Mending a broken heart: innovations in cardiac surgery
5 September 2006
The Bristol Heart Institute is internationally famous for its pioneering developments in the field of cardiac surgery.
During surgery the heart is normally paralysed by a cardioplegic solution, while blood is diverted from the vascular system and pumped through plastic tubing outside the body. This artificial pump temporarily performs the functions of the heart and lungs during surgery so circulation of the blood continues, ensuring that body tissues, particularly those of brain and other vital organs, remain alive. This type of surgery is known as ‘on-pump’ surgery.
Keep the heart beating
For many years on-pump surgery has represented the gold standard in restoring coronary blood vessel function – during vein-graft operations, for example, where a piece of leg vein is used to bypass a blocked artery in the heart. But when compared with 20 years ago, patients referred for such bypass surgery today are older, have a higher incidence of infections after surgery, greater severity of coronary heart disease, and more frequently require urgent or emergency procedures. On-pump surgery in these high-risk groups is associated with high compli-cation rates, substantially increased death rates and increased costs.
But in 1995 a new technique was pioneered in Bristol – beating heart surgey. This required the development of a special clamp to keep a small part of the heart still so the surgeon could operate on that part while the rest of the heart kept beating. This is known as ‘off-pump’ surgery, since there is no need for the artificial pump. Clinical trials confirmed that short-term benefits to patients were much better if the heart did not have to stop beating – there were fewer post-surgery complications such as infections due to inadequate clearance of fluid from the lungs and temporary kidney failure as well as less blood loss and transfusion requirement, and reduced damage to the heart muscle itself.
Monitoring long-term outcome for these patients (survival rates and quality of life), and the provision of training for cardiac surgeons in off-pump techniques are now under-way to determine whether off-pump surgery performed on the beating heart will supersede conventional surgery.
Reshaping the heart
Heart failure commonly results from inadequate blood supply to the heart, due, for example, to atherosclerosis. If severe enough, the heart muscle cells will die in the area originally supplied by the atherosclerotic vessel. The dead cells are replaced with scar tissue, the size of which varies according to the amount of damage.
The presence of this scar tissue initiates a vicious cycle of events. The heart gradually gets bigger, resulting in a gradual reduction of the overall heart pumping function and increased strain on the walls of the heart, with a stretching effect on the remainder of living heart cells. Patients with this condition have hearts that are about twice normal size. Whilst various drugs can restore heart function to some extent, none can address the basic problem – that the heart has become too big for it to work properly.
Using a new procedure of ‘left-ventricular reshaping surgery’, surgeons at the Bristol Heart Institute have pioneered a new way to cut through the scar tissue to enter the heart. They then pull the remainder of the good muscle together, effectively removing the large scar from the pumping part of the heart. They can then use the scar tissue as a firm surface to sew onto, to close the heart cavity. This restores the heart’s normal shape, releases the remaining muscle from the stretching effect of the scar, and so allows the remaining living heart cells to regain their pumping effectiveness. In just a few months this produces rapid and dramatic improvements in heart function and hence in patients’ quality of life.
But, like all new operations, it has to be proved to be beneficial over current therapies. A major international effort is ongoing, with cardiovascular centres in 15 countries participating – the first study of its kind in this field of research. It will provide evidence as to whether a reduction in left ventricular volume improves survival, and whether it is able to revert or stop further heart enlarge-ment. Hopefully this technique will prove as beneficial as initial results suggest.
Recovery after cardiac surgery
Anaesthesia and the trauma of surgery cause inflammation, which stimulates the patient’s immune system and wound-healing defence mechanisms. This is essential for recovery, but any abnormality in the inflammatory response can cause infections that may lead to septicaemia (blood poisoning). A wide variation is seen in individuals’ response to infection and recovery after surgery, and researchers are investigating whether a person’s genetic make up may explain this.
It has even been proposed that patients could carry a silicon chip containing their genetic profile by the year 2010. Such technology could provide individually targeted therapy and improve clinical outcome after surgery.