2.1

Study groups

The study population was divided into three groups: 1) Support catheter and wire based CTO group (CTO-SW): This was defined as successful proximal to distal lumen crossing of chronic total occlusion using a variety of wires and support catheters. 2) Re-entry device based CTO group (CTO-RE): This was defined as successful re-entry into the distal true lumen using re-entry devices such as the Outback or Pioneer catheters. 3) Non-CTO group (non-CTO): This group of patients did not have a CTO but had severe obstructive lesions. Given that the CTO groups had very long lesions only patients with TASC C lesions were enrolled into the non-CTO group.

2.2

Procedural details

All procedures were performed through a contralateral femoral approach. Interventions were performed after therapeutic dose of heparin was given to maintain an APTT greater than 200 throughout the procedure. The initial approach to cross most CTOs was with the use of the support catheter and wire (choice of devices was at operator discretion). Specialized crossing devices (Frontrunner, Truepath, etc.) were used in less than 5% of CTO cases as per operator discretion. The re-entry device strategy typically involves blunt dissection using a formed knuckle with a hydrophilic wire with a support catheter. The dissection was extended all the way down to the vessel distal to the CTO and re-entry was achieved using either a Pioneer (Volcano Corporation, San Diego, CA) or an Outback (Cordis Corp., Miami, FL) catheter. In non-CTO lesions, the lesion was typically crossed with a wire followed by balloon angioplasty and stenting. The lesions were first prepared with aggressive 1:1 balloon dilatation, followed by implantation of a variety of self-expanding stents that were sized 1 mm larger than the reference vessel diameter. Post dilation was performed with a balloon that was sized 1:1 to the reference vessel diameter. The type of stent used was at the discretion of the operator, typically to optimize the treatment of the lesion after suboptimal balloon angioplasty or in the event of flow limiting dissections.

2.3

Follow up

Within the first year, all patients underwent clinical follow-up in conjunction with ankle–brachial index (ABI)/pulse-volume recording (PVR) study at least every 3 months, and then every 6 months thereafter (or sooner if symptoms occurred). In-stent restenosis (ISR) was suspected if one or a combination of the following findings were observed: ABI drop of ≥0.15 from immediate post-procedure baseline and/or if the patient became symptomatic with claudication or limb ischemia. These findings led to further confirmatory testing using non-invasive imaging (arterial duplex – PSV ratio > 4; computed tomography angiography – stenosis of >60%) or invasive angiography with angiographic restenosis- defined as >60% reduction of the vessel diameter by visual estimation. The diagnosis of obstructive ISR established by the above-mentioned tests was an endpoint for the study.

Patients who presented for ISR revascularization procedures underwent fluoroscopy/CINE imaging using at least two different orthogonal views for detection of stent fracture (SF). Stent fracture was defined as clear interruption of stent struts (>1 mm) identified by fluoroscopy/CINE with resulting kink or misalignment along the axial length of the stent.

In addition, we also analyzed several demographic, procedural characteristics, and laboratory parameters that have been reported in the literature as potential predictors of ISR, including age, weight, medications, creatinine levels, calculated glomerular filtration rate (GFR), white blood cell count (WBC), blood pressure, lipid level, random blood sugar, history of diabetes and chronic kidney disease, lesion length, and run-off score.

2.4

Statistical analysis

All covariates were tested for normality by visual inspection using frequency distribution curves and Q-Q plots. Normal variables are presented as mean and standard deviation (SD), and variables with skewed distribution as median and interquartile ranges. Categorical variables, such as the prevalence of various metabolic syndrome definitions, are presented as percentages. Confounding variables were identified by a literature search. Univariate and multivariate Cox proportional-hazards regression analyses were performed . Two-tailed P values <0.05 were considered statistically significant. All statistical procedures were performed using Statistical Analysis Systems version 9.1 (SAS Institute, Cary, NC) statistical software package.

2.1

Study groups

The study population was divided into three groups: 1) Support catheter and wire based CTO group (CTO-SW): This was defined as successful proximal to distal lumen crossing of chronic total occlusion using a variety of wires and support catheters. 2) Re-entry device based CTO group (CTO-RE): This was defined as successful re-entry into the distal true lumen using re-entry devices such as the Outback or Pioneer catheters. 3) Non-CTO group (non-CTO): This group of patients did not have a CTO but had severe obstructive lesions. Given that the CTO groups had very long lesions only patients with TASC C lesions were enrolled into the non-CTO group.

2.2

Procedural details

All procedures were performed through a contralateral femoral approach. Interventions were performed after therapeutic dose of heparin was given to maintain an APTT greater than 200 throughout the procedure. The initial approach to cross most CTOs was with the use of the support catheter and wire (choice of devices was at operator discretion). Specialized crossing devices (Frontrunner, Truepath, etc.) were used in less than 5% of CTO cases as per operator discretion. The re-entry device strategy typically involves blunt dissection using a formed knuckle with a hydrophilic wire with a support catheter. The dissection was extended all the way down to the vessel distal to the CTO and re-entry was achieved using either a Pioneer (Volcano Corporation, San Diego, CA) or an Outback (Cordis Corp., Miami, FL) catheter. In non-CTO lesions, the lesion was typically crossed with a wire followed by balloon angioplasty and stenting. The lesions were first prepared with aggressive 1:1 balloon dilatation, followed by implantation of a variety of self-expanding stents that were sized 1 mm larger than the reference vessel diameter. Post dilation was performed with a balloon that was sized 1:1 to the reference vessel diameter. The type of stent used was at the discretion of the operator, typically to optimize the treatment of the lesion after suboptimal balloon angioplasty or in the event of flow limiting dissections.

2.3

Follow up

Within the first year, all patients underwent clinical follow-up in conjunction with ankle–brachial index (ABI)/pulse-volume recording (PVR) study at least every 3 months, and then every 6 months thereafter (or sooner if symptoms occurred). In-stent restenosis (ISR) was suspected if one or a combination of the following findings were observed: ABI drop of ≥0.15 from immediate post-procedure baseline and/or if the patient became symptomatic with claudication or limb ischemia. These findings led to further confirmatory testing using non-invasive imaging (arterial duplex – PSV ratio > 4; computed tomography angiography – stenosis of >60%) or invasive angiography with angiographic restenosis- defined as >60% reduction of the vessel diameter by visual estimation. The diagnosis of obstructive ISR established by the above-mentioned tests was an endpoint for the study.

Patients who presented for ISR revascularization procedures underwent fluoroscopy/CINE imaging using at least two different orthogonal views for detection of stent fracture (SF). Stent fracture was defined as clear interruption of stent struts (>1 mm) identified by fluoroscopy/CINE with resulting kink or misalignment along the axial length of the stent.

In addition, we also analyzed several demographic, procedural characteristics, and laboratory parameters that have been reported in the literature as potential predictors of ISR, including age, weight, medications, creatinine levels, calculated glomerular filtration rate (GFR), white blood cell count (WBC), blood pressure, lipid level, random blood sugar, history of diabetes and chronic kidney disease, lesion length, and run-off score.

2.4

Statistical analysis

All covariates were tested for normality by visual inspection using frequency distribution curves and Q-Q plots. Normal variables are presented as mean and standard deviation (SD), and variables with skewed distribution as median and interquartile ranges. Categorical variables, such as the prevalence of various metabolic syndrome definitions, are presented as percentages. Confounding variables were identified by a literature search. Univariate and multivariate Cox proportional-hazards regression analyses were performed . Two-tailed P values <0.05 were considered statistically significant. All statistical procedures were performed using Statistical Analysis Systems version 9.1 (SAS Institute, Cary, NC) statistical software package.