JOURNAL OF THE

VOLUME X X l V

OCTOBER 1976

Copyright 0 1976 by the American Geriatrics Society

JMBER 1 0 Printed in U.S.A.

Clinical Implications of Left Ventricular Function in Patients with Acute Myocardial Infarction RAVI PRAKASH, MD, FACP* and WILBERT S. ARONOW, MD, FACP**

The Cardiology Section, Medical Service, Long Beach Veterans Administration Hospital, and the University of California College of Medicine, Irvine, California ABSTRACT: Correlation of left ventricular filling pressure (55 patients) with the left ventricular stroke work index (61 patients) provided a rapid means of objectively determining ventricular performance after myocardial infarction. Pressure was monitored by means of the Swan-Ganz balloon-tipped catheter and thermal indicators were used for measuring cardiac output. A hemodynamic grouping of these myocardial infarction patients on the basis of the stroke work index showed close correlation with morbidity and mortality and provided a more accurate prognostic indicator than did the commonly used clinical predictors. Serial assessment of ventricular function further aided in defining the prognosis when it was not clear on admission. Thus, the levels of. normal or abnormal ventricular function and the effect of therapeutic measures can be rapidly evaluated by determining the pressures and flows in patients with acute myocardial infarction. The use of anti-arrhythmic agents in the coronary care unit has virtually abolished arrhyth-

mias as a significant primary cause of death during acute myocardial infarction. The remaining cause of most deaths, therefore, has been power failure, i.e., either severe progressive heart failure or cardiogenic shock. Although cardiogenic shock may be On pounds, lesser degrees of power failure may not be readily recognized because peripheral compensatory mechanisms may mask significant deterioration in cardiac function for a period of time. In such patients,it would be beneficial to be able to dict which patients would be likely to develop severe pump failure and, therefore, be candidates

* Chief, Noninvasive Cardiac Laboratory, Research Cardiologist to the Coronary Care Unit, and Director of Cardiology Education and Training Program, Long Beach VA Hospital; Assistant Professor of Medicine, University of California, Irvine. Requests for reprints to be addressed to: Ravi Prakash, MD, Cardiology Section, Veterans Administration Hospital, Long Beach, CA 90822. ** Chief, Cardiovascular Section, and Assistant Chief of Medicine for Research, Long Beach VA Hospital; Professor of Medicine, Vice-Chief, Cardiovascular Division and Chief, Cardiovascular Research, University of California, Irvine.

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for early application of newer therapeutic techniques. Several clinical and biochemical prognostic indicators have been described to identify high-risk myocardial infarction patients (1, 2). However, hemodynamic evaluation of patients with acute myocardial infarction presents a picture which frequently may be different from what is suggested by the clinical evaluation (3-7). It is the purpose of this communication to present data suggesting that monitoring of hemodynamics can be useful in objectively assessing the left ventricular function of patients with acute myocardial infarction. Measurement of left ventricular stroke work, on admission, is particularly useful in serving as an accurate prognostic indicator and helps in guiding appropriate therapy in selected patients (5). METHODS AND MATERIALS Methods

Previously, techniques involving standard cardiac catheterization procedures have been employed to obtain hemodynamic information from the right and left heart in patients with acute myocardial infarction. Recently, a significant development has been the introduction of the SwanGanz balloon-tipped catheter for obtaining this information (8). The Swan-Ganz catheter does not require fluoroscopy and can be advanced with pressure monitoring to the right atrium, where the small balloon is inflated; the balloon flow directs the catheter into the pulmonary artery. Once in the pulmonary artery, the catheter can be deflated and then advanced and re-inflated to obtain pulmonary capillary or wedge pressures. This catheter was used in obtaining data for the present report. The measurement of cardiac output in patients with acute myocardial infarction has involved the standard indicator dilution technique, the Fick method, the noninvasive technique of echocardiography, and the radioisotope method. In order to obtain the data, we used the newer technique developed for measuring cardiac output by means of thermal indicators (9, 10). These are injected into the right atrium, with sampling from the pulmonary artery.

following criteria: 1) a history of oppressive chest pain lasting longer than 10 minutes; 2) an electrocardiogram (ECG) demonstrating new Q waves of 0.04-sec duration with evolutionary changes developing in the S-T segments and T waves; and 3) transient elevations in the serum levels of transaminase (SGOT), lactate dehydrogenase (LDH), and creatine phosphokinase (CPK). A complete history and physical examination were obtained at the time of admission, and the presence or absence of left ventricular failure, arrhythmias, or shock was determined (4, 5). CZinicaZ Groups. On the basis of the physical examination, the patients were placed according to three clinical categories (Table 1): I a-no rales or cardiac gallop rhythm. b-rales in the lower half of the posterior chest, or a third heart sound, or both. I1 -rales in both the upper and lower half of the posterior chest. 111 -cardiogenic shock. Cardiogenic shock was defined by the following criteria: 1)systolic arterial pressure below 90 mm Hg, or 30 mm below the prior basal level for 30 minutes or longer; and 2) evidence of reduced organ perfusion by lactic acidemia or two of the following: a) confusion or obtundation; b) cyanosis of the extremities; and c) urine output less than 20 ml/hour. Determinations and patients

Left ventricular filling pressure (LVFP) was used interchangeably with pulmonary artery end-diastolic or pulmonary capillary wedge pressure, and was measured in 55 patients (4, 5). The left ventricular stroke work index (SWI) was calculated by the following formula (5) in 61 patients: SWI (gm-M/beat/M2) = MAP (mm Hg) x SI (ml/beat/M2) x 0.0144. In this equation, MAP refers to mean arterial pressure, SI is the stroke index, and 0.0144 stands TABLE 1 Acute Myocardial Infarction - Clinical Classification

Group I

a. No heart failure

b. Mild heart failure

Definitions

The diagnosis of acute myocardial infarction was made in the presence of a t least two of the

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Group 11

Severe heart failure

Group I11

Cardiogenic shock

No rales or gallop rhythm Rales in lower half of post. chest, or a 3rd heart sound, or both Rales in upper and in lower half of post. chest

October 1976

LV FUNCTION IN ACUTE MYOCARDIAL INFARCTION

for the constant for conversion of mm Hg to cm H20, and ml of blood to gm of blood. Hemodynamic Groups. On the basis of the calculated SWI, three hemodynamic groups were formed: Hemodynamic group I included patients with a SWI of more than 60 gm-M/beat/M2. Hemodynamic group I1 included patients with a SWI ranging from 25 to 60 gm-M/beat/M2. Hemodynamic group I11 included patients with , a SWI of less than 25 gm-M/beat/M2(Table 2).

TABLE 4 Acute Myocardial Infarction- Survival Rates According to Hernodynamic Classification (LV Stroke Work Index) Hemodynamic Group Group I (SWI > 60) Group I1 (SWI 25-60) Grow I11 (SWI < 25)

ACUTE MYOCARDIAL INFARCTION

HEMODYNAMIC CLASS1 FlCATlON 90

PREDICTION OF MORTALITY BY CLINICAL EVALUATION Survival rates in the three clinical classes of patients are shown in Table 3. There were no significant differences in survival rates between clinical groups Ia (no failure) and Ib (moderate failure). However, significant differences were observed between groups I, I1 and I11 (P < 0.001). The mortality rate was 7 percent in clinical group I (combinationof Ia and Ib), 54.percent in group I1 (severe left ventricular failure), and 100 percent in group I11 (cardiogenic shock) (5). PREDICTION OF MORTALITY BY HEMODYNAMIC EVALUATION

No. of Non-surviPatients Survivors vors 13 13 (100%) 0 33 28 (85%) 5 (15%) 15 1 (6%) 14 (94%)

80

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(61 Patients) 0 Survivors

Non-survivors

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20 2 50 \

I

k

40

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30 20

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All the hemodynamic group I patients survived; mortality was 15 percent in group I1 patients and 94 percent in group I11 patients (Table 4) (5). The differences in mortality were significant between all hemodynamic groups (P < 0.001), as shown in Figure 1.

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TABLE 2 Acute Myocardial Infarction -Hemodynamic Classification Left Vent. Stroke Work Index (gm-M/beat/M*) >60 Group I 25 to 60 Group 11 Group I11

Clinical implications of left ventricular function in patients with acute myocardial infarction.

JOURNAL OF THE VOLUME X X l V OCTOBER 1976 Copyright 0 1976 by the American Geriatrics Society JMBER 1 0 Printed in U.S.A. Clinical Implications...
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