Veterinary Cardiology Quiz

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Questions and Answers

Which of the following is NOT a criterion for treating ventricular premature complexes (VPCs)?

R-on-T phenomenon

Multiformity

Underlying heart disease (correct)

Ventricular tachycardia

A heart rate greater than 250 beats per minute in a dog can lead to:

Increased risk of sudden death

Congestive heart failure

Ventricular fibrillation

All of the above (correct)

What is the significance of a single ventricular premature complex (VPC)?

It is likely to cause sudden death.

It is always indicative of underlying heart disease.

It does not usually cause clinical signs or increase the risk of sudden death. (correct)

It can lead to immediate clinical signs like weakness and syncope.

What is the recommended approach for managing a patient with documented VPCs but no other clinical signs?

Consideration of longer-term ECG monitoring. Signup and view all the answers

What is the first step in a systematic approach to ECG interpretation?

Note the lead and paper speed settings. Signup and view all the answers

What is the most common approach to rate control in dogs and cats?

Oral antiarrhythmics Signup and view all the answers

Which ECG characteristic is NOT typically associated with a ventricular premature depolarization (VPD)?

Narrow QRS complex Signup and view all the answers

What is the typical width of a QRS complex for a ventricular premature depolarization (VPD) in a dog?

Greater than 0.06 seconds Signup and view all the answers

What is the term commonly used in human medicine to describe a premature ventricular complex (PVC)?

Premature ventricular contraction Signup and view all the answers

What is the ECG characteristic that describes a QRS of a VPC occurring early enough to land on the T wave of the preceding beat?

R-on-T phenomenon Signup and view all the answers

Which statement regarding ventricular premature depolarizations (VPDs) is NOT correct?

VPDs always indicate a serious heart condition Signup and view all the answers

What is the significance of identifying VPCs on an ECG?

VPCs can be a precursor to more serious arrhythmias and warrant further evaluation Signup and view all the answers

What is the term used to describe when two consecutive VPCs occur?

Couplet Signup and view all the answers

What occurs when a wavefront of negative charges moves directly toward an electrode in parallel with the lead axis?

It leads to the largest possible deflection. Signup and view all the answers

In a normal cardiac activation sequence, which structure is activated immediately after the SA node?

Atrial muscle Signup and view all the answers

How is the recording lead axis related to the origin of a wavefront during depolarization?

The axis must be parallel to the wavefront for maximal deflection. Signup and view all the answers

Which electrode is treated as positive in the provided depolarization diagram?

Lead A Signup and view all the answers

What type of charge does the membrane outside of the cell exhibit at rest?

It is positively charged. Signup and view all the answers

What is the heart rate threshold that may indicate severe underlying heart disease or syncope in dogs?

250 bpm Signup and view all the answers

What is the potential fatal progression from ventricular tachycardia?

Ventricular fibrillation Signup and view all the answers

In a first-degree AV block, what is the characteristic ECG finding?

Prolonged PR interval Signup and view all the answers

What treatment is indicated for ventricular fibrillation?

Trans-thoracic shock Signup and view all the answers

Which of the following is true about first-degree AV block?

It is usually benign. Signup and view all the answers

What is a potential consequence of sustained ventricular tachycardia?

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

What is NOT a characteristic of ventricular flutter?

Regular rhythm Signup and view all the answers

What is the normal threshold for the PR interval in a healthy dog?

0.20 sec Signup and view all the answers

At a paper speed of 50 mm/sec, how long does it take to cover the length of a standard Bic pen (150 mm)?

3 seconds Signup and view all the answers

To calculate heart rate using QRS complexes in a 3-second period at 25 mm/sec, how many beats will result from 5 QRS complexes?

100 beats/minute Signup and view all the answers

What is the criterion for determining a consistent PR interval in sinus rhythm?

P is consistently linked to QRS complexes Signup and view all the answers

If 11 QRS complexes are observed within the pen length at 25 mm/sec, what is the corresponding heart rate?

110 beats/minute Signup and view all the answers

Which condition indicates the presence of an underlying sinus rhythm?

Presence of positive P waves in lead II Signup and view all the answers

At what paper speed does a big box (5 mm) equal 0.1 seconds?

50 mm/sec Signup and view all the answers

How should P waves appear in lead II to indicate正常心律when originating from the sinus node?

Positive and consistent Signup and view all the answers

What multiplication factor is used to determine heart rate when calculating based on a 3-second count at 50 mm/sec?

20 Signup and view all the answers

What is defined as any alteration in the rate, regularity, or normal sequence of electrical activation of the heart?

Arrhythmia Signup and view all the answers

Which arrhythmia is specifically noted for causing loss of atrial-ventricular synchrony?

Atrial fibrillation Signup and view all the answers

What effect does a super fast heart rate have on stroke volume?

Decreases stroke volume Signup and view all the answers

What is a possible consequence of sustained very slow heart rhythms?

Hypotension Signup and view all the answers

Which of the following is NOT a category of bradyarrhythmias?

Atrial fibrillation Signup and view all the answers

Which characteristic is typical of a ventricular origin arrhythmia?

Wide and bizarre QRS complex Signup and view all the answers

What heart rhythm is associated with inadequate cardiac output during physical exertion?

Bradycardia Signup and view all the answers

Which of the following potentials can cause clinical signs and cardiac injury?

Arrhythmias Signup and view all the answers

What represents a common origin of supraventricular arrhythmias?

Atria or AV junction Signup and view all the answers

What is a distinct feature of a normal QRS complex generated by the sinus node?

Skinny and upright in lead II Signup and view all the answers

Signup and view all the answers

Study Notes

Electrocardiography Principles

Electrocardiography (ECG or EKG) records the heart's electrical activity from the body surface.
ECG records extracellular signals resulting from depolarization/repolarization waves through cardiac myocytes.
The graph depicts voltage (mV, y-axis) over time (sec, x-axis).
Changes in voltage are recorded as waves/complexes, using letters (e.g., P, QRS, T).

Learning Objectives

Students will be able to label the ECG's x- and y-axes.
Students will be able to describe cell surface events during upward ECG deflections.
Students will be able to list the normal cardiac activation sequence from memory.
Students will be able to describe the conduction velocity for each component of the cardiac conduction system.
Students will be able to determine if normal pacemaker activity is expected for each component.
Students will be able to describe a 6-lead ECG recording method in a dog and a base-apex ECG in a horse.
Students will be able to mark individual ECG waves and explain the correlated cellular events.

Physiology Review: Cardiac Electrophysiology

At rest, cardiac myocytes are polarized (membrane negatively charged - inside vs. outside).
Stimulation causes resting myocytes to depolarize (membrane polarity reverses).
Depolarization spreads as a wave, stimulating adjacent cells.
Extracellular currents associated with the depolarization wave are detected by the ECG.
Cells must repolarize to allow the cycle to repeat.

ECG Electrodes

ECG electrodes placed on either side of a depolarization wave allow measurement of the electrical field.
By convention, if a wavefront of negative extracellular charges moves toward the positive electrode, an upward deflection is recorded on the ECG.

Effect of Depolarization Wavefront Orientation

When a wavefront moves directly toward an electrode in parallel with the lead axis, the largest possible deflection is recorded.

Normal Cardiac Conduction System

The sinoatrial (SA) node is the primary pacemaker, setting the heart rate at ~60-250 impulses/minute for most species
The sinoatrial (SA) node initiates the electrical impulse at approximately 60-250 beats (impulses) per minute in most species.
The atrioventricular (AV) node slows conduction to allow the atria to empty into the ventricles before ventricular contraction.
The His-Purkinje system rapidly distributes the depolarization wave through the ventricles.

Method for Recording a 6-Lead Surface ECG in Small Animals

Patients are placed in right lateral recumbency.
Limbs are positioned parallel to each other, perpendicular to the trunk.
Electrodes are placed on the elbows (white/black) and stifles (red/green) to avoid contact with the trunk and each other.

Method for Recording a Base-Apex ECG in Horses and Ruminants

No universal lead system exists.
Position electrodes over the right jugular furrow (white) and left apex beat (black).
Lead axis is oriented cranio-caudally (head to tail).

The Normal (Lead II) ECG Tracing

Depolarization waves are shown as blue regions on ECG diagrams with corresponding arrows showing the direction of depolarization.

Electrical Correlates of ECG Waves/Intervals

P wave: Atrial depolarization (positive in lead II); often bifid (M-shaped) in some species.
PR interval (PQ interval): Atrial, AV node, and Bundle of His depolarization; approximately 0.13 seconds in dogs and 0.09 seconds in cats.
QRS complex: Ventricular depolarization (typically tall, skinny and upright in lead II for small animals); typically under 0.06 seconds in dogs and 0.04 seconds in cats
ST segment: All ventricular cells depolarized, no current flow (isoelectric line connecting the S and T waves).
T wave: Ventricular repolarization (can be negative, positive, or biphasic).

Normal Base-Apex ECG in Horses/Ruminants

Bifid P waves are common in horses.
Negative QRS complexes are normal in horses/ruminants.

Sinus Arrhythmia

The sinus rhythm is characterized by cyclic slowing and speeding, commonly linked with respiration.
This is a normal finding in dogs and fit horses but is uncommon in clinical feline cases

Sinus Tachycardia

Tachycardia is defined by a sinus rhythm with a rapid heart rate.
Rate cutoffs for tachycardia diagnosis vary by species

Atrial Fibrillation (A-fib)

Characterized by irregular, "sawtooth" baseline (no P waves).
Supraventricular QR complexes are narrow and upright in lead II.
Irregularly irregular rhythm (no pattern in R-R intervals).
Rapid heart rate.

Atrioventricular (AV) Block

Conduction between atria and ventricles inhibited at the AV node (resulting in a dissociation between P-wave and QRS complex activity)

1st-Degree AV Block

Characterized by a lengthened PR interval (and no other clinical or rhythm disturbances).

2nd-Degree AV Block

Types I and II are characterized by differing degrees of AV nodal block (Type I AV block demonstrates progressive prolongation of PR interval prior to the complete interruption from the AV node) with clinical significance (or lack thereof), depending on the degree.

3rd-Degree AV Block

Complete dissociation of atrial and ventricular excitation (separate, unrelated rhythms).

Ventricular Premature Depolarizations/Complexes

Premature ventricular complexes (VPCs) occur early during the cardiac cycle, before the next expected sinus beat.
The QRS complexes are wide and bizarre and lack a related P wave
Characterized by wide/bizarre QRS complexes lacking a related P wave and may be associated with several specific underlying conditions.
"R-on-T phenomenon" occurs when a VPC lands on the T wave of the proceeding beat, increasing ventricular fibrillation risk.

Ventricular Tachycardia (V-tach)

Characterized by four or more consecutive VPCs at a rate exceeding 160 beats per minute in dogs, 200 beats per minute in cats, or 40 beats per minute in horses.
QRS complexes are wide and bizarre; no related P waves.
The rhythm is usually regular (consistent interval between beats)
Ventricular tachycardia is a potentially fatal and very dangerous rhythm.

Ventricular Flutter

A rapid rhythm with characteristic "sine wave" morphology, lacking isoelectric periods between beats, originating from the ventricles.

Ventricular Fibrillation

Extremely disorganized, chaotic ventricular activity, typically lethal if untreated.

Additional notes

The provided study notes are based on the information you shared.
The diagrams provide visual aids, but the content focuses on the actual text
The data from many sources can be more complicated.

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Description

Test your knowledge on the treatment and management of ventricular premature complexes (VPCs) in veterinary medicine. This quiz covers ECG interpretation, rate control, and key characteristics associated with VPCs. Perfect for veterinary students and professionals alike.