Ch. 12 Cardiac Arrhythmias

Question 1

1. When would bradycardia be considered normal?

Answer 1

Sinus bradycardia is normal during rest or sleep. It also can be normal in highly trained athletes – I remember learning in the past that some athletes that have such a low heart rates wear a medical alert bracelet to let medical professionals know they have low heart rates normally, if there were even an emergency situation.

Question 2

2. Name the causes of pathological bradycardia.

Answer 2

Intrinsic disease of the SA node and extrinsic factors such as medications that suppress the SA node or metabolic causes.

Question 3

3. What is sick sinus syndrome? What are the symptoms? In what clinical population is it most common?

Answer 3

This is an intrinsic issue with the SA node that causes times of inappropriate bradycardia. Symptoms would include dizziness, confusion, and/or syncope. This is most common in the elderly.

Question 4

4. When do escape rhythms emerge?

Answer 4

Escape rhythms happen when the SA node is impaired or there is some type of block of conduction, an escape rhythm will happen as a protective mechanism.

Question 5

5. What are the three different types of AV block? Define them & describe their causes, if they require treatment & details unique to each conduction block.

Answer 5

(1) First Degree AV Block – This is when the conduction is still coming through from atria to ventricles, but there is a delay causing the PR interval to be long (over 0.20 sec). This block usually doesn’t require treatment but should be watched to make sure it doesn’t progress to a more severe AV block. Some of the causes could be from heightened vagal tone, AV node ischemia, drugs, or structural defects. (2) Second Degree AV Block – there are two types to this block, Mobitz Type I where the PR interval gets longer and longer until an entire beat is dropped due to a complete block of conduction to the ventricle. The other is Mobitz Type II where there isn’t a change in the PR interval duration but there are sudden drops of the QRS complex because of the sudden intermittent loss of AV conduction. Mobitz Type II is more dangerous than type I, treatment may include IV atropine or isoproterenol, and possibly a permanent pacemaker. (3) Third Degree AV Block/Complete Heart Block – This is a complete dissociation between the atria and the ventricles and they beat independently from one another. There will be more P waves than QRS complexes. The most common cause is acute MI and chronic degeneration of conduction pathways due to age. Treatment is a permanent pacemaker.

Question 6

6. Name the mechanisms that are associated with tachyarrhythmias.

Answer 6

(1) Automaticity (2) Reentry (3) Triggered activity

Question 7

7. There should be 12 supraventricular tachyarrhythmias. What are they? Briefly describe each one & their subsets, (for example, AVNRT, AVRT are subsets of SVTs). Provide treatments available, if indicated.

Answer 7

see individual flashcards for each arrhythmia :)

Question 8

a. (1) Sinus Tachycardia

Answer 8

this is a fast (over 100 bpm) firing of the SA node causing a fast sinus rhythm. You would treat the underlying cause.

Question 9

b. (2) Premature Atrial Contractions

Answer 9

caused by automaticity or reentry in the atria outside of the SA node. Sometimes they are symptomatic and sometimes they don’t cause much issue. If they are symptomatic, they can be treated with Beta Blockers.

Question 10

c. (3) Atrial Flutter

Answer 10

this is rapid, regular atrial activity that has a rate of 180-350 bpm caused by reentry. The P-waves have a distinctive sawtooth pattern. Antiarrhythmic medication can be prescribed or ablation.

Question 11

d. (4) Atrial Fibrillation

Answer 11

this is chaotic atrial rhythm that varies in 530 – 600 bpm range. The p-waves are not very discernible and the rhythm is irregular due to multiple wandering reentrant circuits in the atrium. Treatments can include anticoagulation therapy, ventricular rate control, antiarrhythmics, cardioversion, and/or catheter ablation.

Question 12

e. (5) Paroxysmal Supraventricular Tachycardias

Answer 12

sudden onset and termination of tachycardia at rates from 140 – 250 bpm. Usually a reentry circuit involving the AV node, atrium, or accessory pathway.

Question 13

f. (6) AVNRT

Answer 13

this is a PSVT reentry in the AV node where the conduction uses both the slow and fast pathway causing a tachycardia. Valsalva maneuver or carotid sinus massage may terminate it, IV adenosine, CCBs, BBs, digoxin, or catheter ablation of the slow pathway can be used for treatments.

Question 14

g. (7) AVRT

Answer 14

this uses a reentrant loop of an accessory pathway.

Question 15

h. (8) Wolff-Parkinson-White syndrome (WPW)

Answer 15

this is an arrhythmia that can be life-threatening if not corrected. The impulse can conduct in an anterograde direction through the AV node and the accessory pathway and stimulate the ventricles early which is why a delta wave shows on the ECG. This slur makes for a very short PR interval and a wide QRS. When pre-excited arrhythmias are present, the conduction could be due to orthodromic AVRT or antidromic AVRT directions. Treatment can include sodium channel blockers, cardioversion, and/or catheter ablation following an EP study.

Question 16

i. (9) Lown-Ganong-Levine Syndrome (LGL

Answer 16

LGL has a short PR interval but a normal QRS from an enhanced conduction through the AV node.

Question 17

j. (10) Concealed Accessory Pathways

Answer 17

these are usually due to retrograde conduction and ventricles are depolarized normally through the AV node so you can’t see them on an ECG. It can be treated with IV adenosine, CCBs, BBs, digoxin, or catheter ablation following an EP study.

Question 18

k. (11) Focal Atrial Tachycardias

Answer 18

can be due to automaticity or reentry of atrial ectopic sites. They can be treated with BBs, CCBs, Class IA, IC & III antiarrhythmics, or ablation.

Question 19

l. (12) Multifocal Atrial Tachycardias

Answer 19

several foci in the atria cause abnormal automaticity. Verapamil can be effective to slow the ventricular rate, but many patients with this are very sick.

Question 20

8. What is the difference between sustained & non-sustained VT? In what clinical population is VT common?

Answer 20

Sustained VT happens for over 30 seconds therefore the patient experiences negative consequences from it and this VT typically requires cardioversion or antiarrhythmic drugs to stop it. Non-sustained VT can still causes issues for the patient but this VT is self-terminating episodes. Both of these VTs are common in patients with HD.

Question 21

9. What is the difference between mechanisms that cause monomorphic & polymorphic VT?

Answer 21

Monomorphic VT is usually due to a reentry circuit because of scar from on old MI or CM. Sometimes it can be an ectopic ventricular focus causing idiopathic VT. Polymorphic VT is due to multiple ectopic foci and common causes are Torsade’s de pointes and acute MI. Some genetic predispositions can cause polymorphic VT and sudden death.

Question 22

10. How can one distinguish between VT & other arrhythmias? Explain.

Answer 22

Monomorphic VT will have a wide QRS whereas SVT will have a narrow QRS and with SVT with aberrant conduction the QRS morphology will be the same as when the patient is in sinus rhythm. VT will have no relationship between P waves and QRS complexes.

Question 23

11. How is VT managed?

Answer 23

If the VT is hemodynamically stable treatment may include IV antiarrhythmics such as amiodarone, procainamide, lidocaine, it could include a cardioversion, and any factors that are causing the VT must be treated/corrected. An ICD may be placed to prevent future VT episodes. Anytime there is an underlying cause of VT it must be corrected right away. With hemodynamically unstable VT defibrillation is done and placement of an ICD.

Question 24

12. What does VT degenerate into, if not treated in a timely fashion?

Answer 24

Ventricular Fibrillation, which is a deadly arrhythmia.

Question 25

13. What is the ONLY effective therapy for VF?

Answer 25

Electrical defibrillation asap.