linear quantities and substituting it into the Poyedintsev–Voronova equation of hemodynamics, the volumetric values are calculated. The 7 phase volumes of blood are calculated in this way. The next step is the cardiac muscle contraction function evaluation in each phase of the ECG. Although this procedure is considered to be a qualitative evaluation, it is based on quantitative measurement of the ECG amplitude in each phase, which is equivalent to the cardiac muscle contraction amplitude. It characterizes the compensatory mechanism of hemodynamics self-regulation. Results: Blood phase volumes measurements allowed us to determine the mechanisms of hemodynamics maintenance and to classify the range of cardiac function changes from norm to extreme pathology. Conclusions: The method can evaluate age-related changes in hemody- namics. It also effectively evaluates the effect of physical activity on the healthy heart. The authors succeeded in revealing the criteria for sudden cardiac death prediction. OPTOGENETICS: CONTROLLING CARDIAC DEPOLARIZATION AND HYPERPOLARIZATION USING COMBINED CELL AND GENE THERAPY AND LIGHT-SENSITIVE PROTEINS U. Nussinovitch, R. Shinnawi, L. Gepstein Bruce Rappaport Faculty of Medicine and Technion Institute of Technology, Haifa, Israel. Background: Optogenetics has proved to be a reliable method for precise control of excitable tissue both in vitro and in vivo. Much of the research on optogenetics has been devoted to neural cell excitation. Therefore, our aim was to investigate whether optogenetics could be used to control cardiac depolarization and hyperpolarization by using combined gene and cell therapy. Methods: NIH3T3 fibroblasts and HEK293 cells were transfected with either the light-sensitive depolarizing Channelrhodopsin-2 (NIH-ChR2) ion channel or the hyperpolarizing light-sensitive Archaerhodopsin-3 (HEK- Arch) proton pump, respectively. A whole-cell patch-clamp study of the transfected cells was conducted, and the mean light-induced ion currents were calculated. Transfected cells were cocultured with either neonatal rat cardiomyocytes (NRCM) or human embryonic stem cell-derived cardio- myocytes (hESC-CMs), and plated on a 252-electrode multielectrode array (MEA). Conduction maps, tissue activation times, and beating frequencies were calculated before and after illumination (470 or 590 nm). Results: A whole-cell patch-clamp study of NIH-ChR2 cells demonstrated inward cation currents dependent on the presence and intensity of a 470-nm monochromic light. NIH-ChR2 cells were able to induce precisely con- trolled rapid cardiomyocyte depolarization and cause cardiac cell resyn- chronization by shortening tissue activation time. HEK-Arch cells, in contrast, were able to completely silence electrical and mechanical activity of vigorous cardiac cells and to cause conduction blocks in a beating cardiomyocytes monolayer. Hyperpolarization was reversed following termination of light exposure. Conclusions: Combined gene and cell therapy, using light-sensitive proteins, could be applied efficiently for controlling cardiomyocyte activa- tion and inactivation. Effects were similarly demonstrated in both NRCM and hESC-CMs. Therefore, it is suggested that this novel method could be used for treatment of tachyarrhythmias and bradyarrhythmias. c-Src REGULATION OF CONNEXIN43 REMODELING IN ISCHEMIC HEART DISEASE C. Rutledge 1 , F. Ng 2 , M. Sulkin 2 , I. Greener 1 , D. Arasu 1 , J. Gemel 3 , A. Sovari 1 , E. Beyer 3 , I. Efimov 2 , S. Dudley 3 1 UIC, Chicago, IL, 2 Washington University, St. Louis, MO, 3 University of Chicago, Chicago, IL. Background: Ischemic heart disease (IHD) is associated with decreased cardiac conduction, providing a substrate for reentrant arrhythmia and sudden cardiac death. Connexin43 (Cx43) is the principal gap junction protein responsible for allowing current to pass through cardiomyocytes in the ventricles. Cx43 expression is known to be reduced in the left ventricle following IHD. Recently, we showed that ROS stimulates c-Src phosphor- ylation (p-Src), allowing p-Src binding to the scaffolding protein zonula occludens-1 (ZO-1) and destabilizing Cx43, leading to Cx43 lateralization and degradation. We tested whether Src inhibition would prevent Cx43 degradation in IHD. Methods: Coronary artery occlusion was performed on 12-week-old mice causing myocardial infarction (MI). MI mice were treated with PP1, a p-Src inhibitor, or PP3, an inactive analogue. PP1, PP3, and sham hearts were compared functionally by echocardiography, optical mapping, ECG tele- metry analysis, and arrhythmia inducibility by ventricular pacing. Tissues were collected for immunohistochemistry and Western blot analysis. Results: Scar borders of PP1 groups demonstrated restored conduction velocity compared with PP3-treated mice (PP1 ¼ 33 cm/s, PP3 ¼ 18 cm/s). In PP1-treated mice, there was a 60 % decrease in p-Src activation and a 25% increase in Cx43 expression at the scar border compared with PP3 groups. PP1 did not change infarct size, ECG pattern, or cardiac function (ejection fraction: sham ¼ 61  1, PP1 ¼ 39  2, PP3 ¼ 39  2). Conclusions: Src inhibition improves Cx43 levels and conduction velocity after MI. Src inhibitors may represent a new class of antiarrhythmic compounds. A NOVEL METHODOLOGY TO MEASURE SERIAL CHANGES IN LEFT VENTRICULAR PRESSURE IN AMBULATORY CANINES AFTER HEART FAILURE INDUCTION AND NEUROMODULATORY THERAPY S.P. Brooks, J.B. Garlie, C. Corr, S. Mehta, P. Chen, S. Lin, J.C. Lopshire Krannert Institute of Cardiology, Indianapolis, IN. Background: A novel technique to measure hemodynamic function in ambulatory canines was used to quantify serial changes in left ventricular hemodynamic function after myocardial infarction (MI), pacing-induced heart failure (HF), and treatment with spinal cord stimulation (SCS). Methods: Telemetric devices were implanted into 6 canines to continuously measure left ventricular pressure (LVP) in freely moving ambulatory canines. Data were collected for 1 day in each of the following stages: baseline (6 canines), 7 days after foam embolization of the left anterior descending artery to induce MI (4 canines), and 1 day after high-rate right ventricular pacing to induce HF (3 canines). Left ventricular end-diastolic pressure (LVEDP) and max positive and negative dP/dt were extracted from LVP waveforms for 10-minute intervals over each hour of the day to produce a daily mean. Left ventricular ejection fraction (LVEF) was also obtained using echocardiography at baseline and after HF. Results: Results are presented in the table. LVEDP, þdP/dt, and –dP/dt were not significantly changed after MI. However, these parameters were signifi- cantly changed after HF. In 2 animals, 5 weeks of therapy with SCS restored þdP/dt (1780 mm Hg/s) and –dP/dt (–1666 mm Hg/s) to baseline levels. Treatment Parameter Baseline MI HF LVEDP (mm Hg) 5  2 4  4 25  24 þdP/dt (mm Hg/s) 1907  202 1970  314 1189  294 -dP/dt (mm Hg/s) -1659  97 -1708  36 -1275  286 LVEF (%) 58  5 — 22  2 P value Parameter Baseline to MI MI to HF Baseline to HF LVEDP (mm Hg) .671 .14 .067 þdP/dt (mm Hg/s) .716 .021* .0033* -dP/dt (mm Hg/s) .372 .027* .017* LVEF (%) — — .00002* *Statistical significance indicated by P o.05. Conclusions: HF reduces LVEF, dP/dt, and LVEDP compared with baseline. HF also reduces dP/dt compared with post-MI. Infarction has no 1910 Heart Rhythm, Vol 9, No 11, November 2012