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Effect of preload change on resting and exercise cardiac performance in hypertrophic cardiomyopathy
W L Chan1, D M Gilligan, E L Ang
1Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
Insights
This study on hypertrophic cardiomyopathy found that changes in fluid volume did not significantly alter cardiac output during rest or exercise. Patients appear to operate on a plateau of the left ventricular Frank-Starling curve.
Area of Science:
- Cardiology
- Physiology
Background:
- Hypertrophic cardiomyopathy (HCM) is a complex cardiac condition affecting heart muscle function.
- Understanding hemodynamic responses in HCM is crucial for managing exercise capacity and symptoms.
Purpose of the Study:
- To investigate the impact of altered circulating volume on hemodynamic responses in patients with hypertrophic cardiomyopathy.
- To assess cardiac function at rest and during exercise under varying fluid conditions.
Main Methods:
- 13 patients with HCM underwent maximal exercise tests.
- Hemodynamic parameters were measured after intravenous fluid loading (0.9% saline) and diuretic administration (frusemide).
- Swan-Ganz and radial arterial cannulation were used for pressure and cardiac output measurements.
Main Results:
- Resting pressures (right atrial, pulmonary capillary wedge) varied with volume status but cardiac and stroke indexes showed no significant change in supine rest.
- Upright exercise showed higher cardiac index and stroke index after fluid loading.
- Despite increased filling pressures during exercise, key hemodynamic outputs and exercise capacity remained unchanged compared to diuretic state.
Conclusions:
- Circulating volume changes do not significantly influence cardiac index and stroke index in HCM patients.
- HCM patients may operate on the plateau of the left ventricular Frank-Starling function curve.
- Preload alterations have a limited effect on cardiac performance in this patient group.
Abstract:
The purpose of this study was to investigate the hemodynamic responses, at rest and on exercise, of patients with hypertrophic cardiomyopathy to changes in circulating volume. After Swan-Ganz and radial arterial cannulation, 13 patients with hypertrophic cardiomyopathy performed maximal exercise tests after diuretic (frusemide 20 mg intravenously) and after fluid loading (0.9% saline at 10 ml/kg body weight intravenously) on different days. At rest, right atrial and pulmonary capillary wedge pressures increased with volume loading and decreased with a diuretic. There were no significant changes in the resting, supine cardiac or stroke indexes but in the upright position, the cardiac index and stroke index were higher after volume loading (2.5 +/- 0.7 vs 2.2 +/- 0.5 liters/min/m2, p less than 0.05; 33 +/- 11 vs 27 +/- 9 ml/m2, p less than 0.005, respectively). Although the right atrial, pulmonary arterial and pulmonary capillary wedge pressures were higher during exercise after volume loading, there were no significant differences in exercise heart rate, systemic blood pressure, cardiac index, stroke index, systemic vascular resistance index or overall exercise capacity compared to exercise after diuresis. The data show that the cardiac index and stroke index, at supine rest and during upright exercise, were not influenced by the preload changes induced in these patients with hypertrophic cardiomyopathy. The results suggest that these patients are operating on the plateau of left ventricular Frank-Starling function (filling pressure/output) curve.