Page 737 - Cardiac Nursing

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C HAP TE R 2 9 / Acquired Valvular Heart Disease 713

Complications of Prosthetic Valves infection. Presence of a new murmur and signs of heart failure
alert the clinician to paravalvular leaks. The patient’s clinical
Thromboembolism remains the most common complication of pa- course should be followed; when the leak becomes significant, sur-
tients with prosthetic valves. Anticoagulant therapy with warfarin gical repair or replacement is indicated. Hemolysis may also ac-
is begun in all patients 48 hours after surgery. All patients with company paravalvular leaks.
mechanical valves require life-long anticoagulation because of the Hemolytic anemia is a consequence of shortened red cell sur-
risk of thrombosis and embolization. The highest thromboem- vival time in all patients with prosthetic valves. Movement of the
bolic risk for mechanical and biologic valves occurs in the first few valve ball or disk causes varying degrees of destruction of the red
days to months after implantation, before the valve is fully en- blood cells. Hemolysis may also occur with paravalvular leak.
dothelialized. The AHA and the ACC recommend international Commonly, hemolysis is mild and the patient can compensate
normalized ratio of 2.0 to 3.0 for mechanical aortic valves and in- by increasing red blood cell production. Rarely, hemolytic ane-
ternational normalized ratio of 2.5 to 3.5 for mechanical mitral mia occurs. Chronic intravascular hemolysis results in loss of
valves. 34 Tissue valves other than homografts also usually require iron in the urine; iron deficiency anemia may result after several
anticoagulation for 6 to 12 weeks after surgery, after which pa- years.
tients have their therapy converted to aspirin. Homografts or the
Ross procedure require no anticoagulation.
Prosthetic valvular thrombosis is a serious complication and can
result in severe hemodynamic compromise. In patients with pros- MITRAL INSUFFICIENCY
thetic valves who are not anticoagulated into a therapeutic range,
thrombosis of the prosthetic valve can occur. Thrombus or pan- Cause
nus formation on the valve may occlude the orifice or entrap the Mitral insufficiency (also termed regurgitation) may be either
pivoting mechanisms, causing acute stenosis or regurgitation. chronic or acute (Table 29-5). Acute mitral regurgitation can be
Symptoms of valve thrombosis include embolic events and CHF. caused by endocarditis, myxomatous degeneration, rupture of
If there are large thrombi or valve dysfunction, urgent or emer- chordae tendineae, papillary muscle disorders, prosthetic valve
gency valve replacement is usually indicated. Fibrinolytic therapy failure, or trauma. 10 Chronic mitral regurgitation may be the re-
may be used for right-sided valve thrombosis or left-sided throm- sult of a number of abnormalities including, but not limited to,
bosis with a small clot burden. 10 rheumatic heart disease, injury after radiation, cardiomyopathies,
Although symptoms of prosthetic valve endocarditis are similar infiltrative disease, ischemic damage to the subvalvular apparatus,
to those of native valve endocarditis, the infection may be difficult infective endocarditis, myxomatous degeneration, hypertrophic
to control with antibiotics alone because of the prosthetic material cardiomyopathy, diet-drug-induced lesions, or marked left ven-
involved. Early prosthetic valve endocarditis (within the first 60 days) tricular dilation. 36
carries a high mortality rate. Early prosthetic valve endocarditis oc-
curs in less than 1% of patients who have had valve replacements
and frequently requires the patient to undergo additional opera- Pathology
35
tions. The most common organism in early prosthetic valve en- Primary mitral regurgitation occurs when the mitral valve annu-
docarditis is Staphylococcus epidermidis. Fever, heart failure, new lus, leaflets, chordae, or papillary muscles are affected by ischemia,
murmur, and embolic events are common manifestations. Late pros- collagen disease, infection, calcification, trauma, or degenerative
thetic valve endocarditis (more than 60 days after surgery) occurs changes, causing incompetent coaptation of the mitral leaflets.
most commonly in patients with bioprosthetic valves in the aortic Secondary mitral regurgitation occurs with ventricular dilation
position. The incidence is less than 1% per year and is generally when ventricular geometry is changed, causing malalignment of
caused by the same bacterial species that cause subacute bacterial the papillary muscles.
endocarditis. 35
Prosthesis malfunction is uncommon for the first 10 years after
artificial valve implantation. The best-known problems with me-
chanical failures were those affecting the Bjork-Shiley convexo- Table 29-5 ■ ETIOLOGIES OF ACQUIRED MITRAL
concave tilting-disk valves first manufactured in 1978, with the REGURGITATION
peak incidence of valve failure in the 1981 to 1982 models. Sub-
sequent modifications improved the valve area but also increased Chronic Mitral Regurgitation Acute Mitral Regurgitation
stress forces. Although these valves have been withdrawn from the Rheumatic heart disease Myocardial infarction causing:
market, approximately 40,000 had been implanted worldwide. Ischemia to subvalvular apparatus Papillary muscle rupture or
Because acute valve strut fracture can be fatal, patients with these Infective endocarditis dysfunction
valves should be evaluated for partial strut fracture using high- Myxomatous degeneration Rupture of chordae
resolution cineradiography. Valve degeneration is the primary com- Hypertrophic cardiomyopathy Infective endocarditis
Left ventricular dilation
Trauma
plication of patients with tissue prostheses. Degeneration of bio- Systemic lupus erythematosus Myxomatous degeneration with
logic prostheses can occur as lipid or calcium deposits cause valve Marfan syndrome chordal rupture
cusps to stiffen and become stenotic. Failure of tissue valves often Calcification of annulus
occurs slowly over months to years and presents as progressive Ankylosing spondylitis
heart failure. Prosthetic valve degeneration and failure are most Scleroderma
Ehlers–Danlos syndrome
easily diagnosed with echocardiography. Prosthetic paravalvular leak
Paravalvular leaks between the prosthetic ring and the annulus Deterioration of prosthetic mitral valve
occur because of tearing of the suture line, spontaneously or after