A major concern in cardiac transplantation, acute rejection (AR) of heart transplants requires careful surveillance through endomyocardial biopsies (EMBs). A novel highlysensitive cardiac troponin I (hs-cTnI) assay has been shown to accurately detect very low levels of circulating cTnI in patients with stable coronary artery disease, and, as demonstrated by Patel et al. in a study published in Circulation: Heart Failure, the assay may have some utility in diagnosing AR after orthotopic heart transplant (OHT).

Investigators matched stored serum samples to EMBs in 98 recipients of OHT who survived at least 3 months posttransplant. Cross-sectional analyses determined the association of cTnI concentrations with rejection and ISHLT grade, as well as the performance metrics of cTnI for the detection of AR. Among the 98 subjects, 37% had at least one AR episode (defined as ISHLT grade 2R or higher cellular rejection, acellular rejection, or allograft dysfunction of uncertain etiology leading to treatment for presumed rejection).

As the authors hypothesized, cTnI concentrations were significantly higher in AR versus non-AR samples: median 57.1 vs. 10.2 ng/L (p < 0.0001). This association increased in a graded manner with higher biopsy scores. Using a cut point of 15 ng/L, the sensitivity of this assay was 94%, specificity 60%, positive predictive value 18%, and negative predictive value 99%.

Given the high negative predictive value of this assay, Patel et al. wrote, hs-cTnI could provide a low-cost, noninvasive approach to rejection surveillance. While the hs-cTnI assay shows some promise to rule out AR in cardiac transplant recipients, this method needs to be validated through prospective studies before a strategy of serial monitoring with an hs-cTnI assay could be implemented.

Patel PC, Hill DA, Ayers CR, et al. Circ Heart Fail. 2014 April 14. [Epub ahead of print]

Keywords: Troponin I, Cross-Sectional Studies, Biopsy, Heart Transplantation

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