Rationale and Design of Prospective, Multicenter, Double-Arm Clinical Trial to Investigate the Efficacy of Tofogliflozin on Left Ventricular Diastolic Dysfunction in Patients with Heart Failure with Preserved Ejection Fraction and Type 2 Diabetes Mellitus (TOP-HFPEF Trial).

BACKGROUND: Recent large clinical trials have revealed that sodium-glucose cotransporter 2 (SGLT2) inhibitors improve cardiovascular outcomes not only in patients with heart failure with reduced ejection fraction, but also in patients with heart failure with mildly reduced or preserved ejection fraction (HFpEF). However, the effect of SGLT2 inhibitors on left ventricular (LV) diastolic function is still controversial. METHODS AND RESULTS: The TOP-HFPEF trial (Efficacy of Tofogliflozin on Left Ventricular Diastolic Dysfunction in Patients with Heart Failure with Preserved Ejection Fraction and Type 2 Diabetes Mellitus) is a multicenter, double-arm, open-label, confirmatory, investigator-initiated clinical study to investigate the effect of SGLT2 inhibitor on LV diastolic function in patients with HFpEF and type 2 diabetes mellitus. The participants are randomly assigned (1:1) to the tofogliflozin group (20 mg once daily) or the control group (administration or continuation of antidiabetic drugs other than SGLT2 inhibitors). The estimated number of patients to be enrolled in this trial is 90 in total (45 in each group). The participants are followed up for 52 weeks with tofogliflozin or control drugs. The primary endpoint is the change in E/e' assessed by echocardiography from the baseline to the end of this study (52 weeks). This trial will also evaluate the effects of tofogliflozin on cardiovascular events, biomarkers, other echocardiographic parameters, the occurrence of atrial fibrillation, and renal function. CONCLUSIONS: The TOP-HFPEF trial will clarify the efficacy of an SGLT2 inhibitor, tofogliflozin, on LV diastolic function in patients with HFpEF and type 2 diabetes mellitus.

Leadless Pacemaker Implantation in Severe Kyphosis: Challenging Implantation for Tortuous IVC and Narrow RA.

Leadless pacemaker implantation is recognized as safe and effective for treating bradycardia. However, there are limited descriptions of its use in patients with complex anatomical considerations. Here, we present a case detailing the successful implantation of a leadless pacemaker with a tortuous inferior vena cava and a narrow right atrium.

Unique Extraction of a Fractured Pacemaker Lead Adhered to the Spermatic Vein.

Transvenous lead extraction has been increasingly recognized as a safe and effective method of lead extraction, but there are only few references for extracting leads migrating outside the heart. We present a successful extraction of a fractured pacemaker lead from the spermatic vein using several approaches and multiple tools.

Successful Extraction of Guidewire Entrapped in the Tricuspid Valve Leaflet Using a Laser Sheath.

Right ventriculography is a necessary step for implantation of leadless pacemaker and is considered a safe procedure. However, an inappropriate manipulation of the guidewire can lead to serious complications. We present a case where the guide-wire was entrapped in the tricuspid valve, and its successful extraction using a laser sheath. (Level of Difficulty: Advanced.).

Comparison of MECHANISM of early and late vascular responses following treatment of ST-elevation acute myocardial infarction with two different everolimus-eluting stents: a randomized controlled trial of biodegradable versus durable polymer stents.

The early and mid-term arterial healing profile of biodegradable polymer-coated everolimus-eluting stents (BP-EES) is unclear, especially in ST-segment elevation myocardial infarction (STEMI) culprit lesions. This study aimed to compare early- and mid-term arterial healing between durable polymer-coated everolimus-eluting stents (DP-EES) and BP-EES in STEMI patients. In a prospective, multicenter, non-inferiority trial, STEMI patients were randomized to receive BP-EES (n = 60) or DP-EES (n = 60). The primary endpoint of this study was the mean percentage of covered struts (%covered struts) on FD-OCT 2 weeks post-PCI. Key secondary endpoints included the percentage of uncovered struts, frequency of abnormal intra-stent tissue, and percentage of malapposed struts by FD-OCT 2 weeks and 12 months post-PCI. They underwent serial frequency-domain optical coherence tomography (FD-OCT) evaluations immediately after percutaneous coronary intervention, and at 2 weeks and at 12 months after the procedure. The primary endpoint of %covered struts at 2 weeks was 71.4% in BP-EES and 72.3% in DP-EES [risk difference - 0.94%, lower limit of one-sided 95% confidence interval (CI) - 5.6; Pnon-inferiority = 0.0756]. At 12 months, the mean percentage of uncovered struts was significantly lower [1.73% (95% CI 0.28-3.17) vs. 4.81% (95% CI 3.52-6.09); p = 0.002], and the average malapposed volume was significantly smaller in the BP-EES group than in the DP-EES group (p = 0.002). At 12 months, BP-EES had a significantly larger average neointimal area with a significantly smaller average intra-stent tissue unevenness score than DP-EES, suggesting more uniform neointimal coverage with BP-EES. Strut coverage was comparable between BP-EES and DP-EES at 2 weeks. Non-inferiority could not be proven because of an insufficient sample size. The significantly better arterial healing with BP-EES at 12 months suggests a safer profile for STEMI culprit lesions.Trial registration: jRCTs022180024 https://jrct.niph.go.jp/en-latest-detail/jRCTs022180024.

[Clipping of a Large Unruptured Basilar Artery Trunk Large Aneurysm Using Rapid Ventricular Pacing:A Case Report].

Neck clipping of basilar trunk aneurysms, particularly those of a large size, is challenging because of its location. Here, we report a case of a basilar artery aneurysm successfully treated with neck clipping using rapid ventricular pacing(RVP). A 67-year-old woman was referred to our hospital for treatment of a large basilar artery aneurysm. Although coiling was considered, we performed neck clipping of this aneurysm because of the expected radical therapeutic effect. The patient was positioned in the right park-bench position, and right suboccipital craniotomy was performed. The aneurysm was mainly approached via the right supracerebellar route. RVP softened the aneurysm for easy dissection and insertion of multiple clips. The postoperative course was uneventful, and she was discharged 1 week later without neurological deficits. RVP should be considered for the treatment of complex aneurysms as adjunctive techniques.

OPtical frequency domain imaging vs. INtravascular ultrasound in percutaneous coronary InterventiON in patients with Acute Coronary Syndrome: Study protocol for a randomized controlled trial.

BACKGROUND: A recent clinical trial demonstrated that optical frequency domain imaging (OFDI) guidance in percutaneous coronary intervention (PCI) is noninferior to intravascular ultrasound (IVUS) guidance in patients with coronary artery disease with regard to target vessel failure (composed of cardiac death, myocardial infarction attributed to the target vessel, and clinically-driven target vessel revascularization) at 12 months. The impact of OFDI guidance in PCI for patients with acute coronary syndrome (ACS) remains uncertain. METHODS: OPINION ACS is a multicenter, prospective, randomized, controlled, open-label, parallel group, non-inferiority trial in Japan. Eligible patients will be randomly assigned to receive either OFDI- or IVUS-guided PCI. PCI is performed using the sirolimus-eluting stent in accordance with certain OFDI and IVUS criteria for optimal stent deployment. All patients will undergo follow-up angiography and OFDI imaging at 8 months. The primary endpoint is the minimum lumen area, as measured by OFDI at 8 months. CONCLUSION: The OPINION ACS trial outcomes will provide insights regarding the impact of OFDI-guided PCI on in-stent restenosis at 8 months in patients with ACS.

An Unexpected Complication of Subcutaneous ICD Implantation and its Successful Management.

Subcutaneous implantable cardioverter-defibrillator implantation is known to be a safe procedure. However, inappropriate lead insertion can lead to serious complications. We present a case where an inappropriate lead placement resulted in puncturing the lung parenchyma, and successful management of the lead-related pneumothorax through thoracoscopic lead removal and partial lung resection. (Level of Difficulty: Intermediate.).

Predictors and prognostic impact of secondary mitral regurgitation in myocardial infarction with preserved ejection fraction.

BACKGROUND: Secondary or functional mitral regurgitation (FMR) has been reported associated with poor prognosis in patients with ischemic or non-ischemic cardiomyopathy. Prognostic impact of the FMR in myocardial infarction with preserved ejection fraction (MIpEF) is unknown. The aim of this study was to investigate predictors and prognostic impact of FMR in MIpEF. METHODS: A total of 556 patients with MIpEF were selected from the Bell Land General Hospital MI (BELAMI) registry (n = 953). Patients were grouped according to the presence or absence of severe FMR. Clinical endpoint was all-cause death. RESULTS: Severe FMR was present in 26 patients (4.7%) (FMR group) and absent in 530 patients (control). FMR group was older (77.5 ± 7.2 vs. 67.3 ± 11.3 years, P < 0.01) and had more female gender (54% vs. 28%, P < 0.01). By echocardiography, FMR group had larger left atrial diameter and left ventricular end-systolic volume. E and E/e' were significantly higher and deceleration time of E was significantly shorter in FMR group. By Kaplan-Meier analysis, survival was significantly lower in FMR group than in control (log-rank, P = 0.004). CONCLUSION: Severe FMR is rare in MI patients with preserved EF but is associated with poor long-term prognosis.

Early and Mid-Term Vascular Responses to Optical Coherence Tomography-Guided Everolimus-Eluting Stent Implantation in Stable Coronary Artery Disease.

BACKGROUND: Analysis of pooled clinical data has shown the safety of 3 months of dual antiplatelet therapy with everolimus-eluting cobalt-chromium stents (Co-Cr EESs). This study evaluated early and mid-term vascular responses to Co-Cr EESs in patients with stable coronary artery disease. METHODS: The Multicenter Comparison of Early and Late Vascular Responses to Everolimus-Eluting Cobalt-Chromium Stent and Platelet Aggregation Studies in Patients With Stable Angina Managed as Elective Case (MECHANISM-Elective) study (NCT02014818) is a multicenter optical coherence tomography (OCT) registry. Enrolled patients were evaluated by OCT immediately after everolimus-eluting stent implantation were prospectively allocated to 1 month (n = 50) or 3 months (n = 50) OCT follow-up and then received a 12-month OCT evaluation. The incidences of intrastent thrombus (IS-Th) and irregular protrusion (IRP) were also assessed. RESULTS: The percentage of uncovered struts was 6.4% ± 10.3% at 1 month (P < 0.001 vs. postprocedure) and 0.5% ± 0.9% at 12 months (P < 0.001 vs. 1 month). The corresponding values in the 3-month cohort were 2.0% ± 2.5% (P < 0.001 vs. postprocedure) and 0.5% ± 1.5% (P < 0.001 vs. 3 months). The incidence of IS-Th was 32.7% at 1 month, 5.4% at 3 months, and 2.0% at 12 months. IRP was observed in 21.8% of patients post-EES but had totally resolved at 1, 3, and 12 months. CONCLUSION: Early and mid-term vascular reactions after Co-Cr EES implantation in stable patients with coronary artery disease in the MECHANISM-Elective included dynamic resolution of IS-Th and IRP and rapid decrease in uncovered struts. Thus, EES may allow shortening of dual antiplatelet therapy duration less than 3 months in this patient subset.

Early vascular responses to everolimus-eluting cobalt-chromium stent in the culprit lesions of st-elevation myocardial infarction: results from a multicenter prospective optical coherence tomography study (MECHANISM-AMI 2-week follow-up study).

The use of cobalt-chromium everolimus-eluting stents (CoCr-EES) for ST-segment elevation myocardial infarction (STEMI) reduces the incidence of stent thrombosis compared with bare metal stents, and a substantial difference is apparent in the initial 2 weeks. However, vascular behavior during this early period remains unclear. This was a prospective study (MECHANISM-AMI-2W) to investigate early vascular responses in STEMI patients immediately after CoCr-EES implantation and at 2-week follow-up using frequency domain-optical coherence tomography (FD-OCT). The study enrolled 52 patients (age 63.7 ± 11.7 years, male 85.0%), of whom 44 patients were available for complete serial FD-OCT analyses. Both % uncovered struts and % malapposed struts were improved at 2-week follow-up (63 ± 20 vs. 21 ± 14%, p < 0.0001 and 7.3 ± 9.0 vs. 4.7 ± 5.9%, p = 0.005, respectively). Thrombus was decreased, with significant changes in longitudinal length to stent (28.8 ± 27.7 vs. 18.1 ± 20.2%, p = 0.0001) and maximal area (0.93 ± 0.84 vs. 0.65 ± 0.63 mm2, p = 0.034). As a result, the average lumen area was significantly larger at 2 weeks (6.49 ± 1.82 vs. 6.71 ± 1.89 mm2, p = 0.048, respectively). The number of dissection flaps was lower (0.86 ± 1.11 vs. 0.52 ± 0.90%, p = 0.024). In conclusion, this study showed early vascular responses to CoCr-EES for STEMI lesions-including a significant reduction of thrombus-that resulted in lumen enlargement, earlier progression of strut coverage, and improvements in strut apposition and dissection. The combination of these factors may therefore be responsible for the safety of CoCr-EES within the initial 2 weeks.

Multiple coronary artery spasms triggering life-threatening ventricular arrhythmia associated with the radiofrequency ablation of ganglionated plexuses of the left atrium.

We report a case of multiple coronary spasms leading to life-threatening ventricular arrhythmia, during left atrium (LA) ablation. Coronary artery spasm is a rare complication during radiofrequency catheter ablation of atrial fibrillation (AF). Previous reports mention that autonomic imbalance leads to coronary artery spasm and ST-segment elevation in the inferior leads, during trans-septal LA catheterization and AF ablation procedures. However, there are few reports detailing the association between ablation sites and changes in the electrocardiogram. We encountered transient ST-segment elevation and refractory ventricular arrhythmia, associated with coronary artery spasm, during radiofrequency ablation of ganglionated plexuses (superior surface of left and right atrium). .

Vascular response to biolimus A-9 eluting stent in patients with shorter and prolonged dual antiplatelet therapy: optical coherence tomography sub-study of the NIPPON trial.

Dual antiplatelet therapy (DAPT) with thienopyridine and aspirin is the standard care for the prevention of stent thrombosis. However, the optimal duration and effect of the duration of DAPT on intra-stent thrombus (IS-Th) formation are unknown. The NIPPON study (Nobori Dual Antiplatelet Therapy as Appropriate Duration) was an open label, randomized multicenter, assessor-blinded, trial designed to demonstrate the non-inferiority of shorter (6-month) DAPT to prolonged (18-month) DAPT, after biolimus A9 eluting stent implantation in 3773 patients at 130 sites in Japan. Among them, 101 patients were randomly allocated for an optical coherence tomography (OCT) sub-study to assess the difference of local IS-Th formation between the two groups. In addition to standard OCT parameters, the number of IS-Th formed was counted in each target stent at 8 months. Baseline patient characteristics were not different between the 6- and 18-month groups. IS-Th was detected in 9.8% of the cases and the presence of IS-Th was not significantly different between the two groups (10.9% in 6-month vs. 9.1% in 12-month, P = 0.76). Furthermore, the number of IS-Th formed was not significantly different between the two groups. This OCT sub-study was in line with the main NIPPON study which demonstrated the non-inferiority of 6-month DAPT to 18-month DAPT. Shorter DAPT duration did not promote progressive IS-Th formation at the mid-term time point.

Optical frequency domain imaging vs. intravascular ultrasound in percutaneous coronary intervention (OPINION trial): one-year angiographic and clinical results.

AIMS: Optical frequency domain imaging (OFDI) is a recently developed, light-based, high-resolution intravascular imaging technique. Intravascular ultrasound (IVUS) is a widely used, conventional imaging technique for guiding percutaneous coronary intervention (PCI). We aimed to demonstrate the non-inferiority of OFDI-guided PCI compared with IVUS-guided PCI in terms of clinical outcomes. METHODS AND RESULTS: We did a prospective, multicentre, randomized (ratio 1:1), active-controlled, non-inferiority study to compare head-to-head OFDI vs. IVUS in patients undergoing PCI with a second generation drug-eluting stent. The primary endpoint was target vessel failure defined as a composite of cardiac death, target-vessel related myocardial infarction, and ischaemia-driven target vessel revascularization until 12 months after the PCI. The major secondary endpoint was angiographic binary restenosis at 8 months. We randomly allocated 829 patients to receive OFDI-guided PCI (n = 414) or IVUS-guided PCI (n = 415). Target vessel failure occurred in 21 (5.2%) of 401 patients undergoing OFDI-guided PCI, and 19 (4.9%) of 390 patients undergoing IVUS-guided PCI, demonstrating non-inferiority of OFDI-guided PCI to IVUS-guided PCI (hazard ratio 1.07, upper limit of one-sided 95% confidence interval 1.80; Pnon-inferiority = 0.042). With 89.8% angiographic follow-up, the rate of binary restenosis was comparable between OFDI-guided PCI and IVUS-guided PCI (in-stent: 1.6% vs. 1.6%, P = 1.00; and in-segment: 6.2% vs. 6.0%, P = 1.00). CONCLUSION: The 12-month clinical outcome in patients undergoing OFDI-guided PCI was non-inferior to that of patients undergoing IVUS-guided PCI. Both OFDI-guided and IVUS-guided PCI yielded excellent angiographic and clinical results, with very low rates of 8-month angiographic binary restenosis and 12-month target vessel failure. CLINICAL REGISTRATION: ClinicalTrials.gov, number NCT01873027.

Life-threatening pulmonary embolism associated with multiple venous aneurysms.

Popliteal venous aneurysms (PVAs) are often reported as a cause of pulmonary embolism. Previous reports documented the association between a single PVA and pulmonary embolism. We experienced a rare case with multiple venous saccular and fusiform aneurysms resulting in a nearly fatal pulmonary embolism. Surgical ligation is usually considered the first-line treatment for PVAs. In our patient, however, we selected inferior vena cava filter implantation and anticoagulant therapy to avoid the phlegmasia cerulea dolens caused by ligation of multiple aneurysms in both legs. We report a patient with multiple venous aneurysms, including PVAs, causing a nearly fatal pulmonary embolism.

Indications and outcomes of excimer laser coronary atherectomy: Efficacy and safety for thrombotic lesions-The ULTRAMAN registry.

BACKGROUND: Excimer laser coronary atherectomy (ELCA) recently became available in Japan, but ELCA's effectiveness and safety are not clear. METHODS AND RESULTS: We enrolled consecutive patients who underwent ELCA and were registered in the Utility of Laser for Transcatheter Atherectomy-Multicenter Analysis around Naniwa (ULTRAMAN) registry comprising six Japanese medical centers around Naniwa in Japan with patients registered from April 2006 to June 2015. We evaluated the catheter sizes used and compared the success rate, thrombolysis in myocardial infarction (TIMI) flow, blush score, and complications between the rich-thrombus (RT) group [acute coronary syndrome (ACS) and saphenous vein graft (SVG)] and the poor-thrombus (PT) group [in-stent restenosis (ISR), chronic total occlusion (CTO), calcification, and long or bifurcation (L&B) lesions]. Of the 328 patients, 6 (1.8%) were treated for an SVG, 175 (53.4%) were treated for ACS, 18 (5.5%) for CTO, 106 (32.4%) for ISR, 8 (2.4%) for calcification, and 15 for L&B lesions (4.6%). A 1.7-mm (concentric)-diameter ELCA catheter was used most frequently (59.4%). High success rates were achieved in both the RT and PT groups, but the TIMI flow grade and blush score were significantly lower and the complications rate was significantly higher in the RT group (n=181). CONCLUSIONS: In Japan, the major indications for ELCA have been ACS and ISR. ELCA can provide a safe and effective treatment even for RT lesions.

Comparison of Left Ventricular Relaxation and Left Atrial Function in Patients With Heart Failure and Preserved Ejection Fraction Versus Patients With Systemic Hypertension and Healthy Subjects.

Heart failure with preserved ejection fraction (HFpEF) may be characterized as impaired left ventricular (LV) relaxation and/or left atrial (LA) function, both of which are age and gender dependent. The aim of this study was to investigate LV relaxation and the LA function in HFpEF. A total of 71 HFpEF (mean age 73 years, 38 men) were studied. Late transmitral flow velocity (A), late mitral annular velocity (a'), and early mitral annular velocity (e') were measured and compared with age- and gender-matched normal control subjects (CTL; n = 71) and hypertensive patients (HT; n = 71). To clarify prognostic impact of the LA function, cardiac event-free survival was compared between high a' (≥7.9 cm/s, n = 36) and low a' (<7.9 cm/s, n = 35) groups. Cardiac event was defined as a composite of all-cause death and hospitalization due to recurrent congestive heart failure. In both HFpEF and HT groups, e' was significantly and similarly decreased compared with CTL group (p = 0.005). Although A was similar among the 3 groups, a' was significantly lower in HFpEF group than in HT and CTL groups (7.9 ± 2.1 vs 9.0 ± 1.9 vs 9.3 ± 1.96 cm/s, p <0.0001). HFpEF with low a' showed significantly lower cardiac event-free survival than HFpEF with high a' (log rank, p = 0.02). By multivariate Cox proportional analysis, low a' was the only independent predictor of cardiac events (hazard ratio 2.896, 95% confidence interval 1.004 to 8.355, p = 0.049). Both LV relaxation and LA function are impaired in HFpEF. Impaired LA function may be associated with worse prognosis in HFpEF.

Renin-angiotensin system inhibitors in patients with myocardial infarction and secondary mitral regurgitation.

OBJECTIVES: Secondary mitral regurgitation (MR) is negatively related to the prognosis of patients with myocardial infarction (MI). Renin-angiotensin system inhibitors (RASI) may favourably affect left ventricular remodelling and reduce afterload and thereby improve prognosis of secondary MR. The aim of this study was to investigate if use of RASI improves prognosis of patients with MI with secondary MR. METHODS: A total of 953 patients with MI were enrolled in this study. Long-term prognosis was compared between patients with MI with no/mild MR (n=657), moderate MR (n=196) and severe MR (n=100). Patients with MI with significant (≥moderate) secondary MR were further divided into those treated with and without RASI. Survival and cardiac-event (all-cause death and congestive heart failure)-free survival were compared. RESULTS: Long-term survival was significantly associated with severity of MR (log-rank, p<0.0001). In patients with significant MR (n=296), RASI was used in 130 patients (44%) and not used in 166 patients (56%). Ejection fraction (47.3±12.2 vs 46.6±13.4%, p=NS) and E/e' (18.4±8.1 vs 16.5±7.0, p=NS) were similar between the two groups. Kaplan-Meier curves for cardiac-event-free survival demonstrated that use of RASI was associated with better survival (p=0.006) as well as event-free survival (p=0.02). By univariable and multivariable Cox proportional hazard analysis, age (HR 1.046, 95% CI 1.002 to 1.091, p=0.039) and RASI (HR 0.480, 95% CI 0.231 to 0.995), p=0.048) were independent predictors of cardiac events. CONCLUSIONS: Secondary MR affects prognosis in patients with MI. Use of RASI may be associated with better long-term prognosis in patients with MI with significant MR.

Long-term prognostic impact of the attenuated plaque in patients with acute coronary syndrome.

Several intravascular ultrasound studies have reported that culprit lesion-attenuated plaque (AP) is related to slow flow/no reflow after percutaneous coronary intervention (PCI). Long-term prognostic impact of the AP is unknown. The aim of this study was to investigate acute and long-term clinical impact of the AP in patients with acute coronary syndrome (ACS). A total of 110 ACS patients who underwent successful PCI were enrolled. Acute and long-term clinical outcomes were compared between patients with AP (AP group: n = 73) and those without AP (non-AP group: n = 37). Long-term cardiac event was defined as a composite of death and ACS. Baseline characteristics in 2 groups were similar. AP was associated with higher TIMI frame count immediately after the first balloon inflation. After thrombectomy and intracoronary drug administration, final TIMI frame count became similar between AP and non-AP group. Although AP was associated with higher incidence of fatal arrhythmia during hospitalization, in-hospital mortality did not differ between the 2 groups. During follow-up (median 6.2 years), cardiac event-free survival did not differ between the 2 groups. Despite the initial unfavorable effect on coronary reflow, presence of AP did not affect acute as well as long-term clinical outcome in patients with ACS.

Insulin resistance is associated with coronary plaque vulnerability: insight from optical coherence tomography analysis.

AIMS: Previous studies have reported that insulin resistance plays an important role in the progression of atherosclerosis. However, the relationship between insulin resistance and coronary plaque instability is not well established. The purpose of this study was to assess the relationship between insulin resistance and coronary plaque characteristics identified by optical coherence tomography (OCT). METHODS AND RESULTS: This study enrolled 155 consecutive patients undergoing percutaneous coronary intervention. OCT image acquisitions were performed in the culprit lesions. Insulin resistance was identified using the homeostasis model assessment of insulin resistance (HOMA-IR). Subjects were divided into three tertiles according to the HOMA-IR values. Patients in the higher HOMA tertile had more frequent prevalence of lipid-rich plaques than those in the middle and lower tertiles (83 vs. 62 vs. 57%; P = 0.01). The thin-cap fibroatheroma (TCFA) prevalence rates among the higher (>2.5), middle (1.4-2.5), and lower HOMA-IR (<1.4) tertiles were 50, 29, and 26% (P = 0.02). The microvessel prevalence rates of the three tertiles were 54, 39, and 28% (P = 0.02). Furthermore, in the higher HOMA-IR group, the fibrous cap was significantly thinner compared with the other two tertiles (vs. lower HOMA-IR, P = 0.009; vs. middle HOMA-IR, P = 0.008). On multivariate analysis, acute coronary syndrome [odds ratio (OR): 17.98; 95% confidence interval (CI): 7.12-52.02; P < 0.0001] and HOMA-IR >2.50 (OR: 3.57; 95% CI: 1.42-9.55; P = 0.007) were independent predictors for the presence of TCFA. CONCLUSION: This study suggests that insulin resistance might be associated with coronary plaque vulnerability.