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Chronic total occlusion (CTO) percutaneous coronary intervention (PCI) continues to evolve. This review summarizes recent publications categorized by outcomes, techniques, complications, and ongoing studies in this rapidly growing area.

Objectives: There is limited data on race and outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI). The authors sought to evaluate CTO PCI techniques and outcomes in different racial groups., Methods: We examined the baseline characteristics and procedural outcomes of 11 806 CTO PCIs performed at 44 US and non-US centers between 2012 and March 2023. In-hospital major adverse cardiac events (MACE) included death, myocardial infarction, repeat target-vessel revascularization, pericardiocentesis, cardiac surgery, and stroke prior to discharge., Results: The most common racial group was White (84.5%), followed by Black (5.7%), "Other" (3.9%), Hispanic (2.9%), Asian (2.4%), and Native American (0.7%). There were significant differences in the baseline characteristics between different racial groups. When compared with non-White patients, the retrograde approach and antegrade dissection re-entry were more likely to be the successful crossing strategies in White patients without any significant differences in technical success (86.4% vs 86.4%; P = .93), procedural success (84.8% vs 85.0%; P = .79), and in-hospital MACE (2.0% vs 1.5%; P = .15) between the 2 groups. The technical success rate was significantly higher in the "Other" racial group (91.0% vs 86.4% in White, 86.9% in Asian, 84.5% in Black, 84.5% in Hispanic, and 83.3% in Native American; P = .03) without any significant differences in procedural success or in-hospital MACE rates between the groups., Conclusions: Despite differences in baseline characteristics and procedural techniques, the procedural success and in-hospital MACE of CTO PCI were not significantly different between most racial groups.

Several studies suggest differences in burnout and coping mechanisms between female and male physicians. We conducted an international, online survey exploring sex-based differences in the well-being of interventional cardiologists. Of 1251 participants, 121 (9.7%) were women. Compared with men, women were more likely to be single and under 50 years old, and they asked more often for development opportunities and better communication with administration. Overall burnout was similar between women and men, but women interventional cardiology attendings were more likely to think that they were achieving less than they should. Improved communication with administration and access to career development opportunities may help prevent or mitigate burnout in women interventional cardiologists.

(1) Background: Heart failure is an extremely impactful health issue from both a social and quality-of-life point of view and the rate of patients with this condition is destined to rise in the next few years. Transplantation remains the mainstay of treatment for end-stage heart failure, but a shortage of organs represents a significant problem that prolongs time spent on the waiting list. In view of this, the selection of donor and recipient must be extremely meticulous, considering all factors that could predispose to organ failure. One of the main considerations regarding heart transplants is the risk of graft rejection and the need for immunosuppression therapy to mitigate that risk. In this study, we aimed to assess the characteristics of patients who need immunosuppression treatment for rejection within one year of heart transplantation and its impact on mid-term and long-term mortality. (2) Methods: The United Network for Organ Sharing (UNOS) Registry was queried to identify patients who solely underwent a heart transplant in the US between 2000 and 2021. Patients were divided into two groups according to the need for anti-rejection treatment within one year of heart transplantation. Patients' characteristics in the two groups were assessed, and 1 year and 10 year mortality rates were compared. (3) Results: A total of 43,763 patients underwent isolated heart transplantation in the study period, and 9946 (22.7%) needed anti-rejection treatment in the first year. Patients who required treatment for rejection within one year after transplant were more frequently younger (49 ± 14 vs. 52 ± 14 years, p < 0.001), women (31% vs. 23%, p < 0.001), and had a higher CPRA value (14 ± 26 vs. 11 ± 23, p < 0.001). Also, the rate of prior cardiac surgery was more than double in this group (27% vs. 12%, p < 0.001), while prior LVAD (12% vs. 11%, p < 0.001) and IABP (10% vs. 9%, p < 0.01) were more frequent in patients who did not receive anti-rejection treatment in the first year. Finally, pre-transplantation creatinine was significantly higher in patients who did not need treatment for rejection in the first year (1.4 vs. 1.3, p < 0.01). Most patients who did not require anti-rejection treatment underwent heart transplantation during the new allocation era, while less than half of the patients who required treatment underwent transplantation after the new allocation policy implementation (65% vs. 49%, p < 0.001). Patients who needed rejection treatment in the first year had a higher risk of unadjusted 1 year (HR: 2.25; 95% CI: 1.88-2.70; p < 0.001), 5 year (HR: 1.69; 95% CI: 1.60-1.79; p < 0.001), and 10 year (HR: 1.47; 95% CI: 1.41-1.54, p < 0.001) mortality, and this was confirmed at the adjusted analysis at all three time-points. (4) Conclusions: Medical treatment of acute rejection was associated with significantly increased 1 year mortality compared to patients who did not require anti-rejection therapy. The higher risk of mortality was confirmed at a 10 year follow-up. Further studies and newer follow-up data are required to investigate the role of anti-rejection therapy in the heart transplant population.

This study aims to evaluate the impact that the presence of interventional collaterals has on the outcomes of CTO PCI. We examined the clinical and angiographic characteristics and procedural outcomes of 11 205 patients who underwent 11 444 CTO PCIs at 45 US and non-US centers between 2012 and 2023.

Background: There is limited information on the impact of the target vessel on the procedural techniques and outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI)., Methods: We analyzed the baseline clinical and angiographic characteristics and procedural outcomes of 11,580 CTO PCIs performed between 2012 and 2022 at 44 centers., Results: The most common CTO target vessel was the right coronary artery (RCA) (53.1%) followed by the left anterior descending artery (LAD) (26.0%) and the left circumflex artery (LCX) (19.8%). RCA CTOs were longer and more complex, with a higher Japanese CTO score compared with LAD or LCX CTOs. Technical success was higher among LAD (88.8%) lesions when compared with RCA (85.7%) or LCX (85.8%) lesions (P less than .001). The incidence of major adverse cardiovascular events (MACE) was overall 1.9% (n = 220) and was similar among target vessels (P=.916). There was a tendency toward more frequent utilization of the retrograde approach for more proximal occlusions in all 3 target vessels. When compared with all other RCA lesions combined, distal RCA lesions had higher technical success (87.7% vs 85.3%; P=.048). Technical success was similar between various locations of LAD CTOs (P=.704). First/second/third obtuse marginal branch had lower technical success when compared with all other LCX lesion locations (82.7% vs 86.8%; P=.014). There was no association between MACE and CTO location in all 3 target vessels., Conclusions: LAD CTO PCIs had higher technical and procedural success rates among target vessels. The incidence of MACE was similar among target vessels and among various locations within the target vessel.

Background: We examined the effect of atrial fibrillation on the outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI)., Methods: We examined the baseline characteristics and procedural outcomes of 9,166 CTO PCIs performed at 39 US and non-US centers between 2012 and 2023., Results: Atrial fibrillation was present in 1122 (12%) patients. These patients were older and had a higher incidence of comorbidities, such as hypertension, dyslipidemia, heart failure, cerebrovascular disease, and peripheral arterial disease, lower left ventricular ejection fraction, and lower eGFR. Their CTOs were more likely to have moderate to severe calcification and longer lesion length. They also had higher mean J-CTO and PROGRESS-CTO complications (Acute MI, MACE, Mortality, Perforation, and Pericardiocentesis) scores. Patients with atrial fibrillation had higher prevalence of uncrossable and undilatable CTO lesions and required longer procedure (107 vs 119 min; P less than .001) and fluoroscopy (40 vs 43 min; P=.005) time. Technical success and MACE, including procedural/in-hospital bleeding, were similar in patients with and without atrial fibrillation. Although the crude incidence of MACE on follow-up (median 61 days) was significantly higher in patients with atrial fibrillation, the latter was not independently associated with adverse events on Cox proportional hazards analysis., Conclusions: Patients with atrial fibrillation undergoing CTO PCI are older, have more comorbidities, higher lesion complexity, and longer procedure time, but similar technical success and in-hospital MACE. They have higher MACE and mortality during follow-up, but the difference is not significant after adjusting for potential confounding variables.

Background: Coronary artery dissection is a feared and potentially life-threatening complication of percutaneous coronary intervention (PCI)., Methods: We examined the clinical, angiographic, and procedural characteristics, and outcomes of coronary dissection at a tertiary care institution., Results: Between 2014 and 2019, unplanned coronary dissection occurred in 141 of 10,278 PCIs (1.4%). Median patient age was 68 (60, 78) years, 68% were men, and 83% had hypertension. The prevalence of diabetes (29%), and prior PCI (37%) was high. Most target vessels were significantly diseased: 48% had moderate/severe tortuosity and 62% had moderate/severe calcification. The most common cause of dissection was guidewire advancement (30%), followed by stenting (22%), balloon angioplasty (20%), and guide-catheter engagement (18%). TIMI flow was 0 in 33% and 1-2 in 41% of cases. Intravascular imaging was used in 17% of the cases. Stenting was used to treat the dissection in 73% of patients. There was no consequence of dissection in 43% of patients. Technical and procedural success was 65% and 55%, respectively. In-hospital major adverse cardiovascular events occurred in 23% of patients: 13 (9%) had an acute myocardial infarction (MI), 3 (2%) had emergency coronary artery bypass graft surgery, and 10 (7%) died. During a mean follow up of 1612 days, 28 (20%) patients died, and the rate of target lesion revascularization was 11.3% (n=16)., Conclusion: Coronary artery dissection is an infrequent complication of PCI, but is associated with adverse clinical outcomes, such as death and acute MI.

Background: Although discouraged, ad hoc chronic total occlusion (CTO) percutaneous coronary intervention (PCI) is occasionally performed., Methods: We examined the clinical, angiographic characteristics, and procedural outcomes of patients who underwent ad hoc CTO PCI in the Prospective Global Registry for the Study of CTO Intervention (PROGRESS-CTO, NCT02061436)., Results: Of the 10,998 patients included in the registry, 899 (8.2%) underwent ad hoc CTO PCI. The incidence of ad hoc CTO PCI decreased from 18% in 2016 to 3% in 2022. Ad hoc CTO PCI patients had a lower prevalence of comorbidities and less complex angiographic characteristics demonstrated by lower J-CTO score (1.9±1.2 vs 2.4±1.3, P < .001). In these patients, PROGRESS-CTO major adverse cardiovascular events (MACE) (1.9±1.4 vs 2.5±1.7), mortality (1.2±1.0 vs 1.6±1.1), and perforation (1.5±1.2±2.2 vs 1.5) scores were lower (P < .001). Technical success was similar between the groups (86%). MACE were lower in the ad hoc CTO PCI group (.8% vs 2.0%, P=.009). Ad hoc CTO PCI was not associated with MACE after adjusting for potential confounders, odds ratio: .69 (95% confidence interval, .30-1.57). In patients with higher J-CTO scores, planned CTO PCI was associated with higher technical success (P < .001)., Conclusion: Approximately 8% of CTO PCI procedures are performed ad hoc, usually in less complex lesions and patients with lower complication risk. While ad hoc CTO PCI might be appropriate for carefully selected cases, a staged approach is recommended for most CTO PCI.

Background: The retrograde strategy is a common approach used in complex chronic total occlusion (CTO) percutaneous coronary intervention (PCI). The ERCTO Retrograde score is a tool that aims to predict the likelihood of technical success for retrograde CTO PCI procedures by evaluating 5 parameters: calcification, distal opacification, proximal tortuosity, collateral connection classification, and operator volume., Methods: We evaluated the performance of the ERCTO Retrograde score using data from 2341 patients enrolled in the Prospective Global Registry for the Study of Chronic Total Occlusion Intervention (PROGRESS-CTO) at 35 centers between 2013 and 2023., Results: Retrograde CTO PCI was the primary crossing strategy in 871 cases (37.2%) and a secondary crossing strategy in 1467 cases (62.8%). Technical success was achieved in 1,810 cases (77.3%). The technical success rate was higher for primary retrograde cases compared with secondary retrograde cases (79.8% vs 75.9%; P=.031). The ERCTO Retrograde score was positively associated with the likelihood of procedural success. The c-statistic of the ERCTO retrograde score was 0.636 (95% confidence intervals [CI]: .610-.662) for all cases and 0.651 (95% CI: .607-.695) for primary retrograde cases., Conclusions: The ERCTO Retrograde score has modest predictive capacity for technical success in retrograde CTO PCI.

Background: The incidence, indications, and outcomes of coronary angiography (CAG) performed within 30 days following coronary artery bypass graft surgery (CABG) have received limited study., Methods: We reviewed patients who underwent CAG within 30 days following CABG between April 2018 and September 2021 at a large quaternary healthcare system., Results: Of 2209 patients who underwent CABG during the study, 111 (5%) underwent CAG within 30 days following CABG. Mean age was 65 ± 10 years and they had high prevalence of comorbidities. Graft utilization was as follows: left internal mammary artery (LIMA) (84%); saphenous vein graft(s) (SVG) (81%); and right internal mammary artery (RIMA) (22%). The most common presentations/indications for angiography were cardiogenic shock (41%), ST-segment-elevation myocardial infarction (32%), and achieving complete revascularization by percutaneous coronary intervention (PCI) (16%). The LIMA, RIMA, and SVGs were completely/partially occluded in 41 (44%), 10 (42%), and 11 (50%) of patients, respectively. Of the 111 patients who underwent CAG, 55 (50%) underwent PCI, including 47 (85%) to the native vessel and 8 (15%) to the bypass graft, and 19 (17%) underwent repeat sternotomy. Overall, 29 patients (26%) required 30-day readmission following CAG and 19 (17%) died., Conclusion: The incidence of CAG within 30 days following CABG is approximately 5%. Patients who need CAG following CABG have high complication rates (26% readmission and 17% mortality, respectively, at 30 days).

The impact of a previous failure on procedural techniques and outcomes of chronic total occlusion (CTO) percutaneous coronary intervention (PCI) has received limited study. We examined the clinical and angiographic characteristics and procedural outcomes of 9,393 patients who underwent 9,560 CTO PCIs at 42 United States and non-United States centers between 2012 and 2022. A total of 1,904 CTO lesions (20%) had a previous failed PCI attempt. Patients who underwent reattempt CTO PCI were more likely to have a family history of coronary artery disease (37% vs 31%, p <0.001) and dyslipidemia (87.9% vs 84.3%, p <0.001) but were less likely to have heart failure (25.1% vs 29.5%; p <0.001) and cerebrovascular disease (8.7% vs 10.4%, p = 0.04). Patients with previous failure had a higher Japanese CTO (3.33 ± 1.16 vs 2.12 ± 1.19, p <0.001) score and required longer procedure (120 vs 111 minutes, p <0.001) and fluoroscopy (46.9 vs 40.4 minutes, p <0.001) times and higher air kerma radiation dose (2.3 vs 2.1 gray, p = 0.013). Technical success rates (84.3% vs 86.5%, p = 0.011) were lower in patients with a previous failure compared with patients who underwent first-attempt CTO PCI with no significant difference in in-hospital major adverse cardiac events. After adjusting for potential confounders, a previous failure was not associated with technical failure. Operators performing >30 CTO PCIs annually were more likely to achieve technical success in patients with previous failure. In conclusion, a previous failed CTO PCI attempt was associated with higher lesion complexity, longer procedure time, and lower technical success; however, the association with lower technical success did not remain significant in multivariable analysis., Competing Interests: Disclosures Dr. Choi reports Medtronic advisory board. Dr. Poommipanit: consultant for Asahi Intecc, and Abbott Vascular. Dr. Khatri has received personal honoraria for proctoring and speaking from Abbott Vascular, Medtronic, Terumo, Shockwave, and Boston Scientific. Dr. Jaber has received fees from Medtronic and proctoring fees from Abbott. Dr. Rinfret has received fees from Abbott Vascular, Abiomed, Boston Scientific, and SoundBite Medical and has been a consultant for Teleflex. Dr. Nicholson has been a proctor for and on the speaker bureau and advisory boards for Abbott Vascular, Boston Scientific, and Asahi Intecc and he reports intellectual property with Vascular Solutions. Dr. Jaffer has done sponsored research for Canon, Siemens, Shockwave, Teleflex, Mercator, and Boston Scientific and has been a consultant for Boston Scientific, Siemens, Magenta Medical, IMDS, Asahi Intecc, Biotronik, Philips, and Intravascular Imaging Inc; has equity interest in Intravascular Imaging Inc, DurVena; and has the right to receive royalties through Massachusetts General Hospital licensing arrangements with Terumo, Canon, and Spectrawave. Dr. Ybarra reports consultant for SoundBite Medical; speaker honoraria for Abbott Vascular. Dr. Rinfret reports consultant for Boston Scientific, Teleflex, Abbott Vascular, Biotronik, and SoundBite Medical Dr. Alaswad has been a consultant and speaker for Boston Scientific, Abbott Cardiovascular, Teleflex, and CSI. Dr. Karmpaliotis has received honoraria from Boston Scientific, Teleflex, Abiomed, and Abbott Vascular and has equity in Saranas, SoundBite Medical, Nanowear, and Traverse Vascular. Dr. Brilakis reports consulting/speaker honoraria from Abbott Vascular, American Heart Association (associate editor Circulation), Amgen, Asahi Intecc, Biotronik, Boston Scientific, Cardiovascular Innovations Foundation (Board of Directors), CSI, Elsevier, GE Healthcare, IMDS, Medicure, Medtronic, Siemens, Teleflex, and Terumo; research support: Boston Scientific, GE Healthcare; owner, Hippocrates LLC; shareholder: MHI Ventures, Cleerly Health, Stallion Medical. The remaining authors have no conflicts of interest to declare., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Chronic total occlusion (CTO) percutaneous coronary intervention (PCI) is associated with high incidence of complications. We queried PubMed and the Cochrane Library (last search: October 26, 2022) for CTO PCI-specific periprocedural complication risk scores. We identified 8 CTO PCI-specific risk scores: (1) Angiographic coronary artery perforation (OPEN-CLEAN [Outcomes, Patient Health Status, and Efficiency iN (OPEN) Chronic Total Occlusion (CTO) Hybrid Procedures - CABG, Length (occlusion), EF <50%, Age, CalcificatioN] perforation, c-statistic 0.75): previous coronary artery bypass graft surgery, occlusion length 20 to 60 mm or ≥60 mm, left ventricular ejection fraction (LVEF) <50%, age 50 to 70 years or ≥70 years, heavy calcification. (2) Major adverse cardiovascular events (MACE) (PROGRESS-CTO complication, c-statistic 0.76): age >65 years, lesion length ≥23 mm, retrograde strategy, and (3) MACE (PROGRESS-CTO MACE, c-statistic 0.74): age ≥65 years, female gender, moderate/severe calcification, blunt/no stump, anterograde dissection and re-entry (ADR) or retrograde strategy. (4) All-cause mortality (PROGRESS-CTO mortality, c-statistic 0.80): age ≥65, moderate/severe calcification, LVEF ≤45%, ADR or retrograde strategy. (5) Perforation requiring pericardiocentesis (PROGRESS-CTO pericardiocentesis, c-statistic 0.78): age ≥65 years, moderate/severe calcification, female gender, ADR or retrograde strategy. (6) Acute myocardial infarction (PROGRESS-CTO acute myocardial infarction, c-statistic 0.72): previous coronary artery bypass graft surgery, atrial fibrillation, blunt/no stump. (7) Perforation requiring any treatment (PROGRESS-CTO perforation, c-statistic 0.74): age ≥65 years, moderate/severe calcification, blunt/no stump, ADR, or retrograde strategy. (8) Contrast-induced acute kidney injury (c-statistic 0.84): age ≥75, LVEF <40%, serum creatinine >1.5 mg/100 ml, serum albumin ≤30, 3040 g/L. There are 8 CTO PCI periprocedural risk scores that may facilitate risk assessment and procedural planning in patients who underwent CTO PCI., Competing Interests: Disclosures Dr. Azzalini received consulting fees from Teleflex, Abiomed, GE Healthcare (Little Chalfont, United Kingdom), Asahi Intecc, Philips, Abbott Vascular, and Cardiovascular Systems, Inc. Dr. Kearney received consulting fees from Abiomed, Abbott Vascular, Boston Scientific, Medtronic, Teleflex, and Cardiovascular Systems, Inc. Dr. Hirai received consulting fees from Siemens Healthineers, Asahi Intecc, and Zeon Medical. Dr. Burke: shareholder, Egg medical shareholder, MHI Ventures. Dr. Brilakis received consulting/speaker honoraria from Abbott Vascular, American Heart Association (associate editor Circulation), Amgen, Asahi Intecc, Biotronik, Boston Scientific, Cardiovascular Innovations Foundation (Board of Directors), CSI, Elsevier, GE Healthcare, IMDS, Medicure, Medtronic, Siemens, and Teleflex; research support Boston Scientific, GE Healthcare; owner, Hippocrates LLC; shareholder: MHI Ventures, Cleerly Health, Stallion Medical. The remaining authors have no conflicts of interest to declare., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Percutaneous coronary intervention (PCI) of chronic total occlusion (CTO) lesions can be challenging to perform. In the present review we summarize recent publications in this rapidly evolving area grouped according to indications, outcomes, technique, and complications.

Background: There are limited data on the use of bivalirudin for chronic total occlusion (CTO) percutaneous coronary intervention (PCI)., Methods: We compared CTO-PCIs performed using bivalirudin vs unfractionated heparin in the Prospective Global Registry for the Study of Chronic Total Occlusion Intervention (PROGRESS-CTO; NCT02061436). The primary endpoint was net adverse cardiac events (NACE), defined as major adverse cardiac events (MACE) and vascular complications., Results: Between 2012 and 2022, a total of 73 of 9723 procedures (0.75%) were performed using bivalirudin. The J-CTO score (2.4 ± 1.2 vs 2.4 ± 1.3; P=.73) and the PROGRESS-CTO score (1.4 ± 0.9 vs 1.2 ± 1.0; P=.31) were similar in both groups, and the retrograde approach was used less often in the bivalirudin group (15% vs 30%; P<.01). Procedural success (89% vs 85%; P=.35), in-hospital NACE (1.4% vs 2.1%; P>.99), incidence of MACE (0% vs 0.76%; P=.64), and vascular access complications (1.4% vs 0.9%; P=.48) were not different between the 2 groups. On multivariable analysis, use of bivalirudin was not associated with an increased risk of NACE (odds ratio, 0.99; 95% confidence interval, 0.13-7.27)., Conclusion: Bivalirudin is infrequently used during retrograde CTO-PCI. While the incidence of adverse events was similar with unfractionated heparin, larger studies are needed to assess the safety of bivalirudin.

Background: Chronic total occlusion (CTO) percutaneous coronary intervention (PCI) is associated with a considerable risk of complications, and risk stratification is of utmost importance., Aims: To assess the clinical usefulness of the recently developed PROGRESS-CTO (NCT02061436) complication risk scores in an independent cohort., Methods: Individual patient data pooled analysis of 3 registries was performed., Results: Of the 4569 patients who underwent CTO PCI, 102 (2.2%) had major adverse cardiovascular events (MACE). Patients with MACE were older (69 ± 11 vs. 65 ± 10, p < 0.001), more likely to have a history of prior coronary artery bypass graft surgery, and unfavorable angiographic characteristics J-CTO score (2.4 ± 1.2 vs. 2.1 ± 1.3, p = 0.007), including blunt stump (59% vs. 49%, p = 0.047). Technical success was lower in patients with MACE (59% vs. 86%, p < 0.001). The area under the receiver operating characteristic curve of the PROGRESS-CTO complication risk models were as follows: MACE 0.72 (95% confidence interval [CI], 0.67-0.76), mortality 0.73 (95% CI, 0.61-0.85), and pericardiocentesis 0.69 (95% CI, 0.62-0.77) in the validation dataset. The observed complication rates increased with higher PROGRESS-CTO complication scores. The PROGRESS-CTO MACE score showed good calibration in this external cohort, with MACE rates similar to the original study: 0.7% (score 0-1), 1.5% (score 2), 2.2% (score 3), 3.8% (score 4), 4.9% (score 5), 5.8% (score 6-7)., Conclusion: Given the good discriminative performance, calibration, and ease of calculation, the PROGRESS-CTO complication scores could help assess the risk of complications in patients undergoing CTO PCI., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Background: Balloon uncrossable lesions are defined as lesions that cannot be crossed with a balloon after successful guidewire crossing. Methods: We analyzed the association between balloon uncrossable lesions and procedural outcomes of 8671 chronic total occlusions (CTOs) percutaneous coronary interventions (PCIs) performed between 2012 and 2022 at 41 centers. Results: The prevalence of balloon uncrossable lesions was 9.2%. The mean patient age was 64.2 ± 10 years and 80% were men. Patients with balloon uncrossable lesions were older (67.3 ± 9 vs. 63.9 ± 10, p < 0.001) and more likely to have prior coronary artery bypass graft surgery (40% vs. 25%, p < 0.001) and diabetes mellitus (50% vs. 42%, p < 0.001) compared with patients who had balloon crossable lesions. In-stent restenosis (23% vs. 16%. p < 0.001), moderate/severe calcification (68% vs. 40%, p < 0.001), and moderate/severe proximal vessel tortuosity (36% vs. 25%, p < 0.001) were more common in balloon uncrossable lesions. Procedure time (132 (90, 197) vs. 109 (71, 160) min, p < 0.001) was longer and the air kerma radiation dose (2.55 (1.41, 4.23) vs. 1.97 (1.10, 3.40) min, p < 0.001) was higher in balloon uncrossable lesions, while these lesions displayed lower technical (91% vs. 99%, p < 0.001) and procedural (88% vs. 96%, p < 0.001) success rates and higher major adverse cardiac event (MACE) rates (3.14% vs. 1.49%, p < 0.001). Several techniques were required for balloon uncrossable lesions. Conclusion: In a contemporary, multicenter registry, 9.2% of the successfully crossed CTOs were initially balloon uncrossable. Balloon uncrossable lesions exhibited lower technical and procedural success rates and a higher risk of complications compared with balloon crossable lesions.

Cardiac involvement is the leading cause of death in patients with cardiac amyloidosis. Early recognition is crucial as it can significantly change the course of the disease. Until now, the imaging modality of choice for diagnosing cardiac amyloidosis has been cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE). LGE-CMR in patients with cardiac amyloidosis reveals characteristic LGE patterns that lead to a diagnosis while also correlating well with disease prognosis. However, LGE-CMR has numerous drawbacks that the newer CMR modality, T1 mapping, aims to improve. T1 mapping can be further subdivided into native T1 mapping, which does not require the use of contrast, and ECV measurement, which requires the use of contrast. Numerous T1 mapping techniques have been developed, each one with its own advantages and disadvantages when it comes to procedure difficulty and image quality. A literature review to identify relevant published articles was performed by two authors. This review aimed to present the value of T1 mapping in diagnosing cardiac amyloidosis, quantifying the amyloid burden, and evaluating the prognosis of patients with amyloidosis with cardiac involvement., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)