Increased beat-to-beat variation in diastolic phase percentages in patients with congestive heart failure

Diastolic time (DT) may reflect the functioning status of cardiac relaxation/diastolic filling. Previous studies shown that beat-to-beat variation in RR interval (i.e., HRV) is preferentially expressed in the variation in DT series, raising up a question that whether DT possesses intrinsic variation, or whether the DT variation is simply a surrogate of HRV without additional information. In this study, we defined the diastolic phase percentages (DP) by correcting DT by the corresponding RR interval and proposed to analyze DP variation (DPV) in order to eliminate the masking effect of HRV. We studied DPV of 60 patients with congestive heart failure (CHF) and 60 healthy control subjects. Radial artery pressure (RAP) was monitored in synchrony with electrocardiography (ECG) for 5 min in order to extract the proposed DPV. Additionally, DPV was corrected by the individual mean DP level which resulted in the coefficient of DPV (cDPV). The differences in DPV and cDPV between the two groups were determined by linear regression models controlled for age and sex. Results showed that both DPV and cDPV increased significantly in CHF patients compared with healthy control subjects (both p <; 0.05). Those results, highly endorsing the existence of intrinsic physiological variation in DT, may suggest that CHF patients have less stable cardiac relaxation (that is not due to HRV) or/and less stable contractility (since the diastolic and systolic phases are mutually complementary). This study may provide helpful reference for the noninvasive evaluation of cardiac functionality and for the further understanding of multiple physiological variabilities.