HEART disease patients will be offered a new lease of life using one of their back muscles when Grantham Hospital introduces a revolutionary alternative to heart transplant in the next few months. Surgeons at the hospital are in the final stages of preparing for Hong Kong's first cardiomyoplasty operation which involves wrapping a heart patient's back muscle around his failing organ to make it strong again. Hospital chief executive Dr Leung Sau-chi said: ''This operation could help a number of people who are awaiting heart transplants and we hope to be ready to begin using the technique by the middle of this year.'' Although the hospital has not yet started to assess heart disease patients to find out who would be suitable for the technique, a cardiac surgeon is preparing to perform the first operation. Dr Leung added: ''The technique has been shown to have more than 60 per cent success rate and we are working very hard to be able to offer patients an alternative to cardiac transplant.'' Instead of waiting, often in vain, for a cadaveric heart donation, patients are given muscle from their own back which is wrapped around the heart and electrically stimulated by a modified pacemaker to produce rhythmic contractions. It has been found that the muscle can even be ''trained'' to change its characteristics so that, like the heart muscle itself, it can operate continuously and never tire. The technique was invented in the United States but tried out for the first time in Paris in 1985. The procedure was used in Britain for the first time last October on a 53-year-old man whose heart was working at only 11 per cent efficiency and who desperately needed a heart transplant. Following the successful operation he can now garden for half an hour, swim five lengths and go for walks. British doctors and scientists are working on a more advanced method in which the same long latissimus dorsi muscle of the back is shaped into an additional heart chamber to provide an extra pump working alongside the failing original. The introduction of cardiomyoplasty to Hong Kong will mean that people as old as 70 could be treated - 55 being considered the upper age limit for a heart transplant. At about $140,000 for an operation the technique is also cheaper than a transplant, while patients do not need expensive anti-rejection drugs. A heart transplant costs about $290,000 with each patient needing about $70,000 of anti-rejection drugs for a year following the surgery. It is not yet clear how many of the 9,000 or so people who die each year from heart disease or strokes in Hong Kong could be helped by cardiomyoplasty. But the pioneering operation could be a last resort for some heart disease patients given the notoriously low number of cadaveric organ donations in Hong Kong. Surgeons at Grantham Hospital performed Hong Kong's first and only heart transplant operation in December 1992 and have since received just three more heart donations which they were unable to use.