Author + information
- Hugues Bader, MD
We thank Dr. Bax and colleagues for their interest in our study (1) and, above all, for raising several important issues. As they mentioned in their letter, various studies have demonstrated or at least suggested that left ventricular (LV) dyssynchrony might predict response to cardiac resynchronization therapy (CRT). A recent study published in the Journal(2) has showed that patients with a narrow QRS complex and with LV electromechanical dyssynchrony could benefit from CRT (even with a larger pacing-induced QRS width compared with spontaneous rhythm) at the same level of hemodynamic and clinical improvement than patients with large QRS complexes (>120 ms). These new data can at least suggest that, independent of the QRS width, the presence of dyssynchrony is likely to be the key point for selecting candidates to CRT. However, one issue still remains: what is the best predictive echocardiographic method (among the different Doppler tissue imaging techniques) for selecting those patients? This requires larger studies comparing the positive and negative predictive values of several techniques already published.
From this point, it can be emphasized that heart failure patients (New York Heart Association functional class III or IV) with mechanical LV dyssynchrony should systematically benefit from CRT. So far, no study has clearly demonstrated that medical treatment by itself could reduce the level of ventricular dyssynchrony. If the future confirms that drugs have no significant effect on ventricular dyssynchrony, CRT should be applied systematically in such patients.
Concerning the absence of relationship between the QRS complex morphology and region of latest activation, we fully agree with Bax et al. Ansalone et al. (3) already have demonstrated that placing the LV pacing lead in regard to the region of latest activation could further improve patients benefiting from CRT. However, we think that this might be suitable only in patients with primitive dilated cardiomyopathy. Indeed, by considering patients with severe ischemic heart disease, regions with the latest activation could be highly ischemic, so that pacing from such ventricular areas could be first, potentially arrhythmogenic and second hemodynamically detrimental because it might induce a new dyssynchrony resulting from the low conduction velocity in such regions. For that reason, further studies are crucially needed to definitely state on this point.
Finally, we also agree that the best way to reach optimal LV pacing sites should be the epicardial surgical approach via thoracoscopy or mini-thoracothomy procedures. The transseptal approach with endocardial LV pacing could also be considered with the advantage of preserving the endovenous approach and permitting free access to the four ventricular walls.
- American College of Cardiology Foundation
- Bader H.,
- Garrigue S.,
- Lafitte S,
- et al.
- Achilli A.,
- Sassara M.,
- Ficili S,
- et al.