DECREASED HEART-RATE-VARIABILITY PARAMETERS IN AMITRIPTYLINE TREATED DEPRESSED-PATIENTS - BIOLOGICAL AND CLINICAL-SIGNIFICANCE

One hundred-four depressed patients treated with amitriptyline (mean d osage: 163 mg/d; mean plasma level: 239 ng/ml) and 52 normal control s ubjects matched for age and sex underwent a standardized cardiovascula r test battery (various autonomic cardiac parameters, which are largel y independent from heart rate, namely the coefficients of variation (C V) while resting and during deep respiration, a spectral analysis of h eart rate, the Valsalva ratio, and a posture index were determined). T he tests included the determination of time- and frequency-derived mea surements of heart rate variability (HRV), which is rather independent from heart rate. As compared to the controls the patients showed a si gnificant plasma concentration-dependent decrease of R-R variation in the electrocardiogram (p < 0.0001), while their heart rate was signifi cantly elevated (p < 0.0001). The markedly reduced parameters of sinus arrhythmia in amitriptyline treated patients are suggested to be main ly due to the anticholinergic effect of this drug, although it can not be excluded that the affective disorder itself might be associated wi th low heart rate variability. The results indicate that autonomic hea rt rate parameters are a valuable tool for the detection of tricyclic antidepressant (TCA) intake in unconscious patients, especially in int ensive care and emergency wards.