Transcatheter Aortic Valve Implantation (TAVI) Outcome According to Standardized Endpoint Definitions by the Valve Academic Research Consortium (VARC)

ABSTRACT: Background. Transcatheter aortic valve implantation (TAVI) has become an accepted treatment option for severe aortic stenosis (AS) in high-risk individuals. Yet, current results are difficult to compare given the lack of standardized definitions. Methods and Results. TAVI was performed in 130 high-risk individuals. The Edwards SAPIEN (n = 50) and the Medtronic CoreValve (n = 80) prostheses were implanted by transfemoral (75%) or transapical (25%) access. Outcomes at 30 days and 1 year are reported according to the newly established Valve Academic Research Consortium (VARC) criteria. Median follow-up was 235 days (range, 44–490 days). Thirty-day device success was high (91.5%). Combined safety endpoint at 30 days was 20.8%, with an all-cause mortality of 11.5%. Major vascular complications (11.5%), life-threatening or disabling bleeding (8.5%), and acute kidney injury (6.2%) were further major adverse events. At 1-year follow-up, valve performance was accurate in 94.7% of patients. However, prosthetic-valve associated complications, such as new left bundle branch block (20.0%) or permanent pacemaker implantation (34.7%), were common; cumulative prosthetic-valve associated complications were significantly more frequent in patients treated with a Medtronic CoreValve prosthesis (p = 0.0012). Overall 1-year survival was 80%, with the VARC combined efficacy endpoint (composite of survival, freedom from therapy failure, and accurate valve performance) met in 70.2%. In particular, at 1 year, 68.5% of the patients were living independently at home. Conclusion. The newly established VARC standardized definitions are useful for TAVI outcome reporting.

J INVASIVE CARDIOL 2011;23:307–312

Key Words: Edwards Sapien, Medtronic CoreValve, valve replacement

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Degenerative aortic stenosis (AS) is the most common isolated valve disease in Western communities.¹ The current prevalence in individuals aged more than 75 years is 4.8%, and the incidence is steadily increasing as a result of the ageing population.² Once symptoms develop, the disease rapidly progresses; without treatment, patients usually die within 2–3 years.^3,4 Surgical aortic valve replacement (SAVR) is considered the standard treatment for symptomatic AS.^4,5 However, due to significant comorbidities, elderly patients often are at high operative risk, and hence, are not suitable candidates for surgery. Indeed, about 30% of patients with symptomatic severe AS are thus not referred to surgery.^3,4,6 Since the first-in-man procedure by Alain Cribier in 2002, transcatheter aortic valve implantation (TAVI) has become a valuable less invasive treatment option for these high-risk individuals.^7,8

Comprehensive clinical testing and outcome assessment is a key issue in interventional cardiology and the basis for evidence-based medicine in the field. TAVI — particularly given this new technology’s explosive growth — should follow the same rules. Yet, the lack of uniform outcome measures for this entirely different catheter-based therapy did not allow for meaningful comparisons. Most recently, the Valve Academic Research Consortium (VARC) proposed standardized consensus definitions for clinical endpoints, including device success, safety, and efficacy at defined points in time.⁹ Although primarily intended for application in clinical trials, the VARC standardized definitions may generally improve the outcome reporting of TAVI, and thus also facilitate future comparisons among the numerous ongoing studies and registries.

Recently, two centers revisited their TAVI outcomes according to the VARC criteria.^10,11 Both registries included one prosthesis type only and outcome was limited to 30 days. In this study, single-center 30-day and 1-year TAVI outcomes of both currently available prosthesis types, the Medtronic CoreValve (Medtronic, Minneapolis, Minnesota) and the Edwards SAPIEN prosthesis (Edwards Lifesciences, Irvine, California), are reported according to the recently defined VARC definitions.

Methods

Patients. The present analysis includes all 130 consecutive patients who underwent TAVI at our institution between May 2008 and October 2010. The indication for TAVI was symptomatic severe native AS in individuals not amenable to open-heart surgery for one of the following reasons: 1) excessive estimated risk as expressed by a logistic EuroSCORE ≥ 20%; 2) specific surgical contraindications, such as porcelain aorta or previous chest irradiation; or 3) expected high perioperative morbidity as a result of preexisting specific conditions, including critical liver disease, critical lung disease (FEV1 ≤ 1 L), and age ≥ 88 years. Severe AS was defined as either a mean transaortic systolic pressure gradient ≥ 40 mmHg or an aortic valve area of < 1.0 cm² or < 0.6 cm²/m². The decision for the procedure was made by the “heart team,” a multidisciplinary team consisting of at least one interventional and clinical cardiologist, at least one cardiothoracic surgeon, one cardiac anesthesiologist, and one imaging specialist. Definite acceptance required both technical feasibility (primarily determined by a native aortic annulus diameter in the range of 18–27 mm), as well as general agreement that the risk associated with conventional SAVR was prohibitive. Active endocarditis, myocardial infarction within 14 days, cardiogenic shock, and a life expectancy of < 1 year were considered contraindications. Written informed consent was obtained.

Preinterventional patient assessment typically included transthoracic and transesophageal echocardiography (TEE), coronary angiography, and multislice computed tomography (MSCT) of the aortic root and aortoiliofemoral system. Transapical access was used in patients with small iliofemoral artery diameters as a result of small body size or atherosclerotic disease.

Devices. Both prostheses that are currently commercially available in Switzerland were utilized: the Medtronic Core-Valve prosthesis (26 and 29 mm; n = 80; 62%) and the Edwards SAPIEN prosthesis (23 and 26 mm; n = 50; 38%). As previously described, both prostheses consist of a tri-leaflet pericardial tissue valve sewn into a stent-like metal frame.¹² The majority of patients received the self-expanding Medtronic CoreValve prosthesis, consisting of porcine tissue and a nitinol stent. The second-generation, balloon-expandable Edwards SAPIEN TFX 9000, which is made out of bovine tissue and a stainless-steel frame, was implanted in all 33 transapical cases and the initial 13 out of 17 patients treated with the transfemoral Edwards system. Most recently, in a limited number of transfemoral cases (n = 4), the newest balloon-expandable cobalt-chromium prosthesis (Edwards SAPIEN XT) was utilized.

Procedures. Both transfemoral and transapical procedures were performed in the cardiac catheterization laboratory as previously described.^7,13,14 In brief, TAVI was performed under general anesthesia and TEE guidance (n = 128; 98%), except for 2 transfemoral cases with local anesthesia and prosthesis positioning solely based on fluoroscopy. In transfemoral cases, access was primarily percutaneous by direct puncture of the common femoral artery. Transapical cases were performed via mini-thoracotomy. Access size for Medtronic CoreValve transfemoral and Edwards SAPIEN transapical procedures was fixed to 18 and 26 French (Fr), respectively. In contrast, access size in patients receiving an Edwards SAPIEN prosthesis via the femoral route ranged from 18–24 Fr depending on the prosthesis size and the use of the RetroFlex 3 or the latest NovaFlex delivery catheter (all manufactured by Edwards Lifesciences). In all patients, prosthesis implantation was preceded by balloon aortic valvuloplasty under rapid burst ventricular pacing to reduce cardiac output. Similarly, rapid burst pacing was utilized during implantation of balloon-expandable prostheses. Selection of the prosthesis size was based on pre- and intraprocedural assessment of the annulus by MSCT and TEE, respectively. The 23 mm Edwards SAPIEN or 26 mm Medtronic CoreValve were chosen for smaller annulus sizes of 18–21 mm and 20–23 mm, respectively. Larger annulus sizes up to 25 mm were covered with the 26 mm Edwards SAPIEN or up to 27 mm with the 29 mm Medtronic CoreValve. Closure of transapical access was surgical, whereas in transfemoral procedures, percutaneous closure with the Prostar XL device was primarily attempted.

Data collection and VARC definitions. Data collection included demographic and procedural variables, as well as clinical and echocardiographic pre- and postprocedural information. Clinical follow-up and transthoracic echocardiography were routinely performed 1, 6, and 12 months after the procedure. Outcomes were reported according to the VARC definitions.⁹ In brief, device success is defined as successful vascular access, delivery and deployment of one prosthesis, correct position and performance of the prosthetic valve, and complete retrieval of the delivery system. Combined safety endpoint at 30 days includes all-cause and cardiovascular mortality, major stroke, life-threatening or disabling bleeding, acute kidney injury stage 3 including renal replacement therapy, periprocedural myocardial infarction, major vascular complications, and repeat interventional or surgical therapy. Furthermore, prosthetic valve performance and valve-associated complications, as well as clinical benefit endpoints and therapy-specific endpoints, were assessed.

Statistical analysis. Continuous variables are presented as means ± standard deviations when normally distributed and as medians and interquartile ranges when not normally distributed. Categorical variables are given as frequencies and percentages. Continuous variables before and after TAVI were tested for differences with the Wilcoxon signed-rank test. Categorical variables were tested by the Pearson’s x² test or the Fisher’s exact test, as appropriate. Time-to-event relations were constructed on the basis of all available follow-up data, presented as Kaplan-Meier curves, and tested for differences with the log-rank test. A two-sided p-value of < 0.05 was considered statistically significant. All statistical analyses were performed with the use of SAS version 9.1 (SAS Institute Inc, Cary, North Carolina).

Funding sources. Lukas Altwegg has partially been supported by grants of the Swiss National Research Foundation (Special Programme University Medicine: Grant Nr 33CM30-1241112/1 and 3100-068118.02/1).

Results

Baseline characteristics. TAVI was attempted in 130 consecutive patients (median age, 83 years; range, 78.8–86 years; 49.2% male). Access was either transfemoral (n = 97; 75%) or transapical (n = 33; 25%). All patients had severe AS with a mean systolic pressure gradient of 49 mmHg (range, 38–57 mmHg) and a calculated aortic valve area of 0.6 cm² (range, 0.5–0.7 cm²). Symptoms of AS were congestive heart failure (n = 96; 73.8%), angina (n = 24; 18.5%), and syncope (n = 10; 7.7%). Patients were at high surgical risk as documented by a median logEuroSCORE of 23 (range, 14.7–30.3). Patients who were not at increased risk as assessed by logEuroSCORE had other specific comorbidities that contributed to excessive surgical risk. Baseline characteristics are shown in Table 1. Median follow-up was 235 days (range, 44–490 days).

Device success at 30 days. Device success at 30 days was achieved in 91.5% of patients (Table 2). Two patients with attempted Medtronic CoreValve implantation died due to major bleeding prior to valve deployment, and 3 patients (2.3%) had a second valve implanted because of prosthesis malposition/embolization during the first attempt. Prosthetic aortic regurgitation ≥ grade 3 was observed in 8 patients (6.2%), whereas prosthetic valve stenosis did not occur. Median hospital stay was 11 days (range, 8–18.5 days). Median hospital stay was shorter in patients with device success as compared to those with device failure [11 days (range, 8–18 days) versus 22 days (range, 19–23.5 days); p = 0.04)]. Furthermore, device failure translated into increased mortality at 30 days, as 54.6% of these patients died compared to 7.6% of the patients with a successful procedure (p = 0.0003). Device success was 88.7% in transfemorally treated patients, whereas complete device success was achieved in transapically treated patients. However, this difference did not reach statistical significance (p = 0.06). There was a clear trend toward more unsuccessful procedures with the Medtronic CoreValve prosthesis, as 10 of 11 patients with failed device success were treated with this prosthesis  (p = 0.05).

Therapy-specific endpoints at 30 days. Therapy-specific endpoints were observed in 11 patients (8.5%). Six of them (4.6%) developed cardiac tamponade, and 5 (3.8%) had prosthetic valve embolization, which was procedural malpositioning/malplacement rather than frank embolization. Embolization/malpositioning occurred solely in patients treated with a Medtronic CoreValve (p = 0.08). No late embolization was noted beyond 30 days.

Combined safety endpoint at 30 days. At 30 days, combined safety endpoint was 20.8% with an all-cause mortality of 11.5% (Table 2). All deaths were due to cardiovascular causes. Life-threatening or disabling bleeding was observed in 11 patients (8.5%) and was related to access-site or access-related bleedings. Major vascular complications were observed in 15 patients (11.5%), 14 of whom were treated with a transfemoral approach (transfemoral versus transapical: p = 0.11). Eight patients (6.2%) developed acute kidney injury stage 3 or needed renal replacement therapy. Bleeding and major vascular complications were each associated with an increased 30-day mortality (p = 0.0003); however, acute kidney injury stage 3 or renal replacement therapy did not translate into increased mortality in our patient cohort (p = 0.23). Periprocedural myocardial infarction occurred in 2 patients (1.5%), and stroke in 1 patient (0.8%). Combined major adverse events translated into a longer median hospital stay [29.5 days (range, 12.5–60 days) versus 11 days (range, 8–17 days); p = 0.002] and an increased 30-day mortality (p < 0.0001).

Prosthetic valve performance at 1 year. Mean aortic valve gradient decreased from 49 mmHg (range, 38–57 mmHg) at baseline to 9 mmHg (range, 7–10 mmHg) 1 month after TAVI (p = 0.0001), and remained stable over the 1-year follow-up period (9 mmHg; range, 7–10 mmHg). Left ventricular ejection fraction at baseline was 59% (range, 47–65%) and was preserved over the entire follow-up period. At 1 year, prosthetic valve dysfunction was observed in 6 patients (8%), all with a transfemoral approach. Failure was due to valve regurgitation (n = 4; 5.3%) and prosthetic valve thrombosis (n = 2; 2.7%). Neither prosthetic valve stenosis nor endocarditis were observed within the first post-procedural year.

Prosthetic-valve associated complications at 1 year. Cumulative combined prosthetic-valve associated complications were observed in 60% of the patients at 1 year. New left bundle branch block developed in 15 patients (20%) and new supraventricular or ventricular arrhythmia developed in 45 patients (60%). Permanent pacemaker implantation (< 30 days) was needed in 26 patients (34.7%). Coronary obstruction was seen in 1 patient. Prosthetic-valve associated complications did not differ significantly between transfemorally and transapically treated patients. However, cumulative prosthetic-valve associated complications were significantly more frequent in patients with a Medtronic CoreValve as compared to those with an Edwards SAPIEN prosthesis (p = 0.004; Figure 1). Excluding permanent pacemaker implantation, cumulative prosthetic-valve associated complications did not differ between the two prosthesis types (p = 0.19).

Combined efficacy endpoint at 1 year. Cumulative combined efficacy endpoint (composite of survival, freedom from therapy failure, and accurate valve performance) was met in 70.2% of the patients at 1 year. All-cause mortality beyond 30 days was 10.5%; and was comparable between transfemorally and transapically treated patients as well as between Medtronic CoreValve and Edwards SAPIEN prostheses. Repeat admission for valve-related complications or congestive heart failure after 1 month was required in 14 patients (20.9%). Readmission did not translate into an increased 1-year mortality (p = 0.72). Beyond 30 days, late aortic regurgitation ≥ grade 3 was observed in 3 patients (4.5%). No prosthetic valve stenosis was observed (Figure 2).

Survival, symptoms, and living status at 1 year. Overall 1-year survival was 80%. Reasons for mortality at 1-year follow-up were as follows: heart failure (n = 9); unexplained sudden death (n = 4); myocardial infarction (n = 1); and multi-organ failure (n = 1).

At baseline, 3 patients (2.3%) were in New York Heart Association (NYHA) class I, 33 (25.4%) in class II, 71 (54.6%) in class III, and 23 (17.7%) in class IV. One month after the procedure, only 10 (9.8%) and 3 (2.9%) of 102 patients were in class III and IV, respectively, representing a clear improvement in symptom status (p = 0.0001). At 1-year follow-up, none of the patients were in class III and IV (p = 0.0001).

At baseline, 95 patients (73.1%) lived at home independently, 34 (26.2%) needed home care or were in an assisted living facility, and 1 patient (0.8%) was in hospital. At 1-year follow-up, 37 (68.5%) lived at home independently, 15 (28.8%) needed assisted living, and 2 (3.7%) were hospitalized. Interestingly, living status did not differ at 1-year post TAVI as compared to baseline (p = 0.33).

Discussion

Single-center TAVI outcome is reported according to the recently defined VARC definitions, including both prosthesis types, the Medtronic CoreValve and the Edwards SAPIEN prosthesis, and providing a 30-day and 1-year follow-up. Standardized VARC definitions appear to facilitate outcome reporting beyond randomized clinical trials.^10,11 Major findings in this patient cohort were a high device success and a combined safety endpoint of 20.8%, with a mortality of 11.5% at 30 days. Analysis according to the VARC definitions further highlighted the bulk of prosthetic-valve associated complications, which were significantly different between prosthesis type. Overall 1-year survival was 80% and the VARC efficacy endpoint was met in 70.2%. In particular, 68.5% of patients were living independently at home at 1 year after the procedure.

Device success and combined safety endpoint. Thirty-day device success was high (91.5%). Device success according to the VARC definitions cannot be compared to procedural success rates previously reported in other trials, as both are differently defined. Procedural success is often specified as implantation of a functioning prosthetic valve within the aortic annulus.^15–18 However, absence of prosthesis stenosis or regurgitation and correct implantation of one prosthesis are required for a successful implantation of the device according to the VARC definitions. As expected, failed device success translated into a longer hospital stay and an increased mortality; indeed, 55% of patients with failed device success died as compared to 8% of patients with a successful procedure.

Combined safety endpoint at 30 days was observed in 20.8% of patients. Life-threatening or disabling bleeding episodes were observed in 8.5% of patients, and major vascular complications in 11.5%, which is in line with previously reported data.^19–21 In our patient cohort, acute kidney injury as one of the most common complications following TAVI was observed in 6.2% of patients. This is comparable with recently reported data applying the VARC definitions,¹⁰ and slightly less than previously reported rates of approximately 11.7–28%.^11,22,23

Prosthetic-valve associated complications. At 1-year follow-up, prosthetic-valve associated complications, such as new left bundle branch block, permanent pacemaker implantation, or new arrhythmias, were frequently observed. Indeed, 60% of patients displayed these complications. However, prosthetic-valve associated complications neither translated into increased mortality nor a prolonged hospital stay. Hence, prosthetic-valve associated complications do not seem to substantially influence outcome or prolong hospital stay of patients following TAVI, as prompt and successful treatment is usually available. Cumulative prosthetic-valve associated complications were more frequent in patients treated with a Medtronic CoreValve as compared to those treated with a Edwards SAPIEN prosthesis. This difference was caused by a higher number of patients requiring a permanent pacemaker following Medtronic CoreValve implantation. However, further studies with larger patient cohorts are needed to fully investigate this issue.

Survival, symptoms, and living status. Thirty-day mortality in our patient cohort was 11.5%, and was unexceptional due to cardiovascular causes. Overall 1-year survival was 80%. Heart failure, sudden death, myocardial infarction, and multi-organ failure were causes of death. The reported 30-day mortality for patients undergoing TAVI ranges from 5–12.7%, and 1-year mortality is reported to be approximately 20–30%.^{10,11,15,16,24–26} Hence, our results are in line with previous findings. Besides failed device success and combined safety endpoints, severe comorbidities influence mortality in this elderly patient population.

In our patient cohort, median hospital stay was 11 days without any significant difference between transfemorally and transapically treated patients. Indeed, shorter hospital stays of 6–8 days have been reported, and a longer stay for transapical treated patients has been observed.^5,15,27 However, longer hospital stays of 12–17 days have also been observed in German registries.^17,28,29 Hence, besides medical reasons, varying cultural and social habits may account for these differences.

In this elderly patient population, improvement of quality of life is important. TAVI is clearly associated with a significant reduction in symptoms as assessed with NYHA classification and 6-minute walking test.^15,24 A remarkable improvement in functional class was also observed in our patient cohort, which was sustained over the follow-up period, as all patients who survived to 1 year were in NYHA class I or II. Similar results have been observed in the FRANCE registry and in the PARTNER trial, where at 1 year, the majority of patients were in class I or II.^16,24

TAVI outcome reporting must go beyond the assessment of mortality rates, procedural complications, and functional improvement to the investigation of the impact on quality of life and social situation. It has been demonstrated that perceived quality of life is significantly improved after TAVI.²⁷ However, the effect on living status has not been assessed thus far. In our cohort, most patients who survived to 1 year were living independently at home without needing any help for daily living. Hence, TAVI enables independent living for this elderly frail population, and early admissions to nursing homes may be postponed or even become unnecessary in patients with a favorable outcome after TAVI. These findings clearly underline the value of TAVI in octogenarians.

Conclusion

Although developed for applications in clinical trials, the present study demonstrates how the established VARC criteria also facilitate outcome reporting of TAVI registries. Applying VARC definitions, TAVI appears to be an effective, less invasive treatment option in high-risk patients with severe AS. Besides decreased mortality and improved functional status, TAVI allows independent living for this elderly population. However, risk assessment and case selection remains challenging, and a multidisciplinary team approach is mandatory for appropriate patient selection.

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^*Joint first authors.
From the ¹Department of Cardiology and ²Clinic for Cardiovascular Surgery, Cardiovascular Center, ³Department of Anesthesiology, and ⁴Institute for Diagnostic Radiology, University Hospital Zürich, Zürich, Switzerland.
Lukas Altwegg is a proctor for Edwards Lifesciences, Irvine, California. Volkmar Falk has received lecture honoraria from Medtronic, Minneapolis, Minnesota.
Manuscript submitted May 23, 2011 and accepted June 13, 2011.
Address for correspondence: Lukas Altwegg, MD, Department of Cardiology, Cardiovascular Center, University Hospital Zürich, Rämistrasse 100, 8091 Zürich, Switzerland. Email: lukas.altwegg@access.uzh.ch