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Ann Thorac Surg 1998;65:1481-1482
© 1998 The Society of Thoracic Surgeons

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Control of Endoaortic Clamp Position During Port-Access Mitral Valve Operations Using Transcranial Doppler Echography

^a Department of Cardiac Surgery, Herzzentrum, Universität Leipzig, Leipzig, Germany

Accepted for publication December 8, 1997.

Address reprint requests to Dr Mohr, Herzzentrum, Klinik für Herzchirurgie, Universität Leipzig, Russenstraße 19, D-04289 Leipzig, Germany

	Abstract

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The technique of computer-aided transcranial Doppler echography for continuous control of cerebral perfusion during minimally invasive mitral valve operations using the Port-Access system is described. Temporary displacement of the endoclamp in the aortic arch (brachiocephalic trunk, left carotid artery) is followed by cerebral embolic signals and a sudden decrease in the blood flow velocity in the middle cerebral arteries.

	Introduction

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Cerebral ischemia caused by cerebral emboli (air bubbles, atheromatous plaques) and hypoperfusion of the brain are important factors in the etiology of neurologic dysfunction after cardiopulmonary bypass [1]. As shown by Barbut and colleagues [2], transcranial Doppler echography can effectively monitor cerebral emboli and determine the embolic load during coronary bypass graft procedures.

Minimally invasive mitral valve operations can be performed using the Port-Access technique (Heartport, Redwood City, CA), which is based on a closed-chest cardiopulmonary bypass system. Aortic clamping, cardioplegic arrest, and decompression of the heart are achieved by means of an Endoaortic Clamp (Heartport) that is placed via the femoral artery in the ascending aorta [3]. Distal translocation of the clamp may lead to temporary obstruction of the brachiocephalic trunk and left carotid artery, potentially resulting in hypoperfusion of the brain. Postoperative transient or permanent neurologic damage, which has been described in some cases after Port-Access minimally invasive mitral valve procedures, may be caused by this sequela [4]. Intraoperative transesophageal echocardiography was used to guide and continuously assess placement and position of the Endoaortic Clamp. With transesophageal echocardiography it was noted that the Endoaortic Clamp tends to migrate in the ascending aorta in some cases [5]. Once the left atrium is opened, transesophageal echocardiography fails to locate the Endoaortic Clamp because of air between the transducer and tissue. Application of transcranial Doppler echography to detect cerebral emboli and to continuously monitor blood flow velocity in the middle cerebral arteries (MCAs) was used to bridge this echo-blind period.

	Technique

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Intraoperative computer-aided transcranial Doppler measurement was performed using a Multi Dop X4 machine (DWL Elektronische Systeme GmbH, Sipplingen, Germany) on 21 patients undergoing minimally invasive mitral valve operations. Two-MHz pulsed-wave probes—fixed by a spectacle frame—were positioned transtemporally in front of the ear above the right and left zygomatic arch. The MCAs were simultaneously sonicated to a depth of 53 mm and 48 mm, respectively (multirange principle). This principle allows monitoring of blood flow velocity and detection of cerebral emboli in the MCAs. In 1 patient who underwent minimally invasive mitral valve reconstruction, a sudden decrease in blood flow velocity and simultaneously an appearance of embolic signals in the right MCA were noted during the procedure. Immediate repositioning of the Endoaortic Clamp was followed by an increase of blood flow velocity in the right MCA to a normal level and no more cerebral embolic signals were detected. The event was subsequently reproduced in a 48-year-old male patient with nonischemic mitral insufficiency undergoing minimally invasive mitral valve repair. The Endoaortic Clamp was introduced after initiation of femorofemoral cardiopulmonary bypass. Under transesophageal echocardiographic guidance the clamp was placed over a guidewire in front of the brachiocephalic trunk and partially inflated for a few seconds. Meanwhile the heart was vented through the endopulmonary vent and the distal lumen of the Endoaortic Clamp in the ascending aorta. Again a sudden decrease in blood flow velocity of the right MCA could be demonstrated (Fig 1), whereas there was no evident change in right radial artery pressure.

View larger version (50K): [in this window] [in a new window]   Fig 1. Sudden decrease of blood flow velocity (first arrow) in the right middle cerebral artery and occurrence of embolic signals during positioning of the Endoaortic Clamp in front of the brachiocephalic trunk. After repositioning (second arrow), normal cerebral blood flow velocity (normal Doppler pattern during cardiopulmonary bypass) is demonstrated.

	Comment

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We conclude that computer-aided transcranial Doppler echography is a reliable, noninvasive method to monitor Endoaortic Clamp position during minimally invasive mitral valve operations. Routine transcranial Doppler measurements may help to minimize the possible risk of intraoperatively induced neurologic damage and should be used during minimally invasive mitral valve operations with the Port-Access system.

	References

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1. Barbut D., Lo Y.W., Gold J.P., et al. Impact of embolization during coronary artery bypass grafting on outcome and length of stay. Ann Thorac Surg 1997;63:998-1002.[Abstract/Free Full Text]
2. Barbut D., Yao F.S.F., Lo Y.W., et al. Determination of size of aortic emboli and embolic load during coronary artery bypass grafting. Ann Thorac Surg 1997;63:1262-1267.[Abstract/Free Full Text]
3. Schwartz D.S., Ribakove G.H., Grossi E.A., et al. Minimally invasive mitral valve replacement: Port-Access technique, feasibility and myocardial functional preservation. J Thorac Cardiovasc Surg 1997;113:1022-1031.[Abstract/Free Full Text]
4. Falk V., Walther T., Diegeler A., et al. Echocardiographic monitoring of minimally invasive mitral valve surgery using an endoaortic clamp. J Heart Valve Dis 1996;5:639-647.
5. Mohr F.W., Falk V., Diegeler A., et al. Videoassisted minimally invasive mitral valve surgery using the Port-Access system. Thorac Cardiovasc Surg 1997;45(Suppl 1):171.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Volkmar Falk Thomas Walther Friedrich W. Mohr Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Schneider, F. Articles by Mohr, F. W. Search for Related Content PubMed PubMed Citation Articles by Schneider, F. Articles by Mohr, F. W.