DECREASED HEART-RATE-VARIABILITY IN PATIENTS WITH CONGESTIVE-HEART-FAILURE AND CHRONOTROPIC INCOMPETENCE

Heart rate variability was studied in 41 patients (aged 48 +/- 12 year s) with congestive heart failure secondary to idiopathic dilated cardi omyopathy. All patients underwent a treadmill exercise test and 24-hou r Holter ECG monitoring. Chronotropic incompetence was defined as the failure to achieve greater than or equal to 80% of the predicted maxim al heart rate response given by 220 - age (years) at peak exercise. Sp ectral heart rate variability was analyzed from 24-hour Holter ECGs an d was expressed as total (0.01-1.00 Hz), low (0.04-0.15 Hz), and high (0.15-0.40 Hz) frequency components. The standard deviation of all nor mal RR intervals (SDNN) was also computed. Chronotropic incompetence w as observed in ten patients. Peak oxygen consumption was significantly lower in patients with chronotropic incompetence compared with those without chronotropic incompetence. The total (5.11 +/- 1.26 In [ms(2)] vs 6.41 +/- 0.92 In [ms(2)]; P = 0.009) and low (3.38 +/- 1.65 In [ms (2)] vs 5.45 +/- 1.34 In [ms(2)]; P = 0.003), but not the high (3.42 /- 1.04 ln [ms(2)] vs 4.00 +/- 1.12 In [ms(2)]; P = 0.249) frequency c omponents of heart rate variability were significantly lower in patien ts with chronotropic incompetence, although there was no significant d ifference in mean heart rate (88 +/- 20 beats/min vs 86 +/- 15 beats/m in; P = 0.831) or left ventricular ejection fraction (22% +/- 10% vs 2 4% +/- 10%; P = 0.619). SDNN was also significantly lower in patients with chronotropic incompetence compared with those without chronotropi c incompetence (64 +/- 34 ms vs 102 +/- 37 ms; P = 0.030). Conclusions : The observation that heart rate variability is significantly decreas ed in patients with congestive heart failure who have chronotropic inc ompetence suggests that chronotropic incompetence may relate to an abn ormal autonomic influence on the heart in these patients.