however , it has not been systematically investigated whether the reduction in heart rate variability in those post myocardial infarction patients who later suffer death or severe arrhythmias is caused by a reduction of short-term variability of heart rate ( such as respiratory arrhythmia ) or whether the differences in long term variability ( such as diurnal rhythm ) are involved .
C0003811
arrhythmias
C0428977
reduction