HEART-RATE-VARIABILITY AND FUNCTIONAL SEVERITY OF CONGESTIVE-HEART-FAILURE SECONDARY TO CORONARY-ARTERY DISEASE

To investigate the behaviour of heart rate variability (HRV) with the advancing severity of heart failure (CHF) we studied 20 normal subject s and 80 coronary artery disease (CAD) patients in sinus rhythm. CAD p atients were selected consecutively in order to form four equal groups of 20 subjects with different degrees of CHF according to the New Yor k Heart Association (NYHA) functional classification. In each subject a 24 h ECG Holter tape was recorded and subsequently analysed to obtai n measures of heart rate and HRV. We used several measures of HR and b oth spectral and non-spectral measures of HRV. Among these we employed the width of the R-R interval distribution over 24 h at three differe nt heights (TV, 10%Var, 50%Var). The CAD group showed significantly lo wer HRV counts and smaller spectral components than controls. However, these differences were due to the presence of CHF rather than to CAD. Indeed a progressive and significant increase in heart rate and a con temporary decrease in HRV was observed with the advancing severity of CHF. Class IV patients had the smallest HR variation, the spectral com position in this group was barely detectable. Tile decrease in time do main measures of HRV followed the increase in NYHA Class in a progress ive mid regular pattern, while the low frequency and high frequency sp ectral power showed the largest reduction from NYHA Class I to NYHA Cl ass II patients. No significant change was demonstrated in NYHA Class I patients as compared to Controls. A significant direct correlation w as found between left ventricular ejection fraction (EF) and all the m easures of HRV examined (EF vs SDNN, r=0.77, P<0.0001). However, this relationship was not evident when both Controls and the single CHF Cla sses, were considered separately. Both EF and the clinical status sign ificantly and independently affected HRV (multiple regression analysis ; NYHA Class vs EF, P<0.002 and vs 10%Var, P<0.0001). These data show that the extent of HRV reduction in CAD is related to the severity of the functional impairment and it is significantly affected by the degr ee of left ventricular dysfunction.