Background: Cardiac allograft vasculopathy (CAV) in patients who have undergone heart transplantation leads to graft dysfunction and is still the major concern for long-term survival. Evaluation of coronary flow velocity reserve (CFR) has been established for diagnosis of CAV. Systemic application of adenosine vs intracoronary testing for CFR has been validated in adults; however, its accuracy in pediatric patients has not yet been proven.
Methods: CFR was prospectively measured in 33 clinically asymptomatic pediatric heart transplant recipients. CFR measurements were made in the left anterior descending (LAD) artery using a 0.014-inch Doppler FloWire (Cardiometrics). CFR was defined as the ratio of hyperemic (after adenosine injection) to basal (before adenosine) average peak velocity (APV). Adenosine (Adrekar) was administered by intracoronary (15 or 30 mug bolus) and systemic (0.1 mg/kg) injection in each patient. Epicardial CAV was evaluated in coronary angiograms (Stanford criteria) and microvasculopathy was diagnosed in endomyocardial biopsies (evidence of luminal stenosis) blinded to clinical data.
Results: Thirty-three patients were included in this study. Their median age (range) was 11.9 (1.4 to 17) years and median post-transplant time 4.3 (1 to 11.7) years. Seventeen of the 33 patients had epicardial CAV (mainly peripheral obliterations or B1 and B2 lesions) and microvascular CAV. Epicardial CAV only was found in 4 patients and microvasculopathy only was present in only 1 patient. CFR was significantly reduced in patients with epicardial CAV and microvasculopathy when compared with patients without any signs of CAV: 206 +/- 53 vs 276 +/- 39 (p < 0.001) for the systemic application and 213 +/- 50 vs 271 +/- 45 (p = 0.004) for the intracoronary application.
Conclusions: CFR and coronary vasoreactivity to adenosine are decreased in pediatric patients with CAV and correlate with histopathologic and angiographic evidence of microvascular disease. Measurement of CFR with intracoronary and systemic application of adenosine is comparable, while systemic application is necessary for non-invasive measurement of CFR in pediatric patients.