Set 6 Flashcards
Define acute bacterial endocarditis
Acute bacterial endocarditis denotes infection of a normal valve.
Before antibiotics became widely available, patients with acute bacterial endocarditis usually died within 6 weeks.
Define subacute bacterial endocarditis.
Subacute bacterial endocarditis denotes infection of an abnormal valve.
Patients with mitral valve prolapse, prosthetic cardiac valves, or rheumatic heart disease are at risk for this type of endocarditis.
On 2D echo, what are the main differences between mechanical and bioprosthetic valves?
With mechanical prosthetic valves, more valve masking is present and more reverberations emanate from the valve disc, leaflets, or ball.
With bioprosthetic valves, some masking is present because the central area of these valves is fabricated of a biologic material, however, comparatively few reverberations emanate from this area.
From the patients standpoint, what are the main differences between mechanical and bioprosthetic valves?
Mechanical valves are extremely durable (over 30 years without complications) but necessitate lifelong anticoagulation therapy.
Mechanical valves also make more noise (especially the caged-ball valves) than bioprosthetic ones.
Although bioprosthetic valves are less durable (10-12 years), they do not require anticoagulation.
Name a commonly used caged-ball prosthetic valve
The Starr-Edwards valve was a commonly used caged-ball mechanical prosthetic valve. This type is no longer implanted.
What are the advantages and disadvantages of caged-ball valves?
The advantage of caged-ball prosthetic valves is their durability. Starr-Edwards valves commonly last 15-30 years.
The disadvantage is that patients must take lifelong anticoagulants. Caged-ball valves also have a higher transvalvular gradient than other prosthetic valves.
What is the normal flow velocity through the pulmonic valve, as assessed by Doppler ultrasound in both adults and children?
In adults, the normal pulmonic flow is a mean of 0.7 m/sec with a range of 0.5 to 0.9 m/sec
In children the normal mean pulmonic flow velocity is slightly higher at 0.8 m/sec
Name a commonly used tilting-disc prosthetic valve
The Bjork-Shiley valve was a commonly used tilting-disc prosthesis.
Such valves have much better flow dynamics than valves that have a central occlusion such as the Star-Edwards caged-ball prosthesis
What are the advantages and disadvantages of tilting-disc prosthetic valves?
Tilting-disc valves offer good flow dynamics, characterized by low transvalvular gradient and decreased turbulence.
Disadvantages include questionable durability (disc fractures and stent breakage have been reported) and more prosthetic regurgitation than is associated with other valves.
All prosthetic mechanical valves cause some degree of stenosis and built in regurgitation
How is a porcine (pig) prosthetic valve made?
A porcine (pig) aortic valve is preserved in glutaraldehyde and then attached to a polypropylene stent, which is a Dacron sewing ring.
Because the preserved leaflets are nonviable, valve rejection is not a problem.
What are the advantages and disadvantages of porcine prosthetic valves?
The main advantage of porcine valves is their low thrombogenicity.
Therefore, unlike mechanical valves, porcine bioprosthesis do not necessitate anticoagulation. All but the smaller valve sizes have low transvalvular gradients. Porcine bioprostheses offer less durability and longevity than mechanical valves. Over a 10-15 year period, the porcine leaflets may become thickened and stenosed.
Describe the appearance of a normal porcine mitral valve, as observed with 2D echo.
The parasternal long axis view of the porcine mitral valve shows 2 of the valve stents. Because valvular reverberations are minimized, it is often possible to see leaflet movement between the stents.
The apical views usually offer a better picture of leaflet morphology and motion because in these views, the ultrasound beam is perpendicular to the valve leaflets.
Describe the appearance of flow through a normal porcine mitral valve, as observed with color flow Doppler imaging.
The apical views are best for assessing mitral flow with the color flow Doppler technique because forward flow is directed toward the left ventricular apex.
As it passes through the valve, the red color jet is centrally located and mostly laminar in appearance
In using M-mode echo to evaluate the function of a caged-ball (Starr-Edwards) prosthetic mitral valve, where should you place the transducer?
In evaluating a caged-ball (Starr-Edwards) prosthetic mitral valve, the transducer should’ve placed at the left ventricular apex, so that the full excursion of the ball can be documented as it moves into the open position. This view also allows evaluation of the balls timing
If the caged-ball valve were in the aortic position, where would you place the M-mode transducer?
The M-mode transducer should be placed about the valve, either in the suprasternal or the right supraclavicular window. This placement will allow the balls excursion and timing to be documented.
What is the function of the pericardium?
Because surgical removal of the pericardium may not produce any ill effects, the exact function of the pericardium is unclear.
In general, the pericardium limits ventricular filling, reduces the friction that results from cardiac motion, and may act as a barrier to infectious organisms
Describe the appearance of flow through a normal mitral caged-ball valve, as observed with the color flow Doppler technique.
Normally shows flow on both sides of the ball.
If flow is detected only on one side, a thrombus or vegetative mass should be suspected.
What is the major limitation of chest wall echo in evaluating prosthetic mitral valves?
In evaluating prosthetic mitral valves, the major limitation of chest wall echo is valve “masking” which makes it difficult to detect regurgitation. Even if regurgitation is seen, the “masking” or shadowing prohibits accurate quantitation.
Transesophageal echo allows excellent evaluation of the atrial side of prosthetic mitral valves and is the best technique for evaluating regurgitation.
Name 7 complications of prosthetic valve dysfunction
Prosthetic valve dysfunction can result from the following complications:
- Perivalvular leakage
- Bioprosthetic stenosis/degeneration
- Valve dehiscence/strut failure
- Ring abscess
- Thrombus formation
- Endocarditis
- Hemolysis
Who is responsible for making sure the informed consent is properly signed before a TEE?
The physician has overall responsibility for making sure the informed consent is properly signed before a TEE
How would you evaluate a prosthetic valve for possible stenosis?
Evaluation of prosthetic valve stenosis is difficult because prosthetic valves have a wide range of normal gradients depending on valve type, valve size, and cardiac output.
Ideally, a previous Doppler study will be available for comparison of cardiac function, heart rate, and valve gradient.
Normally, the transvalvular gradient is < 5 mmHg mean gradient for prosthetic mitral valves
And < 20 mmHg mean gradient for prosthetic aortic valves
In 2D echo, what is the best way of differentiating between pericardial effusions and pleural effusions?
In the PLAX the descending aorta is used as a landmark. Pericardial effusions will be seen between the left atrium and the descending aorta. In some patients, the descending aorta will be displaced posteriorly.
On the other hand, pleural effusions will be posterior to the descending aorta and will not displace the aorta away from the left atrium.
Define pericarditis
Pericarditis is an inflammation of the pericardium. In response to this inflammation, the visceral pericardium exudes serous fluid.
Pericarditis is more common in men than women; it is also more prevalent in adults than young children
What are 3 classic physical findings associated with pericarditis and/or pericardial effusions?
- Chest pain, which is atypical and often positional, being most severe in the supine position and relieved by sitting up or leaning forward
- A pericardial friction rub (scratchy high pitched sound) that classically has 3 components: early diastolic filling, atrial systole, and ventricular systole
- Dyspnea
Name 8 etiologies of pericardial effusions
- Idiopathic or nonspecific disorder (most common cause)
- A viral infection
- A bacterial infection
- Uremia
- Radiation therapy
- Acute myocardial infarction
- Dressler’s syndrome, or delayed post myocardial infarction
- Postpericardiotomy syndrome
Define cardiac tamponade
Cardiac tamponade is an impairment of diastolic filling, caused by an increase in intrapericardial pressure.
Tamponade most often results from a moderate to large pericardial effusion, although it may result from a small, rapidly accumulated effusion (as when a ventricle is accidentally perforated during cardiac catheterization)
What are the classic physical findings associated with cardiac tamponade?
- Pulsus paradoxus, which causes a > 10 mmHg decrease in the systolic blood pressure during inspiration
- Tachycardia
- Dyspnea
- Beck’s Triad (elevated venous pressure, hypotension, and a quiet precordium)
What are the 2D findings associated with cardiac tamponade?
- Right ventricular diastolic collapse
- Right atrial systolic collapse
- Right and left ventricular volume changes associated with respiration (these changes are better appreciated with M-mode)
- A dilated inferior vena cava without inspiratory collapse
What are the Doppler findings associated with cardiac tamponade?
In cardiac tamponade, Doppler investigation is aimed at measuring transvalvular flow velocities and detecting respiration-related changes in flow. Normally mitral inflow varies by less than 10%.
In tamponade the peak velocity may vary by as much as 40%. In general, tamponade may be indicated by respiration-related flow changes greater than 25% for the mitral valve and greater than 50% for the tricuspid valve.
Which is a more accurate echo technique in diagnosing cardiac tamponade: 2D imaging or Doppler imaging?
Doppler flow measurements correlate better with the clinical hemodynamics of tamponade than do the 2D echo secondary signs such as right ventricular wall collapse
Why might an anterior echo free space yield a false-positive diagnosis of pericardial effusion?
Loculated effusions are relatively rare.
Therefore, isolated anterior echo free spaces usually represent excess pericardial/epicardial fat, especially in obese patients.
In what clinical settings might pericardial thickening be seen?
Pericardial thickening may be seen in patients who have chronic pericarditis or a long term history of steroid use. Such thickening may also be observed after radiation therapy
What is the normal gradient across the pulmonic valve?
1-3 mmHg
