Ann Thorac Surg 2006;82:1917-1918
© 2006 The Society of Thoracic Surgeons
How To Do It
Improved Technique to Diagnose a Patent Foramen Ovale During Left Ventricular Assist Device Insertion
Rana E. Majd, BSa,
Minoo N. Kavarana, MDa,
Michael Bouvette, MDb,
Robert D. Dowling, MDa,*
a Division of Thoracic and Cardiovascular Surgery, Louisville, Kentucky
b Departments of Surgery and Anesthesiology, University of Louisville School of Medicine, Louisville, Kentucky
Accepted for publication September 9, 2005.
* Address correspondence to Dr Dowling, 201 Abraham Flexner Way, Suite 1200, Louisville, KY 40202. (Email: jwalsh{at}ucsamd.com).
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Abstract
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Diagnosis of a patent foramen ovale prior to left ventricular assist device placement can be quite difficult, and if missed may result in a significant hypoxemia due to a right to left shunt. We describe a simple and precise way to increase the diagnostic accuracy of patent foramen ovale detection prior to initiating cardiopulmonary bypass for left ventricular assist device placement.
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Introduction
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Placement of left ventricular assist devices (LVADs) as a bridge to heart transplantation is now considered standard therapy for select patients with end-stage heart disease. Due to prolonged waiting times, a significant number of potential heart transplant recipients require varying intervals of LVAD support. Recently the HeartMate LVAD (Thoratec Corp, Pleasanton, CA) has been approved for destination therapy, which may significantly increase the number of devices implanted [1, 2].
A patent foramen ovale (PFO) is present in approximately 25% of the population [3]. Transesophageal echocardiography (TEE) is the best technique for diagnosis of a PFO. In the general population, the diagnostic accuracy of TEE is 86% despite color flow Doppler and bubble studies with standard provocative maneuvers [4]. After initiating LVAD support, the presence of an undetected PFO may result in significant right to left shunting due to the acute drop in left atrial pressure. This can result in significant hypoxemia even with small PFOs, which requires reinstitution of cardiopulmonary bypass (CPB) with attendant morbidity. In addition to hypoxemia, air and debris may be embolized through the PFO with serious systemic consequences. We propose a simple, reliable technique to increase the accuracy of TEE evaluation for the presence of a PFO prior to initiating CPB for LVAD placement.
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Technique
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A 44-year-old man presented with worsening heart failure refractory to medical therapy who required placement of an LVAD. After induction of general anesthesia, TEE was performed. This demonstrated severe left ventricular dysfunction with severe mitral regurgitation. There was significant bowing of the interatrial septum toward the right atrium. On evaluating the heart for possible PFO, color flow imaging was negative. A bubble study was performed after holding the intrathoracic pressure at 50 cm of water. The bubble study was negative. However the interatrial septum remained bowed toward the right atrium upon release of the intrathoracic pressure (Fig 1). The study was repeated twice and failed to show the presence of a PFO. An implantable LVAD was placed in the preperitineal space and the driveline was brought through the abdominal wall. The patient was given a full dose of heparin, and the outflow cannula was then anastomosed to the ascending aorta prior to instituting CPB. Once this anastomosis was completed, aortic cannulation was performed. At this point, the echocardiographer reexamined the atrial septum. The surgeon then manually performed partial occlusion of the pulmonary artery, which resulted in an increase in right atrial pressure and a significant decrease in left atrial pressure. This maneuver was continued until the TEE demonstrated bowing of the septum toward the left atrium. Color flow and bubble studies were then performed (Fig 2). These studies clearly demonstrated the presence of an interatrial shunt. Bi-caval cannulation was performed and CPB was initiated. Examination of the atrial septum demonstrated a PFO that was readily closed. The remainder of the operation was completed using standard techniques. After implantation of the LVAD, the TEE demonstrated bowing of the septum toward the left atrium without the presence of a shunt.
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Fig 1. Transesophageal echocardiography demonstrates bowing of atrial septum toward the right atrium and absence of an atrial shunt. (PFO = patent foramen ovale.)
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Fig 2. Transesophageal echocardiography demonstrates bowed atrial septum toward left atrium and presence of an atrial shunt. (PA = pulmonary artery.)
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We have performed this maneuver in 10 additional patients immediately prior to placement of an LVAD. Standard maneuvers did not demonstrate a PFO in these patients. However, in 2 of these patients the technique previously described suggested the presence of a PFO. Exploration of the atrial septum confirmed the presence of a PFO in these 2 patients. After implantation of the LVAD, no patients demonstrated an interatrial shunt.
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Comment
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A complete echocardiographic examination is essential in patients prior to LVAD placement. The preoperative echocardiogram is done primarily to assess right ventricular function, determine if there is significant aortic insufficiency, and determine if a PFO is present [5]. Diagnosis of a PFO can often be missed in the patients due to equal ventricular compliance that results in no flow across the septum [4]. Patients with predominant left ventricular failure have elevated left atrial pressures and may have no flow across the septum due to apposition of the septum primum and the back of the limbus, which may persist despite standard color flow Doppler and bubble studies.
After institution of LVAD support, even a small PFO may result in significant right to left shunting with subsequent hypoxemia. Standard therapy would consist of reinstituting CPB support and PFO closure, which may have a deleterious effect on right ventricular function and result in worsening coagulopathy, multiorgan dysfunction, morbidity, and mortality [6]. After observing this situation clinically, we sought to determine if there were any maneuvers that would increase the accuracy of echocardiography in the diagnosis of a PFO. We demonstrated that partial occlusion of the pulmonary artery can be safely performed, which results in increased right atrial pressure and decreased left atrial pressure. This results in a marked deviation of the atrial septum toward the left atrium. In the presence of a PFO, this results in right to left shunting, which can be demonstrated on repeat color flow Doppler and bubble study. If the patient does not tolerate this maneuver, rapid institution of CPB can be performed. In addition, this maneuver can be used in any open case to facilitate the diagnosis of a PFO.
In summary, a simple provocative maneuver is described that may improve the diagnostic accuracy of echocardiography in the detection of PFO prior to CPB for LVAD placement.
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References
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- Frazier OH, Rose EA, McCarthy O, et al. Improved mortality and rehabilitation of transplant candidates treated with long-term implantable left ventricular assist system Ann Surg 1995;222:327-338.[Medline]
- Poirier VL. Worldwide experience with the TCI HeartMate system: issues and future perspective Thorac Cardiovasc Surg 1999;47(Suppl 2):316-320.
- Persaud TVN, Moore KL. The developing human: clinically oriented embryology. Philadelphia: Saunders; 2003. pp. 354.
- Sukernick M, Mets B, Benett-Guerrero E. Patent foramen ovale and its significance in the preoperative period Anesth Analg 2001;93:1137-1146.[Free Full Text]
- Augoustides J, Mancini DJ, Horak J, Pochettino A, Dupont F, Dowling RD. Case 1-2003 the use of intraoperative echocardiography during insertion of ventricular assist devices J Cardiothorac Vasc Anesth 2003;17:113-120.[Medline]
- Kavarana MN, Pessin-Minsley MS, Urtecho J, et al. Right ventricular dysfunction and organ failure in left ventricular assist device recipients: a continuing problem Ann Thorac Surg 2002;73:745-750.[Abstract/Free Full Text]
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Abstract
Introduction
