Renography before heart transplantation in patients with cardiomyopathy

In patients with ischemic cardiomyopathy (CM), abnormal renograms may result not only from circulatory failure (which should reverse after transplantation) but also from intrinsic renal disease (which contraindicates heart transplantation). Here, the outcome of heart transplantation was related to preoperative renograms, and the differentiating and prognostic value of renography was analyzed. Methods: The study population consisted of 50 patients with ischemic CM expecting heart transplantation. Anatomical renal pathology was excluded in all patients. Dynamic renal scintigraphy was performed with (99m)Tc-mercaptoacetyltriglycine. Background-subtracted renograms were inspected visually and characterized numerically. Mean parenchymal transit time (mPTT), renal tracer content at 15 min (RTC15) and retention index (RI) were determined. The parametric renogram values were related to a normal reference group of 64 patients. The preoperative renograms were matched with the postoperative outcome. Results: Three characteristic types of symmetrical findings in the kidneys were found: no pathological findings, mildly delayed peak and excretion phase and severely delayed peak and excretion phase. Pathological renograms were observed in 36 of 50 (72%) patients. The mean parametric renogram values in ischemic CM were as follows: Group-A (normal kidney function), mPTT = 142 +/- 26.6 sec, RTC15 = 22.3% +/- 4.6% and RI = 24.7 +/- 11.9; Group B (mild dysfunction), mPTT = 210 +/- 44.0 sec, RTC15 = 42.6% +/- 10.3% and RI = 101.4 +/- 50.5; Group C (severe dysfunction), mPTT = 320 +/- 94.2 sec, RTC15 = 79.6% +/- 15.9% and RI = 347.7 +/- 194.7; and reference patients (normal kidney function), mPTT = 137 +/- 31.1 sec, RTC15 = 22.8% +/- 3.8% and RI = 24.6 +/- 7.9. Postoperative serum creatinine levels were <1.5 mg/dl in all Group A patients, between 1.5 and 2.5 mg/dl in 78% of Group B patients and > 2.5 mg/dl in 75% of Group C patients. Conclusion: Renography revealed abnormal kidney function when structural pathology was excluded. The renographic abnormalities in ischemic CM did not reflect simply the circulatory failure. The numerical grading of renograms allowed patient stratification, suggestive of possible renal insufficiency after cardiac transplantation and immunosuppressive therapy. With further experience, renography may become a useful tool for predicting postoperative outcome in ischemic CM.