58-year-old woman with progressive shortness of breath
A 58-year-old woman with cirrhosis secondary to metabolic dysfunction-associated steatohepatitis presents to the clinic for a routine follow-up. Over the past three months, she has noted progressive shortness of breath when standing to organize library archives or prepare dinner, which consistently resolves within minutes of lying down. She has no cough, chest pain, fever, orthopnea, or lower-extremity swelling. Her medications are spironolactone, furosemide, and propranolol. Physical examination reveals spider telangiectasias across the upper chest and mild digital clubbing. Jugular venous pressure is 6 cm H2O. Cardiac auscultation demonstrates a regular rhythm, normal heart sounds, and no murmurs. Lungs are clear to auscultation bilaterally. The abdomen is soft and non-distended, with a liver edge palpable 2 cm below the costal margin and no shifting dullness. Supine blood pressure is 114/68 mm Hg, heart rate is 74/min, and oxygen saturation is 95% on ambient air. After standing for four minutes, her oxygen saturation falls to 88% with a heart rate of 82/min. A chest radiograph demonstrates clear lung fields with normal vascularity and a normal cardiac silhouette. Which of the following is the most appropriate diagnostic test?
See the answer and explanation below:
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A
Explanation
Clinical Pearl:
Hepatopulmonary syndrome is characterized by the clinical triad of advanced liver disease, arterial hypoxemia, and intrapulmonary vascular dilatations producing platypnea-orthodeoxia. Contrast-enhanced transthoracic echocardiography with agitated saline is the initial diagnostic test of choice, identifying right-to-left transpulmonary bubble transit delayed by three to six cardiac cycles.
Explanation:
This patient has hepatopulmonary syndrome, marked by underlying cirrhosis, progressive dyspnea, and arterial desaturation provoked by upright posture and relieved by recumbency (platypnea-orthodeoxia) in the setting of clear lung fields. Transthoracic echocardiography with agitated saline is the established initial diagnostic test in society guidance, as it detects intrapulmonary vascular dilatations when microbubbles transit to the left atrium after a three- to six-cycle delay. High-resolution computed tomography of the chest evaluates parenchymal lung disorders like pulmonary fibrosis, but normal auscultation, a clear radiograph, and postural desaturation make primary alveolar or interstitial disease unlikely. Right heart catheterization with pulmonary angiography evaluates portopulmonary hypertension, which causes exertional rather than positional dyspnea and presents with signs of right ventricular overload. Radionuclide ventilation-perfusion lung scintigraphy is used to quantify shunt fraction when intrinsic lung disease coexists, but it lacks the sensitivity of contrast echocardiography for establishing the diagnosis. Diagnostic overnight polysomnography with capnography evaluates sleep-disordered breathing and nocturnal hypoventilation, neither of which accounts for daytime orthodeoxia.
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