Adaptation to the stress of tachycardia in patients with coronary artery disease: insight into the mechanism of the warm-up phenomenon.

Abstract

Adaptation to exercise or the "warm up phenomenon" has been observed in some patients with angina pectoris. To investigate adaptation, eleven patients with exertional angina pectoris and angiographic evidence of coronary artery disease underwent two identical bouts of sequential tachycardia stress separated by a brief recovery period. Manifestations of ischemia were less during the second stress, as evidenced by a reduction in the severity of angina pectoris, less ST segment depression, and improved lactate extraction. Peak coronary blood flow during the second stress (81 + 20 ml/min) was not significantly different from that during the first (95 + 32 ml/min). Regional myocardial oxygen consumption, however, was significantly (p = .03) lower during the second stress (8.8 2.4 ml 02/min) when compared with the first (1 1.4 + 3.0 ml 02/min). Thus, patients with coronary artery disease can develop anginal tolerance to the stress of tachycardia similar to that observed after repeated bouts of exercise. A relative reduction in myocardial oxygen consumption, rather than an increase in coronary blood flow, appears to account for this phenomenon. Circulation 71, No. 4, 687492, 1985. IN 1785, William Heberdeen described a patient in whom angina pectoris initially developed during exercise but then paradoxically disappeared as exercise was continued.' This phenomenon has been termed "walk through" or "second wind" angina. A related form of angina has also been acknowledged wherein a patient, after terminating exercise because of the development of angina, is subsequently able to resume angina-free exercise. This latter adaptation has been termed the "warm up phenomenon" or "angina of first effort."Several investigators have documented reduced myocardial ischemia in patients demonstrating either walk-through angina or the warm-up phenomenon during exercise stress testing. MacAlpin and Kattus2 described 12 patients who were able to adapt to treadmill exercise. Nine patients demonstrated the disappearance or lessening of anginal pain and ischemic ST segment depression with continued walking. Three patients showed increased exercise capacity after having been "warmed up" by a prior exercise period that re-

Effects of KATPchannel blockade by glibenclamide on the warm-up phenomenon

“…In placebo-treated patients, the blood glucose level before the exercise test (96 10 mg . 100 ml 1 ) was similar to that found in glibenclamide-treated patients (P=ns) ( Table 1). …”

“…The warm-up phenomenon usually refers to increased tolerance to myocardial ischaemia during the second of two sequential exercise tests [1][2][3][4][5] . Although this phenomenon was described in anginal patients more than 50 years ago [6] , its underlying mechanisms remain poorly known.…”

Synergistic Adaptations to Exercise in the Systemic and Coronary Circulations That Underlie the Warm-Up Angina Phenomenon

“…10,11 Warm-up is also unexplained by the recruitment of collateral vessels. 20 Instead, it has been suggested that warm-up is a result of attenuation of increased regional myocardial oxygen consumption (MVO 2 ), possibly mediated by adenosine A 1 receptor activation, a signaling system known to improve tolerance to ischemia.…”

Consequences of Brief Ischemia: Stunning, Preconditioning, and Their Clinical Implications

“…110 Regional myocardial oxygen consumption was lower during the second test than the first, and flow through the cardiac vein did not differ between tests. Williams et al 111 induced angina by pacing-induced tachycardia at the time of catheterization. Two identical periods of pacing were separated by a 5-to 15-minute rest phase.…”