A Comparative Study of Nitroglycerin and Propranolol

Abstract

The action of sublingual nitroglycerin (0.6 mg) and intravenous propranolol (0.1 mg/kg) on shortening of right ventricular fibers was investigated in patients with and without coronary artery disease. This was accomplished with a newly devised strain gauge catheter. Hemodynamic parameters and changes in the oxidation-reduction potential of heart muscle were determined. Nitroglycerin results in decrease in shortening and velocity of shortening of ventricular fibers, heart rate, left ventricular end-diastolic and systemic pressure, dp/dt, tension-time index, stroke index, peripheral resistance, and left ventricular minute work in normal and arteriosclerotic subjects. Intravenous propranolol leads to a fall in velocity of shortening of myocardial fibers, heart rate, dp/dt, stroke index, and left ventricular minute work. However, there is an increase in tension-time index and peripheral resistance with no change in systemic pressure. Left ventricular end-diastolic pressure rises significantly in arteriosclerotic patients. The myocardial oxidation-reduction potential increases after nitroglycerin whereas it falls after propranolol in normal and arteriosclerotic patients. Additional Indexing Words: HemodynamicsVelocity of fiber shorte:Lactic-pyruvic acid ratio

Exercise Testing and Indirect Assessment of Myocardial Oxygen Consumption in Evaluation of Angina Pectoris

“…As shown in figure 4, the triple product is reduced for a given level of stress and angina is delayed. Although the triple product at angina after //-adrenergic blockade is similar to that of the control study in the example displayed, this finding is uncommon and our data [32] and those of others [33] generally demonstrate a reduction in triple product or rate-pressure product at angina after administration of /?-adrenergic blocking drugs. This may be related to a possible increase in ventricular size due to the depressant effect of these agents on myocardial contractility or to reduction in coronary blood flow.…”

Synergistic Actions of Nitrite-β-Adrenergic Blocking Agents in the Therapy of Angina Pectoris

“…Nitroglycerin does lower the triple product at any given level of exercise when compared to a placebo, suggesting that it improves exercise performance by lowering M V02 [27], Therefore, attention has turned increasingly to the likelihood that the efficacy of nitroglycerin is actually due to a reduction in MVO,2 at a given level of body work. Indeed, some studies [16,46,51,56,57,68,70,73] have suggested that nitrites decrease the hemodynamic load on the heart, and result therefore in relief of angina primarily by their action on the peripheral vascular circulation. Sublingual nitroglycerin results in a decrease in venous tone and in pooling of blood in the peripheral venous system and the pulmonary vasculature.…”

“…By blocking the cardiac ^-receptors which are activated during stress or exertion, ^-blockers reduce the increase in heart rate and myocardial contractility and have a direct, although modest, negative inotropic effect of their own [13]; arterial pressure may also be lowered because of the decreased cardiac output [5,13,22,43,53,56,67], /9-Blockade of the venous system also reduces venous tone and thus diminishes venous return [65]. These effects on the circulation all tend to prevent the in crease in MV02 associated with stress or exertion.…”

“…These effects are, among others: (a) increased ven tricular size [9] ; (b) increased left ventricular end-diastolic pressure [30] ; (c) prolongation of the duration of the systolic ejection period [56], and (d) peripheral arteriolar vasoconstriction, secondary to unopposed et-adrenergic stimulation. The first three changes tend to increase MVOa by in creasing both the time duration and the magnitude of myocardial tension.…”

Effect of propranolol on indices of intermittent myocardial ischemia, assessed by exercise testing and ambulatory st‐segment monitoring

“…Propranolol is a nonselective betaadrenoreceptor antagonist. It was the first clinically acceptable drug to be used in angina therapy, and continues to be the most popular with physicians (Robin et al, 1967). Any new antianginal agent must be compared with this drug, not only to prove its efficacy but also to demonstrate its comparative effects on cardiovascular mechanics.…”