ECG Final

Myocardial Ischemia Definition

A temporary lack of oxygenated blood flow to the myocardium, characterized on an ECG by ST-segment depression or T-wave inversion.

Myocardial Injury Definition

An advanced stage of localized cell damage due to prolonged lack of blood supply, characterized on an ECG by ST-segment elevation.

Myocardial Infarction (Necrosis) Definition

Irreversible death of heart tissue, characterized on an ECG by the development of pathologic Q waves and symmetrical T-wave inversions.

Pathologic Q Wave Criteria

A Q wave that has a duration of 0.04 seconds or greater, or an amplitude greater than 25% of the succeeding R wave, present in two or more contiguous leads.

Subendocardial Ischemia Pattern

An electrical shift that directs the ST vector inward toward the endocardium, resulting in visible ST-segment depression.

Transmural (Epicardial) Injury Pattern

An electrical shift directing the ST vector outward toward the epicardium, resulting in visible ST-segment elevation.

Anterior MI Lead Group

Leads V1, V2, V3, and V4; typically indicates an occlusion of the Left Anterior Descending (LAD) coronary artery.

Inferior MI Lead Group

Leads II, III, and aVF; typically indicates an occlusion of the Right Coronary Arteries (RCA).

Lateral MI Lead Group

Leads I, aVL, V5, and V6; typically indicates an occlusion of the Circumflex coronary artery.

Posterior MI Reciprocal Changes

Characterized by tall, pathologic R waves, ST-segment depression, and tall upright T waves in leads V1 and V2.

Right Ventricular Infarction Criteria

Identified by ST-segment elevation in the right-sided precordial chest leads V3R through V6R.

Right Bundle Branch Block (RBBB) Diagnostic Leads

Leads V1 and V2; characterized by a wide QRS complex with a classic RSR' (rabbit ears) morphology.

Left Bundle Branch Block (LBBB) Diagnostic Leads

Leads I, aVL, V5, and V6; characterized by a wide QRS complex with a blunted or notched monophasic RR' wave.

Bundle Branch Block QRS Cutoff

The QRS duration must be 0.12 seconds or greater (3 small boxes) to diagnose a complete bundle branch block.

Premature Ventricular Contraction (PVC) Features

A premature, wide, and bizarre QRS complex measuring 0.12 seconds or greater with no associated or preceding P wave.

Ventricular Bigeminy vs Trigeminy

Bigeminy is when every other beat is a PVC; Trigeminy is when every third beat is a PVC.

PVC Couplet

Two premature ventricular contractions occurring consecutively back-to-back.

Ventricular Tachycardia (V-Tach) Rate Range

A rapid ventricular rhythm originating below the His bundle with a rate typically between 150 and 250 bpm.

Precordial QRS Concordance

A hallmark feature of Ventricular Tachycardia where all QRS complexes in chest leads V1 through V6 point in the exact same vertical direction.

Ventricular Fibrillation (V-Fib) Features

Chaotic ventricular depolarization with multiple firing foci, an extremely irregular fibrillatory baseline (300-600 bpm), and zero cardiac output.

Asystole Definition & Protocol

Complete absence of ventricular electrical activity (flatline); must always be verified in a secondary lead to rule out fine Ventricular Fibrillation.

Normal Sinus Rhythm Rate

A regular rhythm originating from the SA node with a rate strictly between 60 and 100 bpm.

Atrial Fibrillation (A-Fib) Rates & Features

Grossly irregular ventricular rhythm with an unmeasurable atrial rate exceeding 400 bpm, showing wavy fibrillatory (f) waves.

Atrial Flutter Rate & Feature

An ectopic atrial rhythm characterized by a classic "saw-tooth" baseline wave pattern with an intrinsic atrial rate of 250 to 350 bpm.

Paroxysmal Atrial Tachycardia (PAT) Rate

A regular, rapid ectopic atrial rhythm with a rate spanning from 150 to 250 bpm.

Idioventricular Rhythm Rate

A slow ventricular escape rhythm with wide, bizarre QRS complexes and an intrinsic rate of 40 bpm or less.

Accelerated Idioventricular Rhythm Rate

A ventricular rhythm with wide QRS complexes and an intrinsic rate between 40 and 110 bpm, commonly seen during an acute MI.

Junctional Escape Rhythm Rate Range

A regular rescue rhythm originating from the AV junction with an intrinsic escape rate of 40 to 60 bpm.

Accelerated Junctional Rhythm Rate Range

A regular junctional rhythm overriding the SA node with an active rate between 60 and 100 bpm.

Junctional Tachycardia Rate Range

A regular rapid junctional rhythm with an active rate exceeding 100 bpm.