Background: Despite the high efficiency of beta blockers in controlling increased blood pressure in hypertensive patients, these types of drugs have clinically remained as one of the main etiologies of atrioventricular (AV) blocks and arrhythmias. The present study aimed to assess the electrophysiological pattern in patients treated with beta blockers after discontinuing the drug use and also to assess the relationship between these electrophysiological findings and the recurrence of bradyarrhythmias in these patients.
Methods: In a prospective cohort study, 159 patients who were treated with different types of beta blockers and referred to Shariati Hospital in 2014 because of the onset of bradyarrhythmias were included into the study. All the participants were followed up for 6 months with respect to the recurrence of bradyarrhythmias.
Results: The rate of the occurrence of different AV blocks ranged between 13.8% and 23.3%, while these blocks also appeared within the follow-up period in the range of 7.5% to 11.3%, indicating a high recurrence rate of these blocks even after electrophysiological study (EPS) or pacemaker implantation. Assessing the relationship between the type of baseline rhythm and baseline characteristics showed a significant difference in the type of rhythm between the young and older patients (P=0.002), between patients with wide and narrow QRS complexes (p<0.001), and between those with normal and reduced left ventricular ejection fractions (P<0.001). Also, the type of baseline rhythm was significantly associated with HV interval in EPS (P<0.001), AV Wenckebach period (P<0.001), AERPAVN (P<0.001), and type of His disorder (P<0.001). The deteriorating effect of beta blockers as AV blocks type II or complete AV block can be more expected in patients with HV>55, AVWP>500, AERPAVN>500, as well as in infra-Hisian disorder.
Conclusion: The recurrence of bradycardia after administrating beta blockers is a common finding. Along with old age, QRS complex widening, and left ventricular dysfunction, the presence of some cut-off points of EPS indices, including HV>55, AVWP>500, and AERPAVN>500, as well as in infra-Hisian disorder can be considered as the main determinants of beta blockers-induced bradyarrhythmias.