Impairment of Venous Drainage Due to Atrial Septal Aneurysm During Open-Heart Surgery

Impairment of Venous Drainage Due to Atrial Septal Aneurysm During Open-Heart Surgery Sanghun Kim, MD, and Hong Liu, MD I T IS NOT UNCOMMON to encounter inadequate venous drainage during cardiopulmonary bypass. Some common causes include poor positioning and obstruction of the venous cannula, increased resistance due to the small diameter of the venous cannula, and kinks in the tubing that connects the venous cannula to the venous reservoir. We report a case of atrial septal aneurysm (ASA) impairing venous drainage from a 2-stage venous cannula in right atrium during a routine cardiac surgery case requiring cardiopulmonary bypass (CPB). Intraoperative transesophageal echocardiogram (TEE) was instrumental in diagnosis and treatment of the decreased venous drainage. CASE REPORT A 70-year-old male with a history of aortic stenosis presented with worsening dyspnea on exertion. His past medical history was notable for hypertension and hyperlipidemia. Transthoracic echocardiogram (TTE) revealed worsening of aortic stenosis with the aortic valve area about 0.9 cm 2 , transaortic valve mean pressure gradient of 42 mmHg, peak pressure gradient about 80 mmHg, trace aortic regurgitation, and diastolic dysfunc- tion with preserved biventricular systolic function (ejection fraction: 58%). ASA was not speciﬁcally noted on TTE report. TTE videos reviewed at a later time conﬁrmed the initial report. Cardiac catheterization showed severe coronary artery disease involving left anterior descending artery, left circumﬂex artery, and right coronary artery. He presented to the operating room for aortic valve replacement and coronary artery bypass grafting. After induction of general anesthesia, intraoperative TEE showed a large ASA of 20 mm base that moves equal distance towards both right and left atria by 15 mm (Figs 1 and 2 and Video Clips 1 and 2). A 3D TEE midesophageal bicaval view also clearly demonstrated the aneurysm (Fig 3). There was no evidence of patent foramen ovale (PFO) by color ﬂow Doppler interrogation. A saline contrast test was not speciﬁcally done to look for PFO. After heparinization and placement of an arterial cannula in ascending aorta and a 2-stage venous cannula in the right atrium, CPB was initiated without incident. Within a few minutes, however, venous drainage was noted to be sluggish. Due to inadequate venous drainage, full ﬂow could not be achieved on CPB. Because manipulation of the venous cannula and the tubing failed to improve venous drainage adequately, a vacuum was applied to the venous tubing to augment its drainage. However, the venous drainage became signiﬁcantly worse after adding the vacuum. Upon investigation with TEE in midesophageal bicaval view, a portion of ASA was noted to be “sucked” into proximal ports of the venous cannula (Fig 4). The right atrium did not appear to be markedly enlarged indicating there is some venous drainage through distal ports of venous cannula. To relieve worsening of venous drainage, the vacuum was removed and venous tubing was clamped to ﬁll the right atrium and allow separation of the aneurysm from the venous cannula. After readjustment of the venous cannula, there was no evidence of adherence of ASA to the proximal port on TEE. There were no further difﬁculties with venous drainage during cardiopulmonary bypass. The patient received a 25 mm St. Jude Epic porcine bioprosthetic valve (St. Jude Medical, Minneapolis, MN) and coronary artery bypass graft times 3 without repair of the aneurysm. Weaning from cardiopulmo- nary bypass was uneventful. Post bypass TEE showed the bioprosthetic valve in good position with no paravalvular leak, unchanged mitral valve, preserved ventricular function, and intact ASA. DISCUSSION Atrial septal aneurysm is described as a saccular deformity of the interatrial septum that bulges into the right or left atrium with a prevalence of 1% based on an autopsy study. 1 By echocardio- gram, it is deﬁned as protrusion of the aneurysm greater than 10mm beyond the plane of the atrial septum. 2 With widespread use of TTE in the 1980s, several studies found its prevalence to be ranging from 0.2% to 1.9%. 3,4 A recent study based on TEE put its prevalence at 4.3% 5 and suggests that it is a more sensitive diagnostic tool than TTE. 5,6 Although 3D TEE clearly showed the aneurysm in this case, 2D TEE is sufﬁcient to make a diagnosis of ASA. Several studies have classiﬁed ASA based on morphology and movement of the aneurysm. 3,4,7 Based on the most recent study on a classiﬁcation by morphology and movement during the cardiorespiratory cycle, 4 this patient has a type 5 ASA that moves equal distance to both right and left atria (Table 1). While there were occasional case reports of cerebrovascular embolic events in patients with ASA, its clinical signiﬁcance was not appreciated until routine use of echocardiogram found high prevalence of stroke of embolic origin in those patients. 5,9,10 Although not deﬁnitively proven, mechanism is presumed to be due to paradoxical interatrial shunting of thrombus since a high percentage of patients with ASA has PFO. 5,6 Presence of spontaneous echo contrast in the aneur- ismal cavity has been previously reported and thought to be a precursor to thrombus formation. 8 In a patient who presented for routine coronary artery bypass graft surgery, massive thrombus was noted within the aneurismal cavity that subse- quently caused intraoperative embolic stroke. 11 These ﬁndings suggest that source of emboli could be cardiac in origin due to thrombus formation within the aneurysm. It is also not uncommon that thrombus within ASA has been mistaken as an atrial mass preoperatively and found out to be an aneurysm encasing thrombus during surgery for excision of the mass. 12,13 In this case, ASA was not surgically repaired given that it was an incidental ﬁnding with no prior neurological events and evidence of PFO. Other associated congenital cardiac abnormalities shown through echocardiogram include patent foramen ovale, atrial septal defect, mitral valve prolapse, and ventricular septal defect. 2,14 This is the ﬁrst case report describing decreased venous drainage due to ASA during a routine cardiac case requiring CPB. Venous drainage during cardiopulmonary bypass is determined by a cross sectional area of the lumen of the venous cannula, volume of blood in the cannulated vessel or chamber providing central venous pressure, and hydrostatic pressure difference between the cannula location and the From the Department of Anesthesiology and Pain Medicine, Uni- versity of California Davis School of Medicine, Davis, CA. This work was supported by the Department of Anesthesiology and Pain Medicine, University of California Davis Health System. Address reprint requests to Hong Liu, MD, University of California Davis School of Medicine, Department of Anesthesiology and Pain Medicine, TB-170 One Shields Avenue, Davis, CA 95616. E-mail: hualiu@ucdavis.edu © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.jvca.2013.09.001 Key words: atrial septal aneurysm, cardiac surgery Journal of Cardiothoracic and Vascular Anesthesia, Vol 27, No 6 (December), 2013: pp 1339–1342