4.2.2 Coarctectomy and Classic End-to-End Anastomosis without Cardiopulmonary Bypass
Exposure and dissection for this operation does not extend into the transverse arch, which may be the reason why it has failed in so many cases. Figure 4.5 is a diagrammatic cartoon showing the line of resection (dotted lines) for the eventual operation. Figure 4.6 shows the clamps being applied to the transverse arch distal to the left subclavian artery and the descending aorta downstream of the resected coarcted segment. Figure 4.7 shows the completed anastomosis. This operation is rarely performed now because of the success of the extended end-to-end anastomosis. It is shown here because an adult congenital heart surgeon may encounter patients who have had this operation.
4.2.3 Patch Aortoplasty
Patch aortoplasty for coarctation repair is not used routinely in the present era because long-term clinical outcomes have documented a high incidence of false aneurysms. False aneurysm formation appears to be more common when the posterior coarctation shelf is shaved and results in a weakening of the aortic wall opposite the patch (the wall that becomes aneurysmal). In addition, false aneurysm formation may be associated more often with the use of Dacron as a patch than with the use of Gore-Tex. This operation can be used in some circumstances, however, such as in patients with a long segment of coarcted aortic tissue (Fig. 4.8). It may also be employed in patients who have had recurrent coarctation as a result of previous repairs, although close follow-up after such an operation is warranted. Figure 4.9 shows the application of the clamps, with an incision being made in the dotted area to expose the coarcted area for a patch aortoplasty (Fig. 4.10). Figure 4.11 shows the method of trimming the ovoid polytetrafluoroethylene (PTFE) patch, which can be placed to account for growth of the surrounding aortic tissue. Figure 4.12 shows PTFE aortoplasty using running suture technique in process. Figure 4.13 shows the distal portion of the patch aortoplasty being accomplished, and Fig. 4.14 shows a completed PTFE patch aortoplasty. As noted, PTFE aortoplasty is now reserved for long-segment coarctation or reoperative surgery, mainly because of the associated complications, which include aortic aneurysm of the opposite side of the graft (possibly caused by overenthusiastic resection of the posterior shelf) and false aneurysm owing to weakening of the aortic wall, suture line disruption, or infection.
4.2.4 Subclavian Flap Aortoplasty
The idea that subclavian flap aortoplasty could be successful was based on clinical experience with the classic Blalock-Taussig shunt that required distal ligation of the subclavian artery and was reasonably well tolerated in the infant population on which it was practiced. In addition, subclavian artery when used as a patch could undergo somatic growth and therefore ensure that the repaired coarcted segment would maintain unobstructed flow and avoid the problems of recurrent coarctation. Figure 4.15 shows the relevant anatomy, highlighting the extent of the subclavian artery dissection. The dotted lines indicate the longitudinal incision that is required for the subclavian flap aortoplasty and the area of subclavian artery transection. Figure 4.16 shows application of the transverse arch and descending aorta clamps, with the ductus arteriosus ligated and divided. The subclavian artery has been ligated, incised, and is now free to be placed onto the coarcted segment for repair. Figure 4.17 shows the subclavian flap being sutured to the edges of the aorta, thereby completing the flap aortoplasty (Fig. 4.18).
4.2.5 Coarctectomy and Interposition Graft Using Partial Cardiopulmonary Bypass
In general, left heart (partial) bypass is typically used to ensure adequate distal perfusion pressure (>40 mmHg) in the older patient. Left heart bypass is almost always necessary in the setting of recoarctation because there is typically less collateralization. Test occlusion of the aorta proximally and distally with analysis of the radial and femoral artery pressures can be performed; if the distal pressure is easily maintained above 40 mmHg, left heart bypass can be avoided. Importantly, if the perfusion pressure is less than 40 mmHg and the anesthesia team is administering high doses of inotropes in an attempt to maintain an acceptable distal perfusion pressure (that usually results in a very high proximal aortic pressure), then left heart bypass should be applied to avoid any potential spinal cord injury.
Although no categorical reason for paraplegia has been identified in patients who undergo coarctation repair, several risk factors have been noted in the literature. It appears that a long cross-clamp time, hyperthermia during the cross-clamp time, and decreased distal perfusion pressure in the lower extremities are important considerations for the development of paraplegia and should be avoided. We avoid cross-clamp times longer than 30 min, preferring periods between 15 and 20 min, and we never apply an aortic cross-clamp if the somatic temperature is above 37° C. If the temperature is above 37 °C, we place iced saline in the chest to decrease the temperature before the application of a cross-clamp. In a similar protective manner, we also measure the distal aortic pressure in patients to determine the perfusion pressure. When the perfusion pressure is below 40 mmHg (as measured by a distal arterial line), we consider partial (left heart) cardiopulmonary bypass. Figure 4.19 shows a completed dissection of the transverse arch, ductus arteriosus, and descending aorta in preparation for coarctectomy and interposition graft repair. When the perfusion pressure in the lower extremity falls below 40 mmHg, preparations can be made for partial cardiopulmonary bypass. After systemic heparinization, an arterial line is placed in the descending aorta (if a femoral arterial line is not in place), well away from the area of coarctectomy. Figure 4.20 shows a longitudinal incision in the pericardium just posterior to the phrenic nerve for identification and isolation of the left superior pulmonary vein or left atrial appendage. Once the left atrium is identified, a purse-string suture is placed at the junction of the left superior pulmonaryvein and left atrium. A pulmonary venous cannula (right angle 22 or 24) is placed, making sure to avoid any air entry. Cardiopulmonary bypass can then be commenced in this manner by adjusting the arterial flow to approximately 40% of cardiac output and adjusting left atrial drainage to allow upper extremity pressure in the normal range for the patient. Selective right lung ventilation is carried out during this time. Figure 4.21 shows partial cardiopulmonary bypass in process; the arrows illustrate the bypass circuit flow. Two clamps are placed, isolating the stenotic segment; the dotted lines show the anticipated resection. In this case, an interposition graft may be employed. Figure 4.22 shows the proximal anastomosis in process, using a Dacron graft. Note that the recurrent laryngeal nerve is identified and preserved. Figure 4.23 shows the completed repair after separation from cardiopulmonary bypass with the interposition graft in place; this provides an anatomic reconstruction of the descending thoracic aorta. In our experience, resection and end-to-end anastomosis is usually not feasible without undue tension at the anastomosis, so an interposition graft is used routinely.