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[Effect of dynamic exercise on left ventricular hemodynamics in obstructive cardiomyopathy]
Insights
Dynamic exercise partially normalizes left ventricular outflow tract obstruction in hypertrophic obstructive cardiomyopathy (HOCM). Increased end-diastolic volume during exercise appears to be the primary factor improving obstruction in HOCM patients.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Context:
- Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by dynamic left ventricular (LV) outflow tract obstruction.
- Understanding the impact of exercise on this obstruction is crucial for patient management.
Purpose:
- To investigate the behavior of LV outflow tract obstruction in HOCM patients during dynamic exercise.
- To determine the hemodynamic changes associated with exercise in HOCM.
Summary:
- Nine HOCM patients underwent cardiac catheterization with dynamic supine bicycle exercise (80 watts).
- Resting LV intraventricular pressure gradients (mean 41 mmHg) decreased significantly to 16 mmHg during exercise.
- This improvement correlated with increased LV end-diastolic pressure and dP/dt max, suggesting partial normalization of obstruction.
Impact:
- Exercise can favorably alter LV outflow tract obstruction in HOCM.
- Increased end-diastolic LV volume is a likely mechanism for improved obstruction during exercise.
- These findings may inform exercise recommendations for HOCM patients.
Abstract:
The behavior of left ventricular (LV) outflow tract obstruction in hypertrophic obstructive cardiomyopathy (HOCM) during dynamic exercise was studied in 9 patients during cardiac catheterization. Pressure measurements were carried out with high fidelity tip manometers and cardiac output was measured by the thermodilution method. Resting intraventricular pressure gradients varied from 5 to 75 mm Hg (mean 41 +/- 30 mm Hg) and all patients had postextrasystolic gradients of more than 100 mm Hg. Under supine bicycle exercise (mean work load 80 watts) heart rate increased from 74 +/- 9 to 97 +/- 10 min-1, cardiac output rose from 4.32 +/- 0.7 to 8.36 +/- 2.0 l/min, and LV intraventricular pressure gradient dropped significantly to 16 +/- 4 mm Hg. This improvement of LV outflow tract obstruction was associated with an increase in LV enddiastolic pressure from 14 +/- 5 mm Hg to 25 +/- 2 mm Hg, an augmentation of dP/dt max from 1225 +/- 300 to 1748 +/- 200 mm Hg/sec and a deterioration of systolic to diastolic pressure-time index ratio. These preliminary results indicate partial normalization of the LV outflow tract obstruction in HOCM during supine bicycle exercise; this favorable effect is probably due to an increased enddiastolic LV volume.