Hypertrophic Cardiomyopathy – symptoms, investigations, treatment
Hypertrophic cardiomyopathy is a disease of the myocardium with a variable evolution, characterized by hypertrophy of the left ventricle without associated conditions that may explain the hypertrophy (eg, hypertension, aortic stenosis, athlete heart). It is a genetically transmitted disease, being the most common from the group of cardiovascular diseases. The main feature of hypertrophic cardiomyopathy is the presence of left ventricular hypertrophy, heart weight quite frequently exceeds the value of 500 mg. The most common sites of the hypertrophy are the anterior interventricular septum, rarely posterior or basal, rarely in the anterolateral and posterior wall. There are cases in which hypertrophy is localized at the apex (apical hypertrophic cardiomyopathy).
Microscopic, cardiac myocytes in this disease are increased in size and have a changed shape therefore the typical organization is lost, being installed a very disorganized architecture. It also increases the amount of collagen and coronary arteries abnormalities (thickened of intima and media with luminal narrowing).
Patients with hypertrophic cardiomyopathy may be asymptomatic or can be diagnosed incidentally in case of family screening. Symptoms that may occur are limiting the ability to perform effort, appearance of dyspnoea (shortness of breath, air hunger) and fatigue, chest pain like angina pectoris or atypical chest pain, dizziness, faintness or syncope, palpitations. In these patients can occur ventricular arrhythmias (ventricular tachycardia) or supraventricular arrhythmias (atrial fibrillation).
First step investigations are the electrocardiogram and transthoracic echocardiography. ECG shows changes in 90% of patients with this condition, represented by signs of left ventricular hypertrophy and repolarization changes (negative T waves), abnormal Q waves, left bundle branch block. Echocardiographic diagnosis of HCM is done by evaluating wall thickness, cardiac chambers sizes, left ventricular function study and evaluation of the obstruction in the outflow tract of the left ventricle. Ultrasound can also detect a systolic anterior motion of the anterior mitral valve cusp.
Second step investigations are stress echocardiography, exercise testing, Holter ECG monitoring (annually, detection of nonsustained ventricular tachycardia and atrial fibrillation episodes), coronary angiography (detection of atherosclerotic disease, preoperative quantification of the pressure gradient).
Treatment is aimed to relieve symptoms and decrease the risk of sudden death. It will be established a drug treatment in symptomatic patients and in those with severe hypertrophy or obstruction of the outflow from the left ventricle. Beta-blockers associated with calcium channel blockers are the treatment of choice. This therapy will reduce the systolic obstruction with an inotropic (contractile) and chronotropic negative effect, the ventricular relaxation will be improved and increase the diastole, myocardial oxygen consumption will be reduced and consequently the microvascular ischemia. Calcium channel blockers such as verapamil improve ventricular relaxation and filling. Diuretics are administered only in symptomatic patients to lower filling pressures and pulmonary congestion. Arrhythmias will be controlled by the administration of amiodarone and if arrhythmias are present a cardiodefibrilator implantation will be discussed. Surgical treatment is considered in patients with symptoms refractory to medical treatment, for those who have significant hypertrophy or important obstruction of the left ventricular ejection. The surgical treatment consists of septal myomectomy known as Morrow procedure.
Interventional treatment consists in alcohol septal ablation. This procedure involves injecting alcohol in a septal branch of the main anterior descending coronary artery to determine an area of necrosis. The results of this procedure depends on the coronary anatomy. Improvement of symptoms may occur almost immediately after intervention in 2/3 of patients or can progress during 6-12 months.
Major risk factors for sudden death in hypertrophic cardiomyopathy: cardiac arrest by ventricular fibrillation, sustained ventricular tachycardia, family history of sudden death, syncope of unknown cause, ventricular wall thickness greater than 30mm, an abnormal response of blood pressure to exercises. Minor risk factors: atrial fibrillation, myocardial ischemia, left ventricle outflow tract obstruction, intense exercise (sports).
Complications of the disease include sudden death, syncope, atrial fibrillation, infective endocarditis.