Associations of Perioperative, Donor, and Recipient Factors with Functional Exercise Capacity after Orthotopic Heart Transplantation

Abstract

<h3>Purpose</h3> Low functional exercise capacity (FEC) is directly associated with reduced quality of life and poor prognosis after orthotopic heart transplant (OHT). Due to inconsistencies in the literature, the purpose of this study is to investigate several proposed independent risk factors for poor FEC post-OHT. <h3>Methods</h3> Thirty OHT recipients (22 males; <3 months post-OHT) performed a graded cardiopulmonary exercise test on an upright cycle ergometer or a treadmill dependent on fall risk in an outpatient cardiac rehab setting. FEC was dichotomized into high (≥14 ml/kg/min, or ≥12 ml/kg/min if on beta blockers) and low (<14 ml/kg/min, or <12 ml/kg/min if on beta blockers). Univariable and multivariable regression were used to study associations with FEC. Variable selection was facilitated using lasso and backwards selection. <h3>Results</h3> 15 patients exhibited high FEC. Characteristics were similar between groups, with the high FEC group having higher cardiac index (CI) and cardiac output (CO), longer ischemic time (IT), less chance of falling (all <i>p</i><0.04), higher anaerobic threshold (AT) and metabolic equivalents (both <i>p</i><.01) (Table 1). Each 30-min increase in IT was associated with a 40% [95% CI: 1.04, 2.09] increase in the odds of testing with high FEC, which remained significant following adjustment for AT and CI. Univariable linear association of IT with FEC was not significant. However, IT was an important factor in multivariable analysis with CPET duration, exertion, hemodynamics and test modality. Each 30-min increase in IT was associated with a 0.31 [95% CI: 0.04, 0.57] increase in FEC with all other variables constant. <h3>Conclusion</h3> Lower cardiac output and index as well as higher fall risk were associated with low FEC. Shorter IT was paradoxically associated with low FEC. Higher FEC despite longer IT suggest centers may be willing to travel further for donor hearts, although other perioperative factors may contribute to poor FEC.