EKG Basics Flashcards

In a patient with third-degree (complete) AV block, which statement is true?

Answer: P waves and QRS complexes are completely dissociated

Third-degree AV block means no atrial impulses conduct to the ventricles, causing total P-QRS dissociation.

What is the normal duration of the QRS complex?

Answer: 0.06 to 0.10 seconds

A normal QRS complex lasts between 0.06 and 0.10 seconds (1.5 to 2.5 small boxes).

Which of the following rhythms is most immediately life-threatening and requires defibrillation?

Answer: Ventricular fibrillation

Ventricular fibrillation produces no effective cardiac output and is fatal without immediate defibrillation.

The limb lead aVR records electrical activity from which direction?

Answer: Right shoulder toward the heart

aVR is an augmented unipolar lead that views the heart from the right arm/shoulder perspective.

A patient's EKG shows a P wave before every QRS, but some P waves are not followed by a QRS and the PR interval progressively lengthens. This describes:

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

Wenckebach (Mobitz I) block is characterized by progressive PR prolongation until a QRS is dropped, then the cycle repeats.

Which condition can cause a prolonged QT interval on EKG, predisposing to Torsades de Pointes?

Answer: Hypomagnesemia

Low magnesium levels prolong the QT interval and are a known risk factor for Torsades de Pointes ventricular tachycardia.

When preparing a patient for a 12-lead EKG, the medical assistant should place limb electrodes on:

Answer: Fleshy areas of the arms and legs, avoiding bony prominences

Limb leads are placed on fleshy, non-bony areas of the upper and lower extremities to minimize artifact.