Transcatheter aortic valve implantation (TAVI) has been available as the more effective and reliable management for symptomatic severe aortic stenosis (SSAS) since 2002 (Yamamoto et al., 2013). It serves as a replacement for the traditional and highly invasive open-heart surgical aortic valve replacement (SAVR) (Vavuranakis et al., 2015). In this review of available literature, the complications related to TAVI post-treatment are examined.
The search process produced 1093 research articles, 15 of which were then accepted and reviewed. Five complications were found: atrioventicular blocks, major vascular complications, mortality, bleeding, and disabling strokes. However, the review has also identified many other potential problems that were not considered by the researchers. The study provides directions that can be valuable for future research and help improve the TAVI procedure, making it safer.
Introduction
Conventional open-heart surgical aortic valve replacement (SAVR) is the definitive symptomatic severe aortic stenosis (SSAS) treatment. Physicians have used SAVR since the 1960s, and it was the mainstay standard of care for SSAS up to 2002 (Dalby et al., 2019). Indeed, doctors globally perform about 200,000 SAVR procedures annually (TAVI Today, n.d.). However, due to technological advancements over the years, a new SSAS treatment technique, known as transcatheter aortic valve implantation (TAVI), is evolving. TAVI, also called transcatheter AVR or TAVR, is a less invasive SAVR replacement first undertaken in 2002 (Möllmann et al., 2015). Today, physicians use both SAVR and TAVI to attain enough hemodynamic parameters as evidence of effective care.
Medical practitioners also utilize the two treatment options to help patients minimize SSAS symptoms while also improving their rate of survival (Schaff, 2011). Clinical trials in patients aged 80 years and above have shown significant improvements in survival rates, proving the efficacy of the TAVI procedure (Würschinger et al., 2018). When an SSAS patient is referred to a care facility’s cardiovascular team, the concerned doctors will assess him or her and determine whether to use SAVR or TAVI (Schymik et al., 2015). The decision is mostly dependent on the patient’s clinical, technical, and anatomical characteristics (Tamburino et al., 2011).
Several clinical trials since the first TAVI procedure in 2002 show a continued evolution of the approach with excellent efficacy irrespective of surgical risk (Lauck et al., 2018). In the past few years, more than 70 countries worldwide have performed over 500,000 TAVI procedures, with its indication now expanding to low-risk patients (TAVI Today, n.d.). In this regard, it is essential to understand the risks and possible complications of the approach to influence more secure applications (Czerwińska-Jelonkiewicz et al., 2013). Such a comprehension will help scholars find ways of reducing the risks and enhancing the treatment (Czerwińska-Jelonkiewicz et al., 2013). It will also inform the recommendation of the process, the release of adequate advisory against it, or the development of appropriate policies and regulations to help in its application in SSAS treatment (Amat‐Santos et al., 2018). The way to gaining this understanding is by conducting more research.
Using a systematic review of the available literature, a report was produced on the complications associated with the TAVI procedure as documented by scholars. The research question guiding and directing the study is based on the PICO (S) criterion. As such, it takes the following form: in patients who have undergone TAVI (P), how many and what complications (O) does the procedure (I) cause in comparison with the patients’ prior state (C)? To answer this question, a systematic review of the literature (S) has been conducted.
The rationale of the study is that the number of TAVI operations has increased significantly since 2002, and it is important to investigate them to identify any related complications to help the research community address them (Doshi et al., 2018). Without awareness of the problems and the extent of their spread, it is considerably more challenging to guide research to address current issues.
The patient’s health characteristics determine the usability of the TAVI technique and the patient’s recovery process. Individuals with general good health are more likely to recover faster from the treatment than those with other medical conditions (Masson et al., 2009; Assmann et al., 2013; Leon et al., 2010). Notably, it is possible to conduct TAVI on a patient presenting with other sicknesses, provided these conditions do not require concomitant treatment. Patients with healthier habits like exercising have a better developed immune system, which helps them fight sicknesses and recover quickly from an operation.
Methods
Search Strategy and Selection Criteria
PubMed, Embase, Cochrane Library, and Google Scholar were the databases searched for articles on the topic. A recency criterion was implemented of only searching for studies that were published after January 1, 2010. To find as many eligible studies as possible while minimizing irrelevant results, a number of primary keywords were used, such as “TAVI,” “transcatheter aortic valve implantation,” “complications,” “post-TAVI heart blocks,” “conduction disturbance post-TAVI,” and “para prosthetic leaks,” combined with secondary keywords such as the names of the conditions serving as prerequisites for the procedure.
From the search results, the top results were then analyzed for relevance based on their titles and abstracts, with those deemed deserving of further examination retrieved in full-text form. With that said, due to time constraints, analysis of all of the articles proved impossible, and only 24 of the 88 thus considered were ultimately processed. The analysis process is presented in the PRISMA diagram depicted in Fig. 1 below.
Statistical Analysis
Meta-analysis was conducted for the gathered data to determine the overall incidence of different complications across a large number of cases. A fixed-effect model was employed for the analysis, assuming that there was little to no variation in the effects of the treatment across different studies. Where available, 30-day outcomes were selected to ensure the homogeneity of the testing conditions and expand the pool of eligible studies.
The means and standard deviations of each detected complication were calculated under the assumption that they followed a normal distribution. The assumption was made that the patients showed no sign of the complication before the operation, so the control means would all be equivalent to 0, which means the presentation of the means is sufficient for most purposes. 95% confidence intervals were also constructed for each complication to provide a more accurate representation of the situation across the population. The Stata software suite was used to conduct the analysis, the results of which are presented below.
Results
A search of four electronic databases produced a total of 1093 studies after the removal of duplicates, with Google Scholar contributing the most due to its relatively broad search algorithm. However, a subsequent screening of article titles and abstracts eliminated most of the produced results, leaving a total of 43 studies deemed suitable for further analysis. Twenty more were then removed during a full-text search, as it was found that they did not constitute primary research or had different purposes than those needed for the review. Another eight articles were rejected during the data extraction process, as the process was unnecessarily difficult for them or omitted too many important data points. Ultimately, 15 studies were left that collectively covered 34,338 patients from a variety of locations. A more detailed overview of the characteristics of patients from each study, as well as the overall results, is presented in Table 1.
Table 1: Patient characteristics from the gathered studies.
As can be seen from the table, studies tend to focus on patients over 80 years old, which are at the highest risk from cardiovascular conditions. The genders are split roughly evenly, though overall, there are somewhat more women than men in the sample. The Society of Thoracic Surgeons (STS) score, EuroSCORE I, and the New York Heart Association (NYHA) class are all mostly interchangeable risk measures that complement each other.
Different studies choose to provide some or all of them, with that by Doshi, Shlofmitz, and Meria (2018) omitting them altogether. Overall, a majority of patients were found to be in high-risk categories, which justified the performance of the procedure. Lastly, the mean aortic gradient and the aortic valve area measures were provided because they demonstrate the need for a valve replacement. The former indicates the strain on the current valve, which can lead to damage over time and has been found to be significantly higher than normal. Conversely, the latter demonstrates the severity of stenosis (if it is the condition leading to the valve installation) and was also found to be significantly below healthy values.
In terms of complications, five significant categories of issues have been discovered throughout the literature: mortality, strokes, particularly of the disabling variety, major vascular complications of different types, bleeding, and the need for a permanent pacemaker installation. Death will be discussed due to all causes, as in many cases, it is challenging to determine what has led to it given the patient’s condition and the recovery from the procedure.
Disabling strokes are another factor often discussed in the literature, sometimes equated with outright death. Major vascular complications include “iliofemoral dissections and stenoses, femoral perforations and vessel ruptures, and bleeding with or without hemodynamic compromisation” (Dimitriadis et al., 2017). However, for the purposes of this review, they will be grouped together like they typically are in the literature. Bleeding can occur at different levels of severity, but for this study’s purposes, only incidents classified as major or life-threatening were included. Lastly, per Erkapic et al. (2012), TAVI is associated with the risk of atrioventicular blocks developing, which necessitates the usage of a permanent pacemaker. The studies reviewed discuss the procedure rather than the cause, which is the reason for its inclusion.
Table 2: The rates and confidence intervals for different complications.
As is shown in Table 2, the results across different studies are considerably disparate, with mortality reaching as high as 17% in one case and 1.2% in another. However, overall, there is a substantial number of cases and information on different complications that allows for mostly accurate inferences to be drawn. As Fig. 2 shows, atrioventicular blocks, represented by a need for permanent pacemaker installation, are the most prominent complication.
Major vascular complications follow at 6.9%, and mortality is in third place at 5%, though both of these outcomes mandate additional discussion. Bleeding is second last at 3.1%, though the 12.2% standard deviation as well as the omission of minor hemorrhages both warrant additional attention. Finally, disabling stroke appears to occur at a rate of 1.1%, though this finding also warrants additional consideration. All of these considerations will be further deliberated upon in the next section, Discussion.
Discussion
Most Significant Complications
The findings regarding the need for a permanent pacemaker installation require additional context for understanding. It is consistent with findings in other literature, such as the claim by Gaede et al. (2018) that approximately every fifth TAVI recipient will need the device within the first 30 days. The same is not the case for the surgical version of the procedure, where concerns over blockage are much lower. Per Erkapic et al. (2012), 90% of such cases happen within the first week after the operation, especially if they have manifested a right bundle branch block beforehand. This increased likelihood is a significant disadvantage of TAVI compared to the surgical alternative that should be considered before operating. With that said, it is not necessarily a reason to abandon the procedure, given its numerous advantages over the more invasive option.
Vascular complications remain overall understudied, possibly due to the variety that they exhibit compared to other TAVI-related problems. With that said, research has been ongoing into their causes and overall predictors. Walas et al. (2020) claim that percutaneous access is associated with an overall higher incidence of vascular complications as opposed to open surgical access, while left-side access and the female sex are independently also related to more serious danger.
Further research into vascular complications is necessary because of the effort necessary to correct them and the further danger to which it exposes patients. Raju et al. (2019) state that the majority of the procedures performed to address this type of problem involves surgery, which mitigates the advantages of TAVI over the alternatives. A better understanding of the causes and predictors is required to reduce the incidence of vascular complications and mitigate the damage they cause.
The 5% mortality figure is not necessarily as problematic as it originally appears. It is all-cause mortality rather than that associated specifically with TAVI, which means that there may have been many other reasons for the patient’s death. Additionally, the average age of the patients in the analysis is 81.9 years, which, considering their heart issues, is also likely associated with many other comorbidities. As such, the specific influence of the procedure on mortality is challenging to determine, especially compared to a lack of any treatment. With that said, research should continue into the predictors of mortality after TAVI, both short and long-term.
For example, Eichler et al. (2018) find that adjustments to nutrition and mobility after the procedure improve patients’ survival rate in a one-year timeframe after it. Through similar research, the medical system’s overall ability to preserve patient lives will improve regardless of the specific predictors.
While TAVI is not as invasive as surgical valve replacement, it still involves making incisions into the patient’s body and installing the new device. While bleeding does not appear to be a particularly prevalent problem, a discussion into its mitigation is still warranted. Wang et al. (2017) find that the usage of transapical access and a history of atrial fibrillation serve as significant predictors of hemorrhaging while others such as the STS score, EuroSCORE, aortic valve area, and mean pressure gradient had no effect on it. Bleeding is particularly problematic because it can be challenging to stop and endanger the patient’s life significantly.
Wang et al. (2017) discover that major and life-threatening bleeding is associated with a 410% mortality increase compared to their absence. As such, a more precise determination of the risk factors and ways to mitigate them is critical given the prevalence of the problem.
The final complication that was found across the different works is the danger of major or disabling stroke. It is a severe problem that some studies among those analyzed in this paper compare to death or equate to it. With that said, given the patients’ overall poor cardiovascular health that has led them to need TAVI, strokes are likely to be highly challenging to avoid. Research is still necessary to understand the predictors of stroke as well as the measures that can help prevent it. According to Shah et al. (2018), the incidences of stroke after TAVI and SAVR are similar, meaning the procedure researched in this paper does not necessarily endanger patients more. Still, combined, these five complications endanger the patient significantly and demonstrate numerous current weaknesses of TAVI that need to be addressed.
Gaps in the Literature
The first significant gap in the literature is the absence of discussion surrounding various problems specific to TAVI. For example, there is a lack of studies on the incidence of paravalvular leakage, though it is a recognized problem, and its causes are being researched. Mangieri et al. (2018) discuss postoperative conduction abnormalities such as left bundle branch blocks, which are still not well-understood despite often requiring the permanent installation of pacemakers.
The search was unable to produce a significant amount of information about the rates at which any of these complications arise, and most of the studies identified focused on the five primary problems identified above. However, most of these outcomes can manifest for reasons other than the performance of TAVI, especially considering the patient population. As such, research with more specificity is necessary to understand the overall effects of the procedure when compared to the alternatives and improve it.
The second problem in the research is the overall lack of differentiation between different patient categories. Only a small number of the studies selected reviewed outcomes for men and women separately, and only one considered different ethnicities and races, albeit briefly.
However, as noted above, researchers have found that vascular complications are more likely to emerge in women post-TAVI than in men. Considering that there are other known differences in cardiovascular health between genders and ethnicities, this lack of research is problematic, especially considering the relative ease with which trial data could be separated. Gathering sufficiently large ethnic or racial groups within the same overall environment for comparison purposes may be challenging, but doing so may still be advisable. Overall, the research into the effects of TAVI is currently overly broad and lacks discussion of specific circumstances and problems that may be essential to understanding and improving the procedure.
Implications for Future Research
This review has identified several weaknesses in the current research that should be addressed in the future. It is overall too focused on comparisons between SAVR and TAVI, as the latter is typically considered a superior alternative to the former. As a result, studies have considered the prevalent problems of traditional open surgery and the improvements that TAVI offers over it at the expense of the specific risk factors associated with the newer procedure.
As such, future research will need to address these problems, determining the frequency with which different issues listed above manifest. It should also investigate the causes of these problems in more detail and consider different ways of prevention. Lastly, research should consider longer timeframes than 30 days, determining the long-term effects of the procedure in addition to short-term ones. With these efforts, the research should be able to cover its gaps and offer suggestions for the improvement of the procedure.
Limitations
The most significant limitation of the study is the sample size of the studies analyzed. While the number of patients is sufficiently large, there are only 15 studies that represent distinct environments and provide considerably disparate results. Moreover, the sample sizes vary wildly, with the research by Eggebrecht et al. (2016) providing approximately half of the overall population considered while that by Eggebrecht et al. (2011) features less than 100 people.
Additionally, the studies collected and presented information differently, with many not presenting analyses of specific complications or not segmenting strokes into minor or disabling varieties. These omissions of information may have skewed the results of the analysis somewhat, leading to understatements of the incidence rates for specific problems. The lack of a control group also reduces the usefulness of the data, as it is sometimes challenging to isolate TAVI as the cause of the problem based on the results. With that said, the study has still been able to achieve most of its broad purposes and identify the problems preventing it from reaching the rest of its targets.
Conclusion
Overall, the review has found five primary complications that are frequently discussed in the literature as associated with TAVI: atrioventicular blocks, major vascular complications, mortality, bleeding, and disabling strokes. All of these problems are significant but not necessarily more dangerous than the dangers of SAVR. With that said, some of them are still highly prevalent and require further research and innovation.
The study has also discovered significant gaps in the research, particularly that of the incidence of less general problems that are more specific to TAVI and the lack of consideration for comorbidities and factors such as gender. Future research should address these problems and create a more specific overview of TAVI that takes both its advantages and its dangers into account to create an improved version of the procedure. Additionally, with these problems addressed, improved, more specific and accurate versions of this review can be produced to identify additional problems.
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