Relative Merits of Left Ventricular Dyssynchrony, Left Ventricular Lead Position, and Myocardial Scar to Predict Long-Term Survival of Ischemic Heart Failure Patients Undergoing Cardiac Resynchronization Therapy
Does myocardial scar, left ventricular (LV) lead position, or dyssynchrony predict response to cardiac resynchronization therapy (CRT) in heart failure?
Echocardiography-derived two-dimensional speckle tracking with radial strain analysis was used to measure LV mechanical activation and dyssynchrony prior to CRT therapy in 397 patients with ischemic cardiomyopathy (LV ejection fraction ≤35%), New York Heart Association class III-IV heart failure, and a QRS ≥120 ms. LV dyssynchrony was defined as a delay of ≥130 ms between the anteroseptal and posterior segments. Strain measures were also used to define areas of myocardial scar (peak radial strain <16.5%). The primary endpoint was the composite of heart failure hospitalization and mortality.
Mean patient age was 67 ± 10 years, 81% were in sinus rhythm, and 44% had evidence of LV dyssynchrony. After a mean 21 months of CRT therapy, 39 patients (10%) were hospitalized 88 times and 88 (22%) patients died. In those with radial dyssynchrony, survival (82% vs. 65%) and survival free of the composite endpoint (75% vs. 63%) were higher than in those without dyssynchrony. Survival and survival free of the composite endpoint were also higher in patients whose LV lead was positioned at the site of latest mechanical activation and in those whose lead was not positioned within myocardial scar. Discordant LV lead position (hazard ratio [HR], 2.1; 95% confidence interval [CI], 1.3-3.3), myocardial scar at the lead (HR, 2.9; 95% CI, 1.7-4.9), and smaller LV radial dyssynchrony were (HR, 0.995; 95% CI, 0.992-0.998 per ms) multivariable correlates of mortality and offered good discrimination for outcome.
The authors concluded that LV dyssynchrony, myocardial scar, and LV lead position predict outcome following CRT.
Identification of subjects who will and will not benefit from CRT remains challenging. This analysis used contemporary preimplant echocardiographic measurements to identify potential responders to CRT. Independent validation in a separate cohort of patients, along with an assessment of inter- and intra-reader correlation of the echocardiography measures, is warranted. These findings do not apply to those without an ischemic etiology for heart failure.
Keywords: Cicatrix, Ventricular Function, Left, Cardiomyopathies, Heart Failure, New York, Heart Ventricles, Hospitalization, Cardiac Resynchronization Therapy, Echocardiography
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