Abstract Body (Do not enter title and authors here): Background: Aortic stenosis (AS) and septal hypertrophy are significant causes of left ventricular outflow tract obstruction (LVOTO). When both are present, the severity of LVOTO increases. For symptomatic patients, the treatment involves relieving both sources of obstruction through aortic valve replacement (AVR) and septal myectomy. AVR is associated with symptomatic improvement and better long-term outcomes in valvular causes of LVOTO. However, the long-term outcomes of AVR combined with septal myectomy in patients with coexisting septal hypertrophy and AS are not well studied.

Aims: This study aims to assess the long-term outcomes, associated risk factors, and prognostic indicators in patients with left ventricular outflow tract obstruction who underwent aortic valve replacement and concomitant septal myectomy.

Methods: We identified a retrospective cohort of 82 patients who underwent aortic valve replacement and concomitant septal myectomy for symptomatic LVOTO at the University of Pennsylvania between 2007 and 2021. We assessed preoperative and postoperative symptoms, electrocardiograms, echocardiograms, operative data, follow-up data, and mortality.

Results: The mean age of the cohort was 68.2 ± 15.1 years (range 19 to 88). Of the patients, 52% underwent AVR and concomitant myectomy only, while 48% underwent AVR, myectomy, and additional cardiac procedures. Postoperatively, the mean IVSd/PWd ratio was significantly reduced (Figure 1, p<0.01). Atrial fibrillation occurred in 45% of patients, and complete heart block occurred in 30%, but neither was associated with increased mortality (Figure 2, all p>0.05). The survival rates at 5 and 10 years post-operation were 74.6% and 44.8%, respectively. Additional cardiac procedures, alongside AVR and septal myectomy, did not increase mortality. Postoperative NYHA classifications at follow-up were markedly improved (Figure 3).

Conclusion: Patients with symptomatic LVOTO who underwent AVR with concomitant septal myectomy have long-term symptomatic improvement. Postoperative arrhythmias are common sequelae but are not associated with increased mortality.