Heart Rhythm & ECG Interpretation

Vocabulary practice flashcards covering heart rhythms, cardiac electrophysiology, ECG interpretation, dysrhythmias, conduction blocks, emergency interventions, and pacemaker concepts for NCLEX-RN review.

Dysrhythmia

An abnormal heart rhythm.

Arrhythmia

The absence of rhythm, though commonly used interchangeably with dysrhythmia in medical literature.

Parasympathetic Nervous System (Cardiac Effect)

Nervous control mediated by the vagus nerve that decreases the firing of the SA node and slows impulse conduction through the AV node.

Sympathetic Nervous System (Cardiac Effect)

Nervous control that increases SA node firing, speeds impulse conduction through the AV node, and increases cardiac contractility.

Automaticity

The ability of cardiac cells to generate an electrical impulse spontaneously.

Excitability

The ability of cardiac cells to respond to an electrical impulse.

Conductivity

The ability of cardiac cells to transmit an electrical impulse to neighboring cells.

Contractility

The ability of cardiac muscle to contract in response to electrical stimulation.

Refractoriness

The period during which cardiac cells cannot respond normally to another electrical impulse.

Depolarization

Electrical activation of cardiac cells that leads to mechanical contraction.

Repolarization

Electrical recovery of cardiac cells following depolarization.

Telemetry

Continuous ECG monitoring that commonly utilizes $5\text{ leads}$ to monitor cardiac rhythm.

12-Lead ECG

A diagnostic tool utilizing $12\text{ leads}$ to provide a quick snapshot of the heart's electrical activity from multiple views.

P Wave

The ECG waveform representing atrial depolarization in response to SA node triggering.

PR Interval

The ECG measurement from the beginning of the P wave to the beginning of the QRS complex, representing the AV node delay and normally lasting $0.12\text{--}0.20\text{ seconds}$.

QRS Complex

The ECG waveform representing ventricular depolarization that triggers main pumping contractions, normally lasting $< 0.12\text{ seconds}$.

ST Segment

The portion of the ECG representing the beginning of ventricle repolarization, which should normally be flat.

T Wave

The ECG waveform representing ventricular repolarization and electrical recovery.

QT Interval

The ECG measurement from the beginning of the QRS complex to the end of the T wave, representing total ventricular depolarization through repolarization.

ECG Small Box

A single small grid square on ECG paper representing $0.04\text{ seconds}$ of time.

ECG Large Box

A large grid square on ECG paper comprising $5\text{ small boxes}$, representing $0.20\text{ seconds}$ of time.

Six-Second Method

A rate calculation method where the number of R waves (or P waves) in a $6\text{-second}$ ECG strip is multiplied by $10$ to determine heart rate per minute.

Synchronized Cardioversion

A procedure where the defibrillator synchronizes with the R wave to deliver a shock during ventricular depolarization, avoiding the vulnerable T wave period.

Defibrillation

An unsynchronized electrical shock delivered immediately for cardiac arrest rhythms (pulseless VT or VFib) where no organized R wave is present.

Atropine

The first-line medication used in the management of unstable or symptomatic sinus bradycardia.

Atrial Fibrillation (AFib)

An atrial dysrhythmia characterized by an irregular baseline, chaotic atrial activity, and an irregular ventricular response.

Atrial Flutter

An atrial dysrhythmia managed in stable patients with vagal maneuvers, rate-control drugs, and anticoagulants, or with synchronized cardioversion if unstable.

Premature Atrial Contractions (PACs)

Premature ectopic beats originating in the atria earlier than the next expected sinus impulse.

Unifocal PVCs

Premature ventricular contractions originating from a single ectopic focus in the ventricles, appearing identical in morphology on the ECG.

Multifocal PVCs

Premature ventricular contractions originating from multiple ectopic foci in the ventricles, displaying differing shapes and directions on the ECG.

Bigeminy

A repetitive dysrhythmia pattern where every second beat is a premature ventricular contraction (PVC).

Trigeminy

A repetitive dysrhythmia pattern where every third beat is a premature ventricular contraction (PVC).

Quadrigeminy

A repetitive dysrhythmia pattern where every fourth beat is a premature ventricular contraction (PVC).

PVC Couplet

Two consecutive premature ventricular contractions occurring back-to-back.

Monomorphic Ventricular Tachycardia

A fast ventricular rhythm where wide QRS complexes maintain a consistent shape and morphology from beat to beat.

Polymorphic Ventricular Tachycardia

A fast ventricular rhythm where wide QRS complexes continuously vary in shape, size, and direction from beat to beat.

Torsades de Pointes

A specific form of polymorphic ventricular tachycardia characterized by QRS complexes twisting around the isoelectric line, typically associated with a prolonged QT interval.

Non-Sustained Ventricular Tachycardia

Ventricular tachycardia lasting at least $3\text{ consecutive beats}$ but less than $30\text{ seconds}$ before terminating spontaneously.

Sustained Ventricular Tachycardia

Ventricular tachycardia lasting $\text{30 seconds}$ or longer, or requiring clinical intervention due to hemodynamic instability.

Pulseless Ventricular Tachycardia

A cardiac arrest rhythm characterized by rapid, wide QRS complexes without palpable cardiac output or pulse, requiring immediate CPR and unsynchronized defibrillation.

Reversible Causes of Cardiac Arrest (H's)

The key physiological etiologies of cardiac arrest: Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hypo-/Hyperkalemia, and Hypothermia.

Reversible Causes of Cardiac Arrest (T's)

The key anatomical and pharmacological etiologies of cardiac arrest: Tension pneumothorax, Tamponade (cardiac), Toxins, Thrombosis (pulmonary), and Thrombosis (coronary).

Ventricular Fibrillation (VFib)

A shockable cardiac arrest rhythm characterized by chaotic, rapid, wide irregular ventricular complexes with no recognizable waves or cardiac output.

Idioventricular Rhythm (IVR)

A slow intrinsic ventricular rhythm ($20\text{--}40\text{ bpm}$) that occurs when higher pacemakers (SA and AV nodes) fail, leaving the ventricles to pace the heart.

Asystole

A non-shockable cardiac arrest state characterized by the complete absence of electrical activity (flatline), requiring high-quality CPR, epinephrine, and treatment of reversible causes.

First-Degree AV Block

A conduction delay where every P wave is conducted to the ventricles, but the PR interval is prolonged ($> 0.20\text{ seconds}$) and remains constant.

Second-Degree AV Block: Mobitz I (Wenckebach)

An AV conduction abnormality characterized by progressive lengthening of the PR interval until a QRS complex is completely dropped ("longer, longer, longer, drop").

Second-Degree AV Block: Mobitz II

An AV conduction abnormality characterized by constant PR intervals with periodic dropped QRS complexes occurring without prior PR prolongation.

Third-Degree AV Block (Complete Heart Block)

A severe conduction block where atria and ventricles function independently with no relationship between P waves and QRS complexes.

Junctional Rhythm

A rhythm originating from the AV junction at $40\text{--}60\text{ bpm}$, featuring normal narrow QRS complexes and P waves that are absent or inverted.

Premature Junctional Complex (PJC)

An early extra beat originating from the AV junction rather than the SA node, exhibiting an absent or inverted P wave and a short PR interval ($< 0.12\text{ seconds}$).

Pacemaker Failure to Sense

A pacemaker malfunction where the artificial device fails to detect intrinsic cardiac activity, resulting in inappropriate firing of pacing spikes.

Pacemaker Failure to Capture

A pacemaker malfunction where a delivered electrical stimulus fails to depolarize the myocardium, visible on ECG as a spike unassociated with a QRS complex.

Pacemaker Failure to Pace

A pacemaker malfunction where the device fails to initiate an electrical impulse when programmed to fire.

Cardiac Resynchronization Therapy (CRT)

A heart failure intervention that uses biventricular pacing to resynchronize the contraction cycle of both ventricles.