Conventional aortic valve replacement (AVR) is the definitive treatment for severe aortic stenosis (AS). If untreated and symptoms of angina, syncope, or heart failure are allowed to develop, the average survival is 2 to 3 years, with a high risk of sudden death [
1]. However, conventional AVR is associated with a high risk of operative mortality in elderly patients with significant comorbidities such as, severe respiratory dysfunction, renal insufficiency, and compromised cardiac function [
2]. Therefore, the development of minimally invasive therapeutic options is comsidered important. The clinical use of transcatheter aortic valve implantation (TAVI) was first reported in 2002 [
3]. TAVI is now considered a valid alternative to conventional surgery in selected high-risk patients in Europe and North America. The present report describes the first attempt of transfemoral TAVI in Korea and 30-day follow-up.
Discussion
Although conventional AVR is the gold standard treatment for symptomatic severe AS, and operative mortality is low in ideal candidates, its use is limited in the elderly with comorbidities [
2]. Percutaneous balloon valvuloplasty was initially designed to treat valve stenosis less invasively. However, stenosis typically returns within 6 months following valvuloplasty [
4]. Hence, TAVI was developed, and has been widely performed in selected high-risk patients, mainly in Europe and North America. The advantages of TAVI include avoidance of a sternotomy, cardiopulmonary bypass and cardiac arrest, along with a short hospital stay and fast return to functional status [
5].
Recent National Institute for Health and Clinical Excellence (NICE) guidelines and licensing regulations have restricted the use of TAVI to selected patients not suitable for surgical AVR due to high operative mortality and risk of severe complications [
6]. The EuroSCORE is usually used as a predictive risk model [
2] and TAVI is recommended in patients with a logistic EuroSCORE over 20%. Comprehensive baseline examination and careful patient selection is important to avoid complications at implantation. Patients underwent transthoracic echocardiography, coronary and aortofemoral angiography, and a multidetector CT to confirm adequate vascular dimensions and lack of tortuosity or intravascular thrombus. There are several contraindications of TAVI, which may change as the technology develops. These include bicuspid aortic valve (because the altered anatomy makes secure placement of the transcatheter valve which are potentially unstable), previous mechanical AVR, endocarditis, recent myocardial infarction or cerebrovascular accident, moderate to severe mitral or tricuspid valve regurgitation, left ventricular or atrial thrombus, an aortic annular diameter less than 18 mm or over 25 mm, an ascending aorta diameter over 45 mm, severe vascular calcification and aortic disease [
7].
A hybrid operation room (a standard operation room with an additional angiography system equivalent to a standard catheterization laboratory) is recommended for the TAVI as a precaution for emergency such as device embolization, prolonged ventricular fibrillation, and massive hemorrhage. In our cases, the procedure was performed in the cardiac catheterization laboratory with operating room-like sterile precautions. A cardiac surgeon took active part in the procedure, and a vascular surgeon was on call and aware of the ongoing procedure. A perfusionist was present to institute emergency CPB. The anesthesiologist took a participatory role in monitoring and standards of care in the catheterization laboratory for this procedure.
General anesthesia or local anesthesia plus sedation can be used. Elective general anesthesia has many advantages, which includes facilitation of sheath placement, removal, and eventual surgical repair of the arterial access site, immobility during valve deployment, periprocedural TEE, airway management, minimal patient movement, avoidance of breathing artifacts, and rapid CPB institution when necessary [
8]. Anesthetic preparation is identical to that for open cardiac surgery. Short-acting anesthetics are used to facilitate emergence and extubation at the end of the procedure.
The complication rates associated with TAVI have yet to be determined. Reported complications include poor recovery of cardiac function after RVP, paravalvular leakage, AR, myocardial ischemia and device embolization, complete heart block, new-onset arrhythmia, neurological dysfunction or stroke, damage to the vascular access site, and radiocontrast induced acute renal failure [
7]. RVP and cessation of mechanical ventilation interrupt cardiac ejection and minimize cardiac motion, facilitating exact prosthesis positioning within the native annulus. After termination of RVP, heart rate, rhythm, and arterial blood pressure usually return to baseline, but a bolus injection of a vasopressor or defibrillation may be required to restore stable hemodynamics. Both present patients showed stable hemodynamics after RVP. Intermittent bolus injections of phenylephrine (100 µg/ml) were used without continuous infusion of norepinephrine in both patients. Phenylephrine or norepinephrine is adequate for increasing systemic vascular resistance. Catecholamines such as epinephrine may worsen hypotension when administered to patients with left ventricular hypertrophy [
9] and should be used with caution. The second present patient with intermediate coronary artery disease showed aggravation of ST segment elevation despite continuous isosorbide dinitrate infusion. That means deterioration of coronary artery flow after RVP. Therefore, it is necessary to consider the underlying coronary status and allow for sufficient rest periods of 1-2 minutes after RVP. Paravalvular regurgitation is often present immediately after valve deployment, but improves after 24-48 hours as valve morphology alters at body temperature [
7]. Reinflation of the deployment balloon within the prosthesis or further expansion of the valve within the annulus is often employed for treatment of paravalvular AR. Significant AR suggests overexpansion of the prosthesis, which may require deployment of a second prosthetic valve within the first one [
10]. Prosthetic valve embolization occurred in the first present case. We assumed it was the result of the insufficient cardiac standstill. To prevent this, a few seconds of delay for non-pulsatile flow through the aortic valve may be required. Previous reports documented that valve embolization has been experienced during initial attempts with the procedure [
10]. Management of this complication requires repositioning of the prosthesis, implantation of an additional valve prosthesis, or an emergency sternotomy, CPB, aortic cross-clamping, and aortotomy to remove the embolized valve and perform open AVR [
10]. Vascular injury at the access site is the most common complication and causes sudden and significant hemorrhage. Anesthesiologists should be alert to the possibility of a major vascular rupture, which requires urgent repair. To minimize the risk of this complication, careful evaluation of the arterial anatomy is necessary and the diameter of both the femoral and iliac arteries should be large enough for introducer sheath insertion. Also, those arteries should be free of severe calcification and not be tortous. In the first present case, althought the femoral and iliac arteries were considered large enough, sheath insertion was found to be difficult due to intra-arterial calcification. We assumed that rupture of the common iliac artery occurred due to forceful insertion and removal of the sheath. The introducer sheath should be inserted and removed smoothly, and if it becomes stuck as our case, it should be removed in the operating room with preparation for emergency.
Systemic anticoagulation should be commence before TAVI and continue postoperatively. Usually, administering aspirin 300 mg and clopidogrel 300 mg before the procedure and starting regular dose of aspirin 100 mg and clopidogrel 75 mg, soon after the end of the procedure, are recommended [
8]. These are normally continued for 3-6 months. If a patient has been medicated as in our cases, loading dose of aspirin and clopidogrel are not necessary. Patients who re-present after TAVI for non-cardiac surgery can be managed similarly to patients after conventional AVR. There is no evidence that discontinuing anti-platelet drugs increases the risk of valve thrombosis perioperatively, and full heparinization is not required [
7].
Although the procedure is still in its infancy and long-term outcomes are not yet known, the results from the first generation have been encouraging, demonstrating satisfactory technical feasibility, substantial reduction of the transaortic pressure gradient, and fast left ventricular function recovery [
11]. Previous reports demonstrated that perioperative mortality and in-hospital mortality were 0-6% and 6.7-12%, respectively, and that there was no evidence of structural device failure during 2 year follow-up [
7,
10,
11].
In conclusion, TAVI has become an alternative to surgical AVR for the elderly with comorbidities who have a high operative mortality rate or are deemed non-operable. However, judicious selection of patients is important because TAVI can cause several serious complications. A multidisciplinary approach including a trained cardiac surgeon, interventional cardiologist, and cardiac anesthesiologist and a hybrid operation room is essential to provide safe and successful service. Anesthesiologists must be aware of entire procedure and be prepared for sudden hemodynamic deterioration, which may require inotropic support, defibrillation, massive fluid infusion, or emergency surgery.