I. Resynchronization
Cardiac resynchronization therapy is an innovative pacemaker-based approach to the management of patients with left bundle branch block, right bundle branch block, and nonspecific intraventricular conduction delay as manifested electrocardiographically. It appears that resynchronization provides electromechanical coordination and improved ventricular synchrony in patients with intraventricular conduction defects and heart failure. A pacemaker lead is placed through the right atrium through the coronary sinus and into a cardiac vein on the lateral wall of the left ventricle. The left ventricular lead constitutes the key difference between resynchronization therapy and the standard dual-chamber pacing that is used for other conditions requiring a pacemaker. One lead is in the left ventricle, one lead is placed in right atrium, and the third lead is placed in the right ventricle. Beneficial documented effects of resynchronization therapy include reverse remodeling which results in decreased heart size and ventricular volumes, an improvement in ejection fraction, and a decrease in mitral regurgitation.
Unfortunately in the MIRACLE clinical trial testing resynchronization therapy, 32% of patients had no change or had a deterioration in the New York Heart Association class after resynchronization therapy. In addition, other studies have reported about a 30% nonresponse rate after biventricular pacing. Because of the cost of this moda¬lity, an important question to ask is how to determine in advance of implantation which patients will respond to resynchronization therapy. Resynchronization therapy has not been shown to improve survival in patients with heart failure and further trials are underway.

Страницы: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15