1. Answer: C. The term patient prosthesis mismatch (PPM) refers to the situation in which the effective orifice area (EOA) of a prosthesis is too small relative to the patient’s body size resulting in abnormally high postoperative gradients. Although bioprostheses rather than mechanical valves are generally selected for women anticipating pregnancy as well as for patients with a prior history of drug abuse, these situations are not considered PPM. Children with prosthetic valves may outgrow their valves and develop PPM but this may be unavoidable regardless of whether a mechanical or a bioprosthetic valve is implanted.

2. Answer: D. For prostheses in the aortic position, the cutoff for PPM has been established to be a body surface area (BSA)-indexed EOA of ≤0.85 cm²/m² based on the observation that at smaller areas there is a rapid increase in transvalvular gradients. BSA-corrected aortic prosthetic EOA ≤0.65 cm²/m² is considered severe PPM. The major adverse outcomes associated with PPM are reduced short-term and long-term survival, particularly if associated with LV dysfunction. The high gradients associated with PPM may be distinguished echocardiographically from prosthetic valve dysfunction by comparing the echo-calculated EOA with published normal values for individual valves and by excluding imaging evidence of valve dysfunction.

3. Answer: C. Pressure recovery refers to the situation in which there is a localized pressure drop at the central orifice of a bileaflet mechanical valve that is partially recovered distally as flow from the lateral two orifices merges with the central flow jet (Figure 19-16). Since Doppler records the maximal pressure drop, it will yield a gradient higher than that measured at catheterization with catheters placed proximal and distal to the valve. Clinically significant pressure recovery is most often encountered in the setting of small bileaflet mechanical valves in the aortic position particularly when the cardiac output is increased. Answer A is incorrect because the direct measure of LV to aorta gradients used in this patient is superior to the pullback approach. It would be dangerous to attempt to cross this valve retrograde. Answer B is incorrect because a relatively higher cardiac output at catheterization would result in a relatively higher (not lower) transvalvular gradient. Answer D is incorrect. Although it is possible to mistake a mitral regurgitant for a transaortic Doppler spectrum, the peak MR velocities are typically much higher than 3.5 m/s (peak gradient = 49 mm Hg), reflecting large gradients from the left ventricle to left atrium. Answer E is incorrect. In the case of patient prosthesis mismatch, elevated gradients are noted both by echocardiography and catheterization. Clinically significant pressure recovery is not commonly observed unless the ascending aorta diameter is less than 3 cm.

4. Answer: B. Echocardiographic displays are calibrated based on the velocity of sound through tissue and the assumption that only tissue will be encountered by the ultrasound beam. The speed of sound in a Starr-Edwards valve ball is slower than that in tissue. Consequently, the ball is misrepresented echocardiographically as being larger than it actually is.

5. Answer: C. Depending on the size and valve type, there is significant variability in the normal values reported for aortic prosthetic valves. A peak velocity of 2.5 m/s is well within the normal range for many valves, and as such, would not be helpful in determining the type of prosthesis that has been implanted. In general, velocities >3.0 m/s prompt concern about pathologic elevation due to a variety of causes including patient prosthesis mismatch and intrinsic valve pathology. However, velocities of >3.0 m/s may be normal for some valves (Figure 19-17). Stroke volume as an index of cardiac output is measured by multiplying the velocity time integral of the pulsed Doppler spectrum of the left ventricular outflow tract by the left ventricular outflow tract cross-sectional area.

6. Answer: C. Gradients across mitral and tricuspid prostheses are very heart rate dependent. Although a mean gradient of 10 mm Hg at a heart rate of 60 beats/min would be abnormal, the same gradient at a heart rate of 120 beats/min would be “normal” for most mitral prostheses. While height and weight (Choices A and B) and calculated BSA are important in evaluating patients for patient prosthesis mismatch (BSA-indexed EOA <1.2 cm²/m² for mitral prostheses), this assessment requires the calculation of effective orifice area, which is not possible with mean gradient only. It is important to record blood pressure (Choice D) at the time of echocardiography for patients with mitral disease; however, its major impact is on regurgitation rather than stenosis. Gender has no direct impact on valve gradients.

7. Answer: E. With harmonic imaging, microcavitations are frequently seen with normally functioning mechanical valves. While their origin is uncertain, they are not imaging artifacts. In the era of fundamental imaging, microcavitations were reported as markers of hemolysis which may be a feature of paravalvular regurgitation. In the absence of intravenously injected microbubbles, a patent foramen ovalis and associated right-to-left shunt will not result in left-sided microbubbles.

8. Answer: A. Effective orifice area (EOA) is calculated using the continuity equation and is equivalent to the calculation of valve area in native valves. Thus:

Choice C represents a formula that can be used to calculate the Doppler velocity index (DVI). By comparing calculated EOA with published norms, the diagnosis of prosthetic stenosis can be established (Table 19-1). Prosthetic valve size should not be used as a surrogate for measured left ventricular outflow tract diameter.

9. Answer: A. See also discussion of Question 3. Pressure recovery is typically encountered in small bileaflet or ball and cage valves.

10. Answer: A. Imaging features of restricted thickened cusps support the diagnosis of prosthetic stenosis as the basis for the elevated gradients. A small valve (19 mm) as in Choice B may be associated with elevated gradients even in a structurally normal valve if there is patient prosthesis mismatch (the valve is too small for the patient). The aortic root may be dilated (Choice C) in patients with native aortic valve disease and does not regress following aortic valve replacement in the absence of aortic reconstructive surgery. Choice D: The normal hematocrit excludes anemia-associated high output which may be associated with elevated gradients in structurally normal valves. Choice E: Reduced LVEF is typically associated with low gradients and provides no explanation for the elevated gradients noted here.

11. Answer: E. The pressure half-time should not be used to calculate effective orifice area in patients with prosthetic valves. The pressure half-time measurement may be used on serial studies to monitor for development of prosthetic valve stenosis. Significant increases in pressure half-time may be associated with prosthetic valve obstruction.

12. Answer: C. All mechanical prosthetic valves have physiologic “regurgitation” that consists of a closing volume (a displacement of blood caused by the motion of the occluder) and leakage at the perimeter of or at hinge points of the occluders. Studies have shown bileaflet mechanical valves (e.g., St. Jude) to have the largest degree of physiologic regurgitation with central as well as peripheral jets. While Medtronic-Hall valves have the most prominent central jets, the total amount of regurgitation is less when compared to mechanical bileaflet valves.

13. Answer: C. The Doppler velocity index is defined as the ratio of aortic subvalvular VTI or peak velocity to prosthetic VTI or peak velocity (i.e., subvalvular VTI/prosthetic VTI or subvalvular peak velocity/peak velocity), respectively. It is particularly useful when image quality precludes accurate measurement of the left ventricular outflow tract as is needed to calculate effective orifice area. A Doppler velocity index of <0.25 is suggestive of prosthetic aortic stenosis.

14. Answer: A. Due to acoustic shadowing and the eccentricity of paravalvular jets, transthoracic echocardiography is relatively insensitive for paravalvular regurgitation. Thus, TEE is indicated whenever paravalvular regurgitation is suspected. Elevated mitral gradients (Choices B and C) favor mitral regurgitation. When jets are eccentric, normal (S dominant) flow may be preserved in pulmonary veins remote from the jet. All apical views should be used to assess for paravalvular regurgitation but no single view is ideal.

15. Answer: C. The Ross procedure consists of moving the patient’s pulmonary valve to the aortic position (aortic autograft) and placing a homograft (cadaveric) valve in the pulmonic position (pulmonary homograft). Of the possible correct answers, aortic autograft regurgitation or aortic regurgitation is the most common.

16. Answer: A. The prosthesis is identifiable as a stented bioprosthesis by the presence of clearly demarcated stents. There is a mitral regurgitant jet which clearly originates outside the sewing ring and extends to the back of the left atrium: this is paravalvular regurgitation. Although the image has not been optimized for PISA-based quantitation, note the clearly demarcated PISA shell. While spontaneous valve dehiscence may occur, hemodynamically significant new paravalvular jets raise the possibility of endocarditis as the cause.

17. Answer: D. The mitral struts are seen angled toward the interventricular septum. The systolic frame shows turbulent flow in the left ventricular outflow tract at the level of the mitral struts. While rare, high-profile mitral prostheses may cause significant left ventricular outflow tract obstruction. Patients at greatest risk are those with small hypertrophied ventricles. Mitral systolic anterior motion and LVOT obstruction may be a complication of mitral repair but not mitral valve replacement. Notably, in patients with MV replacement for active endocarditis, the mitral chords and leaflets are typically not preserved. Mitral stenosis would be associated with high-velocity flow in diastole not systole. There is no evidence of mitral regurgitation (high-velocity flow is in the left ventricular outflow tract not left atrium.)

18. Answer: E. Although there are no large series of published normal values for tricuspid prosthetic gradients, the existing literature supports the diagnosis of prosthetic tricuspid stenosis whenever the mean gradients are over 6 mm Hg. The mean gradient of 11 mm Hg at a slow heart rate is consistent with severe prosthetic stenosis. It is unlikely that this patient has a high output state with a heart rate of 55 beats/min and even a significantly elevated stroke volume would typically not be associated with gradient elevation of this degree at a heart rate of 55 beats/min. Pressure recovery does not occur with large bioprosthetic valves in the tricuspid position. Note that the pressure half-time method has not been validated for prosthetic tricuspid valves and should not be used as a means of determining effective orifice area.