3 Arrhythmias and Conduction Disorders Free Online FlashCards

What QRS duration distinguishes narrow from wide complexes?

A narrow QRS is less than $120\,\text{ms}$; a wide QRS is $120\,\text{ms}$ or longer.

What is the conventional adult definition of bradycardia?

In adults, bradycardia is conventionally a heart rate below $60$ beats per minute. A slow rate alone does not establish an emergency.

What ECG pattern defines first-degree AV block?

Every P wave conducts to a QRS, but the PR interval is prolonged beyond $200\,\text{ms}$ and remains constant.

What ECG features characterize atrial fibrillation?

Atrial fibrillation has no consistent discrete P waves and an irregularly irregular ventricular rhythm.

How is an uncertain wide-complex tachycardia generally treated in emergency decision-making?

When a wide-complex tachycardia cannot be confidently identified, it is generally treated as ventricular tachycardia in emergency decision-making because mistaking it for ordinary SVT can be dangerous.

What pattern identifies Mobitz I (Wenckebach) AV block?

The PR interval progressively lengthens until a P wave is not followed by a QRS; then the cycle repeats.

What pattern identifies Mobitz II AV block?

Conducted beats have a stable PR interval, but some P waves are suddenly not followed by QRS complexes.

What defines third-degree (complete) AV block?

P waves and QRS complexes occur independently, with no consistent PR relationship. A slower junctional or ventricular escape rhythm may maintain the ventricular rate.

Why may a 2:1 AV block resist classification as Mobitz I or II?

A 2:1 AV block has one conducted QRS for every two P waves. There are too few consecutive conducted beats to classify it from the ECG alone as Mobitz I or II.

What atrial waveform pattern suggests atrial flutter?

Atrial flutter produces repeating, uniform flutter waves, often with a sawtooth appearance. Ventricular rhythm can be regular or irregular depending on conduction.

What ECG findings distinguish multifocal atrial tachycardia?

Multifocal atrial tachycardia has an irregular rhythm, at least three distinct P-wave shapes, and varying PR intervals.

What rhythm is associated with a prolonged QT interval and twisting QRS complexes?

Torsades de pointes is polymorphic ventricular tachycardia associated with a prolonged QT interval; its QRS complexes appear to twist around the baseline.