Ch. 16 Basic Cardiac Monitoring: The Electrocardiogram

Action Potential

Processes of depolarization and repolarization of the cardiac membrane

Arrythmia

Irregularity of cardiac actions associated with physiologic or pathalogic interruption of the neuroconductive tissues of the heart (also synonymous with dysrhythmia)

Asystole

• There is no evidence of any cardiac neuroconductive activity (full cardiac arrest).

• Straight line tracing

Automaticity

Process whereby cardiac cell membranes spontaneously depolarize at recurrent periods

Bradycardia

Slowness of the heartbeat, as evidenced by slowing of the pulse rate to less than 60 beats/min

Cardiac Cycle

Events that occur from the beginning of one ventricular contraction (systole) until the beginning of another

Cardiac Output

Amount of blood ejected from the ventricles each minute; calculated as the product of stroke volume times heart rate

Depolarization

Myocardial cells are stimulated to contract

Fibrillation

Quivering contraction of cardiac muscle fibers

Repolarization

Myocardial muscle cells relax

Tachycardia

Heart rate above 100 beats/min

Cardiac Output

The vital event necessary to maintain blood flow throughout the cardiovascular system

Electrocardiograph

A device used to assess the heart’s ability to perform its vital function

Electrocardiogram

Action potential that spread throughout the muscle sheets of the heart may be detected by surface electrodes to record and produce a tracing

Sinoatrial (SA) node

Know as the pacemaker of the heart

Sinoatrial (SA) node

The electrical sequence of a cardiac cycle is initiated by the ___

P wave

First deflection. Represents depolarization of atrial muscle cells

QRS Complex

Represents depolarization of ventricular muscle cells

Q portion

Initial downward deflection of QRS Complex

R portion

Initial upward deflection of QRS Complex

S portion

Return to the baseline (isoelectric point) of QRS Complex

T wave

Represents Repolarization of ventricular muscle

U wave

Represents repolarization of the papillary muscles and Purkinje fibers

PR Interval

Measured from the beginning of the P wave to the beginning of the R portion of the QRS complex.

PR Interval

Commences with atrial muscle depolarization and ends with the start of ventricular depolarization

Tachycardia

May involve the atria or ventricle abnormalities

Bradycardia

Typically involves either Sinoatrial (SA) or Atrioventricular (AV) node abnormalities

Cardioversion Therapy

Useful for treating atrial-related causes of arrhythmias including atrial fibrillation

Cardioversion Therapy

It involves external shock therapy to the chest to restore normal cardiac rhythm

Ablation therapy

Involves either heating or freezing tissues within a chamber of the heart that is considered to be the cause of the arrhythmia

Pacemaker

Used most often to treat bradycardia

Implantable Cardioverter-defibrillator (ICD)

Typically used to treat tachycardia and irregular contraction disorders involving the ventricles of the heart. Can also treat bradycardia.