Left ventricular pacing minimizes diastolic ventricular interaction, allowing improved preload-dependent systolic
R A Bleasdale1, M S Turner, C E Mumford
1Department of Cardiology, Wales Heart Research Institute, Heath Park, Cardiff CF14 4XN, United Kingdom. bleasdalera@aol.com
Circulation
|October 13, 2004
Summary
Left ventricular (LV) pacing reduces external constraint on LV filling, improving effective filling pressure and stroke volume in heart failure patients. This mechanism enhances cardiac output via the Starling mechanism.
Area of Science:
- Cardiology
- Biomedical Engineering
- Heart Failure Research
Background:
- Left ventricular (LV) pacing is known to improve hemodynamics in heart failure patients.
- A potential mechanism for this benefit involves minimizing external constraint on LV filling due to ventricular interaction.
Purpose of the Study:
- To investigate the hypothesis that LV pacing reduces external constraint to LV filling.
- To quantify the impact of LV pacing on LV filling pressures and volumes.
Main Methods:
- Utilized the conductance catheter method to simultaneously measure LV pressure and volume in 13 heart failure patients (NYHA class III/IV).
- Measured external constraint to LV filling using the end-diastolic pressure-volume relation during inferior vena caval occlusion, with and without LV pacing.
Main Results:
- LV pacing significantly reduced external constraint to LV filling (P<0.01).
- Effective filling pressure increased by 4.0 mm Hg (P<0.01), leading to a 10 mL increase in LV end-diastolic volume (P=0.01).
- Stroke volume increased by 11 mL (P<0.01), accompanied by increases in LV stroke work and maximum dP/dt.
Conclusions:
- LV pacing effectively minimizes external constraint to LV filling, a key mechanism for hemodynamic improvement.
- The reduction in external constraint increases effective filling pressure, augmenting LV end-diastolic volume and stroke volume through the Starling mechanism.
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