Abstract 17975: Improvement in Exercise Capacity After Surgical Septal Myectomy in Obstructive Hypertrophic Cardiomyopathy Patients is Related to Peak Exercise Strain Rate and Mechanical Reserve

Abstract

Background: Significant improvements in functional capacity are noted after septal myectomy in symptomatic patients with obstructive hypertrophic cardiomyopathy (oHCM). However, the underlying mechanism behind these improvements is unclear. Methods: Conventional and strain echocardiography, at rest and post-exercise, was performed pre-and post-septal myectomy in 59 OHCM patients (42 men; mean age 50±12years). Exercise capacity was expressed as metabolic equivalents (METs) after treadmill exercise testing. Global longitudinal peak systolic strain (S) and stain rate (SR) were measured at rest and peak-exercise. Results: After myectomy, outflow gradient decreased significantly (resting gradient: 69±43 to 13±8mmHg; provoked gradient: 141±50 to 40±21mmHg; both p<0.001) with no significant change in ejection fraction (66±5% to 65±4%, p=NS). METs improved significantly (9.5±3.2 to 10.6±2.9, p=0.001). There was no significant change in S and SR at rest (S: -15.17±2.89% to -15.27±2.75%; SR:-0.95±0.18S-1 to -0.92±0.15S-1, both p=NS) or post-exercise (S: -17.06±3.63% to -16.68±2.79%; SR: -1.45±0.30S-1 to -1.52±0.28S-1, both p=NS). Mechanical reserve (MRES, change in systolic SR with exercise) increased significantly (55±30% to 67±32%, p=0.02). METs correlated significantly with exercise SR and MRES determined pre-myectomy (exercise SR: r=-0.41, p=0.003; MRES: r=0.33, p=0.017) and post-myectomy (exercise SR: r=-0.53, p<0.001; MRES: r=0.51, p<0.001). Improvement in METs was significantly correlated with changes in MRES (r=0.36, p=0.019). Multivariable linear regression confirmed an independent correlation between exercise SR and MRES with METs. Conclusions: Resting and peak exercise myocardial contractility (longitudinal S and SR) do not change significantly after septal myectomy. Post-myectomy MRES improves significantly and exercise capacity post-myectomy correlates significantly with pre- and post-myectomy functional status.