Incidence of left ventricular function improvement after primary prevention ICD implantation for non-ischaemic dilated cardiomyopathy: A multicentre experience

Background: The SCD-HeFT study demonstrated a benefit of primary prevention implantable cardioverter-defibrillator (ICD) implantation in patients with non-ischaemic dilated cardiomyopathy (NIDCM). However, NIDCM may improve spontaneously, even after waiting 6-9 months on optimal medical treatment. Objective: To assess the incidence of left ventricular (LV) function improvement in patients receiving primary prevention ICDs for NIDCM. Methods: All patients with NIDCM receiving primary prevention ICDs (non-cardiac resynchronisation therapy) from 2005 to the present at our institutions were retrospectively studied. All patients had NIDCM confirmed by a lack of significant stenoses on coronary angiography, a lack of significant valvular abnormalities on echo, and LV dysfunction with ejection fraction (EF) <35%. All patients had to have had a diagnosis of NIDCM for at least 9 months and be receiving optimal medical treatment for at least 3 months before implant according to the guidelines. All patients had at least New York Heart Association (NYHA) II symptoms. Baseline and follow-up EF was documented by quantitative echo and/or multi-gated acquisition scan. Results: 332 patients were identified by a database search. Patients were aged 67±11 years, 75% of them were male, NYHA 2.3±0.7, with EF 25±13%, and LV diastolic diameter 61±10 mm. Time from initial NIDCM diagnosis to implant was 11±6 months and duration of medical treatment before implant was 8±5 months. Treatment at the time of implant included ACE inhibitors or ARBs (85%), β blockers (77%), spironolactone (53%), loop diuretic (63%) and digoxin (50%). Repeat EF assessment was available in 309/332 (93%) 8±6 months after implant. EF improved to >35% in 37/309 (12%) patients. Patients who improved had a shorter time from diagnosis to implant (9±3 vs 13±5 months respectively, p=0.03). No other significant predictors were identified for patients with improved EF. Conclusions: In spite of following guidelines for implantation of primary prevention ICDs in patients with NIDCM, a substantial number of patients (12%) experience improvement in LV function to levels above those recommended for ICD implant. A shorter time from diagnosis to implant may predict post-implant improvement.