Impairment in quantitative microvascular function in non-ischemic cardiomyopathy as demonstrated using cardiovascular magnetic resonance

Myocardial Perfusion Imaging with Cardiovascular Magnetic Resonance in Nonischemic Cardiomyopathies: An In-Depth Review of Techniques and Clinical Applications

Background and Objectives: Nonischemic cardiomyopathies comprise a wide spectrum of heart muscle disorders characterized by different morphological, functional, and tissue abnormalities. Cardiovascular magnetic resonance (CMR) represents the gold standard imaging modality for assessing cardiac morphology, systolic function, and tissue characterization, thereby aiding in early diagnosis, precise phenotyping, and tailored treatment. The aim of this review is to provide an up-to-date overview of CMR techniques for studying myocardial perfusion and their applications to nonischemic cardiomyopathy, not only to rule out an underlying ischemic aetiology but also to investigate the pathophysiological characteristics of microcirculatory dysfunction in these patients. Materials and Methods: We performed a structured review of the literature focusing on first-pass gadolinium perfusion sequences, stress protocols, and emerging pixel-wise perfusion mapping approaches. Studies were selected to illustrate the methods for image acquisition, post-processing, and quantification of myocardial blood flow (MBF) and myocardial perfusion reserve (MPR), as well as to highlight associations with clinical endpoints. Results: First-pass CMR perfusion imaging reliably detects diffuse and regional microvascular dysfunction across cardiomyopathies. Semi-quantitative parameters (e.g., upslope, MPRI) and quantitative MBF mapping (mL/g/min) have demonstrated that impaired perfusion correlates with disease severity, extent of fibrosis, and adverse outcomes, including heart failure hospitalization, arrhythmias, and mortality. Novel automated pixel-wise mapping enhances reproducibility and diagnostic accuracy, distinguishing coronary microvascular dysfunction from balanced three-vessel disease. Microvascular dysfunction-present in approximately 50-60% of dilated cardiomyopathy (DCM), 40-80% of hypertrophic cardiomyopathy (HCM), and >95% of cardiac amyloidosis (CA) patients-has emerged as a key driver of adverse outcomes. Perfusion defects appear early, often preceding overt hypertrophy or fibrosis, and provide incremental prognostic value beyond conventional CMR metrics. Conclusions: CMR represents a powerful tool for detecting myocardial perfusion abnormalities in nonischemic cardiomyopathies, improving phenotyping, risk stratification, and personalized management. Further standardization of quantitative perfusion techniques will facilitate broader clinical adoption.

Evolution of Coronary Microvascular Dysfunction Prevalence over Time and Across Diagnostic Modalities in Patients with ANOCA: A Systematic Review

Background: A considerable number of patients with angina undergo invasive coronary angiography, which might reveal non-obstructive coronary arteries (ANOCA). In this setting, they might have coronary microvascular disease (CMD). Its prevalence significantly varies in the literature. This systematic review aims to document the prevalence of CMD over time according to the diagnostic modalities. Methods: A systematic literature review was conducted using PubMed, the Cochrane Library, and Embase, covering publications from inception to 1 May 2024. Among 1471 identified articles, 297 full-text articles were assessed for eligibility. All studies reporting the prevalence of CMD in ANOCA patients based on invasive coronary artery (ICA), positron emission tomography-computed tomography (PET-CT), transthoracic echocardiography (TTE), or cardiac magnetic resonance (CMR) were included. Results: The review included 53 studies (published between 1998 and 2024), encompassing a total of 16,602 patients. Of these studies, 23 used ICA, 15 used PET-CT, 8 used TTE, and 7 used CMR. A statistically significant increase in CMD prevalence over time was observed across all diagnostic modalities (p < 0.05), except for PET-CT, which showed a consistent and stable prevalence over time. Notably, the prevalence rates from all of the diagnostic methods converged towards the 50% prevalence detected by PET-CT. Conclusions: The prevalence of CMD in patients with ANOCA is subject to debate. However, the current data suggest that regardless of the diagnostic method used, the most recent studies tend to converge towards a prevalence value of 50%, which has been consistently reported by PET-CT from the beginning.

Next-Generation Cardiac Magnetic Resonance Imaging Techniques for Characterization of Myocardial Disease

Purpose of the Review

Many novel cardiac magnetic resonance imaging (cMR) techniques have been developed for diagnosis, risk stratification, and monitoring of myocardial disease. The field is changing rapidly with advances in imaging technology. The purpose of this review is to give an update on next-generation cMR techniques with promising developments for clinical translation in the last two years, and to outline clinical applications.

Recent Findings

There has been increasing widespread clinical adoption of T1/T2 mapping into standard of care clinical practice. Development of auto segmentation has enabled clinical integration, with potential applications to minimize the use of contrast. Advances in diffusion tensor imaging, multiparametric mapping with cardiac MRI fingerprinting, automated quantitative perfusion mapping, metabolic imaging, elastography, and 4D flow are advancing the ability of cMR to provide further quantitative characterization to enable deep myocardial disease phenotyping. Together these advanced imaging features further augment the ability of cMR to contribute to novel disease characterization and may provide an important platform for personalized medicine.

Summary

Next-generation cMR techniques provide unique quantitative imaging features that can enable the identification of imaging biomarkers that may further refine disease classification and risk prediction. However, widespread clinical application continues to be limited by ground truth validation, reproducibility of the techniques across vendor platforms, increased scan time, and lack of widespread availability of advanced cardiac MRI physicists and expert readers. However, these techniques show great promise in minimizing the need for invasive testing, may elucidate novel pathophysiology, and may provide the ability for more accurate diagnosis of myocardial disease.

Acute Heart Failure and Coronary Blood Flow in ST-Elevation Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention: An Observational Cohort Study

Background and objective The Global Registry of Acute Coronary Events (GRACE) study showed poor outcomes in ST-elevation myocardial infarction (STEMI) patients with acute heart failure (AHF) at hospital admission in terms of increased in-hospital and six-month mortality and readmission rates. In this study, we aimed to examine the effects of AHF at the time of admission on the coronary thrombus burden and post-primary percutaneous coronary intervention (PPCI) coronary flow among STEMI patients. Methods We conducted a cohort study involving 210 consecutive STEMI patients who presented to a single PPCI centre between June 2016 and January 2017. We classified them into two groups based on their Killip class at the time of presentation to the emergency department: no heart failure (NHF) and AHF groups. The primary outcome was the incidence of Thrombolysis In Myocardial Infarction (TIMI) flow grade of less than 3 in the stented coronary artery in the absence of mechanical obstruction or dissection (also known as no-reflow). The secondary outcome was the presence of a heavy thrombus burden (TIMI grade 4 or 5) at the time of angiography. Results The AHF group had a significantly higher incidence of no-reflow than the NHF group (25% vs. 8.4%, p=0.019). However, the prevalence of heavy thrombus burden did not differ significantly between the two groups (50% in the AHF group vs. 43.16% in the NHF group, p=0.557). The multivariable logistic regression analysis showed that AHF was an independent predictor of no-reflow in STEMI patients post-PPCI [Odds ratio (OR): 3.59, 95% confidence interval (CI): 1.09-11.83, p=0.035]. Conclusion Based on our findings, AHF is associated with an increased risk of no-reflow in STEMI patients post-PPCI, irrespective of the coronary thrombus load.