Effectiveness of Multidomain Cardiac Rehabilitation After Myocardial Infarction by Patient Frailty: Prespecified Subgroup Analysis of the PIpELINe Trial.

Abstract

BACKGROUND: Frailty is common among older patients surviving myocardial infarction, is associated with adverse outcomes, and is often perceived as a barrier to cardiac rehabilitation (CR). The aim of this study is to determine whether frailty influences prognosis after myocardial infarction, and whether frailty modifies the clinical benefit of multidomain CR. METHODS: We performed a prespecified subgroup analysis of the PIpELINe (Physical Activity Intervention in Elderly Patients With Myocardial Infarction) randomized clinical trial conducted in Italy, which enrolled 512 patients aged ≥65 years recovering from myocardial infarction and randomized them in a 2:1 ratio to CR or usual care. Frailty was assessed using the Fried Frailty Phenotype, and patients were categorized as nonfrail (robust) or prefrail/frail. Time-to-event outcomes were analyzed using Kaplan-Meier estimates and Cox proportional hazards models, including treatment-by-frailty interaction terms to evaluate effect modification of the multidomain CR. The primary outcome was a composite of cardiovascular death or unplanned hospitalization for cardiovascular causes within 1 year after randomization. RESULTS: Overall, 350 patients (68.4%) were classified as prefrail/frail, of whom 232 were randomized to intervention arm (66%). Frail patients were older (median age, 80 [75-85] years) and more frequently female (41.7% versus 24.7%). Compared with robust patients, prefrail/frail patients had a higher risk of the primary outcome (16 [9.9%] versus 62 [17.7%]; hazard ratio, 1.59 [95% CI, 0.89-2.82]; adjusted P=0.117). Among prefrail/frail patients, assignment to multidomain CR was associated with a lower risk of the primary outcome compared with usual care (hazard ratio, 0.57 [95% CI, 0.34-0.94]; P=0.028), with no statistically significant interaction in the treatment effect on the primary end point (P=0.57). CONCLUSIONS: Among older patients recovering from myocardial infarction, frailty is associated with worse prognosis but does not diminish the benefit of multidomain CR. These findings support the use of frailty assessment to guide rather than limit access to CR. REGISTRATION: ClinicalTrials.gov; Unique identifier: NCT04183465.