Physicians can now use the telephone to reach out and treat patients suffering from a heart attack at a distant location.

MDphone, a device containing a telephone and a defibrillator, about the size of a small attache' case, recently received approval for marketing by the Food and Drug Administration. It will be prescribed for patients recovering from a heart attack who are still at risk, said Dr. Rodolphe Ruffy, a cardiologist at the Jewish Hospital at Washington University in St. Louis who was involved in the clinical trials of the device.

When MDphone is prescribed, the person's medical history is entered into a computer along with the telephone number of a local hospital. If another heart attack occurs, a family member or friend opens the case, and the device automatically dials the hospital. A synthesized voice instructs the bystander on how to attach the electrodes of the defibrillator to the patient's chest.

At the hospital, the person's medical history along with an electrocardiogram appears on a computer terminal. The doctor can decide if electric shock is needed.

Defibrillation is a treatment to control rapid and uncoordinated contractions of the heart muscle. People experiencing a heart attack usually have a very irregular heartbeat and may require defibrillation to steady it.

If a person is having a heart attack and is unattended, he can survive four to five minutes, Ruffy said. "The MDphone system saves you a lot of time because the shock can be delivered within a minute after the suitcase is opened," said Ruffy.

Ruffy pointed out that cardiopulmonary resuscitation -- manual pressing on the chest and blowing into the mouth -- is also a good way to keep heart attack victims alive until help arrives.

There are other home-based automatic defibrillators on the market, Ruffy said, but the entire responsibility of performing the defibrillation is in the hands of the bystander. The phone system lets a doctor decide.

S. Eric Wachtel, president and chairman of the board of MEDphone Corp., the company that developed MDphone, sees other uses for the device. "Corporate America could have one of these units in their offices for any medical emergency," he said. "Once the case is open, you can be in touch with a doctor."

MDphone costs about $6,000 to $7,000 and can be leased for $125 to $150 a month.