Current Devices and Techniques

Access routes for TAVI include: peripheral arteries (femoral, axillary), peripheral veins (trans-septal), the LV apex via a small thoracotomy, or the ascending aorta via a mini-sternotomy. According to international registries, the most commonly used approaches currently are transfemoral and transapical (Table 19.1).

A number of prosthetic valves are available. These are generally categorized as balloon-inflated or self-expanding (Figure 19.1). Current areas of focus for new valve design are the ability to retrieve and reposition after deployment, the expansion of the indications by facilitating safe deployment in non-calcified native valves or within bioprosthetic valves and to address some common complications observed with early devices.

(A) Sapien 3 Valve (Edwards Lifesciences).

(B) CoreValve Evolut R (Medtronic).

(C) Acurate neo valve (Symetis).

(D) JenaValve (JVT).

(E) Portico valve (St. Jude Medical).

(F) Direct Flow valve (Direct Flow Medical).

(G) Engager valve (Medtronic).

(H) Lotus valve (Boston Scientific).

Figure 19.1 Valves available for TAVI in Europe.

Procedural Risks

The majority of patients undergoing TAVI are elderly, frail and have numerous co-morbidities. It is therefore crucial to consider not only procedural mortality but also the frequency of non-fatal complications, which are likely to significantly impact the quality of life.

Not surprisingly, TAVI is associated with considerable morbidity, ranging from mild acute kidney injury to catastrophic aortic root rupture. However, there are several complications in particular which are significantly more common with TAVI than with SAVR, and these continue to be a focus of study (Box 19.1). One of the most common complications with early devices was vascular injury, particularly femoral or aortoiliac injury when using large first-generation 22–24 Fr access devices. Design improvements have decreased current access systems to 14–16 Fr, increasing the number of eligible patients and reducing vascular complications. Technological advancements have also reduced the frequency of a paravalvular leak (PVL), a complication much more common with TAVI and, if significant, it is associated with increased mortality. Other important complications more common with TAVI include stroke and conduction block, requiring a permanent pacemaker.

It is important to note that the incidence of specific complications varies with the choice of valve and route of approach. As TAVI teams gain experience with multiple manufacturer systems, this allows a customized approach based on individual risk tolerance and anatomical considerations.

Patient Selection

Symptomatic severe AS has a poor prognosis that can be dramatically improved with valvular intervention. Traditionally, the option of SAVR has been offered on the basis that the risks of the underlying disease outweigh the risks of surgery. For patients with exceedingly high predicted surgical mortality, TAVI represents an alternative intervention that offers a lower risk than the natural history of the disease. As the populations of patients eligible for TAVI or SAVR now overlap significantly, there is a clear role for a multidisciplinary team decision-making (Figure 19.2). Current guidelines recommend that the multidisciplinary team includes an anaesthetist. While the relative risk of the two approaches to valve intervention are generally based on age and risk score (e.g. EuroSCORE-II), TAVI can have a particularly useful role in patients with specific surgical risks such as previous sternotomy with patent coronary grafts or patients with a ‘porcelain’ aorta.

Figure 19.2 Cumulative patient-related risk in AS influences the decision between TAVI and SAVR. Patients with an intermediate risk profile are being studied currently to determine the optimal treatment strategy. Names of large trials providing the evidence underpinning this framework are listed within the risk categories at the bottom of the figure.

From Grube et al. Eur Heart J 2014, 35(8): 490.

A common exclusion criterion for TAVI is the presence of severe co-morbid illness or frailty, indicating that the patient is unlikely to receive any meaningful benefit from a procedure targeted at the AV. This includes an anticipated life expectancy of less than a year after AV replacement. Anatomical constraints also exist – although the number of valve sizes has increased, the options remain much more limited than for SAVR. Furthermore, careful evaluation and sizing of the aortic root must be performed, often with multiple imaging modalities, and an appropriate access point through the peripheral vasculature, the left chest or the mediastinum must be available.

Finally, TAVI does not currently have an established role in patients with cardiac disease other than calcific AS. The presence of concurrent coronary or other structural heart disease reduces the anticipated benefit from TAVI relative to open surgery and could also significantly increase the risks of rapid ventricular pacing during valve deployment. The potential utility of TAVI for AR or bicuspid AV disease is questionable and these are currently considered contraindications. This is largely because the most widely used valves depend on significant radial forces, applied against a calcified annulus, for proper anchoring and prevention of a PVL. Furthermore, the presence of concomitant aortic pathology in such patients may mandate surgery in itself. Nevertheless, the potential for TAVI using newer devices in these patients is being investigated.

Anaesthetic Technique

A standard preoperative cardiac anaesthetic assessment should be performed in all TAVI patients. As previously stated, they are often elderly and have numerous co-morbidities – these should be evaluated thoroughly and optimized as necessary. The procedure may take place in the cardiac catheterization lab or in a hybrid operating theatre. In either case, appropriate preparations for the emergency institution of CPB should be made. This includes an agreed plan for surgical rescue, the immediate availability of appropriate equipment and personnel, and clarification of the planned cannulation approach in patients chosen for TAVI because of difficult surgical access. Furthermore, this includes the clear identification of patients for whom surgical intervention and CPB are not considered appropriate.

Knowledge of the planned approach is essential, as this can greatly influence the anaesthetic technique chosen. In many instances general anaesthesia, regional anaesthesia or sedation may be used. The advantages of general anaesthesia include a secured airway in case of respiratory or haemodynamic compromise, guaranteed immobility and access to TOE. In an effort to improve recovery and reduce the length of hospital stay, a regional nerve block supplemented with sedation is becoming increasingly common. Avoiding general anaesthesia minimizes the haemodynamic consequences of anaesthetic agents and positive pressure ventilation and reduces the incidence of arrhythmias and the requirement for vasoactive support. This can be one component of an enhanced recovery strategy, which minimizes benzodiazepines, avoids unnecessary invasive lines and urinary catheterization and promotes early mobilization once haemostasis is assured. When sedation is used, arterial monitoring can be achieved by ‘sharing’ the cardiologist’s arterial access, eliminating the need for a separate arterial line. Central venous access – routinely obtained for rapid ventricular pacing – can be used by the anaesthetic team for drug and fluid administration.