CMR-based assessment of left ventricular hemodynamics in obstructive hypertrophic cardiomyopathy treated with septal reduction therapy

Abstract Background The current guidelines suggested patients with hypertrophic obstructive cardiomyopathy (HOCM) be treated with septal reduction therapy（SRT）, primarily including surgical septal myectomy(SSM) and alcohol septal ablation(ASA). However, studies on the effects of SRT on cardiac hemodynamic changes are still limited. Objectives The study aimed to compare the changes of cardiac hemodynamics before and after SRT, by left ventricle(LV) hemodynamic force (HDF) assessment based on cardiac magnetic resonance (CMR). Methods We enrolled patients with HOCM who underwent SRT, simultaneously with cardiac magnetic resonance imaging (CMR) examination both before and after SRT.The LV HDF assessment was performed on 2-, 3- and 4-chamber CMR deformation imaging by measurement of mitral and aortic in/outflow valve width. LV HDF was reported as a percentage of gravitational acceleration to represent the distribution of force vectors that drive blood acceleration within the ventricles. All patients were followed up regularly. Results A total of 67 patients with HOCM were enrolled，including 28 patients with SSM (17 males; age 40±15 years)and 39 patients with ASA(12 males; age 54±16 years)（sex P=0.03,age P0.001）. The symptomatic benefit in patients with HOCM following SRT was associated with a significant reduction in the LV outflow tract pressure gradient, particularly in SSA (Pre: 70.57 ± 33.32 mmHg vs. Post: 30.71 ± 6.99 mmHg), compared to ASA (Pre: 71.1 ± 19.71 mmHg vs. Post: 54.89 ± 23.19 mmHg).In the SSM group, LVEF (62.87 ± 5.3% vs. 57.30 ± 8.53%, P = 0.004) and RVEF (60.58 ± 7.52% vs. 55.83 ± 8.32%, P = 0.024) significantly decreased postoperatively. Patients after SSA had decreased global HDF in longitude direction (IQR 14.56-26.87 vs. 12.96-17.67,P=0.007) and systolic function, assessed by systolic peak (50.80±27.36% vs 36.62±15.83%, P= 0.020), systolic impulse (31.48±16.88% vs.21.68±8.1%, P=0.011). However, no significant differences were observed in HDF assessment in patients after ASA.For patients who underwent CMR beyond one year post-SRT, pronounced hemodynamic changes were observed in LV longitudinal force and other systolic function parameters，including systolic peak and systolic impulse. However, for patients who underwent CMR within one year after srt, there was no significant difference in hemodynamics compared to pre-SRT values. During the mean follow-up period of 52 months, 6 patients who underwent ASA required reoperation due to LVOTO, and 9 patients were readmitted for heart failure. The prognosis of ASA patients was relatively worse compared to those who underwent SSM. Conclusions In HOCM, SRT can lead to varying degrees of hemodynamic improvement, primarily observed after one year post-SRT. Compared to ASA, SSM results in better cardiac function recovery, greater hemodynamic improvement, and more favorable prognosis.Left ventricular HDF using cine CMR Changes in HDF before and after SRT