Normal Cardiac Function Research Articles

Tachycardia-Induced Cardiomyopathy in an Infant with Atrial Flutter and Prolonged Recovery of Cardiac Function.

Background: Tachycardia-induced cardiomyopathy (TIC) is caused by prolonged tachycardia, leading to left ventricular dilatation and systolic dysfunction with heart failure. Although TIC is more common in adults, it is rare in early infancy. Methods: Clinical testing was performed as part of medical evaluation and management. Next-generation sequencing (NGS) was conducted for a patient with TIC. A literature review on TIC was also conducted. Results: The case involved a 5-month-old infant referred to the hospital due to symptoms of heart failure lasting at least two months. The infant's heart rate was 200 beats per minute, the left ventricular ejection fraction fell below 14%, and electrocardiograms showed atrial flutter, suggesting TIC. After cardioversion, there was no recurrence of atrial flutter, and cardiac function improved 98 days after tachycardia arrest. The NGS did not identify any pathogenic variants. The literature review identified eight early infantile cases of TIC. However, no previous reports described a case with such a prolonged duration of TIC as ours. Conclusions: This is the first report of a case of prolonged TIC in a child with the documented time to recover normal cardiac function. The improvement of cardiac function depends on the duration of TIC. Early recognition and intervention in TIC are essential to improve outcomes for infantile patients, as timely treatment offers the potential for recovery.

Doxorubicin induces phosphorylation of lamin A/C and loss of nuclear membrane integrity: A novel mechanism of cardiotoxicity

Lamin A/C, essential inner nuclear membrane proteins, have been linked to progeria, a disease of accelerated aging, and many other diseases, which include cardiac disorder. Lamin A/C mutation and its phosphorylation are associated with altering nuclear shape and size. The role of lamin A/C in regulating normal cardiac function was reported earlier. In the present study, we hypothesized that Doxorubicin (Dox) may alter total lamin A/C expression and phosphorylation, thereby taking part in cardiac injury. An in vitro cellular injury model was generated with Dox (0.1–10.0 μM) treatment on cardiomyoblast cells (H9c2) to prove our hypothesis. Increased size and irregular (ameboid) nucleus shape were observed in H9c2 cells after Dox treatment. Similarly, we have observed a significant increase in cell death on increasing the Dox concentration. The expression of lamin A/C and its phosphorylation at serine 22 significantly decreased and increased, respectively in H9c2 cells and rat hearts after Dox exposure. Phosphorylation led to depolymerization of the lamin A/C in the inner nuclear membrane and was evidenced by their presence throughout the nucleoplasm as observed by immunocytochemistry techniques. Thinning and perforation on the walls of the nuclear membrane were observed in Dox-treated H9c2 cells. LMNA-overexpression in H9c2 protected the cells from Dox-induced cell death, reversing all changes described above. Further, improvement of lamin A/C levels was observed in Dox-treated H9c2 cells when treated with Purvalanol A, a CDK1 inhibitor and N-acetylcysteine, an antioxidant. The study provides new insight regarding Dox-induced cardiac injury with the involvement of lamin A/C and alteration of inner nuclear membrane structure.

Atrial fibrillation induced by carbon monoxide poisoning: Case report

Background: Carbon monoxide (CO) poisoning is known to have direct toxic effects on the cardiovascular system, including the potential to cause arrhythmias by prolonging the QTc interval. The arrhythmogenic properties of CO are believed to be attributed to its impact on cardiac membranes. Case Presentation: This case report presents the clinical course and management of a 21-year-old male who presented to the Emergency Department (ED) with an altered level of consciousness following exposure to carbon monoxide while cooking on a gas cylinder in a closed room. The patient had no history of chronic medical illness and was a non-smoker. Physical examination revealed stable vital signs, clear breath sounds, and a lax, soft, and non-tender abdomen. Laboratory investigations showed elevated troponin levels indicative of cardiac muscle injury but normal potassium levels. ECG revealed atrial fibrillation with a fast ventricular rate and transient ST elevation. The patient received high flow oxygen. The carboxyhemoglobin level decreased significantly after high-flow oxygen administration, confirming the successful treatment of carbon monoxide poisoning. Echocardiography and coronary angiography demonstrated normal cardiac function and ruled out coronary artery disease, respectively. The patient received high-flow oxygen therapy, continuous cardiac monitoring, and supportive care during hospitalization. Following stabilization and restoration of sinus rhythm, the patient was discharged in stable condition. Conclusion: This case highlights the importance of prompt recognition and management of carbon monoxide poisoning, as well as the need for careful evaluation of cardiac function in such cases. The patient responded well to high-flow oxygen therapy, leading to a decrease in the carboxy hemoglobin level and resolution of symptoms. Timely recognition and appropriate management of carbon monoxide poisoning are crucial in preventing adverse cardiac events and ensuring a favorable outcome for the patient.

Comparison of Left Ventricular End-Diastolic Volume Approximated from Mean Blood Pressure and Stroke Volume and End-Diastolic Volume Calculated from Left Ventricular-Aortic Coupling.

Objectives: The purpose of this study was to compare left ventricular end-diastolic volume (EDV), derived from left ventricular arterial coupling (Ees/Ea), and mean arterial blood pressure. Both of these methods of measuring EDV require some invasive procedure. However, the method of measuring EDV approximate is less invasive than the EDV coupling measuring method. This is because EDV approximate only requires arterial pressure waveform as an invasive procedure. Methods: This study included 14 patients with normal cardiac function who underwent general anesthesia. The point when blood pressure stabilized after the induction of anesthesia was taken as a baseline according to the study protocol. At the point when systolic arterial blood pressure fell 10% or more from the baseline blood pressure, 300 mL of colloid solution was administered over 15 min. EDV approximate and EDV coupling were calculated for each of the 14 patients at three points during the course of anesthetic. Each value was obtained by calculating a 5 min average. The timing of these three points was 5 min before, 5 min during, and 5 min after infusion loading. Results: The total number of comparable points was 42; 3 points were taken from each of the 14 participants. Both EDV approximate and EDV coupling increased through the infusion load testing. Scatter plots were prepared, and regression lines were calculated from the obtained values. A high correlation was shown between EDV approximate and EDV coupling (R2 = 0.96, p < 0.05). Conclusions: In patients with good cardiac function, EDV approximate can be substituted for EDV coupling, suggesting the possibility that EDV can be continuously and less invasively calculated under the situation of general anesthesia.

Cardiomyocyte Notch1 signaling is essential for protection of the maternal heart from peripartum stress

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft Background Peripartum cardiomyopathy (PPCM) is a life-threatening disease in women without known cardiovascular disease and is characterized by a sudden onset of heart failure (HF) before, under or after delivery. Previous studies suggest impaired endothelial to cardiomyocyte crosstalk as a major pathomechanism of the disease. Purpose Analyses of the role of Notch1 signaling for the endothelial-cardiomyocyte crosstalk in PPCM. Methods and results Serum from PPCM patients with acute HF reduced Notch1 expression in induced pluripotent stem cell derived cardiomyocytes (-20%, P&amp;lt;0.05) compared to serum from postpartum-matched healthy controls (PP-Ctrl). Beside miRNA-146a previously described to be up-regulated in PPCM plasma (6.8-fold, P&amp;lt;0.01), additional miRNAs targeting Notch1 signaling (miR-30a-3p, miR-34a, miR-200b-3p, miR-200c-3p, miR-429-3p, miR-449a) were up-regulated in PPCM plasma. Overexpression of these miRNAs in cardiomyocytes (CM) reduces Notch1 protein levels. Mice with a CM-restricted knockout of Notch1 (N1-KO) are born at the expected Mendelian ratio and nulli pari (NP) N1-KO female mice do not show a distinct cardiac phenotype at the age of 3 to 4 months compared to WT female mice (%FS WT: 41±5 vs N1-KO: 37±6; n= 9-12). However, they develop mild HF at the age of 6 months (%FS WT: 44±4 vs N1-KO: 31±8; n=11-14; P&amp;lt;0.01). Mated N1-KO females displayed normal cardiac function and LV dimensions in the last week of the first pregnancy. After 3 pregnancies and nursing periods, N1-KO developed severe HF (%FS WT PP: 30±5 vs N1-KO PP: 16±5; n=8-12; P&amp;lt;0.01), and show enhanced mortality (P&amp;lt;0.01). N1-KO-NP and N1-KO-PP displayed significant increase in the cardiac expression of the stress markers ANP and BNP compared to respective WT-NP and WT-PP. RNA-Seq analysis of N1-KO-PP revealed 1380 transcripts (adj. P&amp;lt;0.01) differently regulated genes, among them down-regulation of ErbB4, a known driver in PPCM onset. SiRNA-mediated knockdown of Notch1 in CM were associated with a decrease in ErbB4 protein expression. Treatment with bromocriptin (BR) was not able to improve survival and to rescue cardiac function and LV dimensions in postpartum N1-KO females (WT: 37±4, N1-KO: 23±10; n=7-8). Moreover, RNA-Seq analysis revealed that BR had no effect on the dysregulated cardiac mRNA. In conclusion, the pathophysiology of PPCM is associated with reduced cardiac Notch1 expression, which results in part from 16-kDa-prolactin mediated upregulation of miRNAs targeting Notch1. The reduced cardiac Notch1 expression contributes to PPCM as indicated with severe postpartum HF and high mortality in N1-KO mice. Inhibition of prolactin secretion with BR failed to rescue the development of PPCM in N1-KO mice suggesting that deregulated Notch1 is downstream of the 16-kDa prolactin-miRNA pathophysiology.

Targeting serotonin receptor 7 to improve survival after myocardial infarction

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) Background Myocardial infarction (MI) is among the leading causes of death worldwide. Survival and long-term recovery are highly dependent on regeneration of the cardiac tissue, mediated by precisely regulated inflammatory processes and invading immune cells. The serotonergic system is known to regulate the functions of various cells of the immune system, and is also affected in several cardiovascular diseases. Purpose We investigated the role of the serotonin receptor 7 (5-HT7R) in regulation of the inflammatory response after MI and its contribution to cardiac outcome. Methods Permanent left ascending coronary artery ligation (LAD) in mice was used as a model for MI. We compared the impact of MI on heart function and tissue integrity in WT and 5-HT7R-KO mice. In addition, we performed a systemic treatment with the selective 5-HT7R agonist LP-211. Results Murine C57BL/6N hearts reveal an upregulation of 5-HT7R mRNA expression in the infarct region compared to remote myocardium and sham operated mice at 3, 7 and 14 days after MI. Immunohistochemistry demonstrates 5-HT7R expression mainly on CD68+, CD206+ and CD80+ macrophages but not on cardiomyocytes and fibroblasts. Systemic 5-HT7R-KO mice display normal cardiac function and dimensions at 3-4 months of age comparable to their wildtype (WT) littermates. In response to MI, 5-HT7R-KO mice show a higher decrease in left ventricular (LV) function (assessed by transthoracic echocardiography as fractional area change, FAC%) and increased signs of tissue inflammation 14 days post-MI, while the infarct size remains unchanged. Interestingly, systemic treatment with the selective 5-HT7R agonist LP-211 enhances survival rates 14d post MI, without improving cardiac functional output. Conclusion 5-HT7R expression is upregulated post-MI in heart-invading inflammatory cells, such as macrophages. Loss of systemic 5-HT7R may contribute to pronounced functional cardiac impairment 14 days after MI, while systemic activation of 5-HT7R shows positive effects on survival, possibly through mediated inflammatory signalling of immune cells. Therefore, 5-HT7R activity could represent a novel therapeutic target to dampen inflammation and improve cardiac repair.

Prior cardiac ischemic injury exacerbates immune checkpoint inhibitor-induced cardiotoxicity

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Momentum grant of the Hungarian Academy of Sciences Introduction Immune checkpoint inhibitors (ICI), such as monoclonal antibodies targeting programmed death ligand-1 (PD-1), revolutionized cancer treatment. However, they can lead to several cardiovascular adverse effects, ranging from mild cardiac dysfunction to fulminant, lethal myocarditis. Nevertheless, the mechanisms and risk factors behind the diverse forms of ICI-induced cardiotoxicity are not entirely understood currently. Purpose In this study, we hypothesized that a prior cardiac ischemic injury, leading to acute immune cell infiltration and activation, but without subsequent heart failure, can exacerbate the cardiotoxicity and cardiac inflammation caused by anti-PD-1 monoclonal antibodies. Furthermore, we aimed to investigate in our mouse model whether abatacept, an inhibitor of T-cell co-stimulation, can ameliorate ICI-induced cardiac effects. Methods First, we treated 8 weeks-old C57BL/6J mice with isoprenaline (ISOP group, 160 mg/kg, n = 43) or with its solvent (CON group, n = 38), to induce reversible cardiac ischemia. Validation of the ischemic injury was performed in 6 randomly selected animals from each group two days after the treatment with histology and echocardiography. After this, the animals underwent 16 weeks of recovery period, followed by echocardiography to confirm cardiac functional recovery. Here, mice from both groups were randomized to three further treatment groups: isotype control, anti-PD-1 alone, or anti-PD-1 combined with abatacept and were treated for two weeks, with three weekly intraperitoneal injections (immune checkpoint inhibition phase). Echocardiography, qRT-PCR and histology was performed to evaluate cardiac function and inflammation. Results Two days after the initial ISOP treatment, mice displayed significant reduction in ejection fraction and infiltration of inflammatory cells were seen on histology. During the recovery period, 8 mice from the ISOP group and one mouse from the CON died. After the immune checkpoint inhibition phase, mice with prior ischemic injury and anti-PD-1 treatment (ISOP + anti-PD-1 alone) showed significant cardiac dysfunction on echocardiography, while animals with abatacept treatment (ISOP+anti-PD-1+abatacept) showed normal cardiac function. With qRT-PCR and histology, increased infiltration of T-cells and macrophages was seen in the myocardium of the ISOP+anti-PD-1 treated group compared to CON animals, with increased expression of pro-inflammatory cytokines, including Il17a, Il23 and Ifng. However, no cardiac infiltration was seen in mice without prior ischemic injury and the pro-inflammatory cytokine response was less pronounced as well. Conclusions Prior cardiac ischemic injury without overt cardiac dysfunction exacerbates cardiac inflammation and cardiotoxicity induced by anti-PD-1 immune checkpoint inhibition therapy. Patients with pre-existing ischemic heart disease may be at greater risk for developing ICI-induced severe cardiac adverse events.Hypothesis

A study on the application of radiomics based on cardiac MR non-enhanced cine sequence in the early diagnosis of hypertensive heart disease

BackgroundThe prevalence of hypertensive heart disease (HHD) is high and there is currently no easy way to detect early HHD. Explore the application of radiomics using cardiac magnetic resonance (CMR) non-enhanced cine sequences in diagnosing HHD and latent cardiac changes caused by hypertension.Methods132 patients who underwent CMR scanning were divided into groups: HHD (42), hypertension with normal cardiac structure and function (HWN) group (46), and normal control (NOR) group (44). Myocardial regions of the end-diastolic (ED) and end-systolic (ES) phases of the CMR short-axis cine sequence images were segmented into regions of interest (ROI). Three feature subsets (ED, ES, and ED combined with ES) were established after radiomic least absolute shrinkage and selection operator feature selection. Nine radiomic models were built using random forest (RF), support vector machine (SVM), and naive Bayes. Model performance was analyzed using receiver operating characteristic curves, and metrics like accuracy, area under the curve (AUC), precision, recall, and specificity.ResultsThe feature subsets included first-order, shape, and texture features. SVM of ED combined with ES achieved the highest accuracy (0.833), with a macro-average AUC of 0.941. AUCs for HHD, HWN, and NOR identification were 0.967, 0.876, and 0.963, respectively. Precisions were 0.972, 0.740, and 0.826; recalls were 0.833, 0.804, and 0.863, respectively; and specificities were 0.989, 0.863, and 0.909, respectively.ConclusionsRadiomics technology using CMR non-enhanced cine sequences can detect early cardiac changes due to hypertension. It holds promise for future use in screening for latent cardiac damage in early HHD.

Introduction of ex vivo perfusion of extended-criteria donor hearts in a single center in Asia.

The shortage of organs for heart transplantation has created a need to explore the use of extended-criteria organs. We report the preliminary use of normothermic TransMedics Organ Care System-an ex vivo approach to preserve extended-criteria brain-dead donor hearts. This System maintains a normal temperature, provides continuous perfusion and oxygenation, reduces ischemic time, and enables additional viability assessment options. In a retrospective single-centre study conducted from April 2020 to March 2023, four extended criteria brain-dead donor hearts were perfused and monitored using the Organ Care System. Suitability for transplantation was assessed based on stable or decreasing lactate levels, along with appropriate perfusion parameters. The Organ Care for use of the Organ Care System were coronary artery disease, left ventricular hypertrophy, high-dose inotrope use in the donor, a downtime exceeding 20min, and a left ventricular ejection fraction of 40-50%. Three out of the four donor hearts were transplanted, while one was discarded due to rising lactate concentration. The three recipients had a higher surgical risk profile for heart transplant. All showed normal cardiac function and no primary graft dysfunction postoperatively. At 2-3years post-transplant, all recipients have a ventricular function of > 60%, with only one showing evidence of mild rejection. The Organ Care System enables the successful transplantation of marginal donor organs in high-risk recipients, showcasing the feasibility of recruiting donors with extended criteria. This technique is safe and promising, expanding the donor pool and addressing the organ shortage in heart transplantation in Hong Kong.

Potential Diaphragm Muscle Weakness-related Dyspnea Persists 2 Years after COVID-19 and Could Be Improved by Inspiratory Muscle Training: Results of an Observational and an Interventional Clinical Trial.

Rationale: Diaphragm muscle weakness might underlie persistent exertional dyspnea, despite normal lung and cardiac function in individuals who were previously hospitalized for acute coronavirus disease (COVID-19) illness. Objectives: The authors sought, first, to determine the persistence and pathophysiological nature of diaphragm muscle weakness and its association with exertional dyspnea 2 years after hospitalization for COVID-19 and, second, to investigate the impact of inspiratory muscle training (IMT) on diaphragm and inspiratory muscle weakness and exertional dyspnea in individuals with long COVID. Methods: Approximately 2 years after hospitalization for COVID-19, 30 individuals (11 women, 19 men; median age, 58 years; interquartile range [IQR] = 51-63) underwent comprehensive (invasive) respiratory muscle assessment and evaluation of dyspnea. Eighteen with persistent diaphragm muscle weakness and exertional dyspnea were randomized to 6 weeks of IMT or sham training; assessments were repeated immediately after and 6 weeks after IMT completion. The primary endpoint was change in inspiratory muscle fatiguability immediately after IMT. Measurements and Main Results: At a median of 31 months (IQR = 23-32) after hospitalization, 21 of 30 individuals reported relevant persistent exertional dyspnea. Diaphragm muscle weakness on exertion and reduced diaphragm cortical activation were potentially related to exertional dyspnea. Compared with sham control, IMT improved diaphragm and inspiratory muscle function (sniff transdiaphragmatic pressure, 83 cm H2O [IQR = 75-91] vs. 100 cm H2O [IQR = 81-113], P = 0.02), inspiratory muscle fatiguability (time to task failure, 365 s [IQR = 284-701] vs. 983 s [IQR = 551-1,494], P = 0.05), diaphragm voluntary activation index (79% [IQR = 63-92] vs. 89% [IQR = 75-94], P = 0.03), and dyspnea (Borg score, 7 [IQR = 5.5-8] vs. 6 [IQR = 4-7], P = 0.03). Improvements persisted for 6 weeks after IMT completion. Conclusions: To the best of the authors' knowledge, this study is the first to identify a potential treatment for persisting exertional dyspnea in long COVID and provide a possible pathophysiological explanation for the treatment benefit. Clinical trial registered with www.clinicaltrials.gov (NCT04854863, NCT05582642).

DIASTOLIC DYSFUNCTION EVALUATION IN CARDIAC AMYLOIDOSIS: BEYOND TRADITIONAL PARAMETERS TO DISCRIMINATE BETWEEN TRUE HEART FAILURE WITH PRESERVED EJECTION FRACTION AND MIMICS

Abstract Background Diastolic dysfunction in cardiac amyloidosis (CA), according to current guidelines, can be classified using mitral flow velocities, mitral annular e’ velocity, E/e’ ratio, tricuspid regurgitation jet and left atrial (LA) maximal volume. However, LA minimal volume and the ratio between LA and left ventricular (LV) volumes at end–diastole, known as left atrio–ventricular coupling index (LACI), have recently been proposed to refine prognosis and peak atrial longitudinal strain (PALS) has been demonstrated to better stratify diastolic dysfunction. Aim of the Study To evaluate, in patients with CA: 1) the role of LACI as marker of LV diastolic dysfunction; 2) whether LACI could discriminate cardiomyopathy from normal cardiac function; 3) whether LACI and/or PALS could help discriminate between true heart failure with preserved ejection fraction (HFpEF) and amyloidotic cardiomyopathy (HFpEF–mimic). Methods We retrospectively analyzed 63 patients with CA and compared them with 80 true HFpEF patients and 70 healthy people; echocardiography was performed at the time of the diagnosis and diastolic function was characterized according to current guidelines. Results In patients with CA, LACI significantly increased as diastolic dysfunction worsened (P for trend &amp;lt; 0.0001) and significantly correlated with LV filling pressures estimated by E/e’ ratio (beta = 0.65, P &amp;lt; 0.0001) and pulmonary artery systolic pressure (beta = 0.63, P &amp;lt; 0.0001). LACI, after adjustment for age, gender and body mass index (BMI), was significantly higher in CA [0.62 (95%CI 0.52–0.70)] and in HFpEF [0.61 (95%CI 0.55–0.68)] than in controls [0.29 (95%CI 0.19–0.39)], while the difference between the two diseased populations was not statistically significant; a cut–off value of 0.45 was able to discriminate between controls and diseased patients (sensitivity = 95%, specificity = 94%, area under ROC curve = 0.98). PALS, after adjustment for age, gender and BMI, was significantly lower in CA [11.1 (95%CI 8.4–13.8%) and 8.4 (95%CI 3.5–13.3%) respectively in ATTR and AL] than in HFpEF [17.4 (95%CI 15.6–19.3%)], and a cut–off value of 9.9% was able to discriminate between them (sensitivity = 89%, specificity = 73%, area under ROC curve = 0.86). Conclusions LACI is a novel index able to discriminate between normal and diseased patients. In CA, it shows good correlation with diastolic dysfunction and LV filling pressures. PALS can be used to discriminate between true HFpEF and CA.

Adropin Treatment Restores Cardiac Function and Metabolic Flexibility in Diabetic Cardiomyopathy

Background: Diabetic cardiomyopathy (DCM) is a major complication of diabetes, and has been recognized as a cause of heart failure independent of other common risk factors. Metabolic inflexibility is a hallmark feature, where increased free fatty acid availability and decreased myocardial glucose uptake lead to an over-reliance on fatty acid oxidation, reducing cardiac work effciency. Energetic ineffciency in diabetic hearts may have profound implications for cardiac function under conditions of increased workload, and therefore therapeutic approaches are warranted. Adropin is a liver- and brain-secreted peptide hormone shown to regulate fuel metabolism in the heart. Adropin levels are significantly reduced in obese and diabetic human subjects, and this decrease is linked to increased adiposity, insulin resistance, and impaired glucose tolerance. Our lab recently showed that acute adropin treatment restores glucose oxidation activity in the hearts of prediabetic obese mice. However, the effects of chronic adropin exposure in the heart remains unknown. Hypothesis: We hypothesize that adropin treatment will exhibit beneficial effects on cardiac fuel metabolism that may lead to long-term improvements in functional output. Methods: We used a preclinical model of DCM to investigate the effects of long-term adropin treatment on cardiac structural and metabolic remodeling. Mice were treated with adropin daily for four weeks, and subjected to echocardiography, glucose tolerance tests, histopathology, RNA-sequencing, and metabolomics. Results: We report that long-term adropin treatment restores normal cardiac structure and metabolic function in the diabetic heart, by inhibiting flux of non-oxidative glycolytic intermediates into the hexosamine biosynthetic pathway. Conclusions: Our findings highlight the therapeutic potential of adropin signaling to attenuate cardiac remodeling in DCM. The project described was supported by NIDDK 1F31DK134089 and NHLBI R01HL147861. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Genetic modification of cardiac fibroblasts in adult rats using adeno-associated virus serotype 9

Cardiac fibrosis is a process involving pathological extracellular matrix remodeling as well as cardiac fibroblast (CF) activation in response to cardiac injury and stress, which is frequently associated with cardiac dysfunction. Therefore, understanding the molecular mechanisms underlying CF activation is critical to develop successful therapies for treating cardiac fibrosis. CF-specific gene modifications in mouse models have been reported as key tools for cardiac fibrosis research. Although rat cardiac disease models also offer many of the same advantages as the mouse models, there are no rat models that employ CF-specific conditional gene modification. Here, we attempted CF-specific gene introduction in rats using adeno-associated virus serotype 9 (AAV9), allowing us to develop fast and simple rat cardiac disease models rather than establishing transgenic rat lines. AAV9 carrying a CF-specific human TCF21 (hTCF21) promoter and a transgene of interest was generated and introduced into adult rats via tail vein injections. Since we previously reported in cultured CFs that protein kinase D (PKD) activation at the outer mitochondrial membrane (OMM) induces mitochondrial fragmentation via phosphorylation of a mitochondrial fission protein DRP1, we generated an OMM-targeted dominant-negative mutant of PKD (termed mt-PKD-DN) to specifically inhibit PKD activity at the OMM in CFs in vivo. In vivo cardiac function, gene expression, protein expression, and mitochondrial morphology were assessed 2-10 weeks after AAV9 injection by echocardiography, quantitative RT-PCR, immunohistochemistry, and transmission electron microscopy (TEM), respectively. AAV9-hTCF21-injected rats maintained normal cardiac dimensions and contractile function compared to aged-matched control rats. Using AAV9-hTCF21-EGFP, we confirmed organ-specific (i.e., heart) and cell type-specific (i.e., CF-specific) expression of GFP. Next, we injected AAV9-hTCF21-mt-PKD-DN or -luciferase (Luc) as a control in adult rats. TEM images from fixed rat ventricular tissues revealed a significant increase in mitochondrial aspect ratio and mitochondrial perimeter in CFs with AAV9-hTCF21-mt-PKD-DN compared to AAV9-hTCF21-Luc, indicating that PKD inhibition at the OMM induces mitochondrial elongation in CFs in vivo. In contrast, no significant change in mitochondrial morphology was observed in the cardiomyocyte area. In summary, we successfully achieved a CF-specific gene delivery to the adult rat hearts in vivo, demonstrating the potential of a simplified CF-specific rat transgenic model using the AAV9-hTCF21 system. NIH/NHLBI R01HL160699. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Unraveling the Mechanism Behind the Ketogenic Diet-Mediated Reversal of Heart Failure in Mice

It has become clear that heart failure involves a host of metabolic alterations, and nutritional or pharmacologic modulation of cardiac metabolism can improve heart failure. We previously studied the role of the mitochondrial pyruvate carrier (MPC) in heart failure, and observed that pyruvate transport into the mitochondria of cardiac myocytes was critical for maintenance of normal cardiac size and function. However, we were also able to prevent or reverse heart failure in cardiac-specific MPC2−/− (cs-MPC2−/−) mice by feeding a low carbohydrate, high fat “ketogenic” diet. Intriguingly, while ketosis was associated with this reversal in heart failure, it was observed that cardiac ketone body oxidation enzymes were downregulated in these hearts, and direct administration of ketone bodies without altering dietary fat did not improve heart failure. The objective of this current study was to define whether ketone body oxidation was necessary for improving heart failure with a ketogenic diet. Wildtype mice were subjected to combined transverse aortic constriction and apical myocardial infarction (TAC-MI) to induce heart failure, were imaged by echocardiography two weeks later and randomized to either low fat control or ketogenic diet for an additional two weeks before repeat echocardiography and euthanasia. Cardiac size and function was also assessed in cs-MPC2−/− mice, mice with cardiac deletion of betahydroxybutyrate dehydrogenase 1 (cs-BDH1−/−, the first enzyme in ketone body oxidation), and cs-MPC2/BDH1−/− double KO mice. Mice were aged to 16 weeks, when MPC−/− hearts have developed dilated cardiomyopathy, and then fed either low fat control or ketogenic diet for 3 weeks before echocardiography and euthanasia. Of the WT mice subjected to TAC-MI, being fed a LF control diet led to further cardiac remodeling and worsened contractile function. However, ketogenic diet feeding completely prevented the progression of cardiac remodeling. cs-BDH1−/− hearts maintained normal size and function, suggesting that lack of ketone oxidation has no overt effect on cardiac function or remodeling. However, as previously reported, cs-MPC2−/− hearts developed dilated cardiomyopathy, which was not significantly altered by combined deletion of BDH1. Switching cs-MPC2−/− or cs-MPC2/BDH1−/− mice to a ketogenic diet was able to significantly reverse the heart failure, suggesting that enhanced ketone oxidation is not the mechanism for improved heart failure. Gene expression from these hearts suggests that ketogenic diet suppresses ketolytic gene expression and enhances expression of fat oxidation genes. Altogether, these findings suggest that improving heart failure with a ketogenic diet is due to stimulation of cardiac fat oxidation and not ketone body metabolism. Project was funded by NIH R00 HL136658 and SLU institutional funds. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cardiomyocyte-specific deletion of adhesion G protein-coupled receptor F5 (ADGRF5) increases susceptibility to stress and arrhythmia

G-Protein Coupled Receptors (GPCR) represent the largest family of cell surface receptors in the human body and serve as targets for more than 30% of all approved drugs. Adhesion GPCRs (AGPCR) are an understudied GPCR family containing numerous extracellular domains that interact with extracellular proteins, including many known mediators of cardiac remodeling responses to pathologic stress. However, their relative expression in the heart and impact on cardiac function normally or during disease has been largely unstudied. To address this, we evaluated RNASeq-attained AGPCR expression from left ventricular (LV) samples of adult mice, of which Adgrf5 was one of the most highly expressed. Notably, decreased ADGRF5 expression is observed across numerous failing human LV tissue GEO datasets, and C57BL6/J mice subjected to transaortic constriction (TAC) surgery to induce pressure overload-induced HF also displayed reduced LV Adgrf5 expression by 12 weeks post-TAC. Analysis of published single cell (sc)-RNASeq datasets confirmed Adgrf5 expression in cardiomyocytes (CM), which also decreased following TAC in mice and in CM from failing human hearts. To investigate the impact of CM-specific ADGRF5 on cardiac function and remodeling normally or during disease progression, we crossed floxed ADGRF5 (ADGRF5f/f) and αMHC-Cre mice to generate constitutive, CM-specific ADGRF5 knockout mice (F5cmKO). These mice display normal cardiac structure and function at 12 weeks of age versus αMHC-Cre mice, as assessed via echocardiography, gravimetrics and immunohistochemistry. However, F5cmKO mice develop cardiac dysfunction, maladaptive remodeling, and increased mortality over time, even in the absence of pathologic insult, suggesting a homeostatic function of CM-specific ADGRF5. Following TAC surgery, F5cmKO mice display similar outcomes including enhanced cardiac dysfunction with accelerated remodeling and increased mortality. To attain mechanistic insight into these outcomes, we performed RNA-sequencing on LV tissue of 12-week-old F5cmKO mice, identifying and subsequently validating Scn1b as significantly upregulated in F5cmKO CM. Scn1b encodes for the β subunits of voltage-gated sodium channels (Scnβ1/β1B), which regulate gating and kinetics of Nav1.5 as well as adhesive CM-CM interactions, disruption of which could lead to arrhythmias. Indeed, conscious electrocardiogram (ECG) readings via telemetry indicated F5cmKO mice had a high burden of premature ventricular contractions (PVC), including ventricular tachycardia associated with cardiac enlargement. Using a combination of luciferase and fluorescence resonance energy transfer (FRET) reporters and gene expression analyses in neonatal rat ventricular myocytes (NRVM), we confirmed that ADGRF5 controls Scn1b expression in a Gαq/11 protein-dependent manner. In all, we have discovered that loss of CM-specific ADGRF5 leads to increased Scn1b expression with enhanced susceptibility to stress, arrythmias and sudden death, thus may provide a novel GPCR target to promote the maintenance of cardiac rhythm. AHA Predoctoral Fellowship 834906 to J.M.E. P01 HL147841 to D.T. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The spatial ventricular gradient is associated with inducibility of ventricular arrhythmias during electrophysiology study

BackgroundMyocardial electrical heterogeneity is critical for normal cardiac electromechanical function, but abnormal or excessive electrical heterogeneity is proarrhythmic. The spatial ventricular gradient (SVG), a vectorcardiographic measure of electrical heterogeneity, has been associated with arrhythmic events during long-term follow-up, but its relationship with short-term inducibility of ventricular arrhythmias (VAs) is unclear. ObjectiveThis study was designed to determine associations between SVG and inducible VAs during electrophysiology study. MethodsA retrospective study was conducted of adults without prior sustained VA, cardiac arrest, or implantable cardioverter-defibrillator who underwent ventricular stimulation for evaluation of syncope and nonsustained ventricular tachycardia or for risk stratification before primary prevention implantable cardioverter-defibrillator implantation. The 12-lead electrocardiograms were converted into vectorcardiograms, and SVG magnitude (SVGmag) and direction (azimuth and elevation) were calculated. Odds of inducible VA were regressed by logistic models. ResultsOf 143 patients (median age, 69 years; 80% male; median left ventricular ejection fraction [LVEF], 47%; 52% myocardial infarction), 34 (23.8%) had inducible VAs. Inducible patients had lower median LVEF (38% vs 50%; P < .0001), smaller SVGmag (29.5 vs 39.4 mV·ms; P = .0099), and smaller cosine SVG azimuth (cosSVGaz; 0.64 vs 0.89; P = .0007). When LVEF, SVGmag, and cosSVGaz were dichotomized at their medians, there was a 39-fold increase in adjusted odds (P = .002) between patients with all low LVEF, SVGmag, and cosSVGaz (65% inducible) compared with patients with all high LVEF, SVGmag, and cosSVGaz (4% [n = 1] inducible). After multivariable adjustment, SVGmag, cosSVGaz, and sex but not LVEF or other characteristics remained associated with inducible VAs. ConclusionAssessment of electrical heterogeneity by SVG, which reflects abnormal electrophysiologic substrate, adds to LVEF and identifies patients at high and low risk of inducible VA at electrophysiology study.

The Regulatory Role of microRNA-21 in Coronary Microcirculation in Metabolic Syndrome

Coronary vasculature is essential to supply oxygen and nutrients to the heart and maintain normal cardiac function. Obstruction of large vessels of coronaries (atherosclerosis) is well studied, but coronary microvascular dysfunction (CMD), which is associated with diabetic cardiomyopathy, Takotsubo cardiomyopathy, Ischemia with the non-obstructive coronary artery (INOCA), and HFpEF, is understudied. CMD is characterized by impaired endothelial-dependent vasodilation, but detailed mechanisms have yet to be elucidated. The anti-fibrotic role of microRNA-21 (miR-21) is reported in the HFrEF induced by ischemia/reperfusion or pressure overload, but how miR-21 regulates CMD is not entirely understood. Our recent study shows miR-21 ablation ameliorated impaired vasodilation in isolated coronaries of mice fed on high fat and high sugar (HFHS) diet. In this study, we examined the coronary flow reserve (CFR), the relationship between myocardial blood flow (MBF) and cardiac work (doppler) under hyperemia, cardiac function (echocardiography and exercise exertion test), fibrosis and gene expression of miR-21 knockout and wild-type (WT) mice fed on chow or HFHS diet. Our preliminary data show that MBF and CFR were decreased, cardiac index, stroke volume, and running distance were reduced, and the E/E’ ratio was increased in WT mice fed on the HFHS diet compared to the WT mice fed on the chow diet. The perivascular fibrosis was increased in the WT mice fed on the HFHS diet compared to WT mice on the chow diet. The ablation of miR-21 reversed all these changes in the mice treated with HFHS, suggesting miR-21 deficiency ameliorated CMD in metabolic syndrome. Moreover, we used endothelial-specific miR-21 knockout to study the endothelial miR-21 function. Interestingly, the endothelial mi-R21 KO phenocopied the global knockouts, suggesting the benefit of miR-21 deficiency to coronary microvascular function in metabolic syndrome is from endothelial cells. The study provides the potential therapeutic strategy to target vascular endothelial cells with miR-21 antagomir for CMD in metabolic syndromes. AHA 970663,1R56HL165207,1 R01 HL165207-01A1 to LY and 1 F31 HL156726-01A1 to CJ. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Septin4 Promotes Fibrosis In The Heart After Pressure Overload

Background: In response to cardiac injury, the heart undergoes a remodeling process, which may be defined by a complex set of genomic, expression, molecular, cellular and interstitial changes, which can become maladaptive and contribute to the development of heart failure (HF). One of the most important components in cardiac remodeling is the development of fibrosis, which is characterized by excessive deposition of extracellular matrix (ECM) proteins by cardiac fibroblasts, which disrupts the myocardial architecture and function, thus predisposing the progression of cardiac diseases to HF. The small GTPase Septin4 (Sept4) has been described to regulate regeneration and apoptosis in several organs. However, the role of Sept4 in regulating the cardiac stress response is unknown. The present study was designed to investigate if Sept4 would be mediating the alterations associated with cardiac remodeling induced by cardiac pressure overload. Hypothesis: We hypothesized that Sept4 deletion prevents the fibrotic response associated with cardiac remodeling, and the development and progression of HF triggered by transverse aortic constriction (TAC). Methods: 10-week-old wild type (WT) and Sept4 knockout (KO) mice were subjected to TAC to induce cardiac pressure overload. Functional and molecular analyses on WT and KO hearts were performed either at baseline, 1- or 4-weeks post-injury timepoints. Results: After TAC injury, WT mice showed a significant reduction of cardiac function and the development of heart failure, while KO mice were able to maintain normal cardiac function. KO hearts exhibited decreased levels of cardiac ECM deposition and fibrosis compared with WT hearts. Furthermore, KO hearts were more compliant and demonstrated improved end diastolic pressure compared with their WT counterparts. The differentiation of fibroblasts into myofibroblasts was impaired in KO hearts compared with WT controls, which appeared to be associated with attenuated TGF-β-triggered signaling pathway in KO hearts after TAC injury. In line with these findings, we verified in cultured cardiac fibroblasts (CFBs) that Sept4 deletion resulted in reduced myofibroblasts differentiation and a blunted ability of CFBs to contract. Conclusion: Our results demonstrate that Sept4 is an important regulator of ECM remodeling in the heart. Sept4 deletion leads to reduced levels of cardiac fibrosis and attenuation of pressure overload-induced cardiac dysfunction. These findings highlight Sept4 as a potential target to prevent fibrosis in cardiac stress response. This study was supported by grants from the National Institutes of Health (HL155993 and HL160665). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Normal baseline cardiac autonomic function and increased pupillary parasympathetic tone in patients with vasovagal syncope.

It is controversial whether people with vasovagal syncope (VVS) have abnormal autonomic responses at baseline and whether specific diagnostic manoeuvres have a diagnostic value. We investigated whether the pupillary light reflex and cardiac autonomic tests can be used to identify autonomic dysfunction in volunteers with a medical history of VVS. The study groups included 128 healthy volunteers, of whom 31 reported a history of typical VVS. The right pupil was evaluated using an automated, commercial infra-red pupillometer under strict conditions. In addition to miosis and mydriasis kinetics, pupil diameters were measured. Heart rate variability at rest and heart rate changes to standing were quantified with high-resolution electrocardiography and designated software. The demographic and clinical characteristics of both groups were statistically similar. Average constriction velocity (ACV) was significantly higher in VVS patients following a univariate analysis (3.83 ± 0.59vs. 3.56 ± 0.73 mm/s, p = 0.042) and after correcting for potential confounders (p = 0.049). All other pupillometric and heart rate indices were comparable between groups. Patients with a history of VVS depict pupillary parasympathetic overactivity in response to light stimuli, manifested as increased ACV. The prognostic implications of this finding and the significance of using this simple clinical tool to identify patients who are at risk for developing frequent episodes of VVS or physical injuries following a syncope merits further study.

Multiple thrombi mimicking metastases in the right atrium of patients with non-Hodgkin’s lymphoma diagnosed by multimodal cardiac imaging: one case report

BackgroundRight-side heart mass can be found incidentally on routine transthoracic echocardiography (TTE). Accurate diagnosis of cardiac mass often requires more than one imaging method. We present a mid-age woman with non-Hodgkin lymphoma who was found to have multiple right atrial masses mimicking metastases on routine TTE, which were finally diagnosed as thrombi by multimodal cardiac imaging.Case presentationA 52-year-old woman was diagnosed with primary mediastinal diffuse large B cell lymphoma (DLBCL) almost six months prior. The TTE revealed multiple masses in the right atrium with normal cardiac function when she was being evaluated for the next chemotherapy. On arrival, she was hemodynamically stable and asymptomatic. Physical examination was no remarkable. Laboratory findings showed leukocytosis of 17,900 cells/mm3, hemoglobin of 7.5 mg/dL, and a normal D-dimer level. The suspicious diagnosis of right atrial metastasis was made by TEE. However, the diagnosis of right atrial thrombi was made by contrast CMR. Finally, the 18 F-FDG PET-CT demonstrated no metabolic activity in the right atrium, which further supported the diagnosis of thrombi. Eventually, the masses were removed by cardiopulmonary bypass thoracotomy because of a high risk of pulmonary embolism. Histopathology confirmed the diagnosis of thrombi.ConclusionsThis case highlights the importance of multimodality cardiac imaging in the appropriate diagnosis of a RA masses in patient of lymphoma. Diagnosis of RA masses can be made using multimodal cardiac imaging like TTE, TEE and CMR, even PET. Echocardiography is the most commonly used on multimodal imaging in cardiac thrombus. CMR has high specificity in differentiating a tumor from thrombus, while 18 F-FDG PET has good sensitivity to determine the nature of the masses.