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CARDIOVASCULAR ANESTHESIOLOGY

Incidental Discovery of a Large Patent Ductus Arteriosus in an Adult During Aortic Reconstruction: Echocardiographic Findings and Diagnostic Dilemmas

From the Brigham and Women's Hospital, Department of Anesthesiology, Perioperative, and Pain Medicine, Boston, Massachusetts.

Address correspondence to Jochen D. Muehlschlegel, MD, Brigham and Women's Hospital, Department of Anesthesiology, Perioperative, and Pain Medicine, 75 Francis St., Floor L1, Boston, MA 02115. Address e-mail to jmuehlschlegel{at}partners.org

A 61-yr-old woman presented with sudden back pain. She had had a Stanford type A aortic dissection 15 yr earlier repaired with a Bentall procedure with a St. Jude aortic valve replacement. Her prior reconstruction extended from the aortic root to the brachiocephalic artery. An intraoperative echocardiogram was not performed at the time. She subsequently developed a chronic Stanford type B dissection at the distal aortic arch.

On her current presentation, chest magnetic resonance imaging (MRI) showed chronic dissection and new intramural hemorrhage, involving the proximal descending thoracic aorta. The MRI also showed a severe dilation of the main, left, and right pulmonary arteries. She underwent total aortic arch reconstruction and antegrade descending aortic stent graft placement via reoperative midline sternotomy with right axillary cannulation, deep hypothermic circulatory arrest, and antegrade cerebral perfusion.

Intraoperative transesophageal echocardiogram showed an enlarged right atrium (RA), right ventricle, and main pulmonary artery (PA). Her PA pressure, measured via a PA catheter located in the right PA, was 45/20 mm Hg; arterial blood pressure was 120/70 mm Hg in the left and right radial artery. Color flow and pulsed wave Doppler showed a high velocity jet (2.0 m/s) from the aortic false lumen to the main PA (Fig. 1 and Video Clip; please see video clip available at www.anesthesia-analgesia.org).

View larger version (38K): [in this window] [in a new window]   Figure 1. Upper esophageal aortic arch short-axis view of the dissected aorta. The aorta is in short axis with a true and false lumen; the enlarged main pulmonary artery in long axis. An aliasing color flow jet from left to right with a Nyquist limit of 55 cm/s originates from the aorta's false lumen. UE = upper esophageal; SAX = short axis; PA = pulmonary artery.

The anatomical position of the jet suggested a patent ductus arteriosus (PDA) with left-to-right shunting. Injection of agitated saline into the RA showed no echolucency in the main PA (Fig. 2). There was no increase in the partial pressure of oxygen between the RA and pulmonary capillary blood aspirated from the distal lumen of the PA catheter.

View larger version (39K): [in this window] [in a new window]   Figure 2. The dissected aorta and main PA viewed as in Figure 1 after injection of 10 mL of agitated saline. The absence of echolucency in the region of the suspected PDA argues against left-to-right flow in this area. No bubbles could be seen in the aorta, arguing against a right-to-left shunt. UE = upper esophageal; SAX = short axis; PA = pulmonary artery; PDA = patent ductus arteriosus.

Aortic resection revealed an 8 mm wide by 1 cm long conduit connecting the false lumen of the aorta to the main PA. Based on anatomic location and gross appearance, this was diagnosed intraoperatively as a PDA. On postoperative review of her preoperative MRI, a connection between the aortic false lumen and the main PA was noted.

The fetal ductus arteriosus arises from the aorta opposite the origin of the left subclavian artery. It connects the aorta to the bifurcation of the PA at the origin of the left PA. The ductus arteriosus normally closes in the weeks after birth, but persists in 10% of cases of adult congenital heart disease (1). It may cause a murmur at the left sternal border, and may be seen, if calcified, on chest radiograph. Persistent left-to-right shunting can cause LV volume overload, right ventricular pressure overload, and pulmonary hypertension. Increasingly higher right-sided pressures may eventually lead to Eisenmenger's physiology, with bidirectional or right-to-left shunting (2). Congestive heart failure and endocarditis may also occur. During cardiopulmonary bypass, a PDA would provide blood flow to the PA, potentially causing LV filling and distention in the absence of an LV vent.

Transesophageal echocardiography can demonstrate a PDA in the upper esophageal ascending aortic short axis view with color Doppler flow mapping, showing left-to-right shunting as high-velocity flow in the region of the left PA (1,3). IV agitated saline injection may show microbubbles in the descending aorta with bidirectional shunting (4), or echolucency in the main PA with left-to-right flow. The Qp/Qs ratio quantifies the amount of shunting and can be calculated using blood oximetry or two-dimensional echocardiography and Doppler.

The anatomic features of a PDA limit the sensitivity of echocardiographic and clinical confirmatory tests; its distal location relative to more proximal intracardiac shunts, such as a patent foramen ovale, may make agitated saline studies less sensitive. Also, a comparison of RA and pulmonary capillary blood may not show an increase in oxygenation from left-to-right shunting if PDA flow was directed into the left PA, away from a right-sided PA catheter.

In our case, the presence of an aortic dissection complicated the diagnosis of a PDA. The expected systolic gradient across the conduit would have been 75 mm Hg systolic blood pressure–PA systolic pressure. In reality, the velocity across the PDA was 2 m/s, yielding an observed peak gradient of 16 mm Hg (Modified Bernoulli Equation; Gradient = 4 x (2 m/s)²). The large difference between the expected and the observed gradients could be explained by kinking of the PDA at its origin by the dissection, by flow originating from the low-pressure aortic false lumen, or by under-estimation of jet velocity due to the intercept angle between the jet and the Doppler beam. The lack of an increase in oxygenation between the RA and pulmonary capillary blood could have been due either to sampling of blood from the right PA, which was not receiving PDA blood flow, or to shunting of deoxygenated blood from the aortic false lumen to the PA.

The presence of a large, silent PDA is surprising in a patient of this age. We offer two explanations for the absence of Eisenmenger's physiology or other late sequelae of left-to-right shunting in this patient. One previous report posits the reopening of a closed ductus arteriosus by an aortic dissection (5). Our patient's chronic dissection may have recannulated her PDA. Alternately, the conduit we identified may have been an aorta-to-PA fistula. Of note, the location of the conduit seen on the patient's preoperative MRI suggested the possibility of an aorta-to-PA fistula rather than a PDA. Although such a structure could be a complication of this patient's longstanding aortic disease, its location and gross appearance in situ suggested a PDA.

Footnotes

This article has supplementary material on the Web site: www.anesthesia-analgesia.org.

Accepted for publication July 17, 2007.

Reprints will not be available from the author.

REFERENCES

1. Russell IA, Rouine-Rapp K, Stratmann G, Miller-Hance WC. Congenital heart disease in the adult: a review with internet-accessible transesophageal echocardiographic images. Anesth Analg 2006;102:694–723[Free Full Text]
2. Webb GD, Smallhorn JF, Therrien J, Redington AN. Congenital heart disease. In: Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's heart disease: a textbook of cardiovascular medicine. 7th ed. Philadelphia: Elsevier Saunders, 2005;1489–552
3. Shyu KG, Lai LP, Lin SC, Chang H, Chen JJ. Diagnostic accuracy of transesophageal echocardiography for detecting patent ductus arteriosus in adolescents and adults. Chest 1995;108:1201–5[Web of Science][Medline]
4. Pantin EJ, Cheung AT. Transesophageal echocardiographic evaluation of the aorta and pulmonary artery. In: Konstat SN, Shernan S, Oka Y, eds. Clinical transesophageal echocardiography: a problem-oriented approach. 2nd ed. Philadelphia: Lippincott, Williams & Wilkins, 2003;214–44
5. Festic E, Steiner RM, Spatz E. Aortic dissection with extension to a patent ductus arteriosus. Int J Cardiovasc Imaging 2005;21:459–62[Web of Science][Medline]

This Article Full Text (PDF) Echo Loop Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Neuman, M. D. Articles by Muehlschlegel, J. D. Search for Related Content PubMed PubMed Citation Articles by Neuman, M. D. Articles by Muehlschlegel, J. D. Related Collections Cardiovascular Monitoring (Cardiac) Echo Rounds Video Clip