In elderly patients with chronic bifascicular block, widespread conduction system lesions are common, but the progression to complete AV block and mortality is relatively low (2.4% and 1.1% per year, respectively).
Supports watchful waiting in stable elderly bifascicular block; leaves open pacing thresholds for prospective trials.
Thirty patients (22 males and 8 females, aged 64 to 89 years) with chronic bifascicular block were studied electrophysiologically and prognosis was assessed. Three had RBBB with LPH, 17 had RBBB with LAH, and 10 had LBBB. AH interval was prolonged in 12 (43%) of 28 patients and HV interval was prolonged in 11 (37%) of 30 patients. Of 16 patients with first or second degree AV block, 11 (69%) had prolonged AH interval and 8 (50%) had prolonged HV interval. Effective refractory period of the right atrium was prolonged in 8 (50%) of 16 patients and that of atrioventricular node was prolonged in 9 (64%) of 14 patients. Second degree AV block was observed at lower rates of atrial pacing (130 beats/min or less) in 14 (74%) of 19 patients. Sinus node dysfunction was present in 16 (62%) of 26 patients. During the follow-up period (37.1 +/- 6.1 months), advanced or complete AV block developed in 2 of 27 patients (2.4% per year) and a patient died of acute myocardial infarction (1.1% per year). The present study showed that prolongation of AH interval was observed more frequently than that of HV interval, and the presence of widespread lesions in the conduction system was suggested in chronic bifascicular block, and in spite of these facts prognosis was not so unfavorable as reported previously.
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Inoue et al. (1979) studied this question.
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