Cardiac Resynchronization Therapy

Abstract

Cardiac resynchronization therapy (CRT) has been used extensively over the last years in the therapeutic management of patients with end-stage heart failure. Data from 4,017 patients have been published in eight large, randomized trials on CRT. Improvement in clinical end points (symptoms, exercise capacity, quality of life) and echocardiographic end points (systolic function, left ventricular size, mitral regurgitation) have been reported after CRT, with a reduction in hospitalizations for decompensated heart failure and an improvement in survival. However, individual results vary, and 20% to 30% of patients do not respond to CRT. At present, the selection criteria include severe heart failure (New York Heart Association functional class III or IV), left ventricular ejection fraction <35%, and wide QRS complex (>120 ms). Assessment of inter- and particularly intraventricular dyssynchrony as provided by echocardiography (predominantly tissue Doppler imaging techniques) may allow improved identification of potential responders to CRT. In this review a summary of the clinical and echocardiographic results of the large, randomized trials is provided, followed by an extensive overview on the currently available echocardiographic techniques for assessment of LV dyssynchrony. In addition, the value of LV scar tissue and venous anatomy for the selection of potential candidates for CRT are discussed.

Quantitative Gated SPECT–Derived Phase Analysis on Gated Myocardial Perfusion SPECT Detects Left Ventricular Dyssynchrony and Predicts Response to Cardiac Resynchronization Therapy

“…However, a substantial number of the selected patients do not show response to CRT (2,(5)(6)(7)(8). Therefore, efforts have been made to improve current selection criteria for CRT, and previous studies have demonstrated that LV dyssynchrony is related to CRT response and may have additional value in the selection of potential candidates for CRT (6)(7)(8).…”

“…Although CRT provides considerable benefit, one third of the patients meeting the current selection criteria do not respond to this form of therapy (5)(6)(7)(8), and attention has shifted toward improved patient selection for CRT (9,10). Particularly, observational trials have shown the significance of LV dyssynchrony for the prediction of response to CRT (6)(7)(8).…”

The clinical effectiveness and cost-effectiveness of cardiac resynchronisation (biventricular pacing) for heart failure: systematic review and economic model

“…98 Bax and colleagues concluded that ECHO is the most practical approach to evaluate dyssynchrony and predict response to CRT. 99 A number of ECHO techniques can be used to make this assessment, including…”

Left Ventricular Resynchronization Is Mandatory for Response to Cardiac Resynchronization Therapy

“…[5][6][7][8][9][10] Indeed, patient selection based on echocardiographic detection of LV dyssynchrony resulted in a superior response rate compared with patient selection based on QRS duration alone. [5][6][7][8][9][10] However, the presence of preimplantation LV dyssynchrony may not be the only determinant of response to CRT because some patients with preimplantation LV dyssynchrony still do not respond to CRT. It is currently unclear whether a reduction in LV dyssynchrony (LV resynchronization) after implantation of the CRT device is man-datory for a positive response.…”