Accurately Measured Isovolumic Relaxation Time is a Valuable Diagnostic Marker of Diastolic Dysfunction

Introduction: Doppler-based diagnosis of diastolic dysfunction (DD) is often challenging, particularly in the presence of atrial fibrillation, tachycardia and poor imaging. Doppler-based measurement of isovolumic relaxation time (IVRT) suffers from limited reproducibility. We developed a novel echocardiographic method, the “cardiac six-phase plot”, which analyzes myocardial wall dynamics at high frame rates and allows for accurate identification of cardiac valve opening and closing times. We hypothesized that this method could improve IVRT accuracy and DD diagnosis.

Methods: Sixteen patients (aged 63.37 ± 5.64 years, 56.25% female) underwent echocardiography assessments, including Doppler-based techniques, IVRT measurement via the six-phase plot, and HFpEF-ABA scoring that is based exclusively on clinical variables.

Results: DD assessments were feasible in 9 patients (6 patients with atrial fibrillation and one with poor image quality were not assessed), whereas the six-phase plot quantified IVRT in all 16 patients with a temporal resolution of 8.8±0.7ms. IVRT strongly correlated with DD grade (r=0.87, p<0.001), following the linear regression: IVRT = 14.1*[DD grade]+75 ms. Patients with septal e’ <= 7 had significantly higher IVRTs than those with septal e` > 7, 119.30 ± 8.15ms versus 87.13 ± 10.71ms, respectively (p<0.05). An IVRT threshold of 98 ms determined via ROC analysis, differentiated between patients with e’ £ 7 and e` > 7 with high accuracy (AUC=0.85, TPR=1.0). Four patients without Doppler measurement exhibited prolonged IVRTs (127.2±11.3) and had high HFpEF-ABA scores of 5.00±0.57.

Conclusions: This novel six-phase plot method enables precise and objective measurement of the IVRT by analyzing the full cross-section wall dynamics and the entire isovolumetric phase, rather than relying on a single anatomical point and a single peak flow time-point. This method offers a robust index for diagnosing diastolic dysfunction, particularly in cases where Doppler-based indices are not feasible.