Stent and Dual Antiplatelet Therapy Duration Comparisons in the Setting of a Multicenter Randomized Controlled Trial: Can the Operator Experience Affect the Study Results?
Background Operator experience influences outcomes after percutaneous coronary intervention, but this association in the controlled setting of a randomized, clinical trial is unclear.
Methods and Results We investigated operator‐related outcomes (30‐day and 2‐year efficacy and safety end points) among patients undergoing percutaneous coronary intervention and randomized to different dual antiplatelet therapy durations and stent types. A total of 2003 patients were analyzed, and 7 operator groups were compared. The majority of preprocedural and postprocedural characteristics were imbalanced. The primary end point of the study, the composite of death, myocardial infarction, or cerebrovascular accidents, did not differ among operators at 30 days or 2 years. There were no significant differences also for all other individual and composite end points analyzed at 30 days and 2 years, except for 2‐year stent thrombosis (P=0.048) and bleeding events (P=0.022 for Bleeding Academic Research Consortium type 2, 3, or 5). Adjusted comparisons for the main end points showed slight differences among operators at 30 days, but not at 2 years. There was no interaction of operator with dual antiplatelet therapy duration (P=0.112) or stent type (P=0.300). Results remained entirely consistent when operators were stratified by their experience.
Conclusions There was a weak signal of heterogeneity across study operators for the 30‐day, but not the 2‐year, main study outcomes. No clear effect of operator or operator experience was observed for the comparative efficacy and safety profile of the randomized stent types or dual antiplatelet therapy duration regimens.
Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT00611286.
What Is New?
Observational studies suggest that operator volume/experience influences outcomes after percutaneous coronary intervention, but this is poorly explored in randomized, clinical trials, and there is ongoing debate on whether operator experience may influence reliability of trials findings.
We compared operators in PRODIGY (Prolonging Dual Antiplatelet Treatment After Grading Stent‐Induced Intimal Hyperplasia Study), a 4‐by‐2 randomized multicenter all‐comer percutaneous coronary intervention trial comparing 4 stent types and 2 dual antiplatelet therapy duration regimens.
We observed imbalances in the patient's and procedural characteristics and found weak differences in rates of clinical outcomes.
After adjustment, there was a weak signal of heterogeneity across operators for 30‐day, but not 2‐year, main outcomes.
When operators were stratified by their experience, no effect on clinical outcomes was observed.
What Are the Clinical Implications?
No significant interactions were found between operators or operator experience and randomized dual antiplatelet therapy duration or stent type; thus, overall findings of the trial remained consistent.
A prolonged dual antiplatelet therapy regimen failed to improve outcomes, irrespective of the operators.
The routine collection of high‐quality data sets should be encouraged to evaluate and improve operator competence and to allow investigation of operator as effect modifier of findings, especially for short‐term outcomes after percutaneous coronary intervention, even in the controlled setting of a randomized, clinical trial.
Owing to innovations in device technology and improved operator techniques, percutaneous coronary intervention (PCI) has become a widely used and reproducible therapeutic procedure for the entire spectrum of coronary artery disease.1, 2
Complications during and after PCI have dramatically declined during the past decades. Yet, periprocedural and postprocedural ischemic and bleeding adverse events still occur in a sizable proportion of patients. Although patient‐related factors are known to play a key role for those occurrences, it is currently unknown to which degree these adverse events may be also operator dependent. Overall number of procedures performed and the operator experience may affect outcomes of patients undergoing PCI, but this evidence is mainly based on observational studies.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 Randomized, controlled trials have played a major role in informing the community on the incidence, predictors, and implications of PCI‐related adverse events. However, although the role of the center is often investigated or at least accounted for as a source of heterogeneity for the primary end point results, little is known on the potential impact of different operators on results of PCI studies. Operator expertise and the potential impact on outcomes has recently become a contentious topic for studies assessing access site.12, 13, 14, 15, 16 Whether operators may also affect outcomes of studies assessing the performance of various stent platforms or durations of dual antiplatelet therapy (DAPT) after coronary stenting remains unclear. This analysis is frequently hampered by lack of proper data collection or inclusion of few cases by each single operator.
The aim of this study is to investigate whether an interoperator performance variation may exist in terms of efficacy and safety in the setting of the all‐comer PRODIGY (Prolonging Dual Antiplatelet Treatment After Grading Stent‐Induced Intimal Hyperplasia Study; NCT00611286) where patient recruitment was carried out by few interventional cardiologists, each recruiting a high number of patients.
The design and main findings of the PRODIGY trial have been previously reported.17, 18, 19 PRODIGY is a 4‐by‐2 randomized, multicenter, open‐label clinical trial designed to evaluate the efficacy and safety of prolonging the duration of clopidogrel therapy for up to 24 months in all‐comer patients receiving a balanced mixture of stents with various anti‐intimal hyperplasia potency and belonging to both first‐ and second‐generation drug‐eluting stent. Briefly, all‐comer PCI patients (n=2013) were randomly allocated in a 1:1:1:1 fashion to 1 of 4 stent types, including everolimus‐eluting stent, paclitaxel‐eluting stent, zotarolimus‐eluting Endeavor Sprint stent, or thin‐strut bare metal stent. Patients alive at 30 days (n=1970) were then randomly allocated to either 6 or 24 months of DAPT. Selection criteria were broad, reflecting routine clinical practice. Randomization to 6‐ or 24‐month DAPT was stratified by center, ongoing ST‐segment‐elevation myocardial infarction, presence of diabetes mellitus, and need for intervening for at least 1 in‐stent restenotic lesion. The study was conducted in accord with the principles of the Declaration of Helsinki. The Ethics Committees of the 3 participating centers independently approved the protocol, and all participants gave written informed consent.
Interventional cardiologists of the 3 participating centers were trained operators, each with >500 cumulative PCI volume as first operator and all involved in the 24‐hour on‐call duty schedule at their referral institutions. During the trial, 6 operators performed PCI in the majority of patients enrolled, with each treating more than 50 patients. For the present study, each of them will represent an independent group. In order to explore the effect of PCI experience, operators were also further stratified in “More Experienced” and “Experienced” based on: (1) number of active years as first operator, (2) overall PCI volume, and (3) PCI volume/year in the 2 years before the trial initiation. “More experienced” operators were those with >5 years, >1000 overall PCI, and >75 PCI/year, whereas “Experienced” were those with <5 years, 500 to 1000 overall PCI, and <75/year. Few other operators performed less than 50 procedures each, thus they were pooled in the seventh group named “other operators” overall including 142 patients/procedures (Figure 1).
Treatment Protocol and Follow‐up
All patients received aspirin (80–160 mg orally indefinitely) and clopidogrel (75 mg/day) according to the randomization scheme as follows: for either 6 months in the short DAPT arm or 24 months in the prolonged DAPT arm irrespective of the previously implanted stent type or indication for PCI.
The randomized patients returned for study visits at 30 days and then every 6 months up to 2 years. During follow‐up visits, patients were examined and assessed for adverse events, asked for the antiplatelet therapy compliance, and 12‐lead ECG recordings were obtained.
Study End Points
The primary efficacy end point of the PRODIGY trial was the composite of death, MI, or cerebrovascular accident, whereas the key safety end point included Bleeding Academic Research Consortium (BARC) type 2, 3, or 5 bleeding. The net effect on the combined ischemic and bleeding complications was obtained by 2 net adverse clinical event (NACE) end points that were generated by combining the primary efficacy end point of death, MI, or cerebrovascular accident with either the primary safety end point of BARC type 2, 3, or 5 bleeding or with BARC type 3 or 5 events. Other end points included each component of the primary efficacy end point, cardiovascular death, stent thrombosis (ST) defined on the basis of the Academic Research Consortium criteria, and BARC type 3 or 5 bleeding. Other safety end points included bleeding events adjudicated according to the thrombolysis in myocardial infarction and global use of strategies to open occluded coronary arteries scales. All study end point definitions were previously reported.
All end points were confirmed on the basis of documentation collected at each hospital and were centrally adjudicated by the clinical events committee, whose members were unaware of the patients' treatment‐group assignments. The time frame of interest for the primary end point was from 30 days (ie, after the primary end point randomization) to 24 months.
The PRODIGY trial was designed to enroll at least 1700 patients to detect a 40% reduction in the relative risk of the primary end point in the 24‐month clopidogrel group compared with 6‐month duration of clopidogrel therapy, with statistical power of >80% at a 2‐sided significance level of 0.05. The planned sample size was finally increased up to 2000 to allow for fatalities occurring within the first 30 days, noncompliance, and loss to follow‐up as previously described.17, 18, 19
Categorical variables were expressed as frequency (percentage), whereas continuous variables were expressed as mean and SD. Baseline and procedural characteristics among the 7 groups were compared using chi‐square test for categorical variables and ANOVA F test for continuous variables. Crude events among groups were compared with likelihood ratio P values testing the shared frailty effect across operators using an inverse gamma distribution in Weibull time‐to‐event regression. Estimation of the cumulative major adverse cardiovascular event (MACE) rate, as well as of BARC bleeding and NACE, was performed by the Kaplan–Meier method.
In order to compare clinical outcomes among groups, hazard ratios with 95% confidence intervals were calculated from adjusted Weibull time‐to‐event regression comparing each operator (operator 2 to operator 6) versus operator 1 who was elected as reference because of the highest number of patients/procedures performed. The adjustment was performed including the following variables: age, sex, body mass index, hypertension, dyslipidemia, current smoking, family history of coronary artery disease, previous PCI, previous coronary artery bypass graft, peripheral arterial disease, creatinine clearance, left ventricular ejection fraction, acute coronary syndrome, femoral access, multivessel PCI, PCI performed by 2 or more operators (versus 1 operator only), 1 or more complex lesions, 1 or more restenotic lesions, randomized stent (4 categories), total stent length, and CRUSADE (Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the ACC/AHA Guidelines) score.
Proportional‐hazards assumption was tested on the basis of Schoenfeld residuals after fitting a Cox regression model for each of the 4 end points (P≥0.7 in each case).
Univariate analysis was conducted to explore whether operator category may predict 2‐year MACE, BARC type 2, 3, or 5, or NACE.
Interaction testing was performed to determine whether the effect of randomization to DAPT duration or to stent type on the primary end point was consistent irrespective of operator category or volume of PCI performed by each operator.
To explore the effect of operator experience, all the analyses were also computed contrasting “more experienced” versus “experienced” operators on study end points.
A 2‐sided probability value of <0.05 was considered significant. All analyses were performed with Stata Statistical Software (release 14; StataCorp LP, College Station, TX).
A total of 2013 patients were recruited into the study and randomly assigned to 1 of the 4 stent types. Ten patients withdrew consent. Thirty‐three (1.6%) patients died within 30 days, thus 1970 patients were randomly allocated at 1 month to undergo 24‐month versus 6‐month duration of clopidogrel therapy. Seven operator groups were created by matching cases to first treating operator as follows: operator 1 (n=503), operator 2 (n=425), operator 3 (n=373), operator 4 (n=306), operator 5 (n=157), operator 6 (n=97), and other operators including 10 operators performing each less than 50 procedures and cumulatively recruiting 142 patients into the study (Figure 1).
Baseline and Procedural Characteristics
Table 1 reports baseline and procedural characteristics according to the operator groups. There were notable imbalances across operators that were mainly driven by the other operators group, which recruited patients who were slightly younger, more frequently affected by stable coronary artery disease (one fourth of patients in this group presented acute coronary syndrome as compared with three fourths of patients in all other operator groups), with preserved renal and left ventricular function, and lower bleeding risk. Operator 1 treated the highest rate of past MI or ST‐segment‐elevation myocardial infarction patients or those requiring more frequently left main coronary artery intervention, or presenting with the mean lowest mean left ventricular ejection fraction (Table 1). On the other hand, operator 6 treated the highest number of lesions per procedure, with at least 1 complex lesion per procedure as well as more patients with past coronary artery bypass graft. Multivessel or saphenous vein graft intervention was more frequently accomplished by operator 2, whereas operator 5 performed the lowest number of multivessel/multilesion interventions (Table 1). Radial access was the default access site across all operators.
At 30 days, there were no significant differences among operator groups for any analyzed individual or composite end points (Table 2). The highest rate of the primary end point was observed for operator 6, who experienced, however, the lowest number of any or access‐site bleeding events. Operator 2 had the highest rate of cerebrovascular accident, BARC bleeding, as well as NACE. Operator 1 was the one experiencing the lowest rate of death and cerebrovascular accident, whereas operator 5 was associated with the lowest rate of MACE and NACE. Operator 1 and 2 were associated with the highest rate of access‐site–related bleeding (Table 2). In the group of other operators, none of the patients died or had stroke or ST or target vessel revascularization or bleeding, and all events within 30 days were MI.
At 2‐year follow‐up, there were no significant differences among operators for the primary end point as well as the majority of secondary end points, except for ST, mainly driven by no event in the other operator group and for BARC type 2, 3, or 5, mainly driven by difference for BARC 2 across operator groups (Table 3). ST was more frequently observed with operator 2, whereas operator 5 was associated with the highest rate of overall and most severe bleeding events. On the other hand, operator 5 was associated with the lowest rate of MI, ST, and target vessel revascularization. Operator 6 was the one with highest rate of the primary end point, as well as NACE, predominantly driven by the highest rates of death and MI (Table 3), whereas the primary end point was lowest for operator 3. Overall, the group of other operators who treated more stable patients was associated with lowest rates of death, bleeding, and composite end points (Table 3).
Adjusted comparisons for the main efficacy and safety end points at 30 days and 2 years are shown in Table 4. At 30 days, MACE and NACE were significantly increased with operator 2 compared with operator 1. Trends toward higher risk of MACE (49–56%) and NACE (45–52%) were also noted for Operator 4 and 6 as compared with operator 1, mainly attributable to increased risk of ischemic events. At 2 years, there was, however, no notable difference in operators' performances. Operator category did not predict 2‐year MACE (P=0.74), BARC type 2, 3, or 5 (P=0.31), or NACE (P=0.66 and 0.85 for NACE with BARC 2, 3, or 5, and BARC 3 or 5, respectively).
Operator Interaction With DAPT and Stent Randomized Groups for the Primary Outcome
When the primary end point of all‐cause death, MI, or cerebrovascular accident was stratified according to the operators, no significant interaction emerged between operator and DAPT randomization (P=0.112; Figure 2), and this was confirmed at 6‐month landmark analysis (from 6 months to 2 years: P=0.425; Figure S1).
Similarly, interaction testing between operator and stent type (P=0.300; Figure 2) was negative. Also, no interaction was observed between operator and DAPT or randomized stent at stratified analysis by operator volume (Figures S2 and S3). Three‐way interaction among operator‐randomized DAPT duration‐randomized stent was similarly negative (P=0.210).
When analyses were conducted comparing “More experienced” with “Experienced” operators, no significant effect emerged on clinical outcomes at 30‐day or 2‐year and no interaction was noted with respect to randomized DAPT duration or stent type (Tables S1 through S4; Figures S4 and S5).
The present study explored the interoperator impact on clinical outcomes of patients undergoing PCI in the setting of a randomized, clinical trial. Across each operator stratum, there were several differences for patient and procedural characteristics, making interpretation of unadjusted clinical outcomes problematic. After adjustment, there were some differences for 30‐day outcomes, mainly owing to different risks of ischemic events across operators. However, adjusted analyses failed to show heterogeneous outcomes across operator groups at 2 years, and operators did not impact on the comparative efficacy or safety profile of different DAPT durations or stent types. Therefore, the present analysis provides reassurance that operator per se or operator experience/operator volume was not a significant effect modifier of our study findings.
The optimal duration of DAPT after PCI is a matter of ongoing discussion, attributed to a clear trade‐off between benefits and risks. A prolonged DAPT regimen prevents recurrent or new MI related or not to stent thrombosis. Furthermore, procedural complexity has emerged as an important driver of DAPT duration, with prolonged DAPT being beneficial in more‐complex procedures.20 Accordingly, it is plausible that different operators with different technical skills, expertise, and case volume, as well as different procedural tactics (predilatation and postdilatation, duration and pressure of dilatation, stent implantation sizing and technique, use of intravascular imaging modalities, etc) may be associated with different clinical outcomes. In this respect, however, we did not find significant interaction between operator, type of stent, and DAPT regimen, suggesting that our overall study results were consistent across operators, which has notable implications for the external validity of our findings. There was, however, signal that operator may impact on outcomes in the early period after PCI when indeed operator and procedural factors are more likely to play a role. On the contrary, at 2 years, we did not observe significant differences across operator groups, likely as a reflection that procedural technicalities adopted by each operator have limited impact on long‐term outcomes.
Physician competence is a critical component in the provision of optimal health care. All physicians must have the appropriate training, fund of knowledge, clinical decision making, and technical skills. In the setting of PCI, operators must perform these procedures at a requisite level of proficiency and competency.
Patients treated by high‐volume operators and at high‐volume centers have been shown to experience a higher rate of procedural success and lower rates of mortality and postprocedural complications.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 As a consequence, standards of assistance have been recommended for PCI operators.1, 2, 6 Recently, in an observational study, operator experience has emerged as an important prognostic factor in a complex intervention, such as left main PCI, where patients treated by high‐volume and experienced operators had better outcomes.9 Operators were shown to impact on outcomes in the setting of different complex procedures, such as chronic total occlusions,21 the implantation of specific devices as bioresorbable vascular scaffolds,22 and structural interventions.23
During the past decades, the cardiology community has been largely informed in terms of clinical practice by the results of many randomized trials. In order to achieve enough of a number of observations, and to reduce the bias related to single‐center studies, multicenter studies are frequently performed and currently regarded as the study design allowing for the greatest external validity. Multicenter PCI studies can, however, also critically depend on expertise and proficiency of the multiple operators involved. Although subgroup analyses are frequently performed to explore the consistency of study results across different geographical locations, and sometimes randomization is stratified by center, the role of each operator within each center is almost never appropriately investigated. Operators are very rarely matched with the corresponding treated patients within each multicenter study, and even when this information is available, each study operator generally contributes with a limited number of patients within each study. There are, however, relevant exceptions. Interoperator variation was previously investigated in 1071 patients enrolled in the TAPAS (Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction Study) trial.16 The primary end point of the study, which was myocardial blush grade 3, was analyzed across 6 operator groups, and it was shown to significantly differ across operators after adjustment for baseline and procedural imbalances. This post‐hoc analysis suggested that, even in a controlled setting, significant interoperator variation might exist in the efficacy of primary PCI.16 Interestingly, however, no data on patient outcomes were available across operators at long‐term follow‐up.
More recently, the operator experience, and its potential impact on outcomes, has become a matter of debate in the comparison of radial versus femoral access site for PCI. In the MATRIX‐Access (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX),12 the benefit of radial versus femoral access appeared consistent across major patient subgroups including tertiles of the centers' annual volume of PCI. However, positive tests for trend were found across tertiles of the centers' percentage of radial PCI for both co‐primary end points and all‐cause mortality at 30 days, suggesting a more‐pronounced benefit of radial access in centers that did 80% or more‐radial PCI,12 and this generated great interest.13, 14, 15, 24, 25 Whether these differences will remain detectable also at longer‐term follow‐up remains currently unclear.
All together, our results are consistent with previous observations that operators may impact on procedural or PCI short‐term (ie, 30‐day) clinical outcomes whereas such an effect seems to vanish at time frames more remote from the index intervention. This may reflect the existence in contemporary practice of well‐standardized percutaneous techniques and improved biomedical technologies for the treatment of patients with coronary artery disease. In this context, factors, which are largely unrelated to the revascularization procedure per se, such as adherence to and optimal titration of secondary prevention medication as well as comorbidities and disease progression, may affect long‐term outcomes more than procedural technical features. On the other hand, the effect of operator on PCI outcomes seemed to be, at best, minimal, and when operators were stratified for their volume/experience before the trial initiation, this effect disappeared. The absence of a definite experience‐outcome relationship for individual operators should not be regarded as surprising in such a context where centers and operators were at high volume of PCI. However, volume per se might not be an appropriate marker of quality (high volume may not correspond to high quality because practice/volume by itself is of little value if the procedure is not properly executed).2, 26
Therefore, our current findings extends previous results of the PRODIGY trial by suggesting that the impact of stent selection or DAPT durations on ischemic and bleeding outcomes remained consistent across study operators.
This is a post hoc analysis sharing limitations of other not prespecified and not powered analyses. PRODIGY is a 3‐center trial, and it cannot be excluded that, in larger trials with many different centers and operators involved, a certain degree of interoperator variation may exist and may have a significant interaction with safety and efficacy end points.
Although the comparisons between operators were adjusted for main variables, it cannot be excluded that other confounders may affect these findings.
The number of events in some cases (ie, stroke or ST) was too low to allow an appropriate adjusted comparison among 6 or 7 groups.
After adjustment for multiple patient‐ and procedure‐related imbalances, there was a weak signal of heterogeneity across individual study operators for the 30‐day, but not the 2‐year, main study outcomes, and no differences were observed across operators' past PCI volumes. Accordingly, no clear effect of the operator was observed for the comparative efficacy and safety profile of the randomized stent types or DAPT duration regimens in our study, which has notable implications for the external validity of the PRODIGY study results.
Gargiulo receives research grant support from the Cardiopath Ph.D. program and the U. Veronesi Foundation. Valgimigli reports grants from The Medicines Company, Terumo, and AstraZeneca and personal fees from Terumo, St Jude Vascular, and Abbott Vascular, outside the submitted work. Windecker reports research grants to the institution from Bracco, Boston Scientific, and Terumo. Other authors have nothing to disclose.
Table S1. Baseline and Procedural Characteristics According to Operator Experience
Table S2. Clinical Outcomes at 30 Days According to Operator Experience
Table S3. Clinical Outcomes at 2 Years According to Operator Experience
Table S4. Unadjusted and Adjusted Hazard Ratios for Main Clinical Outcomes According to Operator Experience
Figure S1. Stratified effect of operators on the DAPT randomization by landmark approach.
Figure S2. Stratified effect of operator volume of procedures (2 strata) on the DAPT and stent type randomizations.
Figure S3. Stratified effect of operator volume of procedures (3 strata) on the DAPT and stent type randomizations.
Figure S4. Stratified effect of operator experience on the DAPT randomization.
Figure S5. Stratified effect of operator experience on the DAPT randomization by landmark approach.
- ↵Levine GN, Bates ER, Blankenship JC, Bailey SR, Bittl JA, Cercek B, Chambers CE, Ellis SG, Guyton RA, Hollenberg SM, Khot UN, Lange RA, Mauri L, Mehran R, Moussa ID, Mukherjee D, Nallamothu BK, Ting HH. 2011 ACCF/AHA/SCAI guideline for percutaneous coronary intervention. A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Society for Cardiovascular Angiography and Interventions. J Am Coll Cardiol. 2011;58:e44–e122.
- ↵Harold JG, Bass TA, Bashore TM, Brindis RG, Brush JE Jr., Burke JA, Dehmer GJ, Deychak YA, Jneid H, Jollis JG, Landzberg JS, Levine GN, McClurken JB, Messenger JC, Moussa ID, Muhlestein JB, Pomerantz RM, Sanborn TA, Sivaram CA, White CJ, Williams ES. ACCF/AHA/SCAI 2013 update of the clinical competence statement on coronary artery interventional procedures: a report of the American College of Cardiology Foundation/American Heart Association/American College of Physicians Task Force on Clinical Competence and Training (writing committee to revise the 2007 clinical competence statement on cardiac interventional procedures). J Am Coll Cardiol. 2013;62:357–396.
- ↵Badheka AO, Patel NJ, Grover P, Singh V, Patel N, Arora S, Chothani A, Mehta K, Deshmukh A, Savani GT, Patel A, Panaich SS, Shah N, Rathod A, Brown M, Mohamad T, Tamburrino FV, Kar S, Makkar R, O'Neill WW, De Marchena E, Schreiber T, Grines CL, Rihal CS, Cohen MG. Impact of annual operator and institutional volume on percutaneous coronary intervention outcomes: a 5‐year United States experience (2005–2009). Circulation. 2014;130:1392–1406.
- ↵Hulme W, Sperrin M, Rushton H, Ludman PF, De Belder M, Curzen N, Kinnaird T, Kwok CS, Buchan I, Nolan J, Mamas MA. Is there a relationship of operator and center volume with access site‐related outcomes? An analysis from the British Cardiovascular Intervention Society. Circ Cardiovasc Interv. 2016;9:e003333.
- ↵King SB III., Aversano T, Ballard WL, Beekman RH III., Cowley MJ, Ellis SG, Faxon DP, Hannan EL, Hirshfeld JW Jr., Jacobs AK, Kellett MA Jr., Kimmel SE, Landzberg JS, McKeever LS, Moscucci M, Pomerantz RM, Smith KM, Vetrovec GW, Creager MA, Hirshfeld JW Jr., Holmes DR Jr., Newby LK, Weitz HH, Merli G, Pina I, Rodgers GP, Tracy CM. ACCF/AHA/SCAI 2007 update of the clinical competence statement on cardiac interventional procedures: a report of the American College of Cardiology Foundation/American Heart Association/American College of Physicians Task Force on Clinical Competence and Training (writing committee to update the 1998 clinical competence statement on recommendations for the assessment and maintenance of proficiency in coronary interventional procedures). J Am Coll Cardiol. 2007;50:82–108.
- ↵Strom JB, Wimmer NJ, Wasfy JH, Kennedy K, Yeh RW. Association between operator procedure volume and patient outcomes in percutaneous coronary intervention: a systematic review and meta‐analysis. Circ Cardiovasc Qual Outcomes. 2014;7:560–566.
- ↵Xu B, Redfors B, Yang Y, Qiao S, Wu Y, Chen J, Liu H, Chen J, Xu L, Zhao Y, Guan C, Gao R, Genereux P. Impact of operator experience and volume on outcomes after left main coronary artery percutaneous coronary intervention. JACC Cardiovasc Interv. 2016;9:2086–2093.
- ↵Moscucci M, Share D, Smith D, O'Donnell MJ, Riba A, McNamara R, Lalonde T, Defranco AC, Patel K, Kline Rogers E, D'Haem C, Karve M, Eagle KA. Relationship between operator volume and adverse outcome in contemporary percutaneous coronary intervention practice: an analysis of a quality‐controlled multicenter percutaneous coronary intervention clinical database. J Am Coll Cardiol. 2005;46:625–632.
- ↵Doll JA, Dai D, Roe MT, Messenger JC, Sherwood MW, Prasad A, Mahmud E, Rumsfeld JS, Wang TY, Peterson ED, Rao SV. Assessment of operator variability in risk‐standardized mortality following percutaneous coronary intervention: a report from the NCDR. JACC Cardiovasc Interv. 2017;10:672–682.
- ↵Valgimigli M, Gagnor A, Calabro P, Frigoli E, Leonardi S, Zaro T, Rubartelli P, Briguori C, Ando G, Repetto A, Limbruno U, Cortese B, Sganzerla P, Lupi A, Galli M, Colangelo S, Ierna S, Ausiello A, Presbitero P, Sardella G, Varbella F, Esposito G, Santarelli A, Tresoldi S, Nazzaro M, Zingarelli A, de Cesare N, Rigattieri S, Tosi P, Palmieri C, Brugaletta S, Rao SV, Heg D, Rothenbuhler M, Vranckx P, Juni P. Radial versus femoral access in patients with acute coronary syndromes undergoing invasive management: a randomised multicentre trial. Lancet. 2015;385:2465–2476.
- ↵Le May MR, Singh K, Wells GA. Efficacy of radial versus femoral access in the acute coronary syndrome: is it the operator or the operation that matters? JACC Cardiovasc Interv. 2015;8:1405–1409.
- ↵Valgimigli M, Campo G, Percoco G, Monti M, Ferrari F, Tumscitz C, Zuffi A, Colombo F, Kubbajeh M, Cavazza C, Cangiano E, Tebaldi M, Minarelli M, Arcozzi C, Scalone A, Frangione A, Borghesi M, Marchesini J, Parrinello G, Ferrari R. Randomized comparison of 6‐ versus 24‐month clopidogrel therapy after balancing anti‐intimal hyperplasia stent potency in all‐comer patients undergoing percutaneous coronary intervention design and rationale for the prolonging dual‐antiplatelet treatment after grading stent‐induced intimal hyperplasia study (PRODIGY). Am Heart J. 2010;160:804–811.
- ↵Valgimigli M, Campo G, Monti M, Vranckx P, Percoco G, Tumscitz C, Castriota F, Colombo F, Tebaldi M, Fuca G, Kubbajeh M, Cangiano E, Minarelli M, Scalone A, Cavazza C, Frangione A, Borghesi M, Marchesini J, Parrinello G, Ferrari R. Short‐ versus long‐term duration of dual‐antiplatelet therapy after coronary stenting: a randomized multicenter trial. Circulation. 2012;125:2015–2026.
- ↵Valgimigli M, Borghesi M, Tebaldi M, Vranckx P, Parrinello G, Ferrari R. Should duration of dual antiplatelet therapy depend on the type and/or potency of implanted stent? A pre‐specified analysis from the prolonging dual antiplatelet treatment after grading stent‐induced intimal hyperplasia study (PRODIGY). Eur Heart J. 2013;34:909–919.
- ↵Giustino G, Chieffo A, Palmerini T, Valgimigli M, Feres F, Abizaid A, Costa RA, Hong MK, Kim BK, Jang Y, Kim HS, Park KW, Gilard M, Morice MC, Sawaya F, Sardella G, Genereux P, Redfors B, Leon MB, Bhatt DL, Stone GW, Colombo A. Efficacy and safety of dual antiplatelet therapy after complex PCI. J Am Coll Cardiol. 2016;68:1851–1864.
- ↵Habara M, Tsuchikane E, Muramatsu T, Kashima Y, Okamura A, Mutoh M, Yamane M, Oida A, Oikawa Y, Hasegawa K. Comparison of percutaneous coronary intervention for chronic total occlusion outcome according to operator experience from the Japanese retrograde summit registry. Catheter Cardiovasc Interv. 2016;87:1027–1035.
- ↵Tamburino C, Latib A, van Geuns RJ, Sabate M, Mehilli J, Gori T, Achenbach S, Alvarez MP, Nef H, Lesiak M, Di Mario C, Colombo A, Naber CK, Caramanno G, Capranzano P, Brugaletta S, Geraci S, Araszkiewicz A, Mattesini A, Pyxaras SA, Rzeszutko L, Depukat R, Diletti R, Boone E, Capodanno D, Dudek D. Contemporary practice and technical aspects in coronary intervention with bioresorbable scaffolds: a European perspective. EuroIntervention. 2015;11:45–52.
- ↵Tommaso CL, Bolman RM III., Feldman T, Bavaria J, Acker MA, Aldea G, Cameron DE, Dean LS, Fullerton D, Hijazi ZM, Horlick E, Miller DC, Moon MR, Ringel R, Ruiz CE, Trento A, Weiner BH, Zahn EM. Multisociety (AATS, ACCF, SCAI, and STS) expert consensus statement: operator and institutional requirements for transcatheter valve repair and replacement, part 1: transcatheter aortic valve replacement. J Am Coll Cardiol. 2012;59:2028–2042.
- ↵Shah R, Gardner JD. Radial versus femoral access for cardiac catheterisation. Lancet. 2015;386:2392–2393.
- ↵Dehmer GJ, Holper EM. Does practice make perfect? JACC Cardiovasc Interv. 2017;10:928–930.