Clinical, Angiographic, and Procedural Correlates of Very Late Absorb Scaffold Thrombosis: Multistudy Registry Results

OBJECTIVES: The aim of this study was to identify independent correlates of very late scaffold thrombosis (VLST) from an analysis of consecutively treated patients from 15 multicenter studies. BACKGROUND: Recent analyses suggest an increased risk for VLST with the Absorb Bioresorbable Vascular Scaffold compared with drug-eluting stents, but insights as to correlates of risk are limited. METHODS: A total of 55 patients were identified with scaffold thrombosis. They were matched 2:1 with control subjects selected randomly from patients without thrombosis from the same study. Quantitative coronary angiography was available for 96.4% of patients. Multiple logistic and Cox regression analysis were used to identify significant independent outcome correlates from 6 pre-specified characteristics. RESULTS: Patients had scaffold thrombosis at a median of 20 months (interquartile range: 17 to 27 months). Control subjects were followed for 36 months (interquartile range: 24 to 38 months). For the combined groups, reference vessel diameter (RVD) was 2.84 0.50 mm, scaffold length was 26 16 mm, and post-dilatation was performed in56%. Univariate correlates of thrombosis were smaller nominal scaffold/RVD ratio (linear p»0.001; ratio<1.18:1; odds ratio: 7.5; p»0.002) and larger RVD (linear p»0.001;>2.72 mm; odds ratio: 3.4; p»0.001). Post-dilatation at$16 atm, post-dilatation balloon/scaffold ratio, final percentage stenosis, and dual antiplatelet therapy were not correlated with VLST. Only scaffold/RVD ratio remained a significant independent correlate of VLST (p»0.001), as smaller ratio was correlated with RVD (p<0.001). Post hoc analysis of 8 other potential covariates revealed no other correlates of outcome. CONCLUSIONS: In the present analysis, the largest to date of its type, relative scaffold undersizing was the strongest determinant of VLST. Given current understanding of "scaffold dismantling," this finding likely has ramifications for all bioresorbable scaffolds.

Clinical, angiographic, and procedural correlates of acute, subacute, and late absorb scaffold thrombosis

OBJECTIVES: The authors sought to identify and verify independent correlates of device thrombosis from an analysis of multicenter trials and registries. BACKGROUND: Recent analyses suggest an increased risk of device thrombosis with Absorb bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, California) implantation compared with metallic drug-eluting stents, and data from moderate size studies suggest a risk relationship to vessel size and technique. METHODS: From 8,771 consecutively treated patients, 105 patients (1.2%) were identified with scaffold thrombosis within 1 year of implantation. They were matched 2:1 with controls selected randomly from nonthrombosis patients. Data-restricted multiple logistic analysis was used to identify significant independent covariates of the outcome. RESULTS: Early (within 1 month) scaffold thrombosis occurred in 69 patients and late (1 to 12 months) thrombosis occurred in 36 patients. Modelling found significant correlations of thrombosis to be final minimal lumen diameter 1.1:1 balloon/scaffold ratio (OR: 2.3; p = 0.022), and reference vessel diameter <2.40 mm (OR: 2.1; p = 0.036).CONCLUSIONS:Suboptimal vessel sizing, procedural technique, angiographic outcomes, and dual antiplatelet therapy discontinuation appear to be the principal determinants of Absorb scaffold thrombosis risk through 12 months after implantation.

Efficacy and Safety of the Absorb Everolimus-Eluting Bioresorbable Scaffold for Treatment of Patients With Diabetes Mellitus: Results of the Absorb Diabetic Substudy

OBJECTIVES The study sought to evaluate the efficacy and safety of the Absorb everolimus-eluting bioresorbable vascular scaffold (BVS) (Abbott Vascular, Abbott Park, Illinois) in patients with diabetes mellitus.BACKGROUND Randomized, controlled trials have demonstrated comparable clinical outcomes following percutaneous coronary intervention with either Absorb BVS or metallic Xience everolimus-eluting stent. However, these trials lack power required to provide reliable treatment effect estimates in this high-risk population.METHODS In a pre-specified, powered analysis, patients with diabetes who received $1 Absorb were pooled from the ABSORB II, III, and JAPAN randomized trials and from the single arm ABSORB EXTEND registry. The study composite primary endpoint was target lesion failure (TLF) at 1 year following Absorb BVS compared with a performance goal of 12.7%.RESULTS Among 754 diabetic patients included in analysis (27.3% insulin treated), the 1-year TLF rate was8.3% (upper 1-sided 95% confidence limit: 10.1%; p » 0.0001 vs. performance goal). Scaffold thrombosis(definite or probable) was observed in 2.3% of patients. Multivariable regression identified older age, insulin treatment, and smaller pre-procedure reference vessel diameter as significant independent predictors of 1-year TLF.CONCLUSIONS The Absorb diabetic substudy suggests efficacy and safety of the Absorb BVS for treatment of patients with diabetes mellitus.

One-year clinical outcomes after sirolimus-eluting coronary stent implantation in diabetics enrolled in the worldwide e-SELECT registry

BACKGROUND:Diabetes mellitus has worse outcome after percutaneous coronary intervention.AIM:We assessed stent thrombosis (ST), major adverse cardiac events (MACE), and major bleeding rates at 1 year after implantation of sirolimus-eluting stents (SES) in patients with diabetes mellitus in a large multicenter registry.METHODS:From May 2006 to April 2008, 15,147 unselected consecutive patients were enrolled at 320 centers in 56 countries in a prospective, observational registry after implantation of ≥ 1 SES. Source data were verified in 20% randomly chosen patients at > 100 sites. Adverse events were adjudicated by an independent Clinical Event Committee.RESULTS:Complete follow-up at 1 year was obtained in 13,693 (92%) patients, 4,577 (30%) of whom were diabetics. Within diabetics, 1,238 (9%) were insulin-treated diabetics (ITD). Diabetics were older (64 vs. 62 years, P < 0.001), with higher incidence of major coronary risk factors, co-morbidities, and triple-vessel coronary artery disease. Coronary lesions had smaller reference vessel diameter (2.88 ± 0.46 vs. 2.93 ± 0.45 mm, P < 0.001) and were more often heavily calcified (26.1% vs. 22.6%, P < 0.001). At 1 year, diabetics had higher MACE rate (6.8% vs. 3.9%, P < 0.001) driven by ITD (10.6% vs. 5.5%, P < 0.001). Finally, diabetics had significant increase in ST (1.7% vs. 0.7%, P < 0.001), principally owing to ITD (3.4% vs. 1.1%, P < 0.001). There was an overall low risk of major bleeding during follow-up, without significant difference among subgroups.CONCLUSIONS:In the e-SELECT registry, diabetics represented 30% of patients undergoing SES implantation and had significantly more co-morbidities and complex coronary lesions. Although 1-year follow-up documented good overall outcome in diabetics, higher ST and MACE rates were observed, mainly driven by ITD.

Long term follow-up of drug eluting versus bare metal stents in the treatment of saphenous vein graft lesions.

INTRODUCTION: The safety and effectiveness of drug-eluting stent (DES) compared with bare metal stents (BMS) for the treatment of saphenous vein graft (SVG) disease is controversial, especially because of the lack of long-term follow-up. The aim of this study was to address the late outcome of DES versus BMS for the treatment of SVG lesions. METHODS: A matched, case-control study included 82 patients in each group. Patients groups were matched by gender, age, clinical presentation, and diabetes. The primary study end point was occurrence of major adverse cardiovascular events (MACE). Secondary end points included death, cardiac death, myocardial infarction (MI), and target vessel revascularization (TVR). RESULTS: Clinical and angiographic characteristics were similar between the groups. At 6 months, TVR (hazard ratio [HR] 6.12, 95% confidence interval [CI] 1.39 to 26.93, P = 0.05), and MACE (HR 2.54, 95% CI 1.08 to 5.98, P = 0.04) were higher in the BMS group. At 4 years the risks of MI (P = 0.21), TVR (P = 0.99), and MACE (P = 0.21) were similar between both groups. However, the rates of death (HR 2.74, 95% CI 1.11 to 6.74, P = 0.04) and cardiac death (HR 4.26, 95% CI 1.59 to 11.35, P = 0.01) were significantly higher in the BMS group. CONCLUSIONS: These results suggest that the use of DES compared with BMS in the treatment of SVG lesions reduces TVR and MACE at 6 months of follow-up, a benefit that was lost over the next 3-4 years.

One-year outcome of small-vessel disease treated with sirolimus-eluting stents: a subgroup analysis of the e-SELECT registry

Objectives: To investigate the characteristics and one-year outcomes following sirolimus-eluting CYPHER Select Plus stent (SES) implantation in small (SmVD) and non-small vessel disease (NSmVD) in the internationale-SELECT registry.Background: Large-scale registry data are lacking on DES outcomes in SmVD treatment.Methods: There were 4,700 SmVD (at least one vessel with estimated reference vessel diameter [RVD] < 2.5 mm, excluding 283 patients with unknown RVD vessels) and 10,139 NSmVD only patients.Results: The SmVD population was older, with more women, diabetics, and vessels treated, higher mean CharlsonComorbidity Index score (CCI), shorter lesions, and less STEMI presentation. The 1-year stent thrombosis (ST) rate (primary end-point), was significantly higher (1.3% vs. 0.7%) in SmVD versus NSmVD, mainly driven by early events. One-year major adverse cardiac event (MACE), myocardial infarction (MI), and clinically indicated target-lesion revascularization (TLR) rates were significantly higher in SmVD although death and major bleeding rates were similar in both groups. Complication rates were similar between pure (3,188 patients; only RVD < 2.5 mm) and mixed (1,795 patients; some RVD < 2.5 mm or unknown RVD) SmVD. Multivariate predictors for 1-year MACE in SmVD included saphenous vein graft or bifurcation lesions, major bleeding, any antiplatelet therapy discontinuation within 1 month, age, number of stents implanted, CCI, acute coronary syndrome, and insulin-dependent diabetes mellitus.Conclusion: SES implantation for SmVD occurs more frequently in women, diabetics, and those with multivesseldisease and comorbidities. One-year ST, MACE, MI, and clinically indicated TLR rates are higher, although low overall, in SmVD or mixed SmVD patients while death rates are similar to NSmVD.

The sirolimus-eluting Cypher Select coronary stent for the treatment of bare-metal and drug-eluting stent restenosis: insights from the e-SELECT (Multicenter Post-Market Surveillance) registry.

OBJECTIVES: This study sought to compare the 1-year safety and efficacy of Cypher Select or Cypher Select Plus (Cordis Corporation, Bridgewater, New Jersey) sirolimus-eluting stents (SES) with the treatment of bare-metal stents (BMS) and drug-eluting stent (DES) in-stent restenosis (ISR) in nonselected, real-world patients. BACKGROUND: There is paucity of consistent data on DES for the treatment of ISR, especially, DES ISR. METHODS: The e-SELECT (Multicenter Post-Market Surveillance) registry is a Web-based, multicenter and international registry encompassing virtually all subsets of patients and lesions treated with at least 1 SES during the period from 2006 to 2008. We enrolled in this pre-specified subanalysis all patients with at least 1 clinically relevant BMS or DES ISR treated with SES. Primary endpoint was major adverse cardiac events and stent thrombosis rate at 1 year. RESULTS: Of 15,147 patients enrolled, 1,590 (10.5%) presented at least 1 ISR (BMS group, n = 1,235, DES group, n = 355). Patients with DES ISR had higher incidence of diabetes (39.4% vs. 26.9%, p < 0.001), renal insufficiency (5.8% vs. 2.3%, p = 0.003), and prior coronary artery bypass graft (20.5% vs. 11.8%, p < 0.001). At 1 year, death (1.4% for BMS vs. 2.1% for DES, p = 0.3) and myocardial infarction (2.4% for BMS and 3.3% for DES, p = 0.3) rates were similar, whereas ischemia-driven target lesion revascularization and definite/probable late stent thrombosis were higher in patients with DES ISR (6.9% vs. 3.1%, p = 0.003, and 1.8% vs. 0.5%, p = 0.04, respectively). CONCLUSIONS: Use of SES for either BMS or DES ISR treatment is safe and associated with low target lesion revascularization recurrence and no apparent safety concern.

The sirolimus-eluting cypher select coronary stent for the treatment of bare-metal and drug-eluting stent restenosis

Objectives This study sought to compare the 1-year safety and efficacy of Cypher Select or Cypher SelectPlus (Cordis Corporation, Bridgewater, New Jersey) sirolimus-eluting stents (SES) with the treatment of baremetalstents (BMS) and drug-eluting stent (DES) in-stent restenosis (ISR) in nonselected, real-world patients.Background There is paucity of consistent data on DES for the treatment of ISR, especially, DES ISR.Methods The e-SELECT (Multicenter Post-Market Surveillance) registry is a Web-based, multicenterand international registry encompassing virtually all subsets of patients and lesions treated with atleast 1 SES during the period from 2006 to 2008. We enrolled in this pre-specified subanalysis allpatients with at least 1 clinically relevant BMS or DES ISR treated with SES. Primary endpoint wasmajor adverse cardiac events and stent thrombosis rate at 1 year.Results Of 15,147 patients enrolled, 1,590 (10.5%) presented at least 1 ISR (BMS group, n 1,235,DES group, n 355). Patients with DES ISR had higher incidence of diabetes (39.4% vs. 26.9%,p 0.001), renal insufficiency (5.8% vs. 2.3%, p 0.003), and prior coronary artery bypass graft(20.5% vs. 11.8%, p 0.001). At 1 year, death (1.4% for BMS vs. 2.1% for DES, p 0.3) and myocardialinfarction (2.4% for BMS and 3.3% for DES, p 0.3) rates were similar, whereas ischemia-driven target lesion revascularization and definite/probable late stent thrombosis were higher inpatients with DES ISR (6.9% vs. 3.1%, p 0.003, and 1.8% vs. 0.5%, p 0.04, respectively).Conclusions Use of SES for either BMS or DES ISR treatment is safe and associated with low target lesionrevascularization recurrence and no apparent safety concern. (J Am Coll Cardiol Intv 2012;5:64–71) © 2012by the American College of Cardiology Foundation.

One-year clinical outcomes after sirolimus-eluting coronary stent implantation for acute myocardial infarction in the worldwide e-SELECTregistry

Background: The aim was to ascertain the 1-year clinical outcomes of 1,234 patients who underwent implantationsof sirolimus-eluting stents (SES) for acute myocardial infarction (MI) in the multinational e-SELECT registry.Methods: Fifteen thousand and one hundred and forty-seven patients treated with SES were entered in thee-SELECT registry, of whom 1,234 presented within <24 hours of onset of acute MI.Results: At 1 year, the rates of major adverse cardiac events (MACE) (5.5% vs. 4.8%; P = 0.28) were similarlylow in the acute and no acute MI groups. The rates of definite/probable stent thrombosis (ST) were higher inthe acute MI group (2.1%vs; 0.88%, P < 0.001). ST was a strong independent predictor of death at 1 year(HR 13.4; 95% CI 5.0, 36.0; P < 0.001) and MI (HR 58.9; 95% CI 26.9, 129.1; P < 0.001). Dual antiplatelettherapy (DAPT) compliance at 6 months was 96.0% in the acute MI versus 94.5% in the no acute MI group(P = 0.03).Conclusion: In selected patients presenting within <24 hours of acute MI onset and highly compliant with DAPT,SES implantation was associated with similar rates of MACE, though higher rates of ST, as compared to no acuteMI patients.Condensed abstractIn the e-SELECT registrywhich included 15,147 patients treated with sirolimus-eluting stent (SES), we ascertainedthe 1-year clinical outcomes of 1,234 patients who presented within <24 hours of acute MI onset. In acute MIpatients SES implantation was associated with similar rates of MACE, though higher rates of ST, as comparedto no acute MI patients (MACE: 5.5% vs. 4.8%; P = 0.28; ST: 2.1 vs. 0.88%, P < 0.001). (J Interven Cardiol2012;25:253–261).

Sirolimus-eluting coronary stents in octogenarians: a 1-year analysis of the worldwide e-SELECT Registry.

OBJECTIVES: The aim of this study was to identify the worldwide practice of Cypher Select (Cordis Corporation, Bridgewater, New Jersey) or Cypher Select Plus sirolimus-eluting stent (SES) in patients 80 years of age (octogenarian) and to identify clinical outcomes in this patient population. BACKGROUND: The use of drug-eluting stents in elderly patients may have different features compared with younger patients. METHODS: Between 2006 and 2008, 15,147 patients from 320 hospitals in 56 countries were enrolled in a registry. Initial implantation and follow-up outcome information obtained at 1-year follow-up in 675 octogenarian patients were compared with those in 14,472 nonoctogenarian patients. RESULTS: Octogenarians had significantly more comorbidities and had higher Charlson comorbidity index scores (1.5 ± 1.6 vs. 1.0 ± 1.3, p < 0.001). Rates of cardiac death (3.3% vs. 0.9%, p < 0.001), myocardial infarction (2.3% vs. 1.9%, p = 0.021), and definite or probable stent thrombosis (2.3% vs. 0.9%, p = 0.0002), and major bleeding (2.0% vs. 0.9%, p = 0.015) were significantly higher in octogenarians at 1 year; however, there was no significant difference in the rate of target lesion revascularization between the 2 groups (3.2% vs. 2.2%, p = 0.12). In octogenarians, a high Charlson comorbidity index was an independent predictor of death and stent thrombosis up to 360 days from the index procedure (hazard ratio: 1.3, 95% confidence interval: 1.1 to 1.5, p < 0.001, and hazard ratio: 1.5, 95% confidence interval: 1.3 to 1.8, p < 0.001, respectively). CONCLUSIONS: Stenting with SES may be an effective therapeutic option in elderly patients, with acceptable rates of complications and a very low rate of repeat revascularization as demonstrated by this e-SELECT (A Multi-Center Post-Market Surveillance Registry) subgroup analysis.

Stent thrombosis and bleeding complications after implantation of sirolimus-eluting coronary stentsin an unselected worldwide population a report from the e-SELECT (Multi-Center Post-Market Surveillance) registry

Objectives The aim of this study was to ascertain the 1-year incidence of stent thrombosis (ST) and major bleeding (MB) ina large, unselected population treated with sirolimus-eluting stents (SES).Background Stent thrombosis and MB are major potential complications of drug-eluting stent implantation. Their relativeincidence and predisposing factors among large populations treated worldwide are unclear.Methods The SES were implanted in 15,147 patients who were entered in a multinational registry. We analyzed the incidenceof: 1) definite and probable ST as defined by the Academic Research Consortium; and 2) MB, with theSTEEPLE (Safety and efficacy of Enoxaparin in PCI) definition, together with their relation to dual antiplatelettherapy (DAPT) and to 1-year clinical outcomes.Results The mean age of the sample was 62 11 years, 30.4% were diabetic, 10% had a Charlson comorbidity index 3, and 44% presented with acute coronary syndrome or myocardial infarction. At 1 year, the reported compliancewith DAPT as recommended by the European Society of Cardiology guidelines was 86.3%. Adverse eventrates were: ST 1.0%, MB 1.0%, mortality 1.7%, myocardial infarction 1.9%, and target lesion revascularization2.3%. Multivariate analysis identified 9 correlates of ST and 4 correlates of MB. Advanced age and a high Charlsonindex were associated with an increased risk of both ST and MB. After ST, the 7-day and 1-year all-causemortality was 30% and 35%, respectively, versus 1.5% and 10% after MB. Only 2 of 13,749 patients (0.015%)experienced both MB and ST during the entire 1-year follow-up period.Conclusions In this worldwide population treated with 1 SES, the reported compliance with DAPT was good, and the incidenceof ST and MB was low. Stent thrombosis and MB very rarely occurred in the same patient.

A randomized trial of 5 versus 7 French guiding catheters for transfemoral percutaneous coronary stent implantation.

Comparative studies between 5 French guiding catheter and others of larger size using the transfemoral approach to coronary stenting have not been described. Coronary stent implantation was performed in 90 patients in a randomized trial. The primary end-point was to compare the incidence of successful uncomplicated stent implantation per lesion with the 5F and 7F guiding catheters. Patients were excluded for excessive vessel tortuosity or anticipated need for equipment not fitting through a 5 catheter. Baseline characteristics and the use of direct stenting did not differ between the two groups. The primary success rate was 97.8% per patient in both groups and 98% per lesion in the 5 French and 97.9% in the 7 French. Guiding catheter change was necessary in 1 patient in each group to successfully complete the procedure in both groups. The amount of contrast used was 63 +/- 27.3 mL in the 5 French and 76 +/- 25 mL in the 7 French groups (P < 0.05). Vascular complications and blood transfusions occurred somewhat more frequently in the 7 French group (P = 0.058). The manual compression time after sheath removal was 5.1 +/- 2.0 min and 8.0 +/- 4.3 min, respectively, in the 5 and 7 French groups (P < 0.01). In conclusion, the 5 French guiding catheters showed a similar success rate with coronary stenting when compared to the 7 French, but the amount of contrast used and manual compression time after sheath removal, as well as the rate of vascular and bleeding complications, were reduced in the 5 French group.

Impaired myocardial perfusion score and inflammatory markers in patients undergoing primary angioplasty for acute myocardial infarction

BACKGROUND: Microcirculatory dysfunction during acute myocardial infarction is mediated by various mechanisms including inflammation, thrombus, or plaque embolization. We hypothesize that patients with acute myocardial infarction and admission Thrombolysis in Myocardial Infarction (TIMI) myocardial perfusion grade (TMP) < 2 had increased inflammatory status as measured by high sensitivity C-reactive protein (hs-CRP). METHODS: From January 2002 to December 2003, 166 patients (178 lesions) were referred for primary percutaneous coronary intervention. Patients were stratified based on pre-PCI TMP < 2 or TMP 2. Univariate and multivariate predictors of in-hospital and 30-day death were determined with logistic regression. RESULTS: Pre-PCI TMP < 2 was found in 66% vs 34% with TMP 2 (P < .001). Hs-CRP levels were high in both groups but not significantly different (37.9 +/- 6 vs 33.7 +/- 6 mg/L, P = .63). Patients with TMP < 2 had higher WBC (12.83 +/-4.55 x 10(-3) vs 10.83 +/- 3.00 x 10(-3), P = .04), lower ejection fraction (40 +/- 11% vs 46 +/- 12%, P < .001), and higher admission CK-MB levels (116 +/- 13 ng/mL vs 55 +/- 13 ng/mL, P = .006). Death occurred in 12% in the poorTMP group vs 1.8% in the good TMP group (P = .03). Advanced age, use of an intra-aortic balloon pump, and elevated admission WBC were independently associated with in-hospital and 30-day death. CONCLUSIONS: High hs-CRP levels were not associated with impaired myocardial perfusion score. Microcirculatory impairment may be related to an increased inflammatory process, independent from high hs-CRP levels.

Impaired myocardial perfusion score and inflammatory markers in patients undergoing primary angioplasty for acute myocardial infarction.

BACKGROUND: Microcirculatory dysfunction during acute myocardial infarction is mediated by various mechanisms including inflammation, thrombus, or plaque embolization. We hypothesize that patients with acute myocardial infarction and admission Thrombolysis in Myocardial Infarction (TIMI) myocardial perfusion grade (TMP) < 2 had increased inflammatory status as measured by high sensitivity C-reactive protein (hs-CRP). METHODS: From January 2002 to December 2003, 166 patients (178 lesions) were referred for primary percutaneous coronary intervention. Patients were stratified based on pre-PCI TMP < 2 or TMP 2. Univariate and multivariate predictors of in-hospital and 30-day death were determined with logistic regression. RESULTS: Pre-PCI TMP < 2 was found in 66% vs 34% with TMP 2 (P < .001). Hs-CRP levels were high in both groups but not significantly different (37.9 +/- 6 vs 33.7 +/- 6 mg/L, P = .63). Patients with TMP < 2 had higher WBC (12.83 +/-4.55 x 10(-3) vs 10.83 +/- 3.00 x 10(-3), P = .04), lower ejection fraction (40 +/- 11% vs 46 +/- 12%, P < .001), and higher admission CK-MB levels (116 +/- 13 ng/mL vs 55 +/- 13 ng/mL, P = .006). Death occurred in 12% in the poorTMP group vs 1.8% in the good TMP group (P = .03). Advanced age, use of an intra-aortic balloon pump, and elevated admission WBC were independently associated with in-hospital and 30-day death. CONCLUSIONS: High hs-CRP levels were not associated with impaired myocardial perfusion score. Microcirculatory impairment may be related to an increased inflammatory process, independent from high hs-CRP levels.

New frontiers in interventional cardiology / New frontiers in interventional cardiology

The latest statistics from the American Heart Association are disturbing: In 2004, an estimated 865 000 Americans will developed a new acute coronary syndrome. Another 700 000 will have a stroke. Unfortunately, the contribution of percutaneous coronary intervention (PCI) to prevent such catastrophic outcomes has been limited.