An implanted heart monitor which can send data down a phone line is going on trial in the US.

The device will mean that patients can be checked by their physician while they are hundreds of miles apart.

Hopefully serious problems can be spotted before they become life-threatening, and the patient called in for treatment.

We can be way out ahead of any serious heart problems that might develop Dr William Abraham, Ohio State University

The system has been developed by researchers at Ohio State University.

A small group of patients has volunteered to test the device, which is approximately the size of a book of matches.

It is implanted in the upper chest, and a sensor is threaded through a vein into one of the chambers of the heart.

It can measure heart rate, heart temperature and blood pressure inside the heart.

Patients pass a magnetic "wand" over their chest and send a signal to the device to transmit data to the doctor via a telephone line.

Altered medication

This is similar system to that used by some heart pacemaker systems, but these only report back technical information about the condition of the implant, rather than gather extensive data about the condition of the patient.

One patient, who lives an hour and a half away from the medical centre running the trial, has had regular adjustments to her medication and treatment as a result of her transmissions back to her doctor's office.

Dr William Abraham, director of cardiology at Ohio State University, said: "With access to data from the implanted monitor around the clock, 365 days a year, we can be way out ahead of any serious heart problems that might develop.

"If we do see something in the data that we can't correct with an adjustment in medication or adjunct therapy, we can ask the patient to come in for further testing.

"People living with heart failure are conditioned to think 'heart problem' whenever they feel ill.

"A quick look at the data transmitted from the monitor often is all that is needed to rule out a serious problem and save the patient some anguish."

The device is still not approved by the Food and Drug Administration in the US, and these trials, and others, are expected to last at least two or three years.