Cardiac resynchronization therapy prognosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief:: Bhaskar Purushottam, M.D. [2] Synonyms and Keywords: CRT
Overview
Non-responders
30% of the CRT recipients are considered non-responders. A patient is considered a non-responder if there are no significant clinical or functional improvement after CRT as measured in the landmark trials (as mentioned above under clinical benefits). There are several plausible causes to explain a non-responder. As mentioned earlier, not all patients with QRS duration greater than or equal to 0.12 seconds have mechanical dyssynchrony. Unfortunately, the PROSPECT[1] trial which set out to examine the various echocardiographic parameters to predict CRT response was not successful. Some of the major limitations in the study were the technical difficulties in obtaining the dyssynchrony parameters and the discrepancies among the different centers. The other reasons could be lead placement in regions of the left ventricle which is not dyssynchronous or fibrosis with no live myocardium. In fact, anterior left ventricular lead placement has been associated with worsening hemodynamics. Also, lack of sufficient biventricular pacing could result in a non-responder secondary to high left ventricular capture thresholds, lead dislodgement, a long atrioventricular delay, atrial tachyarrhythmias with rapid ventricular response and frequent premature ventricular contractions. Lack of optimal atrioventricular and ventricular to ventricular (i.e., right ventricle to left ventricle) timing can result in a non-responder.
Unmet Needs
The following are remaining unmet needs:
- The identification of patients who would definitely benefit from CRT (i.e. reducing the number of non-responders). Different imaging modalities and dyssynchrony parameters may accurately reveal mechanical dyssynchrony and therefore predict a CRT responder, especially in patients with a narrow QRS complex.
- Further confirmatory evidence regarding the benefit of atrioventricular ablation versus pharmacological rate control in optimizing the clinical benefits is needed. In addition to atrioventricular and Ventricular-Ventricular optimization, other device based changes need to be explored so as to reap the complete benefits of CRT.
References
- ↑ Chung ES, Leon AR, Tavazzi L, Sun JP, Nihoyannopoulos P, Merlino J; et al. (2008). "Results of the Predictors of Response to CRT (PROSPECT) trial". Circulation. 117 (20): 2608–16. doi:10.1161/CIRCULATIONAHA.107.743120. PMID 18458170.