ECG Interpretation: Rate, Rhythm, and Sinus Arrhythmias

Vocabulary practice flashcards covering ECG rate and rhythm calculations, normal sinus rhythm, and sinus node arrhythmias (sinus bradycardia and sinus tachycardia) with their clinical characteristics and medical management.

Systematic ECG Rhythm Strip Analysis

A step-by-step examination of an ECG strip used to determine cardiac rate and rhythm, detect arrhythmias and conduction disorders, and identify evidence of myocardial ischemia, injury, and infarction.

Small Box Method

A technique for calculating heart rate in a regular rhythm by dividing $1500$ by the total number of small boxes counted between two consecutive R waves (RR interval).

6-Second Method

A method used to estimate heart rate during an irregular rhythm by counting the number of complete RR intervals within a $6$-second strip ($15$ large boxes horizontally) and multiplying that count by $10$.

Regular Rhythm

A cardiac rhythm classification where the intervals between successive cycles are identical or the difference between the intervals is less than $0.8\text{ seconds}$ throughout the entire strip.

Irregular Rhythm

A cardiac rhythm classification identified when the measured intervals between cycles (such as RR intervals or PP intervals) differ throughout the ECG strip.

P:QRS Ratio

A component of systematic arrhythmia analysis that evaluates the relationship between atrial and ventricular depolarization by determining the number of P waves present for each QRS complex.

Normal Sinus Rhythm (NSR)

The normal heart rhythm originating in the SA node with a regular rate of $60\text{ to }100\text{ bpm}$, consistent P waves preceding every QRS complex, a PR interval between $0.12\text{ and }0.20\text{ seconds}$, and a $1:1$ P:QRS ratio.

Sinus Bradycardia

A sinus node arrhythmia characterized by an impulse originating at a rate of less than $60\text{ bpm}$ in an adult, featuring a regular rhythm, normal P waves, a PR interval between $0.12\text{ and }0.20\text{ seconds}$, and a $1:1$ P:QRS ratio.

Atropine

An intravenous anticholinergic medication given as a rapid $0.5\text{ mg}$ bolus every $3\text{ to }5\text{ minutes}$ up to a maximum dose of $3\text{ mg}$ for patients presenting with symptomatic, clinically unstable sinus bradycardia.

Transcutaneous Pacing

An emergency cardiac pacing method instituted for clinically unstable bradycardia when the patient remains unresponsive to atropine administration.

Sinus Tachycardia

A sinus node arrhythmia characterized by a regular impulse rate greater than $100\text{ bpm}$ (usually under $120\text{ bpm}$), normal QRS complexes, consistent P waves preceding each QRS, and a normal PR interval of $0.12\text{ to }0.20\text{ seconds}$.

Non-paroxysmal

A descriptor for arrhythmias such as sinus tachycardia that develop and resolve gradually rather than starting or ending abruptly.

Vagal Maneuvers

Physical actions such as carotid sinus massage, gagging, bearing down against a closed glottis, forceful sustained coughing, or applying a cold stimulus to the face that stimulate parasympathetic activity to interrupt tachycardia.

Synchronized Cardioversion

The delivery of a timed electrical shock synchronized with the patient's own QRS complex, used as the primary treatment of choice for persistent tachycardia causing hemodynamic instability.