Correlation between myocardial strain and adverse remodeling in a non-diabetic model of heart failure following empagliflozin therapy

OBJECTIVES

The sodium-glucose cotransporter type 2 inhibitors reduce mortality and heart failure (HF) hospitalizations. The underlying mechanisms remain unclear but seem to be irrespective of glucose-lowering properties. This study aims to evaluate the impact of empagliflozin on myocardial biomechanics and correlation with markers of adverse remodeling.

METHODS

Following myocardial infarct induction to create a model of HF, 14 pigs were randomly assigned in a 1:1 ratio to receive either empagliflozin 10 mg daily or placebo for 2 months. Speckle-tracking echocardiography (STE) and feature-tracking cardiac magnetic resonance (FTCMR) were performed at baseline and at the end of the study to analyze myocardial deformation. The results were correlated with markers of adverse cardiac remodeling.

RESULTS

Empagliflozin significantly improved STE indices. These parameters significantly correlated with adverse cardiac remodeling. In contrast, FTCMR indices showed only a trend toward improved myocardial deformation and without significant correlation with adverse cardiac remodeling. The correlation between both techniques to assess myocardial deformation was low.

CONCLUSION

Empagliflozin enhances myocardial deformation, assessed by STE techniques, in a non-diabetic porcine model of ischemic HF. This may be related to a mitigation of adverse cardiac remodeling following ischemia reperfusion injury. In contrast, FTCMR technique needs further development and validation.

Comparison of Hemodynamic Support by Impella vs. Peripheral Extra-Corporeal Membrane Oxygenation: A Porcine Model of Acute Myocardial Infarction

Objectives: Several mechanical circulatory assist devices are used to treat critically ill patients requiring hemodynamic support during post-myocardial infarction or cardiogenic shock. However, little guidance is available to choose an appropriate device to match a particular patient's needs. An increased understanding of hemodynamic effects of the pump systems and their impact on myocardial pre-/afterload might help to better understand their behavior in different clinical settings. Methods: This was an open-labeled, randomized acute animal experiment. A model of acute univentricular myocardial injury by temporary balloon occlusion was used. The experiment was carried out in 10 juveniles female Piétrain pigs. The animals were randomized to mechanical hemodynamic support either by peripheral veno-arterial (VA-)ECMO or Impella CP. Results: While both devices were able to provide flows above 3 L/min and maintain sufficient end-organ perfusion, support by Impella resulted in a significantly more pronounced immediate effect on myocardial unloading: At the onset of device support, the remaining native cardiac output was reduced by 23.5 ± 15.3% ECMO vs. 66.2 ± 36.2% (Impella, p = 0.021). Native stroke volume was significantly decreased by Impella support compared to ECMO, indicating less mechanical work being conducted by the Impella-supported hearts despite similar total assisted cardiac output. Conclusions: Peripheral VA-ECMO and the transaortic Impella pump resulted in contrasting hemodynamic fingerprints. Both devices provided sufficient hemodynamic support and reduce left ventricular end-diastolic pressure in the acute setting. Treatment with the Impella device resulted in a more effective volume unloading of the left ventricle. A significant reduction in myocardial oxygen consumption equivalent was achieved by both devices: The Impella device resulted in a left-shift of the pressure-volume loop and a decreased pressure-volume-area (PVA), while VA-ECMO increased PVA but decreased heart rate. These data highlight the importance of specifically targeting heart rate in the management of AMI patients on hemodynamic support.

Serum immunoglobulin G antibody titer to Fusobacterium nucleatum is associated with unfavorable outcome after stroke

Stroke can be a cause of death, while in non-fatal cases it is a common cause of various disabilities resulting from associated brain damage. However, whether a specific periodontal pathogen is associated with increased risk of unfavorable outcome after stroke remains unknown. We examined risk factors for unfavorable outcome following stroke occurrence, including serum antibody titers to periodontal pathogens. The enrolled cohort included 534 patients who had experienced an acute stroke, who were divided into favorable (n = 337) and unfavorable (n = 197) outcome groups according to modified ranking scale (mRS) score determined at 3 months after onset (favorable = score 0 or 1; unfavorable = score 2-6). The associations of risk factors with unfavorable outcome, including serum titers of IgG antibodies to 16 periodontal pathogens, were examined. Logistic regression analysis showed that the initial National Institutes of Health stroke scale score [odds ratio (OR) = 1·24, 95% confidence interval (CI) = 1·18-1·31, P < 0·001] and C-reactive protein (OR = 1·29, 95% CI = 1·10-1·51, P = 0·002) were independently associated with unfavorable outcome after stroke. Following adjustment with those, detection of the antibody for Fusobacterium nucleatum ATCC 10953 in serum remained an independent predictor of unfavorable outcome (OR = 3·12, 95% CI = 1·55-6·29, P = 0·002). Determination of the antibody titer to F. nucleatum ATCC 10953 in serum may be useful as a predictor of unfavorable outcome after stroke.

FTO-Dependent N6-Methyladenosine Regulates Cardiac Function During Remodeling and Repair

BACKGROUND

Despite its functional importance in various fundamental bioprocesses, studies of N⁶-methyladenosine (m6A) in the heart are lacking. Here, we show that the FTO (fat mass and obesity-associated protein), an m6A demethylase, plays a critical role in cardiac contractile function during homeostasis, remodeling, and regeneration.

METHODS

We used clinical human samples, preclinical pig and mouse models, and primary cardiomyocyte cell cultures to study the functional role of m6A and FTO in the heart and in cardiomyocytes. We modulated expression of FTO by using adeno-associated virus serotype 9 (in vivo), adenovirus (both in vivo and in vitro), and small interfering RNAs (in vitro) to study its function in regulating cardiomyocyte m6A, calcium dynamics and contractility, and cardiac function postischemia. We performed methylated (m6A) RNA immunoprecipitation sequencing to map transcriptome-wide m6A, and methylated (m6A) RNA immunoprecipitation quantitative polymerase chain reaction assays to map and validate m6A in individual transcripts, in healthy and failing hearts, and in myocytes.

RESULTS

We discovered that FTO has decreased expression in failing mammalian hearts and hypoxic cardiomyocytes, thereby increasing m6A in RNA and decreasing cardiomyocyte contractile function. Improving expression of FTO in failing mouse hearts attenuated the ischemia-induced increase in m6A and decrease in cardiac contractile function. This is performed by the demethylation activity of FTO, which selectively demethylates cardiac contractile transcripts, thus preventing their degradation and improving their protein expression under ischemia. In addition, we demonstrate that FTO overexpression in mouse models of myocardial infarction decreased fibrosis and enhanced angiogenesis.

CONCLUSIONS

Collectively, our study demonstrates the functional importance of the FTO-dependent cardiac m6A methylome in cardiac contraction during heart failure and provides a novel mechanistic insight into the therapeutic mechanisms of FTO.

A Novel Large Animal Model of Thrombogenic Coronary Microembolization

Coronary microembolization is one of the main causes of the “no-reflow” phenomenon, which commonly occurs after reperfusion of an occluded coronary artery. Given its high incidence and the fact that it has been proven to be an independent predictor of cardiac morbidity and mortality, there is an imperative need to study its underlying mechanisms and pathophysiology. Large animal models are essential to perform translational studies. Currently there is no animal model that recapitulates a clinical scenario of thrombogenic microembolism with preceding myocardial ischemia. Therefore, the goal of this study was to develop and characterize a novel pig model of coronary microembolization using autologous thrombus injection (CMET). Twenty-three pigs underwent myocardial infarction through percutaneous balloon occlusion of the left anterior descending artery (LAD). Each animal was enrolled in one of two groups: (1) the CMET group, in which the LAD occlusion was followed by delivery of autologous clotted blood in the LAD (distal to the balloon occlusion) and reperfusion; (2) the ischemic reperfusion (I/R) group, in which the LAD ischemia was followed by reperfusion. Surviving animals underwent functional and morphological characterization at 1-week post-procedure. Three sham operated animals were used as a control. CMET resulted in impaired left ventricular function compared to I/R pigs at 1 week. Three-dimensional echocardiography demonstrated reduced ejection fraction in the CMET group (CMET vs. I/R: 35.6 ± 4.2% vs. 47.6 ± 2.4%, p = 0.028). Invasive hemodynamic measurements by Swan-Ganz and left ventricular pressure-volume catheters revealed that CMET impaired left ventricular contractility and diastolic function. This was confirmed by both load-dependent indices including cardiac output (CMET vs. I/R: 2.7 ± 0.2 l/min, vs. 4.0 ± 0.1 l/min, p = 0.002) and load independent indices including preload-recruitable stroke work (CMET vs. I/R: 25.8 ± 4.0 vs. 47.5 ± 6.5 mmHg, p = 0.05) and end-diastolic pressure-volume relationship (slope, 0.68 ± 0.07 vs. 0.40 ± 0.11 mmHg/ml, p = 0.01). Our unique closed-chest model of coronary microembolization using autologous thrombus injection resembles the clinical condition of thrombogenic coronary microembolization in I/R injury. This model offers opportunities to conduct translational studies for understanding and treating coronary microembolization in myocardial infarction.

Recent highlights and advances in cardiac gene therapy

There has been significant progress in the field of gene therapy toward clinical application in recent years. Cardiac gene therapy has followed this trend, but at a slower pace compared to therapies targeting retinal, spinal, and blood disorders. New approaches targeting monogenic disorders are being developed at a rapid pace and studies in large animal models show promise. Meanwhile, several clinical trials are underway to prove the efficacy of gene therapy for cardiovascular diseases such as heart failure. In this concise review, we attempt to summarize recent highlights in technological advancements, preclinical studies, and clinical trials of cardiac gene therapy.

P599Native T1 mapping is useful for detection of myocardial fibrosis in cases with ischemic and non-ischemic myocardial diseases

Background

Evaluation of myocardial fibrosis (MF) as late gadolinium enhancement (LGE) on MRI is useful for differential diagnosis of various myocardial diseases and prediction of future adverse cardiac events in some specific myocardial diseases. Gadolinium contrast is contraindicated for cases with severe renal dysfunction, therefore non contrast MRI is necessary for detection of MF in cases with both myocardial disease and severe renal dysfunction.

Purpose

We aimed to evaluate diagnostic accuracy of native T1 mapping for detection of MF compared with LGE in cases with various myocardial diseases, including ischemic and non-ischemic myocardial diseases.

Methods

We selected consecutive 40 patients who were suspected of having various myocardial diseases and underwent cardiac MRI, using 1.5T MRI (Ingenia, Philips) in 10 cases (25%) or 3T MRI (Ingenia, Philips) in 30 cases (75%), including native T1 mapping (without contrast) and LGE using contrast media from Jan 2018 to Feb 2019 in our institution. We evaluated diagnostic accuracy for detection of MF in left ventricular myocardium (LVM) of native T1 mapping image compared with LGE as the gold standard, in a patient-based and segment-based analysis. In T1 mapping images, segmental high T1 lesions were defined as MF. In a segment-based analysis, MF was evaluated using 17 LVM segments model in American Heart Association.

Results

MF was detected in 139 LVM segments in 25 (63%) cases. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of native T1 mapping for detection of MF were 90%, 89%, 95%, 80% and 90% in a patient-based analysis, and 63%, 96%, 84%, 89% and 88% in a segment-based analysis (left figure). Native T1-values of LVM with MF were significantly higher than LVM without LGE (1351±79 vs 1093±124 in 1.5T and 1562±131 vs 1291±43 in 3T) (p<0.05 and p<0.01). Interobserver agreement of native T1 mapping and LGE were not significantly different (0.88 and 0.89, P=0.70). Overall diagnostic accuracy of native T1 mapping for detection of MF in a patient-based analysis, was not significantly different in between the cases with ischemic (n=18) and non-ischemic (n=22) myocardial disease (90% and 83.3%, P=0.10).

Conclusion

Native T1 mapping (without contrast) is useful for detection of MF in various myocardial diseases and high diagnostic accuracy is expected especially in a patient-based analysis.

P6182Combination of a new iterative reconstruction technique with low tube voltage and high tube current has important role of detection of late enhancement on 320 slice CT

Background

New iterative reconstruction tecniques, including Adaptive Iterative Dose Reduction 3D (AIDR 3D) and Forward Projected Model-based Iterative Reconstruction SoluTion (FIRST), have been recently available on new generation 320 slice CT, and they can provide high-quality CT images.

Purpose

The aim of this study was to evaluate the diagnostic performance of detection of abnormal late enhancement (LE) in left ventricular (LV) myocardium (LVM) using 320-slice CT with new iterative reconstruction techiniques, AIDR 3D (Figure A) and FIRST (Figure B).

Methods

A total of 100 patients who were suspected of having various myocardial diseases and underwent late phase acquisition both on cardiac CT and CMR within 3 months were analyzed. The first 50 consecutive patients (Group 1) underwent 320-slice CT with AIDR 3D, 120 Kv tube voltage, 519±71 mA tube current. The next 50 consecutive patients (Group 2) underwent 320-slice CT with FIRST, 80 or 100Kv tube voltage, 803±20 mA tube current. We compared diagnostic accuracy of CT for detection of LE in LVM against that of CMR (the gold standard) in between the 2 groups.

Results

On patient-by-patient analysis, sensitivity, specificity, positive (PPV) and negative predictive values (NPV), and overall accuracy for detection of LE on CT vs CMR were 87, 95, 96, 82, and 90% in Group 1, and 97, 83, 91, 88, and 90% in Group 2. There were no significant difference of diagnostic accuracy on patient-by-patient analysis in between the 2 groups (Figure C). However, on a segment-by-segment analysis (using 17 American Heart Association LV segment model), these values for detection of LE on CT vs CMR were 60, 95, 73, 91, and 88% in Group 1, and 85, 95, 86, 95, and 93% in Group 2. Sensitivity, PPV, NPV and overall accuracy were significantly higher in Group 2 than in Group 1 (all P<0.01) (Figure D).

Conclusions

Diagnostic accuracy of detection of LE in LVM on CT combining low tube voltage and high tube current acquisition on a new generation 320-slice CT with FIRST was superior to 320-slice CT with AIDR 3D.

Acknowledgement/Funding

TSUCHIYA MEMORIAL MEDICAL FOUNDATION

P6578Development of the novel program to diagnose atrial fibrillation using automated blood pressure monitor

Background

Atrial fibrillation (AF) is often asymptomatic and contributes to an increased risk of strokes. The development of proper screening device of AF is unmet medical needs worldwide. Recently, we had reported that multiple measurements using Omron automated blood pressure (BP) monitor with irregular heartbeat detection showed high sensitivity and specificity for AF detection in general cardiac patients, however, this method had limitations in discriminating between AF and other arrhythmias.

Purpose

The aim of this study is to develop a novel program that can accurately diagnose AF by discriminating it from other arrhythmias using the pressure pulse waveform data outputted from Omron automated BP monitor.

Methods

In our previous clinical research, BP measurements were performed 3 times each for 303 general cardiac patients (mean age: 72.2 years, 69.8% male) with recording the real-time single lead ECG, and a total of 909 pressure pulse waveforms were obtained. Among them, 840 pressure pulse waveforms from 280 patients (include 40 AF patients) used for further analysis. We developed a program to analyze and visualize uniquely the characteristics of AF waveform through the autocorrelation-based waveform processing system produced by Melody International Ltd, Kagawa, Japan. All visualized results were judged and classified into Sinus, Non-AF and AF by two individuals blinded to the results. For each patient who obtained 3 results, a two by two contingency table was created and sensitivity, specificity, and accuracy for diagnosing AF were calculated.

Results

Among 840 pressure pulse waveforms, only 21 (2 Sinus and 19 Non-AF) out of 720 Sinus and Non-AF waveforms were judged as AF, and 7 out of 120 AF waveforms were judged as Non-AF. None of AF waveforms was absolutely misjudged as Sinus. In analysis for each patient, when one or more AF judgements were found in 3 waveforms, the diagnosis of AF has sensitivity and specificity of 100% and 95.8%, respectively. When two or more AF judgements were found in 3 waveforms, the diagnosis of AF has sensitivity and specificity of 100% and 97.9%, respectively. In this rule, the diagnostic accuracy of AF reached up to 98.8%, and no sinus patients were misjudged as AF.

Conclusion

The novel program, which applied autocorrelation methods uniquely to analysis of the pressure pulse waveforms recorded by automated BP monitor, showed high sensitivity and high specificity for AF diagnosis in general cardiac patients. This program is expected to be useful for early diagnosis for asymptomatic AF patients.

Acknowledgement/Funding

The present research is supported by a grant through the SCOPE from the Ministry of Internal Affairs and Communications, Japan.

Human Cardiac Gene Therapy

In the past 10 years, there has been tremendous progress made in the field of gene therapy. Effective treatments of Leber congenital amaurosis, hemophilia, and spinal muscular atrophy have been largely based on the efficiency and safety of adeno-associated vectors. Myocardial gene therapy has been tested in patients with heart failure using adeno-associated vectors with no safety concerns but lacking clinical improvements. Cardiac gene therapy is adapting to the new developments in vectors, delivery systems, targets, and clinical end points and is poised for success in the near future.

Honeycomb blocks composed of carbonate apatite, β-tricalcium phosphate, and hydroxyapatite for bone regeneration: effects of composition on biological responses

Synthetic scaffolds exhibiting bone repair ability equal to that of autogenous bone are required in the fields of orthopedics and dentistry. A suitable synthetic bone graft substitute should induce osteogenic differentiation of mesenchymal stem cells, osteogenesis, and angiogenesis. In this study, three types of honeycomb blocks (HCBs), composed of hydroxyapatite (HAp), β-tricalcium phosphate (TCP), and carbonate apatite (CO3Ap), were fabricated, and the effects of HCB composition on bone formation and maturation were investigated. The HC structure was selected to promote cell penetration and tissue ingrowth. HAp and β-TCP HCBs were fabricated by extrusion molding followed by sintering. The CO3Ap HCBs were fabricated by extrusion molding followed by sintering and dissolution-precipitation reactions. These HCBs had similar macroporous structures: all harbored uniformly distributed macropores (∼160 ​μm) that were regularly arrayed and penetrated the blocks unidirectionally. Moreover, the volumes of macropores were nearly equal (∼0.15 ​cm3/g). The compressive strengths of CO3Ap, HAp, and β-TCP HCBs were 22.8 ​± ​3.5, 34.2 ​± ​3.3, and 24.4 ​± ​2.4 ​MPa, respectively. Owing to the honeycomb-type macroporous structure, the compressive strengths of these HCBs were higher than those of commercial scaffolds with intricate three-dimensional or unidirectional macroporous structure. Notably, bone maturation was markedly faster in CO3Ap HCB grafting than in β-TCP and HAp HCB grafting, and the mature bone area percentages for CO3Ap HCBs at postsurgery weeks 4 and 12 were 14.3- and 4.3-fold higher and 7.5- and 1.4-fold higher than those for HAp and β-TCP HCBs, respectively. The differences in bone maturation and formation were probably caused by the disparity in concentrations of calcium ions surrounding the HCBs, which were dictated by the inherent material resorption behavior and mechanism; generally, CO3Ap is resorbed only by osteoclastic resorption, HAp is not resorbed, and β-TCP is rapidly dissolved even in the absence of osteoclasts. Besides the composition, the microporous structure of HC struts, inevitably generated during the formation of HCBs of various compositions, may contribute to the differences in bone maturation and formation.

Acute Left Ventricular Unloading Reduces Atrial Stretch and Inhibits Atrial Arrhythmias

BACKGROUND

Left atrium (LA) physiology is influenced by changes in left ventricular (LV) performance and load.

OBJECTIVES

The purpose of this study was to define the effect of acute changes in LV loading conditions on LA physiology in subacute myocardial infarction (MI).

METHODS

MI was percutaneously induced in 19 Yorkshire pigs. One to 2 weeks after MI, 14 pigs underwent acute LV unloading using a percutaneous LV assist device, Impella. The remaining 5 pigs underwent acute LV loading by percutaneous induction of aortic regurgitation. A pressure-volume catheter was inserted into the LA using a percutaneous transseptal approach, and LA pressure-volume loops were continuously monitored. Atrial arrhythmia inducibility was examined by burst-pacing of the right atrium. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) levels and ryanodine receptor phosphorylation were examined in LA tissues to study the potential effect of stretch-dependent oxidative stress.

RESULTS

MI resulted in reduced LV ejection fraction and increased LV end-diastolic pressure with concomitant increase in LA pressure and volumes. Acute LV unloading resulted in a reduction of LV end-diastolic pressure, which led to proportional decreases in mean LA pressure and maximum LA volume. LA pressure-volume loops exhibited a pump flow-dependent, left-downward shift. This was associated with reduced LA passive stiffness, suggesting the alleviation of the LA stretch that was present after MI. Prior to acute unloading of the LV, 71% of the pigs were arrhythmia-inducible; LV unloading reduced this to 29% (p = 0.02). Time to spontaneous termination of atrial arrhythmias was decreased from median 55 s (range 5 to 300 s) to 3 s (range 0 to 59 s). In contrast, acute LV loading with aortic regurgitation increased LA pressure without a significant effect on arrhythmogenicity. Molecular analysis of LA tissue revealed that NOX2 expression was increased after MI, whereas acute LV unloading reduced NOX2 levels and diminished ryanodine receptor phosphorylation.

CONCLUSIONS

Acute LV unloading relieves LA stretch and reduces atrial arrhythmogenicity in subacute MI.

Abstract 326: FTO-mediated mRNA Demethylation Regulates Cardiac Contractile Protein Expression and Function

Background: Exciting new discoveries in RNA biology underscore the importance of post-transcriptional chemical modifications to mRNAs (epitranscriptome) in regulating RNA stability, nuclear export, cellular compartmentalization, splicing, translation and degradation. The most abundant and functionally relevant modification in RNA, N6-methyladenosine (m6A) is reversibly demethylated by one of the m6A demethylases, fat mass and obesity-associated protein (FTO) whose function in the mammalian heart remains incompletely understood.

Materials and Methods: We used clinical human samples, preclinical pig and mouse models and primary cardiomyocytes to study m6A and FTO in the heart and in cardiomyocytes. We modulated FTO expression using AAV9 (in vivo), adenovirus (in vivo and in vitro) and siRNAs (in vitro). We investigated m6A-induced changes to contractile protein expression using m6A RNA immunoprecipitation sequencing (MeRIP-seq) and stable isotope labeling of amino acids in cell culture (SILAC).

Results: We discovered in human heart failure that reduced FTO expression is associated with aberrant increase in m6A mRNA methylation, which is conserved in swine and mouse models of myocardial ischemia (MI). AAV9-mediated FTO gene delivery in mouse MI attenuated m6A increase and improved cardiac function with enhanced contractility, angiogenesis and reduced fibrosis. At the molecular level, FTO-mediated mRNA demethylation serves to increase contractile protein expression in mouse hearts as well as in isolated primary cardiomyocytes. By comparing human and mouse transcriptome-wide m6A maps with SILAC proteomic profiling from cardiomyocytes, we identified FTO-mediated m6A demethylation is transcript-specific and leads to altered protein expression of several key contractile, angiogenic and regenerative proteins.

Conclusion: Using new RNA-based investigations, we uncovered a novel regulatory layer beyond the genome working at the level of epitranscriptome governing cardiac function. Our findings on the dynamic nature of the cardiac m6A-epitranscriptome will lead to deeper understanding of the mechanism of cardiac remodeling on one hand and innovative therapeutic interventions on the other.

Pig Model of Increased Cardiac Afterload Induced by Ascending Aortic Banding

Increase in cardiac afterload as represented by hypertension is an established risk factor for cardiovascular diseases. Animal models of increased cardiac afterload offer studies aiming at identifying key molecular mechanisms and developing new therapeutic approaches. We have reported that banding of the ascending aorta in pigs results in significant cardiac hypertrophy and increased myocardial fibrosis at the chronic stages. These changes were accompanied by increased stiffness of the heart, but not by systolic dysfunction. In this chapter, we describe methods to surgically band the ascending aorta in pigs. After 3 months, animals develop systolic left ventricular pressure of >200 mmHg with above described changes in the heart.