Repair of ascending aortic aneurysm after heart-lung transplantation – A paediatric case report

Introduction

Ascending aortic aneurysm is a rare but fatal complication after heart-lung transplantation. ¹ Mortality is reduced if unruptured aneurysms are promptly detected and repaired. ² The site of anastomosis of donor and recipient aorta is a potential source of complications because of infection, compliance mismatch and hemodynamic factors. An abrupt change in systolic pressure after heart transplantation puts the entire thoracic aorta at risk of aneurysm formation. In the general population, aortic aneurysms contribute significantly to global cardiovascular morbidity and mortality, with over 150,000 fatalities estimated each year. According to prevalence surveys, thoracic aortic aneurysms can occur in 1.6% to 7.2% of older persons in some situations. Although data on transplant patients are limited, one large US inpatient sample reported a 0.81% prevalence of aortoiliac aneurysms in heart transplant recipients. The frequencies of aortoiliac aneurysms were 0.81% in heart transplant recipients, 1.37% in single lung recipients, 0.91% in double lung recipients, 0.42% in liver recipients and 0.42% in kidney recipients. ³

Most patients present to emergency as acute dissections or ruptured aneurysm which is fatal. Unruptured aneurysms tend to progress at a rate that varies from patient to patient, and prompt surgical treatment is advised to prevent any catastrophic events. ⁴

Case report

A 13-year-old girl with idiopathic primary pulmonary hypertension underwent heart-lung transplantation. The donor was a 26-year-old female who suffered a massive intracranial bleed. She was discharged on postop day 20 and was under regular follow-up and medication.

Eight months later, she presented with dysphonia, dysphagia and dry cough. There was no infection, echocardiography showed normal ejection fraction, valves and aortic root. Computed tomographic scan: Large sacculo-fusiform aneurysm of the ascending aorta (67 × 53 mm) 2.3 cm distal to aortic root to 1.8 cm proximal to brachiocephalic artery origin (Figure 1).

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Figure 1.

(A) Site of anastomosis of donor and recipient aorta; (B) reconstructed images of Computed tomographic (CT) scan done 8 months after transplant (1. Aortic Root; 2. Aneurysm; 3. Innominate Artery; 4. Descending Aorta).

Redo sternotomy was performed, sub-sternal and pleural adhesions were released. Fusiform aneurysm of the ascending aorta with uneven margins, measuring 10 × 8 × 8 cm noted occupying pericardial cavity.

Cardiopulmonary bypass (CPB) was established using peripheral cannulation. Adhesions around the aneurysm were released. Cross clamps applied just proximal to innominate origin. Transverse aortotomy was done, and direct ostial delnido cardioplegia was given. Aneurysmal aorta had thinned-out walls and was exercised completely. Ascending aorta replaced with 18 mm woven collagen-coated polyester tube graft with continuous 5.0 prolene supported by Teflon felt. Patient was rewarmed and weaned off CPB in normal sinus rhythm. She had an uneventful post-operative course and was discharged on post-operative day 8. Intraop specimens for microbiology and histopathology showed no infection, normal aortic tissue and no evidence of connective tissue disorder (Figure 2).

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Figure 2.

Intra-operative pictures of aneurysm repair. (A) Aneurysm; (B) Right ventricle; (C) Resected aneurysm with thinned-out walls; (D) Cross clamp; (E) Graft.

Discussion

Common aortic complications after transplantation include aortic dissection, mycotic pseudoaneurysm and less commonly true aneurysms. The aneurysm was non-infective, unruptured and discovered in a hemodynamically stable patient, a circumstance that has received comparatively less attention in the literature. ²

The angle of incidence of donor aorta with the recipient aorta plays a role in creating wall stress: sharper the angle, more linear the flow, and hence, the lower the asymmetric systolic tension on the recipient aorta. Preventing excessive donor aorta length and limiting the angle of incidence to 45 degrees reduce the stress at the anastomosis. ⁵

Atherosclerosis and hypertension can predispose patients to the formation of aneurysms or dissections. Screening transplanted patients for aortic aneurysms via echocardiography will increase detection and facilitate elective repair. Given transplant recipients’ immunosuppressive status and lifelong exposure to vascular risk factors (hypertension, steroids, chronic inflammation), a surveillance imaging protocol (e.g., annually or biennially) of the entire ascending aorta (donor and recipient segments) may be justified. Screening of the donor for the presence of connective tissue disorders or genetic mapping of the donor tissue before the transplant or during the post-operative endomyocardial biopsy specimen collection may help in predicting the risk of aneurysm development.

In conclusion, the site of aortic anastomosis is a potential source of aneurysm. Discrepancy in tissue quality between the donor and recipient aorta is responsible for compliance mismatch that causes a difference in wall tension, causing critical stress at the anastomosis. Tendency of donor heart for any connective tissue disorders plays an important role in post-operative aortic complications. Screening for any such diseases or genes predisposing to them can help in post-operative risk assessment. Prompt diagnosis and early repair of aneurysm help in avoiding expansion of aneurysm and prevention of rupture.