The modified Bentall procedure for aortic root replacement

AORN Journal,  July, 2006  by Cecile Cherry,  Starla DeBord,  Carol Hickey

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The article "The modified Bentall procedure for aortic root replacement" is the basis for this AORN Journal independent study. The behavioral objectives and examination for this program were prepared by Rebecca Holm, RN, MSN, CNOR, clinical editor, with consultation from Susan Bakewell, RN, MS, BC, education program professional, Center for Perioperative Education.

Participants receive feedback on incorrect answers. Each applicant who successfully completes this study will receive a certificate of completion. The deadline for submitting this study is July 31, 2009.

Complete the examination answer sheet and learner evaluation found on pages 73-74 and mail with appropriate fee to

AORN Customer Service

c/o Home Study Program

2170 S Parker Rd, Suite 300

Denver, CO 80231-5711

or fax the information with a credit card number to (303) 750-3212.

You also may access this Home Study via AORN Online at http://www.aorn.org/journal/homestudy/default.htm.

BEHAVIORAL OBJECTIVES

After reading and studying the article on performing the modified Bentall procedure for aortic root replacement, nurses will be able to

1. discuss the pathophysiology of aortic abnormalities,

2. list diagnostic tools used to identify aortic abnormalities,

3. discuss nursing care of a patient undergoing aortic root replacement surgery, and

4. describe the aortic root replacement surgical procedure.

The Bentall procedure is a surgical repair of an ascending aortic aneurysm or an aortic root aneurysm that is accompanied by aortic valve incompetence. Less commonly, this procedure is used to repair aortic dissection affecting the aortic root and valve. The procedure uses a composite aortic graft (ie, a vascular tube graft with an attached mechanical or biologic valve) to replace the proximal ascending aorta and the aortic valve. Circulation to the coronary arteries is maintained by implanting the proximal end of the coronary arteries into openings made in the aortic graft.

This procedure was first described by H. H. Bentall, MD, and A. DeBono, MD, in 19681 and still is performed today with some modifications. Currently, a full-thickness "button" of aorta surrounding the coronary ostia (ie, where the proximal coronary arteries attach to the aorta) is removed, making it easier to implant the proximal coronary arteries into the aortic vascular graft.

ANATOMY AND PHYSIOLOGY

The heart is a muscular, four-chambered pump that provides the power to move blood through the circulatory system. The heart is about the size of an adult's fist, located slightly to the left of the midline of the mediastinum, directly behind the sternum (Figure 1). The four chambers of the heart consist of the right and left atria and ventricles. Oxygenated blood from the heart exits through the aorta to enter systemic circulation. (2)

[FIGURE 1 OMITTED]

The aorta exits from the left ventricle, arches upward and then down through the thorax and abdomen, and branches into the iliac arteries. The diaphragm separates the thoracic and abdominal portions of the aorta. The thoracic aorta is subdivided further into the ascending aorta, aortic arch, and descending aorta. (3)

The aorta is the largest artery in the body, and it supplies blood to all major arteries in the body. Like all arteries, the aorta consists of three layers: the tunica intima, the tunica media, and the tunica adventitia. The tunica intima is the innermost layer, consisting of endothelial cells and elastic tissues that give the aorta its elasticity and strength. (3) The tunica media is the middle layer that contains smooth muscle tissue and elastic fibers. The tunica adventitia is the outermost layer, consisting of connective tissue. (4) The aortic root includes the section of the ascending aorta that exits from the heart, the aortic valve, and the coronary ostia (ie, openings where the coronary arteries enter the aorta). The left and right main coronary arteries branch off from the ascending aorta to supply the heart muscle with oxygenated blood (Figure 2).

[FIGURE 2 OMITTED]

THE HEART VALVES. The purpose of the heart valves is to ensure that blood flows through the heart in one direction. The valves open and close passively, as a result of differences in the pressure gradients between the heart chambers. As blood accumulates in the heart's chambers, the pressure behind the valve increases until it is greater than pressure beyond the valve. The valve opens allowing blood to flow through the valve and then closes as the pressure in front of the valve rises. (5) There are four heart valves: the aortic and pulmonic valves (ie, semilunar valves) and the mitral and tricuspid valves (ie, atrioventricular valves). (5) The mitral valve has two cusps; the other three valves are each composed of three cusps. The aortic valve is attached to the aortic wall and left ventricular muscle. (6)

THE CARDIAC CYCLE. The term cardiac cycle refers to the contraction and relaxation cycle of one heartbeat. An average cardiac cycle is about 0.8 seconds. Systole is the phase of the cardiac cycle associated with ventricular contraction and ejection of blood into systemic circulation, which accounts for one-third of the cardiac cycle. The atria contract to complete filling of the ventricles that began passively filling during systole. As the aortic and pulmonic valves open, the mitral and tricuspid valves close, producing the first heart sound, S1. The aorta stretches and expands, temporarily storing a portion of the blood ejected from the ventricle. (7)