Distribution Of Grafts In Aortocoronary Bypass Surgery: Cardiovascular Surgery Fellowship Experience.
J C Eze
coronary artery bypass, graft, off-pump, on-pump, vessel disease
J C Eze. Distribution Of Grafts In Aortocoronary Bypass Surgery: Cardiovascular Surgery Fellowship Experience. . The Internet Journal of Thoracic and Cardiovascular Surgery. 2014 Volume 17 Number 1.
During cardiovascular surgery fellowship training programme at Texas Heart Institute (THI), aortocoronary artery bypass (ACB) surgery was a common procedure. This operation has not been carried out at University of Nigeria Teaching Hospital (UNTH) but with knowledge transfer this may become possible in future.
This is a prospective study of cases that I played role as a cardiovascular fellow between September 2005 and August 2006. Age, gender, name of diseased vessel, type of and number of grafts among other things were recorded postoperatively.
A total of 52 patients were involved with age range 41-84 years. Majority were in 70-79 years age range. Males were 39 with male to female ratio of 3:1. Fourteen patients had 3-vessel disease and 13 had single vessel lesion. Saphenous vein graft was used 92 times while internal mammary artery (LIMA) was used 43 times. Left anterior descending (LAD) artery was the most frequently involved vessel, 47 times. LIMA was used most of the time for LAD. The surgery was usually carried out with cardiopulmonary bypass machine but 6 cases were done off pump.
Multiple vessel disease is commoner and the experience gained at THI could be used to start this bypass surgery in Nigeria in view of known cases of preventable cardiac death that are related to coronary artery occlusion.
Presented at 35th Annual General and Scientific Conference of Nigerian Cardiac Society (NCS) in Benin City, Nigeria from September 27 – 29, 2006.
During a one-year cardiovascular surgery fellowship program at Texas Heart Institute (THI) in Houston, USA, aortocoronary bypass (ACB) surgery was a common procedure. The operation does improve survival in symptomatic patients when left ventricular dysfunction coexists with double and triple-vessel disease1. It is done commonly as elective operation. A strategy of initial bypass surgery is associated with lower mortality than one of medical management with delayed surgery if necessary, especially in high risk and medium risk patients with stable coronary heart disease.2 Improved surgical techniques and other support services have made this procedure safe at this center3. Concomitant lesions such as valvular heart disease and great vessel disease were also attended to at the same sitting.4, 5 On-pump and off-pump bypass procedures were done. This operation has not been carried out at my centre, University of Nigeria Teaching Hospital (UNTH), Enugu or any other centre in Nigeria. Patients in Nigeria do have symptoms of coronary heart disease and some were treated at THI while I was there. Based on knowledge transfer, there is therefore every need to start offering the patients in Nigeria this type of treatment option at home in view of many cases of sudden death that are cardiac in origin among active middle aged citizens.
PATIENTS AND METHODS
This study is a prospective study of patients that were assigned to my operating room and I took part in carrying out the ACB surgery between September 2005 and August 2006. They were elective cases only. They were recruited sequentially. Preoperative coronary artery catheterization angiography diagram and video were displayed and reviewed in the operating room. Age, sex, name and number of diseased vessels, type and number of grafts were recorded post operatively. Analysis of data was by simple arithmetic and percentages.
Typical elective bypass surgery as is routinely done in THI involves operation room setting, review of cardiac catheterization report such as coronary angiogram and team work approach. Coronary angiogram shows the vessels that are involved and this range from single-vessel to diffuse coronary artery disease. In brief, intravenous anesthetic agent was used for induction of general anesthesia with patient in supine position. This was maintained with a narcotic alternating with an inhalation agent. Arterial, central venous pressure and urinary catheter were also routinely placed preoperatively for monitoring. Open chest surgery was carried out. Prior to the use of the heart–lung machine, internal mammary artery and great saphenous vein harvesting were done simultaneously by two teams. Graft was also occasionally taken from the radial artery. The vein and radial artery harvesting were mainly via endoscopic assistance.
With the grafts ready, patient circulation was carried on by heart-lung machine after cannulation of ascending aorta. Subsequently, the superior and the inferior vena cava were cannulated accordingly via two separate right atriotomies. Coronary sinus was cannulated for retrograde cardioplegia in addition to ante grade cardioplegia infusion. Blood cardioplegia was commonly used for myocardial protection along with topical cardiac cooling. Moderate systemic hypothermia was achieved. Distal end of the internal mammary artery was transected and anastomosed to the coronary artery just distal to the occluded area. One end of the prepared saphenous vein without the valves was anastomosed distal to occluded site while the proximal end was anastomosed to the ascending aorta. Temporary pacing wires were routinely placed in the epicardium in anticipation of post operative cardiac arrhythmia.
Thoracic catheters were also placed in the pericardial, mediastinal and left pleural space to monitor blood loss as well as allow lung re-expansion post operatively. Incidentally all the patients uneventfully left the operating room to continue treatment in the recovery room and subsequently intensive care unit for about 2 days.
A total of 52 patients were involved with age range of 41-84years as shown in Table I.
Males were 39 (75.00%) while females were 13 (25.00%) with male to female ratio of 3:1. Age range 70-79 years accounted for the highest number of patients which is 21 (40.38%) out of the 52 patients. Fourteen patients (26.92%) had 3-vessel disease and 13 (25.00%) had 1-vessel lesion. There was a patient with six vessel disease. All the 52 patients had a combined total of 144 diseased coronary vessels that were successfully bypassed through grafting. See Table II for graft distribution.
Saphenous vein graft (SVG) was used 95 times (65.97%) while left internal mammary artery (LIMA) was used 46 times (31.94%). Table III has the detail.
Left anterior descending (LAD) artery was the most frequently involved vessel, 49 times (34.03%). Table IV has the coronary artery distribution.
LIMA was used most of the time for LAD. The surgery was carried out under cardiopulmonary bypass machine in 46 (88.46%) patients while 6 (11.54%) patients were operated off-pump. All the patients had restoration of cardiac rhythm in the operating room before transfer to recovery room.
Atherosclerosis, a non-communicable cardiovascular disease, has been identified as a cause of occlusion of the coronary artery with its attendant complications.6 As a result, bypass surgery of the lesion has been in use to prevent catastrophic cardiovascular event such as myocardial infarction, fatal cardiac arrhythmia and sudden death.
Through aortocoronary artery bypass (ACB) surgery, blood flow bypasses the blocked site. THI uses the term ACB and it appears on the operation list. This procedure is also called other names by different groups such as coronary artery bypass graft (CABG) and coronary artery graft surgery (CAGS).
Image magnification using surgical loupe aided the eyes in the anastomoses and handling of the small sized sutures. This description of anastomosis was illustrated by George Reul.7.This procedure increases blood flow to the previously ischemic part of the heart. Each patient was treated as was the standard practice at the centre. This shows textbook high level of care that goes on at the operating room. Individual team members were efficient. In view of the known benefit of this operation, improved cardiac function was the expected outcome.1,8 Some studies have shown that ACB surgery prolongs life in most clinical and angiographic subgroups of patients with severe proximal LAD and left circumflex coronary artery disease.9 Highest number had triple bypass followed by those with single bypass. It has not been agreed that the number of bypass is directly related to the state of the heart, rather it is the particular vessel that determines severity.
Majority of the cases were done on-pump but before embarking on off-pump technique provision was made for conversion to on-pump technique if necessary. Li Yan et al 10 reported that off pump technique has favorable early outcome in the elderly population but worse long-term results.
Other alternatives for the treatment of coronary artery occlusion include medical management and percutaneous coronary intervention11. Future of healthcare and technology will cause the gold standard status of ACB to change once these alternatives show better quality outcomes as well as good quality of life and are readily available. Patients that were operated were selected from many patients that visit THI and St Luke’s Hospital for consultation. In the report by King 12 patients with extensive multi vessel disease and especially with diabetes mellitus fared better with surgery throughout the era of balloon angioplasty and stenting. THI being both for research and referral, some of the patients were for redo coronary artery bypass grafting. This is because for countries with well established treatment protocol, redo coronary artery bypass surgery has become a commonplace. Steps that are routine in first time ACB required more careful decision making in redo coronary artery surgery.13
From the foregoing, it is obvious that the care of patients with coronary heart disease is currently highly limited to empirical treatment in my local environment. This is due to the challenges of medical care especially in running a heart care program in Nigeria where first ACB was reportedly done this year14. A leaf should be borrowed from those that are already in the business of caring for the heart. Also, steps can be taken based on this experience to investigate the need to develop this type of service at the UNTH.
Multiple vessel disease is commoner and the treatment improves the health status of the victim. Knowledge of the care of patient through this method has been transferred. As it was an exchange program, the experience demands that it should impact my centre directly through improvement in the overall care of patients with coronary artery disease.
My gratitude goes to the Texas Heart Institute surgical associates whose patients were included in this study and Dr James Livesay needs special mention. All others who saw that the cardiovascular fellowship took place are hereby acknowledged as well.