EKG Lecture Notes

A set of flashcards covering key concepts, definitions, and terms related to EKG interpretation.

P wave

Represents depolarization of the atrial myocardial cells.

Depolarization

The process that causes a change in the electrical charge of a cell, making it less negatively charged than its environment.

QRS complex

Represents depolarization of the ventricular myocardial cells.

T wave

Represents repolarization of the ventricular myocardial cells.

PR interval

Represents the time from the beginning of atrial depolarization to the beginning of ventricular depolarization, measured from the beginning of the P wave to the beginning of the QRS complex.

J point

The point where the QRS complex ends and the ST segment begins.

ST segment

Represents the time between the end of ventricular depolarization and the beginning of ventricular repolarization.

QT interval

Measured from the beginning of the QRS complex to the end of the T wave, encompassing the time from ventricular depolarization to the end of repolarization.

Atrial Fibrillation

Characterized by a grossly irregular rhythm and absence of discernible P waves.

Mobitz type I

A form of second-degree AV block where PR intervals progressively lengthen until a QRS complex is dropped.

Mobitz type II

A form of second-degree AV block where PR intervals are consistent but some P waves do not conduct.

Ventricular Tachycardia

A rapid heartbeat originating from the ventricles, characterized by a wide QRS complex.

Defibrillation

The use of electric shock to restore a normal heart rhythm in a pulseless patient.

Sinoatrial (SA) node

The primary pacemaker of the heart, generating a normal intrinsic rate of 60-100 bpm.

Atrial Tachycardia

A rapid heart rhythm originating from the atria, often with consistent P waves before each QRS complex.

Superior wall MI

Myocardial infarction that primarily affects the anterior wall of the heart, typically indicated by ST elevations in leads V1 to V4.

Cardioversion

A medical procedure that restores a normal heart rhythm in people with arrhythmias.

Acute Coronary Syndrome (ACS)

A range of conditions associated with sudden, reduced blood flow to the heart, which includes myocardial infarction.

Ectopy

The occurrence of extra heartbeats originating from abnormal electrical impulses.

RIGHT CORONARY ARTERY LEADS

"LEADS II AND III AND AVF (augmented vector foot)" VIEW THE INFERIOR WALL. POSTERIOR WALL

LEFT ANTERIOR DESCENDING ARTERY LEADS

LEADS V1 AND V2" VIEW SEPTAL AND LATERAL WALLS.

LEFT ANTERIOR DESCENDING ARTERY

"LEADS V3 AND V4" VIEW THE ANTERIOR WALL.

CIRCUMFLEX

"LEADS I AND V5 AND V6 AND AVL (augmented vector left)" VIEW THE LATERAL WALL.

EACH LITTLE BOX =

.04 SECONDS

5 BOXES (1 BOLD BOX) =

.20 SECONDS

NARROW QRS

• ORIGINATE FROM THE ATRIA

• <3 SMALL SQUARES / <.12

WIDE QRS

• ORIGINATE FROM THE VENTRICLES

• >3 MORE SQUARES / >.12

ATRIAL FLUTTER

SPEED

“SAWTOOTH”

A Single Rogue Loop (Atrial Flutter): One spot in the atrium is firing in a perfect, high-speed circle.

In Atrial Flutter, the electricity gets caught in a re-entry circuit

The QRS: Usually narrow (< 0.12s) because once the signal passes the AV node, it uses the "high-speed expressway."

The Ratio: This is where the "Bouncer" (AV Node) comes in. You will see a consistent ratio, like 2:1, 3:1, or 4:1.

ATRIAL FIBRILLATION (THE "DEATH SHIVER" 💀) A-FIB - TOP OF THE HEART (CHOAS)

• CARDIAC OUTPUT = ZERO. 🛑

• Multiple Rogue Spots (Atrial Fibrillation): Hundreds of tiny spots are firing all at once, creating a "quivering" effect.

  • Total Chaos: There are no QRS complexes. No P-waves. No T-waves.

  • The Visual: It looks like a jagged, shaky line. It can be "Coarse" (big waves) or "Fine" (tiny waves).

• In textbooks, you'll see it called "Disorganized Electrical Activity," but "Death Shiver" captures the mechanical reality: the heart muscle is shivering so fast and so chaotically that it's consuming oxygen but producing zero stroke volume.

• The "A-Fib TRAP”

  • "Here is a firm nudge for the OR: If your patient flips into A-Fib and their BP drops, do not reach for the Cardizem first. Cardizem is a Calcium Channel Blocker—it slows the heart, but it also decreases contractility (negative inotrope) and causes vasodilation. If they are already hypotensive, Cardizem might 'fix' the rhythm but 'kill' the pressure. Stabilize the pressure first with a pressor (like Neo-Synephrine) before you slow the rate."

V-FIB - BOTTOM OF THE HEART

• SHOCKABLE W/O PULSE

  • FLOPPING AROUND LIKE A SHOELACE

V-TACH

• V-TACH WITH A PULSE = CARDIOVERSION

• SHOCKABLE W/O PULSE

• THE LOOK: IT LOOKS LIKE A SERIES OF WIDE, UNIFORM "MOUNTAINS" OR TOMBSTONES. V-TACH TOMBSTONES BECAUSE THEY HAVE BIG “ARCH”

• THE WIDTH: THE QRS IS WIDE (>0.12s).

  • CLINICAL NUDGE: WHY IS IT WIDE? BECAUSE THE SIGNAL IS STARTING IN THE "BACKWOODS" OF THE VENTRICLE MUSCLE. IT DOESN'T HAVE ACCESS TO THE HIGH-SPEED PURKINJE EXPRESSWAY, SO THE ELECTRICITY HAS TO CRAWL THROUGH THE MUSCLE CELL-TO-CELL. THAT SLOW TRAVEL TIME CREATES A WIDE WAVE.

• Cardiac Output drops. The heart is beating so fast it's basically just "vibrating" with a little bit of squeeze, leading to a massive drop in blood pressure.