Cardiac resynchronization therapy produces a long-term improvement in the clinical symptoms of patients with HF who have a ventricular conduction delay. The differences between optimized biventricular and univentricular therapy appear to be small for short-term treatment.

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.)

on behalf of the Pacing Therapy for Chronic Heart Failure II (PATH-CHF-II) Study Group Background-Cardiac resynchronization therapy (CRT) improves systolic function in heart failure patients with ventricular conduction delay by stimulating the left ventricle (LV) or both ventricles (biventricular, BV). Optimal LV site selection is of major clinical interest for CRT device implantation; however, the dependence of hemodynamics on LV stimulation site has not been established. Thus, the objective of this study was to compare the hemodynamic response to CRT for 2 LV coronary vein sites: the free wall and anterior wall. Methods and Results-A total of 30 patients (mean NYHA class, 2.7; mean QRS interval, 152 ms; mean PR interval, 194 ms) enrolled in the PATH-CHF-II trial were studied. CRT was administered with LV and BV stimulation in VDD mode at 4 AV delays. LV stimulation was at the lateral free wall or anterior wall, whereas right ventricular stimulation was fixed near the apex. LVϩdP/dt max and aortic pulse pressure changes from baseline during CRT were compared for LV sites. Free wall sites with LV and BV stimulation yielded significantly larger LVϩdP/dt max (14% versus 6%, PϽ0.001 for LV; 12% versus 5%, PϽ0.001 for BV) and pulse pressure (8% versus 4%, PϽ0.001 for LV; 9% versus 5%, PϽ0.001 for BV) compared with anterior sites. In one third of patients, CRT at free wall sites increased LVϩdP/dt max , whereas it decreased at anterior sites over most AV delays. Key Words: heart failure Ⅲ bundle-branch block Ⅲ pacing Ⅲ contractility Ⅲ electrical stimulation C ardiac resynchronization therapy (CRT) has been demonstrated to improve systolic function in heart failure patients with conduction system disorders. Stimulation chamber seems to be a dominant factor in determining the short-term hemodynamic response to CRT. 1,2,3 The impact of stimulation chamber on hemodynamic improvement is known to depend on the type of the conduction system defect. 4 For example, in patients with left bundle-branch block, stimulating the left ventricle (LV) has been shown to improve systolic performance more than stimulating the right ventricle (RV). 1 In addition to stimulation chamber, initial reports have suggested that the stimulation site within a chamber might play an important role in the outcome of CRT. 5,6 To date, however, no study has systematically evaluated the impact of LV stimulation site on short-term hemodynamics. Because choosing an optimal stimulation site is of major clinical interest for long-term CRT, it is important to investigate whether individual transvenous stimulation sites can affect systolic performance. Therefore, the objective of this study was to compare the short-term hemodynamic impact of CRT at the 2 most accessible areas of the LV using coronary vein-based lead systems 5 -namely, the free wall and the anterior wall. Conclusion-CRT Methods Study GroupThe PATH-CHF II study was prospectively designed to test shortterm hemodynamic changes during CRT delivered via multiple stimulation configurations. The ma...

Functional mitral regurgitation is reduced by CRT in patients with HF and LBBB. This effect is directly related to the increased closing force (LV+dP/dt(max)). The results support the hypothesis that an increase in TMP, mediated by a rise in LV+dP/dt(max) due to more coordinated LV contraction, may facilitate effective mitral valve closure.

Left ventricular pacing significantly improves exercise tolerance and quality of life in patients with chronic HF, LV systolic dysfunction, and a QRS interval over 150 ms.

After prolonged AF, atrial contractility was reduced by 75%. The impairment of beta-adrenergic modulation of contractile force cannot be explained by downregulation of ss-adrenoceptors or changes in G proteins. Dysfunction of the sarcoplasmic reticulum does not occur after prolonged AF. Failure of Bay K8644 to restore contractility suggests that the L-type Ca(2+) channel is responsible for the contractile dysfunction. The restoration of contractile force by high extracellular Ca(2+) shows that the contractile apparatus itself is nearly completely preserved after prolonged AF.

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.

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