Comparison of global and regional abnormalities in 99mTc-sestamibi and cardiac magnetic resonance imaging in dilated cardiomyopathy

Novel indices representing heterogeneous distributions of myocardial perfusion imaging

INTRODUCTION

Heterogeneous distribution in myocardial perfusion images (MPI) obtained by scintigraphy is often observed in cardiac diseases with normal myocardial perfusion. However, quantitative assessments of such heterogeneity have not been established. We hypothesized that the heterogeneity in MPI can be quantitatively evaluated through histogram analysis, calculating the standard deviation (SD), the 95% bandwidth (BW95%), and entropy.

METHODS

We examined resting 99mTc-MIBI images in 20 healthy subjects and 29 patients with cardiac disease who had none or very-mild reduced myocardial perfusion evaluated as a low summed rest score (0 to 4, the range of the studied healthy subjects). Two nuclear medicine specialists blindly divided them into two groups: non-heterogeneity or heterogeneity group, based solely on their visual assessments of heterogeneity on splash and polar maps generated from single-photon emission computed tomography (SPECT) images. The %uptake was determined by dividing the tracer count of each pixel by the tracer count of the pixel with the highest value in the LV myocardium. SD, BW95%, and entropy from histogram patterns were analyzed from the polar map data array of each %uptake. We investigated whether heterogeneity could be assessed using SD, BW95, and entropy in two groups classified by visual assessments. Additionally, we evaluated the area under the curve (AUC) to identify heterogeneity in the receiver operating characteristic curve analysis.

RESULTS

Based solely on visual assessments, 11 (22%) and 38 (78%) cases were classified into the non-heterogeneity and heterogeneity groups, respectively. The non-heterogeneity group consisted of only healthy subjects, and all patients with cardiac disease were classified into the heterogeneity group. The cases in the heterogeneity group had significantly higher values of heterogeneity indices (SD, BW95%, and entropy) in %uptake than those in the non-heterogeneity group (p < 0.05 for all). The AUCs of the heterogeneity indices were sufficiently high (AUCs > 0.90 for all) in distinguishing cases with visually heterogeneous distribution or patients with cardiac disease.

CONCLUSIONS

Heterogeneity in MPI can be evaluated using SD, BW95%, and entropy through histogram analysis. These novel indices may help identify patients with subtle myocardial changes, even in images that show preserved perfusion (345/350).

Focal severe decrease in myocardial technetium-99 m sestamibi uptake indicates ventricular irreversibility in patients with dilated cardiomyopathy

OBJECTIVE

Technetium-99 m sestamibi (^99mTc-MIBI) scintigraphy can identify non-viable left ventricular (LV) myocardium. However, the optimal cut-off value and the details of decreased ^99mTc-MIBI uptake of the non-viable LV myocardium in patients with dilated cardiomyopathy (DCM) have not been well established. This study aimed to evaluate the decrease in ^99mTc-MIBI uptake in each segment and in the whole LV myocardium, and to determine cut-off values for identifying non-viable LV myocardium in DCM patients.

METHODS

Overall, 53 DCM patients with reduced LV ejection fraction (LVEF ≤ 40%) who underwent ^99mTc-MIBI scintigraphy and any optimization of heart failure treatments were evaluated. LV myocardium was classified as viable or non-viable based on the absolute increase in LVEF of ≥ 10% unit leading to an LVEF of > 40% at follow-up, respectively. The decrease in myocardial ^99mTc-MIBI uptake in each of the 17 segments was evaluated using three indices determined by different thresholds or standard references: segmental %uptake, rest score, and defect extent. Changes in the whole LV myocardium were evaluated by the minimum %uptake, and the summed rest score (SRS) and extent of LV defect were obtained using summed data of 17 segments.

RESULTS

Segmental evaluation indicated a mild decrease in ^99mTc-MIBI uptake in 18 patients with viable LV myocardium, whereas focal severe decrease in uptake was observed in patients with non-viable LV myocardium. In the receiver-operating characteristic curve analysis, the cut-off values of minimum %uptake, SRS, and LV defect extent for predicting non-viable LV were 39% (p < 0.01, area under the curve [AUC]: 0.87), 10 (p < 0.01, AUC: 0.91), and 23% (p < 0.01, AUC: 0.92), respectively.

CONCLUSIONS

In DCM patients, myocardial ^99mTc-MIBI %uptake of < 40% indicated non-viable myocardium. The focal and severe decrease in uptake in approximately more than a quarter of the LV myocardium may indicate non-viable LV.

Intra-cardiac distribution of late gadolinium enhancement in cardiac sarcoidosis and dilated cardiomyopathy

Cardiac involvement of sarcoid lesions is diagnosed by myocardial biopsy which is frequently false-negative, and patients with cardiac sarcoidosis (CS) who have impaired left ventricular (LV) systolic function are sometimes diagnosed with dilated cardiomyopathy (DCM). Late gadolinium enhancement (LE) in magnetic resonance imaging is now a critical finding in diagnosing CS, and the novel Japanese guideline considers myocardial LE to be a major criterion of CS. This article describes the value of LE in patients with CS who have impaired LV systolic function, particularly the diagnostic and clinical significance of LE distribution in comparison with DCM. LE existed at all LV segments and myocardial layers in patients with CS, whereas it was localized predominantly in the midwall of basal to mid septum in those with DCM. Transmural (nodular), circumferential, and subepicardial and subendocardial LE distribution were highly specific in patients with CS, whereas the prevalence of striated midwall LE were high both in patients with CS and with DCM. Since sarcoidosis patients with LE have higher incidences of heart failure symptoms, ventricular tachyarrhythmia and sudden cardiac death, the analyses of extent and distribution of LE are crucial in early diagnosis and therapeutic approach for patients with CS.

Role of Cardiac MRI in the Assessment of Cardiomyopathy

OPINION STATEMENT

Combining the diagnostic utilities of cardiac structures, myocardial perfusion, and various tissue characterizing pulse sequence methods in matching scan planes within a single imaging session, cardiac magnetic resonance imaging (CMR) provides a novel interrogation of myocardial physiology and abnormal anatomy from various forms of cardiomyopathy. Establishment of technical imaging standards and clinical adaptation in the past years has helped recognize the distinguishing features of different cardiomyopathies, with CMR currently assuming a pivotal role in the diagnosis of cases of new-onset cardiomyopathy in experienced centers. Quantitative measurements such as ventricular volumes, myocardial iron content, and extent of late gadolinium enhancement can effectively monitor disease status, guide medical therapy, and impact patient outcomes in specific clinical settings. This chapter will aim to summarize these current CMR applications with case examples.

Severity of mitral stenosis and left ventricular mechanics: a speckle tracking study

BACKGROUND

It has been shown that mitral stenosis (MS) impairs left ventricular (LV) systolic function; however, this issue has not been studied comprehensively. We aimed to evaluate the role of 2D strain in the assessment of subclinical LV systolic dysfunction in patients with MS.

METHODS

Seventy-two patients with isolated MS (mild, moderate and severe) and 31 healthy control subjects constituted the study population. 2D echocardiography images were obtained from LV apical 4-chamber (4C), long axis (LAX), and 2-chamber (2C) views. Peak longitudinal strain and strain rate (Sr) were obtained from 4C, LAX, and 2C views. Global strain and Sr were calculated by averaging the three apical views.

RESULTS

There were no significant differences in LV ejection fraction and LV systolic or diastolic dimensions between the groups. Patients with MS had significantly lower LV longitudinal strain and Sr measurements than the control group. In addition, there were no significant differences in MS subgroups with respect to LV strain and Sr measurements.

CONCLUSION

We demonstrated that patients with MS had lower LV functions using 2D strain imaging, and this is independent of the hemodynamic severity of MS. In the detection of subclinical LV dysfunction in patients with MS, 2D strain imaging appears to be useful.