The goal of this study was to determine the effects of a stressful procedure (coronary angiogram) on measures of heart rate variability (HRV) in patients with coronary artery disease (CAD). Sixty patients who had a coronary angiogram underwent 48-hour Holter monitoring during a period of high stress beginning 4-hours post-angiography (day 1 and 2), and again two weeks later during a period of low stress (day 3 and 4). Both time domain and power spectral measures were computed. Standard deviation of normal RR-intervals over 24-hour (SDNN) was significantly reduced during day 1 ([horizontal bar over]x±SE; 111.1 ± 6.4 ms) versus day 4 (124.8 ± 7.7 ms; p<0.05). Other time domain measures were not found to be significantly different. In the frequency domain, low frequency to high frequency area ratio(LF:HF area) was significantly greater during day 1 (1.8 ± 0.1) versus day 4 (1.7 ± 0.1; p<0.05). There was a main effect for time on total area (TA) of the power spectra. Over a 24-hour period, TA was the lowest at 3:00 am compared to all other times (p≤0.001). Our results demonstrated consistent reproducibility between day 1 and day 2, as well as between day 3 and day 4, for both time and frequency domain indices. These findings suggest that stress induced by an invasive procedure such as coronary angiogram, enhances sympathetic input to the SA node in the heart and thereby alters the sympathovagal balance, which is restored by 2 weeks following the angiogram.
E-22 POSTER CARDIOVASCULAR