QT dispersion in patients with acromegaly

Abstract

Acromegaly is a rare condition caused by a pituitary adenoma that secretes growth hormone. The mortality rate is 72 % higher in patients with acromegaly than in the general population according to meta-analyses. Mortality analysis has shown as many as 60 % of acromegalic patients die due to cardiovascular disease. Sudden cardiac death may occur in patients with acromegaly and malignant ventricular arrhythmia may play an important role in this fatal complication; however, the precise mechanism is not fully known. QT dispersion (dQT) is an electrophysiological factor known to be associated with a tendency for ventricular arrhythmia and sudden cardiac death. This study aimed to evaluate dQT as an early predictor of ventricular tachyarrhythmia, as sudden cardiac death commonly occurs in acromegalic patients. This cross-sectional case–control study enrolled 20 patients (10 female and 10 male) with acromegaly and 20 healthy controls (11 female and 9 male) after exclusion criteria were applied. Each participant underwent 12-lead electrocardiography, including ≥3 QRS complexes, at a speed of 25 mm/s after a 15-min rest. In each participant, the QT interval (beginning of the Q wave to the end of the T wave) was corrected (QTc) for heart rate using Bazett’s formula $\left( {\text{QTc\, =\, QT}}/\sqrt {R}-R {\text{ s}} \right)$ QTc dispersion (dQTc) (QTc max – QTc min) was also calculated. There was no significant difference in median dQTc between the acromegalic patients (0.79 s) and the controls (0.45 s) (p > 0.05). Active acromegalic patients (n = 14) were estimated to have a median dQTc of 0.82 s, after excluding from the analysis six patients that were under full biochemical control, and that had randomly obtained growth hormone levels <0.4 ng/mL, GH <1 ng/mL based on oral glucose tolerance test, and normal IGF-I for age and gender. A significant difference was noted in median dQTc between the active acromegalic patients and the controls (p = 0.015). The dQT in active acromegalic patients was longer than that in the control group, which indicates that patients with active acromegaly might have an elevated risk for ventricular arrhythmia. We think that a non-invasive, simple and inexpensive marker—measurement of dQT—as part of cardiac monitoring could be valuable for screening complications in acromegalic patients.