Veterans Affairs Heart Team Experience With Transcatheter Aortic Valve Replacement and Minimally Invasive Surgical Aortic Valve Replacement

Abstract: Objectives. Aortic valve disease is prevalent in the veteran population. Transcatheter aortic valve replacement (TAVR) and minimally invasive surgical aortic valve replacement (MIAVR) are minimally invasive approaches predominantly performed at higher-volume cardiac centers. The study aim was to evaluate our experience with minimally invasive techniques at a Veterans Affairs Medical Center (VAMC), since outcomes from lower-volume federal facilities are relatively unknown. Methods. This study examined retrospective data from 228 consecutive patients who underwent treatment for isolated aortic valve disease with MIAVR or TAVR via intent-to-treat at a VAMC between January 2011 and July 2017. Perioperative outcomes were analyzed using Stata version 15. Results. Operative mortality was 1.1% for MIAVR and 0.7% for TAVR (χ² P=.79). Median length of hospital stay was 10 days (interquartile range [IQR], 7-14 days) for MIAVR and 4 days for TAVR (IQR, 3-6 days; Mann-Whitney P<.001). Postoperative new-onset atrial fibrillation occurred in 52% of MIAVR patients and 5.2% of TAVR patients (χ² P<.001). Stroke occurred in 2.2% of MIAVR patients and 3.0% of TAVR patients (χ² P=.71). In patients who underwent MIAVR, 5.4% required placement of a permanent pacemaker postoperatively, compared with 14% of TAVR patients (χ² P=.04). Mild paravalvular leak (PVL) affected 2.2% of MIAVR and 28% of TAVR patients, with moderate PVL reported in 2.2% of MIAVR and 3% of TAVR patients (χ² P<.001). Conclusions. The VAMC heart team offers MIAVR and TAVR to veterans with isolated aortic valve disease, and has achieved excellent outcomes despite relatively lower case volumes. Both offer excellent hemodynamic results, with low mortality in a complex population.

J INVASIVE CARDIOL 2019;31(8):217-222. Epub 2019 May 15.

Key words: atrial fibrillation, minimally invasive surgical aortic valve replacement, MIAVR

Aortic valve replacement (AVR) is the only effective treatment for patients with severe symptomatic aortic stenosis (AS) or aortic regurgitation (AR).^1-3 AVR remains one of the most commonly performed procedures in cardiac surgery, with ~67,500 surgical AVR (SAVR) procedures and 24,808 transcatheter AVR (TAVR) procedures performed annually in the United States.^4,5 The Veterans Affairs (VA) Healthcare System services ~9 million patients at 144 hospitals nationwide.⁶ In 2016, 53% of the veteran population was reported to be aged 65 years or older.⁷ Since AS predominantly affects the elderly, it is imperative that VA medical centers not only offer excellent outcomes, but also offer the latest treatments for aortic valve disease. Most VA cardiac care centers are affiliated with academic centers of excellence, and are ideal for increasing access to innovative, advanced techniques and targeting a population in need.^8,9

In recent years, TAVR and minimally invasive AVR (MIAVR) have demonstrated significantly increased case volumes in the United States, with patients demanding less-invasive surgical options and TAVR expanding indications into intermediate-risk populations and ongoing trials in low-risk patients.^10,11 The smaller incisions of MIAVR confer the advantages of reduced pain, less surgical trauma, and reduced bleeding, in addition to shorter hospital stays and earlier functional recovery.^11-15 Despite the increasing popularity of MIAVR and TAVR, few studies have directly compared the outcomes of these techniques, and none have done so at low-volume federal institutions.¹⁶ Due to the technical complexity and multidisciplinary nature of the heart team required for TAVR, and advanced surgical skills required for MIAVR, the majority of these procedures are performed at high-volume cardiac-care facilities.^15,17 As a result, the current literature disproportionately reports outcomes from these high-volume cardiac centers, and outcomes at lower-volume federal facilities are unknown and excluded from the national Society of Thoracic Surgeons (STS) database.⁹

Methods

This retrospective, single-center, intent-to-treat series evaluates consecutive AVRs via MIAVR or TAVR. Patients who received concomitant cardiac surgical procedures were excluded. The Institutional Review Board at San Francisco VAMC (SFVAMC) and Committee on Human Research at University of California San Francisco (UCSF) Medical Center approved this study. A total of 228 patients underwent treatment for isolated aortic valvular disease at our VAMC between January 25, 2011 and July 31, 2017; a total of 93 patients underwent MIAVR and 135 patients underwent TAVR. Only 15% of isolated SAVR patients underwent full sternotomy over this time period, but 100% of SAVRs were performed via MIAVR by 2016. All patients received extensive preoperative screening, including cardiac catheterization, echocardiography, and computed tomographic angiography (CTA). Medical records were used to assess patients’ demographics, risk profiles, clinical presentations, operative characteristics, and postoperative morbidity and mortality. Relevant preoperative data comparing MIAVR and TAVR cohorts were evaluated using variables from the STS risk score for predicted risk of mortality (PROM, or the risk of death at 30 days after the procedure).¹⁸

Operative characteristics. MIAVR patients received mini-sternotomy (100%), planned using preoperative CTA. Details on the MIAVR procedure have been previously described.^12,19,20 Sixty-four patients (68.8%) undergoing MIAVR received Carpentier-Edwards model 3300TFX Perimount bioprosthesis (Edwards Lifesciences), twenty-three patients (24.7%) received Edwards Intuity model 8300AB Rapid Deployment sutureless bioprosthesis (Edwards Lifesciences), and 6 patients (6.5%) received other mechanical aortic valves (St. Jude Medical).

In TAVR patients, CTA was used to size aortic annulus, assess the burden of femoral arterial disease, and determine optimal vascular access. The majority of patients underwent transfemoral TAVR, with 2 patients undergoing transapical TAVR due to extensive peripheral arterial disease. Sixteen TAVR patients (11.9%) received Sapien, 31 patients (23.0%) received Sapien XT, and 45 patients (33.3%) received Sapien 3 (Edwards Lifesciences), while 16 patients (11.9%) received CoreValve and 27 patients (20.0%) received EvolutR (Medtronic) transcatheter heart valves (THVs) using standard techniques previously described.²¹

Statistical analysis. Statistical analyses were performed using Stata version 15 (StataCorp). Data are presented as median with interquartile range (IQR) for continuous variables and percentages for categorical variables. Univariate analysis using Mann-Whitney-Wilcoxon test and Chi-squared (χ²) test was performed for statistical analysis, with statistical significance defined as P<.05.

Results

Baseline risk profile. Baseline patient characteristics are detailed in Table 1. Overall, TAVR patients were significantly older, and had a greater proportion of comorbidities, including hypertension, prior stroke, lower ejection fraction, and higher New York Heart Association class congestive heart failure. A majority of patients (90% MIAVR and 99% TAVR) underwent treatment for AS. Severity of AS was comparable between the two cohorts, with a median transvalvular gradient of 47 mm Hg (IQR, 40-55 mm Hg) in MIAVR patients and 44 mm Hg (IQR, 38-50 mm Hg) in TAVR patients (P=.06). Of MIAVR patients, 99% were low risk (STS PROM <4%) and 1.1% were intermediate risk (STS PROM 4%-8%).²² The TAVR cohort was deemed intermediate, high, or prohibitive risk by two cardiac surgeons during preoperative multidisciplinary heart team case conferences. STS did not capture certain variables, such as frailty, cirrhosis, pulmonary hypertension, or porcelain aorta.

Procedural outcomes. Perioperative characteristics and outcomes are presented in Table 2. There was no significant difference in operative mortality between the two groups (MIAVR 1.1% and TAVR 0.7%; P=.79). No TAVR patients required conversion to SAVR. All outcomes are reported per Valve Academic Research Consortium (VARC)-2  endpoint definitions.²³

Median length of hospital stay was 10 days (IQR, 7-14 days) for MIAVR and 4 days (IQR, 3-6 days) for TAVR (P<.001). Two MIAVR patients (2.2%) and 4 TAVR patients (3.0%) experienced stroke within 30 days of procedure (P=.71). One MIAVR patient (1.2%) experienced transient ischemic attack in the postoperative period, while none were reported in the TAVR cohort (P=.23). There was a notably higher rate of new-onset postoperative atrial fibrillation after MIAVR, occurring in 48 patients (52.0%), compared to 7 patients (5.2%) after TAVR (P<.001). Postoperative complete heart block necessitating permanent pacemaker (PPM) implantation at index hospitalization occurred in 19 TAVR patients (14.0%) vs 5 MIAVR patients (5.4%; P=.04).

Hemodynamic outcomes. Sixty-nine of 92 MIAVR patients received sutured valves (median size, 23 mm; IQR, 21-25 mm), and 23 received sutureless valves (median size, 25 mm; IQR, 25-27 mm). There was a significant difference in implanted valve size between patients who received sutured vs sutureless valves (P<.01). Median valve size for 134 TAVR patients was 29 mm (IQR, 26-29 mm). Similarly, there was a statistically significant difference in implanted valve size between sutureless valves and TAVR (P<.001). Postoperative mean pressure gradient was 14 mm Hg (IQR, 10-17 mm Hg) in sutured MIAVR, 6.1 mm Hg (IQR, 3.9-10 mm Hg) in sutureless MIAVR, and 8.3 mm Hg (IQR, 6-11 mm Hg) in the TAVR cohort. The difference in postoperative mean pressure gradient was statistically significant between sutured and sutureless MIAVR (P<.001); however, no significant difference was found between sutureless MIAVR and TAVR (P=.07). Qualitative paravalvular leak (PVL) was noted to be worse in TAVR than MIAVR patients, with 37 TAVR patients (28.0%) experiencing mild and 4 (3.0%) experiencing moderate PVL, compared with 2 MIAVR patients (2.2%) experiencing mild and 2 (2.2%) experiencing moderate PVL (χ² P<.001).

Follow-up data. Figure 1A shows Kaplan-Meier survival curves: actuarial survival rates for TAVR were 91.0 ± 2.5% at 1 year, 79.6 ± 3.6% at 2 years, and 58.6 ± 6.0% at 5 years; actuarial survival rates for MIAVR were 97.8 ± 1.5% at 1 year and 2 years, and 88.8 ± 4.6% at 5 years (P<.01). Figure 1B shows actuarial freedom from late thromboembolism: TAVR rates were 97.7 ± 1.3% at 1 year, 94.8 ± 2.1% at 2 years, and 81.2 ± 12.7% at 5 years; MIAVR rates were 98.9 ± 1.1% at 1 year, 95.0 ± 2.4% at 2 years, and 89.3 ± 4.0% at 5 years (P=.73). Figure 1C demonstrates actuarial freedom from late structural valve deterioration, defined as mean gradient ≥20 mm Hg and <40 mm Hg on echocardiography per recently defined guidelines:²⁴ TAVR rates were 99.2 ± 0.8% at 1 year, 96.3 ± 1.8% at 2 years, and 78.4 ± 12.6% at 5 years; MIAVR rates were 100 ± 0% at 1 year, 100 ± 0% at 2 years, and 96.5 ± 3.4% at 5 years (P=.01). Figure 1D shows actuarial freedom from late endocarditis: TAVR rates were 99.2 ± 0.8% at 1 year, 99.2 ± 0.8% at 2 years, and 95.9 ± 3.3% at 5 years; MIAVR rates were 100 ± 0.0% at 1 year, 100 ± 0.0% at 2 years, and 96.6 ± 3.4% at 5 years (P=.37). Figure 1E shows actuarial freedom from late bleeding events: TAVR rates were 97.6 ± 1.4% at 1 year and 96.7 ± 1.6% at 2 years and 5 years; MIAVR rates were 98.9 ± 1.1% at 1 year, 97.6 ± 1.7% at 2 years, and 95.3 ± 2.8% at 5 years (P=.91).

Discussion

Aortic valve disease in veterans is on the rise, due to a high proportion of elderly individuals.^7,25 As a result, the number of isolated AVRs performed at VAMCs across the country has increased.⁸ We report here a single-center, retrospective study of TAVR vs MIAVR given the limited penetrance of both TAVR and MIAVR nationally across VAMCs. Our VAMC was the fourth TAVR center to be approved, with the number of VA TAVR centers still limited nationally. Limited MIAVR numbers performed in VA centers nationally preclude multicenter analyses. While TAVR has been rapidly adopted, MIAVR still has limited adoption in the STS database, with an estimate of 12% MIAVR in the United States, 12% in the United Kingdom, and ~25% in Germany.²⁶ At Cleveland Clinic, a high-volume United States center, MIAVRs increased from 12.4% to 29.6% of total SAVRs over 18 years in 2013.¹⁵ These reflect estimates of MIAVR performance rates at higher-volume cardiac surgery centers. Much of MIAVR literature is from a single institution or from propensity-matched cohorts, and does not capture regional or institutional practices of MIAVR vs conventional SAVR. Nevertheless, our VAMC has prioritized providing patients with the latest in AVR technology and converted our standard of care for isolated aortic valve disease exclusively to MIAVR or TAVR.²⁷

TAVR demonstrated lower overall survival, reflecting a higher-risk elderly population, as evidenced by increased age and greater presence of STS comorbidities, ie, hypertension, prior stroke, prior myocardial infarction, end-stage renal disease on dialysis, and presence of PPM/automatic implantable cardioverter-defibrillator prior to procedure. We have demonstrated that MIAVR and TAVR can be performed safely at our institution, with a low incidence of operative mortality that does not differ between the two approaches and compares similarly with results reported by high-volume facilities.²⁷ Terwelp et al reported outcomes from a propensity-matched, multi-institution, retrospective review of 2571 patients undergoing full-sternotomy SAVR, MIAVR, and TAVR. Postoperative complication rates observed in our patients mirrored their results. They found higher incidence of stroke in TAVR and higher incidence of atrial fibrillation in MIAVR; we similarly found higher incidence of atrial fibrillation in MIAVR, but no differences in stroke between the two cohorts.²⁷ Taken in conjunction with our results, these data support the notion that MIAVR and TAVR can be safely and effectively adopted into practice at both higher-volume and lower-volume cardiac centers.

Outside the United States, two studies directly compared MIAVR and TAVR postoperative outcomes, exclusively in high-risk patients.^28,29 Santarpino et al specifically examined TAVR vs MIAVR with sutureless valves.²⁸ They reported higher incidence of PPM requirement in MIAVR patients (10.8%) vs TAVR patients (2.7%), whereas we found a higher rate of PPM in TAVR patients (14.0%) vs MIAVR patients (5.4%).²⁸ This difference is likely due to their use of sutureless valves, because in our cohort, the majority of patients received sutured bioprostheses until sutureless valves were approved by the Food and Drug Administration and commercially available in 2016. They similarly reported no difference in stroke rate between the two groups and significantly higher incidence of PVL in TAVR patients (13.5%) vs MIAVR patients (0.0%).²⁸ A study by Miceli et al similarly compared TAVR with MIAVR using sutureless valves through a right anterior mini-thoracotomy, while our MIAVRs were performed via mini-sternotomy.²⁹ They demonstrated no significant difference in operative mortality or stroke rates, but significantly worse PVL rate in TAVR, with worse 1-year and 2-year survival rates in this cohort.²⁹ We did not observe TAVR mortality related to PVL, likely due to recent TAVR devices having design modifications that reduced PVL.^30,31 In our study, TAVR patients were higher risk than MIAVR patients. TAVR patients were categorized as intermediate risk or greater during heart team discussions. Direct comparisons of similar intermediate-risk and high-risk patients between TAVR and MIAVR in our patients were not possible because the transitions to both technologies occurred during the same time frame; thus, no retrospective cohort of MIAVR in those higher-risk categories existed for comparison. In addition, this time frame reflects TAVR expansion toward intermediate-risk patients nationally.

One notable finding of our study is the equivalent hemodynamics between sutureless MIAVR and TAVR. Studies have suggested improved hemodynamics with TAVR over SAVR given the smaller SAVR bioprosthetic sizes implanted vs larger TAVR size with its stent’s ability to widen left ventricular outflow tract (LVOT) and improve flow.^32-34 Our median MIAVR size implanted was indeed larger than our traditional SAVR bioprosthetic size, in part due to the CTA sizing algorithm used. Aortic annulus measurements obtained from preprocedural CTA helped to true-size MIAVR sutureless bioprosthesis, rather than under-sizing per manufacturer recommendations. An additional factor leading to excellent gradients with MIAVR sutureless bioprostheses was the design element of the cuffed stent anchoring the valve, which expanded the LVOT similar to TAVR. We found no significant differences in mean gradients between TAVR and MIAVR, where MIAVR had mean gradients <10 mm Hg. Since moderate structural valve deterioration has now been defined as gradient >20 mm Hg, achieving initial low gradients with TAVR or SAVR is important in order to achieve optimal valve performance and ensure the best long-term outcomes.²⁴

Conclusion

We report outcomes of minimally invasive techniques for AVR offered by a VAMC heart team, demonstrating these procedures can be performed safely and with excellent outcomes at low-volume federal facilities comparable with those published by high-volume cardiac centers. This study is important since: (1) clinical outcomes from lower-volume institutions are not often presented in the literature, and as such it is crucial to demonstrate similar safety and feasibility of adopted techniques; (2) outcomes from federal facilities are not captured by national STS databases and such results should be evaluated and presented for clarity and transparency in this era; and (3) MIAVR is not widely adopted at federal facilities for a multicenter study, and these results encourage adoption of TAVR and MIAVR techniques in the veteran population. While MIAVR and TAVR differ in their associated postoperative complications relative to one another, both are safe and feasible at lower-volume federal institutions with excellent clinical outcomes comparable with those reported for high-volume centers.

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^*Joint first authors.

From the ¹Division of Cardiothoracic Surgery and ²Division of Cardiology, University of California San Francisco and San Francisco Veterans Affairs (VA) Medical Centers, San Francisco, California.

Presented at the Association of VA Surgeons Annual Meeting on May 7th, 2018 in Miami Beach, Florida.

Funding: This study was supported by a National Institutes of Health grant (R01HL119857-01A1).

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Tseng reports grants from the University of California, NIH, VA, and Canadian Health Institutes; editor-in-chief of Journal Heart Valve Disease; patent holder for TAVR device (US10034748B2). The remaining authors report no conflicts of interest regarding the content herein.

Manuscript submitted January 9, 2019, accepted January 21, 2019.

Address for correspondence: Elaine E. Tseng, MD, San Francisco VA Medical Center, 4150 Clement St., 112D, San Francisco, CA 94121. Email: Elaine.tseng@ucsf.edu