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Results of permanent dual-chamber pacing in symptomatic nonobstructive hypertrophic cardiomyopathy
R O Cannon1, D Tripodi, V Dilsizian
1Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
Insights
Dual-chamber pacing improved symptoms and exercise duration in nonobstructive hypertrophic cardiomyopathy patients. However, it led to reduced cardiac and stroke volumes, indicating potential hemodynamic trade-offs.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Dual-chamber (DDD) pacing benefits obstructive hypertrophic cardiomyopathy (HC).
- Its efficacy in nonobstructive HC with significant symptoms is less understood.
Purpose of the Study:
- To assess the impact of DDD pacing on symptomatic patients with nonobstructive HC.
Main Methods:
- 12 patients with nonobstructive HC underwent echocardiography, exercise testing, and hemodynamic measurements before and after DDD pacing.
- Evaluations included rest and exercise hemodynamics, exercise duration, and cardiac imaging.
Main Results:
- 10 of 11 patients reported improved symptoms.
- Treadmill exercise duration increased significantly (p < 0.01).
- Cardiac and stroke volume indexes significantly decreased (p < 0.01).
Conclusions:
- DDD pacing offers symptomatic and exercise benefits for nonobstructive HC.
- Reduced cardiac and stroke volumes warrant further investigation regarding long-term implications.
Abstract:
Because dual-chamber (DDD) pacing has been shown to be of benefit regarding symptoms, rest and pacing hemodynamics, and exercise duration in patients with obstructive hypertrophic cardiomyopathy (HC), the effect of DDD pacing was assessed in patients with nonobstructive HC who were significantly symptomatic despite medical management. Echocardiography, treadmill exercise testing, thallium-201 scintigraphy, radionuclide angiography, and invasive measurement of rest and semi-erect bicycle exercise hemodynamics were performed in 12 patients before and approximately 4 months after permanent DDD pacing. One patient died 3 months after pacemaker implantation, because of worsening diastolic heart failure. Of the remaining 11 patients, 10 improved regarding symptoms, and treadmill exercise duration was longer during DDD pacing than during the baseline study in sinus rhythm (6.8 +/- 2.8 to 8.5 +/- 2.8 minutes; p < 0.01), with a significant increase in the peak double product achieved (28.9 +/- 6.1 to 31.0 +/- 6.8 x 10(3); p < 0.05). However, there were significant reductions in cardiac (3.7 +/- 0.9 to 3.1 +/- 0.5 ml/min/m2; p < 0.01) and stroke volume (47.4 +/- 11.4 to 38.7 +/- 6.5 ml/beat/m2; p < 0.01) indexes, and a trend toward reduction in submaximal stroke volume index during DDD pacing as compared with the baseline study in sinus rhythm (44.7 +/- 13.5 to 40.9 +/- 10.9 ml/beat/m2; p = 0.097). No change in peak heart rate, cardiac or stroke volume index, mean blood pressure, or pulmonary artery or pulmonary capillary wedge pressure occurred with peak exercise during DDD pacing as compared with the initial exercise study in sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)