Delayed atrioventricular conduction in type 2 diabetic patients with vitamin D deficiency

Background Vitamin D deficiency is common especially in diabetes patients, and is linked to abnormal calcium metabolism and cardiovascular risk factors. However, the relations between vitamin D deficiency and electrocardiogram (ECG) parameters were unclear. PR prolongation is a recognised cardiovascular risk marker. Objective To investigate the relation of vitamin D deficiency with ECG parameters on atrioventricular conduction and ventricular repolarization. Methods We studied 275 Type 2 diabetes patients (mean age 64.7 ± 10.6 yrs; male 58%) recruited from medical outpatient clinics (all diagnosed >6 months). Serum 25-hydroxyvitamin D [25(OH)D] was measured by ELISA assay. Vitamin D deficiency was defined as 25(OH)D <20ng/mL. PR interval and QTc interval as determined from complete 12-lead ECG was respectively used as indicators of atrioventricular conduction and ventricular repolarization. Results 36% (99/275) diabetic patients were vitamin D-deficient. Mean PR interval was 166 ±28 ms. Vitamin D deficiency was associated with increased PR interval (B=9.3 ms, 95%CI: 2.4 to 16.3, P=0.008, age and sex-adjusted) but not with QTc interval (P=0.997). The association between vitamin D deficiency and increased PR interval remained statistically significant after adjustment for age, sex, prior coronary disease/ stroke, body-mass index, physical activity, caloric intake, smoking, systolic/ diastolic blood pressure, resting pulse rate, serum LDL and HDL-cholesterol, triglycerides, HbA1c, creatinine and the use of beta-blocker, calcium channel blockers/ angiotensin-converting enzyme inhibitors/ angiotensin receptor blockers, aspirin and statins (B=10.7ms, 95%CI: 0.02 to 1.81, P=0.019). Conclusions In patients with Type 2 diabetes, vitamin D deficiency is associated with delayed atrioventricular conduction. Clinical implications of such observations and underlying mechanistic basis will require further studies.