Heart Rate Variability and QT Dispersion in Patients with Slow Coronary Flow

Abstract

Slow coronary flow is a very rare finding in normal coronary arteries. Reserve abnormality of the coronary microvasculature and increased activity of adrenergic system are accused for slow flow. We could not find any study investigating the effects of slow coronary flow on heart rate variability(HRV) and repolarisation of the myocardium. Therefore, we decided to make this trial. Twenty-nine patients with slow coronary flow and normal coronary arteries were included in the study. Twenty-two healthy subjects were accepted as control group. In the slow coronary flow group, TIMI frame counts from coronary angiography, QTc dispersion from 12 lead ECG, HRV from 24 hour ambulatory ECG monitoring were determined. In healthy subjects, HRV and QTc were determined by the same methods. Mean SDNN (109±29), pNN50 (11±7) and triangular index (462±119) of the slow coronary flow group were more depressed than the mean SDNN (146±44), pNN50 (20±16) and triangular index (584±142) of the control group (p values were 0.019, 0.037 and 0.008, respectively). There was no direct correlation between TIMI frame count and HRV indices in the slow coronary flow group. As a result, we suggested that HRV and QTc parameters are changed in the coronary slow flow patients in order to support the theory of increased adrenergic activity may be cause of abnormal coronary flow reserve at the microvascular level and slow coronary flow. Decreased HRV and increased heterogenity of repolarisation of myocardium may be cause of sudden cardiac death in some patients. For this purpose, larger and longer follow-up trials must be conducted in this patient group.