dogs in Series 3 did not affect right ventricular +dp/dtmax, -dp/dtmin, or heart rate. However, this antagonist substantially decreased the vagal-induced increases in right ventricular +dp/dtmax, -dp/dtmin, and heart rate by 85, 63, and 71% (P < 0.005), respectively.

CONCLUSION

The present experiments suggest that vagal nerve stimulation releases vasoactive intestinal peptide (VIP) or a "VIP-like substance' that significantly increases right ventricular contraction, relaxation, and heart rate.