10-Year All-Cause Mortality Following Percutaneous or Surgical Revascularization in Patients With Heavy Calcification

Impact of serum cholinesterase on calcified nodules in patients with stable coronary artery disease

BACKGROUND

Calcified nodules (CNs) are an advanced stage of coronary calcification that can have significant clinical implications. We investigated factors associated with CNs, the etiology of which is not fully understood.

METHODS

We retrospectively evaluated 619 patients with stable coronary artery disease who underwent intravascular ultrasound (IVUS)-guided percutaneous coronary intervention (PCI). CNs in the culprit lesion were evaluated via IVUS, and all-cause mortality and major cardiovascular and cerebrovascular events (MACCEs) were compared between the CN and non-CN groups.

RESULTS

The CN group (n = 40 patients) had a significantly lower survival rate and a higher incidence of MACCE than the non-CN group (P = 0.020 and P < 0.001, respectively). Multivariate logistic regression analysis models revealed that chronic kidney disease and serum cholinesterase (ChE) level were associated with CN formation [odds ratio (OR): 3.15, 95% confidence interval (CI): 1.30-7.69, P = 0.001 and OR: 0.94, 95% CI: 0.88-0.99, P = 0.042]. The optimal cutoff of serum ChE level as per the receiver operating characteristic curve was 309 units/l (Area under the curve = 0.67, sensitivity = 93%, specificity = 40%, P = 0.001). The low-ChE group divided according to the optimal cutoff value showed significantly higher cumulative incidence of MACCEs after PCI than the high-ChE group as per Kaplan-Meier analysis.

CONCLUSION

The presence of CNs is significantly associated with a poor prognosis and MACCE after PCI among patients with stable coronary artery disease. Serum ChE levels may affect CN formation.

Advances in Technology and Technique in Percutaneous Coronary Intervention: A Clinical Review

Percutaneous coronary intervention (PCI) has become the standard procedure for patients with angina and acute coronary syndrome. From the perspective of technology and technique, PCI has advanced over the last four decades, resulting in considerably improved clinical outcomes in patients with coronary artery disease in the current era. In this review article, we summarize recent advances, promising technologies, and areas for research in the field of PCI.

The Current State of Coronary Revascularization: Coronary Artery Bypass Graft Surgery Versus Percutaneous Coronary Interventions

PURPOSE OF REVIEW

The optimal revascularization strategy for coronary artery disease depends on various factors, such as disease complexity, patient characteristics, and preferences. Including a heart team in complex cases is crucial to ensure optimal outcomes. Decision-making between percutaneous coronary intervention and coronary artery bypass grafting must consider each patient's clinical profile and coronary anatomy. While current practice guidelines offer some insight into the optimal revascularization approach for the various phenotypes of coronary artery disease, the evidence to support either strategy continues to evolve and grow. Given the large amount of contemporary data on revascularization, this review aims to comprehensively summarize the literature on coronary artery bypass grafting and percutaneous coronary intervention in patients across the spectrum of coronary artery disease phenotypes.

RECENT FINDINGS

Contemporary evidence suggests that for patients with triple vessel disease, coronary artery bypass grafting is preferred over percutaneous coronary intervention due to better long-term outcomes, including lower rates of death, myocardial infarction, and target vessel revascularization. Similarly, for patients with left main coronary artery disease, both percutaneous coronary intervention and coronary artery bypass grafting can be considered, as they have shown similar efficacy in terms of major adverse cardiac events, but there may be a slightly higher risk of death with percutaneous coronary intervention. For proximal left anterior descending artery disease, both percutaneous coronary intervention and coronary artery bypass grafting are viable options, but coronary artery bypass grafting has shown lower rates of repeat revascularization and better relief from angina. The Synergy Between PCI with Taxus and Cardiac Surgery score can help in decision-making by predicting the risk of adverse events and guiding the choice between percutaneous coronary intervention and coronary artery bypass grafting. European and American guidelines both agree with including a heart team that can develop and lay out individualized, optimal treatment options with respect for patient preferences. The debate between coronary artery bypass grafting versus percutaneous coronary intervention in multiple different scenarios will continue to develop as technology and techniques improve for both procedures. Risk factors, pre, peri, and post-procedural complications involved in both revascularization strategies will continue to be mitigated to optimize outcomes for those patients for which coronary artery bypass grafting or percutaneous coronary intervention provide ultimate benefit. Methods to avoid unnecessary revascularization continue to develop as well as percutaneous technology that may allow patients to avoid surgical intervention when possible. With such changes, revascularization guidelines for specific patient populations may change in the coming years, which can serve as a limitation of this time-dated review.

Association between apolipoprotein C-III levels and coronary calcification detected by intravascular ultrasound in patients who underwent percutaneous coronary intervention

There are few reports on the association between apolipoprotein C-III (ApoC-III) and coronary calcification using intravascular modalities. This study aimed to investigate the impacts of ApoC-III levels on coronary calcification using grayscale intravascular ultrasound (IVUS). Consecutive 263 culprit lesions for 202 patients who underwent percutaneous coronary intervention using grayscale IVUS were included in this study and divided into four groups based on quartile ApoC-III values. This study assessed plaque characteristics, including severe calcification (>180° arc) at the minimum lumen area site and presence of calcified nodules within the culprit lesion using grayscale IVUS, and evaluated whether ApoC-III levels were associated with coronary calcified plaques. The highest ApoC-III quartile [Quartile 4 (Q4)] had a higher proportion of complex lesions, calcified plaques, severe calcification, calcified nodules, plaque burden, and total atheroma volume than the lowest ApoC-III quartile [Quartile 1 (Q1)]. Additionally, multivariable logistic regression analysis showed that Q4 was significantly associated with severe calcification and calcified nodules, with Q1 as the reference (odds ratio [OR]: 2.70, 95% confidence intervals [CIs]: 1.04-7.00, p = 0.042; and OR: 3.72, 95% CIs 1.26-11.0, p = 0.017, respectively). Furthermore, ApoC-III level (1-mg/dl increase) was a strong significant predictor of severe calcification (OR: 1.07, 95% CIs: 1.00-1.15, p = 0.040) and calcified nodules (OR: 1.09, 95% CIs: 1.01-1.19, p = 0.034) according to the multivariable logistic regression analysis. This study is the first to verify that elevated ApoC-III levels are associated with the development of severe calcification and progression to calcified nodules as detected by grayscale IVUS.

Prospective investigation of calcium score in optical coherence tomography-guided revascularization to identify lesions with low risk for stent under expansion: the CORAL study

The optical coherence tomography (OCT)-based calcium scoring system was developed to guide optimal lesion preparation strategies for percutaneous coronary intervention (PCI) of calcified lesions. However, the score was derived retrospectively, and a prospective investigation is lacking. The CORAL (UMIN000053266) study was a single-arm, prospective, multicenter study that included patients with calcified lesions with OCT-calcium score of 1-2 to investigate whether these lesions could be optimally treated with a balloon-only preparation strategy using a non-compliant/scoring/cutting balloon. The primary endpoint was strategy success (successful stent placement with a final percent diameter stenosis [%DS] < 20% and Thrombolysis In Myocardial Infarction flow grade III without crossover to rotational atherectomy/orbital atherectomy/intravascular lithotripsy [RA/OA/IVL]). A superiority analysis for the primary endpoint was performed by comparing the study cohort with a performance goal of 83.3%. One hundred and eighteen patients with 130 lesions were enrolled. The mean age was 79.0 ± 10.3 years, and 79 patients (66.9%) were male. The OCT-calcium score was 1 for 81 lesions (62.3%) and 2 for 49 lesions (37.7%). The %DS improved from 47.0 ± 14.8% preprocedure to 11.1 ± 5.6% postprocedure. Stent expansion ≥ 70% was achieved in 90.2%. The strategy success rate was 93.1% (95% confidence interval: 87.3-96.8), and superiority against the performance goal was achieved without any crossover to RA/OA/IVL (P = 0.0027). The OCT-calcium score could identify mild/moderately calcified lesions treatable by PCI with the balloon-first strategy using a non-compliant/scoring/cutting balloon for predilatation, with a high strategy success rate. These results support the intravascular imaging-based treatment algorithm for calcified lesions proposed by CVIT.

Procedural and clinical impact of intravascular lithotripsy for the treatment of peri-stent calcification

BACKGROUND

Use of intravascular lithotripsy (IVL) for treating peri-stent calcification is increasing. However, this indication remains 'off-label'. We aimed to investigate the efficacy and clinical outcomes of in-stent IVL.

METHODS

Patients from five European centers who underwent in-stent IVL were included between 2019 and 2023. Demographic, clinical, procedural and follow-up data were collected from electronic hospital records. Angiographic and intracoronary imaging (ICI) data were analyzed in a centralized core-laboratory.

RESULTS

Of 101 patients (71.2 ± 9.2 years), 56(55 %) received in-stent IVL for late stent failure (median 109 days post-PCI) due to calcific neoatherosclerosis or extra-stent calcification(late-IVL), while 45(45 %) underwent bail-out IVL due to stent infraexpasion (immediate-IVL). Both late-IVL and immediate-IVL significantly improved angiographic %diameter stenosis (73.7[59.6-89.8]% to 16.4 [10.4-26.9]%;p < 0.0001 and 28.6[22.5-43.3]% to 14.1[10.3-29.4]%;p < 0.0001, and minimum lumen area (MLA) (3.4 ± 1.2 to 8.6 ± 2.5 mm2;p < 0.002 and 5.4 ± 1.9 to 7.3 ± 1.9;p < 0.0001).Device(98 %) and procedural success(80 %) were high. MACE rates in-hospital (2 %), 30-days (3 %),6-months(5 %) and 1-year(7 %) were low and comparable in both groups. Acute diameter gain was lower in immediate-IVL (2.1 ± 0.7 mm vs. 0.5 ± 0.4 mm;p < 0.0001). This, however, was explained by significant differences in pre-IVL angiographic and ICI parameters (%diameter stenosis 73.7[59.6-89.8] vs. 28.6[22.5-43.3]%; p < 0.0001 and MLA (3.4 ± 1.2 vs 5.4 ± 1.9 mm2; p < 0.0001), whereas post-IVL percentage diameter stenosis (16.4(10.4-26.9) vs. 14.1(10.3-29.4);p = 0.914) and MLA (8.6 ± 2.5vs. 7.4 ± 1.9 mm2;p = 0.064) in late- and immediate-IVL were comparable.

CONCLUSIONS

IVL in-stent due to peri-stent calcification is an effective strategy, both late and immediately after stent implantation. Overall, MACE rates at short- and mid-term were low and comparable in both groups, although clinical findings should be taken with caution.

SCAI Expert Consensus Statement on the Management of Calcified Coronary Lesions

The prevalence of calcification in obstructive coronary artery disease is on the rise. Percutaneous coronary intervention of these calcified lesions is associated with increased short-term and long-term risks. To optimize percutaneous coronary intervention results, there is an expanding array of treatment modalities geared toward calcium modification prior to stent implantation. The Society for Cardiovascular Angiography and Interventions, herein, puts forth an expert consensus document regarding methods to identify types of calcified coronary lesions, a central algorithm to help guide use of the various calcium modification strategies, tips for when using each treatment modality, and a look at future studies and trials for treating this challenging lesion subset.

Impact of left ventricular ejection fraction on 10-year mortality in the SYNTAX trial

BACKGROUNDS

The impact of reduced left ventricular ejection fraction (LVEF) on very long-term prognosis following percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) has been debated. The aim of this study was to investigate the impact of LVEF at baseline on 10-year mortality in the SYNTAX trial.

METHODS

Patients (n = 1800) were categorized into three sub-groups: reduced (rEF ≤ 40 %), mildly reduced (mrEF 41-49 %), and preserved LVEF (pEF ≥ 50 %). The SYNTAX score 2020 (SS-2020) was applied in patients with LVEF<50 % and ≥ 50 %.

RESULTS

Ten-year mortalities were 44.0 %, 31.8 %, and 22.6 % (P < 0.001) in patients with rEF (n = 168), mrEF (n = 179), and pEF (n = 1453). Although no significant differences were observed, the mortality with PCI was higher than with CABG in patients with rEF (52.9 % vs 39.6 %, P = 0.054) and mrEF (36.0 % vs. 28.6 %, P = 0.273), and comparable in pEF (23.9 % vs. 22.2 %, P = 0.275). Calibration and discrimination of the SS-2020 in patients with LVEF<50 % were poor, whilst they were reasonable in those with LVEF≥50 %. The proportion of patients eligible for PCI who had a predicted equipoise in mortality with CABG was estimated to be 57.5 % in patients with LVEF≥50 %. CABG was safer than PCI in 62.2 % of patients with LVEF<50 %.

CONCLUSIONS

Reduced LVEF was associated with an increased risk of 10-year mortality in patients revascularized either surgically or percutaneously. Compared to PCI, CABG was safe revascularization in patients with LVEF≤40 %. In patients with LVEF≥50 % individualized 10-year all-cause mortality predicted by SS-2020 was helpful in decision-making whilst the predictivity in patients with LVEF<50 % was poor.

Coronary calcification in patients presenting with acute coronary syndromes: insights from the MATRIX trial

AIMS

The role of coronary calcification on clinical outcomes among different revascularization strategies in patients presenting with acute coronary syndromes (ACSs) has been rarely investigated. The aim of this investigation is to evaluate the role of coronary calcification, detected by coronary angiography, in the whole spectrum of patients presenting with acute ACS.

METHODS AND RESULTS

The present study was a post hoc analysis of the MATRIX programme. The primary endpoint was major adverse cardiovascular events (MACE), defined as the composite of all-cause mortality, myocardial infarction (MI), or stroke up to 365 days. Among the 8404 patients randomized in the MATRIX trial, data about coronary calcification were available in 7446 (88.6%) and therefore were included in this post hoc analysis. Overall, 875 patients (11.7%) presented with severe coronary calcification, while 6571 patients (88.3%) did not present severe coronary calcification on coronary angiography. Fewer patients with severe coronary calcification underwent percutaneous coronary intervention whereas coronary artery bypass grafting or medical therapy-only was more frequent compared with patients without severe calcification. At 1-year follow-up, MACE occurred in 237 (27.1%) patients with severe calcified coronary lesions and 985 (15%) patients without severe coronary calcified lesions [hazard ratio (HR) 1.91; 95% confidence interval (CI) 1.66-2.20, P < 0.001]. All-cause mortality was 8.6% in patients presenting with and 3.7% in those without severe coronary calcification (HR 2.38, 1.84-3.09, P < 0.001). Patients with severe coronary calcification incurred higher rate of MI (20.1% vs. 11.5%, HR 1.81; 95% CI 1.53-2.1, P < 0.001) and similar rate of stroke (0.8% vs. 0.6%, HR 1.35; 95% CI 0.61-3.02, P = 0.46).

CONCLUSION

Patients with ACS and severe coronary calcification, as compared to those without, are associated with worse clinical outcomes irrespective of the management strategy.

Lifetime management of severely calcified coronary lesions: the treatment algorithm focused on the shape of calcification

The concept of lifetime management has not been discussed in the field of percutaneous coronary intervention (PCI), because the durability of drug-eluting stent (DES) is considered to be long enough for most patients. Furthermore, even if in-stent restenosis occurs, the treatment for in-stent restenosis is simple in most cases. On the other hand, the long-term clinical outcomes after DES implantation are worse in severely calcified coronary lesions than in non-calcified lesions. Moreover, the treatment for in-stent calcified restenosis or restenosis due to stent underexpansion is not simple. The concept of lifetime management of severely calcified lesions may be necessary like that of aortic stenosis. Recently, several algorithms have been published in PCI to severely calcified lesions, partly because of the emergence of IVL. These algorithms focus on the selection of cracking and debulking devices for the preparation of stenting. However, the optimal stent expansion does not guarantee the long-term patency, when the target lesion includes calcified nodules. Stent restenosis due to calcified nodules is difficult to manage. In this review article, we propose the algorithm for severely calcified lesions focused on the shape of calcification. We do not need to hesitate stenting when multiple cracks on circumferential calcification are observed by intravascular imaging devices. However, DCB may be an option as final device in some situations, when lifetime management of severely calcified lesions is considered.

Angiographic Coronary Calcification: A Simple Predictor of Long-Term Clinical Outcomes in Patients with Acute Myocardial Infarction

AIMS

Coronary calcification detected by coronary angiography is a simple risk marker for long-term clinical outcomes in stable coronary artery disease. However, the significance of angiographic coronary calcification in the culprit lesion of acute myocardial infarction (AMI) has not been fully discussed. The purpose of this retrospective study was to assess the usefulness of angiographic coronary calcification as a risk marker for long-term clinical outcomes following percutaneous coronary intervention to the culprit lesions of AMI.

METHODS

We included 1209 patients with AMI and divided them into the none-mild calcification group (n=923) and the moderate-severe calcification group (n=286) according to angiographic coronary calcification in the culprit lesion of AMI. The primary endpoint was the occurrence of major adverse cardiac events (MACE), which was defined as a composite of all-cause death, nonfatal MI, readmission for heart failure, and ischemia-driven target vessel revascularization.

RESULTS

The median follow-up duration was 542 (Q1: 182, Q3: 990) days. A total of 345 MACE were observed during the study period. The occurrence of MACE was significantly greater in the moderate-severe calcification group than in the none-mild calcification group (43.4% vs. 23.9%, p＜0.001). In the multivariate Cox hazard model, moderate-severe calcification was significantly associated with MACE (hazard ratio 1.302, 95% confidence interval 1.011-1.677, p=0.041) after controlling multiple confounding factors.

CONCLUSIONS

Angiographically moderate to severe calcification in AMI culprit lesion was associated with long-term worse clinical outcomes. Angiographic coronary calcification can be a simple risk marker in patients after AMI.

Current Management of Highly Calcified Coronary Lesions: An Overview of the Current Status

The amount of coronary calcium strongly correlates with the degree of atherosclerosis and, therefore, with the rate of future cardiac events. Calcified coronary lesions still represent a challenge for interventional cardiologists, bringing not only a higher risk of immediate complications during percutaneous coronary interventions (PCI), but also a higher risk of late stent failure due to under-expansion and/or malapposition, and therefore, have a relevant prognostic impact. Accurate identification of the calcified plaques together with the analysis of their distribution pattern within the vessel wall by intracoronary imaging is important to improve the successful treatment of these lesions. The aim of this review is to guide readers through the assessment of the calcified plaque distribution using intracoronary imaging in order to select the best devices and strategies for plaque debulking and lesion preparation.

The Role of Intracoronary Imaging for the Management of Calcified Lesions

Interventional cardiologists in everyday practice are often confronted with calcified coronary lesions indicated for percutaneous transluminal coronary angioplasty (PTCA). PTCA of calcified lesions is associated with diverse technical challenges resulting in suboptimal coronary stenting and adverse long-term clinical outcomes. Angiography itself offers limited information regarding coronary calcification, and the adjuvant use of intracoronary imaging such as intravascular ultrasound (IVUS) and Optical Coherence Tomography (OCT) can guide the treatment of calcified coronary lesions, optimizing the different stages of the procedure. This review offers a description of why, when, and how to use intracoronary imaging for PTCA of calcified coronary lesions in order to obtain the most favorable results. We used the PubMed and Google Scholar databases to search for relevant articles. Keywords were calcified coronary lesions, intracoronary imaging, IVUS, OCT, coronary calcium modification techniques, PTCA, and artificial intelligence in intracoronary imaging. A total of 192 articles were identified. Ninety-one were excluded because of repetitive or non-important information.

Mid-Term Angiographic and Intracoronary Imaging Results Following Intracoronary Lithotripsy in Calcified Coronary Artery Disease: Results From Two Tertiary Referral Centres

BACKGROUND

Intracoronary lithotripsy (IVL) is a safe and effective treatment for coronary calcification. Angiographic and intracoronary imaging follow-up have not yet been described. We aimed to describe the mid-term angiographic outcomes following IVL.

METHODS

Patients successfully treated with IVL in two tertiary referral hospitals were included. Repeat angiography and intracoronary imaging was performed. Quantitative coronary angiography (QCA) and optical coherence tomography (OCT) analyses were performed using dedicated workstations.

RESULTS

Twenty patients were included; mean age 67.1 years, left anterior descending artery 55 %. Median IVL balloon size was 3.0 mm and a median of 60 pulses were delivered per vessel. Percentage stenosis by QCA was 60 % [IQR 51-70] reducing to 20 % post stenting (p < 0.001). On OCT, 88.9 % had circumferential calcium. IVL resulted in fractures in 88.9 %. Resulting minimum stent expansion was 91.75 % [IQR 81.5-108]. Follow-up was at a median of 22.7 months [IQR16.4-25.5]. Percentage stenosis by QCA was 22.5 % [IQR 14-30] and not significantly different from the index procedure (p > 0.05). Minimum stent expansion by OCT was 85 % [IQR 72-97]. Late luminal loss was 0.15 mm [IQR -0.25 to 0.69]. Binary angiographic instent restenosis (ISR) was 10 % (2 of 20 patients). OCT demonstrated a predominantly homogenous neointimal pattern with high backscatter.

CONCLUSION

Following successful IVL treatment, repeat angiography demonstrated preserved stent parameters in the majority of patients with favorable vascular healing properties by OCT. A binary restenosis rate of 10 % was observed. These results suggest durable results following IVL treatment of severe coronary calcification however larger studies are warranted.

Advances in Clinical Cardiology 2022: A Summary of Key Clinical Trials

INTRODUCTION

Over the course of 2022, numerous key clinical trials with valuable contributions to clinical cardiology were published or presented at major international conferences. This review seeks to summarise these trials and to reflect on their clinical context.

METHODS

The authors reviewed clinical trials presented at major cardiology conferences during 2022, including the American College of Cardiology (ACC), European Association for Percutaneous Cardiovascular Interventions (EuroPCR), European Society of Cardiology (ESC), Transcatheter Cardiovascular Therapeutics (TCT), American Heart Association (AHA), European Heart Rhythm Association (EHRA), Society for Cardiovascular Angiography and Interventions (SCAI), TVT-The Heart Summit (TVT) and Cardiovascular Research Technologies (CRT). Trials with a broad relevance to the cardiology community and those with potential to change current practice were included.

RESULTS

A total of 93 key cardiology clinical trials were identified for inclusion. Interventional cardiology data included trials evaluating the use of new generation novel stent technology and new intravascular physiology strategies such as quantitative flow ratio (QFR) to guide revascularisation in stable and unstable coronary artery disease. New trials in acute coronary syndromes and intervention focused on long-term outcomes of optimal medical therapy (OMT), revascularisation in ischaemic dysfunction and left main (LM) intervention. Structural intervention trials included latest data on optimal timing and anticoagulation strategies in transcatheter aortic valve replacement (TAVR), in addition to expanding evidence in mitral and tricuspid valve interventions. Heart failure data included trials with sodium-glucose cotransporter 2 (SGLT2) inhibitors, iron replacement and novel drugs such as omecamtiv. Prevention trials included new data on proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors and polypill strategies. In electrophysiology, new data regarding optimal timing of ablative therapy for atrial fibrillation (AF) in addition to novel screening strategies were evaluated.

CONCLUSION

This article presents a summary of key clinical cardiology trials published and presented during the past year and should be of interest to both practising clinicians and researchers.

Clinical expert consensus document on rotational atherectomy from the Japanese association of cardiovascular intervention and therapeutics: update 2023

The Task Force on Rotational Atherectomy of the Japanese Association of Cardiovascular Intervention and Therapeutics (CVIT) proposed the expert consensus document to summarize the techniques and evidences regarding rotational atherectomy (RA) in 2020. Because the revascularization strategy to severely calcified lesions is the hottest topic in contemporary percutaneous coronary intervention (PCI), many evidences related to RA have been published since 2020. Latest advancements have been incorporated in this updated expert consensus document.

Clinical Outcomes and Unique Restenosis of Calcified Nodule in Heavily Calcified Coronary Artery

AIMS

Calcified nodule (CN) has been known as the advanced stage of coronary calcification. However, clinical outcomes following percutaneous coronary intervention (PCI) to CN remain unknown. This study aimed to compare clinical outcomes, including target lesion revascularization (TLR), between calcified coronary lesions with and without CN.

METHODS

Two hundred forty-nine lesions undergoing intravascular ultrasound-guided PCI with rotational atherectomy (RA) were enrolled and divided into the CN group (n=100) and the non-CN group (n=149) according to the presence of CN. The cumulative incidence of clinically driven TLR (CD-TLR) and the reasons for CD-TLR were compared between the CN and non-CN groups.

RESULTS

The incidence of CD-TLR was significantly higher in the CN group than in the non-CN group. In the landmark analysis at 1 year, the CN group showed a significantly higher incidence of CD-TLR within 1 year. However, the incidence of CD-TLR beyond 1 year was numerically lower in the CN group than in the non-CN group. In the multivariate Cox hazard model, CN was significantly associated with CD-TLR. In the CN group, in-stent CN was the major reason for CD-TLR (52%) and was observed mainly within 1 year (90%).

CONCLUSIONS

In the heavily calcified lesions requiring RA, CN was the factor associated with the higher rate of CD-TLR especially within 1 year. The timing of CD-TLR in lesions with CN may indicate that the process of CN protruding through the struts was progressed monthly.

A Novel Algorithm to Estimate the Significance Level of a Feature Interaction Using the Extreme Gradient Boosting Machine

Recent studies have revealed the importance of the interaction effect in cardiac research. An analysis would lead to an erroneous conclusion when the approach failed to tackle a significant interaction. Regression models deal with interaction by adding the product of the two interactive variables. Thus, statistical methods could evaluate the significance and contribution of the interaction term. However, machine learning strategies could not provide the p-value of specific feature interaction. Therefore, we propose a novel machine learning algorithm to assess the p-value of a feature interaction, named the extreme gradient boosting machine for feature interaction (XGB-FI). The first step incorporates the concept of statistical methodology by stratifying the original data into four subgroups according to the two interactive features. The second step builds four XGB machines with cross-validation techniques to avoid overfitting. The third step calculates a newly defined feature interaction ratio (FIR) for all possible combinations of predictors. Finally, we calculate the empirical p-value according to the FIR distribution. Computer simulation studies compared the XGB-FI with the multiple regression model with an interaction term. The results showed that the type I error of XGB-FI is valid under the nominal level of 0.05 when there is no interaction effect. The power of XGB-FI is consistently higher than the multiple regression model in all scenarios we examined. In conclusion, the new machine learning algorithm outperforms the conventional statistical model when searching for an interaction.