From the Guidelines
Hypertrophic Obstructive Cardiomyopathy (HOCM) is characterized by left ventricular hypertrophy, often asymmetric in distribution, with a nondilated and hyperdynamic chamber, and systolic anterior motion (SAM) of the mitral valve leading to left ventricular outflow tract obstruction (LVOTO) 1. The presence of orthopnea and paroxysmal nocturnal dyspnea (PND) in HOCM patients may indicate severe disease, often necessitating initiation or intensification of beta-blocker therapy, such as metoprolol succinate, at a dose of 25-100 mg daily, to alleviate symptoms and reduce outflow tract obstruction 1.
Key Characteristics
- Dynamic LVOT obstruction: obstruction is sensitive to ventricular preload, afterload, and contractility, and can be provoked by maneuvers such as the Valsalva strain or exercise 1
- Diastolic dysfunction: impaired diastolic filling due to abnormal relaxation and increased chamber stiffness, leading to elevated left atrial and LV end-diastolic pressures 1
- Systolic function: usually normal, but can be impaired in advanced disease, leading to heart failure and increased risk of sudden cardiac death 1
- Mitral regurgitation: often associated with SAM and LVOTO, and can contribute to symptoms and disease progression 1
Diagnostic Evaluation
- Echocardiography: two-dimensional and Doppler echocardiography can demonstrate LVH, SAM, and LVOTO, and assess diastolic function and mitral regurgitation 1
- Exercise stress testing: can provoke LVOTO and assess functional capacity and risk stratification 1
- Cardiac magnetic resonance imaging: can provide additional diagnostic information, particularly in patients with technically difficult echocardiograms or unusual locations of hypertrophy 1
From the Research
Characteristics of Hypertrophic Obstructive Cardiomyopathy (HOCM)
- HOCM is a primary myocardial disease characterized by left ventricular hypertrophy in the absence of other etiologies 2
- Clinical presentation may vary from asymptomatic to sudden cardiac death 2
- HOCM is a hereditary condition that affects myocardial contraction 3
Symptoms and Treatment
- Symptoms of HOCM include dyspnea, angina, and syncope 2, 3
- Medical treatment is the first-line therapy for symptomatic patients 2
- Extended left ventricular septal myectomy is the procedure of choice if medical treatment is unsuccessful or intolerable 2
- Alternative approaches include surgical myectomy, percutaneous transluminal septal myocardial ablation, and radiofrequency ablation 3
- Alcohol septal ablation has been considered an alternative to surgical myectomy, with benefits including shorter hospital stay, less discomfort, and fewer complications 3
Echocardiographic Insights
- Nonsurgical septal reduction therapy (NSRT) reduces left ventricular outflow tract (LVOT) obstruction in patients with HOCM 4
- Echocardiographic studies have shown significant changes after NSRT, including widening of the LVOT, thinning and akinesis of the septal base, and decrease in the angle between LV systolic flow and the protruding mitral leaflets 4
- Radiofrequency ablation (RFA) has been shown to be an effective and safe treatment for patients with HOCM, with sustained and significant gradient reduction observed in 75.7% of patients 5
Treatment Outcomes
- Septal myectomy effectively and definitively relieves LVOT obstruction and cardiac symptoms in patients with obstructive HCM 2
- More than 90% of severely symptomatic patients have improvement by at least two functional classes after septal myectomy 2
- Relief of LVOT obstruction with septal myectomy dramatically improves symptoms and exercise capacity in symptomatic patients with obstructive HCM 2