Related Experiment Videos
Left ventricular pump function in effort angina. Influence of nitroglycerin, propranolol, verapamil, and coronary
Insights
Severe angina patients showed improved exercise tolerance after surgery, not medication. Coronary bypass surgery enhanced left ventricular function, unlike anti-anginal drugs which may improve tolerance by reducing heart workload.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Severe effort angina limits exercise capacity due to myocardial ischemia.
- Understanding left ventricular function during ischemia is crucial for treatment evaluation.
- Pharmacological and surgical interventions aim to improve exercise tolerance in angina patients.
Purpose of the Study:
- To assess hemodynamic and left ventricular function changes in severe effort angina patients during exercise.
- To compare the effects of anti-anginal drugs (nitroglycerin, propranolol, verapamil) versus coronary bypass surgery on exercise tolerance and left ventricular performance.
- To elucidate the mechanisms underlying improved exercise tolerance post-intervention.
Main Methods:
- Hemodynamic measurements and left ventricular function curves were obtained in 57 severe effort angina patients during graded exercise.
- Exercise tolerance and ventricular function were assessed before and after administration of nitroglycerin, propranolol, and verapamil.
- Similar assessments were performed in 10 patients after coronary bypass surgery with successful revascularization.
Main Results:
- Left ventricular function curves showed a peak stroke work index at a left ventricular end-diastolic pressure of 30 mm Hg, declining thereafter.
- Anti-anginal drugs significantly increased exercise tolerance but did not significantly improve stroke work index, except for nitroglycerin which increased left ventricular power.
- Coronary bypass surgery resulted in marked increases in both stroke work index and left ventricular power during exercise, correlating with improved exercise tolerance.
Conclusions:
- Increased exercise tolerance after coronary bypass surgery is associated with enhanced left ventricular work and power.
- The improved exercise tolerance observed with anti-anginal drugs is likely due to mechanisms reducing left ventricular workload, not necessarily improving contractile function.
- Differential effects of surgery and medication on left ventricular performance highlight distinct therapeutic benefits in managing severe effort angina.
Abstract:
Patients with severe effort angina were studied hemodynamically and left ventricular function curves were obtained during successively increasing myocardial ischemia provoked by exercise. The mean left ventricular function curve of 57 patients showed a slow increase in stroke work index with increasing left ventricular end-diastolic pressure at the beginning of exercise and stroke work index reached a maximum value of 0.79 (+/- 0.21) J/beat/m2 BSA at a left ventricular end diastolic pressure 30 (+/- 7) mm Hg. Despite a continuous increase in left ventricular end-diastolic pressure to 37 (+/- 6) mm Hg at the breaking point, stroke work index fell to its lowest value (0.64 +/- 0.21) J/beat/m2 BSA. A repeated exercise 20 min after the first in 10 patients did not influence the exercise tolerance or the left ventricular function curve. Although all the drugs nitroglycerin, propranolol and verapamil significantly increased the exercise tolerance none of the drugs enabled the patients to reach a significantly higher stroke work index. Only after nitroglycerin was there a significant increase (p greater than 0.05) of left ventricular power. After coronary bypass surgery with successful revascularization, however, there was a marked increase of both stroke work index and left ventricular power during exercise. Thus the increased exercise tolerance after surgery was accompanied by an increased left ventricular work and power but after medication no such effect on stroke work index and left ventricular power was seen. It is therefore suggested that the increased exercise tolerance after the anti-anginal drugs studied is a result of their different mechanisms of unloading the left ventricle.