Implantations are performed in a hybrid operating room with the capabilities of both a traditional cardiac operating room and an angiographic suite. The left-sided femoral artery and vein are accessed percutaneously with standard diagnostic vascular introducers to provide for hemodynamic measurements, continuous monitoring, transvenous right ventricular pacing, injection of contrast media, and vascular access for emergent initiation of femoral-femoral cardiopulmonary bypass (CPB). Right and left heart diagnostic catheterization is performed, including measurement of the AV gradient and aortic root contrast injection. The aortic annulus must measure between 18 and 25 mm for use of the Edwards bioprosthesis.
Detailed operative descriptions of the venous transfemoral antegrade, arterial transfemoral retrograde, and transapical ventricular approach have been published in the cardiology and surgical literature.21–23 We will focus on the aspects of particular importance to the anesthesiologist.
Retrograde Transfemoral Approach
The right femoral artery is accessed percutaneously with a 12F sheath, and a 20–23 mm balloon tipped valvuloplasty catheter is advanced into the AV annulus. Rapid ventricular pacing at 200 bpm creates a low cardiac output state, as indicated by the abrupt fall in systemic pulse pressure (Fig. 3A), and temporary interruption of mechanical ventilation limits respiratory translocation of the heart, both performed to limit displacement of the balloon during inflation. Inflation of the balloon tipped catheter within the AV annulus performs the valvuloplasty. Without rapid ventricular pacing and temporary cessation of cardiac ejection, significant distal movement of the catheter can occur during balloon inflation (Video 1; please see video clips available at www.anesthesia-analgesia.org). After valvuloplasty, a process that takes approximately 10 s, rapid ventricular pacing is terminated, cardiac output is restored (Fig. 3B), and ventilation resumed. The AV gradient is measured again and aortic regurgitation (AR) assessed with transesophageal echocardiography (TEE) and aortic root contrast injection. The 12F sheath in the right femoral artery is then exchanged for the 24F or 26F (depending on prosthesis size) device introducer sheath. Using fluoroscopic guidance, the prosthetic valve, on the deployment catheter, is advanced over a guidewire and positioned within the AV annulus. After rapid ventricular pacing is reinitiated and ventilation paused, the prosthetic valve is deployed by inflating the catheter’s balloon (Fig. 4, Video 2; please see video clips available at www.anesthesia-analgesia.org). Rapid ventricular pacing is promptly terminated and ventilation resumed. Valve deployment takes 10–15 s. Prosthetic valve position and function, blood flow, and ventricular function are immediately assessed with fluoroscopy and TEE (Figs. 5A and B, Videos 3 and 4; please see video clips available at www.anesthesia-analgesia.org). Postimplantation diagnostic heart catheterization is performed, and the delivery system is removed from the right femoral artery.
The large device introducer sheath is removed under direct vision, to allow suturing and patch repair of the femoral arteriotomy. This is often the most time-consuming aspect of the transfemoral procedure.
Antegrade Transapical Approach
A cardiac surgeon performs a left anterolateral mini-thoracotomy, approximately 10 cm long, in the fifth intercostal space, over the LV apex. After opening the pericardium and placement of epicardial pacing wires, purse-string sutures are placed in the apex of the LV. The LV apex is pierced with a hollow needle between the purse-string sutures, and a guidewire advanced through the LV and across the AV into the ascending aorta by fluoroscopic and TEE guidance, taking care not to ensnare the mitral apparatus. A 16F introducer sheath is placed over the wire and positioned in the LVOT; through which the balloon tipped valvuloplasty catheter is advanced antegrade across the AV. Valvuloplasty is performed as with the transfemoral approach, and the AV gradient and regurgitation are assessed. The valvuloplasty sheath in the apex is exchanged for a 33F device introducer sheath and the prosthetic valve deployed as with the transfemoral approach (Fig. 6 and Video 5; please see video clips available at www.anesthesia-analgesia.org). The device and introducer are removed from the apex, as the purse string sutures are tied down. After intercostal nerve blockade with 0.25% bupivicaine, the surgeon closes the thoracotomy in standard fashion.
Complications reflect both the access route to the AV and the valvular procedure itself.
Inherent to the transapical route, minithoracotomy and LV puncture carry risks of LV rupture and postthoracotomy respiratory debilitation.
Inherent to the transfemoral route, large bore vascular cannulation presents surgical challenges upon catheter removal. Femoral and iliac artery damage is common, with variable degrees of hemorrhage.
Irrespective of approach, complications of valvuloplasty, valve implantation, and aortic instrumentation include stroke and aortic dissection. Ascending aortic dissection, a devastating complication, requires open repair. In one case report, iliac vascular tissue, transported to the aortic arch by the device catheter, resulted in fatal embolic stroke.24 There are no specific mechanisms to limit embolic debris during these maneuvers. As mentioned in the “role of TEE,” the presence of high-grade aortic atheroma supports utilization of the transapical approach. Calcification of the native valve provides a strong structural contact for prosthesis implantation but may potentiate perivavular AR. These perivalvular leaks, as discussed in the TEE and results sections, occurred frequently, with variable severity and effect.
Valve embolization has been experienced during initial attempts with the procedure but was not observed in our series. Management of this complication requires repositioning of prosthesis, implantation of an additional valve prosthesis, or emergent sternotomy, CPB, aortic cross-clamping, and aortotomy to remove the embolized valve and perform open AVR.25 As with most developing procedures, a learning curve exists. Practitioners become more precise and successful with valve sizing, positioning, and appropriate strength of implantation, after the first few procedures.23 Ensuring that the majority of the valve rests on the ventricular side of the annular plane during implantation remains an important learning point.
Theoretical complications, which have neither been experienced nor reported, include obstruction of coronary ostia by a malpositioned prosthesis and interference with mitral valve function during catheter positioning or after valve deployment by impingement on the annulus fibrosis.
The complication rates of stroke, cognitive dysfunction, arrhythmias, and respiratory insufficiency, poor outcomes typically associated with cardiac surgery, have yet to be determined. Radiocontrast exposure, particularly in patients with preexisting renal disease, may worsen the propensity for acute kidney injury.
As a consequence to TEE and the surgical intervention typically required for transcatheter valve implantation, all patients at our institution receive general anesthesia with endotracheal intubation. Our approach to the anesthetic care is similar to that of a high risk conventional AV replacement, except that we tailor the narcotic and benzodiazepine administration to allow for emergence and extubation at the end of the procedure. After completion, patients are transferred to a coronary care unit or cardiac surgical intensive care unit (ICU).
A radial artery catheter is placed for dedicated continuous systemic blood pressure monitoring before anesthetic induction. External defibrillating pads and standard American Society of Anesthesiologist monitors are applied. We do not employ thoracic epidural anesthesia, regardless of the potential benefits of intraoperative pain control and postoperative respiratory recovery, because the thoracotomy is small and systemic anticoagulation begins before surgery and continues postoperatively. Patients are loaded with clopidogrel, 300 mg, before the procedure and then continued at a daily dose of 75 mg for 6 mo. Patients are started on aspirin, 325 mg, once daily, postoperatively. Intraoperatively, patients receive 5000 U of heparin before valvuloplasty and then, as needed, to maintain an activated coagulation time >250 s.
After induction of general anesthesia, a single-lumen endotracheal tube is placed, and the TEE is probe positioned in the patient’s esophagus. Despite the left thoracotomy performed during the transapical approach, isolated right lung ventilation with a double-lumen endotracheal tube is not necessary for ventricular apical exposure. Consequently, we avoid exchanging the double-lumen tube to a single-lumen tube at the end of the procedure, in the event that mechanical ventilation should be continued postoperatively. A multilumen vascular introducer sheath with a large infusion port is placed in a central vein, followed by insertion of a pulmonary artery catheter. Infusion pumps are connected. In addition to the vasopressor support often given to anesthetized patients with severe aortic stenosis, vasopressor boluses are commonly given just before periods of rapid ventricular pacing. The consequent increase in vascular tone limits the drop in systemic blood pressure during the marked reduction of cardiac output, maintaining coronary perfusion during and after inflation of the device balloon. After deployment of the valve and termination of rapid ventricular pacing, cardiac rate and rhythm and arterial blood pressure typically return to baseline (Fig. 3B), but bolus administration of a vasopressor or direct current defibrillation via cutaneous defibrillator pads may be required to restore stable hemodynamics. It remains important to assess each patient’s hemodynamic response to rapid ventricular pacing initiation and termination during each of the three pacing periods. The first brief pacing period, during pacing wire capture testing, is less disruptive than the second pacing period, which is longer and includes complete interruption of LV ejection during valvuloplasty, which remains still less disruptive than the third pacing period, which includes more prolonged interruption of LV ejection, during prosthesis deployment. We examine TEE and arterial, central venous, and pulmonary artery waveforms carefully during these periods. If initial pacing wire testing or valvuloplasty creates severe or prolonged hypotension during and after rapid ventricular pacing, the patient may require a larger bolus of a vasopressor before the subsequent pacing period. Key points are summarized in Table 1.
Considerable acute blood loss may occur during removal of the device deployment sheath from the femoral artery or the LV apex.
ROLE OF TEE
All patients receive TEE monitoring during valve implantation. The TEE probe is inserted after endotracheal intubation and removed at the end of the procedure. As with open AVR, one anesthesiologist can perform TEE and manipulate anesthetic and vasoactive drugs during the procedure. However, we typically have two anesthesia providers and often a cardiologist. A comprehensive baseline examination is performed to confirm the diagnosis, assess baseline ventricular function, and detect associated valvular lesions such as mitral and tricuspid regurgitation. Measurements of the AV annulus, LVOT, and proximal aorta are made from the mid-esophageal AV long-axis view to assist size selection of the prosthetic valve and confirm feasibility of successful implantation. The annulus must be between 18 and 21 mm or 22 and 25 mm in diameter, for use of the 23 or 26 mm Edwards’ prosthesis, respectively. The ascending aorta and arch are evaluated for the presence of atheroma. Severe mobile plaque supports utilization of the transapical approach, which avoids manipulation of large catheters in the aorta. Unlike the self-expanding CoreValve, the Edwards’ prosthesis seats solely within the native annulus, eliminating ascending aorta dilation as a contraindication.
TEE and arterial waveform observation are used to verify the lack of ventricular contraction and peripheral arterial pulse-waves during testing of rapid ventricular pacing.
Although fluoroscopy is the primary imaging modality utilized during positioning of the crimped catheter-seated prosthesis within the native annulus, we confirm appropriate positioning with the AV long-axis view. Valve function depends on exact positioning of the deployment catheter and valve. The 14 or 16-mm long Edwards prosthesis relies on traction with the native annulus for postdeployment stability. Although the prosthesis must be positioned distal enough to permanently stent open the native AV cusps, slightly more than half of the prosthesis should remain on the ventricular side of the AV annulus. Deployment of the apparatus at the level of the sinuses of valsalva is too distal, may lead to AR, and risks valve embolization. The catheter is positioned so that the proximal end of the valve sits 2–3 mm proximal to the origin of the anterior mitral leaflet on AV long-axis view. Because temporary rapid ventricular pacing appropriately abolishes cardiac ejection, deployment of the valve results in minimal movement of the valve with relationship to the annulus. Although one group noticed 2–4 mm of distal movement during deployment,26 we found postdeployment valve location consistent with predeployment catheter position. Both TEE and fluoroscopy can be used for exact catheter positioning. It may be necessary to withdraw the TEE probe to the level of the aortic arch to prevent obstruction during fluoroscopic imaging.
After valve implantation, short and long-axis AV and ascending aorta TEE views assess the prosthesis position within the AV annulus and the integrity of the ascending aorta. Transgastric and mid-esophageal 4-chamber and 2-chamber views assess ventricular function, wall motion, and mitral valve function. Expected findings include unchanged ventricular function, unchanged or decreased LV end-systolic and end-diastolic volume, unchanged or reduced mitral regurgitation, intact ascending aorta, mild AS, and variable AR. Color flow Doppler assesses AR. Severity is graded by examining the vena contracta, width of regurgitant jet within the LVOT, and depth of regurgitant jet into the LV.8 TEE allows the accurate differentiation between transvalvular and perivalvular AR, a distinction difficult to make by fluoroscopy and aortic root contrast injection.(Videos 6–9; please see video clips available at www.anesthesia-analgesia.org) Reinflating the deployment balloon within the prosthesis, further expanding the valve within the annulus, is often employed for treatment of perivalvular AR. One group utilized this technique in 36% of their transcatheter AV implantations.25 Significant transvalvular AR suggests over expansion of the prosthesis, which may require deployment of a second prosthetic valve within the first (Fig. 7).
Although the aortic valvular prosthesis sits within the aortic annulus, remaining in tight contact with the mitral annulus via the annulus fibrosis, prosthesis implantation does not lead to deleterious changes in mitral function. In fact patients may experience less mitral regurgitation after deployment, secondary to reduced aortic valvular gradient and the consequent decrease in ventricular systolic pressures and volume.
As with any major cardiac intervention, TEE remains invaluable for monitoring intraoperative cardiac function (Table 2). As with open AVR, relief of significant ventricular outflow obstruction increases ventricular ejection and alters cardiac filling. TEE aids in directing fluid resuscitation and vasopressor and inotrope administration.
After institutional review board approval, we examined all patients enrolled in the Revival Trial, within our institution. Columbia University Medical Center is a study site for the Revival Trial, a multicenter, prospective, nonrandomized, feasibility study that examines transcatheter AV implantation in high-risk patients, using the Cribier-Edwards prosthesis. The Revival Trial has institutional review board approval and all patients gave informed, written consent before participation. Enrollment criteria for the Revival Trial included calculated AV area <0.7 cm2 within 6 mo of the procedure, age ≥70 yr, associated comorbid factors such that the surgeon and cardiologist coprinciple investigators agreed that the predicted risk of operative mortality was at least 15%, and a minimum Society of Thoracic Surgery (STS) score of 10.
Between February 8, 2006 and March 22, 2007, 36 study patients underwent transcatheter prosthetic AV implantation, 29 by transfemoral arterial approach and seven by transapical approach. Relevant clinical information is summarized for each patient in Table 3. Median (interquartile range) STS score predicted mortality was 10% (6.3, 17.8),21 and EuroSCORE logistic predicted perioperative mortality was 31% (21.5, 44).27 Two thirds of the patients were female. The median (IQR) age was 84 (78, 89) yr.
The transfemoral approach cohort had a median (IQR) procedure duration of 5.5 (4.5, 6.5) h. The transapical approach cohort had a median (IQR) procedure duration of 4.3 (3.8, 4.5) h.
In our experience, 31 of 36 patients received some vasopressor support during the procedure, but only 5 of 36 received inotropic drugs. For increasing systemic vascular resistance before periods of rapid ventricular pacing, phenylephrine (200–400 μg) or norepinephrine (4–16 μg) was adequate. After these periods, no patients failed to return to their preprocedure cardiac rhythm or were left with severe prolonged hypotension.
The median (IQR) estimated blood loss was 250 (100, 700) mL for the transfemoral group and 200 (100, 500) mL for the transapical group. Fifty-two percentage of the transfemoral patients and 43% of the transapical patients received blood products during the procedure.
Postimplantation AR was common. As assessed by intraoperative TEE, all patients had at least trace central AR, and perivalvular AR ranged from none to severe. Four of the 36 patients had moderate perivalvular AR, and one patient had severe perivalvular AR after prosthesis implantation.
Aortic stenosis in all patients was reduced from severe to mild after balloon valvuloplasty and prosthesis implantation.
Twenty (71%) of the transfemoral patients and three (43%) of the transapical patients met extubation criteria at the end of the procedure. One transapical patient required emergency CPB to control bleeding and repair the LV apex, after removal of the device introducer and securing of the purse string.
We found femoral and iliac artery damage common, with variable degrees of hemorrhage. Twenty-five of the 29 transfemoral patients underwent open surgical patch repair of the arterial access site. This procedure became standard after the first few transfemoral procedures. Three of these patients had femoral/iliac transections requiring ilio-femoral bypass with a synthetic graft, and one patient had their aortic procedure aborted because of iliac artery injury, necessitating immediate major repair in the vascular suite. One of the seven transapical patients underwent patch repair of the left femoral artery access site.
One of the transfemoral procedures was aborted because of persistent kinking of the delivery introducer resulting in inability to properly position the prosthesis within the native valve.
Irrespective of approach, upon valvuloplasty balloon inflation, two patients experienced acute aortic dissection. In one of these patients, this dissection was complicated by severe aortic valvular insufficiency, unstable hemodynamics, and emergent sternotomy, initiation of CPB, and open AV and ascending aorta replacement. This patient died postoperative day (POD) 3 secondary to heart failure. The other patient’s acute aortic dissection encompassed the left main coronary artery and occluded all three aortic arch vessels, leading to death on POD 1.
Four of 36 patients died in our series, two previously mentioned as a consequence of aortic dissection. Another patient had severe postprocedure perivalvular AR and underwent open AVR, mitral valve replacement, and coronary artery bypass grafting on POD 1. After a protracted ICU course, this patient died on POD 41. And finally, a fourth patient underwent an uncomplicated operative course, was transferred to the step-down unit on POD 4, but languished with dyspnea and weakness for 30 days, before readmission to the ICU, and eventual death, also on POD 41, secondary to pneumonia and sepsis.
Transcatheter AV implantation has developed out of an interest and a need for ameliorating aortic valvular disease, specifically degenerative calcific valvular stenosis in elderly high-risk patients. In a recent review, Iung et al.28 found that one third of patients who could benefit from AVR do not receive such treatment because of advanced age or significant comorbidities. Our anesthetic experiences have revealed this procedure to be feasible, even with a high-risk population. Transcatheter valve implantation might provide these high-risk surgical candidates the opportunity for definitive treatment of their aortic stenosis.
Our small case series had a perioperative mortality of 2/36 (5.6%) and an in-hospital mortality of 4/36 (11.1%). This perioperative mortality percentage is comparable with that of open surgery, even though the predicted STS and EuroSCORE logistic perioperative mortality of our patient cohort was higher. Our cohort revealed significant differences between the projected risks of the STS scoring system and the EuroSCORE logistic system. These differences, however, are consistent with other projected risk reports of AVR in high-risk patients and point to concerns of the validity of these preoperative risk-stratifying systems specific to this patient population. In a retrospective analysis of 638 patients whom underwent isolated AVR, Dewey et al.29 found significant bias similar to ours with respect to STS and EuroSCORE systems, particularly with regard to high-risk patients. For proper analysis of outcomes with regard to risk stratification, of different transcatheter approaches, and compared with open AVR, randomized controlled trials are needed and underway (The Partner Trial: Placement of Aortic Transcatheter Valve; clintrials.gov identifier NCT00530894).
Because our series did not randomize or match patients between the two approaches utilized, only a few differences between the transfemoral and the transapical implantations will be discussed. Transfemoral implantation procedures had a significantly longer operative time. Transfemoral procedure patients also tended to have more blood loss. Both of these differences are likely due to the peripheral vasculature injury and meticulous repair after removal of the femoral 24F–26F introducer sheath. And finally, transfemoral patients tended to be extubated earlier than transapical patients. Although speculative, avoiding the mini-thoracotomy inherent to the transapical approach could provide for prompter extubation and less postoperative respiratory morbidity.
The current technology and procedure necessitates general anesthesia, endotracheal intubation, and TEE. TEE provides specific benefits in valve sizing, prosthesis positioning, postimplantation evaluation, cardiac assessment, and anesthetic management. As also demonstrated with the CoreValve prosthesis,30 TEE shows excellent visual agreement with fluoroscopy. TEE facilitates the detection and management of procedure-related complications. In particular, significant perivalvular AR is often treated by additional balloon dilation of the prosthetic AV. Despite these benefits, some centers are performing transcatheter AV implantation with monitored anesthesia care and without TEE.20 This could be advantageous considering the mortality and morbidity risk of general anesthetic induction in patients with significant aortic stenosis.31 However, as a larger range of devices become available, TEE will perform an even more important function in matching patient anatomy with prosthesis selection. Intracardiac ultrasound might be another useful technique that obviates general anesthesia. This imaging technique has not been reported and could interfere with procedure catheters. If performing the transapical approach, the thoracotomy and ventricular puncture will always require general anesthesia.
Although rarely required, rapid conversion of this minimally invasive technique to an open procedure with sternotomy, full heparinization, and CPB may be required. More commonly, hemorrhage may be sudden and significant, necessitating rapid manipulation of vascular tone and intravascular volume resuscitation. Despite utilization of a less invasive approach, transfusion of blood products was needed in approximately half of our case series. Given the hemodynamic perturbations and serious perioperative risks of transcatheter AV implantation, anesthesiologists will be required for cardiovascular management and emergent resuscitation.
More centers will likely begin addressing aortic valvular disease with transcatheter valve implantations in hybrid operative suites.32 Anesthesiologists will care for these debilitated patients, applying the expertise necessary to effectively manage severe cardiac and noncardiac disease, within a multidisciplinary team, at an offsite location. The advent of transcatheter AV implantation requires anesthesiologists to apply familiar concepts, methods, and techniques to a novel procedure.
The authors thank Roy Pizzarello, MD, and Linda Gillam, MD, for echocardiograms.
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© 2009 International Anesthesia Research Society
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