A brief, concise, yet informative and easy to learn introduction to Cardiac Electrophysiology. Includes nicely animated GIFs for better understanding. Download and view with Microsoft Powerpoint 2013 for best quality.

1. By: Nik-Othman Abdullah

2.  Electrophysiology is the study of the electrical
nature of tissues and cells.
 It involves the movement and measurement of
voltage and current coursing through the tissues
through the ion channel proteins;
 It also includes the movement and adverse effects of
currents in whole organs such as the heart
 In medicine, an Electrophysiology study (EP Test) is
used to study abnormal heart rhythms (arrhythmia)
and other related cardiophysiological functions that
involves movement (tachycardia, bradycardia etc.)

3.  Cardiac dysrhythmia or arrhythmia is the abnormal rate or
rhythm of the heart’s beat
 An irregular heartbeat must not be confused with an
irregular heart rate. Arrhythmias, irregular heart beating,
may occur during regular and irregular heart rates
 It can either cause the heart to beat faster, slower or
irregularly
 Though most arrhythmias are harmless, some could be
serious and life-threatening; the heart may not be able to
pump enough blood throughout the body, which can be fatal
for vital organs that requires sufficient blood flow eg. brain,
lungs, liver etc.

4.  During a heartbeat, the electrical impulses travel in a specific and organized pathway. When the
impulses are interrupted this causes the heart to produce an irregular heartbeat
 Coronary artery diseases such as atherosclerosis (artery hardening), ischemia (blood-supply
restriction to tissues) and angina (chest pain due to restriction of blood-supply to muscles)
 Blood electrolyte imbalance (lack of sodium and potassium in the diet, hyponatrimia etc.)
 Smoking, drinking and use of CNS-acting drugs such as cocaine, methamphetamine, cannabis
etc.
 Strong emotional stress such as anger, depression or even surprise
 Genetic or congenital heart defects
 The phrase “heart skipped a beat” refers to arrhythmia, which occurs when seeing or
experiencing something staggering. This is caused by the elevated hormone levels produced by
the body, which in turn causes the heart to work profusely in an unexpected manner; this
sudden surge of hormones may trigger an arrhythmia

5. DRUGS
SMOKING
SMOKING
STRONG EMOTIONAL STRESS
STRONG EMOTIONAL STRESS
STRONG EMOTIONAL STRESS
STRONG
EMOTIONAL
STRESS
DRINKING
ARRYTHMIA

6.  An Intracardiac electrophysiological study (EPS) is
a test to measure if the heart’s electrical signals
are properly functioning
 In the course of an average human lifespan, the
possibility of having one or more abnormal heart
functions is relatively high
 An EPS is a minimally invasive procedure that
helps physicians and specialists, such as
cardiologist, determine heart rhythm problems
and abnormal heart function

7.  Wire electrodes will be placed in the heart.
These electrodes measure the electrical
activity in the heart
 The groin or neck area will be cleansed
and a topical anesthetic will be applied
• IV sheaths will then be inserted through
the groin or the neck area
• The physician then uses a fluoroscope
(moving x-ray images) to guide the
catheter to the heart, placing the
electrodes in the right places
• The electrodes pick up the heart’s
electrical impulses for measurement
• The electrodes may produce controlled
impulses to induce arrhythmia. This will
help the physician understand the causes
and location of the abnormalities lie.

8.  Living things are composed of electrical
properties running through our cells and
tissues. They are transferred and run across
different parts of our bodies through the ion
channels of the cells
 The study of electrophysiology involves
measuring these electrical charges to
determine whether a part of the tissue, or
even a whole organ is working and
functioning properly
• Electrophysiology measures the bioelectricity of living things
• In neuroscience, it includes the electrical properties of neurons

9.  Involves the measurement of voltage and current
across the protective membrane of a cell
 The tip of a fine microelectrode will be inserted into
the cell so that the membrane potential can be
measured
 The tips have a diameter of less than 1 micrometer
and a resistance of 7 megaohms
 A typical membrane potential of a healthy cell is -60
to -80 mV and the action potential +40 mV

10.  This technique allows the physiologist to
clamp, or hold onto a desired cell
potential value
 This allows easier measurement of how
much ionic current crosses a cell’s
membrane at a specific voltage
 Many of the ion channels in the
membrane of a neuron are voltage-gated
ion channels, which only opens at a
specific voltage range
 This is made possible by the near-
simultaneous currents that passes as
the recording electrode are charged to
alter the cell potential

11.  This technique records the membrane potential by injecting a specifically
measured current through the electrode
 The electrode then records and transmits the current. Unlike voltage clamp, the
current clamp has the freedom in varying, and the amplifier records the voltage
 This is used to study how a cell responds when current enters a cell, which is
important in understanding how neurons respond to neurotransmitters

12.  As we know, the body requires electricity or “bioelectricity” in order to
contract and expand muscles, which in turn results to movements
 The heart’s electrical system controls the rate and rhythm of the heart
 In each and every heartbeat, an electrical signal spreads from the top part of
the heart and surges through the bottom. This causes the heart to contract
and expand, hence, the pumping mechanism of our heart, also, the
heartbeat
 These electrical signal begins in the sinoatrial node and travels to and fro
via the ion-channels, which is located in the right atrium
 As the current travel from the right atrium to the left atrium, the atria
contracts causing blood to be pumped into the ventricles
 The current then moves downward the atrioventricular node, sited in
between atria and ventricles. The signals here slows down a tad allowing
the ventricles to be filled with blood
 As the electrical signal leaves the AV node or “the bundle of His”, the signal
causes a contraction action which allows the heart to pump blood into the
lungs and the rest of the body

13.  Cardiac electrophysiology is the science in diagnosing and treatment of the
electrical activities of the heart
 It is usually done by using invasive catheters with electrodes to either record and
induce programmed electrical stimulation (PES)

14.  When the signals arise in the SA node and
stimulates the atria to contract, which then travels
to the AV node, stimulus is conducted through the
bundle of His to the Purkinje fibers.
 It travels towards the endocardium at the heart’s
apex and finally rests at the ventricular epicardium
 On a microscopic point of view, the wave
depolarization propagates and travels through
adjacent cells via the gap junctions
 The heart, being a functional syncytium, freely
allows propagation of electrical impulse in all
direction, which results in a single contractile
function

15.  The cardiac muscles are similar to neurons and skeletal
muscles
 A myocardial cell has a negative membrane potential at
rest, the same as a neuron
 During a stimulation above the treshold value, the voltage-
gated ion channels open up and allows flooding of cations
into the cell
 The positively charged ions entering the cell causes
depolarization of an action potential
 Similar to skeletal muscles, depolarization causes the
opening of calcium channels and release of Ca2+
 This causes calcium-calcium induction release from the
sarcoplasmic reticulum, hence, causes muscle contraction
 Potassium channels then reopen, allowing potassium to
flood out of the cells causing repolarization

16.  Electrical activity is spontaneously
generated by the SA node
 The SA node is the physiological
pacemaker, responsible for the hearts
mechanism
 Electrical impulses are propagated
throughout the right atrium all the
way to the left atrium, stimulating
the myocardium of the atria to
contract
 The activity of the electrical impulse
throughout the atria is visualize as
the P wave in an ECG
 Electrical charges spreads
throughout the atria via intermodal
tracts, from the SA node to the AV
node

17.  An electrocardiogram is used to examine the electrical
conduction of the heart
 A pacemaker is used to stabilize the heart’s rhythm. It
is surgivally placed and inserted into the heart’s
conduction system