Brugada Syndrome Behind Complete Right Bundle Branch Block
Background—The characteristic electrocardiogram of BS can be masked by right CRBBB and exposed by resolution of the block or pharmacological or pacing maneuvers.
Methods and Results—The study consisted of eleven patients who had BS and CRBBB. BS was diagnosed before the development of CRBBB (n=7), on the resolution of CRBBB, or from new characteristic ST changes that could be due to BS (n=4). Structural heart diseases were excluded, and coronary spasm was excluded based on a provocation test at catheterization. In seven patients, BS was diagnosed before the development of CRBBB. In one patient, BS was diagnosed when CRBBB resolved spontaneously. The precipitating cause for the resolution of CRBBB was, however, not apparent. On repeated ECGs, new additional upward-convex ST elevation was found in V2 and/or V3 in three patients. In two patients, new ST elevation was induced by IC drugs. The QRS duration was more prolonged in the patients with BS and CRBBB, compared to the age- and sex-matched controls: 170±13 ms versus 145±15 ms in V1, and 144±19 ms versus 128±7 ms in V5 (both P<0.0001). The amplitude of R in V1 was larger in the BS patients than in the controls (P=0.0323), but that of R' was similar (P=0.0560).
Conclusions—BS can coexist behind CRBBB, and CRBBB can completely mask BS. BS might be demonstrated by relief of CRBBB or by spontaneous or drug-induced ST elevation. The prevalence, mechanism and clinical significance of a combination of CRBBB and BS are yet to be determined.
- Received May 1, 2013.
- Revision received July 15, 2013.
- Accepted July 18, 2013.