QRS Area Is a Strong Determinant of Outcome in Cardiac Resynchronization Therapy

Abstract

Background: The combination of left bundle branch block (LBBB) morphology and QRS duration is currently used to select patients for cardiac resynchronization therapy (CRT). These parameters, however, have limitations. This study evaluates the value of QRS area compared with that of QRS duration and morphology in the association with clinical and echocardiographic outcomes in a large cohort of CRT patients. Methods: A retrospective multicentre study was conducted in 1492 CRT patients. LBBB morphology, QRS duration, and QRS area in the baseline 12-lead ECG were evaluated for their association with the occurrence of the combined primary end point of all-cause mortality, cardiac transplantation, and left ventricular assist device implantation. Secondary end points were heart failure hospitalization within the first year after implantation and echocardiographic reduction in left ventricular end-systolic volume. Results: During a mean follow-up period of 3.4 years, 32% of patients reached the primary end point. The association of QRS area with all outcomes was stronger than that of LBBB morphology and QRS duration separately and at least as strong as their combination. QRS area identified patients who did not experience the primary end point better than QRS morphology and QRS duration (area under the curve, 0.61 versus 0.55 and 0.51, respectively; P <0.001). Furthermore, QRS area identifies patients with echocardiographic remodeling in response to CRT better than QRS morphology and duration (area under the curve, 0.69 versus 0.58 and 0.58, respectively; P <0.001). QRS area was the only independent electrocardiographic determinant associated with the primary end point; hazard ratio, 0.50 (0.35–0.71). Furthermore, QRS area showed significant association with outcomes in both patients with and without LBBB and QRS ≥150 ms. Conclusions: QRS area has a strong association to clinical and echocardiographic response to CRT, at least as strong as current patient selection parameters. QRS area may be particularly useful to predict CRT response in patients without a wide LBBB.

Lead one ratio in left bundle branch block predicts poor cardiac resynchronization therapy response

“…Patients with LOR <12 had significantly lower mean QRS area than patients with LOR ≥12. QRS area is a measure of nonopposed electrical forces, and high values suggest more significant dyssynchrony and have also been associated with greater response to CRT 6,7 . When QRS area was included in multivariable models along with QRS duration, LOR <12 remained strongly predictive of clinical outcomes.…”

“…Cardiac resynchronization therapy (CRT) improves cardiac function, facilitates LV reverse remodeling, and reduces mortality in patients with LBBB 3 . Electrocardiogram (ECG) features such as QRS duration, area, and morphology have been previously shown to be important predictors of response to CRT 4‐7 . Prior work has demonstrated that LBBB patients with a low ECG lead one ratio (LOR) of positive/negative amplitudes have lower LV ejection fraction (LVEF) and worse clinical outcomes 8 .…”

Prevention of non-response to cardiac resynchronization therapy: points to remember

“…The latest studies have reported a strong positive correlation between QRS area and CRT response and that this correlation is as valuable as the other current ECG criteria. QRS area may be predictive of CRT response in patients with non-wide left bundle branch block [12]. In addition to ECG, magnetic resonance and other tests were used in recent studies to determine left ventricular dyssynchrony.…”

Defining left bundle branch block-Is this a roadblock to CRT delivery?

“…There has been a great deal of interest in attempting to predict the exact site of LBBB as this could have important implications not only for the siting of the coronary sinus LV lead but also predicting positive LV remodeling. A number of ECG markers of remodeling have been proposed including QRS duration, QRS area and the morphology of the intrinsicoid deflection (9)(10)(11)(12). Fundamentally, if there is an excess of fibrosed myocardium, it is unlikely there is sufficient myocardial reserve to achieve adequate remodeling even if the lead is targeted outside scar.…”

“…However, only a small proportion of patients have such broad QRS durations which has spurred investigation of other ECG markers to predict response even in non-LBBB cases. A recent study evaluated the QRS area which is an indicator of focal fibrosis in 1492 CRT recipients (9,11). QRS area identified patients who did not experience the primary end point (death, transplantation, left ventricular assist device implantation) & echocardiographic remodeling better than QRS morphology and QRS duration.…”