Microprocessor-based electrocardiography instruments are helping combat the No.1 killer of people in the United States: heart disease. The new ECG instruments not only capture and display real-time and recorded measurements of heart rates, waveforms, and rhythms, but they also process and transfer the data to a remote site for analysis by a cardiologist or a computer. Analysis can point to problems in the electrical conduction networks, heart muscles, valves or blood flow. The latest ECG equipment uses the microprocessor's software-derived intelligence to diagnose some heart defects or to record and warn of abnormal heart rhythms. Microprocessors are also turning up in other medical applications that are making diagnoses and even medication less prone to error. Among these applications are the following: Bedside monitoring of patient circulatory, respiratory, and central nervous systems, along with metabolic and acid/base control systems. Monitoring of heart signals in ambulatory patients through the recording of data on a tape cassette worn by patients. Feedback control of the breathing of bed patients and the automatic infusion of intravenous fluids. Automatic chemistry analyzers for laboratories that allow blood counts to be made by relatively unskilled personnel.