Six Second ECG Glossary

helping you understand the technical terms of ECG interpretation

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12-Lead ECG

The 12-lead ECG provides 12 views of the heart. The 12 views are generated through only 10 electrodes. Four limb electrodes attach to the inner...

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12-Lead ECG – lead views

The ten electrodes combine to provide 12 views of the heart. The limb leads combine to provide the three bipolar leads (leads I, II, and...

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12-Lead ECG – systematic analysis

Equipped with a carefully formed clinical impression of the patient, a systematic approach to 12-lead ECG interpretation makes the 12-lead ECG a reliable assessment tool....

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12-Lead Views

The ten electrodes combine to provide 12 views of the heart. The limb leads combine to provide the three bipolar leads (leads I, II, and...

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15 and 18 Lead ECG

A 12 Lead ECG provides a fairly good electrical picture of the left side of the heart. The right side of the heart is somewhat...

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Aberrant Conduction

For about 15% of rhythms with wide QRS complexes, impaired bundle branch conductivity prolongs ventricular depolarization. Ischemia, infarction, and antiarrythmics can slow or block transmission...

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Abnormal P Wave

A normal wave is typically upright in leads I, II and aVF, and biphasic in lead V1. An abnormal P wave can possess several alternate...

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Abnormal T Wave

A wave that includes both an upright (positive) and downward (negative) deflection. Expect a T wave to follow every QRS complex. The T wave is...

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Absolute Refractory Period

Period when the cardiac cells cannot depolarize irrespective of the strength of the electrical impulse. 1. Six Second ECG Guidebook (2012), T Barill, p. 189

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Accelerated Idioventricular Rhythm

Cardiac rhythm that originates from the ventricular with a rate of 40-100/minute; QRS is wide with P waves absent. Pacemaker sites can deliver impulses faster...

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Accelerated Junctional Rhythm

A cardiac rhythm that originates from the AV junction with a rate of 60-100/minute; QRS complex is most often narrow with P waves that are...

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Accelerated Rhythms

Rhythms that are not quite tachycardias but are faster than what is expected from a pacemaker site. These rhythms are called accelerated rhythms. For example,...

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Accessory Pathway

Alternative connecting pathway between the atria and the ventricles (beside the bundle of His); resulting syndrome is called Woolf-Parkinson-White syndrome. 1. Six Second ECG Guidebook...

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Actin

One of two types of fibres that lie parallel to each other; with the influx of calcium into the cell the fibres bind together and...

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Action Potential

The electrical activities of a cell from depolarization to repolarization; 5 phases (0-4) take place largely involving the sodium, potassium and calcium ions. 1. Six...

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Action Potential – Phase 0

Phase of depolarization: for myocardial cells the slow sodium channels open, and then, if threshold potential is reached, fast sodium channels open; note that cells...

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Action Potential – Phase 1

Depolarization has now completed; repolarization begins with the efflux of potassium from the cell. 1. Six Second ECG Guidebook (2012), T Barill, p. 202

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Action Potential – Phase 2

Potassium leaves the cell while calcium enters the cell resulting in an electrical plateau; the calcium entering the cell is significant because it initiates the...

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Action Potential – Phase 3

Potassium leaves the cell resulting in the cell becoming increasingly negative; at 60-70 mV, the cell’s fast sodium channels begin to be receptive to causing...

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Action Potential – Phase 4

The polarized state of the cell with resting negative potential of approximately –90 mV; early in this phase, the sodium-potassium ATP pump restores the cell...

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Aerobic Metabolism

Metabolism that utilizes oxygen is called aerobic metabolism. Energy production through oxygenation (with oxygen) yielding 32 ATP molecules from the interaction of one glucose and...

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Afterload

The pressure that the ventricle (right or left) must overcome to eject blood (i.e. the left ventricle pumps against aortic diastolic pressure and systemic vascular...

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Agonal Rhythm

A fatal dysrhythmia with rates usually less than 20/minute and common widening of the QRS; also referred to as the dying heart. Asystole is characterized...

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Alpha Stimulation

The peripheral vasoconstriction that results from circulating catecholamines (epinephrine & norepinephrine). 1. Six Second ECG Guidebook (2012), T Barill, p. 190

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Amplitude

The height or depth of waves and complexes of an ECG in millimetres; represents millivolts where 10 mm is 1 millivolt with a properly calibrated...

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Anaerobic Metabolism

Energy production without oxygen with only 2 ATP produced as well as lactic and pyruvic acid. When energy demands surpass the supply of vital energy...

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ANCC

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Angina

Chest discomfort – usually pressure or tightness – that results from a relative poor oxygen supply to cardiac tissue (ischemia). 1. Six Second ECG Guidebook...

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Anterior Fascicle

The left bundle branch splits into the septal, anterior and posterior fascicles. Normal ventricular depolarization begins with the septal fascicle of the left bundle branch...

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Anterior Infarction and R wave progression

Poor R wave progression (i.e. not until leads V5 or V6) may signal an anterior infarction. In line with QRS axis deviation, abnormal R wave...

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Anterograde Conduction

Forward conduction of the electrical impulse across the atria & ventricles; the expected route of electrical conduction from top to bottom. 1. Six Second ECG...

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Anterolateral MI

As a general rule, a patient experiencing a left ventricular infarction – anterior, lateral or anterolateral MI – should be managed with particular attention to...

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Anteroseptal Myocardial Infarction

When combined with congruent clinical findings, a diagnosis of an anteroseptal myocardial infarction (MI) is strongly supported. Since the anteroseptal region of the heart involves...

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Aorta

Begins with the aortic valve, the largest main vessel that carries oxygenated blood from the ventricles to the body. 1. Six Second ECG Guidebook (2012),...

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Aortic Arch

The left ventricle ejects blood into the aortic arch to the body. Within the arch, the coronary arteries branch off first followed by three main...

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Apex (of heart)

The bottom of the heart (inferior aspect) located usually around the 5th intercostal space. The heart is a wondrous organ about the size of your...

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Arrhythmia

Technically the absence of rhythm, arrhythmia is commonly used interchangeably with the term dysrhythmia. 1. Six Second ECG Guidebook (2012), T Barill, p. 190

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Artery

Main vessels carrying blood from the heart; the arteries have minimal elasticity and contain approximately 20% of the blood supply. 1. Six Second ECG Guidebook...

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Artifact

Electrocardiograms typically measure electrical activity across the heart. Occasionally additional electrical activity can show up on an ECG. This includes electrical activity of other muscles...

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Ashman Phenomenon

With premature beats, the His-Purkinje fibers may not completely repolarize before the next wave arrives. The ion channels may not yet be fully operational. The...

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Asynchronous Pacemaker

Pacemaker (non-demand mode) fires irrespective of the person’s intrinsic firing; note that the risk for R-on-T phenomena and resulting ventricular tachycardia/fibrillation is higher than synchronous...

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Asystole

Absence of electrical activity demonstrated by a straight ECG line. Most students of dysrhythmia courses arrive with the claim that they are at least skilled...

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Atria

Right and left atria (1/3 volume and muscle mass of the ventricles) pump blood to the ventricles. 1. Six Second ECG Guidebook (2012), T Barill,...

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Atrial Conduction

Once the SA node initiates an electrical impulse, the resulting electrical wave moves across the right and left atria. The atrial septum serves as an...

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Atrial Enlargement

Atrial enlargement and dilation can be caused by tricuspid and bicuspid (mitral) valve disease, hypertension, and ventricular hypertrophy among other causes. A P wave can...

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Atrial Fibrillation

One of the most common dysrhythmias, the atria have a host of sites that are concurrently firing at a combined rate of 350-600/minute; since the...

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Atrial Flutter

A rapid atrial rhythm (approximately 300/minute in the atria) caused by a re-entry loop within the atria; since the junction is unable to conduct 300...

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Atrial Kick

The contraction of the atria prior to ventricular contraction causes an increased volume and stretch to the ventricles – resulting in increased force of contraction...

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Atrial Natriuretic Factor

One of the hormones released by the endocardium is atrial natriuretic factor (ANF); which is released by the atria to oppose the activity of epinephrine,...

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Atrial Sensed Ventricular Paced Rhythm

An implanted cardiac pacemaker with a sensor lead in the right atrium and a second pacing lead in the right ventricle, senses atrial activity, allows...

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Atrial Tachycardia

A fast rhythm with rates commonly 150-240/minute; QRS complex is most often narrow; rhythm is usually generated from a re-entry loop – often making use...

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Atrioventricular (AV) Dissociation

The atria and the ventricles are firing independently of each other (i.e. complete heart block and ventricular tachycardia). The presence of an entirely chaotic PR...

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Atrioventricular (AV) Valves

The atrioventricular (AV) valves lie between the atria and the ventricles of the right and left heart. The valves that connect the atria to the...

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Atrioventricular Blocks

Atrioventricular blocks (AV blocks) result from a conduction disturbance at or just below the AV junction. The 3rd step of the 3 step process prompts...

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Augmented Voltage Leads

These lead views are mathematically created from the limb electrodes to view the heart from three distinct positions towards the centre of the heart. Therefore,...

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Autobahn

An electrical wave envelops the ventricles very quickly IF the Bundle Branches and the Purkinje Network are utilized. This is comparable to getting off the...

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Automaticity

A cardiac cell’s (usually pacemaker cells such as the SA node, AV node or His-Purkinje network) ability to self-initiate an impulse; note that abundant catecholamines...

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Autonomic Nervous System

Involuntary nervous system consisting of the sympathetic and parasympathetic nervous systems. The autonomic nervous system has dramatic effects on the cardiovascular system. When regards to...

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AV Dissociation

The atria and the ventricles are firing independently of each other (i.e. complete heart block and ventricular tachycardia). The presence of an entirely chaotic PR...

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AV Junction

Conducts the impulse through the fibrous plate that separates the atria and the ventricles; consists of the AV node and the bundle of His; functions...

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