Patients Undergoing Chronic Total Occlusion Percutaneous Coronary Intervention Research Articles

Outcomes of the retrograde approach through epicardial versus non-epicardial collaterals in chronic total occlusion percutaneous coronary intervention.

The retrograde approach through epicardial collaterals (EC) for chronic total occlusion (CTO) percutaneous coronary intervention (PCI) is a challenging procedure. Our study aim was to evaluate the outcomes of patients undergoing CTO PCI using a retrograde approach through epicardial versus non-epicardial collaterals (NEC). We collected data from our single-center registry of consecutive patients undergoing retrograde CTO PCI, performed by an experienced operator through EC and NEC (septals and bypass grafts). Clinical, angiographic and procedural data were recorded. The primary endpoint (major adverse cardiac events, MACE) was a composite of cardiac death, target-vessel myocardial infarction (MI) and target-vessel revascularization (TVR) on follow-up. During the study period, 318 CTO PCIs were performed. Of these, 81 procedures (25%) were performed retrogradely in 75 patients (38 using NEC [31 septals, 7 bypass grafts], 37 through EC [34 contralateral, 3 ipsilateral]). Clinical characteristics were balanced between EC and NEC. J-CTO score was 2.1±1.1 and 2.2±1.2, respectively (p=0.92). Collateral tortuosity was more marked in EC. Technical and procedural success was lower in EC (35% vs. 76%, p<0.001; 30% vs. 76%, p<0.001; respectively). There were two perforations (5%) with need for intervention in EC, and none in NEC (p=0.15). After a median follow-up of 443 (331-744) days, MACE were observed in 12.9% (n=4) of EC vs. 5.4% (n=2) in NEC patients (p=0.28). In our experience, retrograde CTO PCI through EC was associated with lower success rate, and a numerically higher rate of perforation, as compared with NEC. Clinical outcomes on follow-up were similar.

Impact of multi-vessel versus single-vessel disease on outcomes after percutaneous coronary interventions for chronic total occlusions.

Successful chronic total occlusion (CTO) revascularization has been associated with prognostic benefits. Whether the extent of coronary artery disease interferes with these benefits has not been investigated yet. We sought to compare the survival after percutaneous coronary intervention (PCI) for CTO between patients with multi- (MVD) and single-vessel disease (SVD). A total of 2002 consecutive patients undergoing CTO PCI between 01/2005 and 12/2013 were identified and stratified according to the presence/absence of MVD. The primary endpoint was all-cause mortality. Median follow-up was 2.6 (interquartile range 1.1-3.1) years. A total of 1634 (81.6%) patients had MVD. Procedural success rates were 81.5 and 89.7% in the MVD and SVD groups (p < 0.001). All-cause mortality during entire follow-up was higher in MVD as compared to SVD patients (13.5 versus 5.7%, p < 0.001), and differences were attenuated after multivariable adjustment for baseline characteristics [adjusted hazard ratio (HR) 1.51, 95% CI 0.98-2.33, p = 0.06]. The effect of successful CTO PCI on all-cause mortality was consistent among patients with MVD [11.0 versus 24.5%; adjusted HR 0.60, 95% CI 0.45-0.80, p < 0.001] and SVD [5.2 versus 10.5%; adjusted HR 0.74, 95% CI 0.24-2.26, p = 0.59, P int = 0.65]. However, due to the greater baseline risk in the former group, the absolute survival benefit after successful CTO PCI was higher. Successful recanalization of a CTO is a strong independent predictor for reduced long-term mortality. Due a higher baseline risk, the absolute benefit in patients with MVD is substantially larger than in patients with SVD.

Long-term outcomes of rotational atherectomy for the percutaneous treatment of chronic total occlusions.

To study the long-term outcomes of rotational atherectomy (RA) for chronic total occlusion (CTO) percutaneous coronary intervention (PCI). There is little evidence on the incidence, procedural results and long-term outcomes of RA for CTO PCI. This registry included data from consecutive patients undergoing CTO PCI at four specialized centers. Major adverse cardiac events (MACE: cardiac death, target-vessel myocardial infarction and ischemia-driven target-vessel revascularization) on follow-up were the primary endpoint. A total of 1003 patients were included. Of these, 35 (3.5%) required RA. As compared with Conventional PCI, RA patients were older (68.9 ± 9.5 vs. 64.6 ± 10.7 years, P = 0.02), had higher prevalence of diabetes (58% vs. 37%, P = 0.01) and of a J-CTO score ≥2 (80% vs. 58%, P = 0.009), driven by severe calcification. Antegrade wire escalation was used more frequently in RA (74% vs. 53%, P = 0.08). RA was performed for balloon failure-to-cross in 51% and failure-to-expand in 49%. One burr was utilized in 86%. The 1.25-mm burr was the largest burr used in 43%. Slow flow/no-reflow was observed in 17%. No other serious RA-related complications were observed. Procedural success was 77% vs. 89% (P = 0.04) in RA vs. Conventional PCI. After a mean follow-up of 658 ± 412 days, MACE rates were similar between groups (15% vs. 13%, P = 0.70). The use of RA in CTO PCI was safe, despite a worse patient risk profile and higher procedural complexity, as compared with conventional techniques. Although procedural success was lower in the RA group, there were no differences in long-term clinical outcomes between groups. © 2016 Wiley Periodicals, Inc.

Procedural and longer-term outcomes of wire- versus device-based antegrade dissection and re-entry techniques for the percutaneous revascularization of coronary chronic total occlusions

BackgroundThere are few data regarding the procedural and follow-up outcomes of different antegrade dissection/re-entry (ADR) techniques for chronic total occlusion (CTO) percutaneous coronary intervention (PCI). MethodsWe compiled a multicenter registry of consecutive patients undergoing ADR-based CTO PCI at four high-volume specialized institutions. Patients were divided according to the specific ADR technique used: subintimal tracking and re-entry (STAR), limited antegrade subintimal tracking (LAST), or device-based with the CrossBoss/Stingray system (Boston Scientific, Marlborough, MA). Major adverse cardiac events (MACE: cardiac death, target-vessel myocardial infarction and target-vessel revascularization) on follow-up were the main outcome of this study. Independent predictors of MACE were sought with Cox regression analysis. ResultsA total of 223 patients were included (STAR n=39, LAST n=68, CrossBoss/Stingray n=116). Baseline characteristics were similar across groups. Technical and procedural success was lower with STAR (59% and 59%), as compared with LAST (96% and 96%) and CrossBoss/Stingray (89% and 87%; p<0.001 for both). At 24-month follow-up, MACE rates were higher in STAR (15.4%) and LAST (17.5%), as compared with device-based ADR with CrossBoss/Stingray (4.3%, p=0.02), driven by TVR (7.7% vs. 15.5% vs. 3.1%, respectively; p=0.02). Multivariable Cox regression analysis identified wire-based ADR (STAR and LAST) and total stent length as independent predictors of MACE. ConclusionsIn this multicenter cohort of patients undergoing CTO PCI with ADR techniques, STAR had lower success rates, as compared with the CrossBoss/Stingray system and LAST. The CrossBoss/Stingray system was independently associated with lower risk of MACE on follow-up, as compared with wire-based ADR techniques.

Comparison of Characteristics and Complications in Men Versus Women Undergoing Chronic Total Occlusion Percutaneous Intervention

Gender differences exist in clinical outcomes after routine percutaneous coronary intervention (PCI), but studies reporting such outcomes after chronic total occlusion (CTO) PCI are limited. We assessed the characteristics and outcomes of female patients undergoing CTO PCI. We retrospectively analyzed a dedicated national (United Kingdom) prospective CTO database from 2011 to 2015 for outcomes and characteristics of female patients undergoing CTO PCI (unmatched and propensity matched). Female patients constituted 20.5% (n= 260 of 1,271) of the unmatched cohort and 33.3% (n= 233 of 699) of the matched cohort and were more likely to be older (women aged >70years, 48% in the unmatched and 45% in the matched cohort). An increased inhospital complication rate was observed in female patients (unmatched: 10% women vs 4.45% men, p= 0.0012, and matched 9.87% women vs 3.86% men, p= 0.0032). Coronary perforation, bleeding, and contrast-induced nephropathy were more frequently observed in female patients. Femoral access site with >6 French sheath was associated with an increased risk of bleeding. Presence of calcification in the CTO artery was associated with coronary perforation (grade III) in female patients in the matched cohort (p= 0.007). Female patients undergoing CTO PCI were older and experienced increased of inhospital complications. Increased awareness of these complications could influence the selection of access site and sheath size, the need for prehydration, judicious choice of balloon size, collateral selection, and wire placement in female patients undergoing CTO PCI.

Coronary artery spatial distribution of chronic total occlusions: Insights from a large US registry.

To assess the spatial distribution of chronic total occlusions (CTOs) within the coronary arteries and describe procedural strategies and outcomes during CTO percutaneous coronary intervention (PCI). Acute occlusions due to plaque rupture tend to cluster within the proximal third of the coronary artery. We examined the clinical and procedural characteristics of 1,348 patients according to lesion location within the coronary tree. A total of 1,369 lesions in 1,348 patients (mean age 66 ± 10 years, 85% male) were included. CTO PCI of proximal segments (n = 633, 46%) was more common than of mid (n = 557, 41%) and distal segments (n = 179, 13%). Patients undergoing CTO PCI of proximal segments were more likely to be smokers (P < 0.01), have prior coronary artery bypass graft surgery (P = 0.03) and lower ejection fraction (P = 0.04). CTOs occurring in proximal segments had longer length (P <0.01), proximal cap ambiguity (P < 0.01), and moderate/severe calcification (P < 0.01) compared to mid or distally located CTOs. Interventional collaterals were more often present in CTO PCI of proximal segments (64%, 53%, 56%, P < 0.01) consistent with the higher use of retrograde approach (47%, 33%, 37%, P < 0.01) relative to antegrade wire escalation (67%, 82%, 82%, P < 0.01). Procedural complexity was higher in CTO PCI of proximal segments (vs. mid and distal): contrast volume= 275 ml (200-375), 260 ml (200-350), 250 ml (175-350), P = 0.01; fluoroscopy time 53 minutes (32-83), 39 minutes (24-65), 40 minutes (22-72), P < 0.01. However, procedural success (87%, 90%, 85%, P = 0.1), technical success (89%, 91%, 88%, P = 0.24), and complications rates (2.8%, 2.5%, 2.2%, P = 0.88) were not different. The most common target vessel location for CTO PCI is the proximal coronary segment. PCI of proximal occlusions is associated with adverse clinical and angiographic characteristics and often requires use of the retrograde approach, but can be accomplished with high procedural and technical success and low complication rates. © 2016 Wiley Periodicals, Inc.

Impact of body mass index on long-term mortality in women and men undergoing percutaneous coronary intervention for chronic total occlusion

BackgroundThe obesity paradox has been described in different patient populations. Data on the relation between obesity and outcomes in patients undergoing percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) are lacking. Therefore, long-term mortality in patients undergoing CTO PCI was assessed according to different body mass index (BMI) categories. MethodsA total of 1993 patients undergoing CTO PCI at a tertiary care center between January 2005 and December 2013 were divided into five different BMI categories: underweight, <18.5kg/m2; normal BMI, 18.5–24.9kg/m2; overweight, 25.0–29.9kg/m2; obese, 30.0–34.9kg/m2; and very obese, ≥35.0kg/m2. The primary endpoint was all-cause mortality. ResultsMedian follow-up was 2.6 (interquartile range 1.1–3.1) years. Of the 1993 patients, 461 (23.1%) were of normal weight, 985 (49.4%) overweight, 396 (19.9%) obese, and 144 (7.2%) very obese. Compared with normal weight BMI patients (16.3%), overweight patients had a lower all-cause mortality (10.2%, Log Rank p=0.001), while obese (11.1%, Log Rank p=0.08) and severely obese (13.2%, Log Rank p=0.39) patients had similar mortality rates. Being overweight was significantly associated with a lower all-cause mortality (HR 0.69, 95% CI 0.53–0.89, p=0.005), and associations remained significant after multivariable adjustments for confounding factors (HR 0.73, 95% CI 0.56–0.95, p=0.02). While being overweight was linked with a reduced all-cause mortality in men (HR 0.65, 95% CI 0.48–0.88, p=0.005), it was not in women (HR 1.25, 95% CI 0.60–2.52, p=0.58). ConclusionsOverweight is associated with an improved survival in patients undergoing PCI for CTO, particularly in men.

Optical coherence tomography findings after chronic total occlusion interventions: Insights from the "AngiographiC evaluation of the everolimus-eluting stent in chronic Total occlusions" (ACE-CTO) study (NCT01012869).

There is limited information on optical coherence tomography (OCT) findings after percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs). OCT allows high resolution imaging that can enhance understanding of the vascular response after stenting of chronically occluded vessels. The Angiographic Evaluation of the Everolimus-Eluting Stent in Chronic Total Occlusions (ACE-CTO) study collected angiographic and clinical outcomes from 100 patients undergoing CTO PCI with the everolimus-eluting stent (EES). OCT was performed 8-months post stenting in 62 patients. Every third frame was analyzed throughout the course of the stented arterial segment. Lumen contours were semi-automatically traced and stent struts were manually delineated, with automatic measurement of the strut to lumen distance. Struts on the luminal side of the lumen contour were classified as malapposed if the distance to the lumen contour exceeded 0.108mm. A total of 44,450 struts in 6047 frames were analyzed, of which 4113 9.3%, 95% confidence intervals [CI] 9.0% to 9.5%) were malapposed and 1230 (2.8%, 95% CI 2.6% to 2.9%) were uncovered. Fifty-five of 62 patients (88.7%, 95% CI 78.5% to 98.4%) had at least one malapposed stent strut and 50 patients (80.7%, 95% CI 69.2% to 88.6%) had at least one uncovered stent strut. Mean strut-intimal thickness of the apposed and malapposed struts was 0.126±0.140mm and -0.491±0.440mm, respectively. High rates of stent strut malapposition and incomplete stent strut coverage were observed after CTO PCI using EES, highlighting unique challenges associated with stent implantation in CTOs.

Abstract 14955: Factors Associated With High Contrast Utilization During Chronic Total Occlusion Percutaneous Coronary Intervention: Insights From a Contemporary Multicenter Registry

Background: High contrast utilization during chronic total occlusion (CTO) percutaneous coronary intervention (PCI) may lead to peri-procedural complications, in particular contrast-induced nephropathy (CIN). Methods: We examined the association between several clinical and angiographic variables and contrast volume utilization during CTO PCI among 950 consecutive procedures performed at 10 experienced US centers between May 2012 and March 2015. Results: Mean age was 65±10 years, 87% of patients were men, and 34% had prior coronary artery bypass graft surgery (CABG). Technical and procedural success was 91% and 90%, respectively. The median contrast volume utilization was 260 (IQR:195, 360) mL. Approximately 33% of patients received &gt;310mL of contrast (high contrast utilization). On univariable analysis male gender (p=0.017), moderate or severe calcification (p=0.002) and tortuosity (p=0.004), proximal cap ambiguity (p=0.002), distal cap at a bifurcation (p=0.001), side branch at proximal cap (p=0.02), blunt/no stump (p=0.003), occlusion length (p&lt;0.0001), high J-CTO score (p=0.012), guide catheter size (&gt;7F) (p&lt;0.0001), retrograde approach (p=0.006), ad-hoc CTO PCI (p&lt;0.0001) and dual arterial access (p&lt;0.0001) were associated with higher contrast administration, whereas history of diabetes mellitus (p=0.008) and in-stent restenosis (p=0.049) were associated with less contrast use. On multivariable analysis proximal cap ambiguity (p=0.030), bigger guide catheter size (p=0.007), ad-hoc CTO PCI (p&lt;0.0001) and dual arterial access (p=0.002) were independently associated with higher contrast use during CTO PCI. On the other hand, in-stent restenosis (p=0.027) and presence of interventional collaterals (p&lt;0.0001) were associated with lower contrast use. Conclusions: Approximately 1 in 3 patients undergoing CTO PCI receive high contrast volume (&gt;310 mL). Several baseline clinical and angiographic characteristics can help predict the likelihood of high contrast volume administration. This knowledge could be used pre-procedurally and intra-procedurally to guide and intensify efforts to reduce contrast utilization and reduce the risk of contrast-induced complications during CTO PCI.

Procedural outcomes of chronic total occlusion percutaneous coronary intervention: a report from the NCDR (National Cardiovascular Data Registry).

The aim of this study was to describe contemporary frequency, predictors, and outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI) in the United States. CTO PCI can provide significant clinical benefits, yet there is limited information on its success and safety in unselected patient populations. We analyzed the frequency and outcomes of CTO PCI compared with non-CTO PCI in elective patients, and of successful versus failed CTO PCI between July 1, 2009, and March 31, 2013, in the National Cardiovascular Data Registry CathPCI Registry. Generalized estimating equations logistic regression modeling was used to generate independent variables associated with procedural success and procedural complications. During the study period, CTO PCI represented 3.8% of the total PCI volume for stable coronary artery disease (22,365 of 594,510). Overall, patients undergoing CTO PCI required greater contrast volume and longer fluoroscopy time and had lower procedural success (59% vs. 96%, p < 0.001) and higher major adverse cardiac event (1.6% vs. 0.8%, p < 0.001) rates than non-CTO PCI patients. On multivariable analysis, several parameters (including older age, current smoking, previous myocardial infarction, previous coronary artery bypass graft, previous peripheral arterial disease, previous cardiac arrest, right coronary artery CTO target vessel, and less operator experience) were associated with a lower likelihood of CTO PCI procedural success, whereas operators' annual CTO PCI volume was associated with improved success without a significant increase in major complications. CTO PCI is currently performed infrequently in the United States for stable coronary artery disease and is associated with lower procedural success and higher complication rates compared with non-CTO PCI. Procedural success was associated with several patient factors and operator experience.

Predictors of contrast-induced nephropathy in chronic total occlusion percutaneous coronary intervention

Contrast-induced nephropathy (CIN) is a leading cause of morbidity and mortality in patients undergoing percutaneous coronary intervention (PCI). Limited data, however, are available on predictors of CIN in PCI for chronic total occlusion (CTO) lesions. The aim of the study was to determine the risk of developing CIN in patients undergoing CTO PCI by studying the effects of clinical variables, interventional techniques, and CTO lesion characteristics on renal function. This retrospective analysis included consecutive patients referred for CTO PCI between January 2002 and December 2009. CIN was defined as an elevated serum creatinine level ≥25% of baseline serum creatinine level at 48-72 hours after procedure. Patient characteristics, Mehran score, lesion characteristics, interventional procedure, and devices used were compared between CIN and non-CIN groups. For the 516 patients eligible for analysis, the incidence of CIN was 5.4% (28/516). Two patients needed transient haemodialysis (0.4%, 2/516). Analysis of risk using Mehran scoring found that the incidence of CIN was 0.5% (1/207) among low-risk patients, 3.4% (7/205) among moderate-risk patients, 15.9% (14/88) among high-risk patients and 37.5% (6/16) among very high-risk patients. The Mehran score high-risk group (11-15) and the very high-risk group (≥16) were definitely predictors of CIN after CTO PCI (OR: 27.022 [95% CI: 2.787-262.028, p=0.004]; OR: 32.512 [95% CI: 2.149-491.978, p=0.012]). Severe tortuosity was the only predictor of CIN after CTO PCI in angiographic and procedural findings (OR: 6.621 [95% CI: 1.090-40.227, p=0.040]). Being in the Mehran score high-risk group (11-15) or the very high-risk group (≥16) and severe tortuosity were predictors of CIN after CTO PCI.

Long‐term clinical outcomes after percutaneous coronary intervention for chronic total occlusions in elderly patients (≥75 Years)

To investigate procedural success rates and long-term clinical outcome of percutaneous coronary intervention (PCI) for chronic total occlusions (CTO) in elderly patients. Little is known about procedural success and long-term clinical outcome of PCI for CTO in the elderly. A total of 1,791 consecutive patients with 1,852 CTO underwent PCI at three large centers in USA, Italy, and South Korea. Outcomes included procedural success and major adverse cardiac events (MACE, composite of mortality, myocardial infarction, or coronary artery bypass graft surgery [CABG]).Time-to-event analyses were performed using Kaplan-Meier statistics, and the log-rank statistic was used to test for differences between patients aged ≥75 and patients aged <75 years. Two hundred and thirteen patients (12%) were aged ≥75 years. Procedural success rates were similar in elderly patients compared with patients <75 years (63.8% vs. 69.1%, P = 0.12). Median follow-up was 890 days (IQR: 380-1,480 days). MACE rates after successful versus failed PCI were 25.8% versus 42.3% in the elderly (P = 0.02) and 11.2 versus 20.8% in younger patients (P < 0.01). In elderly patients, this reduction in MACE after successful PCI was mainly driven by a reduction in CABG (0.0% vs. 20.4%, P < 0.01), there were no significant differences in terms of mortality (19.6% vs. 24.6%, P = 0.13) or MI (11.5% vs. 8.0%, P = 0.87). CTO PCI in patients ≥75 years has similar success as in patients <75 years. In elderly patients undergoing CTO PCI, MACE rates were relatively high but successful revascularization is associated with a reduction in MACE at 5-year follow-up in both elderly and younger patients.

307 Percutaneous Coronary Intervention To Chronic Total Occlusions Can Be Safely And Effectively Performed In Standalone PCI Centres

Successful percutaneous coronary intervention (PCI) for chronic total occlusions (CTO) has been shown to reduce angina symptoms, reduce the need for coronary bypass surgery and may improve survival. With the development of retrograde and contemporary anterograde approaches the success rates of CTO PCI continues to improve. There remains much debate whether CTO PCI can be performed safely and effectively in high volume stand alone PCI centres. The Royal Alexandra Hospital has been performing PCI without on site surgery over the last 30 years. We identified all patients undergoing CTO PCI between January 2010 and March 2012. Patient demographics, angiographic features, procedure details and clinical outcomes were collected from local medical records the APPROACH database. 170 patients (85.8% male; 63.15 years) underwent PCI to 172 CTO lesions. Clinical presentations of the patients were stable angina (91.78%), non ST elevation MI (7.05%) and left ventricular failure ((LVF) 1.17%). The overall PCI success rate was 74.41%.Success rates of ad hoc, elective first, and subsequent reattempts were 59.1%, 68% and 69.7% respectively. Retrograde approach was attempted in 15% of the cases. Arterial access used was radial only in 63.6%, femoral only in 21.2% and radial-femoral combination in 15.2%. Bilateral injections were used in 37.2% of cases. Mean procedure time was 75.2 minutes. Mean radiation dose was 3.4±0.2 Gy/cm2. Mean contrast volume used was 297±10 ml. Complications of coronary perforation and coronary dissection occurred in 2% and 3% respectively with no occurrence of cardiac tamponade. Periprocedural myocardial infarction occurred in 1%. There were no periprocedural deaths and no patients required emergency cardiac surgery. The mean hospital stay in patients presenting with the stable angina, NSTEMI and LVF were 1.5, 9 and 4 days respectively. At mean follow up of 285 days, target vessel revascularisation (TVR) was only 3.1%. After successful CTO PCI, patient's CCS angina class decreased significantly from 2.2 to 0.5 (p<0.0001). Successful CTO PCI significantly improves angina symptoms with overall low rates of periprocedural complications. Using contemporary anterograde and retrograde techniques, CTO PCI can be safely and effectively performed in experienced stand alone PCI centres.

Changes in myocardial ischemic burden following percutaneous coronary intervention of chronic total occlusions

We assessed the potential for percutaneous coronary intervention (PCI) of a chronic total occlusion (CTO) to decrease myocardial ischemia and established objective criteria to predict post-procedure improvement. Optimal treatment for CTO of coronary arteries is controversial, and selection criteria for PCI of CTO are subjective. All patients undergoing CTO PCI at a single center between 2002 and 2007 were included if myocardial perfusion imaging (MPI) was performed within 12 ± 3 months before and a follow-up study within 12 ± 3 months after PCI. Average summed difference scores were calculated and converted to percent ischemic myocardium to classify patients as having normal/minimal, mild, moderate, or severe ischemia. A significant improvement in ischemia following PCI was classified as an absolute ≥5% decrease in ischemic myocardium. Receiver operating characteristic (ROC) curves were used to identify ischemic thresholds predictive of decreased and increased ischemic burden on follow-up MPI. In 301 patients, average baseline ischemic burden was 13.1% ± 11.9% and decreased to 6.9% ± 6.5% (P < 0.001) during follow-up. Overall, 53.5% of patients met criteria for improvement following PCI. These patients were more likely to be male, without diabetes, with CTO in the left anterior descending artery, and classified as having high ischemic burden at baseline. ROC analysis identified a baseline 12.5% ischemic burden as optimal in identifying those most likely to have a significantly decreased ischemic burden post-PCI. Those with a baseline ischemic burden less than 6.25% were more likely to have an increased ischemic burden post-PCI. Ischemic burden is reduced following CTO PCI, and the decrease is greater at high ischemic burden. A threshold of 12.5% ischemic burden is suggested as a criterion for performing PCI in the setting of CTO.