Impact of gender and age on in vivo virtual histology-intravascular ultrasound imaging plaque characterization (from the global Virtual Histology Intravascular Ultrasound [VH-IVUS] registry)

Interplay of Age and Risk Factor Control Upon Coronary Atheroma Progression

BACKGROUND & AIM

The extent and composition of coronary plaque, and its progression differ with patients' age. The interplay of patient's age with respect to risk factor control, upon atheroma progression has not been evaluated. We tested the hypothesis that risk factor control modulates the association between age and coronary atheroma progression.

METHOD

We performed a posthoc pooled analysis of data from 10 prospective, randomised trials involving serial coronary intravascular ultrasonography (IVUS) (n=5,823). The percent atheroma volume (PAV) was calculated as the proportion of the entire vessel wall occupied by atherosclerotic plaque.

RESULTS

Mean overall age was 58±9 years (28% women). In a fully adjusted multivariable analysis (following adjustment of sex, body mass index, systolic blood pressure [SBP], smoking, high-density lipoprotein and low-density lipoprotein [LDL]-cholesterol, triglyceride levels, peripheral vascular disease, diabetes mellitus, trial, region, and baseline PAV), an increase in age by one standard deviation was linked with PAV progression (β-estimate 0.097; 95% confidence interval 0.048-0.15; p<0.001). In patients with good risk factor control (LDL-cholesterol <1.8 mmol/L and SBP <130 mmHg), increasing age remained associated with PAV progression (0.123; 0.014-0.23; p=0.027). Lower effect sizes for the association of age with PAV progression were observed for patients with partial control of LDL-cholesterol and SBP and were not significantly associated with PAV progression when both LDL-cholesterol and SBP were not controlled (0.099; 0.032-0.167; p=0.004 and 0.042; -0.056 to 0.14; p=0.40, respectively).

CONCLUSIONS

Patient age is directly associated with coronary atheroma progression independently of traditional cardiovascular risk factors. In the setting of poor risk factor control, the influence of age on coronary artery disease progression is attenuated.

Advancing the access to cardiovascular diagnosis and treatment among women with cardiovascular disease: a joint British Cardiovascular Societies' consensus document

Despite significant progress in cardiovascular pharmacotherapy and interventional strategies, cardiovascular disease (CVD), in particular ischaemic heart disease, remains the leading cause of morbidity and mortality among women in the UK and worldwide. Women are underdiagnosed, undertreated and under-represented in clinical trials directed at management strategies for CVD, making their results less applicable to this subset. Women have additional sex-specific risk factors that put them at higher risk of future cardiovascular events. Psychosocial risk factors, socioeconomic deprivation and environmental factors have an augmented impact on women's cardiovascular health, highlighting the need for a holistic approach to care that considers risk factors specifically related to female biology alongside the traditional risk factors. Importantly, in the UK, even in the context of a National Health Service, there exist significant regional variations in age-standardised mortality rates among patients with CVD. Given most CVDs are preventable, concerted efforts are necessary to address the unmet needs and ensure parity of care for women with CVD. The present consensus document, put together by the British Cardiovascular Society (BCS)'s affiliated societies, specifically portrays the current status on the sex-related differences in the diagnosis and treatment of each of the major CVD areas and proposes strategies to overcome the barriers in accessing diagnoses and treatments among women. This document aims at raising awareness of the scale of the current problem and hopes to stimulate a multifaceted approach to address sex disparities and enable future comprehensive sex- and gender-based research through collaboration across different affiliated societies within the BCS.

Coronary atherosclerotic plaque phenotype and physiopathologic mechanisms: Is there an influence of sex? Insights from intracoronary imaging

Coronary artery disease (CAD) is the leading cause of disability and death in both women and men; considerable differences in clinical presentation, natural history and prognosis are reported between sexes. Different pathophysiological mechanisms play a major role, including sex-related and gender-related features or a combination of both. Reports from intracoronary imaging studies pointed towards morphological plaque features, which seemed to differ between men and women, albeit results reported so far were not conclusive. The purpose of this review is to shed light on differences in the pathophysiology underlying CAD in women vs men including the description of coronary plaque phenotype and mechanisms of plaque instability, as assessed by intracoronary imaging. We will also discuss potential clinical implications with the aim to move towards a sex and gender-based personalized approach in CAD patients.

Assessing engineered tissues and biomaterials using ultrasound imaging: In vitro and in vivo applications

Quantitative assessment of the structural, functional, and mechanical properties of engineered tissues and biomaterials is fundamental to their development for regenerative medicine applications. Ultrasound (US) imaging is a non-invasive, non-destructive, and cost-effective technique capable of longitudinal and quantitative monitoring of tissue structure and function across centimeter to sub-micron length scales. Here we present the fundamentals of US to contextualize its application for the assessment of biomaterials and engineered tissues, both in vivo and in vitro. We review key studies that demonstrate the versatility and broad capabilities of US for clinical and pre-clinical biomaterials research. Finally, we highlight emerging techniques that further extend the applications of US, including for ultrafast imaging of biomaterials and engineered tissues in vivo and functional monitoring of stem cells, organoids, and organ-on-a-chip systems in vitro.

Sex-specific features of optical coherence tomography detected plaque vulnerability related to clinical outcomes: insights from the CLIMA study

PURPOSE

To investigate the different impact of optical coherence tomography (OCT)-derived vulnerable plaque features on future adverse events (AEs) according to the biological sex.

METHODS

The prospective multicenter CLIMA study (ClinicalTrials.gov: NCT02883088) enrolled 1003 patients with OCT plaque analysis of non-treated coronary plaques located in the proximal left anterior descending artery. Sex-specific differences in plaque composition and vulnerable features were described. We investigated the incidence of AEs, including cardiac death, any myocardial infarction and target vessel revascularization at 1-year.

RESULTS

Among 1003 patients, 24.6% were women. Women were older and more frequently affected by chronic kidney disease. Dyslipidemia, prior MI and smoking habit were more common in men. At OCT analysis, women had shorter plaque length (p < 0.001), ticker fibrous cap (p = 0.001), smaller maximum lipid arc (p = 0.019), lower macrophage infiltration (p < 0.001) and intra-plaque layered tissue (p = 0.007). During follow-up, 65 AEs were registered. The presence of a thin fibrous cap and a large macrophage infiltration (> 67°) predicted AEs in both sexes. The presence of macrophages (HR 3.38, p = 0.018) and a small minimum lumen area (HR 4.97, p = 0.002) were associated with AEs in women but not in men, while a large lipid arc (> 180°) was associated with AEs in men (HR 2.56, p = 0.003) but not in women.

CONCLUSION

This subanalysis of the CLIMA study investigated for the first-time sex-specific OCT features of plaque vulnerability associated with AEs. Local inflammation was associated with AEs in women and a large lipid arc was predictive in men. OCT may help develop sex-specific risk stratification strategies.

Efficacy of intravascular imaging-guided drug-eluting stent implantation: a systematic review and meta-analysis of randomized clinical trials

Background

Traditional angiography only displays two-dimensional images of the coronary arteries during stent implantation. However, intravascular imaging can show the structure of the vascular wall, plaque characteristics. This article aims to evaluate the efficacy of intravascular imaging-guided drug-eluting stent (DES) implantation.

Method

We conducted a systematic review and meta-analysis of randomized controlled trials of intravascular imaging-guided, including patients with DES implantation guided by intravascular ultrasound or optical coherence tomography and traditional angiography. The databases of PubMed, EMBASE, web of science, and Cochrane Library were searched. The primary outcome was target lesion revascularization (TLR). The secondary outcomes included the target vessel revascularization (TVR), myocardial infarction (MI), stent thrombosis (ST), cardiac death, all-cause death, and the major adverse cardiac events (MACE) during the 6–24 months follow-up. The fixed-effects model was used to calculate the relative risk (RR) and 95% confidence interval of the outcome event. Meanwhile, the trial sequence analysis was employed to evaluate the results.

Result

This meta-analysis included fourteen randomized controlled trials with 7307 patients. Compared with angiography-guided, intravascular imaging-guided DES implantation can significantly reduce the risk of TLR (RR 0.63, 0.49–0.82, P = 0.0004), TVR (RR 0.66, 0.52–0.85, P = 0.001), cardiac death (RR 0.58; 0.38–0.89; P = 0.01), MACE (RR 0.67, 0.57–0.79; P < 0.00001) and ST (RR 0.43, 0.24–0.78; P = 0.005). While there was no significant difference regarding MI (RR 0.77, 0.57–1.05, P = 0.10) and all-cause death (RR 0.87, 0.58–1.30, P = 0.50).

Conclusions

Compared with angiography, intravascular imaging-guided DES implantation is associated with better clinical outcomes in patients with coronary artery disease, especially complex lesions (Registered by PROSPERO, CRD 42021289205).

Systemic and Coronary Hemodynamic Effects of Tobacco Products on the Cardiovascular System and Potential Pathophysiologic Mechanisms

Tobacco product usage is the single most preventable cause of death in the United States. Smoking promotes atherosclerosis, producing disease in the coronary arteries, the aorta, the carotid and cerebral arteries and the large arteries in the peripheral circulation. The cardiovascular consequences of tobacco products have been the subject of intensive study for several decades. Despite the overwhelming epidemiologic association between smoking and vascular disease, the pathophysiologic mechanisms by which smoking exerts its deleterious effects remain incompletely understood. This review addresses the acute and long-term systemic and coronary hemodynamic effects of tobacco, with an emphasis of the impact on coronary blood flow and pathophysiologic mechanisms.

Differences in Culprit Lesions Between Premenopausal and Postmenopausal Women With Acute Coronary Syndrome: An Optical Coherence Tomography Study

BACKGROUND

Differences in culprit lesion characteristics remain unclear between premenopausal and postmenopausal women with acute coronary syndrome (ACS). Optical coherence tomography (OCT) enables high-resolution in vivo identification of plaques. We investigated potential differences in culprit lesions between premenopausal and postmenopausal women with ACS by means of OCT.

METHODS

We included 191 ACS patients who had undergone preinterventional OCT and stratified them into 2 groups according to their menopausal status: premenopausal (n = 97) and postmenopausal (n = 94). The characteristics of culprit lesions were compared between the 2 groups.

RESULTS

Multivessel lesions were more commonly noted on angiography in the postmenopausal group than in the premenopausal group (40.21% vs 72.34%; P < 0.0001). On OCT, the most common type of culprit plaque was the fibrous plaque in the premenopausal group and the lipid plaque in the postmenopausal group. Compared with the premenopausal group, plaque rupture was more common in the postmenopausal group (39.18% vs 55.32%; P = 0.0254); culprit lesions had more vulnerable features, including macrophage accumulation (58.76% vs 87.23%; P < 0.0001), microchannel (38.14% vs 84.04%; P < 0.0001), cholesterol crystals (30.93% vs 62.77%; P < 0.0001), lipid-rich plaque (32.99% vs 58.51%; P < 0.0001), thin-cap fibroatheroma (3.09% vs 21.28%; P = 0.0001), and calcium (20.62% vs 44.68%; P = 0.0004); maximum lipid arc was larger (121.06 ± 110.99° vs 220.12 ± 115.47°, P < 0.0001); and lipid length was longer (5.78 ± 5.29 mm vs 12.90 ± 8.97 mm; P < 0.0001).

CONCLUSIONS

Compared with premenopausal women with ACS, postmenopausal women with ACS had more vulnerable culprit lesions. These finding suggest potential optimised lipid-lowering therapy for postmenopausal women with ACS.

Sex differences in coronary plaque changes assessed by serial computed tomography angiography

Long-term data on sex-differences in coronary plaque changes over time is lacking in a low-to-intermediate risk population of stable coronary artery disease (CAD). The aim of this study was to evaluate the role of sex on long-term plaque progression and evolution of plaque composition. Furthermore, the influence of menopause on plaque progression and composition was also evaluated. Patients that underwent a coronary computed tomography angiography (CTA) were prospectively included to undergo a follow-up coronary CTA. Total and compositional plaque volumes were normalized using the vessel volume to calculate a percentage atheroma volume (PAV). To investigate the influence of menopause on plaque progression, patients were divided into two groups, under and over 55 years of age. In total, 211 patients were included in this analysis, 146 (69%) men. The mean interscan period between baseline and follow-up coronary CTA was 6.2 ± 1.4 years. Women were older, had higher HDL levels and presented more often with atypical chest pain. Men had 434 plaque sites and women 156. On a per-lesion analysis, women had less fibro-fatty PAV compared to men (β -1.3 ± 0.4%; p < 0.001), with no other significant differences. When stratifying patients by 55 years age threshold, fibro-fatty PAV remained higher in men in both age groups (p < 0.05) whilst women younger than 55 years demonstrated more regression of fibrous (β -0.8 ± 0.3% per year; p = 0.002) and non-calcified PAV (β -0.7 ± 0.3% per year; p = 0.027). In a low-to-intermediate risk population of stable CAD patients, no significant sex differences in total PAV increase over time were observed. Fibro-fatty PAV was lower in women at any age and women under 55 years demonstrated significantly greater reduction in fibrous and non-calcified PAV over time compared to age-matched men. (ClinicalTrials.gov number, NCT04448691.)

Age- and Gender-Related Differences in Coronary Lesion Plaque Composition on Optical Coherence Tomography

BACKGROUND

The pathophysiology and chronological course of atherosclerosis seems to be different between men and women due to biological differences, and age and gender differences in plaque composition of coronary lesions remain to be elucidated.

METHODS AND RESULTS

A total of 860 consecutive patients with a median age of 69 years (IQR, 60-78 years) who underwent optical coherence tomography (OCT) of culprit lesions was included. The composition of culprit plaque on OCT was compared between female (n=171) and male (n=689) subjects in younger (<70 years old) and elderly (≥70 years old) patients. In elderly patients, the prevalence of thin-cap fibroatheroma (TCFA) was significantly higher in women than in men (30.6 vs. 15.2%, P<0.001). In younger patients, the prevalence of large calcification was significantly higher in women than in men (60.0 vs. 32.8%, P<0.001). The prevalence of other vulnerable plaque characteristics (i.e., macrophages, microchannels, and spotty calcification), was similar between women and men. Elderly women had a significantly higher prevalence of TCFA (OR, 2.13; 95% CI: 1.33-3.44, P=0.002) than other patients.

CONCLUSIONS

Women had a higher prevalence of TCFA and of large calcification than men in patients ≥70 and <70 years old, respectively. This may facilitate the understanding of gender differences in the pathogenesis of coronary atherosclerosis, and the tailoring of therapy and of prevention according to age and gender.

Coronary plaque tissue characterization in patients with premature coronary artery disease

Premature coronary artery disease (CAD) studies rarely involve coronary plaque characterization. We characterize coronary plaque tissue by radiofrequency intravascular ultrasound (IVUS) in patients with premature CAD. From July 2015 to December 2017, 220 patients from the Department of Cardiology, Affiliated Hangzhou First People’s Hospital, Zhejiang University School of Medicine with first occurrence of angina or myocardial infarction within 3 months were enrolled. Patients with premature CAD (n = 47, males aged < 55 years, and females aged < 65 years) or later CAD (n = 155) were retrospectively compared for cardiovascular risk factors, laboratory examination findings, coronary angiography data, gray-scale IVUS, and iMap-IVUS. The mean age was 53.53 ± 7.24 vs. 70.48 ± 8.74 years (p < 0.001). The groups were similar for traditional coronary risk factors except homocysteine (18.60 ± 5.15 vs. 17.08 ± 4.27 µmol/L, p = 0.043). After matching for baseline characteristics, LDL cholesterol (LDL-C) was higher for premature CAD than later CAD (2.50 ± 0.96 vs. 2.17 ± 0.80 mmol/L, p = 0.019). Before the matching procedure, the premature CAD group had shorter target lesion length [18.50 (12.60–32.00) vs. 27.90 (18.70–37.40) mm, p = 0.002], less plaque volume [175.59 (96.60–240.50) vs. 214.73 (139.74–330.00) mm³, p = 0.013] than the later CAD group. After the matching procedure, the premature CAD group appeared to be less plaque burden (72.69 ± 9.99 vs. 74.85 ± 9.80%, p = 0.005), and positive remodeling (1.03 ± 0.12 vs. 0.94 ± 0.18, p = 0.034), and lower high risk feature incidence (p = 0.006) than the later CAD group. At the plaque’s minimum lumen, premature CAD had more fibrotic (p < 0.001), less necrotic (p = 0.001) and less calcified areas (p = 0.012). Coronary plaque tissue was more fibrotic with less necrotic and calcified components in premature than in later CAD, and the range and degree of atherosclerosis were significantly lower.

Carotid Plaque Characterization with Contrast-Enhanced Ultrasound Imaging and its Histological Validation

Introduction

Better methods are needed to determine the course of intervention in patients with atherosclerosis; therefore, plaque characterization is increasing in importance. Current guidelines suggest that the degree of stenosis and symptoms are the only criteria for the selection of the surgical intervention. However, there remain some challenges. The characterization of plaque morphology may help determine the best course of therapy. Magnetic resonance imaging and computed tomography are current standard techniques to evaluate plaque morphology, but they are expensive and unsuitable for long term surveillance and monitoring.

Objective

In this research, an ultrasound-based methodology for the characterization of carotid plaques is shown. This technique requires the injection of a small volume (approximately 1.5 mL) of contrast agent and the acquisition of postcontrast images. The rationale of this technique is that poorly perfused tissues (such as lipids) show a lower contrast enhancement with respect to highly perfused tissues (such as fibrous and muscular tissue).

Methods

The technique consists of two steps. First, the plaque region is automatically segmented by a completely user-independent algorithm. Then, the portion of the wall corresponding to the plaque is analyzed and color-coded intensity is assigned to a specific tissue. Performance evaluation was performed against histology. Twenty plaque specimens were sent to pathology for reporting. Correlation of the histology report and of the contrast-enhanced ultrasound analysis was performed.

Results

Plaque components that could be effectively identified were thrombi, lipids, fibrous/muscular tissue, and calcium. Overall the errors on 20 plaques between automated classification and histology were: 3.1 ± 1.1% for thrombus, 4.2 ± 1.5% for lipids, 5 ± 3.4% for fibrous/muscular tissue, and 3.2 ± 1.0% for calcium.

Conclusion

Despite the need for further investigation and a quantitative evaluation of the results, this methodology showed encouraging results. This analysis architecture is undergoing validation in a neurology division and is aimed at being used for the follow-up of patients and quantification of drug therapy effects.

Culprit plaque characteristics in women vs men with a first ST-segment elevation myocardial infarction: In vivo optical coherence tomography insights

BACKGROUND

It is unclear whether more severe coronary atherosclerosis is a prerequisite to an initial acute coronary event in women vs men.

HYPOTHESIS

Women may have more severe coronary atherosclerosis than men in patients with acute coronary event.

METHODS

We used intravascular optical coherence tomography (OCT) to evaluate gender differences in culprit-plaque morphology in patients with a first ST-segment elevation myocardial infarction (STEMI).We retrospectively enrolled 211 consecutive patients who experienced a first STEMI and underwent an OCT examination of their infarct-related artery before primary percutaneous coronary intervention.

RESULTS

Of the 211 patients enrolled, 162 (76.7%) were men and 49 (23.2%) were women. The women were significantly older than the men (mean age, 60.2 ± 8.2 vs 55.7 ± 11.2 years; P = 0.01) and less likely to be current smokers (P = 0.02). Moreover, the delay from symptom onset to reperfusion was longer in women than in men (7.6 ± 6.1 vs 5.5 ± 4.4 hours; P = 0.01). The OCT data indicated that there were no gender differences in culprit-plaque morphology, including lipid length, lipid arc, minimum fibrous cap thickness, or minimum lumen area. Additionally, no gender differences were found in the prevalence of plaque rupture, thin-cap fibroatheroma, residual thrombus, microvessels, macrophages, cholesterol crystals, or calcification.

CONCLUSIONS

Among patients presenting with a first STEMI, there were no differences in culprit plaque features between women and men.

Long-term effects intensive medical therapy on the development and progression of subclinical atherosclerosis and the metabolic syndrome in Chinese patients with type 2 diabetes mellitus

BACKGROUND

Few studies have investigated the progression of subclinical atherosclerosis and metabolic syndrome (MetS) in Chinese patients with type 2 diabetes mellitus (T2DM). This study was to compare the long-term effects of intensive medical therapy on the development and progression of subclinical atherosclerosis and MetS in Chinese T2DM patients with that of a conventional treatment regimen.

METHODS

A total of 316 T2DM patients were randomized to receive conventional pharmacological treatment or intensive medical therapy, consisting of diet and exercise counseling, from 2002 to 2014 at our hospital in Changsha, China. Clinical indicators of subclinical atherosclerosis and MetS were evaluated over the 12-year follow-up period. A χ analysis or t tests was used to compare the data between the 2 groups. Risk factors for subclinical atherosclerosis were identified using Cox proportional hazard models.

RESULTS

The incidence of subclinical atherosclerosis increased in both groups over time, and did not differ significantly between the 2 groups at the end of the study. However, after 6 years of treatment, the risk of subclinical atherosclerosis was significantly lower in the intensive medical therapy group, based on intima-media thickness (IMT) measurements, compared with that in the conventional treatment (44.2% vs. 69.7%; P < 0.01). Age, creatinine, and IMT of the common iliac artery were significantly associated with subclinical atherosclerosis. Although the indicators of MetS did not differ significantly at the end of study, the success rate for the management of MetS in the intensive medical therapy group was significantly higher than that in the conventional treatment group in 2006, 2008, 2010, and 2012.

CONCLUSIONS

The incidence of atherosclerosis in the intensive medical therapy group was significantly lower than that in the conventional treatment group from 2006 to 2010 (P < 0.05), and the incidence of MetS in the intensive medical therapy group was significantly higher than that in the conventional treatment group from 2006 to 2012. Kaplan-Meier estimations showed that the risk of subclinical atherosclerosis in the intensive medical therapy group was significantly lower than that in the conventional treatment group (P < 0.001), whereas the risk of MetS was not significantly different between the treatment groups (P > 0.05).

Comparison of coronary plaque, coronary artery calcification and major adverse cardiac events in Chinese outpatients with and without type 2 diabetes

Objective

Diabetes substantially increases the risk of cardiovascular disease (CAD) and is associated with an increased risk of CAD mortality. The purpose of this study was to investigate the differences in coronary artery plaque, coronary artery calcification (CAC) measured in outpatients with and without type 2 diabetes, and the occurrence rate of a major adverse cardiac event (MACE) throughout follow-up with the same patients.

Methods

Five hundred eighty-eight outpatients with suspected CAD comprising 208 diabetic and 380 non-diabetic patients were enrolled in this study. Coronary artery plaque and CAC scores were detected and measured by dual-source computed tomography. The major MACE during the follow-up period (4.0–20 months) was recorded and its relationship to type 2 diabetes and CAC was investigated.

Results

The diabetes group had higher CAC scores in the left anterior descending, left circumflex, and right coronary arteries and total CAC burden than the group without diabetes. The diabetes group had more diseased coronary segments and more obstructed vessels than the non-diabetes group. Logistic regression analysis demonstrated that diabetes is positively associated with mixed coronary plaque and non-calcified plaque. All patients in the diabetes group and all patients with higher CACs in both groups had a higher incidence rate of MACEs.

Conclusion

Patients with type 2 diabetes have a higher prevalence of obstructive CAD, higher CAC scores, and a higher incidence rate of MACEs than those without diabetes. Diabetes and higher CAC scores were the important predictors of the occurrence of MACEs throughout follow-up with patients.

Controversies in the Treatment of Women with ST-Segment Elevation Myocardial Infarction

Coronary artery disease is the leading cause of death in women. Women with ST-segment elevation myocardial infarctions continue to have worse outcomes compared with men despite advancements in therapies. Furthermore, these differences are particularly pronounced among young men and women with myocardial infarctions. Differences in the pathophysiology of coronary artery plaque development, disease presentation, and recognition likely contribute to these outcome disparities. Despite having worse outcomes compared with men, women clearly benefit from aggressive treatment and the latest therapies. This article reviews the treatment options for ST-segment elevation myocardial infarctions and the outcomes of women after treatment with reperfusion therapies.

Ultrasound Imaging Techniques for Spatiotemporal Characterization of Composition, Microstructure, and Mechanical Properties in Tissue Engineering

Ultrasound techniques are increasingly being used to quantitatively characterize both native and engineered tissues. This review provides an overview and selected examples of the main techniques used in these applications. Grayscale imaging has been used to characterize extracellular matrix deposition, and quantitative ultrasound imaging based on the integrated backscatter coefficient has been applied to estimating cell concentrations and matrix morphology in tissue engineering. Spectral analysis has been employed to characterize the concentration and spatial distribution of mineral particles in a construct, as well as to monitor mineral deposition by cells over time. Ultrasound techniques have also been used to measure the mechanical properties of native and engineered tissues. Conventional ultrasound elasticity imaging and acoustic radiation force imaging have been applied to detect regions of altered stiffness within tissues. Sonorheometry and monitoring of steady-state excitation and recovery have been used to characterize viscoelastic properties of tissue using a single transducer to both deform and image the sample. Dual-mode ultrasound elastography uses separate ultrasound transducers to produce a more potent deformation force to microscale characterization of viscoelasticity of hydrogel constructs. These ultrasound-based techniques have high potential to impact the field of tissue engineering as they are further developed and their range of applications expands.

Noninvasive quantification of in vitro osteoblastic differentiation in 3D engineered tissue constructs using spectral ultrasound imaging

Non-destructive monitoring of engineered tissues is needed for translation of these products from the lab to the clinic. In this study, non-invasive, high resolution spectral ultrasound imaging (SUSI) was used to monitor the differentiation of MC3T3 pre-osteoblasts seeded within collagen hydrogels. SUSI was used to measure the diameter, concentration and acoustic attenuation of scatterers within such constructs cultured in either control or osteogenic medium over 21 days. Conventional biochemical assays were used on parallel samples to determine DNA content and calcium deposition. Construct volume and morphology were accurately imaged using ultrasound. Cell diameter was estimated to be approximately 12.5–15.5 µm using SUSI, which corresponded well to measurements of fluorescently stained cells. The total number of cells per construct assessed by quantitation of DNA content decreased from 5.6±2.4×10⁴ at day 1 to 0.9±0.2×10⁴ at day 21. SUSI estimation of the equivalent number of acoustic scatters showed a similar decreasing trend, except at day 21 in the osteogenic samples, which showed a marked increase in both scatterer number and acoustic impedance, suggestive of mineral deposition by the differentiating MC3T3 cells. Estimation of calcium content by SUSI was 41.7±11.4 µg/ml, which agreed well with the biochemical measurement of 38.7±16.7 µg/ml. Color coded maps of parameter values were overlaid on B-mode images to show spatiotemporal changes in cell diameter and calcium deposition. This study demonstrates the use of non-destructive ultrasound imaging to provide quantitative information on the number and differentiated state of cells embedded within 3D engineered constructs, and therefore presents a valuable tool for longitudinal monitoring of engineered tissue development.

Mechanisms of myocardial infarction without obstructive coronary artery disease

Angiography in patients with myocardial infarction (MI) most commonly reveals one or more significantly narrowed coronary arteries, but a substantial minority of patients with spontaneous MI have no obstructive coronary artery disease (CAD) at angiography. This review summarizes evidence for the most commonly hypothesized mechanisms, including plaque disruption, plaque erosion, vasospasm, embolism, and spontaneous coronary dissection. In addition, tako-tsubo syndrome and myocarditis are discussed. The best treatment of MI without obstructive CAD is likely to differ substantially based on the underlying cause. Additional mechanistic research is needed to facilitate the design of research studies aimed at documenting the best treatments for these patients, numbering as many as 225,000 per year in the US.

Diagnosing and characterizing coronary artery disease in women: developments in noninvasive and invasive imaging techniques

Cardiovascular disease is the leading cause of death in men and women in the USA; yet, coronary artery disease (CAD) continues to be underrecognized and underdiagnosed in women. Noninvasive and invasive imaging techniques are constantly being developed in order to more accurately assess CAD. At the same time, the impact of gender on the interpretation and accuracy of these studies is still being elucidated. Furthermore, new imaging techniques have improved our understanding of CAD pathophysiology and progression and have begun to reveal gender differences in the development of CAD. This article will review current imaging techniques and their application to diagnosing and understanding CAD in women.

Impacts of age on coronary atherosclerosis and vascular response to statin therapy

Age is a well-established risk factor for cardiovascular disease. Recent trials using intravascular ultrasound (IVUS) have shown that lipid-lowering therapy with statins halts the progression or induces the regression of coronary artery plaques. However, impacts of age on coronary atherosclerosis and vascular response to statin therapy have not been fully evaluated. The effects of 8-month statin therapy on coronary atherosclerosis were evaluated using virtual histology-IVUS. IVUS data were analyzed from 119 patients who were divided into two groups according to age: elderly patients (≥65 years, n = 72) and non-elderly patients (<65 years, n = 47). No patients were taking statins or other lipid-lowering therapies at baseline. At baseline, external elastic membrane (EEM) volume (17.27 vs. 14.95 mm(3)/mm, p = 0.02) and plaque volume (9.49 vs. 8.11 mm(3)/mm, p = 0.03) in the elderly patients were significantly greater than in the non-elderly patients. The EEM volume (-2.4 %, p = 0.007) and plaque volume (-3.1 %, p = 0.007) after 8-month of statin therapy had significantly decreased in the non-elderly patients but not in the elderly patients. A significant positive correlation was observed between age and percentage change in plaque volume (r = 0.265, p = 0.004). A multivariate regression analysis showed that age was a significant predictor of the percentage change in plaque volume during statin therapy (β = 0.223, p = 0.02). Coronary atherosclerosis was more advanced and vascular responses to statin therapy were attenuated in the elderly patients compared to the non-elderly patients.

Ultrasound-assessed non-culprit and culprit coronary vessels differ by age and gender

AIM: To investigate age- and gender-related differences in non-culprit versus culprit coronary vessels assessed with virtual histology intravascular ultrasound (VH-IVUS).

METHODS: In 390 patients referred for coronary angiography to a single center (Luzerner Kantonsspital, Switzerland) between May 2007 and January 2011, 691 proximal vessel segments in left anterior descending, circumflex and/or right coronary arteries were imaged by VH-IVUS. Plaque burden and plaque composition (fibrous, fibro-fatty, necrotic core and dense calcium volumes) were analyzed in 3 age tertiles, according to gender and separated for vessels containing non-culprit or culprit lesions. To classify as vessel containing a culprit lesion, the patient had to present with an acute coronary syndrome, and the VH-IVUS had to be performed in a vessel segment containing the culprit lesion according to conventional coronary angiography.

RESULTS: In non-culprit vessels the plaque burden increased significantly with aging (in men from 37% ± 12% in the lowest to 46% ± 10% in the highest age tertile, P < 0.001; in women from 30% ± 9% to 40% ± 11%, P < 0.001); men had higher plaque burden than women at any age (P < 0.001 for each of the 3 age tertiles). In culprit vessels of the lowest age tertile, plaque burden was significantly higher than that in non-culprit vessels (in men 48% ± 6%, P < 0.001 as compared to non-culprit vessels; in women 44% ± 18%, P = 0.004 as compared to non-culprit vessels). Plaque burden of culprit vessels did not significantly change during aging (plaque burden in men of the highest age tertile 51% ± 9%, P = 0.523 as compared to lowest age tertile; in women of the highest age tertile 49% ± 8%, P = 0.449 as compared to lowest age tertile). In men, plaque morphology of culprit vessels became increasingly rupture-prone during aging (increasing percentages of necrotic core and dense calcium), whereas plaque morphology in non-culprit vessels was less rupture-prone and remained constant during aging. In women, necrotic core in non-culprit vessels was very low at young age, but increased during aging resulting in a plaque morphology that was very similar to men. Plaque morphology in culprit vessels of young women and men was similar.

CONCLUSION: This study provides evidence that age- and gender-related differences in plaque burden and plaque composition significantly depend on whether the vessel contained a non-culprit or culprit lesion.

Interventions for ST Elevation Myocardial Infarction in Women

The management of ST-segment elevation myocardial infarction (STEMI) has significantly advanced from supportive care to reperfusion therapies with thrombolytics and percutaneous coronary revascularization techniques. These advances have improved the outcomes of patients with STEMI. Although cardiovascular disease is the leading cause of death in both men and women, the minority of patients in trials studying the impact of these therapies on outcomes are women. Multiple studies have shown that men and women do not have equivalent outcomes after STEMI. This article reviews the treatment options for STEMI and the outcomes of women after treatment with reperfusion therapies.

High platelet reactivity on clopidogrel therapy correlates with increased coronary atherosclerosis and calcification: a volumetric intravascular ultrasound study

OBJECTIVES

This study sought to evaluate the relationship between platelet reactivity and atherosclerotic burden in patients undergoing percutaneous coronary intervention (PCI) with pre-intervention volumetric intravascular ultrasound (IVUS) imaging.

BACKGROUND

Atherosclerosis progresses by the pathologic sequence of subclinical plaque rupture, thrombosis, and healing. In this setting, increased platelet reactivity may lead to more extensive arterial thrombosis at the time of plaque rupture, leading to a more rapid progression of the disease. Alternatively, abnormal vessel wall biology with advanced atherosclerosis is known to enhance platelet reactivity. Therefore, it is possible that by either mechanism, increased platelet reactivity may be associated with greater atherosclerotic burden.

METHODS

This study included patients who underwent PCI with pre-intervention IVUS imaging and platelet reactivity functional assay (P2Y(12) reaction units) performed >16 h after PCI, after the stabilization of clopidogrel therapy (administered before PCI). Platelet reactivity >230 P2Y(12) reaction units defined high on-treatment platelet reactivity (HPR).

RESULTS

Among 335 patients (mean age 65.0 years, 71% men), there were 109 patients with HPR (32.5%) and 226 without HPR (67.5%), with HPR being associated with diabetes and chronic renal insufficiency. By IVUS analysis, patients with HPR had significantly greater target lesion calcium lengths, calcium arcs, and calcium indexes. Furthermore, patients with HPR tended to have longer lesions and greater volumetric dimensions, indicating higher plaque volume, larger total vessel volume, and also greater luminal volume, despite similar plaque burden. By multivariate analysis controlling for baseline clinical variables, HPR was the single consistent predictor of all IVUS parameters examined, including plaque volume, calcium length, and calcium arc.

CONCLUSIONS

Increased platelet reactivity on clopidogrel treatment, defined as >230 P2Y(12) reaction units, is associated with greater coronary artery atherosclerotic disease burden and plaque calcification.

Noninvasive, quantitative, spatiotemporal characterization of mineralization in three-dimensional collagen hydrogels using high-resolution spectral ultrasound imaging

As tissue engineering products move toward the clinic, nondestructive methods to monitor their development and ensure quality are needed. In this study, high-resolution spectral ultrasound imaging (SUSI) was used to noninvasively characterize mineral content in collagen hydrogels. SUSI was used to generate three-dimensional (3D) grayscale (GS) images of construct morphology with submillimeter resolution. Spectral analysis of the backscattered radio frequency (RF) ultrasound signals was used to determine the midband fit (MBF) and slope of the linearized RF spectrum. These parameters are operator and instrument independent, and were used to characterize the spatial distribution of mineral in constructs supplemented with hydroxyapatite particles. GS and MBF correlated closely with mineral content, while slope was not dependent on concentration. SUSI also was used to monitor mineralization of collagen constructs by immersion in simulated body fluid (SBF) over 21 days. The construct surface was mineralized before the interior, and there was a dose-dependent effect of SBF concentration on degree of mineralization and deposited particle size. MBF density was closely correlated with the amount of calcium deposited. These data demonstrate that SUSI has utility as a noninvasive imaging method for quantitative analysis of mineralization in 3D protein constructs. Such techniques may assist the development of engineered orthopedic tissues.

Takotsubo cardiomyopathy is not due to plaque rupture: an intravascular ultrasound study

BACKGROUND

Plaque rupture with subsequent transient thrombotic coronary occlusion by a fast-dissolving clot is one of the proposed pathogenic mechanisms in Takotsubo cardiomyopathy (TC).

HYPOTHESIS

The aim of this study was to seek evidence for the hypothesis of transient coronary thrombosis as the underlying mechanism of TC by means of intravascular ultrasound (IVUS).

METHODS

In our database of 63 consecutive patients with TC we identified 10 patients (16%) who had undergone IVUS during their initial left heart catheterisation.

RESULTS

A median length of 67 mm of the left anterior descending artery was analyzed (interquartile range [IQR]: 63.3-70.1 mm). Median lumen diameter, median vessel diameter, median plaque and media volume were 2.9 mm (IQR: 2.7-3.1 mm), 4.2 mm (IQR: 3.8-4.4 mm), and 90.9 mm(3) (IQR: 70.4-101.4 mm(3)), respectively. Plaque rupture, positive remodeling, and presumed intracoronary thrombus were absent in all patients.

CONCLUSION

In conclusion, plaque rupture does not account for the regional wall motion abnormalities observed in TC. The previously reported observation of plaque rupture in TC seems to constitute an incidental finding. We suggest that the theory of aborted myocardial infarction as the underlying cause of TC should be abandoned once and for all.