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 ventricular enlargement
  • Right atrial enlargement
  • Right ventricular enlargement
  • Left atrial enlargement (correct)

    • 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 (correct)
  • Right atrial enlargement
  • Right ventricular enlargement
  • Left atrial enlargement

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

  • Because it is unable to detect severe enlargement
  • Due to the presence of false-positive findings
  • Due to the absence of waveform abnormalities in chamber enlargement
  • Because of its unacceptably low level of accuracy (correct)

    • 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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