Six Second ECG Glossary
helping you understand the technical terms of ECG interpretation
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...
Read More12-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...
Read More12-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....
Read More12-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...
Read More15 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...
Read MoreAberrant 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...
Read MoreAbnormal 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...
Read MoreAbnormal 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...
Read MoreAbsolute 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
Read MoreAccelerated 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...
Read MoreAccelerated 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...
Read MoreAccelerated 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,...
Read MoreAccessory 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...
Read MoreAction 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...
Read MoreAction 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...
Read MoreAction 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
Read MoreAction 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...
Read MoreAction 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...
Read MoreAction 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...
Read MoreAerobic 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...
Read MoreAgonal 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...
Read MoreAlpha Stimulation
The peripheral vasoconstriction that results from circulating catecholamines (epinephrine & norepinephrine). 1. Six Second ECG Guidebook (2012), T Barill, p. 190
Read MoreAnaerobic 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...
Read MoreAnterior 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...
Read MoreAnterior 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...
Read MoreAnterograde 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...
Read MoreAnterolateral MI
As a general rule, a patient experiencing a left ventricular infarction – anterior, lateral or anterolateral MI – should be managed with particular attention to...
Read MoreAnteroseptal 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...
Read MoreAortic 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...
Read MoreApex (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...
Read MoreArrhythmia
Technically the absence of rhythm, arrhythmia is commonly used interchangeably with the term dysrhythmia. 1. Six Second ECG Guidebook (2012), T Barill, p. 190
Read MoreAshman 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...
Read MoreAsynchronous 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...
Read MoreAtrial 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...
Read MoreAtrial 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...
Read MoreAtrial 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...
Read MoreAtrial 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...
Read MoreAtrial 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...
Read MoreAtrial 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,...
Read MoreAtrial 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...
Read MoreAtrial 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...
Read MoreAtrioventricular (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...
Read MoreAtrioventricular (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...
Read MoreAtrioventricular 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...
Read MoreAugmented 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,...
Read MoreAutomaticity
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...
Read MoreAutonomic 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...
Read MoreAV 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...
Read MoreAV 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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