Cardiac Arrhythmias & Conduction Blocks – Vocabulary Review

Vocabulary flashcards covering key arrhythmias, heart blocks, and emergency rhythms discussed in the lecture.

Sinus Rhythm

Normal heart rhythm with distinct P-QRS-T sequence; RR interval 3–5 small boxes and uniform P waves preceding every QRS.

Premature Atrial Contraction (PAC)

Early ectopic atrial beat marked by an early P′ wave with different shape and a shorter (red-bar) RR interval compared with baseline (green).

Premature Ventricular Contraction (PVC)

Early, wide, and bizarre QRS originating in a ventricle; often appears in patterns such as bigeminy (every other beat is a PVC).

Bigeminy

Rhythm pattern in which every normal beat is followed by a PVC, producing pairs of beats (normal–PVC, normal–PVC…).

Atrial Flutter

Regular tachyarrhythmia with classic sawtooth F-waves; distinguish from sinus tachycardia (no round P/T) and from atrial fibrillation (rhythm in flutter is regular).

Atrial Fibrillation

Chaotic atrial activity with no discernible P waves and an irregularly irregular ventricular rhythm; easiest to see variable RR intervals in a long lead II strip.

First-Degree AV Block

Conduction delay where each P is followed by a QRS but PR interval is > 200 ms (longer than one big box); rhythm remains regular.

Second-Degree AV Block – Mobitz I (Wenckebach)

Progressive PR lengthening (“going going going DROP”) followed by a non-conducted P wave, creating an irregular rhythm.

Second-Degree AV Block – Mobitz II

Intermittent non-conducted P waves WITHOUT preceding PR prolongation; irregular rhythm and risk of progressing to complete block.

Third-Degree (Complete) AV Block

No atrioventricular conduction; P waves and QRS complexes march independently (AV dissociation) with T waves following each QRS.

ST-Segment Elevation Myocardial Infarction (STEMI)

Acute MI pattern with elevated ST segment where QRS appears to blend into the T wave; may show inverted QRS in V1-3 and subtler changes in V4-6.

Ventricular Tachycardia (VT)

Regular, rapid rhythm originating in the ventricles; wide QRS complexes and uniform rate distinguish it from ventricular fibrillation.

Ventricular Fibrillation (VF)

Chaotic, irregular ventricular activity with no organized QRS complexes; immediately life-threatening and not regular like VT.

Torsades de Pointes

Polymorphic VT characterized by twisting QRS amplitudes—smaller ‘calmer’ spikes flanked by larger ones—often related to prolonged QT interval.

Agonal Rhythm

Terminal, very slow ventricular rhythm with sporadic, low-frequency electrical activity (0.5–27 Hz); usually precedes asystole.

Asystole

Complete absence of ventricular activity (flatline) lasting > 10 s; patient may briefly feel disoriented before collapse and requires immediate intervention.