Set 10 Flashcards
If the primary flow direction through a shunt is left to right, why are contrast echo studies so sensitive in detecting atrial shunts?
Even when shunt flow is primarily left to right, a small right to left component is usually present at end diastole.
If the contrast study yields a negative result, performing another injection during the release phase of the Valsalva maneuver may produce a positive result, because the right sided pressures will undergo a transient increase
What is a persistent left superior vena cava?
A persistent left superior vena cava is a congenital venous malformation where the left arm drains into the coronary sinus instead of the superior vena cava
Returning blood from the left arm still goes to the right atrium, it just takes a detour through the coronary sinus.
What is the prominent 2D finding in a patient with a persistent left superior vena cava?
The prominent 2D finding in a patient with a persistent left superior vena cava is a dilated coronary sinus, usually best seen in the parasternal long axis view
How is the diagnosis of a persistent left superior vena cava confirmed?
The diagnosis of a persistent left superior vena cava is confirmed by performing a saline contrast study with the injection into the patients left arm. This way the bubbles (contrast) will appear in the dilated coronary sinus first and then the right atrium and ventricle
Describe the most common types of ventricular septal defects
Ventricular septal defects may take the form of:
- Perimembranous defect - near the aortic valve (this is the most common type, accounting for 75% of ventricular septal defects)
- Inlet defect - in the posterior portion of the septum, close to the tricuspid valve
- Outlet or supracristal defect - in the right ventricular outflow tract
- Muscular defect - low in the ventricular septum and is completely surrounded by muscular tissue
Multiple muscular ventricular septal defects may coexist
Which technique is more useful in detecting a ventricular septal defect: Doppler or contrast echo?
Doppler imaging is more useful than contrast echo is detecting a ventricular septal defect
A pulsed or color flow approach should be used to locate the defect, and continuous wave studies are preferred for estimating the gradient between the ventricles.
Because blood is almost always shunted from left to right, saline contrast echo has limited success in detecting these defects.
What is the primary direction of flow across a ventricular septal defect?
At normal ventricular pressures, the primary direction of flow across a ventricular septal defect is left to right
Describe the physiology of Eisenmenger’s syndrome
In Eisenmenger’s syndrome, a long standing left to right shunt, in the form of a ventricular or atrial septal defect, causes pulmonary hypertension.
When the pulmonary pressures exceed the systemic (LV) pressure, the shunt reverses direction and becomes right to left
How does a ventricle septal defect affect the cardiac chambers?
Small ventricular septal defects do not usually affect either the right or left cardiac chambers
Moderate to large ventricular septal defects cause the right ventricle to enlarge as a result of pressure/volume overload
Right ventricular hypertrophy can also result from pressure overload of the right ventricle.
The atria are rarely affected by a ventricular septal defect
What is a patent ductus arteriosus (PDA)?
Patent ductus arteriosus (PDA) is an anomaly in which the ductus arteriosus fails to close after birth
The ductus arteriosus is a fetal communication between the pulmonary artery and the descending aorta. In the fetal circulation, this ductus shunts blood away from the lungs, towards the aorta
Which echo view and technique is best for assessing a patent ductus arteriosus?
The parasternal short axis view, at the level of the aorta, is the best echo view for detecting patent ductus arteriosus in adults. Color flow Doppler imaging is the best technique for detecting shunt flow.
Usually blood flows through the shunt in a left to right direction (from the aorta to the pulmonary artery)
In coarctation of the aorta, which portion of the aorta is usually involved?
Although coarctation may involve any portion of the aorta, this anomaly usually occurs just distal to the origin of the left subclavian artery
This area is known as the aortic isthmus
How is the severity of an aortic coarctation quantitated?
The severity of obstruction at the site of the coarctation can be quantified with continuous wave Doppler
From the aortic suprasternal notch, the Doppler beam can be aligned with the descending aorta, allowing the peak gradient to be measures.
Forward flow may also be present across the coarctation during diastole (such flow is known as diastolic flow)
What is Ebstein’s anomaly?
Ebstein’s anomaly is a congenital malformation with apical displacement of one or more tricuspid leaflets
Although the degree of leaflet displacement varies, at least part of the morphological right ventricle becomes “atrialized”
The tricuspid annulus is often positioned normally and moderate to severe tricuspid regurgitation is usually present
What congenital lesion is often associated with Ebstein’s anomaly?
Secundum atrial septal defects are often associated with Ebstein’s anomaly
What conduction disturbance is associated with Ebstein’s anomaly?
Patients with Ebstein’s anomaly have an increased incidence of Wolff-Parkinson-White (WPW) syndrome, usually with a right accessory pathway
Describe the 3 types of aortic dissection
The 3 types of aortic dissection are (DeBakey Classification):
- Type 1 - originates in the proximal ascending aorta and extends into the descending aorta
- Type 2 - originates in the proximal ascending aorta and is confined to the ascending aorta
- Type 3 - originates in the descending aorta and extends into the abdominal aorta
Which types of aortic dissection are usually associated with aortic regurgitation?
Aortic regurgitation is seen in both type 1 and type 2 aortic dissection because these types involve the aortic root.
Aortic regurgitation is not seen in type 3
Describe the 2D echo appearance of a sinus of Valsalva aneurysm
Sinus of Valsalva aneurysms involve the right coronary sinus in 70% of cases, the noncoronary sinus in 25% of cases, and the left coronary sinus in 5% of cases
2D echo best reveals such aneurysms in the parasternal short axis at the aortic level. Because aneurysms rarely involve more than one sinus, identification of the affected sinus is facilitated by comparing the size and wall thickness of all 3 sinuses.
An aneurysmal sinus is larger than normal and has thin walls
These aneurysms can rupture and if this complication occurs, color flow Doppler imaging is very useful in identifying the direction and volume of flow
What are the echo findings associated with aortic dissection?
Echocardiographically, aortic dissection is associated with local or generalized dilation of the aorta. The aortic wall has a double-layered appearance (either anteriorly or posteriorly)
The intimal flap appears as a thin, mobile structure that divides the aorta into a true and a false channel
What is the best echo technique for evaluating an aortic dissection?
Chest CT or Transesophageal echo is the best technique for diagnosing an aortic dissection and evaluating its extent
What echocardiographic finding may help differentiate miscellaneous aortic dilatation from Marfan Syndrome?
Most patients (70%) with Marfan Syndrome have mitral valve prolapse
Marfan Syndrome is a connective tissue disease in which the chief cardiac abnormalities are aortic aneurysms, aortic regurgitation, and mitral valve prolapse
Aortic dissection is common and accounts for the majority of premature deaths
In the presence of a ventricular septal defect, how would you calculate the right ventricular systolic pressure (RVSP)?
In the presence of a ventricular septal defect, the right ventricular systolic pressure (RVSP) can be calculated by:
- Measuring the gradient between the ventricles on the bases of the flow velocity across the ventricular septal defect (VSD)
- Converting the result to mmHg with the Bernoulli equation (4V2)
- Subtracting the gradient from the systolic blood pressure (SBP).
The equation is RVSP = SBP - VSD gradient
What is the color flow Doppler technique?
The color flow Doppler technique is a pulsed method for recording and displaying flow information, superimposed on anatomic images (M-mode or 2D)
Color flow displays usually involve 2D images; by convention, flow toward the probe appears red, and flow away from the probe appears blue. The display indicates the flow velocity and direction by changing the hues of these colors.
In color flow Doppler imaging, what is a pulse packed?
To accurately determine the direction and velocity of blood flow, a group of ultrasound pulses is transmitted, received, and compared with respect to phase shift. This group of pulses is called a pulse packet
Why are color Doppler pulse packets important?
The larger the pulse packet, the more accurate the flow related information.
The bad news is that a large packet size takes longer to transmit and receive so image frame-rate decreases.
Note: for satisfactory blood flow sensitivity, it is generally best to use a larger packet size and to gain back an acceptable frame rate by decreasing the depth or narrowing the color sector
What is continuous wave Doppler mode?
In the continuous wave Doppler mode, two transducer elements (or sets of elements) are used to record flow. One element continuously transmits ultrasound signals, and the other element continuously receives such signals.
The received signals are analyzed for Doppler frequency shifts and the resulting information is displayed on the screen.
What are the main advantages and disadvantages of the continuous wave Doppler mode, compared to the pulsed wave Doppler mode?
The main advantage of the continuous wave Doppler mode is its ability to record high velocity flow without aliasing
The disadvantage of this mode is that, although flow along the ultrasound beam is recorded, the location of this flow is not known
What is the most important part of the Doppler equation?
The most important part of the Doppler equation is the cosine of the angle theta
Theta denotes the angle between the ultrasound beam and the moving target (blood). As long as this angle is less than 20 degrees, the calculated velocity is accurate.
When the angle is greater than 20 degrees, the velocity is underestimated by the Doppler equation
