The invention is directed to techniques for delivering electrical stimulation to a gastrointestinal tract of a patient via an implantable stimulator and monitoring electrical activity of a patient's heart by sensing cardiac signals via electrodes coupled to the implantable stimulator. The implantable stimulator may analyze the cardiac signals and generate a cardiac therapy recommendation for the patient, or may communicate the cardiac signals via telemetry circuitry to an external device for analysis. The sensed cardiac signals may be electrocardiogram (ECG) signals.