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Reversal of Pacing-Induced Cardiomyopathy After CRT
Study Questions:
What is the extent and time course, and what are the predictors of improvement following cardiac resynchronization therapy (CRT) upgrade among pacing-induced cardiomyopathy (PICM)?
Methods:
This single-center retrospective study assessed 1,279 consecutive patients who underwent CRT (including CRT upgrade from dual-chamber or single-chamber) between 2003 and 2016. All pacemakers were programmed to favor intrinsic atrioventricular conduction whenever possible. They defined PICM as decrease of ≥10% in left ventricular ejection fraction (LVEF), resulting in LVEF <50% among patients experiencing ≥20% right ventricular pacing without an alternative cause of cardiomyopathy. They defined severe PICM as pre-upgrade LVEF ≤35%. They identified clinical, electrocardiographic, and echocardiographic characteristics associated with both the extent of LVEF recovery and with post-upgrade LVEF of >35% among those with severe PICM. They utilized a multivariable model on variables showing significant (p < 0.10) associations with LVEF improvement on univariate testing.
Results:
Of the 1,279 patients undergoing CRT-related procedures during the study period, 472 underwent CRT upgrade of an existing pacemaker. Of those 472 patients, 376 had an alternative potential cause of cardiomyopathy, resulting in 69 patients who underwent CRT upgrade for suspected PICM. Of these 69 PICM patients, LVEF improved from 29.3% to 45.3% over a median 7.0 months. Of 54 patients with severe PICM, 39 (72.2%) improved to LVEF >35% over a median 7.0 months. Most improvement occurred within the first 3 months, although improvement continued over the remainder of the first year. In linear regression, narrower native QRS was associated with greater LVEF improvement following CRT upgrade (+2.00% per 10-ms decrease; p = 0.05). In multivariable analysis, narrower native QRS (odds ratio [OR] 1.92 per 10-ms decrease; 95% confidence interval [CI], 1.09-5.00; p = 0.06, bundle branch blocks excluded) remained marginally associated with improvement to LVEF >35% post-upgrade. In a secondary multivariate analysis including all native QRS complexes, narrower native QRS was not significantly associated with LVEF >35% post-upgrade (OR, 1.21 per 10-ms decrease; 95% CI, 0.94-1.61; p = 0.10).
Conclusions:
The study authors concluded that CRT is highly efficacious in reversing PICM, with 72% of severe PICM patients achieving LVEF >35% and most of the improvement occurring within 1 year. Based on these data, they recommended an initial upgrade to a CRT pacemaker with consideration of further upgrade to a CRT defibrillator after 1 year if LVEF remains ≤35%.
Perspective:
Although this is a retrospective study, the findings are important because it suggests that recovery of LV function with CRT in PICM is robust and that this substantial improvement will occur despite long-standing decreases in LVEF. The next step would be to do a prospective study, including cost-effectiveness, of this approach.
Keywords: Arrhythmias, Cardiac, Bundle-Branch Block, Cardiac Resynchronization Therapy, Cardiomyopathies, Defibrillators, Echocardiography, Electrocardiography, Geriatrics, Heart Failure, Pacemaker, Artificial, Stroke Volume
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