Betablockers and Calcium Antagonists: Mode of Action in Angina pectoris
The different effects of betablockers and calciumantagonists on LV hemodynamics and coronary blood flow (CBF) are discussed based on studies performed with atenolol, propranolol and nifedipine. LV hemodynamics were recorded in coronary patients at rest, measuring LV volumes and pressures simoultaneously during angiography with the use of Millar tip manometers. CBF was assessed at rest and during atrial pacing up to ischemia (ST depression ± angina) without and with the drug using the precordial xenon clearance technique (gamma camera, CDC 1700 computer). Basic differences were present both for hemodynamics as for coronary dynamics: under betablockade LV contractility, cardiac output and ejection fraction decreased, enddiastolic volume increased and the pressure-volume relation was shifted upwards and flattened, indicating both an increase in diastolic wall stress and a decrease in passive elastic stiffness. During atrial pacing CBF decreased both in the normal as well as in the ischemic (poststenotic) zone, when compared to control, a result of the decrease in MVO2 due to the reduced contractility. After Nifedipine LV function improved slightly, contractility and cardiac output increasing, and peripheral resistance decreasing; enddiastolic volume and pressure remained unchanged. After the drug, CBF during pacing showed a further (not sign.) increase in the ischemic zone and remained unchanged in the normal area, inspite of a sign, decrease in MVO2 i.e. in the rate pressure product. Hence, calcium antagonists improve stable angina, i.e. ischemia due to increased O2 demand (exercise, pacing) by increasing O2 supply in the ischemic zone and decreasing demand through afterload reduction, whereas betablockers decrease both O2 demand and supply, the latter by autoregulatory changes of CBF.
Today, the treatment of angina pectoris is based on nitrates, betablockers and most recently, on calcium antagonists, three different therapeutic principles with different indications. Their mode of action varies both with regard to their influence on myocardial oxygen consumption as well as on coronary blood flow. The following presentation, which concentrates mainly on the difference between betablockers and so-called calcium antagonists, describes the hemodynamic effects and the action on the coronary circulation of both groups of drugs in patients with coronary artery disease.
KeywordsCalcium Antagonist Myocardial Blood Flow Coronary Blood Flow Atrial Pace Regional Myocardial Blood Flow
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- 2.Amende I, Simon R, Lichtlen PR (1980) Early effects of nifedipine on left ventricular diastolic function in man. Circulation 62: 111–259Google Scholar
- 4.Engel H-J, Lichtlen PR (1980) Effect of nifedipine on regional myocardial blood flow of coronary patients at rest and during rapid atrial pacing. In: Puech P, Krebs R (eds) 4th International Adalat Symposium: new Therapy of Ischemic Heart Disease. Excerpta Medica, Amsterdam, p 55Google Scholar
- 5.Engel H-J, Hundeshagen H, Lichtlen PR (1980) Prevention of pacing-induced ischemia by propranolol - changes of regional myocardial blood flow and coronary sinus O2- content. Circulation 62: 111 - 296Google Scholar
- 7.Freudenberg H, Lichtlen PR (1981) Das normale Wandsegment bei Koronarstenosen. Z f Kardiol (in press)Google Scholar
- 11.Leutenegger F, Rafflenbeul W, Gahl K, Walpurger G, Engel H-H, Lichtlen P (1980) Quantitative Koronarangiographie: Dilatation von Koronarstenosen nach Nifedipin. Schweiz Med Wochenschr 110: 1703Google Scholar
- 12.Lichtlen PR (1975) Coronary and left ventricular dynamics under nifedipine in comparison to nitrates, beta-blocking agents and dipyridamole. In: Lochner W, Braasch W, Kroneberg G (eds) 2nd International Adalat Symposium: New Therapy of Ischemic Heart Disease. Springer, Berlin Heidelberg New York, p212Google Scholar
- 14.Lichtlen PR, Engel H-J (in press) Relation between myocardial blood flow and degree of coronary obstruction under increased oxygen demand induced by rapid atrial pacing. In: Detection of ischemic myocardium with exercise. Symposium of the European Society of Cardiology, Düsseldorf, Springer-Verlag Berlin Heidelberg New YorkGoogle Scholar
- 15.Lichtlen PR, Engel H-J, Amende I, Rafflenbeul W, Simon R (1976) Mechanisms of various antianginal drugs. Relationship between regional flow behaviour and contractility. In: Jatene AD, Lichtlen PR (eds) 3rd International Adalat Symposium. Excerpta Medica, Amsterdam, p 14Google Scholar
- 17.Lichtlen PR, Engel H-J, Hundeshagen H (1977) Regional myocardial blood flow in normal and poststenotic areas after nitroglycerin, betablockade (atenolol), coronary dilatation (dipyridamole) and calcium antagonism (nifedipine). Herz 2: 81Google Scholar
- 18.Lichtlen PR, Engel H-J, Hundeshagen H (1978) Clinical application and results of the assessment of coronary blood flow by the regional precordial xenon residue detection technique. Nucl Med 17: 161Google Scholar
- 19.Lichtlen PR, Engel H-J, Amende I, Hundeshagen H (1978) Effect of beta blockade on regional myocardial blood flow in coronary heart disease. In: Gross F (ed) Modulation of sympathetic tone in the treatment of cardiovascular diseases. Huber, Bern, p 134Google Scholar
- 22.Simon R, Amende I, Lichtlen PR (1979) Das linksventrikuläre Angiogramm. In: Lichtlen PR (ed) Koronarangiographie. Straube, Erlangen, p249Google Scholar