Acute and Chronic Response to CRT in Narrow QRS Patients

Abstract

Previous studies suggest that CRT may benefit narrow QRS patients with mechanical dyssynchrony (MD). We conducted an acute and chronic study, evaluating the response of heart failure patients with a narrow QRS to cardiac resynchronization therapy (CRT). ESTEEM-CRT was a multi-center, single-arm, feasibility study that evaluated ICD-indicated, medically-optimized patients with EF ≤ 35%, NYHA class III heart failure, QRS duration <120 ms, and MD as defined by the standard deviation of time to peak systolic velocity of 12 segments (Ts-SD). Sixty-eight patients received a CRT defibrillator, exercise testing, and echo exams, and 47 of these patients underwent invasive hemodynamic testing at implant. Follow-up was at 6 and 12 months. The average maximal improvement in LV dP/dt(max) was minor (2 ± 2%). NYHA and quality of life scores were substantially improved at 6 and 12 months (P < 0.001), while exercise capacity and LV volumes were unchanged. The echo indices of MD were difficult to collect, discordant, and failed to predict clinical outcomes. ESTEEM-CRT patients with a narrow QRS and MD as defined in this study did not improve as measured by acute hemodynamics, chronic exercise performance, or reverse remodeling. These multi-center results support the notion that dyssynchrony indices are ineffective or at least require greater refinement for the selection of narrow QRS patients for CRT.

Cardiac Resynchronization Therapy in Patients With Heart Failure and a QRS Complex <120 Milliseconds

“…Importantly, LESSER-EARTH, like the Resynchronization Therapy in Normal QRS (RETHINQ) 14 and Evaluation of Screening Techniques in Electrically-Normal, MechanicallyDyssynchronous Heart Failure Patients (ESTEEM-CRT) 15 trials, relied on functional metrics and indexes of reverse remodeling as opposed to hard clinical outcomes such as mortality. Nevertheless, these studies have consistently failed to demonstrate a benefit from CRT in patients with a narrow QRS complex.…”

“…Nevertheless, these studies have consistently failed to demonstrate a benefit from CRT in patients with a narrow QRS complex. The primary outcome for RETHINQ 14 and ESTEEM-CRT 15 was maximum oxygen uptake (peak . Vo 2 ) as assessed by cardiopulmonary exercise testing, which has been criticized for its lack of sensitivity in detecting therapeutic responses, potential to be poorly tolerated by patients with HF, and need for careful calibration.…”

“…14 Moreover, a single-arm feasibility study of CRT in 68 patients with a QRS duration <120 milliseconds was recently abandoned because of lack of benefit. 15 The primary outcome for both studies was maximum oxygen uptake (peak . Vo 2 ), which has been criticized for its poor sensitivity in detecting therapeutic responses.…”

Cardiac Resynchronization Therapy

“…Initially, several single center studies have observed that CRT is effective in patients with QRS duration <120 or <130 ms in combination with mechanical dyssynchrony. [15][16][17][18] However, the 4 randomized studies in this field have consistently been neutral 19,20 or negative. 21,22 The RethinQ study randomized 172 patients to CRT or no CRT.…”

Cardiac-Resynchronization Therapy in Heart Failure with a Narrow QRS Complex

“…8 Small, randomized clinical studies that were not powered to assess clinically relevant outcomes [9][10][11][12][13][14] have suggested the existence of true clinical equipoise, thereby setting the stage for a definitive outcome trial. We therefore initiated the Echocardiography Guided Cardiac Resynchronization Therapy (EchoCRT) study to investigate the effect of CRT on morbidity and mortality among patients with symptomatic heart failure, a narrow QRS complex, and echocardiographic evidence of left ventricular dyssynchrony.…”