European Heart Journal Advance Access originally published online on November 22, 2006
European Heart Journal 2006 27(24):3075; doi:10.1093/eurheartj/ehl387
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QRS duration alone to select patients for cardiac resynchronization therapy: flying in the face of the evidence? reply
Department of Cardiology
University Hospital of North Staffordshire
Keele University School of Medicine
Stoke-on-Trent ST4 6QG
UK
E-mail address: John.Sanderson{at}uhns.nhs.uk
I thank Hawkins et al. for their interest in my editorial on the question of detecting dyssynchrony and its relation to outcome after biventricular pacing or cardiac resynchronization therapy (CRT).1 Their response is perhaps predictable because my comments on their previous paper were provocative, as much as their's were in the first place.2 I assume that they would agree to the proposition that not all patients improve with biventricular pacing (perhaps at least 30–40% in most large clinical trials) and indeed some may deteriorate.3,4 Therefore, by definition, selection for CRT is not good using the current ECG-based criteria. Hence, there are unnecessary costs, waste of valuable resources, and risks for patients; there must be a better way. Furthermore, devices are not the same as pills, and should not be treated as such, as they suggest.2 Biventricular pacing is associated with significant risks that are mainly up-front at the time of implantation as are the costs, unlike medical therapy that can be stopped at any time removing any further risks and saving money. Thus, for a device therapy identifying patients who will not respond is vitally important. Dismissing all echocardiographic techniques that appear to do this because they were not part of the inclusion criteria in the major clinical trials is pedantic.
Many studies have shown that the degree of mechanical dyssynchrony by Doppler-echocardiography is related to the success of CRT whether that is assessed by symptoms or the degree of reverse remodelling.4 Remodelling is a major process in heart failure and all treatments that have been shown to reduce mortality and improve quality of life prevent or reduce remodelling.5 And, after CRT, Yu et al.6 have shown that reverse remodelling (a reduction of end-systolic volume of 10%) predicts long-term survival. It is true that a number of indices of dyssynchrony have been proposed but in a thorough analysis of regional functional indices. Yu et al. have shown that those based on a 12-segment model appear to be most reliable.4 Using a global functional measurement, Duncan et al. were able to gain good separation of responders from non-responders defined by clinical criteria (not volumes alone).1 As suggested in my editorial, a combination of both regional and global indices would probably be the best.1 Obviously, these new methods for selection need to be tested in larger trials, which was also stated in the editorial. In particular, we need to know if CRT can produce benefit in those who do not have mechanical dyssynchrony despite a widened QRS (which occurs in 30%),4 or in those with a normal QRS duration and dyssynchrony who have been excluded from previous trials. After all, the QRS duration criteria are just a historical accident because it was the only available measure of abnormal activation at the time. Finally, no one is against guidelines but they are just that, guidelines; they are not immutable. They can change quickly with new information and progress is often made when guidelines are challenged. The history of medicine is littered with examples of erroneous guidelines.
References
- Sanderson JE. (2006) Assessment of ventricular dyssynchrony: global or regional function? Eur Heart J 27:2380–2381.
[Free Full Text] - Hawkins NM, Petrie MC, MacDonald MR, Hogg KJ, McMurray JV. (2006) Selecting patients for cardiac resynchronization therapy: electrical or mechanical dyssynchrony? Eur Heart J 27:1270–1281.
[Abstract/Free Full Text] - Yu CM, Fung WH, Zhang Q, Sanderson JE. (2005) Understanding non-responders of cardiac resynchronization therapy-current and future perspectives. J Cardiovasc Electrophysiol 16:1117–1124.[CrossRef][Web of Science][Medline]
- Bax JJ, Abraham T, Barold SS, Breithardt OA, Fung JW, Garrigue S, Gorcsan J III, Hayes DL, Kass DA, Knuuti J, Leclercq C, Linde C, Mark DB, Monaghan MJ, Nihoyannopoulos P, Schalij MJ, Stellbrink C, Yu CM. (2005) Cardiac resynchronization therapy: Part 1—issues before device implantation. J Am Coll Cardiol 46:2153–2167.
[Abstract/Free Full Text] - Mann DL and Bristow MR. (2005) Mechanisms and models in heart failure: the biomechanical model and beyond. Circulation 111:2837–2849.
- Yu CM, Bleeker GB, Fung JW, Schalij MJ, Zhang Q, van der Wall EE, Chan YS, Kong SL, Bax JJ. (2005) Left ventricular reverse remodeling but not clinical improvement predicts long-term survival after cardiac resynchronization therapy. Circulation 112:1580–1586.
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