Hemodynamic and metabolic responses to vasodilator therapy in acute myocardial infarction

The beneficial hemodynamic effects of afterload reduction by sodium nitroprusside during rewarming from experimental hypothermia

BACKGROUND

Rewarming from hypothermia is associated with depressed cardiac function, known as hypothermia-induced cardiac dysfunction (HCD), and increased systemic vascular resistance (SVR). Previous studies on pharmacological treatment of HCD have demonstrated beneficial effects when using drugs with the combined effects; cardiac inotropic support and peripheral vasodilation. The presented study aims to investigate the isolated effects of arterial dilatation on cardiac functional variables during rewarming from hypothermia using sodium nitroprusside (SNP).

METHODS

We utilized a rat model designed to induce HCD following 4 h at 15 °C and rewarming. To study effects on left ventricular (LV) functional variables in response to afterload reduction by SNP during rewarming a conductance catheter was used. Index of LV contractility, preload recruitable stroke work (PRSW), was obtained with inferior vena cava occlusions at 37 °C before and after hypothermia. Pressure signals from a catheter in the left femoral artery was used to pharmacologically adjust SVR.

RESULTS

After rewarming both animal groups showed significant reduction in both SV and CO as a manifestation of HCD. However, compared to saline controls, SV and CO in SNP-treated animals increased significantly during rewarming in response to afterload reduction displayed as reduced SVR, mean arterial- and end-systolic pressures. The cardiac contractility variable PRSW was equally reduced after rewarming in both groups.

CONCLUSION

When rewarming the present model of HCD a significant increase in SVR takes place. In this context, pharmacologic intervention aimed at reducing SVR show clear positive results on CO and SV. However, a reduction in SVR alone is not sufficient to fully alleviate CO during HCD, and indicate the need of additional inotropic support.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Treatment of Acute Heart Failure

OBJECTIVES

To provide an evidence-based review of pharmacotherapies to treat acute heart failure. To accomplish this objective, we will discuss circulatory physiology, vasoactive agents, and their indications in the management of acute heart failure.

DATA SOURCE

A MEDLINE-baseline review of the literature.

CONCLUSIONS

The optimal selection of vasoactive agents requires a consideration of circulatory physiology and the tailored application of pharmacotherapies to treat patients with acute heart failure.

Preoperative evaluation of the surgical patient

A thorough preoperative evaluation to identify correctable medical abnormalities and understand the residual risk is mandatory for all patients undergoing any surgical procedure, including oral surgery. Routine preoperative evaluation will vary among patients, depending on age and general health. This article addresses the preoperative evaluation of surgical patients in general, and the evaluation for general anesthesia in the operating room.

Beneficial effects of prostaglandin E1 on myocardial energetics and pump performance in severe CHF

To provide more effective vasodilator agents for the therapy of severe left ventricular (LV) failure the cardiocirculatory actions of prostaglandin E1 (PGE1) were evaluated in nine coronary patients. PGE1 infusion modestly decreased mean systemic blood pressure (85 to 76 mm Hg, p less than 0.025) and LV filling pressure (19 to 15 mm Hg, p less than 0.01) while heart rate was unchanged (p less than 0.05). Simultaneously, PGE1 augmented cardiac index from 1.9 to 2.5 1/min/m2 (p less than 0.005), raised stroke index from 28 to 35 ml/beat m2 (p less than 0.01) and increased stroke work index from 26 to 30 g-m/m2 (p less than 0.02). Additionally, total systemic vascular resistance decreased from 1862 to 1282 dynes-sec-cm-5 (p less than 0.02) and double product of heart rate and systolic blood pressure diminished from 9492 to 8278 mm Hg (p less than 0.02) while the effective endocardial perfusion pressure was maintained (p less than 0.05). Concomitantly, forearm vascular resistance fell, forearm blood flow was raised, and forearm venous tone remained unchanged. Thus, our results demonstrate that PGE2 is a potent arteriolar vasodilator with markedly beneficial effects of myocardial energetics and on cardiac function in patients with severe ischemic congestive cardiac failure.

Vasodilators in the management of acute heart failure

Recent guidelines by the Heart Failure Society of America have recommended consideration for use of nitroprusside, nitroglycerin, or nesiritide in addition to diuretics to achieve hemodynamic and symptomatic improvement. This article reviews the results of previous studies evaluating the pharmacologic and clinical effects and safety profiles of these drugs in patients with heart failure.

Overview of current noninodilator therapies for acute heart failure syndromes

Several treatment strategies exist for patients hospitalized with acute heart failure syndromes (AHFS). These therapies traditionally focus on improving hemodynamics and relieving congestion. This review focuses on noninodilator therapies, including diuretics, nitrovasodilators (nitroprusside and nitroglycerin), vasodilators (nesiritide), digoxin, and intravenous angiotensin-converting enzyme inhibitors. These agents are used based on their associated symptomatic improvements alone. In the hospitalized setting, none of these agents have demonstrated benefits on long-term outcomes. Future work in AHFS should strive to understand the influence of conventional and new pharmacologic therapies on the underlying pathophysiology of AHFS, the processes that lead to myocardial injury and progressive heart failure, and measurable clinical outcomes.

Effects of afterload-reducing drugs on pathogenesis of antioxidant changes and congestive heart failure in rats

OBJECTIVES

The present study sought to evaluate the effects of the afterload-reducing drugs captopril and prazosin on changes in antioxidants as well as oxidative stress in relation to hemodynamic function in congestive heart failure (CHF) subsequent to myocardial infarction (MI).

BACKGROUND

Afterload reduction therapy has been shown to reduce morbidity and mortality in patients with MI. CHF subsequent to MI in rats is associated with a decrease in myocardial endogenous antioxidants and an increase in oxidative stress.

METHODS

The left anterior descending coronary artery in male Sprague-Dawley rats was ligated. Sham and experimental (post-MI [PMI]) animals were assessed for hemodynamic function as well as lung and liver weights at 1, 4 and 16 weeks after operation. At 4 weeks, some rats were also treated with captopril (2 g/liter in drinking water daily) or prazosin (0.2 mg/kg body weight subcutaneously daily) and assessed at 16 weeks. Hearts were isolated to study the activity of superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and catalase as well as for thiobarbituric acid reactive substances (TBARS).

RESULTS

CHF at 4 and 16 weeks in the infarcted rats was indicated by an increase in left ventricular end-diastolic pressure and wet/dry weight lung and liver ratios and depressed left ventricular systolic pressure and dyspnea. All these changes were attenuated in both the captopril- and prazosin-treated groups. SOD, GSHPx and catalase activity in the untreated PMI groups was decreased at 4 and 16 weeks. However, treatment with captopril resulted in a significant improvement in SOD, GSHPx and catalase activity in the 16-week PMI group. With prazosin, only SOD activity was improved in the treated 16-week PMI group. Lipid peroxidation as indicated by TBARS was significantly increased in the 16-week PMI group, and both captopril and prazosin modulated this increase.

CONCLUSIONS

Occurrence of an antioxidant deficit and an increase in oxidative stress in the myocardium may play a role in the pathogenesis of CHF subsequent to MI. Attenuation of these changes in antioxidant activity with vasodilator (or antioxidant?) therapy mitigates the process of heart failure.

Effect of sodium nitroprusside-induced hypotension on the blood flow in subcutaneous and intramuscular BT4AN tumors and normal tissues in rats

PURPOSE

To examine the effect of infusion of the vasodilator sodium nitroprusside (SNP) on the blood flow in normal tissues and BT4An tumors growing subcutaneously or intramuscularly in BD IX rats.

METHODS AND MATERIALS

Sodium nitroprusside was given as a continuous intravenous infusion to keep the mean arterial pressure stable at 60 mmHg. The cardiac output, organ blood flow, and perfusion of the BT4An tumors were measured by injection of radiolabelled microspheres at control conditions and after 20 min SNP infusion in each animal. Two series of experiments were performed with two anesthetics with different mechanisms of action, Inactin and the midazolam-fentanyl-fluanisone combination (MFF), to secure reliable conclusions.

RESULTS

Cardiac output, heart rate, and blood flow to the skeletal muscles, heart, and liver increased during SNP infusion in either anesthetic group. In the kidneys and particularly the skin, decreased blood flow by SNP was observed. When located subcutaneously on the foot, the blood flow in the tumor fell to 23.4% and 21.4% of the control values in the MFF- and Inactin-anesthetized animals, respectively. This was accompanied by a similar fall in the blood flow in the foot (tumor bed) itself. In the intramuscular tumor, the blood flow fell to 24.8% of the control value in the MFF group, whereas the corresponding figure was 36.2% in the Inactin group. In the surrounding muscle (tumor bed) the blood flow increased significantly, most pronounced in the MFF experiment, where it was tripled.

CONCLUSION

The fall in the tumor perfusion by SNP may be exploited therapeutically to increase the tumor temperature during hyperthermia. Predominant heating of the tumor compared to the tumor bed can be expected if the tumor is growing in or near skeletal muscles.

Capillary blood flow and arteriolovenular shunt in various organs in hypotensive states induced by nitroglycerine, nitroprusside, and nicardipine

The capillary blood flow of 14 organs was measured in dogs using the microsphere (9μm diameter) trapping method under hypotension induced by administration of either nitroglycerin (NTG), nitroprusside (SNP), or nicardipine (NIC). Simultaneously, blood flow through the arteriolovenular shunt in the brain, kidney, liver, mesenteric organs, skeletal muscles of the pelvic limb, and all organs in the body, except the lungs, were measured by collecting venous blood drained from the organs at 4.8 ml·min^-1 for 2 min. Capillary blood flow remained unchanged in most organs under hypotension with either NTG or SNP, but in increased in most organs, together with an increase in cardiac output, under hypotension with NIC. Arteriolovenular shunt tended to increase in four organs, with the exception of the liver, and increased in the whole body under hypotension with NTG. However, arteriolovenular shunt remained unchanged under hypotension with SNP. Arteriolovenular shunt increased in the mesenteric organs under hypotension with NIC, but decreased in the skeletal muscles of the pelvic limb. These results indicated that none of these hypotensive drugs impairs the nutrient supply to organs; further, NIC protects it much more since it does not increase the shunt flow through major organs.

The effects of afterload reduction on myocardial carbon 11-labeled acetate kinetics and noninvasively estimated mechanical efficiency in patients with dilated cardiomyopathy

METHODS AND RESULTS

With echocardiography and dynamic carbon 11-labeled acetate (C-11 acetate) positron emission tomographic imaging, C-11 acetate kinetics and a parameter that estimates mechanical ventricular efficiency (the work metabolic index) were defined in eight patients with dilated cardiomyopathy. The effect of afterload reduction with nitroprusside on these parameters was evaluated in six of these patients. Nitroprusside increased stroke work index but decreased the C-11 clearance rate. The work metabolic index determined noninvasively increased and correlated well with an invasive approach. The work metabolic index was inversely correlated with systemic vascular resistance. Nitroprusside shifted this relationship upward and to the left.

CONCLUSION

This method of estimating efficiency is feasible and may represent a unique noninvasive approach for the evaluation of cardiac performance and responses to therapy.

Acute effects of dobutamine on myocardial oxygen consumption and cardiac efficiency measured using carbon-11 acetate kinetics in patients with dilated cardiomyopathy

OBJECTIVES

The aim of this study was to use positron emission tomography (PET)-derived carbon (C)-11 acetate kinetics to determine the effects of dobutamine on oxidative metabolism and its effects on myocardial efficiency in a group of patients with dilated cardiomyopathy.

BACKGROUND

Dobutamine is known to improve myocardial function but may do so at the expense of myocardial oxygen consumption, which could be a potential deleterious effect. Carbon-11 acetate kinetics correlate with myocardial oxygen consumption as shown in animal models. Combining these scintigraphic measurements of oxygen consumption with estimates of cardiac work results in a work-metabolic index, which reflects cardiac efficiency.

METHODS

Eight patients with nonischemic dilated cardiomyopathy underwent dynamic PET imaging, echocardiography and hemodynamic measurements. Seven of these patients were also studied while receiving dobutamine. Direct measurements of myocardial oxygen consumption using coronary sinus catheterization were obtained with eight of the PET studies to validate C-11 acetate in patients with cardiomyopathy.

RESULTS

The mean (+/- SD) C-11 clearance rate significantly increased with dobutamine from 0.105 +/- 0.027 to 0.155 +/- 0.023 min-1 (p = 0.001). Directly measured myocardial oxygen consumption had a linear relation to the mean C-11 clearance rate (r = 0.8, p = 0.018). Dobutamine was noted to significantly reduce systemic vascular resistance as well as the severity of mitral regurgitation. The work-metabolic index determined using hemodynamic variables and PET data increased from 2 +/- 0.7 x 10(4) to 2.6 +/- 0.6 x 10(4) (p = 0.04). Efficiency, estimated by employing the oxygen consumption to k2 relation, also increased from 13 +/- 4.5% to 16.9 +/- 6.4% (p = 0.04).

CONCLUSIONS

Despite an increase in myocardial oxygen consumption, dobutamine led to an increase in work-metabolic index in patients with dilated nonischemic cardiomyopathy. Dobutamine reduced systemic vascular resistance and mitral regurgitation, suggesting that in this group of patients, it had important vasodilatory action in addition to its inotropic effects. The use of the C-11 acetate PET for determining myocardial oxygen consumption and estimating efficiency could potentially complement existing clinical measures of ventricular performance and may allow improved and objective evaluation of therapy in patients with heart failure.

Measurement of oxygen consumption after uncomplicated acute myocardial infarction

BACKGROUND

Oxygen consumption (VO2) has been shown to be decreased after acute myocardial infarction (AMI) complicated by cardiogenic shock.

STUDY OBJECTIVE

To evaluate early measurement of VO2 by indirect calorimetry after an uncomplicated AMI (UAMI).

STUDY DESIGN

Prospective nonrandomized case study.

SETTING

Emergency department of a large urban hospital.

PARTICIPANTS AND INTERVENTIONS

Twenty-six consecutive patients presenting with confirmed UAMI. VO2 was measured by indirect calorimetry (Deletrac, Datex Ins,) which is noninvasive. All patients received buccal or intravenous nitroglycerin and thrombolytic therapy, and none received opiates before VO2 measurement.

RESULTS

Two groups of patients were identified by subsequent development of cardiogenic shock. Group 1 did not develop cardiogenic shock, and group 2 developed shock within 24 h of admission. Group 1 (n = 22) had a significantly higher VO2 compared to group 2 (n = 4), mean 154(SD 25) vs mean 100(SD 13) ml/min.m2, p < 0.002. Group 1 had a significantly higher increase in basal metabolic rate than group 2, mean 30 percent (SD 11) vs mean 10(SD 15) percent, p < 0.007. There was no significant difference in age, heart rate (HR), shock index (SI), or rate-pressure product (RPP) between groups 1 and 2. All patients in group 2 developed cardiogenic shock despite thrombolytic therapy, and two died within 24 h of admission.

CONCLUSION

VO2 is increased in UAMI and represents increased metabolic demands of peripheral tissues and not cardiac oxygen uptake. A reduction in VO2 (< 100 ml/min.m2) after AMI may be an early predictor of subsequent development of cardiogenic shock. Measurement of VO2 in UAMI by indirect calorimetry in the emergency department may be of value to identify patients at high risk and could influence their management.

Comparison of isradipine with nitroprusside for control of blood pressure following myocardial revascularization: effects on hemodynamics, cardiac metabolism, and coronary blood flow

The effects of isradipine (ISR) on cardiac performance, myocardial metabolism, and coronary blood flow were compared with those of sodium nitroprusside (SNP) when used to control blood pressure following myocardial revascularization. Twenty patients were randomized to receive either intravenous ISR or SNP if arterial blood pressure increased above 130 mm Hg systolic. Hemodynamic and metabolic parameters were studied using radial, pulmonary arterial, and coronary sinus catheters. Cardiac output and coronary blood flows were measured by thermodilution and blood was taken for calculation of myocardial oxygen consumption and lactate extraction. Electrocardiographic changes were recorded by Holter monitoring throughout the study. ISR and SNP both produced a satisfactory reduction in blood pressure accompanied by a decreased systemic vascular resistance (P less than 0.001). ISR infusion was associated with increases in cardiac output and stroke index (P less than 0.01), which were not apparent in the SNP group. Tachycardia occurred with SNP (P less than 0.01) but not with ISR therapy. Right and left ventricular stroke work indices and myocardial oxygen consumption were reduced with SNP. The ISR group showed unchanged myocardial oxygen consumption with increased right ventricular stroke work index. Coronary vascular resistance decreased (P less than 0.01) during ISR infusion but decreased only slightly in the SNP group. Great cardiac vein blood flow was significantly increased with ISR but not with SNP, resulting in a significant difference between the groups (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Haemodynamic profile of an inhibitor of phosphodiesterase III, adibendan (BM 14.478): comparison with nitroprusside and dobutamine in conscious dogs

1. This study was performed to investigate whether cardiac positive inotropic as well as peripheral vasodilator properties of adibendan contribute to its overall haemodynamic profile in conscious dogs. 2. Haemodynamic measurements were carried out in conscious chronically instrumented dogs after administration of adibendan, sodium nitroprusside or dobutamine. 3. The cardiovascular changes induced by adibendan (0.01 and 0.03 mg kg-1) resembled those of dobutamine (1.0-4.0 micrograms kg-1 min-1): left ventricular dP/dt60 (LV dP/dt60), stroke volume (SV) and cardiac output (CO) increased to a similar extent, but mean arterial pressure (MAP) and heart rate (HR) remained unchanged. 4. In contrast to dobutamine, higher doses of adibendan (0.1-1.0 mg kg-1) decreased MAP and LVEDP. These effects were of a similar magnitude to those observed following nitroprusside administration (0.5-12.5 micrograms kg-1 min-1). In contrast to nitroprusside, adibendan still showed additional effects on LV dP/dt60 and CO. 5. From these results, it is concluded that both the peripheral vasodilator and the cardiac positive inotropic action of adibendan contribute to its overall haemodynamic profile.

Long-term clinical results after vasodilator evaluation in patients with primary (unexplained) and secondary precapillary pulmonary hypertension: acute hemodynamic comparisons and long-term survival

Acute hemodynamic and long-term clinical effects of 6 different vasodilators (oxygen, isoproterenol, isosorbide, phentolamine, diazoxide, and hydralazine) were evaluated in 16 consecutive patients with precapillary pulmonary hypertension. Acute symptomatic and quantitative hemodynamic responses to different vasodilators in different patients were nonuniform and unpredictable. For the whole patient group, cardiac outputs increased slightly after all drugs except oxygen. Mean pulmonary pressure decreased after oxygen and increased after isoproterenol. In general, the hemodynamic effects of vasodilators in primary and secondary precapillary pulmonary hypertension were similar. In 10 patients, an acute increase in cardiac output (4.4 to 5.4 l/min, P less than 0.005) was associated with a small but significant decrease in the mean pulmonary artery pressures (59 to 53 mm Hg, P less than 0.05) after one of the oral vasodilators, and continued treatment with this drug transiently decreased symptoms in 6 of these 10 patients. However, only 1 patient could be continued on treatment beyond 5 months. Long-term survival was related to initial New York Heart Association Functional Class (P less than 0.02) and the initial cardiac output (r2 = 0.84, P less than 0.002). Patient stratification according to these variables may be useful in future clinical trials treating patients with precapillary pulmonary hypertension.

Congestive heart failure--advances in treatment. Hemodynamic studies--their uses and limitations

Hemodynamic studies are useful in the diagnosis of the pathophysiologic mechanisms of pump failure and low output state in patients with acute heart failure. Hemodynamic monitoring is extremely useful for the appropriate manipulation of the vasoactive drugs to optimize hemodynamic and clinical improvement of patients with acute heart failure and to stabilize patients with severe refractory or unstable chronic heart failure. Determinations of the hemodynamic indexes of left ventricular function during hemodynamic studies also provide information regarding prognosis of patients with acute or chronic heart failure. In patients with stable chronic heart failure, correlations between the changes in hemodynamics after initiation of vasodilator therapy and subsequent changes in the clinical status and exercise tolerance are poor; thus, the value of hemodynamic studies for vasodilator therapy in patients with stable chronic heart failure is limited.

Changes in regional blood flow distribution induced by infusions of dopexamine hydrochloride or dobutamine in anesthetized dogs

Systemic blood flow distribution was determined using radionuclide-labeled microspheres in anesthetized dogs during infusions of dopexamine hydrochloride or dobutamine. Three doses of the drugs were administered intravenously, in the form of 22-minute infusions (3 X 10(-9), 10(-8), 3 X 10(-8) mol/kg/min [1.3 to 12.9 micrograms/kg/min] dopexamine hydrochloride and 10(-8), 3 X 10(-8), 10(-7) mol/kg/min [3.4 to 34.0 micrograms/kg/min] dobutamine). Both drugs induced dose-dependent acceleration of the heart rate. Blood pressure was maintained during infusions of dobutamine, while dopexamine hydrochloride induced arterial hypotension. As a result, the increments in heart rate-blood pressure product were smaller with dopexamine hydrochloride than with dobutamine. Dopexamine hydrochloride induced blood flow increments in the heart, several sections of the gastrointestinal tract, kidney and skeletal muscle. Quantitatively, these changes were different from those induced by dobutamine in only 3 organs. The myocardial blood flow increments during infusions of dopexamine hydrochloride were smaller than those of dobutamine, whereas in the stomach and in skeletal muscle, the flow increments induced by dopexamine hydrochloride were significantly greater than those induced by dobutamine. The findings suggest that dopexamine hydrochloride, by virtue of its agonist activity at beta 2-adrenergic and DA1- and DA2-dopaminergic receptors, is a powerful vasodilator.

Prognostic importance of the immediate hemodynamic response to nifedipine in patients with severe left ventricular dysfunction

To determine the clinical significance of the occurrence of hemodynamic deterioration after the administration of calcium channel blocking drugs, nifedipine (20 mg orally) was administered to 29 patients with severe left ventricular dysfunction. Thirteen patients showed hemodynamic improvement with the drug (Group 1), as shown by a notable increase in cardiac index associated with a modest decrease in mean arterial pressure. The other 16 patients exhibited hemodynamic deterioration after nifedipine (Group 2), as reflected by a decline in right and left ventricular stroke work indexes accompanied by a marked hypotensive response. These differences were not related to differences in the peripheral vascular response to nifedipine, because both groups showed similar decreases in systemic and pulmonary vascular resistances. Groups 1 (hemodynamic improvement) and 2 (hemodynamic deterioration) were similar with respect to all demographic variables and pretreatment left ventricular performance (cardiac index, left ventricular filling pressure and systemic vascular resistance). Yet, the 1 year actuarial survival in patients in Group 1 was substantially better than that in patients in Group 2 (67 versus 23%, p = 0.009). Group 2, however, had higher values for plasma renin activity (17.7 +/- 6.0 versus 4.3 +/- 1.4 mg/ml per h, p less than 0.05), lower values for serum sodium concentration (134.6 +/- 1.2 versus 139.2 +/- 0.6 mEq/liter, p less than 0.05) and higher values for mean right atrial pressure (15.8 +/- 2.0 versus 7.9 +/- 1.4 mm Hg, p less than 0.01) than did patients in Group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in regional myocardial blood flow after nitroprusside and nitroglycerin in patients with and without significant coronary artery disease

To evaluate vasodilator-induced redistribution of regional myocardial blood flow, intravenous sodium nitroprusside and nitroglycerin were administered in doses producing matched reductions (15%) in mean arterial pressure at constant heart rate. Anterior left ventricular great cardiac vein blood flow (thermodilution) was measured in 14 patients without angiographic anterior collateral supply. Global coronary sinus blood flow remained constant with both nitroprusside and nitroglycerin administration, despite significant reductions in mean arterial pressure. However, nitroglycerin reduced great vein flow by 25 +/- 17% and nitroprusside by 10 +/- 16% (p less than 0.01). Subgroup analysis indicated that the nitroglycerin-nitroprusside regional blood flow differences were more pronounced in patients without significant left anterior descending coronary artery narrowing. Neither vasodilator produced significant differences in arterial-coronary sinus oxygen or lactate contents, calculated myocardial oxygen consumption, left ventricular dP/dt, or electrocardiographic or clinical signs of myocardial ischemia. Despite qualitatively similar hemodynamic effects, comparisons of vasodilator-induced relative reductions in normally supplied anterior left ventricular regional coronary blood flow suggest a mechanism of the reported beneficial effects of nitroglycerin on potentially ischemic myocardial regions.

Hemodynamic abnormalities in acute myocardial infarction

Great strides have been made in the management of patients with acute myocardial infarction since the advent of coronary care units. However, congestive heart failure continues to be the major cause of in-hospital mortality. The accurate diagnosis and classification of hemodynamic abnormalities allow the application of specific therapies for each patient. Because clinicians can now routinely measure left and right ventricular preload, systemic and pulmonary vascular resistance, cardiac output, and arteriovenous oxygen difference, pharmacologic and surgical interventions can be applied in a scientific manner. In addition, mechanical complications can be promptly recognized and aggressively treated. Although the mortality rate for patients with severe left ventricular dysfunction after myocardial infarction remains high, expert management offers an improved prognosis for many patients.

Left ventricular dysfunction and altered autonomic activity: a possible link to sudden cardiac death

There is now a growing body of clinical evidence that suggests a strong association between left ventricular dysfunction and sudden cardiac death in patients recovering from myocardial infarction. The mechanisms underlying this association remain to be determined. Alterations within the autonomic nervous system may represent one factor that links an impairment in cardiac function to an increased mortality. Since ventricular dysfunction would tend to reduce stroke volume, an increased sympathetic and/or decreased parasympathetic efferent activity may compensate for this fall in stroke volume by increasing heart rate and/or the force of contraction (inotropic state) in an attempt to maintain a more normal cardiac output. Similar changes in autonomic activity are, in fact, known to increase the vulnerability to ventricular fibrillation. Therefore, I propose that myocardial infarction induces changes in cardiac function which in turn elicits autonomic efferent changes. As a consequence of these compensatory reflex changes the heart becomes less electrically stable and thereby more prone to lethal arrhythmias.

Mechanisms of improving regional and global ventricular function by preload alterations during acute ischemia in the canine left ventricle

We examined the influence of left ventricular end-diastolic pressure (LVEDP) on the mechanical interaction between ischemic and nonischemic areas during acute myocardial ischemia. Circumferentially oriented ultrasonic segment gauges were implanted in the midwall of the anterior apex and posterior apex of the left ventricle in seven anesthetized dogs. Stroke volume was measured with a flow probe around the ascending aorta in five of these animals. We varied LVEDP with vena caval occlusion and dextran infusions to three matched levels (7, 12, and 19 mm Hg) before and 30 min after complete occlusion of the mid left anterior descending coronary artery. With acute ischemia, the anterior apex or ischemic zone demonstrated marked segmental lengthening during isovolumetric systole (end-diastole to aortic valve opening) and akinesis during the ejection phase (aortic valve opening to closure). In the posterior apex or nonischemic area, isovolumetric shortening increased and ejection phase shortening decreased during acute ischemia when compared with those under control conditions at the same LVEDP. Thus, a portion of the shortening generated by the nonischemic area was expended in stretching the ischemic zone during isovolumetric systole, thereby reducing the amount of ejection phase shortening. As LVEDP was increased, there was a parallel decrease in both the amount of isovolumetric lengthening in the ischemic zone and the isovolumetric shortening in the nonischemic area. As a result, acute ischemia produced less of a reduction in ejection phase shortening in the nonischemic area and in stroke volume at high as compared with low LVEDP. We conclude that the ischemic zone imposes a mechanical disadvantage on the nonischemic area, the magnitude of which is directly proportional to the amount of isovolumetric lengthening or bulge in the ischemic zone. An increase in LVEDP during acute ischemia improves regional and global ventricular function by both the Frank-Starling mechanism in the nonischemic (but not the ischemic) area and by reducing the mechanical disadvantage that the ischemic zone imposes on the nonischemic area.

Preoperative assessment of high-risk surgical patients

From the foregoing accounts of preoperative assessment of myocardial performance, as well as preload and afterload status it is clear that the proper anesthesia techniques and agents can be selected. Physiologically optimal adjustments of preload, afterload, and myocardial function can be attained by the appropriate, harmonious selection of anesthesia technique and vasoactive drugs made on the basis of close hemodynamic monitoring preoperatively, intraoperatively, and in the immediate postoperative period.

Acute hemodynamic effects of nitroprusside in children with isolated mitral regurgitation

The acute hemodynamic responses to nitroprusside during cardiac catheterization were evaluated in 12 children with isolated mitral regurgitation (MR) of congenital origin. The patients were classified into 2 groups. Group I consisted of 5 patients who received digitalis or diuretic drugs and group II consisted of 7 patients who received no medication. Hemodynamic measurements were performed using a multisensor catheter system during infusion of nitroprusside at a dose of 2.0 micrograms/kg/min. With nitroprusside, the mean right atrial pressure decreased an average of 50% in group I (from 6 +/- 1 to 3 +/- 1 mm Hg) and 75% in group II (from 4 +/- 1 to 1 +/- 1 mm Hg), and the mean decrease of pulmonary artery wedge pressure was 50% in group I (from 14 +/- 3 to 7 +/- 3 mm Hg) and 56% in group II (from 9 +/- 2 to 4 +/- 1 mm Hg). Administration of nitroprusside also caused a significant reduction in systemic vascular resistance by 40% in both groups (from 25 +/- 6 to 15 +/- 5 U/m2 in group I and from 25 +/- 2 to 15 +/- 3 3 U/m2 in group II), whereas forward cardiac output increased markedly, by an average of 48% in group I (from 3.3 +/- 0.5 to 4.9 +/- 0.9 liters/min/m2) and 58% in group II (from 3.3 +/- 0.3 to 5.2 +/- 0.8 liters/min/m2). No significant differences in hemodynamic response between groups I and II were noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional O2 supply/consumption in normal and ischaemic rabbit myocardium: effect of nifedipine

The effect of nifedipine infusion on myocardial O2 supply and consumption in flow-restricted and normal regions of the left ventricle was tested in anaesthetized open-chest rabbits after ligation of the left anterior descending coronary artery for one hour. Ten min after occlusion, nifedipine-treated animals were given either a low or high dose of the drug: a 5 micrograms/kg bolus followed by 1 micrograms/kg per min infusion or a 10 micrograms/kg bolus and 10 micrograms/kg per min infusion, respectively. Regional blood flow was measured before and after occlusion using radioactive microspheres and O2 saturation was measured microspectrophotometrically; the Fick Principle was then employed to determine regional O2 consumption. After a 60 min occlusion, blood flow was reduced overall to 51% of pre-ligation flows in the occluded region, and treatment with nifedipine or vehicle did not significantly alter this flow reduction. Blood flow in nonoccluded regions increased 1.6-fold only with the high dose of nifedipine and was unchanged in all other groups. Microspectrophotometric analysis of low dose nifedipine and control hearts showed that O2 extraction was greater in occluded than in normal myocardium (9.0, s.d. = 0.9, ml O2/100 ml blood vs 7.2, s.d. = 0.7, respectively) and that subendocardial extraction exceeded subepicardial. These data suggest that nifedipine administration at this dose had no apparent beneficial effect on O2 supply or O2 consumption in normal or flow-restricted regions of the left ventricle during 1 h of coronary artery occlusion.

Treatment of congestive heart failure by altering loading conditions of the heart

We have not emphasized the traditional approaches to the treatment of congestive heart failure, because there is abundant literature detailing the importance of rest and comfort for the patient, reduction of solute load, and administration of digitalis and diuretics. Instead, we have sought to emphasize the therapeutic interventions that are aimed at changing the mechanical loading conditions of the heart. Treatment expectations must be viewed within an age- or maturity-dependent framework. Thus, when a preterm or full-term newborn infant requires cardiocirculatory support, diminished cardiac reserve limits the benefits derived from diverse treatment methods. This unique fragility of the developing heart and circulation places a premium on the astute manipulation of all of the factors that determine optimum cardiovascular adaptation to stress. Beyond infancy, although cardiovascular reserve increases, it remains imperative to modify therapy by using cardioactive drugs that deal specifically with the separate mechanical and contractile variables to assure optimum survival.

New concepts and drugs in the treatment of congestive heart failure

This article seeks to make clear the basic differences in the treatment of heart failure between therapeutic maneuvers that are aimed at improving the mechanical loading conditions of the heart and those that are aimed at augmenting the fundamental contractile or inotropic state of the myocardium. Emphasis is placed on recognizing that treatment expectations must be viewed within an age- or maturity-dependent framework, since a diminished margin of cardiocirculatory reserve exists in the smallest and youngest patients that limits the extent of benefit that may be derived from diverse treatment approaches.