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Mechanism of hemodynamic improvement by dual-chamber pacing for severe left ventricular dysfunction: an acute Doppler
R A Nishimura1, D L Hayes, D R Holmes
1Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
Insights
Dual-chamber pacing can improve heart function in some patients with severe left ventricular dysfunction by optimizing atrial and ventricular timing. This therapy may enhance cardiac output and reduce mitral regurgitation in select individuals.
Area of Science:
- Cardiology
- Biomedical Engineering
Background:
- Dual-chamber pacing is a potential treatment for dilated cardiomyopathy symptoms.
- Severe left ventricular dysfunction presents significant challenges in cardiac care.
Purpose of the Study:
- To investigate the mechanism of hemodynamic improvement with dual-chamber pacing.
- To assess the impact of varying atrioventricular (AV) intervals on cardiac function.
Main Methods:
- Studied 15 patients with severe left ventricular systolic dysfunction.
- Utilized AV sequential pacing at multiple AV intervals.
- Employed Doppler velocity, high-fidelity manometry, and thermodilution for hemodynamic assessment.
Main Results:
- Overall, no significant change in cardiac output or left atrial pressure across all patients.
- Group I (PR interval > 200 ms) showed significant cardiac output increase (3.0 to 3.9 L/min) at optimal AV intervals.
- Group I also experienced improved diastolic filling, reduced left ventricular end-diastolic pressure, and abolished diastolic mitral regurgitation.
Conclusions:
- Dual-chamber pacing can acutely improve hemodynamics in specific dilated cardiomyopathy patients.
- Optimization of atrial and ventricular mechanical synchrony is the primary mechanism.
- Improved diastolic filling and reduced mitral regurgitation contribute to benefits.
Objectives:
This study was undertaken to determine the mechanism by which improvement in hemodynamic variables may occur with dual-chamber pacing in patients with severe left ventricular dysfunction.
Background:
Dual-chamber pacing has recently been proposed as a therapeutic alternative for the relief of symptoms in patients with dilated cardiomyopathy.
Methods:
Fifteen patients with severe left ventricular systolic dysfunction were studied acutely during atrioventricular (AV) sequential pacing at various AV intervals (60, 100, 120, 140, 180 and 240 ms) with use of combined Doppler velocity curves and pressures obtained by high fidelity manometer-tipped catheters and thermodilution cardiac output.
Results:
Neither cardiac output nor mean left atrial pressure was significantly different when hemodynamic variables in the baseline state were compared with those during AV sequential pacing at the various AV intervals in all patients. The patients were classified into two groups. In group I (eight patients with PR intervals > 200 ms on the rest 12-lead electrocardiogram), cardiac output was significantly increased when AV sequential pacing at the optimal AV interval to output was compared with that at the baseline state (3.0 +/- 1.0 vs. 3.9 +/- 0.43 liters/min, p = 0.005) because timing of mechanical atrial and ventricular synchrony was optimized. In addition, left ventricular end-diastolic pressure and duration of diastolic filling were increased, and diastolic mitral regurgitation was abolished. In group II (seven patients who had normal AV conduction at rest), cardiac output during AV pacing decreased from the baseline value without change in the diastolic filling period.
Conclusions:
Dual-chamber pacing may improve acute hemodynamic variables in selected patients with dilated cardiomyopathy, mainly by optimization of the timing of mechanical atrial and ventricular synchrony. Reestablishment of the optimal diastolic filling period and abolition of diastolic mitral regurgitation may also contribute to hemodynamic improvement.