Method and device for treatment of a heart after harvesting and before transplantation. The device comprises a container (32) intended to comprise the heart (31) a first line (54) for connection to an aorta (30) of the heart a fluid circuit comprising an oxygenator (37) for oxygenating said fluid and a heater/cooler (38) for regulating the temperature of said fluid and a pump (36) for perfusion of said fluid through the coronary blood vessels of the heart. The fluid comprises an oncotic agent exerting an oncotic pressure larger than about 30 mmHg and is cardioplegic by comprising a potassium concentration, which is between 15mM and 30 mM. A control device is arranged for controlling the pump to perform said perfusion intermittently, whereby the perfusion time is less than half of the cycle time. The perfusion is performed at a pressure, which is at least 15 mmHg and at least 15 mmHg lower than said oncotic pressure. The container (32) may be purged with fluid bypassing the heart between the perfusion steps. The perfusion cycle time may be 75 minutes and the perfusion time may be 15 minutes.
