Correlations of left ventricular diastolic parameters and heart rate: assessment through right ventricular pacing

This study evaluated the correlations between left ventricular (LV) diastolic parameters assessed by equilibrium radionuclide angiography (ERNA) and heart rate (HR) through right ventricular pacing. Twelve patients with a permanent right ventricular apex pace-maker were included. Serial ERNA studies were performed under 6 sets of pacing cycle length (heart rate = 52, 62, 72, 82, 92, 104 beats/min) for each patient. The left ventricular ejection fraction was 49.9% +/- 3.1% under pacing HR of 52 bpm and 43.8% +/- 3.1% under pacing HR of 104 bpm. The peak filling rate (PFR) increased very significantly with HR (r = 0.98, P less than 0.001). When the relative changes of end-diastolic volume were taken into account, the correlation between PFR and HR remained significant (r = 0.94, P less than 0.001). The absolute time to PFR (TPFR) did not significantly change with HR, but the ratio of TPFR to cycle length strongly correlated with HR. Our study clearly demonstrates that the PFR assessed by ERNA increases and the TPFR occupies an increasing proportion of the cycle length as HR increases. Therefore, LV diastolic parameters should be normalized for HR in clinical applications. In particular, HR changes should be considered when LV diastolic parameters are used for the assessment of therapeutic interventions.