Cardiology and EKG Basics - Rhythm, Blocks, STEMI, and Arrhythmias

A comprehensive set of Q&A flashcards to review EKG basics, arrhythmias, blocks, STEMI patterns, and related pathophysiology from the lecture notes.

What does each small EKG box represent in time?

0.04 seconds.

How long is a normal PR interval in seconds and small boxes?

About 0.12 to 0.20 seconds (3–5 small boxes).

What is the normal QRS duration in seconds?

Less than 0.12 seconds (fewer than 3 small boxes).

How can you determine if a rhythm strip is regular?

If the QRSs march out consistently when you place calipers on them.

What are the key features of a normal sinus rhythm on an EKG?

Regular rhythm with a P wave in front of every QRS, P waves that look the same, and a QRS for every P.

What is sinus bradycardia and what are common causes?

Heart rate < 60 bpm with regular rhythm; causes include marathon fitness, hyperkalemia, hypothyroidism, beta-blockers, calcium channel blockers, digoxin, lithium toxicity, and hypothermia.

What is sinus tachycardia?

Heart rate > 100 bpm with a regular rhythm and a P wave before every QRS.

How is atrial fibrillation characterized on an EKG?

Chaotic baseline with no distinct P waves and an irregularly irregular rhythm.

How is atrial flutter described on EKG?

Sawtooth flutter waves with more atrial than ventricular activity; P waves look like sawtooth waves.

What is a premature atrial contraction (PAC)?

A beat with a P wave that looks different from the others, followed by a normal QRS and a compensatory pause.

What is a premature ventricular contraction (PVC)?

A wide QRS complex with an opposite deflection and a compensatory pause after the beat.

How is ventricular tachycardia (VT) identified on an EKG?

Wide, regular, monomorphic QRS complexes with no discernible P waves.

How is ventricular fibrillation (VF) identified and treated?

Chaotic rhythm with no pulse; requires CPR and defibrillation.

What defines first-degree AV block?

PR interval longer than 0.20 seconds (more than 5 small boxes).

What is Wenckebach (second-degree AV block type I)?

Progressive PR interval prolongation with eventual dropped QRS (longer PRs until a beat is skipped).

What is Mobitz type II (second-degree AV block)?

Intermittent dropped QRS with constant PR intervals when conducted; more P waves than QRS. Often requires a pacemaker.

What characterizes third-degree (complete) heart block?

No relationship between P waves and QRS; AV dissociation; may rely on Purkinje system; typically requires pacing.

What is sick sinus syndrome and its treatment?

Episodes of atrial tachycardia with slow rates and pauses due to sinus node dysfunction; treated with a pacemaker.

What is sinus arrhythmia and who is it common in?

Beat-to-beat variation with respiration; normal variant, especially in young people.

What is the QT interval and its maximum duration?

Should be no more than 450 ms (about 12 small boxes). Prolongation risks torsades de pointes.

What can cause QT prolongation?

Electrolyte abnormalities and drugs such as antiarrhythmics (e.g., amiodarone), some antibiotics (e.g., levofloxacin), antipsychotics (e.g., quetiapine/Seroquel), hypothermia, and ischemic heart disease.

What is torsades de pointes and how is it treated?

Polymorphic ventricular tachycardia associated with prolonged QT; treated with IV magnesium; defibrillation if needed.

How can you tell left bundle branch block on EKG leads V1–V6?

V1–V3 show typical patterns; LBBB shows wide QRS with rabbit ears in V4–V6 and inverted T waves in aVL, V5, and V6.

How can you tell right bundle branch block on EKG leads V1–V3?

V1 shows an RSR' pattern (RSR prime); “dead giveaway” for RBBB; QRS is wide.

What is the clinical significance of a new RBBB vs a new LBBB in chest pain?

New RBBB with chest pain can suggest acute PE; new LBBB with chest pain can suggest acute MI.

Which arteries supply the inferior, lateral, and anterior walls of the heart in STEMI analysis?

Inferior: right coronary artery (RCA); Lateral: circumflex (CX); Anterior: left anterior descending (LAD).

What are the typical STEMI patterns and their leads?

Inferior STEMI: ST elevation in II, III, aVF (RCA); Lateral STEMI: ST elevation in I, aVL, V5, V6 (CX); Anterior STEMI: ST elevation in V2, V3, V4 (LAD).

How is posterior STEMI detected on a standard 12-lead EKG?

Subtle ST elevations in the posterior-related leads (often no clear elevation in V1–V3); look for ST depression in V1–V3 and consider posterior leads V7–V9 or flip V2 to observe elevation.

What is WPW and what causes the delta wave on EKG?

Wolff-Parkinson-White syndrome; delta wave due to preexcitation from an accessory pathway causing fast SVT; can be treated with ablation.

What does a dual-chamber pacemaker look like on an EKG?

A small spike before the P wave followed by a larger spike before the QRS (AV sequential pacing).

What is a typical digoxin toxicity pattern on EKG?

Diffuse sagging/ST depression in multiple leads (e.g., II, III, aVF, V leads); check the digoxin level.

What is the significance of a Q wave on EKG in the context of infarction?

A Q wave can indicate an old infarct (age undetermined) in the corresponding leads.

What is the basic guideline for STEMI management timing?

Activate the cath lab and open the blocked artery within about 90 minutes of presentation; give aspirin, heparin, and a P2Y12 inhibitor (e.g., clopidogrel or ticagrelor).