Cardiac Conduction, ECG & ABG Study Guide

This set of flashcards covers cardiac conduction, ECG waveforms, common arrhythmias, emergency treatments, and arterial blood gas (ABG) procedures based on the study guide.

SA Node (Sinoatrial Node)

The heart's natural pacemaker located in the right atrium that initiates electrical impulses and causes atrial depolarization with a normal rate of $60-100\,bpm$.

AV Node (Atrioventricular Node)

The structure that delays the electrical impulse to allow ventricles to fill; it has an intrinsic backup rate of $40-60\,bpm$.

P wave

The part of an ECG representing atrial depolarization.

PR interval

The period representing the impulse traveling from the atria through the AV node toward the ventricles, normally measuring $0.12-0.20\,seconds$ or $3-5$ small boxes.

QRS complex

The part of an ECG representing ventricular depolarization.

ST segment

The phase where ventricles are completely depolarized and early repolarization begins; elevation can indicate acute myocardial injury or STEMI.

T wave

The part of an ECG representing ventricular repolarization.

First-degree AV block

A condition defined by a constant PR interval greater than $0.20\,sec$ where every P wave still produces a QRS complex.

Bradycardia

A heart rate less than $60\,bpm$, which may require treatment with Atropine if the patient is symptomatic.

Atrial flutter

A rhythm characterized by classic sawtooth flutter waves and an atrial rate commonly around $300/min$.

Modified Allen Test

A test performed before a radial artery ABG to check collateral blood flow to the hand via the ulnar artery.

Radial artery ABG angle

The typical puncture angle for the preferred radial site, which is $30-45^{\circ}$.

Brachial artery ABG angle

The typical puncture angle for an ABG at the brachial site, which is $45-60^{\circ}$.

Femoral artery ABG angle

The typical puncture angle for an ABG at the femoral site, which is $90^{\circ}$.

Third-Degree / Complete Heart Block

A state where electrical communication between atria and ventricles is completely blocked, causing P waves and QRS complexes to occur independently.

PVC (Premature Ventricular Contraction)

An early, wide, and bizarre ventricular beat originating outside the normal pathway, usually without a preceding P wave.

Ventricular Fibrillation (VF)

A chaotic, pulseless waveform with no organized QRS; this is a shockable rhythm treated with CPR and immediate defibrillation.

Asystole

A near-flat line on an ECG indicating no ventricular electrical activity; it is non-shockable and treated with CPR and epinephrine.

Atrial fibrillation

An irregularly irregular rhythm with no consistent P waves and an irregular ventricular response.

Supraventricular Tachycardia (SVT)

A rapid rhythm occurring above the ventricles, usually regular with a narrow QRS and a rate commonly between $150-250\,bpm$.

Adenosine

A medication used for stable regular narrow-complex SVT after vagal maneuvers.

Synchronized cardioversion

The indicated treatment for unstable tachycardia.