SYSTOLIC AND DIASTOLIC FUNCTION WITH ALTERNATE AND COMBINED SITE PACING IN THE RIGHT VENTRICLE

We hypothesized that pacing at two ventricular sites simultaneously wo uld activate the myocardium more rapidly and improve ventricular funct ion. We studied the effect of pacing at the right ventricular outflow tract (RVOT) and the RV apex (RVA) on systolic and diastolic function. In 14 patients with a reduced systolic ejection fraction < 40% (mean EF 32% +/- 4%) we measured RV pressures, left ventricular pressures, E F, cardiac output, peak dP/dt, peak negative dP/dt, and the time const ant of relaxation, Tau, during intrinsic rhythm, atrial pacing and DVI pacing at the RVA, the RVOT, and both RV sires combined in random ord er. Repeated measures analysis of variance showed no significant diffe rences in any of these parameters. The highest absolute values of dP/d t were observed during sinus rhythm and the lowest with RVA pacing. Th is parameter tended to improve progressively with pacing in the RVOT a nd at both sites. Peak negative dP/dt showed a similar nonsignificant trend. Conclusion: These data suggest that in patients with poor LV fu nction, there may be subtle improvements in diastolic and systolic fun ction with pacing in the RVOT and at combined sites in the RV compared to traditional RVA pacing.