Intravascular ultrasound assessment of the association between spatial orientation of ruptured coronary plaques and remodeling morphology of culprit plaques in ST-elevation acute myocardial infarction

Prediction of optimal debulking segments before rotational atherectomy based on pre-procedural intravascular ultrasound findings

This study evaluated whether intravascular ultrasound (IVUS) examination before rotational atherectomy (RA) can predict the optimal route of passage of the RA burr along the vessel. 30 patients with calcified lesions who underwent IVUS before and immediately after RA were enrolled. IVUS analyses were performed at the minimum lumen area (MLA) site and at 0.5 mm intervals. Each IVUS cross-section was divided into 4 quadrants around the center of the lumen, and pre- and post-RA IVUS cross-section images were merged. Of 1140 cross-sections, 498 (44%) contained debulked regions. When the guidewire and IVUS were located within the same quadrant, the debulked region were distributed within the same quadrant in 96% of cross-sections. The debulked region and the guidewire were distributed within the same quadrant in 81% and the debulked region and the IVUS in 72% of cross-sections, in case the guidewire and IVUS were located in different quadrants. When the guidewire and the IVUS was apart > 1.0 mm, the debulked regions were distributed within the same quadrant as the guidewire in 100% and the IVUS in 0% of cross-sections. The position of the guidewire rather than that of the IVUS catheter on pre-RA IVUS images could predict the course of the RA burr's passage, especially when the guidewire and IVUS catheter were located apart from each other.

Impact of Longitudinal Lesion Geometry on Location of Plaque Rupture and Clinical Presentations

OBJECTIVES

This study sought to investigate the impact of longitudinal lesion geometry on the location of plaque rupture and clinical presentation and its mechanism.

BACKGROUND

The relationships among lesion geometry, external hemodynamic forces acting on the plaque, location of plaque rupture, and clinical presentation have not been comprehensively investigated.

METHODS

This study enrolled 125 patients with plaque rupture documented by intravascular ultrasound. Longitudinal locations of plaque rupture were identified and categorized by intravascular ultrasound. Patients' clinical presentations and TIMI (Thrombolysis In Myocardial Infarction) flow grade in an initial angiogram were compared according to the location of plaque rupture. Longitudinal lesion asymmetry was quantitatively assessed by the luminal radius change over the segment length (radius gradient [RG]). Lesions with a steeper radius change in the upstream segment compared with the downstream segment (RG_upstream > RG_downstream) were defined as upstream-dominant lesions.

RESULTS

On the basis of the site of maximum rupture aperture, 56.0%, 16.0%, and 28.0% of the patients had upstream, minimal lumen area, and downstream rupture, respectively. Patients with upstream rupture more frequently presented with ST-segment elevation myocardial infarction (45.7%, 40.0%, 22.9%; p = 0.030) and with TIMI flow grade <3 (32.9%, 20.0%, 17.1%; p = 0.042). According to the ratio of upstream and downstream RG, 69.5% of lesions were classified as upstream-dominant lesions, and 30.5% were classified as downstream-dominant lesions. Among the 66 upstream-dominant lesions, 65 cases (98.5%) had upstream rupture, and the RG ratio (RG_upstream/RG_downstream) was an independent predictor of upstream rupture (odds ratio: 1.481; 95% confidence interval: 1.035 to 2.120; p = 0.032). Upstream-dominant lesions more frequently manifested with ST-segment elevation myocardial infarction than did downstream-dominant lesions (48.5% vs. 24.1%; p = 0.026).

CONCLUSIONS

Both clinical presentation and degree of flow limitation were associated with the location of plaque rupture. Longitudinal lesion asymmetry assessed by RG, which can affect regional distribution of hemodynamic stress, was associated with the location of rupture and with clinical presentation.

The Spatial Distribution of Plaque Vulnerabilities in Patients with Acute Myocardial Infarction

Objective

Although the plaque characteristics have been recognized in patients with acute myocardial infarction (AMI), the plaque spatial distribution is not well clarified. Using color-mapping intravascular ultrasound (iMAP-IVUS), we examined culprit lesions to clarify plaque morphology, composition and spatial distribution of the sites of potential vulnerability.

Methods

Sixty-eight culprit lesions in 64 consecutive AMI patients who underwent angiography and IVUS examinations before intervention were analyzed. Plaque morphology and composition were quantified with iMAP-IVUS. The spatial distribution of the sites of potential vulnerability was assessed with longitudinal reconstruction of the consecutive IVUS images. The plaque characteristics were also compared between ruptured and non-ruptured lesions, and between totally occlusive (TO) and non-TO lesions.

Results

The sites with maximum necrotic area (maxNA), maximum plaque burden (maxPB) and most severely narrowed (minimal luminal area, MLA) were recognized vulnerability. In the majority of cases, maxNA sites were proximal to the maxPB sites, and MLA sites were distal to the maxNA and maxPB sites. Ruptures usually occurred close to maxNA sites and proximal to maxPB and MLA sites. The average distance from the site of rupture to the maxNA site was 0.33 ± 4.04 mm. Ruptured lesions showed significant vessel remodeling, greater plaque volume, and greater lipidic volume compared to those of non-ruptured lesions. Both the length and plaque burden (PB) of TO lesions were greater than those of non-TO lesions.

Conclusions

Instead of overlapping on maxPB sites, most maxNA sites are proximal to the maxPB sites and are the sites most likely to rupture. Plaque morphology and composition play critical roles in plaque rupture and coronary occlusion.

Apelin: a potential marker of coronary artery stenosis and atherosclerotic plaque stability in ACS patients

Apelin was shown to play an important role in atherosclerosis in mice. However, the involvement of apelin in atherosclerosis in humans has not been investigated.

AIMS

To characterize plasma apelin levels following acute coronary syndrome (ACS) and to examine their relationship with coronary stenosis and atherosclerotic plaque stability.The study enrolled 196 patients admitted with ACS, and another 171 outpatients with no coronary heart disease as control. Plasma concentrations of apelin, N-terminal pro-brain natriuretic peptide (NT-proBNP), and matrix metalloproteinase-9 (MMP-9) were measured 2 hours and 6 months after admission, respectively. The severity of coronary artery stenosis of ACS patients was evaluated using the Gensini score. The stability and components of atherosclerotic plaque was assessed by intravascular ultrasound (IVUS). All statistical analyses were performed using SPSS version 16.0.Apelin concentration was reduced compared with healthy controls following ACS (0.54 ± 0.25 versus 3.22 ± 1.08 ng/mL, P < 0.001) and remained low to 6 months. The plasma level of apelin in the ACS group was negatively correlated with the Gensini score (r = -0.382, P = 0.009). Moreover, in the ACS patients, apelin levels were significantly lower in the group with the ruptured plaque than in those with the nonruptured plaque (0.42 ± 0.24 versus 0.68 ± 0.30 ng/mL, P = 0.042). Apelin levels were negatively correlated with plaque cross-sectional area (CSA) (r = -0.425, P = 0.018) and positively correlated with external elastic membrane (EEM) CSA (r = 0.311, P = 0.037).

CONCLUSIONS

Plasma apelin levels were inversely correlated with the severity of coronary artery stenosis and positively related with the stability of atherosclerotic plaque in humans with ACS.

Effect of myocardial contractility on hemodynamic end points under concomitant microvascular disease in a porcine model

In this study, coronary diagnostic parameters, pressure drop coefficient (CDP: ratio of trans-stenotic pressure drop to distal dynamic pressure), and lesion flow coefficient (LFC: ratio of % area stenosis (%AS) to the CDP at throat region), were evaluated to distinguish levels of %AS under varying contractility conditions, in the presence of microvascular disease (MVD). In 10 pigs, %AS and MVD were created using angioplasty balloons and 90-μm microspheres, respectively. Simultaneous measurements of pressure drop, left ventricular pressure (p), and velocity were obtained. Contractility was calculated as (dp/dt)max, categorized into low contractility <900 mmHg/s and high contractility >900 mmHg/s, and in each group, compared between %AS <50 and >50 using analysis of variance. In the presence of MVD, between the %AS <50 and >50 groups, values of CDP (71 ± 1.4 and 121 ± 1.3) and LFC (0.10 ± 0.04 and 0.19 ± 0.04) were significantly different (P < 0.05), under low-contractility conditions. A similar %AS trend was observed under high-contractility conditions (CDP: 18 ± 1.4 and 91 ± 1.4; LFC: 0.08 ± 0.04 and 0.25 ± 0.04). Under MVD conditions, similar to fractional flow reserve, CDP and LFC were not influenced by contractility.

Serum tenascin-C level is associated with coronary plaque rupture in patients with acute coronary syndrome

Tenascin-C, a large oligometric glycoprotein of the extracellular matrix, increases the expression of matrix metalloproteinases that lead to plaque instability and rupture, resulting in acute coronary syndrome (ACS). We hypothesized that a high serum tenascin-C level is associated with plaque rupture in patients with ACS. Fifty-two consecutive ACS patients who underwent emergency percutaneous coronary intervention (PCI) and, as a control, 66 consecutive patients with stable angina pectoris (SAP) were enrolled in this study. Blood samples were obtained from the ascending aorta just prior to the PCI procedures. After coronary guide-wire crossing, intravascular ultrasonography (IVUS) was performed for assessment of plaque characterization. Based on the IVUS findings, ACS patients were assigned to two groups according to whether there was ruptured plaque (ruptured ACS group) or not (nonruptured ACS group). There were 23 patients in the ruptured group and 29 patients in the nonruptured group. Clinical characteristics and IVUS measurements did not differ between the two groups. Tenascin-C levels were significantly higher in the ruptured ACS group than in the SAP group, whereas there was no significant difference between the nonruptured ACS and SAP groups. Importantly, in the ruptured ACS group, tenascin-C levels were significantly higher than in the nonruptured ACS group (71.9 ± 34.9 vs 50.5 ± 20.5 ng/ml, P < 0.005). Our data demonstrate that tenascin-C level is associated with pathologic conditions in ACS, especially the presence of ruptured plaque.

A rare case of myocardial infarction related to diagnostic intravascular ultrasound

A 71-year-old man underwent intracoronary stent implantation for acute inferior myocardial infarction (MI). Immediately after diagnostic intravascular ultrasound (IVUS) at 8 months' follow-up, an acute occlusion of the sinus node (SN) artery appeared, which developed sinus arrest with junctional escape rhythm. The serum level of high-sensitivity troponin T (TpT) was markedly elevated on the day after the procedure (2.1-32.5 ng/l), which was indicative of MI related to IVUS. Under continuous intravenous infusion of unfractionated heparin, the escape rhythm changed to lower atrial rhythm on the 4th day, and recovered to sinus rhythm on the 14th day. Coronary angiography (CAG) on 15th day showed a recanalization of the SN artery, but optical coherence tomography identified that disrupted plaque and white thrombus still existed in the ostium of the SN artery. The patient was discharged on maintenance anticoagulation therapy. We hypothesized from this case that IVUS-related myocardial injury may exist without clinical problems. Our retrospective investigation showed that the median levels of high-sensitivity TpT in 20 patients who underwent CAG and subsequent diagnostic IVUS significantly increased from 0.6 (interquartile range 0.3-1.1) to 1.6 (0.7-3.6) ng/l (P < 0.05), suggesting that IVUS may induce very low levels of myocardial injury. In conclusion, we experienced a rare case of IVUS-related MI caused by an acute occlusion of the SN artery. This case reaffirms that we should pay more attention to manipulation of IVUS catheters.

Urotensin II promotes the production of LTC4 in rat aortic adventitial fibroblasts through NF-κB-5-LO pathway by p38 MAPK and ERK activations

Adventitia is the outer part of the arterial wall where the inflammatory response often occurs. Urotensin II (UII) is a potent vasoconstrictive peptide that also promotes the inflammatory process in patients with cardiovascular disease. Leukotriene C4 (LTC4), a lipid mediator, was recently found to play a role in the inflammatory process in the artery. We hypothesized that the adventitia is one of the resources of LTC4 and that UII may promote LTC4 production through the 5-LO (5-lipoxygenase) pathway in adventitial fibroblasts. Rat adventitial fibroblasts were isolated and incubated in serum-free medium with either UII alone or in combination with inhibitors of p38 MAPK, ERK, and UII receptors. The expression of 5-LO was detected using real-time polymerase chain reaction and Western blot. The translocation and binding activity of nuclear factor (NF)-κB were measured using immunofluorescence and electrophoretic mobility shift assay, respectively. The production of LTC4 was measured by enzyme-linked immunosorbent assay. The results indicated that: (1) adventitial fibroblasts were a source of LTC4 production; (2) UII increased the expression of the 5-LO mRNA and the protein by NF-κB activation through p38 MAPK and ERK pathways; and (3) UII promoted the LTC4 release in fibroblasts through the 5-LO pathway by p38 MAPK and ERK activations. The 5-LO pathway mediates LTC4 production, which may be a new mechanism in the pathogenesis of the vascular adventitial inflammation caused by UII.