Hemodynamic effects of nitroglycerin in acute myocardial infarction. Decrease in ventricular preload at the expense of cardiac output

D. O. Williams, Ezra A Amsterdam, D. T. Mason

Research output: Contribution to journalArticle

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Abstract

Nitroglycerin (NTG) has recently been suggested to decrease myocardial ischemia and enhance cardiac pump function during acute myocardial infarction (AMI). To evaluate the sublingual agent in this condition, the hemodynamic effects of 0.4 mg NTG administered to 16 supine patients during the first 72 hr of AMI were determined serially 5, 10 to 15, and 20 to 30 min post NTG. Data were evaluated for the entire group, as well as for 6 patients with normal pulmonary artery wedge pressure (PAW) (≤ 12 mm Hg; mean 7) who formed group I and for 10 patients with elevated PAW (> 12 mm Hg; mean 19) who comprised group II. In the 16 patients, NTG resulted in significant decreases in PAW (14 to 7 mm Hg; P < .01), mean systemic arterial pressure (MAP) (95 to 82 mm Hg; P < .01), cardiac index (CI) (1.79 to 1.46 L/min/m2; P < .02), stroke index (SI) (24 to 18 cc/m2; P < .01) and stroke work index (SWI) (27 to 20 gm m/m2; P < .01). These alterations were significant in both subgroups, with the decline in PAW greater (P < .02) in group II (19 to 9 mm Hg) than in group I (7 to 4 mm Hg). The decrease in SWI related to the fall in PAW was significantly greater (P < .05) in group I (2.03 gm m/m2) compared to group II (0.82), thereby indicating greater impairment of ventricular function in the group II patients. Heart rate (HR) increased slightly in the 16 patients (77 to 82 beats/min; P < .05) and in group I (71 to 80 beats/min, P < .05), while there was no change in group II. There was no significant change in total peripheral vascular resistance (TPVR) for the entire group or in the 2 subgroups. This study demonstrates that, regardless of initial left ventricular filling pressure, sublingual NTG given in the acute phase of AMI results in rapid fall in PAW, concomitant with decreases in systemic blood pressure, cardiac output and SWI, without changes in TPVR and with little or no effect on heart rate. Since TPVR was unaltered, the decline in MAP was due to fall in cardiac output. Thus, the principal action of sublingual NTG in AMI appears to be systemic venodilation with consequent reduction of ventricular preload. This effect is translated into decline of pump output even in patients with high initial filling pressures. Although NTC may rapidly relieve pulmonary congestion and lower myocardial oxygen consumption, use of the agent sublingually is limited in AMI because these salutary effects are accompanied by potentially deleterious fall in cardiac output and systemic blood pressure.

Original languageEnglish (US)
Pages (from-to)421-427
Number of pages7
JournalCirculation
Volume51
Issue number3
StatePublished - 1975

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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