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Eur J Cardiothorac Surg 2007;31:16-21. doi:10.1016/j.ejcts.2006.10.023
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved
Divisions of Cardiac Surgery and Cardiology, St. Paul's Hospital, University of British Columbia, Vancouver, Canada
Received 31 August 2006; received in revised form 3 October 2006; accepted 6 October 2006.
* Corresponding authors. Address: Division of Cardiothoracic Surgery, St. Paul's Hospital, Room 489, 1081 Burrard Street, Vancouver, BC, Canada V6Z 1Y6. Tel.: +1 604 806 9349; fax: +1 604 806 8375. (Email: jye{at}providencehealth.bc.ca; svlichtenstein{at}providencehealth.bc.ca).
| Abstract |
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Key Words: Aorta Catheter Stenosis Valves Valvuloplasty
| 1. Introduction |
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Several groups have pursued the development of transcatheter valves [713]. Percutaneous aortic valve implantation (AVI) in humans was first performed as a femoral transvenous procedure with antegrade access to the aortic valve [1416]. Subsequently, Webb and co-workers [17,18] reported a femoral transarterial procedure. Our group's initial animal developmental work utilized direct balloon catheter implantation of an aortic valve through the left ventricular apex [12]. Recently, we reported the first successful case in which the transarterial delivery system was utilized to implant an aortic valve via the apex of the left ventricle without CPB in human [19,20]. Subsequently, we have reported our 1-month follow-up data in seven patients who underwent transapical transcatheter aortic valve implantation [21]. We have now completed 6-month clinical and echocardiographic follow-up in this cohort of patients who underwent transapical aortic valve implantation via a left mini-thoracotomy without CPB.
| 2. Methods |
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2.1 Patients
All patients had symptomatic severe aortic stenosis and were judged to be at unacceptably high risk for routine open-heart AVR with CPB because of significant co-morbidity. Mortality risk as estimated by logistic Euroscore [22] was 31 ± 23%. Patients were initially assessed for percutaneous transfemoral arterial valve implantation but were unsuitable due to atherosclerosis or unfavorable anatomy in the aorta and/or ilio-femoral arteries. The clinical characteristics of our initial seven patients are shown in Table 1
. The Euroscore of each patient is listed in Table 1. Three patients (Patients 2, 4, and 5) had low Euroscore, however, they were not accepted for conventional AVR because in patient 2 conventional AVR was abandoned due to porceline aorta, patient 4 had multiple stroke with dementia, and patients 5 had end-stage lung disease.
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2.3 Procedure
Patients were premedicated with aspirin, clopidogrel, and vancomycin. Procedures were performed by a team of cardiac surgeons and cardiologists in an operating room equipped with fluoroscopy. General anesthesia was utilized. Double lumen intubation was found to be unnecessary because lung deflation was not required during the procedure. We now use single lumen intubation in all cases. The apex of the left ventricle was identified by palpation and fluoroscopy. The pleural space overlying the apex (the fifth or sixth intercostal space) was entered via an approximately 5 cm anterolateral mini-thoracotomy. The pericardium over the apex of the left ventricle was identified and opened. Temporary epicardial ventricular pacing wires were placed on the left ventricle. Reliable capture was assured at a rate of between 160 and 220 beats per minute with a reduction in systemic systolic arterial pressure to below 60 mmHg. During valvuloplasty and prosthesis deployment, rapid pacing was utilized to minimize transaortic flow and cardiac motion [19,21].
The thin portion of the left ventricular apex was identified by finger palpation and confirmed by simultaneous transesophageal echocardiographic imaging (TEE). Two paired orthogonal U-shaped sutures with pledgets were placed into the myocardium and passed through tensioning tourniquets. Heparin was administered to achieve an activated clotting time of >250 s. An arterial needle puncture allowed placement of a 7 French sheath through the apex into the left ventricular cavity utilizing a standard over the wire technique. A wire (0.035 in. J-curve Amplatz extra stiffTM, Cook Inc.) was advanced through the aortic valve, around the arch and into the descending aorta for stability. If necessary a balloon catheter (BermanTM, Cook Inc.) was utilized to direct the wire in the direction of arterial flow past mitral chordae and around the aortic arch (rarely required). The 7F sheath was then exchanged for a 14 French sheath. A valvuloplasty balloon (2022 mm, Z-MedTM, Numed Inc., Hopkington, NY) was advanced over the wire to the level of the ascending aorta, evacuated of air and test inflated with diluted contrast. The balloon was withdrawn to the level of the valve as determined by fluoroscopy and TEE. Rapid pacing was initiated and when an adequate reduction in systemic arterial pressure was achieved the balloon was rapidly inflated and deflated [19,21].
The 14 French sheath was exchanged over the wire for a 24 French sheath for valve delivery. The prosthetic valve mounted on a delivery balloon supported by a steerable catheter was introduced through the sheath over the Amplatzer wire. The prosthetic valve was advanced to the aortic valve and placed at the level of fluoroscopically visible valvular calcium. Aortic root angiography via a pigtail catheter introduced from the femoral artery and TEE were used to further aid positioning. When an adequate reduction in systemic arterial pressure was achieved with rapid pacing, the prosthetic valve was deployed using a rapid manual inflation/deflation of the delivery balloon (Fig. 2 ). Following deployment, valve function was assessed by TEE (Fig. 3 ) and angiography. In two of the seven patients, paravalvular insufficiency was excessive and dilatation of the prosthesis was repeated. After removal of the left ventricular sheath, hemostasis was secured with the previously placed pledgeted sutures. The pericardium was approximated to prevent myocardial herniation but allow drainage. A left chest tube was placed [19,21]. Patients were maintained on aspirin indefinitely and clopidogrel for at least 1 month. Transthoracic echocardiography was performed prior to discharge or transfer to another hospital. The authors did not observe any obstruction of coronary ostia in this cohort of patients after the deployment of the tissue valve.
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2.5 Statistical analysis
Normally distributed data were reported as mean ± standard deviation. Non-parametric data were reported as median (inter quartile range). No statistical analysis was performed due to limited sample size in this series.
| 3. Results |
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3.3 Echocardiographic follow-up
Echocardiography was performed prior to hospital discharge (seven patients), and at 1 month (six patients) and 6 month (four patients). Echocardiography performed prior to hospital discharge demonstrated (1) well-seated aortic valves with normal valve function in all seven patients, (2) moderate paravalvular regurgitation in one patient, mild paravalvular regurgitation in two patients, and non or trivial paravalvular regurgitation in four patients, (3) aortic valve area of 1.6 ± 0.6 cm2, and (4) mean transaortic gradient of 10 ± 7 mmHg. These measurements were maintained at 1- and 6-month follow-up (Table 3
). In no patient did paravalvular insufficiency appear clinically significant. Decreases in mitral regurgitation were observed at 1- and 6-month echocardiographic follow-up (Table 3). LV function shows an improving trend at 6-month follow-up (Table 3).
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| 4. Discussion |
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Unfortunately, many potential surgical candidates have significant co-morbid conditions and open-heart surgery with CPB may pose risks that are unacceptable to them or their physicians. According to the Society of Thoracic Surgery Database (19982001) surgical aortic valve replacement carries a rate of serious complication or mortality of 16.8%. Operative risk is increased in the setting of co-morbid conditions including advanced age [24,25]. Our patients were judged poor candidates for routine surgery with an estimated logistic Euroscore operative mortality of 31 ± 23%. The observed 30-day mortality of 14% is encouraging.
The feasibility of percutaneous valve implantation was first demonstrated in an animal model by Anderson et al. [7]. Subsequently several groups, including our own, pursued the development of percutaneous heart valves [713]. Percutaneous aortic valve implantation in humans was first performed as a transvenous transseptal procedure with antegrade access to the aortic valve by Cribier et al. [14,15]. However, the technical complexity and associated risks with this procedure appear likely to limit its widespread application.
Authors reported the development of a transarterial retrograde technique with which initial results have been favorable [17,18]. Evaluation of this procedure is ongoing and remains encouraging. Although the transfemoral arterial procedure has proven successful, some patients are poorly suited to this approach due to femoral, iliac or aortic size, tortuosity, aneurysm, atheroma, or dissection. This has led to the further development of an alterative approach via the left ventricular apex for aortic valve implantation, which is independent of central and/or peripheral arterial size, anatomy, or diseases. Our initial percutaneous valve development had utilized direct balloon catheter implantation from the left ventricular apex in a porcine model [12]. Subsequently, we reported the first successful case of aortic valve implantation via a left mini-thoracotomy and the left ventricular apex without CPB in human [19] and our initial experience in this approach [21].
Valvuloplasty data suggests that stroke is a surprisingly infrequent occurrence despite heavy aortic valve calcification [6,23]. It is likely that the calcific debris familiar to surgeons replacing the aortic valve results from violation of the aortic valve endothelium when resecting the valve. If this covering is kept intact during valvuloplasty and valve deployment, embolization does not occur despite displacement or even crumbling of the calcium within this covering. Coronary obstruction or stroke could conceivably occur due to embolization of friable valvular debris, although this has not been observed with percutaneous valve implantation [17]. In this initial series of seven patients, aortic valvuloplasty and deployment of the aortic prostheses were not associated with stroke or coronary obstruction. Device embolization was an unpredictable concern during early percutaneous experience. However, with accurate positioning, sizing, and deployment techniques, prosthesis embolization appears to be rare as reflected in this initial apical access experience. Furthermore, the inappropriate positioning of prosthesis may be less frequent using the left ventricular apex approach given the nature of its antegrade approach and very short distance to reach the valve.
The transapical transcatheter approach to aortic valve implantation is safe and reliable with minimal operative risks and good early outcome as reflected in this series. The postoperative recovery, length of hospital stay, and late survival are dependent on preoperative comorbidities. This minimally invasive aortic valve implantation appears to be an acceptable approach to symptomatic aortic stenosis in patients who are deemed to be non-surgical candidates. The procedure provides immediate relief of AS-related symptoms and significantly improves quality of life.
Trivial to mild paravalvular regurgitation appears to be common immediately after successful deployment of prosthesis. However, no worsening of the paravalvular regurgitation was observed during the 6-month follow-up, and in no patient did the residual paravalvular leak appear clinically significant in this series. Significant prosthetic regurgitation was not observed in any patients, and aortic valvular area and transvalvular gradient were stable during 6-month follow-up.
In summary, aortic valve implantation is feasible via a minimally invasive apical approach without the need for cardiopulmonary bypass. The early results in the initial series are favorable. This initial experience suggests minimally invasive transapical approach is a new, viable alternative for patients in whom open-heart surgery is not feasible or poses unacceptable risks.
| Appendix A |
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Dr O. Oto (Izmir, Turkey): As I had presented at the ESC meeting in Barcelona this year, this incision can be done over the aorta easily with just 5 cm of incision, and minimally invasive aortic valve replacement can be easily done with the pump with completely conventional surgical armamentarium. Then this operation can cover any surgical risks, any high-risk patients as well. So while you are making an incision, why dont you do it with a routine conventional surgical armamentarium so that we can perform it on any case with any kind of valve?
Dr Ye: You mentioned minimally invasive aortic valve replacement. I believe that to do the aortic valve replacement you still need use cardiopulmonary bypass, right? You still need cardiopulmonary bypass during the minimally invasive procedure. For this procedure basically you dont need any cannulation or bypass equipment. Our patients were sick with very high operative risk. In some patients predicted mortality was 50 or 60%. And I believe if you dont use cardiopulmonary bypass, perioperative mortality and morbidity would be significantly reduced. This approach without use of cardiopulmonary bypass system would be safer for the very elderly person or sick patient.
Dr H. Alsisi (Cairo, Egypt): First, do you have any way to measure the degree of calcification that in some cases you will not be able to dilate the aortic valve before inserting this valve through the apex of the heart and the risks of emboli from the calcific lesions when you extend the balloon and comment about the paravalvular leak, or any failure? Did you have any failure to dilate the aortic valve, and what do you do if there is severe aortic regurg and you should not inflate the valve at this time?
Dr Ye: I have not had this kind of situation so far. For a severely calcified aortic valve, there is a possibility of having difficulty to dilate the valve. In our series we havent seen this kind of problem.
Dr Alsisi: What is the backup strategy if something happens like this? You will have the bypass ready to go immediately on bypass, or what do you do preoperatively if this situation would happen? It is not in the mind that this might happen?
Dr Ye: I guess there is a possibility, but actually I havent had this experience. I just want to emphasize that this procedure is only for a compassionate use in our patient group. So basically the patient would not be a surgical candidate. We already discussed it with the patient before the procedure. All the patients were assessed by two cardiologists and two cardiac surgeons independently to determine if the patient was a surgical candidate or not. If there is anyone who is a surgical candidate, we will not proceed with this procedure. Before the procedure the patients were told that if any disaster happened, we would not going to put them on the pump. That is why there is no cardiopulmonary bypass pump in OR.
| Footnotes |
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| References |
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