Results show benefits of CRT ...
During the last decade, the clinical effects of long-term CRT with or without a combined defibrillation function have been extensively assessed in randomised trials with cross-over (MUSTIC and PATH-CHF) or parallel (mainly, COMPANION and CARE-HF) treatment assignments. Most of these studies were conducted in Europe. Usual enrolment criteria were:1) NYHA functional class III or IV despite optimal pharmacological treatment2) LVEF <35% and ventricular dilatation, 3) normal sinus rhythm, and intrinsic QRS width >120 ms as evidence of ventricular dyssynchrony. Results provided consistent evidence that CRT, in addition to optimal pharmacological treatment, improves symptoms and quality of life, reduces major HF morbidity, decreases all-cause mortality and the risk of sudden cardiac death, and reverses ventricular remodelling. The beneficial effect is sustained over time (up to 36 months in CARE-HF).Newly-published ESC Guidelines recommend CRT
Based on the strong clinical evidence, newly published ESC guidelines on cardiac pacing and resynchronisation therapy recommend the use of CRT to reduce morbidity and mortality (Class I, level of evidence A) in HF patients who meet the above-mentioned criteria.
Additionally, guidelines introduce new expert-consensus based recommendations (Class IIa, level of evidence C) for the use of CRT in two other dyssynchronised HF populations: patients with a concomitant pacemaker indication, and patients with permanent atrial fibrillation.
Newly-published ESC Guidelines recommend CRT 
Based on the strong clinical evidence, newly published ESC guidelines on cardiac pacing and resynchronisation therapy recommend the use of CRT to reduce morbidity and mortality (Class I, level of evidence A) in HF patients who meet the above-mentioned criteria. Additionally, guidelines introduce new expert-consensus based recommendations (Class IIa, level of evidence C) for the use of CRT in two other dyssynchronised HF populations: patients with a concomitant pacemaker indication, and patients with permanent atrial fibrillation.
Key questions however still remain
Despite these spectacular advances, many key questions still remain unresolved and new directions have to be explored:
- 1) Improving response to CRT: the current response rate of 60-70% of patients is unacceptably low as regards to the risk/benefit ratio and the cost of this invasive therapy. Future improvement is expected from two complementary approaches: i) improving patient selection probably by substituting imaging criteria to the ECG, ii) improving therapy delivery by optimising ventricular pacing lead configurations.
- 2) Selecting the right device for the right patient, with regards to the real clinical benefit and cost-effectiveness ratio. The incremental benefit of a CRT-D device over a simple resynchronisation pacemaker is still unclear.
- 3) Investigating the role of electrical therapies in new CHF populations: i) Patients with mild heart failure or asymptomatic LV systolic dysfunction (NYHA Class I-II) with the objective of preventing disease and heart failure progression. Two large randomised trials are ongoing, REVERSE and MADIT-CRT and first results are expected in 2008; ii) Patients with “narrow” QRS (<120 msec), but investigating the general question of patient selection will help to clarify the role of CRT in this specific population; iii) HF patients with preserved ventricular systolic function: assessing the clinical value of electrical therapies in this population that accounts for 40-50% of all HF patients is a major challenge for the future.
So should CRT trials begin?
But are the epidemiological data enough to initiate CRT trials, already? No; we still ignore the exact prevalence and the prognostic significance of cardiac dyssynchrony in this setting. The priority is to clarify these epidemiological aspects first, by conducting large prospective multi-centre registries.
After a major contribution in initiating and validating the concept of CRT, Europe has now to confirm its leading position in this highly challenging domain of cardiovascular medicine.