Page 735 - Cardiac Nursing

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C HAPTER 2 9 / Acquired Valvular Heart Disease 711
Acquired tricuspid stenosis is uncommon, recognized in approx-
imately 5% of patients with rheumatic heart disease, and usually
17
does not occur without involvement of the mitral valve. Tricuspid
stenosis has a pathologic process similar to that of mitral stenosis.
The murmur of tricuspid stenosis is comparable to the murmur of
mitral stenosis, including an opening snap followed by a diastolic
rumble. The murmur of tricuspid stenosis is a diastolic decrescendo
murmur along the left sternal border (see Table 29-2). Common
symptoms of tricuspid stenosis include fatigue, minimal orthopnea,
paroxysmal nocturnal dyspnea, hepatomegaly, and anasarca.
PROSTHETIC VALVES
Prosthetic cardiac valves have been used since the mid 1960s to
treat acquired valvular heart disease. Because no “perfect” pros-
thetic valve exists, the patient with valvular heart disease is man-
aged medically as long as it is safely feasible. Timing of valve re-
placement depends on the patient’s functional status, ventricular
dysfunction, and the natural course of the lesion.
Before a decision is made to use a particular valve, factors in
valve design, specifically durability, thrombogenic potential, and
hemodynamic properties, are weighed against annulus size and cer- ■ Figure 29-4 Photographic (top row), radiographic (middle row),
tain clinical conditions such as the desirability of long-term anti- and echocardiographic (bottom row) appearance of prosthetic valves.
coagulation. Table 29-4 summarizes the characteristics considered From left to right: Bjork-Shiley single tilting disk, St. Jude’s Medical
in selection of prosthetic valves. Because of their proven durability, bileaflet mechanical valve, and Carpentier–Edwards xenograft (radi-
mechanical valves are most often chosen for patients younger than ographs courtesy of Dr. Carolyn van Dyke). (Adapted from Garcia,
M. L. [1998]. Prosthetic valve disease. In E. J. Topol, R. M. Califf, J.
65 to 70 years unless contraindicated (e.g., previous bleeding prob- M. Isner, et al. [Eds.], Textbook of cardiovascular medicine [p. 580].
lems, desire to become pregnant, or poor compliance with med- Philadelphia: Lippincott-Raven.)
ication and follow-up). Prosthetic heart valves differ in design,
echocardiography image, and radiologic appearance (Fig. 29-4).
Mechanical Valves The tilting-disk valve is a low-profile valve consisting of a disk
that sits in a seating ring; the flat or convexo-concave disk tilts in
Mechanical (nonbiologic) valves have excellent durability but are response to pressure changes. The Medtronic Hall valve is a tilt-
usually thrombogenic. Bileaflet and tilting-disk valves are the me- ing-disk valve commonly used today. Tilting-disk valves open to
chanical valves in common use today. Caged-ball valves are used an angle of 60 to 75 degrees in relation to the seating ring. When
less frequently in the United States but may be used in other areas open, tilting-disk valves produce a minor and major orifice for
of the world. In patients with aneurysm or dissection of the as- blood to pass through. Tilting disks have more central flow, but
cending aorta, composite grafts of conduit and mechanical valves usually more turbulence, than caged-ball valves. Tilting disks close
may be used. with an audible click. The technology for production of tilting-
Bileaflet valves, such as St. Jude, ATS (advancing the standard), disk valves has evolved so that a single piece of metal is used to
and the CarboMedic are low-profile valves that have centrally avoid welded struts.
mounted leaflets attached to the seating ring with butterfly Caged-ball valves have been used since the 1960s and have an
hinges. These hinges allow the leaflets to open to 85 degrees, mak- excellent durability record. Changes in pressure cause the ball to
ing these valves the least obstructive of the mechanical valves. move forward and back within its caged structure. Flow is directed
These valves are composed of pyrolytic carbon. With adequate an- laterally through the valve rather than centrally. Because of its
ticoagulation, thromboembolic risk is low with bileaflet valves. high profile, the caged-ball valve prosthesis can become obstruc-
tive, especially when used in patients with small aortic roots or
small left ventricles. The Starr–Edwards and the Sutter were two
of the most commonly used caged-ball valves. Caged-ball pros-
Table 29-4 ■ SELECTION OF TYPE OF PROSTHETIC VALVE
theses have been largely abandoned in favor of lower-profile
BASED ON PATIENT CHARACTERISTICS
bileaflet valves.
Biologic Valve Mechanical Valve
Tissue Valves
History of bleeding Age 65 years
Inability to take warfarin Already on anticoagulation
Desire to become pregnant History of embolic cerebral vascular Tissue (biologic) valves are characterized by having low rates of
History of thrombosis with accident thrombotic episodes associated with their use. Porcine or bovine
mechanical valve History of atrial fibrillation tissue is strengthened and made nonviable by treatment with glu-
Age 65 years taraldehyde. Homografts are tissue valves from cadavers. They are
preserved cryogenically, but are difficult to procure, and their