Auditing the safety and efficacy of interventional septal reduction therapies in hypertrophic obstructive cardiomyopathy at a specialized tertiary centre

Abstract Funding Acknowledgements Type of funding sources: None. Background Hypertrophic cardiomyopathy (HCM) is a recognized cause of sudden cardiac death and dysrhythmias. Patients with HCM and marked left ventricular outflow tract obstruction (LVOTO) may benefit from invasive therapies such as septal myectomy or alcohol septal ablation (ASA) (1). This study aimed to compare patient outcomes post-ASA and post-septal myectomy within a specialized tertiary centre. Purpose To establish the efficacy and safety outcomes of septal reduction therapies. Postoperative conduction abnormalities are the most common long-term postoperative complications in this population (2); however, specific patient outcomes at our tertiary heart centre were previously unknown. Methods This retrospective analysis included patients who underwent ASA (n= 66) or septal myectomy (n=151) between 2015 and 2021. Ethical approval was obtained before commencing the study. Two independent investigators extracted the preoperative and postoperative data from echocardiograms, electrocardiograms, clinic letters, and discharge forms. Normally distributed variables were reported as mean and standard deviation and analysed using an unpaired T-test with Welch's correction. Non-normally distributed variables were reported as median and interquartile range and analysed using the Mann-Whitney U test. Results The mean follow-up time was 2.69 ±1.37 years in the ASA cohort and 1.38 ±1.18 years in the myectomy cohort. There were no differences in gender or ethnic composition; however, on average, patients in the ASA cohort were 10.40 ± 1.82 years older than those in the myectomy cohort (95% CI: 13.99 to 6.81, p< 0.0001). Significant improvements in New York Heart Association (NYHA) class occurred across both cohorts (p< 0.0001). Post-ASA resting LVOT gradients decreased from 54.00 to 13.00 mmHg (95% CI: -45.00 to -21.00, p< 0.0001). Post-myectomy resting LVOT gradients decreased from 60.00 to 4.90 mmHg (95% CI: -57.00 to -41.00, p< 0.0001) and were significantly lower than post-ASA (p= 0.0007). In addition, re-intervention rates were higher post-ASA compared to post-myectomy 40% vs 1.32% respectively, (p< 0.0001). ASA also carried a greater risk of permanent pacemaker implantation 18% vs. 8% (p=0.0270), complete heart block 22% vs. 6% (p= 0.0016), and right bundle branch block 28% vs 0% (p< 0.0001) compared to septal myectomy. In contrast, septal myectomy had a greater risk of postoperative atrial fibrillation 20% vs 1.5% (p= 0.0004), and left bundle branch block 60% vs 7% (p< 0.0001) compared to ASA. Perioperative mortality was 0 (0%) in both cohorts. Conclusion In conclusion, both interventions were safe and provided significant symptomatic relief and effective gradient reduction. However, conduction abnormalities remain a considerable risk of septal reduction therapies and may contribute to patient morbidity. More research is needed to minimize intervention risks and further improve patient outcomes.