A 54-year-old woman with a history of mechanical mitral valve replacement for endocarditis is brought to the emergency department for dyspnea. She reports 2 weeks of progressive fatigue, exertional dyspnea, and orthopnea. A CT angiogram of the chest shows diffuse ground-glass opacities and interstitial thickening and is negative for pulmonary embolism. A bedside cardiac ultrasound is performed, and the parasternal short axis view is shown in the figure tbelow.
Which of the following assessments will likely lead to the diagnosis in this case?
Correct Answer: D
This ultrasound image shows a dilated RV and an interventricular septum that is shifted toward the left ventricle. Acute RV failure from pressure overload is associated with a dilated and septal shifting toward the LV. In a short-axis view, this results in the LV forming a “D” shape.
In this patient with cardiogenic shock, a history of mitral valve replacement, and a dilated, hypokinetic RV, the two most likely differential diagnoses are pulmonary embolism and mitral stenosis. The PE was ruled out by the CT chest already. To investigate the gradient across the mitral valve, continuous-wave Doppler should be placed across the valve, making D the correct answer. In mitral stenosis, the pressure gradient across the stenotic valve will result in high velocity flow through the valve. In severe mitral stenosis, the elevated left atrial pressures result in postcapillary pulmonary hypertension that can result in right-sided heart failure.
Demonstration of lower-extremity venous thrombus would not be useful after a PE has already been ruled out. Color Doppler of the main PA would likely not show any abnormality, even if a PE were present. The IVC will likely be plethoric, but again will not tell us the specific diagnosis.
Reference:
In ultrasound assessment of a pericardial effusion, which of the following findings is most specific for cardiac tamponade?
Correct Answer: B
Cardiac ultrasound is extremely sensitive for the detection of pericardial effusions. It is also useful for determining the hemodynamic significance of pericardial effusions. In the setting of a pericardial effusion, signs of cardiac tamponade include IVC dilation, RA and RV diastolic collapse, elevated respiratory variation in trans-mitral and trans-tricuspid inflow, and septal “bounce.” Of these, RA collapse in greater than one-third of the cardiac cycle is the most sensitive and specific for cardiac tamponade, making it the correct answer in this case.
Collapse of a cardiac chamber in tamponade occurs when the pericardial pressure exceeds the pressure in that chamber. As pericardial pressure increases, the right atrium will collapse first in early diastole. The longer the chamber remains collapsed, the longer the pericardial pressure exceeds the atrial pressure and the worse the tamponade.
The IVC will generally be plethoric in tamponade, but this can also be seen in other cardiac pathologies and is not specific to tamponade. The same applies to inspiratory variation in AV valve inflow. The size of the pericardial effusion correlates poorly with hemodynamic significance. A large pericardial effusion does not necessarily indicate tamponade.
An 85-year-old woman underwent a transapical transcatheter aortic valve replacement (TAVR) for severe symptomatic aortic stenosis. After an uneventful procedure, she is brought to the ICU intubated and sedated. In the 30 minutes after arrival to the ICU she develops progressive tachycardia and hypotension, which prompts the placement of a TEE probe. The mid-esophageal 4-chamber view is shown in the figure below:
Based on the findings in the image, what is the most appropriate next step in management?
The image above shows a focal pericardial fluid collection adjacent to the left atrium. The fluid collection clearly distorts the left atrial anatomy and is responsible for the hypotension in this case. This is a good example of focal tamponade that can occur after cardiac surgery. That patient population tends not to have the classic hypoechoic and free-flowing pericardial effusion seen in classic tamponade, instead showing localized areas of semi-thrombosed blood products that impinge on specific cardiac chambers. Note the swirling echogenicity within the fluid collection here that is typical of static blood products.
The most common cause of pericardial bleeding after TAVR is RV perforation. However, aortic root rupture or LA/LV bleeding is possible and should be considered in surgical planning for this case. The correct management here is surgical evacuation of the fluid collection. The posterior and lateral location of the fluid collection precludes percutaneous drainage. Because the fluid is pericardial and not pleural, chest tube placement would not be appropriate.
A 35-year-old woman with no prior medical history presents to your hospital’s emergency department with a complaint of dyspnea that started acutely 2 hours ago. She appears moderately distressed and has a room air oxygen saturation of 85%, so you are consulted for possible ICU admission. Bedside cardiac ultrasound reveals grossly normal biventricular size and function. Thoracic ultrasound shows lung sliding and A lines in all fields bilaterally. There is no evidence of B lines, consolidated lung, or pleural effusion.
Which of the following ultrasound examinations is most indicated next?
Correct Answer: A
Thoracic ultrasound provides a tool for the rapid assessment of patients with acute dyspnea. Lichtenstein and colleagues proposed an algorithmic diagnostic approach to respiratory failure. The first step is to look for lung sliding bilaterally. If present, lung sliding essentially rules out a pneumothorax. Then, evidence of interstitial or alveolar edema in the form of B lines is sought. If there is no evidence of pneumothorax, pulmonary edema, consolidation, or pleural effusion on lung ultrasound, the next differential to consider is pulmonary embolism. The next step in this case would be to look for venous thrombosis. If venous thrombus is demonstrated, then pulmonary embolism is very likely. An absence of DVT, however, does not rule out pulmonary embolism and further studies must be pursued.
Mitral regurgitation, which would be seen on color Doppler assessment, would result in pulmonary edema and B lines on imaging, which were absent on the examination. Abdominal fluid would not explain her acute dyspnea in the absence of other symptoms. Tissue Doppler assessment of diaphragmatic contraction velocity has been preliminarily investigated to predict ventilator weaning failure but has not been validated in the assessment of acute dyspnea.
References:
Which of the following thoracic ultrasound patterns will most likely be present in severe ARDS?
Cross-sectional CT imaging of the noncardiogenic pulmonary edema seen in ARDS tends to show ground-glass opacities in the anterior (nondependent) lung fields and consolidation in the posterior (dependent) fields. On ultrasound examination, this presents as B lines in the areas containing interstitial edema and the appearance of consolidated lung in the dependent fields.
Consolidated lung on ultrasound will have a variable appearance depending on the pathophysiology. The first principle to remember is that normal lung is never ultrasonically visible. If lung can be “imaged” on ultrasound, then the alveoli are no longer gas filled. In the dense atelectasis that accompanies pleural effusions, the lung has a fine-textured uniform hypoechoic appearance similar to that of liver and spleen. The fluid-filled alveoli in pneumonia and ARDS create a different appearance on ultrasound. A hallmark of ARDS is the significant heterogeneity in consolidation density and aeration between lung units. This leads to areas of hypoechoic lung immediately adjacent to areas of better-aerated lung or bronchus, which will appear hyperechoic. The borders between these areas tend to be irregular and jagged, so the presence of a jagged interface between consolidated and aerated lung is known as the “shred sign.”
Of the answer choices above, diffuse B lines without evidence of consolidation is more compatible with cardiogenic pulmonary edema. Large hypoechoic spaces subpleurally is consistent with pleural effusions. Answer choice C describes “lung point,” which is a specific finding in pneumothorax. This is the ultrasound appearance of lung sliding (due to apposed visceral and parietal pleura) moving into and out of the imaged area of pneumothorax (lack of lung sliding) through the respiratory cycle.
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