Coronary fractional flow reserve

p53 Acetylation Exerts Critical Roles in Pressure Overload-Induced Coronary Microvascular Dysfunction and Heart Failure in Mice

BACKGROUND

Coronary microvascular dysfunction (CMD) has been shown to contribute to cardiac hypertrophy and heart failure (HF) with preserved ejection fraction. At this point, there are no proven treatments for CMD.

METHODS

We have shown that histone acetylation may play a critical role in the regulation of CMD. By using a mouse model that replaces lysine with arginine at residues K98, K117, K161, and K162R of p53 (p534KR), preventing acetylation at these sites, we test the hypothesis that acetylation-deficient p534KR could improve CMD and prevent the progression of hypertensive cardiac hypertrophy and HF. Wild-type and p534KR mice were subjected to pressure overload by transverse aortic constriction to induce cardiac hypertrophy and HF.

RESULTS

Echocardiography measurements revealed improved cardiac function together with a reduction of apoptosis and fibrosis in p534KR mice. Importantly, myocardial capillary density and coronary flow reserve were significantly improved in p534KR mice. Moreover, p534KR upregulated the expression of cardiac glycolytic enzymes and Gluts (glucose transporters), as well as the level of fructose-2,6-biphosphate; increased PFK-1 (phosphofructokinase 1) activity; and attenuated cardiac hypertrophy. These changes were accompanied by increased expression of HIF-1α (hypoxia-inducible factor-1α) and proangiogenic growth factors. Additionally, the levels of SERCA-2 were significantly upregulated in sham p534KR mice, as well as in p534KR mice after transverse aortic constriction. In vitro, p534KR significantly improved endothelial cell glycolytic function and mitochondrial respiration and enhanced endothelial cell proliferation and angiogenesis. Similarly, acetylation-deficient p534KR significantly improved coronary flow reserve and rescued cardiac dysfunction in SIRT3 (sirtuin 3) knockout mice.

CONCLUSIONS

Our data reveal the importance of p53 acetylation in coronary microvascular function, cardiac function, and remodeling and may provide a promising approach to improve hypertension-induced CMD and to prevent the transition of cardiac hypertrophy to HF.

A comprehensive approach to prediction of fractional flow reserve from deep-learning-augmented model

The underuse of invasive fractional flow reserve (FFR) in clinical practice has motivated research towards non-invasive prediction of FFR. Although the non-invasive derivation of FFR (FFRCT) using computational fluid dynamics (CFD) principles has become a common practice, its clinical application has been limited due to the considerable time required for computation of resulting changes in haemodynamic conditions. An alternative to CFD technology is incorporating a neural network into the computational process to reduce the time necessary for running an effective model. In this study we propose a cascade of data-driven and physic-based neural networks (DP-NN) for predicting FFR (DL-FFRCT). The first network of cascade network DP-NN includes geometric features, and the second network includes physical features. We compare the differences between data-driven neural network (D-NN) and DP-NN for predicting FFR. The training and testing datasets were obtained by solving the three-dimensional incompressible Navier-Stokes equations. Coronary flow and geometric features were used as inputs to train D-NN. In DP-NN the training process involves first training a D-NN to output resting ΔP as one input feature to the DP-NN. Secondly, the physics-based microcirculatory resistance as another input feature to the DP-NN. Using clinically measured FFR as the "gold standard", we validated the computational accuracy of DL-FFRCT in 77 patients. Compared to D-NN, DP-NN improved the prediction of ΔP (R2 = 0.87 vs. R2 = 0.92). Statistical analysis demonstrated that the diagnostic accuracy of DL-FFRCT was not inferior to FFRCT (85.71 % vs. 88.3 %) and the computational time was reduced by a factor of approximately 3000 (4.26 s vs. 3.5 h). DP-NN represents a near real-time, interpretable, and highly accurate deep-learning network, which contributes to the development of high-performance computational methods for haemodynamics. We anticipate that DP-NN will enable near real-time prediction of DL-FFRCT in personalized narrow blood vessels and provide guidance for cardiovascular disease treatments.

Fractional flow reserve and non-hyperemic indices: Essential tools for percutaneous coronary interventions

Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact. Fractional flow reserve (FFR) received a class IA recommendation from the European Society of Cardiology for the assessment of angiographically moderate stenosis. FFR evaluation of coronary artery disease offers improvement of the therapeutic strategy, deferring unnecessary procedures for lesions with a FFR > 0.8, improving patients' management and clinical outcome. Post intervention, an optimal FFR > 0.9 post stenting should be reached and > 0.8 post drug eluting balloons. Non-hyperemic pressure ratio measurements have been validated in previous studies with a common threshold of 0.89. They might overestimate the hemodynamic significance of some lesions but remain useful whenever hyperemic agents are contraindicated. FFR remains the gold standard reference for invasive assessment of ischemia. We illustrate this review with two cases introducing the possibility to estimate also non-invasively FFR from reconstructed 3-D angiograms by quantitative flow ratio. We conclude introducing a hybrid approach to intermediate lesions (DFR 0.85-0.95) potentially maximizing clinical decision from all measurements.

P53 Acetylation Exerts Critical Roles In Pressure Overload Induced Coronary Microvascular Dysfunction and Heart Failure

Coronary microvascular dysfunction (CMD) has been shown to contribute to cardiac hypertrophy and heart failure with preserved ejection fraction. At this point, there are no proven treatments for CMD. We have shown that histone acetylation may play a critical role in the regulation of CMD. By using a mouse model that replaces lysine with arginine at residues K98/117/161/162R of p53 (p534KR), preventing acetylation at these sites, we test the hypothesis that acetylation-deficient p534KR could improve coronary microvascular dysfunction and prevent the progression of hypertensive cardiac hypertrophy and heart failure. Wild-type (WT) and p534KR mice were subjected to pressure overload (PO) by transverse aortic constriction to induce cardiac hypertrophy and heart failure (HF). Echocardiography measurements revealed improved cardiac function together with reduction of apoptosis and fibrosis in p534KR mice. Importantly, myocardial capillary density and coronary flow reserve (CFR) were significantly improved in p534KR mice. Moreover, p534KR upregulated the expression of cardiac glycolytic enzymes and glucose transporters, as well as the level of fructose-2,6-biphosphate; increased PFK-1 activity; and attenuated cardiac hypertrophy. These changes were accompanied by increased expression of HIF-1α and proangiogenic growth factors. Additionally, the levels of SERCA-2 were significantly upregulated in sham p534KR mice as well as in p534KR mice after TAC. In vitro, p534KR significantly improved endothelial cell (EC) glycolytic function and mitochondrial respiration, and enhanced EC proliferation and angiogenesis. Similarly, acetylation-deficient p534KR significantly improved CFR and rescued cardiac dysfunction in SIRT3 KO mice. Our data reveal the importance of p53 acetylation in coronary microvascular function, cardiac function, and remodeling, and may provide a promising approach to improve hypertension-induced coronary microvascular dysfunction (CMD) and to prevent the transition of cardiac hypertrophy to heart failure.

Histone Acetyltransferase p300 Inhibitor Improves Coronary Flow Reserve in SIRT3 (Sirtuin 3) Knockout Mice

Background

Coronary microvascular dysfunction is common in patients of myocardial infarction with non‐obstructive coronary artery disease. Coronary flow reserve (CFR) reflects coronary microvascular function and is a powerful independent index of coronary microvascular dysfunction and heart failure. Our previous studies showed that knockout of SIRT3 (Sirtuin 3) decreased CFR and caused a diastolic dysfunction. Few studies focus on the treatment of impaired CFR and heart failure. In the present study, we explored the role of C646, a histone acetyltransferase p300 inhibitor, in regulating CFR and cardiac remodeling in SIRT3 knockout (SIRT3KO) mice.

Methods and Results

After treating with C646 for 14 days, CFR, pulse‐wave velocity, and cardiac function were measured in SIRT3KO mice. SIRT3KO mice treated with C646 showed a significant improvement of CFR, pulse‐wave velocity, ejection fraction, and fractional shortening. Treatment with C646 reversed pre‐existing cardiac fibrosis, hypertrophy, and capillary rarefaction in SIRT3KO mice. Mechanistically, knockout of Sirtuin 3 resulted in significant increases in p300 expression and H3K56 acetylation. Treatment with C646 significantly reduced levels of p300 and H3K56 acetylation in SIRT3KO mice. Furthermore, treatment with C646 increased endothelial nitric oxide synthase expression and reduced arginase II expression and activity. The expression of NF‐κB (nuclear factor kappa‐light‐chain‐enhancer of activated B cells) and VCAM‐1 (vascular cell adhesion molecule 1) was also significantly suppressed by C646 treatment in SIRT3KO mice.

Conclusions

C646 treatment attenuated p300 and H3K56 acetylation and improved arterial stiffness and CFR via improvement of endothelial cell (EC) dysfunction and suppression of NF‐κB.

Angiographic Characteristics of Catheter-Induced Spasm of the Left Main Coronary Artery

Spasm of the left main coronary artery (LM) is considered to be rare. We investigated the angiographic characteristics of the LM in patients with combined LM and disease involving additional vessels, who underwent coronary artery bypass grafting (CABG) and underwent repeat coronary angiography within 5 years of the CABG, to examine the apparent frequency of spasm of the LM on initial angiography and its possible predictors. A retrospective analysis was performed of patients who underwent coronary angiography in our institute, who were found to have significant LM stenosis and disease involving additional vessels, underwent CABG and repeat coronary angiography within 5 years of the CABG. Data on angiographic characteristics of the LM on the initial angiogram were investigated. Of 84 patients, 17 (20%) were found to have a normal LM on repeat angiography (group A), and 67 (80%) demonstrated significant stenosis (group B). The degree of LM stenosis was milder in the initial angiogram in group A than in group B (64 ± 15% vs 72 ± 14%, p = 0.047). Most patients in group A demonstrated tubular LM stenosis at initial catheterization in comparison to group B (71% vs 18%). Using multivariate analysis, the only predictor for a normal LM at repeat catheterization was found to be tubular stenosis at initial catheterization (odds ratio 123, 95% confidence interval 4.0 to 3696). In conclusion, LM coronary spasm is a common finding, particularly in those with the appearance of tubular stenosis, and it should be excluded even in patients with additional coronary disease in certain instances to prevent unnecessary CABG.

Value of FFR in clinical practice

Fractional flow reserve is an important tool in the cardiac catheterization lab to assess the physiological significance of coronary lesions. This article discusses the basic concepts about FFR and its utility in clinical decision making.