Usefulness of ambulatory silent myocardial ischemia added to the prognostic value of exercise test parameters in predicting risk of cardiac death in patients with stable angina pectoris and exercise-induced myocardial ischemia

[Long term electrocardiography (Holter monitoring)]

During the past almost 50 years Holter monitoring has become an established non-invasive diagnostic tool in clinical electrophysiology. It allows ECG recording independent of stationary monitoring facilities during daily life and, therefore, contains much information. In the beginning the main interest was directed towards quantitative and qualitative assessment of arrhythmias, their circadian behaviour, and the circadian behaviour of the heart rate. With advances in technology the analysis spectrum of Holter monitoring expanded, and it was used also for detection of silent myocardial ischaemia. New digital recorders and computers with large capacities made it possible to measure every single heart beat very accurately, which was a prerequisite for heart rate variability and QT-interval analysis, which provided new knowledge about the autonomic modulation of the heart rate and the circadian dynamicity of the QT interval, respectively. Beyond arrhythmia analysis Holter monitoring was increasingly used to assess prognosis in different cardiac conditions. It can also be valuable in assessing transient symptoms possibly related to arrhythmias or device dysfunction, which will not necessarily be revealed by simple device control.

Long-term continuous external electrocardiographic recording: a review

Ambulatory electrocardiographic (AECG) monitoring is an essential tool in the diagnostic evaluation of patients with cardiac arrhythmias. Recent advances in solid-state technology have improved the quality of the ECG signals and new dedicated algorithms have expanded the clinical application of software-based AECG analysis systems. These advances, in addition to the availability of inexpensive large storage capacities, and very long-term continuous high-quality AECG monitoring, have opened new potential uses for AECG. New digital recorders have the capability of multichannel simultaneous recordings (from 3 to 12 leads) and for telemetred signal transduction. These possibilities will expand the traditional uses of AECG for arrhythmia detection, as arrhythmia monitoring to assess drug and device efficacies has been further defined by new studies. The analysis of transient ST-segment deviation still remains controversial, but considerably more data are now available, especially about the prognostic value of detecting asymptomatic ischaemia. Heart rate variability analysis has shown promise for predicting mortality rates in cardiac patients at high risk. We review recent advances in this field of non-invasive cardiac testing.

Contemporary management of silent ischemia: the role of ambulatory monitoring

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

Gender significance of ST-segment deviation detected by ambulatory (Holter) monitoring

OBJECTIVE

To evaluate the gender influence in diagnostic and prognostic value of Holter-detected ST-segment deviation.

METHODS

Two-hundred seventy-seven consecutive patients (196 men) who underwent coronary angiography for evaluation of chest pain were studied with 24-h Holter monitoring within 72 h of coronary angiography, and were followed up for 65+/-21 months.

RESULTS

Men had a higher prevalence of coronary artery disease (169 of 196, 86%) compared to that of women (54 of 81, 67%), p<0.00025. Thirty-three (17%) men and 15 (19%) women had ST-segment deviation during 24-h recording. The sensitivity, specificity and positive predictive values of ST-segment deviation (elevation, depression, or both) for the detection of significant coronary artery disease were similar in men and women. The negative predictive values were significantly higher in women than men for ST-segment deviation (36% vs. 15%, p<0.001), ST-segment elevation (35% vs. 14%, p<0.001), and ST-segment depression (34% vs. 15%, p<0.001). Similarly, the diagnostic accuracies were significantly higher in women than men for ST-segment deviation (44% vs. 29%, p<0.025), ST-segment elevation (38% vs. 19%, p<0.001), and ST-segment depression (40% vs. 24%, p<0.025). There was no significant difference in composite end-point of events (mortality, nonfatal myocardial infarction, unstable angina, and coronary revascularization) in men versus women with ST-segment deviation (elevation, depression, or both).

CONCLUSION

Holter-detected ST-segment deviation has a higher negative predictive value and diagnostic accuracy for detection of significant coronary artery disease in women than in men, although the prognostic values are not significantly different between men and women.

Diagnostic and prognostic value of Holter-detected ST-segment deviation in unselected patients with chest pain referred for coronary angiography: a long-term follow-up analysis

OBJECTIVE

To evaluate the diagnostic and prognostic significance of ST-segment deviation detected by ambulatory Holter monitoring in unselected chest pain patients referred for coronary angiography.

METHODS

Two hundred seventy-seven patients (71% were men) who underwent coronary angiography for evaluation of chest pain were studied with 24-h ambulatory Holter monitoring within 72 h of angiography. A lumen diameter reduction of > or = 50% was considered coronary artery disease. The ST-segment deviation was defined as > or = 1-mm deviation from the baseline lasting > or = 1 min separated by a minimum of 1 min. The patients were followed up for 65 +/- 21 months (mean +/- SD) for occurrences of death, myocardial infarction, hospitalization for unstable angina, and need for revascularization.

RESULTS

Of the 277 patients, 223 (80%) had coronary artery disease. The prevalence of coronary artery disease was not significantly different in patients with (43 of 48 patients; 90%) and without (180 of 229 patients; 79%) Holter-detected ST-segment deviation. The diagnostic accuracy of Holter-detected ST-segment deviation in predicting the presence of coronary artery disease was poor (33%), with a sensitivity of 19% and a specificity of 91%. The presence of Holter-detected ST-segment deviation was not predictive of future cardiac events or death.

CONCLUSION

The ST-segment changes detected on ambulatory Holter monitoring are of limited value in identifying coronary artery disease and predicting the future adverse cardiac events or death in unselected patients with chest pain.

Treating ambulatory ischemia in coronary disease by manipulating the cell biology of atherosclerosis

Obstructive coronary artery disease is the most common cause of morbidity and mortality in the developed world. Our understanding of the pathobiology of coronary atherosclerosis provides us with new opportunities to reduce myocardial ischemia by interventions that address these mechanisms directly. These interventions include lipid-lowering therapies that improve local coronary vasomotion, inflammation, and the procoagulant state. These interventions have also been shown to result in important reductions in clinical events, including angina pectoris, myocardial ischemia and infarction, and death. Ambulatory electrocardiography provides a versatile and quantifiable measure of regional myocardial ischemia. Reductions in ischemia, as quantified by this diagnostic modality, are associated with improved clinical outcomes that may reflect improvements in the cellular pathophysiology of coronary atherosclerosis. This review discusses new information regarding the interactions between low-density lipoprotein cholesterol, the cell biology of atherosclerosis, and the activity of ischemia in patients with coronary artery disease.

Prognostic implications of ambulatory myocardial ischemia and arrhythmias and relations to ischemia on exercise in chronic stable angina pectoris (the Angina Prognosis Study in Stockholm [APSIS])

The prognostic significance of ambulatory ischemia, alone and in relation to ischemia during exercise was assessed in 686 patients (475 men) with chronic stable angina pectoris taking part in the Angina Prognosis Study In Stockholm (APSIS), who had 24-hour ambulatory electrocardiographic registrations and exercise tests at baseline (n = 678) and after 1 month (n = 607) of double-blind treatment with metoprolol or verapamil. Ambulatory electrocardiograms were analyzed for ventricular premature complexes and ST-segment depression. During a median follow-up of 40 months, 29 patients died of cardiovascular (CV) causes, 27 had a nonfatal myocardial infarction, and 89 underwent revascularization. Patients with CV death had more episodes (median 5 vs. 1; p<0.01) and longer median duration (24 vs. 3 minutes; p<0.01) of ST-segment depression than patients without events. For those who had undergone revascularization, the duration was also longer (12 vs. 3 minutes; p<0.05). In a multivariate Cox model including sex, history of previous myocardial infarction, hypertension, and diabetes, the duration of ST-segment depression independently predicted CV death. When exercise testing was included, ambulatory ischemia carried additional prognostic information only among patients with ST-segment depression > or =2 mm during exercise. When the treatment given and treatment effects on ambulatory ischemia were added to the Cox model, no significant impact on prognosis was found. Ventricular premature complexes carried no prognostic information. Thus, in patients with stable angina pectoris, ischemia during ambulatory monitoring showed independent prognostic importance regarding CV death. Ambulatory electrocardiographic monitoring and exercise testing provide complementary information, but only among patients with marked ischemia during exercise. Treatment reduced ambulatory ischemia, but the short-term treatment effects did not significantly influence prognosis.

Prognostic significance of myocardial ischemia detected by ambulatory electrocardiography, exercise treadmill testing, and electrocardiogram at rest to predict cardiac events by one year (the Asymptomatic Cardiac Ischemia Pilot [ACIP] study)

Myocardial ischemia identified by ambulatory electrocardiography (AECG), exercising treadmill testing, (ETT), or 12-lead electrocardiogram at rest is associated with an adverse prognosis, but the effect of improving these ischemic manifestations by treatment on outcome is unknown. The Asymptomatic Cardiac Ischemia Pilot (ACIP) study was a National Heart, Lung, and Blood Institute funded study to determine the feasibility of conducting a large-scale prognosis study and to assess the effect of 3 treatment strategies (angina-guided strategy, AECG ischemia-guided strategy, and revascularization strategy) in reducing the manifestations of ischemia as indicated by AECG and ETT. The study cohort for this database study consisted of 496 randomized patients who performed the AECG, ETT, and 12-lead electrocardiogram at rest at both the qualifying and week 12 visits. The effect of modifying ischemia by treatment on the incidence of cardiac events (death, myocardial infarction, coronary revascularization procedure, or hospitalization for an ischemic event) at 1 year was examined. In the 2 medical treatment groups (n = 328) there was an association between the number of ambulatory electrocardiographic ischemic episodes at the qualifying visit and combined cardiac events at 1 year (p = 0.003). In the AECG ischemia-guided patients there was a trend associating greater reduction in the number of ambulatory electrocardiographic ischemia episodes with a reduced incidence of combined cardiac events (r = -0.15, p = 0.06). In the revascularization strategy patients this association was absent. In the medical treatment patients the exercise duration on the baseline ETT was inversely associated with an adverse prognosis (p = 0.02). The medical treatment strategies only slightly improved the exercise time and the exercise duration remained of prognostic significance. In the revascularization group strategy patients this association was absent. Thus, myocardial ischemia detected by AECG and an abnormal ETT are each independently associated with an adverse cardiac outcome in patients subsequently treated medically.

Association between angina pectoris and ischemic indexes during exercise testing and ambulatory monitoring

We examined the relation between anginal symptoms and ischemic indexes during ischemia on exercise testing and daily activities in 76 patients (59 men and 17 women, mean age 61.5 years) with documented coronary artery disease and exercise-induced ischemia. All patients underwent upright bicycle exercise testing and 48-hour ambulatory electrocardiographic monitoring (AECG). Angina was reported in 28 patients (37%) during exercise-induced ischemia. A total of 287 ischemic episodes were detected from 44 patients (58%) during AECG. There was a mean number of 7.4 episodes and a mean total duration of 75 min/48 hours. There were no differences in the prevalence and the magnitude of ambulatory ischemia between patients with and without angina during exercise testing. Among the 44 patients who had ischemia during both tests, 50% of patients with angina during exercise testing had symptomatic ischemia during AECG compared to 14% in patients with silent ischemia during exercise testing (p = 0.01). Ninety-two percent of ischemic episodes were preceded by an increase in heart rate (HR) of > 10 beats/min. There was a strong positive correlation (r = 0.70, p < 0.01) between HR at onset of 1 mm ST depression (ischemic threshold) during exercise testing and during AECG. We conclude that (1) patients with exercise-induced angina have significantly more symptoms during ambulatory ischemia, (2) ischemic threshold during exercise testing and daily life are positively correlated, and (3) our findings emphasize the role of increased myocardial oxygen demand in the development of ambulatory ischemia.

Persistent transient myocardial ischemia despite beta-adrenergic blockade predicts a higher risk of adverse cardiac events in patients with coronary artery disease

OBJECTIVES

We evaluated the prevalence and prognostic significance of transient myocardial ischemia despite beta-adrenergic blockade in patients with coronary artery disease.

BACKGROUND

Persistence of transient ischemia despite therapy may correspond to a subset of high risk patients with coronary disease. The impact of beta-blocker withdrawal in these patients remains unknown.

METHODS

Patients (n = 313) with documented coronary artery disease and beta-blocker therapy, with (group I, n = 84) or without (group II, n = 229) transient ischemia on ambulatory electrocardiographic monitoring, were followed up during 21 +/- 9 months for cardiac events (death, myocardial infarction, percutaneous transluminal coronary angioplasty, coronary artery bypass surgery and worsening angina). Occurrence of events was compared by log-rank test.

RESULTS

The number of coronary stenoses did not differ significantly between groups I and II. Beta-blocker therapy was discontinued more frequently during follow-up in group II (25% vs. 14% in group I, p = 0.04). Cumulative percentage of death or myocardial infarction, or both, tended to be higher in group I a 30 months (17% vs. 5% in group II, p = 0.09). Coronary angioplasty and bypass surgery were significantly more frequent in group I (p = 0.01 and 0.0008, respectively). Transient ischemia was associated with a higher cumulative probability of adverse events (p = 0.004). The number of coronary stenoses, presence of transient ischemia and beta-blocker withdrawal were the only significant prognostic factors of cardiac events in the Cox model. In group I patients, the relative hazard of cardiac events was increased threefold when beta-blocker therapy was interrupted.

CONCLUSIONS

These data suggest that 1) the occurrence of transient ischemia despite beta-blocker therapy identifies a subset of high risk patients with coronary artery disease, and 2) the interruption of beta-blocker therapy increases the risk of adverse cardiac events.

Relation between blood pressure at rest and perception of angina pectoris during exercise testing

We demonstrated that the prevalence of painful myocardial ischemia during exercise testing was 20% in patients with high blood pressure at rest (systolic blood pressure >140 mm Hg) and 36% in patients with normal blood pressure at rest(systolic blood pressure < or = 140 mm Hg). Thus, blood pressure at rest appears to be related to pain perception in cardiac patients.

Prognostic importance of myocardial ischemia detected by ambulatory monitoring early after acute myocardial infarction

BACKGROUND

After an acute myocardial infarction, it is important to determine the risk of a subsequent coronary event. We studied the prognostic value of myocardial ischemia detected by ambulatory electrocardiographic (ECG) monitoring in patients who had recently had an acute myocardial infarction.

METHODS

Five to seven days after acute myocardial infarction, 406 patients underwent 48-hour ambulatory ECG monitoring, with submaximal exercise testing before discharge and measurement of the left ventricular ejection fraction within 28 days after infarction. Death, nonfatal myocardial infarction, and admission to the hospital because of unstable angina were the principal end points recorded during the one-year follow-up period.

RESULTS

The overall incidence of myocardial ischemia detected by ambulatory ECG monitoring was 23.4 percent. The mortality rates at one year were 11.6 percent among the patients with ischemia and 3.9 percent among those without ischemia (P = 0.009); 3.9 percent among the patients with a positive exercise test, 3.0 percent among those with a negative exercise test, and 16.4 percent among those in whom an exercise test was not performed (P < 0.001); and 3.6 percent among the patients with an ejection fraction greater than 50 percent, 3.5 percent among those with an ejection fraction between 35 and 50 percent, and 18.2 percent among those with an ejection fraction below 35 percent (P = 0.001). Using multiple logistic regression, we found that no diagnostic test performed after myocardial infarction provided additional prognostic information beyond that provided by the standard clinical variables used to predict the risk of death. When nonfatal myocardial infarction and admission to the hospital because of unstable angina were also included as outcome variables, ambulatory monitoring for ischemia was the only test that contributed significantly to the model. For the patients with ischemia detected by ambulatory monitoring, as compared with those who did not have evidence of ischemia, the odds ratio was 2.3 (95 percent confidence interval, 1.2 to 4.5) for death or nonfatal myocardial infarction (P = 0.009) and 2.8 (95 percent confidence interval, 1.6 to 4.8) for death, nonfatal myocardial infarction, or admission to the hospital because of unstable angina (P < 0.001).

CONCLUSIONS

Myocardial ischemia detected by ambulatory ECG monitoring is common early after acute myocardial infarction and provides prognostic information beyond that available from standard clinical information.

Ischemia monitoring with on-line vectorcardiography compared with results from a predischarge exercise test in patients with acute ischemic heart disease

Information from 24-hour monitoring with on-line vectorcardiography, starting immediately after admission, was compared with results from a predischarge exercise test 3-13 days after admission. A total of 169 patients with acute myocardial infarction and 73 patients with unstable angina pectoris were investigated. Patients were followed for 487 +/- 135 days. During the follow-up period, 19 patients (8%) died from cardiac causes and 34 (14%) were hospitalized for a myocardial infarction. The QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM), ST vector magnitude (ST-VM), and ST vector leads X, Y, Z were monitored. Patients with ST depression on the exercise test showed higher occurrence of transient, supposedly ischemic, episodes of QRS-VD, STC-VM, and ST-VM than patients without ST depression. The sensitivity and specificity of identifying patients with ST depression at the exercise test were respectively, 71 and 47% for QRS-VD episodes, 58 and 56% for ST-VM episodes, and 55 and 65% for STC-VM episodes. The maximum ST depression at the exercise test was related to the maximum ST depression in vector lead X (r = .44, P < .001) and the number of STC-VM (r = .40, P < .001), ST-VM (r = .37, P < .001), and QRS-VD (r = .33, P < .001) episodes on the VCG. In multivariate analysis, maximum ST depression in vector lead X and STC-VM episodes were the best determinants for ST depression at the exercise test. In a Cox regression model, the optimal combination of exercise test data in patients who died from cardiac causes exhibited a global chi-square value of 20.0. The combination of these data and the number of STC-VM episodes increased the global chi-square value to 30.6. This study indicates that in patients with acute ischemic heart disease, early continuous vectorcardiographic monitoring may predict the results from a predischarge exercise test and also contributes independent prognostic information beyond that of exercise test data.

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

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

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

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

Silent ischemia after uncomplicated myocardial infarction: lack of incremental clinical significance

To determine the potential utility of the detection of silent myocardial ischemia after acute myocardial infarction for clinical decision making, we investigated the hypothesis that the occurrence of silent myocardial ischemia on ambulatory electrocardiographic (EGG) monitoring after acute myocardial infarction is independently predictive of adverse outcome in patients in whom conventional clinical and investigative parameters indicate favourable prognosis on medical therapy. Among 465 consecutive patients admitted to our Coronary Care Unit with acute myocardial infarction, 42 patients (39% of those eligible) were randomly selected for study. Twenty-four hour ambulatory ECG monitoring was carried out 13 +/- 10 (standard deviation) days post-acute myocardial infarction. Ninety-eight percent of patients were receiving prophylactic anti-ischemic medications and 81% on aspirin. Silent myocardial ischemia was detected in 14%. During the follow-up period of 16 +/- 3 months, acute ischemic events occurred in 33% of those with silent myocardial ischemia and 19% of those without previous silent myocardial ischemia (P = 0.59). The sensitivity of the test for prediction of future acute ischemic events was 22% (95% confidence interval: 3-60%), specificity 87% (95% confidence interval: 72-97%), positive predictive value 33% (95% confidence interval: 4-78%) and negative predictive value 81% (95% confidence interval: 64-92%). Therefore the detection of ambulatory silent myocardial ischemia after acute myocardial infarction is not of sufficient incremental value as a predictor of the occurrence of adverse cardiac events to justify its routine clinical use in this subgroup of patients.

Does ambulatory monitoring contribute to exercise testing and myocardial perfusion scintigraphy in the prediction of the extent of coronary artery disease in stable angina?

The role of ambulatory myocardial ischemia detection, in addition to exercise testing and myocardial perfusion scintigraphy, in the prediction of the angiographic severity of coronary artery disease in patients with stable angina was examined. Ninety-seven patients underwent ambulatory electrocardiographic monitoring, exercise testing with scintigraphy, and coronary angiography. In addition to the number of diseased vessels involved, proximal arterial segment and coronary artery jeopardy scores were calculated to evaluate the extent of disease and amount of myocardium at risk. Thirty patients (31%) had 1.8 +/- 1.8 episodes/24 hours of ambulatory ischemia (94% of episodes were asymptomatic) and were similar to 67 without ambulatory ischemia in regard to clinical characteristics, left ventricular function and mean number of diseased vessels involved. Proximal arterial segment and coronary artery jeopardy scores were greater in: (1) 30 patients with versus 67 without ambulatory ischemia (3.3 +/- 1.8 vs 1.9 +/- 1.5 [p = 0.0002] and 6.6 +/- 3.6 vs 5.0 +/- 3.4 [p = 0.03], respectively); (2) 78 with versus 19 without a positive exercise test (2.6 +/- 1.8 vs 1.4 +/- 0.8 [p = 0.0001] and 6.1 +/- 3.5 vs 3.0 +/- 2.5 [p = 0.0003], respectively); and (3) 69 with versus 6 without a positive perfusion scan (2.4 +/- 1.8 vs 1.0 +/- 0 [p = 0.0008] and 5.5 +/- 3.6 vs 2.3 +/- 2.0 [p = 0.03], respectively). In multivariate analysis, ambulatory ischemia was the best predictor of the proximal segment score, whereas exercise testing and myocardial perfusion imaging were predictive of the coronary jeopardy score.

Comparison of the prognostic values of ischemia during daily life and ischemia induced by treadmill exercise testing

Although silent ischemia is common in patients with stable coronary artery disease (CAD), controversy surrounds the issue regarding the most appropriate method for detection. Routinely performed exercise tolerance testing provides important prognostic information. However, ambulatory electrocardiographic monitoring (AEM) has the distinct advantage of enabling evaluation of silent ischemia during daily life. Although numerous AEM studies have found a greater occurrence of silent ischemia than symptomatic ischemia in patients with stable angina pectoris, the independent prognostic value of AEM findings has not been definitively established. Several recent studies have addressed the question of whether AEM supplies additional information beyond that obtained from exercise testing. The results of these studies revealed that myocardial ischemia during daily life that is detected by AEM provides additional and independent prognostic information in patients with stable CAD who have evidence of ischemia during exercise testing.

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.