Resynchronization Therapy in Heart Failure

Cardiac resynchronization therapy (CRT) is the correction of disturbed left ventricular (LV) function due to atrioventricular, interventricular and intraventricular conduction delay by cardiac stimulation. The addition of CRT to optimal medical therapy in patients with heart failure improves symptoms, quality of life, functional capacity, and decreases rate of hospitalization and also improves LV function and structure. Furthermore, studies reporting decrease in mortality are present. However, despite appropriate application of guideline criteria, 30% to 50% of patients do not respond to therapy. The precise determination of patients that will respond to CRT is crucial and individual evaluation is required in patient selection. Currently, presence and quantity of intraventricular asynchrony is accepted as the most important predictor of hemodynamic improvement and response to therapy after CRT. Before CRT, LV segments should be mapped by such methods as tissue Doppler imaging and the LV wall that has the longest delay relative to the septum should be determined. If possible, LV electrode should be implanted to this wall. In addition, intraventricular asynchrony was detected in approximately half of the patients with narrow QRS complexes. In future, it is expected that QRS width which was until recently an important criterion in patient selection will not be taken into consideration and the presence and quantity of intraventricular asynchrony will become more important. (Türk Kardiyol Dern Arş 2004; 32: 376-389)