Effect of percutaneous transluminal coronary angioplasty on QT dispersion and heart rate variability parameters

BACKGROUND The aim of the study was to analyse parameters reflecting the sympathovagal control of ventricular depolarisation and repolarisation [heart rate variability (HRV) and QT interval dispersion (QTd)] in patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA), and determine whether HRV correlates with QT dispersion parameters. METHODS The study consisted of 26 consecutive patients (16 men, 10 women) with single-vessel coronary artery disease (CAD) who underwent elective coronary angioplasty. HRV analyses of all subjects were obtained with the time- and frequency-domain methods. For frequency-domain analysis, low-frequency HRV (LF), high-frequency HRV (HF) and the LF:HF ratio were measured. For time-domain analysis, standard deviations of the normal-to-normal QRS intervals (SDNN) and square roots of the mean squared differences of successive N-N intervals (rMSSD) were obtained. QT intervals were also corrected for heart rate using the Bazett's formula, and the corrected QT interval dispersion (QTcd) was then calculated. All measurements (HRV parameters and QTcd) were made before and immediately after PTCA. RESULTS QTcd was significantly decreased after PTCA (52.2 +/- 3.5 vs 42 +/- 3.9 ms). SDNN (94.1 +/- 22 vs 123.9 +/- 35.2 ms), rMSSD (43.7 +/- 20.1 vs 73.4 +/- 14.5 ms) and HF (51.1 +/- 48.8 vs 64.2 +/- 28.6 ms(2)) were significantly higher after PTCA, whereas LF (142 +/- 41.5 vs 157.2 +/- 25.9 ms(2)) and the ratio of LF:HF (3.3 +/- 1.9 vs 2.1 +/- 1.2) were significantly decreased after PTCA. We observed a significant negative correlation after PTCA between QTcd and LF (r = -0.87, p = 0.01) and between QTcd and the ratio of LF:HF (r = -056, p < 0.05). CONCLUSION Among the patients with CAD undergoing PTCA, QTcd significantly decreased after PTCA, and negatively correlated with LF, the parameter reflecting the sympathetic system.