Late “Adult Form” Scimitar Syndrome Presenting with “Infant Form” Complications

Scimitar syndrome is a rare congenital cardiopulmonary anomaly that carries a poor prognosis for individuals who are diagnosed within their first year of life.¹ These patients often present with pulmonary hypertension and right-sided congestive heart failure, presenting a challenge for medical and surgical management. Conversely, scimitar syndrome is generally asymptomatic and often an incidental finding for patients diagnosed after infancy.² We describe a previously healthy elderly patient who presented with pulmonary hypertension and congestive heart failure, and was eventually diagnosed with scimitar syndrome. Although surgical correction for this anomaly is indicated for symptomatic individuals or patients with significant right-to-left shunt to prevent development of pulmonary hypertension, this is the first reported case of “adult form” scimitar syndrome progressing to develop “infant form” complications. Case Report. A previously healthy 85-year-old woman with a medical history significant only for well-controlled hypertension and a distant history of breast and colon cancer presented to a local emergency department complaining of presyncope and palpitations. She was fairly active prior to presentation, living alone and doing her own shopping, cooking and cleaning. On review of systems, she reported shortness of breath with moderate activity for as long as she could remember. Her physical exam was notable for an oxygen saturation of 87%, bibasilar rales, jugular venous pressure that was elevated to the angle of the jaw at 45 degrees, a loud pulmonic closure sound, a III/VI harsh holosystolic murmur at the left lower sternal border and hepatojugular reflux. An electrocardiogram showed a wandering atrial pacemaker, and a portable chest X-ray revealed cardiomegally, an increased prominence of the pulmonary vasculature and an “abnormal opacity in the right lower lung with a convex appearance”. The patient’s brain naturetic peptide level was > 1,300 pg/ml (Biosite, San Diego, California). The patient was admitted to the hospital with a diagnosis of new-onset heart failure and ruled out for myocardial infarction. An echocardiogram was performed and revealed normal left ventricular ejection fraction with Doppler evidence of diastolic dysfunction, moderate left atrial enlargement, moderate right ventricular (RV) enlargement with moderate global hypokinesis and severe right atrial enlargement (Figure 1). A saline microcavitation study demonstrated passage of microbubbles to the left atrium consistent with an atrial-level shunt. With concern for a complicated atrial septal defect, the patient underwent diagnostic cardiac catheterization. Right heart catheterization revealed a pulmonary artery systolic pressure of 70 mmHg, which did not improve during inhalation of 100% oxygen or 40 ppm of nitric oxide. A small atrial septal defect was well visualized by angiography. The oxygen saturation run confirmed atrial-level shunting, but was most notable for an elevated oxygen saturation at the level of the inferior vena cava (IVC), initially disregarded as being erroneous. Transesophogeal echocardiography was performed to size the atrial septal defect ( Discussion. Scimitar syndrome is a rare, congenital cardiopulmonary anomaly characterized by partial or complete anomalous drainage of the right pulmonary veins into the inferior vena cava. In most cases, the right lower lobe pulmonary vein and, occasionally, the right middle lobe pulmonary vein form an abnormal vein that courses inferiorly and medially before passing through the diaphragm and draining into the upper inferior vena cava.³ This condition is often associated with other anomalies including right lung hypoplasia, dextroposition of the heart and anomalous systemic arterial supply to the right lung from the subdiaphragmatic aorta or its main branches. The anatomic abnormalities of scimitar syndrome were first described independently in 1836 by Drs. Chassinat and Cooper.⁴ The name was coined by Dr. Neill, et al. in 1960 after the appearance of the anomalous vein on chest X-ray: a tubular opacity paralleling the right cardiac border and resembling a curved Turkish sword or “scimitar.”⁵ The incidence of the syndrome is approximately 1 to 3 per 100,000 live births, but the true incidence may be higher, as many individuals can remain asymptomatic for long periods of time. Scimitar syndrome has been described in the medical literature in three different forms: “the infant form”, the “adult form”, and the “form associated with other complex or serious cardiac malformations”.² In the infant form, patients become symptomatic within the first year of life, usually developing severe pulmonary hypertension and cardiac failure. In the adult form of scimitar syndrome, patients are asymptomatic during childhood and usually have normal pulmonary pressures at the time of diagnosis. The final variant is seen in association with complex cardiac malformations such as hypoplastic left ventricle, aortic arch obstruction, subaortic stenosis, stenotic left pulmonary veins and anomalous left coronary artery. These disorders modify the natural history of the disease to the point that the scimitar vein is usually of little concern.¹ Patients with the infantile scimitar usually have evidence of pulmonary hypertension, severe right-sided heart failure, cyanosis and failure to thrive at the time of diagnosis. Physical exam is notable for a fixed split S2 with a prominent pulmonary component, elevated jugular venous pressure, hepatomegally and extremity edema.⁶ In contrast, most patients with adult scimitar are asymptomatic and the defect is usually discovered as a result of incidental chest X-ray findings or workup for a cardiac murmur. Most of these cases are normally detected by age 12, but diagnoses have been made in individuals up to 77 years of age.⁷ The most frequent symptoms of adult-form scimitar include repeated episodes of pneumonia, minor dyspnea on exertion and occasionally hemoptysis. Pulmonary hypertension is extremely rare in these patients, and if present, is mild and not associated with right heart failure.² Physical exam findings are nonspecific, but may include a holosystolic murmur and right lower lobe crackles. Definitive diagnosis in these patients is usually made by computerized tomography,⁸ magnetic resonance imaging⁹ and/or angiography. These modalities allow for direct visualization of the anomalous vein, identification of associated malformations and measurement of shunt. Although the expected elevation of oxygen saturation in the inferior vena cava is frequently present, oximetry can be misleading due to reduced blood flow through the right lung and the contribution of highly oxygenated blood from the renal veins. Patients with adult scimitar generally remain asymptomatic and lead fairly normal lives. Conversely, even with aggressive surgical management, patients with infant scimitar generally have a poor prognosis. Surgical correction of patients with adult scimitar is not recommended unless the patient is symptomatic or has a pulmonary-to-systemic shunt blood flow ratio exceeding 1.5 to 2:1. Classic surgical repair consists of constructing a long intra-atrial baffle from the entry point of the scimitar vein into the inferior vena cava to the left atrium through an atrial septal defect.¹⁰ More recently, approaches include the direct anastomosis of the scimitar vein to the posterior aspect of the left atrium.¹¹ Other interventions that can sometimes reduce pulmonary hypertension, particularly in infants, include ligation or embolization of an anomalous artery and, as a last resort, partial or complete right pneumonectomy. Percutaneous and surgical interventions for palliation of pulmonary venous obstruction have had very little success.¹⁰ Recently, a percutanous approach to scimitar repair has been described.¹² Dual drainage of the scimitar vein (to the IVC and the left atrium) must first be documented and then the scimitar vein is occluded above the opening to the IVC. This should result in diversion of the pulmonary venous return back to the left atrium and correct the shunt. Unfortunately in our patient, adequate vascular channels to the left atrium were not found. Although patients with adult scimitar and large shunts may, in theory, develop pulmonary hypertension, thus presenting similar to infant-form scimitar, this is the first reported case to document such a progression. Also, while it is possible that the atrial septal defect played a role in the pulmonary vascular complications in our patient, defects of this size are usually associated with low-level shunting and unlikely to result in pulmonary vascular disease. In conclusion, this case illustrates that the boundary between the adult and infant form of scimitar syndrome is not as definitive as previously believed. Identifying patients such as this one with considerable shunting and right heart volume overload before pulmonary hypertension has developed may offer the opportunity to intervene and prevent future complications.

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