Coronary Artery Surgical Interventions

Percutaneous Coronary Intervention (PCI)

• These interventions include balloon angioplasty, intracoronary stent implantation, as well as rotational and laser atherectomies (The surgical procedure to remove plaque from an artery).

• Uses the same technique as coronary angiography/cardiac catheterization – access to the arterial system is obtained, via femoral

artery– A catheters is advanced, up through aorta to the left

and right coronary arteries– Radiopaque contrast is injected and imaging taken of

the flow through the coronary artery• to clearly define the vascular anatomy and to quantify the

severity of occlusive lesions

PCI procedure

– A guidewire, with a balloon tipped-catheters can then be advanced across the stenosis and inflated

• This stretches and dilates the affected vessel, restoring the lumen to its predisease dimensions. (40% restenosis)

– The use of nitinol scaffolding stents has greatly reduced restenosis rates to nearly 15%; they are used in nearly 90% of percutaneous procedures in the United States.

– the latest advancement is the drug-eluting stent, with antiproliferative drugs impregnated into the walls

– Reports of stent thrombosis have raised concerns, and indefinite use of antiplatelets is recommended.

Coronary Artery Bypass Grafting (CABG)

INTRO• Since its inception in 1967, coronary artery

bypass grafting (CABG) has increased in volume • This growth has slowed in the last decade

presumably from improved percutaneous and medical treatments

• Despite the recent trends, CABG continues to be among the most frequent, successful, and well-studied procedures performed in medicine.

• PRINCIPLE OF CABG: to restore normal

myocardial perfusion by creating alternative routes for blood to reach the vulnerable tissue 

MAKING THE CONDUIT/S• A variety of conduits may be chosen• the most traditional and still most frequently utilized

is the saphenous vein, gained via a saphenectomy. • the internal mammary artery can also be mobilized

from the chest wall and anastomosed to a coronary artery. Most commonly the L internal mammary is anastomosed to the LAD. The right can also be used, but using both risk of sternal ischemia and surgical wound-healing complications

• internal mammary graft has better patency then saphenous vein grafts.

Preparing for grafting

• the standard approach for coronary bypass grafting is via the median sternotomy to expose the heart and great vessels.

• The left thoracotomy could be alternatively used, particularly after previous heart surgery where sternal reentry could hazard injury to adhesed cardiac structures or patent grafts.

• Preparation is then made to institute cardiopulmonary bypass (CPB).

Cardiopulmonary Bypass

• Insert canulla into R atria to drain blood to cardiotomy reserve, and insert canulla into ascending aorta to receive back the ‘arterial inflow’ ie. bypass the lungs and heart

• The machine oxygenates the blood but also cools the blood to 28–32 °C to reduce tissue oxygen requirements and organ injury.

• Cardioplegic arrest is then initiated by cross-clamping the ascending aorta and infusing

– autologous blood with crystalloid solution cooled to 12 °C containing citrate to bind ionic calcium, dextrose, pH buffers, and potassium to arrest cardiac activity.

• With the arrested heart, a dry and motionless surgical field is created

Ready to do grafting….

• the sites for grafting/bypass are determined on the basis of information from the preoperative angiography. An arteriotomy is created on the exposed vessel, and it is extended for approximately 5 mm. The conduit is positioned and the anastomosis created

• After completion of all anastomoses, weaning from CPB is prepared

– The patient is warmed to normothermia. – As the heart begins to warm, ventricular fibrillation

often occurs, requiring electrical defibrillation. – Mechanical ventilation is resumed, and the patient is

gradually weaned from CPB. – Pharmacologic inotropic support may be required

• Once haemostasis is adequate, chest closure is performed with stainless steel wires. The pericardium is typically left open to avoid constriction of the atria or kinking of the bypass grafts.

Outcomes

• Overall, risk of perioperative death remains at 1–3%.• Multivariate predictors of death include advanced age,

recent myocardial infarction, decreased ventricular function, renal insufficiency, and female gender.

• Late failures appear to occur at a rate of 5% per year, with 10-year patency approximately 40–50%. Late failures are primarily attributed to accelerated atherosclerosis of the vein conduit

• The pedicled internal mammary artery has far superior patency, particularly when anastomosed to the LAD. With adequate target vessel runoff, 10-year patency rates of 90–95% have been reported in multiple independent studies

Future of CABG• Recently, attempts to reduce the invasive nature of coronary bypass

grafting and the potential complications of CPB have been introduced.

• Techniques to perform bypass grafting without CPB have improved

• Off-pump coronary bypass grafting (OPCAB) have potential advantages in reducing neurologic complications associated with air and atheroemboli, as well as reducing blood transfusion requirements and cost.

• The procedure involves manipulation and stabilization of the beating heart to expose the epicardial targets. Particularly for vessels on the posterior and posterolateral surfaces, hemodynamic instability can result while the heart is elevated and rotated for optimal exposure

• Still has reduced graft patency rates so not increased over the last several years.

Indications for surgical intervention

• The decision to proceed with revascularization, as opposed to continuing medical therapy, is made in three groups of stable patients:– Patients with activity-limiting symptoms despite maximum

medical therapy – Active patients who want PCI for improved quality of life

compared to medical therapy, such as those who are not tolerating medical therapy well, or who want to increase their activity level.

– Patients with anatomy for which revascularization has a proven survival benefit such as significant left main coronary artery disease (greater than 50 percent luminal narrowing) or multivessel coronary artery disease (CAD) with a reduction left ventricular ejection fraction and a large area of potentially ischemic myocardium.

CABG VERSUS PCI 

The choice of CABG versus PCI is dependent upon a number of factors:• particularly the location and number of vessels involved:

– PCI with drug-eluting stents has been preferred in patients with one or two vessel disease

– CABG has been preferred when there is a large amount of myocardium at risk, eg. left main coronary disease, and diffuse three-vessel coronary disease

Patient factors– PCI may be attempted in younger patients who may otherwise be expected to

require one or more bypass operations in their lifetime due to progression of CAD and to saphenous vein graft degeneration. Reoperation is associated with higher perioperative mortality and is less often fully successful.

– PCI preferred in older patients or those with significant comorbidity who may have prohibitively high operative risks or short life expectancies.

– Patients who refuse open heart surgery

References• Haft, J.

CURRENT Diagnosis & Treatment: Surgery, 13e. The Heart: I. Surgical Treatment of Acquired Cardiac Disease. Accessed: www.assessmedicine.com.au

• Up- to-date. 2010. Bypass surgery versus percutaneous intervention. Accessed: www.uptodate.com