Background-Previous studies of pacing therapy for dilated congestive heart failure (CHF) have not established the relative importance of pacing site, AV delay, and patient heterogeneity on outcome. These variables were compared by a novel technique that evaluated immediate changes in hemodynamic function during brief periods of atrial-synchronous ventricular pacing. Methods and Results-Twenty-seven CHF patients with severe left ventricular (LV) systolic dysfunction and LV conduction disorder were implanted with endocardial pacing leads in the right atrium and right ventricle (RV) and an epicardial lead on the LV and instrumented with micromanometer catheters in the LV, aorta, and RV. Patients in normal sinus rhythm were stimulated in the RV, LV, or both ventricles simultaneously (BV) at preselected AV delays in a repeating 5-paced/15-nonpaced beat sequence. Maximum LV pressure derivative (LVϩdP/dt) and aortic pulse pressure (PP) changed immediately at pacing onset, increasing at a patient-specific optimal AV delay in 20 patients with wide surface QRS (180Ϯ22 ms) and decreasing at short AV delays in 5 patients with narrower QRS (128Ϯ12 ms) (PϽ0.0001). Overall, BV and LV pacing increased LVϩdP/dt and PP more than RV pacing (PϽ0.01), whereas LV pacing increased LVϩdP/dt more than BV pacing (PϽ0.01). Conclusions-In this population, CHF patients with sufficiently wide surface QRS benefit from atrial-synchronous ventricular pacing, LV stimulation is required for maximum acute benefit, and the maximum benefit at any site occurs with a patient-specific AV delay. (Circulation. 1999;99:2993-3001.)
Echocardiographic quantification of LV asynchrony identifies patients likely to have improved systolic function with CRT. Improved synchrony is directly related to improved hemodynamic systolic function in type 2 patients.
We characterized the relationship between systolic ventricular function and left ventricular (LV) end-diastolic pressure (LVEDP) in patients with heart failure (HF) and baseline asynchrony during ventricular stimulation. The role of preload in the systolic performance improvement that can be obtained in HF patients with LV stimulation is uncertain.We measured the maximum rate of increase of LV pressure, LVEDP, aortic pulse pressure (PP) and the atrioventricular mechanical latency (AVL) between left atrial systole and LV pressure onset in 39 patients with HF. Two subgroups were identified: "responder" if PP improved, or "nonresponder."Maximum hemodynamic improvement occurred at an atrioventricular (AV) delay that did not decrease LVEDP. Left ventricular and biventricular (BV) stimulation increased systolic hemodynamics significantly, despite no significant increase in LVEDP. All parameters decreased when the LVEDP was decreased by shorter AV delay. Left ventricular and BV stimulation provided better hemodynamics than right ventricular (RV) stimulation. For the nonresponder subgroup, systolic hemodynamics only worsened during AV delay shortening. For the responder subgroup, optimum PP was achieved when AVL was near zero. Restoration of optimal left atrial-ventricular mechanical timing partly contributes to the hemodynamic improvements observed in this patient subgroup. However, preload alone cannot explain the differences seen between RV and BV stimulation and the contradictory PP decreases even at maximal preload in the nonresponder subgroup. These results may be explained by a site-dependent mechanism such as the degree of ventricular synchrony. Caution should be taken in these patients when optimizing AV delays using echocardiography techniques that focus on LV inflow.
Medical therapy often fails to control symptoms of severe heart failure. The possibility of modifying to some degree the global ventricular performance with the implantation of a physiological dual chamber pacemaker, set with a short atrioventricular delay (100 msec), has been adopted in two patients with severe heart failure due to coronary artery disease. The baseline clinical condition of both patients was characterized by leg edema, ascites, dyspnea at rest, or even orthopnea with a functional New York Heart Association (NYHA) class III-IV. Acute measurements of hemodynamic and echocardiographic parameters during stepwise shortening of AV interval guided the pacemaker implantation and setting of AV delay in the chronic phase. Within a few days after pacemaker implantation, both patients considerably improved their clinical status as well as their functional NYHA class, improving to class II in one patient and to class II-III in the other patient. In addition, modification of systolic and diastolic parameters paralleled these improvements functional class and clinical condition. Pacemaker therapy in severe heart failure refractory to medical therapy can be of considerable benefit in patients whose quality-of-life is severely compromised when pharmacological therapy is no longer effective. Acute hemodynamic and echocardiographic testing is useful in assessing the most appropriate AV delay and pacing mode.
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