Histomorphometric features predict 1-year outcome of patients with idiopathic dilated cardiomyopathy considered to be at low priority for cardiac transplantation.

Cardiac transplantation for patients with idiopathic dilated cardiomyopathy (IDC) and poor left ventricular function usually is postponed until symptoms have become intolerable. However, the short-term prognosis of this subset of patients has been defined poorly. Accordingly, the 1-year outcome was investigated in 30 patients with IDC with an ejection fraction < or = 25% who showed a stabilized clinical condition at assessment for transplantation and were therefore considered at low priority for surgery. During follow-up, 10 patients (group A) showed a poor outcome: 2 died suddenly, and 8 had hemodynamic failure (4 of whom underwent transplantation and 4 of whom died from heart failure while on the waiting list). The remaining 20 patients (group B) had a benign outcome. At assessment for cardiac transplantation, clinical and electrocardiographic features, left ventricular dimension, and ejection fraction were similar between the two groups. However, group A patients had higher left ventricular end-diastolic pressure (p < 0.03) and lower cardiac index (p < 0.02) and stroke volume index (p < 0.03) with respect to group B patients. In addition, the former had a lower myofibril volume fraction (p < 0.001) and a higher nuclear area (p < 0.001) compared with the latter. Multivariate analysis selected myofibril volume fraction (p < 0.001) and nuclear area (p < 0.005) as the only independent predictors of a poor 1-year outcome. The combination of myofibril volume fraction < or = 89% and nuclear area > 50 microns 2 was found in all group A patients (sensitivity 100%) but in only 2 group B patients (specificity 90%). It is concluded that in patients with IDC considered at low priority for cardiac transplantation: (1) the 1-year freedom from a cardiac event is lower than that currently expected with surgery; (2) histomorphometric features, that is, the concurrency of low myofibril volume fraction and increased nuclear area, predict short-term outcome; and (3) endomyocardial biopsy at assessment for cardiac transplantation might improve the rationalization of the timing of the procedure.