Post COVID-19 syndrome with impairment of flow-mediated epicardial vasodilation and flow reserve

Functional or structural impairment of flow-mediated epicardial vasodilation may precede coronary microvascular dysfunction

Background

The aim was to investigate whether functional and/or structural impairment of flow-mediated epicardial vasodilation (IEV) may precede coronary microvascular dysfunction (CMD) in a cardiometabolic risk population.

Methods

13N-ammonia positron emission tomography/computed tomography evaluated global and longitudinal myocardial blood flow (MBF) during pharmacologically induced hyperemia and at rest. Normal coronary microvascular function (nCMF) was defined by a myocardial flow reserve (MFR = MBFstress/MBFrest) of ≥ 2.0, while an abnormal MFR of < 2.0 (predominantly due to decreases in hyperemic MBF) denoted classical CMD. Normal flow-mediated epicardial vasodilation (NEV) was defined as longitudinal hyperemic MBF gradient < -0.10 mL/g/min, whereas a value ≥ -0.10 mL/g/min signifiedIEV. Patients were grouped as follows: group 1 (G1): nCMF and NEV (n = 93); group 2 (G2): nCMF and IEV (n = 62), and group 3 (G3): CMD and IEV (n = 78). From non-gated CT, a semiquantitative four-point scoring system was used to indicate coronary artery calcifications score (CCS).

Results

The prevalence of diffuse coronary artery calcification was highest in G1 with 51 %, followed by G3 with 46 % and G2 with 34 %. The extent of CCS was mild-to-moderate and did not differ significantly among groups (p = 0.222). Overall, IEV was present in 60 %, while there was a comparable prevalence of IEV between G2 and G3 (27 % and 33 %, p = 0.27). The hyperemic MBF gradient was highest in G2, intermediate in G3, and lowest in G1 (-0.22 ± 0.11 and -0.18 ± 0.10 vs. 0.03 ± 0.08 mL/g/min; p < 0.001, respectively).

Conclusions

In this cardio-metabolic risk population, in about one third of these symptomatic patients functional and/or structural impairment of flow-mediated epicardial vasodilation may precede coronary microvascular dysfunction.

COVID-19 in the Initiation and Progression of Atherosclerosis: Pathophysiology During and Beyond the Acute Phase

The incidence of atherosclerotic cardiovascular disease is increasing globally, especially in low- and middle-income countries, despite significant efforts to reduce traditional risk factors. Premature subclinical atherosclerosis has been documented in association with several viral infections. The magnitude of the recent COVID-19 pandemic has highlighted the need to understand the association between SARS-CoV-2 and atherosclerosis. This review examines various pathophysiological mechanisms, including endothelial dysfunction, platelet activation, and inflammatory and immune hyperactivation triggered by SARS-CoV-2 infection, with specific attention on their roles in initiating and promoting the progression of atherosclerotic lesions. Additionally, it addresses the various pathogenic mechanisms by which COVID-19 in the post-acute phase may contribute to the development of vascular disease. Understanding the overlap of these syndromes may enable novel therapeutic strategies. We further explore the need for guidelines for closer follow-up for the often-overlooked evidence of atherosclerotic cardiovascular disease among patients with recent COVID-19, particularly those with cardiometabolic risk factors.

MRI of cardiac involvement in COVID-19

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has led to a diverse pattern of myocardial injuries, including myocarditis, which is linked to adverse outcomes in patients. Research indicates that myocardial injury is associated with higher mortality in hospitalized severe COVID-19 patients (75.8% vs 9.7%). Cardiovascular Magnetic Resonance (CMR) has emerged as a crucial tool in diagnosing both ischaemic and non-ischaemic myocardial injuries, providing detailed insights into the impact of COVID-19 on myocardial tissue and function. This review synthesizes existing studies on the histopathological findings and CMR imaging patterns of myocardial injuries in COVID-19 patients. CMR imaging has revealed a complex pattern of cardiac damage in these patients, including myocardial inflammation, oedema, fibrosis, and ischaemic injury, due to coronary microthrombi. This review also highlights the role of LLC criteria in diagnosis of COVID-related myocarditis and the importance of CMR in detecting cardiac complications of COVID-19 in specific groups, such as children, manifesting multisystem inflammatory syndrome in children (MIS-C) and athletes, as well as myocardial injuries post-COVID-19 infection or following COVID-19 vaccination. By summarizing existing studies on CMR in COVID-19 patients and highlighting ongoing research, this review contributes to a deeper understanding of the cardiac impacts of COVID-19. It emphasizes the effectiveness of CMR in assessing a broad spectrum of myocardial injuries, thereby enhancing the management and prognosis of patients with COVID-19 related cardiac complications.

Inflammation and Myocardial Blood Flow in Cardiac Sarcoidosis

PURPOSE OF THE REVIEW

Cardiac involvement in systemic sarcoidosis or isolated cardiac sarcoidosis plays a pivotal role in the clinical manifestation and prognostication. Active-inflammatory cardiac sarcoidosis is associated with a regional impairment of coronary microvascular function that may confer further detrimental effects on myocardial function needing further characterization.

RECENT FINDINGS

Clinical investigations with cardiac positron emission tomography/computed tomography in conjunction with 18F-fluorodeoxyglucose to determine myocardial inflammation and 13N-ammonia to quantify myocardial blood flow (MBF) in patients with known or suspected cardiac sarcoidosis outlined that sarcoidosis-induced myocardial inflammation was associated with adverse effects on corresponding regional coronary microvascular function. Notably, immune-suppressive treatment caused reductions in myocardial inflammation were paralleled by improvements of coronary microvascular dysfunction outlining direct adverse effect of inflammation on coronary arteriolar function. This review summarizes contributions of cardiac PET imaging in the identification and characterization of active-inflammatory cardiac sarcoidosis, its effect on coronary microvascular function, treatment responses, and prognostic implications.

PET-determined myocardial perfusion and flow in coronary artery disease characterization

Positron emission tomography (PET) myocardial perfusion imaging in conjunction with tracer-kinetic modeling enables the concurrent assessment of myocardial perfusion and regional myocardial blood flow (MBF) of the left ventricle in absolute terms in milliliters per gram per minute (mL/g/min). The non-invasive quantification of MBF during pharmacologically induced hyperemia, at rest, and corresponding myocardial flow reserve (MFR) opens a new avenue for the identification and characterization of classical or endogen type of coronary microvascular dysfunction (CMD) as functional substrate for microvascular angina in patients with non-obstructive coronary artery disease (CAD) and/or no CAD at all. Further, PET-MBF quantification expands the scope of conventional myocardial perfusion imaging from the identification of advanced, and flow-limiting, epicardial CAD to early stages of atherosclerosis and/or CMD. Adding MBF assessment to myocardial perfusion may also reliably unravel diffuse ischemia owing to significant left main stenosis and/or multivessel CAD, commonly confirmed by peak stress transient ischemic cavity dilation of the left ventricle during maximal vasomotor stress compared to rest on gated PET images. Owing to high spatial and contrast resolution in conjunction with photon-attenuation free myocardial perfusion PET images, PET is preferentially used for CAD detection in advanced obesity and women with pronounced breast habitus. With increasing clinical use of cardiac PET perfusion and MBF assessment, individualized, and image-guided cardiovascular treatment decisions in CAD patients is likely to ensue, while its translation into improved cardiovascular outcome remains to be investigated.

PET/CT Assessment of Flow-Mediated Epicardial Vasodilation in Obesity and Severe Obesity

Background

It is not known whether the transition from obesity and severe obesity, as 2 different metabolic disease entities, affect flow-mediated and, thus, endothelium-dependent epicardial vasodilation.

Objectives

The purpose of this study was to investigate the effect of obesity and severe obesity on flow-mediated epicardial vasomotion with positron emission tomography/computed tomography-determined longitudinal decrease in myocardial blood flow (MBF) from the base-to-apex direction of the left ventricle or gradient.

Methods

13N-ammonia positron emission tomography/computed tomography evaluated global MBF during pharmacologically induced hyperemia and at rest for assessment of coronary microvascular function. In addition, the Δ longitudinal MBF gradient (hyperemia minus rest) was determined. Patients were then grouped according to the body mass index (BMI) into normal weight (NW) (BMI 20.0-24.9 kg/m2, n = 27), overweight (OW) (BMI 25.0-29.9 kg/m2, n = 29), obesity (OB) (BMI 30.0-39.9 kg/m2, n = 53), and severe obesity (morbid obesity: BMI ≥40 kg/m2, n = 43).

Results

Compared to NW, left ventricular Δ longitudinal MBF gradient progressively declined in OW and OB (0.04 ± 0.09 mL/g/min vs -0.11 ± 0.14 mL/g/min and -0.15 ± 0.11 mL/g/min; P ≤ 0.001, respectively) but not significantly in SOB (-0.01 ± 0.11 mL/g/min, P = 0.066). Regadenoson-induced global hyperemic MBF was lower in OB than in NW (1.88 ± 0.40 mL/g/min vs 2.35 ± 0.32 mL/g/min; P ≤ 0.001), while comparable between NW and SOB (2.35 ± 0.32 mL/g/min vs 2.26 ± 0.40 mL/g/min; P = 0.302). The BMI of the study population was associated with the Δ longitudinal MBF gradient in a U-turn fashion (r = 0.362, standard error of the estimate = 0.124; P < 0.001).

Conclusions

Increased body weight associates with abnormalities in coronary circulatory function that advances from an impairment flow-mediated, epicardial vasodilation in overweight and obesity to coronary microvascular dysfunction in obesity, not observed in severe obesity. The U-turn of flow-mediated epicardial vasomotion outlines obesity and severe obesity to affect epicardial endothelial function differently.

Purinergic signaling: decoding its role in COVID-19 pathogenesis and promising treatment strategies

The pathogenesis of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), is complex and involves dysregulated immune responses, inflammation, and coagulopathy. Purinergic signaling, mediated by extracellular nucleotides and nucleosides, has emerged as a significant player in the pathogenesis of COVID-19. Extracellular adenosine triphosphate (ATP), released from damaged or infected cells, is a danger signal triggering immune responses. It activates immune cells, releasing pro-inflammatory cytokines, contributing to the cytokine storm observed in severe COVID-19 cases. ATP also promotes platelet activation and thrombus formation, contributing to the hypercoagulability seen in COVID-19 patients. On the other hand, adenosine, an immunosuppressive nucleoside, can impair anti-viral immune responses and promote tissue damage through its anti-inflammatory effects. Modulating purinergic receptors represents a promising therapeutic strategy for COVID-19. Understanding the role of purinergic signaling in COVID-19 pathogenesis and developing targeted therapeutic approaches can potentially improve patient outcomes. This review focuses on the part of purinergic signaling in COVID-19 pathogenesis and highlights potential therapeutic approaches targeting purinergic receptors.

PET-determined prevalence of coronary microvascular dysfunction and different types in a cardio-metabolic risk population

Background

The aim was to investigate the prevalence of "classical" (predominantly related to alterations in hyperemic MBFs) and "endogen" (predominantly related to alterations in resting MBF) normal coronary microvascular function (nCMF) or coronary microvascular dysfunction (CMD) in a clinical population without flow-limiting obstructive CAD.

Methods

We prospectively enrolled 239 symptomatic patients with normal pharmacologically-stress and rest myocardial perfusion on ¹³N-ammonia PET/CT. ¹³N-ammonia PET/CT concurrently assessed myocardial flow reserve (MFR = MBF stress/MBF rest). Normal nCMF was defined by a MFR of ≥ 2.0, while an abnormal MFR of < 2.0 signified CMD. In addition, patients were subgrouped into classical and endogen type of nCMF and CMD, respectively.

Results

In the whole study population, CMD was present in 54% (130/239). The classical type was more prevalent than the endogen type of CMD (65% vs 35%, p ≤ 0.008). The classical type of CMD was paralleled by a high prevalence of diabetes mellitus, metabolic syndrome, and obesity, while the endogen type of CMD was accompanied by a higher prevalence of arterial hypertension, obesity, and/or morbid obesity. Further, the classical type of nCMF was more frequently observed that the endogen type (74% vs. 26%, p ≤ 0.007). The endogen type of nCMF was related to lower heart rate and/or arterial blood pressures.

Conclusions

In this contemporary clinical study population, slightly more than half of symptomatic patients had CMD with predominance of the classical type. These observations emphasize the need for standardized reporting of CMD to gear individualized and/or intensified medical treatment to improve symptoms and/or clinical outcome in these patients.

Stress native T1 and native T2 mapping compared to myocardial perfusion reserve in long-term follow-up of severe Covid-19

Severe Covid-19 may cause a cascade of cardiovascular complications beyond viral pneumonia. The severe inflammation may affect the microcirculation which can be assessed by cardiovascular magnetic resonance (CMR) imaging using quantitative perfusion mapping and calculation of myocardial perfusion reserve (MPR). Furthermore, native T1 and T2 mapping have previously been shown to identify changes in myocardial perfusion by the change in native T1 and T2 during adenosine stress. However, the relationship between native T1, native T2, ΔT1 and ΔT2 with myocardial perfusion and MPR during long-term follow-up in severe Covid-19 is currently unknown. Therefore, patients with severe Covid-19 (n = 37, median age 57 years, 24% females) underwent 1.5 T CMR median 292 days following discharge. Quantitative myocardial perfusion (ml/min/g), and native T1 and T2 maps were acquired during adenosine stress, and rest, respectively. Both native T1 (R² = 0.35, p < 0.001) and native T2 (R² = 0.28, p < 0.001) correlated with myocardial perfusion. However, there was no correlation with ΔT1 or ΔT2 with MPR, respectively (p > 0.05 for both). Native T1 and native T2 correlate with myocardial perfusion during adenosine stress, reflecting the coronary circulation in patients during long-term follow-up of severe Covid-19. Neither ΔT1 nor ΔT2 can be used to assess MPR in patients with severe Covid-19.

PET for Detection and Reporting Coronary Microvascular Dysfunction: A JACC: Cardiovascular Imaging Expert Panel Statement

Angina pectoris and dyspnea in patients with normal or nonobstructive coronary vessels remains a diagnostic challenge. Invasive coronary angiography may identify up to 60% of patients with nonobstructive coronary artery disease (CAD), of whom nearly two-thirds may, in fact, have coronary microvascular dysfunction (CMD) that may account for their symptoms. Positron emission tomography (PET) determined absolute quantitative myocardial blood flow (MBF) at rest and during hyperemic vasodilation with subsequent derivation of myocardial flow reserve (MFR) affords the noninvasive detection and delineation of CMD. Individualized or intensified medical therapies with nitrates, calcium-channel blockers, statins, angiotensin-converting enzyme inhibitors, angiotensin II type 1-receptor blockers, beta-blockers, ivabradine, or ranolazine may improve symptoms, quality of life, and outcome in these patients. Standardized diagnosis and reporting criteria for ischemic symptoms caused by CMD are critical for optimized and individualized treatment decisions in such patients. In this respect, it was proposed by the cardiovascular council leadership of the Society of Nuclear Medicine and Molecular Imaging to convene thoughtful leaders from around the world to serve as an independent expert panel to develop standardized diagnosis, nomenclature and nosology, and cardiac PET reporting criteria for CMD. This consensus document aims to provide an overview of the pathophysiology and clinical evidence of CMD, its invasive and noninvasive assessment, standardization of PET-determined MBFs and MFR into "classical" (predominantly related to hyperemic MBFs) and "endogen" (predominantly related to resting MBF) normal coronary microvascular function or CMD that may be critical for diagnosis of microvascular angina, subsequent patient care, and outcome of clinical CMD trials.