Electrocardiography (ECG): Principles and Clinical Applications

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HISTORY

On Italian scientist Carlo Matteucci realizes that electricity is associated with the heart beat

On French physiologist Etienne-Jules Marey analyzed the electric pattern of a frog's heart

On Dutch physician and physiologist Willem Einthoven was credited for the invention of EKG and later received the Nobel Prize in Physiology and Medicine in nineteen twenty-four

Nineteen oh six

On Using the string electrometer EKG, Willem Einthoven diagnosed some heart problems

WHAT IS AN ECG?

A recording of the electrical potentials generated by electrical currents from the heart into the adjacent tissues, which are detected by electrodes placed on the surface of the body.

ECGs help in the diagnosis of cardiac and noncardiac disorders:

Arrhythmias and Conduction Blocks

Myocardial ischemia and infarction

Chamber hypertrophy

Pericarditis

Pericardial effusion/tamponade

Electrolyte disturbances

Drug toxicity

ACTION POTENTIAL, ELECTRICAL STIMULATION, AND CARDIAC CONTRACTION

The ECG in relation to the Cardiac Cycle

One Complete Cardiac Cycle - Imagine one heartbeat as a loop:

P WAVE, ATRIAL DEPOLARIZATION, ATRIAL CONTRACTION

BLOCK FOUR

PR Interval, AV Nodal Delay

QRS Complex, Ventricular Depolarization, Ventricular Contraction

ST Segment, Ventricles Fully Depolarized, Plateau Phase

T Wave, Ventricular Repolarization, Ventricular Relaxation

Relationship to Heart Sounds

The Cardiac Conduction System

SINOATRIAL NODE (SA NODE)

AV NODE

BUNDLE OF HIS

THE PURKINJE NETWORK

THE CARDIAC ACTION POTENTIALS

The Ventricular Myocyte Action Potential

Mechanism of excitation-contraction coupling and relaxation in cardiac muscle

Differences between Sinus-Nodal and Ventricular Muscle Action Potentials

TRANSMISSION OF CARDIAC IMPULSE THROUGH THE HEART

FUNDAMENTAL CARDIAC ELECTROPHYSIOLOGY PRINCIPLES

Depolarization vs. Repolarization Waves

Conduction through the Bundle Branches and Ventricular Septum

Plateau Phase

Summary:

THE STANDARD ELECTROCARDIOGRAM RECORDING (ECG PAPER)

ECG Intervals

Three Unipolar Augmented Leads

Three Bipolar Limb Leads

Three Augmented Unipolar Limb Leads:

Six Precordial (Chest) Leads

Limb Leads Axes (The Hexaxial System)

Right-sided and Posterior Chest Leads (Non-standard)

Twelve-Lead ECG Recordings

Arrangement of Leads on the ECG

THE CARDIAC ACTION POTENTIALS

SUMMARY:

Example:

VECTORIAL ANALYSIS AND DETERMINATION OF THE MEAN ELECTRICAL AXIS

DIRECTION OF VECTOR

THE QRS AXIS

DETERMINING THE ELECTRICAL AXIS (SHORTCUT METHOD)

One. PHYSIOLOGIC AXIS DEVIATIONS

Two. PATHOLOGIC AXIS DEVIATIONS

QRS Complexes in Left Ventricular Hypertrophy

Four. CONDITIONS THAT CAUSE ABNORMAL VOLTAGES OF THE QRS COMPLEX

Four. CONDITIONS THAT CAUSE BIZARRE QRS COMPLEX MORPHOLOGIES

ELECTROCARDIOGRAMINATION OF HEART RATE

· Calculating Heart Rate using a twelve-second rhythm strip.

. Shortcut Method.

Variable Shapes of ST-segment Elevations in Acute Myocardial Infarction.

E. T WAVE (VENTRICULAR REPOLARIZATION).

F. QT INTERVAL (VENTRICULAR DEPOLARIZATION AND

G. U WAVE.

ST-Segment Elevation.

MYOCARDIAL INFARCTION LOCALIZATION.

Anterior Myocardial Infarction

Lateral Myocardial Infarction

Inferior Myocardial Infarction

Localize the Myocardial Infarction:

ELECTROCARDIOGRAMOSIS OF BUNDLE BRANCH BLOCKS (BBB) - NORMAL IMPULSE CONDUCTION

Complete Right Bundle Branch Block

Complete Right Bundle Branch Block: There is RSR in V1 and V2. Complete Right Bundle Branch Block is common in females in their twenties. Does not cause any hemodynamic abnormalities.

Mobitz Type Two - Second Degree Atrioventricular Block

Third Degree (Complete) Atrioventricular Block

MISCELLANEOUS DISORDERS (CONT'D.)

Atrial Fibrillation

Ventricular Tachycardia

Ventricular Fibrillation

Pacemaker Rhythm

Acute Pericarditis

Cardiac Tamponade

NORMAL SINUS RHYTHM

Overview

The document discusses the fundamental principles of electrocardiography (ECG), detailing the electrical activity of the heart and its phases, including depolarization and repolarization. It outlines the relevance of ECG in diagnosing various cardiac conditions and explains the mechanics of the cardiac cycle as it relates to electrical events.

Key Points

1ECG records the electrical activity of the heart, crucial for diagnosing conditions like arrhythmias and ischemia
2The cardiac cycle consists of phases where electrical events trigger mechanical contractions
3Key ECG components include the P wave, QRS complex, and T wave, each representing specific heart activities
4Understanding cardiac conduction and action potentials is essential for interpreting ECG results
5Abnormalities in ECG readings can indicate serious cardiac issues, including blockages and ischemia

Details

Category: Health and Medicine

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