Nonobstructive Atherosclerotic Plaque Research Articles

Coronary CT angiography and coronary atherosclerosis : Where do we stand today?

Cardiac computed tomography (CT) has made substantial progress in recent years. The main field of application is CT coronary angiography for visualization of the coronary arteries and for the detection and exclusion of coronary artery stenosis. This has been included in international guidelines for the management of stable coronary artery disease or chronic coronary syndrome as well as for the diagnostic work-up of patients with acute chest pain; however, it must be taken into account that the diagnostic validity is only sufficiently high when the image quality is good and therefore alternative diagnostic procedures should be included in patients where an unrestricted good image quality is not to be expected. The fact that CT angiography enables the detection not only of coronary stenosis but also of nonobstructive atherosclerotic plaque is interesting for the estimation of the risk of atherosclerotic events. It is practically certain that in the absence of detectable atherosclerotic plaque in CT angiography, statin treatment does not lower the risk of atherosclerotic events. To what extent CT is suitable to provide indications for statin treatment and the threshold for which the presence of nonobstructive plaque should prompt initiation of statin treatment are currently the subject of intensive research.

Myocardial infarction with nonobstructive coronary arteries: from pathophysiology to therapeutic strategies.

Myocardial infarction with nonobstructive coronary arteries (MINOCA) is a heterogeneous group of clinical entities characterized by clinical evidence of acute myocardial infarction (AMI) with normal or near-normal coronary arteries on coronary angiography (stenosis < 50%) and without an over the alternative diagnosis for the acute presentation. Its prevalence ranges from 6% to 11% among all patients with AMI, with a predominance of young, nonwhite females with fewer traditional risks than those with an obstructive coronary artery disease (MI-CAD). MINOCA can be due to either epicardial causes such as rupture or fissuring of unstable nonobstructive atherosclerotic plaque, coronary artery spasm, spontaneous coronary dissection and cardioembolism in-situ or microvascular causes. Besides, also type-2 AMI due to supply-demand mismatch and Takotsubo syndrome must be considered as a possible MINOCA cause. Because of the complex etiology and a limited amount of evidence, there is still some confusion around the management and treatment of these patients. Therefore, the key focus of this condition is to identify the underlying individual mechanisms to achieve patient-specific treatments. Clinical history, electrocardiogram, echocardiography, and coronary angiography represent the first-level diagnostic investigations, but coronary imaging with intravascular ultrasound and optical coherent tomography, coronary physiology testing, and cardiac magnetic resonance imaging offer additional information to understand the underlying cause of MINOCA. Although the prognosis is slightly better compared with MI-CAD patients, MINOCA is not always benign and depends on the etiopathology. This review analyzes all possible pathophysiological mechanisms that could lead to MINOCA and provides the most specific and appropriate therapeutic approach in each scenario.

Relationship Between Coronary Artery Calcium and Atherosclerosis Progression Among Patients With Suspected Coronary Artery Disease

BackgroundAmong symptomatic patients, it remains unclear whether a coronary artery calcium (CAC) score alone is sufficient or misses a sizeable burden and progressive risk associated with obstructive and nonobstructive atherosclerotic plaque. ObjectivesAmong patients with low to high CAC scores, our aims were to quantify co-occurring obstructive and nonobstructive noncalcified plaque and serial progression of atherosclerotic plaque volume. MethodsA total of 698 symptomatic patients with suspected coronary artery disease (CAD) underwent serial coronary computed tomographic angiography (CTA) performed 3.5 to 4.0 years apart. Atherosclerotic plaque was quantified, including by compositional subgroups. Obstructive CAD was defined as ≥50% stenosis. Multivariate linear regression models were used to measure atherosclerotic plaque progression by CAC scores. Cox proportional hazard models estimated CAD event risk (median of 10.7 years of follow-up). ResultsAcross baseline CAC scores from 0 to ≥400, total plaque volume ranged from 30.4 to 522.4 mm3 (P < 0.001) and the prevalence of obstructive CAD increased from 1.4% to 49.1% (P < 0.001). Of those with a 0 CAC score, 97.9% of total plaque was noncalcified. Among patients with baseline CAC <100, nonobstructive CAD was prevalent (40% and 89% in CAC scores of 0 and 1-99), with plaque largely being noncalcified. On the follow-up coronary CTA, volumetric plaque growth (P < 0.001) and the development of new or worsening stenosis (P < 0.001) occurred more among patients with baseline CAC ≥100. Progression varied compositionally by baseline CAC scores. Patients with no CAC had disproportionate growth in noncalcified plaque, and for every 1 mm3 increase in calcified plaque, there was a 5.5 mm3 increase in noncalcified plaque volume. By comparison, patients with CAC scores of ≥400 exhibited disproportionate growth in calcified plaque with a volumetric increase 15.7-fold that of noncalcified plaque. There was a graded increase in CAD event risk by the CAC with rates from 3.3% for no CAC to 21.9% for CAC ≥400 (P < 0.001). ConclusionsCAC imperfectly characterizes atherosclerotic disease burden, but its subgroups exhibit pathogenic patterns of early to advanced disease progression and stratify long-term prognostic risk.

Innovative Approaches to Assess Intermediate Cardiovascular Risk Subjects: A Review From Clinical to Metabolomics Strategies.

Current risk stratification strategies for coronary artery disease (CAD) have low predictive value in asymptomatic subjects classified as intermediate cardiovascular risk. This is relevant because not all coronary events occur in individuals with traditional multiple risk factors. Most importantly, the first manifestation of the disease may be either sudden cardiac death or acute coronary syndrome, after rupture and thrombosis of an unstable non-obstructive atherosclerotic plaque, which was previously silent. The inaccurate stratification using the current models may ultimately subject the individual to excessive or insufficient preventive therapies. A breakthrough in the comprehension of the molecular mechanisms governing the atherosclerosis pathology has driven many researches toward the necessity for a better risk stratification. In this Review, we discuss how metabolomics screening integrated with traditional risk assessments becomes a powerful approach to improve non-invasive CAD subclinical diagnostics. In addition, this Review highlights the findings of metabolomics studies performed by two relevant analytical platforms in current use–mass spectrometry (MS) hyphenated to separation techniques and nuclear magnetic resonance spectroscopy (NMR) –and evaluates critically the challenges for further clinical implementation of metabolomics data. We also discuss the modern understanding of the pathophysiology of atherosclerosis and the limitations of traditional analytical methods. Our aim is to show how discriminant metabolites originated from metabolomics approaches may become promising candidate molecules to aid intermediate risk patient stratification for cardiovascular events and how these tools could successfully meet the demands to translate cardiovascular metabolic biomarkers into clinical settings.

Diagnostic and prognostic value of coronary artery calcium score of zero: is it time for guidelines to change?

Abstract Introduction Cardiac computed tomography (CT) use has progressively increased as the preferred initial test to rule out coronary artery disease (CAD) when clinical likelihood is low. Coronary artery calcium (CAC) detected by CT is a well-established marker for cardiovascular risk. However, it is not recommended for diagnosis of obstructive CAD. Absence of CAC, defined as an Agatston score of zero, has been associated to good prognosis despite underestimation of non-calcified plaques. Purpose To evaluate whether zero CAC score could help ruling out obstructive CAD in a safely manner. Methods Observational study based on a prospective database of patients (pts) referred to cardiac CT between 2017 and 2019. Pts with an Agatston score of zero were selected. Results We included 176 pts with zero CAC score and non-invasive coronary angiography performed. The median duration of follow-up was 23.9 months. Baseline characteristics of the population are shown in Table 1. In 117 pts (66.5%), cardiac CT was indicated as part of their chest pain evaluation. Mean age was 57.2 years old, 68.2% were women and only and 9.4% were active smokers. Normal coronary arteries were found in 173 pts (98.3%). Obstructive CAD, defined as ≥50% luminal diameter stenosis of a major vessel, was present in 1/176 (0.6%); while non-obstructive atherosclerotic plaques were found in 2 pts (1.1%). During follow-up, one patient died of out-of-hospital cardiac arrest. None either suffered from myocardial infarction or needed coronary revascularization. Conclusions In our cohort, a zero CAC score detected by cardiac CT rules out obstructive coronary artery disease in 98.3%, with only 1.7% of non-calcified atherosclerosis plaques and 0.6% of major adverse events. Although further research on this topic is needed, these results support the fact that non-invasive coronary angiography could be avoided in patients with low clinical likelihood of CAD and zero CAC score, facilitating the management of the increasing demand for coronary CT and reduction of radiation dose. Funding Acknowledgement Type of funding source: None

Stress Myocardial Perfusion Imaging vs Coronary Computed Tomographic Angiography for Diagnosis of Invasive Vessel-Specific Coronary Physiology

Stress imaging has been the standard for diagnosing functionally significant coronary artery disease. It is unknown whether novel, atherosclerotic plaque measures improve accuracy beyond coronary stenosis for diagnosing invasive fractional flow reserve (FFR) measurement. To compare the diagnostic accuracy of comprehensive anatomic (obstructive and nonobstructive atherosclerotic plaque) vs functional imaging measures for estimating vessel-specific FFR. Controlled clinical trial of diagnostic accuracy with a multicenter derivation-validation cohort of patients referred for nonemergent invasive coronary angiography. A total of 612 patients (64 [10] years; 30% women) with signs and symptoms suggestive of myocardial ischemia from 23 sites were included. Patients were recruited from 2014 to 2017. Data analysis began in August 2018. Patients underwent invasive coronary angiography with measurement of invasive FFR, coronary computed tomographic angiography (CCTA) quantification of atherosclerotic plaque and FFR by CT (FFR-CT), and semiquantitative scoring of rest/stress myocardial perfusion imaging (by magnetic resonance, positron emission tomography, or single photon emission CT). Multivariable generalized linear mixed models were derived and validated calculating the area under the receiver operating characteristics curve. The primary end point was invasive FFR of 0.80 or less. Of the 612 patients, the mean (SD) age was 64 (10) years, and 426 (69.9%) were men. An invasive FFR of 0.80 or less was measured in 26.5% of 1727 vessels. In the derivation cohort, CCTA vessel-specific factors associated with FFR 0.80 or less were stenosis severity, percentage of noncalcified atheroma volume, lumen volume, the number of lesions with high-risk plaque (≥2 of low attenuation plaque, positive remodeling, napkin ring sign, or spotty calcification), and the number of lesions with stenosis greater than 30%. Fractional flow reserve-CT was not additive to this model including stenosis and atherosclerotic plaque. Significant myocardial perfusion imaging predictors were the summed rest and difference scores. In the validation cohort, the areas under the receiver operating characteristic curve were 0.81 for CCTA vs 0.67 for myocardial perfusion imaging (P < .001). A comprehensive anatomic interpretation with CCTA, including quantification of obstructive and nonobstructive atherosclerotic plaque, was superior to functional imaging in the diagnosis of invasive FFR. Comprehensive CCTA measures improve prediction of vessel-specific coronary physiology more so than stress-induced alterations in myocardial perfusion. ClinicalTrials.gov Identifier: NCT02173275.

Evolving, innovating, and revolutionary changes in cardiovascular imaging: We’ve only just begun!

In this review, we highlight the need for innovation and creativity to reinvent the field of nuclear cardiology. Revolutionary ideas brought forth today are needed to create greater value in patient care and highlight the need for more contemporary evidence supporting the use of nuclear cardiology practices. We put forth discussions on the need for disruptive innovation in imaging-guided care that places the imager as a central force in care coordination. Value-based nuclear cardiology is defined as care that is both efficient and effective. Novel testing strategies that defer testing in lower risk patients are examples of the kind of innovation needed in today’s healthcare environment. A major focus of current research is the evolution of the importance of ischemia and the prognostic significance of non-obstructive atherosclerotic plaque and coronary microvascular dysfunction. Embracing novel paradigms, such as this, can aid in the development of optimal strategies for coronary disease management. We hope that our article will spurn the field toward greater innovation and focus on transformative imaging leading the way for new generations of novel cardiovascular care.

Prognosis of non-obstructive coronary plaques with high-risk CT morphology

Coronary computed tomography angiography (CTA) is an accurate non-invasive method for the detection of and especially ruling out obstructive coronary artery disease (CAD) in appropriately selected patients. After its arrival, it has become possible to evaluate both coronary anatomy and functional significance of stenosis non-invasively by combined or hybrid coronary CTA and myocardial perfusion imaging (MPI).1 Functionally significant CAD is currently the cornerstone for selection of further medical and invasive therapy,1 but the non-obstructive plaques are also common in patients referred for coronary CTA and might have significant implications for patients' prognosis.2 The majority of coronary thrombi and subsequent acute coronary syndromes (ACS) are caused by plaque rupture. Prototype of the rupture-prone plaque contains a large, lipid-rich necrotic core that is covered by a thin and inflamed fibrous cap, so-called thin-cap fibroatheroma (TCFA).3 The TCFA phenotype on radiofrequency intravascular ultrasound (IVUS virtual histology) imaging was associated with an increased risk of recurrent coronary events after an ACS in a prospective follow-up study.4 Of the events not related to the previous culprit lesion, most occurred at sites with TCFA, whereas the degree of stenosis was a poor predictor of plaque rupture as the average stenosis of culprit lesions at baseline was only 30%.4 The extent and composition of non-obstructive atherosclerotic plaque …

Unsuccessful treatment of accelerated hypertension and persistent hyperkinetic state in a haemodialysed patient with high-output arteriovenous fistula

The case we describe concerns a rapid progression of heart failure (HF) in a patient with hypertension crises (HC), haemodialysed (HD) with the use of a high-output arteriovenous fistula (AVF). The 48-year-old male with a body mass index of 19.27 kg/m2, renal insufficiency due to glomerulonephritis, treated with HD for two years (3 × 4.0 h/week), and with uncontrolled hypertension was admitted to the Military Institute of Medicine. On examination, reduced exercise tolerance, paroxysmal nocturnal dyspnoea and blood pressure (BP) 190/90 mm Hg were found. Laboratory tests revealed NT-pro B-type natriuretic peptide 302,009.0 pg/mL (n < 300.0). Echocardiography (ECHO) showed left ventricular (LV) hypertrophy (LV mass index [LVMI] 345.81 g/m2), enlarged LV diastolic diameter [LVDD] 7.15 cm), with slightly decreased ejection fraction (EF 49%), Doppler signs of elevated cardiac output (CO 15.05 L/min; cardiac index (CI) 8.91 L/min/m2), and pseudonormalised pattern of mitral inflow with elevated LV diastolic pressure (E/E’ 31). In ultrasonographic examination of left shoulder AVF, an aneurysmal expansion of the lumen from 5.5 mm to 35 mm (Fig. 1), and significantly increased flow up to 2,532 mL/min (Fig. 2) were detected. Cardiopulmonary recirculation rate (CPR) was 0.17. Computed tomography excluded renal artery stenosis. In polysomnography, heavy central apnoea with an apnoea/hypopnoea index of 35.4/h was found. In 48-h ambulatory BP monitoring (ABPM), BP was 162/95 mm Hg. Treatment of sleep apnoea was implemented by a continuous positive airway pressure device, but this did not improve BP control. Upon discharge from hospital, the patient was overtreated with eight hypotensive drugs. After a month, HC occurred (BP 220/120 mm Hg) associated with acute coronary syndrome without ST-segment elevation. Coronarography found non-obstructive atherosclerotic plaques. Because of the suspicion of hyperkinetic state related to a lack of BP control, AVF was narrowed by implanting a polytetrafluorethylene graft of 4 mm diameter (Fig. 3). Despite AVF flow being reduced to 1,400 mL/min, after two months another HC (BP 220/125 mm Hg) with pulmonary oedema was presented. The next HC took place three months later. Although ECHO showed features of LV hypertrophy regression (LVMI 335.62 g/m2), and significant decreases of CO (8.16 L/min) and CI (4.86 L/min/m2), a decrease of EF (40%) and an LV dilatation enlargement (LVDD 7.7 cm) were also observed. AVF flow increased up to 1,750 mL/min and significant CPR 0.21 was indicated. In 24-h ABPM, BP was 173/105 mm Hg. The hypotensive treatment used has been confirmed by experts and seems to be optimal and safe for the cardiovascular system. Probably, AVF banding was performed too late, and progression of HF and lack of BP control improvement were observed. In hyperkinetic AVF, blood flow exceeds 2,000 mL/min and CPR is over 0.2–0.3. Currently, in cases of difficulties in surgical AVF creation and the necessity of haemodialysotherapy termination as a result of a lack of vascular access, banding or closure of the AVF is a very rare event. However, in some cases, early ligation of AVF may be the only effective procedure, especially when there is rapid progression of HF.

PP-193 RESULTS OF PERCUTANEOUS CORONARY INTERVENTION FOR CHRONIC TOTAL OCCLUSIONS OF CORONARY ARTERIES WITH NOVEL EQUIPMENT: A SINGLE CENTER REPORT

positioning, the case was considered unsuitable for distal protection device. We proceeded with plain balloon angioplasty. A 4.0×16mm balloon was placed and inflated up to 16 atm. After angioplasty the angiographic result was acceptable with little residual haziness. IVUS study revealed organized thrombus adhered to the vessel wall and a non-obstructive atherosclerotic plaque (Figure 1D). The patient was put on medical therapy (aspirin + klopidogrel + coumadin) and discharged. Coronary angiography which was performed two months after the angioplasty revealed normal coronary arteries (Figure 1C). Discussion: Younger patients presenting with ACS generally have a larger thrombus burden in the absence of a significant coronary stenosis. In patients who have a large thrombus burden and no significant coronary stenosis, plain balloon angioplasty without stenting may provide an optimal solution saving the patient from issues related to stenting.

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

Association of Coronary Atherosclerosis Detected by Multislice Computed Tomography and Traditional Risk-Factor Assessment

Framingham risk score is an office-based tool used for long-term coronary heart disease risk stratification. Most acute coronary events occur in association with proximal nonobstructive atherosclerotic plaque. Multislice computed tomography detects both obstructive coronary artery disease (CAD) and proximal atherosclerotic plaque with high accuracy. The association of Framingham risk score with obstructive CAD and proximal atherosclerotic plaque was tested. Coronary multislice computed tomography was performed in 295 patients (61% men, mean age 54 +/- 13 years) without documented CAD referred for evaluation of cardiac symptoms. Framingham risk score was computed and patients were stratified according to 10-year risk (n = 213 [72%] low, n = 74 [25%] intermediate, and n = 8 [3%] high). Obstructive CAD was defined as > or =50% stenosis in > or =1 epicardial coronary artery. Proximal atherosclerotic plaque was defined as calcified or noncalcified plaque in the left main or proximal left anterior descending artery. In the low- and intermediate-Framingham risk score groups, there was a high frequency of proximal atherosclerotic plaque (44% and 75%) and obstructive CAD (16% and 34%), although both findings were more prevalent in the high-Framingham risk score group (63% for atherosclerotic plaque, 88% for obstructive CAD), respectively. Proximal atherosclerotic plaque was noncalcified in approximately 13 of patients. In women (n = 114) and younger (<55 years) patients (n = 148), most (93% and 91%, respectively) had a low Framingham risk score. There were 48 women and 51 younger patients with proximal atherosclerotic plaque, of whom only 40% (in each group) were on statin therapy. In conclusion, of patients with a low and intermediate Framingham risk score, a significant proportion had proximal atherosclerotic plaque or obstructive CAD.

Ephedrine-Induced Acute Myocardial Infarction in a Young Athlete: A Case of Thrombus Management

A case of acute myocardial infarction in a young athlete provoked by ephedrine abuse has been described in this study. An intracoronary thrombus found in the left anterior descending coronary artery at urgent angiography was successfully removed using the Pronto (Vascular Solutions, Minneapolis, Minnesota) aspiration catheter. The intravascular ultrasound examination performed thereafter showed a nonobstructive atherosclerotic plaque in the culprit artery; there was no evidence whatsoever of possible plaque disruption. The result of percutaneous coronary intervention was satisfactory, and no stent implantation was needed. The patient experienced no adverse events until his outpatient visit 3 months later.

Abstract 2594: Coronary Multidetector Computed Tomography in the Prognostic Assessment of Patients with Equivocal or Mildly Abnormal Non-Invasive Cardiac Stress Tests

Background: Patients with low or moderate pre-test probability of significant coronary artery disease (CAD) and equivocal or mildly abnormal non-invasive cardiac stress tests represent a frequent management challenge. Coronary multidetector computed tomography (MDCT) has been shown to have excellent diagnostic accuracy to exclude the presence of significant CAD. Methods: The study included 218 patients (mean age 59±12 years, 60% male) with equivocal or mildly abnormal exercise electrocardiography (n=93), stress SPECT perfusion scans (n=121), stress echocardiography (n=3) and stress cardiac MRI (n=1). Patients were either asymptomatic (n=113) or had atypical chest pain (n=105). All patients underwent contrast-enhanced 64-slice MDCT coronary angiography and datasets were evaluated for the presence of coronary atherosclerotic plaques and significant coronary artery stenosis. Patients were followed for 8±3 months and the endpoints evaluated were: cardiac death, myocardial infarction, revascularization procedure performed &gt;3 months after MDCT coronary angiography and unstable angina requiring hospitalization. Results: MDCT coronary angiography was either normal (n=90; 41%), demonstrated non-obstructive coronary atherosclerotic plaques (n=66; 30%) or exhibited significant coronary stenosis (n=62; 29%). Event-free survival was 100% for patients with normal coronary angiography, 98% for patients with non-obstructive plaques and 92% for patients with coronary stenosis (log-rank test P=0.01). One patient with a non-obstructive plaque involving the left main coronary artery died following an AMI (hazard ratio, 0.38; 95% confidence interval, 0.04 to 3.24). Among patients with coronary stenosis, 3 underwent revascularization procedures and 2 died (hazard ratio, 12.59; 95% confidence interval, 1.47 to 107.86). Conclusion: Among patients with equivocal or mildly abnormal non-invasive cardiac stress tests, a normal MDCT coronary angiography is associated with a very low risk for subsequent cardiac events. Further studies are necessary to determine the clinical significance of non-obstructive atherosclerotic plaques detected by MDCT coronary angiography in this patient population.

The Vulnerable Atherosclerotic Plaque: Strategies for Diagnosis and Management

Renu Virmani, Jagat Narula, Martin B. Leon, James T. Willerson, eds 375 pages. Malden, MA: Blackwell Futura; 2007. $174.95. ISBN 1–40515–859–X The term “vulnerable plaque” was coined in 1989 by Dr. James E. Muller to describe nonobstructive atherosclerotic plaques that were prone to rupture, leading to acute clinical syndromes. This term has evolved over the ensuing 2 decades and is now often called the “high risk plaque.” Many investigators argue that atherosclerosis is a systemic problem and therefore the proper terminology should be the “vulnerable patient.” Regardless of semantics, identification of the vulnerable plaque has significant implications for clinical care. Novel therapies to pacify plaques, both medical and interventional, are under development and an enhanced understanding both of the risk factors and methodologies used to recognize unstable plaques are poised to advance the field of cardiovascular medicine. The Vulnerable Atherosclerotic Plaque: Strategies for Diagnosis and Management reviews our understanding of the vulnerable plaque from a broad perspective, including its pathology, potential triggers, diagnostic techniques, and management, in a well-organized manner that progresses from topic to topic quite logically. The book successfully minimizes overlap between chapters. Clinical and basic information is well-integrated and the authors who contributed to the work are outstanding. …

New Technology for Noninvasive Evaluation of Coronary Artery Disease

Cardiac computed tomography (CT) and positron emission tomography (PET) are emerging as powerful noninvasive imaging tools for the evaluation of atherosclerosis in patients with known or suspected coronary artery disease (CAD). Unlike invasive coronary angiography, CT coronary angiography (CTA) not only assesses disease within the coronary lumen but can also provide direct qualitative and quantitative information about nonobstructive atherosclerotic plaque burden within the vessel wall. Thus, it is possible that CTA-based patient evaluation may provide more clinically relevant information on which to base risk assessments compared with conventional “lumenography.” On the other hand, PET is rapidly growing as a powerful and efficient alternative to conventional single-photon emission CT (SPECT) imaging to evaluate regional myocardial perfusion and metabolism in patients with CAD. In addition, PET scanners are now being converted to hybrid PET/CT devices, which, in the setting of CAD, offer the potential for a comprehensive noninvasive cardiac evaluation of anatomy and function. This review will discuss current and potential future applications of cardiovascular CT, PET, and hybrid PET/CT, with a particular focus on ischemic heart disease. The information provided by noninvasive imaging generally falls into 1 of 3 categories: myocardial perfusion, left ventricular (LV) function, or coronary artery anatomy. The clinical utility, value, and role of a noninvasive modality are based on 2 test characteristics: What type of information is provided (eg, stress perfusion, stress and/or rest LV function, coronary anatomy), and what is the accuracy of the information provided. For example, SPECT and PET both provide stress and rest perfusion information, but the latter will be a superior clinical tool if the imaging data better represent the actual defect size and are subject to less artifact. The advantage of PET over SPECT will be further enhanced, as will be discussed later, if it provides additional clinically relevant information not …

Neurologic symptoms associated with nonobstructive plaque at carotid bifurcation. Analysis by real-time B-mode ultrasonography.

Real-time B-mode ultrasonography was employed to image nonobstructive atherosclerotic plaque formation in the carotid artery bifurcation. Hemodynamic factors were assessed by pneumo-oculoplethsymography and Doppler flow study. Hemodynamically obstructive lesions were associated with a significantly higher incidence of cerebral ischemic symptoms than were nonobstructive plaques. Two types of nonobstructive plaques were delineated: isolated nodular plaques and mural plaques along the wall of the carotid sinus. Nodular plaques were associated with significantly fewer ischemic symptoms and strokes than were obstructive lesions. Mural plaques also had a lower incidence of symptoms than obstructive lesions, but the difference was not significant. Noninvasive determination of the morphologic and physiologic characteristics of atherosclerotic lesions at the carotid bifurcation can be of considerable value in the management of patients with transient ischemic attacks.