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Ann Thorac Surg 2006;82:e29-e30
© 2006 The Society of Thoracic Surgeons

Case Reports

Neoaortic Root Modification for Late Thrombosis After Norwood Palliation

Eric M. Graham, MDa,*, Huzaifa Shakir, MDb, Andrew M. Atz, MDa, Jeremy M. Ringewald, MDa, Scott M. Bradley, MDb

a Division of Pediatric Cardiology, Medical University of South Carolina, Charleston, South Carolina
b Division of Cardiothoracic Surgery, Medical University of South Carolina, Charleston, South Carolina

Accepted for publication July 19, 2006.

* Address correspondence to Dr Graham, Division of Pediatric Cardiology, Medical University of South Carolina, 165 Ashley Ave, PO Box 250915, Charleston, SC 29425. (Email: grahamem{at}musc.edu).


   Abstract
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 Abstract
Introduction
 Comment
 References
 
A 5-year-old child with hypoplastic left heart syndrome presented with myocardial infarction 2 years after Fontan completion. Evaluation identified a thrombus in his native aortic root. Retrospective review of a prior catheterization revealed stasis in the native aortic root. Surgical thrombectomy was performed after failed medical management. The neoaortic root was revised at the time of thrombectomy in an attempt to reduce stasis in the native aortic root. This case suggests the need to identify anatomic findings that may predispose to coronary artery thrombus formation after Norwood palliation.


   Introduction
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 Abstract
 Introduction
Comment
 References
 
Impairment of coronary blood flow after Norwood palliation has been implicated as the leading cause of death in hypoplastic left heart syndrome (HLHS) [1]. Thrombus in the native aortic root is one potential cause of coronary artery occlusion and myocardial ischemia. A single case in the literature describes successful surgical thrombectomy in this setting [2]. We report a 5-year-old child with HLHS presenting 2 years after Fontan completion with myocardial infarction. Subsequent evaluation revealed thrombus in his native aortic root.

The patient was a 5-year-old boy who was born with HLHS consisting of mitral and aortic valve and left ventricular hypoplasia, with aortic annulus and ascending aortic diameters of 5 mm at birth. He underwent a Norwood palliation at 4 days of age consisting of a side-to-side anastomosis of the proximal aorta and pulmonary artery, homograft arch reconstruction, atrial septectomy, and 3.5-mm modified Blalock-Taussig shunt. He underwent a hemi-Fontan procedure at 7 months and an intraatrial lateral-tunnel fenestrated Fontan procedure at 2.5 years. He was clinically well, maintained only on aspirin.

On the day of admission, he presented to a local emergency department with acute complaints of malaise, nausea, and abdominal pain. An electrocardiogram showed global ST-segment depression. Laboratory data confirmed myocardial ischemia, with levels of creatine kinase at 3255 U/L (normal, 25 to 260 U/L), creatine kinase MB at 177 ng/mL (normal, <4.9 ng/mL), and troponin-I at 430 ng/mL (normal, <0.2 ng/mL). A transthoracic echocardiogram showed new-onset severe global dysfunction, but no intracardiac or aortic root thrombus was seen.

He required intubation, mechanical ventilation, and inotropic medications. The use of extracorporeal membrane oxygenator or mechanical cardiac support was not required. During the following 3 weeks, serial echocardiograms showed gradual improvement in ventricular function. Owing to residual depressed ventricular function, warfarin sodium (Coumadin, Bristol-Myers Squibb, Princeton, NJ) therapy was added to aspirin.

A routine echocardiogram 3 weeks after the acute event revealed a large (about 1 cm) thrombus in the native aortic root that appeared adherent to the aortic valve leaflets and extended just below the coronary arteries (Fig 1). The following day, the thrombus had extended into the left ventricle. A retrospective review of his pre-Fontan catheterization showed the native ascending aorta functioning as a low flow "blind pouch" area with stagnant contrast on aortogram.


Figure 1
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  		Fig 1. Transthoracic echocardiography image from the parasternal long axis window showing the left atrium (LA), hypoplastic left ventricle (LV) and native aortic root (Ao) with a large thrombus in the native aortic root (*).

 
After 56 hours of thrombolytic therapy with intravenous tissue plasminogen activator, no significant change was noted in the aortic root thrombus size, although it was no longer seen in the left ventricle. He was taken to the operating room for surgical thrombectomy. A transverse opening was made in the ascending neoaorta just distal to the sinotubular junction of the native pulmonary and aortic valves. Inspection revealed a 1.5-cm x 1.2-cm thrombus filling most of the native aortic root. The native aortic valve was quite redundant, and was oversewn given the predilection for thrombus formation in the left ventricle.

At the point at which the main pulmonary artery and aorta were approximated, an incision was made inferiorly, going through the sinotubular junction of the native aorta as well as the native pulmonary artery, just posterior to the facing commissure of the pulmonary valve. The incision was extended into the posterior sinus of the native pulmonary root and into the native aortic root to the level of the left coronary artery. The cut edges of the native pulmonary and aortic roots were then approximated side-to-side, leaving a widened opening between the native pulmonary artery and aorta.

The patient had an uneventful recovery and was discharged 10 days later with Coumadin and aspirin therapy. An echocardiogram showed no flow across the native aortic valve, no thrombus, and moderate ventricular dysfunction.


   Comment
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 Abstract
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 Comment
References
 
Impairment of coronary blood flow after Norwood palliation has been implicated as the leading cause of mortality in HLHS. A postmortem examination of 122 patients after Norwood palliation revealed impairment of coronary blood flow in 27%. This was typically caused by precoronary stenosis at the site of the reconstructed neoascending aorta and native aortic root; however, thromboembolus did occur in 2 patients [1]. Another study looking at unexpected deaths after Norwood palliation found 58% of 12 autopsied specimens had some form of myocardial necrosis, ischemia, fibrosis, or calcification [3].

In addition to autopsy cases, positron emission tomography has shown decreased myocardial perfusion and oxygen delivery in infants after Norwood palliation [4]. Given these findings and the dependence on retrograde filling of the native aortic root and coronary arteries, it is not surprising that a sizable thrombus in this location is likely to be lethal.

This patient's ascending aorta at birth was of relatively good size (5 mm) despite severely hypoplastic left ventricle, mitral, and aortic valves. The neoaortic root was revised in an attempt to reduce stasis in the native aortic root. We hypothesize that in the setting of minimal prograde flow across the aortic valve, a larger native aortic root may be predisposed to stasis and thus thrombus formation. This case suggests the need to identify anatomic findings that may predispose to thrombus formation and to surgically modify the reconstructed neoaorta in addition to thrombectomy if thrombus occurs.


   References
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 Abstract
 Introduction
 Comment
 References
 

  1. Bartram U, Grunenfelder J, Van Praagh R. Causes of death after the modified Norwood procedure: a study of 122 postmortem cases Ann Thorarc Surg 1997;64:1795-1802.
  2. Brennan TV, Rodefeld, MD, Tacy TA, Reddy VM, Hanley FL. Late thrombosis of the native aortic root after Norwood reconstruction for hypoplastic left heart syndrome J Thorarc Cardiovasc Surg 2001;121:580-582.
  3. Mahle WT, Spray TL, Gaynor JW, Clark III BJ. Unexpected death after reconstructive surgery for hypoplastic left heart syndrome Ann Thorac Surg 2001;71:61-65.[Abstract/Free Full Text]
  4. Donnelly JP, Raffel DM, Shulkin BL, et al. Resting coronary flow and coronary flow reserve in human infants after repair or palliation of congenital heart defects as measured by positron emission tomography J Thorarc Cardiovasc Surg 1998;115:103-110.



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