Medium- and long-term survival after pacemaker implant: Improved survival with right ventricular outflow tract pacing.
BACKGROUND
Long-term prognosis after pacemaker implant depends on numerous variables, particularly structural heart disease. There is evidence that apical stimulation could favor the development of heart failure and, therefore, influence mortality. Other right ventricular pacing sites have been studied, for example the outflow tract, but no reports regarding long-term clinical outcome are available.


OBJECTIVE
Compare all-cause mortality between two different sites of stimulation in the right ventricle.


METHODS
We retrospectively analyzed 150 consecutive patients who underwent pacemaker implantation because of complete AV block (spontaneous or after AV node ablation), symptomatic second-degree AV block, and symptomatic atrial fibrillation with slow ventricular response. All patients were implanted at the same institution with the standard technique. Apical stimulation was performed with a passive or active fixation lead and outflow tract pacing with an active fixation lead. Data collection period began in July 1999 and ended on December 2004. All patients included were greater than 70% ventricular paced during pacemaker follow-up. Patients older than 85 years were excluded from the analysis. Age, pacemaker mode, sex, ejection fraction, diabetes, and structural cardiac disease were analyzed. Mean age was 72+/-7 years (median 74 years, range 27-85 years), 101 (67%) were male, 56 had implanted a VVI PM, and 94 patients a DDD PM. Patients were divided into two groups: outflow tract (55 patients) and apical pacing (95 patients). Mean follow-up was 1,231+/-642 days (median 1,158 days, range 9 to 2,694 days), which ended on July 2007. Total mortality was examined with the Kaplan-Meier method to construct overall survival curves. Multivariate Cox proportional hazards regression models were performed.


RESULTS
All patients or relatives were contacted personally or by phone. There were no major statistical differences in patient background between the two groups. During follow-up, 18 patients (32%) died in the outflow tract group and 49 (51%) in the apical group (log-rank p=0.02). Cox regression multivariate analysis showed that outflow tract pacing and a low left ventricular ejection fraction (<40%) were the only independent variables with significant correlation with survival (p=0.006 and 0.003, respectively).


CONCLUSIONS
Outflow tract pacing appears to improve medium- and long-term survival. Prospective randomized trials with a greater amount of patients are necessary to confirm the findings of this study.
Vanerio
Gabriel
G
Arrhythmia Service CASMU-INCC, Montevideo, Uruguay. gabvaner@mednet.org.uy
Vidal
Juan L
JL
Fernández Banizi
Pablo
P
Banina Aguerre
Daniel
D
Viana
Pablo
P
Tejada
Jorge
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D054537:Atrioventricular Block / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate