Other Surgical Treatments
In addition to coronary artery bypass grafting (CABG) surgery and valve surgery, various surgical treatments may be performed by cardiovascular surgeons. They may be performed alone or in combination with other procedures. The goal with all of these surgeries is to decrease the number and severity of complications after heart surgery and improve quality of life.
Objectives
In this chapter, you will learn:
1. Treatments for atrial fibrillation that are performed in the operating room
2. When a patient might benefit from transmyocardial revascularization
3. When a ventricular assist device might be used in a patient
TREATMENT OF ATRIAL FIBRILLATION
Atrial Fibrillation
Many patients with valve disease develop atrial fibrillation before surgical intervention due to stretching and irritation of atrial tissue. Many other patients without preexisting atrial fibrillation develop this complication after surgery due to irritation, inflammation, or edema of the atria resulting from surgery. This is especially true for patients who undergo mitral valve surgery.
Atrial fibrillation is the result of chaotic electrical activity and disorganized depolarization in the atria. Atrial fibrillation may be classified as paroxysmal (starts and stops spontaneously within 7 days), persistent (fails to convert within 7 days; can be converted to sinus rhythm with medications or cardioversion), or permanent (present for more than a year; cardioversion has not been attempted or has failed). Paroxysmal atrial fibrillation may recur over and over with varying frequency.
While a patient is in atrial fibrillation, the atria do not contract to eject blood into the ventricles (known as atrial kick), so ventricular filling is completely due to passive atrial emptying. Due to the loss of atrial kick, the ventricle loses some stretch of muscle fibers, which causes the force of contraction of the ventricle to be smaller, leading to a decrease in cardiac output. This decrease in cardiac output can be especially detrimental to patients who have recently undergone surgery. In addition, atrial fibrillation puts patients at risk of stroke, since blood is stagnant and clots may form in the atria. These clots may break loose, embolize to the vessels in the brain, and cause a stroke. In addition, both the right and left atria have a pouch, called an atrial appendage, where clots are especially prone to form.
FAST FACTS in a NUTSHELL 
Atrial fibrillation may occur before or after cardiac surgery and is a common but serious complication of cardiac surgery. It also increases the risk of stroke.
Atrial fibrillation is often difficult to treat. One treatment for atrial fibrillation is to limit the chaotic electrical activity by creating lines of nonconductive tissue through the atria. Creating these lines around the pulmonary veins has been found to be effective in treating atrial fibrillation in many people. This can be done via ablation or a maze procedure.
Ablation
Ablation refers to the destruction of myocardial tissue in a particular place. Areas of dead tissue heal and form scar tissue, which does not conduct electrical current. There are several methods of creating these lines of dead tissue. Radiofrequency ablation uses radio waves to heat tissue in a localized area to the point that the myocardial cells die. Cryoablation uses extreme cold to freeze cells to the point that they expand and die. Either way, lines of dead tissue are formed that will become scar tissue and prevent the spread of electrical activity beyond these lines. Either radiofrequency ablation or cryoablation may be done during surgery while the chest is open or during a minimally invasive procedure (see Chapter 8).
For patients with paroxysmal atrial fibrillation, using ablation to surround and isolate the pulmonary veins is an effective treatment 90% of the time. For patients with persistent or permanent atrial fibrillation, a maze procedure has the best success rate.
Maze Procedure
The maze procedure is most commonly performed as an adjunct to mitral valve surgeries. Patients with mitral valve disease are particularly prone to atrial fibrillation both before and after mitral valve surgery. During the maze procedure, the surgeon cuts along specified lines in the atrium and then sews the cut areas closed. As the tissue heals, scar tissue forms, which prevents propagation of electrical activity beyond these lines. The maze procedure creates lines of scar tissue that electrically isolate the pulmonary veins, located in the left atrium (Figure 7.1). Sometimes lines are also cut in the right atrium.
FAST FACTS in a NUTSHELL
Both ablation and a maze procedure create lines of scar tissue through the atria, usually focusing on isolating the pulmonary veins. These lines prevent the chaotic spread of electrical activity that characterizes atrial fibrillation.
FIGURE 7.1 Lines cut in the atria during a maze procedure to stop the propagation of chaotic electrical activity associated with atrial fibrillation.
Removal of the Atrial Appendage
When a patient is in atrial fibrillation, clots frequently form in the atrial appendages. Clots in the left atrial appendage can embolize and cause stroke. A way to reduce the risk of stroke in patients with atrial fibrillation is to surgically remove the left atrial appendage. This is frequently done in conjunction with a maze procedure. The right atrial appendage is sometimes removed as well.
TRANSMYOCARDIAL REVASCULARIZATION
It is not always possible to revascularize (return blood flow to) every area of the heart. In addition, not every patient who needs additional blood flow to the heart is able to undergo the stresses of surgery. There are not many options to restore blood flow and reduce symptoms for these patients. One possible option is transmyocardial revascularization (TMR), which may be done as an adjunct to CABG surgery or through a small thoracotomy incision. TMR involves using a laser or CO2 to drill holes into the myocardial tissue in the area that cannot be revascularized. These holes will soon close, but the resulting inflammatory response stimulates the growth of new vessels (called angiogenesis).
FAST FACTS in a NUTSHELL
