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CARDIOVASCULAR ANESTHESIOLOGY

An Unusual Case of Postoperative Hypoxemia Diagnosed with Transesophageal Echocardiography

From the Cleveland Clinic Foundation, Cleveland, Ohio.

Address correspondence and reprint requests to Michel Rheault, MD, 980 Larche, Quebec, Canada G2K1M2. Address e-mail to michel.rheault{at}gmail.com.

On the second postoperative day after a successful double-baffle technique correction (Fig. 1) of a partial anomalous pulmonary venous return (PAPVR) and coronary fistulae ligation, a 31-yr-old man was diagnosed with progressive hypoxemia. The patient, using a nonrebreather bag with an Fio₂ of 100%, had low oxygen saturation (91%) and Pao₂ (69 mm Hg). A routine workup assessing the common causes of hypoxemia was inconclusive. It included arterial blood gases, electrocardiogram, chest radiograph, and a computed tomography. A transthoracic echocardiogram (TTE) did not offer a sufficient level of precision in its assessment of the interatrial septum because of suboptimal imaging windows. A transesophageal echocardiogram (TEE) was performed in the intensive care unit after the patient was adequately sedated and endotracheally intubated to address the possibility that a baffle malfunction had occurred. The TEE revealed a moderate right ventricular (RV) dysfunction and dehiscence of the patch repair, as well as the presence of bidirectional interatrial blood flow (Fig. 2, Video 1; please see video clip available at www.anesthesia-analgesia.org). In addition, the TEE revealed an anatomically correct presence of the redirected PAPVR toward the left atrium (LA). Despite a turbulent color flow Doppler (CFD) pattern in the redirected baffle the pulsed wave Doppler(PWD) imaging of the baffle blood flow showed normal velocities with the spectral envelope returning to the baseline. These findings confirmed increased flows through an unobstructed baffle. During the reoperation the TEE findings were confirmed and a caudal portion of the partially dehisced patch was corrected (Video 2; please see video clip available at www.anesthesia-analgesia.org, Fig. 3).

View larger version (36K): [in this window] [in a new window]   Figure 1. Midesophageal bicaval view. Color flow Doppler imaging showing surgical correction of the right upper pulmonary vein anomalous return with pericardial patch baffle to the left atrium (top). Pulsed wave Doppler showing unobstructed flow in the baffle (middle). Schematic midesophageal bicaval view (bottom). LA = left atrium; RA = right atrium; RAA = right atrial appendage; RUPV = right upper pulmonary vein to LA baffle; SVC = superior vena cava.

View larger version (31K): [in this window] [in a new window]   Figure 2. Midesophageal bicaval view (top). Partial patch dehiscence with large ASD. Same schematic midesophageal bicaval view (bottom). ASD = atrial septal defect; IVC = inferior vena cava; LA = left atrium; RA = right atrium; RB = dehisced patch; SVC = superior vena cava.

View larger version (53K): [in this window] [in a new window]   Figure 3. Midesophageal bicaval view. Pulsed wave Doppler in the baffle showing unobstructed flow after surgical repair of the dehiscent patch.

PAPVR is a rare condition with an incidence of 0.4%–0.7% on autopsy reports. The most frequent anomaly is when the right upper pulmonary vein (48.5%) communicates with the superior vena cava (SVC) or the right atrium-SVC junction,1,2 with a single pulmonary vein draining the entire lung.2 Because of lower right atrial pressures compared with the LA, blood is preferentially shunted through the anomalous vein, which results in a volume overload of the RV.2 Therefore, the patient’s symptoms are determined by the location and extent of the PAPVR as well as the presence of associated anomalies.2 The surgical management is reserved for patients with symptomatic PAPVR with signs of RV volume overload or RV failure. In addition, it is used to treat asymptomatic patients with a pulmonary-to-systemic flow ratio exceeding 1.5.3 Patients often have associated cardiac anomalies, such as atrial septal defects (ASD), which should be repaired concurrently.1

The double-baffle technique is one of many methods used to redirect the PAPVR flow to the LA.4 Two patches are used for directing the blood flow through an iatrogenic ASD and enlarging the SVC, respectively. In comparison with other techniques, double-baffle repair is associated with a decreased incidence of postoperative baffle and SVC obstruction.4

The comprehensive preoperative TEE examination should include a midesophageal bicaval view to assess the interatrial septum, SVC, and inferior vena cava as well as pulmonary veins location and flow patterns. When detecting the position of an abnormal vein, one can start at 0°, in high esophageal view. The probe is then turned to the left and slowly advanced. The proximity of the left-upper-pulmonary-vein to the LA appendage will help localize it. For the right-sided veins, starting at the same high esophageal position, the probe is turned to the right and then advanced.5 This method helps to identify misconnection of the SVC to the right atrium as well as associated congenital abnormalities.

The comprehensive postoperative TEE examination should focus on localizing and assessing the characteristics of redirected blood flow through the baffle and remaining SVC. The obstruction of the blood flow through the baffle may lead to venous congestion and pulmonary edema. The CFD turbulent patterns can be seen in patients with either obstruction or increased velocities but without the obstruction of blood flow. The addition of PWD imaging may aid in the more accurate assessment of blood flow. The peak pressure gradient obtained via PWD of <6 mm Hg is suggestive of a nonobstructive blood flow.4 In addition, the nonobstructive flow pattern is characterized by the PWD velocity spectral envelope reaching its baseline (zero velocity; Figs. 1 and 3). Interatrial septum should be assessed for residual communications using CFD with a Nyquist limit of 20–30 cm/s, improving the detection of low velocity flows between the atria. Uncorrected interatrial defects may lead to RV volume overload as well as an acute onset of dyspnea or supraventricular arrhythmias.3

Because of the proximity of the TEE probe to the LA, two-dimensional and CFD result in better imaging resolution compared with TTE enabling an accurate perioperative diagnosis of ASD.2 In addition, sensitivity of the TEE in characterizing pulmonary veins and their commitment to the LA is higher than with the TTE.2 Postoperative complications, such as residual shunts, misconnection, or dehiscence of the baffle repair, as well as pulmonary vein baffle and SVC obstruction, can cause hypoxemia and be diagnosed by TEE.

Footnotes

Accepted for publication June 5, 2008.

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

REFERENCES

1. Al-Ahmari S, Chandrasekaran K, Brilakas E, Tahlil W, Dearani J, Malouf J, Gilman G, Seward JB, Tajik AJ. Isolated partial anomalous pulmonary venous connection: diagnostic value of suprasternal color flow imaging and contrast echocardiography. J Am Soc Echocardiogr 2003;16:884–9[Web of Science][Medline]
2. Ammash NA, Seward JB, Warnes CA, Connolly HM, O’Leary PW, Danielson GK. Partial anomalous pulmonary venous connection: diagnosis by transesophageal echocardiography. J Am Coll Cardiol 1997;29:1351–8[Abstract]
3. Aboul Hosn JA, Criley JM, Stringer WW. Partial anomalous pulmonary venous return: case report and review of the literature. Catheter Cardiovasc Interv 2003;58:548–52[Web of Science][Medline]
4. Iyer AP, Somanrema K, Pathak S, Manjunath PY, Pradhan S, Krishnan S. Comparative study of single and double-patch techniques for sinus venosus atrial septal defect with partial anomalous pulmonary venous connection. J Thorac Cardiovasc Surg 2007;133:656–9[Abstract/Free Full Text]
5. Pascoe RD, Oh JK, Warnes CA, Danielson GK, Tajik AJ, Seward JB. Diagnosis of sinus venosus atrial septal defect with transesophageal echocadiography. Circulation 1996;94:1049–55[Abstract/Free Full Text]

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