Electrical dyssynchrony and resynchronization in tetralogy of Fallot

t a e t o v i o c Introduction Among congenital heart defects causing cyanosis, tetralogy of Fallot (TOF) is the most common. Major progress has been made since 1954, when Lillehei performed the first surgical repair, such that most children operated today reach adulthood. The follow-up of adults presenting with various conenital heart diseases and management of the specific compliations they have are challenging. While, in the case of TOF, he shortand intermediate-term surgical results are generally xcellent, the longer term clinical course may be complicated y right heart failure, life-threatening ventricular tachyarrhythias, major impulse propagation disorders, and sudden eath. Right heart failure is due to the combined effects of pressure and volume overloads and of the myocardial lesions inflicted during and after the operation. Right bundle branch block (BBB) almost invariably develops after surgical repair of TOF. Furthermore, a wide QRS is prognostically important, and QRS duration and risk of developing ventricular arrhythmias are closely correlated. The hemodynamic consequences of right BBB might play a predominant role in the long-term clinical outcomes of these patients, and a relationship probably exists between electrical and mechanical dysfunction, as well as links between myocardial remodeling, rhythm disturbances, and electromechanical dyssynchrony. Depressed contractility and remodeling may be promoted by mechanical dyssynchrony, which, therefore, may be a desirable therapeutic target. Emulating studies of left ventricular (LV) stimulation in patients with left heart failure and left BBB, a few cases of resynchronization in patients with congenital