Serial contrast-enhanced cardiac magnetic resonance imaging demonstrates regression of hyperenhancement within the coronary artery wall in patients after acute myocardial infarction

Contrast-enhanced cardiovascular magnetic resonance imaging of coronary vessel wall: state of art

Coronary wall imaging by cardiovascular magnetic resonance (CMR) emerges as a promising method to detect vascular injury and remodeling directly within the coronary vascular wall. In this review, the current evidence on coronary wall enhancement using CMR is presented and summarized, with particular focus on its ability to detect inflammation in atherosclerosis, Takayasu's arteritis, acute coronary syndromes and immune-mediated inflammatory vasculitides. The authors review the possible mechanisms of coronary wall contrast enhancement on CMR and discuss the technical considerations and limitations. Lastly, the potential clinical applications and possibilities for future research are proposed.

High-intensity signals in coronary plaques on noncontrast T1-weighted magnetic resonance imaging as a novel determinant of coronary events

OBJECTIVES

The aim of this study was to determine whether coronary high-intensity plaques (HIPs) visualized by noncontrast T1-weighted imaging can predict future coronary events.

BACKGROUND

Coronary HIPs are associated with characteristics of vulnerable plaques, including positive remodeling, lower Hounsfield units, and ultrasound attenuation. However, it remains unclear whether the presence of HIPs is associated with increased risk for coronary events.

METHODS

The signal intensity of coronary plaques was prospectively examined in 568 patients with suspected or known coronary artery disease (CAD) who underwent noncontrast T1-weighted imaging to determine the plaque-to-myocardium signal intensity ratio (PMR).

RESULTS

During the follow-up period (median 55 months), coronary events were observed in 55 patients. Receiver-operating characteristic curve analysis identified a PMR of 1.4 as the optimal cutoff for predicting prognosis. Multivariate Cox regression analysis identified the presence of plaques with PMRs ≥1.4 as the significant independent predictor of coronary events (hazard ratio: 3.96; 95% confidence interval: 1.92 to 8.17; p < 0.001) compared with the presence of CAD (hazard ratio: 3.56; 95% confidence interval: 1.76 to 7.20; p < 0.001) and other traditional risk factors. Among the 4 groups based on PMR cutoff and the presence of CAD, coronary event-free survival was lowest in the group with PMRs ≥1.4 and CAD and highest in the group with PMRs <1.4 but no CAD. Importantly, the group with PMRs ≥1.4 and no CAD had an intermediate rate of coronary events, similar to the group with PMRs <1.4 and CAD.

CONCLUSIONS

HIPs identified in a noninvasive, quantitative manner are significantly associated with coronary events and may thus represent a novel predictive factor.

MR imaging of the arterial vessel wall: molecular imaging from bench to bedside

Cardiovascular diseases remain the leading cause of morbidity and mortality in the Western world and developing countries. In clinical practice, in vivo characterization of atherosclerotic lesions causing myocardial infarction, ischemic stroke, and other complications remains challenging. Imaging methods, limited to the assessment luminal stenosis, are the current reference standard for the assessment of clinically significant coronary and carotid artery disease and the guidance of treatment. These techniques do not allow distinction between stable and potentially vulnerable atherosclerotic plaque. Magnetic resonance (MR) imaging is a modality well suited for visualization and characterization of the relatively thin arterial vessel wall, because it allows imaging with high spatial resolution and excellent soft-tissue contrast. In clinical practice, atherosclerotic plaque components of the carotid artery and aorta may be differentiated and characterized by using unenhanced vessel wall MR imaging. Additional information can be gained by using clinically approved nonspecific contrast agents. With the advent of targeted MR contrast agents, which enhance specific molecules or cells, pathologic processes can be visualized at a molecular level with high spatial resolution. In this article, the pathophysiologic changes of the arterial vessel wall underlying the development of atherosclerosis will be first reviewed. Then basic principles and properties of molecular MR imaging contrast agents will be introduced. Additionally, recent advances in preclinical molecular vessel wall imaging will be reviewed. Finally, the clinical feasibility of arterial vessel wall imaging at unenhanced and contrast material-enhanced MR imaging of the aortic, carotid, and coronary vessel wall will be discussed.

The emerging role of cardiovascular magnetic resonance in the evaluation of Kawasaki disease

Kawasaki disease (KD) is a vasculitis affecting the coronary and systemic arteries. Myocardial inflammation is also a common finding in KD post-mortem evaluation during the acute phase of the disease. Coronary artery aneurysms (CAAs) develop in 15-25% of untreated children. Although 50-70% of CAAs resolve spontaneously 1-2 years after the onset of KD, the remaining unresolved CAAs can develop stenotic lesions at either their proximal or distal end and can develop thrombus formation leading to ischemia and/or infarction. Cardiovascular magnetic resonance (CMR) has the ability to perform non-invasive and radiation-free evaluation of the coronary artery lumen. Recently tissue characterization of the coronary vessel wall was provided by CMR. It can also image myocardial inflammation, ischemia and fibrosis. Therefore CMR offers important clinical information during the acute and chronic phase of KD. In the acute phase, it can identify myocardial inflammation, microvascular disease, myocardial infarction, deterioration of left ventricular function, changes of the coronary artery lumen and changes of the coronary artery vessel wall. During the chronic phase, CMR imaging might be of value for risk stratification and to guide treatment.

Magnetic resonance coronary angiography: where are we today?

Although cardiovascular magnetic resonance allows the non-invasive and radiation free visualization of both the coronary arteries and veins, coronary vessel wall imaging is still undergoing technical development to improve diagnostic quality. Assessment of the coronary vessels is a valuable addition to the analysis of cardiac function, cardiac anatomy, viability and perfusion which magnetic resonance imaging reliably allows. However, cardiac and respiratory motion and the small size of the coronary vessels present a challenge and require several technical solutions for image optimization. Furthermore, the acquisition protocols need to be adapted to the specific clinical question. This review provides an update on the current clinical applications of cardiovascular magnetic resonance coronary angiography, recent technical advances and describes the acquisition protocols in use.

Delayed contrast-enhanced MRI of the coronary artery wall in takayasu arteritis

BACKGROUND

Takayasu arteritis (TA) is a rare form of chronic inflammatory granulomatous arteritis of the aorta and its major branches. Late gadolinium enhancement (LGE) with magnetic resonance imaging (MRI) has demonstrated its value for the detection of vessel wall alterations in TA. The aim of this study was to assess LGE of the coronary artery wall in patients with TA compared to patients with stable CAD.

METHODS

We enrolled 9 patients (8 female, average age 46±13 years) with proven TA. In the CAD group 9 patients participated (8 male, average age 65±10 years). Studies were performed on a commercial 3T whole-body MR imaging system (Achieva; Philips, Best, The Netherlands) using a 3D inversion prepared navigator gated spoiled gradient-echo sequence, which was repeated 34-45 minutes after low-dose gadolinium administration.

RESULTS

No coronary vessel wall enhancement was observed prior to contrast in either group. Post contrast, coronary LGE on IR scans was detected in 28 of 50 segments (56%) seen on T2-Prep scans in TA and in 25 of 57 segments (44%) in CAD patients. LGE quantitative assessment of coronary artery vessel wall CNR post contrast revealed no significant differences between the two groups (CNR in TA: 6.0±2.4 and 7.3±2.5 in CAD; p = 0.474).

CONCLUSION

Our findings suggest that LGE of the coronary artery wall seems to be common in patients with TA and similarly pronounced as in CAD patients. The observed coronary LGE seems to be rather unspecific, and differentiation between coronary vessel wall fibrosis and inflammation still remains unclear.

Cardiovascular magnetic resonance imaging in ischemic heart disease

Ischemic heart disease is the most frequent etiology for cardiovascular morbidity and mortality. Early detection and accurate monitoring are essential to guide optimal patient treatment and assess the individual's prognosis. In this regard, cardiovascular magnetic resonance (CMR), which entered the arena of noninvasive cardiovascular imaging over the past two decades, became a very important imaging modality, mainly due to its unique versatility. CMR has proven accuracy and is a robust technique for the assessment of myocardial function both at rest and during stress. It also allows stress perfusion analysis with high spatial and temporal resolution, and provides a means by which to differentiate tissue such as distinguishing between reversibly and irreversibly injured myocardium. In particular, the latter aspect is a unique benefit of CMR compared with other noninvasive imaging modalities such as echocardiography and nuclear medicine, and provides novel information concerning the presence, size, transmurality, and prognosis of myocardial infarction. This article is intended to provide the reader with an overview of the various applications of CMR for the assessment of ischemic heart disease from a clinical perspective.

Gadolinium-Based Contrast Agents for Vessel Wall Magnetic Resonance Imaging (MRI) of Atherosclerosis

Cardiovascular disease due to atherosclerosis is the number one killer in the Western world, and threatens to become the major cause of morbidity and mortality worldwide. It is therefore paramount to develop non-invasive methods for the detection of high-risk, asymptomatic individuals before the onset of clinical symptoms or events. In the recent past, great strides have been made in the understanding of the pathological mechanisms involved in the atherosclerotic cascade down to the molecular details. This has allowed the development of contrast agents that can aid in the in vivo characterization of these processes. Gadolinium chelates are among the contrast media most commonly used in MR imaging. Originally used for MR angiography for the detection and quantification of vascular stenosis, more recently they have been applied to improve characterization of atherosclerotic plaques. In this manuscript, we will briefly review gadolinium-chelates (Gd) based contrast agents for non-invasive MR imaging of atherosclerosis. We will first describe Gd-based non-targeted FDA approved agents, used routinely in clinical practice for the evaluation of neovascularization in other diseases. Secondly, we will describe non-specific and specific targeted contrast agents, which have great potential for dissecting specific biological processes in the atherosclerotic cascade. Lastly, we will briefly compare Gd-based agents to others commonly used in MRI and to other imaging modalities.

Intracranial atherosclerotic plaque enhancement in patients with ischemic stroke

BACKGROUND AND PURPOSE

Inflammation of an atherosclerotic plaque is a well-known risk factor in the development of ischemic stroke and myocardial infarction. MR imaging is capable of characterizing inflammation by assessing plaque enhancement in both extracranial carotid arteries and coronary arteries. Our goal was to determine whether enhancing intracranial atherosclerotic plaque was present in the vessel supplying the territory of infarction by using high-resolution vessel wall MR imaging.

MATERIALS AND METHODS

High-resolution vessel wall 3T MR imaging studies performed in 29 patients with ischemic stroke and intracranial vascular stenoses were reviewed for presence and strength of plaque enhancement.

RESULTS

Sixteen patients were studied during the acute phase (<4 weeks from acute stroke), 5 patients in the subacute phase (4-12 weeks), and 8 patients in the chronic phase (>12 weeks) of the ischemic injury. In all of the acute phase patients, atherosclerotic plaque in the vessel supplying the stroke territory demonstrated strong enhancement. There was a trend of decreasing enhancement as the time of imaging relative to the ischemic event increased.

CONCLUSIONS

Strong pathologic enhancement of intracranial atherosclerotic plaque was seen in all patients imaged within 4 weeks of ischemic stroke in the vessel supplying the stroke territory. The strength and presence of enhancement of the atherosclerotic plaque decreased with increasing time after the ischemic event. These findings suggest a relationship between enhancing intracranial atherosclerotic plaque and acute ischemic stroke.

Cardiovascular magnetic resonance by non contrast T1-mapping allows assessment of severity of injury in acute myocardial infarction

BACKGROUND

Current cardiovascular magnetic resonance (CMR) methods, such as late gadolinium enhancement (LGE) and oedema imaging (T2W) used to depict myocardial ischemia, have limitations. Novel quantitative T1-mapping techniques have the potential to further characterize the components of ischemic injury. In patients with myocardial infarction (MI) we sought to investigate whether state-of the art pre-contrast T1-mapping (1) detects acute myocardial injury, (2) allows for quantification of the severity of damage when compared to standard techniques such as LGE and T2W, and (3) has the ability to predict long term functional recovery.

METHODS

3T CMR including T2W, T1-mapping and LGE was performed in 41 patients [of these, 78% were ST elevation MI (STEMI)] with acute MI at 12-48 hour after chest pain onset and at 6 months (6M). Patients with STEMI underwent primary PCI prior to CMR. Assessment of acute regional wall motion abnormalities, acute segmental damaged fraction by T2W and LGE and mean segmental T1 values was performed on matching short axis slices. LGE and improvement in regional wall motion at 6M were also obtained.

RESULTS

We found that the variability of T1 measurements was significantly lower compared to T2W and that, while the diagnostic performance of acute T1-mapping for detecting myocardial injury was at least as good as that of T2W-CMR in STEMI patients, it was superior to T2W imaging in NSTEMI. There was a significant relationship between the segmental damaged fraction assessed by either by LGE or T2W, and mean segmental T1 values (P < 0.01). The index of salvaged myocardium derived by acute T1-mapping and 6M LGE was not different to the one derived from T2W (P = 0.88). Furthermore, the likelihood of improvement of segmental function at 6M decreased progressively as acute T1 values increased (P < 0.0004).

CONCLUSIONS

In acute MI, pre-contrast T1-mapping allows assessment of the extent of myocardial damage. T1-mapping might become an important complementary technique to LGE and T2W for identification of reversible myocardial injury and prediction of functional recovery in acute MI.

In vivo assessment of intraplaque and endothelial fibrin in ApoE(-/-) mice by molecular MRI

OBJECTIVE

Molecular magnetic resonance imaging (MRI) has emerged as a promising non-invasive modality to characterize atherosclerotic vessel wall changes on a morphological and molecular level. Intraplaque and endothelial fibrin has recently been recognized to play an important role in the progression of atherosclerosis. This study aimed to investigate the feasibility of intraplaque and endothelial fibrin detection using a fibrin-targeted contrast-agent, FTCA (EPIX Pharmaceuticals, Lexington, MA), in a mouse model of atherosclerosis.

METHODS

Male apolipoproteinE-knockout mice (ApoE(-/-)) were fed a high fat diet (HFD) for one to three months. MRI of the brachiocephalic artery was performed prior to and 90 min after the administration of FTCA (n=8 per group). Contrast to noise ratios (CNR) and longitudinal relaxation rates (R1) of plaques were determined and compared to ex vivo fibrin density measurements on immunohistological sections stained with a fibrin-specific antibody and gadolinium concentrations measured by inductively coupled mass spectroscopy (ICP-MS).

RESULTS

Molecular MRI after FTCA administration demonstrated a significant increase (p<0.05) in contrast agent uptake in brachiocephalic artery plaques. In vivo CNR measurements were in good agreement with ex vivo fibrin density measurements on immunohistochemistry (y=2.4x+11.3, R(2)=0.82) and ICP-MS (y=0.95x+7.1, R(2)=0.70). Late stage atherosclerotic plaques displayed the strongest increase in CNR, R1, ex vivo fibrin staining and gadolinium concentration (p<0.05).

CONCLUSION

This study demonstrated the feasibility of intraplaque and endothelial fibrin imaging using FTCA. Direct in vivo fibrin detection and quantification could be useful for characterization and staging of coronary and carotid atherosclerotic lesions, which may aid diagnosis and intervention.

Coronary imaging with cardiovascular magnetic resonance: current state of the art

Cardiovascular magnetic resonance allows noninvasive and radiation-free visualization of both the coronary arteries and veins, with the advantage of an integrated assessment of cardiac function, viability, perfusion, and anatomy. This combined approach provides valuable integrated information for patients with coronary artery disease and patients undergoing cardiac resynchronization therapy. Moreover, magnetic resonance offers the possibility of coronary vessel wall imaging, therefore assessing the anatomy and pathology of the normal and diseased coronary vessels noninvasively. Coronary magnetic resonance angiography is challenging because of cardiac and respiratory motion and the small size and tortuous path of the coronary vessels. Several technical solutions have been developed to optimize the acquisition protocol to the specific clinical question. The aims of this review are to provide an update on current technical improvements in coronary magnetic resonance angiography, including how to optimize the acquisition protocols, and to give an overview of its current clinical application.

Noninvasive detection of coronary artery wall thickening with age in healthy subjects using high resolution MRI with beat-to-beat respiratory motion correction

PURPOSE

To demonstrate coronary artery wall thickening with age in a small healthy cohort using a highly efficient, reliable, and reproducible high-resolution MR technique.

MATERIALS AND METHODS

A 3D cross-sectional MR vessel wall images (0.7 × 0.7 × 3 mm resolution) with retrospective beat-to-beat respiratory motion correction (B2B-RMC) were obtained in the proximal right coronary artery of 21 healthy subjects (age, 22-62 years) with no known cardiovascular disease. Lumen and outer wall (lumen + vessel wall) areas were measured in one central slice from each subject and average wall thickness and wall area/outer wall area ratio (W/OW) calculated.

RESULTS

Imaging was successful in 18 (86%) subjects with average respiratory efficiency 99.3 ± 1.7%. Coronary vessel wall thickness and W/OW significantly correlate with subject age, increasing by 0.088 mm and 0.031 per decade respectively (R = 0.53, P = 0.024 and R = 0.48, P = 0.046). No relationship was found between lumen area and vessel wall thickness (P = NS), but outer wall area increased significantly with vessel wall thickness at 19 mm(2) per mm (P = 0.046). This is consistent with outward vessel wall remodeling.

CONCLUSION

Despite the small size of our healthy cohort, using high-resolution MR imaging and B2B-RMC, we have demonstrated increasing coronary vessel wall thickness and W/OW with age. The results obtained are consistent with outward vessel wall remodeling.

Detection of intracoronary thrombus by magnetic resonance imaging in patients with acute myocardial infarction

BACKGROUND

Persistent intracoronary thrombus after plaque rupture is associated with an increased risk of subsequent myocardial infarction and mortality. Coronary thrombus is usually visualized invasively by x-ray coronary angiography. Non-contrast-enhanced T1-weighted magnetic resonance (MR) imaging has been useful for direct imaging of carotid thrombus and intraplaque hemorrhage by taking advantage of the short T1 of methemoglobin present in acute thrombus and intraplaque hemorrhage. The aim of this study was to investigate the use of non-contrast-enhanced MR for direct thrombus imaging (MRDTI) in patients with acute myocardial infarction.

METHODS AND RESULTS

Eighteen patients (14 men; age, 61±9 years) underwent MRDTI within 24 to 72 hours of presenting with an acute coronary syndrome before invasive x-ray coronary angiography; MRDTI was performed with a T1-weighted, 3-dimensional, inversion-recovery black-blood gradient-echo sequence without contrast administration. Ten patients were found to have intracoronary thrombus on x-ray coronary angiography (left anterior descending, 4; left circumflex, 2; right coronary artery, 4; and right coronary artery-posterior descending artery, 1), and 8 had no visible thrombus. We found that MRDTI correctly identified thrombus in 9 of 10 patients (sensitivity, 91%; posterior descending artery thrombus not detected) and correctly classified the control group in 7 of 8 patients without thrombus formation (specificity, 88%). The contrast-to-noise ratio was significantly greater in coronary segments containing thrombus (n=10) compared with those without visible thrombus (n=131; mean contrast-to-noise ratio, 15.9 versus 2.6; P<0.001).

CONCLUSION

Use of MRDTI allows selective visualization of coronary thrombus in a patient population with a high probability of intracoronary thrombosis.

Congenital heart disease: cardiovascular MR imaging by using an intravascular blood pool contrast agent

PURPOSE

To compare the image quality and diagnostic performance of a contrast agent-specific inversion-recovery (IR) steady-state free precession (SSFP) magnetic resonance (MR) imaging sequence performed by using an intravascular contrast agent (gadofosveset trisodium) with those of a commonly used T2-prepared SSFP sequence performed by using an extravascular (gadopentetate dimeglumine) and an intravascular (gadofosveset trisodium) contrast agent in patients with congenital heart disease (CHD).

MATERIALS AND METHODS

The local ethics committee and the United Kingdom Medicines and Healthcare products Regulatory Agency approved this study. Patient informed consent was obtained. Twenty-three patients with CHD were examined by using a 1.5-T MR imaging unit and a 32-channel coil. Gadopentetate dimeglumine and gadofosveset trisodium were used in the same patient on consecutive days. Vessel wall sharpness, contrast-to-noise ratios (CNRs), image quality, and diagnostic performance achieved by using the IR SSFP sequence with gadofosveset trisodium were compared with those achieved by using the T2-prepared SSFP sequence with gadopentetate dimeglumine and gadofosveset trisodium and with those achieved at respective contrast material-enhanced MR angiographic examinations. The Wilcoxon rank sum test was used to compare categoric variables; t tests were used to compare continuous variables.

RESULTS

Use of the IR SSFP sequence with gadofosveset trisodium significantly improved vessel wall sharpness, CNRs, and image quality (P < .05 for all) for all investigated intra- and extracardiac structures compared with the T2-prepared SSFP sequence with gadopentetate dimeglumine and gadofosveset trisodium and the respective contrast-enhanced MR angiographic examinations. With use of the IR SSFP sequence with gadofosveset trisodium, new, unsuspected diseases (five [22%] of 23) were diagnosed, while other diseases could be excluded (15 [65%] of 23). Information available from echocardiography (n = 23), conventional angiography (n = 4), and/or surgery (n = 1) confirmed all diagnoses.

CONCLUSION

IR SSFP with gadofosveset trisodium improved image quality and diagnostic performance, allowing a more accurate and complete assessment of cardiovascular anatomy in patients with CHD compared with T2-prepared SSFP with gadopentetate dimeglumine and gadofosveset trisodium and respective contrast-enhanced MR angiographic examinations.

Assessment of atherosclerotic plaque burden with an elastin-specific magnetic resonance contrast agent

Atherosclerosis and its consequences remain the main cause of mortality in industrialized and developing nations. Plaque burden and progression have been shown to be independent predictors for future cardiac events by intravascular ultrasound. Routine prospective imaging is hampered by the invasive nature of intravascular ultrasound. A noninvasive technique would therefore be more suitable for screening of atherosclerosis in large populations. Here we introduce an elastin-specific magnetic resonance contrast agent (ESMA) for noninvasive quantification of plaque burden in a mouse model of atherosclerosis. The strong signal provided by ESMA allows for imaging with high spatial resolution, resulting in accurate assessment of plaque burden. Additionally, plaque characterization by quantifying intraplaque elastin content using signal intensity measurements is possible. Changes in elastin content and the high abundance of elastin during plaque development, in combination with the imaging properties of ESMA, provide potential for noninvasive assessment of plaque burden by molecular magnetic resonance imaging (MRI).

CMR assessment of endothelial damage and angiogenesis in porcine coronary arteries using gadofosveset

BACKGROUND

Endothelial damage and angiogenesis are essential for atherosclerotic plaque development and destabilization. We sought to examine whether contrast enhanced cardiovascular magnetic resonance (CMR) using gadofosveset could show endothelial damage and neovessel formation in balloon injured porcine coronary arteries.

METHODS AND RESULTS

Data were obtained from seven pigs that all underwent balloon injury of the left anterior descending coronary artery (LAD) to induce endothelial damage and angiogenesis. Between one - 12 days (average four) after balloon injury, in vivo and ex vivo T1-weighted coronary CMR was performed after intravenous injection of gadofosveset. Post contrast, CMR showed contrast enhancement of the coronary arteries with a selective and time-dependent average expansion of the injured LAD segment area of 45% (p = 0.04; CI95 = [15%-75%]), indicating local extravasation of gadofosveset. Vascular and perivascular extravasation of albumin (marker of endothelial leakiness) and gadofosveset was demonstrated with agreement between Evans blue staining and ex vivo CMR contrast enhancement (p = 0.026). Coronary MRI contrast enhancement and local microvessel density determined by microscopic examination correlated (ρ = 0.82, p < 0.001).

CONCLUSION

Contrast enhanced coronary CMR with gadofosveset can detect experimentally induced endothelial damage and angiogenesis in the porcine coronary artery wall.

Quantitative cardiovascular magnetic resonance for molecular imaging

Cardiovascular magnetic resonance (CMR) molecular imaging aims to identify and map the expression of important biomarkers on a cellular scale utilizing contrast agents that are specifically targeted to the biochemical signatures of disease and are capable of generating sufficient image contrast. In some cases, the contrast agents may be designed to carry a drug payload or to be sensitive to important physiological factors, such as pH, temperature or oxygenation. In this review, examples will be presented that utilize a number of different molecular imaging quantification techniques, including measuring signal changes, calculating the area of contrast enhancement, mapping relaxation time changes or direct detection of contrast agents through multi-nuclear imaging or spectroscopy. The clinical application of CMR molecular imaging could offer far reaching benefits to patient populations, including early detection of therapeutic response, localizing ruptured atherosclerotic plaques, stratifying patients based on biochemical disease markers, tissue-specific drug delivery, confirmation and quantification of end-organ drug uptake, and noninvasive monitoring of disease recurrence. Eventually, such agents may play a leading role in reducing the human burden of cardiovascular disease, by providing early diagnosis, noninvasive monitoring and effective therapy with reduced side effects.

Rationale and approach to evaluation of the impact of medical therapies on progression of atherosclerosis with arterial wall imaging

BACKGROUND

Despite the benefit of medical therapies, there remains a substantial residual risk of cardiovascular events. Atherosclerosis imaging has been used to assess new therapies.

SCOPE

A selective review of current imaging techniques used to evaluate novel anti-atherosclerotic therapies.

FINDINGS

Noninvasive and invasive arterial wall imaging permits characterization of the quantity and composition of atherosclerotic plaque. Serial imaging enables assessment of the impact of therapies on the natural history of disease progression.

CONCLUSION

Both noninvasive and invasive imaging modalities can be used in development programs to provide an early assessment of the impact of novel anti-atherosclerotic agents.

Imaging of the unstable plaque: how far have we got?

Rupture of unstable plaques may lead to myocardial infarction or stroke and is the leading cause of morbidity and mortality in western countries. Thus, there is a clear need for identifying these vulnerable plaques before the rupture occurs. Atherosclerotic plaques are a challenging imaging target as they are small and move rapidly, especially in the coronary tree. Many of the currently available imaging tools for clinical use still provide minimal information about the biological characteristics of plaques, because they are limited with respect to spatial and temporal resolution. Moreover, many of these imaging tools are invasive. The new generation of imaging modalities such as magnetic resonance imaging, nuclear imaging such as positron emission tomography and single photon emission computed tomography, computed tomography, fluorescence imaging, intravascular ultrasound, and optical coherence tomography offer opportunities to overcome some of these limitations. This review discusses the potential of these techniques for imaging the unstable plaque.