Assessment of myocardial ischemia with cardiovascular magnetic resonance

Quantitative Assessment of Myocardial Ischemia With Positron Emission Tomography

Recent advances in positron emission tomography (PET) technology and reconstruction techniques have now made quantitative assessment using cardiac PET readily available in most cardiac PET imaging centers. Multiple PET myocardial perfusion imaging (MPI) radiopharmaceuticals are available for quantitative examination of myocardial ischemia, with each having distinct convenience and accuracy profile. Important properties of these radiopharmaceuticals ( 15 O-water, 13 N-ammonia, 82 Rb, 11 C-acetate, and 18 F-flurpiridaz) including radionuclide half-life, mean positron range in tissue, and the relationship between kinetic parameters and myocardial blood flow (MBF) are presented. Absolute quantification of MBF requires PET MPI to be performed with protocols that allow the generation of dynamic multiframes of reconstructed data. Using a tissue compartment model, the rate constant that governs the rate of PET MPI radiopharmaceutical extraction from the blood plasma to myocardial tissue is calculated. Then, this rate constant ( K1 ) is converted to MBF using an established extraction formula for each radiopharmaceutical. As most of the modern PET scanners acquire the data only in list mode, techniques of processing the list-mode data into dynamic multiframes are also reviewed. Finally, the impact of modern PET technologies such as PET/CT, PET/MR, total-body PET, machine learning/deep learning on comprehensive and quantitative assessment of myocardial ischemia is briefly described in this review.

Prognostic value of dipyridamole stress perfusion cardiovascular magnetic resonance in elderly patients >75 years with suspected coronary artery disease

AIMS

There are only very few data on the prognostic value of stress cardiovascular magnetic resonance (CMR) in elderly people, while life expectancy of the general population is steadily increasing. Therefore, this study aims to assess the prognostic value of vasodilator stress perfusion CMR in elderly >75 years.

METHODS AND RESULTS

Between 2008 and 2017, we included consecutive elderly >75 years without known coronary artery disease (CAD) referred for dipyridamole stress CMR. They were followed for the occurrence of major adverse cardiovascular events (MACE) including cardiac death or non-fatal myocardial infarction. Univariate and multivariate analyses were performed to determine the prognostic value of ischaemia or late gadolinium enhancement. Of 754 elderly individuals (82.0 ± 3.9 years, 48.4% men), 659 (87.4%) completed the follow-up with median follow-up of 4.7 years. Using Kaplan-Meier analysis, the presence of myocardial ischaemia was associated with the occurrence of MACE [hazard ratio (HR) 5.38, 95% confidence interval (CI): 3.56-9.56; P < 0.001]. In a multivariable Cox regression including clinical characteristics and CMR indexes, inducible ischaemia was an independent predictor of a higher incidence of MACE (HR 4.44, 95% CI: 2.51-7.86; P < 0.001). In patients without ischaemia, the occurrence of MACE was lower in women when compared with men (P < 0.01).

CONCLUSION

Stress CMR is safe and has discriminative prognostic value in elderly, with a significantly lower event rate of future cardiovascular event or death in subjects without ischaemia or infarction.

Vasodilatation stress cardiovascular magnetic resonance imaging: Feasibility, workflow and safety in a large prospective registry of more than 35,000 patients

BACKGROUND

Cardiovascular magnetic resonance imaging (CMR) is an accurate technique for assessing ventricular function, myocardial perfusion and viability; its development remains limited mainly because of logistical and time constraints. Data regarding optimization of a dedicated stress CMR workflow are needed.

AIMS

This study aimed to describe the optimization of a dedicated workflow, and to assess the feasibility and safety of stress CMR in a large registry of>35,000 patients.

METHODS

A large single-centre French registry of vasodilator stress CMR included consecutive patients referred between 2008 and 2019 for the detection of inducible ischaemia. Stress CMR was performed at 1.5 Tesla using dipyridamole. Clinical and demographic data, test quality, CMR findings, haemodynamic data and complications were recorded prospectively. A locally optimized workflow was described and evaluated.

RESULTS

Among the 35,862 patients referred for vasodilator stress CMR (mean age 68.9±11.8 years; 64.1% male), the stress CMR protocol was completed in 35,013 (97.6%) patients; 144 (0.3%) patients with missing baseline data were excluded. The mean examination duration was 27±5min, with image quality optimal in 90.8%, suboptimal in 7.1% and poor in 0.5% of cases. Images were diagnostic in 97.9% of patients. No patients died during or immediately after CMR. Fifty-six (0.16%) patients had severe complications. The incidence of non-severe complications was low (1.5%), whereas minor symptoms occurred frequently (35.5%). The presence of ischaemia was associated with a higher incidence of severe complications, non-severe complications and minor symptoms (all P<0.001).

CONCLUSIONS

This single-centre prospective registry of>35,000 referral patients with known or suspected CAD showed that stress CMR was feasible in clinical routine practice, with high diagnostic image quality and an excellent safety profile. Inducible ischaemia was associated with severe complications, non-severe complications and minor symptoms.

Exercise Cardiac Magnetic Resonance Imaging in Boys With Duchenne Muscular Dystrophy Without Cardiac Disease

BACKGROUND

Duchenne muscular dystrophy is caused by mutations in the DMD gene, resulting in cardiomyopathy in all affected children by 18 years. Although cardiomyopathy is now the leading cause of mortality in these children, there is ongoing debate regarding timely diagnosis, secondary prevention, and treatment of this condition. The purpose of this study was to use exercise cardiac magnetic resonance imaging in asymptomatic young boys with Duchenne muscular dystrophy to describe their heart function and compare this with healthy controls.

METHODS

We studied 11 boys with Duchenne muscular dystrophy aged 8.6 to 13.9 years and 11 healthy age- and sex-matched controls.

RESULTS

Compared with the controls, boys with Duchenne muscular dystrophy had lower ejection fraction at rest (57% versus 63%; P = 0.004). During submaximal exercise, they reached similar peak tachycardia but increased their heart rate and cardiac output only half as much as controls (P = 0.003 and P = 0.014, respectively). End-systolic volume remained higher in boys with Duchenne muscular dystrophy both at rest and during exercise. When transthoracic echocardiography was compared with cardiac magnetic resonance imaging, 45% of the echocardiograms had suboptimal or poor views in the Duchenne muscular dystrophy group.

CONCLUSIONS

Boys with Duchenne muscular dystrophy had abnormalities in left ventricular systolic function that were exaggerated by exercise stress. Exercise cardiac magnetic resonance imaging is feasible in a select population of children with Duchenne muscular dystrophy, and it has the potential to unmask early signs of cardiomyopathy.

Cardiovascular Imaging in Obesity

Obesity represents one of the most challenging public health problems of our century. It accounts for approximately 5% of deaths worldwide, mostly owing to cardiovascular disease and its associated complications. Cardiovascular noninvasive imaging may provide early accurate information about hypertrophy and ischemia/fibrosis in obese subjects. Echocardiography and nuclear cardiology have serious limitations in obese subjects owing to poor acoustic window and attenuation artifacts, respectively. Coronary computed tomography angiography can provide information about obstructive coronary disease; however, the use of radiation is a serious disadvantage. Finally, cardiac magnetic resonance (CMR) holds the promise of an "all in one" examination by combining evaluation of function, wall motion/thickness, stress rest/perfusion, replacement and diffuse fibrosis without radiation. Future studies are required to document the cost/benefit ratio of the CMR in the evaluation of cardiovascular risk in overweight/obese children and adolescents.

Prognostic value of vasodilator stress perfusion CMR in patients with previous coronary artery bypass graft

AIMS 

The accuracy and prognostic value of stress perfusion cardiac magnetic resonance (CMR) are established in coronary artery disease (CAD) patients. Because myocardial contrast kinetics may be altered after coronary artery bypass graft (CABG), most studies excluded CABG patients. This study aimed to assess the prognostic value of vasodilator stress perfusion CMR in CABG patients.

METHODS AND RESULTS 

Consecutive CABG patients referred for stress CMR were retrospectively included and followed for the occurrence of major adverse cardiovascular events (MACE) including cardiovascular (CV) death or non-fatal myocardial infarction (MI). Cox regression analyses were performed to determine the prognostic association of inducible ischaemia and late gadolinium enhancement (LGE) by CMR. Of 866 consecutive CABG patients, 852 underwent the stress CMR protocol and 771 (89%) completed the follow-up [median (interquartile range) 4.2 (3.3-6.2) years]. There were 85 MACE (63 CV deaths and 22 non-fatal MI). Using Kaplan-Meier analysis, the presence of inducible ischaemia identified the occurrence of MACE [hazard ratio (HR) 3.52, 95% confidence interval (CI): 2.27-5.48; P < 0.001] and CV death (HR 2.55, 95% CI: 1.52-4.25; P < 0.001). In a multivariable stepwise Cox regression including clinical characteristics and CMR indexes, the presence of inducible ischaemia was an independent predictor of a higher incidence of MACE (HR 3.22, 95% CI: 2.06-5.02; P < 0.001) and CV death (HR 2.15, 95% CI: 1.28-3.62; P = 0.003), and the same was observed for LGE (both P = 0.02).

CONCLUSION 

Stress CMR has a good discriminative prognostic value in patients after CABG, with a higher incidence of MACE and CV death in patients with inducible ischaemia and/or LGE.

Feasibility and Prognostic Value of Vasodilator Stress Perfusion CMR in Patients With Atrial Fibrillation

OBJECTIVES

The aim of this study was to assess the feasibility and prognostic value of vasodilator stress perfusion cardiovascular magnetic resonance (CMR) in patients with atrial fibrillation (AF).

BACKGROUND

Because most studies have excluded arrhythmic patients, the prognostic value of stress perfusion CMR in patients with AF is unknown.

METHODS

Between 2008 and 2018, consecutive patients with suspected or stable chronic coronary artery disease and AF referred for vasodilator stress perfusion CMR were included and followed for the occurrence of major adverse cardiovascular event(s) (MACE), defined as cardiovascular death or nonfatal myocardial infarction. The diagnosis of AF was defined by 12-lead electrocardiography before and after CMR. Univariate and multivariate Cox regressions were performed to determine the prognostic value of inducible ischemia or late gadolinium enhancement (LGE) by CMR.

RESULTS

Of 639 patients (mean age 72 ± 9 years, 77% men), 602 (94%) completed the CMR protocol, and 538 (89%) completed follow-up (median 5.1 years); 80 had MACE. Using Kaplan-Meier analysis, the presence of ischemia (hazard ratio [HR]: 7.56; 95% confidence interval [CI]: 4.86 to 11.80) or LGE (HR: 2.41; 95% CI: 1.55 to 3.74) was associated with the occurrence of MACE (p < 0.001 for both). In a multivariate Cox regression including clinical and CMR indexes, the presence of ischemia (HR: 5.98; 95% CI: 3.68 to 9.73) or LGE (HR: 2.61; 95% CI: 1.89 to 3.60) was an independent predictor of MACE (p < 0.001 for both).

CONCLUSIONS

In patients with AF, stress perfusion CMR is feasible and has good discriminative prognostic value to predict the occurrence of MACE.

Echocardiographic global longitudinal strain is associated with infarct size assessed by cardiac magnetic resonance in acute myocardial infarction

The aim of this study was to investigate if there was an association between infarct size (IS) measured by cardiac magnetic resonance (CMR) and echocardiographic global longitudinal strain (GLS) in the early stage of acute myocardial infarction in patients with preserved left ventricular ejection fraction (LVEF). Patients with ST-segment elevation myocardial infarction who underwent primary percutaneous coronary intervention were assessed with CMR and transthoracic echocardiogram within 1 week of hospital admission. Two-dimensional speckle tracking was performed using a semi-automatic algorithm (EchoPac, GE Healthcare). Longitudinal strain curves were generated in a 17-segment model covering the entire left ventricular myocardium. GLS was calculated automatically. LVEF was measured by auto-LVEF in EchoPac. IS was measured by late gadolinium enhancement CMR in short-axis views covering the left ventricle. The study population consisted of 49 patients (age 60.4 ± 9.7 years; 92% male). The study population had preserved echocardiographic LVEF with a mean of 45.8 ± 8.7%. For each percent increase of IS, we found an impairment in GLS by 1.59% (95% CI 0.57–2.61), P = 0.02, after adjustment for sex, age and LVEF. No significant association between IS and echocardiographic LVEF was found: −0.25 (95% CI: −0.61 to 0.11), P = 0.51. At the segmental level, the strongest association between IS and longitudinal strain was found in the apical part of the LV: impairment of 1.69% (95% CI: 1.14–2.23), P < 0.001, for each percent increase in IS. In conclusion, GLS was significantly associated with IS in the early stage of acute myocardial infarction in patients with preserved LVEF, and this association was strongest in the apical part of the LV. No association between IS and LVEF was found.

Imaging the heart to detect cardiomyopathy in Duchenne muscular dystrophy: A review

Duchenne Muscular Dystrophy is the most common paediatric neuromuscular disorder. Mutations in the DMD gene on the X-chromosome result in progressive skeletal muscle weakness as the main clinical manifestation. However, cardiac muscle is also affected, with cardiomyopathy becoming an increasingly recognised cause of morbidity, and now the leading cause of mortality in this group. The diagnosis of cardiomyopathy has often been made late due to technical limitations in transthoracic echocardiograms and delayed symptomatology in less mobile patients. Increasingly, evidence supports earlier pharmacological intervention in cardiomyopathy to improve outcomes. However, the optimal timing of initiation remains uncertain, and the benefits of prophylactic therapy are unproven. Current treatment guidelines suggest initiation of therapy once cardiac dysfunction is detected. This review focuses on new and evolving techniques for earlier detection of Duchenne muscular dystrophy-associated cardiomyopathy. Transthoracic echocardiography or cardiac magnetic resonance imaging performed under physiological stress (dobutamine or exercise), can unmask early cardiac dysfunction. Cardiac magnetic resonance imaging can define cardiac function with greater accuracy and reliability than an echocardiogram, and is not limited by body habitus. Improved imaging techniques, used in a timely fashion, offer the potential for early detection of cardiomyopathy and improved long-term outcomes.

Right Ventricle Remodeling and Function in Scleroderma Patients

Scleroderma, known also as systemic sclerosis (SSc), is a severe disease associated with high mortality rates, and right ventricular (RV) remodeling and dysfunction, along with pulmonary artery hypertension (PAH), are among the most important internal organ manifestations of this disease. PAH has a higher prevalence in patients with SSc compared to the general population and represents a significant predictor of mortality in SSc. In patients with SSc, the morphological remodeling and alteration of RV function begin even before the setting of PAH and lead to development of a specific adaptive pattern of the RV which is different from the one recorded in patients with IAPH. These alterations cause worse outcomes and increased mortality rates in SSc patients. Early detection of RV dysfunction and remodeling is possible using modern imaging tools currently available and can indicate the initiation of specific therapeutic measures before installation of PAH. The aim of this review is to summarize the current knowledge related to mechanisms involved in the remodeling and functional alteration of the RV in SSc patients.

Novel Imaging Techniques for Heart Failure

Imaging techniques play a main role in heart failure (HF) diagnosis, assessment of aetiology and treatment guidance. Echocardiography is the method of choice for its availability, cost and it provides most of the information required for the management and follow up of HF patients. Other non-invasive cardiac imaging modalities, such as cardiovascular magnetic resonance (CMR), nuclear imaging-positron emission tomography (PET) and single-photon emission computed tomography (SPECT) and computed tomography (CT) could provide additional aetiological, prognostic and therapeutic information, especially in selected populations. This article reviews current indications and possible future applications of imaging modalities to improve the management of HF patients.

Cardiac magnetic resonance imaging for ischemic heart disease: update on diagnosis and prognosis

Despite significant advancements in the treatment of ischemic heart disease (IHD), IHD remains a leading cause of mortality and morbidity. In addition, there remains clinical equipoise regarding a number of important management issues across the spectrum of IHD, from evaluating patients with chest pain in the emergency department, to deciding whether patients with chronic stable angina or severe ischemic cardiomyopathies should undergo invasive revascularization procedures. Recent data over the past 2 decades has demonstrated that cardiac magnetic resonance imaging is highly accurate and carries robust prognostic value in the evaluation of patients with both acute and chronic IHD. The combination of cine imaging for cardiac structure and function, late gadolinium enhancement imaging of myocardial scar, qualitative and quantitative measures of myocardial fibrosis, and stress perfusion imaging for the presence and extent of ischemia provides a comprehensive and detailed characterization of cardiac anatomy and physiology that guides critical treatment decisions for patients. This review aims to cover both the diagnostic and prognostic utility of cardiac magnetic resonance imaging for the spectrum of IHD.

Vasodilator stress perfusion CMR imaging is feasible and prognostic in obese patients

OBJECTIVES

This study sought to determine feasibility and prognostic performance of stress cardiac magnetic resonance (CMR) in obese patients (body mass index [BMI] ≥30 kg/m(2)).

BACKGROUND

Current stress imaging methods remain limited in obese patients. Given the impact of the obesity epidemic on cardiovascular disease, alternative methods to effectively risk stratify obese patients are needed.

METHODS

Consecutive patients with a BMI ≥30 kg/m(2) referred for vasodilating stress CMR were followed for major adverse cardiovascular events (MACE), defined as cardiac death or nonfatal myocardial infarction. Univariable and multivariable Cox regressions for MACE were performed to determine the prognostic association of inducible ischemia or late gadolinium enhancement (LGE) by CMR beyond traditional clinical risk indexes.

RESULTS

Of 285 obese patients, 272 (95%) completed the CMR protocol, and among these, 255 (94%) achieved diagnostic imaging quality. Mean BMI was 35.4 ± 4.8 kg/m(2), with a maximum weight of 200 kg. Reasons for failure to complete CMR included claustrophobia (n = 4), intolerance to stress agent (n = 4), poor gating (n = 4), and declining participation (n = 1). Sedation was required in 19 patients (7%; 2 patients with intravenous sedation). Sixteen patients required scanning by a 70-cm-bore system (6%). Patients without inducible ischemia or LGE experienced a substantially lower annual rate of MACE (0.3% vs. 6.3% for those with ischemia and 6.7% for those with ischemia and LGE). Median follow-up of the cohort was 2.1 years. In a multivariable stepwise Cox regression including clinical characteristics and CMR indexes, inducible ischemia (hazard ratio 7.5; 95% confidence interval: 2.0 to 28.0; p = 0.002) remained independently associated with MACE. When patients with early coronary revascularization (within 90 days of CMR) were censored on the day of revascularization, both presence of inducible ischemia and ischemia extent per segment maintained a strong association with MACE.

CONCLUSIONS

Stress CMR is feasible and effective in prognosticating obese patients, with a very low negative event rate in patients without ischemia or infarction.

Rapid ungated myocardial perfusion cardiovascular magnetic resonance: preliminary diagnostic accuracy

BACKGROUND

Myocardial perfusion cardiovascular magnetic resonance (CMR) is a well-established method for detection of ischemic heart disease. However, ECG gating problems can result in image degradation and non-diagnostic scans, particularly in patients with arrhythmias.

METHODS

A turboFLASH saturation recovery pulse sequence was used without any ECG triggering. One saturation pulse followed by 4-5 slices of undersampled radial k-space images was acquired rapidly, on the order of 40-50 msec per image. The acquisition of the set of 4-5 slices was continuously repeated approximately 4 times per second. An iterative constrained reconstruction method was used to reconstruct the ungated images. The ungated perfusion images were post-processed into three different sets of images (ungated, self-gated to near systole, and self-gated to near diastole). To test the ungated approach and compare the different processing methods, 8 patients scheduled for coronary angiography underwent stress and rest perfusion imaging with the ungated acquisition. Six patients had a history of atrial fibrillation (AF). Three blinded readers assessed image quality and presence/absence of disease.

RESULTS

All 8 subjects successfully completed the perfusion CMR protocol and 7/8 underwent coronary angiography. Three patients were in atrial fibrillation during CMR. Overall, the CMR images were of high quality as assessed by the three readers. There was little difference in image quality between patients in AF compared to those in sinus rhythm (3.6±0.7 vs. 3.3±0.5). Stress/rest perfusion imaging showed normal perfusion in 4 patients, fixed perfusion defects in 2 patients, and reversible perfusion defects in 2 patients, corresponding with angiographic results. Pooled results from the independent readers gave a sensitivity of 0.92 (CI 0.65-0.99) and specificity of 0.92 (CI 0.65-0.99) for the detection of coronary artery disease using ungated perfusion imaging. The same sensitivity, and a specificity of 1 (CI 0.76-1), was achieved when the images were self-gated after acquisition into near systole or near diastole.

CONCLUSIONS

Ungated radial dynamic perfusion CMR can give high quality imaging in patients in sinus rhythm and during atrial fibrillation. In this small cohort, high diagnostic accuracy was possible with this rapid perfusion imaging sequence. An ungated approach simplifies the acquisition and could expand the role of perfusion CMR to include patients with arrhythmia and those with gating problems.