Intraventricular Flow during Isovolumic Relaxation: Comparison of Normal and Paced Ectopic Excitation under Varied Loading Conditions

In this study, isovolumetric relaxation time (IVRT) flow velocities recorded by pulsed Doppler were induced or augmented in nine patients (aged 60 ± 20 years) with permanent pacemakers. Six subjects had evidence of IVRT flow (≥ 0.2 m/sec) during native rhythm, only three of whom exhibited cavity obliteration. Mean ± SD left ventricular (LV) ejection fraction and end-diastolic and end-systolic volumes were 60% ± 5%, 104 ± 50 mL, and 39 ± 27 mL, respectively. IVRT flows were induced or augmented (P < 0.003) in all patients during paced ectopic stimulation of the right ventricle and during pacing combined with sublingual nitroglycerin (NTG; 0.4 mg). However, IVRT flows were not significantly increased with NTG alone. IVRT flow duration was prolonged > 50% by pacing (P < 0.05). These data suggest that IVRT flows may be present in patients without cavity obliteration and may be accentuated by asynchronous LV relaxation.