Cardiac and coronary CT comprehensive imaging approach in the assessment of coronary heart disease

Cardiac Computed Tomography Perfusion: Contrast Agents, Challenges and Emerging Methodologies from Preclinical Research to the Clinics

Computed Tomography (CT) has long been regarded as a purely anatomical imaging modality. Recent advances on CT technology and Contrast Agents (CA) in both clinical and preclinical cardiac imaging offer opportunities for the use of CT in functional imaging. Combined with modern ECG-gating techniques, functional CT has now become a reality allowing a comprehensive evaluation of myocardial global and regional function, perfusion and coronary angiography. This article aims at reviewing the current status of cardiac CT perfusion and micro-CT perfusion with established and experimental scanners and contrast agents, from clinical practice to the experimental domain of investigations based on animal models of heart diseases.

Quantification of extracellular volume fraction by cardiac computed tomography for noninvasive assessment of myocardial fibrosis in hemodialysis patients

Extent of myocardial fibrosis in hemodialysis patients has been associated with poor prognosis. Myocardial extracellular volume (ECV) quantification using contrast enhanced cardiac computed tomography (CT) is a novel method to determine extent of myocardial fibrosis. Cardiac CT-based myocardial ECV in hemodialysis patients with those of propensity-matched non-hemodialysis control subjects were compared. Twenty hemodialysis patients (mean age, 67.4 ± 9.6 years; 80% male) and 20 propensity-matched non-hemodialysis controls (mean age, 66.3 ± 9.1 years; 85% male) who underwent comprehensive cardiac CT consisted of calcium scoring, coronary CT angiography, stress perfusion CT and delayed enhancement CT were evaluated. Myocardial ECV was significantly greater in the hemodialysis group than in the control group (33.8 ± 4.7% versus 26.6 ± 2.9%; P < 0.0001). In the hemodialysis group, modest correlation was evident between myocardial ECV and left atrial volume index (r = 0.54; P = 0.01), while there was no correlation between myocardial ECV and other cardiac parameters including left ventricular mass index and severity of myocardial ischemia. Cardiac CT-based myocardial ECV may offer a potential imaging biomarker for myocardial fibrosis in HD patients.

Heart Infection Prognosis Analysis by Two-dimensional Spot Tracking Imaging

Cardiovascular death is one of the leading causes worldwide; an accurate identification followed by diagnosing the cardiovascular disease increases the chance of a better recovery. Among different demonstrated strategies, imaging on cardiac infections yields a visible result and highly reliable compared to other analytical methods. Two-dimensional spot tracking imaging is the emerging new technology that has been used to study the function and structure of the heart and test the deformation and movement of the myocardium. Particularly, it helps to capture the images of each segment in different directions of myocardial strain values, such as valves of radial strain, longitudinal strain, and circumferential strain. In this overview, we discussed the imaging of infections in the heart by using the two-dimensional spot tracking.

CT coronary angiographic evaluation of suspected anginal chest pain

Non-invasive imaging plays a critical role in the assessment of patients presenting with suspected angina chest pain. However, wide variations in practice across Europe and North America highlight the lack of consensus in selecting the appropriate first-line test for the investigation of coronary artery disease (CAD). CT coronary angiography (CTCA) has a high negative predictive value for excluding the presence of CAD. As such, it serves as a potential 'gatekeeper' to downstream testing by reducing the rate of inappropriate invasive coronary angiography. Two recent large multicentre randomised control trials have provided insights into whether CTCA can be incorporated into chest pain care pathways to improve risk stratification of CAD. They demonstrate that using CTCA enhances diagnostic certainty and improves the targeting of appropriate invasive investigations and therapeutic interventions. Importantly, reductions in cardiac death and non-fatal myocardial infarction appear to be attained through the more appropriate use of preventative therapy and coronary revascularisation when guided by CTCA. With this increasing portfolio of evidence, CTCA should be considered the non-invasive investigation of choice in the evaluation of patients with suspected angina pectoris due to coronary heart disease.

CLINICAL TRIAL NUMBER

NCT01149590, post-results.

Strain analysis from 4-D cardiac CT image data

Strain is a discriminative parameter of regional myocardial dysfunction. Despite the large body of research on myocardial strain analysis in echocardiography and MR images, such techniques have not often been applied to cardiac CT data. Reasons for this include the challenges of sparse image deformation clues and the low temporal resolution. In the current study, we propose an algorithm that uses cardiac CT data to evaluate the mechanical function of the left ventricle. The algorithm is based on a deformable LV model that contains both the myocardium and the blood pool regions and that accounts for the elasticity and incompressibility of the myocardium with the rapid contraction of the blood pool. Our algorithm uses the image intensities of the trabeculle and papillary muscles as well as the border edges in an optical flow manner to extract the 3-D velocities. The resulting strains and rotational values derived from a set of normal patients correlate highly with values from the research literature. We validated our algorithm against 2-D speckle tracking analysis and against visual scores obtained by an expert. Our study shows that strain analysis using CT data can be used in clinical practice.

Diagnostic performance of high-sensitive troponin T in patients with renal insufficiency

In the present study, we wanted to (1) evaluate whether high-sensitive troponin T levels correlate with the grade of renal insufficiency and (2) test the accuracy of high-sensitive troponin T determination in patients with renal insufficiency for diagnosis of acute myocardial infarction (AMI). In this cross-sectional analysis, all patients who received serial measurements of high-sensitive troponin T from August 1, 2010, to October 31, 2012, at the Department of Emergency Medicine were included. We analyzed data on baseline characteristics, reason for referral, medication, cardiovascular risk factors, and outcome in terms of presence of AMI along with laboratory data (high-sensitive troponin T, creatinine). A total of 1,514 patients (67% male, aged 65 ± 16 years) were included, of which 382 patients (25%) had moderate to severe renal insufficiency and significantly higher levels of high-sensitive troponin T on admission (0.028 vs 0.009, p <0.0001). In patients without AMI, high-sensitive troponin T correlated inversely with the estimated glomerular filtration rate (R = -0.12, p <0.0001). Overall, sensitivity of an elevated high-sensitive troponin for diagnosis of AMI was 0.64 (0.56 to 0.71) and the specificity was 0.48 (0.45 to 0.51). The area under the curve of the receiver operating characteristic for all patients was 0.613 (standard error [SE] 0.023), whereas it was 0.741 (SE 0.029) for patients with a Modification of Diet in Renal Disease estimated glomerular filtration rate >60 ml/min presenting with acute chest pain or dyspnea and 0.535 (SE 0.056) for patients with moderate to severe renal insufficiency presenting with acute chest pain or dyspnea. In conclusion, the diagnostic accuracy for presence of AMI of a baseline measurement of high-sensitive troponin in patients with renal insufficiency was poor and resembles tossing a coin.

Integrating anatomical and functional imaging for the assessment of coronary artery disease

Coronary artery disease (CAD) is a leading cause of morbidity and mortality. Invasive cardiac angiography with fractional flow reserve measurement allows for the anatomical and functional assessment of CAD. Given the invasive nature of invasive cardiac angiography and the risks of procedure-related complications, research has focused upon noninvasive methods for anatomical and functional measures of CAD. As such, there is growing interest in the development of hybrid imaging because it may provide incremental diagnostic information over each imaging modality alone. We will provide an overview of the evidence to date on the anatomical and functional stratification of CAD and current hybrid techniques.

Assessment of myocardial perfusion and viability by positron emission tomography

An important evolution has taken place recently in the field of cardiovascular Positron Emission Tomography (PET) imaging. Being originally a highly versatile research tool that has contributed significantly to advance our understanding of cardiovascular physiology and pathophysiology, PET has gradually been incorporated into the clinical cardiac imaging portfolio contributing to diagnosis and management of patients investigated for coronary artery disease (CAD). PET myocardial perfusion imaging (MPI) has an average sensitivity and specificity around 90% for the detection of angiographically significant CAD and it is also a very accurate technique for prognostication of patients with suspected or known CAD. In clinical practice, Rubidium-82 ((82)Rb) is the most widely used radiopharmaceutical for MPI that affords also accurate and reproducible quantification in absolute terms (ml/min/g) comparable to that obtained by cyclotron produced tracers such as Nitrogen-13 ammonia ((13)N-ammonia) and Oxygen-15 labeled water ((15)O-water). Quantification increases sensitivity for detection of multivessel CAD and it may also be helpful for detection of early stages of atherosclerosis or microvascular dysfunction. PET imaging combining perfusion with myocardial metabolism using (18)F-Fluorodeoxyglucose ((18)F FDG), a glucose analog, is an accurate standard for assessment of myocardial hibernation and risk stratification of patients with left ventricular dysfunction of ischemic etiology. It is helpful for guiding management decisions regarding revascularization or medical treatment and predicting improvement of symptoms, exercise capacity and quality of life post-revascularization. The strengths of PET can be increased further with the introduction of hybrid scanners, which combine PET with computed tomography (PET/CT) or with magnetic resonance imaging (PET/MRI) offering integrated morphological, biological and physiological information and hence, comprehensive evaluation of the consequences of atherosclerosis in the coronary arteries and the myocardium.

Evaluation of the aortic and mitral valves with cardiac computed tomography and cardiac magnetic resonance imaging

Cardiac computed tomography (CT) produces high-quality anatomical images of the cardiac valves and associated structures. Cardiac magnetic resonance imaging (MRI) provides images of valve morphology, and allows quantitative evaluation of valvular dysfunction and determination of the impact of valvular lesions on cardiovascular structures. Recent studies have demonstrated that cardiac CT and MRI are important adjuncts to echocardiography for the evaluation of aortic and mitral valvular heart diseases (VHDs). Radiologists should be aware of the technical aspects of cardiac CT and MRI that allow comprehensive assessment of aortic and mitral VHDs, as well as the typical imaging features of common and important aortic and mitral VHDs on cardiac CT and MRI.