Significance of isolated H-V interval prolongation in symptomatic patients without documented heart block

Paced and unpaced control groups were followed to establish the roles of pacers and infranodal (H-V) conduction in 59 patients with symptoms consistent with intermittent heart block (HB). To reduce the number of variables compared with previous studies, patients were included only when (1) prior ECG monitoring and medical-neurologic evaluation failed to document HB or other cause for symptoms; (2) His bundle studies were normal or showed only H-V prolongation, and (3) there was no history of a recent myocardial infarction. Of 35 patients with prolonged H-V interval, 18 received permanent pacers, while 17 remained unpaced. Eighteen unpaced patients constituted the normal H-V Group (after two were lost to follow-up and four received pacers). All groups were similar in types of heart diseases, NYHA classification, general medical condition, age and sex, thus providing adequate controls. All patients with normal H-V intervals remained stable (no deaths or progression to HB) for a mean follow-up period of 22 months. Among 18 patients with prolonged H-V intervals who received pacers, there were three deaths, none sudden, during a mean of 23 months; four patients developed HB unaccompanied by symptoms. Among 17 patients with prolonged H-V intervals who were not paced, eight died (three suddenly) and three progressed to HB with symptoms, leaving only six stable after six months follow-up. All these parameters were significantly worse in the unpaced patients with prolonged H-V intervals. These results suggest that patients with intermittent symptoms consistent with heart block, whose H-V interval is ≥ 60 msec. should receive a permanent pacer even if intermittent HB cannot be documented before implant.