Technology Insight: cardiac CT angiography

Lipid profile as a strong indicator of coronary plaques: noninvasive assessment by multislice computerized tomography

BACKGROUND

Most acute coronary syndrome disorders occur as a consequence of atherosclerotic plaque rupture. Lipids are involved in atherosclerotic plaque buildup. Advances in image quality of coronary computed tomography have enabled improved characterization of coronary plaques. The aim of our study was to evaluate the association between lipid profile and coronary plaque presence in general and soft plaques in particular.

METHODS

In this cross-sectional survey, 258 consecutive patients presenting with chest pain either or both with low-to-moderate risk for coronary artery disease, were included. All patients were tested for lipid profile prior to cardiac imaging on a 64-slice computer tomography. Multivariate logistic regression models were used to assess the odds ratios (ORs) and 95% confidence interval (CI) for the relationship between blood lipid levels and prevalence of coronary plaques.

RESULTS

Age, total cholesterol levels, hypertension, hyperlipidemia (dichotomous) and risk factor index, all were independently associated with prevalence all kind of plaques, especially with soft plaques. No significant relationships were detected among BMI, current smoking, diabetes or triglycerides levels. In a multivariate logistic regression, hyperlipidemia was associated with presence of coronary plaque risk with adjusted OR of 2.28 (95% CI 1.30-4.01), total cholesterol with adjusted OR = 1.05 (95% CI 1.01-1.06), and risk factor index (1-6) with adjusted OR = 2.23 (95% CI 1.40-3.55).

CONCLUSION

Hyperlipidemia is strongly associated with prevalence of coronary plaques (P < 0.001) in individuals with low-to-intermediate risk for coronary artery disease, based on cardiac CT. Cardiac CT may serve as a noninvasive alternative for the early diagnosis of CAD in such individuals.

Understanding the genetics of coronary artery disease through the lens of noninvasive imaging

Coronary artery disease is a common condition with a known heritable component that has spurred interest in genetic research for decades, resulting in a handful of candidate genes and an appreciation for the complexity of its genetic contributions. Recent advances in sequencing technologies have resulted in large-scale association studies, possibly adding to our current understanding of the genetics of coronary artery disease. Sifting through the statistical noise, however, requires the selection of effective phenotypic markers. New imaging technologies have improved our ability to detect subclinical atherosclerosis in a safe and reproducible manner in large numbers of patients. In this article, we propose that advances in imaging technology have generated improved phenotypic markers for genetic association studies of coronary artery disease.

A decomposition-based CT reconstruction formulation for reducing blooming artifacts

Cardiac computed tomography represents an important advancement in the ability to assess coronary vessels. The accuracy of these non-invasive imaging studies is limited, however, by the presence of calcium, since calcium blooming artifacts lead to an over-estimation of the degree of luminal narrowing. To address this problem, we have developed a unified decomposition-based iterative reconstruction formulation, where different penalty functions are imposed on dense objects (i.e. calcium) and soft tissue. The result is a quantifiable reduction in blooming artifacts without the introduction of new distortions away from the blooming observed in other methods. Results are shown for simulations, phantoms, ex vivo, and in vivo studies.

Methods of plaque quantification and characterization by cardiac computed tomography

The pathologic evolution of coronary artery atherosclerosis occurs slowly over decades, which may provide an opportunity for diagnostic imaging to identify patients before clinical events evolve. Cardiac computed tomography (CT) is an emerging noninvasive imaging tool, which can visualize the entire coronary tree with submillimeter resolution. We reviewed the current status of cardiac CT to qualitatively and quantitatively determine coronary plaque dimensions and composition, and its potential to improve our understanding of the natural history of coronary artery disease as well as prevention of cardiovascular events.

Randomized comparison of 64-slice single- and dual-source computed tomography coronary angiography for the detection of coronary artery disease

OBJECTIVES

The purpose of this study was to analyze the influence of a systematic approach to lower heart rate for coronary computed tomography (CT) angiography on diagnostic accuracy of 64-slice single- and dual-source CT.

BACKGROUND

Coronary CT angiography is often impaired by motion artifacts, so that routine lowering of heart rate is usually recommended. This is often conceived as a major limitation of the technique. It is expected that higher temporal resolution, such as with dual-source 64-slice CT, would allow diagnostic imaging even without systematic pre-treatment for lowering the heart rate.

METHODS

Two hundred patients with suspected coronary artery disease were first randomized to either 64-slice single-source CT (n = 100) or dual-source CT (n = 100) for contrast-enhanced coronary artery evaluation. In each group, patients were further randomized to either receive systematic heart rate control (oral and intravenous beta-blockade for a target heart rate < or =60 beats/min) or receive no premedication. Evaluability of datasets and diagnostic accuracy were compared between groups against the results obtained from invasive angiography.

RESULTS

Systematic pre-treatment lowered heart rate during CT coronary angiography by 10 beats/min. Heart rate control significantly improved evaluability in single-source CT (93% vs. 69% on a per-patient basis, p = 0.005), whereas it did not in dual-source CT (96% vs. 98%). In evaluable patients, sensitivity to detect the presence of at least 1 coronary stenosis by single-source CT was 86% and 79%, respectively, with and without heart rate control (p = NS). For dual-source CT, it was 100% and 95%, respectively (p = NS). The rate of correctly classified patients, defined as evaluable and correct classification as to the presence or absence of at least 1 coronary artery stenosis, was significantly improved by heart rate control in single-source CT (78% vs. 57%, p = 0.04), whereas there was no such influence in dual-source CT (87% vs. 93%).

CONCLUSIONS

Systematic heart rate control significantly improves image quality for coronary visualization by 64-slice single-source CT, whereas image quality and diagnostic accuracy remain unaffected in dual-source CT angiography. Improved temporal resolution obviates the need for heart rate control.

Review of acute coronary syndrome diagnosis and management

Acute coronary syndrome (ACS) refers to a group of clinical conditions caused by myocardial ischemia including unstable angina, non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). Appropriate and accurate diagnosis has life-saving implications and requires a quick but thorough evaluation of the patient's history, physical examination, electrocardiogram, radiographic studies, and cardiac biomarkers. The management of patients with suspected or confirmed ACS continues to evolve as new evidence from clinical trials is considered and as new technology becomes available to both primary care physicians and cardiologists. Low- and intermediate-risk patients have frequently been managed in a chest pain center or in the emergency department. While stress testing with or without radionuclide imaging is the most common evaluation method, a CT angiogram is sometimes substituted. High-risk patients are often managed with an early invasive strategy involving left heart catheterization with a goal of prompt revascularization of at-risk, viable myocardium. With the increased availability of cardiac catheterization facilities, patients with STEMI are more commonly being managed with primary percutaneous coronary intervention, although thrombolysis is still used where such facilities are not immediately available. This article provides primary care physicians with a concise review of the pathophysiology, clinical evaluation, and management of ACS based on the best available evidence in 2008.

Cardiac PET-CT

Integrated positron emission tomography computed tomography (PET/CT) scanners allow a true integration of the structure and function of the heart. Myocardial perfusion PET provides a high sensitivity (91%) and specificity (89%) for the diagnosis of obstructive coronary artery disease (CAD). But, as with single photon emission CT, relative perfusion PET often uncovers only the territory subtended by the most severe coronary stenosis, leading to underestimation of the extent of CAD. In contrast, quantitative PET provides a noninvasive assessment of myocardial blood flow and coronary flow reserve and improves detection of preclinical and multivessel coronary atherosclerosis. Similarly, CT coronary angiography is an accurate means to image the entire continuum of anatomic coronary atherosclerosis from nonobstructive to obstructive CAD. However, not all coronary stenoses are hemodynamically significant and <50% of the patients with obstructive CAD on CT angiography demonstrate stress induced perfusion defects. Stress PET data complement the anatomic information on the CT angiogram by providing instant readings about the ischemic burden of coronary stenoses. Thus, combined PET/CT may be potentially superior to CT angiography alone for the guiding revascularization decisions. Further, fusion of the PET and CT angiogram images allows identification of the culprit stenosis in patients presenting with chest pain. Finally, the advances in molecular imaging and image fusion may soon make noninvasive detection of vulnerable coronary plaques a clinical reality. In summary, integrated PET/CT is a powerful new noninvasive modality that offers the potential for refined diagnosis and management of the entire spectrum of coronary atherosclerosis.