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01:18Dysrhythmias IV: Characteristics of Bradyarrhythmias
Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...
01:29Dysrhythmias III: Characteristics of Dysrhythmias
Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute.
01:30Cardiac Action Potential
Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
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Related Experiment Video
Updated: Jul 16, 2026
05:36
Standardized Model of Ventricular Fibrillation and Advanced Cardiac Life Support in Swine
Published on: January 30, 2020
Porcine defibrillation thresholds with chopped biphasic truncated exponential waveforms.
Joseph L Sullivan1, Sharon B Melnick, Fred W Chapman
1Medtronic Emergency Response Systems, 11811 Willows Rd NE, P.O. Box 97006, Redmond, WA 98073-9706, USA.
Resuscitation
|March 27, 2007
Summary
Chopped biphasic truncated exponential (BTE) waveforms require significantly more energy for defibrillation than unchopped waveforms in swine models. Further research is needed to evaluate chopped waveform efficacy in human cardiac arrest patients.
Area of Science:
- Cardiovascular Research
- Biomedical Engineering
- Medical Device Technology
Background:
- Biphasic truncated exponential (BTE) waveforms are standard for defibrillation.
- Limited data exists on "chopping modulated" BTE shocks, with conflicting prior results.
- This study investigates the defibrillation thresholds (DFTs) of chopped versus unchopped BTE waveforms.
Purpose of the Study:
- To compare the defibrillation thresholds (DFTs) of various chopped and unchopped biphasic truncated exponential (BTE) waveforms.
- To determine if waveform chopping impacts defibrillation energy requirements.
- To provide data for optimizing defibrillation waveform selection.
Main Methods:
- Six anesthetized pigs underwent defibrillation after induced ventricular fibrillation (VF).
- Three waveform types (unchopped BTE, short-duration chopped, long-duration chopped) were tested with 50, 100, and 200 microF capacitances.
- Defibrillation thresholds were determined using a randomized up-down protocol and analyzed with Bayesian logistic regression.
Main Results:
- Unchopped BTE waveforms had DFTs of 122-126 J.
- Short chopped waveforms required at least 75 J more energy than unchopped waveforms.
- Long chopped waveforms required an additional 66 J compared to short chopped waveforms, with high probability that chopped waveforms exceed unchopped DFTs.
Conclusions:
- Chopped BTE waveforms demand higher energy for defibrillation in swine models with short-duration VF.
- The findings suggest unchopped waveforms may be more energy-efficient for defibrillation.
- Further investigation is necessary to ascertain the clinical utility of chopped waveforms in human cardiac arrest.