EKG Fundamental Concepts and Interpretation

Flashcards covering EKG basics, including intervals, axis determination, chamber enlargement, bundle branch blocks, and electrolyte abnormalities based abnormalities.

What is the time value represented by 1 small box and 5 small boxes on an EKG tracing?

1 small box = $0.04\text{ seconds}$ and 5 small boxes = $0.2\text{ sec}$.

How is a normal QRS axis determined using Lead I and Lead aVF?

If the main deflection (net polarity) of the QRS is positive ($+$) in Lead I and positive ($+$) in Lead aVF, the axis is normal ($0\text{ to } +90^{\circ}$).

What are the primary EKG findings for Right Atrial Enlargement (RAE)?

Tall, narrow, peaked P-waves in lead II and biphasic P-waves in V1 with an amplitude $\ge 2$ small boxes.

What characterizes Left Atrial Enlargement (LAE) in Lead II and Lead V1?

Wide, notched P-waves in lead II ($> 3$ small boxes) and a terminal component of a biphasic P-wave in lead V1 that is $|> 1\times 1$$ small box wide/deep.

What is the standard measurement for a normal PR interval, and what does a value $> 0.20\text{ sec}$ indicate?

The normal PR interval is $0.12 - 0.20\text{ sec}$; a fixed value $> 0.20\text{ sec}$ indicates 1st degree AV block (AVB).

How does Mobitz II (Type II 2nd-degree AVB) differ from Mobitz I (Wenckebach) regarding the PR interval?

In Mobitz II, the PR interval remains fixed (constant) before a dropped QRS, whereas in Mobitz I, the PR interval progressively lengthens before a drop.

What is the 'Rabbit Ears' morphology, and in which lead is it diagnostic?

It is the R-S-R' QRS morphology found in Lead V1, which is characteristic of Right Bundle Branch Block (RBBB).

What is the characteristic QRS morphology of Left Bundle Branch Block (LBBB) in leads I, aVL, V5, and V6?

A broad R-R' ("mu"-shaped or "M"-shaped) morphology.

According to the 'Rule of Thumb,' how is a normal QT interval estimated?

It should be less than $\frac{1}{2}$ of the preceding RR interval when the heart rate is between $65-90\text{ bpm}$.

What are the components of the 'S1-Q3-T3' EKG finding associated with Pulmonary Embolism (PE)?

A deep S-wave in lead I, a Q-wave in lead III, and an inverted T-wave in lead III.

What criteria for ST elevation suggest an acute MI in the limb and precordial leads?

ST elevation $> 1\text{ mm}$ in limb leads and $> 2\text{ mm}$ in precordial (chest) leads.

What are the differences between T-waves in hyperkalemia and hypokalemia?

Hyperkalemia presents with pointy T-waves with a narrow base and sharp apex, while hypokalemia presents with flat T-waves and potentially prominent U-waves.

What is the 'delta wave' on an EKG, and what syndrome does it indicate?

A 'delta wave' is a slurring of the upstroke of the QRS complex, which indicates Wolff-Parkinson-White (WPW) syndrome.

What voltage criteria in leads V1 and V5 or V6 define Left Ventricular Hypertrophy (LVH)?

Sum of S-wave depth in V1 and R-wave height in V5 or V6 $> 35\text{ mm}$ amplitude.

What is the EKG hallmark of Wellens syndrome, and what does it signify?

Marked T-wave inversions (TWI) in leads V2 and V3, signifying critical stenosis of the LAD (left anterior descending artery).