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Quantifying long-term improvements in exercise capacity after cardiac transplantation


 
 
 Cardiac transplantation (CT) is known to improve exercise capacity in patients with advanced heart failure (HF). However, it is unclear whether continued improvements occur after the initial post-operative recovery and whether baseline demographic and disease-related factors influence this improvement.
 
 
 
 We aimed to quantify the degree of improvement in exercise capacity over time in CT recipients and establish whether baseline characteristics influenced this improvement.
 
 
 
 Retrospective review of the medical records of patients who underwent CT at a single centre was performed. Cardiopulmonary exercise (CPEX) testing is routinely offered pre-CT and at 3, 6, 9, 12, 24, 36 and 48 months post-CT, unless there are contraindications. Baseline demographic and clinical characteristics pre-CT were also collected.
 
 
 
 A total of 199 patients underwent CT, of which 138 (69%) were male. The mean age was 44 (SD 14.0) years and mean pre-CT body mass index (BMI) was 25.3 (SD 4.2). In 125 (63%) patients, the underlying aetiology of HF was dilated cardiomyopathy (DCM). 32 (16%) patients had a durable left ventricular assist device (LVAD) as a bridge to CT.
 Pre-transplant CPEX was undertaken in 131 (66%) patients, with a mean peak VO2 of 15.5 (SD 6.2) ml/kg/min. Peak VO2 was higher in males (16.6; SD 6.7 vs 13.1; SD 4.0, p=0.002) and those under 50 years old (16.8; 7.2 vs 13.8; 3.9, p=0.005) but was not affected by the underlying aetiology (DCM vs others: 16.3, 6.6 vs 14.1, 5.1, p=0.051), the presence of an LVAD (17.3, 5.0 vs 15.1, 6.3, p=0.119) or pre-transplant obesity (14.5, 3.2 vs 15.7, 6.5, p=0.437).
 Peak VO2 increased within the first year post-CT (Figure 1 and 2). Ongoing improvements were also observed beyond the 1-year time-point, although only the 3-year vs 1-year comparison remained significantly when corrected for multiple comparisons. When analysed with mixed models, time post-CT was a significant predictor of peak VO2 (p=0.001). Additionally, there was a significant interaction between peak VO2 over time with gender (p=0.038), but not with age under 50 years (p=0.244), underlying aetiology being DCM (p=0.05), a previous LVAD (p=0.664) and pre-transplant obesity (p=0.301). Post-hoc analysis showed that males had a greater mean improvement than females in peak VO2 at 1-year compared to pre-CT (7.7, SD 5.5 vs 4.8, SD 4.0 ml/kg/min).
 
 
 
 These results demonstrate that exercise capacity improves up to and beyond the first year post-CT. The degree of improvement may be greater in males, although it is not influenced by age, BMI, underlying disease aetiology or the presence of an LVAD pre-CT.
 
 
 
 Type of funding sources: None.
