On 2014 Jun 12, Gaetano Santulli commented:

Goldenberg et al. (1) report that cardiac resynchronization therapy with a defibrillator (CRT-D) is associated with a significant long-term survival benefit in patients with mild heart failure, left ventricular dysfunction, and left bundle-branch block (LBB), whereas no benefit was found in patients without LBB. The Authors, however, do not provide data elaborating whether CRT-D improved any measurable variable of mechanical dyssynchrony. Therefore it is unclear whether the long-term clinical failure of CRT-D observed in patients without LBB resulted from persistent mechanical dyssynchrony or other underlying mechanisms, including myocardial fibrosis and myocardial stress (2). This aspect is particularly relevant since CRT-D has been demonstrated to primarily improve electrical dyssynchrony but does not uniformly decrease morbidity and mortality, even in patients with a wide QRS complex (3). Moreover, given the issues recently raised regarding the importance of QRS measurements, the Authors should have provided more data on the methodology used to measure QRS duration (4).

References

1.Goldenberg I, Kutyifa V, Klein HU, et al. Survival with Cardiac-Resynchronization Therapy in Mild Heart Failure. The New England journal of medicine 2014;370:1694-701.

2.Bilchick KC, Kuruvilla S, Hamirani Y, et al. Impact of Mechanical Activation, Scar, and Electrical Timing on Cardiac Resynchronization Therapy Response and Clinical Outcomes. Journal of the American College of Cardiology 2014;63:1657-66.

3.Kass DA. Predicting cardiac resynchronization response by QRS duration: the long and short of it. Journal of the American College of Cardiology 2003;42:2125-7.

4.De Guillebon M, Thambo JB, Ploux S, et al. Reliability and reproducibility of QRS duration in the selection of candidates for cardiac resynchronization therapy. Journal of cardiovascular electrophysiology 2010;21:890-2.

Celestino Sardu, MD¹, Gaetano Santulli, MD, PhD²

¹Second University of Naples, Naples, Italy; ²Columbia University Medical Center, New York, NY, USA

On 2014 Jun 12, Gaetano Santulli commented:

Goldenberg et al. (1) report that cardiac resynchronization therapy with a defibrillator (CRT-D) is associated with a significant long-term survival benefit in patients with mild heart failure, left ventricular dysfunction, and left bundle-branch block (LBB), whereas no benefit was found in patients without LBB. The Authors, however, do not provide data elaborating whether CRT-D improved any measurable variable of mechanical dyssynchrony. Therefore it is unclear whether the long-term clinical failure of CRT-D observed in patients without LBB resulted from persistent mechanical dyssynchrony or other underlying mechanisms, including myocardial fibrosis and myocardial stress (2). This aspect is particularly relevant since CRT-D has been demonstrated to primarily improve electrical dyssynchrony but does not uniformly decrease morbidity and mortality, even in patients with a wide QRS complex (3). Moreover, given the issues recently raised regarding the importance of QRS measurements, the Authors should have provided more data on the methodology used to measure QRS duration (4).

References

1.Goldenberg I, Kutyifa V, Klein HU, et al. Survival with Cardiac-Resynchronization Therapy in Mild Heart Failure. The New England journal of medicine 2014;370:1694-701.

2.Bilchick KC, Kuruvilla S, Hamirani Y, et al. Impact of Mechanical Activation, Scar, and Electrical Timing on Cardiac Resynchronization Therapy Response and Clinical Outcomes. Journal of the American College of Cardiology 2014;63:1657-66.

3.Kass DA. Predicting cardiac resynchronization response by QRS duration: the long and short of it. Journal of the American College of Cardiology 2003;42:2125-7.

4.De Guillebon M, Thambo JB, Ploux S, et al. Reliability and reproducibility of QRS duration in the selection of candidates for cardiac resynchronization therapy. Journal of cardiovascular electrophysiology 2010;21:890-2.

Celestino Sardu, MD¹, Gaetano Santulli, MD, PhD²

¹Second University of Naples, Naples, Italy; ²Columbia University Medical Center, New York, NY, USA