HOCM with Severe AS: Prevalence and Clinical Significance
The combination of hypertrophic obstructive cardiomyopathy (HOCM) and severe aortic stenosis is uncommon but increasingly recognized in clinical practice, particularly in older patients with calcific aortic valve disease superimposed on pre-existing HCM. 1, 2, 3
Epidemiologic Context
The coexistence of HOCM and severe AS represents a rare clinical entity that is now more frequently encountered as both conditions have increased in recognition and the population ages. 3 While specific prevalence data are limited in the guidelines, case series and clinical reports consistently describe this combination as uncommon but not rare in contemporary practice. 1, 2, 4
Why This Combination Occurs
Calcific degeneration of the aortic valve can develop in patients with pre-existing HCM as they age, creating a dual obstruction scenario. 3, 5
The high prevalence of cardiovascular risk factors (hypertension in 63%, hyperlipidemia in 75%) in patients with both conditions suggests that traditional atherosclerotic risk factors contribute to aortic valve calcification even in HCM patients. 5
The combination creates two distinct levels of obstruction: dynamic left ventricular outflow tract (LVOT) obstruction from HCM and fixed valvular obstruction from AS. 3, 4
Critical Diagnostic Challenges
The presence of both conditions creates profound diagnostic complexity because each disease confounds the echocardiographic assessment of the other. 3, 4
Doppler assessment becomes technically challenging because the high LVOT gradient from HOCM can mask or exaggerate the severity of AS, making it difficult to determine which lesion is dominant. 2, 3
The rapid systolic flow acceleration from LVOT obstruction can artificially elevate transvalvular gradients, potentially leading to overestimation of AS severity. 2, 4
In one recent case series of 6 patients with both conditions, AS severity was downgraded in 3 of 6 cases after alcohol septal ablation relieved the LVOT obstruction, demonstrating how HOCM can falsely elevate AS gradients. 2
Transesophageal echocardiography may be crucial for accurate diagnosis when transthoracic imaging is inconclusive. 4
Clinical Outcomes and Management Implications
A combined surgical approach with myectomy and aortic valve replacement in patients with both severe HOCM and moderate-to-severe AS yields excellent outcomes, with longer-term survival similar to age-sex-matched general population. 5
In a series of 191 consecutive patients undergoing combined myectomy and AVR, 1-, 2-, and 5-year survival was 94%, 91%, and 83% respectively, with only 1.5% in-hospital mortality. 5
The mean age in this surgical cohort was 67±6 years, and 70% had no traditional HCM sudden death risk factors, suggesting these are typically older patients with acquired AS rather than young HCM patients. 5
Staged intervention strategies are emerging as viable alternatives, with alcohol septal ablation or mavacamten used first to relieve LVOT obstruction, followed by reassessment of AS severity and subsequent TAVR if needed. 2, 3
Key Clinical Pitfalls
Rapid hemodynamic decompensation can occur if AS is corrected first without addressing significant LVOT obstruction, as patients with HOCM cannot adjust quickly to the sudden decrease in afterload. 3
Treating AS alone when significant LVOT obstruction exists may unmask or worsen the dynamic obstruction, leading to clinical deterioration. 3
The presence of LVOT obstruction should be specifically sought and quantified before any aortic valve intervention, as it will not improve and may worsen after AS correction. 6