Homograft Dysfunction Subject to severe tissue calcification Usually reserved for complex aortic root abscesses Hyperlipidemia accelerates prosthesis calcification Secondary prevention may slow this process
Physical Exam Findings
TTE valve area and regurgitation exclude significant obstruction Flow velocity is crucial measurement Often inadequate for infection or small structural changes (strut fracture, small vegetation, paravalvular leak) TEE inspection of valve apparatus and seating may not accurately quantify valve flow velocities Echocardiographic Evaluation
Normal Appearance PV
Normal Doppler Clicks
Normal Doppler Flow Patterns
Fluid Dynamics and Velocities
Normal Finding: Regurgitation
Pathologic Regurgitation Characterized by: An eccentric or large jet An eccentric or large jet Marked variance on the color flow display Marked variance on the color flow display A jet that originates around the valve sewing ring A jet that originates around the valve sewing ring Visualization of a proximal flow acceleration region on the LV side of the mitral valve Visualization of a proximal flow acceleration region on the LV side of the mitral valve
Prosthetic Valve Regurgitation
Prosthetic Valve Stenosis Pressure gradients - Calculated using the Bernoulli equation (4v 2 ) - Good correlation when validated against invasive pressure measurements - mechanical valves, especially bileaflet, result in overestimation of the gradient due to differing fluid dynamics
Prosthetic Aortic Valve Area
Prosthetic AVA: Velocity Ratio Measure velocity increase across valve Ratio of outflow tract velocity/aortic jet velocity reflects degree of stenosis Ratio = 1 if no obstruction present Given inherent stenosis, normal range is 0.35 to 0.5 for aortic prosthesis
Prosthetic Mitral Valve Area Can be estimated using the pressure half- time approach as for native mitral valve stenosis. The expected half-time for a PV is longer than with a native valve.
Incidence of Thromboembolic Complications Fatal Complication Non-Fatal Complication Valve Thrombosis Aortic 0.2 per 100 patient years 1.0 to 2.0 per 100 patient years 0.1 percent per year Mitral- 2.0 to 3.0 per 100 patient years 0.35 percent per year
Prosthetic Valve Thrombosis TEE is often negative if the thrombi are small or if new thrombus has not formed since the initial embolic event. Thus an embolic event in a patient with a prosthetic valve (esp mechanical) must be presumed to be related to the PV even if the TEE is negative.
Prosthetic Valve Endocarditis Difficult to detect with TTE Often involves sewing ring and annulus, resulting in paravalvular abscess rather than a discrete vegetation
Prosthetic Valve Endocarditis
Patient Prosthesis Mismatch Size of prosthesis results in inadequate blood flow given metabolic demands Prosthesis itself functions well Indexed effective orifice area < or = 0.85cm2/m2 Predicts high transvalvular gradients, persistent LVH and increased rate of cardiac events following AVR
Objectives Types of prostheses Prosthetic dysfunction Echocardiographic surveillance of prostheses
Recommended Surveillance Baseline echocardiogram 6-8 weeks postoperatively Routine echocardiographic surveillance annually thereafter Evaluate for Regression of hypertrophy or dilation Regression of hypertrophy or dilation Recovery of LV systolic function Recovery of LV systolic function Changes in PA pressures Changes in PA pressures
Summary Prosthetic valve dysfunction is well detected by echocardiography Dysfunction includes Structural failure Structural failure Thromboembolic complications Thromboembolic complications Endocarditis Endocarditis PPM PPM Distinguishing normal from pathologic function can be challenging; most useful is comparison to baseline post-prosthesis
References Otto, C. Textbook of Clinical Echocardiography, Fourth Edition Libby et al. Braunwald’s Heart Disease. Eighth Edition Pibarot, P and Dumesnil JG. Prosthesis-patient mismatch: definition, clinical impact, and prevention. Heart 2006;92: Bonow RO, Carabello BA, Chatterjee K, et al: ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to revise the 1998 Guidelines for the Management of Patients with Valvular Heart Disease): Developed in collaboration with the Society of Cardiovascular Anesthesiologists: endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons. Circulation 2006; 114:e84.