Abnormal mitochondrial function and morphology in heart transplanted patients with cardiac allograft vasculopathy

Cardiac allograft vasculopathy (CAV) remains the Achilles' heel of long-term survival of HTx patients. Mitochondrial dysfunction has been reported in both arteriosclerotic coronary disease and heart failure. However, myocardial mitochondrial function has not been examined in HTx patients with CAV.

43 HTx patients (21 patients with CAV and 22 patients without CAV) ≥12 months after HTx were enrolled. Endomyocardial biopsies were analyzed using high-resolution respirometry for glucose-coupled mitochondrial respiration. Number and area of mitochondria profiles as well as cristae morphology were assessed by transmission electron microscopy. Echocardiography and coronary angiography were used to measure global longitudinal strain (GLS) and grade CAV.

Complex I+II-linked respiration was reduced in patients with CAV compared with patients without CAV (82.7 ± 31.9 pmol O2/(s•mg) vs 116 ± 35.9 pmol O2/(s•mg), p = 0.003). Mitochondrial respiratory function measured as oxidative phosphorylation coupling efficiency was positively associated with left ventricular GLS (r = 0.49, p = 0.002) and negatively associated with elevated biomarkers (Troponin T: r=-0.33, p = 0.04 and NT-proBNP: r = -0.41, p = 0.009). Mitochondrial profile number and area did not differ. However, patients with CAV had a larger proportion of mitochondria with abnormal cristae morphology (p < 0.001).

Myocardial mitochondrial respiration is impaired in patients with CAV and is associated with an abnormal cristae morphology. The mitochondrial dysfunction appears to be associated with reduced myocardial contractile function and elevated biomarkers. These results highlight that mitochondrial targeted treatment in patients with CAV should be assessed in future clinical studies.