Myocardial ischemia during daily activities: the importance of increased myocardial oxygen demand

Rate-Pressure Product is a Novel Predictor for Short- and Long-Term Mortality in Patients with Acute Coronary Syndrome Undergoing Primary PCI/Immediate Invasive Strategy

BACKGROUND

Rate-pressure product (RPP) calculated by multiplying heart rate by systolic blood pressure, is a convenient indicator closely associated with cardiac work or myocardial oxygen consumption. It has been reported to relate strongly to important indices of cardiovascular risk in patients with myocardial ischemia. However, its relationship with short- and long-term mortality in patients with acute coronary syndrome (ACS) undergoing primary PCI/immediate invasive strategy has not been defined.

METHODS

This study analyzed 1301 consecutive ACS patients who had undergone primary PCI, between January 2018 and September 2021. Patients with systolic BP < 90 mmHg were excluded to avoid the confounding effect of cardiogenic shock. RPP values were collected on admission and were divided into four groups: RPP ≤ 7.4, 7.4 ≤ 8.8, 8.8 <8.8 < RPP8, and RPP > 10.8. Clinical endpoints were in-hospital cardiac and long-term all-cause mortality. The predictive performance was assessed by C-statistic, multivariate analysis and survival analysis.

RESULTS

Multivariate analysis showed that these in the highest vs lowest category of RPP (>10.8 vs ≤7.4) had OR of 4.33 (95% CI=1.10 -17.01; P = 0.036) in in-hospital cardiac mortality and 3.15 (95% CI=1.24 -8.00; P = 0.016) in long-term all-cause mortality. In C-statistic analyses, RPP was a strong predictor in ACS, STEMI or UA/NSTEMI group for in-hospital cardiac mortality (AUC = 0.746, 95% CI = 0.722-0.770, p < 0.001) and long-term all-cause mortality (AUC = 0.701, 95% CI = 0.675-0.725, p < 0.001). The Kaplan-Meier event rate for long-term survival of RPP > 10.8 was significantly lower than that of RPP ≤ 10.8.

CONCLUSION

RPP showed a positive association with in-hospital cardiac or long-term all-cause mortality in ACS patients undergoing primary PCI/immediate invasive strategy, and RPP > 10.8 can be as an independent predictor.

Sex-specific associations between markers of arterial stiffness and bone mineral density in Indian men and women

BACKGROUND

Osteoporosis and cardiovascular disease (CVD) share common risk factors, yet both are usually underdiagnosed in the absence of major complications. We investigated associations between arterial stiffness, cardiac workload, carotid intima media thickness (CIMT) and areal bone mineral density (aBMD) in Indian adults.

METHODS

Men and women aged >45 years from the Andhra Pradesh Children and Parents Study (APCAPS) were included for cross-sectional analysis (521 women and 696 men). Dual energy x-ray absorptiometry (DXA) measured aBMD at the whole body, total hip and lumbar spine. Supine blood pressure and heart rate were measured and used to calculate rate pressure product and pulse pressure; augmentation index, pulse wave velocity and CIMT were measured. Sex-interactions were tested (denoted as p-int); adjustments were made for confounders. Data were expressed as SD differences with 95 % confidence intervals.

RESULTS

There were significant negative associations between pulse pressure and aBMD at all sites in women only. In unadjusted analyses, for every 1SD increase in pulse pressure, women had greater negative differences in aBMD at the whole body (-0.13 vs 0.007), total hip (-0.20 vs -0.05) and lumbar spine (-0.12 vs 0.05) compared with men. After adjustments, sex differences remained. Similar negative associations were seen between pulse wave velocity and augmentation index with aBMD in women only. There were no sex differences between CIMT and rate pressure product with aBMD.

CONCLUSIONS

Markers of arterial stiffness are associated with poorer bone health in Indian women, but not in men. There is a need to identify the shared risk factors and markers of arterial stiffness and poor bone health to detect those who require co-management of these diseases to prevent cardiovascular events and fractures.

Influence of systolic blood pressure on outcomes in Nigerians with peripartum cardiomyopathy

BACKGROUND

The relationship between blood pressure (BP) trajectories and outcomes in patients with peripartum cardiomyopathy (PPCM) is not clear. Aim: The study aimed to assess the clinical features and outcomes (all-cause mortality and unrecovered left ventricular [LV] systolic function) of PPCM patients grouped according to their baseline systolic BP (SBP).

PATIENTS AND METHODS

PPCM patients presenting to 14 tertiary hospitals in Nigeria were consecutively recruited between June 2017 and March 2018 and then followed up till March 2019. SBP at first presentation was used to categorize the patients into seven groups: <90, 90-99, 100-109, 110-119, 120-129, 130-139, and ≥140 mmHg. Unrecovered LV systolic function was defined as echocardiographic LV ejection fraction (LVEF) below 55% at the last profiling.

RESULTS

Two hundred and twenty-seven patients were recruited and followed up for a median of 18 months. Of these, 4.0% had <90 mmHg, 16.3% had 90-99 mmHg, 24.7% had 100-109 mmHg, 24.7% had 110-119 mmHg, 18.5% had 120-129 mmHg, 7.5% had 130-139 mmHg, and 4.4% had ≥140 mmHg of SBP at presentation. The highest frequency of all-cause mortality was recorded among patients with SBP ≤90 mmHg (30.8%) followed by those with 90-99 mmHg (20.5%) (P = 0.076), while unrecovered LV systolic function did not differ significantly between the groups (P = 0.659). In a Cox proportional regression model for all-cause mortality, SBP <90 mmHg had a hazard ratio (HR) of 4.00 (95% confidence interval [CI] 1.49-10.78, P = 0.006), LVEF had an HR of 0.94 (95% CI 0.91-0.98, P = 0.003, B = 0.06%), and use of angiotensin-converting enzyme or angiotensin receptor and/or β-receptor blockers had an HR of 1.71 (95% CI 0.93-3.16, P = 0.085). However, SBP was not associated with LV function recovery.

CONCLUSION

In our cohort of PPCM patients, one-fifth was hypotensive at presentation. SBP <90 mmHg at presentation was associated with a four-fold higher risk of all-cause mortality during a median follow-up of 18 months.

Dynamic detection and reversal of myocardial ischemia using an artificially intelligent bioelectronic medicine

Myocardial ischemia is spontaneous, frequently asymptomatic, and contributes to fatal cardiovascular consequences. Importantly, myocardial sensory networks cannot reliably detect and correct myocardial ischemia on their own. Here, we demonstrate an artificially intelligent and responsive bioelectronic medicine, where an artificial neural network (ANN) supplements myocardial sensory networks, enabling reliable detection and correction of myocardial ischemia. ANNs were first trained to decode spontaneous cardiovascular stress and myocardial ischemia with an overall accuracy of ~92%. ANN-controlled vagus nerve stimulation (VNS) significantly mitigated major physiological features of myocardial ischemia, including ST depression and arrhythmias. In contrast, open-loop VNS or ANN-controlled VNS following a caudal vagotomy essentially failed to reverse cardiovascular pathophysiology. Last, variants of ANNs were used to meet clinically relevant needs, including interpretable visualizations and unsupervised detection of emerging cardiovascular stress. Overall, these preclinical results suggest that ANNs can potentially supplement deficient myocardial sensory networks via an artificially intelligent bioelectronic medicine system.

Sex-Specific Associations Between Cardiac Workload, Peripheral Vascular Calcification, and Bone Mineral Density: The Gambian Bone and Muscle Aging Study

Noncommunicable diseases (NCD) are rapidly rising in Africa, with multimorbidity increasing the burden on health and social care. Osteoporosis and cardiovascular disease (CVD) share common risk factors; both often remain undiagnosed until a major life-threatening event occurs. We investigated the associations between cardiac workload, peripheral vascular calcification (PVC), and bone parameters in Gambian adults. The Gambian Bone and Muscle Aging Study (GamBAS) recruited 249 women and 239 men aged 40 to 75+ years. Body composition and areal bone mineral density (aBMD) were measured using dual-energy X-ray absorptiometry; peripheral quantitative computed tomography (pQCT) scans were performed at the radius and tibia. Supine blood pressure and heart rate were measured and used to calculate rate pressure product and pulse pressure. Presence of PVC was determined from tibia pQCT scans. Sex interactions were tested (denoted as p-int); adjustments were made for residuals of appendicular lean mass (ALM) and fat mass (FM). There were negative associations between rate pressure product and aBMD in women only, all p-int < .05; after adjustment for ALM residuals, for every 10% increase in rate pressure product, aBMD was lower at the whole body (-0.6% [-1.2, -0.1]), femoral neck (-0.9% [-1.8, -0.05]), L1 to L4 (-0.6% [-1.7, 0.5]), and radius (-1.9% [-2.8, -0.9]); there were similar associations when adjusted for FM residuals. Similar negative associations were found between pulse pressure and aBMD in women only. PVC were found in 26.6% men and 22.5% women; women but not men with calcification had poorer cardiac health and negative associations with aBMD (all sites p-int < .001). There were consistent associations with cardiac parameters and pQCT outcomes at the radius and tibia in women only. Multiple markers of cardiac health are associated with poorer bone health in Gambian women. In the context of epidemiological transition and changing NCD burden, there is a need to identify preventative strategies to slow/prevent the rising burden in CVD and osteoporosis in Sub-Saharan Africa. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Total and differential white blood cell counts and hemodynamic parameters in first-episode psychosis

There is evidence for blood inflammatory abnormalities in patients with first-episode psychosis (FEP). The monocyte- and neutrophil-to-lymphocyte ratios (MLR; NLR) are markers of inflammation and endothelial dysfunction, and predictors of cardiovascular disease, the leading cause of death in schizophrenia. We investigated relationships between white blood cell (WBC) counts and hemodynamic parameters associated with cardiovascular disease risk in 25 subjects age 18-50 hospitalized for FEP and 44 controls. Subjects had a blood draw, vital signs, and medical history. Patients with FEP had significantly higher NLR, MLR, pulse pressure, and rate pressure product (RPP) than controls (p < 0.05 for each), after controlling for potential confounders. In linear regression analyses, higher monocytes were a significant predictor of higher pulse pressure (p = 0.033) and higher MLR predicted RPP at the trend level (p = 0.051) in FEP, after controlling for potential confounders. To our knowledge, ours is the first report of increased RPP, a measure of myocardial workload, in FEP. We also replicated findings of increased NLR, MLR and pulse pressure in FEP. Our findings underscore that measurement of routine vital signs and blood total and differential WBC counts are germane to the clinical care of patients with psychosis as markers of cardiovascular disease risk.

Ivabradine in combination with Beta-blockers in patients with chronic stable angina after percutaneous coronary intervention

Introduction

The anti-anginal efficacy of ivabradine is well established. We describe a post hoc analysis in the ADDITIONS database to investigate effectiveness and tolerability of ivabradine in combination with beta-blocker in patients with angina who have had a percutaneous coronary intervention (PCI).

Methods

ADDITIONS was a non-interventional, multicenter prospective study including 2,330 patients with stable angina. In addition to beta-blocker, patients were treated with ivabradine in approved dosages for 4 months. We divided the population according to whether they had previously had a PCI or not, and explored the effect of ivabradine on heart rate, number of weekly angina attacks, frequency of nitrate consumption, as well as quality of life (QoL) and tolerability.

Results

Data were available for 2,319 patients, of whom 51.4% had previously had a PCI. There was no difference in the effect of ivabradine on mean heart rate between patients with a previous PCI [64.4 ± 7.6 beats per minute (bpm)] than those without (66.8 ± 8.5 bpm) at 4 months (both P < 0.0001). Similarly, the number of angina attacks decreased from 1.9 ± 2.4 to 0.5 ± 1.5 per week in patients with a previous PCI and 1.5 ± 2.0 to 0.3 ± 1.0 per week in patients without a previous PCI (both P < 0.0001). The frequency of nitrate consumption fell from 2.7 ± 3.7 to 1.0 ± 1.9 per week and 1.8 ± 2.8 to 0.6 ± 1.5 per week (both P < 0.0001) in patients with and without a previous PCI, respectively. There was no difference in the improvements in Canadian Cardiovascular Society class of angina, QoL, and physicians’ assessment of effectiveness and tolerability between patients with a previous PCI and those without.

Conclusion

Ivabradine is an effective and well-tolerated anti-anginal treatment in patients with stable angina after PCI. Ivabradine reduced the frequency of weekly angina attacks and nitrate consumption, led to an improvement in Canadian Cardiovascular Society class and a substantial improvement in the QoL of stable angina patients.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-015-0182-8) contains supplementary material, which is available to authorized users.

Reduction of resting heart rate with antianginal drugs: review and meta-analysis

The benefit of heart rate (HR) reduction in patients with stable coronary artery disease is well demonstrated for symptom prevention and relief, and benefits on outcomes are being actively investigated. We aimed to quantify the reduction in resting HR induced by 5 antianginal drugs frequently used for symptom prevention (diltiazem, verapamil, atenolol, metoprolol, and ivabradine) in stable angina pectoris. We identified studies published between 1966 and 2007 in PubMed, Embase, and the Cochrane database and reviewed the bibliographies to locate additional studies. Eligible studies were double-blind, randomized, placebo-controlled trials in patients with stable angina. Trials were combined using weighted mean difference and fixed-effect model meta-analysis. The main outcome measure was resting HR at the study end. For diltiazem, resting HR reduction versus placebo ranged from -0.08 beats per minute (bpm) [95% confidence interval (CI) -1.5 to +1.4] for 120 mg/d to -8.0 bpm (95% CI, -11.1 to -5.0) with 360 mg/d. For sustained-release diltiazem, there was a reduction in resting HR of -4.5 bpm (95% CI, -6.4 to -2.5), with no dose-response relationship (heterogeneity P = 0.62). Resting HR reductions for the other agents were -3.2 bpm (95% CI, -5.1 to -1.3) for verapamil (with no dose-response relationship, heterogeneity P = 0.87); -19.0 bpm (95% CI, -20.4 to -17.6) for atenolol; -13.2 bpm (95% CI, -14.7 to -11.7) for metoprolol (with greater reductions for 150 mg/d and long-acting 190 mg/d); and between -9.3 bpm (95% CI, -13.8 to -4.8) and -19.6 bpm (95% CI, -23.8 to -15.4) for ivabradine. Ivabradine, atenolol, and metoprolol give similar reductions in resting HR (-10 to -20 bpm), whereas verapamil and diltiazem produce only marginal reductions (<10 bpm).

Strength training improves submaximum cardiovascular performance in older men

PURPOSE

To determine if 16 weeks of strength training can improve the cardiovascular function of older men during submaximum aerobic exercise.

METHODS

Twenty four men aged 70-80 yr were randomly assigned to a strength training (ST; n = 12) and control group (C; n = 12). Training consisted of 3 sets of 6 - 10 repetitions at 70% to 90% of 1RM, 3 times per week, on an incline squat machine for 16 weeks, followed by 4 weeks detraining. Leg strength and maximum oxygen consumption (VO2 max) were assessed every 4 weeks of the 20-week study. Cardiovascular function was assessed during submaximum cycle exercise at 40 Watts, 50% and 70% of VO2 max before training, after 16 weeks training, and after 4 weeks detraining.

RESULTS

At 40 Watts, heart rate (HR), systolic blood pressure, and rate pressure product (RPP) were lower and stroke volume (SV) significantly higher after 16 weeks training and 4 weeks detraining: at 50% VO2 max, HR and RPP were lower after 16 weeks training and 4 weeks detraining: at 70% VO2 max, cycle ergometry power, VO2 and arterio-venous oxygen difference (a - vO2 ) were higher after 16 weeks training. Leg strength and VO2 max increased after 16 weeks training, with leg strength remaining above pre-training levels after 4-weeks detraining.

CONCLUSIONS

Sixteen weeks of strength training significantly improves the cardiovascular function of older men. Therefore strength training not only increases muscular strength and hypertrophy but also provides significant cardiovascular benefits for older individuals.

Resistance training reduces the blood pressure response of older men during submaximum aerobic exercise

OBJECTIVE

The objective of this study was to determine whether 16 weeks of resistance training (RT) can reduce the blood pressure response and improve the cardiovascular function of men aged 70-80 years during submaximum aerobic exercise.

METHODS

Twenty-four men aged between 70 and 80 years were randomly assigned to an RT group (n = 12) and control group (n = 12). Training consisted of three sets of six to 10 repetitions at 70-90% of one repetition maximum, three times per week, on an incline squat machine for 16 weeks. Blood pressure and cardiovascular function were assessed during submaximum cycle exercise at 40 W, and 50 and 70% of maximum oxygen consumption (VO2max) before training and after 16 weeks of training. Leg strength and VO2max were assessed every 4 weeks of the 16-week study.

RESULTS

At 40 W, heart rate, systolic blood pressure, and rate pressure product were lower and stroke volume was significantly higher after 16 weeks of training. At 50% VO2max, heart rate and rate pressure product were lower after 16 weeks of training and at 70% VO2max, cycle ergometry power, VO2, and arterio-venous oxygen difference were higher after 16 weeks of training. Leg strength significantly increased after 16 weeks of training.

CONCLUSION

Sixteen weeks of RT significantly reduces the blood pressure response and improves the cardiovascular function of older men during submaximum aerobic exercise. Therefore, RT not only increases muscular strength and hypertrophy but also provides significant cardiovascular benefits for older individuals.

Exploring Emotion-Regulation and Autonomic Physiology in Metastatic Breast Cancer Patients: Repression, Suppression, and Restraint of Hostility

We examined relationships between three emotion-regulation constructs and autonomic physiology in metastatic breast cancer patients (N = 31). Autonomic measures are not often studied in breast cancer patients and may provide evidence of an increase in allostatic load. Patients included participated as part of a larger clinical trial of supportive-expressive group therapy. Systolic and diastolic blood pressure and heart rate were assessed at a semi-annual follow-up. We averaged 3 resting assessments and used measures of Repression, Suppression, Restraint of Hostility, and Body Mass Index as predictors of autonomic response. We found that higher repression was significantly associated with higher diastolic blood pressure, while higher restraint of hostility was significantly associated with higher systolic blood pressure. A repressive emotion regulation style may be a risk factor for higher sympathetic activation possibly increasing allostatic load, while restraint of hostility may be a protective factor for women with metastatic breast cancer.

Contemporary management of silent ischemia: the role of ambulatory monitoring

Silent ischemia is highly prevalent among patients with ischemic heart disease and is associated with a poor prognosis in moderate/high risk outpatients who either exhibit exercise- or pharmacological-induced myocardial ischemia, or in those patients who demonstrate silent ischemia following an acute coronary syndrome. Pharmacotherapy, including beta-blockers, angiotensin-converting enzyme inhibitors, statins, calcium channel antagonists and antiplatelet agents, have all demonstrated a reduction in silent ischemia and an improvement in cardiac prognosis. The management of patients with ischemic heart disease is currently based on patients' report of anginal symptoms: documentation of silent ischemia, usually using ambulatory electrocardiography, is not incorporated into the routine management of coronary artery disease. Yet studies comparing ambulatory electrocardiography with exercise testing have shown these tests to be complementary. We review the evidence concerning the prognostic value of ambulatory electrocardiography for monitoring silent ischemia and the prognostic value of attenuating silent ischemia. Mitigation of silent ischemia improves cardiac prognosis and ambulatory electrocardiographic monitoring before and after treatment of silent ischemia can play a valuable role in the management of coronary artery disease.

Comparison of circadian rhythm characteristics of blood pressure and heart rate in patients before and after elective coronary artery bypass surgery

Coronary artery bypass grafting surgery (CABGS) is done to reperfuse the ischemic myocardium of coronary disease patients. This study was designed to analyze the circadian rhythm characteristics of blood pressure (BP) and heart rate (HR) of patients before and after CABGS. Fifty-one patients undergoing elective CABGS were studied; 21 patients received one, 12 two and 18 three or more grafts. BP was monitored for 24h before and after CABGS while patients were recumbent in the hospital. Systolic (S) and diastolic (D) BP and HR were assessed every 30 min. Of the 51 patients, 37 (73%) had nondipper 24h BP patterns (nocturnal decline in BP < 10% of daytime mean level) in the preoperative baseline assessment. The peak and MESOR (rhythm-adjusted 24h mean) values of the circadian rhythm in SBP, DBP, and pulse pressure (PP) significantly declined following surgery, while HR and rate-pressure product (RPP = SBP x HR) markedly increased. The double amplitude (peak-to-trough variation) of the circadian rhythm in SBP and DBP was significantly reduced postoperatively, and that of the rhythm in HR and RPP significantly increased. The slopes of the morning rise and evening dip in the 24h SBP profile were reduced significantly after bypass grafting. The corresponding slopes of the HR profile, in contrast, were markedly increased.

Blood pressure changes during transient myocardial ischemia: insights into mechanisms

OBJECTIVES

We investigated the contribution of changes in systemic blood pressure to the genesis of spontaneous myocardial ischemia.

BACKGROUND

Although increases in heart rate often precede the development of spontaneous myocardial ischemia, it remains a subject of controversy whether these are accompanied by simultaneous changes in blood pressure.

METHODS

Using an ambulatory monitoring device that triggered blood pressure recordings from the level of the ST segment, we documented systolic and diastolic blood pressure and heart rate changes related to episodes of ST segment depression in 17 patients with stable coronary artery disease.

RESULTS

Systolic blood pressure and heart rate, but not diastolic pressure, increased significantly before the onset of ST segment depression and persisted throughout the ischemic episode. There was a significant correlation between the changes in heart rate and systolic blood pressure during episodes of myocardial ischemia (r = 0.5, p = 0.0005) and between heart rate and systolic blood pressure changes at 1-mm ST segment depression during treadmill exercise testing and ambulatory monitoring (r = 0.73, p = 0.0005 for heart rate; r = 0.77, p = 0.0008 for systolic blood pressure), indicating that patients with a low heart rate threshold during ischemic episodes also had a lower systolic blood pressure threshold before ischemia during both tests. Circadian changes in systolic blood pressure paralleled the variations in heart rate and ischemic episodes, with the lowest values at night.

CONCLUSIONS

Significant increases in myocardial oxygen demand, including systolic blood pressure, occur during episodes of spontaneous myocardial ischemia. Patients with a lower heart rate threshold during ischemic episodes had a lower systolic blood pressure threshold during both ambulatory monitoring and treadmill exercise. The effects of antianginal therapy on blood pressure changes during ischemia need to be explored further.

Frequency, significance, and mechanism of myocardial ischemia during daily activities detected by Holter dynamic electrocardiogram

Exercise testing (EX) and Holter ECG (DCG) were performed consecutively in 52 patients with ischemic heart disease. A total of 100 episodes of myocardial ischemia (IE) were recorded during DCG in 30 patients, who constituted 94% of the patients with myocardial ischemia under 6 metabolic equivalents (METs) during EX. A significant increase in heart rate (HR) was observed before the development of IE. The duration of this increase in HR was longer in IE than in periods in which the HR increased above the ischemic threshold, but without ischemia. The incidence of IE showed two peaks at 8-10 am and 4-6 pm. The frequency of IE among all of the periods with increased HR was highest at 8-10 am (51%). IE in the morning was associated with a lower HR than that in the afternoon, and LF/HF, which reflects sympathetic activity, evaluated using power spectral analysis, increased before IE in the morning. The early appearance of myocardial ischemia in EX can predict its appearance in daily life. The increase in HR and its duration appear to be associated with the development of IE. The increases in sympathetic activity in the morning and the increase in myocardial oxygen demand accompanied by physical activity in the afternoon most likely contributed to the circadian variation in the incidence of ischemic episodes.

Diabetics with coronary disease have a prevalence of asymptomatic ischemia during exercise treadmill testing and ambulatory ischemia monitoring similar to that of nondiabetic patients. An ACIP database study. ACIP Investigators. Asymptomatic Cardiac Ischemia Pilot Investigators

BACKGROUND

There are conflicting data as to whether diabetics have a higher prevalence of asymptomatic ST-segment depression during exercise treadmill testing (ETT) and ambulatory ECG (AECG) monitoring. This study was conducted to determine whether diabetic patients with coronary disease enrolled in the Asymptomatic Cardiac Ischemia Pilot (ACIP) have more episodes of asymptomatic ischemia during ETT and 48-hour AECG monitoring than nondiabetic patients and to compare differences in angiographic variables and the magnitude of ischemia as measured by standard ETT and AECG criteria.

METHODS AND RESULTS

Angiographic variables and the prevalence and magnitude of ischemia during the qualifying ETT and 48-hour AECG were compared by the presence and absence of diabetes mellitus in 558 randomized ACIP patients. Seventy-seven patients had a history of diabetes and were taking oral hypoglycemics or insulin (diabetic group); 481 patients did not meet these criteria (nondiabetic group). Multivessel disease (87% versus 74%, P = .01) was more frequent in the diabetic group. The percentages of patients without angina during the ETT were similar in the diabetic and nondiabetic groups (36% and 39%, respectively). Time to onset of > or = 1-mm ST-segment depression and time to onset of angina were similar in both groups. The percentages of patients with only asymptomatic ST-segment depression during the 48-hour AECG were similar in the diabetic and nondiabetic groups (94% versus 88%, respectively). However, total ischemic time per 24 hours (15.0 +/- 21.4 versus 23.6 +/- 31.1 minutes, P = .02), ischemic time per episode (6.3 +/- 4.6 versus 9.0 +/- 8.7 minutes, P < .01), and the maximum depth of ST-segment depression tended to be less in the diabetic group.

CONCLUSIONS

Patients enrolled in ACIP were selected on the basis of an abnormal ETT and 48-hour AECG and ability to undergo coronary revascularization. When patients with diabetes mellitus were compared with those without diabetes, there was a similar prevalence of asymptomatic ischemia during ETT and 48-hour AECG monitoring. Despite more extensive and diffuse coronary disease, diabetic ACIP patients tended to have less measurable ischemia during the 48-hour AECG.

Hemodynamic changes as triggers of cardiovascular events

Although a large number of clinical studies during the past decade have documented that myocardial ischemia, acute myocardial infarction, and sudden cardiac death have definite circadian patterns, recently published work suggests that it is not necessarily a specific time of the day but the sleep/wake cycle and postural changes as well as the balance between triggers and protective factors that determine the onset of cardiovascular events. A clear understanding of the pathophysiologic processes responsible for ischemic events and the specific roles played by various triggers would be helpful in better defining the therapeutic strategies designed for the prevention and treatment of acute cardiac events. Because changes in hemodynamic parameters are of paramount importance in initiating an ischemic event, it is critical to review their role and relationship in the pathogenesis of acute coronary events.

Effects of a new calcium antagonist, mibefradil (Ro 40-5967), on silent ischemia in patients with stable chronic angina pectoris: a multicenter placebo-controlled study. The Mibefradil International Study Group

OBJECTIVES

The purpose of this study was to evaluate the effects of mibefradil (Ro 40-5967) on the frequency and duration of episodes of asymptomatic ischemia in patients with stable angina pectoris and to determine the most efficient single therapeutic dose of this drug.

BACKGROUND

Mibefradil is a novel calcium channel antagonist that shows a high bioavailability, induces no reflex tachycardia and has no negative inotropic effects.

METHODS

In a multicenter, double-blind, placebo-controlled, parallel-design trial, 126 patients with chronic stable angina pectoris were studied. After 1 week of a placebo run-in period, patients were randomized to receive 25, 50, 100, 150 mg of mibefradil or placebo for 2 weeks. Ambulatory 48-h electrocardiographic (ECG) monitoring was performed at the end of both the placebo run-in period and the active treatment period.

RESULTS

Compared with placebo, mibefradil was associated with significantly less ischemia as manifested during ambulatory ECG monitoring. In the 150- and 100-mg groups, respectively, the drug resulted in a 73% and 63% reduction in the frequency of episodes of ST segment depression and a 78% and 58% reduction in the total duration of ST segment depression. Highly significant linear dose-response relations were present across all treatment groups for ischemic episodes and ischemia duration (p < 0.001). Electrocardiographic abnormalities related to treatment were first-degree atrioventricular block, sinus bradycardia and short Wenckebach episodes, observed during sleep on Holter monitoring. All ECG events were dose related.

CONCLUSIONS

Mibefradil is a new, safe, well tolerated and very effective dose-dependent anti-ischemic calcium channel antagonist.

Increased heart rate response to laboratory-induced mental stress predicts frequency and duration of daily life ambulatory myocardial ischemia in patients with coronary artery disease

This study assessed the relation between hemodynamic data during a standardized mental stressor and ambulatory ischemia to determine if laboratory-induced responses could predict the magnitude of daily life ischemia. Forty-two men and 11 women, aged 46 to 79 years (mean 61), with coronary artery disease and exercise-induced ischemia were studied. All patients underwent 24- to 48-hour ambulatory electrocardiographic (ECG) monitoring (mean 43 +/- 0.8 hours) and laboratory-induced mental stress using a public speaking task. Hemodynamic data were obtained at rest and every minute during mental stress. Thirty-three of 53 patients (62%) had at least 1 ischemic episode during ECG monitoring. In patients who had ambulatory ischemia, there was a mean number of 7.9 +/- 1.8 episodes (mean total duration 79.2 +/- 24.1 minutes/48 hours). Significant positive correlations were found for peak heart rate and changes in heart rate during mental stress and ambulatory ischemia (r = 0.353 to 0.462, p < 0.05) in patients who had ambulatory ischemia. There was no correlation between systolic blood pressure during mental stress and ambulatory ischemia. Results of this study demonstrate that heart rate response during laboratory-induced mental stress correlates with magnitude of ischemia on ambulatory ECG monitoring in patients with coronary artery disease.

Transient myocardial ischemia in patients with chronic angina: relation to heart rate changes and variability in exercise threshold. BAY r 1999 in Chronic Angina Study Group

This study was undertaken to assess the relation of ambulatory myocardial ischemia to heart rate changes and variability in exercise threshold in patients with chronic angina. The study involved 118 patients with chronic angina and proven coronary artery disease who had a 'positive' exercise test result. All patients underwent a first exercise test followed by a 48-h period of ambulatory electrocardiographic monitoring. A second exercise test was performed 4 days later. A total of 101 ischemic episodes were recorded in 35 patients. The heart rate at the appearance of 1-mm ST segment depression during ambulatory electrocardiographic monitoring was > or = 20 beats/min lower than that during exercise testing in 58 ischemic episodes (57%, Group A), 10-19 beats/min lower in 26 (26%, Group B), and < or = 9 beats/min lower or higher in 17 (17%, Group C). Thirty-five percent of the Group A ischemic episodes, 69% of Group B, and 71% of Group C were preceded by an increase in heart rate of > or = 10 beats/min. Thirty patients showed a variable exercise threshold. The prevalence of Group A and B ischemic episodes was not significantly different in patients with fixed or variable exercise threshold, whereas that of Group C episodes was 22% in the former and 0% in the latter (P = 0.036). These results suggest that increased coronary tone may be one of the mechanisms contributing to modulate the occurrence of transient myocardial ischemia in most patients with chronic angina and transient myocardial ischemia at ambulatory electrocardiographic monitoring. This occurs regardless of whether the patients have a variable or fixed exercise threshold.

Medical treatment to reduce total ischemic burden: total ischemic burden bisoprolol study (TIBBS), a multicenter trial comparing bisoprolol and nifedipine. The TIBBS Investigators

OBJECTIVES

We compared the effects of bisoprolol on transient myocardial ischemia with those of nifedipine in patients with chronic stable angina.

BACKGROUND

Both beta-adrenergic blocking agents and calcium antagonists reduce transient ischemic episodes, but comparisons of these agents have been made in only a few larger studies.

METHODS

The Total Ischemic Burden Bisoprolol Study (TIBBS) was a randomized double-blind controlled study with two parallel groups; 330 patients from 30 centers in seven European countries with stable angina pectoris, a positive exercise test and more than two transient ischemic episodes during 48 h of Holter monitoring (central evaluation) were included. Of these patients 161 were randomized to receive bisoprolol and 169 to receive nifedipine slow release. There were two treatment phases of 4 weeks each, with 48-h Holter monitoring after each phase. During phase 1, patients received either 10 mg of bisoprolol daily or 2 x 20 mg of nifedipine slow release. During phase 2, they received either 20 mg of bisoprolol daily or 2 x 40 mg of nifedipine slow release.

RESULTS

In phase 1 of the trial, 4 weeks of bisoprolol therapy (10 mg daily) reduced the mean [+/- SD] number of transient ischemic episodes from 8.1 +/- 0.6 to 3.2 +/- 0.4/48 h. Nifedipine (2 x 20 mg) reduced transient ischemic episodes from 8.3 +/- 0.5 to 5.9 +/- 0.4/48 h. Total duration of ischemia was reduced from 99.3 +/- 10.1 to 31.9 +/- 5.5 min/48 h with bisoprolol and from 101 +/- 9.1 to 72.6 +/- 8.1 min/48 h with nifedipine. Reductions were statistically significant for both drugs; the difference between bisoprolol and nifedipine was also significant (p < 0.0001). Bisoprolol reduced the heart rate at onset of episodes by 13.7 +/- 1.4 beats/min from a baseline value of 99.5 +/- 1.2 beats/min (p < 0.001). Heart rate was unchanged with nifedipine. Bisoprolol had significantly higher responder rates than nifedipine. Doubling of the dose in phase 2 of the trial had small additive effects. Only bisoprolol showed a marked circadian effect by reducing the morning peak of transient ischemic episodes (by 68% at peak time, 8:00 to 8:59 AM).

CONCLUSIONS

Both bisoprolol and nifedipine reduced the number and duration of transient ischemic episodes in patients with chronic stable angina. Bisoprolol was significantly more effective than nifedipine in both doses tested and reduced the morning peak of ischemic activity.

Use of exercise test parameters to predict presence and duration of ambulatory ischemia in patients with coronary artery disease

Myocardial ischemia is an indicator of adverse prognosis. In patients with stable angina and positive exercise tests, prolonged cumulative ischemia on ambulatory electrocardiographic monitoring identifies a high-risk group with severe coronary artery disease and poor survival. To determine whether features of the exercise test can accurately (1) predict the occurrence of ambulatory ischemia, and (2) classify patients into subgroups at varying levels of risk for ambulatory ischemia, we studied 48 patients with a history of angina and documented coronary disease who underwent the standard Bruce protocol and ambulatory monitoring. All patients had a positive exercise treadmill test, and 26 had ischemia on Holter monitoring (total of 2,922 minutes, 173 episodes, 94% with silent ischemia). The remaining 22 patients did not have ischemia. The exercise test parameters showing significant differences between the 2 groups were (1) time to > or = 1 mm ST-segment depression (p < 0.0003), (2) maximal ST-segment depression (p < 0.004), and (3) exercise capacity (p < 0.037). These data were used to develop a model for predicting the presence and the severity of ambulatory ischemia. Time to onset of > or = 1 mm ST-segment depression and maximal ST-segment depression on exercise treadmill testing can be used to determine the likelihood of mild (1 to 5 episodes or lasting < or = 60 minutes) or severe prolonged (> 5 episodes or lasting > 60 minutes) ambulatory ischemia. Patients with a very high or very low probability of ischemia on Holter monitoring can be identified by certain exercise test parameters and may not need to undergo monitoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of myocardial oxygen demand in the pathogenesis of silent ischemia during daily life

The role of myocardial oxygen demand in the pathogenesis of silent ambulatory myocardial ischemia was evaluated by reviewing and assessing the methods and results of recent studies. The performance of simultaneous ambulatory electrocardiographic and blood pressure monitoring in 25 men with proven coronary artery disease (CAD) revealed significant increases in heart rate and blood pressure (p < 0.001) preceding most silent ischemic events. By plotting the mean heart rate obtained at 5-minute intervals during the 30 minutes before an ischemic event, the ischemic heart rate was shown to be significantly higher (95 +/- 15 vs 74 +/- 11 beats per minute [bpm]; p < 0.01) than the nonischemic heart rate. The evaluation of heart rate changes during ambulatory ischemia (in patients with CAD and ischemia induced by an exercise test using gradual work load increments) showed a significant heart rate increase (> 10 bpm) at 1-5 minutes preceding the onset of ST-segment depression. Heart rate increases during exercise testing according to the gradual work load increments of the National Institutes of Health protocol were compared with the heart rate preceding ischemic events during daily life monitored by ambulatory electrocardiography and were found to be closely related. In contrast, heart rate increases that occurred during exercise testing using the standard Bruce protocol were higher and correlated less with those preceding ischemia in daily life. Heart rate and blood pressure increased significantly in most silent ischemic episodes, indicating that increased myocardial oxygen demand plays a significant role in the pathogenesis of myocardial ischemia during daily life.