Relation of “inotropic reserve” to functional capacity in heart failure secondary to ischemic or nonischemic cardiomyopathy

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Abstract

Exercise capacity in patients with dilated cardiomyopathy, measured by peak oxygen consumption (VO2) during exercise, has virtually no relation to resting left ventricular (LV) function. We hypothesized that exercise-induced inotropic reserve may explain some of the variation between peak VO2 and resting LV function. Treadmill stress echocardiography was performed simultaneously with peak VO2 measurements in 35 patients with dilated cardiomyopathy. Resting and immediate postexercise echocardiographic images were scored for change in segmental contractility using the American Society of Echocardiography 16-segment system. Segment scores were summed and divided by 16 to determine the wall motion index. Right ventricular (RV) function was quantified on a 4-point scale. Patients had a mean age of 52 ± 12 years (8 women) and a mean ejection fraction of 30 ± 10 (25 nonischemic patients). Average peak VO2 was 17.0 ± 6 ml/kg/min. Patients were divided into 2 groups by peak VO2: a high VO2 group, >17 ml/kg/min (17 patients) and a low VO2 group, ≤17 ml/kg/min (18 patients). LV ejection fraction was similar between the high and low VO2 groups (31 ± 9% vs 28 ± 11%, p = NS) as were etiology of heart failure, medications used, and LV volume. In the high VO2 group, wall motion index improved from 2.28 ± 0.20 to 2.12 ± 0.31 during exercise (p = 0.009). There was no improvement in the low VO2 group. Resting RV function was significantly better in the high VO2 group (1.4 ± 0.8 vs 0.6 ± 0.6 p = 0.004). Therefore, in patients with dilated cardiomyopathy and similar resting LV function, the presence of demonstrable LV inotropic reserve and preserved RV function partially account for variation in exercise performance.

Section snippets

Study patients:

We conducted a retrospective study examining a consecutive series of 35 patients with a dilated cardiomyopathy having an LV end-diastolic dimension >6.0 cm and an LVEF <50%. These patients were clinically stable and receiving optimized medical management of their heart failure. A summary of patient characteristics and their medical therapy is shown in Table 1. This retrospective review was approved by the University of Wisconsin Human Subjects Committee.

Exercise testing:

Exercise tests were performed to evaluate

Resting echocardiographic data (Table 2):

At rest LV systolic function was severely depressed, LV size markedly increased, and the regional wall motion index significantly depressed. RV function was only mildly impaired. There were heterogenous abnormalities of LV filling. Although the mean E/A ratio was increased and the mean deceleration time relatively decreased, only 50% of the study group had an E/A ratio >2.0, and only 43% a deceleration time <130 ms. Several patients (35%) had an E/A ratio <1.0, and a small group (14%) had a

Discussion

The major finding of this study is that peak VO2 is significantly related to both LV inotropic reserve and RV function. For the right ventricle, the strongest factor was resting systolic function, evident in the group with higher functional capacity having either normal or only mildly reduced RV function, whereas RV function in the group with lower functional capacity was typically mildly or moderately reduced. These findings are consistent with previous studies that have calculated

References (27)

  • E Traversi et al.

    Mitral flow velocity changes after 6 months of optimized therapy provide important hemodynamic and prognostic information in patients with chronic heart failure

    Am Heart J

    (1996)
  • J.A Franciosa et al.

    Pulmonary versus systemic hemodynamics in determining exercise capacity of patients with chronic left ventricular failure

    Am Heart J

    (1985)
  • K.T Weber et al.

    Oxygen utilization and ventilation during exercise in patients with chronic cardiac failure

    Circulation

    (1982)
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