BACKGROUND AND OBJECTIVES: Long-term right ventricular (RV) apex pacing has been associated with left ventricular (LV) systolic dysfunction. However, pacing in the RV outflow tract (RVOT) is associated with a narrower QRS duration and may have a more normal LV activation in comparison to RV apical (RVA) pacing. We hypothesized that RVOT pacing is associated with less mechanical dyssynchrony compared to RVA pacing and that it also more closely resembles mechanical activation in normal controls with a narrow QRS. SUBJECTS AND METHODS: We studied 9 patients with RV pacing, 9 with left bundle branch block (LBBB), and 15 normal controls with a narrow QRS. In the RV pacing group, we paced from the RVA and RVOT. At the end of each pacing train, we obtained echocardiographic images in the apical 4- and 2-chamber views and obtained the following parameters: the compression/expansion crossover point (CEP) for myocardial strain and the time from QRS onset to the CEP in the strain image. The degree of dyssynchrony was evaluated using the dispersion and standard deviation of CEP times in 12 segments of the LV. RESULTS: Significant dyssynchrony was observed in the RVOT pacing group compared to the group with normal QRS. No significant difference was observed in LV mechanical dyssynchrony among the RVOT pacing, RVA pacing, and LBBB groups. CONCLUSION: RVOT pacing is associated with significant LV dyssynchrony. Although the RVOT has been recommended as an alternative site for pacing, this approach may have adverse effects on long-term LV function.
Bundle-Branch Block ; Heart Ventricles ; Humans ; Sprains and Strains

BACKGROUND AND OBJECTIVES: The number of permanent pacemakers (PPMs) implanted in patients in Japan and Korea differs significantly. We aimed to investigate the differences in decision making processes of implanting a PPM. MATERIALS AND METHODS: Our survey included 15 clinical case scenarios based on the 2008 AHA/ACC/HRS guidelines for device-based therapy of cardiac rhythm abnormalities (class unspecified). Members of the Korean and Japanese Societies of Cardiology were asked to rate each scenario according to a 5-point scale and to indicate their decisions for or against implantation. RESULTS: Eighty-nine Korean physicians and 192 Japanese physicians replied to the questionnaire. For the case scenarios in which there was a class I indication for PPM implantation, the decision to implant a PPM did not differ significantly between the two physician groups. However, the Japanese physicians were significantly more likely than the Korean physicians to choose implantation in class IIa scenarios (48% vs. 37%, p<0.001), class IIb scenarios (40% vs. 19%, p<0.001), and class III scenarios (36% vs. 18%, p<0.001). These results did not change when the cases were categorized based on disease entity, such as sinus node dysfunction and conduction abnormality. CONCLUSION: Korean physicians are less likely than Japanese physicians to favor a PPM implantation when considering a variety of clinical case scenarios, which probably contributes to the relatively small number of PPMs implanted in patients in Korea as compared with those in Japan.
Asian Continental Ancestry Group ; Atrioventricular Block ; Cardiology ; Decision Making* ; Humans ; Japan* ; Korea* ; Pacemaker, Artificial ; Sick Sinus Syndrome