EKG Analysis and Interpretation for Cardiac Rhythms and Blocks

Pacemaker spikes

The pacing spike is an artifact in the EKG tracing that is a result of the electrical impulse produced by an artificial pacemaker.

Atrial pacing

Atrial pacing with spike noted prior to P wave.

Amplitude

Gain or voltage.

Time measurement

Each small block horizontally on the EKG graph paper represents 0.04 seconds.

P wave

Represents atrial depolarization and begins when the sinoatrial (SA) node fires.

QRS complex

Represents ventricular depolarization.

J point

Represents the exact point in time where ventricular depolarization stops, and ventricular repolarization starts.

Ischemia

Decrease in oxygenation of tissues due to poor blood flow.

T wave

Represents ventricular repolarization.

U wave

Represents a repolarization of the bundle of His and Purkinje fibers.

PR interval

Represents the time it takes for the SA node to fire, atria to depolarize, and electricity to travel through the AV node.

P-P interval

Represents the amount of time between atrial depolarization cycles (between P waves).

R-R interval

Represents the amount of time between ventricular depolarization cycles (between R waves).

QT interval

Represents one complete ventricular cycle.

PR segment

Represents the time between the end of atrial contraction and the beginning of ventricular contraction.

ST segment

Represents the early phase of ventricular repolarization.

Cardiac arrest

The absence of cardiac activity.

Ventricular fibrillation

Symptoms include dizziness, a feeling of impending doom, chest discomfort, shortness of breath, and seizure activity.

Ventricular tachycardia

Often results in precipitous drops in blood pressure and level of consciousness due to a decreased cardiac output.

Asystole

The complete cessation of electrical activity in the heart.

Myocardial infarction

Ischemia leading to death of heart muscle tissue; also known as a heart attack.

Complete heart block

A heart rhythm that demonstrates third-degree AV block, which can progress to cardiac arrest.

Bradycardia

A slow heart rate, typically less than 60 beats per minute.

Tachycardia

A rapid heart rate, typically greater than 100 beats per minute.

SA node

The natural, primary pacemaker of the heart located in the right atrium.

Junctional pacemaker

The secondary pacemaker located at the junction between the atria and ventricles, firing at 40 to 60 beats per minute.

Purkinje fibers

The final pacemaker that stimulates the ventricles, firing at 20 to 40 beats per minute.

Normal sinus rhythm

Indicated by a present P wave, duration less than 110 milliseconds, upright and rounded P wave, narrow QRS complex, and P wave amplitude less than 2.5 mm.

Sinus bradycardia

A normal EKG tracing with a heart rate of less than 60 beats per minute.

Sinus tachycardia

A normal EKG with a heart rate greater than 100 beats per minute.

Sinus dysrhythmia

A slight irregularity in the rhythm, often associated with normal breathing patterns.

Sinus arrest

A break in the normal EKG pattern due to failure of the SA node to fire, significant if lasting longer than 6 seconds.

Atrial flutter

A condition where the atria contract at a rate much faster than the ventricles.

Atrial fibrillation

A severe condition with no organized contraction of the atria, leading to a quivering state.

Junctional arrhythmias

Arrhythmias occurring at the AV node or tissue, resulting in inverted P wave configurations.

Premature junctional complex (PJC)

An early impulse occurring before the next expected beat, causing rhythm irregularity.

Junctional escape rhythm

An impulse originating from the AV node acting as a back-up pacemaker, potentially resulting in absent or inverted P waves.

Accelerated junctional rhythm

Similar to junctional escape rhythm but with a heart rate of 60 to 100 beats per minute.

Junctional tachycardia rhythm

A rhythm with a heart rate between 100 and 150 beats per minute.

Supraventricular tachycardia (SVT)

A rapid heart rate greater than 150 beats per minute, originating from any area above the ventricles.

Ventricular arrhythmias

Arrhythmias that are urgent and life-threatening if medical intervention is not initiated.

Premature ventricular complexes (PVCs)

Occur when the ventricles contract out of the normal sequence, often resulting in palpitations.

PVCs

Occasional benign PVCs are felt as palpitations or fluttering in the throat or chest.

Occasional PVCs

One to five PVCs in 1 minute.

Frequent PVCs

Six or more PVCs per minute.

Unifocal PVC

Single early PVC indicates one irritable area.

Multifocal PVC

PVCs with multiple shapes indicate more than one irritable area.

Interpolated PVC

PVC occurs with no interruption in the normal rhythm.

Bigeminy

PVCs occur every second beat.

Trigeminy

PVCs occur every third beat.

Quadgeminy

PVCs occur every fourth beat.

Coupling

Two PVCs occur back to back.

Ventricular tachycardia (VT)

Three or more PVCs in a row with a ventricular rate greater than 100/min.

Ventricular fibrillation (VF)

Emergency state where ventricles are quivering and there is no cardiac output.

Idioventricular rhythm

Occurs when only the ventricular pacemaker is functioning with a rate of 20 to 40/min.

Agonal rhythm

Results when all pacemakers of the heart have failed with a ventricular rate less than 20/min.

Heart blocks

Occur when there is a block in the electrical conduction pathway, resulting in delayed or absent ventricular depolarization.

Bundle branch block

Occurs when there is interference in one of the bundle branches.

Left bundle branch block (LBBB)

Current moves through the right bundle branch for right ventricular contraction, but the left bundle current moves to the left ventricle via the septum.

Right bundle branch block (RBBB)

Septum is depolarized normally while the left ventricle is activated by the left bundle branch.

First-degree atrioventricular block

Represents a delay in conduction from the SA node to the AV node with a PR interval greater than 0.20 seconds.

Second-degree atrioventricular block, type I

Also known as Mobitz I or Wenckebach; characterized by progressively longer PR intervals until a QRS is dropped.

Second-degree atrioventricular block, type II

Also known as Mobitz II; the PR interval remains constant, but P waves are present with no QRS complex.

Third-degree atrioventricular block

Also known as complete heart block; all electrical impulses originating above the ventricles are blocked.

Caliper

An instrument used to measure distances on an EKG tracing.

Depolarization

The process of contraction or diastole.

QRS waveform

Representative of ventricular depolarization; irregular intervals in Q waves can represent ventricular dysfunction.

Regular rhythm

Occurs when the QRS complexes are separated by the exact same distance across the EKG tracing.

Irregular rhythm

Identified when there is a noted difference in the spacing of the waveforms.

Regularly irregular rhythm

A consistent, noticeable irregular pattern.

Irregularly irregular rhythm

Varies without any consistency throughout the tracing.

Heart rate

Can be measured or estimated by reviewing the EKG tracing using various techniques and formulas.

1500 method

Counts the number of small boxes between two R waves and divides 1500 by that number to determine the ventricular rate.

Sequence method

Calculates heart rate using large boxes instead of small ones; not as accurate as the 1500 method.

6-second method

Counts the number of QRS complexes in a 6-second period and multiplies by 10.

Maximum heart rate

Calculated using the formula: 220 - Patient's age.

Target heart rate

Calculated by taking 70% of the maximum heart rate.

QRS duration

Measured from the beginning of the Q wave to the end of the J point.

Sinus rhythm

Has one P wave per QRS complex, a rate of 60 to 100/min, and a PR interval of less than 0.2 seconds.

Junctional rhythm

Does not have upright P waves.

P wave configuration

Should have a consistent shape throughout the tracing and be positively deflected.

QRS interval

The duration of the QRS complex measured in boxes.

Atrial rate

Calculated by counting the small boxes between two P waves.

Ventricular rate

Calculated by counting the small boxes between two R waves.

EKG tracing

A record of the electrical activity produced by the heart.