Medical treatment of patients with severe exertional and rest angina: double blind comparison of beta blocker, calcium antagonist, and nitrate

The Clinical Outcomes of Ventricular Septal Rupture Secondary to Acute Myocardial Infarction: A Retrospective, Observational Trial

Background

Ventricular septal rupture (VSR) is a severe mechanical complication secondary to acute myocardial infarction (AMI) with a dreadful prognosis. The goal of our study was to evaluate the mortality and to identify the predictors of mortality for this population.

Methods

From June 2012 to July 2021, patients with VSR secondary to AMI were initially screened for eligibility in this study. The potential risk predictors were determined using appropriate logistic regression models.

Results

In this retrospective study, a total of 50 cases were included, and 14 patients survived and got discharged successfully. Univariable analyses indicated that the heart rate (HR), white blood cell (WBC) count, neutrophils count, serum glucose, serum creatinine, serum lactic acid, and the closure of rupture were significantly associated with mortality among these special populations.

Conclusion

This study found that such high mortality in patients with VSR after AMI was significantly correlated with these risk factors representing sympathetic excitation and large infarct size. Coronary revascularization combined with the closure of rupture might be helpful in improving their prognosis.

A review on coronary artery disease, its risk factors, and therapeutics

Coronary artery disease (CAD) is one of the major cardiovascular diseases affecting the global human population. This disease has been proved to be the major cause of death in both the developed and developing countries. Lifestyle, environmental factors, and genetic factors pose as risk factors for the development of cardiovascular disease. The prevalence of risk factors among healthy individuals elucidates the probable occurrence of CAD in near future. Genome-wide association studies have suggested the association of chromosome 9p21.3 in the premature onset of CAD. The risk factors of CAD include diabetes mellitus, hypertension, smoking, hyperlipidemia, obesity, homocystinuria, and psychosocial stress. The eradication and management of CAD has been established through extensive studies and trials. Antiplatelet agents, nitrates, β-blockers, calcium antagonists, and ranolazine are some of the few therapeutic agents used for the relief of symptomatic angina associated with CAD.

Chronic coronary artery disease: diagnosis and management

Coronary artery disease (CAD) is the single most common cause of death in the developed world, responsible for about 1 in every 5 deaths. The morbidity, mortality, and socioeconomic importance of this disease make timely accurate diagnosis and cost-effective management of CAD of the utmost importance. This comprehensive review of the literature highlights key elements in the diagnosis, risk stratification, and management strategies of patients with chronic CAD. Relevant articles were identified by searching the PubMed database for the following terms: chronic coronary artery disease or stable angina. Novel imaging modalities, pharmacological treatment, and invasive (percutaneous and surgical) interventions have revolutionized the current treatment of patients with chronic CAD. Medical treatment remains the cornerstone of management, but revascularization continues to play an important role. In the current economic climate and with health care reform very much on the horizon, the issue of appropriate use of revascularization is important, and the indications for revascularization, in addition to the relative benefits and risks of a percutaneous vs a surgical approach, are discussed.

Chronobiology and chronotherapy of ischemic heart disease

The occurrence of the clinical manifestations of ischemic heart disease (IHD)--myocardial ischemia and angina pectoris, acute myocardial infarction, and sudden cardiac death--is unevenly distributed during the 24 h with greater than expected events during the initial hours of the daily activity span and in the late afternoon or early evening. Such temporal patterns result from circadian rhythms in pathophysiological mechanisms plus cyclic environmental stressors that trigger ischemic events. Both the pharmacokinetics (PK) and pharmacodynamics (PD) of many, though not all, anti-ischemic oral nitrate, calcium channel blocker, and beta-adrenoceptor antagonist medications have been shown to be influenced by the circadian time of their administration. The requirement for preventive and therapeutic interventions varies predictably during the 24 h, and thus therapeutic strategies should also be tailored accordingly to optimize outcomes. During the past decade, two first generation calcium channel blocker chronotherapies have been developed, trialed, and marketed in North America for the improved treatment of IHD. Nonetheless, there has been relatively little investigation of the administration-time (circadian rhythm) dependencies of the PK and PD of conventional anti-ischemic medications, and there has been little progress in the development of new generation IHD chronotherapies. Available epidemiologic, pharmacologic, and clinico-therapeutic evidence demonstrates how the chronobiologic approach to IHD can contribute new insight and opportunities to improve drug design and drug delivery to enhance therapeutic outcomes.

Long term outcome in patients with silent versus symptomatic ischaemia during dobutamine stress echocardiography

OBJECTIVES

To compare the long term prognosis of patients having silent versus symptomatic ischaemia during dobutamine stress echocardiography (DSE).

DESIGN

Observational study.

SETTING

Tertiary referral centre.

PATIENTS

931 patients who experienced stress induced myocardial ischaemia during DSE.

RESULTS

Silent ischaemia was present in 643 of 931 patients (69%). The number of dysfunctional segments at rest (mean (SD) 9.6 (5.1) v 8.8 (5.0), p = 0.1) and of ischaemic segments (3.5 (2.2) v 3.8 (2.1), p = 0.2) was comparable in both groups. During a mean (SD) follow up of 5.5 (3.3) years, there were 169 (18%) cardiac deaths and 86 (9%) non-fatal infarctions. Multivariable Cox regression analysis showed age (hazard ratio (HR) 1.1, 95% confidence interval (CI) 1.02 to 1.05), previous myocardial infarction (HR 1.4, 95% CI 1.1 to 2.0), and number of ischaemic segments during the test (HR 2.0, 95% CI 1.0 to 3.7) as independent predictors of cardiac death and myocardial infarction. For every additional ischaemic segment there was a twofold increment in risk of late cardiac events. The annual cardiac death or myocardial infarction rate was 3.0% in patients with symptomatic ischaemia and 4.6% in patients with silent ischaemia (p < 0.01). Silent induced ischaemia was an independent predictor of cardiac death and myocardial infarction (HR 1.7, 95% CI 1.1 to 2.0). During follow up symptomatic patients were treated more often with cardioprotective therapy (p < 0.01) and coronary revascularisation (145 of 288 (50%) v 174 of 643 (27%), p < 0.001).

CONCLUSIONS

Patients with silent ischaemia had a similar extent of myocardial ischaemia during DSE compared to patients with symptomatic ischaemia but received less cardioprotective treatment and coronary revascularisation and experienced a higher cardiac event rate.

Silent myocardial ischemia: concepts and controversies

Silent myocardial ischemia is a relatively common, but poorly understood, clinical entity. The most accurate means of detecting silent myocardial ischemia and the precise treatment endpoints remain unclear. However, the amount of ischemic myocardium appears to correlate with the likelihood of future adverse cardiac events. Evidence suggests that patients at highest risk of severe myocardial ischemia, even in the absence of symptoms, derive the greatest benefit from an aggressive diagnostic and therapeutic approach. This paper reviews the diagnosis and treatment of silent myocardial ischemia, and its clinical implication in select patient groups: those without coronary artery disease, those with coronary artery disease, diabetic patients, postrevascularization patients, and women.

Circadian variation in myocardial ischemia: the possible mechanisms involving in this phenomenon

Circadian rhythms have long been recognized to occur in many biologic phenomena, including secretion of hormones as well as autonomic nervous system. There is increasing evidence that circadian rhythms have been also found in cardiovascular events, for example, myocardial infarction, sudden cardiac death as well as stroke have shown a circadian pattern of the distribution. Transient myocardial ischemia, detected by ambulatory ST segment monitoring, is also unevenly distributed during the day. The pathophysiology and the mechanism underlying these variations are the focus of much investigation, while it is not full understood up to date. Heart rate, blood pressure, neural and humoral vasoactive factors such as plasma norepinephrine levels and renin activity, and probably also contractility are increased in the morning hours, indicating that increase in myocardial oxygen demand contribute importantly to the increased prevalence of ischemia in the morning. Our recent study found that circadian rhythm of ischemic threshold detected by repetitive exercise treadmill tests in patients with chronic coronary artery disease is also apparently associated with levels of plasma ET-1. This information should enable better understanding as well as treatment on patients on circadian variation of cardiovascular events.

Combination and triple therapy in patients with stable angina pectoris not adequately controlled by optimal β-blocker therapy

In 60 to 80% of patients with stable angina pectoris at low risk for future coronary events, monotherapy with a β-blocker is an effective treatment. When patients with stable angina pectoris and low risk for events do not respond adequately to optimal β-blocker monotherapy, combination therapy or even triple therapy is may be recommended, but little is known of the actual benefit of such a strategy. We reviewed the evidence from the literature on the effectiveness of combination and triple therapy. Combination therapy with a calcium antagonist or nitrate was found to be more effective than β-blocker monotherapy in the majority of studies, but only an estimated 30% of patients objectively benefit from these combination therapies. Direct comparison shows that combination therapy of a β-blocker with a calcium antagonist is more effective than the combination of a β-blocker with a nitrate. An inadequate response to β-blocker monotherapy is more effectively improved by addition of a calcium antagonist than by alternative use of a calcium antagonist. The use of triple therapy is controversial and not recommended in patients with mild angina pectoris, while for patients with severe angina pectoris not responding to combination therapy of a β-blocker with a nitrate, triple therapy may be of advantage, although the number of patients studied has been small.

Trends in the post-hospitalization medical treatment of unstable angina pectoris: 1990 to 1995

This study provides data on post-hospitalization medication treatment trends for unstable angina between 1990 and 1995. We conducted an observational cohort study at the Veterans Affairs Puget Sound Health Care System (VAPSHCS). Computerized records of hospital discharges and cardiac catheterizations were used to identify unstable angina diagnoses among veterans between 1990 and 1995. Discharge medications issued within 90 days after discharge were ascertained from computerized outpatient pharmacy records. Of the 1,100 veterans discharged with unstable angina, 885 (80%) filled a prescription through the VAPSHCS within 90 days after discharge. Neither use of aspirin nor use of beta blockers increased between 1990 and 1995: overall use averaged 76% for aspirin (78% of those without potential contraindications) and 32% for beta blockers (36% of those without potential contraindications). Use of non-dihydropyridine calcium antagonists--primarily diltiazem--decreased from 57% to 40% (p <0.01), whereas use of dihydropyridine calcium antagonists increased from 12% to 26% (p <0.01). Thus, pharmacy records indicated that aspirin use was high although it was lower than expected, possibly due to ready availability outside the VAPSHCS pharmacy. The low frequency of beta-blocker use and the increasing reliance on dihydropyridine calcium antagonists through 1995 to treat unstable angina may be an opportunity to improve veteran care according to Agency for Health Care Policy Research recommendations.

Choosing the most appropriate treatment for stable angina. Safety considerations

The goals of stable angina pectoris treatment are: (i) symptom relief and increase in angina-free walking time; and (ii) reduction of mortality and adverse outcome. Strategies used for plaque stabilisation resulting in a reduction in cardiovascular mortality and morbidity are: smoking cessation; aspirin (acetylsalicylic acid); blood pressure control; lipid lowering agents when low density lipoprotein cholesterol is elevated despite dietary therapy; coronary bypass surgery in patients with left main stem disease or triple vessel coronary disease and diminished left ventricular function; and use of estrogen in postmenopausal women. For symptom relief and to increase angina-free walking time, long acting nitrates, beta-blockers, calcium antagonists and potassium channel openers can be used. Drugs from these 3 classes are all effective when used optimally and choice of initial therapy should consider the presence of concomitant disease and underlying left ventricular function. However, none of the long acting nitrates provide continuous prophylaxis because nitrate tolerance develops during long term therapy. In patients with uncomplicated stable angina, nitrates, beta-blockers and calcium antagonists are all effective. Intermittent nitrate therapy is not associated with tolerance, but headache is a common adverse effect and the patient is unprotected at night and in the early hours of the morning. Concomitant treatment with a beta-blocker may be beneficial if the patient experiences withdrawal or early morning angina. For patients with stable angina and hypertension, therapy with a beta-blocker or a calcium antagonist rather than nitrate is indicated. beta-Blockers are preferred in patients who have had a myocardial infarction, or in those with a history of supraventricular tachyarrhythmias. beta-Blockers may produce excessive slowing of the heart rate, fatigue and bronchospasm in susceptible patients. Calcium antagonists are indicated as initial therapy when beta-blockers are either not tolerated or contraindicated. beta-Blockers and nondihydropyridine calcium antagonists should not be used in patients with sinus bradycardia and those with greater than first degree atrioventricular (AV) block because of the possibility of further slowing of heart rate and/or the development of high grade AV block. When monotherapy with one class is ineffective or associated with adverse effects, the patient should be switched to another class rather than given an additional drug. Optimal monotherapy is often as effective as combination therapy. If maximum monotherapy is only partially effective, a combination therapy which is not additive in terms of adverse effects should be chosen. Triple therapy may be deleterious and no more effective than dual therapy.

Calcium channel antagonists in the management of anginal syndromes: changing concepts in relation to the role of coronary vasospasm

Despite the increasing evidence that alterations in coronary vascular tone can and do occur in patients with anginal syndromes, only in a minority of such patients with Prinzmetal's angina is there decisive evidence that the coronary vasodilation induced by calcium channel antagonists (CCAs) plays a specific therapeutic role. CCAs may also give therapeutic benefit in a number of conditions in which coronary vasoconstriction may contribute to ischemia, such as hyperventilation, cold-induced angina, or silent ischemia not caused by an increase in heart rate. Thus, the decision of whether or not to use CCAs in angina syndromes will often have to be made on grounds other than what appears to be a minor role of vasospasm in the overall spectrum of angina. There are preliminary indications that the long-term prognosis may be different among different categories of CCAs.

Treatment of silent ischemia in unstable angina: a randomized comparison of sustained-release verapamil versus metoprolol

Silent ischemia is a frequent finding in patients with unstable angina and portends a poor prognosis. We compared the efficacy of sustained-release (SR) verapamil and metoprolol in reducing silent ischemia in patients with unstable angina and assessed whether detection of silent ischemia was related to unfavorable outcomes in the contemporary setting of concurrent therapy with heparin and aspirin. Holter monitoring (leads a VF, V2, V5) for the first 72 h was used to assess the frequency and duration of ST-shift episodes. There were 37 patients in the verapamil-SR group and 40 patients in the metoprolol group, with both groups having similar baseline characteristics. There were more episodes of angina in the verampamil-SR group (29 vs. 12, p = 0.05). There was no difference between the two groups in the frequency (51 vs. 49 episodes, p = 0.9) or duration (23 +/- 48 vs. 18 +/- 50 min, p = 0.6) of ST-shift episodes. There were 20 unfavorable in-hospital outcomes distributed equally between the two groups (p = 0.9). Patients with unfavorable outcomes had ST shift more often (50 vs. 28%, p = 0.07) and for a longer duration (40 +/- 69 vs. 13 +/- 38 min, p = 0.03). Patients with ST shift > or = 60 min had a 60% probability of unfavorable outcome compared with 33% for ST shift of 1-59 min duration and 20% for no ST shift (p = 0.04). We conclude that metoprolol appears to reduce symptoms better than verapamil-SR, but no difference in silent ischemia or unfavorable outcomes was seen. Silent ischemia remains a common occurrence in these patients despite heparin and aspirin therapy and its detection continues to have prognostic value.

Can nitroglycerin convert effort-induced angina in men into silent myocardial ischemia?

The relief of anginal pain with nitroglycerin may not correspond to the disappearance of ischemia. To evaluate the possible lack of the elimination of ischemia with sublingual nitroglycerin, we studied 25 male patients with stable angina pectoris who underwent exercise stress testing with recording of blood pressure, pulse, and ST-segment displacement. The stress test was repeated 30 minutes after administration of 0.4 mg of sublingual nitroglycerin. All 25 patients had angina and ischemic ST-segment changes in the first stress test. On repeat stress testing, 15 patients had angina and ST-segment changes, 2 patients had angina but no ST-segment changes, and 4 patients had no ST-segment changes and no angina. Four patients, however, had no angina but persistent ischemic ST-segment changes suggesting that angina was converted into silent ischemia. The mean exercise duration was 311 +/- 66 seconds before and 421 +/- 81 seconds after the nitroglycerin test. Peak heart rate and systolic blood pressure before the nitroglycerin stress test were 109 +/- 18 and 155 +/- 23 mm Hg; in the repeat stress test, they increased to 123 +/- 21 and 162 +/- 20 mm Hg, respectively.

Chronobiology and chronotherapy in medicine

There is a fascinating and exceedingly important area of medicine that most of us have not been exposed to at any level of our medical training. This relatively new area is termed chronobiology; that is, how time-related events shape our daily biologic responses and apply to any aspect of medicine with regard to altering pathophysiology and treatment response. For example, normally occurring circadian (daily cycles, approximately 24 hours) events, such as nadirs in epinephrine and cortisol levels that occur in the body around 10 PM to 4 AM and elevated histamine and other mediator levels that occur between midnight and 4 AM, play a major role in the worsening of asthma during the night. In fact, this nocturnal exacerbation occurs in the majority of asthmatic patients. Because all biologic functions, including those of cells, organs, and the entire body, have circadian, ultradian (less than 22 hours), or infradian (greater than 26 hours) rhythms, understanding the pathophysiology and treatment of disease needs to be viewed with these changes in mind. Biologic rhythms are ingrained, and although they can be changed over time by changing the wake-sleep cycle, these alterations occur over days. However, sleep itself can adversely affect the pathophysiology of disease. The non-light/dark influence of biologic rhythms was first described in 1729 by the French astronomer Jean-Jacques de Mairan. Previously, it was presumed that the small red flowers of the plant Kalanchoe bloss feldiuna opened in the day because of the sunlight and closed at night because of the darkness. When de Mairan placed the plant in total darkness, the opening and closing of the flowers still occurred on its intrinsic circadian basis. It is intriguing to think about how the time of day governs the pathophysiology of disease. On awakening in the morning, heart rate and blood pressure briskly increase, as do platelet aggregability and other clotting factors. This can be linked to the acrophase (peak event) of heart attacks. During the afternoon we hit our best mental and physical performance, which explains why most of us state that "I am not a morning person." Even the tolerance for alcohol varies over the 24-hour cycle, with best tolerance around 5 pm (i.e. "Doctor, I only have a couple of highballs before dinner"). Thus, all biologic functions, from those of the cell, the tissue, the organs, and the entire body, run on a cycle of altering activity and function.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of amlodipine, atenolol and their combination on myocardial ischemia during treadmill exercise and ambulatory monitoring. Canadian Amlodipine/Atenolol in Silent Ischemia Study (CASIS) Investigators

OBJECTIVES

This study compared the effects of amlodipine, atenolol and their combination on ischemia during treadmill testing and 48-h ambulatory monitoring.

BACKGROUND

It is not known whether anti-ischemic drugs exert similar effects on ischemia during ambulatory monitoring and exercise treadmill testing.

METHODS

Patients with stable coronary artery disease and ischemia during treadmill testing and ambulatory monitoring were randomized to receive amlodipine (n = 51) or atenolol (n = 49). Each group underwent a counterbalanced, crossover evaluation of single drug and placebo, followed by evaluation of the combination.

RESULTS

Amlodipine and the combination prolonged exercise time to 0.1-mV ST segment depression by 29% and 34%, respectively (p < 0.001) versus 3% for atenolol (p = NS). During ambulatory monitoring, the frequency of ischemic episodes decreased by 28% with amlodipine (p = 0.083 [NS]), by 57% with atenolol (p < 0.001) and by 72% with the combination (p < 0.05 vs. both single drugs; p < 0.001 vs. placebo). Suppression of ischemia during exercise testing and ambulatory monitoring was similar in patients with and without exercise-induced angina. Exercise time to angina improved by 29% with amlodipine (p < 0.01), by 16% with atenolol (p < 0.05) and by 39% with the combination (p < 0.005 vs. placebo, atenolol and amlodipine). In patients with angina, total exercise time improved by 16% with amlodipine (p < 0.001), by 4% with atenolol (p = NS) and by 19% with the combination (p < 0.05 vs. placebo and either single drug). In those patients without angina, no therapy significantly improved total exercise time.

CONCLUSIONS

Ischemia during treadmill testing was more effectively suppressed by amlodipine, whereas ischemia during ambulatory monitoring was more effectively suppressed by atenolol. The combination was more effective than either single drug in both settings.

Daily life cardiac ischaemia. Should it be treated?

Daily life cardiac ischaemia is defined as reversible myocardial cellular hypoxia that occurs during activities of daily living, without artificial provocation. Most of these daily life ischaemic episodes are not associated with symptoms. However, it is not practical to distinguish silent versus symptomatic daily life ischaemia as both are associated with haemodynamic abnormalities and future adverse outcomes. Daily life cardiac ischaemia is best detected using ambulatory electrocardiogram (ECG) monitoring; however, there are other diagnostic tools (e.g. exercise treadmill) that can be used. Once detected, the optimal therapy for daily life myocardial ischaemia has yet to be identified. However, it does appear that usual antianginal medications including nitrates, beta-blockers, calcium antagonists and antiplatelet drugs are effective in reducing the incidence and severity of daily life myocardial ischaemia. Medical therapy and revascularisation should be utilised to obliterate all episodes of daily life cardiac ischaemia to prevent future cardiac events. Moreover, the efficacy of the chosen therapeutic regimen for each patient should be documented with follow-up objective testing. The diagnosis and management of daily life myocardial ischaemia is continually evolving. Future research as well as economic considerations will shape future management strategies.

Nitrates in silent ischemia

In recent years it has become clear that episodes of transient myocardial ischemia commonly occur in patients with coronary artery disease in the absence of chest pain or angina equivalent. These episodes of "silent myocardial ischemia" are particularly well documented during continuous ambulatory electrocardiographic monitoring in daily life. Evidence suggests that these episodes represent true ischemia, and appear to be a marker of unfavorable outcome. While the pathophysiology is not completely understood, it appears as though the mechanisms of angina and silent ischemia are the same. Both forms of ischemia respond to conventional antianginal medication. While long-acting nitrates are effective in reducing or preventing myocardial ischemia, because of their propensity to cause tolerance they should be used intermittently and in association with either beta-blockers or calcium antagonists. Nitrates are safe and comparatively inexpensive, and will continue to play an important role in the treatment and prevention of angina. However, in the light of current knowledge, there is no specific indication for the treatment of silent ischemia by nitrates.

Effects of treatment on outcome in mildly symptomatic patients with ischemia during daily life. The Atenolol Silent Ischemia Study (ASIST)

BACKGROUND

Detection of asymptomatic ischemia in patients with coronary artery disease has been associated with increased risk for adverse outcome, but treatment of patients with asymptomatic ischemia remains controversial. Accordingly, the purpose of this study was to determine if treatment reduces adverse outcome in patients with daily life ischemia.

METHODS AND RESULTS

A multicenter, randomized, double-blind, placebo-controlled study of asymptomatic or minimally symptomatic outpatients with daily life silent ischemia due to coronary artery disease was conducted. The primary outcome measure was event-free survival at 1 year by Kaplan-Meier analysis. Events were death, resuscitated ventricular tachycardia/fibrillation, myocardial infarction, hospitalization for unstable angina, aggravation of angina, or revascularization. The secondary outcome was ischemia during ambulatory ECG monitoring at 4 weeks. Three hundred six outpatients with mild or no angina (Canadian Cardiovascular Society class I or II), abnormal exercise tests, and ischemia on ambulatory monitoring were randomized to receive either atenolol (100 mg/d) or placebo. After 4 weeks of treatment, the number (mean +/- SD, 3.6 +/- 4.2 versus 1.7 +/- 4.6 episodes, P < .001) and average duration (30 +/- 3.3 versus 16.4 +/- 6.7 minutes, P < .001) of ischemic episodes per 48 hours of ambulatory monitoring decreased in atenolol- compared with placebo-assigned patients (4.4 +/- 4.6 to 3.1 +/- 6.0 episodes and 36.6 +/- 4.1 to 30 +/- 5.5 minutes). Event-free survival improved in atenolol-treated patients (P < .0066), who had an increased time to onset of first adverse event (120 versus 79 days) and fewer total first events compared with placebo (relative risk, 0.44; 95% confidence intervals, 0.26 to 0.75; P = .001). There was a nonsignificant trend for fewer serious events (death, resuscitation from ventricular tachycardia/fibrillation, nonfatal myocardial infarction, or hospitalization for unstable angina) in atenolol-treated patients (relative risk, 0.55; 95% confidence intervals, 0.22 to 1.33; P = .175). The most powerful univariate and multivariate correlate of event-free survival was absence of ischemia on ambulatory monitoring at 4 weeks. Side effects were mild and generally similar comparing atenolol- and placebo-treated patients, although bradycardia was more frequent with atenolol.

CONCLUSIONS

Atenolol treatment reduced daily life ischemia and was associated with reduced risk for adverse outcome in asymptomatic and mildly symptomatic patients compared with placebo.

Comparison of nifedipine gastrointestinal therapeutic system and atenolol on antianginal efficacies and exercise hemodynamic responses in stable angina pectoris

A gastrointestinal therapeutic system (GITS) of nifedipine has been developed to provide a once-daily dosing, and predictable, relatively constant plasma concentrations. This study compared the antianginal efficacy of nifedipine GITS with a once-a-day beta-receptor blocker, atenolol. Seventeen patients with documented coronary artery disease and stable stress-induced angina pectoris were studied during a 2-week, single-blind, placebo baseline phase and a 12-week randomized, double-blind, active drug crossover efficacy phase, using the bicycle exercise test and ambulatory electrocardiographic recordings. Patients exercised significantly longer with nifedipine GITS (883 +/- 47 seconds) and atenolol (908 +/- 44 seconds) than with placebo (794 +/- 41 seconds). Nifedipine GITS reduced systolic blood pressure at all stages of exercise compared with placebo but, because heart rate tended to increase more during nifedipine therapy, there was no difference in rate-pressure products between the placebo and nifedipine GITS periods. In contrast, atenolol reduced heart rate, systolic blood pressure and rate-pressure product during exercise compared with placebo. Whereas left ventricular ejection fractions (by radionuclide angiocardiography) increased with exercise, the maximal increase was smaller with atenolol than with placebo and nifedipine. The net increase in left ventricular ejection fraction at the end of exercise was greater with nifedipine than with placebo or atenolol. Ambulatory electrocardiograms showed only a small number of ischemic events. Neither nifedipine GITS nor atenolol reduced the number of ischemic events or total duration of ST-segment deviations significantly. It is concluded that nifedipine GITS is as effective an antianginal agent as atenolol, but the hemodynamic effects of the 2 agents differ.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of atenolol and diltiazem on exercise tolerance and ambulatory ischaemia

Twenty-five normotensive patients with stable angina, angiographically documented coronary disease and normal left ventricular function were randomized to a crossover study comparing atenolol 100 mg x 1, sustained-release diltiazem 120 mg x 2, and their combination. A maximal symptom limited bicycle exercise test and a 24-h ambulatory electrocardiographic (ECG) monitoring were performed at the end of each treatment period. Exercise duration was increased equally in the different treatment groups. Time to onset of 1-mm ST-segment depression was longer with atenolol (P < 0.02) and combination therapy (P < 0.01) than with diltiazem. The maximal ST-segment depression was decreased with atenolol (P < 0.05) and combination therapy (P < 0.02), whereas, time to onset of angina was prolonged only with combination therapy (P < 0.03). The number of ischaemic episodes during ambulatory monitoring was lower with atenolol and combination therapy than with diltiazem (P < 0.01). The difference between atenolol and diltiazem was mainly due to lower ischaemic activity with atenolol between 06:00 h and 12:00 h (P < 0.05). Anginal frequency (P < 0.01) and nitroglycerin consumption (P < 0.05) were lower with combination therapy than with monotherapy. Thus, while comparable effects were achieved on clinical variables, atenolol appeared to be more effective than diltiazem, reducing myocardial ischaemia during exercise and ambulatory monitoring. With combination therapy, both clinical and electrocardiograph signs of ischaemia were improved.

Silent myocardial ischemia

The documentation of abnormalities related to myocardial ischemia, whether symptomatic or silent, is of central importance. Whenever this information is available, it should be used in the overall assessment of the patient at risk for adverse outcome. The level of concern for treatment of CAD should be based on the risk implications associated with the ischemia-related abnormalities detected during objective testing rather than on the presence or absence of pain. The exercise stress test is still the single most useful test to begin the evaluation of a patient with an analyzable ST segment. In persons suspected of having CAD, the detection of ischemic-type ST-segment depression, at a low workload (e.g., < 120 beats/min or < 6.5 METS) of > 2 mm magnitude or persisting for more than 6 min implies high risk for adverse outcome. Asymptomatic ischemia during everyday activities, detected by Holter monitoring, in the high-risk patient, most probably adds additional risk beyond the risk of an abnormal stress test alone. Left ventricular imaging by two-dimensional echocardiography, RNA, angiogram, vest, etc, showing an ejection fraction > or = 40%, reversible wall motion abnormalities in multiple regions and redistribution defects or a failure to increase ejection fraction during exercise even if the patient remains asymptomatic, also imply high risk. The presence of any of these abnormal findings, regardless of symptoms, should therefore prompt as high a degree of concern as with ischemia-related signals associated with pain. Thus any therapy chosen should be directed toward elimination of transient ischemia, not just relief of symptoms that may or may not be ischemia related. If this course is chosen, the efficacy of the therapeutic regimen and possible progression of CAD should be assessed with follow-up testing for ischemia. We believe that risk factor modification and aspirin should be considered for most, if not all, patients in whom ischemia, silent or symptomatic, is suspected or detected. If symptoms or ischemia suggesting low risk is present, anti-ischemic medical therapy may be considered, but follow-up is advised. If a high-risk ischemic signal, even without symptoms, is detected, medical therapy should be used to attempt to modify the signal. If the ischemic signal suggesting high risk persists despite medical therapy, revascularization should be considered. Until additional data from large clinical trials are available, this approach appears to have the greatest likelihood of modifying the adverse outcome of CAD.

Comparative efficacy of nifedipine gastrointestinal therapeutic system versus diltiazem when added to beta blockers in stable angina pectoris

To determine the relative efficacy of nifedipine gastrointestinal therapeutic system (GITS) and diltiazem, 20 patients with angina pectoris and coronary artery disease were studied in a double-blinded, placebo-controlled randomized crossover trial. All patients were taking concomitant beta blockers. Efficacy was assessed by symptoms, exercise treadmill testing, and ambulatory ST-segment monitoring at baseline and after 6 weeks on each medication. Mean daily dose was titrated to 119 +/- 7 mg (nifedipine GITS) and 342 +/- 59 mg (diltiazem). The addition of either nifedipine GITS or diltiazem resulted in a significant reduction in angina frequency, improvement in exercise treadmill duration (7 vs 7 and 8 minutes; baseline vs nifedipine GITS and diltiazem), time to angina onset (4 vs 7 and 7 minutes; baseline vs nifedipine GITS and diltiazem), and time to ST-segment depression (5 vs 6 and 7 minutes; baseline vs nifedipine GITS and diltiazem). There was no significant difference between nifedipine GITS and diltiazem with respect to the magnitude of improvement in anginal symptoms or exercise test parameters. Both nifedipine GITS and diltiazem reduced the overall frequency and duration of ischemic episodes on ambulatory monitoring, but this reduction was not statistically different. Thus, nifedipine GITS and diltiazem at maximally tolerated doses were equally effective at reducing angina and increasing exercise tolerance as beta blockers alone.

Transient myocardial ischemia during nifedipine therapy in stable angina pectoris, and its relation to coronary collateral flow and comparison with metoprolol

There are conflicting results concerning the anti-ischemic effect of nifedipine in patients with chronic stable angina. Therefore, the purpose of this study was to assess whether the anti-ischemic effect of nifedipine may be related to coronary collateral circulation. Forty-one patients with stable angina and coronary artery disease were randomized to a parallel double-blind study with nifedipine and metoprolol, and compared for effects on transient ischemic episodes during ambulatory electrocardiographic monitoring and exercise-induced ischemia. The effects were correlated to the presence of collateral circulation. In 17 patients, angiographically poor or no collateral flow was observed (group 1), and 24 had good collateral flow (group 2). Nifedipine was administered to 20 patients (8 in group 1, and 12 in group 2). In group 1, nifedipine reduced the frequency of total and asymptomatic ischemic episodes (p < 0.05), whereas significant increases in both total (p < 0.05) and silent (p < 0.01) ischemia were observed in group 2. Exercise variables were slightly improved (p = NS) during nifedipine therapy in group 1, and slightly worsened (p = NS) in group 2. Reflex tachycardia was not observed at either the onset of transient ischemia out of the hospital or exercise-induced ischemia. This was in contrast with the effect in 21 patients treated with metoprolol (9 in group 1, and 12 in group 2) where significant reductions were observed in the frequency of both total (p < 0.01) and silent (p < 0.01) ischemia in both groups. Furthermore, a beneficial effect was observed on all exercise variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of increases in heart rate in determining the occurrence and frequency of myocardial ischemia during daily life in patients with stable coronary artery disease

OBJECTIVES

The goal of this study was to investigate the role of increases in heart rate in the development of ischemic episodes recorded during ambulatory electrocardiographic (ECG) monitoring in patients with stable coronary artery disease and to establish the importance of such increases in determining the frequency of ambulatory myocardial ischemia.

BACKGROUND

The factors that determine the occurrence and frequency of episodes of myocardial ischemia that patients with stable coronary artery disease experience during daily life have not been clearly defined. In particular, the role of increases in heart rate in the development of myocardial ischemia is controversial.

METHODS

To address these issues, 54 patients (42 men and 12 women, mean age 60.5 +/- 8 years) with proved coronary artery disease who had > or = 1 mm ST segment depression during exercise testing underwent an exercise treadmill test with use of the National Institutes of Health combined protocol and a 48-h period of ambulatory ECG monitoring. The exercise ischemic threshold was determined as the heart rate at the onset of ST segment depression during exercise testing.

RESULTS

During monitoring, 48 (89%) of the 54 patients had at least one episode of ST segment depression (mean +/- SD 6.6 +/- 5 episodes, range 0 to 22). The majority (320 of 359 or 89%) of ischemic episodes were preceded by an increase in heart rate > or = 10 beats/min; the most significant increase (22.3 +/- 10 beats/min) occurred during the 5-min period before the onset of the episode. An ischemic episode occurred 80% of the times the heart rate reached the exercise ischemic threshold. A strong correlation was observed between the number of times the exercise ischemic threshold was reached during monitoring and both the number and the duration of ischemic episodes (r = 0.90 and 0.71, respectively, p < 0.0001).

CONCLUSIONS

Increases in heart rate that exceed the exercise ischemic threshold are commonly observed before the onset of episodes of ambulatory myocardial ischemia in patients with stable coronary artery disease. Moreover, such increases constitute an important determinant of the frequency of myocardial ischemia during daily life. These findings may explain the variability observed in the number of ischemic episodes and may have important implications for the mechanisms that contribute to myocardial ischemia in daily life and for the clinical evaluation of patients with coronary artery disease.

Daily life ischemia and nitrate therapy

Daily life ischemia has generated considerable interest because most of it is silent and associated with increased risk of adverse outcome. Coronary vasomotion, as well as increases in myocardial oxygen demand, seem important in the pathogenesis of this form of ischemia, so treatment with nitrates seems rational. Administration of sublingual nitroglycerin hourly, over 12 hours, was shown to decrease both silent and painful ischemic episodes in patients with effort angina. Subsequently, isosorbide dinitrate or mononitrate, given either as an intravenous infusion or orally, was shown to decrease both silent and painful ischemic episodes in patients with unstable rest angina and in those with severe angina. More recently, 6 studies have reported using transdermal nitroglycerin for daily life ischemia. Three of these reported open-label uncontrolled observations and suggested that ischemia frequency may be reduced approximately 60-80% during treatment with doses of 10-30 mg/day, with a duration of treatment ranging from 1 hour to 14 days. In 2 of these reports the duration of ischemia also decreased. The other 3 studies were randomized, double-blind, placebo-controlled studies with a total enrollment of 86 patients. These studies provided mixed results. One suggested that evidence for partial tolerance develops within 1 day of treatment, using large continuous or intermittent doses (mean, 52 mg/day). Another suggested that no tolerance develops to intermittent dosing (18 mg/16 hr out of 24 hr) during exercise testing but no effect is seen on daily life ischemia. The remaining study suggested that tolerance does not develop using small doses (15 mg/day) continuously over 14 days for ischemia during daily life, and that this response is different from that observed using the calcium antagonist nifedipine. These limited observations and conflicting results underscore a need for additional larger controlled trials, employing topical nitrate therapy in low intermittent doses for daily life ischemia.

Treatment strategies for daily life silent myocardial ischemia: A correlation with potential pathogenic mechanisms

Recent investigations of SMI occurring during daily life have advanced our understanding of the pathophysiology of myocardial ischemia. These contributions have directed our attention away from "chest pain" alone and physical exertion as the central provoking factor toward transient myocardial ischemia and its broader triggers and consequences. Transient myocardial ischemic episodes, the majority of which are silent, are found in a subset of patients with any clinical manifestations of CAD (eg, stable angina, unstable angina, myocardial infarction, and sudden death), as well as in those patients with CAD who are and have been totally asymptomatic. These episodes are an independent predictor of increased risk for future cardiac events. Most medical therapy and revascularization therapies have the potential to prevent or relieve these silent episodes; however, we do not yet know which method is superior in reducing SMI episodes or preventing future cardiac events. Furthermore, the benefit of reducing SMI versus the cost and potential morbidity of these chosen therapies is not known. At least three trials are now underway to examine some of these concerns (Table 2). Focus on pain relief alone does not appear to be an adequate approach to alter outcome in patients with CAD and may prove insufficient to control SMI. Until these issues are resolved, we believe a conservative approach to the management of patients with CAD is warranted. Documentation of ischemia (painful or painless) is essential. Three general principles should be kept in mind. First, the presence of detectable ischemia is of central importance. This information should be used in the overall risk assessment of the patient. Second, the level of concern or aggressiveness of treatment should be based on the risk associated with the ischemic abnormalities documented (Table 3). The exercise stress test is the most useful to begin this process. The detection of ischemic-type ST-segment depression, either silent or painful, at a low workload (eg, less than or equal to 120 beats per minute or less than or equal to 6.5 metabolic equivalents [METS]) implies high risk for adverse outcome. Likewise, these ST-segment changes occurring in leads that reflect multiple coronary artery distribution, of greater than 2 mm in magnitude and persisting for greater than 6 minutes, are all markers for high risk. Thallium redistribution defects occurring at low work loads, in multiple areas, associated with increased lung uptake and enlargement of the cardiac pool all imply high risk.(ABSTRACT TRUNCATED AT 400 WORDS)

The total ischemic burden European trial (TIBET): design, methodology, and management. The TIBET Study Group

TIBET is a European multicenter, double-blind parallel group trial with the main objective of investigating whether total ischemic burden has important prognostic implications in patients with stable angina on treatment. A secondary objective is to compare the antianginal and antiischemic effects of atenolol (50 mg bid), nifedipine (20-40 mg bid), and their combination using standardized exercise testing and Holter monitoring techniques. The main primary end points are cardiovascular morbidity and mortality. The secondary end points are time to onset of significant ischemia, angina on exercise stress testing, exercise capacity at onset of angina, 1-mm ST-segment depression and termination of exercise, total duration and number of significant ischemic episodes during 48 hours of Holter monitoring, and their circadian distribution. The target population, the assessments, and the management of the trial are described in detail.

Efficacy of a single dose of slow-release isosorbide dinitrate in the treatment of silent or painful myocardial ischemia in stable angina pectoris

A double-blind study was performed in 32 patients with stable angina pectoris to assess the effects of slow-release isosorbide dinitrate (ISDN) (a single dose of 120 mg/day) on the frequency and duration of painless and painful ischemic episodes, and on electrocardiographic changes and exercise tolerance. Forty-eight-hour electrocardiographic monitoring and treadmill exercise tests were performed before, and at 20 and 21 days of therapy. Holter monitoring showed a significant decrease in the frequency of painful and silent episodes (p less than 0.001), and in the duration of painful (1,623 +/- 664 seconds vs 323 +/- 161 seconds; p less than 0.001) and silent episodes (2,818 +/- 1,496 seconds vs 223 +/- 102 seconds; p less than 0.001). The magnitude of painful and silent ST-segment depression was significantly reduced (2.7 +/- 0.9 mm to 0.7 +/- 0.7 mm and 2.0 +/- 1.1 mm to 0.7 +/- 0.5 mm, respectively; p less than 0.001). Time of exercise testing to the onset of ST-segment depression (442 +/- 137 seconds vs 858 +/- 110 seconds; p less than 0.001) or anginal pain was doubled (461 +/- 128 seconds vs 830 +/- 130 seconds; p less than 0.001). The work load increased from 6 to 10 METs (p less than 0.001). ISDN in a single dose of 120 mg/day is a valuable drug for stable angina pectoris, decreasing the frequency of silent and painful ischemic episodes and the magnitude of ST-segment depressions, and increasing exercise tolerance. It particularly shortened the duration of silent episodes. For patients' compliance, a once-daily dose of ISDN could be advantageous.

The predictive value of silent ischemia at an exercise test before discharge after an episode of unstable coronary artery disease. RISC Study Group

The prognostic value of silent ischemia during a symptom-limited predischarge exercise test (ET) was evaluated in 740 men after an episode of unstable angina or non-Q wave myocardial infarction. The 51% of patients with ST depression at the ET had a higher rate of myocardial infarction or death after 1 year (18%) compared with those without ST depression (9%; p less than 0.01). This increased risk was not influenced by the presence or absence of pain at the ET: 18.3% in patients with painful ischemia compared with 18.1% in patients with silent ischemia. However, ST depression combined with pain at the ET predicted a higher incidence of class III or IV angina at follow-up (43.9% compared with 16.7% in the group with asymptomatic ST depression; p less than 0.001). Because revascularization in addition to alleviating symptoms also enhances the prognosis in certain groups of patients, selections for coronary angiography and possible revascularization should not be made only on the basis of symptoms but also on the presence of myocardial ischemia, whether symptomatic or not.

Paradoxical effect of long-term treatment of nifedipine on total ischemic load in patients with stable angina pectoris

In 50 patients with stable effort angina the effect of three drugs, metoprolol, nifedipine, and diltiazem was assessed by analyzing exercise stress test response and ambulatory ECG recordings. Both metoprolol and diltiazem caused a significant increase in time to ischemic threshold during exercise and a significant decrease of maximum ST-segment depression (during exercise and ambulatory ECG monitoring) and in the average number of daily ischemic episodes. Only metoprolol significantly reduced heart rate and rate-pressure product at the ischemic threshold during exercise. In the group of patients treated with nifedipine no significant improvement was observed in exercise tolerance or in number of ischemic episodes/24 h. Moreover, the subset of nonresponders in the two methods was larger than in the other two groups. In some of these patients a clearcut worsening of total ischemic load was observed, despite the control of symptoms. This adverse effect might be attributed to the different consequences of the vasodilatory effect of nifedipine on blood flow through stenosed vessels.

Calcium antagonists and silent myocardial ischaemia

Silent myocardial ischaemia results from an imbalance between myocardial oxygen supply and demand. There is evidence in favour of both increased coronary vasomotor tone and increased oxygen demand as major independent causes of silent ischaemia. An ongoing study is assessing the efficacy of a slow release formulation of the calcium antagonist gallopamil in patients with stable angina pectoris. In a nonblind comparison with placebo in 13 patients, slow release gallopamil 100mg twice daily produced a marked reduction in exercise-induced myocardial ischaemia, and a moderate reduction in spontaneous ischaemia. The significance of these preliminary findings will emerge in the double-blind, placebo-controlled phase of the study. Studies using long term ECG monitoring to compare the anti-ischaemic efficacy of various calcium antagonists indicate that agents with negative inotropic actions suppress silent myocardial ischaemia to a greater extent than calcium antagonists such as nifedipine, which tend to increase heart rate. Also, beta-adrenoceptor blockers have produced excellent results in the treatment of myocardial ischaemia, despite their theoretical disadvantage of not reducing coronary vasomotor tone. The role of pharmacological therapy in the suppression of silent myocardial ischaemia will only be established when the drugs concerned have been adequately characterised with regard to their effect on prognosis, adverse effects and risk:benefit ratio.

Atenolol. A reappraisal of its pharmacological properties and therapeutic use in cardiovascular disorders

Atenolol is a selective beta 1-adrenoceptor antagonist with a duration of activity of at least 24 hours. The scope of therapeutic use of the drug has been expanded and become better defined since it was first reviewed in the Journal in 1979. Atenolol is effective and generally well tolerated in patients with all grades of hypertension. Data from comparative studies show that when administered orally, atenolol reduces blood pressure to a similar extent, and in a similar proportion of patients, as usual therapeutic doses of other beta-adrenoceptor antagonists (such as acebutolol, celiprolol, betaxolol, indenolol, metoprolol, nadolol, pindolol, propranolol, tertatolol), angiotensin converting enzyme (ACE) inhibitors (e.g. captopril, enalapril and lisinopril), calcium antagonists (e.g. amlodipine, diltiazem, felodipine, isradipine, nitrendipine, nifedipine, verapamil), doxazosin, ketanserin and alpha-methyldopa. Atenolol effectively lowers blood pressure in elderly patients with hypertension and in women with hypertension associated with pregnancy, and improves objective and subjective indices in patients with stable angina pectoris. Oral atenolol is used for preventing recurrence of supraventricular arrhythmias once control is achieved by intravenous administration of atenolol. Early intervention with intravenous atenolol followed by oral maintenance therapy reduces infarct recurrence and cardiovascular mortality in patients with known or suspected myocardial infarction. There is also encouraging evidence of reduced mortality from cardiovascular disease during long term therapy with atenolol in patients with hypertension. Atenolol is well tolerated in most patients. Increases in plasma levels of both total triglycerides and very low density lipoprotein (VLDL) triglycerides have accompanied atenolol therapy although the clinical relevance, if any, of longer term metabolic effects has yet to be determined. Its low lipid solubility and limited brain penetration results in a lower incidence of central nervous system effects than that associated with propranolol. After many years of clinical usage atenolol is a well established treatment option in several areas of cardiovascular medicine such as mild to moderate hypertension and stable angina pectoris. Furthermore, it has also shown potential in the treatment of some cardiac arrhythmias and has been associated with reduced cardiovascular mortality in patients with hypertension and in patients with myocardial infarction.

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

The role of increased myocardial oxygen demand in the pathophysiology of myocardial ischemia occurring during daily activities was evaluated in 50 patients with coronary artery disease and exercise-induced ST segment depression. Each patient underwent ambulatory electrocardiographic (ECG) monitoring for ST segment shifts during normal daily activities and symptom-limited bicycle exercise testing with continuous ECG monitoring. All 50 patients had ST depression greater than or equal to 0.1 mV during exercise. A total of 241 episodes of ST depression were noted in the ambulatory setting in 31 patients; only 6% of these were accompanied by angina pectoris. Significant (0.1 mV) ST depression during ambulatory monitoring was preceded by a mean increase in heart rate of 27 +/- 12 beats/min. Patients with ischemia during daily activities developed ST depression earlier during exercise (7.9 +/- 4.4 vs. 14.2 +/- 6.4 min, p less than 0.001) and tended to have significant ECG changes at a lower exercise heart rate and rate-pressure product than did those without ST depression during ambulatory monitoring. In the 31 patients with ischemia during daily activities, the mean heart rate associated with ST depression in the ambulatory setting was closely correlated with the heart rate precipitating ECG changes during exercise testing (r = 0.74, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The prognostic and economic implications of a strategy to detect and treat asymptomatic ischemia: the Atenolol Silent Ischemia Trial (ASIST) protocol

Although silent ischemia may be linked to increases in cardiovascular morbidity and mortality, the long-term effects of a strategy aimed at the detection and treatment of this asymptomatic condition have not been fully explored. We therefore have developed the Atenolol Silent Ischemia Trial (ASIST), the first multicenter, randomized, prospective study of the prognostic implications of silent ischemia in asymptomatic and minimally symptomatic patients with coronary artery disease. Inclusion criteria for study patients were documented coronary artery disease, evidenced angiographically or by previous myocardial infarction, and transient ischemia, evidenced by abnormalities of regional wall motion, stress thallium-201, or exercise electrocardiogram. The main objective of ASIST is to assess the influence of frequency and duration of symptomatic and asymptomatic ischemic episodes on the occurrence of fatal and nonfatal cardiac events. Atenolol, a beta 1-selective adrenergic blocker, was chosen as the therapeutic intervention because of its potential benefits in treating both symptomatic and asymptomatic ischemia. Ambulatory electrocardiographic monitoring will be used to measure the frequency and duration of ischemic episodes during daily life. The predictive ability of short-term (4-week) effects on long-term (52-week) response to atenolol treatment is also being assessed, along with the economic impact of this diagnostic and therapeutic strategy. Given the current emphasis on reducing morbidity and mortality associated with coronary artery disease, ASIST results should shed light onto the long-term management and prognostic implications of this otherwise asymptomatic condition.

Transient myocardial ischemia during daily life in rest and exertional angina pectoris and comparison of effectiveness of metoprolol versus nifedipine

The clinical characteristics of 65 patients with mixed angina were classified by means of (1) a questionnaire investigating the proportion of symptoms occurring at rest and on effort, (2) an exercise stress test, (3) 24-hour ambulatory Holter monitoring, and (4) coronary arteriography. According to the questionnaire, the proportion of effort-induced anginal episodes ranged from 1 to 99%. The ischemic threshold during exercise testing ranged from 110 x 10(2) to 350 x 10(2) mm Hg x beats/min. At least 1 episode of ST-segment depression was observed in 29 of the 65 patients during Holter monitoring. Ischemic episodes during Holter monitoring were more frequent (p less than 0.05) in patients reporting greater than or equal to 50% of anginal attacks on effort, with moderate to severe limitation of exercise capacity and with multivessel coronary artery disease. The effect on ambulatory ischemia of a 6-week treatment with a beta blocker (metoprolol CR, 200 mg once daily) or a dihydropyridine calcium antagonist (nifedipine retard 20 mg twice daily) were then compared according to a double-blind, parallel group design. Metoprolol significantly reduced the number and duration of the ischemic episodes during daily life (p less than 0.05) irrespective of the patients' clinical characteristics. Nifedipine was ineffective, particularly in patients with angina predominantly on effort and with a moderate to severe reduction in exercise tolerance. It is concluded that in patients with mixed angina, ischemic episodes during daily life are more likely to occur in patients with a clinical presentation suggesting poor coronary reserve.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of atenolol alone, nifedipine alone and their combination on ambulant myocardial ischemia

The effects of atenolol (100 mg/day) and nifedipine (20 mg 3 times daily) and their combination on ambulant myocardial ischemia were investigated using a randomized, double-blind, placebo-controlled, crossover trial. Eighteen men with symptomatic coronary artery disease, exercise-induced ischemia and minimal symptoms, underwent 4 blinded treatment periods of 2 weeks' duration (2 placebo, 1 atenolol, 1 nifedipine). Those that did not have ischemia eliminated by monotherapy received combination therapy with both drugs. Forty-eight-hour ambulatory electrocardiographic monitoring was used to quantitate ischemic parameters at the end of each period. Both nifedipine and atenolol as monotherapy reduced the number of ischemic episodes and the average duration of each episode compared with placebo (p less than 0.05). Compared with placebo, nifedipine reduced the total duration of ischemia (p less than 0.05) but the effect of atenolol on ischemia duration was of borderline significance (p = 0.066). There were no differences in reduction of ischemic parameters when atenolol was compared with nifedipine (difference not significant). In the 9 patients who continued to have ischemia with monotherapy, combination therapy eliminated it in 2 and reduced the duration by greater than 50% in the remaining patients compared with placebo. In conclusion, monotherapy with nifedipine or atenolol is similarly effective in eliminating or reducing ambulant ischemia. Combination therapy can provide additional benefit in those with continued ischemia.

Anti-ischemic effects of atenolol versus nifedipine in patients with coronary artery disease and ambulatory silent ischemia

The anti-ischemic effects of atenolol and nifedipine were compared in a randomized double-blind crossover manner in 24 patients with stable exertional angina and transient silent ischemia during ambulatory electrocardiographic (ECG) monitoring. Both atenolol and nifedipine were effective (p less than 0.005) in reducing the average number and duration of transient ischemic events, but therapy with atenolol was associated with a significantly greater reduction in the mean number (p less than 0.05) and duration (p less than 0.01) of silent ischemic events. Analyses of the silent ischemic activity during the morning hours revealed that only therapy with atenolol produced a significant reduction in the average duration per patient (139 +/- 54 vs. 1,609 +/- 468 s, p less than 0.01) and in the average duration of silent ischemia per event between 6 AM and 12 noon (62 +/- 21 vs. 208 +/- 24 s, p less than 0.005). There were fewer adverse experiences during therapy with atenolol. These results show that although both atenolol and nifedipine are effective in reducing silent ischemic events, treatment with atenolol is associated with significantly greater efficacy, particularly on the morning surge of silent myocardial ischemia.

Atenolol and ischaemic heart disease: an overview

Data generated to date on the use of beta-blockers, especially atenolol, in ischaemic heart disease are reviewed and compared with the results available with the calcium antagonists. Atenolol appears to be effective as an anti-ischaemic agent in patients with obstructive coronary artery disease when reduction in myocardial oxygen supply (ischaemia not preceded by an increase in heart rate and due presumably to functional coronary stenosis) or increase in demand are the likely causes. Based on current concepts and available data, there is convincing evidence to support the use of atenolol across the spectrum of ischaemic heart disease. In contrast, results with the calcium antagonists have been disappointing and variable. Atenolol, to date, is the only beta-blocker which has been demonstrated to have a life-saving benefit in acute intervention (within 12 hours of onset) in myocardial infarction. This cardioprotective aspect of the drug is likely to be applicable to other areas of ischaemic heart disease, including silent ischaemia.

Circadian variation of heart rate is affected by environment: a study of continuous electrocardiographic monitoring in members of a symphony orchestra

Twenty four hour ambulatory ST segment monitoring was performed on 48 members (43 players and five members of the management/technical team) of the British Broadcasting Corporation (BBC) symphony orchestra without a history of cardiac disease. This period included final rehearsals and live performances (for audience and radio) of music by Richard Strauss and Mozart at the Royal Festival Hall (n = 36) and Rachmaninov and Tchaikovsky at the Barbican Arts Centre (n = 21). During the period of monitoring one person (2%) had transient ST segment changes. Mean heart rates were significantly higher during the live performances than during the rehearsals. Mean heart rates during the live performance of Rachmaninov and Tchaikovsky were significantly higher than during Strauss and Mozart in those (n = 6) who were monitored on both occasions. Mean heart rates in the management and technical team were higher than those of the players. The recognised circadian pattern of heart rate, with a peak in the morning waking hours, was altered similarly during both concert days, with a primary peak occurring in the evening hours and a lesser peak in the morning for both musicians and management/technical staff. This study showed that environmental factors are of primary importance in defining the circadian pattern of heart rate. This has important implications when identifying peak periods of cardiovascular stress and tailoring drug treatment for patients with angina pectoris.

Effects of theophylline, atenolol and their combination on myocardial ischemia in stable angina pectoris

The effects of theophylline (400 mg twice a day), atenolol (50 mg twice a day) and their combination on myocardial ischemia were studied in 9 patients with stable angina pectoris in a randomized, single-blind, triple crossover trial. Placebo was administered to the patients during the run-in and the run-off periods. A treadmill exercise test and 24-hour ambulatory electrocardiographic monitoring were obtained at the end of each treatment period. Compared with placebo, theophylline significantly improved the time to onset of myocardial ischemia (1 mm of ST-segment depression) from 7.8 +/- 3.7 to 9.5 +/- 3.7 minutes (p less than 0.03) and the exercise duration from 9 +/- 3.4 to 10.1 +/- 3.5 minutes (p less than 0.04). During atenolol and during combination treatment, the time to the onset of ischemia and the exercise duration were similar (10.8 +/- 4.2 and 11.2 +/- 3.2 minutes, 11.2 +/- 3.6 and 11.5 +/- 3.2 minutes, respectively) and longer than during theophylline administration (p less than 0.05). Ambulatory electrocardiographic monitoring showed that, during theophylline administration, the heart rate was higher than during placebo throughout the 24 hours (p less than 0.05). During atenolol and during combination treatment the heart rate was similar and in both cases lower than during placebo (p less than 0.05). Compared with placebo, theophylline decreased the total ischemic time from 97 +/- 110 to 70 +/- 103 minutes (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-blocker duration of action and implications for therapy

Two studies were conducted to measure the effect of serum half-life on beta-blocker-related heart rate reduction throughout the 24-hour period. In the first study, nadolol, atenolol and pindolol were associated with significant (p less than 0.01) heart rate reduction even at 24 hours after dose. Nadolol, with a plasma half-life of 15.5 hours, had the most pronounced heart rate-lowering effect 24 hours after the daily dose compared to pindolol, which had a half-life of 5.5 hours. In a randomized, double-blind, crossover study, nadolol and atenolol had similar effects 3 to 4 hours after the daily dose. Nadolol, however, produced greater suppression of heart rate and double product (blood pressure x heart rate) than atenolol (compared to placebo) 24 hours after ingestion of the daily dose. On ambulatory electrocardiography 24 hours after medication administration, 80 to 100% of the heart rate-attenuating effect of nadolol was maintained versus only 20 to 45% of atenolol's effect. Statistically significant (p less than 0.05) reductions in heart rate were produced by nadolol, but not by atenolol, between 4 and 5 A.M., 6 and 7 A.M., 8 and 9 A.M. and 9 and 10 A.M. Furthermore, nadolol remained at 52% of peak blood level at 24 hours, whereas atenolol was at 20%. The data from these 2 studies indicate that significant differences in duration of action exist between beta blockers.