Assessment of myocardial viability: comparison of echocardiography versus cardiac magnetic resonance imaging in the current era

Detecting viable myocardium, whether hibernating or stunned, is of clinical significance in patients with coronary artery disease and left ventricular dysfunction. Echocardiographic assessments of myocardial thickening and endocardial excursion during dobutamine infusion provide a highly specific marker for myocardial viability, but with relatively less sensitivity. The additional modalities of myocardial contrast echocardiography and tissue Doppler have recently been proposed to provide further, quantitative measures of myocardial viability assessment. Cardiac magnetic resonance (CMR) has become popular for the assessment of myocardial viability as it can assess cardiac function, volumes, myocardial scar, and perfusion with high-spatial resolution. Both 'delayed enhancement' CMR and dobutamine stress CMR have important roles in the assessment of patients with ischaemic cardiomyopathy. This article reviews the recent advances in both echocardiography and CMR for the clinical assessment of myocardial viability. It attempts to provide a pragmatic approach toward the patient-specific assessment of this important clinical problem.     

The Role of Imaging in Hypertensive Heart Disease

Hypertensive heart disease (HHD) describes a spectrum of target organ response that includes left ventricular hypertrophy, systolic, and diastolic dysfunction. A variety of imaging techniques can be used to assess the various aspects of HHD. Echocardiography has for many years been the main imaging technique in the evaluation of HHD, but there is an increasing role for cardiovascular magnetic resonance (CMR) imaging due to its ability to provide an unrestricted field of view and noninvasive tissue characterization. This article reviews the current role of imaging for HHD with particular focus on echocardiography and CMR applications.     

Cardiac involvement in Duchenne and Becker muscular dystrophy

Duchenne and Becker muscular dystrophy (DMD/BMD) are X-linked muscular diseases responsible for over 80% of all muscular dystrophies. Cardiac disease is a common manifestation, not necessarily related to the degree of skeletal myopathy; it may be the predominant manifestation with or without any other evidence of muscular disease. Death is usually due to ventricular dysfunction, heart block or malignant arrhythmias. Not only DMD/BMD patients, but also female carriers may present cardiac involvement. Clinically overt heart failure in dystrophinopathies may be delayed or absent, due to relative physical inactivity. The commonest electrocardiographic findings include conduction defects, arrhythmias (supraventricular or ventricular), hypertrophy and evidence of myocardial necrosis. Echocardiography can assess a marked variability of left ventricular dysfunction, independently of age of onset or mutation groups. Cardiovascular magnetic resonance (CMR) has documented a pattern of epicardial fibrosis in both dystrophinopathies’ patients and carriers that can be observed even if overt muscular disease is absent. Recently, new CMR techniques, such as postcontrast myocardial T1 mapping, have been used in Duchenne muscular dystrophy to detect diffuse myocardial fibrosis. A combined approach using clinical assessment and CMR evaluation may motivate early cardioprotective treatment in both patients and asymptomatic carriers and delay the development of serious cardiac complications.     

Cardiac magnetic resonance imaging: A teaching atlas with emphasizing current clinical indications

Cardiovascular magnetic resonance (CMR) is an amazing technology that continues to provide new innovative approaches for evaluating the heart and blood vessels. It can assess cardiac morphology, function, perfusion, viability, coronary and peripheral arteries, and metabolism and tissue characterization. The basic pulse sequences of CMR include; Spin Echo, Gradient echo, and Steady stet free precision. Current clinical indications of CMR are multiple and continuously evolving. CMR often works in complementary fashions to other cardiac imaging techniques or to resolve residual diagnostic dilemma. The purpose of this illustrative review is to review current clinical applications of CMR and to provide physicians and technologists with simple, and regular CMR cases form daily practice. Each case discusses briefly the related clinical history, followed by CMR imaging findings, and simple discussion to highlight the role of CMR in a particular cardiovascular disorder.     

The role of cardiovascular magnetic resonance in heart failure

Cardiovascular Magnetic Resonance (CMR) is an accepted gold standard for non-invasive, accurate, and reproducible assessment of cardiac mass and function. The interest in its use for viability, myocardial perfusion and coronary artery imaging is also widespread and growing rapidly as the hardware and expertise becomes available in more centres, and the scans themselves become more cost effective. In patients with heart failure, accurate and reproducible serial assessment of remodelling is of prognostic importance and the lack of exposure to ionizing radiation is helpful. The concept of an integrated approach to heart failure and its complications using CMR is fast becoming a reality, and this will be tested widely in the coming few years, with the new generation of dedicated CMR scanners.     

Improvement of myocardial function and perfusion after successful percutaneous revascularization in patients with chronic total coronary occlusion

Background

Percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) of a coronary artery can provide benefits in terms of myocardial function and survival but the procedure is complex and the success rate is relatively low. To assess these benefits, myocardial function, ischemia and viability should be clearly determined by means of a reliable diagnostic test. This study aimed to assess ventricular function and myocardial ischemia before and after PCI for CTO using cardiac magnetic resonance (CMR). NYHA functional class was also assessed before and after PCI.

Methods and results

CMR studies were performed in 43 consecutive patients (7 females; aged 64 ± 9.6 y.o.) with CTO scheduled for PCI and repeated 6 months post-PCI. PCI was successful in 33 (77%) of them. In this group CMR had shown inducible perfusion defects in 26 (79%) before PCI, while they were observed in 10 (30%) post-PCI CMR study (p < 0.001). The number of segments showing inducible perfusion defect (3.4 ± 2 prevs. 2.9 ± 4.5 post-PCI, p = 0.002) was significantly reduced in this group. Regional contractile function of segments showing viability also improved significantly in the group with successful CTO PCI compared to the group with an unsuccessful procedure. NYHA functional class for angina also improved in patients with successful revascularization while it remained unchanged in the group with unsuccessful procedures.

Conclusions

A successful CTO PCI leads to a reduction in inducible myocardial ischemia and to an improvement in regional wall motion, which results in clinical improvement.     

Left Ventricular Diastolic Dysfunction in β-Thalassemia Major with Heart Failure

We studied the clinical, electrocardiographic, echocardiographic, Doppler and T2* cardiac magnetic resonance (CMR) data of all adult β-thalassemia major (β-TM) patients with heart failure (HF) consecutively observed at our referral center of the Sicilian region between 2008 and 2016. There were 16 patients enrolled in the study. Echocardiographic examination showed that only one patient had HF with systolic dysfunction of the left ventricle (HFrEF), whereas the others had HF with preserved systolic function of the left ventricle (HFpEF). Systolic dysfunction of the right ventricle (RV) was observed in 13 cases. Furthermore, 30.0% of the patients presented T2* CMR values consistent with intermediate risk of systolic dysfunction of the left ventricle (LV) due to iron overload, whereas 70.0% had normal values. Typical electrocardiographic abnormalities (wide T wave inversion and low voltages) were observed in 11 out of 16 patients. In conclusion, in the adult β-TM patients with HF recently observed at our center, the predominant form was that with diastolic dysfunction of the LV, and with systolic dysfunction of the RV. Only 30.0% had low values of T2* CMR. Typical electrocardiographic abnormalities were found in 69.0%.     

Mitral valve regurgitation: paradoxical behavior of dobutamine stress cardiac magnetic resonance imaging

A 62-year-old woman with mitral regurgitation (MR) underwent cardiac magnetic resonance (CMR) and dobutamine stress CMR imaging, a widely used method to analyze left ventricular function and MR volumes. During dobutamine provocation at escalating doses, the left ventricular end-diastolic diameter (LVEDD) decreased, with a corresponding decrease in MR. At peak dobutamine dose, the LVEDD further decreased, with near complete relief of MR. Upon cessation of dobutamine provocation, the MR returned to predobutamine level. This case thereby demonstrates that MR may be reversible under certain conditions.     

Clinical Applications for Cardiovascular Magnetic Resonance Imaging at 3 Tesla

Cardiovascular magnetic resonance (CMR) imaging has evolved rapidly and is now accepted as a powerful diagnostic tool with significant clinical and research applications. Clinical 3 Tesla (3 T) scanners are increasingly available and offer improved diagnostic capabilities compared to 1.5 T scanners for perfusion, viability, and coronary imaging. Although technical challenges remain for cardiac imaging at higher field strengths such as balanced steady state free precession (bSSFP) cine imaging, the majority of cardiac applications are feasible at 3 T with comparable or superior image quality to that of 1.5 T. This review will focus on the benefits and limitations of 3 T CMR for common clinical applications and examine areas in development for potential clinical use.     

The emerging clinical role of cardiovascular magnetic resonance imaging

Starting as a research method little more than a decade ago, cardiovascular magnetic resonance (CMR) imaging has rapidly evolved to become a powerful diagnostic tool used in routine clinical cardiology. The contrast in CMR images is generated from protons in different chemical environments and, therefore, enables high-resolution imaging and specific tissue characterization in vivo, without the use of potentially harmful ionizing radiation.CMR imaging is used for the assessment of regional and global ventricular function, and to answer questions regarding anatomy. State-of-the-art CMR sequences allow for a wide range of tissue characterization approaches, including the identification and quantification of nonviable, edematous, inflamed, infiltrated or hypoperfused myocardium. These tissue changes are not only used to help identify the etiology of cardiomyopathies, but also allow for a better understanding of tissue pathology in vivo. CMR tissue characterization may also be used to stage a disease process; for example, elevated T2 signal is consistent with edema and helps differentiate acute from chronic myocardial injury, and the extent of myocardial fibrosis as imaged by contrast-enhanced CMR correlates with adverse patient outcome in ischemic and nonischemic cardiomyopathies.The current role of CMR imaging in clinical cardiology is reviewed, including coronary artery disease, congenital heart disease, nonischemic cardiomyopathies and valvular disease.     

Familiaridade e perceções dos cardiologistas portugueses acerca da ressonância magnética cardíaca e angio-TC cardíaca - dimensão da tarefa à nossa frente

IntroductionRapid advances in cardiac magnetic resonance (CMR) and cardiac computed tomography angiography (CCTA) pose challenges for practicing physicians in terms of awareness of their indications, contraindications, advantages and pitfalls.MethodsWe conducted a nationwide online survey assessing the familiarity, perceptions and patterns of use concerning these imaging modalities based on a questionnaire sent to all physician members of the Portuguese Society of Cardiology.ResultsThe responses from 205 physicians (21% response rate) were analyzed. Roughly half of them requested less than one CMR (51%) or CCTA (52%) per week.Suspected coronary artery disease in symptomatic patients with intermediate pretest probability was considered a good or excellent indication for CCTA by 59% of respondents when performed as a second-line exam, and by 29% as a first-line exam. Cardiac masses, congenital heart disease and cardiomyopathies were considered good or excellent indications for CMR by over 90% of respondents, while assessment of myocardial viability and acute myocardial infarction with normal coronary arteries were considered good or excellent indications by 75% and 65% of respondents, respectively. Less than half (39%) answered all the questions regarding contraindications for CMR correctly, and 15% were unaware that CMR does not involve ionizing radiation. The main reasons for not referring a patient for CMR were limited availability (45%) and cost (36%).ConclusionsPortuguese cardiologists appear to be moderately aware of the indications, contraindications and advantages of these new imaging modalities. Greater efforts should be made to improve physician education on this subject in order to improve patient care.     

Safety and diagnostic accuracy of stress cardiac magnetic resonance imaging vs exercise tolerance testing early after acute ST elevation myocardial infarction

Objective

To determine the safety and diagnostic accuracy of adenosine‐stress cardiac magnetic resonance (CMR) perfusion imaging early after acute ST elevation myocardial infarction (STEMI) compared with standard exercise tolerance testing (ETT).

Design and setting

Cross sectional observational study in a university teaching hospital.

Patients

35 patients admitted with first acute STEMI.

Interventions

All patients underwent a CMR imaging protocol which included rest and adenosine‐stress perfusion, viability, and cardiac functional assessment. All patients also had an ETT (modified Bruce protocol) and x ray coronary angiography.

Main outcome measures

Safety and diagnostic accuracy of adenosine‐stress perfusion CMR vs ETT early after STEMI in identifying patients with significant coronary stenosis (⩾70%) and the need for coronary revascularisation. Also, to determine if CMR can distinguish between ischaemia in the peri‐infarct zone and ischaemia in remote myocardium.

Results

CMR imaging was well tolerated (all patients completed the protocol) and no complications occurred. CMR was more sensitive (86% vs 48%, p = 0.0074) and more specific than ETT (100% vs 50%, p<0.0001) for detecting significant coronary stenosis, and more sensitive for predicting revascularisation (94% vs 56%, p = 0.039). Inducible ischaemia in the infarct related artery territory was seen in 21 of 35 patients and was associated with smaller infarct size and less transmurality of infarction.

Conclusions

Adenosine‐stress CMR imaging is safe early after acute STEMI and identifies patients with significant coronary stenosis more accurately than ETT.     

Principles, current status and clinical implications of ischaemic heart disease assessment by cardiac magnetic resonance imaging

Cardiac magnetic resonance imaging (CMR) has matured into a robust, accurate and highly reproducible imaging modality for the assessment of cardiac function and ischaemic heart disease. The unique physical properties of CMR permit depiction of pathology-specific tissue contrast based on differences in tissue composition, such as myocardial oedema, necrosis and fibrosis. This can be imaged at high spatial resolution allowing characterisation of the acuity of an ischaemic event, the presence and extent of myocardial ischaemia, necrosis and viability. Prognostically important information obtained from CMR evaluation of ischaemic heart disease, such as left ventricular ejection fraction, infarct size and transmurality, infarct location and the presence of intraventricular mechanical dyssynchrony may be used to guide coronary revascularisation, device and medical therapies.     

Assessment of right ventricular function using echocardiographic speckle tracking of the tricuspid annular motion: comparison with cardiac magnetic resonance

Background: Assessment of right ventricular (RV) function is difficult due to the complex shape of this chamber. Tricuspid annular plane systolic excursion (TAPSE) measured with M-mode echocardiography is frequently used as an index of RV function. However, its accuracy may be limited by ultrasound beam misalignment. We hypothesized that two-dimensional (2D) speckle tracking echocardiography (STE) could provide more accurate estimates of RV function. Accordingly, STE was used to quantify tricuspid annular displacement (TAD), from which RV longitudinal shortening fraction (LSF) was calculated. These STE derived indices were compared side-by-side with M-mode TAPSE measurements against cardiac magnetic resonance (CMR) derived RV ejection fraction (EF). Methods: Echocardiography (Philips iE33, four-chamber view) and CMR (Siemens, 1.5 T) were performed on the same day in 63 patients with a wide range of RV EF (23–70% by CMR). TAPSE was measured using M-mode echocardiography. TAD and RV LSF were obtained using STE analysis (QLAB CMQ, Philips). TAPSE, TAD and RV LSF values were compared with RV EF obtained from CMR short axis stacks. Results: STE analysis required <15 seconds and was able to track tricuspid annular motion in all patients as verified visually. Correlation between RV EF and TAD (0.61 free-wall, 0.65 septal) was similar to that with M-mode TAPSE (0.63). However, STE-derived RV LSF showed a higher correlation with CMR EF (r = 0.78). Conclusion: RV LSF measurement by STE is fast and easy to obtain and provides more accurate evaluation of RV EF than the traditional M-mode TAPSE technique, when compared to CMR reference. (Echocardiography 2012;29:19-24)     

Cardiac MRI is an important complementary tool to Doppler echocardiography in the management of patients with pulmonary regurgitation

Cardiac MRI (CMR) is a noninvasive diagnostic tool with comprehensive capabilities similar to that of two-dimensional echocardiography with Doppler. In addition to the ability to evaluate the etiology and severity of pulmonary valve regurgitation (PR), CMR is well designed to serially monitor the impact of the PR on the right ventricle (RV). Importantly, RV dilation and dysfunction is a critical determinate to time surgical intervention. CMR gives the silent RV, suffering from PR, a voice.     

Current perspective the expanding role of cardiovascular magnetic resonance in the identification of myocardial viability.

Cardiovascular magnetic resonance (CMR) is becoming a widespread diagnostic tool available to cardiologists to image different cardiovascular diseases. Among the main applications CMR has proven to be useful in the evaluation of patients with coronary artery disease. Particularly important seems the evaluation of coronary artery disease patients with left ventricular dysfunction. As a matter of fact CMR can identify myocardial viability by using different methods. CMR can accurately measure diastolic wall thickness and demonstrate a contractile reserve in segments with wall motion abnormalities when coupled to low-dose dobutamine infusion. In both applications CMR has proven to be superior to other diagnostic tools that use the same target of viability. By using gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) administration it has recently been shown that CMR can accurately detect myocardial viability. In fact, irreversibly damaged myocardial segments show a delayed hyperenhancement compared to normal segments. Due to its excellent spatial resolution one of the most important information that CMR offers in this application is the transmural extent of necrosis/viability that no other method can offer. The available data suggest that Gd-DTPA CMR could be superior to any other currently used methods in the identification of both stunning and hibernation.     

Fatty liver disease,heart rate and cardiac remodelling: Evidence from the UK Biobank

Background and Aims

Growing evidence supports an association between fatty liver disease (FLD) and cardiac dysfunction and remodelling, leading to cardiovascular disease and heart failure. Herein, we investigated the independent contribution of FLD to cardiac dysfunction and remodelling in participants from the UK Biobank with cardiac magnetic resonance (CMR) data available.

Methods

A total of 18 848 Europeans without chronic viral hepatitis and valvular heart diseases, with liver magnetic resonance imaging and CMR data were included in the analyses. Clinical, laboratory and imaging data were collected using standardized procedures. Multivariable regression models were used to test the association between FLD and CMR endpoints, after adjusting for several cardiometabolic risk factors. Linear regression models with regularization (Least Absolute Shrinkage and Selection Operator [LASSO], Ridge and Elastic Net) were used to generate predictive models for heart-related endpoints.

Results

FLD was independently associated with higher average heart rate, higher cardiac remodelling (higher eccentricity ratio and lower remodelling index), lower left and right ventricular volumes (end-systolic, end-diastolic and stroke volumes) as well as with lower left and right atrial maximal volumes (p < 0.001). FLD was the strongest positive predictor for average heart rate, followed by age, hypertension and type 2 diabetes. Male sex was the strongest positive predictor for eccentricity ratio followed by FLD, age, hypertension and BMI. For LV volumes, FLD was the strongest negative predictor along with age.

Conclusions

FLD is an independent predictor of higher heart rate and early cardiac remodelling associated with reduced ventricular volumes.     

The differential diagnosis of splachnic vein thrombosis – response to Chatziantoniou & Hunt

The age at which it is necessary to start Cardiovascular Magnetic Resonance (CMR) T2* screening in thalassaemia major (TM) is still uncertain. To clarify this point, we evaluated the prevalence of myocardial iron overload (MIO), function and fibrosis by CMR in TM patients younger than 10 years. We retrospectively selected 35 TM patients enrolled in the Myocardial Iron Overload in Thalassaemia network. MIO was measured by T2* multislice multiecho technique. Biventricular function parameters were evaluated by cine images. To detect myocardial fibrosis, late gadolinium enhancement images were acquired. Patients’ age ranged from 4·2 to 9·7 years. All scans were performed without sedation. Nine patients showed no MIO, 22 patients had heterogeneous MIO with a T2* global value ≥20 ms; two patients had heterogeneous MIO with a T2* global value <20 ms and two patients showed homogeneous MIO. No patient showed myocardial fibrosis. Among the patients with heart T2*<20 ms, the youngest was 6 years old, none showed heart dysfunction and the iron transfused was <35 g in all cases. Cardiac iron loading can occur much earlier than previously described. The first cardiac T2* assessment should be performed as early as feasible without sedation, especially if chelation is started late or if poor compliance is suspected.     

Echocardiography vs cardiac magnetic resonance imaging assessment of the systemic right ventricle for patients with d‐transposition of the great arteries status post atrial switch

Objective: Patients with Dextro-transposition of the great arteries status post atrial switch (dTGA s/p atrial switch) are “at-risk” for systemic right ventricular (RV) dysfunction. Due to complex RV geometry, echocardiography (Echo) does not allow accurate determination of ejection fraction (EF), but cardiac magnetic resonance imaging (CMR) allows quantitative right ventricular assessment. Measures of ventricular deformation may be precursors to global ventricular dysfunction. The primary aim of this study was to characterize imaging and clinical findings for adult patients with dTGA s/p atrial switch.
Design: This was a retrospective cohort study of patients with dTGA s/p atrial switch operation (February 1966 to August 1988) with CMR performed at Children’s Hospital of Wisconsin (from September 2005 to May 2015). Eligible patients had clinic visit, Echo, and exercise stress test within 1 year of CMR.
Results: This study enrolled twenty-seven patients (16 males, 11 females) with dTGA s/p atrial switch (18 with Mustard operation and 9 with Senning operation; median age 30 years; 74% New York Heart Association class 1 and 26% class 2). Seventy-four percentage had normal RV systolic function (RV EF >45% by CMR). No correlation was observed between Echo strain data and clinical status (EF, exercise endurance, VO2 max, or New York Heart Association class). Cardiac magnetic resonance imaging RV global circumferential strain GCS and RV EF had moderate negative correlation (r = −0.65, P < .001). Global circumferential strain was significantly different for those with RV EF above and below 45%, while global peak longitudinal strain (GLS) was not. Patients had reduced CMR myocardial strain values compared with healthy controls.
Conclusions: Reduced RV CMR GCS (for those with RV EF <45%) suggests that CMR evaluation may enhance early detection of detrimental changes in the systemic RV myocardium.