Alex Gavish

Prognostic significance of ischemic episodes in patients with previous myocardial infarction.

This study assessed the prognostic significance of ischemic changes during daily activity as recorded by ambulatory electrocardiographic monitoring in a group of 224 low-risk postinfarction patients. Of the 224 patients studied, 74 (33%) had transient ischemic episodes on Holter monitoring. During the 28 months of follow-up the frequency of cardiac events (cardiac death, reinfarction, hospitalization for unstable angina, balloon angioplasty or coronary bypass surgery) was 51% among those with ischemic episodes on Holter monitoring, compared with 12% in those without such changes (p less than 0.0001). The 74 patients with positive results in their exercise tests and Holter monitoring had a 51% event rate, compared with 20% among the 44 patients with a positive exercise test result but negative Holter results (p less than 0.001). The event rate in those without ischemic changes either on the exercise test or on Holter was only 8.5%. Among patients with good (greater than 40%) or reduced (less than 40%) left ventricular ejection fraction, those with transient ST depression on Holter had a significantly higher cardiac event rate compared with those without it. A similar event rate was found in patients with only silent, only symptomatic and with silent and symptomatic ischemic episodes.

Comparison of mortality and myocardial infarction rates in stable angina pectoris with and without ischemic episodes during daily activities

The prognostic significance of ischemic changes during daily activities was assessed in 56 patients with stable angina pectoris. All patients had positive results on the treadmill stress test and angiographic evidence of significant coronary artery disease. Forty-three (77%) had ischemic episodes on Holter monitoring during everyday activities. During the follow-up period (mean 2 years), there were 6 deaths and 6 myocardial infarctions among the 43 patients with ischemic episodes, compared with none among the 13 patients without such changes (p less than 0.03). All 14 patients referred for coronary bypass surgery belonged to the group with ischemic episodes (p less than 0.02). The extent of coronary disease, the treadmill test parameters, and the duration and frequency of ischemia during daily activities were identical in the patients with and without subsequent cardiac events. Patients with only symptomatic ischemic episodes or those with both silent and symptomatic episodes had a frequency of cardiac events similar to that of patients with only silent episodes. Thus, it seems that patients with stable angina pectoris and ischemic episodes during daily activities have a worse prognosis than patients free from such episodes.

Myocardial ischemia during daily activities and stress

Twenty-four-hour, 2-channel Holter monitoring during daily activities was performed in 210 patients; during the same day a Bruce protocol treadmill test was also performed and the electrocardiogram was recorded using the same Holter system. Significant ST-segment depression was observed during daily activities in 97 patients, while similar changes were recorded during the treadmill test in 122 patients. Thus, 77% of patients with ST depression during the provocation of the treadmill test had ischemic episodes during their everyday life. On the other hand, 3 patients with proven significant coronary artery disease had spontaneous ischemic episodes during daily activities, but had a negative stress test. The ischemic changes during daily activity developed at a lower heart rate than during stress testing (94 beats/min vs 109 beats/min, respectively, p less than 0.05). A total of 351 ischemic episodes were recorded during daily activities, 241 (69%) of these were asymptomatic. In 46 patients all episodes were asymptomatic, in 15 all were symptomatic, while in 36 both symptomatic and silent episodes were detected. The mean duration of the symptomatic episodes was 13.7 minutes and that of the asymptomatic ones was 14.9 minutes (difference not significant). The degree of ST depression in these 2 groups was also similar. Because of more advanced symptomatology in 143 patients, coronary arteriography was performed; 43 had normal and 100 had pathologic coronary arteries. In this selected group, the sensitivity of Holter monitoring during daily activity was 87% and during stress 97%; the specificity during daily activity was 95% and during stress 88%.(ABSTRACT TRUNCATED AT 250 WORDS)

Holter recording during treadmill testing in assessing myocardial ischemic changes

One hundred forty-four patients underwent a Bruce protocol treadmill exercise test during which an electrocardiogram (ECG) was recorded simultaneously with a 2-channel Holter recorder with bipolar V3- and V5-like leads and by a conventional 12-lead system. Sixty-eight patients had no ST depression on either the Holter or on the 12-lead ECG during the exercise test, whereas in 70 patients ischemic changes were recorded by both methods; thus, in 138 of the 144 patients (96%), the results of the 2 tests were concordant. The severity of ST depression, as judged by the heart rate at which ischemic changes were first noted and the maximal ST depression observed, were similar on both recording systems. The Holter system identified 6 of the 7 patients whose ischemic changes were confined to the inferior wall on the 12-lead ECG. The addition of the V3 lead as a second ischemic lead increased the ischemia detection by 10%. Ninety-five patients also underwent coronary arteriography. In these patients the sensitivity of the Holter system during exercise in detecting significant coronary artery disease was 81% and that of 12-lead ECG was 84%, the specificity was 85% and 85%, respectively, and the positive predictive value 91% and 91%, respectively. Thus, the 2-channel Holter recording system with bipolar V3- and V5-like leads was as accurate as the 12-lead system in detecting ischemic changes during exercise and proved that ambulatory monitoring system can reliably reproduce ST segment.

Day-to-day variability of myocardial ischemic episodes in coronary artery disease

Twenty patients with chronic stable angina pectoris, proved coronary artery disease, positive treadmill stress test response, and at least 2 episodes of ischemia per day underwent 72 hours of Holter monitoring during daily activities. During this period they had 389 ischemic episodes: 104 (27%) symptomatic and 285 (73%) silent. Marked variability was observed between patients in the number of ischemic episodes (range 2 to 15 per day, mean 6.5), duration of ischemia (range 6 to 419 minutes/day, mean 76.5), maximal ST depression (range 1 to 6 mm, mean 3.4) and heart rate at the beginning of ST depression (range 75 to 105 beat/min, mean 91). The day-to-day variability in individual patients between the different days in the number of ischemic episodes was 36%, in duration 51%, and in maximal degree of ST depression 31%. Only 9% variability was noted in heart rate at the beginning of ST depression. Similar day-to-day variability in individual patients was noted in the symptomatic and silent episodes. For clinical purposes of evaluation of ischemia during daily activities, 1 day of monitoring appears to be sufficient because within the first day, 78% of the maximal number of ischemic episodes, 64% of their duration, and 84% of the maximal degree of ST depression were detected. However, for evaluation of anti-ischemic drugs at least 2 monitoring days are required.

Changes in myocardial ischemic threshold during daily activities

This study assesses the variations in myocardial ischemic threshold (heart rate at the onset of ischemia) during daily activities in patients with ischemic episodes on Holter monitoring. Eighty patients with known coronary artery disease, positive treadmill stress test results and greater than or equal to 2 ischemic episodes during a 24-hour period of Holter monitoring were studied. The lowest and the highest ischemic thresholds were determined for each patient. The mean lowest ischemic threshold was 85 beats/min, and the mean highest ischemic threshold was 109 beats/min. The highest ischemic threshold was identical to ischemic threshold values noted during exercise. Of the 895 ischemic episodes, 654 (74%) were preceded by a moderate (greater than 10%) increase in heart rate. The variability of ischemic threshold (difference in percentage between the highest and lowest ischemic thresholds) increased with the number of ischemic episodes (range 2 to 60%). However, in different patients with a similar number of ischemic episodes, different variability was observed. These differences in ischemic thresholds are probably indirect indicators of the vasomotor activity of the coronary arteries in different patients.

Effects of transdermal nicotine patches on ambulatory ECG monitoring findings: A double-blind study in healthy smokers

SummaryThe cardiovascular effects and safety of transdermal nicotine patches were assessed in 50 healthy smokers using repeated 48 hour ambulatory electrocardiographic monitoring as a part of a smoking cessation program. Following baseline measurements, subjects were randomized to active (n=25) or placebo (n=25) treatment groups for a period of 2 weeks. Twenty-two patients in each group completed the trial. During the treatment period, subjects also received behavioral supportive therapy. Heart rate and blood pressure were signilicantly reduced relative to baseline both groups. In the active treatment group, mean values at baseline and after 2 weeks of double-blind treatments were as follows: heart rates, 74.0 and 71.3 beats/min, respectively; systolic blood pressure, 108.9 and 106.9 mmHg; and diastolic blood pressure, 69.7 and 68.2 mmHg, respectively. Values for the placebo group were as follows: heart rate, 73.2 and 69.6 beats/min; systolic blood pressure, 110.6 and 105.3 mmHg; diastolic blood pressure, 71.4 and 70.5 mmHg. The confidence intervals of the mean for the differences between the groups are as follows: heart rate,-4.0 + 8.2; systolic blood pressure, -6.7, +10.1; diastolic blood pressure, -7.9, +3.9. There were no changes in the frequency of atrial or ventricular arrhythmia as documented by repeated 48 hour ambulatory ECG recordings from baseline period before stopping smoking compared with the treatment period in the active as well as in the placebo groups. No ischemic events were detected in any of the volunteers during either the baseline or treatment periods. As a measure of smoking abstinence, we assessed the level of carbon monoxide in expired air; in the active group, the mean levels fell from 14.2 to 4.4 ppm after smoking cessation and in the placebo group from 13.2 to 4.2 ppm. The mean urine cotinine level fell from 8.18 mmol/l at baseline to 5.74 mmol/l after 2 weeks of treatment in the active group and from 8.78 to 3.93 mmol/l in the placebo group. The number of cigarettes smoked per week in both treatment groups was significantly reduced: from 175.2 to 8.4 for the active group and from 136 to 8.6 for the placebo group. Eleven out of 22 subjects in each group quit smoking completely. Smoking withdrawal symptoms during the first week of treatment were more severe in the placebo group than in those on active treatment. There were no significant side effects in either the placebo or the active treatment groups. These results indicate that nicotine delivered by transdermal system is free of cardiac adverse effects in healthy volunteers.

Ischemic threshold during two exercise testing protocols and during ambulatory electrocardiographic monitoring

OBJECTIVES The aim of this study was to examine the dependence of the ischemic threshold during exercise testing on the exercise protocol employed and to determine the relation between the ischemic thresholds observed during exercise and during daily activity. BACKGROUND The ischemic threshold (heart rate at 1-mm ST segment depression) during daily activity has been reported to be lower than that observed during exercise testing. Recent reports have hypothesized that this difference is probably dependent on the exercise protocol employed. METHODS Twenty-two patients with known coronary artery disease, not receiving antianginal medications, were evaluated by repeated exercise testing according to the Bruce and the modified Davidson protocols and by 48-h ambulatory electrocardiographic monitoring. RESULTS Although the heart rate at 1-mm ST segment depression was somewhat lower with the Davidson than with the Bruce protocol (112 +/- 14 vs. 115 +/- 14 beats/min), the rate-pressure product at 1-mm ST segment depression was similar during the two protocols (16,900 +/- 4,000 vs. 17,700 +/- 3,600). The mean heart rate (100 + 12 beats/min) at 1-mm ST segment depression during ambulatory ischemic episodes (n = 137) was significantly lower than that observed during both exercise protocols (p < 0.001 for both comparisons). CONCLUSIONS Exercise-induced ischemia occurs at a relatively fixed threshold that is mainly dependent on myocardial oxygen demand and is independent of the exercise protocol employed. Ischemia on ambulatory monitoring, however, occurs at a much more variable threshold that is commonly lower than that observed during exercise and is therefore dependent on other factors in addition to increased demand.

Clinical outcome of silent myocardial ischemia

Asymptomatic coronary artery disease can be detected by an abnormal electrocardiogram at rest, by a positive exercise test result unaccompanied by pain, or by the demonstration of silent ischemic episodes during daily activities. However, the clinical outcome of patients with silent myocardial ischemia has not yet been clearly defined. In a study of 356 patients with documented coronary disease--211 of whom had previous myocardial infarction--the prognostic information of spontaneous ST-segment depression was found to be independent of that associated with a positive exercise test result, ejection fraction, and extent of arteriographically documented coronary artery disease. Patients with asymptomatic ischemia had a higher coronary event rate than those without ischemia. Cardiac event rates followed a similar pattern for patients with silent, symptomatic and mixed ischemia--whether or not there was previous myocardial infarction.

Usefulness of severity of myocardial ischemia on exercise testing in predicting the severity of myocardial ischemia during daily activities.

To determine the relation between myocardial ischemic indexes on exercise testing and on ambulatory Holter recording, 60 patients with stable coronary artery disease who exhibited an ischemic response to both testing procedures were studied. All patients performed a Bruce protocol exercise test and underwent 24-hour Holter recording within 2 weeks without antianginal medications. Mean exercise duration was 7.4 +/- 2.8 minutes, mean heart rate at 1-mm ST depression was 118 +/- 20 beats/min and mean maximal ST depression during exercise was 2.2 +/- 1 mm. During Holter recording the average number of ischemic episodes was 4.7 +/- 2.6 per patient, mean duration of daily ischemia was 62 +/- 54 minutes, mean maximal ST depression was 3.2 +/- 1.3 mm and average heart rate at 1-mm ST depression was 93 +/- 17 beats/min. Overall, the correlations between ischemic indexes on both testing procedures were very weak (mean r2 = 0.054). The only exercise variable that had a significant correlation (p less than 0.05) with all Holter variables was heart rate at 1-mm ST depression, yet it correlated very weakly (0.064 less than or equal to r2 less than or equal to 0.125) with most Holter covariates and had a better correlation (r2 = 0.256) only with average heart rate at 1-mm ST depression during Holter. Thus, ischemic indexes on exercise testing cannot accurately predict ischemic indexes on ambulatory Holter recording in patients with stable coronary artery disease who exhibit ischemic changes on both tests.(ABSTRACT TRUNCATED AT 250 WORDS)