IM BOARD REVIEW /¡D L. LONGWORTH, MD, JAMES K. STOLLER, MD, EDITORS

JOSH MILLER, DO JANET MAURER, MD ATUL MEHTA, MD Department of Pulmonary and Critical Head, Section of Transplantation, Head, Section of Bronchology; Vice Care Mediane, Cleveland Clinic Department of Pulmonary and Critical Chairman, Department of Pulmonary Care Medicine, Cleveland Clinic and Critical Care Medicine, Cleveland Clinic

A 43 -yearmold woman with

43-YEAR-OLD WOMAN presents with • shortness of breath while sitting or • Orthodeoxia standing. The problem began approximately 3 • months ago. Five months previously she underwent a right pneumonectomy to remove The patient has platypnea: shortness of breath an adenocarcinoma of stage T2, with no in the upright or standing position. Her arter- lymph node involvement and no distant ial blood gas values indicate she also has orth- metastases. Ten days after surgery, her postop- odeoxia, ie, significantly more oxygen desatu- erative course was complicated by a stump leak ration when standing than when lying clown. requiring surgical correction. One month later Orthopnea describes shortness of breath in the she started to have episodes of shortness of supine position, which is a clue that the heart breath, especially while bending forward. Her may be involved. is dyspnea in the symptoms gradually progressed until now she right c^r left lateral decubitus position, which can obtain relief only in the supine position. can occur with intraptilmonary shtmting or a The patient is confined to a wheelchair ventilation/perfusion mismatch. and is cyanotic, TABLE 1 shows her arterial blood gas values in the lying and standing positions Case continued while room air. The patient has already undergone a ventila- tion/perfusion scan, duplex ultrasonography of • DYSPNEA WHILE STANDING both lower extremities, pulmonary angiogra- phy, transesophageal echocardiography, and What term best describes dyspnea while dobutamine echocardiography at another hos- Istanding? pital, and all of the results were normal. • Trepopnea Catheterization of the right side of the TABLE 1 heart reveals normal pulmonary artery pres- sures (20/10 mm Hg). As time goes on, the The patient's arterial blood patient's platypnea grows worse, and she gas values on admission requires supplemental oxygen.

MEASUREMENT VALUE VALUE NORMAL • WHAT IS THE CAUSE OF HER SUPINE STANDING RANGE SYMPTOMS? 7.44 7.46 7.35-7.45 PH Which of the following is the most likely Pco2, mm Hg 29.8 26.3 34-46 2 cause of this patient's symptoms?

Pao2, mm Hg 59.5 44.8 85-95 • • Primary pulmonary hypertension 20.8 18.5 22-26 HCO3, mmol/L • Severe restrictive impairment as a conse-

02 saturation, % 88 77 95-98 quence of the pneumonectomy • Coronary artery disease • A right-to-left interatrial shunt

588 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 66 • NUMBER 1 0 NOVEMBER / DECEMBER 1999 Downloaded from www.ccjm.org on October 1, 2021. For personal use only. All other uses require permission. The normal findings on her duplex studies, tion, gravity can enlarge the opening, making ventilation/perfusion scans, and pulmonary the shunting worse.2 angiogram rule out pulmonary embolism, and Pulmonary arteriovenous malformations her normal right heart pressures rule out pri- also cause anatomic abnormalities. mary pulmonary hypertension. Significant Approximately 65% occur in the lower lobes, coronary artery disease and left ventricular dys- perhaps because blood flow and pressure are function can be ruled out on the basis of the highest there, particularly in the upright posi- normal dobutamine stress echocardiogram. tion.3 The patient's pulmonary function tests Although most patients with COPD showed a restrictive pattern, ie, a diminished experience the opposite problem—orthop- vital capacity (VC) but a normal forced expi- nea—a very few experience orthodeoxia and ratory volume in 1 second (FEVj). This find- platypnea. Altman and Rohird ascribed this ing could explain her dyspnea, but not neces- paradoxical situation to a diffuse zone 1 phe- sarily her platypnea and orthodeoxia. nomenon. (The can be divided into Moreover, a pure restrictive impairment three zones on the basis of alveolar and vascu- would lead to alveolar lar pressures. In zone 1 the alveolar pressure (increased PCO2), whereas this patient had exceeds the pulmonary artery pressure, and partially compensatory respiratory alkalosis the alveoli therefore collapse the surrounding

(decreased Pco2). pulmonary capillaries, creating areas of respi- Of the given conditions, only a right-to- ratory dead space, ie, ventilated but underper- left interatrial shunt, especially in the upright fused segments of lung. Elevation of the tho- position, cannot be excluded. rax when standing would further lower die pulmonary arterial pressure in the upper lungs, • DIFFERENTIAL DIAGNOSIS accentuating the decrease in pulmonary blood flow there. In zone 2 the alveolar pressure is Which one of the following disorders does less than the pulmonary artery pressure but 3 not cause platypnea and orthodeoxia? greater than the pulmonary pressure, and • Hepatopulmonary syndrome in zone 3 the alveolar pressure is less than the From 16% to • Chronic obstructive pulmonary disease pulmonary vein pressure.) 24% of the (COPD) • Pulmonary arteriovenous shunts • WHAT FURTHER TESTS ARE NEEDED? general LI Intracardiac light-to-left malformations population has • Idiopathic pulmonary fibrosis Which of the following tests can aid in the 4 diagnosis of an interatrial shunt? a patent Platypnea and orthodeoxia are primarily due • Echocardiography with a bubble study foramen ovale to right-to-left shunting (ie, a process that • Magnetic resonance imaging of the heart allows deoxygenated blood to return from the • Perfusion lung scan right side of the heart to the left without • Computed tomography undergoing oxygenation), occurring preferen- • Arterial blood gasses while breathing tially in the upright position. 100% oxygen This phenomenon is unlikely to occur in idiopathic pulmonary fibrosis. It has been One can detect intracardiac shunts by means reported in patients with the other conditions of an echocardiogram with a bubble study—a listed, although the physical basis is different technique that uses microscopic bubbles in each of them. injected into the venous circulation as a con- For example, in hepatopulmonary syn- trast medium. The bubbles normally diffuse drome, the shunting takes place in intrapul- out into the alveoli and thus do not traverse monary vascular dilations, mainly in the lower the lungs. Thus, if they appear in the left atri- lobes.1 um, a shunt probably is present. Intracardiac shunts involve actual Magnetic resonance imaging (MRI) with anatomic abnormalities—defects in the atrial a contrast dye (the turbo fast low-angle shot— or ventricular septums. In the upright posi- turboFLASH—technique) can also reveal

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present; however, it will show increased uptake of radioactive microaggregates in the brain and kidneys suggestive of a right-to-left intracardiac shunt. Measuring arterial blood gas levels on 100% oxygen is a simple way to calculate the shunt fraction. CT scanning has not been shown to help in the diagnosis of an intracardiac shunt. Our patient underwent a turboFLASH MRI scan (FIGURE 1), which showed enhanced mobility of the right atrium and a patent fora- men ovale, which was asymptomatic prior to the pneumonectomy. Another trans- esophageal echocardiogram using color con- trast was performed, which revealed right-to- left flow. The shunt was more pronounced when the patient assumed the upright posi- tion from a supine position.

• PATENT FORAMEN OVALE

What is the prevalence of a patent fora- 5 men ovale in the general population? • 1% to 3% • 4% to 8% TurboFLASH MRI • 10% to 15% can demonstrate • 16% to 24% a cardiac shunt Studies have shown that 16% to 24% of the population have a patent foramen ovale.2 The patient underwent surgical correc- tion of the patent foramen ovale, and her symptoms resolved completely. FIGURE 1. Three magnetic resonance imaging scans (sequential from top to bottom), per- • RIGHT-TO-LEFT INTERATRIAL SHUNT formed using the turbo fast low-angle shot FOLLOWING RIGHT PNEUMONECTOMY (turboFLASH) technique. Note the movement of the contrast material (arrow) from the right Loss of alveolar volume, restrictions of the vas- ventricle (RV) in the first image to the left atri- cular bed, chest wall pain, and diaphragmatic um (LA) in the second and third images. The dysfunction are common causes of shortness of failure of the contrast to enter the lung (L) is breath after a pneumonectomy. Right-to-left evidence of a right-to-left shunt. interatrial shunts are a rare cause, with only 18 other reported cases in the literature.5-11 intracardiac shunts. This type of MRI allows However, with the high prevalence of patent the radiologist to assess the first-pass effect of foramen ovale in the general population, this the contrast to determine if there is a shunt complication is likely to occur frequently, and and also to estimate the flow through the we suspect it is underdiagnosed. shunt. The exact mechanism of platypnea and A perfusion lung scan will not show any orthodeoxia is not fully understood. One perfusion defects if an intracardiac shunt is explanation may be that right atrial pressures

590 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 66 • NUMBER 10 NOVEMBER / DECEMBER 1999 Downloaded from www.ccjm.org on October 1, 2021. For personal use only. All other uses require permission. exceed left atrial pressures, owing to increased pressures. Surgical correction of the defect is pulmonary vascular resistance due to changes the only treatment. A high degree of suspicion produced by the surgery. The increased pres- is needed to diagnose this condition. MRI, sure would reroute the flow of blood preferen- transesophageal echocardiography with color tially through the patent foramen ovale. contrast, or both are the tests of choice to However, this does not seem to be the case, as establish the diagnosis. £3 in most of the reported cases the patients had normal right heart pressures.9 • REFERENCES LaBresh et al6 and van Rossum et al8 Lange PA, Stoller JK. The hepatopulmonary syndrome. believe that postoperative changes in medi- Ann Intern Med 1995; 122:521-529. astinal structures lead to anatomic alterations Bedford DE. The anatomical types of : in the relationship of the two atria, causing their incidence and clinical diagnosis. Am J Cardiol 1960; 6:568. distortions of the foramen ovale while the Goodenberger DM. Pulmonary arteriovenous malforma- patient is standing and cause preferential tions. In: Fishman A, editor. Fishman's Pulmonary Diseases shunting of blood from the inferior vena cava and Disorders, 3rd ed. New York: McGraw-Hill; even in the face of lower right atrial pressures. 1998:1375-1385. 10 Altman M, Robin ED. Platypnea (diffuse zone I phenome- Merko et al concur that a "streaming" of non?) N Engl J Med 1969; 281:1347-1348. blood from the inferior vena cava through a McLeroy MB, Bates DV. Respiratory function after pneu- patent foramen ovale is the cause of the shunt. monectomy. Thorax 1956; 11:303-311. LaBresh KA, Pietro DA, Coates EO, Khuri SF, Folland ED, The mediastinal shift that occurs after pneu- Parisi AF. Dyspnea after left pneumonectomy. Chest 1981; monectomy and the weight of the heart while 79:605-607. standing pulls the interatrial septum down- Seward JB, Hayes DL, Smith HC, et al. Platypnea-orth ward, causing the foramen ovale to widen or odeoxia: clinical profile, diagnostic workup, management, and report of seven cases. Mayo Clin Proc 1984; newly open. 59:221-231. van Rossum P, Plokker HW, Ascoop CA. Breathlessness • CONCLUSION and hypoxia in the upright position after pneumonecto- my. Eur Heart J 1988; 9:1230-1233. Smeek FW, Twisk SP, Berreklouw E, Gooszen HC, Postmus A right-to-left intracardiac shunt can cause PE. Dyspnea after pneumonectomy. Eur Respir J 1991; We suspect this platypnea and orthodeoxia as described in this 4:243-245. problem is case. The most likely cause of right-to-left 10. Mercho N, Stoller JK, White RD, Mehta AC. Right-to- left interatrial shunt causing platypnea after pneu intracardiac shunting after a right pneumonec- monectomy. A recent experience and diagnostic value underdiagnosed tomy is a change in the mediastinal anatomy of dynamic magnetic resonance imaging. Chest 1994; that leads to direct streaming of blood from the 105:931-933. 11. Bakris NC, Siddiqi AJ, Fraser CD Ir, Mehta AC. Right-to- inferior vena cava through a patent foramen left interatrial shunt after pneumonectomy. Ann Thorac ovale even in the face of normal right heart Surg 1997; 63:198-201.

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