Diagnosis of early myocarditis after respiratory or gastrointestinal tract viral infection: insights from cardiovascular magnetic resonance

Update on Myocarditis: From Etiology and Clinical Picture to Modern Diagnostics and Methods of Treatment

Although the frequency of myocarditis in the general population is very difficult to accurately determine due to the large number of asymptomatic cases, the incidence of this disease is increasing significantly due to better defined criteria for diagnosis and the development of modern diagnostic methods. The multitude of different etiological factors, the diversity of the clinical picture, and the variability of the diagnostic findings make this disease often demanding both for the selection of the diagnostic modality and for the proper therapeutic approach. The previously known most common viral etiology of this disease is today overshadowed by new findings based on immune-mediated processes, associated with diseases that in their natural course can lead to myocardial involvement, as well as the iatrogenic cause of myocarditis, which is due to use of immune checkpoint inhibitors in the treatment of cancer patients. Suspecting that a patient with polymorphic and non-specific clinical signs and symptoms, such as changes in ECG and echocardiography readings, has myocarditis is the starting point in the diagnostic algorithm. Cardio magnetic resonance imaging is non-invasive and is the gold standard for diagnosis and clinical follow-up of these patients. Endomyocardial biopsy as an invasive method is the diagnostic choice in life-threatening cases with suspicion of fulminant myocarditis where the diagnosis has not yet established or there is no adequate response to the applied therapeutic regimen. The treatment of myocarditis is increasingly demanding and includes conservative methods of treating heart failure, immunomodulatory and immunospressive therapy, methods of mechanical circulatory support, and heart transplantation. The goal of developing new diagnostic and therapeutic methods is to reduce mortality from this complex disease, which is still high.

The utility of cardiac magnetic resonance imaging in the diagnosis of adult patients with acute myocarditis: A systematic review and meta-analysis

BACKGROUND

The presence of myocardial late gadolinium enhancement (LGE) indicates myocyte necrosis, and assists with the diagnosis of acute myocarditis (AM). Cardiac magnetic resonance (CMR) measures other than LGE i.e. tissue characterization and myocardial structural and functional parameters, play an important diagnostic role in assessment for inflammation, as seen in AM. The aim of this systematic review was to appraise the evidence for the use of quantitative CMR measures to identify myocardial inflammation in order to diagnose of AM in adult patients.

METHODS

A systematic literature search of medical databases was performed using PRISMA principles to identify relevant CMR studies on AM in adults (2005-2020; English; PROSPERO registration CRD42020180605). Data for a range of quantitative CMR measures were extracted. Continuous variables with low heterogeneity were meta-analyzed using a random-effects model for overall effect size measured as the standard mean difference (SMD).

RESULTS

Available data from 25 studies reporting continuous quantitative 1.5 T CMR measures revealed that AM is most reliably differentiated from healthy controls using T1 mapping (SMD 1.80, p < 0.01) and T2 mapping (SMD 1.63, p < 0.01), respectively. All other measures examined including T2-weighted ratio, extracellular volume, early gadolinium enhancement ratio, right ventricular ejection fraction, and LV end-diastolic volume, mass, ejection fraction, longitudinal strain, circumferential strain, and radial strain also had discriminatory ability although with smaller standard mean difference values (|SMD| 0.32-0.96, p < 0.01 for all).

CONCLUSIONS

Meta-analysis shows that myocardial tissue characterization (T1 mapping>T2 mapping) followed by measures of left ventricular structure and function demonstrate diagnostic discriminatory ability in AM.

SARS-CoV-2 Myocarditis in a High School Athlete after COVID-19 and Its Implications for Clearance for Sports

This case report describes a high school athlete with palpitation, myalgia, fatigue, and dyspnea on exertion after SARS-CoV-2 infection with evidence of myocarditis by cardiac magnetic resonance (CMR), but echocardiography and troponin were normal. This case is unusual as the standard cardiac tests recommended by the American Heart Association for sports clearance, including ECG, echocardiography, and cardiac biomarkers, were normal. Still, she continued to be symptomatic after mild COVID-19. The CMR was performed to evaluate her unexplained palpitation and showed patchy myocardial edema two months after her initial SARS-CoV-2 infection. In this case, the diagnosis of myocardial involvement would be missed by normal echocardiograms and cardiac bio-markers without CMR. Because acute myocarditis is a risk factor for sudden death in competitive athletes, pediatric cardiologists should consider performing additional tests such as cardiac MRI in symptomatic COVID-19 patients, even if cardiac biomarkers and echocardiograms are normal.

Diagnostic value of 3.0 T cardiac MRI in children with suspected myocarditis: multi-parameter analysis for the evaluation of acute and chronic myocarditis

BACKGROUND

Cardiac magnetic resonance (CMR) is an established tool for detection of myocarditis. However, no comprehensive data for CMR based on the "Lake Louise" criteria in pediatric myocarditis exists to date.

PURPOSE

To evaluate the value of multi-parameter CMR in children with suspected acute (AMC) and chronic myocarditis (CMC).

MATERIAL AND METHODS

We examined 73 pediatric patients with clinically suspected AMC (n = 25) and CMC (n = 48). We compared them to 17 controls. All individuals underwent CMR, including function analyses, T2 ratio, early gadolinium enhancement ratio (EGEr), and late gadolinium enhancement (LGE).

RESULTS

In AMC, 19 (76%) patients were abnormal in any two of three parameters (T2 ratio, EGEr, and LGE). There was a significant difference between AMC and controls in LVEF (51.2% vs. 61.3%), mass (130.2 ± 14.0 vs. 120.5 ± 13.9 g), T2 ratio (1.96 ± 0.2 vs. 1.69 ± 0.13), and EGEr (4.1 ± 0.27 vs. 3.4 ± 0.39) (P < 0.05). In CMC, 26 (54.1%) patients were abnormal in any two of three parameters. There was no significant difference between CMC and controls in LVEF and mass, but there was a statistical difference in T2 ratio (1.88 ± 0.18 vs. 1.69 ± 0.13) and in EGEr (3.93 ± 0.22 vs. 3.4 ± 0.39) (P < 0.05). There was an increase in LVEF while both T2 ratio and EGEr significantly decreased (P < 0.05) during follow-up of acute fulminant myocarditis.

CONCLUSION

Comprehensive CMR may serve as a powerful tool in children with suspected AMC. CMR in assessment of CMC may be valuable, but it is not satisfactory.

T2-weighted cardiac magnetic resonance image and myocardial biomarker in hypertrophic cardiomyopathy

The phenomenon of high signal intensity on T2-weighted imaging of cardiac magnetic resonance in hypertrophic cardiomyopathy (HCM) has been previously studied. However, the underlying histopathologic mechanism remains unclear. Elevated cardiac troponin can be detected in some HCM patients. A reasonable hypothesis is that high myocardial T2 signal is a potential marker of myocardial injury in HCM. We sought to investigate the association between cardiac troponin and the extent of high T2 signals in HCM patients.Forty-four HCM patients underwent 3.0T cardiac magnetic resonance scanning. On T2-weighted images, the number of segments with high-signal intensity (myocardium-to-skeletal muscle signal intensity ratio >2) and the percentage of high-signal area (>2 standard deviation above the remote tissue) were measured in 16 myocardial segments along the LV mid-myocardial circumference on 3 short-axis images. The level of high-sensitivity cardiac troponin T (hs-cTnT) was also assessed.Myocardial high T2 signals were identified in 33 (75%) patients and 144 (20.5%) segments. Elevated hs-cTnT was observed in 28 (63.6%) patients. The Cochran-Armitage test showed a statistically significant trend of increasing levels of hs-cTnT with elevated number of segments with myocardial high T2 signal (P = .002). Further, the percentage of myocardium with high T2 signal was significantly associated with the hs-cTnT level (Pearson correlation: r = 0.388, P = .009).Myocardium with high T2 signals was very common in patients with HCM.Its extent is related with the level of plasma hs-cTnT.

The best way to assess oedema using T1, T2 mapping or three-dimensional T2-weighted fast-spin-echo triple inversion recovery sequences via cardiovascular MRI in outpatients with suspected myocarditis

AIM

To evaluated T1-, T2 mapping, and a three-dimensional (3D) T2-weighted fast-spin-echo triple inversion recovery sequences (3D STIR) for diagnosing myocardial oedema in patients with suspected early myocarditis and at follow-up.

MATERIALS AND METHODS

Sixteen patients with suspected myocarditis and 15 controls matched for gender and age were examined prospectively. To evaluate oedema, an electrocardiogram-triggered T1 and T2 mapping with a gradient spin echo technique and 3D STIR sequences were used to cover the entire left ventricle. The signal intensity ratio (heart muscle in relation to skeletal muscle) was calculated (3D STIR ratio). All patients underwent repeat examinations at follow-up.

RESULTS

The mean 3D-STIR ratio was 2.14±0.45 at the patients' initial examination as compared to the control patients' 1.54±0.18 in (p=0.0001) and 1.75±0.16 in patients at follow-up (p=0.002 versus first visit). The 3D STIR ratio of the septum, anterior, lateral, and inferior wall also differed significantly between patients and controls. No significant difference was observed in T1 and T2 mapping between patients and controls at baseline and patients at follow-up.

CONCLUSIONS

A significantly higher global signal intensity ratio with 3D-STIR was identified in patients with suspected myocarditis compared to controls, and a significant change during follow-up. No significant difference was detected in T1-, T2 mapping between patients and controls, or between the initial examination and follow-up of patients. The global 3D-STIR ratio may therefore be useful for the diagnosis of myocarditis and should be explored further.

Diagnostic Accuracy of Cardiovascular Magnetic Resonance in Acute Myocarditis: A Systematic Review and Meta-Analysis

OBJECTIVES

The purpose of this systematic review was to explore the diagnostic accuracy of various cardiovascular magnetic resonance (CMR) index tests for the diagnosis of acute myocarditis in adult patients.

BACKGROUND

Acute myocarditis remains one of the most challenging diagnoses in cardiology. CMR has emerged as the diagnostic tool of choice to detect acute myocardial injury and necrosis in patients with suspected myocarditis.

METHODS

We considered all diagnostic cohort and case-control studies. We searched MEDLINE, EMBASE, Cochrane Library, SCOPUS, and Web of Science up to April 21, 2017. We used the Quality Assessment of Diagnostic Accuracy Studies-2 tool to assess the quality of included studies. PROSPERO registration number CRD42017055778 was used.

RESULTS

Twenty-two studies were included in the systematic review. Because significant heterogeneity exists among the studies, we only present hierarchical receiver operator curves. The areas under the curve (AUC) for each index test were for T1 mapping 0.95 (95% confidence interval [CI]: 0.93 to 0.97), for T2 mapping 0.88 (95% CI: 0.85 to 0.91), for extracellular volume fraction (ECV) 0.81 (95% CI: 0.78 to 0.85), for increased T2 ratio/signal 0.80 (95% CI: 0.76 to 0.83), for late gadolinium enhancement (LGE) 0.87 (95% CI: 0.84 to 0.90), for early gadolinium enhancement (EGE) 0.78 (95% CI: 0.74 to 0.81), and for the Lake Louise criteria (LLC) 0.81 (95% CI: 0.77 to 0.84). Native T1 mapping had superior diagnostic accuracy across all index tests. The AUC of T2 mapping was greater than the AUC of increased T2 ratio/signal and EGE, whereas ECV showed no superiority compared with other index tests. LGE had better diagnostic accuracy compared with the classic CMR index tests, similar accuracy with T2 mapping and ECV, and only T1 mapping surpassed it.

CONCLUSIONS

Novel CMR mapping techniques provide high diagnostic accuracies for the diagnosis of acute myocarditis and constitute promising successors of the classic elements of the LLC for routine diagnostic protocols.

Patients with exercise-associated ventricular ectopy present evidence of myocarditis

BACKGROUND

The origin and clinical relevance of exercise-induced premature ventricular beats (PVBs) in patients without coronary heart disease or cardiomyopathies is unknown. Cardiovascular magnetic resonance enables us to non-invasively assess myocardial scarring and oedema. The purpose of our study was to discover any evidence of myocardial anomalies in patients with exercise-induced ventricular premature beats.

METHODS

We examined 162 consecutive patients presenting palpitations and documented exercise-induced premature ventricular beats (PVBs) but no history or evidence of structural heart disease. Results were compared with 70 controls matched for gender and age. ECG-triggered, T2-weighted, fast spin echo triple inversion recovery sequences and late gadolinium enhancement were obtained as well as LV function and dimensions.

RESULTS

Structural anomalies in the myocardium and/or pericardium were present in 85 % of patients with exercise-induced PVBs. We observed a significant difference between patients with PVBs and controls in late gadolinium enhancement, that is 68 % presented subepicardial or midmyocardial lesions upon enhancement, whereas only 9 % of the controls did so (p < 0.0001). More patients presented pericardial enhancement (35 %) or pericardial thickening (27 %) compared to controls (21 % and 13 %, p < 0.0001). Myocardial oedema was present in 37 % of the patients and in only one control, p < 0.0001. Left ventricular ejection fraction did not differ between patients and controls (63.1 ± 7.9 vs. 64.7 ± 7.0, p = 0.13).

CONCLUSIONS

The majority of patients with exercise-associated premature ventricular beats present evidence of myocardial disease consistent with acute or previous myocarditis or myopericarditis.

Effect of physiological heart rate variability on quantitative T2 measurement with ECG-gated Fast Spin Echo (FSE) sequence and its retrospective correction

OBJECT

Quantitative T2 measurement is applied in cardiac Magnetic Resonance Imaging (MRI) for the diagnosis and follow-up of myocardial pathologies. Standard Electrocardiogram (ECG)-gated fast spin echo pulse sequences can be used clinically for T2 assessment, with multiple breath-holds. However, heart rate is subject to physiological variability, which causes repetition time variations and affects the recovery of longitudinal magnetization between TR periods.

MATERIALS AND METHODS

The bias caused by heart rate variability on quantitative T2 measurements is evaluated for fast spin echo pulse sequence. Its retrospective correction based on an effective TR is proposed. Heart rate variations during breath-holds are provided by the ECG recordings from healthy volunteers. T2 measurements were performed on a phantom with known T2 values, by synchronizing the sequence with the recorded ECG. Cardiac T2 measurements were performed twice on six volunteers. The impact of T1 on T2 is also studied.

RESULTS

Maximum error in T2 is 26% for phantoms and 18% for myocardial measurement. It is reduced by the proposed compensation method to 20% for phantoms and 10% for in vivo measurements. Only approximate knowledge of T1 is needed for T2 correction.

CONCLUSION

Heart rate variability may cause a bias in T2 measurement with ECG-gated FSE. It needs to be taken into account to avoid a misleading diagnosis from the measurements.

Evidence of myocardial edema in patients with nonischemic dilated cardiomyopathy

BACKGROUND

Nonischemic dilated cardiomyopathy (DCM) is associated with high mortality and morbidity. Cardiovascular magnetic resonance allows for the noninvasive assessment of function, morphology, and myocardial edema. Activation of inflammatory pathways may play an important role in the etiology of chronic DCM and may also be involved in the disease progression.

HYPOTHESIS

The purpose of our study was to assess the incidence of myocardial edema as a marker for myocardial inflammation in patients with nonischemic DCM.

METHODS

We examined 31 consecutive patients ( mean age, 57 ± 12 years) with idiopathic DCM. Results were compared with 39 controls matched for gender and age (mean age, 53 ± 13 years). Parameters of left ventricular function and volumes, and electrocardiogram-triggered, T2-weighted, fast spin echo triple inversion recovery sequences were applied in all patients and controls. Variables between patients and controls were compared using t tests for quantitative and χ2 tests for categorical variables.

RESULTS

Ejection fraction (EF) was 40.3 ± 7.8% in patients and 62.6 ± 5.0% in controls (P < 0.0001). In T2-weighted images, patients with DCM had a significantly higher normalized global signal intensity ratio compared to controls (2.2 ± 0.6 and 1.8 ± 0.3, respectively, P = 0.0006), consistent with global myocardial edema. There was a significant but moderate negative correlation between signal intensity ratio in T2-weighted images and EF (-0.39, P < 0.001).

CONCLUSIONS

Evidence shows that myocardial edema is associated with idiopathic nonischemic DCM. Further studies are needed to assess the clinical and prognostic impact of these findings.

Electrocardiographic findings and myocardial damage in acute myocarditis detected by cardiac magnetic resonance

Delayed-contrast-enhancement (DCE) magnetic resonance imaging (MRI) can identify areas of myocardial damage in patients with acute myocarditis (AM). The aim of this study was to assess the electrocardiographic findings in AM diagnosed by DCE-MRI. Eighty-one patients (72 men, 35 ± 13 years) with AM were prospectively enrolled. All of them underwent MRI and 12-lead-ECG recordings. In the admission electrocardiogram (ECG 1), as well as in that obtained 48 h later (ECG 2), the following parameters were analyzed: rhythm, PR, QRS, and QTc-intervals, intraventricular conduction, abnormal Q waves, ST segment elevation, and T wave inversion. On admission, 77 patients (95%) were in sinus rhythm, while four patients (6%) manifested severe arrhythmias. No difference between ECG 1 and ECG 2 was observed regarding abnormal Q waves, PR, QRS, and QTc-intervals. Electrocardiogram 1 was normal in 26 patients (32%, normal ECG group), and abnormal in 55 patients (68%, abnormal ECG group). ST elevation was found in 46 patients (57%), inverted T wave in seven patients (9%) and left bundle branch block (LBBB) in two patients (3%). Areas of DCE suggesting AM were found in each patient. No relationship concerning the location of the involved region (s) was found between ECG (leads with ST/T abnormalities) and MRI (areas showing DCE). The ECG in AM can either be normal or reflect abnormalities including arrhythmias, LBBB, ST segment elevation, and T wave inversion. The location of myocardial involvement deduced on the basis of ECG leads showing ST/T changes is not in close relationship with the areas of ventricular damage detected by MRI.

Electrocardiographic findings and myocardial damage in acute myocarditis detected by cardiac magnetic resonance

Delayed-contrast-enhancement (DCE) magnetic resonance imaging (MRI) can identify areas of myocardial damage in patients with acute myocarditis (AM). The aim of this study was to assess the electrocardiographic findings in AM diagnosed by DCE-MRI. Eighty-one patients (72 men, 35 ± 13 years) with AM were prospectively enrolled. All of them underwent MRI and 12-lead-ECG recordings. In the admission electrocardiogram (ECG 1), as well as in that obtained 48 h later (ECG 2), the following parameters were analyzed: rhythm, PR, QRS, and QTc-intervals, intraventricular conduction, abnormal Q waves, ST segment elevation, and T wave inversion. On admission, 77 patients (95%) were in sinus rhythm, while four patients (6%) manifested severe arrhythmias. No difference between ECG 1 and ECG 2 was observed regarding abnormal Q waves, PR, QRS, and QTc-intervals. Electrocardiogram 1 was normal in 26 patients (32%, normal ECG group), and abnormal in 55 patients (68%, abnormal ECG group). ST elevation was found in 46 patients (57%), inverted T wave in seven patients (9%) and left bundle branch block (LBBB) in two patients (3%). Areas of DCE suggesting AM were found in each patient. No relationship concerning the location of the involved region (s) was found between ECG (leads with ST/T abnormalities) and MRI (areas showing DCE). The ECG in AM can either be normal or reflect abnormalities including arrhythmias, LBBB, ST segment elevation, and T wave inversion. The location of myocardial involvement deduced on the basis of ECG leads showing ST/T changes is not in close relationship with the areas of ventricular damage detected by MRI.