Introduction to Cardiac Rhythm Analysis

Overview

This page provides an introduction to cardiac rhythm analysis with links to training materials on this website.

The EKG (ECG) Waveform

EKG waveforms are displayed on monitors or paper. These EKG tracings have important features which can be analyzed to reveal a normal or an abnormal rhythm (a dysrrhythmia).

EKG can include various waveform components which are can be interpreted to understand if the EKG is a sinus rhythm or abnormal:

P Wave PR Interval PR Segment QRS Complex QT Interval ST Segment

The P wave indicates atrial depolarization and it is normally an upward deflection in the EKG tracing. Next the QRS complex indicates ventricle repolarization. It typically starts with a negative deflection, then a large positive movement and then a negative movement, the S wave. A T wave normally follows the QRS complex. It is typically a upwards waveform, indicating repolarization of the ventricles. Intervals such as the PR interval, PR segment, QT interval and ST segment can also be analyzed to understand the heart's condition.

Introduction to Sinus Rhythms

Overview

This page provides an introduction to sinus rhythms and links to training materials on this website.

A normal sinus rhythm refers to both a normal heart rate and rhythm. Normal heart rates are from 60 to 100 beats per minute. The shape of the electrocardiogram (EKG) tracing will exhibit certain key attributes to be considered normal, as discussed below. With normal sinus rhythms, the heart beat's electrical impulse originates in the sinoatrial node (SA). The P waves are upright and appear before each QRS and have the same shape. The intervals between the P waves are regular although some variations can occur with respiration. Sinus rhythms are classified as:

Normal Sinus Rhythm

Sinoatrial Block Sinus Pause Sinus Arrhythmia Sinus Bradycardia Sinus Tachycardia

Sinus Rhythm Categories

Normal Sinus Rhythm

This is the normal rhythm of the heart. The electrical impulse originates within the SA node and travels through the atria to the AV node. After a brief delay, the impulse travels down the bundle branches, thought the Purkinje fibers to the ventricles.

Sinus Pause

Sinus pause includes sinus arrest and sinus exit block. Sinus arrest is caused by failure of the SA node to create an impulse. An interruption in R-R regularity can be observed. With sinus exit block the SA node

generates an impulse but it is blocked before being transmitted through the atria. R-R regularity contines with the beats that follow the missed beat. Depressed ST segments can also be observed.

Sinus Arrhythmia

Sinus arrhythmia looks normal except for slight irregularities. A frequeny cause of sinus arrhythmia can be rhythm variations caused by respiration.

Sinus Bradycardia

Sinus bradycardia is a sinus rhythm with a rate of 40-60 bpm.

Sinus Tachycardia

Sinus tachycardia is a normal sinus rhythm but with a heart rate over 100 bpm. It is a normal response to exercise, excitement and some illnesses.

Introduction to Atrial Rhythms

Overview

This page provides an introduction to atrial rhythms and links to training materials on this website.

Atrial rhythms originate in the atria rather than in the SA node. The P wave will be positive, but its shape can be different than a normal sinus rhythm because the electrical impulse follows a different path to the AV (atrioventricular) node. These EKG differences are covered on our atrial rhythms training module as well as in practice strips which are available via a link in the right column. Atrial rhythms are classified as:

Atrial Fibrillation (afib) Atrial Flutter Multifocal Atrial Tachycardia Premature Atrial Complex Supraventricular Tachycardia Wandering Atrial Pacemaker Wolff-Parkinson-White Syndrome

Atrial Rhythm Categories

Atrial Fibrillation

Irritable sites in the atria fire very rapidly, between 400-600 bpm. This very rapid pacemaking caused the atria to quiver. The ventricles beat at a slower rate due to the AV node's blocking of some of the atrial impulses.

Atrial Flutter

There are two types of atrial flutter. Type I (also called classical or typical) has a rate of 250-350 bpm. Type II (also called non-typical) are faster, ranging from 350-450 bpm. EKG tracings will show tightly spaced waves or saw-tooth waveforms (F-waves).

Multifocal Atrial Tachycardia

When multifocal atrial tachycardia occurs, multiple (non-SA) sites are firing impulses. The P waves will vary in shape and at least three different shapes can be observed. The PR Interval varies. Ventricular rhythm is irregular.

Premature Atrial Complex

This occurs when an ectopic sites within the atria fires an impulse before the next impulse from the SA node. If the ectopic site is near the SA node, the P wave will likely have a shape similar to a sinus rhythm. But this P wave will occur earlier than expected.

Supraventricular Tachycardia

This term covers three types of tachycardia that originate in the atria, AV junction or SA node.

Wandering Atrial Pacemaker

Wandering atrial pacemaker is an irregular rhythm. In is similar to multifocal atrial tachycardia but the heart rate is under 100 bpm. P waves are present but will vary in shape.

Wolff-Parkinson-White Syndrome

This occurs when the impulse travels between the atria and ventricles via an abnormal path, called the bundle of Kent. The impulse, not being delayed by the AV node, can cause the ventricles to contract prematurely. EKG characteristics include a shorter PR Interval, longer QRS complex and a delta wave.

Introduction to Junctional Rhythms

Overview

This page provides an introduction to junctional rhythms and links to training materials on this website.

The SA node is the normal origin of the electrical impulse for a heart beat. When the SA node cannot perform this role, the atrioventricular (AV) node may take-over pacemaking. When this occurs, the EKG will likely have distinctive waveform features that reveal important aspects of these junctional rhythms.

Junctional rhythms include:

Accelerated Junctional Rhythm Junctional Escape Rhythm Junctional Tachycardia Premature Junctional Complex

Junctional Rhythm Categories

Accelerated Junctional Rhythm

Accelerated junctional rhythm occurs when the AV junction fires impulses at above 60 bpm. Rhythm will be very regular. The QRS complex is narrow (0.10 sec or less).

Junctional Escape Rhythm

Junctional escape beats originate in the AV junction and are late in timing. They often occur during sinus arrest or after premature atrial complexes. The QRS complex will be measured at 0.10 sec or less. Rhythm will be regular with a rate of 40-60 bpm.

Junctional Tachycardia

This abnormal rhythm originates in the bundle of His. It is observed as three or more premature junctional complexes (PJCs) appearing in a row. Heart rate will be over 100 bpm.

Premature Junctional Complex

Premature junctional complex (PJC) occurs when an irritable site witinin the AV node fires an impulse before the SA node. This impulse interrupts the sinus rhythm. The QRS complex will be narrow, usually measured at 0.10 sec or less.

Introduction to Ventricular Rhythms

Overview

This page provides an introduction to ventricular rhythms and links to training materials on this website.

When the ventricules handle the pacemaking role, ventricular rhythms can be observed on EKG tracings. This website and related websites provide training, practice drills and quizzes related to ventricular rhythms.

There are several type of ventricular rhythms:

Accelerated Idioventricular Rhythm Asystole Idioventricular Rhythm Premature Ventricular Complex Premature Ventricular Complex - Bigeminy Premature Ventricular Complex - Trigeminy Premature Ventricular Complex - Quadrigeminy Ventricular Fibrillation Ventricular Tachycardia Ventricular Tachycardia Monomorphic Ventricular Tachycardia Polymorphic Torsade de Pointes

Ventricular Rhythm Types

Accelerated Idioventricular Rhythm

Accelerated idioventricular rhythm occurs when three or more ventricular escape beats appear in a sequence. Heart rate will be 50-100 bpm. The QRS complex will be wide (0.12 sec. or more).

Asystole

Asystole is the state of no cardiac electrical activity and no cardiac output. Immediate action is required.

Idioventricular Rhythm

Idioventricular rhythm is a slow rhythm of under 50 bpm. It indicates that then ventricules are producing escape beats.

Premature Ventricular Complex

Premature ventricular complexes (PVCs) occur when a ventricular site generates an impulse. This happens before the next regular sinus beat. Look for a wide QRS complex, equal or greater than 0.12 sec. The QRS complex shape can be bizarre. The P wave will be absent.

Premature Ventricular Complex - Bigeminy

Premature Ventricular Complex - Trigeminy

Premature Ventricular Complex - Quadrigeminy

Ventricular Fibrillation

Ventricular fibrillation originates in the ventricules and it chaotic. No normal EKG waves are present. No heart rate can be observed. Ventricular fibrillation is an emergency condition requiring immediate action.

Ventricular Tachycardia

A sequence of three PVCs in a row is ventricular tachycardia. The rate will be 120-200 bpm. Ventricular Tachycardia has two variations, monomorphic and polymorphic. These variations are discussed separately.

Ventricular Tachycardia Monomorphic

Monomorphic ventricular tachycardia occurs when the electrical impulse originates in one of the ventricules. The QRS complex is wide. Rate is above 100 bpm.

Ventricular Tachycardia Polymorphic

Polymorphic ventricular tachycardia has QRS complexes that very in shape and size. If a polymorphic ventricular tachycardia has a long QT Interval, it could be Torsade de Pointes.

Torsade de Pointes

Torsade de Pointes is a special form of ventricular tachycardia. The QRS complexes vary in shape and amplitude and appear to wind around the baseline.

Introduction to Heart Block Rhythms

Overview

This page provides an introduction to Heart Block rhythms and links to training materials on this website.

Heart block rhythms occur when the cardiac electric impulse is delayed or blocked within the AV node, bundle of His or the Purkinje system. Heart block rhythms are classified into categories including these:

Bundle Branch Block First Degree Heart Block Second Degree Heart Block Type I Second Degree Heart Block Type II Third Degree Heart Block

Heart Block Categories

First Degree Heart Block

First degree heart block is actually a delay rather than a block. It is cause by a conduction delay at the AV node or bundle of His. This means than the PR Interval will be longer than normal (over 0.20 sec.).

Second Degree Heart Block Type I

With second degree heart block, Type I, some impulses are blocked but not all. More P waves can be

observed vs QRS Complexes on a tracing. Each successive impulse undergoes a longer delay. After 3 or 4 beats the next impulse is blocked. On an EKG tracing, PR Intervals will lengthen progressively with each beat until a QRS Complex is missing. After this blocked beat, the cycle of lengthening PR Intervals resumes. This heart block is also called a Wenckebach block.

Second Degree Heart Block Type II

With Mobitz Type II blocks, the impulse is blocked in the bundle of His. Every few beats there will be a missing beat but the PR Interval will not lengthen.

Third Degree Heart Block

With this block, no atrial imulses are transmitted to the ventricles. As a result, the ventricules generate an escape impulse, which is independent of the atrial beat. In most cases the atria will beat at 60-100 bpm while the ventricles asynchronously beat at 30-45 bpm.

Bundle Branch Block

With this conduction block, either the left or right bundle branch is blocked intermittently or fixed. The QRS complex is wider than normal (> 0.12 sec.). Using a 12 lead EKG, blocks in either the left or right bundle branch may be diagnosed.

Introduction to Pacemaker Rhythms

Overview

This page provides an introduction to pacemaker rhythms and links to training materials on this website.

Pacemakers provide an artifical electical impulse to the heart. This impulse and the hearts natural electrical signals can be interpreted. We provide a training module for pacemaker rhythms and links to practice strips of pacemaker patients.

There are multiple types of pacemaker rhythms:

Normal Single Chamber Pacemaker Normal Dual Chamber Pacemaker Failure to Capture Failure to Pace Failure to Sense

Pacemaker Rhythm Sample Tracing

Categories of Pacemaker Rhythms

Normal Single Chamber Pacemaker

Failure to Capture

Failure to capture means that the ventricules fail to response to the pacemaker impulse. On an EKG tracing, the pacemaker spike will appear but it will not be followed by a QRS complex.

Failure to Pace

Failure to pace occurs when the pacemaker does not generate an electrical impulse. On an EKG tracing, pacemaker spikes will be missing.

Failure to SenseFailure to sense occurs when the pacemaker does not detect the patient's myocardial depolarization. This can often be seen on an EKG tracing as a spike following a QRS complex too early.