Coronary Artery Bypass Graft

Dr. Aidah Alkaissi

An-Najah National University- Palestine

Linköping University- Sweden

Coronary Artery Stent• A stent is a woven mesh that provides structural support

to a vessel at risk of acute closure • The stent is placed over the angioplasty balloon• When the balloon is inflated, the mesh expands and

presses against the vessel wall, holding the artery open• The balloon is withdrawn, but the stent is left

permanently in place within the artery• Endothelium covers the stent and it is incorporated into

the vessel wall• Antiplatelets medication , aspirin are given

Atherectomy• The removal of the atheroma, or plaque from a coronary

artery• Direcional and transliminal extraction coronary

atherectomy procedures involve the use of a catheter that removes the lesion and its fragments

• Rotational atherectomy with diamond chips impregnated on the tip (called a butt) that rottes like a dentist´s drill pulvertizing the lesion

• Several passes of these catheters are needed to acheive satisfactory results

Brachytherapy• PTCA and stent implantation caused a cellular reaction in

the coronary artery that promotes proliferation of the intima of the artery, which increases the possibility of arterial obstruction

• Brachytheapy reduces the recurrence of obstruction, preventing vessel restenosis by inhibiting smooth muscle cell proliferation

• Brachytherapy involves the the delivery of gamma or beta tradition by placing a radioisotope close to the lesion

• Radioisotope may be delivered by a catheter or implanted with a stent

Transmyocardial Revascularization• Pat who has cardiac ischemia and who is not candidates for

CABG may benefit from transmyocardial laser revascularization (TMR)

• Procedure performed either percutaneously in the cardiac catheterization lab or through a midsternal or thoracotomy incision in the operating room

• The tip of a fiberoptic catheter is held firmly against the ischemic area of the heart while a laser burns a channel into but not through the muscle

• If the procedure is percutaneous the catheter is positioned inside the ventricle

• If the procedure is surgical, the catheter is positioned on the outer surface of the ventricle

Transmyocardial Revascularization• Each procedure involves making 20-40 chnnels• Some blood flows into the channels, decreasing the ischemia

direcreasing the ischemia directly• Within the next few days to months the channels close as a

result of the body´s inflammatory process of healing a wound• The long term result is the formation of new blood vessels

(angiogenesis) during the inflammatory process that follows the laser burns

• The new blood vessels provide enough blood to decrease the symptoms of cardiac ischemia

Coronary artery bypass graft

• A surgical procedure in which a blood vessel from another part of the body is grafted into the occluded coronary artery below the occlusion in such a way that blood flow bypass the blockage, it is called bypass graft

Candidates• Angina that cannot be controlled by medical therapies• Unstable angina• A positive exercise tolerance test and lesions or blockage that

cannot be treated by PCI (percutaneous coronary intervention)• A left main coronary artery lesion or blockage of more than

60% • Blockage of two or three coronary arteries, one of which is the

proximal left anterior descending artery• Left ventricular dysfunction with blockages in two or more

coronary arteries• Complications from or unsuccessful PCIs

Coronary artery revascularization

• The vessel used is the greater saphenonous vein, followed by the lesser saphenous vein

• Cephalic and basilic veins are used also • The vein is removed from the leg or arm and grafted to the

ascending aorta and to the coronary artery distal to the lesion

• The right and left internal mammary arteries and occasionaly radial arteries are used

• Arterial graft are prefered to vein graft because they do not develop atherosclerotic changes as quickly and remain patent longer

Coronary artery revascularization

• The surgeon leaves the proximal end of the mammary artery intact and detaches the distal end of the artery from the chest wall

• This distal end of the artery is then grafted to the coronary artery distal to the occlusion

• Disadvantages of internal mammary may not be enough or wide enough for the bypass

                                                

                                                

• The surgeon makes a median sternotomy incision and connects the patient to th CPB (Cardio Pulmonary Bypass) machine

• A blood vessel from patient´s body /saphenous vein, left internal mammary artery is grafted distal to the coronary artery lesion, bypassing the obstructions

• CPB is then discontiued and the incision is closed , the pat then is admitted to a critical care unit

Traditional coronary artery bypass graft

Cardiopulmonary bypass (CPB)extracorporeal circulation using

• a heart lung machine to maintain perfusion to other body organs and tissues while the surgeons works in a bloodless surgical held

• CPB, placing a cannula in the right atrium, vena cava or femoral vein to withdraw blood from the body

• The cannula is connected to tubing filled with isotonic crystalloid solution (5% dextrose in Lactated Ringer´s Solution)

• Venous blood removed from the body by the cannula is filtered, oxygenated, cooled or warmed and then returned to the body

• The cannula used to return the oxygenated blood is usually inserted in the ascending aorta, but it may be inserted in the femoral artery

Cardiopulmonary bypass (CPB)extracorporeal circulationusing

• The pat receives heparin, an anticoagulants, to prevent thrombus formation and possible embolization that may occur when blood contacts the foreign surfaces of the CPB circuit and is pumped into the body by a mechanical pump (not the normal blood vessels and heart)

• After the pt is disconnected from the bypass machine, protamine sulfate is administered to reverse the effects of heparine

Cardiopulmonary bypass (CPB)extracorporeal circulationusing

• During the procedure, hypothermia is maintained, 28 degree to 32

• The blood is cooled during CPB, and returned to the body

• The cooled blood slows the body´s basal metabolic rate, therby decreasing its demand for oxygen

• Cooled blood usually has a higher viscosity, but the crystalloid solution used to prime the bypass tubing dilutes the blood

Cardiopulmonary bypass (CPB)extracorporeal circulationusing

• When the surgical procedure is completed, the blood is rewarmed as it passes through the CPB circuit

• Urine out put, blood pressure, arterial blood gas measurements, electrolytes, coagulation studies, and ECG are monitored to asses the patient status during CPB

MINIMALLY INVASIVE DIRECT CABG (MIDCAB)

• For patients with single coronary artery blockages who cannot be treated by PTCA or with contraindications for CPB, an alternative to traditional CABG is minimally invasive direct CABG (MIDCAB).

• With the patient under general anesthesia, the surgeon makes one or more 2- to 4-inch (5- to 10-cm) incisions in the chest wall for a left or right anterior thoracotomy or for a midsternal or midline upper laparotomy.

• The graft is prepared for the bypass.• The surgeon identifies the location of the coronary

artery for the CAB, and a special instrument, a myocardial stabilizer, is put around the site.

• The stabilizer holds the graft site still for the surgeon while the heart continues to beat.

• Other techniques to minimize movement of the beating heart are to temporarily collapse the lung on the side of the chest where the surgery is being performed, decrease the respiratory rate and the volume of each breath, and give medications

• to cause bradycardia or up to 20 seconds of asystole.• Patients treated with MIDCAB may recover from

anesthesia in the postanesthesia care unit (PACU) and then be admitted to a telemetry unit for 1 to 3 days.

• Nursing care is often directed toward routine postoperative pulmonary interventions (especially if a lung was collapsed during the MIDCAB) and incisional pain management (especially if a thoracotomy incision was made).

PORT ACCESS CORONARY ARTERY BYPASS GRAFT

• Port access CABG is another alternative to traditional CABG.

• With the patient under general anesthesia, the surgeon makes three or more incisions (ports) to perform the CABG.

• One 0.5- to 1-inch (1.3- to 2.5-cm) incision in the groin provides access to a femoral artery and vein.

• The femoral artery is used for a multipurpose catheter threaded retrograde through the aorta to the ascending aorta.

• The catheter is used to return blood from CPB to the patient, to occlude the aorta by inflating a balloon near the end of the catheter, to provide a cardioplegia solution to the coronary arteries, and to vent air from the aortic root during the surgical procedure.

• The femoral vein is used for a catheter threaded through the vena cava to the right atrium to drain blood from the patient for CPB.

• Another 0.5- to 1-inch (1.3- to 2.5-cm) incision in the neck provides access to the jugular vein for two catheters.

• One catheter is threaded into the pulmonary artery to remove air, fluid, and blood that may enter the right heart during surgery.

• The other catheter is threaded into the right atrium and the tip positioned in the coronary sinus for retrograde infusion of the cardioplegia solution.

• One or more thoracotomy incisions, usually 2 to 3.5 inches (5 to 9 cm) long, are made for insertion of the surgical instruments. One of the thoracotomy ports may be used for video-assisted imaging equipment.

• CPB is begun when the equipment is in place through the groin, neck, and thoracotomy incisions. The balloon on the aortic catheteris inflated, and the cardioplegia solution is injected into the coronary arteries.

• Cardioplegia solution is a crystalloid and electrolyte liquid used to stop the heart and protect the myocardium during cardiac surgical procedures.

• One lung may be temporarily collapsed to assist with exposing the surgical site.

• The CABG is performed through a thoracotomy incision.

• When the CABG is complete, air is vented from the pulmonary artery and aorta.

• The balloon on the aortic catheter is deflated, and CPB is discontinued.

• The surgical instruments and the catheters are removed.

• The incisions are closed.

• The patient’s postoperative care is similar to that after traditional CABG.

COMBINATION PERCUTANEOUS TRANSLUMINALCORONARY ANGIOPLASTY AND CORONARY

ARTERY BYPASS GRAFT

• Patients who have blockages in the left anterior descending and at least one other coronary artery who are not candidates for traditional CABG or prefer less invasive procedures may be treated with both MIDCAB and PTCA.

• Because patients need their blood be able to clot after MIDCAB, but require anticoagulation after PTCA, the sequence and timing of providing both treatments to the same patient are being investigated.

COMPLICATIONS• CABG may result in complications such as MI, dysrhythmias, and

hemorrhage

• The patient’s underlying heart disease remains, and angina, exercise intolerance, or other symptoms experienced before CABG may develop again.

• Medications required before surgery may need to be continued.

• Lifestyle modifications recommended before surgery remain important to treat the underlying CAD and for the continued viability of the newly implanted grafts

Care of the Patient After Cardiac Surgery (Continued)

• Please go back to the medical surgical book

Chapter 28