Prosthetic Heart Valves Medication

Antibiotics, vasodilators, inotropic agents, and anticoagulants are the therapeutic agents most commonly used in heart-valve complications.

Class Summary

A significant portion of cardiac output is regurgitated through an incompetent valve in acute mitral or aortic valve failure. By increasing peripheral vascular resistance, catecholamines worsen this effect. Vasodilators reduce SVR, which may allow forward flow, improving cardiac output.

Nitroprusside (Nitropress)

Produces vasodilation and increases inotropic activity of the heart. Causes peripheral vasodilation by direct action on venous and arteriolar smooth muscle, reducing peripheral resistance. At higher dosages, may exacerbate myocardial ischemia by increasing heart rate.

Class Summary

These agents increase cardiac output. Agents used in the setting of acute valvular failure should not induce vasoconstriction, as this increases valve regurgitation.

Dobutamine (Dobutrex)

Produces vasodilation and increases inotropic state. At higher dosages, may cause increased heart rate, exacerbating myocardial ischemia. Synthetic direct-acting catecholamine and beta-receptor agonist. Compared with other sympathomimetic drugs, does not significantly increase myocardial oxygen demands, which is its major advantage compared with other direct-acting catecholamines.

Inamrinone (Inocor)

Formerly amrinone. Phosphodiesterase inhibitor with positive inotropic and vasodilator activity. Produces vasodilation and increases inotropic state. More likely to cause tachycardia than dobutamine and may exacerbate myocardial ischemia.

Class Summary

Patients receiving bioprosthetic valves should receive anticoagulants for 3 months. Lifelong anticoagulation is needed in patients with mechanical valves and in patients with atrial fibrillation. Any patients presenting with thromboembolic complications must be promptly anticoagulated if they do not have a therapeutic INR of 2.5-3.5.

Heparin

Augments activity of antithrombin III and prevents conversion of fibrinogen to fibrin. Does not actively lyse but is able to inhibit further thrombogenesis. Prevents reaccumulation of clot after spontaneous fibrinolysis.

Class Summary

These agents are given to patients with prosthetic heart valves prior to performing procedures that may cause bacteremia (see Deterrence/Prevention).

Amoxicillin (Amoxil, Polymox, Trimox)

Derivative of ampicillin and has similar antibacterial spectrum, namely certain gram-positive and gram-negative organisms. Superior bioavailability and stability to gastric acid and has broader spectrum of activity than penicillin. Somewhat less active than that of penicillin against Streptococcus pneumococcus. Penicillin-resistant strains also resistant to amoxicillin, but higher doses may be effective. More effective against gram-negative organisms (eg, N meningitidis, H influenzae) than penicillin. Interferes with synthesis of cell wall mucopeptides during active multiplication, resulting in bactericidal activity against susceptible bacteria. DOC for prophylaxis in nonallergic patients undergoing dental, oral, or respiratory tract procedures. Patients must be able to take oral medications.

Ampicillin (Omnipen, Marcillin)

Broad-spectrum penicillin. Interferes with bacterial cell wall synthesis during active replication, causing bactericidal activity against susceptible organisms. Alternative to amoxicillin when unable to take medication orally.

For prophylaxis in patients undergoing dental, oral, or respiratory tract procedures. Coadministered with gentamicin for prophylaxis in GI or genitourinary procedures.

Azithromycin (Zithromax)

Acts by binding to 50S ribosomal subunit of susceptible microorganisms and blocks dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Nucleic acid synthesis is not affected. Concentrates in phagocytes and fibroblasts as demonstrated by in vitro incubation techniques. In vivo studies suggest that concentration in phagocytes may contribute to drug distribution to inflamed tissues. Treats mild-to-moderate microbial infections.

Plasma concentrations are very low, but tissue concentrations are much higher, giving it value in treating intracellular organisms. Has a long tissue half-life.

Used in penicillin-allergic patients undergoing dental, esophageal, and upper respiratory procedures.

Cefazolin (Ancef)

First-generation semisynthetic cephalosporin that by binding to 1 or more penicillin-binding proteins arrests bacterial cell wall synthesis and inhibits bacterial replication. Poor capacity to cross blood-brain barrier. Primarily active against skin flora, including S aureus. Typically used alone for skin and skin-structure coverage. Regimens for IV and IM dosing are similar. Primarily active against skin flora, including staphylococcal species.

Ceftriaxone (Rocephin)

Third-generation cephalosporin with broad-spectrum, gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Bactericidal activity results from inhibiting cell wall synthesis by binding to one or more penicillin-binding proteins. Exerts antimicrobial effect by interfering with synthesis of peptidoglycan, a major structural component of bacterial cell wall. Bacteria eventually lyse due to the ongoing activity of cell wall autolytic enzymes while cell wall assembly is arrested.

Highly stable in presence of beta-lactamases, both penicillinase and cephalosporinase, of gram-negative and gram-positive bacteria. Approximately 33-67% of dose excreted unchanged in urine, and remainder secreted in bile and ultimately in feces as microbiologically inactive compounds. Reversibly binds to human plasma proteins, and binding has been reported to decrease from 95% bound at plasma concentrations < 25 mcg/mL to 85% bound at 300 mcg/mL.

Cephalexin (Keflex)

First-generation cephalosporin that inhibits bacterial replication by inhibiting bacterial cell wall synthesis. Bactericidal and effective against rapidly growing organisms forming cell walls.

Resistance occurs by alteration of penicillin-binding proteins. Effective for treatment of infections caused by streptococcal or staphylococci, including penicillinase-producing staphylococci. May use to initiate therapy when streptococcal or staphylococcal infection is suspected.

Used orally when outpatient management is indicated.

Clarithromycin (Biaxin)

Semisynthetic macrolide antibiotic that reversibly binds to P site of 50S ribosomal subunit of susceptible organisms and may inhibit RNA-dependent protein synthesis by stimulating dissociation of peptidyl tRNA from ribosomes, causing bacterial growth inhibition.

Used in penicillin-allergic patients undergoing dental, esophageal, and upper respiratory procedures.

Clindamycin (Cleocin)

Inhibits bacterial growth. Widely distributes in the body without penetration of CNS. Protein bound and excreted by the liver and kidneys.

Used in penicillin-allergic patients undergoing dental, oral, or respiratory tract procedures. Useful for treatment against streptococcal and most staphylococcal infections.

Semisynthetic antibiotic produced by 7(S)-chloro-substitution of 7(R)-hydroxyl group of parent compound lincomycin. Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Widely distributes in the body without penetration of CNS. Protein bound and excreted by the liver and kidneys.

Useful in penicillin-allergic patients who require antibiotic prophylaxis prior to dental, oral, gastrointestinal, or respiratory tract procedures.

Gentamicin

Aminoglycoside antibiotic for gram-negative coverage bacteria including Pseudomonas species. Synergistic with beta-lactamase against enterococci. Interferes with bacterial protein synthesis by binding to 30S and 50S ribosomal subunits.

Dosing regimens are numerous and are adjusted based on CrCl and changes in volume of distribution, as well as body space into which agent needs to distribute. Dose of gentamicin may be given IV/IM. Each regimen must be followed by at least trough level drawn on third or fourth dose, 0.5 h before dosing; may draw peak level 0.5 h after 30-min infusion.

Vancomycin (Vancocin)

Potent antibiotic directed against gram-positive organisms and active against Enterococcus species. Useful in the treatment of septicemia and skin structure infections. Indicated for patients who cannot receive or have failed to respond to penicillins and cephalosporins or who have infections with resistant staphylococci. Use creatinine clearance to adjust dose in patients with renal impairment.