Acute effects of dual-chamber pacing on the left ventricular systolic function and relaxation in patients with advanced AV block and sick sinus syndrome.
BACKGROUND
Abnormal activation of the ventricles via right ventricular apical pacing deteriorates cardiac function, which may explain the increased mortality of patients with congestive heart failure receiving permanent pacemakers. We hypothesized that pacing at alternative sites may cause less detrimental effects on the cardiac function.


METHODS
Five symptomatic patients with either advanced AV block (n = 4) or sick sinus syndrome with normal left ventricular (LV) function (n = 1) were studied. During cardiac catheterization, LV pressure was recorded with a high-fidelity catheter-tipped transducer. Baseline rhythms were sinus rhythm or VVI pacing. Sequential VDD pacing with variable AV intervals was performed at the right ventricular apex (RVA), right ventricular septum (RVS), right ventricular outflow tract (RVOT) and coronary sinus (CS). LV systolic function was assessed by calculating dP/dt(max) and LV diastolic function was indexed by calculating the exponential isovolumic relaxation constant (Tau). Percentage changes (mean +/- SE) from baseline to pacing were measured.


RESULTS
RVA pacing reduced dP/dt(max) (-0.8 +/- 8.4%) and prolonged Tau (7.0 +/- 5.6%); RVS pacing enhanced dP/dt(max) (20.7 +/- 15.3%) and shortened Tau (-10.4 +/- 9%); RVOT pacing reduced dP/dt(max) (-8.0 +/- 20.0%) and shortened Tau (-6.0 +/- 12.2%); CS pacing reduced dP/dt(max) (-11.7 +/- 13.0%) and prolonged Tau (10.5 +/- 11.9%). Our results demonstrated that different pacing sites have different effects on LV contractility and relaxation in patients with normal LV function.


CONCLUSIONS
Since pacing at the RVS preferably increased LV dP/dt(max) and shortened Tau, it may be a better alternative than the RVA.
Hsiao
Hsiang-Chiang
HC
Division of Cardiology, Department of Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan, ROC.
Chen
Chen-Huan
CH
Kong
Chi-Woon
CW
Liuln
Chun-Peng
CP
D000368:Aged; D002304:Cardiac Pacing, Artificial; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D012804:Sick Sinus Syndrome / Q000503:physiopathology / Q000628:therapy*; D013599:Systole; D016277:Ventricular Function, Left