ISCHEMIA-INDUCED REFLEX SYMPATHOEXCITATION DURING THE RECOVERY PERIODAFTER MAXIMAL TREADMILL EXERCISE TESTING

Background: Heart rate variability (HRV) analysis is problematic durin g maximal treadmill exercise testing (ET) due to rapidly changing hear t rate. Hypothesis: The aim of this study was to assess HRV spectral c omponents during treadmill ET in patients with coronary artery disease (CAD) and in healthy controls, and to search for possible differences between the two groups, Methods: Thirty patients with CAD and 30 age- matched healthy controls underwent symptom-limited ET and continuous e lectrocardiographic monitoring. For adequate assessment of HRV during maximal ET, we calculated the HRV measures [normalized units (NU)]-low -frequency (0.040-0.150 Hz) power (LF), high-frequency (0.150-0.400 Hz ) power (HF), and the LF/HF ratio-from all the sequential stages of th e ET with Limited changes (20 beats/min) in heart rate (stress 80-100, 100-120, 120-140, 140-160, 160-180/recovery 180-160, 160-140, 140-120 , 120-100, 100-80). Results: Both LF and HF were found to decrease gra dually during ET and to increase during the recovery period in both pa tients and controls (p<0.001). LF values were higher during the recove ry period than during the respective stages of exercise time in both p atients and controls, and LF/HF ratio was higher during recovery in pa tients only. Conclusions: During maximal ET (1) vagal tone withdraws d uring the exercise time and increases during the recovery period; (2) the sympathetic activity predominates during the recovery period, espe cially in patients with CAD and exercise-induced myocardial ischemia, This finding raises the possibility of ischemia-induced cardiocardiac sympathetic excitatory reflexes.