Comparative evaluation of the efficacy of intravenous nitroglycerin and nitroprusside on reducing ventricular ischemia measured by vectorcardiographic-ST magnitude in experimental porcine myocardial infarction

Abstract

COMPARATIVE EVALUATION OF THE EFFICACY OF INTRAVENOUS NITROGLYCERIN AND NITROPRUSSIDE ON REDUCING VENTRICULAR ISCHEMIA MEASURED BY VECTORCARDIOGRAPHIC-ST MAGNITUDE IN EXPERIMENTAL PORCINE MYOCARDIAL INFARCTION James M. Foerster, MD; Zakauddin Vera, MD; David Janzen, BS; Dean T. Mason, MD, FACC, Univ. of Calif., Davis, Calif. Controversy remains concerning clinical effects of nitroglycerin (NTG) and nitroprusside (NP) on extent of muscle damage with acute myocardial infarction (AMI). To evaluate influence of these two vasodilators on degree of such muscle injury, vectorcardiographic-ST magnitude rise (STM) was used to estimate myocardial ischemia that occurred with AM1 in the intact porcine heart, the coronary circulation of which is similar to man. Previously we have shown the Frank XYZ leads ST sum correlates closely with ST sum of multiple epicardial grid leads. In ten pigs, following thoracotomy and coronary ligature, the chest was closed and Frank XYZ leads obtained. Natural evolution of STM over 4 hours was observed in four animals, and in six pigs NTG and NP dose-responses were obtained following AMI. In pharmacologic treated animals, hemodynamics and STM were recorded 30-60 minutes after coronary ligation (pre-drug control) and then remeasured after either NTG or NP; each animal was used as its own control with time allowed between each drug for return of control hemodynamics. Control BP at LVFP at Min STM m LVFP Min STM Min STM attained NTG 103 22 76 21 +81% NP 109 26 82 17 +66% Min STM = minimum STM rise; p = mean blood pressure (mm Hg); LVFP = left ventricular filling pressure (mm Hg). These data indicate that both NTG and NP C ischemia extent in experimental AMI. Moreover, with 4 LVFP, NP appears more effective than NTG in + ischemia with AMI. ATTENUATION OF THE CARDIOVASCULAR EFFECTS OF NITROGLYCERIN BY INDOMETHACIN. Esteban Morcillo, M.D. Bertram Pitt, M.D. and Philip R. Reid, M.D. Johns Hopkins Medical Institutions, Baltimore, Maryland. An earlier report from this laboratory demonstrated that nitroglycerin (TNG) produced a marked increase in myocardial prostaglandins E release when given as a carstant infusion (IOk Kanu Chatterjee, MD, FACC; William Parmley, MD, FACC; Anne Norman, BA: University of California, San Francisco, California. Vasodilators have an established role in the therapy of heart failure. Recent studies have demonstrated hemodynamic improvement in chronic congestive heart failure with oral hydralazine and most recently oral prazosin. This study compares the hemadynamic effects of hydralazine (HD) and prazosin (PR) in the same patients with chronic heart failure. Changes in heart rate (HR), mean arterial pres8ure (MAP), pulmonary artery pressure. pulmonary capillary wedge pressure (PCW), right atria1 pressure, cardiac index (CI), stroke volume index (SVI), stroke work index (WI), systemic (SVR) and pulmonary vascular resistance were determined in 12 patients after 3. 4 and 5 mg of PR and compared to initial control hemodynamics (Cl). After second control hemodynamics (C2) the effects of 75 mg oral HD were determined in the same patients. The results were: MAP PCW CI SVI SW1 HR mHg mHg L/minim2 ml/m2 g *m/m2 SVR* Cl 86?7 07?3 24fl 2.1k.l 26?2 22t3 1776? 8.5 PR-5 mg 07+7 79+3 19?2 2.52.2 3023 25t3 141Ot118 C2 87f7 87?3 2421 2.12.1 2522 22t2 1760+ 86 HD 89f6 7922 2021 3.32.2 3823 3022 10452 60 PR increasedC1 by 19% and decreased SVR by 21%. while in these patients HD increaaedC1 by 52% and decreased SVR by 41%. There was no change in other hemodynamic parameters with either drug. Conclusion: These findings suggest that both PR and HD produce beneficial hemodynamic response and within prescribed doses, HD is twice as effective as PR.