Advances in clinical applications of cardiovascular magnetic resonance imaging

Changing Landscape of Congenital Heart Disease

Congenital heart disease is the most frequently occurring congenital disorder affecting ≈0.8% of live births. Thanks to great efforts and technical improvements, including the development of cardiopulmonary bypass in the 1950s, large-scale repair in these patients became possible, with subsequent dramatic reduction in morbidity and mortality. The ongoing search for progress and the growing understanding of the cardiovascular system and its pathophysiology refined all aspects of care for these patients. As a consequence, survival further increased over the past decades, and a new group of patients, those who survived congenital heart disease into adulthood, emerged. However, a large range of complications raised at the horizon as arrhythmias, endocarditis, pulmonary hypertension, and heart failure, and the need for additional treatment became clear. Technical solutions were sought in perfection and creation of new surgical techniques by developing catheter-based interventions, with elimination of open heart surgery and new electronic devices enabling, for example, multisite pacing and implantation of internal cardiac defibrillators to prevent sudden death. Over time, many pharmaceutical studies were conducted, changing clinical treatment slowly toward evidence-based care, although results were often limited by low numbers and clinical heterogeneity. More attention has been given to secondary issues like sports participation, pregnancy, work, and social-related difficulties. The relevance of these issues was already recognized in the 1970s when the need for specialized centers with multidisciplinary teams was proclaimed. Finally, research has become incorporated in care. Results of intervention studies and registries increased the knowledge on epidemiology of adults with congenital heart disease and their complications during life, and at the end, several guidelines became easily accessible, guiding physicians to deliver care appropriately. Over the past decades, the landscape of adult congenital heart disease has changed dramatically, which has to be continued in the future.

Cardiac involvement in patients with cirrhosis: a focus on clinical features and diagnosis

Cirrhotic heart has been traditionally considered protected from cardiovascular disease, even if a large amount of literature has recently shown that patients affected by chronic liver disease are exposed to cardiovascular events, as well. Since the first recognition of cardiac involvement in cirrhosis, all published studies explain that decompensated cirrhotic patients suffer from haemodynamic changes, currently known as hyperdynamic syndrome, which finally lead to cirrhotic cardiomyopathy. This is defined by the presence of a subclinical systolic dysfunction unmasked under stress conditions, impaired diastolic function and electrophysiological abnormalities, in the absence of any known cardiac disease. In this review, we will discuss the clinical and diagnostic features of this condition, the prevalence of associated comorbidities, echocardiographic, electrocardiographic and cardiac magnetic resonance hallmarks and the possible diagnostic role of serum biomarkers.

Use of wave intensity analysis of carotid arteries in identifying and monitoring left ventricular systolic function dynamics in rabbits

Wave intensity analysis (WIA) of the carotid artery was conducted to determine the changes that occur in left ventricular systolic function after administration of doxorubicin in rabbits. Each randomly selected rabbit was subject to routine ultrasound, WIA of the carotid artery, cardiac catheterization and pathologic examination every week and was followed for 16 wk. The first positive peak (WI1) of the carotid artery revealed that left ventricular systolic dysfunction occurred earlier than conventional indexes of heart function. WI1 was highly, positively correlated with the maximum rate of rise in left ventricular pressure in cardiac catheterization (r = 0.94, p < 0.01) and moderately negatively correlated with the apoptosis index of myocardial cells, an indicator of myocardial damage (r = -0.69, p < 0.01). Ultrasound WIA of the carotid artery sensitively reflects early myocardial damage and cardiac function, and the result is highly consistent with cardiac catheterization findings and the apoptosis index of myocardial cells.

Concordance and diagnostic accuracy of vasodilator stress cardiac MRI and 320-detector row coronary CTA

Vasodilator stress cardiac magnetic resonance (CMR) detects ischemia whereas coronary CT angiography (CTA) detects atherosclerosis. The purpose of this study was to determine concordance and accuracy of vasodilator stress CMR and coronary CTA in the same subjects. We studied 151 consecutive subjects referred to detect or exclude suspected obstructive coronary artery disease (CAD) in patients without known disease or recurrent stenosis or ischemia in patients with previously treated CAD. Vasodilator stress CMR was performed on a 1.5 T scanner. CTA was performed on a 320-detector row system. Subjects were followed for cardiovascular events and downstream diagnostic testing. Subjects averaged 56 ± 12 years (60% male), and 62 % had intermediate pre-test probability for obstructive CAD. Follow-up averaged 450 ± 115 days and was 100% complete. CMR and CTA agreed in 92% of cases (κ 0.81, p < 0.001). The event-free survival was 97 % for non-ischemic and 39% for ischemic CMR (p < 0.0001). The event-free survival was 99% for non-obstructive and 36% for obstructive CTA (p < 0.0001). Using a reference standard including quantitative invasive angiography or major cardiovascular events, CMR and CTA had respective sensitivities of 93 and 98 %; specificities of 96 and 96%; positive predictive values of 91 and 91%; negative predictive values of 97 and 99%; and accuracies of 95 and 97%. Non-ischemic vasodilator stress CMR or non-obstructive coronary CTA were highly concordant and each confer an excellent prognosis. CMR and CTA are both accurate for assessment of obstructive CAD in a predominantly intermediate risk population.

Cardiac imaging in adults with congenital heart disease: unknowns and issues related to diagnosis

OPINION STATEMENT

Many adults with simple and complex congenital heart disease (CHD) survive to adulthood. The goal of imaging is to diagnose the underlying anomalies and to detect late complications of their CHD and past surgical repair, in order to assess the need for further intervention and better prepare for endovascular or open-heart surgery. Cardiac magnetic resonance imaging (MRI) and computerized tomography (CT) are increasingly utilized in this patient population, due to the technical advances made to these modalities in the past decade regarding image acquisition and reconstruction, spatial and temporal resolution, and radiation dose reduction. Here, we aim to review the role of cardiac MR in initial diagnosis, pre-treatment planning and post-surgical follow-up of adults with CHD, and to discuss the ancillary role of cardiac CT in these patients.

Potential of magnetic resonance for imaging the fetal heart

Significant congenital heart disease (sCHD) affects 3.6 per 1000 births, and is often associated with extracardiac and chromosomal anomalies. Although early mortality has been substantially reduced and the rate of long-term survival has improved, sCHD is, after preterm birth, the second most frequent cause of neonatal infant death. The prenatal detection of cardiac and vascular abnormalities enables optimal parental counselling and perinatal management. Echocardiography (ECG) is the first-line examination and gold standard by which cardiac malformations are defined. However, adequate examination by an experienced healthcare provider with modern technical imaging equipment is required. In addition, maternal factors and the gestational age may lower the image quality. Fetal magnetic resonance imaging (MRI) has been implemented over the last several years and is already used in the clinical routine as a second-line approach to assess fetal abnormalities. MRI of the fetal heart is still not routinely performed. Nevertheless, fetal cardiac MRI has the potential to complement ultrasound in detecting cardiovascular malformations and extracardiac lesions. The present work reviews the potential of MRI to delineate the anatomy and pathologies of the fetal heart. This work also deals with the limitations and continuing developments designed to overcome the current problems in cardiac imaging, including fast fetal heart rates, the lack of ECG-gating, and the presence of fetal movements.

Cardiac dysfunction in pneumovirus-induced lung injury in mice

OBJECTIVE

To determine biventricular cardiac function in pneumovirus-induced acute lung injury in spontaneously breathing mice.

DESIGN

Experimental animal study.

SETTING

Animal laboratory.

SUBJECTS

C57Bl/6 mice.

INTERVENTION

Mice were inoculated with the rodent pneumovirus, pneumonia virus of mice.

MEASUREMENTS AND MAIN RESULTS

Pneumonia virus of mice-infected mice were studied for right and left ventricular function variables by high-field strength (7 Tesla) cardiac MRI at specific time points during the course of disease compared with baseline. One day before and at peak disease severity, pneumonia virus of mice-infected mice showed significant right and left ventricular systolic and diastolic volume changes, with a progressive decrease in stroke volume and ejection fraction. No evidence for viral myocarditis or viral presence in heart tissue was found.

CONCLUSIONS

These findings show adverse pulmonary-cardiac interaction in pneumovirus-induced acute lung injury, unrelated to direct virus-mediated effects on the heart.

Cardiovascular magnetic resonance imaging of isolated perfused pig hearts in a 3T clinical MR scanner

PURPOSE

An isolated perfused pig heart model has recently been proposed for the development of novel methods in standard clinical magnetic resonance (MR) scanners. The original set-up required the electrical system to be within the safe part of the MR-room, which introduced significant background noise. The purpose of the current work was to refine the system to overcome this limitation so that all electrical parts are completely outside the scanner room.

METHODS

Four pig hearts were explanted under terminal anaesthesia from large white cross landrace pigs. All hearts underwent cardiovascular magnetic resonance (CMR) scanning in the MR part of a novel combined 3T MR and x-ray fluoroscopy (XMR) suite. CMR scanning included real-time k-t SENSE functional imaging, k-t SENSE accelerated perfusion imaging and late gadolinium enhancement imaging. Interference with image quality was assessed by spurious echo imaging and compared to noise levels acquired while operating the electrical parts within the scanner room.

RESULTS

Imaging was performed successfully in all hearts. The system proved suitable for isolated heart perfusion in a novel 3T XMR suite. No significant additional noise was introduced into the scanner room by our set-up.

CONCLUSIONS

We have substantially improved a previous version of an isolated perfused pig heart model and made it applicable for MR imaging in a state of the art clinical 3T XMR imaging suite. The use of this system should aid novel CMR sequence development and translation into clinical practice.

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.

Quantitative T 2* assessment of acute and chronic myocardial ischemia/reperfusion injury in mice

OBJECT

Imaging of myocardial infarct composition is essential to assess efficacy of emerging therapeutics. T (2) (*) mapping has the potential to image myocardial hemorrhage and fibrosis by virtue of its short T (2) (*) . We aimed to quantify T (2) (*) in acute and chronic myocardial ischemia/reperfusion (I/R) injury in mice.

MATERIALS AND METHODS

I/R-injury was induced in C57BL/6 mice (n = 9). Sham-operated mice (n = 8) served as controls. MRI was performed at baseline, and 1, 7 and 28 days after surgery. MRI at 9.4 T consisted of Cine, T (2) (*) mapping and late-gadolinium-enhancement (LGE). Mice (n = 6) were histologically assessed for hemorrhage and collagen in the fibrotic scar.

RESULTS

Baseline T (2) (*) values were 17.1 ± 2.0 ms. At day 1, LGE displayed a homogeneous infarct enhancement. T (2) (*) in infarct (12.0 ± 1.1 ms) and remote myocardium (13.9 ± 0.8 ms) was lower than at baseline. On days 7 and 28, LGE was heterogeneous. T (2) (*) in the infarct decreased to 7.9 ± 0.7 and 6.4 ± 0.7 ms, whereas T (2) (*) values in the remote myocardium were 14.2 ± 1.1 and 15.6 ± 1.0 ms. Histology revealed deposition of iron and collagen in parallel with decreased T (2) (*) .

CONCLUSION

T (2) (*) values are dynamic during infarct development and decrease significantly during scar maturation. In the acute phase, T (2) (*) values in infarcted myocardium differ significantly from those in the chronic phase. T (2) (*) mapping was able to confirm the presence of a chronic infarction in cases where LGE was inconclusive. Hence, T (2) (*) may be used to discriminate between acute and chronic infarctions.

PET/MRI of inflammation in myocardial infarction

OBJECTIVES

The aim of this study was to explore post-myocardial infarction (MI) myocardial inflammation.

BACKGROUND

Innate immune cells are centrally involved in infarct healing and are emerging therapeutic targets in cardiovascular disease; however, clinical tools to assess their presence in tissue are scarce. Furthermore, it is currently not known if the nonischemic remote zone recruits monocytes.

METHODS

Acute inflammation was followed in mice with coronary ligation by 18-fluorodeoxyglucose ((18)FDG) positron emission tomography/magnetic resonance imaging, fluorescence-activated cell sorting, polymerase chain reaction, and histology.

RESULTS

Gd-DTPA-enhanced infarcts showed high (18)FDG uptake on day 5 after MI. Cell depletion and isolation data confirmed that this largely reflected inflammation; CD11b(+) cells had 4-fold higher (18)FDG uptake than the infarct tissue from which they were isolated (p < 0.01). Surprisingly, there was considerable monocyte recruitment in the remote myocardium (approximately 10(4)/mg of myocardium, 5.6-fold increase; p < 0.01), a finding mirrored by macrophage infiltration in the remote myocardium of patients with acute MI. Temporal kinetics of cell recruitment were slower than in the infarct, with peak numbers on day 10 after ischemia. Quantitative polymerase chain reaction showed a robust increase of recruiting adhesion molecules and chemokines in the remote myocardium (e.g., 12-fold increase of monocyte chemoattractant protein-1), although levels were always lower than in the infarct. Finally, matrix metalloproteinase activity was significantly increased in noninfarcted myocardium, suggesting that monocyte recruitment to the remote zone may contribute to post-MI dilation.

CONCLUSIONS

This study shed light on the innate inflammatory response in remote myocardium after MI.

Four-dimensional phase contrast MRI with accelerated dual velocity encoding

PURPOSE

To validate a novel approach for accelerated four-dimensional phase contrast MR imaging (4D PC-MRI) with an extended range of velocity sensitivity.

MATERIALS AND METHODS

4D PC-MRI data were acquired with a radially undersampled trajectory (PC-VIPR). A dual V(enc) (dV(enc) ) processing algorithm was implemented to investigate the potential for scan time savings while providing an improved velocity-to-noise ratio. Flow and velocity measurements were compared with a flow pump, conventional 2D PC MR, and single V(enc) 4D PC-MRI in the chest of 10 volunteers.

RESULTS

Phantom measurements showed excellent agreement between accelerated dV(enc) 4D PC-MRI and the pump flow rate (R(2) ≥ 0.97) with a three-fold increase in measured velocity-to-noise ratio (VNR) and a 5% increase in scan time. In volunteers, reasonable agreement was found when combining 100% of data acquired with V(enc) = 80 cm/s and 25% of the high V(enc) data, providing the VNR of a 80 cm/s acquisition with a wider velocity range of 160 cm/s at the expense of a 25% longer scan.

CONCLUSION

Accelerated dual V(enc) 4D PC-MRI was demonstrated in vitro and in vivo. This acquisition scheme is well suited for vascular territories with wide ranges of flow velocities such as congenital heart disease, the hepatic vasculature, and others.

Molecular imaging of coronary atherosclerosis and myocardial infarction: considerations for the bench and perspectives for the clinic

Motivated by the promise to transform preclinical research and clinical care, cardiovascular molecular imaging has made advances toward targeting coronary atherosclerosis and heart failure. Here, we discuss recent progress in the field, highlight how molecular imaging may facilitate preventive patient care, and review specific challenges associated with coronary and heart failure imaging. Practical considerations stress the potential of fluorescence imaging for basic research and discuss hybrid protocols such as FMT-CT and PET-MRI.

Myocardial late gadolinium enhancement cardiovascular magnetic resonance in patients with cirrhosis

BACKGROUND

Portal hypertension and cardiac alterations previously described as "cirrhotic cardiomyopathy" are known complications of end stage liver disease (ELD). Cardiac failure contributes to morbidity and mortality, particularly after liver transplantation and transjugular intrahepatic portosystemic shunt (TIPS). We sought to identify myocardial tissue characterization and evaluate cardiovascular magnetic resonance (CMR) for diagnosis of cardiac impairment.

RESULTS

Twenty ELD patients underwent CMR for morphological, functional and tissue characterization by late gadolinium enhancement (LGE). Based on extent of LGE, patients were dichotomized into high and low LGE groups and analyzed regarding liver, cardiocirculatory and renal functions. CMR demonstrated hyperdynamic left ventricular function and a patchy pattern of LGE of the myocardium to a variable extent (range 2-62%) in all patients. There were no significant differences in Model for End-Stage Liver Disease (MELD), Child-Pugh score or the left ventricular ejection fraction between high and low LGE groups. QTc-interval was prolonged in 25% of the patients. E/A ratio was at the upper limit of norm; no difference between groups. Patients showing high LGE had a higher CI (p < 0.05). Biomarkers of myocardial stress were elevated. While NT-proBNP and c-Troponin-T showed no differences, PLGF and sFLT1 were lower in the high LGE group.

CONCLUSION

CMR shows myocardial involvement in patients with ELD resembling appearance of myocarditis. The hyperdynamic circulation in portal hypertension may be an important factor. Larger prospective trials are warranted to confirm the association with severity and outcome of liver disease and to test the predictive power of CMR for patients listed for liver transplantation.

Cardiovascular toxicity caused by cancer treatment: strategies for early detection

Cardiovascular toxicity is one of the most devastating complications of cancer treatment and can arise during or shortly after treatment, or even several years later. Identification of the left ventricular ejection fraction (LVEF) is the most common method to screen for toxic effects on the heart; however, this approach underestimates cardiac damage and additional strategies for the monitoring of treatment-induced cardiotoxicity are being explored. Guidelines for monitoring have been formulated for several cancer treatments; however, appropriate underlying evidence is still largely absent. In this Review, we summarise conventional and contemporary methods for early detection of cardiotoxicity and designate a level of evidence for the basis of each method.

Pathophysiology of coronary artery disease: the case for multiparametric imaging

Interventions to treat coronary artery disease are available but they must be targeted at the correct individuals (and indeed lesions), in order to gain maximal benefit with the minimal adverse effects. Coronary contrast angiography is not able to provide all the information required for the assessment of the effects of artery disease. Other imaging modalities are of growing importance as they can reduce radiation exposure and invasiveness of screening, as well as providing important extra information. The ideal 'multiparametric' imaging technique would assess anatomy, viability and lesion activity in a single quick scan. Currently, MRI is the technology closest to achieving this ideal, although the existing technology still has some limitations. This review discusses the currently available techniques for the imaging of coronary anatomy and of myocardial viability, and considers their benefits and limitations. We also discuss the developing field of imaging molecularly targeted to active coronary lesions. Finally we provide a 5-year view of the current and likely future optimal imaging strategies.