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Clinical Images
Cardiac Magnetic Resonance and “Augmented” Right-to-Left
Intracardiac Shunting through a Patent Foramen Ovale
April 2008
Platypnea-orthodeoxia is an uncommon condition characterized by the development of hypoxia and breathlessness in the upright posture, relieved by resuming a supine position. It was first described by Altman and Robin in 19691, and has since been associated with intracardiac and intrapulmonary shunts, liver disease and a host of other conditions.2 We report an unusual case of episodic breathlessness and hypoxia cured by percutaneous cardiac intervention.
Case Presentation. An independent 83-year-old male presented with a 6-month history of paroxysmal breathlessness and cyanosis of increasing severity on a background of known mild mixed aortic valve disease, mild left ventricular systolic impairment and systemic hypertension. At the time of presentation, clinical examination revealed central cyanosis in the upright-seated position, but no evidence of pulmonary or cardiac disease to suggest an obvious etiology for his symptoms. A chest X-ray revealed clear lung fields, but arterial blood analysis demonstrated severe type 1 respiratory failure: pO2 44mmHg, pCO2 29 mmHg, HCO3 20 mmol/L, pH 7.44 — which failed to respond to supplemental oxygen.
No cause was apparent despite routine investigations including ventilation/perfusion nuclear scintigraphy and high-resolution chest computerized tomography (CT), however it was noted that the hypoxia was of variable severity, exacerbated by an upright posture and almost entirely resolved by lying supine. Proximal aortic dilatation was noted at the time of CT, but was deemed unrelated to the clinical presentation.
Transthoracic echocardiography was hindered by the anatomical distortion of cardiac structures caused by ascending aortic dilatation, but failed to reveal any worsening of preexisting valvular or myocardial dysfunction. Subsequent right and left heart catheterization confirmed normal right heart pressures and minimal coronary artery disease, with no apparent intracardiac shunt.
Despite the negative shunt study at the time of right heart catheterization, the severity of hypoxemia and refractoriness to supplemental oxygen therapy implicated pulmonary-systemic shunting as the most likely cause. Hence, transesophageal echocardiography (TEE) was performed to assess the patient’s cardiac structure in more detail. This revealed a highly mobile interatrial septum with an associated patent foramen ovale (PFO) and positive bubble study (Figure 1), but the precipitant for this man’s recent deterioration remained unclear.
Cardiac MRI, however, elegantly demonstrated “baffling’”of inferior vena caval blood flow through the PFO as a result of the distortion of the right atrial anatomy created by the dilated ascending aorta (Figure 2). The overriding aortic root was noted to have flattened the right atrium anteriorly, distorting right atrial filling and increasing the propensity for inferior vena caval blood flow to cross the interatrial septum. In the upright posture, the degree of right atrial distortion apparently increased, worsening the right-to-left shunt and subsequent hypoxemia.
The PFO was closed percutaneously using an Amplatzer® closure device (AGA Medical, Golden Valley, Minnesota) with dramatic and immediate resolution of the patient’s hypoxemia and symptoms.
Discussion. While PFOs are common in the community, the development of right-to-left shunting in the setting of normal right heart pressures and the associated clinical syndrome of platypnea-orthodeoxia require an intracardiac communication to be associated with a functional or anatomical distortion.3 Such situations include gross ascending aortic dilatation (as in this case). These images highlight the utility of cardiac MRI in the identification of functional distortions of cardiac and mediastinal anatomy that may not be as well characterized by other available imaging modalities. Developments in cardiac MRI in recent years advance this technology as a viable alternative to traditional methods of noninvasive cardiac structural imaging.
Acknowledgement. The authors would like to thank Dr. Karen Teo for her assistance in the performance and interpretation of the Cardiac MRI.
Case Presentation. An independent 83-year-old male presented with a 6-month history of paroxysmal breathlessness and cyanosis of increasing severity on a background of known mild mixed aortic valve disease, mild left ventricular systolic impairment and systemic hypertension. At the time of presentation, clinical examination revealed central cyanosis in the upright-seated position, but no evidence of pulmonary or cardiac disease to suggest an obvious etiology for his symptoms. A chest X-ray revealed clear lung fields, but arterial blood analysis demonstrated severe type 1 respiratory failure: pO2 44mmHg, pCO2 29 mmHg, HCO3 20 mmol/L, pH 7.44 — which failed to respond to supplemental oxygen.
No cause was apparent despite routine investigations including ventilation/perfusion nuclear scintigraphy and high-resolution chest computerized tomography (CT), however it was noted that the hypoxia was of variable severity, exacerbated by an upright posture and almost entirely resolved by lying supine. Proximal aortic dilatation was noted at the time of CT, but was deemed unrelated to the clinical presentation.
Transthoracic echocardiography was hindered by the anatomical distortion of cardiac structures caused by ascending aortic dilatation, but failed to reveal any worsening of preexisting valvular or myocardial dysfunction. Subsequent right and left heart catheterization confirmed normal right heart pressures and minimal coronary artery disease, with no apparent intracardiac shunt.
Despite the negative shunt study at the time of right heart catheterization, the severity of hypoxemia and refractoriness to supplemental oxygen therapy implicated pulmonary-systemic shunting as the most likely cause. Hence, transesophageal echocardiography (TEE) was performed to assess the patient’s cardiac structure in more detail. This revealed a highly mobile interatrial septum with an associated patent foramen ovale (PFO) and positive bubble study (Figure 1), but the precipitant for this man’s recent deterioration remained unclear.
Cardiac MRI, however, elegantly demonstrated “baffling’”of inferior vena caval blood flow through the PFO as a result of the distortion of the right atrial anatomy created by the dilated ascending aorta (Figure 2). The overriding aortic root was noted to have flattened the right atrium anteriorly, distorting right atrial filling and increasing the propensity for inferior vena caval blood flow to cross the interatrial septum. In the upright posture, the degree of right atrial distortion apparently increased, worsening the right-to-left shunt and subsequent hypoxemia.
The PFO was closed percutaneously using an Amplatzer® closure device (AGA Medical, Golden Valley, Minnesota) with dramatic and immediate resolution of the patient’s hypoxemia and symptoms.
Discussion. While PFOs are common in the community, the development of right-to-left shunting in the setting of normal right heart pressures and the associated clinical syndrome of platypnea-orthodeoxia require an intracardiac communication to be associated with a functional or anatomical distortion.3 Such situations include gross ascending aortic dilatation (as in this case). These images highlight the utility of cardiac MRI in the identification of functional distortions of cardiac and mediastinal anatomy that may not be as well characterized by other available imaging modalities. Developments in cardiac MRI in recent years advance this technology as a viable alternative to traditional methods of noninvasive cardiac structural imaging.
Acknowledgement. The authors would like to thank Dr. Karen Teo for her assistance in the performance and interpretation of the Cardiac MRI.
References
1. Altman M, Robin ED. Platypnea (diffuse zone I phenomenon?). N Engl J Med 1969;281:1347–1348.
2. Cheng TO. Platypnea-orthodeoxia syndrome: etiology, differential diagnosis, and management. Catheter Cardiovasc Interv 1999;47:64–66.
3. Cheng TO. Mechanisms of platypnea-orthodeoxia: What causes water to flow uphill? Circulation 2002;105:e47.
