Objective: In Parkinson's disease, striatal dopamine transporter (DAT) binding and cardiac sympathetic function are disturbed. In addition, heart rate (HR)-corrected cardiac repolarisation time (QTc interval), which is partly under autonomic control, is prolonged. Whether there is physiological coupling between striatal DAT binding and QTc time (QTc-DAT relation) is not known. The purpose of this study is to evaluate QTc-DAT relation in healthy young adults.
Methods: Thirty-five participants (18 women, age 26.4+/-1.8 years; mean+/-SD) were studied with iodine-123 labelled 2beta-carbomethoxy-3beta-(4-iodophenyl) nortropane single photon emission tomography. Signal-averaged ECG was recorded at rest from each participant. QTc interval was computed with Bazett's correction and with the approach by Karjalainen, getting QTc and QTk intervals, respectively.
Results: Mean striatal DAT binding, as (striatum-cerebellum)/cerebellum, was 2.63+/-0.31. Mean HR, QT, QTc and QTk intervals were 66+/-9 bpm, 340+/-25 ms, 354+/-18 ms and 351+/-16 ms, respectively. HR-QT correlation was -0.63, P value of less than 0.001. HR was not related to striatal DAT binding. QTc-DAT and QTk-DAT relations were significant, r = -0.50, P = 0.004 and r = -0.59, P = 0.0002, respectively. In linear regression model, striatal DAT binding explained 35% of the variance of QTk interval (95% confidence interval: -46.9 to -13.0, P = 0.0002).
Conclusion: This study suggests significant physiological QTc-DAT relation in young healthy adults. QTc interval measurements might carry diagnostically important information in clinical conditions, which have an effect on both striatal DAT binding and cardiac sympathetic function.