Severe aortic stenosis is one of the most common cardiovascular disease processes and is projected to affect 1.4 million people over the age of 75 in the United States by 2025.¹ Surgical aortic valve replacement (SAVR) has traditionally been the standard treatment for severe aortic stenosis, but over the last 10 years, transcatheter aortic valve replacement (TAVR) has rapidly emerged as an alternative treatment, providing comparable outcomes to SAVR in terms of both survival and quality of life.^2-7 Given that the incidence of aortic stenosis is projected to increase with the aging population and the fact that new healthcare technologies (like TAVR) are generally costly, it is important to take into consideration the economic value of TAVR for the treatment of aortic stenosis.

The standard method for economic evaluation of medical technologies is cost-effectiveness analysis: a systematic approach for comparing the costs and benefits of different treatment strategies. In this approach, benefits are generally measured as quality-adjusted life-years (QALYs), which is an outcome measure in which the quantity of life is weighted by the value of the quality of life that a person experiences. The incremental cost-effectiveness ratio (ICER) for the more effective therapy is then calculated by dividing the difference in costs between alternative therapies by the difference in benefits (in QALYs). Based on American Heart Association and American College of Cardiology guidelines, an ICER < $50,000/QALY gained represents high economic value, an ICER between $50,000 and $150,000/QALY represents intermediate value, and an ICER > $150,000/QALY represents low value within the US healthcare system.⁸

When cost-effectiveness analyses have been performed alongside the major randomized clinical trials comparing TAVR with medical therapy or with SAVR, TAVR has been shown to be cost-effective and even cost-saving in certain populations (Table 1). For example, PARTNER 1B (Placement of Aortic Transcatheter Valve Trial, Cohort B) demonstrated that TAVR using a first-generation balloon-expandable valve was cost-effective when compared with medical therapy alone by providing a large survival benefit at an acceptable lifetime cost (ICER $61,889/QALY gained) in an inoperable population.⁹ When TAVR was compared with SAVR in a high-risk surgical population (mean Society of Thoracic Surgeons [STS] score = 11.7%) in Cohort A of PARTNER 1, TAVR continued to provide intermediate to high economic value compared with SAVR with an ICER of $76,877/QALY gained.¹⁰ Subsequent economic analyses of TAVR using a self-expanding valve versus SAVR in a slightly lower-risk (mean STS score = 7.4%) population resulted in an ICER of $55,090/QALY gained.¹¹ More recently, economic analyses have demonstrated that the cost-effectiveness of TAVR versus SAVR is even more favorable in intermediate-risk patients. Among patients enrolled in the randomized PARTNER 2 (mean STS score = 5.8%), we found that over a lifetime horizon, TAVR led to greater quality-adjusted life expectancy while reducing long-term costs by ~$9,000 compared with SAVR, an economically dominant strategy.¹² For patients treated with TAVR in the S3i registry, long-term cost savings were even greater (more than $11,000 per patient).¹²

Table 1: Summary of Cost-Effectiveness of TAVR According to Patient Population

Population	Trial	Δ Costs	Δ Life Expectancy	ICER
Extreme Risk	PARTNER 1, Cohort B	↑↑↑	↑↑↑	Intermediate to High Value
Very High Risk	PARTNER 1, Cohort A	Similar	Slight ↑	Dominant/High Value
High Risk	CoreValve HR	↑↑	↑↑	Intermediate to High Value
Intermediate Risk	PARTNER 2, Cohort A and S3i	↓↓	↑	Dominant
Low Risk	PARTNER 3 and CoreValve Low Risk	???	???	???

The cost-effectiveness analysis results in the intermediate-risk population may seem surprising given the much higher cost of the TAVR prosthesis compared with the SAVR prosthesis (currently ~$32,000 vs. ~$5000) as well as the earlier finding that TAVR was not cost-saving compared with SAVR in the high-risk population. Although it is likely that these results were due in part to the lower rates of comorbidities in the intermediate-risk patients compared with the high-risk population, there are other factors to consider in this economic equation. First, in the intermediate-risk trials, non-procedural costs for the index hospitalization were substantially lower with TAVR than SAVR with associated savings of ~$23,000 per patient, driven largely by a 4.5-day reduction in length of stay (Table 2).¹² In addition, iterative improvements in the TAVR device and delivery system over the last 10 years as well as improved procedural planning and operator experience have led to lower rates of peri-procedural complications (i.e., major bleeding, disabling stroke, and vascular complications), which are associated with increased length of stay and costs.¹³

Table 2: Resource Use and Costs for XT-TAVR Versus SAVR at 2 Years (PARTNER 2, Cohort A)

Resource Category	XT-TAVR	SAVR	Difference (95% CI)	P-Value
Index Hospital Length of Stay	6.4 ± 5.5	10.9 ± 7.6	-4.5 (-5.1 to -3.9)	<0.001
Follow-Up Hospital Days*	735.5 ± 271.2	842.0 ± 290.2	-106.5 (-134.9 to -78.1)	<0.001
Follow-Up Skilled Nursing Facility/Rehab Days*	1350.8 ± 367.5	2121.1 ± 460.6	-770.4 (-812.6 to -728.1)	<0.001
Costs ($)
Index Hospitalization	61,433 ± 17,532	58,545 ± 32,023	2,888 (562 to 5110)	0.014
Follow-Up Hospitalizations	16,785 ± 29,460	19,220 ± 33,937	-2,435(-5784 to 939)	0.138
Rehab/Skilled Nursing Facility	7082 ± 15,377	11,999 ± 17,564	-4,917 (-6571 to -3189)	<0.001
Outpatient Services	5,353 ± 7,301	6,816 ± 19,562	-1,463 (-3215 to -115)	0.024
Follow-Up Physician Fees	10,075 ± 10,532	10,027 ± 9,787	48 (-1031 to 1025)	0.942
Total Follow-Up Costs	46,284 ± 42,728	55,587 ± 49,348	-9,304 (-13,653 to -5375)	<0.001
Cumulative 2-Year Costs	107,716 ± 48,277	114,132 ± 64,498	-6,416 (-11,571 to -1616)	0.014

Lastly, efforts have been made to streamline resource use intra- and post-procedurally. This "minimalist approach" includes the use of conscious sedation, transthoracic echocardiography, percutaneous femoral artery access and closure, performance of the procedure in the catheterization laboratory (as opposed to the operating suite), reductions in procedural staff (physician and non-physician personnel alike), and post-procedural protocols designed to facilitate early discharge. Variations of this approach have been studied on a small scale and have been shown to be associated with a shorter length of stay and lower cost of index hospitalization without evidence of compromise in either procedural safety or efficacy.^14,15 Hence, it is likely that streamlining of the TAVR procedure itself and advances in post-procedural care have contributed to reductions in both length of stay and hospital cost for TAVR compared with SAVR in the intermediate-risk population. Beyond these important cost offsets during the index hospitalization, TAVR also led to substantial reductions in post-discharge costs, mainly due to lower utilization of rehabilitation or skilled nursing facilities and reductions in repeat hospitalizations during the first 6 months of follow-up (Table 2).

Although TAVR has been shown to be cost-effective in the high-risk population and cost-saving in the intermediate-risk population, the cost-effectiveness of TAVR in the low-risk population remains unknown. That said, given what is known about the cost-effectiveness of TAVR in intermediate- and high-risk populations, it is not unreasonable to speculate about the potential cost-effectiveness of TAVR in the low-risk population. Recently, both PARTNER 3 and the Evolut Low-Risk (Evolut Surgical Replacement and Transcatheter Aortic Valve Implantation in Low Risk Patients) trial have demonstrated that over the first year of follow-up, TAVR appears to perform as well, if not better, than SAVR in low-risk patients.^16,17 In the PARTNER 3 trial, TAVR was found to be superior to SAVR for the composite endpoint of death, stroke, or hospitalization at 1 year (8.5% vs. 15.1%; p = 0.001).¹⁶ The Evolut Low-Risk trial showed that TAVR was non-inferior to SAVR for the composite of death or disabling stroke at 2 years (5.3% vs. 6.7%; posterior probability > 0.99 for non-inferiority).¹⁷ Furthermore, both studies demonstrated reductions in healthcare resource utilization with TAVR in terms of hospital length of stay and readmissions for heart failure.^16,17 Thus, with findings that suggest comparable if not better efficacy and reduced hospital resource utilization (which would likely translate to lower costs) with TAVR, it is certainly possible that TAVR will be cost-saving in the low-risk population as well. Nonetheless, achievement of cost savings with TAVR in the low-risk population will depend on a number of factors that are unknown at the present time, including the duration of intensive and nonintensive care, the frequency of repeat hospitalizations (for heart failure and other causes), and the burden of rehabilitation services and custodial care needed for the two treatment groups. Studies are planned to address these specific issues and should be available in the next 12-18 months.

Even if TAVR is cost-saving compared with SAVR in the low-risk population, it is unlikely to be cost-effective unless long-term outcomes (including survival and quality of life) are similar to those for SAVR. Whether this assumption is correct will ultimately depend on whether there are late differences in valve durability or in the consequences of procedure-related complications that are increased with TAVR (e.g., higher rates of mild paravalvular regurgitation or permanent pacemaker placement). Although long-term survival after TAVR and SAVR has been shown to be similar in high-risk patients,^18,19 these outcomes are driven, in part, by the competing risk of non-valve related mortality. Whether these results will hold up in the younger low-risk population, who may require repeat valve replacements down the road, remains unknown.

Although the 10-year durability of current-generation TAVR devices is unknown, it is worth noting that data on bioprosthetic surgical valve durability remain scant as well. Moreover, recent data from randomized trials would suggest that rates of structural valve deterioration are similar with TAVR and SAVR at 5-6 years.^20,21 If ongoing studies in lower-risk patients continue to demonstrate similar long-term durability with TAVR and SAVR devices, it is likely that late mortality with TAVR and SAVR will be similar as well. However, if there is a difference in durability of the valve implants, which would require more repeat valve replacements in the TAVR cohort, it is possible that both the late costs and outcomes could favor SAVR in the low-risk population.

In summary, despite early concerns about the high cost of treatment, data regarding the cost-effectiveness of TAVR have been uniformly positive to date. Indeed, formal economic evaluation alongside randomized clinical trials has demonstrated that TAVR is cost-effective in both the extreme risk and high-risk populations and cost-saving in the intermediate-risk population, at least from the perspective of the US healthcare system. Whether these trends will continue as TAVR expands to low-risk patients remains unknown and will depend, in large part, on factors like valve durability and the long-term consequences of minor complications such as mild paravalvular regurgitation and the need for permanent pacemaker implantation. As we wait for such data, it will be increasingly important to continue to streamline the TAVR procedure and post-procedural care so that this procedure remains fiscally viable and available to all patients who can benefit.

References

1. Osnabrugge RL, Mylotte D, Head SJ, et al. Aortic stenosis in the elderly: disease prevalence and number of candidates for transcatheter aortic valve replacement: a meta-analysis and modeling study. J Am Coll Cardiol 2013;62:1002-12.
2. Smith CR, Leon MB, Mack MJ, et al. Transcatheter versus surgical aortic-valve replacement in high-risk patients. N Engl J Med 2011;364:2187-98.
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10. Reynolds MR, Magnuson EA, Lei Y, et al. Cost-effectiveness of transcatheter aortic valve replacement compared with surgical aortic valve replacement in high-risk patients with severe aortic stenosis: results of the PARTNER (Placement of Aortic Transcatheter Valves) trial (Cohort A). J Am Coll Cardiol 2012;60:2683-92.
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14. Babaliaros V, Devireddy C, Lerakis S, et al. Comparison of transfemoral transcatheter aortic valve replacement performed in the catheterization laboratory (minimalist approach) versus hybrid operating room (standard approach): outcomes and cost analysis. JACC Cardiovasc Interv 2014;7:898-904.
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16. Mack MJ, Leon MB, Thourani VH, et al. Transcatheter Aortic-Valve Replacement with a Balloon-Expandable Valve in Low-Risk Patients. N Engl J Med 2019;380:1695-705.
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Keywords: Transcatheter Aortic Valve Replacement, Cost-Benefit Analysis, Aortic Valve, Quality-Adjusted Life Years, Cost Savings, Hospital Costs, American Heart Association, Skilled Nursing Facilities, Life Expectancy, Femoral Artery, Quality of Life, Conscious Sedation, Patient Readmission, Aortic Valve Stenosis, Heart Valve Prosthesis, Risk Factors, Echocardiography, Comorbidity, Registries, Outcome Assessment, Health Care, Heart Failure, Catheterization, Stroke, Complementary Therapies, Pacemaker, Artificial, Heart Valve Diseases

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