Primary Hyperparathyroidism Is Associated With Shorter QTc Intervals, but Not Arrhythmia.

Context: Primary hyperparathyroidism (PHPT) is associated with subclinical cardiovascular disease, but data regarding cardiac conduction abnormalities are limited.

Objective And Design: Retrospective cross-sectional comparison of cardiac conduction in patients with PHPT or thyroid disease (TD).

Participants And Setting: Patients ≥40 years old who underwent parathyroidectomy or thyroidectomy at a single tertiary institution from 2013 to 2018.

Methods And Outcomes: Demographics and preoperative electrocardiogram (EKG) parameters were compared using the Mann-Whitney U, chi-square test, and linear regression.

Results: A total of 1242 patients were included: 49.8% PHPT (n = 619) and 50.2% TD (n = 623). Median age was 60.5 years [interquartile range (IQR) 53.6-67.9]. Compared to controls, PHPT patients had higher median serum calcium [10.7 mg/dL (IQR 10.4-11.1) vs 9.5 mg/dL (IQR 9.3-9.8), P < 0.001] as expected, as well as, a higher prevalence of hyperlipidemia (49% vs 36%, P < 0.001) and hypertension (50.1% vs 42.2%, P < 0.01). Based on EKG, there was no difference in PR interval or the prevalence of arrhythmia, atrioventricular block, ST segment/T wave changes, premature ventricular complexes, right bundle branch block, or left bundle branch block after adjusting for covariates. The PHPT group had a lower mean corrected QT interval (414 ± 24) ms vs 422 ± 24 ms, P < 0.01), adjusted for covariates. Serum calcium predicted QTc independently of age, sex, and other covariates.

Conclusions: In the largest study to date, PHPT patients had shorter QTc intervals compared to TD controls but no increased prevalence of arrhythmia based on preoperative EKG.