Introduction It has been previously shown that PBC patients have bioenergetic abnormality in both peripheral and cardiac muscle. In particular they exhibit significantly lower cardiac muscle phosphocreatine-to-ATP ratio (measure of cardiac bioenergetic integrity) compared with control subjects. In other disease settings, such as cardiac failure, changes of this type have been associated with impaired cardiac function and increased risk of cardiac death.
Aim The objective of the present study was to examine whether these changes are reflected in systemic measurements of cardiopulmonary reserve determined by a non-invasive cardiopulmonary exercise test (CPET).
Method Consecutive PBC patients being assessed for liver transplantation underwent CPET. The test was conducted in a consistent environment and reviewed by a trained physician to determine objective measures of cardiorespiratory reserve. A control group of consecutive patients with primary sclerosing cholangitis (PSC), also being assessed for liver transplantation was also tested. We compared the results of CPET of all patients with a diagnosis of PBC with those with PSC. Patient demographics and MELD scores at assessment were also collected. A non-paired t test was used to determine group differences.
Results In total, 38 patients had a diagnosis of either PBC or PSC. Three patients (2 PBC and 1 PSC) did not exercise sufficiently to gather meaningful results and were excluded from the analysis. The PSC patients assessed for transplantation had significantly worse liver disease as assessed by the MELD score. However, all measures of cardiorespiratory reserve derived from CPX testing were significantly lower in the PBC group. There was no statistical difference between the two groups with respect to age, thus excluding age as the underlying factor in decreasing their fitness.
Conclusion In this cohort, patients with PBC, despite having lower MELD scores and equivalent age at transplantation assessment, had significantly impaired cardiorespiratory reserve, when compared to patients with PSC. The results add to the evidence that there is a specific PBC-related bioenergetic effect due to the immunology of PBC that is absent in PSC. This finding could have significant relevance on both future studies and treatment regimes to improve cardiovascular fitness.