Hypertrophic Obstructive Cardiomyopathy: Alcohol Ablation
Hypertrophic Obstructive Cardiomyopathy: Alcohol Ablation
Alcohol septal ablation (ASA) was introduced in 1994 as an alternative to septal myectomy for patients with hypertrophic obstructive cardiomyopathy and symptoms refractory to medical therapy. This procedure alleviates symptoms by producing a targeted, limited infarction of the upper interventricular septum, resulting in an increase in left ventricular outflow tract (LVOT) diameter, a decrease in LVOT gradient, and regression of the component of LV hypertrophy that is due to pressure overload. Clinical success, with improvement in symptoms and reduction in gradient, is achieved in the great majority of patients with either resting or provocable LVOT obstruction. The principal morbidity of the procedure is complete heart block, resulting in some patients in the requirement for a permanent pacemaker. The introduction of myocardial contrast echocardiography as a component of the ASA procedure has contributed to the induction of smaller myocardial infarctions with lower dosages of alcohol and, in turn, fewer complications. Non-randomized comparisons of septal ablation and septal myectomy have shown similar mortality rates and post–procedure New York Heart Association class for the two procedures.
Hypertrophic cardiomyopathy (HCM) is a disease characterized by idiopathic hypertrophy of the left ventricle (LV). Clinical manifestations include diastolic dysfunction and dysrhythmias. Symptoms include dyspnoea, angina, lightheadedness, and syncope. Hypertrophic cardiomyopathy patients with LV outflow tract (LVOT) gradients under resting conditions or with provocation (as with Valsalva manoeuvre or exercise) are classified as having hypertrophic obstructive cardiomyopathy (HOCM). Obstruction results from a combination of interventricular septal hypertrophy, hyperdynamic LV contraction, and drag and Venturi forces, creating systolic anterior motion (SAM) of the anterior leaflet of the mitral valve (Figure 1). Left ventricular outflow tract obstruction at rest is observed in ~25% of the patients with HCM and is an independent predictor of poor prognosis. In one report, the majority of patients with HCM had resting or provocable obstruction.
(Enlarge Image)
Figure 1.
End–systolic frame from a left ventriculogram in left anterior oblique, cranially angulated projection in a patient with hypertrophic obstructive cardiomyopathy. There is systolic anterior motion of the anterior leaflet of the mitral valve (ALMV), which comes into apposition with the interventricular septum (IVS), associated with a left ventricular outflow tract gradient. Ao, aorta; LA, left atrium; LV, left ventricle.
Although symptoms are effectively alleviated in the majority of symptomatic HOCM patients by negative inotropic drugs, namely β-blockers, verapamil, and disopyramide, they are refractory to medical therapy in 5–10% of the patients. Surgical septal myectomy has been performed for half a century, and abolishes the gradient and relieves symptoms in the great majority of patients. Some patients, however, have absolute or relative contraindications to surgery in the form of concomitant medical conditions, advanced age, or previous cardiac surgery. In experienced centres, surgical mortality is <2% in young, otherwise healthy patients, but is higher in older patients and in those requiring concomitant surgical procedures, such as coronary artery bypass grafting. In 1994, Sigwart introduced a catheter treatment that uses absolute alcohol to induce a relatively small, targeted myocardial infarction in the septum as an alternative to surgery.
Intracoronary injection of alcohol had been previously employed for therapy of refractory ventricular tachycardia. Injection of ethanol had caused transmural myocardial necrosis in a canine model. This technique was applied to HOCM after the observation, in patients with septal hypertrophy, that the LVOT gradient was transiently reduced during septal artery occlusion by a balloon catheter. The procedure has gone by a variety of names, including non-surgical myocardial reduction, transcoronary ablation of septal hypertrophy, percutaneous transluminal septal myocardial ablation, and alcohol septal ablation (ASA). Although initially confined to Europe and North America, this technique is now being performed worldwide. In the absence of randomized controlled trials comparing ASA to medical therapy or septal myectomy, our current view of the procedure is based on registry data, meta-analyses, and personal experience.
Abstract and Introduction
Abstract
Alcohol septal ablation (ASA) was introduced in 1994 as an alternative to septal myectomy for patients with hypertrophic obstructive cardiomyopathy and symptoms refractory to medical therapy. This procedure alleviates symptoms by producing a targeted, limited infarction of the upper interventricular septum, resulting in an increase in left ventricular outflow tract (LVOT) diameter, a decrease in LVOT gradient, and regression of the component of LV hypertrophy that is due to pressure overload. Clinical success, with improvement in symptoms and reduction in gradient, is achieved in the great majority of patients with either resting or provocable LVOT obstruction. The principal morbidity of the procedure is complete heart block, resulting in some patients in the requirement for a permanent pacemaker. The introduction of myocardial contrast echocardiography as a component of the ASA procedure has contributed to the induction of smaller myocardial infarctions with lower dosages of alcohol and, in turn, fewer complications. Non-randomized comparisons of septal ablation and septal myectomy have shown similar mortality rates and post–procedure New York Heart Association class for the two procedures.
Introduction
Hypertrophic cardiomyopathy (HCM) is a disease characterized by idiopathic hypertrophy of the left ventricle (LV). Clinical manifestations include diastolic dysfunction and dysrhythmias. Symptoms include dyspnoea, angina, lightheadedness, and syncope. Hypertrophic cardiomyopathy patients with LV outflow tract (LVOT) gradients under resting conditions or with provocation (as with Valsalva manoeuvre or exercise) are classified as having hypertrophic obstructive cardiomyopathy (HOCM). Obstruction results from a combination of interventricular septal hypertrophy, hyperdynamic LV contraction, and drag and Venturi forces, creating systolic anterior motion (SAM) of the anterior leaflet of the mitral valve (Figure 1). Left ventricular outflow tract obstruction at rest is observed in ~25% of the patients with HCM and is an independent predictor of poor prognosis. In one report, the majority of patients with HCM had resting or provocable obstruction.
(Enlarge Image)
Figure 1.
End–systolic frame from a left ventriculogram in left anterior oblique, cranially angulated projection in a patient with hypertrophic obstructive cardiomyopathy. There is systolic anterior motion of the anterior leaflet of the mitral valve (ALMV), which comes into apposition with the interventricular septum (IVS), associated with a left ventricular outflow tract gradient. Ao, aorta; LA, left atrium; LV, left ventricle.
Although symptoms are effectively alleviated in the majority of symptomatic HOCM patients by negative inotropic drugs, namely β-blockers, verapamil, and disopyramide, they are refractory to medical therapy in 5–10% of the patients. Surgical septal myectomy has been performed for half a century, and abolishes the gradient and relieves symptoms in the great majority of patients. Some patients, however, have absolute or relative contraindications to surgery in the form of concomitant medical conditions, advanced age, or previous cardiac surgery. In experienced centres, surgical mortality is <2% in young, otherwise healthy patients, but is higher in older patients and in those requiring concomitant surgical procedures, such as coronary artery bypass grafting. In 1994, Sigwart introduced a catheter treatment that uses absolute alcohol to induce a relatively small, targeted myocardial infarction in the septum as an alternative to surgery.
Intracoronary injection of alcohol had been previously employed for therapy of refractory ventricular tachycardia. Injection of ethanol had caused transmural myocardial necrosis in a canine model. This technique was applied to HOCM after the observation, in patients with septal hypertrophy, that the LVOT gradient was transiently reduced during septal artery occlusion by a balloon catheter. The procedure has gone by a variety of names, including non-surgical myocardial reduction, transcoronary ablation of septal hypertrophy, percutaneous transluminal septal myocardial ablation, and alcohol septal ablation (ASA). Although initially confined to Europe and North America, this technique is now being performed worldwide. In the absence of randomized controlled trials comparing ASA to medical therapy or septal myectomy, our current view of the procedure is based on registry data, meta-analyses, and personal experience.
