Cardiac Recovery During Long-Term LVAD Support
What characterizes patients who undergo cardiac recovery on left ventricular assist device (LVAD) support, and how can they be identified?
The Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS), a registry used for patients with mechanical circulatory support, was used to de-identify LVAD patients to the authors; they used patients who were implanted between March 2006-June 2015. Patients were excluded who received a right ventricular assist device without an LVAD, a total artificial heart, or prior transplantation, limited follow-up, complex congenital heart disease, and hypertrophic or other restrictive cardiomyopathies. The primary outcome was the incidence of cardiac recovery, defined as LVAD explantation due to myocardial recovery. Other outcomes included mortality on LVAD support, transplantation, and LVAD explantation due to nonrecovery reasons. Outcomes were evaluated in the cohort and subgroups based on implantation strategy: bridge-to-recovery (BTR) and non-BTR. These included patients who were bridge-to-transplantation, bridge-to-candidacy, destination therapy, and rescue therapy. A prognostic scoring system was developed dividing patients into categories of low, intermediate, or high probability of cardiac recovery. The prognostic scoring system was externally validated in an independent cohort of patients from the Utah Cardiac Recovery (UCAR) program.
A total of 15,138 patients were included in the INTERMACS cohort. Patients who had an LVAD with a prior BTR strategy were more likely to be young, female with lower body mass index, and more often had nonischemic cardiomyopathies, and had a relatively new diagnosis of heart failure. They were less likely to have an implantable-cardioverter defibrillator (ICD), chronic kidney disease, lower INTERMACS profiles (higher acuity of illness), and more likely to require dialysis or require a biventricular assist device, and less likely to require a temporary mechanical percutaneous device. At a median of 323.3 days, 192 (1.3%) of the INTERMACS population had cardiac recovery, which required LVAD explantation or device deactivation. Recovery occurred in 2.1% of the patients during the first month, 14.6% by 3 months, and 80% of recoveries by 2 years post-LVAD implantation. 11.2% of patients who were implanted as a BTR experienced cardiac recovery versus 1.2% of patients who were non-BTR.
A competing regression analysis in the INTERMACS cohort identified multiple univariable predictors of cardiac recovery. Patients with complex congenital heart disease and restrictive heart disease were less likely to experience cardiac recovery. Six independent predictors of cardiac recovery were identified: age <50 years, nonischemic etiology, time from cardiac diagnosis <2 years, no ICD, serum creatinine ≥1.2 mg/dl, and LV end-diastolic dimension <6.5 cm (c-statistic of 0.85; 95% confidence interval [CI], 0.82-0.88; p < 0.0001). A prognostic score was created called the INTERMACS Cardiac Recovery Score (I-CARS). The score was used to identify three groups of cardiac recovery: low probability (0-3 points), intermediate probability (4-6 points), and high probability (7-9 points). I-CARS was applied to the BTR and non-BTR groups with an area under the receiver operating characteristics curve of 0.84 (95% CI, 0.81-0.87). Pharmacotherapy showed the use of beta-blockers, angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers, and mineralocorticoid receptor antagonists to be associated with cardiac recovery in a univariable analysis.
The validation cohort consisted of 190 patients who were mostly male, median age 60 years, and New York Heart Association class IV patients. I-CARS stratified patients on the basis of their probability of cardiac response and recovery. Patients with a high probability score did have improvement in myocardial function.
Cardiac recovery in LVAD patients is most likely to occur in patients with a predefined strategy of BTR. The I-CARS predictive score can be used to identify those patients with a low to high probability of cardiac recovery with an LVAD.
LVAD therapy has traditionally focused on two patient populations: bridge to transplantation and destination therapy. BTR has been the focus of recent research and best practices guidelines. Cardiac recovery does exist and as implanting physicians, the benefit of LVAD therapy in this patient population can be tremendous and life-saving. When patients are identified as BTR, there appears to be a greater focus amongst the medical team in following for signs of recovery. A predictive scoring tool, such as I-CARS, would be used regularly to assess the potential for recovery, if validated in a larger multicenter cohort.
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