This paper reports recent results from an ongoing effort to develop an implantable accelerometer-based heart-monitoring device for ischemia monitoring. The latest device prototype utilizes a new and more compact accelerometer (1.2 × 1.5 × 0.8 mm3), a prototype device from Bosch SensorTec, Reutlingen, Germany. This paper presents the fabrication and testing of the device, including an explorative study of the effect of the capsule shape on the stability of the implanted device in the heart tissue. The stability study indicated sufficient stability of the device and a higher resistance to retraction for one of the capsule designs. The device was able to carry out acceleration monitoring and it meets the leakage current requirements of the IEC60601 standard.