Relationship of Baseline Electrocardiographic Characteristics with the Response to Cardiac Resynchronization Therapy for Heart Failure

Abstract

Prospective identification of patients most and least likely to respond to cardiac resynchronization therapy (CRT) for congestive heart failure (CHF) will allow clinicians to target this intervention most efficiently. The authors hypothesized that ECG variables including RBBB and indicators of RV dysfunction and extensive prior myocardial infarction would correlate with diminished response to CRT. This study analyzed preimplantation ECGs in 110 patients with ICD indications and CHF due to left ventricular systolic dysfunction randomized to active biventricular pacing in the MIRACLE ICD trial. Clinical and ECG variables on the outcome of change in peak oxygen consumption from baseline to 6 months (Delta-VO2 ) were evaluated. For this cohort, average peak VO2 improved from 13.4 to 14.3 mL/kg per minute. Among clinical variables, the strongest predictors of increasing Delta-VO2 were reduced exercise time and peak VO2 at baseline. A dominant R wave in lead a VR, RBBB, and evidence of prior anterior infarction were each associated with significantly smaller average improvements in Delta-VO2 than their absence in univariate analysis. Alternative ECG criteria, including QRS duration, had no relationship with the outcome. In a multivariate model, only baseline VO2 (beta=-0.3, P=0.001) and ECG evidence of prior anterior infarction (beta=-1.3, P=0.03) were associated with the outcome. ECG markers of anterior infarction and RV dilation may help identify CHF patients unlikely to benefit from biventricular pacing. Further assessment is needed of these and other predictors of therapeutic response to CRT.

Novel measure of electrical dyssynchrony predicts response in cardiac resynchronization therapy: Results from the SMART-AV Trial

“…On one hand, a non-negligible percentage of patients with QRS ≥150 ms do not respond 23 . A marked QRS widening (≥178 ms) as a sign of HF severity was related to less CRT benefit 7 , raising the question that QRS duration is not capable of distinguishing electrical dyssynchrony from severe mechanical dyssynchrony due to LV and frequently accompanied RV dilatation 24, 25 , hypertrophy, and scar, which is not responsive to resynchronization. On the other hand, a high percentage of patients with QRS 120–149 ms does respond, and could even demonstrate super-response, 3, 8 on CRT.…”

“…SAI QRST, by calculating summed area under QRST curve, takes into account amplitudes of orthogonal XYZ leads. Reynolds et al 24 showed that ECG signs of RV dilation in LBBB may help identify HF patients unlikely to benefit from CRT. SAI QRST, by calculating summed area under QRST curve, incorporates all QRST morphology features, which are not taken into account by classical definition of ventricular conduction abnormalities.…”

Paced Left Ventricular QRS Width and ECG Parameters Predict Outcomes After Cardiac Resynchronization Therapy

“…However, subsequent long-term follow-up in large CRT clinical trials found that preimplantation QRS width was a poor predictor of clinical CRT response. 14 In the RethinQ trial, 15 patients with a narrow QRS width and evidence of mechanical dyssynchrony did not benefit from resynchronization. In that study, subgroup analysis demonstrated that patients with a QRS width Ͼ120 ms had a much higher response rate than patients with a QRS width Ͻ120 ms. A previously reported PROSPECT subanalysis examined characteristics associated with good and poor response.…”

Utility of three-dimensional echocardiography in assessing and predicting response to cardiac resynchronization therapy

“…However, none of the methods available today have been shown to predict response before patients undergo the implantation procedure. Electrocardiogram-based platforms, including QRS duration, have been unhelpful (11,22). M-mode-based variables such as septal-to-posterior wall motion delay have been shown to not be significantly different between responders and nonresponders (23,24).…”