Early alterations of myocardial blood flow reserve in heart transplant recipients with angiographically normal coronary arteries

Background: The evaluation of the coronary reserve provides valuable inform ation on the status of coronary vessels. Therefore, we studied with positro n emission tomography (PET) and 13N-ammonia the myocardial blood flow (MBF) reserve in heart transplant: recipients free of allograft rejection and wi th angiographically normal coronary arteries early after heart transplantat ion (HTx). The MBF reserve was calculated as the ratio between MBF after di pyridamole injection and basal MBF normalized for the rate-pressure product . Methods: Patients were studied within 3 months (group A, n = 12) or more th an 9 months (group B, n = 12) after HTx. Five patients have been studied bo th during the early and late period after HTx. Results were compared to tho se obtained in 7 normal volunteers (NL). Results: Group A recipients had a significantly lower dipyridamole MBF (in ml/min/100 gr of tissue) than that of group B recipients (142 +/- 34 vs 195 +/- 59, p < 0.05). This resulted in a significant decrease in MBF reserve early after HTx (group A: 1.82 +/- 0.33) and a restoration to normal values thereafter (group B: 2.52 +/- 0.53 vs NL: 2.62 +/- 0.51,p = ns). Separate analysis of 5 patients studied twice is consistent with these results. Conclusion: This study shows that in heart transplant recipients free of al lograft rejection and with normal coronary angiography, MBF reserve is impa ired early after HTx. Restoration within one year suggests that this abnorm ality does not represent an early stage of cardiac allograft vasculopathy.