Glossary

Ablation is a procedure to restore normal heart rhythm by destroying very small, carefully selected parts of the heart that cause tachycardia.  In most cases, ablation refers to the use of catheters to destroy the selected areas of heart tissue.  Ablation can also be performed during open-heart surgery.

As it pertains to an EKG/ECG, an “artifact” is an erratic, often jagged segment of the tracing of cardiac cycles. Artifacts make interpreting EKGs more difficult because the subtle nuances of some of the smaller waves (P, Q, S and T) are often lost in the irregular lines an artifact creates.

A person moving while taking an EKG reading can cause artifacts (such as when exercising while wearing an event monitor), because movement of all muscles in your body is preceded by an electrochemical pulse, and this electrical activity is picked up through the EKG leads just as the electrical activity of the heart is.

If the heart’s electrical signal does not adequately conduct through the skin to the EKG, artifacts may also be the result. Poor skin/lead contact and sweating are just two of the reasons why the electrical signal may not conduct clearly enough.

In the EKG at the top right (click to enlarge), artifacts from an event monitor can be seen as jagged, erratic lines that make interpreting all but the R wave difficult.

Also known in ECG terms as a flatline, asystole (pronounced ay-SIS-tuh-lee) is the absence of any discernible activity in the heart. While asystole may be considered an arrhythmia, this arrhythmia is characterized by a complete lack of rhythm, patterned or otherwise. During asystole there is no blood being pumped through the body’s organs and no electrical or mechanical activity occuring in the heart..

If a person remains in a state of asystole for 15 minutes or more, they are most likely brain dead, and in a study of 1,635 asystolic patients, only 10% survived long enough to be admitted to the hospital and only 2% survived long enough to be discharged from the hospital.^[1] Asystole is more often used as a confirmation of death than as an arrhythmia to be treated.

References

Atrial Fibrillation (A-Fib or AF) is a disorganized electrical activity in the atria accompanied by an irregular ventricular response that is usually rapid.  The atria quiver instead of pumping in an organized fashion, resulting in compromised ventricular filling and reduced stroke volume.  Stasis of left atrial flow increases the risk of stroke as a result of clot formation.  AF is associated with hypertension, diabetes, age, rheumatic heart disease (left atrial dilation), mitral stenosis, acute myocardial infarction, and heart surgery, or it may be idiopathic (lone AF).  Treatment goals are to control the ventricular rate by creating atrioventricular block, to prevent stroke through the use of anticoagulants, and to convert to sinus rhythm.  Treatment categories include paroxysmal, persistent, and chronic.  AF is called controlled if ventricular response is less than 100.  If ventricular response is 100 or more, it is called uncontrolled atrial fibrillation.

Atrial Flutter (A-Flutter) is a condition similar to atrial fibrillation except that the rapid firing of impulses occurs in a regular patter, rather than uncoordinated.  When it first occurs, it is usually associated with a fast heart rate or tachycardia (230-380 beats per minute), and falls into the category of supra-ventricular tachycardia.  While this rhythm occurs most often in individuals with cardiovascular disease (eg:  hypertension, coronary artery disease, and cardiomyopathy), it may occur spontaneously in people with otherwise normal hearts.  It is typically not a stable rhythm, and frequently degenerates into atrial fibrillation.  It can persist for months to years.

As you might expect, automaticity, when talking about your heart, has to do with your heart’s ability to function automatically.  That is, without receiving outside signals instructing it to contract. There is a specific cluster of cells in your heart that are designed to set off rhythmic electrical signals that spread throughout the rest of the heart, telling it to contract. And they do this without external influence, making them “automatic”.

Explaining it more technically, the sinoatrial node (SA node) in your heart (located at the top of your right atrium) is a special cluster of heart cells called “pacemaker cells.”  These cells have electrochemical properties that allow them build a store of electrical charge and then release that electrical charge, all in regular intervals.  When this wave of electricity reaches the other cells in your heart they discharge as well, passing the electrical charge on to the next cells, generating a coordinated contraction.  What’s special about the SA node cells is that they don’t need a signal from a cell further up the line to tell them to discharge, and their threshold for releasing their electrical charge (called depolarization) is lower than that of other heart cells, making it that much easier for them to lead the other cells into contractions.

Put another way, if a sports stadium were a heart, those over-exuberant guys in section 14B would be the sinoatrial node, starting “The Wave” and getting all the other cells in the stadium to stand up and wave their arms at just the right time.

Nobody told them to do it.  They just did it spontaneously.  Automatically.  And everyone else just followed along.  Maybe it was the 320 drinks that section consumed during the first half that lowered their threshold for depolarization, enhancing their automaticity (for doing the wave).

Arrhythmia problems arise when the automaticity of the SA node fails to be regular, causing arrhythmia.  Automaticity can be affected by electrolyte levels, certain medications, forms of heart disease or changes in autonomic nervous system tone.

AV Nodal Reentrant Tachycardia (AVNRT) is a type of tachycardia (fast rhythm) of the heart.  It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His.  AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia.  It is more common in women that men (approximately 75% of cases occurring in females).  The main symptom is palpitations.  Treatment may be with specific physical maneuvers, medication, or rarely DC cardio version.  Frequent attacks may require radiofrequency ablation, in which the abnormally conducting tissue in the heart is destroyed.