Maintenance of distal aortic perfusion by a heparin-bonded shunt during repair of coarctation of the aorta with minimal collateral circulation

Selection of a Surgical Treatment Approach for Aortic Coarctation in Adolescents and Adults

PURPOSE

Coarctation of the aorta (CoA) in adolescents and adults is relatively rare. Several operative techniques for CoA in adolescents and adults have been reported, but there is still no consensus. This study aims to highlight the use of individual patient characteristics to select optimal treatment strategies for CoA in adolescents and adults.

METHODS

Surgical repair of CoA was performed in five patients (mean age: 34 ± 14 years, range: 13-58 years). All patients had primary CoA, and one had aneurysm above the CoA. One patient had undergone previous aortic valve replacement (AVR) and graft replacement of the ascending aorta. One patient underwent resection of the coarctation without cardiopulmonary bypass (CPB) followed by direct end-to-end anastomosis. Three patients underwent CoA resection with an interposition graft through a lateral thoracotomy with partial CPB. One patient underwent AVR with extra-anatomical bypass (ascending-descending aorta).

RESULTS

No in-hospital deaths occurred, and there were no complications. During the follow-up period, there has been no recurrence of CoA.

CONCLUSION

CoA in adolescents and adults is associated with different issues from those encountered in infant patients, and comprehensive surgery should be performed in all cases.

An Intra-Aortic Shunt Prevents Paralysis During Aortic Surgery in Sheep

INTRODUCTION

Sheep are recommended by the United States Food and Drug Administration as a model for testing cardiovascular tissue, but are particularly prone to spinal cord ischemia and subsequent paralysis during aortic cross-clamping.

METHODS

A shunt consisting of a 9 cm long phosphorylcholine coated 1/4 in. (i.d.) polyvinylchloride tube was inserted through the aortotomy into the aorta to provide blood flow across the operative site. Blood pressure and flow in the distal aorta were measured continuously with an indwelling femoral artery catheter and an ultrasonic aortic flow probe. The hemodynamic effects were measured in seven 45 to 55 kg Suffolk sheep. This shunt was then used to implant decellularized pulmonary artery patches into 25 animals.

RESULTS

Occlusion of the aorta reduced the distal mean aortic pressure from 86.4 +/- 4.6 mmHg to 1.79 +/- 0.4 mmHg (P < 0.001) and opening the intra-aortic shunt restored the distal mean aortic pressure to 67.9 +/- 7.3 mmHg (P = 0.053). Blood flow in the distal aorta was 2.35 +/- 0.37 L/min at baseline and was reduced to -0.01 +/- 0.01 L/min (P < 0.001) with the aorta cross-clamped and returned to 2.49 +/- 0.36 L/min (P = 0.945) when the shunt was opened. Use of this shunt prevented hind leg paralysis in all 24 animals surviving the procedure.

CONCLUSIONS

A simple intra-aortic shunt was effective in restoring blood pressure and flow in the aorta distal to the operative site and prevented hind leg paralysis associated with aortic clamping.

Use of partial cardiopulmonary bypass for coarctation repair through a left thoracotomy in children without collaterals

BACKGROUND

Paraplegia is a devastating complication of coarctation of the aorta (COA) repair. Since 1990 we have used left atrium-to-descending aorta cardiopulmonary bypass (CPB) for COA repair in patients with inadequate collaterals. We reviewed the results with that strategy and compared this CPB group with COA repairs in which CPB was not used to see whether there was any increase in morbidity or delay in recovery.

METHODS

From 1990 to 2006, 11 patients with COA were identified to have inadequate collaterals based on preoperative examination and intraoperative arterial monitoring and test clamp. Left thoracotomy with left atrium-to-descending aorta CPB was used in all. Age ranged from 4.2 to 17.4 years (mean, 8.7 +/- 4.6 years). Two were reoperations for recurrent COA, 3 patients had four prior transcatheter balloon dilatations. One patient had aberrant origin of the right subclavian artery. Operative techniques included resection with extended end-to-end anastomosis (n = 6), interposition graft (n = 4), and patch repair (n = 1). During the same period 71 patients older than 1 year of age had COA repair without CPB. Age ranged from 1.1 to 46.1 years (mean, 7.6 +/- 7.1 years; p = 0.6).

RESULTS

Preoperative imaging of CPB patients demonstrated absence of collaterals (n = 7), possible collaterals (n = 2), small collaterals (n = 1), and anomalous origin of the right subclavian artery (n = 1). Preoperative arm leg gradient in CPB patients was 36.0 +/- 9.0 mm Hg versus 49.9 +/- 15 mm Hg in non-CPB patients (p < 0.01). Mean distal femoral artery pressure with aortic test clamp was 34.3 +/- 4.8 mm Hg in CPB patients versus 49.8 +/- 12.4 mm Hg in non-CPB patients (p < 0.01). Mean CPB flow was 53% +/- 7.3% of calculated total flow. Cardiopulmonary bypass time ranged from 17 to 46 minutes (mean, 27.5 +/- 9.7 minutes). Aortic clamp time in CPB patients ranged from 15 to 33 minutes (mean, 21.6 +/- 6.3 minutes). In the non-CPB group aortic clamp time ranged from 10 to 50 minutes (mean, 23.4 +/- 7.5 minutes; p = 0.5). In the CPB group length of stay ranged from 3 to 7 days (mean, 4.9 +/- 1.3 days), and in the non-CPB group length of stay ranged from 3 to 12 days (mean, 4.7 +/- 1.4 days; p = 0.5). No patient had a neurologic complication. There were no other major complications in the CPB group (eg, bleeding, recurrent laryngeal nerve injury, re-COA).

CONCLUSIONS

Preoperative imaging and a lower arm-to-leg gradient in this series of COA patients suggested inadequate collateral circulation with the potential need for CPB. A femoral artery pressure of less than 45 mm Hg during test clamp was used as an indication for partial CPB. The use of left atrium-to-descending aorta CPB with just over 50% calculated total flow protected the spinal cord in a safe and expeditious fashion. Use of left heart bypass did not affect morbidity or recovery time as compared with COA repair in non-CPB patients.

Repair of aortic coarctation using temporary ascending to descending aortic bypass in children with poor collateral circulation

Aortic coarctation can now be repaired surgically with excellent results. Even though rare, injury to the spinal cord resulting in paraplegia remains a major concern. Preoperative evaluation showing the absence of collateral circulation is valuable in order to introduce protective actions. This report describes our experience using a temporary bypass from the ascending to the descending aorta bypass in children undergoing surgical correction of aortic coarctation in the setting of poorly developed collateral circulation. Between 1990 and 2002, we undertook direct surgical repair in 56 patients with isolated aortic coarctation, 20 as neonates, 11 as infants, and 25 during childhood. From 1998 onwards, we introduced preoperative evaluation of the collateral circulation with magnetic resonance imaging. From that time, we placed a temporary bypass from the ascending to the descending aorta, using a polytetrafluoroethylene tube of 4 to 8 mm diameter, whenever distal pressures were shown to be 25 mmHg or less after test clamping, or when magnetic resonance imaging revealed absence of collateral circulation. We found excellent correlations between the direct intra-operative measurements of distal pressure and the findings at magnetic resonance imaging. Following introduction of the temporary bypass, we observed no neurological complications, nor were there any complications related to bypass. Freedom from restenosis was 96%. Preoperative magnetic resonance imaging, therefore, can accurately visualize poor collateral circulation in children with aortic coarctation. The use of a temporary bypass can possibly eliminate the risk of neurological sequels following direct repair of coarctation in children with poorly developed collateral circulation. The temporary bypass is both easy to apply and safe.

Intraluminal shunt for the thoracic aorta: blood flow and function in chronic studies

BACKGROUND

Aortic cross-clamping during operations on the thoracic aorta may result in paraplegia or kidney failure.

METHODS

A nonshunting method of repair was compared with intraluminal shunting in two groups of young pigs: the no-shunt group, which received simple aortic cross-clamping at the ligamentum for 15 minutes; and the shunt group, which received an aortic graft with a temporary intraluminal shunt and balloon occlusion of the inferior vena cava only during shunt insertion and removal. Blood flow to the spinal cord and viscera was measured with radiolabeled microspheres on days 1, 3, 5, and 7 after operation. Renal and neurologic function and histology also were studied.

RESULTS

In the no-shunt group, there was hyperemia of the lumbar cord compared with the shunt group. There were no significant differences in renal cortex blood flow or creatinine clearance. Seven of 10 animals in the no-shunt group had paraplegia, compared with none in the shunt group. Histologic studies of the lower lumbar cord showed bilateral central necrosis of gray matter in the no-shunt group, but no evidence of necrosis in the shunt group.

CONCLUSIONS

An intraluminal shunt allowed thoracic aorta reconstruction without paraplegia.

Intraluminal shunt for the thoracic aorta: spinal cord and visceral blood flow in acute studies

Aortic cross-clamping during surgery of the thoracic aorta may result in paraplegia or kidney failure. Difficulties associated with external shunts and bypasses have limited their use. Therefore we compared intraluminal shunting to the nonshunting method of repair in neonatal pigs. Blood flow to the spinal cord and viscera was measured with radiolabeled microspheres before, during, and after thoracic aortic cross-clamping or shunting. Two no-shunt groups were studied: One group was clamped distal to the left subclavian artery for 30 minutes and the other for 1 hour. In the intraluminal shunt group, a shunt was placed in the aorta just below the ligamentum arteriosum for 1 hour; it was then removed and the aorta repaired. In the no-shunt groups, there was virtually no blood flow to the lower cord and viscera during the cross-clamp period. Hyperemia of the lower thoracic and lumbar cord occurred in the no-shunt 30-minute group 15 minutes after clamp removal. In the no-shunt 60-minute group, flow initially returned to the lumbar cord but then declined; and after 1 hour of reperfusion it was significantly lower than baseline. Renal blood flow was even more severely affected in the no-shunt 60-minute group, with minimal recovery during the reperfusion period. In the intraluminal shunt group baseline spinal cord and visceral blood flow were maintained during thoracic aortic cross-clamping, without the problems associated with extracorporeal circulation.

Surgical treatment of isolated coarctation of the aorta: 18 years' experience

From March 1967 to February 1985 91 patients aged from 11 months to 53 years underwent surgical treatment of isolated coarctation of the aorta. The surgical procedures in descending order of frequency, were: resection with end to end anastomosis, resection with replacement by a tube graft, patch aortoplasty, and bypass graft. Resection with end to end anastomosis was achieved mainly in younger patients. The number of patients needing other procedures increased with advancing age. Eighty six patients have been followed up (mean 10 years). There were no hospital or late deaths and none of the patients suffered from spinal cord injury. There were three recurrences of the coarctation, all in patients who had had primary reconstruction below the age of one year. The patients were divided into three groups by age: group 1, 0-5 years; group 2, 6-15 years; and group 3, over 15 years. It was found that there was no late hypertension in group 1 while hypertension persisted in 7% of group 2 and in 28% of group 3. Fifty per cent of the patients with persistent hypertension were above the age of 20 years at the time of operation and had resection with replacement by a tube graft. It is recommended that elective surgery for coarctation of the aorta should be performed at the age of 3-5 years to avoid both recurrence of stenosis and persistent hypertension.

Internal temporary aortic shunt for managing lesions of the descending thoracic aorta

An intraaortic shunt was used to maintain distal organ perfusion during experimental descending aortic cross-clamping and graft interposition in the descending aorta. None of the dogs in which this form of shunt was employed developed paraplegia, whereas 60% of the dogs in which no adjunct was used during aortic cross-clamping became paraplegic.