ECG Interpretation and Practice Review

A comprehensive set of 100 practice flashcards covering EKG interpretation, cardiac rhythms, heart blocks, and coronary localization based on Dr. Miriam Cires' lecture notes.

What is the scale of the X-axis (horizontal) on EKG paper?

Time ($25\,mm/sec$)

What is the scale of the Y-axis (vertical) on EKG paper?

Voltage ($10\,mm/mV$)

Which segment is considered a better baseline for EKG analysis than the PR segment?

The TP segment

Is cardiac arrest essentially an electrical problem or a circulation problem?

An electrical problem

Is a heart attack (myocardial infarction) essentially an electrical problem or a circulation problem?

A circulation problem

Which condition occurs when the heart malfunctions and stops beating unexpectedly because of an arrhythmia?

Cardiac arrest

What occurs when blood flow to the heart is blocked, preventing oxygen-rich blood from reaching cardiac tissue?

A heart attack

What are the three common heart attack symptoms specific to women mentioned in the notes?

Shortness of breath, nausea/vomiting, and back or jaw pain

Approximately how many out-of-hospital cardiac arrests occur annually in the United States?

$$360,000$$

What are the common first steps to treat cardiac arrest?

Call 9-1-1, start CPR, and use an Automated External Defibrillator (AED)

What is the normal conduction pathway starting from the SA Node?

SA Node to Internodal Pathways to AV Node to Common Bundle of His to Bundle Branches to Purkinje Fibers

What is the name of the specialized tract that transmits impulses through the inter-atrial septum?

Bachmann bundle

What are the names of the three internodal pathways found in the right atrium?

Anterior, Middle, and Posterior

What is the inherent pacing rate of the SA Node (NSR)?

$$60 - 100\,bpm$$

What is the inherent pacing rate of the atrial foci?

$$60 - 80\,bpm$$

What is the inherent pacing rate of the junctional foci?

$$40 - 60\,bpm$$

What is the inherent pacing rate of the ventricular foci?

$$20 - 40\,bpm$$

In ECG Phase 0, what ION influx causes ventricular depolarization?

Fast $Na^+$ channel influx

What happens during ECG Phase 1 (initial rapid repolarization)?

Closing of fast $Na^+$ channels and introduction of $Cl^-$ into the cell

Which ions balance inflow and outflow during Phase 2 (Plateau stage)?

Slow $Na^+$ and $Ca^{++}$

What occurs during ECG Phase 3 (Repolarization)?

$K^+$ channels open and escape the cell, while $Ca^{++}$ channels close

What mechanism moves ions in Phase 4 (Recover phase)?

The Na-K ATP pump moves $Na^+$ out and $K^+$ into the myocyte

Which limb lead provides a view of the inferior wall of the Left Ventricle (LV)?

Lead II

How many seconds of time are indicated by 15 big boxes on a rhythm strip?

$$3\,\text{seconds}$$

What are the six precordial (chest) leads?

$$V_1, V_2, V_3, V_4, V_5, V_6$$

Which cardiac structures are NOT visualized well by standard chest leads?

The right ventricular wall and the left ventricle posterior wall

In an EKG, what type of deflection occurs when current flows TOWARD the lead arrows?

Upward deflection

In an EKG, what type of deflection occurs when current flows AWAY from the lead arrows?

Downward deflection

What deflection occurs when current flows perpendicular to the axis of the lead?

No deflection

Which leads comprise the horizontal plane (axis rotation) in a 12-lead ECG?

The chest or precordial leads

Which leads comprise the frontal plane (axis deviation) in a 12-lead ECG?

The extremity or limb leads

Which leads are used to localize an inferior wall infarct?

II, III, and aVF

Which artery is typically associated with the lateral wall leads (I, aVL, V5, V6)?

Left Circumflex artery (LCx)

Which artery is localized using the septal (V1, V2) and anterior (V3, V4) leads?

Left Anterior Descending artery (LAD)

What is the formula to calculate heart rate for a regular rhythm using large squares?

$$300 / (\text{number of large squares in an R-R interval})$$

What is the heart rate if there are 4 large squares in an R-R interval?

$$75\,bpm$$

How do you calculate heart rate for an irregular heart rhythm?

Count complexes on a 10-second rhythm strip and multiply by 6

What is defined as a heart rate greater than $100\,bpm$?

Tachycardia

What is defined as a heart rate less than $60\,bpm$?

Bradycardia

What is an 'irregularly irregular' rhythm?

A rhythm that is completely disorganized

What diagnosis is suggested if P waves are absent and the rhythm is irregular?

Atrial fibrillation

What is the normal duration for the PR interval?

$120 - 200\,ms$ (3-5 small squares)

What does a prolonged PR interval ($> 200\,ms$) suggest?

Atrioventricular delay (AV block)

How is First-degree heart block characterized on an EKG?

A fixed prolonged PR interval ($> 200\,ms$)

What is the characteristic EKG pattern of Mobitz type 1 (Wenckebach) AV block?

Progressive prolongation of the PR interval until a QRS complex is dropped

What is the characteristic EKG pattern of Mobitz type 2 AV block?

A consistent PR interval duration with intermittently dropped QRS complexes

What characterizes Third-degree heart block (Complete block)?

Presence of P waves and QRS complexes with no association (complete dissociation)

What is the origin of narrow-complex escape rhythms ($< 0.12\,seconds$)?

Above the bifurcation of the bundle of His

What is the origin of broad-complex escape rhythms ($> 0.12\,seconds$)?

Below the bifurcation of the bundle of His

Where is the anatomical location of a Mobitz I (Wenckebach) block?

In the AV node

Where is the anatomical location of a Mobitz II block?

After the AV node in the bundle of His or Purkinje fibers

A delta wave on an EKG is a sign of what?

Early ventricular activation through an accessory pathway

What two things are required for a diagnosis of Wolff-Parkinson-White syndrome?

Evidence of tachyarrhythmias and a delta wave

What defines a 'narrow' QRS complex?

$$< 0.12\,seconds$$

What defines a 'broad' QRS complex?

$$> 0.12\,seconds$$

Why does a bundle branch block result in a broad QRS complex?

The impulse travels rapidly to one ventricle and then spreads slowly across the myocardium to the other

What is the threshold for 'small' QRS complexes in limb leads?

$$< 5\,mm$$

What is the threshold for 'small' QRS complexes in chest leads?

$$< 10\,mm$$

What do tall QRS complexes typically imply?

Ventricular hypertrophy

Name one index used for measuring Left Ventricular Hypertrophy (LVH) on an EKG.

Sokolow-Lyon index (or Cornell index)

What defines a pathological Q wave?

$> 25\%$ of the R wave size or $> 2\,mm$ in height and $> 40\,ms$ in width

What does a single pathological Q wave in isolation mean?

Usually not a cause for concern; look for them across an entire territory

Where should the transition from S > R wave to R > S wave occur in the chest leads?

$V_3$ or $V_4$

What should be the appearance of the ST segment in a healthy individual?

Isoelectric (at the baseline)

What is the 'J point'?

The point where the S wave joins the ST segment

What is 'High take-off' also known as?

Benign early repolarization

At what age is ischemia more likely than benign early repolarization for ST elevation?

Over the age of 50

In Benign early repolarization, what change happens to the T waves?

The T waves are raised

In a STEMI, how does the T wave size compare to the ST segment elevation initially?

The T wave remains the same size while the ST segment is raised

What is the criteria for significant ST-elevation in limb leads?

Greater than $1\,mm$ in 2 or more contiguous leads

What is the criteria for significant ST-elevation in chest leads?

Greater than $2\,mm$ in 2 or more leads

What is the primary cause of acute ST-elevation?

Full-thickness myocardial infarction

What amount of ST depression indicates myocardial ischemia?

$\geq 0.5\,mm$ in $\geq 2$ contiguous leads

What are the criteria for 'tall' T waves?

$> 5\,mm$ in limb leads and $> 10\,mm$ in chest leads

Which condition is classically associated with 'tall tented T waves'?

Hyperkaliemia (Hyperkalemia)

In which lead is T wave inversion considered a normal finding?

Lead $V_1$ (and Lead III as a variant)

Name three conditions where non-specific T wave inversion may be seen.

Ischemia, Bundle branch blocks, and Pulmonary embolism

What do biphasic T waves look like?

They have two peaks

What can biphasic T waves indicate?

Ischemia and hypokalemia

Flattened T waves are non-specific but may represent what two conditions?

Ischemia or electrolyte imbalance

What is a U wave?

A deflection $> 0.5\,mm$ after the T wave, best seen in $V_2$ or $V_3$

When do U waves become larger?

The slower the bradycardia

List three causes of visible U waves.

Electrolyte imbalances, hypothermia, and antiarrhythmic therapy

What are the very first EKG changes seen during a STEMI, though rarely captured?

Hyperacute T waves

Why do hyperacute T waves appear during STEMI?

Localized hyperkalemia

What EKG abnormality is present in Atrial fibrillation?

Absent P waves and irregular rhythm

Junctional or Nodal rhythms typically have what heart rate characteristic?

Slow rate

What is the heart rate characteristic of Ventricular rhythms like V-tach?

Fast rate or absent

What is classified as a first-degree heart block in terms of conduction transmission?

Delayed current transmission between atria and ventricles

Which dysrhythmias are categorized under atrial rhythms?

Atrial fibrillation, Atrial flutter, and Atrial tachycardia

Which lead shows R wave progression from small to large?

Chest leads ($V_1$ to $V_6$)

What is the definition of narrow-complex escape rhythms?

QRS complexes of $< 0.12\,seconds$ duration

Which piece of conductive tissue exhibits the ability to conduct at different speeds?

The AV node

Where does the impulse originate in an atrial ectopic beat?

The atrium, resulting in a narrow QRS

How long is a typical EKG rhythm strip?

$$10\,\text{seconds}$$

If the heart rate is calculated at $98\,bpm$ and QRS is $114\,ms$, is the rate tachycardia?

No (it is normal, as tachycardia is $> 100\,bpm$)

What is the QRS duration limit mentioned in the case study of the 41-year-old?

$$126\,ms$$

What suspected diagnosis is associated with 'giant' T-wave inversion in leads I and V4-6 in a younger patient?

Apical hypertrophic cardiomyopathy (HCM)

What is the normal troponin level limit mentioned in the patient case study?

$$< 26\,ng/L$$

Which lead axis results in an upward deflection if the current is flowing parallel to it?

The lead axis the current is flowing toward