Antianginal drug therapy for silent myocardial ischemia

Silent myocardial ischemia

Although much progress has been made in reducing mortality from ischemic cardiovascular disease, this condition remains the leading cause of death throughout the world. This might in part be due to the fact that over half of patients have a catastrophic event (heart attack or sudden death) as their initial manifestation of coronary disease. Contributing to this statistic is the observation that the majority of myocardial ischemic episodes are silent, indicating an inability or failure to sense ischemic damage or stress on the heart. This review examines the clinical characteristics of silent myocardial ischemia, and explores mechanisms involved in the generation of angina pectoris. Possible mechanisms for the more common manifestation of injurious reductions in coronary flow; namely, silent ischemia, are also explored. A new theory for the mechanism of silent ischemia is proposed. Finally, the prognostic importance of silent ischemia and potential future directions for research are discussed.

Comparison of controlled-onset, extended-release verapamil with amlodipine and amlodipine plus atenolol on exercise performance and ambulatory ischemia in patients with chronic stable angina pectoris

This multicenter, randomized, double-blind, parallel group, placebo lead-in, placebo-controlled study compared the antianginal and anti-ischemic effects of once-daily bedtime dosing of controlled-onset extended-release (COER-24) verapamil to a once-daily morning dosing of amlodipine +/- atenolol in patients with chronic stable angina. A total of 551 patients with exercise-induced myocardial ischemia and evidence of coronary artery disease were randomized to a 4-week, forced-dose titration treatment period with (1) COER-24 verapamil 240 mg titrated to 480 mg at bedtime (n = 173), (2) amlodipine 5 mg titrated to 10 mg/day (n = 149), (3) amlodipine 5 mg (titrated to 10 mg) plus atenolol 50 mg/day in the A.M. (n = 154), or (4) placebo (n = 75). Treadmill exercise tolerance testing (standard Bruce protocol), and 48-hour ambulatory electrocardiographic (Holter) monitoring were performed at the end of placebo lead-in and double-blind treatment. Each active treatment significantly improved symptom-limited exercise duration and time to moderate angina (p < or = 0.01 vs placebo). For patients with baseline ischemia, amlodipine resulted in a statistically significant increase in total duration of ischemic episodes compared with placebo, whereas COER-24 verapamil and amlodipine plus atenolol resulted in statistically significant decreases compared with placebo and amlodipine. Heart rate at onset of ischemic episodes and ST product were also significantly increased with amlodipine (p < 0.05) compared with either COER-24 or amlodipine plus atenolol. COER-24 and amlodipine alone or in combination with atenolol improved exercise capacity in patients with angina pectoris. COER-24 verapamil monotherapy or amlodipine plus atenolol combination therapy were more effective than amlodipine monotherapy in decreasing ambulatory myocardial ischemia, especially during the hours of 6 A.M. to 12 noon.

Mibefradil in the treatment of chronic stable angina pectoris: comparative studies with other calcium antagonists

The ability of mibefradil, a new T-channel-selective calcium antagonist, to improve exercise tolerance and silent ischemic parameters in patients with chronic stable angina was compared in 3 separate trials with 2 other commonly used calcium antagonists: diltiazem SR (120 mg/twice daily) and amlodipine (10 mg/day). Compared with amlodipine, mibefradil 100 mg given once daily over a 3-week period resulted in a statistically significantly larger increase from baseline in total exercise tolerance test (ETT) duration (treatment difference of 40.9 sec, p = 0.04), time to onset of angina (treatment difference 61.2 sec, p < 0.001), and time to onset of ischemia (treatment difference of 54.4 sec, p = 0.004). The decrease in weekly anginal episodes was 58% with mibefradil versus 19% with amlodipine, and the reduction in nitroglycerin consumption was 58% with mibefradil versus a 10% increase with amlodipine. The decrease in the number of silent ischemic episodes detected by a 48-hour Holter recording was significantly larger (p = 0.03) with mibefradil 100 mg (88%) compared with amlodipine 10 mg (38%). Similarly, a larger decrease in the duration of silent ischemia was observed with mibefradil (69%) compared with that seen with amlodipine (38%). The preliminary results of a second trial comparing mibefradil with amlodipine were consistent with the first demonstrating that the improvement for all 3 ETT parameters was larger for mibefradil (ETT duration: 55.2 sec; delay in onset angina: 74.2 sec; time to onset of ischemia: 63.6 sec), but in this trial the treatment differences did not reach statistical significance. In the trial comparing mibefradil (100 mg once daily) with diltiazem SR (120 mg twice daily), both compounds had equivalent effects on all ETT parameters tested. Mibefradil produced a 21% increase in exercise duration compared with a 20% increase with diltiazem. Although mibefradil yielded larger increases in the time to onset of angina and the time to onset of 1-mm ST-segment depression (42% and 38%, respectively) than did diltiazem (34% and 25%, respectively), the treatment differences did not reach statistical significance. Both mibefradil and diltiazem SR were associated with at least a 70% reduction from baseline in anginal frequency and nitroglycerin consumption. Mibefradil-treated patients showed greater decreases in heart rate and the rate-pressure product at each stage of the ETT than patients treated with amlodipine or diltiazem SR. All 3 drugs were well tolerated. However, compared with mibefradil, amlodipine and diltiazem SR produced a higher incidence of leg edema. In conclusion, the effectiveness of mibefradil in improving all 3 ETT parameters was greater than that of amlodipine and equivalent to that of diltiazem SR. Moreover, mibefradil provided greater reductions in the heart rate and cardiac workload than did the other 2 drugs.

Silent myocardial ischemia: pathophysiology and perioperative management

Silent ischemia has been called the silent killer. Pain does not kill patients with coronary heart disease--ischemia does, whether it happens to be painful or silent. An increased awareness of this still puzzling phenomenon may be of great importance in the pre- and perioperative management of patients with coronary heart disease, and improved detection and management of silent ischemia are likely to reduce the risk of perioperative cardiac events.

Attenuation of the circadian patterns of myocardial ischemia with nifedipine GITS in patients with chronic stable angina

The Nifedipine Gastro-Intestinal Therapeutic System (GITS) Circadian Anti-ischemia Program (N-CAP) was designed to test the effect of nifedipine GITS as monotherapy or in combination with a beta-adrenergic blocking agent on the circadian pattern of angina and silent ischemia in patients with chronic stable angina. At 118 sites in the United States, 1,174 patients were screened for entry into this study. To be eligible for participation patients were required to have at least two episodes of angina a week and at least two episodes of myocardial ischemia during 48-h ambulatory electrocardiographic (ECG) monitoring during the baseline placebo period. A total of 207 patients completed all phases of the study. Beta-blockers were continued in those patients already receiving them. In this 7- to 10-week single-blind placebo withdrawal study, a 1-week placebo run-in was followed by up to 5 weeks of single-blind titration with nifedipine GITS, a 4-week efficacy phase with an established dose and a final single-blind 2-week placebo withdrawal period. Ambulatory ECG monitoring was performed at the end of each placebo phase and at the end of the efficacy phase with a digital monitoring device that was validated in a pilot study. Overall, nifedipine GITS significantly reduced the weekly number of anginal episodes from 5.7 to 1.8 (p = 0.0001) and the number of ischemic events from 7.3 to 4 (p = 0.0001) reported during the 48-h monitoring periods, with a significant increase in both during the placebo withdrawal period. The baseline circadian pattern of ischemia showed an early morning peak and a secondary peak in the afternoon. Nifedipine GITS significantly reduced ischemia during the 48-h period when administered as monotherapy or in combination with a beta-blocker. Patients were also randomized to receive nifedipine GITS in either a morning or an evening dose. The two regimens resulted in equal anti-ischemic benefit. The primary side effect of nifedipine GITS was edema, which was dose related. In summary, nifedipine GITS reduced the number of anginal and ischemic episodes when given alone or in combination with a beta-blocker. Nifedipine GITS had a sustained effect: a single daily dose was effective over 24 h regardless of whether it was administered in the morning or evening. This study also suggests that combination therapy with nifedipine GITS and a beta-blocker is especially efficacious in reducing ischemia.

Silent myocardial ischemia after acute myocardial infarction

Silent ischemia after myocardial infarction has definite prognostic significance but should be interpreted within the context of other prognostic indicators. The rationale for therapeutic intervention is based on the prognostic implications of silent ischemia and the potentially deleterious effect of repeated episodes of ischemia on the integrity of the left ventricle. We measured parameters of ischemia in 20 patients who showed asymptomatic ischemic ST-T changes on exercise testing in the early phase after myocardial infarction. After diltiazem administration, a reduction of exercise-induced ST-T depression from 2.3 +/- 0.8 to 0.7 +/- 0.6 mm (p less than 0.01) occurred, and regional wall-motion score at exercise, determined by radionuclide angiography, improved significantly (p less than 0.02). These and other observations warrant further studies in which the duration, severity and frequency of the ischemic episodes should be quantified and correlated with prognosis after myocardial infarction.

Relations between heart rate, ischemia, and drug therapy during daily life in patients with coronary artery disease

BACKGROUND

Previous studies have shown that little if any increase in heart rate occurs 1 minute before the onset of ischemia in ambulant patients with coronary artery disease. This study tested the hypothesis that there are characteristic relations between heart rate and ischemia in ambulant patients with coronary artery disease.

METHODS AND RESULTS

Twenty-one patients with proven coronary disease demonstrated 212 episodes of ischemia during 504 hours of continuous monitoring of the electrocardiogram. An important increase in heart rate (from 74 +/- 11 to 90 +/- 14 beats/min, p less than 0.001) occurred between 5 and 30 minutes (not 1 minute) before the onset of ischemia. A significantly higher heart rate at onset of ischemia was seen during Bruce protocol exercise testing than during daily life (117 +/- 12 versus 95 +/- 15 beats/min, p less than 0.01). However, when a less-strenuous, but more prolonged, exercise protocol was used in a subgroup of patients (n = 12), ischemia occurred at a heart rate that was significantly lower than during the Bruce protocol (88 +/- 14 versus 103 +/- 15 beats/min, p less than 0.05) and was not significantly different from the threshold heart rate at onset of ischemia during daily life (88 +/- 14 versus 84 +/- 12 beats/min, p = NS). As part of two placebo-controlled trials, treatment with both propranolol and nitroglycerin altered the distribution of ischemic events by heart rate but in opposite directions. Although propranolol largely eliminated events occurring at high (greater than 100 beats/min) and moderate (80-100 beats/min) heart rates, the number of events at low (less than 80 beats/min) heart rates was increased. In contrast, nitroglycerin reduced episodes at low and moderate heart rates only.

CONCLUSIONS

Important increases in heart rate occur before the onset of ischemia during daily life, but this increase occurs much earlier than has been reported. Duration of heart rate increase appears to influence the heart rate threshold for ischemia, and this may contribute to the occurrence of ischemia at lower heart rates during daily life than during standard exercise testing. Last, different classes of drugs appear to have characteristic effects on ischemia occurring at different heart rates that may be useful in planning therapy.

Effect of nifedipine on total ischemic activity and circadian distribution of myocardial ischemic episodes in angina pectoris

A randomized, double-blind, crossover study was conducted in 10 patients to assess the effect of nifedipine versus placebo on total ischemic activity and circadian distribution of ischemic episodes. After baseline exercise treadmill testing and 48-hour ambulatory electrocardiographic ST-segment monitoring, patients received either nifedipine (mean dose, 80 mg/day) or placebo administered 4 times per day, with the initial dose taken immediately upon arising in the morning. Patients were maintained on a stable dose of each study drug for 7 days, after which they underwent repeat exercise treadmill testing and 48-hour ambulatory electrocardiography. During exercise treadmill testing, greater exercise duration was achieved by patients receiving nifedipine than by those receiving placebo (421 +/- 121 vs 353 +/- 155 seconds, respectively; p less than 0.05). Time to greater than or equal to 1 mm ST depression was significantly greater with nifedipine (282 +/- 146 seconds) than at baseline (130 +/- 72 seconds, p less than 0.003) and with placebo (150 +/- 98 seconds, p less than 0.0005). During ambulatory electrocardiographic monitoring, nifedipine reduced both the total number of ischemic episodes (18 vs 54 at baseline and 63 with placebo; p less than 0.02 for both) and the total duration of ischemia (260 vs 874 at baseline and 927 minutes with placebo; p less than 0.02 for both). The surge of ischemia between 06:00 and 12:00 noted at baseline and during placebo therapy was nearly abolished during nifedipine treatment. Nifedipine at this dosage, administered in this manner, is effective in reducing total ischemic activity and may prevent morning surges of ischemic episodes.

Characteristics of silent and painful ischaemia during ambulatory monitoring in patients with coronary arterial disease

We compared the characteristics of silent and painful ischaemia during ambulatory ST segment monitoring in 288 patients with documented coronary arterial disease and stable angina. During 12,436 hours of monitoring, 890 ischaemic episodes were recorded, of which 652 (73%) were silent. Silent and painful ischaemic episodes were similar in terms of heart rate at onset of ischaemia, increase in heart rate prior to ischaemia, duration of ischaemia, and percentage of episodes not preceded by an increase in heart rate. Change in the mean maximal ST segment was greater during painful ischaemic episodes (P less than 0.01). Silent ischaemia is characteristically painful ischaemia without the pain.

Rationale for treatment of silent myocardial ischemia: focus on nifedipine

The realization that the majority of ischemic episodes in ambulatory patients with coronary artery disease are not associated with angina has raised important questions regarding the medical management of such individuals. Data from studies utilizing ambulatory Holter monitoring of the ST segment suggest that ischemia is likely to be due to a combination of a modest rise in myocardial oxygen demand and a concomitant decrease in coronary perfusion. Patients with ambulatory ischemia may have a poorer survival than those without ischemia during daily activities. This paper will address the potential impact these new findings could have on treatment. A growing body of knowledge regarding the use of nifedipine for silent ischemia will be examined. Enthusiasm to make abolition of ischemia an end point of therapy in patients with coronary artery disease will necessitate a reexamination of drugs that have been assessed largely on their ability to provide symptomatic relief.

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.

Ischemia in the ambulatory setting--the total ischemic burden: relation to exercise testing and investigative and therapeutic implications

To establish the relation between treadmill exercise testing and ambulatory St segment monitoring in the detection of ischemia in patients with coronary artery disease, and to assess whether standard medical therapy affects any such relation, 277 patients with stable angina and angiographically documented coronary artery disease were studied with treadmill exercise testing and 48 h ambulatory ST segment monitoring. One hundred forty-six patients (52%) were studied while receiving no routine antianginal therapy, and 131 (48%) while receiving standard medical therapy. In 187 patients (67%) the exercise test was positive for ischemia. During 11,964 h of ambulatory monitoring, 881 episodes of ischemia (645 [73%] silent) were recorded, of which 809 (92%) occurred in patients with a positive exercise test. The mean heart rate at the onset of ischemic episodes during ambulatory monitoring was significantly less than that at the onset of 1 mm ST segment depression during exercise testing (94.5 versus 105.9 beats/min, p less than 0.0001). However, the frequency of ambulatory ischemic episodes was strongly related to a positive exercise test (p less than 0.001), and this relation was similar for both silent and painful ischemia (p less than 0.0001 for both) and in patients who were and were not receiving therapy (p less than 0.0001 for both). The total duration of ischemia was similarly related to a positive exercise test (p less than 0.0001). Only one patient with a negative exercise test had frequent (greater than 5/day) episodes of ischemia on ambulatory monitoring and had documented coronary artery spasm. Thus, exercise testing identifies the majority of patients likely to have significant ischemia during their daily activities.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of diltiazem on cardiac function in silent ischemia after myocardial infarction

In a total group of 56 patients with an acute myocardial infarction who were maximally exercised at predischarge, 20 patients (36%) showed greater than or equal to 1 mm asymptomatic ST-T segment depression during exercise. The site of the infarction was anterior in 12 patients and inferior in eight patients. All 20 patients underwent repeated exercise radionuclide angiography 2 days later, 2 hours following oral intake of 120 mg of diltiazem. Double product was not significantly different before and after diltiazem, both at rest and during exercise. Maximal ST-T depression after diltiazem was reduced from 2.3 +/- 0.8 to 0.7 +/- 0.6 mm (p less than 0.01). Left ventricular (LV) ejection fraction at rest before diltiazem was 54.4 +/- 8.7% and after diltiazem was 56.2 +/- 11.3% (p = NS). During exercise, LV ejection fraction improved after diltiazem from 43.2 +/- 12.2% to 49.8 +/- 10.5% (p less than 0.05). Regional wall motion score (1 = normal, 2 = hypokinetic, 3 = akinetic, 4 = dyskinetic) at rest before diltiazem was 9.6 +/- 2.0 and after diltiazem was 9.1 +/- 1.8 (p = NS). During exercise, regional wall motion score improved after diltiazem from 5.8 +/- 1.3 to 4.3 +/- 1.1 (p less than 0.02). We conclude that silent ischemia occurs in a substantial number of patients after myocardial infarction and that diltiazem has acute beneficial effects on asymptomatic ST-T depression and on global and regional LV function in post-infarction patients with silent ischemia.

Silent myocardial ischaemia in patients referred for coronary bypass surgery because of angina: a comparison with patients whose symptoms were well controlled on medical treatment

The frequency and characteristics of silent ischaemia were prospectively studied in 114 patients with confirmed coronary artery disease and angina. Fifty seven patients who had angina that was not adequately controlled by standard medications were referred for elective coronary artery bypass surgery (group 1). Fifty seven other patients had symptoms that were well controlled on medical treatment (group 2). Patients underwent treadmill exercise testing (n = 109) and 48 hours of ambulatory ST segment monitoring (total 5125 hours). Patients in group 1 had more severe coronary artery disease and a shorter time to 1 mm ST segment depression and maximal exercise. Twenty two patients in group 1 (38%) and 16 in group 2 (28%) had greater than or equal to 1 episode of silent ischaemia during 48 hours of ST monitoring. There was no significant difference in the mean frequency of silent ischaemic episodes in 24 hours between the two groups (group 1 0.72 v group 2 0.64); however, the mean frequency of painful ischaemic episodes in 24 hours was greater in group 1 patients (0.51) than in group 2 (0.11). In both groups the frequency of silent ischaemia was significantly related to a positive exercise test, as was the total duration of silent ischaemia. The circadian variation of silent ischaemia showed a peak of episodes in the evening in both groups. The frequency of silent ischaemia in patients with coronary artery disease and angina receiving standard antianginal medications was not related to the severity of symptoms, but was significantly related to a positive exercise test. Thirty three percent of the patients studied had evidence of silent ischaemia during 48 hours of ambulatory ST segment monitoring; however, only four patients (3.5%) had frequent (>/=5) daily episodes of silent ischaemia.

The Nifedipine-Total Ischemia Awareness Program: a national survey of painful and painless myocardial ischemia including results of antiischemic therapy

The Nifedipine-Total Ischemia Awareness Program was designed to evaluate the prevalence, prognostic implications and effect of therapy on painful and painless myocardial ischemic episodes in a nationwide study of patients with angina pectoris. Three hundred forty-eight patients with at least 2 anginal attacks/week while taking antianginal medications were enrolled at 53 participating centers between September 1, 1986 and March 31, 1988; 312 of the 348 patients formed the study group, while 36 patients formed the control group. At least 1 episode of ST-segment depression during two 48-hour periods of Holter monitoring was present in 136 of the 312 patients in the study group. In these 136 patients, there was a total of 372 episodes of ST-segment depression, of which only 69 (18%) were painful; 85% of the 136 patients had either painless episodes only or both painless and painful episodes. Despite apparently adequate antianginal therapy, 48 patients had greater than or equal to 3 episodes of ST-segment depression/48 hours of ambulatory electrocardiographic monitoring, and 38 patients greater than 60 minutes of ST-segment depression. After nifedipine was administered, there was a 23% reduction in the mean number of episodes of ST-segment depression (2.7 +/- 0.3 to 2.1 +/- 0.2, p less than 0.01). The most pronounced effects were found in the 48 patients with greater than or equal to 3 episodes of ST-segment depression and the 38 patients with greater than or equal to 60 minutes of total ischemic time.(ABSTRACT TRUNCATED AT 250 WORDS)

Total ischemic burden. Implications for prognosis and therapy

Patients with silent myocardial ischemia can be classified as one of three clinical types: those who are totally asymptomatic (type 1), those who are asymptomatic after a myocardial infarction (type 2), and those who demonstrate both asymptomatic and symptomatic episodes (type 3). Total ischemic activity may be similar in any given patient, but the ratio of symptomatic to asymptomatic episodes will differ. Prognosis appears dependent on the degree of total ischemic activity plus the extent of coronary artery disease and left ventricular dysfunction. The effects of therapy can be monitored with exercise testing and/or Holter monitoring. Using the latter technique, the largest multicenter study to date, the Nifedipine Total Ischemia Awareness Program, has demonstrated the advantages of adding a calcium antagonist to nitrate and/or beta-blocker therapy regimens in order to maximize the reduction in total ischemic activity in angina patients.

Silent myocardial ischaemia in chronic stable angina: a study of its frequency and characteristics in 150 patients

One hundred and fifty unselected patients with documented coronary artery disease were studied to establish the frequency and characteristics of silent myocardial ischaemia. Patients underwent ambulatory ST segment monitoring off all routine antianginal treatment (total 6264 hours) and exercise testing (n = 146). Ninety one patients (61%) had a total of 598 episodes of significant ST segment change, of which 446 (75%) were asymptomatic. Twenty seven patients (18%) had only painless episodes; 14 (9%) patients only painful episodes; 50 patients (33%) had both painless and painful episodes. The mean number of ST segment changes per day was 2.58 (1.95 silent); however, 11 patients (7%) had 50% of all silent episodes, and 48 patients (32%) had 91% of all silent episodes. Fifty nine patients (39%) had no ST segment changes on ambulatory monitoring, and 73 patients (49%) had no evidence of silent ischaemia. Episodes of silent ischaemia occurred with a similar circadian distribution to that of painful ischaemia, predominantly between 0730 and 1930. There was a similar mean rise in heart rate at the onset of both silent and painful episodes of ischaemia. Silent ischaemia was significantly more frequent in patients with three vessel disease than in those with single vessel disease, and was also significantly related to both time to 1 mm ST depression and maximal exercise duration on exercise testing. There was a highly significant relation between the mean number and duration of episodes of silent ischaemia in patients with positive exercise tests when compared with those with negative tests. No episode of ventricular tachycardia was recorded in association with silent ischaemic change.

Comparison of coronary artery bypass surgery and medical therapy in patients with exercised-induced silent myocardial ischemia: a report from the Coronary Artery Surgery Study (CASS) registry

To determine whether coronary artery bypass surgery would prolong survival in patients with silent myocardial ischemia during exercise testing, the data on 692 such patients from the Coronary Artery Surgery Study (CASS) registry were analyzed. The patients were followed up for up to 7 years after medical (n = 424) or surgical (n = 268) therapy. Stratification of patients into subsets was based on the results of cardiac catheterization. Surgical benefit was greatest in the patients with three vessel coronary artery disease or abnormal left ventricular function. Among the 75 patients with three vessel coronary disease and left ventricular dysfunction, the 7 year survival rate was 37% for the medical group and 90% for the surgical group (p less than 0.0001). Thus, among patients with silent myocardial ischemia during exercise testing in this nonrandomized study, survival appeared to be enhanced by coronary artery bypass surgery in subsets of patients with severe coronary artery disease and abnormal left ventricular function.

Diltiazem, nifedipine, and their combination in patients with stable angina pectoris: effects on angina, exercise tolerance, and the ambulatory electrocardiographic ST segment

The efficacy and safety of oral nifedipine and diltiazem were compared in 20 patients with stable angina pectoris with use of a placebo run-in, randomized, double-blind titration to maximal effect crossover protocol. The effects of treatment withdrawal were also analyzed. All patients received placebo for 2 weeks and were then randomly assigned to receive either diltiazem or nifedipine. A 2 week drug titration phase in which patients received either diltiazem (180 to 360 mg/day) or nifedipine (30 to 120 mg/day) in three divided doses was followed by a 1 week maintenance phase. Patients then received placebo for 1 to 2 weeks, followed by crossover to the other treatment regimen and a second placebo washout period of 1 week. Patients (n = 13) who remained symptomatic on both diltiazem and nifedipine during the monotherapy periods entered a 3 week combination treatment phase, followed by a final 1 week placebo washout period. Frequency of angina, nitroglycerin consumption, exercise tolerance (Naughton protocol), and frequency of daily episodes of ST segment deviations on the electrocardiogram (1 mm of ST segment depression persisting for at least 1 min with and without chest pain) on an ambulatory electrocardiographic monitor were assessed during the baseline placebo, active monotherapy, placebo withdrawal, and combination treatment phases. Plasma drug levels were also measured. Compared with initial placebo values, the frequency of angina and the amount of nitroglycerin treatment were reduced by both diltiazem (p less than .001) and nifedipine (p less than .02). Diltiazem was more effective than nifedipine in reducing angina (p less than .02). Exercise duration increased with both drugs (p less than .0001). Diltiazem was significantly better than nifedipine in reducing the episodes of ST segment depression on the ambulatory monitor (p less than .01). Diltiazem reduced the resting heart rate (p less than .01); both drugs reduced the resting blood pressure and rate-pressure product. Overall, combination therapy was more effective in patients who did not maximally respond to diltiazem or nifedipine alone with respect to anginal and exercise variables and in reducing blood pressure at rest and during exercise. Plasma drug levels could not predict an individual patient's treatment response. Diltiazem may increase nifedipine drug levels when the drugs are combined. Fewer side effects were observed with diltiazem than nifedipine; the most side effects were seen with combination treatment. There were no apparent withdrawal effects observed with either treatment regimen.(ABSTRACT TRUNCATED AT 400 WORDS)