VETM 529 ECG Interpretation Principles

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Questions and Answers

Which of the following is NOT a characteristic of a ventricular premature depolarization (VPD)?

A wide and bizarre QRS complex

A narrow QRS complex (correct)

Premature occurrence compared to the next expected sinus beat

No related P wave

What indicates that a premature beat originates in the ventricle?

A narrow QRS complex

The presence of a P wave

A regular rhythm

A wide and bizarre QRS complex (correct)

What is the difference between a ventricular couplet and a ventricular triplet?

A couplet is a PVC following a normal beat, while a triplet is a PVC following a premature beat

A couplet is two consecutive premature beats, while a triplet is three consecutive premature beats (correct)

A couplet is a PVC occurring during the T wave of the preceding beat, while a triplet is a PVC occurring during the QRS of the preceding beat

A couplet is a single premature beat, while a triplet is two consecutive premature beats

How does the R-on-T phenomenon occur?

The QRS complex of the VPD occurs early enough to land on the T wave of the preceding beat Signup and view all the answers

What is the significance of the slow depolarization during a VPD?

It results in an elongated QRS complex Signup and view all the answers

What is the maximum QRS duration allowed in a dog before being considered a wide QRS complex?

0.06 seconds Signup and view all the answers

What differentiates a uniform VPC from a multiform VPC?

A uniform VPC is a PVC that has a consistent morphology, while a multiform VPC has varying morphologies Signup and view all the answers

What term is widely used for ventricular premature depolarizations in human medicine?

Ventricular premature complexes Signup and view all the answers

What is the primary cause of ventricular premature depolarizations?

Abnormal impulses arising from ventricular tissue Signup and view all the answers

How do VPCs relate to ventricular tachycardia?

VPCs can lead to more serious heart conditions, including ventricular tachycardia. Signup and view all the answers

What is the heart rate in beats per minute (bpm) of a dog with ventricular flutter?

315 bpm Signup and view all the answers

What is the typical ECG characteristic of ventricular tachycardia progressing to ventricular flutter?

Absence of a "shelf" between ventricular beats Signup and view all the answers

Which of the following is the treatment for ventricular fibrillation?

Transthoracic shock Signup and view all the answers

What is the main characteristic of a first-degree AV block?

Prolonged PR interval Signup and view all the answers

What is the main clinical implication of a first-degree AV block?

It is often benign and doesn't cause clinical signs Signup and view all the answers

What is the name of the condition that manifests as "fast V-tach with “sine wave” morphology"?

Ventricular flutter Signup and view all the answers

What is the potential consequence of sustained ventricular tachycardia?

Congestive heart failure (CHF) Signup and view all the answers

Which of the following conditions can lead to weakness or syncope in a dog?

Severe underlying heart disease with a very rapid rate Signup and view all the answers

What condition is likely to increase the risk for ventricular fibrillation?

Ventricular premature depolarizations Signup and view all the answers

Which of the following is NOT a potential cause of ventricular premature complexes (VPCs)?

Bradycardia Signup and view all the answers

When should treatment for ventricular premature complexes be considered?

Evidence of hemodynamic compromise Signup and view all the answers

Which heart rate is indicative of ventricular tachycardia in dogs?

160 bpm Signup and view all the answers

What is a common characteristic of the ECG in ventricular tachycardia?

Wide and bizarre QRS complexes Signup and view all the answers

What is the function of longer-term ECG monitoring in cases of ventricular premature complexes?

To evaluate for occult complexity Signup and view all the answers

Which of the following factors does NOT contribute to the development of ventricular premature complexes?

High cholesterol Signup and view all the answers

Which ECG finding indicates R-on-T phenomenon?

A specific premature ventricular contraction occurring on a T wave Signup and view all the answers

What is the QRS duration typical of normal heart function?

< 0.06 sec Signup and view all the answers

What is the primary clinical significance of a rapid rhythm originating from the ventricles?

It can lead to sudden cardiac arrest. Signup and view all the answers

What is the typical paper speed for electrocardiograms (ECG) in veterinary medicine?

25 mm/sec Signup and view all the answers

Given the information provided, what is the most likely diagnosis for the ECG shown depicting a 6-month-old German Shepherd dog?

Ventricular premature depolarizations Signup and view all the answers

Which of the following is NOT a step in a systematic approach to ECG interpretation?

Assess the morphology of the T-wave Signup and view all the answers

What is the meaning of being able to determine if a rhythm is controlled by the sinus node?

Assessing the electrical conduction pathway within the heart Signup and view all the answers

What is the significance of observing QRS complex morphology in arrhythmia diagnosis?

Distinguishing between atrial and ventricular arrhythmias Signup and view all the answers

What is NOT a criteria of normal sinus rhythm?

Absence of any premature contractions Signup and view all the answers

How can you determine the origin of a premature beat on an ECG?

By the shape and width of the QRS complex Signup and view all the answers

What is a common approach to determining heart rate when analyzing an ECG?

Counting the number of QRS complexes in a 6-second strip and multiplying by 10 Signup and view all the answers

Study Notes

Principles of Electrocardiography

VETM 529, Cardiovascular, Respiratory & Hemolymph Systems II
Approach to arrhythmia diagnosis (continued)
ECG interpretation steps: systematic, note lead and paper speed settings, determine heart rate, check for underlying sinus rhythm, describe/name any rhythm abnormality if sinus rhythm is absent.

Learning Objectives

List and discuss the steps in ECG interpretation
Determine heart rate (with and without a Bic pen) and whether the rhythm is sinus from an ECG.
Define cardiac arrhythmia and normal sinus rhythm.
Identify ECG criteria of a normal sinus rhythm.
Determine whether rhythm is controlled by the sinus node in lead II electrocardiogram.
Contrast QRS complex appearance in patients with supraventricular versus ventricular arrhythmias.
Describe electrocardiographic criteria and associated conditions/diseases for specific arrhythmias.

General Approach to ECG Interpretation

Be systematic
Note lead and paper speed settings (25 mm/sec, 50 mm/sec are common)
Determine heart rate
Assess for underlying sinus rhythm
If not sinus rhythm: describe and name the rhythm abnormality.

Ventricular Premature Depolarizations/Complexes

Abnormal impulses from ventricular tissue
How to determine ventricular origin of abnormal beats: ECG characteristics
- Premature (earlier than the next sinus beat)
- No related P wave
- "Wide and bizarre" QRS
- QRS duration > 0.06 seconds (dog) or > 0.04 seconds (cat)
Abnormal beats can be single, in pairs (couplets) or threes (triplets)
Different morphologies
"R-on-T" phenomenon: QRS of VPC occurs early enough to land on T wave of preceding beat (increases risk of ventricular fibrillation)
Potential causes of VPCs/tachyarrhythmias
- Heart disease
- Electrolyte imbalances (hyper/hypokalemia, etc.)
- Pain, stress, or certain drugs.
- Splenic disease, sepsis, systemic inflammation

Ventricular Tachycardia (V-tach)

Rapid rhythm originating in ventricles.
4 or more VPCs in a row, at a rate of >160 bpm (dogs), >200 bpm (cats), >40 bpm (horses)
ECG characteristics
- QRS "wide and bizarre"
- No associated P waves.
- Rhythm is usually regular.
- May be uniform or multiform.
This is a VERY dangerous rhythm!
- Severe underlying heart disease or very rapid rate can cause weakness or syncope (fainting).
- If sustained, it can lead to congestive heart failure (CHF).

Ventricular Flutter

Fast V-tach with "sine wave" morphology.
No isoelectric "shelf" between ventricular beats.

Ventricular Fibrillation

Fatally dangerous if untreated.
Should always be treated with transthoracic shock.

Atrioventricular (AV) Block

Slowed or blocked conduction between atria and ventricles.
ECG characteristics and clinical implications depend on the severity/degree of block—first-degree, second-degree (Mobitz type I, II), third-degree

1st-degree AV Block

Prolonged PR interval (>normal).
Never causes clinical signs, and doesn't disrupt rhythm.
Benign rhythm associated with high vagal tone or medications that slow AV nodal conduction.

2nd-degree AV Block (Mobitz type I)

Progressive increase in PR interval until a block occurs.

2nd-degree AV Block (Mobitz type II)

No change in PR interval prior to the block; associated with more serious structural heart problems.

2nd-degree AV block in Horses

Extremely common form of AV block.

3rd-degree AV Block

Complete dissociation of atria and ventricles.
No conducted atrial activity.
Atrial depolarizations (P-waves) and ventricular depolarizations (QRS complexes) do not correlate.
Always pathologic, and commonly requires pacemaker implantation.

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Description

Test your understanding of ECG interpretation principles essential for identifying arrhythmias in the cardiovascular system. This quiz covers systematic approaches to ECG analysis, heart rate determination, and differentiation between sinus rhythm and various arrhythmias. Perfect for students in VETM 529!