Significance of the HV Interval in 517 Patients with Chronic Bifascicular Block

SUMMARY In January 1975, we reported results of a prospective follow-up study (mean 538 ± 42 days) of 119 patients with chronic bifascicular block (BFB), and concluded that BFB patients with normal and prolonged HV (NHV and PHV) had a similar incidence of atrioventricular (AV) block and mortality. In this report, we update these findings in 517 patients with a follow-up of 21 days to 9.8 years (mean 3.4 ± 0.2 years). Three hundred nineteen patients (61%) had NHV and 198 (39%) had PHV (> 55 msec). The NHV and PHV groups were similar in regard to age (NHV vs PHV, 61 ± 1 vs 62 i 1 years) and sex (80 % male, 20 % female vs 82 % male and 18 % female). The following were more common (p < 0.05) in patients with PHV (percent of pa-tients with finding in NHV vs PHV groups): angina (18 % vs 27%), congestive failure (27 % vs 42%), cardio-megaly (48 % vs 66%), New York Heart Association functional class II-IV (34 % vs 56%), premature ventric-ular complexes (20 % vs 29%), and organic heart disease (OHD) (75 % vs 85%). Spontaneous trifascicular block (TFB) developed in two patients (0.6%) with NHV and nine patients (4.5%) with PHV (p < 0.05). Cumulative 7-year incidence of TFB was 3 % with NHV and 12 % with PHV (p < 0.01). Seven-year cumulative cardiovas-cular mortality was 32 % in NHV patients and 57 % in PHV patients (p < 0.005). In conclusion, PHV in patients with chronic BFB was associated with a greater incidence and severity of OHD, and higher total and sudden death mortalities. The risk of spontaneous TFB was small in patients wit