QT/RR Coherence Is Associated with Testosterone Levels in Men with Chronic Spinal Cord Injury

AIM: To evaluate the effect of hypogonadism on temporal characteristics of ventricular repolarization (VR) and QT/RR coherence in men with spinal cord injury (SCI). METHODS: Thirty-four men with SCI (>1 year postinjury) were studied. After clinical evaluation, 20 subjects were diagnosed as hypogonadal and 14 as eugonadal. QT and RT time, heart rate (HR), and Bazett QTc were determined from a digital electrocardiogram during quiet rest and a cold pressor test (CPT). QT/RR coherence was calculated across three spectral frequencies including mean (Mean Coh; 0-0.2 Hz), low (LF Coh; 0.04-0.15 Hz) and high (HF Coh; 0.15-0.40 Hz). Respiration was collected via impedance pneumography. RESULTS: No statistical differences were observed among demographics. Pairwise comparisons demonstrated a significantly reduced Mean Coh at rest in the hypogonadal group compared to the eugonadal; during the CPT, the hypogonadal group had significantly elevated Mean and HF Coh. No group main effects were observed with analysis of variance. Condition main effects were observed in QT, Mean, LF and HF Coh. Significant group-condition interactions were present in Mean and HF Coh, while trends toward significance were observed on LF Coh, HR, QT and RT. Post-hoc pairwise comparisons revealed that the change from rest to CPT in Mean, LF and HF Coh was significant in the eugonadal group, but not the hypogonadal. CONCLUSION: Hypogonadism in SCI appears to adversely affect temporal VR characteristics independently of QTc. QT/RR coherence suggests an autonomic synergism with testosterone. These findings may represent a pathologic sequelae that precedes the well-documented hypogonadic effects on QTc.