Antiarrhythmic Drugs and Cardiac Electrophysiology
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Antiarrhythmic Drugs and Cardiac Electrophysiology

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Questions and Answers

What do wide or notched P waves in lead II indicate in dogs and cats?

Left atrial enlargement

What do tall R waves in leads with the positive electrode on the left and/or caudal aspect of the body indicate?

Left ventricular enlargement

Why is electrocardiography considered to be very insensitive at identifying mild to moderate changes in chamber size?

Because of its unacceptably low level of accuracy

What is the role of the sinus node in a healthy animal's heart?

<p>It is known as the normal pacemaker of the heart</p> Signup and view all the answers

Which type of arrhythmia is most commonly due to a reentrant loop within the atria and is typically characterized on the ECG by a 'saw-toothed' baseline with relatively normal QRS complexes?

<p>Atrial flutter</p> Signup and view all the answers

What is the most common drug used in long-term treatment of supraventricular tachycardia (SVT) in dogs and cats?

<p>Diltiazem</p> Signup and view all the answers

In which species, dogs or cats, is third-degree AV block often produces no clinical signs and thus requires no treatment?

<p>Cats</p> Signup and view all the answers

What should be implanted in dogs with third-degree AV block regardless of clinical signs?

<p>Pacemaker</p> Signup and view all the answers

What is the consecutive occurrence of a series of supraventricular premature complexes called?

<p>Supraventricular tachycardia (SVT)</p> Signup and view all the answers

Which drug is the most commonly used intravenously to 'break' supraventricular tachycardia into sinus rhythm?

<p>Diltiazem</p> Signup and view all the answers

What is the most common treatment for an accessory pathway (bypass tract) that may result in supraventricular tachycardia?

<p>Radiofrequency catheter ablation</p> Signup and view all the answers

At what rate does supraventricular tachycardia (SVT) most commonly range in dogs?

<p>~200 bpm</p> Signup and view all the answers

What is the loading dose of amiodarone for dogs and cats?

<p>8–10 mg/kg, PO, every 12 hours for 7–10 days</p> Signup and view all the answers

What are premature complexes that originate from ectopic sites above the ventricles called?

<p>Supraventricular premature complexes</p> Signup and view all the answers

What is the treatment of choice for animals with chronic bradyarrhythmias due to AV block or sick sinus syndrome?

<p>Pacemaker implantation</p> Signup and view all the answers

What is an accessory pathway (bypass tract) in relation to the normal electrical connection between an atrium and a ventricle called?

<p>Aberrant pathway</p> Signup and view all the answers

What is the dosing regimen for atropine when administered orally to animals?

<p>0.04 mg/kg, PO, every 6–8 hours</p> Signup and view all the answers

In which species are pacemakers implanted successfully, although only rarely, other than dogs and cats?

<p>Horses</p> Signup and view all the answers

Which medication may be administered if pacemaker implantation is not a viable option for animals with chronic bradyarrhythmias?

<p>Phosphodiesterase (PDE) inhibitors</p> Signup and view all the answers

What can occur if third-degree AV block is not identified before anesthesia in cats?

<p>Fainting leading to pacemaker implantation</p> Signup and view all the answers

Which of the following is a characteristic of atrial standstill?

<p>Usually caused by hypokalemia</p> Signup and view all the answers

What is the principal problem in animals with sick sinus syndrome?

<p>Destroyed SA node</p> Signup and view all the answers

What is a possible effect of administering sympathomimetics to increase heart rate in animals with sick sinus syndrome?

<p>Temporary increase in heart rate</p> Signup and view all the answers

What type of AV block is characterized by occasional P waves that are not followed by QRS complexes?

<p>Second-degree AV block</p> Signup and view all the answers

What is the range of heart rate in dogs with persistent atrial standstill?

<p>40–65 bpm</p> Signup and view all the answers

What is the most likely outcome of administering parasympatholytics to increase heart rate in animals with sick sinus syndrome?

<p>Decrease in heart rate</p> Signup and view all the answers

Which valve keeps blood flowing from the atria to the ventricles?

<p>Atrioventricular valve</p> Signup and view all the answers

What is the effect of persistent atrial standstill on the sinus node?

<p>'Is destroyed and replaced by AV nodal (junctional) escape rhythm</p> Signup and view all the answers

What is the typical range of ventricular rhythm in dogs with atrial fibrillation?

<p>150-300 bpm</p> Signup and view all the answers

What characterizes the ECG of dogs and cats with atrial fibrillation?

<p>Normal-appearing QRS complexes and irregular ventricular rhythm</p> Signup and view all the answers

How is the ventricular rate controlled in most dogs and all cats with atrial fibrillation?

<p>By a combination of diltiazem and digoxin</p> Signup and view all the answers

What drugs are used to prolong the refractory period of the AV node and slow AV nodal conduction?

<p>Diltiazem and atenolol</p> Signup and view all the answers

In which dog breeds can atrial fibrillation develop with an otherwise normal heart?

<p>Irish Wolfhounds, Scottish Deerhounds, and Great Danes</p> Signup and view all the answers

What is the goal of treatment of atrial fibrillation in most dogs and all cats?

<p>To control the ventricular rate</p> Signup and view all the answers

Which method is most sensible for converting atrial fibrillation to sinus rhythm in dogs?

<p>Electrical cardioversion combined with amiodarone administration</p> Signup and view all the answers

What can result from variation in the diastolic filling period of the ventricles due to irregular rhythm in animals with atrial fibrillation?

<p>Variability in stroke volume</p> Signup and view all the answers

What do ventricular premature complexes (VPCs) arise from?

<p>'Specialized intraventricular conduction system'</p> Signup and view all the answers

What distinguishes VPCs on ECGs?

<p>Wide QRS complex with large T wave that is opposite in polarity to the QRS complex</p> Signup and view all the answers

What limits the use of amiodarone as a second-line treatment in animals?

<p>Hepatic and thyroid toxicoses</p> Signup and view all the answers

What combination is often more effective than diltiazem alone for rate control in animals with atrial fibrillation?

<p>Diltiazem and atenolol</p> Signup and view all the answers

What is the distinguishing feature of Mobitz type II second-degree AV block?

<p>No change in P-R intervals</p> Signup and view all the answers

What distinguishes high-grade second-degree AV block from third-degree AV block?

<p>2:1 ratio of P wave to QRS complex</p> Signup and view all the answers

What is the characteristic feature of third-degree AV block (complete heart block)?

<p>Absence of superventricular rhythm</p> Signup and view all the answers

What can be indicated by waveform abnormalities in dogs and cats?

<p>Chamber enlargement</p> Signup and view all the answers

What is the ideal treatment for high-grade second-degree AV block and third-degree AV block?

<p>Pacemaker implantation</p> Signup and view all the answers

Which form of AV block is usually due to high vagal tone and is the most common type occurring in puppies?

<p>Mobitz type I second-degree AV block</p> Signup and view all the answers

What distinguishes high-grade second-degree AV block from third-degree AV block?

<p>Presence of an association between QRS complexes and P waves in a 2:1 ratio or more</p> Signup and view all the answers

What type of heart block may be present without outward evidence of cardiac disease?

<p>First-degree AV block</p> Signup and view all the answers

What is the characteristic feature of Mobitz type I second-degree AV block?

<p>Progressively lengthening P-R intervals</p> Signup and view all the answers

What is the distinguishing feature of third-degree (complete) AV block?

<p>Absence of association between QRS complexes and P waves</p> Signup and view all the answers

What is the ideal treatment for symptomatic animals with high-grade second-degree AV block?

<p>Pacemaker implantation</p> Signup and view all the answers

What might waveform abnormalities in dogs and cats indicate?

<p>Chamber enlargement</p> Signup and view all the answers

What is the main reason that the sinoatrial node functions as the pacemaker of the heart?

<p>It depolarizes faster than the atrioventricular node.</p> Signup and view all the answers

Which of the following conditions is characterized by the absence of P waves on the ECG for a short period?

<p>Sinus arrest</p> Signup and view all the answers

What does sinus bradycardia refer to in animals?

<p>A regular sinus rhythm that is slower than expected for a given species and situation.</p> Signup and view all the answers

What can be a cause of sinus tachycardia in animals?

<p>Stress</p> Signup and view all the answers

What is respiratory sinus arrhythmia characterized by?

<p>An increase in heart rate with inspiration and a decrease with expiration.</p> Signup and view all the answers

What happens during sinoatrial block on the ECG?

<p>The P-P interval surrounding the break in sinus rhythm is an exact multiple of the normal P-P interval.</p> Signup and view all the answers

In which animal is sinus arrhythmia considered abnormal in the hospital setting?

<p>Cats</p> Signup and view all the answers

What may be considered for treatment of bradycardia in dogs and cats?

<p>Administration of atropine</p> Signup and view all the answers

What is a characteristic of sinus arrest (sinoatrial arrest, sinus pause)?

<p>It is diagnosed when there are shorter P-P intervals than normal.</p> Signup and view all the answers

What may be administered to resolve the underlying cause of sinus tachycardia?

<p>Beta-blocker (eg, atenolol)</p> Signup and view all the answers

What causes respiratory sinus arrhythmia in dogs?

<p>Variation in vagal tone intensity associated with respiration</p> Signup and view all the answers

What does respiratory sinus arrhythmia refer to?

<p>An increase in heart rate with inspiration and a decrease with expiration.</p> Signup and view all the answers

What is the most common tachyarrhythmia that is treated?

<p>Atrial fibrillation</p> Signup and view all the answers

Which drug is generally preferred to control the ventricular rate in dogs with atrial fibrillation?

<p>Diltiazem</p> Signup and view all the answers

Why is caution warranted when treating patients with Dilated Cardiomyopathy (DCM) with sotalol?

<p>It can worsen existing heart failure</p> Signup and view all the answers

What is the target average heart rate suggested by the text for dogs using a Holter monitor?

<p>$ extless$ 125 bpm</p> Signup and view all the answers

What can ventricular tachycardia degenerate into and cause?

<p>Ventricular fibrillation</p> Signup and view all the answers

What is the primary role of most antiarrhythmic drugs?

<p>To control ventricular rate</p> Signup and view all the answers

How are chamber enlargement indicated in dogs and cats according to the text?

<p>By absent waveform abnormalities</p> Signup and view all the answers

What is the potential effect of some antiarrhythmics on congestive heart failure (CHF)?

<p>They worsen active CHF</p> Signup and view all the answers

What is the role of an automatic implantable defibrillator in human medicine according to the text?

<p>It has reduced the use of some antiarrhythmics</p> Signup and view all the answers

When does fast ventricular tachycardia make dogs most vulnerable to dying suddenly?

<p>When accompanied by severe underlying cardiac disease</p> Signup and view all the answers

What medication combination can effectively decrease or stop episodes of syncope due to ventricular tachycardia in Boxers with ARVC, according to the text?

<p>Mexiletine and atenolol</p> Signup and view all the answers

What does pacing the heart of a dog at a rate $ extgreater$180 bpm result in?

<p>Myocardial failure severe enough to cause CHF within weeks</p> Signup and view all the answers

Which of the following best describes ventricular tachycardia?

<p>It can be divided into slower, benign ventricular tachycardias and faster, malignant ones.</p> Signup and view all the answers

Which condition can commonly cause an accelerated idioventricular rhythm (AIVR) in dogs in the intensive care unit?

<p>Systemic disturbances related to anesthesia</p> Signup and view all the answers

Which treatment effectively controls accelerated idioventricular rhythm (AIVR) in Boxers and usually stops syncope?

<p>Sotalol</p> Signup and view all the answers

What distinguishes a ventricular escape rhythm from a ventricular tachycardia?

<p>Ventricular escape rhythm occurs because higher pacemakers have failed, while ventricular tachycardia doesn't.</p> Signup and view all the answers

What is the primary cause of ventricular fibrillation as a terminal rhythm?

<p>Microreentrant circuits within the ventricular myocardium</p> Signup and view all the answers

Which condition is most likely to cause nonsustained ventricular tachycardia in dogs and cats?

<p>Arrhythmogenic right ventricular cardiomyopathy</p> Signup and view all the answers

What is a distinguishing feature of an accelerated idioventricular rhythm (AIVR) on an ECG?

<p>Relatively slow ventricular tachycardia (usually &lt; 200 bpm)</p> Signup and view all the answers

What is the most prevalent cause of dilated cardiomyopathy (DCM) in dogs?

<p>Progressive loss of myocyte number and/or function</p> Signup and view all the answers

What distinguishes ventricular tachycardia from an accelerated idioventricular rhythm (AIVR)?

<p>Ventricular tachycardia does not result in sudden death, while AIVR can be terminal.</p> Signup and view all the answers

In which scenario does administration of sotalol or a combination of atenolol and mexiletine effectively control the arrhythmia?

<p>If it is causing hemodynamic instability</p> Signup and view all the answers

Which statement best describes the occurrence of fusion beats on an ECG?

<p>They occur as hybrids of sinus beats and premature ventricular contractions.</p> Signup and view all the answers

What distinguishes a ventricular escape rhythm from an idioventricular rhythm?

<p>A ventricular escape rhythm occurs because higher pacemakers have failed, while an idioventricular rhythm doesn't.</p> Signup and view all the answers

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