Endomyocardial biopsy is the reference standard for the diagnosis of cardiac allograft rejection and is performed frequently in cardiac transplant patients. Biopsies are taken percutaneously via the right internal jugular or femoral vein. Fistulas from coronary arteries into the right ventricle following endomyocardial biopsies are a relatively frequent finding. Most of these fistulas are small angiographically, haemodynamically insignificant, and tend to disappear. We report a case of a haemodynamic significant coronary fistula, closed by a percutaneously introduced detachable balloon.