784-6 Unexplained Heart Failure in Cardiac Transplant Recipients: Intracoronary Ultrasound Identifies Two Distinct Subgroups

Cryptogenic heart failure in cardiac transplant recipients (CTR) is frequently attributed to humoral rejection. Histopathology in humoral rejection has identified angiographically silent coronary intimal thickening. We studied transplant patients with unexplained CHF using intracoronary ultrasound (ICUS) to identify occult CAD. Twelve CTR (8 male, 4 female; age 51±15 years; 2–7 years post-transplant) were referred for angiography and ICUS because of recent-onset CHF (radionuclide EF < 30%). All patients had normal coronary arteries by angiography at their previous surveillance catheterization, no recent infections, and no biopsy evidence of cellular rejection. ICUS was performed with 4.3F, 30mHz imaging catheters to the distal LAD andlor LCX. Images were analyzed via computer-planimetry for intimal thickness liT). All 12 patients had normal angiograms. All patients were treated with high-dose IV steroids. Surviving patients had repeat radionuclide EF at 3 months. Five patients (Group I) had significant intimal thickening by ICUS (IT=0.66±0.1 0mm, for ≥ 180° of vessel circumference). Seven patients (Group II) had no abnormal intimal thickening (IT = 0.26±0.06mm). Group I vs. II, P<0.001. At three months, EF in Group I survivors was unchanged (2 patients died); Group II patients (none died) experienced a 21±9 point improvement in EF (p<0.01).ConclusionsICUS segregates CTR with cryptogenic CHF (and normal angiograms) into two groups; one with marked intimal thickening, and one with normal intima. These groups have markedly different prognoses. Group I may represent patients with ongoing humoral rejection; EF in these patients is unchanged at 3 months despite high-dose steroids, Group II may represent cellular rejection not sampled during biopsy, or a steroid-responsive acute myopathy