The rate-pressure product as an index of myocardial oxygen consumption during exercise in patients with angina pectoris

Cardiovascular responses to exercise following adolescent hypertensive pregnancy

With the establishment of hypertension as a risk factor for the development of coronary artery disease, more attention is being given to hypertension in youth. Hypertension during pregnancy has been associated with an increased incidence of hypertension in later years. To determine if this could be identified early, a group of adolescents who had been hypertensive during pregnancy and a control group who had normotensive pregnancies were studied by stress exercise testing and compared 4--6 years post partum. At rest, during each phase of graded exercise, and during the postexercise observation period, mean heart rate was significantly higher in the previously hypertensive group. Double product (heart rate x blood pressure), an index of myocardial oxygen consumption, was also significantly greater in the previously hypertensive group. When corrected for body weight and race, the amplitude of the R wave in lead V5 as well as a change in R-wave height with exercise were significantly greater in the group of adolescents who had been hypertensive during pregnancy. The observation of group differences 4--6 years post partum suggests a continuing abnormality that may predispose this group to develop early hypertensive cardiovascular disease.

Evidence for emotionally-induced coronary arterial spasm in patients with angina pectoris

Twelve executives with typical angina pectoris, given a 12-minute quiz, designed to be psychologically stressful, responded with ST depressions of greater than or equal to 1.0 mm. Each of these patients was given an exercise tolerance test on an upright bicycle to induce an amount of ST depression equivalent to that observed during the quiz. A statistical analysis was made of the products of the heart rate and the systolic blood pressure (rate-pressure product), at the onset of equivalent ST depression on both tests. At the maximal ST depression during the quiz, the mean rate-pressure product was 181 +/- 64 (SD) X 10(2), and at an equivalent ST depression during exercise it was 225 +/- 54 X 10(2); the mean difference was 44 +/- 40 X 10(2). Inasmuch as the rate-pressure product is an index of myocardial oxygen consumption, the differences in rate-pressure product suggest that myocardial ischaemia occurred at a lower myocardial oxygen consumption during emotional stress than during exercise. If equivalent degrees of ST depression during exercise and the quiz are indicative of equivalent ischaemia, than a relative reduction in coronary blood flow during emotional stress, probably by coronary spasm, may be postulated as the most reasonable explanation for these observations.

Clinical guidelines for exercise training

Exercise training may be useful for a variety of patients with and without established cardiovascular disease. The degree to which a patient participates in a prescribed exercise program depends strongly on initial motivation. The primary care physician can provide appropriate reinforcement with careful explanation of the effects of exercise on cardiovascular and metabolic function. Exercise programs may be combined effectively with other life-style adjustments, including weight loss, blood pressure control, and discontinuation of smoking. As a single intervention factor, exercise cannot prevent the evolution of cardiovascular disease in multiple-risk patients. Exercise is best used in combination with a program of comprehensive cardiovascular risk factor modification.

Blood pressure, heart rate, pressure-rate product and electrocardiographic changes in healthy children during treadmill exercise

Heart rate, systolic and diastolic blood pressure, rate-pressure product and electrocardiographic changes were measured in 288 healthy children during treadmill exercise. A constant speed (3.5 miles/hour) protocol was used to facilitate the measurements of physiologic data during exercise. Because responses to exercise vary with size, the children were separated into four groups according to body surface area. Comparisons were also made between male and female and between black and white children. The values for heart rate and systolic pressure showed excellent reproducibility in repeated tests. These data establish for clinical use reference values for children during treadmill exercise.

Studies on the protective effect of prostacyclin in acute myocardial ischemia

The ability of prostacyclin (PGI2) to alter responses to acute myocardial ischemia was studied in open-chest, anesthetized cats. PGI2 was infused intravenously at 0.5 nmoles kg-1 min-1 in cats subjected to 5 h of myocardial ischemia by occlusion of the LAD coronary artery, and in sham-operated controls. GI2 infusion resulted in significantly decreased arterial blood pressure and inhibition of platelet aggregation. Coronary ligation resulted in significant S-T segment elevations lasting 5 h in vehicle-treated animals but only 1 h in cats with myocardial ischemia and receiving PGI2. At 5 h, cats with ischemia and given the vehicle showed S-T segment elevations significantly greater than the other two groups. Ischemic myocardium from vehicle-treated animals exhibited significantly less creatine phosphokinase (CPK) specific activity than normal tissue from the same hearts or myocardial tissue from the other two groups. This loss of CPK from ischemic myocardium of the cats given vehicle was reflected in plasma CPK specific activities which were significantly greater than those of sham-operated cats. The cats with ischemia and treated with PGI2 exhibited lower plasma CPK activities. These changes were moderated by PGI2 infusion during myocardial ischemia. PGI2 infusion may protect the ischemic myocardium by reducing oxygen demand, primarily through reductions in cardiac work, and by perhaps inhibiting platelet aggregation and preserving myocardial cell integrity.

Comparative effect of nadolol and propranolol on exercise tolerance in patients with angina pectoris

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