Update on the Role of Cardiac Magnetic Resonance in Acquired Nonischemic Cardiomyopathies

Diagnostic performance of chest radiography measurements for the assessment of cardiac chamber enlargement

Background:

The cardiothoracic ratio (CTR) is commonly assessed on chest radiography for detection of cardiac chamber enlargement, but the traditional cutpoint of 0.5 has low specificity. We sought to evaluate the diagnostic accuracy of new measurement techniques for the detection of cardiac enlargement on chest radiographs.

Methods:

We obtained retrospective cross-sectional data on consecutive patients who underwent both chest radiography and cardiac magnetic resonance imaging (MRI) within a 14-day interval between 2006 and 2016 at a large academic hospital network. We established the presence of cardiac chamber enlargement using cardiac MRI as the reference standard. We evaluated the diagnostic performance of different techniques for measuring heart size and CTR on frontal chest radiographs.

Results:

Of 152 patients included, 81 (53%) were men and the mean age was 52 years. Maximum heart diameter had the highest area under the receiver operating characteristic curve for detection of cardiac enlargement (0.827, 95% confidence interval 0.760–0.894). In the subgroup of posteroanterior chest radiography studies (n = 101), a CTR cutpoint of 0.50 had only moderate sensitivity (72%) and specificity (72%). In men, a maximum heart diameter cutpoint of 15 cm had a sensitivity of 86% and a negative likelihood ratio of 0.24, and a cutpoint of 19 cm had a specificity of 100% and a positive likelihood ratio of infinity. In women, a maximum heart diameter cutpoint of 13 cm had a sensitivity of 91% and a negative likelihood ratio of 0.15, and a cutpoint of 17 cm had a specificity of 91% and a positive likelihood ratio of 3.5.

Interpretation:

A traditional CTR cutpoint of 0.5 has limited diagnostic value. Simple heart diameter measurements have higher diagnostic performance measures than CTR.

ACR Appropriateness Criteria® Nonischemic Myocardial Disease with Clinical Manifestations (Ischemic Cardiomyopathy Already Excluded)

Nonischemic cardiomyopathies encompass a broad spectrum of myocardial disorders with mechanical or electrical dysfunction without evidence of ischemia. There are five broad variants of nonischemic cardiomyopathies; hypertrophic cardiomyopathy (Variant 1), restrictive or infiltrative cardiomyopathy (Variant 2), dilated or unclassified cardiomyopathy (Variant 3), arrhythmogenic cardiomyopathy (Variant 4), and inflammatory cardiomyopathy (Variant 5). For variants 1, 3, and 4, resting transthoracic echocardiography, MRI heart function and morphology without and with contrast, and MRI heart function and morphology without contrast are the usually appropriate imaging modalities. For variants 2 and 5, resting transthoracic echocardiography and MRI heart function and morphology without and with contrast are the usually appropriate imaging modalities. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Differentiating Nonischemic Dilated Cardiomyopathy With Incidental Infarction From Ischemic Cardiomyopathy by Geometric Indices Derived From Cardiovascular Magnetic Resonance

PURPOSE

The purpose of this study was to differentiate nonischemic dilated cardiomyopathy with incidental myocardial infarction (NICM with incidental MI) from ischemic cardiomyopathy (ICM) by integrating left ventricular (LV) geometric indices and ischemic late gadolinium enhancement (LGE), obtained from cardiac magnetic resonance (CMR) imaging.

MATERIALS AND METHODS

All subjects were studied on a 1.5 Tesla magnetic resonance imaging scanner. All patients had an LV ejection fraction (LVEF) <50% with LV dilation. LV end-diastolic volume (LVEDV), LVEDV index (LVEDVi), LVEF, the number and distribution of ischemic LGE segments, and ratios of volumetric and functional indices to ischemic LGE segments were determined. Logistic regression was used to detect the independent predictor of ICM. Receiver operating characteristic analysis differentiated NICM with incidental MI from ICM.

RESULTS

Of a total of 63 patients enrolled, 45 patients had ICM, and 18 patients had NICM with incidental MI. Both groups had similar LVEF. Compared with ICM, NICM with incidental MI had more LV dilation, whereas ICM had more ischemic LGE segments. A higher number of ischamic LGE segments remained an independent predictor of ICM (odds ratio: 18.2, 95% confidence interval: 1.64-201.34, P=0.018). The optimal cut-off value for detecting NICM with incidental MI is the ratio of LVEDVi to the number of ischemic LGE segments over 25 mL/m2/segment (sensitivity 100%, specificity 91%, P<0.0001).

CONCLUSION

Patients with NICM with incidental MI can be reliably distinguished from ICM using the ratio of LVEDVi divided by the number of ischemic LGE segments. This technique may improve diagnosis and help aid management of patients with cardiomyopathy and coexistent coronary artery disease.

Clinical Significance of Papillary Muscles on Left Ventricular Mass Quantification Using Cardiac Magnetic Resonance Imaging: Reproducibility and Prognostic Value in Fabry Disease

PURPOSE

Accurate and reproducible assessment of left ventricular mass (LVM) is important in Fabry disease. However, it is unclear whether papillary muscles should be included in LVM assessed by cardiac magnetic resonance imaging (MRI). The purpose of this study was to evaluate the reproducibility and predictive value of LVM in patients with Fabry disease using different analysis approaches.

MATERIALS AND METHODS

A total of 92 patients (44±15 y, 61 women) with confirmed Fabry disease who had undergone cardiac MRI at a single tertiary referral hospital were included in this retrospective study. LVM was assessed at end-diastole using 2 analysis approaches, including and excluding papillary muscles. Adverse cardiac events were assessed as a composite end point, defined as ventricular tachycardia, bradycardia requiring device implantation, severe heart failure, and cardiac death. Statistical analysis included Cox proportional hazard models, Akaike information criterion, intraclass correlation coefficients, and Bland-Altman analysis.

RESULTS

Left ventricular end-diastolic volume, end-systolic volume, ejection fraction, and LVM all differed significantly between analysis approaches. LVM was significantly higher when papillary muscles were included versus excluded (157±71 vs. 141±62 g, P<0.001). Mean papillary mass was 16±11 g, accounting for 10%±3% of total LVM. LVM with pap illary muscles excluded had slightly better predictive value for the composite end point compared with LVM with papillary muscles included based on the model goodness-of-fit (Akaike information criterion 140 vs. 142). Interobserver agreement was slightly better for LVM with papillary muscles excluded compared with included (intraclass correlation coefficient 0.993 [95% confidence interval: 0.985, 0.996] vs. 0.989 [95% confidence interval: 0.975, 0.995]) with less bias and narrower limits of agreement.

CONCLUSIONS

Inclusion or exclusion of papillary muscles has a significant effect on LVM quantified by cardiac MRI, and therefore, a standardized analysis approach should be used for follow-up. Exclusion of papillary muscles from LVM is a reasonable approach in patients with Fabry disease given slightly better predictive value and reproducibility.

Prevalence and Clinical Relevance of Extracardiac Findings in Cardiovascular Magnetic Resonance Imaging

PURPOSE

To assess the prevalence of extracardiac findings (ECF) during cardiovascular magnetic resonance (CMR) examinations and their downstream effect on clinical management.

MATERIALS AND METHODS

We retrospectively identified 500 consecutive patients. Trans-axial balanced steady-state free precession nongated images acquired from the upper thorax to the upper abdomen were evaluated independently by 2 radiologists. ECF were classified as nonsignificant (benign, with no need for further investigation), significant (mandatory to be reported/monitored), and major (clinically remarkable pathology, mandatory to be reported/investigated/treated). Fifteen-month clinical follow-up information was collected through hospital records.

RESULTS

Of 500 patients, 108 (21.6%) showed a total of 153 ECF: 59 (11.8% of the entire study population; 38.5% of all ECF) nonsignificant, 76 (15.2%; 49.7%) significant, and 18 (3.6%; 11.8%) major ECF. The most frequent ECF were pleural effusion, hepatic cyst, renal cyst, and ascending aorta dilatation. Of 94 significant and major ECF, 46 were previously unknown and more common in older patients. Newly diagnosed major ECF (n=11, 2.2% of the entire study population, and 7.2% of all ECF)-including 5 tumors (1% of study population)-were confirmed by downstream evaluations and required specific treatment. Patients with major ECF were significantly older than patients without with major ECF. Newly diagnosed clinically significant and major ECF prompted downstream diagnostic tests in 44% and 100% of cases, respectively.

CONCLUSIONS

The detection of significant and major ECF is common during CMR reporting. The knowledge and the correct identification of most frequent ECF enable earlier diagnoses and faster treatment initiation of unknown extracardiac pathologies in patients referred to CMR imaging.

Evaluation of the Cardiac Morphologic Alterations Secondary to Autoimmune Thyroid Disorder Using Cardiac Magnetic Resonance Imaging

Purpose:

Thyroid functional disease is associated with clinically significant cardiovascular changes. The aim of this study was to assess changes in the cardiac magnetic resonance imaging of patients with autoimmune thyroid disorders (AITs).

Materials and Methods:

Forty patients with AIT (12 men, 28 women; age range, 20 to 82 y; mean age, 59 y) were identified and included in our study. In addition, 20 controls (12 men, 8 women; age range, 21 to 76 y; mean age, 50 y) without AIT or cardiac disorders were included.

Results:

In patients with AIT, the mean value calculated for the end diastolic volume was 161.2 mL, the mean end systolic volume value was 95.3 mL, and the mean left ventricular ejection fraction value was 45.2%. In comparing AIT patients with the control group, we found a significant difference in the end systolic volume, ejection fraction, stroke index, cardiac output, cardiac index, and left ventricular diameter (P<0.05).

Conclusions:

We conclude that our data show that there is a correlation between thyroid function and cardiac function, as evaluated with cardiac magnetic resonance imaging. This can be useful in the diagnosis of cardiovascular changes associated with AIT.

Clinics in diagnostic imaging (189). Acute phase cardiac sarcoidosis (CS)

A 44-year-old man presented with breathlessness and episodes of palpitations for the last one year. The imaging diagnosis of cardiac sarcoidosis was made based on chest radiography and cardiac magnetic resonance (MR) imaging findings, and was further confirmed by biopsy. Cardiac sarcoidosis is an uncommon entity, yet is potentially fatal with nonspecific clinical manifestations, including sudden cardiac death. Hence, it is important to diagnose and treat this entity at an early stage to improve morbidity and mortality. Cardiac MR imaging plays a pivotal role in facilitating diagnosis and monitoring therapeutic response. We describe the MR imaging features of cardiac sarcoidosis and discuss imaging features of other cardiomyopathies that may mimic cardiac sarcoidosis.

Utility of magnetic resonance imaging in the evaluation of left ventricular thickening

Left ventricular (LV) thickening can be due to hypertrophy (concentric, asymmetric, eccentric) or remodelling (concentric or asymmetric). Pathological thickening may be caused by pressure overload, volume overload, infiltrative disorders, hypertrophic cardiomyopathy, athlete's heart or neoplastic infiltration. Magnetic resonance imaging (MRI) plays an important role in the comprehensive evaluation of LV thickening, including: establishing diagnosis, determining LV geometry, establishing aetiology, quantification, identifying prognostic factors, serial follow-up and treatment response. In this article, we review the aetiologies and pathophysiology of LV thickening, and demonstrate the comprehensive role of MRI in the evaluation of LV thickening.

TEACHING POINTS

• MRI plays an important role in the evaluation of LV thickening. • LV thickening can be due to either hypertrophy or remodelling. • Pathological thickening can be due to pressure/volume overload or infiltrative disorders.