An implantable coronary perfusion monitoring device for in-vivo determination of a coronary perfusion index (CPI) indicative of the coronary perfusion of a heart has a time measurement unit to determine a blood pressure reflection wave measure t indicating the timely position in the heart cycle of the maximum of a reflected blood pressure wave and in a time period starting at a preset point of time in systole and ending at a local maximum of blood pressure following aortic valve closure and, a diastolic peak pressure measurement unit adapted to determine a diastolic peak blood pressure measure DPP related to diastolic aortic peak pressure and a systolic arterial pressure measurement unit adapted to determine a systolic arterial blood pressure measure SAP related to systolic arterial pressure, and a coronary perfusion index calculating unit adapted to determine said coronary perfusion index CPI as (t·DPP)/SAP.