Recent advances
As with all fields of medicine, research is moving rapidly, and there are always new developments. It would be impossible to cover everything, but we shall deal briefly with some of the most common.
OPCAB
Off-pump coronary artery bypass (OPCAB) surgery is probably the most widely used of the new innovations. A continuously evolving range of new heart stabilisation devices is on the market, allowing safe and effective surgery for appropriate patients. As OPCAB surgery does not require cardiopulmonary bypass, it has the advantages of protection from all the potential bypass-related complications such as stroke. There are a growing number of surgeons who now perform the majority, if not all, of their CABG operations using the OPCAB method. Results of trials to demonstrate a clear advantage over conventional surgery are, however, still awaited. It is not possible to perform valve surgery without cardiopulmonary bypass.
MINIMALLY INVASIVE SURGERY AND ROBOTICS
So-called ‘keyhole surgery’ has been possible for a number of years in some specialities, but is becoming more and more popular in certain areas of heart surgery. It can be performed for CABG, and even valve replacements now, as technology continues to advance. It basically involves a much smaller, or cosmetic, incision, often in the skin fold beneath the left breast, and a couple of small ‘stab’ incisions which will allow the passage of a telescope or instrument. CABG can sometimes be performed without CPB, but this is technically demanding. This type of surgery is only appropriate for certain patients, but the results are promising. A further development on the minimally invasive techniques available is robotic assisted surgery. The surgeon can perform operations such as CABG and even valve replacement by sitting on the other side of the room in a console, much like a machine at an amusement arcade. He or she then controls computerised instruments, which send instructions to the real instruments that are operating on the patient. This may seem unbelievable, but, although still uncommon, it has been proved to work safely.
XENOTRANSPLANTATION
This is a very topical subject in research, the results of which are eagerly awaited. It involves breeding pigs which have had their genes modified so as to create hearts that can be transplanted into humans without danger of rejection. The breeding has been taking place for some years now, and the scientists say that they are nearly ready. Unfortunately, human donors currently remain the only source of hearts for people requiring a transplant, and they are extremely scarce. This exciting development would be a major breakthrough if successful.
ARTIFICIAL HEARTS
The total artificial heart (TAH) would be another option to xenotransplantation in treating end-stage heart disease. Much research has gone into this, and a successfully implanted long-term human device is still elusive; however, there are some that are getting very close. It has been possible to keep people alive on such devices for increasing periods of time, while they wait for a donor to emerge for routine transplantation, but nothing has been shown to be viable for long-term use.
Something in more common use, but still rare, is the ventricular assist device (VAD), which is used in a similar way to a balloon pump for appropriate patients who have problems coming off the heart–lung machine.
POLYMER HEART VALVES
The fact that neither mechanical nor tissue valves are the perfect solution has led scientists to carry out a lot of research combining the best features of each type, and avoiding the disadvantages. Work with polymers has been exciting and several groups have got very close to producing a polymer valve that is ready for human implantation after many years of animal testing. Polymer valves have more strength and durability than tissue valves, therefore lasting longer, but the patient does not need to take warfarin for life as he or she would with mechanical valves.
At present polymer heart valves are in the final stages of testing, but they are likely to be a third alternative in the near future.
