Ann Thorac Surg 1997;64:1171-1173
© 1997 The Society of Thoracic Surgeons
Case Report
Cardiac Entrapment During Minimally Invasive Aortic Valve Replacement
Max B. Mitchell, MD,
James M. Brown, MD,
Martin J. London, MD
Departments of Cardiothoracic Surgery and Anesthesiology, University of Colorado Health Sciences Center and Denver Veterans Affairs Medical Center, Denver, Colorado
Accepted for publication May 8, 1997.
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Abstract
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Reduced exposure during minimally invasive valve operations poses new difficulties in intraoperative management. Transesophageal echocardiography improves intraoperative management. During a minimally invasive aortic valve replacement, we encountered unexpected hypotension due to mechanical compression of the right ventricle against the sternum. Transesophageal echocardiography facilitated rapid diagnosis of this problem. Surgeons performing these procedures should be aware of this potential problem.
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Introduction
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Minimally invasive cardiac procedures are growing in popularity [1]. Although most attention has been directed at myocardial revascularization, Cosgrove and Sabik [2] have recently reported their experience with aortic valve operations using a right-sided parasternal incision. This incision can also be used for mitral valve operations [3]. Smaller incisions may have physiologic or psychological benefits; however, limited cardiac exposure poses new challenges for surgeons and anesthesiologists who may encounter different hemodynamic responses than with routine sternotomy. We report a case of hypotension shortly after weaning from cardiopulmonary bypass in a patient undergoing minimally invasive aortic valve replacement, which resulted from mechanical compression of the right ventricle against the sternum and was diagnosed by intraoperative transesophageal echocardiography (TEE).
A previously healthy 51-year-old man was admitted to the Denver Veterans Affairs Medical Center for evaluation of dyspnea and chest pain on exertion. He also reported presyncopal episodes. A harsh systolic murmur was noted on physical examination. Transthoracic echocardiography revealed severe aortic stenosis (estimated valve area, 0.75 cm2), mild left ventricular hypertrophy, normal right ventricular size and function, and normal atria. Cardiac catheterization demonstrated normal coronary arteries and a measured aortic valve gradient of 72 mm Hg (calculated valve area of 0.6 cm2). The cardiac index was 2.4 L • min-1 • m-2 with an ejection fraction of 0.66.
At operation general anesthesia was induced and a multihertz, biplane TEE probe (V501B; Acuson, Mountain View, CA) interfaced to a 128 XP ultrasound scanner was placed. Examination by the attending anesthesiologist revealed a heavily calcified bicuspid aortic valve with normal atrial and ventricular function, no valvular regurgitation, and mild left ventricular hypertrophy. A 10-cm right parasternal incision was made extending from the top of the second rib to the top of the fifth rib. The medial portions of the second through fourth costal cartilages were excised. The ascending aorta was exposed. The pericardium was opened vertically and suspended to the skin using multiple stay sutures. After systemic heparinization, the ascending aorta was cannulated and a retrograde coronary sinus catheter was introduced through the right atrium using TEE guidance. A dual-stage single venous cannula was inserted through the right atrial appendage. A 14-gauge antegrade cardioplegia/venting needle was inserted into the ascending aorta. A left ventricular vent was placed through a pursestring suture in the right superior pulmonary vein, and cardiopulmonary bypass was instituted. With initial antegrade and subsequent retrograde cold blood cardioplegia the aortic valve was replaced with a 19-mm St. Jude HP valve (St. Jude Medical, Minneapolis, MN). Careful deairing with TEE guidance was accomplished using multiple high-tidal-volume ventilations and the ascending aortic vent. Thereafter, the aortic cross-clamp was removed. The patient was defibrillated using external pads with resumption of normal sinus rhythm. After 15 minutes of reperfusion, the patient was weaned from cardiopulmonary bypass with dopamine at 5 µg • kg-1 • min-1.
During initial volume loading after termination of bypass and removal of the venous cannula, the systolic blood pressure fell to 60 mm Hg and did not respond to further volume loading or increased inotropic support. The central venous pressure became markedly elevated at 22 to 24 mm Hg, and the pulmonary artery catheter tracing, which had been pulsatile, was flattened at a pressure of 7 to 8 mm Hg. Transesophageal echocardiographic examination of the four-chamber, transverse view revealed a distended right atrium with bowing of the intraatrial septum toward the left (Fig 1
). In addition, the outlet portion of the right ventricle appeared compressed. The normal vertical orientation of the heart in this imaging plane was shifted horizontally to the left. Transgastric short-axis imaging through a midventricular plane revealed the right ventricle to be markedly distended and globally akinetic despite a hyperdynamic left ventricle (Fig 2). We thought that this represented compression of the right ventricular outflow tract against the sternum due to excessive retraction with taut pericardial stay sutures. Retraction was reduced and the stay sutures along the left aspect of the incision were removed, allowing the heart to assume a more normal position. This maneuver immediately resulted in hemodynamic stabilization with a systolic blood pressure greater than 100 mm Hg. The pulmonary artery catheter tracing resumed a pulsatile configuration at mildly elevated pressures (30 to 35/18 to 25 mm Hg), and the measured cardiac output was 5.6 L/min. Normalization of right atrial and ventricular function with shift of the heart back to the normal vertical orientation was observed on TEE (Fig 3). No further difficulties were encountered.
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Fig 1. . Transverse long-axis (four-chamber) transesophageal echocardiographic view during period of hemodynamic compromise demonstrating right atrial distention, bowing of the intraatrial septum to the left (arrow), compression of the right ventricle, and abnormal horizontal orientation of the heart. (LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.)
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Fig 2. . Transverse transgastric short-axis view of the right and left ventricle during period of hemodynamic compromise (obtained in systole) demonstrating marked distention of the right ventricle with hyperdynamic function (near cavity obliteration) of the left ventricle. (LV = left ventricle; RV = right ventricle.)
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Fig 3. . Transverse long-axis view immediately after release of pericardial stay sutures and normalization of blood pressure. Note the return of the heart to normal near-vertical orientation, return of intraatrial septum to normal position, and filling of right ventricle. (LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.)
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The remainder of the patient's hospitalization was uneventful. At 3-month follow-up, the patient was well with normal activity and normal exercise tolerance.
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Comment
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Interest in minimally invasive cardiac surgery is high among clinicians as well as the lay public. A variety of techniques are being investigated for myocardial revascularization as reviewed by Calafiore and associates [1]. For valve operations the options are more limited given anatomic limitations and the absolute need for cardiopulmonary bypass. The advantages of the right-sided parasternal incision have yet to be proved, although it may be associated with less postoperative pain, lower potential for wound infection, reduced blood loss, and shorter hospital stays. However, limited exposure of the heart may pose difficulties with intraoperative management as evidenced by this case. Cosgrove and Sabik [2] reported successful aortic valve replacement or repair in 25 patients with no complications. They use intraoperative TEE routinely for deairing of the ventricle after aortic closure. The routine use of intraoperative TEE for cardiac operations and even for minimally invasive coronary artery bypass grafting is not universally accepted [4]; however, we believe our case demonstrates its advantages during valve operations. Although obliteration of the pulmonary artery catheter tracing was another sign that a mechanical problem was present, changes in this modality are subject to other factors (eg, transducer failure). In addition to assisting with placement of the retrograde cardioplegia cannula and deairing, TEE showed the markedly abnormal configuration of the right atrium and ventricle, which led to early recognition and correction of this unusual surgical problem. We now suspend the leftward pericardial edge with more lax stay sutures. This modification prevents excessive tension with retraction, thereby preventing retrosternal compression of the right ventricle.
There are several causes of acute right heart failure after open heart procedures that can be excluded in this case. Protamine had not yet been infused when hemodynamic collapse occurred. Second, air embolism to the right coronary artery was possible but unlikely given a paucity of intracardiac air visualized by TEE before the termination of bypass and the prompt restoration of hemodynamic stability after retraction was released. The immediate restitution of a stable hemodynamic state after repositioning of the heart is also evidence that myocardial protection was adequate. It is also possible that retraction of the heart could have kinked the left pulmonary veins leading to right heart dysfunction; however, the low nonpulsatile pulmonary artery pressure suggests that this was unlikely. A remaining question is why hemodynamic instability was not encountered before the initiation of cardiopulmonary bypass. We believe two factors contributed to our problem. First, while we were inserting the prosthetic valve the retractor was opened beyond the position used before bypass. Second, suspending the left edge of the incised pericardium to a parasternal incision based to the right of the sternum promotes anterior and leftward displacement of the right ventricular outflow tract, bringing the annulus of the pulmonary valve more anterior to the aortic annulus than in the native position. This factor combined with the presence of a rigid prosthetic valve positioned in the aortic annulus creates a situation favoring compression of the right ventricular outflow tract. Surgeons performing valve operations through the limited right parasternal incision should be aware of the potential for cardiac dysfunction due to mechanical distortion of the heart that can occur with minimally invasive exposures.
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Footnotes
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Address reprint requests to Dr Mitchell, Division of Cardiothoracic Surgery, University of Colorado Health Sciences Center, Box C-310, 4200 E 9th Ave, Denver, CO 80262.
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References
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- Calafiore AM, Angelini GD, Bergsland J, Salerno TA. Minimally invasive coronary artery bypass grafting. Ann Thorac Surg 1996;62:1545–8.[Abstract/Free Full Text]
- Cosgrove DM III, Sabik JF. Minimally invasive approach for aortic valve operations. Ann Thorac Surg 1996;62:596–7.[Abstract/Free Full Text]
- Navia JL, Cosgrove DM III. Minimally invasive mitral valve operations. Ann Thorac Surg 1996;62:1542–4.[Abstract/Free Full Text]
- Gayes JM, Emery RW, Nissen MD. Anesthetic considerations for patients undergoing minimally invasive coronary artery surgery: mini-sternotomy and mini-thoracotomy approaches. J Cardiothorac Vasc Anesth 1996;10:531–5.[Medline]
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Abstract
Introduction
