The in vivo rat model of CHF combined with EP analysis could be used to determine the arrhythmogenic potential of new treatments for CHF.

Introduction: We have developed a computer user interface able to provide prescribed programmed electrical stimulation (PES) to induce sustained-ventricular tachycardia (VT) in rats with chronic heart failure (CHF). We propose this program to examine the cardiac electrophysiology (EP) properties and arrhythmogenic potential in varying disease models and as a method of evaluating drug safety in an intact animal. Methods: Using custom MATLAB software developed in our laboratory, we performed monophasic action potential (MAP) recordings and initiated protocols to induce sustained-VT through right ventricular epicardium PES outputs. Studies were performed in adult male Sprague-Dawley rats (N=22) six weeks after left coronary artery ligation under anesthesia and open chest. Results: CHF was verified by standard hemodynamic and echocardiographic parameters as is standard in our laboratory. In the CHF group, 71% (10/14) of the rats exhibited sustained-VT in response to PES versus 0% (0/8) of Sham rats. MAP recordings taken prior-to and during VT induction provided examples of localized activity for arrhythmia mechanisms such as delayed afterdepolarizations. Mechanical alternans, electrical alternans, intermittent pulse generations, and pulseless electrical activity were all observed in this model. EP data analysis showed a decreased (p<0.05) electrogram amplitude in border and infarct zones (Healthy (H): 8.7 ±2.1 mV, Border: 5.3±1.6 mV, Infarct (I): 2.3±1.2 mV), a similar trend for MAP amplitudes, and an increased (p<0.05) repolarization heterogeneity in the border zone (H: 8.1±1.5 ms, B: 20.2±3.1 ms). Conclusions: We have developed a custom computer user interface capable of performing clinically relevant in-vivo EP studies in rats with CHF. This rat model reproduces common clinical prognosis factors such as mechanical alternans, electrical alternans, and pulseless electrical activity. These EP studies demonstrate this program’s ability to test the arrhythmogenic potential of pharmaceutic agents, biologics, and implantables in an intact animal model before clinical advancement. We introduce this program to study an animal model’s EP characteristics before, during, and after treatments for CHF, and potentially other disease states.

Introduction: Aldosterone (Aldo) is synthesized and secreted by the adrenal cortex zona glomerulosa (ZG) cells. In heart failure (HF) patients Aldo is increased and plays a critical role in inducing and maintaining sodium and water retention as well as mediating myocardial remodeling and fibrosis. MANP is a novel Mayo Clinic designer natriuretic peptide (NP) which was demonstrated to inhibit circulating Aldo levels in vivo canines and in human subjects. Importantly, 3′, 5′ cyclic guanosine monophosphate (cGMP) generated by NPs activates protein kinase G (PKG) and also binds to phosphodiesterases (PDEs). Both PKG and PDEs have been suggested to play a role in the actions of NPs. To date no study has defined the direct cellular inhibitory effects of MANP on Aldo in human adrenal cells. Our goals were therefore to define the mechanisms of the inhibitory actions of MANP on Aldo in ZG cells with a special focus on cGMP and PDE's. Hypothesis: We hypothesized that MANP directly inhibits Aldo in adrenal cortex ZG cells and the inhibitory effect is mediated partially through PDEs. Methods: The ZG cell line H295R cells were cultured in 24-well plates for 24 hrs and starved overnight with serum free medium before stimulation/treatment. MANP (10 −8 , 10 −7 or 10 −6 M) was added to cells after starvation. Angiotensin II (ANG II, 10 −8 , 10 −7 or 10 −6 M) was employed to stimulate Aldo release. Supernatants were collected after 24 hrs for Aldo quantification with commercial ELISA kits. The PDE inhibitor IBMX (500 uM) and protein kinase G (PKG) specific cGMP analog 8-CPT-cGMP (100 uM) were used. Data are presented as Mean ± SEM, *P < .05 between two groups by unpaired t-test. Results: Angiotensin II stimulated Aldo secretion in a dose-dependent manner. MANP inhibited ANG II stimulated Aldo in a dose dependent manner (10 −8

Introduction: Previously we have demonstrated that a tissue engineered heart patch comprised of human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) and fibroblasts improves both left ventricular (LV) systolic and diastolic function in a rat model of CHF. In this study we tested the feasibility of upscaling cardiac patch size and surgical deployment in a swine model of CHF to test clinical utility. Methods: Four male Gottingen mini swine 20-25kg and three domestic swine 50-60kg were infarcted using percutaneous methods. Embolizing coils were deployed via catheter distal to the first diagonal branch of the left anterior descending (LAD) coronary artery and animals recovered for 4 weeks. Cardiac patches engineered with bio absorbable polygalactin-910 knitted mesh, dermal fibroblasts and hiPSC-CMs were cultured and implanted on the infarcted epicardium 4 weeks after MI. Cardiac magnetic resonance imaging was performed at baseline, 4 and 8 weeks post MI. All swine were implanted with continuous event recorders to acquire surface electrocardiogram during the entire study. In addition quality of life and functional capacity were assessed through video monitoring and treadmill exertion testing respectively. Infarct size was determined through 2,3,5-triphenyltetrazolium chloride staining. Results: LAD occlusion resulted in a significant (P<0.05) decrease EF (15%), and increase in EDV (59%) and ESV (100%). Average TIMI score decreased from 3.0±0 at time of MI to 1.5±0.6 4wks post MI. Cardiac patches were upsized to 6cm diameter for application in the swine. Patches displayed synchronous and spontaneous contractions within 48hrs. The 6cm patches, when implanted effectively covered the infarcted region bridging viable myocardium. Surgical handling and epicardial deployment was successfully accomplished via median sternotomy. The patches were robust in nature and could be deployed via a minimally invasive robotic procedure. No adverse arrhythmic activity was observed. Implantation of the cardiac patch restored activity levels (quality of life) of patch treated swine vs CHF controls. Conclusion: Our hiPSC-CM cardiac patch can be constructed in a clinical size, easily handled and implanted on the epicardium of the infarcted heart.

Introduction: In the United States, one in three deaths is attributed to cardiovascular disease (CVD). With CVD, sudden cardiac death is a common cause of mortality, specifically by way of ventricular tachycardia (VT) and ventricular fibrillation. We propose the application of our custom software to evaluate the electrophysiologic (EP) properties of animal models of ischemic and non-ischemic dilated cardiomyopathies. Methods: Adult male Sprague-Dawley rats with left coronary artery ligation and adult male and female transgenic Fragile X cardiomyopathic mice were sedated with Inactin and Isoflurane, respectively, and underwent hemodynamic measurements and/or EP testing. Using a PowerLab system and LabChart software, three-lead electrocardiograms were recorded. Using a pressure catheter, hemodynamic parameters were calculated. Using a concentric microelectrode (World Precision Inc.), a clinical EP catheter (Bard Inc.), and custom MATLAB software, local epicardial monophasic action potentials (MAP) and local epicardial voltages were recorded. Using custom MATLAB software for programmed electrical stimulation (PES), VT was induced epicardially with a clinically-accepted drivetrain. Animals underwent eight equidistant ‘S1’ stimulations followed by a premature ‘S2’ stimulation. The S2 stimulation was decreased by 5 milliseconds until loss of capture, indicating the effective refractory period. Sustained ventricular tachycardia (sVT) has been defined as more than fifteen consecutive premature ventricular contractions. Results: The chronic heart failure (CHF) rats had documented hemodynamic heart failure with elevated LV EDPs, and decreased EFs. Mapping and PES was performed on the two groups of rats, namely CHF and Sham-operated. In the CHF group, 71% (27/39) of the rats exhibited sVT, while 0% (0/10) of the Sham-operated rats exhibited sVT. Mapping was also performed on the two groups of mice, namely Wild-Type and Fragile X. Conclusions: We have performed clinically-relevant EP studies in CHF rats and in Fragile X dilated cardiomyopathic mice. These EP studies demonstrate our ability to evaluate and validate the phenotypes of animal models of cardiomyopathies and demonstrate the potential to evaluate the effectiveness of new therapies.