16-69: Upgrading CRT systems from previous pacemakers and ICD's, assessing the clinical outcomes

Abstract

Purpose: Cardiac resynchronization therapy (CRT) is indicated in patients with heart failure and bundle branch block. It is less clear whether this includes patients with pre-existing right ventricular pacemaker/ defibrillator systems, particularly with respect to having a clinical benefit. The indication for CRT therapy has been constantly widened following publication of randomized prospective clinical trials. However, among other important unanswered questions regarding CRT, it has not been assessed whether patients with previously implanted right ventricular pacemakers or cardioverter defibrillator (ICD) systems derive similar benefit from resynchronization therapy compared with patients undergoing de novo CRT implantation. Method: CRT implantation occurred in 147 patients (64 + 11 years) between February 2010-October 2015. From this cohort, we extracted data from 43 patients undergoing a CRT upgrade. The two groups were then compared, (de novo vs upgrade) and clinical outcomes were measured in terms of response, lead repositions and mortality. Inclusion criteria was class III-IV New York Heart Association heart failure symptoms and on optimal medical therapy. Furthermore, an LVEF ≥35% or a QRS width .120 ms was required and in patients with a previously implanted pacemaker or ICD with ventricular pacing, a paced QRS width was ≥160 ms present. Patients were followed up at 1 month in clinic and then at 4 monthly intervals either in clinic or via home monitoring after device implantation. In addition whenever clinical circumstances called for, unscheduled visits were made. At each visit, functional heart failure status (symptoms), and at the 6 months visit either the left ventricular ejection fraction or LV impairment were determined. Concomitant medication was adjusted according to the clinical status of the patient. Patients were considered responders to CRT if they survived to the 6 months follow-up and showed significant improvement in one out of three of the following criteria: improved clinical status (i.e. symptoms), and / or echocardiographic improvement. This was based on either an improved LVEF of .5% or an improved LV function i.e. from severe to moderate. Summary: Mean left ventricular ejection fraction was 27%. Over a mean follow-up of 3.7 +1.5 years, the response rate was significantly higher in the upgraded CRT vs de novo CRT (76%vs 62% (p = 0.03). There was a significant difference between pacemaker upgrades and ICD upgrades. Pacemaker upgrades had the highest percentage of response (76% vs 44% p = 0.05) Heart failure hospitalisation within 30 days showed no significant differences between the two groups (p = 0.15) Mortality rates showed borderline statistical significance (p = 0.051), 10.5% in the patients de novo CRT and 4 (7.2%) mortality in upgraded CRT. Lead repositions were non-significant and occurred in 10.2% of upgrade CRT and 12.6% de novo implants. (p = 1.0) Conclusion: Clinical response to CRT were comparable for patients undergoing de-novo vs. upgrade procedures. Accordingly, patient selection for upgrading should be the same as for new CRT implantation.