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The Arterially Perfused Rabbit Papillary Muscle: A Model to Study Electrical Properties in Myocardial Ischemia
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
André G. Kléber, Christoph Riegger
During the process of uncoupling propagation became inhomogenous. This is illustrated in Figure 7 which depicts recordings of transmembrane action potentials (initial portion) and bipolar extracellular electrograms at different times after interruption of flow. After 8 min of ischemia, the amplitude of the transmembrane action potential decreased from 106 to 94 mV, whereas the amplitude of the extracellular electrogram was unchanged (48 mV). The bipolar extracellular electrogram showed a distinct deflection and inflection, indicating that propagation advanced as a homogenous wavefront under the recording electrodes. The slight increase of the activation time indicated a small decrease of conduction velocity (from 56 to 50 cm/s). At 19 and 25 min after coronary occlusion, progressive uncoupling produced an inhomogenous spread of propagation. This is indicated by the fractionated extracellular electrograms which are much reduced in amplitude, despite the presence of transmembrane action potentials which are relatively well preserved (95 and 93 mV, respectively). Within an interelectrode distance of only 0.8 mm (see enlarged recording after 25 min), several deflections and inflections appeared. This excluded determination of a longitudinal conduction velocity. However, activation of the muscle was significantly delayed as was evident from the increased duration of the extracellular electrogram and the delayed activation of the impaled cell.
Isolated Atrial Preparations
Published in John H. McNeill, Measurement of Cardiac Function, 2020
M.K. Pugsley, E.S. Hayes, M.J.A. Walker
Electrical activity in atrial tissue is often recorded as electrograms, or intracellular potentials. There are several assumptions made with respect to recording bioelectrical events using bipolar techniques, while special properties of myocardial muscle activation have important implications. When using bipolar electrodes it is assumed that the electrode contact surface is small and that the distance between the tissue mass, with respect to the tissue excited, is large.23 Unlike other types of muscle, cardiac muscle does not repolarize until the muscle has been completely activated. Thus, over the distances used to record atrial electrograms, the electrodes will see both activated and inactivated tissue simultaneously. Even though the activity of the tissue closest to the electrode dominates the signal, surrounding tissue also contributes, thus making the three-dimensional structure of the tissue of some importance to electrogram morphology.24
Ablation of ventricular arrhythmias
Published in Ever D. Grech, Practical Interventional Cardiology, 2017
Different mapping techniques are available and often used in conjunction when treating a patient with VA. Utilising a three-dimensional electroanatomical mapping system, mapping during ongoing VA (activation and entrainment mapping) can define the macro–re-entrant circuit but will require haemodynamic stability to complete. The local electrogram is annotated to a stable reference, for example, the surface QRS complex, until the full cycle length of the tachycardia is covered. If the activation map covers less than 70% of the tachycardia cycle length, a focal rather than a macro–re-entrant tachycardia may be present. In the presence of a macro–re-entrant tachycardia, entrainment mapping is performed by placing the catheter at an anatomic site in the ventricle and pacing at slightly faster rate (usually 20 ms faster than the VA cycle length) during VA. This accelerates the VA to the paced cycle length and allows the operator to determine if that anatomic site is within the VA circuit. Entrainment mapping can delineate if the pacing site is in a critical isthmus, in an isolated scar or remote from the VA circuit. Characteristics such as whether the entrainment is manifest or concealed and the post-pacing intervals help to identify whether the pacing site is located in a critical isthmus and these would then serve as a reasonable ablation target.
Cardiovascular and hemodynamic consequences of recombinant placental growth factor administration in Guinea pigs
Published in Hypertension in Pregnancy, 2022
Adelene Y. Tan, Ken Kearney, Courtney Jenkins, S. Ananth Karumanchi, Walter Bee, Paul Kussie
The Langendorff isolated heart preparation was used to assess cardiac electrophysiology and functional responses to PlGF in isolated Guinea pig hearts as described elsewhere (16,24). Briefly, the excised heart was cannulated via the aorta and retrogradely perfused while suspended in a fluid filled chamber. Perfusion began with a constant flow of 15 mL/min; after stabilization, the perfusion was changed to 60 mmHg constant pressure. A rubber balloon on the tip of a cannula was inserted into the left ventricle and inflated with water to achieve a starting end-diastolic pressure between 5 and 15 mmHg. The balloon cannula is attached to a pressure transducer controlled by an IOX Data Acquisition System (Emka Technologies, France). Two unipolar electrodes were placed on the heart, one each on the epicardium of the left ventricle and the right atrium, emulating a Lead II electrogram. The following parameters and end points were evaluated in this study: heart rate (chronotropy), dP/dtmax (inotropy), dP/dtmin (lusitropy), perfusion flow rate, and ECG waveforms and ECG intervals (PR, QRS, QT, QTc, and J-Tpeak) (20,24).
Estimate and reporting of longevity for cardiac implantable electronic devices: a proposal for standardized criteria
Published in Expert Review of Medical Devices, 2021
Federica Censi, Giovanni Calcagnini, Eugenio Mattei, Renato Pietro Ricci, Massimo Zoni Berisso, Maurizio Landolina, Giuseppe Boriani
For each device category, the programming parameters that have the greatest impact on battery life were considered. In particular: The percentage of stimulationThe duration of the stimulation pulseThe amplitude of the stimulation pulseThe presence/absence of the rate-responsive sensorThe stimulation impedanceThe electrogram (EGM) diagnosticsThe number of shocks and the shock energyThe presence and use of remote monitoring and telemetry
Operative approach for right coronary artery to coronary sinus fistula
Published in Baylor University Medical Center Proceedings, 2020
Jonathan Liu, Subbareddy Konda
A 33-year-old woman with Von Willebrand disease presented with frequent chest pain exacerbated by activity and dyspnea for 1 year, and CAF was diagnosed by angiography. Her symptoms worsened after the diagnosis. The electrogram showed no abnormalities, and cardiac troponin levels remained normal. She had no abnormal findings on physical exam. Coronary angiography showed an RCA with a transverse diameter of 7 to 8 mm and an RCA CAF that drained into the right atrium (Figure 1). Preoperative color Doppler showed turbulent blood flow from shunt to right atrium (Figure 2a). She was given prophylactic desmopressin and Alphanate to prevent bleeding complications from Von Willebrand disease. The surgical procedure was performed through a median sternotomy, and aneurysmal RCA was revealed after pericardial dissection. Aortic and bicaval cannulation was performed and cardiopulmonary bypass was initiated, followed by anterograde cardioplegia. The right atrial wall was incised, and there was stenosis of the ostium of the coronary sinus. There was a fistula from the RCA to the coronary sinus with an opening diameter of 4 mm, about 1 cm distal to the coronary sinus ostia, and a diminutive posterior descending coronary artery (Figure 3). The cribriform flap at the ostium was removed and the ostium of the fistula was closed by primary surgical repair. Transesophageal echocardiogram with color Doppler imaging after closure showed no shunt (Figure 2b). Her postoperative course was uncomplicated.