Transcatheter aortic valve replacement (TAVI) has become the standard of care for patients with severe symptomatic aortic stenosis. Since its introduction, the majority of TAVI procedures have been performed under general anesthesia. Initially developed as a less invasive alternative to surgical aortic valve replacement for high-risk or inoperable patients, its use has grown due to innovations in device design, smaller delivery systems, and increased procedural experience (J Thorac Dis 2018;10:S3588-94). These improvements in many aspects of the procedure have made TAVI even less invasive, which has led to a growing interest in “minimalist” TAVI (Front Cardiovasc Med 2018;5:96). An integral component of minimalist TAVI is the use of moderate sedation with monitored anesthesia care instead of general anesthesia.
Both modalities have advantages as well as disadvantages (JACC Cardiovasc Interv 2020;13:1277-87). Consequently, an important question has emerged on whether general anesthesia or monitored anesthesia care is a better anesthetic strategy to optimize outcomes. Here, in the context of TAVI, we discuss the differences between general anesthesia and monitored anesthesia care, review the results and limitations of the currently available data, and discuss the priority questions for future research.
Patients undergoing TAVI are often frail with significant comorbidities. Anesthesiologists and proceduralists often choose general anesthesia for these patients who are considered “more complex,” whereas monitored anesthesia care is reserved for “less complex” patients (asamonitor.pub/3ooC5JI). Thus, general anesthesia can often be arbitrarily selected for patients with an increased frailty or difficult procedural anatomy.
General anesthesia allows for easier management of hemodynamic challenges, more definite control of the airway and ventilation with minimal patient movement, more effective attenuation of stress response during the procedure, while also providing more time for the proceduralists performing TAVI. Additionally, general anesthesia is the preferred strategy in patients with back pain, claustrophobia, severe sleep apnea, or those who are unable to lay in the supine position for an extended period. Moreover, the ability to use transesophageal echocardiography (TEE) leads to fewer complications, such as perivalvular leaks (PVLs) and permanent pacemaker (PPM) implantation, and can possibly reduce the amount of contrast agent used.
Challenges of general anesthesia include the fact that it requires intubation for mechanical ventilation and can result in complications such as pneumonia, increased catecholamine requirements, and lengthy intensive care and hospital days that increase the risk of nosocomial infections and death.
Moderate sedation with monitored anesthesia care
Recent improvements in transcatheter technology have made minimalist approaches that avoid the potential complications of general anesthesia feasible. The monitored anesthesia care approach includes continuous cardiovascular and respiratory monitoring by an anesthesiologist and includes sedation, analgesia, and anxiolysis, as needed. In contrast to general anesthesia, patients under monitored anesthesia care are frequently awake during the procedure and able to communicate with the proceduralists.
Current evidence suggests that the use of monitored anesthesia care for TAVI may prove as effective as general anesthesia while decreasing the complications associated with general anesthesia such as difficult airway, ventilation in patients with chronic lung disease, myocardial depressant effects of anesthetics that necessitate inotropic support, blood transfusions, and delayed awakening from anesthesia (Front Cardiovasc Med July 2018). Other advantages include reduced fluoroscopy time, procedure time, and intensive care unit time (which is associated with lower in-hospital and 30-day mortality), as well as greater likelihood of being discharged, and improved quality of life.
“Recent improvements in transcatheter technology have made minimalist approaches that avoid the potential complications of general anesthesia feasible.”
The shorter procedure time for TAVI with monitored anesthesia care should result in decreased health care resource utilization. In 2017, Toppen et al. compared the cost of monitored anesthesia care with general anesthesia in 225 patients undergoing TAVI and found that the total direct cost that patients undergoing TAVI with monitored anesthesia care was 71.5% of the cost when general anesthesia was used (PLoS One 2017;12:e0173777).
Concerns of monitored anesthesia care for TAVI include that it may pose risks due to inadvertent over sedation with an unprotected airway; using TEE during TAVI under sedation may not be as sensitive as TEE and could possibly lead to an increased incidence of PVL in patients under sedation; and that inadequate hemostasis may cause more bleeding. Additionally, conversion from monitored anesthesia care to general anesthesia may contribute to increased mortality. These factors must be taken into consideration when discussing short- and long-term morbidity and mortality in TAVI under monitored anesthesia care versus general anesthesia.
The randomized SOLVE-TAVI trial
To date, the Second-Generation Self-Expandable Versus Balloon-Expandable Valves and General Versus Local Anesthesia in TAVI (SOLVE-TAVI) trial is the only randomized controlled trial to directly compare clinical outcomes between general anesthesia and monitored anesthesia care in patients undergoing TAVI (Circulation 2020;142:1437-47).
In this prospective, multicenter study conducted at seven German sites from April 2016 through April 2018, Thiele and colleagues compared clinical outcomes in 438 patients undergoing TAVI. Patients were at high to intermediate surgical risk with an age of 81.6±5.5 years, and baseline characteristics were well balanced between the two treatment groups (general anesthesia and monitored anesthesia care).
The study found no differences between general anesthesia and monitored anesthesia care in terms of mortality rate, stroke, myocardial infarction, or moderate to severe paravalvular leak; however, over 5% of the monitored anesthesia care group required urgent conversion to general anesthesia.
Based on the findings, the team concluded that both anesthesia strategies can be used in clinical practice for the treatment of high- to intermediate-risk patients with severe aortic stenosis undergoing TAVI.
Limitations of the currently available data
Despite the trend toward increasing use of monitored anesthesia care for TAVI, certain caveats, however, must be considered while making any definite conclusions (J Cardiothorac Vasc Anesth 2017:2055-7).
First, data on monitored anesthesia care have largely been derived from large registries, retrospective studies, meta-analyses that compare safety and outcomes or carefully selected patients, subjecting these findings to significant selection bias. Moreover, lack of clear criteria for choosing monitored anesthesia care or general anesthesia that likely exists in all the studies, makes the evaluation of confounding difficult.
Second, chronological bias should be considered. Monitored anesthesia care has been performed in more recent years, whereas general anesthesia was more often performed in the earlier years. This nonparallel timing may possibly introduce an era-like effect on the results. Further, because more practiced providers (usually with better outcomes) are the same providers who may be more likely to lean toward monitored anesthesia care for TAVI, the timing of the comparison between monitored anesthesia care and general anesthesia is critical.
Third, the conversion rate from monitored anesthesia care to general anesthesia was rarely recorded in the large-scale registries, and it is uncertain how the converted cases were handled with in most of the studies. Conversion may take place when encountering difficult vascular access, bleeding, or significant procedural complications. Thus, patients converted to general anesthesia may have an amplified ICU or hospital length of stay.
These factors may conceivably affect many adverse outcomes if they are imbalanced between the monitored anesthesia care and general anesthesia groups in clinical studies. Consequently, it is still meaningful to conduct high quality RCTs to truly know if there is an important difference between monitored anesthesia care and general anesthesia for TAVI and to identify the patients who are likely to benefit from the differential selection.
Nevertheless, these studies suggest that monitored anesthesia care in TAVI is both feasible and safe.
Additionally, the studies propose that patient factors, the chosen access site, and operator experience and preferences should play a major role in the decision-making regarding the optimal anesthetic technique for TAVI.