A hospital here is testing a new briefcase-size device that allows doctors to save some heart attack victims no matter where they are by activating a life-saving jolt of electricity via a telephone hookup.

Jewish Hospital will use the portable MDphone transtelephonic defibrillator on a trial basis for nine months to a year, hospital officials said.The electronic device could free certain patients from long hospital stays, said Dr. Rodolphe Ruffy, director of arrhythmia services at the hospital.

The MDphone allow heart patients to stay at home while retaining immediate access to the treatment base station at the hospital, he said.

When a patient or another person opens the unit, which can be plugged into a standard phone jack, the hospital base station's phone number is automatically dialed and medical personnel can give directions over the phone.

Upon application of adhesive electrode pads to the patient's chest, doctors at the hospital can monitor the patient's electrocardiogram on a computer screen at the base station. The patient's history can also be called up.

The doctor then can, if necessary, activate the defibrillator to try to restore a normal heartbeat by administering an electric shock, Ruffy said.

"The MDphone is the first interactive medical system capable of treating life-threatening arrhythmias (irregular heartbeat) by telephone," said S. Eric Wachtel, president of MEDphone Corp. of Paramus, N.J., which developed the device.

"If treatment is not administered within four to six minutes after the onset of fibrillation, brain damage is likely to occur," he said. "Our tests have proven that the MDphone makes it possible for patients to be diagnosed and defibrillated at the scene of the emergency within two minutes of the onset of symptoms, considerably faster than ambulance response time."

Ruffy said the agreement with MEDphone Corp. calls for a fully operational 24-hour emergency response system at Jewish Hospital within about a month.