Variable threshold exertional angina in patients with transient vasospastic myocardial ischemia (original) (raw)
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International Journal of Cardiology, 1995
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 l-mm ST segment depression during ambulatory electrocardiographic monitoring was 2 20 beats/min lower than that during exercise testing in 58 ischemic episodes (57%, Group A), lo-19 beats/min lower in 26 (26%, Group B), and 5 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 2 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.
Journal of The American College of Cardiology, 1991
It is generally accepted that angina pectoris and, presumably, myocardial ischemia occur at a fixed heart rate-systolic blood pressure product in a given patient. This concept of a fixed threshold has recently been challenged. To evaluate the effects of varying exercise intensity on the ischemic threshold, 33 patients with coronary artery disease and provokable myocardial ischemia, documented by thallium-201 myocardial perfusion imaging, underwent two exercise tests 2 to 7 days apart. A symptom-limited incremental treadmill exercise test was followed by a 20 min submaximal treadmill test at an intensity approximating 70% of the peak heart rate attained during the incremental test.During the incremental exercise test, angina pectoris developed in 16 patients and 17 patients were asymptomatic. At least 0.1 mV of ST segment depression developed in all subjects during the incremental exercise test at a mean exercise duration of 5.3 ± 2.6 min, a rate-pressure product of 19,130 ± 5,735 and oxygen uptake of 19.6 ± 7.0 ml/kg per min. During the submaximal exercise test, 28 (85%) of the 33 patients had significant ST segment depression. Of these patients, 24 (86%) were asymptomatic, including 10 patients who had previously reported anginal symptoms during the incremental test. The average time to onset of 0.1 mV ST segment depression during the submaximal test was 8.1 ± 4.5 min. These changes occurred at a rate-pressure product of 15,250 ± 3,705 and an oxygen uptake of 14.3 ± 5.9 ml/kg per min, and were significantly (p < 0.001) lower than values observed during the graded exercise. Six of the 33 patients had angina pectoris during both tests, although 2 patients had no accompanying ST segment depression during the submaximal test.These results demonstrate that myocardial ischemia, whether or not accompanied by angina pectoris, can occur at a lower rate-pressure product and oxygen uptake during submaximal, steady state exercise compared with symptom-limited incremental exercise. It may be concluded that the ischemic threshold varies under different exercise conditions.
“Variant” angina: One aspect of a continuous spectrum of vasospastic myocardial ischemia
The American Journal of Cardiology, 1978
transient reversible episodes of S-T segment elevation were documented in 138 patients (80 with angina only at rest, 58 with angina both on exertion and at rest). Electrocardiographic monitoring in 33 patients with hemodynamic monitoring revealed that (1) during 6,009 transient episodes of myocardial ischemia, pain was always a late phenomenon and, in some patients, often did not occur; (2) during such transient episodes, ST-T wave behavior was often variable in the same patient with alternation of elevation, depression or only T wave changes with or without pain; (3) independent of the direction of the S&T segment and T wave changes, the episodes were never preceded by an increase of the hemodynamic determinants of myocardial demand but were associated with obvious impairment of left ventricular function. Thallium scintigraphy in 32 patients revealed a regional massive and localized reduction of myocardial perfusion during S-T segment elevation and pseudonormalization of T waves. During S-T segment depression the reduction of thallium uptake was diffuse with fuzzy limits. Coronary angiography revealed no significant stenosis in 8 patients and single, double and triple vessel disease in 38, 34 and 26 patients, respectively. Angiography in all 37 patients studied during angina revealed a severe coronary vasospasm involving vessels with extremely variable extent of atherosclerosis. Severe arrhythmias were recorded in 27 patients, and a myocardial infarction occurred in 28. A total of five patients died within 1 month of hospital admission. Thus, variable intensity and extension of coronary vasospasm and the presence of collateral vessels may result in different degrees of ischemia and various electrocardiographic patterns with or without angina1 pain. Vasospastic angina can occur in the presence of extremely variable degrees of coronary atherosclerosis and in any phase of ischemic heart disease. It may evolve into acute myocardial infarction and sudden death: Variant angina appears to be only its most striking electrocardiographic manifestation. When vasospastic angina is appropriately searched for, its incidence rate appears to be high.
The exercise test in variant angina: results in 114 patients
Circulation, 1981
One hundred fourteen patients with variant angina performed bicycle exercise stress tests, and were divided into three groups. Group 1 included 37 patients with a normal exercise test. Coronary arteriography revealed absence of significant coronary stenoses in 18 patients, one-vessel disease in 17 and involvement of two or more vessels in two. Group 2 consisted of 40 patients who had ST-segment elevation during or just after exercise. Coronary arteriography in these cases revealed absence of significant coronary stenoses in nine patients, one-vessel disease in 18 and disease of two or more vessels in 13. Group 3 included 37 patients who had ST-segment depression during exercise. Absence of coronary artery disease was found in only two patients, one-vessel disease was found in 19 and disease of two or more vessels was found in 16. Sixty-one patients repeated the exercise test after a mean of 18 months after hospital discharge. Exercise-induced ST-segment elevation was no longer prese...