Use of an apico-aortic conduit (AAC) serves as an alternative method to treat severe aortic stenosis in elder patients, especially in those with a heavily calcified ascending aorta or prior cardiac surgery. The results of long-term follow-up of AAC are very rare. We reported a case about a successful replacement of late degenerated prosthetic valve following AAC procedure, assisted with extra corporeal membrane oxygenation (ECMO).
An 81-year-old man presented with a severe exertional dyspnea (New York Heart Association (NYHA) class III). Eight years ago, this patient underwent AAC surgery through a left thoracotomy in German Berlin Heart Center due to significant aortic stenosis (peak gradient 80 mmHg (1 mmHg=0.133 kPa), aortic orifice area 0.8 cm2) and porcelain asending aorta. The valved conduit incorporated a 23-mm stentless porcine valve (Freestyle aortic root bioprosthesis, Medtronic Inc., USA) and a 22-mm Dacron graft (Medtronic, Inc.). After the AAC surgery, the patient was all normal at follow-up during outpatient visits for 7 years. But he started to feel progressive dyspnea with exertion in recent 6 months. So he was re-admitted and underwent a thorough systematic evaluation in March 2010. The heart rate was 110 beats/min and blood pressure was 130/50 mmHg. Transesophageal echocardiography (TEE) revealed: (1) The peak gradient (PG) across the native aortic valve was 15 mmHg (aortic orifice area 0.5 cm2), without a detectable antegrade flow through the stenosed valve; (2) AAC was patent (peak flow velocity about 1.8 m/s, PG 13 mmHg) and conduit flow, expressed as a percentage of total cardiac output, was 70%, but severe regurgitation due to a degenerated biological prosthetic valve of AAC was observed (Grade IV) (Figure 1A) ; (3) Left ventricular ejection fraction was 45%. Coronary angiography revealed no stenosis in the coronary arteries. Chest CT revealed severe calcification of the aortic valves, annulus, ascending aorta, and the prosthetic valve. Pulmonary function test showed severe chronic obstructive pulmonary disease (COPD). Replacement of prosthetic valve was needed, and ECMO was planned to be used instead of cardiopulmonary bypass (CPB).
General anesthesia was induced, and intubation was performed with a double-lumen endotracheal tube for single-lung ventilation. The patient was prepped in the right lateral decubitus position. The left thoracotomy was performed in the 6th intercostal space. Dissociation of AAC was carefully performed (Figure 1B). ECMO (Medtronic) was instituted using left femoral cannulation. The ECMO system was complemented with a cell saver (Medtronic, Inc.). The 100 U/kg heparin was injected intravenously before the vessel cannulation. During ECMO, activated coagulation time (ACT) was maintained between 160–180 seconds. ECMO was initiated at the beginning of clamping the AAC and terminated when flow was re-established in the conduit. The flow rate was set at 1.8–2.0 L•m−2min−1, nasopharyngeal temperature was kept under normothermia, and mean arterial blood pressure was maintained at 60–70 mmHg during ECMO. During the operation, the heart was kept beating in sinus rhythm without ventricular fibrillation. The operation time was 326 minutes, but total ECMO time was only 52 minutes.
The degenerated prosthetic valve, including a 5-cm long prosthetic vessel, was excised (Figure 1C), and was replaced with a new composite graft with a size 21 mechanical valve and a 22-mm Dacron graft (Medtronic Inc.). The proximal end of the new composite graft was then anastomosed to the proximal end of the existing conduit with running 4/0 Prolene suture in an end-to-end fashion (Figure 1D), and the distal end was anastomosed to the distal end of the existing conduit with the same suture fashion (Figure 1E-1F). The redundant composite graft was then excised.
The patient was weaned from ECMO smoothly in the operation room. Perioperative bleeding was 1860 ml, the loss blood was transfused back by the treatment of the cell saver. And postoperative bleeding was 708 ml, no blood transfusion after operation. The postoperative hemodynamics was stable, and the patient was supported by ventilator for 8 hours. Intensive care unit stay was 2 days and the patient was discharged 10 days after the procedure. Postoperative CT-scan with re-formatting confirmed good function of AAC. Pre-discharge standard transthoracic echocardiography revealed: (1) AAC was patent (peak flow velocity about 1.5 m/s, PG 9 mmHg); (2) conduit flow, expressed as a percentage of total cardiac output, was 72% without regurgitation; (3) left ventricular ejection fraction was 52%.
The AAC surgery has been applied sporadically to high-risk adult patients with acquired aortic stenosis, with over 100 reported cases.1 Early potential complications include myocardial infarction,2 AAC dehiscence from left ventricular apex,3 and so on. The reports of late complications about AAC dysfunction are very rare. Gammie et al1 reported that they had not identified any conduit valve dysfunction after AAC surgery in the follow-up of 4 years. Our result is different from theirs, and reveals that late complications related to valve conduit malfunctions can take place.
This case was done re-operation and had severe COPD. To avoid the detrimental effects of CPB4 associated with deterioration of pulmonary function, and make potential complications more controllable, it was necessary to select less-invasive procedure instead of CPB. In this case, the apical and descending anastomosis sites of original AAC worked well, we only needed to replace the part of degenerated prosthetic valve structure. Theoretically, off-pump technique was possible procedure. However, the heart of this case had adapted a preponderance of cardiac output though the apico-aortic conduit for 8 years, therefore direct clamping AAC of off-pump would let total cardiac output towards native aortic valve, which would lead to the acute increase of afterload and subsequently acute heart failure.
Therefore, in this case an ECMO was used to reduce the risk. To our knowledge this is the first reported case for using ECMO for successful surgical replacement of degenerated prosthetic valve after AAC surgery. During the operation with ECMO, very little anticoagulation was required for the whole circuit. ACT was maintained at a lower level, thus reducing inflammatory response, a major problem in traditional CPB.5 But ECMO was a closed circuit without blood suction, which means challenge presented in the operation was the intraoperative bleeding. So it was necessary to complement ECMO with a cell saver, a stand-by for rapid transfusion.
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