Intended for healthcare professionals
Original research

Transcatheter aortic valve implantation complexity score

Abstract

Background Increasing demand for transcatheter aortic valve implantation (TAVI) places greater emphasis on the efficiency of pathways and services. A significant limitation to increasing TAVI capacity is the availability of cardiac catheterisation laboratory time. We have developed a novel complexity scoring system (TAVI ComplEXity; TEX score) which can aid in planning lists with appropriate case selection. To validate the TEX score, we have undertaken a retrospective analysis of TAVI cases. The hypothesis is that increasing TEX score correlates with increased procedural duration and reduced valve academic research consortium (VARC) 3 technical and device success.

Methods The TEX score assigns patients to a complexity level of 1 (low), 2 (intermediate) or 3 (high) based on the presence of specific clinical and anatomical variables. For validation purposes, comparisons were made between patients in the three complexity levels with respect to procedural duration as well as VARC-3 technical success, device success and early safety.

Results The validation study included 1034 consecutive patients who underwent TAVI between June 2021 and October 2023. Of these, 582 (56.3%) were classified as level 1 complexity, 377 (36.5%) level 2 and 75 (7.3%) level 3. Significant differences were observed between the three groups with respect to procedural duration (73.7 min vs 85.6 min vs 136 min; p<0.001), VARC-3 technical success (97.9% vs 96.6% vs 92%; p<0.05) and VARC-3 device success (96.2% vs 92.3% vs 86.6%; p<0.001).

Conclusion The TEX score is a simple tool which allows stratification of patients into three levels of complexity. Increasing complexity levels correlate with increasing procedural duration and reduced VARC-3 technical and device success. This is potentially useful for scheduling patients onto appropriate lists.

What is already known on this topic

  • Transcatheter aortic valve implantation (TAVI) has become the dominant form of aortic valve intervention and the demand is forecast to continue rising, placing increasing pressure on healthcare systems. One of the main limitations to increasing TAVI capacity is the availability of cardiac catheterisation laboratory time. We have developed a novel complexity scoring system (TAVI ComplEXity; TEX score) which can aid in planning lists with appropriate case selection.

What this study adds

  • The TEX score is a simple tool which allows stratification of patients into three levels of complexity (low, intermediate or high). In order to validate the scoring system, we have performed a retrospective analysis of 1034 patients who underwent TAVI. This has shown that increasing complexity level correlates with increasing procedural duration and reduced valve academic research consortium-3 technical and device success.

How this study might affect research, practice or policy

  • The TEX score can be used to classify patients’ complexity level prior to TAVI, and the score can be used to plan lists appropriately based on the skill-mix and time available. This has the potential to maximise the use of available resources and reduce the number of case cancellations due to insufficient time.

Introduction

Transcatheter aortic valve intervention (TAVI) has revolutionised the treatment of severe aortic stenosis (AS) and is now an established therapy for patients across the full spectrum of surgical risk.1–3 As a result, TAVI has become the dominant form of aortic valve intervention, with the volume of TAVI procedures carried out exceeding all forms of surgical aortic valve replacement in the USA since 2019 and the UK since 2020.4 5 The forecast is for this expansion to continue; while the patient cohorts eligible for TAVI continue to diversify, recent studies have also highlighted the significant burden of undiagnosed severe AS, with the UK estimated to have 300 000 people who are potentially in need of treatment.6 As a consequence, the pressure on healthcare systems to deliver TAVI will only increase in the coming years and decades, placing an ever-greater emphasis on the efficiency of associated pathways and services.7

One of the main limitations to increasing TAVI capacity is the availability of cardiac catheterisation laboratory time. As such, there is an increasing incentive to maximise available slots by performing as many cases per list as is safely possible and to minimise the number of cancellations. An important way of achieving this is to ensure that patients are listed appropriately based on how long cases are forecast to take and the probability of significant procedural complications. Performing four or five uncomplicated transfemoral TAVI cases in a single day is now routine across many centres, but certain cases may be more complex and require additional time; scheduling these in an already pressurised list may lead to cancellation of patients on the day and result in wasted resources. As a result, we have developed a novel TAVI ComplEXity scoring system (TEX score) which can aid in planning lists with appropriate case selection.

The TEX score is based on a combination of patient factors (eg, body mass index (BMI), clinical instability, left ventricular ejection fraction (LVEF)) and technical factors derived from preprocedural cardiac-gated CT scanning (eg, annular angulation, ileofemoral disease). The scoring system separates patients to three levels of rising complexity. In order to validate the TEX score, we have undertaken a retrospective analysis of TAVI cases carried out at a large TAVI centre in the UK with the hypothesis that increasing TEX score correlates with increased procedural duration and reduced valve academic research consortium (VARC) 3 technical and device success.

Methods

Development of the TEX score

The TEX score was developed based on the consensus of four experienced TAVI operators, together with published evidence on factors influencing procedural outcomes. Patients are assigned a complexity level of 1 (low), 2 (intermediate) or 3 (high) based on the presence or absence of specific clinical and anatomical variables, listed in figure 1. The scoring system is hierarchical rather than points based, such that the presence of the highest-ranked factor determines a patient’s complexity level. For example, a patient who has a bicuspid aortic valve (BAV) is classified as level 2 complexity and remains at this level even if they have other level 2 features such as challenging transfemoral access. However, if the same patient was undergoing TAVI via an alternative access route, they would then be classified as level 3 complexity. The scoring is done by a consultant TAVI operator during the Heart Team meeting.

The component of the TEX score. *Critical pre-operative status is defined as any of the following options: ventricular tachycardia or ventricular fibrillation or aborted sudden death, pre-operative cardiac massage, pre-operative ventilation before anaesthetic room, pre-operative inotropes or intra-aortic balloon pump, pre-operative acute renal failure (anuria or oliguria <10 mL/hour). AR, aortic regurgitation; AV, aortic valve; BASILICA, bioprosthetic or native aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction; LVEF, left ventricular ejection fraction; NEWS, National Early Warning Score; TEX, TAVI ComplEXity; TF, trans-femoral; ViV, valve-in-valve.

Patients in level 1 are deemed to be ‘straightforward’ cases which are suitable for a list of 5 in a day with nurse-led sedation. Those in level 2 are more complex and may be better suited to a list with fewer patients, allowing more time per case. Patients in level 3 are complex and generally require anaesthetic support as well as more procedural time.

Components of the TEX score

  1. Clinical instability: Patients who are clinically unstable pre-TAVI may require enhanced support during the procedure, either respiratory (eg, non-invasive ventilation) or haemodynamic (eg, inotropic agents), and TAVI carried out in an urgent setting has been demonstrated to be associated with higher rates of peri-procedural complication.8

  2. Elevated BMI: Obesity can make achieving optimal vascular access more challenging and has been associated with increased incidence of vascular and bleeding complications.9

  3. Impaired left ventricular systolic function: Patients with a significant reduction in LVEF may tolerate rapid ventricular pacing more poorly and require increased haemodynamic support during TAVI. Left ventricular dysfunction pre-TAVI has been identified as a predictor of procedural difficulty and poor clinical outcomes.10

  4. Challenging transfemoral access and ileofemoral tortuosity: This has been demonstrated to be associated with an increased incidence of vascular and bleeding complications.11

  5. Landing zone calcification: Significant calcification at the aortic annulus or within the left ventricular outflow tract increases the risk of both paravalvular leak and annular or sub-annular rupture.12 13

  6. BAV: BAVs are often associated with larger annulus dimensions, an asymmetric valve orifice, heavy calcification and a dilated and asymmetric aortic root and ascending aorta. TAVI in BAV anatomy has been shown to be associated with an increased risk of significant PVL, non-uniform/non-circular valve deployment, device migration/embolisation and annular rupture .14–17

  7. Risk of coronary obstruction/planned coronary protection or leaflet modification: Acute coronary obstruction during TAVI can result in myocardial infarction and haemodynamic collapse. As a result, it has been demonstrated to be associated with an increased risk of in-hospital mortality.18 Mitigation of this, by either (a) coronary protection (having a guiding catheter and guidewire ± coronary stent in the threatened coronary during valve deployment), (b) up-front chimney stenting or (c) leaflet modification, for example, by bioprosthetic or native aortic scallop intentional laceration to prevent coronary artery obstruction technique (BASILICA) adds complexity and time to the procedure. The factors that determine coronary obstruction risk are derived from the pre-TAVI CT and include coronary height, sinus width, virtual transcatheter heart valve-to-coronary (VTC) distance, culprit leaflet calcium volume and if the cusp height is greater than the coronary height.

  8. Valve-in-valve (ViV) TAVI: ViV TAVI presents a number of additional challenges, including increased risk of coronary obstruction, elevated transvalvular gradients and the potential need for balloon valve fracture (BVF).19 As such, ViV TAVI is associated with increased procedural complexity and complications.

  9. Vertical aortic annulus: This anatomical variation can present a significant challenge to achieving a co-axial position during valve deployment, particularly with use of self-expanding valves (SEVs). When implanting an SEV, the presence of a vertical annulus has been demonstrated to be associated with an increased risk of valve embolisation, increased need for a second valve, greater likelihood of post-dilation and increased fluoroscopy time.20

  10. Alternative access: The default access route for TAVI in the contemporary era is transfemoral. The most commonly used alternative access route in the UK is transaxillary,21 either via surgical cutdown or percutaneous approach. Other access approaches include transcarotid, transcaval and direct aortic. All are associated with increased procedural duration and incidence of complications when compared with transfemoral TAVI.22 23

  11. TAVI in pure aortic regurgitation (AR): ‘Traditional’ devices (ie, SEV or balloon-expandable valves (BEV)) anchor using aortic leaflet calcification. Undertaking TAVI using these valves in the absence of calcification, such as in pure AR, is associated with increased incidence of complications such as valve malpositioning, embolisation or significant paravalvular leak.24

Validation of the TEX score

In order to validate the TEX score, we performed a retrospective analysis of all consecutive TAVI cases carried out between June 2021 and Oct 2023 at Leeds Teaching Hospitals National Health Service (NHS) Trust, a tertiary referral centre for Cardiology and Cardiac surgery. The annual TAVI volume at LTHT for the year 2022–2023 was 409, with all cases being performed in a cardiac catheter laboratory. Since August 2017, the majority of TAVI cases (>60%) have been carried out with nurse-led sedation.

Comparisons were made between patients in the three complexity levels with respect to procedural duration as well as VARC-3 technical success, device success and early safety. The study was designed and reported using the STtrengthening the Reporting of OBservational studies in Epidemiology statement.25

Participants

All patients undergoing elective or acute TAVI for treatment of AS or AR at LTHT between 1 June 2021 and 31 October 2023 were included and were identified from our institutional database. All patients who underwent TAVI did so following a multidisciplinary Heart Team discussion.

Endpoints

The primary endpoint was procedural duration (minutes). This was obtained from the procedural log which is completed prospectively by the cardiac physiologist for every case. Secondary endpoints were VARC-3 technical success, device success and early safety.26

Statistics

Data were analysed using the statistical package Microsoft Excel for Mac (V.16.67). Continuous variables are presented as means±SD and compared using the Kruskal-Wallis test, while categorical data are presented as proportions and compared with χ2 test. P values of less than 0.05 were deemed to be of statistical significance.

Results

A total of 1034 consecutive patients who underwent TAVI between 1 June 2021 and 31 October 2023 at Leeds Teaching Hospitals NHS Trust were included in the validation study. When the TEX score criteria were applied to this cohort, 582 (56.3%) were classified as level 1 complexity, 377 (36.5%) as level 2 complexity and 75 (7.3%) as level 3 complexity.

When assessing the total patient population, the majority (61.9%) were male and the mean age was 80.4 years (table 1). The dominant vascular access type was percutaneous transfemoral (97.1%), with percutaneous axillary the next most commonly used (2.2%). Elective surgical cutdown, whether femoral or subclavian, accounted for only 1.5% of cases. The most frequently used valve type was Medtronic Evolut Pro/Pro+ (46.1%), followed by Edwards SAPIEN 3/Ultra (34%) and Abbott Portico/Navitor (17.6%). The remaining cases were performed using Acurate Neo/Neo 2 and JenaValve Trilogy systems.

Table 1
Baseline and procedural characteristics

Comparing baseline characteristics between patients in the three levels of complexity, the only significant difference between the groups relates to previous cardiac surgery; a greater proportion of patients within complexity level 2 had undergone cardiac surgery than those in levels 1 or 3 (6.7% vs 20.4% vs 13.3%; p<0.05).

There were differences observed between the three groups with respect to type of transcatheter heart valve used. A lower proportion of patients in the level 3 complexity group were treated with an Edwards SAPIEN 3/Ultra compared with levels 1 or 2, and the overall difference between the groups was significant (33% vs 38.5% vs 18.7%; p<0.05). Conversely, a higher proportion of patients in the level 3 complexity group were treated with Abbott Portico/Navitor valves compared with levels 1 or 2, and once again the overall difference between groups was significant (21.1% vs 9.8% vs 29.3%; p<0.001). No significant difference was observed with respect to the use of Medtronic Evolut R/Pro/Pro+ valves across complexity groups (43.3% vs 50.1% vs 48%; p=0.11).

With respect to the primary endpoint of procedural duration, a significant difference was observed between the three groups, with duration rising with each incremental increase in complexity level (73.7 min vs 85.6 min vs 136 min; p<0.001) (table 2 and figure 2). Only a low proportion of patients in levels 2 and 3 complexity groups had a procedural duration which was lower than the mean procedural duration for level 1 patients (14.3% (54/377) and 12% (9/75), respectively).

Table 2
Primary and secondary endpoints based on the TAVI complexity score

Comparison of procedural duration between complexity levels. *p<0.05.

A significant difference was noted between complexity levels with regard to the secondary endpoint of VARC-3 technical success (98.1% vs 97.6% vs 92%; p<0.05). When examining the constituent components, this difference was driven by lower rates of successful access, device delivery and retrieval (99.5% vs 99.2% vs 94.7%) and freedom from heart surgery and major vascular surgery (99.3% vs 99.2% vs 94.7%) in level 3 complexity patients. A significant difference between the three groups was observed with respect to VARC-3 device success (96.2% vs 92.3% vs 86.6%; p<0.001), but not VARC-3 early safety (88.9% vs 86.2% vs 84.0%; p=0.31) (figure 3 and table 2).

Comparison of VARC-3 technical success (A), device success (B) and early safety (C) between complexity levels. *p<0.05. VARC, valve academic research consortium.

Discussion

The volume of TAVI procedures being carried out worldwide has been rising year-on-year, and that growth is projected to continue for the foreseeable future. In the UK, demand for TAVI already far outstrips capacity, resulting in long waits for treatment. In 2019, a survey of 23 UK centres highlighted a median waiting time from referral to TAVI of over 20 weeks.7 Given that the median survival of severe symptomatic AS is worse than that of most metastatic cancers, it is not surprising that long delays to treatment translate into excess mortality; a delay to TAVI of 6 months results in almost a quarter of patients (23.3%) dying on the waiting list.27

Creating new capacity for complex procedures such as TAVI in an already-stretched healthcare system is difficult, so maximising the current level of resources to deliver as many procedures as possible must be a priority for all TAVI centres. Increasing the number of cases carried out per list is an obvious way to boost procedural numbers, but to do so safely and in a way that is sustainable can be challenging. One of the key considerations is to schedule an appropriate combination of cases, based on how long each case is predicted to take and the skill mix of staff available during that list. To this end, we have developed the TEX score, a novel scoring system to enable structured listing of cases. The TEX score uses a combination of specific clinical and anatomical variables to assign patients into three levels of rising complexity. At our institution, each patient listed for TAVI is assigned a complexity level at the time of Heart Team discussion, enabling specialist valve nurses to schedule appropriate lists according to available time and available staff. For example, five level 1 cases can be scheduled for a routine TAVI list with nurse-led sedation, whereas a level 3 case, such as one requiring chimney stenting, would be scheduled to be part of a list with fewer cases and dedicated anaesthetic support.

In order to assess the validity of the TEX score, we undertook a retrospective analysis of over 1000 TAVI cases. The stratification of patients based on the TEX score correlated with procedural duration, such that each incremental increase in TEX score was associated with prolonged procedure time. The TEX score also correlates with the incidence procedural complications; significant differences were noted between groups with respect to VARC-3 technical and device success. The difference in VARC-3 technical success was of particular interest since this relates directly to immediate success of a procedure at the time when the patients leave the operating room. As such, being able to identify patients who are at risk of complications that result in this endpoint not being achieved may influence the planning of lists. From our analysis, the main factor driving the difference in VARC-3 technical success was the increased incidence of vascular complications among patients in the level 3 complexity group.

While established, pre-existing risk scores, such as the Society of Thoracic Surgeons or EuroSCORE II, have been applied to TAVI in order to predict outcomes,28 there remains a paucity of complexity scoring systems with the aim of predicting procedural duration and complication rates in order to planning appropriate scheduling. A scoring system based on CT findings, named TAVI-CT score and developed by Corcione et al, has similarities to the TEX score presented here.29 It also stratified patients into three groups, and a number of the variables which contribute to the score are shared (eg, annulus angulation, ileofemoral disease, landing zone calcification). In a prospective validation study of their scoring system, the group demonstrated that vascular complications were significantly more frequent among those in the highest TAVI-CT scoring group. However, the present paper differs in two key areas: the TEX score comprises a combination of CT and clinical factors, rather than just the former, and our study demonstrates a clear relationship between increasing complexity score and procedural duration.

While the finding that more complex procedures take longer and have a higher incidence of complications than more straightforward ones is fairly intuitive, being able to categorise patients using a simple scoring system is potentially of great utility. It can allow an ambitious but achievable number of cases to be scheduled, while potentially reducing the risk of cancellations due to lists over-running.

Limitations

When considering the TEX score and the validation study, there are a number of limitations that need to be borne in mind. The TEX score was developed based on the consensus of four experienced operators at a single institution. As such, practices related to our institution may influence factors that were included in the final scoring system, potentially limiting the generalisability. For example, a vertical aortic annulus can present difficulties when implanting SEVs, which are the predominant type of valve used at our centre. For centres which implant majority BEVs, a vertical aortic annulus may be less problematic. Finally, the validation study was a retrospective, single-centre analysis and so the results have the potential to be influenced by confounding variables, such as iterative changes in practice during the analysis period or varying proportions of usage of different valve types.

Conclusion

The TEX score is a simple tool which allows stratification of patients into three levels of complexity. Increasing complexity levels correlate with increasing procedural duration and reduced VARC-3 technical and device success. This is potentially useful for scheduling patients onto appropriate lists to allow effective utilisation of cardiac catheterisation laboratory resources and ultimately increased procedural numbers.

Impact on daily practice

Increasing demand for TAVI places an ever-greater emphasis on the efficiency of pathways and services. One of the main limitations to increasing TAVI capacity is the availability of cardiac catheterisation laboratory time. The TEX score is a novel scoring system which enables the stratification of patients into three levels of complexity, which correlate with increasing procedural duration and reduced VARC-3 technical and device success. This is potentially useful for scheduling patients onto appropriate lists to allow effective utilisation of cardiac catheterisation laboratory resources and ultimately increased procedural numbers.

  • AA and PB are joint first authors.

  • X: @Dr_Noman_Ali

  • Contributors: AA and PB were involved in writing of the manuscript. SuA, RH, SaA, AA and PB were involved in data collection and analysis. DJB, CM, MC and NA were involved in reviewing and editing the manuscript. NA is the guarantor.

  • Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests: DJB is a consultant and proctor for Medtronic plc and Abbott Vascular, as well as a consultant for Edwards Lifesciences and Boston Scientific. CM is a proctor for Edwards Lifesciences, Medtronic plc and Abbott Vascular and has received honorary speaking fees from Boston Scientific. MC has received educational speaking fees from Medtronic plc, Abbott Vascular and Boston Scientific. NA has received honorary speaking fees from Medtronic and Abbott Vascular.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Supplemental material: This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

Data availability statement

Data are available on reasonable request. The data that support the findings of this study are available from the corresponding author on reasonable request.

Ethics statements

Patient consent for publication:
Ethics approval:

Institutional approval was granted from the Research and Development department, on the basis of this study constituting a service evaluation, and therefore, not requiring patient consent.

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  • Received: 21 June 2024
  • Accepted: 25 November 2024
  • First published: 4 January 2025