Abstract

Objectives

Valvular aortic stenosis (AS) is a major cardiac valvular disease in geriatric people. Conventional treatment for severe AS is aortic valve replacement through surgery. However, many geriatric patients are considered inoperable due to higher risks for surgery and anesthesia. Transcatheter aortic valve implantation (TAVI), a less invasive procedure, has rapidly developed in recent years as an alternative management option for high-risk AS patients. Herein, we describe our anesthetic experience in the TAVI procedure.

Methods

We included 11 patients who consecutively received transfemoral TAVI in the period from September 2010 to January 2011. All patients received general anesthesia with endotracheal intubation; arterial line placement and central venous catheter insertion were carried out for monitoring hemodynamics. Transesophageal echocardiography was applied for valve evaluation, hemodynamic monitoring, and intraoperative guidance. Patients were transferred to the intensive care unit for further care after surgery. The periprocedural events were recorded.

Results

The mean age of these patients was 82 years. Morphology of the aortic valve in all patients was tricuspid, and the etiology of AS was degenerative calcification. During TAVI, all patients received bolus injections of 5–10 μg norepinephrine just before the rapid pacing stage in order to increase the mean arterial pressure. Only one patient needed continuous infusion of dopamine because of severe preoperative congestive heart failure, and another patient needed continuous infusion of norepinephrine due to relatively old age and suspected low systemic vascular resistance. After TAVI, all patients had the endotracheal tube extubated within 7 hours, except one because of preoperative ventilator dependence. Another male patient stayed in the intensive care unit for 8 days due to postoperative complete atrioventricular block, and he received permanent pacemaker implantation. There was no early mortality.

Conclusion

TAVI is another choice for AS patients who have a high perioperative risk. General anesthesia with endotracheal intubation and application of transesophageal echocardiography can facilitate the use of this new technique by cardiologists. Complete preprocedural evaluation and good intraprocedural cooperation are still the gold standards to achieve successful TAVI and patient safety.

Keywords

anesthesia, generalechocardiography, transesophagealheart valve prosthesis implantationtranscatheter aortic valve implantation;

1. Introduction

Aortic stenosis (AS) is a common valvular heart disease,¹ which is now seen in 2–4% of adults older than 65 years,² and its prevalence is expected to increase with age due to degenerative calcific change of the aortic valve.³ Severe AS is defined as either an aortic valvular area of less than 1 cm² or a mean pressure gradient of the aortic valve of greater than 40 mmHg, diagnosed mainly by echocardiography.⁴ The conventional treatment for severe symptomatic AS is aortic valve replacement through surgery, which is the class-I treatment recommended by American College of Cardiology Foundation, the American Heart Association and European Society of Cardiology guidelines.5, 6 Surgical complications such as stroke, bleeding, and acute renal insufficiency prohibit aortic valve replacement surgery in one-third of elderly patients with severe, symptomatic AS.⁷ These patients are regarded as either inoperable due to poor surgical conditions or being at extreme risk because of poor physical conditions.

Transcatheter aortic valve implantation (TAVI) treats AS by displacing the native valve and replacing it with a bioprosthetic valve, which is delivered using a catheter through the femoral artery (transfemoral placement) or the left ventricular apex (transapical placement).⁸ It obviates sternotomy, cardiopulmonary bypass, and subsequent surgical stress, and thus it enables aortic valve replacement in patients who are not suitable for surgical correction.

Patients with severe AS have high anesthetic risk due to poor cardiac conditions, old age, and coexisting medical problems. The TAVI procedure has many unique aspects that warrant the attention of anesthesiologists. Hemodynamic manipulation is a major concern in TAVI procedures. Herein we have described and analyzed the anesthetic management of the TAVI procedure in our hospital.

2. Patients and methods

The clinical use of transfemoral TAVI was approved by the Department of Health, Executive Yuan. Eleven patients, after providing their written informed consent, received TAVI with the self-expanding CoreValve ReValving System (Medtronic Inc., Minneapolis, MN, USA) during the period from September 2010 to June 2011. They were all diagnosed to have severe AS and were at high perioperative risks according to European System for Cardiac Operative Risk Evaluation (EuroSCORE).⁹ After obtaining the approval of the ethical committee of the hospital, the authors collected data retrospectively.

Preprocedural transthoracic echocardiography (TTE) and coronary angiogram were obtained for all patients. TTE was used to define the characteristics and severity of AS, estimate the valvular size, and evaluate cardiac function. Coronary angiography was performed via the femoral artery to evaluate coronary status, cardiac hemodynamic parameters, aortic morphology, and femoral vascular quality. Prior to TAVI, a combined meeting of anesthesiologists, cardiovascular physicians, cardiovascular surgeons, and technical assistants had taken place, to review the patients’ medical history and discuss the planning of periprocedural management.

The TAVI procedure was performed in the catheterization room. Prior to anesthetic induction, five-lead electrocardiogram, pulse oximetry, and direct radial arterial pressures were monitored in all patients. General anesthesia (GA) was induced with fentanyl (2–3 μg/kg) and etomidate (0.2–0.3 mg/kg), and tracheal intubation was performed under the facilitation with rocuronium (0.6 mg/kg). GA was maintained with sevoflurane in oxygen. After intubation, a central venous catheter was inserted via the left internal jugular vein. A temporary pacemaker was inserted through the right internal jugular vein. A urinary catheter was inserted for monitoring urine output.

Femoral vessels were checked again by standard angiography, and subsequently a cut was made for retrograde advancement of the guidewire to the left ventricle if the femoral artery was not too tortuous. Aortic angiography was performed to check the anatomic structure and locate the coronary arteries. Transesophageal echocardiography (TEE) examination was performed to evaluate the cardiac function and valvular parameters, such as the aortic valve area, pressure gradient, aortic root diameter, and size of sinus of Valsalva. Then valvuloplasty was performed under fluoroscopic guidance.

A CoreValve prosthesis of proper size was advanced through the delivery sheath. Aortic angiography was performed again to clarify the ostium of the coronary arteries. Rapid ventricular pacing (RVP) was used thrice during TAVI: pretest of pacemaker (70–80 beats/minute), balloon valvuloplasty (180 beats/minute for 10 seconds), and deployment (120 beats/minute for 15–20 seconds). We gave all patients a bolus dose of norepinephrine (5–10 μg) prior to the second and third RVP. Then the crimped valve was deployed by withdrawing the sheath under RVP (120/minute) and using fluorography. The position and function of the CoreValve prosthesis was evaluated immediately by fluoroscopy and TEE. Cardiovascular surgeons closed the femoral vessels and wounds, and final femoral angiography was done to check if there were any vascular injuries. All patients were transferred to the cardiac intensive care unit under sedation, where extubation was performed under suitable clinical conditions. The temporary pacemaker was removed 48 hours after the TAVI procedure if it was no more indicated.

Data on variables such as personal profile, aortic valvular parameters (morphology, size of annulus, and postprocedural regurgitation of the aortic valve in TEE), perioperative events, and postprocedural events (time to extubation, days in the intensive care unit, and aortic regurgitation at 1-month TTE follow-up) were collected and expressed as mean ± standard deviation.

3. Results

From September 2010 to June 2011, 11 patients underwent TAVI in our hospital. The demographic data are shown in Table 1. The mean age was 81.7 years (range 76–91 years). All patients received a bolus of 5–10 μg of norepinephrine prior to the rapid pacing stage, to increase the mean arterial pressure. One patient needed continuous infusion of dopamine during the procedure because of a severe preprocedural congestive heart failure, and another needed continuous infusion of norepinephrine due to relatively old age and suspected low systemic vascular resistance. All patients’ cardiac rhythm returned to the baseline within seconds of stopping RVP, without defibrillation. Perioperative TEE was used in every patient, which revealed that the valvular morphology of all patients was tricuspid and the cause of AS was degenerative calcification.

Table 1. Demographic data.

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Periprocedural events are shown in Table 2. Most of our patients recovered smoothly. One of our patients developed acute lung edema 1 day after TAVI, which subsided after the use of diuretics. Another suffered from transient ischemic stroke with loss of consciousness and aphasia 12 days after TAVI, but the disorders were resolved after supportive care. Five patients had new conductive blocks (3 with left bundle branch block, 1 with complete AV block, and 1 with atrial fibrillation with a rapid ventricular rate) in the first 48 hours after TAVI. All these new blocks recovered within 92 hours, except in one patient with complete AV block who needed permanent pacemaker implantation. Six patients showed mild paravalvular leakage, three of whom showed improvement in TTE at 1-month follow-up. Paravalvular AR got worse (from trace to moderate) 1 month after TAVI. The outcome is shown in Table 3. There were no major vascular complications and early mortality.

Table 2. Patient list.

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Table 3. Post-TAVI outcome.

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4. Discussion

TAVI was first performed in humans by Cribier et al¹⁰ in 2002 via femoral venous cannulation, transatrial septal puncture, and antegrade deployment through the left ventricular outflow tract. At present, TAVI is an alternative choice for severe AS patients who are considered inoperable or have prohibitive surgical and anesthetic risks. However, there are still some lethal procedural complications, including hemodynamic collapse. The outcomes were favorable in our first 11 patients, suggesting that the TAVI technique is feasible in selected patients. TAVI is a novel technique and represents a unique challenge to anesthesiologists.

In preprocedural evaluation, anesthesiologists should pay more attention to predictive factors of intraprocedural instability, such as depressed left ventricular ejection fraction (LVEF), elevated pulmonary pressures, significant mitral regurgitation (MR), incomplete revascularization, collateral dependent coronary circulation, chronic obstructive pulmonary diseases (COPD), heart failure, and acute/chronic renal disease.¹¹ Optimal intraoperative management is based on good preprocedural evaluation and careful planning.

Two anesthetic methods have been implicated for the transfemoral TAVI procedure: GA with endotracheal intubation and local anesthesia plus conscious sedation with GA as a standby.¹² We chose GA for all our patients because GA can guarantee airway safety, maintain immobility, and facilitate the procedure. Besides, cardiopulmonary bypass can be instituted quickly if necessary. Periprocedural results of the 11 patients were satisfactory, without GA-associated complications.

Optimal placement of the CoreValve is essential for success and safety. We used RVP (120 beats/min for 15–20 seconds) and temporarily holding of ventilation during deployment to help limit motion of the heart. However, RVP depresses cardiac output and may severely impair hemodynamic status in AS patients with other comorbidities. Limited duration of RVP and maintenance of a mean pressure of >75 mmHg prior to RVP are advised to avoid prolongation of hemodynamic instability.¹¹ Sustained ventricular arrhythmias may occur spontaneously after RVP, and so defibrillator pads should be placed prior to the procedure. In our institution, we gave all patients a bolus dose of norepinephrine (5–10 μg) prior to the second and third RVP for improvement of the mean blood pressure and coronary perfusion. The cardiac rhythm of all patients returned to the baseline level within seconds of stopping RVP, without defibrillation.

Perioperative complications should be emphasized because most of them can result in hemodynamic instability, and some may even lead to sudden death. The most common perioperative complications are as follows: cardiovascular events (thromboembolism, annular and/or root rupture, and cardiac tamponade), arrhythmias (including conductive block), obstruction of coronary ostia, residual AR, and impaired renal function. Bleiziffer et al¹² reported that 19.7% of patients who received the CoreValve system needed a pacemaker. New conductive blocks occur usually within the first 1–3 days and recover usually within the first 48 hours in most cases. The pathogenetic explanation of rhythm disturbance is not clear, but possibly a continuous pressure exerted by the self-expanding stents may affect the conducting tissues located subendocardially in the left ventricular outflow tract and interventricular septum.¹³ One patient suffered from ischemic stroke during hospitalization. Five patients had new conductive blocks (3 with left bundle branch block, 1 with complete AV block, and 1 with atrial fibrillation with a rapid ventricular rate) in the first 48 hours after TAVI. The patient with complete AV block needed permanent pacemaker implantation.

Impaired renal function is a common comorbidity in severe AS patients. In the TAVI procedure, it is necessary to use a contrast medium under fluoroscopic guide; nephrotoxic effects of the contrast medium may aggravate impaired renal function. Protective strategies, including periprocedural intravenous hydration therapy and limited usage of a low-osmolarity contrast medium, should be adopted in patients at risk. Benefits of nephron-protective agents such as N-acetylcysteine or theophylline are controversial, but may be considered in high-risk patients.14, 15 Loop diuretics increase renal injury after application of a contrast medium, and these drugs should be used cautiously.¹⁶ In our series, no patient had severe renal impairment preoperatively. Cardiologists limited the use of contrast media, and we titrated intravenous fluid supply according to the change of blood pressure and heart rate. Only one patient had an obvious renal response to the contrast medium (serum creatinine changed from 1.92 mg/dL preoperatively to 4.7 mg/dL postoperatively) after TAVI. It returned to the baseline value 1 day after adequate hydration.

TEE can facilitate the use of this new technique in valve size decision, intraoperative hemodynamic management, real-time monitoring of valve implantation, and real-time feedback for any complications. In elderly patients, severe calcification can cause acoustic shadow to impair visualization. Preoperatively, TEE is occasionally required if the transthoracic echocardiographic images are of insufficient quality to describe the aortic valve or root anatomy in sufficient details.¹⁷ Intraoperatively, TEE provides better two-dimensional quality and geometry than TTE in left ventricular outflow tract and aortic root.

A precise measurement of annulus dimensions is important for proper choice of CoreValve size. Implanting an oversized prosthesis may cause aortic root damage, increase the risk of high-grade AV block, or impair optimal stent expansion. An undersized prosthesis may result in prosthetic embolism and severe paravalvular aortic regurgitation. Annular measurements tend to be slightly larger on TEE than on TTE, with a difference of 1.36 mm, as reported by Moss et al.¹⁸ Hutter et al¹⁹ prescribed a very small mean difference of <1 mm, and a strong correlation between TEE, TTE, and dual-source computed tomography. However, calcific aortic annulus is usually not a perfect circle. Relevant differences up to 3 mm in measurement of annular diameter by all measurement methods can happen in different measurement angles. Parameters such as annular diameter, width, and height of sinus of Valsalva can be well achieved in both mid-esophageal aortic long- and short-axis views.

Perioperative aortic regurgitation due to paravalvular leakages or inadequate device expansion is a special problem of TAVI. Minor central or paravalvular regurgitation immediately after the deployment of the valve may be acceptable in patients with preserved ventricular function, and it typically disappears after several hours. Moderate- and high-grade regurgitation are considered poor prognostic factors for long-term outcome, and need further management, such as postdeployment balloon dilatation or delivery of a second CoreValve device. In case of severely depressed left ventricular (LV) function, TEE may underestimate the true severity of the situation, and special emphasis on systemic cardiopulmonary function is essential to rule out acute heart failure.²⁰

In conclusion, TAVI is an alternative choice for severe AS patients who have a higher perioperative risk. GA with endotracheal intubation and TEE can facilitate the use of this new technique by cardiologists. Complete preprocedural evaluation and good intraprocedural cooperation are still the gold standards for successful TAVI and patient's safety. A well-experienced anesthesiologist should be a partner of the team and can influence cardiologists to modify the procedure according to the patient's condition.