Dissociation of exercise tolerance and total myocardial ischemic burden in chronic stable angina pectoris

Atherosclerotic vascular disease: management of angina in the office setting

A discussion of primary care issues related to the management of angina in the office setting is warranted because of recent developments. These developments include new pharmacotherapies, recent insights into the pathophysiology of angina, and increased recognition of the role of the diseased endothelium in sequelae of coronary artery disease.

Tenuous link between ischaemic threshold and both ambulatory ischaemia and symptom status over time in stable angina: a 5-year follow-up study

This study evaluates changes in ischaemic threshold over a 5-year period in patients with stable angina pectoris, who did not suffer any intervening cardiac event. Changes in ischaemic threshold are related to alterations in symptomatic status and ambulatory ischaemia. Over long-term follow-up, there is a significant fall in ischaemic threshold in such patients (mean heart rate at onset of ischaemia fell from 104 +/- 17.8 to 97 +/- 17.4 bpm: P < 0.001), but this is not matched by a worsening of either symptoms or ischaemia during daily life. In the 68% of patients that had a reduction in ischaemic threshold of > or = 5 bpm, 68% had either definite reduction or no change in symptoms and 84% had either reduction, abolition or no change in transient ischaemic activity. The dissociation between ischaemic threshold, ambulatory ischaemia and symptoms has implications for long-term monitoring and management of the patient with stable angina.

Intermittent or continuous transdermal nitroglycerin: still an issue, or is the case closed?

After a decade of controversy and debate, many experts have now concluded that continuous nitroglycerin patch treatment leads to complete tolerance development and therefore cannot be recommended for any angina patient. This conclusion is largely based on the disappointing results of the large Transdermal Nitroglycerin Cooperative Study, in which continuous patch treatment in doses of 15-105 mg daily failed to increase exercise duration more than placebo after 2 and 8 weeks of treatment. However, other well-designed studies recently reported maintained efficacy during continuous treatment, and the differences in results has remained unexplained. The disagreeing data may be better understood if certain facts are considered: (1) The cooperative study tested a patient population with a very low first-dose treatment response--only 34 seconds (or 10-12%) improvement compared with placebo. At the end of the study, 25% of the patients terminated exercise for reasons other than angina, and a reduced nitrate responsiveness had developed, even in the placebo group. (2) Patients who demonstrate a large first-dose nitrate responsiveness tend to be less susceptible to tolerance development. (3) Even during continuous therapy, maintained efficacy is often observed in exercise tests done 2-5 hours after patch renewal, while typically no effect is seen at the end of the application period. Attenuation of the initial effects is seen with all long-acting nitrate treatment regimens, but the degree of tolerance varies with the patient population, the efficacy parameter (exercise test vs. attack counts), the timing of the efficacy test, the patch dose, and whether or not nitrate-free (-low) intervals are used. In general, intermittent patch therapy is superior to continuous therapy in improving exercise duration, but even continuous therapy may retain some effect. Rebound phenomena do occur but are clinically relevant only in a minority of the patients. Rebound phenomena are not a problem during continuous therapy, which therefore may be of value in patients with frequent and/or nocturnal angina attacks. Patients experiencing angina during exercise only and with low first-dose effects are likely to benefit more from intermittent therapy. Doses of 0.6-0.8 mg/hr (15-20 mg/24 hr) are usually optimal, and the efficacy is comparable with that observed after oral nitrates.

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.

Ointments and transdermal nitroglycerin patches for stable angina pectoris

Nitroglycerin (NTG) ointment is used for the prophylaxis against angina pectoris, but there are no data to support its effectiveness during long-term therapy. Continuous, once-daily application of isosorbide dinitrate cream produces tolerance with complete loss of efficacy within 1 week. Nitroglycerin patches are very popular and continuous once-daily application is still claimed by some investigators to provide 24 hour antiischemic and antianginal efficacy. This claim is based on data from postmarketing studies in a very large number of patients and placebo-controlled studies in smaller groups of patients from Italy, Yugoslavia, Greece, and Germany. In contrast, studies from the United States, Canada, England, and some centers in Germany have failed to show superiority of patches over placebo during continuous therapy. This controversy was addressed by the NTG cooperative study group, in which a total of 562 patients who were responders to sublingual nitroglycerin were studied. Patients received either placebo or NTG patches delivering low (15-30 mg/24 hr), moderate (45-60 mg/24 hr), or large (75 and 105 mg/24 hr) amounts of NTG. Four hours after the initial application, NTG patches increased exercise duration compared to placebo, but this beneficial effect had disappeared by 24 hours. Furthermore, after 8 weeks of continuous therapy, none of the NTG patches were superior to placebo, whether patients were or were not taking concomitant beta-blockers. Therefore, current opinion is that continuous therapy with NTG patches produces pharmacologic tolerance and is ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of continuous intravenous infusion of isosorbide dinitrate on development of tolerance to vasodilating action in human epicardial coronary arteries

This study was performed to determine the effects of long-term intravenous infusion on the coronary vasodilating actions of continuous intravenous and bolus intracoronary administration of isosorbide dinitrate (ISDN). With quantitative coronary angiography, the coronary diameter and the vasodilating response to intracoronary ISDN (1 mg) at angiographically normal segments were studied before and after intravenous administration of ISDN, 10 to 60 micrograms/min for 1 hour, 2 days, or 5 days. The vasodilating effects of intravenous ISDN were 72% +/- 13%, 65% +/- 21%, and 6% +/- 11% of the response to intracoronary ISDN in the baseline study in each group. Irrespective of the duration of intravenous infusion, subsequent intracoronary ISDN dilated coronary arteries to extent similar to that observed in each baseline study. In conclusion, significant coronary vasodilating effects of intravenous ISDN were observed after a 2-day infusion, whereas tolerance to the vasodilating effects apparently developed within 5 days of infusion. The vasodilating response to bolus intracoronary ISDN was preserved even when the vasodilating effects of intravenous ISDN were no longer present.

Phenomenon of nitrate tolerance

The phenomenon of nitrate tolerance has now been appreciated for almost a century, and our understanding of this process has greatly improved during the past 20 years. Therapeutic nitrates are now recognized as exogenous sources of nitric oxide (or nitrosothiols), which appears to be a primary mediator of natural vasodilatation. Nitrates have been clearly shown to have vasodilatory and antiplatelet effects, both of which diminish during continuous exposure. Nitrate tolerance has been documented with most nitrate preparations when the patient is given continuous nitrate therapy. Tolerance to nitrates may occur in any patient, regardless of underlying illness, medication dose, or serum concentration of NTG. The cause of this phenomenon is multifactorial; there appear to be both cellular and systemic processes involved. To date, no adjuvant pharmacologic intervention has conclusively demonstrated benefit in preventing, abating, or reversing nitrate tolerance. Interruption of nitrate exposure for as little as 8 to 12 hours does appear to be the best means of preventing or reversing tolerance. Nevertheless, some patients with objective tolerance continue to experience relief of symptoms. In addition, despite laboratory-documented cross-tolerance, patients receiving continuous nitrate therapy at usual clinical doses may continue to benefit from the hemodynamic and antianginal effects of SL NTG. Hence, nitrate tolerance is a real entity, but the clinical importance of this phenomenon remains controversial. Finally, further investigation will need to address quality-of-life issues and perhaps assess relief of ischemia by other means.

Effects of bepridil on silent myocardial ischemia and eicosanoid metabolism in chronic stable angina pectoris after healing of myocardial infarction

To investigate the effects of bepridil on silent myocardial ischemia and on eicosanoid metabolism, 10 patients with chronic stable angina underwent exercise treadmill testing and 48-hour ambulatory electrocardiographic monitoring both before and after 4 weeks of bepridil administration (150 mg/day). Fasting venous levels of thromboxane B2, 6-keto-prostaglandin F1 alpha, and leukotriene C4 were measured by radioimmunoassay. Bepridil decreased heart rate responses to daily activities during ambulatory monitoring, and significantly (p < 0.05) reduced the median frequency and duration of silent myocardial ischemic episodes (from 5.5 to 0 events/48 hours and from 86 to 0 minutes/48 hours respectively). Bepridil significantly decreased the blood pressure heart rate product at peak exercise and significantly prolonged the mean exercise tolerance time (from 456.6 to 527.0 second). Bepridil also significantly decreased the plasma levels of thromboxane B2 and leukotriene C4 at rest. These results suggest that bepridil may reduce silent myocardial ischemic episodes either by the reduction of cardiac oxygen demand during daily activities and exercise stress, or by controlling coronary and systemic vasomotor tone. The drug also has a salutary effect on eicosanoid metabolism, to which its efficacy on silent myocardial ischemic episodes may be related.

Angiotensin converting enzyme inhibition in chronic stable angina: effects on myocardial ischaemia and comparison with nifedipine

OBJECTIVES

To determine the anti-ischaemic effects of a new angiotensin converting enzyme inhibitor, benazepril, compared with nifedipine, alone and in combination, in chronic stable angina caused by coronary artery disease.

DESIGN

Placebo controlled, double blind, latin square design.

SETTING

Regional cardiology service for a mixed urban and rural population.

SUBJECTS

40 patients with stable exertional angina producing at least 1 mm ST segment depression on exercise test with the Bruce protocol. 34 patients completed all four phases of the trial.

INTERVENTIONS

Each patient was treated with placebo, benazepril (10 mg twice daily), nifedipine retard (20 mg twice daily), and a combination of benazepril and nifedipine in the same doses, in random order for periods of two weeks.

MAIN OUTCOME MEASURES AND RESULTS

Total duration of exercise was not increased by any treatment. Exercise time to the development of 1 mm ST segment depression was not significantly changed with benazepril alone or in combination with nifedipine but was increased with nifedipine from 4.18 (1.8) min to 4.99 (1.6) min (95% confidence interval (95% CI) 0.28 to 1.34; p < 0.05). There was a significant relation between increase in duration of exercise and resting renin concentration (r = 0.498; p < 0.01). Myocardial ischaemia during daily activity, as assessed by ambulatory electrocardiographic monitoring, was reduced by benazepril and by the benazepril and nifedipine combination. This was significant for total ischaemic burden (451(628) min v 231(408) min; 95% CI -398 to -41 min; p < 0.05) and maximal depth of ST segment depression (-2.47(1.2) mm v -2.16 mm; 95% CI 0.04 to 0.57; p < 0.05) for the combination and for maximal ST segment depth for benazepril monotherapy (-2.47 (1.2) mm v -1.96(1.2) mm; 95% CI 0.18 to 0.91; p < 0.05). Benazepril significantly altered the circadian rhythm of cardiac ischaemia, abolishing the peak ischaemic periods at 0700 to 1200 and 1700 to 2300 (p < 0.05).

CONCLUSIONS

Benazepril, an angiotensin converting enzyme inhibitor, had a modest anti-ischaemic effect in effort angina, but this effect was not as pronounced as with nifedipine. The anti-ischaemic action was more noticeable in asymptomatic ischaemia during daily activity, whereas nifedipine had little effect on this aspect of myocardial ischaemia. The combination of benazepril and nifedipine reduced ischaemia of daily activity.

Discordance between effects of anti-ischemic therapy on ambulatory ischemia, exercise performance and anginal symptoms in patients with stable angina pectoris. The Angina and Silent Ischemia Study Group (ASIS)

OBJECTIVES

We sought to define the extent to which the therapeutic efficacy of three single-drug regimens on ambulatory ischemia paralleled efficacy on other clinical manifestations of ischemia, specifically exercise test performance and anginal symptoms.

BACKGROUND

Some studies have shown that the presence and severity of ambulatory ischemia are predictive of anginal symptoms and exercise test performance, whereas other studies have not. Less is known about effects of antianginal treatment and whether response to therapy for one clinical manifestation reflects therapeutic responses for other clinical manifestations.

METHODS

We studied 50 patients in the Angina and Silent Ischemia Study who had documented coronary disease, an exercise test positive for ischemia, the presence of ambulatory and asymptomatic ischemia on ambulatory electrocardiographic (ECG) Holter monitoring and stable anginal symptoms. Patients received maximally tolerated doses of sustained release propranolol (mean 293 mg/day), sustained release diltiazem (mean 350 mg/day), nifedipine (mean 79 mg/day) and placebo, each for 2-week periods in a double-blind, crossover fashion. Patients' responses to treatment were assessed by 48-h ambulatory ECG monitoring, exercise test (standard Bruce protocol) and diaries of angina. Levels of efficacy for each agent and for each clinical measure were compared using Spearman correlation analysis.

RESULTS

With placebo there was no correlation among the frequency of ischemic episodes by ambulatory ECG monitoring, exercise time to 1.0-mm ST segment depression or frequency of anginal episodes. Furthermore, for a given patient the efficacy of each active medication in reducing ambulatory ischemia was not correlated with response in anginal symptoms or exercise test performance (r = -0.21 to 0.24, p = NS). Within each of these clinical measures, efficacy of one drug was more strongly correlated with efficacy of another drug (r = 0.64 to 0.81 for ambulatory ischemia, 0.48 to 0.56 for exercise test performance and 0.16 to 0.54 for anginal symptoms).

CONCLUSIONS

Different measures of ischemia, specifically ambulatory ischemia assessed by ambulatory ECG monitoring, exercise performance on exercise test and anginal symptoms, are independent. Efficacy for each clinical end point must be assessed separately when considering response to drug treatment.

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.

Transdermal nitroglycerin reduces the frequency of anginal attacks but fails to prevent silent ischemia

OBJECTIVES

The aim of this study was to objectively evaluate the effects of intermittent administration of transdermal nitroglycerin on effort tolerance, frequency of anginal attacks and presence of silent ischemic events that occur during normal daily activities.

BACKGROUND

Previous studies have shown that transdermal nitroglycerin patches reduce the incidence of anginal attacks and improve exercise capacity when given intermittently. However, no carefully controlled studies are available on the effects of these preparations (and their dosing schedule) on the occurrence of "silent" ischemic events during unrestricted daily activities.

METHODS

Twelve men with chronic stable angina, a positive exercise test result and significant coronary artery disease completed a randomized, double-blind, placebo-controlled trial in which patches were worn either continuously or with overnight (8 h) removal. The effects of treatment were objectively assessed by both treadmill exercise testing and 24-h ambulatory electrocardiographic monitoring.

RESULTS

Only the intermittent dosing schedule afforded a small but significant improvement in exercise tolerance and prolonged exercise duration and time to ST segment depression. The frequency of anginal attacks was also reduced by both the continuous and intermittent treatment, but the effects on symptoms were not paralleled by a concomitant reduction in ischemic episodes recorded during ambulatory monitoring.

CONCLUSIONS

The results indicate that when used as monotherapy, intermittent transdermal nitroglycerin preparations lessen symptoms but are ineffective for the long-term prophylaxis of silent myocardial ischemia.

24-hour anti-ischaemic action with once daily nifedipine. Experience obtained with a fatty-alcohol matrix tablet in patients with coronary artery disease

The ability of a fatty-alcohol matrix, slow-release tablet of nifedipine 60 mg to maintain a 24-hour anti-ischaemic action in the fixed dose of 60 mg once daily has been investigated in a randomised, placebo-controlled, double-blind trial. 12 normotensive patients with angiographically proven coronary artery disease (stenosis of at least one major vessel > or = 70%) were studied. The anti-ischaemic response was assessed over a period of 4 days as changes in the exercise-induced ST-segment depression 6 h and 24 h post-dose, and ST-segment changes in 24-h ambulatory ECGs. A measurable anti-ischaemic response was observed in 8 of the 12 patients. Exercise-induced ST-segment depression 6 h after the administration of nifedipine was reduced by 30% compared to placebo, and there was still a measurable anti-ischaemic response 24-h post-dosing. Both responses were independent of changes in exercise blood pressure. In 7 patients with ischaemic episodes in the 24-h ECGs, nifedipine treatment had only a minor effect on the intensity and duration of ischaemia. It is concluded that a significant anti-ischaemic effect lasting 24 h could be demonstrated using effort-induced ST-segment changes in patients with angiographically proven coronary heart disease, who were treated once daily with nifedipine 60 mg as a fatty-alcohol slow release tablet.

The effect of transdermal nitroglycerin on exercise tolerance in relation to patch application time--a meta-analysis

Disagreeing results have been reported in the many studies on continuous treatment with nitroglycerin patches. The effects on exercise tolerance are partly studied at the end of a 24-hour application period, and partly examined only a few hours after patch renewal. The present meta-analysis estimates the overall efficacy of nitroglycerin patches in trials with and without concomitant antianginal therapy, and investigates if the treatment effect depends on the patch application time. A computed search (MEDLINE) identified 110 publications, of which 17 trials on nitrate patch monotherapy and six trials on combined therapy satisfied the inclusion criteria. Data on "exercise duration" and "ST-segment depression" were converted to a standardized treatment effect size d, and pooled to an overall treatment effect size d+. In tests 2-5 hours after patch renewal, moderate but significant effects of nitrate monotherapy were observed; d+ was 1.20 with regard to "ST-segment depression" and 0.39 with regard to "exercise duration" (both p < 0.0001). In contrast, 24 hours after patch application, the values for d+ were 0.09 (not significant) and 0.36 (p < 0.01), respectively. When adding the results from the six trials on combined therapy, d+ with regard to "exercise duration" was reduced to 0.28 (p < 0.0001) 2-5 hours after renewal and to 0.17 (p = 0.04) after 24 hours. Thus, the efficacy of continuous nitroglycerin patch treatment is moderate but evident during exercise tests 2-5 hours after patch renewal; however, it is reduced after 24 hours of patch application.

Effect of diltiazem on silent ischemic episodes, plasma bradykinin and prostaglandin metabolism

Plasma bradykinin and prostaglandin metabolism are related to the anginal pain modulating system in patients with ischemic heart disease. We carried out a placebo controlled single blind test of diltiazem (30 mg three times a day) in 15 patients with chronic stable angina. The effect of diltiazem was evaluated by exercise treadmill testing and 48-h ambulatory electrocardiographic monitoring. Plasma bradykinin, thromboxane B2, and 6-keto-prostaglandin F1 alpha levels were determined by radioimmunoassay prior to and during diltiazem therapy. Diltiazem significantly increased the exercise time and reduced episodes of angina. Diltiazem, however, did not appreciably improve either the frequency of silent myocardial ischemic episodes or the total duration of the silent myocardial ischemic episodes. Diltiazem also tended to decrease plasma bradykinin, thromboxane B2, and 6-keto-prostaglandin F1 alpha levels. When ischemic episodes on ambulatory electrocardiographic monitoring are categorized according to heart rate change at the onset of episode (type A, preceded by heart rate increase > or = 5 beats/min; type B, no preceding heart rate increase), diltiazem was only effective on type A ischemic episodes as well as on symptomatic ischemia. Further, bradykinin was significantly decreased by diltiazem only in patients with exercise-induced silent ischemia or no exercise-induced ischemia, while the thromboxane B2/6-keto-prostaglandin F1 alpha ratio was unaffected by the administration of diltiazem. Thus, silent and symptomatic ischemia may be associated with different bradykinin and prostaglandin responses.

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)

Use of nitrates in ischemic heart disease

The organic nitrates have remarkably diverse actions that are or should be beneficial in patients with ischemic heart disease. These drugs are effective in all the important ischemic syndromes. Preliminary data in patients with acute infarction suggest that the drugs may be truly cardioprotective, resulting in improved mortality. This review has not discussed the role of nitrates in congestive heart failure or LV dysfunction, a subject of great importance. The nitrates are useful adjunctive agents in these syndromes, and the two VeHfT trials support the concept that long-term nitrate administration, in conjunction with hydralazine, may favorably alter the natural history of heart failure. This cardioprotective effect is similar to that suggested for the post-MI patient. The data are not strong enough for definitive conclusions at this time. The clinical benefits of nitrates in decreasing subjective (angina) and objective indices of ischemia in stable and unstable angina, as well as limited data in asymptomatic myocardial ischemia, are unequivocal and are as favorable as those for beta blockers or calcium antagonists. Tolerance is an important problem that unfavorably influences the potential benefits of nitrate therapy. I believe that this problem can be avoided with well-designed dosing regimens. Current research into endothelial biology in health and disease has further supported a physiologic role for the organic nitrates in patients with ischemic heart disease. The nitrate-platelet story, while controversial, is promising and offers another positive rationale for nitrate administration. The concept of nitrates replenishing disordered EDRF release or action is an exciting one. Physicians should feel fortunate to have such a remarkable group of drugs available for their patients.