Abstract 14732: Vortex Formation Time in Patients With Hypertrophic Cardiomyopathy

Abstract

Introduction: Vortex formation time (VFT) is an index reflecting optimal vortex formation and efficiency in blood volume transport. The objective of this study was to investigate the association of VFT index with LV diastolic function and exercise tolerance in patients with hypertrophic cardiomyopathy (HCM) and examine its changes after septal reduction therapy. Methods: We studied 116 HCM patients (median age 57.5 [49-65], 39.7% female) who underwent exercise stress testing with measurement of peak O2 consumption within 2 months of imaging. VFT index was calculated and the cohort was divided into 2 groups (cutoff based on prior work and our own normal controls [n=12]): VFT<3.3 (n= 70) and VFT 3.3-5.5 (n=46). Comparisons were made in the subgroup of HCM patients before and after septal reduction therapy (n=31). Results: Patients with VFT < 3.3 had evidence of more advanced diastolic dysfunction grade (p<0.01) and a more advanced NYHA class in comparison with patients with a VFT in the 3.3 to 5.5 range (p=0.048). In addition, patients with VFT 3.3-5.5 achieved a higher workload (7.5 vs 5.7 METs, p=0.016) and maximal oxygen consumption (21.7 vs. 17.7, p=0.003). Following septal reduction therapy VFT increased significantly from 2.8 to 3.7 (p < 0.001). LVEDV (100.9 to 112.9 mL, p=0.003) and LA volume index (50.6 to 40.0 mL/m2, p < 0.001) remodeling were observed as well as reduced septal thickness (1.9 to 1.5 cm, p<0.001) along with improvement in NYHA class (p<0.001). The change in peak O2 consumption related well to the change in VFT (r =0.9, P<0.001). Conclusions: Patients with HCM and VFT 3.3-5.5 are less symptomatic and have better exercise tolerance. VTF increases after septal reduction therapy in keeping with the NYHA class improvement and the change in peak O2 consumption. VFT appears to be a useful parameter to evaluate cardiac function, its relation to exercise tolerance as well as the response to treatment in HCM patients.