Disclosed is a completely implantable system that can detect the occurrence of a myocardial infarction, i.e., a heart attack, and automatically inject a thrombolytic and/or anti-thrombogenic agent into the bloodstream to promptly dissolve the thrombus that caused the myocardial infarction and prevent the formation of additional thrombi. It is well known that a myocardial infarction can be detected from a patient's electrocardiogram by noting an ST segment voltage deviation as compared to the voltage of the patient's TP or PQ segments. Upon detection of a myocardial infarction, an ST segment deviation electronic detection circuit within the implanted device can produce an output signal that can cause a thrombolytic and/or anti-thrombogenic agent contained within an implanted, pressurized reservoir to immediately and automatically release medications into the patient's bloodstream. A patient warning system is provided by an audio alarm or an electrical tickle within the human body indicating that a myocardial infarction has been detected. The implanted system can also send a radio message to an externally located receiver that automatically dials an emergency rescue team to take the patient to a hospital for continuing treatment of his myocardial infarction. An implantable defibrillator or pacemaker that includes the capability for informing the patient that myocardial infarction has been detected is also disclosed. Still further, this invention could also be used without a defibrillator or pacemaker but as an implanted system (without medications) whose only function would be the detection and warning of myocardial infarction at the earliest possible time.