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Ann Thorac Surg 2005;79:339-341
© 2005 The Society of Thoracic Surgeons

Case report

Spontaneous Atrioventricular Groove Disruption During Off-Pump Coronary Artery Bypass Grafting

Jennifer S. Lawton, MD*,a, Seema P. Deshpande, MDb, Paul B. Zanaboni, MDb, Ralph J. Damiano, Jr, MDa

a Department of Cardiothoracic Surgery, St. Louis, Missouri, USA
b Department of Cardiothoracic Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, USA

Accepted for publication August 19, 2003.

* Address reprint requests to Dr Lawton, Division of Cardiothoracic Surgery, Washington University in St. Louis, One Barnes Jewish Hospital Plaza, Queeny Tower, Ste 3108, St. Louis, MO, USA 63110
lawtonj{at}msnotes.wustl.edu


   Abstract
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 Abstract
Introduction
 Comment
 References
 
Atrioventricular groove tear or disruption is a disastrous and technically challenging complication after mitral valve replacement surgery. This report details the untimely spontaneous occurrence of an atrioventricular tear during manipulation of the heart for off-pump coronary artery bypass grafting and its successful repair. Significant distortion of the mitral annulus and elevation of pulmonary artery pressures in the beating heart likely contributed to the spontaneous tear.


   Introduction
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 Abstract
 Introduction
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 References
 
Disruption or tear of the atrioventricular groove is a devastating complication of cardiac surgery that is technically very difficult to repair and often fatal. Spontaneous atrioventricular groove tear during off-pump coronary artery bypass grafting (CABG) has not been previously reported. We report the successful repair of a spontaneous tear of the left atrioventricular groove that occurred with heart manipulation during off-pump CABG.

A 74-year-old woman was admitted with a myocardial infarction (troponin I, 20.0 ng/mL). Comorbidities included previous myocardial infarction, hypertension, diabetes mellitus, and peripheral vascular disease. Physical examination was unremarkable with the exception of obesity (weight, 117 kg).

Cardiac catheterization revealed a left main coronary artery stenosis of 70%, left anterior descending coronary artery (LAD) stenosis of 70%, right coronary artery (RCA) occlusion, an ejection fraction of 30%, and cardiomegaly. Echocardiogram demonstrated a dilated left ventricle, normal left atrial size (3.8 cm), anteroapical hypokinesis, mild mitral regurgitation, and a small pericardial effusion. There was no evidence of calcification of the mitral annulus. Electrocardiogram demonstrated a left bundle branch block. A roentgenogram demonstrated mild cardiomegaly (Fig 1). During the preoperative period, the patient required a transvenous pacemaker for an episode of symptomatic bradycardia.



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  		Fig 1. Roentgenogram demonstrating mild cardiomegaly.

 
The patient was taken to the operating room 1 week later for off-pump CABG. The LAD was grafted with the left internal mammary artery. A suction stabilization system was used on the apex of the heart and on the area surrounding the LAD. No deep pericardial traction sutures were utilized. The patient experienced slight hypotension and elevation of pulmonary artery pressures (from 44/25 to 80/60 mm Hg) intraoperatively. There were no associated ST-segment elevation changes on the electrocardiogram. The patient improved with inhaled epoprostenol sodium (Flolan, Glaxo Smith Kline, Research Triangle Park, NC), volume supplementation, and small doses of norepinephrine (0.01 µg/kg/min). After completion of the LAD graft, the apex of the heart was manipulated to view the lateral wall by using the suction device and gentle manual manipulation. The right pericardial sutures were released, but the right pleural space was not opened widely. This was associated with hemodynamic instability that corrected with return of the heart to the normal anatomic position. Upon mobilization of the heart again, a large amount of oxygenated blood filled the pericardial well. The patient was placed into the Trendelenburg position and immediately placed on cardiopulmonary bypass while manual pressure was held on the area. After arresting the heart, it was evident that there was a tear of the posterior atrioventricular groove (on the left atrial side just inferior to the left atrial appendage). There was no evidence of myocardial infarction, aneurysm, or wall thinning in this area. The tear was repaired with full thickness interrupted 4-0 Prolene (Ethicon, Somerville, NJ) mattress sutures with PTFE Felt strips (Bard Inc, Murray Hill, NJ) on each side. This was then reinforced with a running suture. It was necessary to obliterate the coronary sinus in the suture line. The remainder of the bypass grafts were then completed (both obtuse marginal branches and the posterior descending artery). The patient was weaned from cardiopulmonary bypass on epinephrine, norepinephrine, and dobutamine.

Postoperatively, the patient was kept on bed rest for 1 day, weaned from pressors, and extubated with complete neurologic recovery. Postoperative electrocardiogram demonstrated left bundle branch block, and myocardial injury was confirmed by elevation in troponin I levels with a peak of 30.9 ng/mL on postoperative day 1. Unfortunately, on postoperative day 4, heparin associated thrombocytopenia was diagnosed and confirmed by antibody testing. The patient was immediately placed on a thrombin inhibitor (Argatroban, Glaxo Smith Kline). She subsequently suffered massive pulmonary emboli and systemic emboli to both lower extremities. Transesophageal echocardiogram demonstrated moderate mitral regurgitation and a clot visible in the superior venae cava, the right atrium, the right ventricle, the main pulmonary artery, and in a patent foramen ovale. The patient ultimately expired on postoperative day 15 when support was withdrawn at the family's request.


   Comment
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 Abstract
 Introduction
 Comment
References
 
Atrioventricular groove tear after mitral valve replacement has a reported incidence of 0.5% to 14% and a mortality ranging from 50% to 75% [1]. This anatomic tear has been classified into three types [2, 3]. Although the case reported was not associated with mitral valve replacement, it is most similar to the type I tear described by Treasure and associates [2]. When this complication is associated with mitral valve replacement, it is typically associated with excessive debridement of the mitral annulus, a calcified or fixed mitral annulus, excessive debridement or excision of the papillary muscles, or aggressive retraction of the apex of the heart after prosthetic valve placement. The cause of the reported spontaneous tear is likely related to the elevated left atrial pressure and overdistention, tension on the atrioventricular groove while the heart is actively ejecting, and the use of an inotropic agent. Other contributing factors include cardiomegaly, previous myocardial infarction, advanced age, and the presence of diabetes mellitus.

The atrioventricular groove provides a naturally weakened transitional area [4]. Embryologically, the atrial and ventricular myocardium begin to separate in fetal life at approximately 7 weeks of gestation and complete separation is seen at 12 weeks [5]. Conduction tissue provides the only muscular continuity between the atria and ventricle in adult life. This vulnerable area provided the pressure release for the patient's overdistended, anatomically manipulated heart.

Significant distortion of the mitral annulus with enlargement of the left atrium and pulmonary veins has been demonstrated during manipulation of the heart for off-pump CABG [6]. George and colleagues [6] reconstructed the mitral valve structure at end diastole during manipulation for off-pump CABG using transesophageal echocardiography. They noted that the greatest distortion of the valve occurred during manipulation of the heart to view the lateral wall. Three-dimensional reconstruction of the mitral valve demonstrated that the intracardiac structures were folded primarily at the atrioventricular groove. The greatest mean percent increase in left atrial pressure (66%) was documented using a left atrial catheter in 6 patients during manipulation to perform the left circumflex coronary artery graft. The left atrial pressure increased by only 13% during performance of the LAD graft and by 51% during the posterior descending artery graft construction. The increase in left atrial pressure was associated with an increase in left atrial dimension from 4 cm to 6 cm. The spontaneous atrioventricular groove tear in the patient reported is likely related to the heart manipulation that led to elevation in the left atrial pressure and size with resultant "pop-off" through the vulnerable atrioventricular groove.

Successful reports of repair of atrioventricular groove tears after mitral valve replacement have been accomplished using a pericardial patch with intracardiac as well as extracardiac repair and with complete explantation of the heart followed by repair and reimplantation [1, 4, 7]. Unlike previously described cases, our reported case began off pump. An attempt at repair of such a catastrophic injury should not be made while the heart is beating. A tension-free repair in normal, healthy tissue is paramount, and this can only be accomplished in the empty and arrested heart. In addition, in the case report we described, the risk of air embolus was extremely high while the heart was ejecting.

The postoperative findings of troponin elevation and moderate mitral regurgitation suggest that papillary muscle ischemia occurred as a result of deep repair sutures in the atrioventricular groove. Both branches of the left circumflex coronary artery were grafted in an attempt to minimize ischemia. The patient suffered no ill effects of coronary sinus ligation and no conduction disturbances as a result of the repair.

This case documents the successful repair of a spontaneous atrioventricular groove tear that occurred during off-pump CABG. This devastating complication requires immediate conversion to cardiopulmonary bypass and a tension-free repair. Caution should be exercised in the decision-making process regarding the use of off-pump CABG in patients with significant cardiomegaly and elevation of pulmonary artery pressure during heart manipulation.


   References
Top
 Abstract
 Introduction
 Comment
 References
 

  1. Wei J, Wu C, Hong G, Tung DY, Chang CY, Chuang YC. Autotransplantation of heart for repair of left ventricular rupture after mitral valve replacement. Trans Proceed. 2001;33:3553–3554
  2. Treasure RL, Rainer WG, Strevey TE, et al. Intraoperative left ventricular rupture associated with mitral valve replacement. Chest. 1974;66:511–514[Abstract/Free Full Text]
  3. Miller DW, Johnson DD, Ivey TD. Does preservation of the posterior chordae tendinae enhance survival during mitral valve replacement? Annals Thorac Surg. 1979;28:22–27
  4. Kalangos A, Jornod N, Rognon R, Faidutti B. Successful repair of a right ventricular rupture at the atrioventricular groove. Ann Thorac Surg. 1996;61:995–997[Abstract/Free Full Text]
  5. Wessels A, Markman MWM, Vermeulen JLM, Anderson RH, Moorman AFM, Lamers WH. The development of the atrioventricular junction in the human heart. Circ Res. 1996;78:110–117[Abstract/Free Full Text]
  6. George SJ, Al-Ruzzeh S, Amrani M. Mitral annulus distortion during beating heart surgery: a potential cause for hemodynamic disturbance. A three-dimensional echocardiography reconstruction study. Ann Thorac Surg. 2002;73:1424–1430[Abstract/Free Full Text]
  7. Tayama E, Akashi H, Hayashida N, et al. Repair of left ventricular rupture following mitral valve replacement concomitant with left atrial reduction procedure: intracardiac patch and extracardiac buttress suture. Jpn Circ J. 2001;65:581–583[Medline]



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