Prospective validation of stress echocardiography as an identifier of cardiac resynchronization therapy responders.

Background: Cardiac resynchronization therapy (CRT) provides benefit for congestive heart failure (CHF), but predictors of the clinical response are debated.
Objective: The aim of this prospective study was to assess the predictive role of dobutamine stress echocardiography (DSE) in identifying a suitable candidate for CRT.
Methods: From March 2001 to December 2003, 71 CHF patients were prospectively enrolled on the basis of four criteria: New York Heart Association (NYHA) class III and IV; QRS > or =150 ms with a left bundle branch block pattern, and left ventricular ejection fraction (LVEF) < or =35% under optimal medical treatment. The combined endpoints were hospital readmission for class IV CHF, heart transplant (HT), and CHF-related death.
Results: The 67 patients completing the study presented with the following characteristics: age (70 +/- 10 years; 11 women); etiology (idiopathic in 44, ischemic in 23); NYHA class (40 in class III and 27 in class IV); LVEF 26% (+/-5%); QRS duration (190 +/- 28 ms); 6-minute walk test 330 m (+/-108); peak oxygen uptake 10.7 (+/-3.3 mL/kg/min); mitral insufficiency in 42 (> or =III grade); interventricular (IV) delay (62 +/- 21 ms); and intraventricular dyssynchrony in 30 patients. Over the follow-up period of 12.1 +/- 8.7 months, 20 (29.9%) of 67 patients presented with at least one hemodynamic event: hospitalization for CHF in 19 (28%) of 67, HT in 2 (3%) of 67, and CHF death in 7 (10%) 67. Univariate analysis identified NYHA class (P = .03), LVEF (P = .015), IV dyssynchrony before (P = .038) and after CRT (P = .0035), IV delay after CRT (P = .002), 6-minute walk distance (P = .01), and DSE Res+ (P = .008) as significant predictors of clinical events. A receiver operating curve established a cut-off value of 1.25 for the DSE responders (Res+: 34 patients at 10 microg/kg/min infusion rates), and the improvement at the 10 microg/kg/min level was 41% +/- 7% in Res+ and 29% +/- 8% in nonresponders (P<.0001). With a cut-off value of 1.25-fold the LVEF increase, the DSE test exhibits 70% sensitivity, 61.7% specificity, 43.8% positive predictive value, and 82.9% negative predictive value. Cox analysis identified IV dyssynchrony before CRT (P = .01) and DSE Res+ (P = .003) as independent predictive factors.
Conclusions: Independent predictive factors of severe hemodynamic clinical outcome in patients with CRT are IV dyssynchrony and DSE.