EKG Interpretation of Complex Arrhythmias Flashcards

An EKG strip shows an irregularly irregular rhythm with no discernible P waves and a variable ventricular rate. What is the most likely interpretation?

Answer: Atrial Fibrillation

Atrial Fibrillation (A-Fib) is characterized by chaotic atrial electrical activity, leading to an irregularly irregular ventricular response and the absence of clear P waves. The baseline may appear chaotic or fibrillatory, which distinguishes it from other rhythms.

On an EKG, you observe a progressively lengthening PR interval until a QRS complex is dropped. Which type of AV block is this?

Answer: Second-degree AV block, Mobitz I (Wenckebach)

Mobitz I, also known as the Wenckebach phenomenon, is a type of second-degree AV block where there is a progressive delay in AV conduction. This is seen on the EKG as a PR interval that gets longer with each beat until a QRS complex is completely blocked or 'dropped'.

A patient's EKG shows a rapid, wide-complex tachycardia with a regular rhythm. What is the most likely life-threatening arrhythmia?

Answer: Ventricular Tachycardia (V-Tach)

Ventricular Tachycardia (V-Tach) is a life-threatening arrhythmia characterized by a rapid heart rate (typically >100 bpm) and wide QRS complexes (>0.12 seconds). It originates in the ventricles and can quickly lead to cardiac arrest if the patient is unstable or pulseless.

Which EKG finding is the hallmark of a third-degree (complete) heart block?

Answer: Complete dissociation between P waves and QRS complexes

In a third-degree AV block, there is no electrical communication between the atria and ventricles. The atria (P waves) and ventricles (QRS complexes) beat independently of each other, resulting in a complete AV dissociation where there is no consistent relationship between P waves and QRS complexes.

An EKG strip displays a regular rhythm with a ventricular rate of 75 bpm. The atrial rate is 300 bpm, and the baseline has a distinct 'sawtooth' appearance. What is this rhythm?

Answer: Atrial Flutter

Atrial Flutter is caused by a re-entrant circuit in the atria, creating rapid, regular atrial depolarizations (flutter waves) that often resemble the teeth of a saw. Not all atrial impulses conduct to the ventricles, resulting in an AV block (e.g., a 4:1 block in this case, 300/75).

What EKG characteristic best describes a Premature Ventricular Contraction (PVC)?

Answer: A wide, bizarre-looking QRS complex that occurs early, not preceded by a P wave

A PVC is an ectopic beat originating from an irritable focus within the ventricles. This results in a premature, wide (>0.12s), and oddly shaped QRS complex because the impulse does not follow the normal conduction pathway. It is not preceded by a P wave and is typically followed by a compensatory pause.

An EKG shows a regular rhythm at a rate of 50 bpm. The QRS complexes are narrow, but P waves are absent or inverted. This rhythm most likely originates from the:

Answer: Atrioventricular (AV) junction

A junctional escape rhythm occurs when the SA node fails to fire, and the AV junction takes over as the pacemaker. Its intrinsic rate is 40-60 bpm, and because the impulse originates in the AV junction, P waves are either absent, inverted (due to retrograde conduction), or buried within the QRS.