Double rhythm in double heart.

We describe the case of a patient with heterotopic transplantation, sinus rhythm originating from the donor heart, ventricular fibrillation of the native heart and right severe decompensation. The double rhythm was easily detected with a surface ECG and the transthoracic echocardiogram, both performed in the left conventional and in the right modified mode. The patient was successfully treated with direct current shock with quick restoration of native heart synchronization and clinical relief of symptoms.