Positron emission tomography for the evaluation and treatment of cardiomyopathy

Correction of respiratory and cardiac motion in cardiac PET/MR using MR-based motion modeling

Cardiac positron emission tomography (PET) imaging suffers from image blurring due to the constant motion of the heart that can impact interpretation. Hybrid PET/magnetic resonance (MR) has the potential to use radiation-free MR imaging to correct for the effects of cardio-respiratory motion in the PET data, improving qualitative and quantitative PET imaging in the heart. The purpose of this study was (i) to implement a MR image-based motion-corrected PET/MR method and (ii) to perform a proof-of-concept study of quantitative myocardial PET data in patients. The proposed method takes reconstructions of respiratory and cardiac gated PET data and applies spatial transformations to a single reference frame before averaging to form a single motion-corrected PET (MC-PET) image. Motion vector fields (MVFs) describing the transformations were derived from affine or non-rigid registration of respiratory and cardiac gated MR data. Eight patients with suspected cardiac sarcoidosis underwent cardiac PET/MR imaging after injection of 5 MBq kg^-1 of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). Myocardial regions affected by motion were identified by expert readers within which target-to-background ratios (TBR) and contrast-to-noise ratios (CNR) were measured on non-MC-non-gated, MC-PET, and double respiratory and cardiac gated PET images. Paired t-tests were used to determine statistical differences in quantitative uptake-measures between the different types of PET images. MC-PET images showed less blurring compared to non-MC-non-gated PET and tracer activity qualitatively aligned better with the underlying myocardial anatomy when fused with MR. TBR and CNR were significantly greater for MC-PET (2.8  ±  0.9; 21  ±  22) compared to non-MC-non-gated PET (2.4  ±  0.9, p  =  0.0001; 15  ±  13, p  =  0.02), while TBR was lower and CNR greater compared to double-gated PET (3.2  ±  0.9, p  =  0.04; 6  ±  3, p  =  0.004). This study demonstrated in a patient cohort that motion-corrected (MC) cardiac PET/MR is feasible using a retrospective MR image-based method and that improvement in TBR and CNR are achievable. MC PET/MR holds promise for improving interpretation and quantification in cardiac PET imaging.

Subclinical Detection of Diabetic Cardiomyopathy with MicroRNAs: Challenges and Perspectives

The prevalence of cardiac diabetic diseases has been increased around the world, being the most common cause of death and disability among diabetic patients. In particular, diabetic cardiomyopathy is characterized with a diastolic dysfunction and cardiac remodelling without signs of hypertension and coronary artery diseases. In an early stage, it is an asymptomatic disease; however, clinical studies demonstrate that diabetic myocardia are more vulnerable to injury derived by acute myocardial infarct and are the worst prognosis for rehabilitation. Currently, biochemical and imaging diagnostic methods are unable to detect subclinical manifestation of the disease (prior to diastolic dysfunction). In this review, we elaborately discuss the current scientific evidences to propose circulating microRNAs as promising biomarkers for early detection of diabetic cardiomyopathy and, then, to identify patients at high risk of diabetic cardiomyopathy development. Moreover, here we summarise the research strategies to identify miRNAs as potential biomarkers, present limitations, challenges, and future perspectives.

The limited clinical value of a specific diabetic cardiomyopathy

AIMS

Diabetic patients show a higher likelihood of developing heart failure (HF), independently of the atherosclerotic process, than their nondiabetic counterparts. This suggests the presence of an intrinsic vulnerability of the heart in patients with diabetes mellitus.

DATA SYNTHESIS

A cardiomyopathy specific to the diabetic patient was first hypothesized by Rubler and co-workers, in 1972 and recognized as a nosologic entity by the World Health Organization (WHO) in 1995. All patients falling under Rubler's definition had ascertained diabetic glomerusclerosis, but were unaffected by major coronary artery disease (CAD). Notably, the mean plasma glucose in those patients was 417 ± 209 mg/dl. Since then, several studies conducted in both animals and in humans have focused on pathogenetic mechanisms, clinical manifestations, diagnostic as well as therapeutic approaches utilized for the treatment of diabetic cardiomyopathy (DCM). Despite the large body of literature available, the clinical entity and significance of this diabetic complication continue to be elusive.

CONCLUSIONS

In the present report, recent pathophysiological findings and diagnostic strategies to treat DCM are reviewed. Particular attention is dedicated to the clinical manifestation of DCM, that is to heart failure (HF), and to the implications of co-morbidities and metabolic control on its evolution.

Quantitative cardiac positron emission tomography: the time is coming!

In the last 20 years, the use of positron emission tomography (PET) has grown dramatically because of its oncological applications, and PET facilities are now easily accessible. At the same time, various groups have explored the specific advantages of PET in heart disease and demonstrated the major diagnostic and prognostic role of quantitation in cardiac PET. Nowadays, different approaches for the measurement of myocardial blood flow (MBF) have been developed and implemented in user-friendly programs. There is large evidence that MBF at rest and under stress together with the calculation of coronary flow reserve are able to improve the detection and prognostication of coronary artery disease. Moreover, quantitative PET makes possible to assess the presence of microvascular dysfunction, which is involved in various cardiac diseases, including the early stages of coronary atherosclerosis, hypertrophic and dilated cardiomyopathy, and hypertensive heart disease. Therefore, it is probably time to consider the routine use of quantitative cardiac PET and to work for defining its place in the clinical scenario of modern cardiology.