Week 4: Basics of EKG Interpretation Flashcards by Daryl Traylor

What is the duration of a small box on EKG paper?

0.04 sec

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What is the duration of a large box on EKG paper?

0.2 sec

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What is the standard speed of EKG paper?

25 mm/sec

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What is the standard voltage of EKG paper?

10 mm/mV

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What is the normal PR interval duration?

0.12–0.20 sec (3–5 small boxes)

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A PR interval greater than 0.20 sec indicates what condition?

1st degree AV block

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What is the normal duration for a QRS interval?

<0.12 sec

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A QRS interval greater than 0.12 sec indicates what conditions?

bundle branch block or ventricular origin

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What is the normal QTc interval duration for men?

<440 ms

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What is the normal QTc interval duration for women?

<460 ms

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An increased QT interval indicates a risk for what?

torsades

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How do you calculate heart rate for a regular rhythm?

300/# of large boxes between R waves

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How do you calculate heart rate for an irregular rhythm?

count QRS in 10 seconds × 6

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What indicates a normal axis in leads I and aVF?

Both positive

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What indicates a left axis deviation (LAD)?

Lead I positive, aVF negative

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What indicates a right axis deviation (RAD)?

Lead I negative, aVF positive

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What is the criteria for left ventricular hypertrophy (LVH)?

S in V1 + R in V5/6 > 35 mm

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What is the criteria for right ventricular hypertrophy (RVH)?

R > S in V1

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What EKG findings are indicative of ischemia/infarction?

ST elevation/depression, T-wave inversions, Q waves

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Which leads correspond to the inferior wall of the heart?

II, III, aVF

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Which coronary artery supplies the inferior wall of the heart?

Right Coronary Artery (RCA)

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Which leads correspond to the lateral wall of the heart?

I, aVL, V5, V6

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Which coronary artery supplies the lateral wall of the heart?

Left Circumflex (LCx)

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Which leads correspond to the septal wall of the heart?

V1, V2

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Which coronary artery supplies the septal wall of the heart?

Left Anterior Descending (LAD)

Which leads correspond to the anterior wall of the heart?

V3, V4

What is the pathophysiology of atrial flutter?

Reentrant circuit in right atrium around tricuspid annulus

What is the typical atrial rate in atrial flutter?

~250–350 bpm

What EKG finding is characteristic of atrial flutter?

Sawtooth flutter waves best in leads II, III, aVF

What is the ventricular rate in atrial flutter with a 2:1 AV block?

~150 bpm

What type of atrial flutter has a counterclockwise circuit?

Typical flutter

What type of atrial flutter has a clockwise or left atrial origin?

Atypical flutter

Atrial fibrillation (AFib) is characterized by what type of electrical activity?

Chaotic atrial electrical activity from multiple reentrant foci

What is the atrial rate in atrial fibrillation?

>350–600 bpm

What EKG findings are seen in atrial fibrillation?

Irregularly irregular QRS complexes, no distinct P waves

What defines paroxysmal AFib?

Terminates spontaneously <7 days

What defines persistent AFib?

>7 days or requires cardioversion

What defines permanent AFib?

Persistent, no attempt to restore sinus rhythm

What is a critical clinical note regarding AFib?

Risk of thromboembolism → CHA₂DS₂-VASc scoring

What is the pathophysiology of ventricular flutter (VFlutter)?

Rapid monomorphic ventricular tachycardia without clear isoelectric intervals

What are the EKG findings for ventricular flutter?

Rapid, wide QRS complexes (~250–300 bpm), sine wave appearance

What is the clinical context of ventricular flutter?

Rarely sustained; often leads to V-fib, medical emergency

What is the pathophysiology of ventricular fibrillation (VFib)?

Multiple disorganized reentrant ventricular circuits

What are the EKG findings for ventricular fibrillation?

Chaotic, irregular baseline, no identifiable P, QRS, or T waves

What is coarse V-fib characterized by?

Larger amplitude fibrillations (>3 mm)

What is fine V-fib characterized by?

Low amplitude (<3 mm); terminal rhythm if prolonged

What is required in a clinical emergency for ventricular fibrillation?

Immediate CPR + defibrillation

What mnemonic can help remember the leads for the inferior wall?

I see inferior things (II, III, aVF)

What mnemonic can help remember the leads for the lateral wall?

L is for Lateral: I, aVL, V5, V6

What mnemonic can help remember the leads for the anterior wall?

V3, V4—face of the heart

What mnemonic can help remember the leads for the septal wall?

V1, V2 in the middle

Atrial fibrillation is characterized by what kind of rhythm?

Irregularly irregular

What are AV blocks?

Conduction delays or failures between the atria and ventricles caused by pathology in the AV node, His bundle, or infra-Hisian system.

What is the primary mechanism of First-degree AV block?

Prolonged conduction, no dropped beats.

Where does Mobitz I (Wenckebach) occur?

AV node.

What characterizes Mobitz II?

Sudden failure of conduction.

What is the primary mechanism of Third-degree AV block?

Complete dissociation between atrial and ventricular activity.

What is the EKG finding for First-degree AV block?

PR interval >200 ms; every P wave is followed by a QRS.

What can cause First-degree AV block?

Medications, increased vagal tone, ischemia.

What is the management for First-degree AV block?

Usually benign, no treatment required.

What is the EKG finding for Mobitz I (Wenckebach)?

Progressive PR lengthening followed by a dropped QRS.

How does Mobitz I affect rhythm?

Regularly irregular rhythm.

What is the pathophysiology of Mobitz I?

AV nodal fatigue leads to increasing delay until impulse fails to conduct.

What is the management for Mobitz I?

Usually benign if asymptomatic; remove causative medications.

What characterizes Mobitz II EKG findings?

Constant PR intervals with intermittently dropped QRS complexes.

Where does Mobitz II typically occur?

Below the AV node, at the bundle of His or bundle branches.

What is the management for Mobitz II?

Unstable/serious; requires permanent pacemaker.

What is the EKG finding for Third-degree AV block?

No relationship between P waves and QRS complexes (AV dissociation).

What is the pathophysiology of Third-degree AV block?

Complete failure of AV conduction; atria and ventricles depolarize independently.

What is the management for Third-degree AV block if hemodynamically unstable?

Atropine and temporary pacing, followed by permanent pacemaker.

What differentiates the PR interval of First-degree AV block?

Prolonged, constant.

What differentiates the PR interval of Mobitz I?

Progressively lengthens.

What differentiates the PR interval of Mobitz II?

Constant.

What differentiates the PR interval of Third-degree block?

Variable.

What is the risk associated with Mobitz II?

High risk of complete block.

What is the treatment for Mobitz II?

Pacemaker.

True or False: Mobitz I improves with exercise.

True.

True or False: Mobitz II improves with atropine.

False.

What type of MI is likely to cause Mobitz I?

Inferior MI (RCA).

What type of MI is more likely to cause infranodal blocks?

Anterior MI (LAD).

Fill in the blank: Wenckebach = ______.

Wenches drop in the AV node.

Fill in the blank: Mobitz II = ______.

More badness down below.