Clinical Outcomes and Bioprosthetic Valve Function After Transcatheter Aortic Valve Implantation Under Dual Antiplatelet Therapy vs. Aspirin Alone

Abstract

Background: Dual antiplatelet therapy (DAPT) is commonly used after transcatheter aortic valve implantation (TAVI); however, the supporting evidence is limited. To determine if aspirin alone is a better alternative to DAPT, we compared the outcomes of patients treated with DAPT or aspirin alone after TAVI.

Methods and Results: We analyzed a total of 144 consecutive patients (92 females, mean age 83±6 years) who underwent implantation of a balloon-expandable transcatheter valve (SAPIEN or SAPIEN XT, Edwards Lifesciences). Patients were divided into DAPT (n=66) or aspirin-alone treatment groups (n=78). At 1 year after TAVI, the composite endpoint, which consisted of all-cause death, myocardial infarction, stroke, and major or life-threatening bleeding complications, occurred significantly less frequently (Kaplan-Meier analysis) in the aspirin-alone group (15.4%) than in the DAPT group (30.3%; P=0.031). Valve function assessed by echocardiography was similar between the 2 treatment groups with respect to effective orifice area (1.78±0.43 cm² in DAPT vs. 1.91±0.46 cm² in aspirin-alone group; P=0.13) and transvalvular pressure gradient (11.1±3.5 mmHg in DAPT vs. 10.3±4.1 mmHg in aspirin-alone group; P=0.31).

Conclusions: Treatment with aspirin alone after TAVI had greater safety benefits and was associated with similar valve function as DAPT. These results suggest that treatment with aspirin alone is an acceptable regimen for TAVI patients.

Transcatheter aortic valve implantation (TAVI) is widely accepted as an alternative therapeutic option to surgical aortic valve replacement in patients with severe aortic valve stenosis who are considered inoperable or have high surgical risk.^1,2 With recent developments in devices and techniques, treatment outcomes of TAVI have improved.^3–5 For example, the 30-day mortality rate in patients who underwent TAVI was only 2.2–3.3% in 2 recent reports.^4,6

Editorial p 308

Antithrombotic therapy after stent-based bioprosthesis implantation is essential to prevent thromboembolism and dysfunction of the implanted valve. Currently, thienopyridine in addition to low-dose aspirin for 1–6 months after the implantation is empirically recommended in the European Society of Cardiology/European Association of Cardiothoracic Surgery and American Heart Association/American College of Cardiology guidelines.^7,8 Two pivotal Japanese clinical trials of TAVI also used 3- or 6-month dual antiplatelet therapy (DAPT) as an adjunctive treatment after the procedure.^9,10 Despite these recommendations, it is still a matter of debate whether patients should be treated with DAPT or aspirin alone. Although DAPT may reduce the incidence of ischemic events and has positive effects on valve function, treatment with dual antiplatelet agents may increase the risk of bleeding complications compared with aspirin alone.¹¹ In addition, the benefit of DAPT for maintaining valve function has not yet been clarified.

The aim of the present study was to elucidate the risk/benefit ratio of treatment with aspirin alone compared with DAPT after TAVI. To this end, we retrospectively assessed clinical events and valvular function based on transthoracic echocardiography (TTE) data in aortic stenosis patients who received either DAPT or aspirin alone after the implantation of a balloon-expandable transcatheter valve.

Methods

Study patients

We retrospectively reviewed 188 consecutive patients who underwent TAVI using balloon-expandable aortic valves at Osaka University Hospital between October 2009 and January 2015 because of severe native aortic valve stenosis. Different antithrombotic strategies following TAVI were adopted according to the time period. From October 2009 to September 2012, patients were administered a combination of lifelong low-dose aspirin (100 mg daily) and 6-month thienopyridine (200 mg ticlopidine or 75 mg clopidogrel daily). From October 2012, patients were treated with lifelong aspirin alone to assess the efficacy and safety of aspirin alone treatment. After excluding patients who had indications for oral anticoagulant therapy before TAVI, the remaining 144 patients were included in this study (Figure 1). All patients treated between October 2009 and September 2012 were allocated to the DAPT group (n=43). Of the patients treated after October 2012, 23 with an indication for DAPT before the procedure, defined as need for both aspirin and thienopyridine (200 mg ticlopidine or 75 mg clopidogrel daily) because of coronary stent or other reasons, were allocated to the DAPT group. The remaining patients were allocated to the aspirin-alone group (n=78). No patients received prasugrel. Finally, 66 patients were included in DAPT group, and 78 patients were included in an aspirin-alone group. This study was approved by the institutional review board of Osaka University Hospital. Written informed consent was given by all patients.

Figure 1.

Flow chart of 188 consecutive patients who underwent transcatheter aortic valve implantation (TAVI) using balloon-expandable valves between October 2009 and January 2015. Patients who had an indication for oral anticoagulant therapy before the TAVI procedure were excluded. The remaining patients were divided into 2 groups according to the different antithrombotic strategies adopted depending on the period. Finally, 66 patients were assigned to the dual antiplatelet therapy (DAPT) group and 78 patients were assigned to the aspirin-alone therapy group.

TAVI Procedure

Patients in both treatment groups started or continued antiplatelet drugs in the perioperative period without loading administration. TAVI was performed using the SAPIEN or SAPIEN XT heart valve system (Edwards Lifesciences, Irvine, CA, USA) via the transfemoral or other alternative approach, such as the transapical, transiliac, or direct aortic approach. The prosthetic valve size was determined by the annulus size measured before the procedure by transesophageal echocardiography or multislice computed tomography. After intravenous administration of unfractionated heparin to achieve an activated clotting time >250 s, the prosthetic aortic valve was implanted as previously described.¹²

Follow-up Data

Follow-up data were obtained for all patients. Adverse events were judged according to the Valve Academic Research Consortium 2 (VARC 2) criteria¹³ during the 1-year follow-up after the TAVI procedure. The composite endpoint consisted of all-cause death, nonfatal myocardial infarction, nonfatal stroke, and major or life-threatening bleeding complications. To investigate the relationship between the learning curve of the procedure and the composite endpoint, we compared the incidence rate of the composite endpoint between patients within the DAPT group who were treated during the first and second halves of the study period (n=33, respectively). Device success and procedural results were also assessed using VARC 2 criteria. TTE was performed at 1, 6 and 12 months after the TAVI procedure to evaluate bioprosthetic valve function. Prosthetic aortic valve stenosis was defined as a mean transvalvular gradient ≥20 mmHg or effective orifice area ≤0.9 cm² at 1-year follow-up.

Statistical Analysis

Continuous variables are expressed as mean±SD, and categorical variables are expressed as absolute numbers and percent values. Student’s t-test was used to compare continuous variables, and the χ² test or Fisher’s exact test was used to compare categorical variables. Chronological changes of aortic valve function in each treatment group were compared by paired t-test. The composite endpoint and bleeding complications rates were calculated by Kaplan-Meier method. The cumulative probability of the groups was compared by log-rank test. Cox proportional-hazards regression was used to adjust for the effect of differences in pertinent variables on the composite endpoint; age, sex, New York Heart Association (NYHA) classification, previous percutaneous coronary intervention (PCI), estimated glomerular filtration rate, aortic valve area and DAPT were entered into the multivariate model.

To increase the comparability of the groups, the composite endpoint and each adverse event rate were compared after propensity score matching. The propensity score model included the following baseline data: age, sex, NYHA classification, previous PCI, estimated glomerular filtration rate and aortic valve area. The one-to-one pair matching was performed by the nearest neighbor method without replacement, within the caliper of 0.2 standard deviation of the logit of the propensity score. The matched pair data were tested using a paired t-test for continuous variables and McNemar’s test for categorical variables.

All analyses were two-sided, and significance was judged at P<0.05. All statistical analyses were performed with JMP software (SAS Institute, Cary, NC, USA).

Results

Patients’ Characteristics

Baseline characteristics and echocardiographic data of the patients are presented in Table 1. Patients had a mean age of 83±6 years and 63.9% were female. Coronary artery disease was observed in 44.4% of patients, and 24.3% of patients had a history of stroke. Mean logistic EuroSCOREs and Society of Thoracic Surgeons scores were 24.8±16.9% and 11.4±10.2%, respectively. In a comparison of patient characteristics between the 2 treatment groups, patients in the DAPT group had a higher frequency of NYHA class III or IV heart failure compared with the aspirin-alone group (66.7% vs. 47.4%, respectively; P=0.028) and had more frequently undergone PCI (37.9% vs. 14.1%, respectively; P=0.0018). Aortic valve area assessed by TTE was also significantly smaller in the DAPT group (0.62±0.17 cm² in DAPT vs. 0.70±0.19 cm² in aspirin-alone group; P=0.007). However, the frequency of a history of stroke, and logistic EuroSCOREs and Society of Thoracic Surgeons scores was similar between the 2 treatment groups. Although most patients in both groups had received proton pump inhibitors (84.7%), omeprazole was used for 4 patients only in the DAPT group. Of these 4 patients, 1 patient had a composite endpoint (bleeding complication) during the 1-year follow-up. Cimetidine was not used in either group.

Table 1. Baseline Characteristics of Patients Under DAPT vs. Aspirin Alone

	Overall (n=144)	DAPT group (n=66)	Aspirin-alone group (n=78)	P value
Patient characteristics
Age, years	83±6	84±6	83±6	0.90
Female	92 (63.9%)	42 (63.6%)	50 (64.1%)	1.0
Body surface area, m2	1.42±0.16	1.42±0.15	1.42±0.17	0.87
NYHA class III or IV	81 (56.3%)	44 (66.7%)	37 (47.4%)	0.028
Diabetes	46 (31.9%)	22 (33.3%)	24 (30.8%)	0.86
Dyslipidemia	106 (73.6%)	47 (71.2%)	59 (75.6%)	0.57
Coronary artery disease	64 (44.4%)	35 (53.0%)	29 (37.2%)	0.065
Previous PCI	36 (25.0%)	25 (37.9%)	11 (14.1%)	0.0018
Previous CABG	20 (13.9%)	10 (15.2%)	10 (12.8%)	0.81
Previous stroke	35 (24.3%)	13 (19.7%)	22 (28.2%)	0.25
eGFR, mL/min/1.73 m2	43.9±21.2	45.9±19.5	42.1±22.5	0.29
Logistic EuroSCORE, %	24.8±16.9	25.5±18.5	24.2±15.6	0.64
STS score, %	11.4±10.2	12.2±12.7	10.7±7.4	0.39
Medication
Statins	69 (47.9%)	31 (47.0%)	38 (48.7%)	0.87
β-blockers	44 (30.6%)	18 (27.3%)	26 (33.3%)	0.47
Proton pump inhibitors	122 (84.7%)	53 (80.3%)	69 (88.5%)	0.25
Echocardiographic parameters
LV ejection fraction <50%	24 (16.7%)	13 (19.7%)	11 (14.1%)	0.38
Aortic valve area, cm2	0.66±0.19	0.62±0.17	0.70±0.19	0.0072
Mean pressure gradient, mmHg	53.0±18.1	56.0±19.0	50.5±17.0	0.068
AR≥mild	112 (77.8%)	49 (74.2%)	63 (80.7%)	0.42

Values are mean±SD or n (%). AR, aortic regurgitation; CABG, coronary artery bypass graft; DAPT, dual antiplatelet therapy; eGFR, estimated glomerular filtration rate; LV, left ventricle; NYHA, New York Heart Association; PCI, percutaneous coronary intervention; STS, Society of Thoracic Surgeons.

Procedural Outcomes

The procedural characteristics and outcomes for the 2 treatment groups are presented in Table 2. The distribution of the implanted valve size differed between groups, with 20-mm valves only being used in the DAPT group. In both groups, the frequency of a transapical approach was similar (43.9% in DAPT vs. 53.9% in aspirin-alone group; P=0.24) and high device success was achieved (93.9% in DAPT vs. 97.4% in aspirin-alone group; P=0.30). The incidences of major vascular complications, conversion to open surgery and cardiac tamponade did not significantly differ between the DAPT and aspirin-alone treatment groups. One patient in the DAPT group had valve-in-valve TAVI because of a severe paravalvular leak caused by valve migration 19 days after the procedure.

Table 2. Procedural Outcomes of Patients Under DAPT vs. Aspirin Alone

Outcome	Overall (n=144)	DAPT group (n=66)	Aspirin-alone group (n=78)	P value
Implanted valve size (20 mm/23 mm/26 mm)	5 (3.5%)/93 (64.6%)/ 46 (31.9%)	5 (7.6%)/45 (68.2%)/ 16 (24.2%)	0 (0.0%)/48 (61.5%)/ 30 (38.5%)	0.015
Transapical approach	71 (49.3%)	29 (43.9%)	42 (53.9%)	0.24
Device success	138 (95.8%)	62 (93.9%)	76 (97.4%)	0.30
Major vascular complications	9 (6.3%)	6 (9.1%)	3 (3.9%)	0.20
New implantation of pacemaker	14 (9.7%)	7 (10.6%)	7 (9.0%)	0.74
Conversion to open surgery	2 (1.4%)	0 (0.0%)	2 (2.6%)	0.19
Cardiac tamponade	4 (2.8%)	2 (3.0%)	2 (2.6%)	0.87
Acute kidney injury (stage ≥2)	5 (3.5%)	3 (4.6%)	2 (2.6%)	0.52

DAPT, dual antiplatelet therapy.

Clinical Outcomes During 1-Year Follow-up

Adverse event rates at 1 year after TAVI in the 2 treatment groups are presented in Figure 2A. During the 1-year follow-up, 20 bleeding complications (13.9%) occurred, which consisted of intracranial bleeding (n=3), cardiac tamponade (n=2), gastrointestinal bleeding (n=1), hemorrhagic pleural effusion (n=1) and access-related bleeding (n=7) in the DAPT group, vs. cardiac tamponade (n=2), gastrointestinal bleeding (n=1) and access-related bleeding (n=3) in the aspirin-alone group. The incidence of the composite endpoint, as calculated by Kaplan-Meier analysis, was significantly lower in the aspirin-alone group (15.4%) than in the DAPT group (30.3%; P=0.031) at 1 year (Figure 3A). The incidences of minor and major stroke and myocardial infarction at 1 year did not differ between the 2 groups; however, major or life-threatening bleeding complications (Kaplan-Meier analysis) occurred more frequently in the DAPT group (21.2% in DAPT vs. 7.7% in aspirin-alone group; P=0.021) (Figure 3B).

Figure 2.

Incidence rates of adverse events at 1 year after transcatheter aortic valve implantation. The composite endpoint consisted of all-cause death, nonfatal myocardial infarction, nonfatal stroke, and major or life-threatening bleeding complications. (A) Before propensity score matching, the composite endpoint, as well as bleeding complications, occurred more frequently in the dual antiplatelet therapy (DAPT) group than in the aspirin-alone group. (B) Propensity score matching extracted a total of 44 pairs. After propensity score matching, there was a tendency toward higher rates of the composite endpoint and bleeding complications in patients treated with DAPT. *McNemar’s test.

Figure 3.

Kaplan-Meier cumulative frequency of the composite endpoint (A) and major or life-threatening bleeding complications (B). Patients treated with dual antiplatelet therapy (DAPT) had higher rates of the composite endpoint and bleeding complications after transcatheter aortic valve implantation.

In the DAPT group, the incidence of the composite endpoint was identical (30.3%) between patients treated during the first and second halves of the study period. In addition, transapical aortic valve implantation, which was used in approximately half of all patients treated with DAPT and aspirin alone, was not associated with an elevated risk of bleeding complications (14.1% for transapical approach vs. 13.7% for non-transapical approach; P=0.95).

The propensity score matching extracted a total of 44 pairs (Table S1). As shown in Figure 2B, patients treated with DAPT had a tendency towards a higher rate of the composite endpoint (29.6% in DAPT vs. 15.9% in aspirin-alone group; P=0.13) and bleeding complications (18.2% in DAPT vs. 4.6% in aspirin-alone group; P=0.058) than those treated with aspirin-alone.

Echocardiographic Follow-up Data

Valve function, as evaluated by the effective orifice area and mean of the transvalvular pressure gradient on TTE, improved significantly after TAVI and was similar between the 2 treatment groups at 1-, 6- and 12-month follow-up (Figure 4). However, 2 patients (1 from the DAPT group and 1 from the aspirin-alone group) had prosthetic aortic valve stenosis at 1 year after valve implantation. The incidence was not different between the groups (1.5% in DAPT vs. 1.3% in aspirin-alone group; P=0.91). In 1 patient from DAPT group, the mean transvalvular gradient increased from 13 mmHg at 1-month follow-up to 21 mmHg at 12-month follow-up. In 1 patient from the aspirin-alone group, the mean transvalvular gradient was elevated at 1-month follow-up (31 mmHg), but remained unchanged at 12-month follow-up (26 mmHg). Only a few patients in each treatment group had mild transvalvular regurgitation at 1 year (4.6% in DAPT vs. 1.3% in aspirin-alone group; P=0.24), and the frequency of at least mild paravalvular leak was similar between the 2 groups (50.0% in DAPT vs. 54.7% in aspirin-alone group; P=0.61).

Figure 4.

Effective orifice area (A) and mean transvalvular pressure gradient (B) of aortic valve remained stable in both treatment groups at 1 year after TAVI. No differences in these parameters were detected between the 2 groups at 30 days, 6 months and 1 year after TAVI. Abbreviations as in Figure 1.

Predictive Factors for the Composite Endpoint

The relationship between background or procedural variables and the composite endpoint, as well as the results of multivariate analysis for identifying independent predictors for the composite endpoint, are presented in Table 3. Lower estimated glomerular filtration rate and use of DAPT were significantly associated with the endpoint, whereas the presence of NYHA III or IV heart failure, history of PCI, baseline aortic valve area measured by TTE, and the implanted valve size were not. After adjustment for baseline data, such as NYHA classification, previous PCI, estimated glomerular filtration rate and aortic valve area, DAPT was still independently associated with the composite endpoint.

Table 3. Factors Associated With the Composite Endpoint

Parameter	HR (95% CI)	P value	Adjusted HR (95% CI)	P value
Age, years (1 year increase)	1.03 (0.97–1.10)	0.39		0.27
Female	0.60 (0.30–1.22)	0.16		0.26
Body surface area, m2 (1 m2 increase)	1.09 (0.12–9.29)	0.94
NYHA class III or IV	1.53 (0.75–3.29)	0.24		0.59
Diabetes	1.34 (0.64–2.71)	0.43
Dyslipidemia	1.08 (0.51–2.57)	0.84
Coronary artery disease	0.99 (0.48–1.98)	0.98
Previous PCI	1.21 (0.53–2.52)	0.64		0.89
Previous CABG	1.57 (0.58–3.57)	0.34
Previous stroke	0.73 (0.27–1.66)	0.48
eGFR, mL/min/1.73 m2 (1 mL decrease)	1.02 (1.01–1.04)	0.0072	1.03 (1.01–1.05)	0.0024
STS score, % (1% increase)	1.02 (0.99–1.04)	0.11
Statins	0.75 (0.36–1.57)	0.41
β-blockers	1.39 (0.66–2.80)	0.38
Proton pump inhibitors	1.05 (0.52–2.26)	0.89
LV ejection fraction <50%	1.49 (0.59–3.26)	0.37
Aortic valve area, cm2 (1 cm2 increase)	0.88 (0.13–5.65)	0.89		0.92
AR≥mild	1.69 (0.71–4.97)	0.26
Implanted valve size (26 mm)	1.30 (0.62–2.62)	0.48
Transapical approach	1.20 (0.60–2.44)	0.60
DAPT	2.14 (1.06–4.51)	0.034	2.36 (1.08–5.35)	0.031

CI, confidence interval; HR, hazard ratio. Other abbreviations as in Table 1.

Discussion

The main findings of the present study are as follows. First, the composite endpoint of death, myocardial infarction, stroke, and bleeding complications occurred less frequently in patients treated with aspirin alone than in those who received DAPT in the first year after TAVI. Second, the incidence of embolic events, such as stroke and myocardial infarction, was similar between the 2 treatment groups, although fewer bleeding complications occurred in the aspirin-alone group. This factor would have strongly contributed to the higher incidence of the composite endpoint that was observed in the patients treated with DAPT after TAVI. Third, the echocardiographically assessed bioprosthetic aortic valve function of patients treated with aspirin alone was well preserved and similar to that in patients treated with DAPT during the first postoperative year. Finally, the use of DAPT was significantly associated with the composite endpoint in our multivariate analysis. Taken together, these findings indicate that treatment with aspirin alone after TAVI is safe and may be a better alternative to DAPT for reducing the incidence of bleeding complications.

DAPT is related to a higher incidence of bleeding complications compared with treatment with single antiplatelet drugs in Japanese patients who have had prior stroke, cardiovascular disease or PCI.^11,14 Aortic stenosis patients often have comorbidities associated with bleeding, such as renal dysfunction and hypertension.¹⁵ The current study results also showed an association between renal function and the composite endpoint that included bleeding complications. In addition, the effect of bleeding increases with increasing age of patients receiving antiplatelet therapy.^15–17 As patients undergoing TAVI are typically over 80 years old, the potential adverse effects of antiplatelet therapy are an important consideration for positive outcomes. Thus, empirical adoption of DAPT for all TAVI patients may not be appropriate. The present findings supported the use of treatment with aspirin alone as an alternative therapy to DAPT because of the lower rate of observed bleeding complications.

Antithrombotic therapy after TAVI mainly aims to prevent thrombus formation on the bioprosthetic valve and the occurrence of thromboembolic events or valve dysfunction. Several reports have shown that the risk of stroke is highest on the first day after TAVI and remains elevated for the first few months.^18,19 Similar to the bioprosthetic valves used in surgical aortic valve replacement, thrombus formation may occur on bioprosthetic TAVI valves.²⁰ De Marchena et al²¹ reviewed 22 patients who had experienced valve thrombosis early after TAVI. These thromboses commonly manifested as TAVI valve stenosis and in nearly all cases the thrombosis occurred within the first year following TAVI. These results highlight the importance of postoperative antithrombotic therapy and clinical assessment, particularly in the early phase after TAVI. In addition, as antithrombotic drugs are effective at reducing ischemic events, such as cerebral and myocardial infarctions, antithrombotic therapy may also be effective in patients undergoing TAVI, as such patients frequently have atherosclerotic disease.

In the present study, the incidence of the composite endpoint was significantly lower in patients taking aspirin alone, and treatment with aspirin alone did not increase the incidence of embolic events compared with DAPT. At 1-year TTE follow-up, bioprosthetic valve function was well preserved, and the effective orifice area and mean of the transvalvular pressure gradient were similar between patients taking dual antiplatelet drugs and aspirin alone. Although bioprosthetic aortic valve stenosis was observed in 1 patient receiving aspirin alone, the severity was mild, and the incidence rate did not differ between the 2 treatment groups. Taken together, the results indicated that treatment with aspirin alone did not cause deterioration of bioprosthetic valve function.

A few recent studies with small cohorts of patients have compared treatment with aspirin alone to DAPT after TAVI.^22–24 For example, in the Single Antiplatelet Therapy for TAVI (SAT-TAVI) study,²² 120 consecutive patients undergoing TAVI were randomly assigned to DAPT (aspirin and 6-month clopidogrel) or aspirin-alone treatment groups. Although no differences in the incidence of stroke or bleeding complications were found at 30 days, vascular complications were reduced in the aspirin-alone group. In a report by Ussia et al,²³ 79 consecutive patients were randomized to 3-month clopidogrel and lifelong aspirin or aspirin-alone groups, and no significant differences in the incidence of myocardial infarction, stroke, or bleeding complications were detected between the 2 groups at 1 or 6 months following TAVI. These findings, taken together with the results of the present study, provide support for the safety of aspirin alone as an antithrombotic therapy after TAVI, if there are no indications for the use of DAPT. In addition, the present observation of less bleeding in the aspirin-alone group and the strong association between DAPT and the composite endpoint is evidence for the superiority of treatment with aspirin alone following TAVI. The results after propensity score matching showed a tendency toward a lower incidence of the composite endpoint and bleeding complications in patients with aspirin-alone treatment; however, the difference was not statistically significant. This might be related to reduced statistical power caused by the limited number of matched patients (n=88). In a retrospective study, Durand et al²⁴ compared mono-antiplatelet therapy with DAPT after TAVI using propensity score matching in a larger patient cohort (n=182 after matching). They observed significantly less bleeding complications in patients treated with monotherapy at 30 days following TAVI. Although the follow-up period differs, their result suggests insufficient statistical power after propensity score matching in the present study. A study with a large number of patients and a long follow-up is required to establish the efficacy and durability of treatment with aspirin alone for patients who undergo TAVI. To this end, a prospective randomized study comparing aspirin alone with aspirin and clopidogrel following TAVI (ARTE trial) is currently ongoing.

Study Limitations

This study has several limitations that warrant mention. First, the patient cohort was small and the study used a non-randomized retrospective design. Thus, it is possible that baseline differences in the frequency of coronary artery disease or unidentified factors influenced the results. However, after adjustment for several prognostic variables, there was still a strong association between DAPT use and the composite endpoint in the Cox proportional-hazards model. Second, the variation in the distribution of the implanted valve size may have also affected bioprosthetic valve function. However, because the bioprosthetic valve size was determined by the size of each patient’s annulus,²⁵ the influence of valve selection on the hemodynamic parameters of the TTE examination was minimalized. Finally, as different antithrombotic strategies were adopted during different stages of the study period, the learning curve of the TAVI procedure may have affected the outcomes. However, the incidence of the composite endpoint did not differ between the first and second halves of the study period in which patients were administered dual antiplatelet drugs.

Conclusions

The present study is the first comparison of different antithrombotic therapies in Japanese patients undergoing TAVI. Treatment with aspirin alone after TAVI did not increase the incidence of either embolic events or bioprosthetic valve dysfunction at 1 year compared with DAPT. Considering the possible merit of less bleeding complications in the patient population most likely to undergo TAVI, aspirin alone may be an acceptable antithrombotic therapy regimen after TAVI.

Acknowledgments

None.

Conflict of Interest Disclosure

Dr. Sakata and Dr. Sawa received research grants from Edwards Lifesciences. Dr. Nakatani received lecture fees from Edwards Lifesciences. The remaining authors declare no conflicts of interest.

Supplementary Files

Supplementary File 1

Table S1. Baseline characteristics of patients after propensity score matching

Please find supplementary file(s);

http://dx.doi.org/10.1253/circj.CJ-16-0903

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