Detection of the vulnerable coronary atheromatous plaque. Where are we now?

Author's response to Letter-to-the-Editor from Chang JS. concerning: "Benefit of respiratory gating in the Danish Breast Cancer Group partial breast irradiation trial"

We appreciate Chang JS.'s interest in the article: "Benefit of respiratory gating in the Danish Breast Cancer Group partial breast irradiation trial". The author's response corroborates the statements and comments of Chang JS.

Automated coronary artery calcium scoring in patients with breast cancer to assess the risk of heart disease following adjuvant radiation therapy

Aim

Validation of coronary artery calcium (CAC) scores as prognostic factors of acute coronary events (ACE) development in breast cancer patients are demanded. We investigated prognostic impact of CAC on ACE development with cardiac exposure to radiation.

Methods

We evaluated breast cancer patients with (n = 511) or without (n = 600) adjuvant radiotherapy (RT) between 2005 and 2013. CAC Agatston scores were analyzed using a deep-learning-based algorithm. Individual mean heart dose (MHD) was calculated, and no RT was categorized as 0 Gy. The primary endpoint was the development of ACE following breast surgery.

Results

In the RT and no-RT cohorts, 11.2% and 3.7% exhibited CAC >0, respectively. Over a 9.3-year follow-up period, the 10-year ACE rate was 0.7%. In the multivariate analysis, the CAC score was a significant risk factor for ACE (CAC >0 vs CAC = 0, 10-year 6.2% vs 0.2%, P < 0.001). In the subgroup with CAC >0, the 10-year ACE rates were 0%, 3.7%, and 13.7% for patients receiving mean heart doses of 0 Gy, 0–3 Gy, and >3 Gy, respectively (P = 0.133). Although CAC score was not predictive for non-ACE heart disease risk (P > 0.05), the 10-year non-ACE heart disease rates were 1.7%, 5.7%, and 7.1% for patients with CAC = 0 receiving MHD of 0 Gy, 0–3 Gy, and >3 Gy, respectively (P < 0.001).

Conclusions

The CAC score was a significant predictor of ACE in patients with breast cancer. Although further studies are required, CAC score screening on simulation CT in patients undergoing breast RT can help identify those with high risk for ACE on a per-patient basis.

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CAC score was successfully validated as a strong predictive factor for ACEs.

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MHD was identified as a significant factor in development of ACE and NAHD.

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Best efforts should be made to keep the dose to cardiac structures as low as possible.

Imaging Inflammation in Atherosclerosis with CXCR4-Directed [68Ga]PentixaFor PET/MRI-Compared with [18F]FDG PET/MRI

(1) This study compared [68Ga]PentixaFor uptake in active arterial segments with corresponding [18F]FDG arterial uptake as well as the relationship with cardiac [68Ga]PentixaFor uptake. (2) Method: Tracer uptake on atherosclerotic lesions in the large arteries was measured and target-to-background ratios (TBR) were calculated to adjust background signals with two investigators blinded to the other PET scan. On a patient-based and lesion-to-lesion analysis, TBR values of two tracers were compared and the relationship with cardiac inflammation was further explored. Furthermore, two cardiovascular risk-related groups were divided to explore the value of risk stratification of the two tracers in atherosclerosis. (3) Results: [68Ga]PentixaFor PET/MRI identified more lesions (88% vs. 48%; p < 0.001) and showed higher uptake than [18F]FDG PET/MRI (TBR, 1.90 ± 0.36 vs. 1.63 ± 0.29; p < 0.001). In the patient-based analysis, the TBR of [68Ga]PentixaFor uptake was also significantly higher than [18F]FDG uptake (1.85 ± 0.20 vs. 1.42 ± 0.19; p < 0.001). The TBR of active lesions for [68Ga]PentixaFor was significantly increased in the high-risk group (n = 9), as compared to the low-risk group (n = 10) (2.02 ± 0.15 vs. 1.86 ± 0.10, p = 0.015), but not for [18F]FDG (1.85 ± 0.10 vs. 1.80 ± 0.07, p = 0.149). (4) Conclusion: [68Ga]PentixaFor PET/MRI identified many more lesions than [18F]FDG PET/MRI. Patients with high-risk cardiovascular factors illustrated an increased uptake of [68Ga]PentixaFor. There was a correlation between the elevated uptake of [68Ga]PentixaFor in the active arterial segments and heart.

Crossing chronic total occlusions with the Ocelot system: the initial European experience

AIMS

The aim of the study was to determine the safety, efficacy and feasibility of a new chronic total occlusion (CTO) device using optical coherence tomography (OCT) technology, the Ocelot catheter (Avinger, Inc., Redwood City, CA, USA), for crossing of SFA CTOs following guidewire failure.

METHODS AND RESULTS

Prospective, multicentre, market preference testing. Thirty-three patients with confirmed CTO (99-100% stenosis by visual estimate) of their superficial femoral artery (SFA) were treated between September 28, 2011, and December 9, 2011, at three European centres. Ocelot crossed 94% (31/33) of CTOs, allowing guidewire placement in the distal true lumen. All (100%) lesions were treated without any major adverse safety events. Procedural time and contrast dose were significantly reduced (p<0.0001) when compared with a similar, non-OCT-guided CTO crossing device (Wildcat catheter; Avinger, Inc.). Overall physician feedback on the catheter performance was positive with an 87% average rating of excellent or good across seven categories. Performance ratings of Ocelot's OCT imaging guidance were consistently positive with an 86% average rating of excellent or good across five OCT categories.

CONCLUSIONS

The Ocelot catheter combines advanced CTO crossing technology with real-time OCT guidance. When compared with a similar non-OCT-guided catheter, crossing efficacy and safety profile improved. Total procedure time and contrast volumes were significantly reduced. The Ocelot is a safe, efficient and effective tool for crossing CTOs.

Preclinical models of atherosclerosis. The future of Hybrid PET/MR technology for the early detection of vulnerable plaque

Cardiovascular diseases are the leading cause of death in developed countries. The aetiology is currently multifactorial, thus making them very difficult to prevent. Preclinical models of atherothrombotic diseases, including vulnerable plaque-associated complications, are now providing significant insights into pathologies like atherosclerosis, and in combination with the most recent advances in new non-invasive imaging technologies, they have become essential tools to evaluate new therapeutic strategies, with which can forecast and prevent plaque rupture. Positron emission tomography (PET)/computed tomography imaging is currently used for plaque visualisation in clinical and pre-clinical cardiovascular research, albeit with significant limitations. However, the combination of PET and magnetic resonance imaging (MRI) technologies is still the best option available today, as combined PET/MRI scans provide simultaneous data acquisition together with high quality anatomical information, sensitivity and lower radiation exposure for the patient. The coming years may represent a new era for the implementation of PET/MRI in clinical practice, but first, clinically efficient attenuation correction algorithms and research towards multimodal reagents and safety issues should be validated at the preclinical level.

Acoustic characterization of echogenic liposomes: frequency-dependent attenuation and backscatter

Ultrasound contrast agents (UCAs) are used clinically to aid detection and diagnosis of abnormal blood flow or perfusion. Characterization of UCAs can aid in the optimization of ultrasound parameters for enhanced image contrast. In this study echogenic liposomes (ELIPs) were characterized acoustically by measuring the frequency-dependent attenuation and backscatter coefficients at frequencies between 3 and 30 MHz using a broadband pulse-echo technique. The experimental methods were initially validated by comparing the attenuation and backscatter coefficients measured from 50-μm and 100-μm polystyrene microspheres with theoretical values. The size distribution of the ELIPs was measured and found to be polydisperse, ranging in size from 40 nm to 6 μm in diameter, with the highest number observed at 65 nm. The ELIP attenuation coefficients ranged from 3.7  ±  1.0 to 8.0  ±  3.3 dB/cm between 3 and 25 MHz. The backscatter coefficients were 0.011  ±  0.006 (cm str)(-1) between 6 and 9 MHz and 0.023 ± 0.006 (cm str)(-1) between 13 and 30 MHz. The measured scattering-to-attenuation ratio ranged from 8% to 22% between 6 and 25 MHz. Thus ELIPs can provide enhanced contrast over a broad range of frequencies and the scattering properties are suitable for various ultrasound imaging applications including diagnostic and intravascular ultrasound.

The role of optical coherence tomography in vascular medicine

Optical coherence tomography (OCT) is an emerging imaging modality that provides high-resolution, microstructural information on atherosclerotic plaques in biological systems. Intracoronary OCT can identify thin-cap fibroatheroma and other vulnerable plaques that may be responsible for acute coronary events. These characteristics make OCT helpful in guiding coronary management and interventions, including stent apposition and early identification of procedure-related complications. OCT is being assessed for its potential role in carotid plaque characterization and in the diagnosis of peripheral arterial atherosclerosis. Its current use in studying carotid and cerebral vasculature and in the diagnosis of peripheral arterial diseases is limited and ill defined, but it is finding increasing application in these areas. Its performance can be further improved by increasing the signal to noise ratio and by using dynamic focus tracking techniques. It can potentially be used to monitor the progression and regression of atherosclerosis in the coronary, cerebral and peripheral vasculature. New indications for its use in vascular medicine are emerging as its technology continues to improve over time.

Developing a novel rabbit model of atherosclerotic plaque rupture and thrombosis by cold-induced endothelial injury

Background

It is widely believed that atherosclerotic plaque rupture and subsequent thrombosis leads to acute coronary events and stroke. However, study of the mechanism and treatment of human plaque rupture is hampered by lack of a suitable animal model. Our aim was to develop a novel animal model of atherosclerotic plaque rupture to facilitate the study of human plaque disruption and thrombosis.

Methods

28 healthy male New Zealand white rabbits were randomly divided into two groups: rabbits in group A (n = 12) were only fed a high-fat diet for eight weeks; rabbits in group B (n = 16) underwent cold-induced endothelial injury with liquid nitrogen, then were given a high-fat diet for eight weeks. After completion of the preparatory regimen, triggering of plaque rupture was attempted by local injection of liquid nitrogen in both groups.

Results

All rabbits in group B had disrupted plaques or rupture-driven occlusive thrombus formation, but none in group A showed any effects. More importantly, the cold-induced plaques in our model were reminiscent of human atherosclerotic plaques in terms of architecture, cellular composition, growth characteristics, and patterns of lipid accumulation.

Conclusion

We successfully developed a novel rabbit model of atherosclerotic plaque rupture and thrombosis, which is simple, fast, inexpensive, and reproducible, and has a low mortality and a high yield of triggering. This model will allow us to better understand the mechanism of human plaque rupture and also to develop plaque-stabilizing therapies.

Assessment on the Prevention of Progression by Rosiglitazone on Atherosclerosis in diabetes patients with Cardiovascular History (APPROACH): study design and baseline characteristics

BACKGROUND

Rosiglitazone, a thiazolidinedione, has effects on insulin sensitivity and cardiovascular risk factors that may favorably impact the progression of coronary atherosclerosis.

METHODS

APPROACH is a double-blind randomized clinical trial comparing the effects of the insulin sensitizer rosiglitazone with the insulin secretagogue glipizide on the progression of coronary atherosclerosis. Patients with type 2 diabetes and coronary artery disease undergoing clinically indicated coronary angiography or percutaneous coronary intervention are randomized to receive rosiglitazone or glipizide for 18 months using a titration algorithm designed to provide comparable glycemic control between treatment groups. The primary end point is change in percent atheroma volume from baseline to study completion in a nonintervened coronary artery, as measured by intravascular ultrasound. Cardiovascular events are adjudicated by an end point committee.

RESULTS

A total of 672 patients were randomized. The mean age was 61 years, hemoglobin A(1c) (HbA(1c)) 7.2%, body mass index 29.5 kg/m(2), and median duration of diabetes 4.8 years. At baseline, approximately half of the participants were receiving oral antidiabetic monotherapy (53.9%) with 27.5% receiving dual combination therapy and 17.9% treated with diet and exercise alone. Approximately two thirds of the participants (68%) had dyslipidemia, 79.9% hypertension, and 24% prior myocardial infarction.

CONCLUSIONS

APPROACH has fully enrolled a high-risk patient population and will compare the glucose-independent effects of rosiglitazone and glipizide on the progression of coronary atherosclerosis, as well as provide additional data on the cardiovascular safety of rosiglitazone in patients with type 2 diabetes and coronary artery disease.

Assessment of coronary plaque morphology by contrast-enhanced computed tomographic angiography: comparison with intravascular ultrasound

BACKGROUND

Computed tomographic (CT) angiography provides accurate noninvasive assessment for coronary artery stenosis. The ability of CT angiography to determine plaque morphology remains unclear.

METHODS

Twelve patients undergoing intravascular ultrasound for clinical indications underwent CT angiography for the evaluation of plaque morphology. Plaque morphology was classified as (1) soft, (2) fibrous, (3) fibrocalcific or (4) calcific. CT angiography data sets were evaluated for the presence and morphology of plaque in the coronary artery segments. The results were blindly compared with intravascular ultrasound results on a segment by segment basis using angiographic landmarks.

RESULTS

Fifty-nine coronary segments were analyzed; 10 segments were normal and 49 contained plaque. Plaque morphology by intravascular ultrasound was soft in 12 segments, fibrous in four, fibrocalcific in 29 and calcific in four. To determine coronary segments with any plaque, CT angiography had a sensitivity of 100% (49 of 49) and specificity of 90% (9 of 10). To determine plaque morphology as calcified (fibrocalcific and calcific) versus noncalcified (soft and fibrous), CT angiography had a sensitivity of 100% (33 of 33) and a specificity of 94% (15 of 16). Overall accuracy for CT angiography to determine plaque morphology was 92% (54 of 59). CT angiography density values (Hounsfield units, mean+/-standard deviation) were significantly different for each plaque morphology: soft 23+/-71, fibrous 108+/-79, fibrocalcific 299+/-112 and calcific 404+/-264 (P<0.0001).

CONCLUSIONS

CT angiography accurately characterized plaque morphology and may be a useful tool in noninvasive evaluation of plaque morphology during drug therapy trials.