CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Gabe B. Bleeker, MD,
Martin J. Schalij, MD, PhD and
Jeroen J. Bax, MD, PhD*
* Leiden University Medical Center, Cardiology, Albinusdreef 2, 2333 ZA, Leiden, Zuid-Holland 2333 ZA, the Netherlands (Email: jjbaxacc{at}lumc.nl).
We thank Dr. Breithardt for his interest in our study on cardiac resynchronization therapy (CRT) in patients with a narrow QRS complex (<120 ms). Our report demonstrates that CRT appears to be beneficial in 33 patients with narrow QRS complex and severe left ventricular (LV) dyssynchrony on tissue Doppler imaging, with similar improvement in symptoms and comparable LV reverse remodeling as in patients with wide QRS complexes (1). Our results are confirmed by the data of Yu et al. (2) in the same issue of the Journal and are in line with 2 earlier studies (3,4), bringing the total of included patients to 118 (2–4). However, none of the studies to date included a control group of narrow QRS patients with inactive pacing, which can be considered as a limitation. We totally agree with Dr. Breithardt that the promising results of CRT in narrow QRS patients in these initial studies will now need confirmation in larger multicenter randomized studies before the current selection criteria can be refined.
A second point raised by Dr. Breithardt is that patients with a narrow QRS may potentially have a shorter PR interval compared to patients with a wide QRS, which may lead to a higher number of patients with fusion of intrinsic activation and the pacing stimuli. However, a narrow QRS complex in these patients may not necessarily be associated with a short PR interval. The (degree of) fusion during CRT is often difficult to assess, and the incidence of fusion in patients with a wide QRS complex is also unknown. As indicated, we cannot exclude that some patients may have had fusion between intrinsic activation and pacing stimuli, but still the application of CRT resulted in a significant improvement in clinical and echocardiographic parameters comparable to patients with a wide QRS complex.
In conclusion, we agree with Dr. Breithardt that there is a clear need for multicenter randomized trials to confirm the promising initial results of CRT in heart failure patients with a narrow QRS complex.
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References
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- Bleeker GB, Holman ER, Steendijk P, et al. Cardiac resynchronization therapy in patients with a narrow QRS complex J Am Coll Cardiol 2006;48:2243-2250.[Abstract/Free Full Text]
- Yu CM, Chan YS, Zhang Q, et al. Benefits of cardiac resynchronization therapy for heart failure patients with narrow QRS complexes and coexisting systolic asynchrony by echocardiography J Am Coll Cardiol 2006;48:2251-2257.[Abstract/Free Full Text]
- Turner MS, Bleasdale RA, Mumford CE, et al. Left ventricular pacing improves haemodynamic variables in patients with heart failure with a normal QRS duration Heart 2004;90:502-505.[Abstract/Free Full Text]
- Achilli A, Sassara M, Ficili S, et al. Long-term effectiveness of cardiac resynchronization therapy in patients with refractory heart failure and "narrow" QRS J Am Coll Cardiol 2003;42:2117-2124.[Abstract/Free Full Text]
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