Basic Dysrhythmia Review

Vocabulary flashcards reviewing basic cardiac dysrhythmias, ECG intervals, rates, conduction mechanisms, heart blocks, and pacemaker functions based on lecture notes.

Sinoatrial (SA) Node

The main pacemaker of the heart's conduction system, which has an inherent rate of $60$ to $100\text{ bpm}$.

AV Junction

A pacemaker site in the conduction system of the heart with an inherent rate of $40$ to $60\text{ bpm}$.

Ventricles (Inherent Rate)

The intrinsic pacemaker site in the lower heart chambers with an inherent rate of $20$ to $40\text{ bpm}$.

Pacemaker Rule

The principle stating that the pacemaker site with the fastest rate will generally control the heart.

Irritability

A state where a site along the conduction pathway speeds up and overrides higher pacemaker sites for control of the heart.

Escape Mechanism

A safety response that occurs when the normal pacemaker slows down or fails, allowing a lower pacemaker site to assume pacemaker responsibilities.

ECG Small Box

A single horizontal division on ECG graph paper representing $0.04\text{ seconds}$ of time.

ECG Large Box

A horizontal division on ECG graph paper consisting of $5$ small boxes, representing $0.20\text{ seconds}$ of time.

P Wave

The waveform on an ECG strip that represents atrial depolarization.

QRS Complex

The waveform on an ECG strip that represents ventricular depolarization, with a normal duration of $0.06$ to $< 0.11\text{ seconds}$.

T Wave

The waveform on an ECG strip that represents ventricular repolarization.

ST Segment

The segment on an ECG connecting the QRS complex to the T wave; it is usually isoelectric (flat), and displacement can indicate myocardial ischemia or injury.

QT Interval

The ECG interval representing total ventricular activity (depolarization and repolarization), with a normal range of $0.34$ to $0.44\text{ seconds}$.

Prolonged QT Interval

A QT interval lasting $> 0.50\text{ seconds}$, indicating a lengthened relative refractory period that puts the patient at risk for life-threatening dysrhythmias such as Torsades de Pointes.

PR Interval (PRI)

The measurement on an ECG representing the time from the beginning of atrial depolarization to the start of ventricular depolarization, with a normal range of $0.12$ to $0.20\text{ seconds}$.

Six-Second Method

A heart rate calculation method used for irregular rhythms where the number of P waves or QRS waves within a $6\text{-second}$ strip ($30$ large boxes) is multiplied by $10$.

Large Box Method

A heart rate calculation method for regular rhythms where the number of large boxes between two consecutive QRS complexes is divided into $300$.

Small Box Method

A heart rate calculation method for regular rhythms where the number of small boxes between two consecutive QRS complexes is divided into $1500$.

Premature Atrial Complex (PAC)

A single early ectopic beat caused by an irritable focus in the atrium firing prematurely, featuring a P wave that differs in shape from normal sinus P waves.

Atrial Flutter

An atrial dysrhythmia caused by a single irritable focus firing at an atrial rate of $250$ to $350\text{ bpm}$, producing a characteristic sawtooth P-wave pattern.

Atrial Fibrillation

An atrial dysrhythmia caused by multiple irritable foci firing chaotic impulses at an atrial rate $> 350\text{ bpm}$, resulting in a grossly irregular ventricular rhythm and fibrillatory waves (f waves).

Controlled Ventricular Rate

An Atrial Fibrillation rhythm in which the ventricular rate is maintained at less than $100\text{ bpm}$.

Retrograde Conduction

Conduction in junctional rhythms where the electrical impulse travels backward to depolarize the atria, causing inverted P waves before, during, or after the QRS complex.

Premature Junctional Complex (PJC)

An extra beat originating prematurely from an irritable focus in the AV junction that interrupts the underlying rhythm.

Junctional Escape Rhythm

A regular, slow rhythm with a rate of $40$ to $60\text{ bpm}$ originating from the AV junction with inverted P waves (if visible), occurring as an escape mechanism.

Accelerated Junctional Rhythm

A junctional rhythm with a rate faster than the inherent AV junction rate, ranging from $61$ to $100\text{ bpm}$.

Junctional Tachycardia

A rapid junctional rhythm with a rate exceeding $100\text{ bpm}$ (up to $180\text{ bpm}$).

Supraventricular Tachycardia (SVT)

A rapid, usually regular tachyarrhythmia originating above the ventricles with a rate of $150$ to $250\text{ bpm}$, where P waves cannot be accurately identified.

Premature Ventricular Complex (PVC)

An early ectopic beat originating from an irritable focus in the ventricle, featuring a wide QRS complex ($> 0.12\text{ seconds}$) and no preceding P wave.

Ventricular Tachycardia (V Tach)

A dysrhythmia caused by an extremely irritable ventricular focus controlling the heart at a rate of $150$ to $250\text{ bpm}$, featuring wide QRS complexes ($> 0.12\text{ seconds}$) and no P waves.

Ventricular Fibrillation (V Fib)

A chaotic rhythm caused by multiple ventricular foci firing in an ineffective manner, resulting in no identifiable waveforms, no heart muscle contractions, and no pulse; treated with CPR and defibrillation.

Idioventricular Rhythm

A slow ventricular escape rhythm with a rate of $20$ to $40\text{ bpm}$, characterized by wide, bizarre QRS complexes and no P waves.

Asystole

The total absence of electrical activity in the heart, represented as a straight line on the ECG strip with no pulse.

First-Degree Heart Block

A conduction delay at the AV node resulting in a prolonged PR interval ($> 0.20\text{ seconds}$) that remains constant for every beat.

Second-Degree Heart Block Type I (Wenckebach)

An intermittent AV block characterized by progressive lengthening of the PR interval until a QRS complex is dropped, resulting in more P waves than QRS complexes.

Second-Degree Heart Block Type II (Mobitz II)

An intermittent AV block where the PR interval remains constant on conducted beats, but periodic non-conducted P waves occur (frequently in ratios like $2:1$, $3:1$, or $4:1$).

Third-Degree Heart Block (Complete Heart Block)

A complete blockage of AV conduction where no SA node impulses reach the ventricles, resulting in complete AV dissociation where atria and ventricles beat independently.

Pacemaker Capture

The successful depolarization of the cardiac tissue following an electrical impulse generated by an artificial pacemaker, visible as a pacer spike followed by a waveform.

Failure to Pace

A pacemaker malfunction in which the artificial pacemaker fails to initiate an electrical stimulus when it should fire.

Failure to Capture

A pacemaker malfunction where an electrical impulse (pacer spike) is emitted, but no subsequent cardiac depolarization occurs.

Pacemaker Sensitivity

The ability of an artificial pacemaker to detect intrinsic cardiac activity, measured in millivolts ($\text{mV}$).

Pacemaker Undersensing

A malfunction where the pacemaker fails to recognize intrinsic myocardial depolarization, resulting in pacer spikes occurring inside P waves, T waves, or too close behind intrinsic QRS complexes.

Pacemaker Oversensing

A malfunction where the pacemaker inappropriately senses non-cardiac electrical signals, causing it to withhold pacing spikes or pace at a rate slower than its preset rate.