Autonomic function and QT interval measurements from ambulatory electrocardiography in normal and CAD subjects

Abstract

Background Coronary artery disease (CAD) subjects have a higher QT-interval variability on Ambulatory Electrocardiography (AECG) than normal subjects. We studied whether or not this variability is spontaneous or mediated by autonomic function. AECG data was used to describe the correlation of autonomic function to the QT-interval in normal and CAD subjects. Methods AECG monitoring (24-hour) was conducted on 106 normal (69 male) and 79 CAD subjects (54 male). RR and QT-intervals were measured from the recordings. Time-domain autonomic parameters of parasympathetic function (rMSSD) and total power (SDNN) were calculated for 24-hours and every 6-hours. Results Higher correlations were found in normal subjects between rMSSD and QT-intervals than in CAD subjects (r=0.394, r=0.238, respectively, p<0.001). The largest difference was seen between 12A and 6A. SDNN was higher in CAD subjects than in the normal subjects. Results are shown in table 1. Conclusions rMSSD was higher in normal subjects. SDNN is higher in CAD subjects. Therefore, we have indirectly shown that CAD subjects are more sympathetically activated than normal subjects. The lack of parasympathetic activity, and longer corrected QT-interval might contribute to a higher rate of arrhythmic death in CAD subjects. Clinical Pharmacology & Therapeutics (2004) 75, P6–P6; doi: 10.1016/j.clpt.2003.11.021 12A to 6A 6A to 12P 12P to 6P 6P to 12A Overall rMSSD v QT CAD 0.112 0.259 0.284 0.202 0.238 Normal 0.333 0.402 0.387 0.388 0.394 SDNN v QT CAD 0.097 0.289 0.297 0.196 0.249 Normal 0.138 0.245 0.236 0.226 0.212