ECG Research




ECG Research

An electrocardiogram (ECG or EKG) is a measure of how the electrical activity of the heart changes over time as action potentials propagate throughout the heart during each cardiac cycle. As the heart beats, membrane polarity changes in the electrical conduction system throughout the heart result in the depolarization and repolarization of the atrial and ventricular cardiac cells, causing them to contract and relax. This results in the chambers pumping blood throughout the body.  This contraction (depolarization) and relaxation (repolarization) can be measured using electrodes placed in different combinations and configurations on the chest and limbs to produce a series of ECG complexes. An ECG complex is comprised of different components, or waves, that represent the electrical activity in specific regions of the heart.  

ECG waves, telemetry ecg lead placement, ecg data, ecg database, cardiac monitor lead placement, ecg signal database

ECG Cycle Breakdown:

  • P Wave – represents the movement of an electrical wave originating at the sinoatrial (SA) node and resulting in the depolarization of the left and right atria.
  • P-R Segment – the pause in electrical activity caused by a delay in conduction of the electrical current at the atrioventricular (AV) node to allow blood to flow from the atria to the ventricles before ventricular contraction occurs.
  • P-R Interval – the time between the beginning of atrial depolarization and the beginning of ventricle depolarization. A change in P-R interval is often an indicator of the activity of the parasympathetic nervous system on the heart.
  • QRS Complex – represents the electrical activity from the beginning of the Q wave to the end of the S wave and the complete depolarization of the ventricles, leading to ventricular contraction and ejection of blood into the aorta and pulmonary arteries
  • S-T Segment – the pause in electrical activity after the complete depolarization of the ventricles to allow blood to flow out of the ventricles before ventricular relaxation begins and the heart fills for the next contraction.
  • S-T Interval – the time between the end of ventricular depolarization (S wave) and the end of repolarization (T wave end).
  • Q-T Interval – the time between the beginning of the ventricular depolarization (Q wave) and the end of repolarization (T wave end).
  • T Wave – represents the repolarization of the ventricles.

Note: The repolarization of the atrial chambers is obscured by the depolarization of the ventricles and is thus not specifically represented within the ECG complex.

ECG Solutions from DSI

DSI offers a variety of solutions for studies requiring ECG endpoints from restrained or freely moving animal models. DSI has developed robust ECG solutions for data acquisition and analysis from signals that were acquired via implantable telemetry, external telemetry, or hardwired methods. Available monitoring solutions cover small to large animal models and offer researchers the ability to collect one or many physiological signals. DSI’s ECG solutions offer flexibility, reliable performance and quality to satisfy your research needs.

Implantable Telemetry

DSI’s PhysioTelTM, PhysioTelTM HD and PhysioTelTM Digital implants are designed for monitoring and collecting data from conscious, freely moving animals.  Implants are offered in different sizes to support a variety of animal species including mice, rats, dogs and non-human primates.  Several telemetry models are capable of monitoring ECG and blood pressure.

 
 
 
 
 
 
 

Telemetry ECG Lead Configurations

Small Animal: A single lead (2 electrode system) ECG is typically collected when using PhysioTel™ implantable telemetry with small animal models. DSI recommends using a modified lead II position for electrode placement to obtain a strong ECG signal with clear morphologies (see Figure 1)

Large Animal: The small animal recommendation is also applicable for large animal models. However, with large animal telemetry, DSI also provides an alternative approach using our Solid Tip ECG lead which has been proven to provide accurate ECG signals while virtually eliminating muscle noise and artifact. 

 

Surgical Support

Please contact DSI Surgical Services for surgical support, guides, and videos for detailed procedures on ECG lead placement.

 
PhysioTel System_SA_MX2
PTD System Hardware




Jacketed External Telemetry (JET)

External telemetry is a non-invasive method offering continuous ECG measurements through surface electrodes using DSI’s Large Animal Jacketed External Telemetry (JET). Common applications for JET include toxicology studies where implantable telemetry may be inappropriate or cost prohibitive, but still require continuous ECG recordings. Respiratory and Blood Pressure endpoints can also be collected using JET.

JET Systems include:

*Blood Pressure Add-On requires the Ambient Pressure Reference (APR-1) and E2S-1.

There are 3 different models of JET devices, each differing in the number of ECG leads that can be acquired per device.

 

 

JET-EA-BP JET-3ETA-BP JET-5ETA-BP

# ECG leads available per device

1 7 9

Table 1: Available ECG leads by JET device

 
 
   

 
 
   

JET system

Jacketed External Telemetry from DSI



 
 
 
 
 

Hardwired Instrumentation

Short durations of data are collected from chemically or physically restrained animals which are connected to external devices capable of monitoring ECG and recording directly into an acquisition and analysis computer system.  DSI offers a Multi-lead ECG Pod. Using an industry standard 10-lead patient cable, 12 simultaneous surface ECG leads can be obtained. 

 

Multi-Lead ECG Pod Systems include:

HW System




 
 
DSI's bibliography search tool may help you find publications known to use DSI technology. It is searchable by keyword, title and author and references of interest can be easily exported. The following publications have been included as references to demonstrate how ECG endpoints can be acquired from restrained or freely moving animal models and applied to specific research applications. 
 

References

Small Animal

Sgoifo, A., et al., “Electrode positioning for reliable telemetry ECG recordings during social stress in unrestrained rats.” Physiology and Behavior. 1996 Mar; 60(6):1397-1401. 

London, B., “Cardiac arrhythmias: From (transgenic) mice to men.” J Cardiovascular Electrophysiology. 2001 Sep; 12(9):1089-1091. 

Hess, P.,Rey, M., Wanner, D., Steiner, B., Clozel, M., “Measurements of blood pressure and electrocardiogram in conscious freely moving guineapigs: a model for screening QT interval prolongation effects.” Laboratory Animals. 2007 Jan; 41:470-480. 

Petric, Clasen, van Weßel, et al., “In vivo electrophysiological characterication of TASK-1 deficient mice.” Cellular Physiology and Biochemistry. 2012.

Large Animal

Hamlin, R. “How many ECG leads are required for in vivo studies in safety pharmacology.” J of Pharmacological and Toxicological Methods. 2008; 57:161-168. 

Holzgrefe, H., Cavero, I., Gleason, C., Warner, W., Buchanan, L., Gill, M., Burkett, D., Durham, S., “Novel probabilistic method for precisely correcting the QT interval for heart rate in telemetered dogs and cynomolgus monkeys.” J of Pharmocological and Toxicological Methods. 2006. 

Stubhan, M., Markert, M., Mayer, K., et al., “Evaluation of cardiovascular and ECG parameters in normal, freely moving Göttingen minipig.” ­ J Phamacological and Toxicological Methods. 2008 Feb; 57:202-211. 

Authier S, Moon LB, Stonerook M, Fournier S, Gervais J, Maghezzi S, Troncy E. “Evaluation of a novel ECG lead placement method in telemetered freely moving cynomolgus monkeys: assessment of an intravascular biopotential lead.” J Phamacological and Toxicological Methods. 2011 Sep-Oct; 64(2):145-150. 

Cools, F., et al., “ECG arrhythmias in non-implanted vs. telemetry-implanted dogs: Need for screening before and sufficient recovery time after implantation.” J Pharmacological and Toxicological Methods. 2011.
 
Prior, H., McMahon, N., Schofield, J., Valentin, J., “Non-invasive telemetric electrocardiogram assessment in conscious beagle dogs.” J Pharmacological and Toxicological Methods. 2009 Jun; 60:167-173.