Hypertrophic cardiomyopathy (HCM) is a common familial autosomal dominant heart condition, with a heterogeneous phenotypic expression, characterized by left ventricular hypertrophy in the absence of associated conditions that could explain it (high blood pressure, aortic stenosis). Hypertrophic cardiomyopathy is probably the most common genetically transmitted cardiovascular disease, with a prevalence in the general population of about 0.2%.
Clinical manifestations in HCM (dyspnea, angina, pulmonary congestion, palpitations, syncope, and sudden death) are caused by diastolic dysfunction, myocardial ischemia, dynamic obstruction of the left ventricular outflow tract, mitral regurgitation and arrhythmias.
Treatment aims symptomatic relief, prevent complications, reduce the risk of sudden death, improving quality of life. Pharmacological treatment options are by drugs with negative inotropic effect (beta blockers, calcium antagonists, amiodarone, disopyramide), treatment with implants of medical devices (pacemakers, cardioverter defibrillator), interventions for enlargement of the left ventricle outflow tract (surgical or interventional technique), and in some cases is recommended heart transplant. In patients with symptoms refractory to medical therapy and in asymptomatic patients with severe left ventricular hypertrophy or significant obstruction of the left ventricular outflow tract are indicated: surgery – septal myectomy performed by transaortic approach, known as the Morrow procedure, and interventional treatment (alcohol septal ablation, embolization of septal artery wih “coil” or microspheres).
Septal artery alcohol ablation
This minimally invasive procedure was first described in 1995 by Ulrich Sigwart. The procedure is indicated in patients with hypertrophic obstructive cardiomyopathy (HOCM) with severe heart failure NYHA class III-IV refractory to medical therapy, with pressure gradient in the left ventricular outflow tract at rest over 30 mmHg or 50 mmHg after challenge and interventricular septum thickness> 16 mm and the appropriate septum artery anatomy.
The procedure involves injecting a small amount of absolute alcohol (98%) in the main septal arteryof anterior descending artery to cause localized necrosis. Septal hypokinesia induced by alcohol causes a reduction of gradient in left ventricular outflow tract, reduction recorded immediate after procedure in two-thirds of patients. In other cases, the gradient decreases gradual in 6-12 months.
Alcohol ablation is effective for reducing obstruction, reducing the degree of mitral regurgitation and symptom relief, but the results depend on the coronary anatomy. The procedure is associated with progressive ventricular remodeling and decreased muscle mass and in the thickness of the septum, this occurring within a few months. Symptomatic relief after alcohol septal ablation is remarkable, being objectified by upgrading exercise capacity. The procedure is well tolerated, the rate of complications is relatively low and long-term effects are supported.
An important complication of transcatheter septal ablation is complete or high atrioventricular block, requiring permanent pacing at about 5-10% of cases in recent years. Another complication, rare but potentially severe is ventricular arrhythmia originating in the scar area caused by ablation, which creates arrhythmogenic substrate, with the possibility of malignant reentrant arrhythmias, procedural mortality is <1%. Approximately 5% of patients develop sustained ventricular tachyarrhythmias during hospitalization.
Best candidates for alcohol ablation are patients over 65 years with multiple comorbidities (obesity, lung, kidney or neurological diseases), no association of pathologies requiring surgery (coronary lesions suitable to bypass, significant organic valvular lesions), the absence of severe pulmonary hypertension, the thickness of the interventricular septum between 15 and 30 mm, corresponding coronary anatomy. It is reasonable that septal alcohol ablation should be performed in patients younger than 65 years, but the indication should take into account the patient’s options after it’s been explained pathophysiological mechanisms of the disease, the benefits and risks of each treatment method.
The advantages of interventional treatment are: shorter hospitalization, faster recovery, no surgical incision, no general anesthesia and no extracorporeal circulation, minimal pain, lower procedural complications, lower rate of occurrence of atrial fibrillation, the procedure can be repeated with the same degree of risk like the first time, faster reintegration into society and return to work. Some disadvantages include incomplete reduction of the gradient of the left ventricular outflow tract in some cases, delays in significant improvement of symptoms in some patients, unknown long-term risk of developing conduction abnormalities or tachyarrhythmias, coronary artery anatomy constraints.
In experienced centers, alcohol septal ablation is a therapeutic alternative to surgical treatment for eligible patients with HCM with severe symptoms refractory to medication and obstruction of the left ventricular outflow tract. Choice of treatment strategy should be made after a full discussion of each procedures with the patient.