ECG Fundamentals
This node is the heart’s natural pacemaker, typically firing 60–100 beats per minute.
What is the SA node?
Normal heartbeat, regular rate between 60–100, with a P wave before each QRS.
What is normal sinus rhythm?
Sudden fast heartbeat above 150, narrow QRS.
What is supraventricular tachycardia (SVT)?
Slow heartbeat from the ventricles, rate 20–40, wide QRS.
What is idioventricular rhythm?
PR interval is longer than 0.20 seconds but every P wave has a QRS after it.
What is first-degree heart block?
One small box on ECG paper represents this many seconds.
What is 0.04 seconds?
Slow heartbeat from the SA node, under 60 beats per minute.
What is sinus bradycardia?
An early beat that starts in the atria, feels like a “skipped beat.”
What is premature atrial contraction (PAC)?
Fast, wide QRS complex rhythm, can be dangerous.
What is ventricular tachycardia (VTach)?
PR interval gets longer each beat until a QRS is dropped.
What is second-degree heart block, Type I (Wenckebach)?
One large box on ECG paper represents this many seconds.
What is 0.20 seconds?
Fast heartbeat from the SA node, over 100 beats per minute.
What is sinus tachycardia?
Heart rhythm is irregular, no clear P waves, common in older adults.
What is atrial fibrillation?
Fast, twisting QRS pattern, often from a long QT interval.
What is Torsades de Pointes?
Some P waves are not followed by QRS, but PR interval stays the same.
What is second-degree heart block, Type II (Mobitz II)?
The normal PR interval is within this range.
What is 0.12–0.20 seconds?
What is ST-segment elevation indicating myocardial injury?
What is a STEMI?
Atrial rhythm with a “sawtooth” pattern on ECG.
What is atrial flutter?
Chaotic ventricles, no pulse, must defibrillate immediately.
What is ventricular fibrillation (V-Fib)?
Complete dissociation between P waves and QRS complexes
What is third-degree (complete) heart block?
The normal QT interval is within this range.
What is 0.28–0.40 seconds?
What is a rhythm that originates from the AV junction with a rate of 40–60 bpm and inverted/absent P waves?
What is Junctional Rhythm?
What is a flatline rhythm with no electrical activity?
What is Asystole
Rhythm shows small spikes before wide QRS complexes.
What is ventricular pacing?
There is electrical activity on ECG but no pulse.
What is pulseless electrical activity (PEA)?