3.2.1. Arrythmias Flashcards Preview

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Flashcards in 3.2.1. Arrythmias Deck (35):
1

What is a Normal Sinus Rhythm?

Normal Sinus Rhythm - a heart rate between 60-100 bpm; originating in the sinus node and normally conducted to the ventricle (with the normal PR interval)

2

What is an arrhythmia? What causes it?

Arrhythmia - any cardiac rhythm that is not normal sinus rhythm; causes a fall in cardiac outputs; results from alterations of impulse conduction, impulse formation, or both

3

Tachycardia vs Bradycardia?

TACHYCARDIA: ventricular rate > 100 bpm BRADYCARDIA: ventricular rate < 60 bpm

4

What is overdrive suppression?

Overdrive Suppression: when the subsidiary pacemaker cells are inactivated due to the net hyperpolarization seen when the SA node is active

5

What is a subsidiary pacemaker? Conditions required for this?

Subsidiary Pacemaker: cells of the AV node and purkinje fibers of the ventricles that also have spontaneously depolarizing phase 4 AP’s; these cells kick in should the sinus node fail Increased concentration of Na+ required

6

What is Decremental conduction? What does it result in?

Decremental Conduction: slower conduction or even a conduction block; caused by the pre-mature RE-stimulation of the AV node which results in less calcium influx, delaying subsequent conductions. Faster stimulation rates = slower conduction due to reduced Ca2+ channel availability

7

What is reentry?

Reentry: self-perpetuating waves of depolarization; results in tachycardia

8

3 things required for reentry besides a good first date (zing)

presence of adjacent cardiac tissues with different refractory periods unidirectional conduction block slow conduction to allow refractory tissue to recover and allow conduction where it was previously blocked

9

What is anatomic reentry?

Anatomic reentry: obstacle around which reentry occurs is anatomic (i.e. tricuspid annulus or a scar); typically has a regular rate and unchanging, monotonous EKG pattern due to the stable nature of the circuit.

10

What is functional reentry? Where do we usually see this?

Functional Reentry: obstacle is a moving area of temporary block resulting from diffuse abnormalities in the tissue. Usually seen in severely damaged atria or ventricles with large areas of ischemia.

11

Two treatments for recurrent tachycardia/reentry

1. 360 Joules of defibrillation 2. electrical countershock depolarizes the entire myocardium, blocking the recurrent wavefront

12

What is circus movement and what does it require?

Circus Movement: another name for recurrent tachycardias (reentry), due to their “circular and self-regenerating” pattern. This phenomenon is dependant upon the presence of heterogeneities between adjacent portions of the heart that allow for simultaneous block and conduction

13

What are AV-Blocks?

A-V Block: inhibition of atrial conduction; causes an increase in the PR length of EKG

14

What is a first degree AV Block? EKG findings? Symptoms of this?

First-Degree AV block: Conduction between atria and ventricles is delayed due to an abnormal AV node. Prolonged PR interval with each P wave followed by a QRS complex. Asymptomatic.

15

What are the types of second degree AV block?

Mobitz Type I (Wenckebach) Mobitz Type II (Hay)

16

Describe Mobitz Type I (Wenckebach) second degree AV block. What EKG findings are associated with it? What symptoms do we see with this?

Intermittent failure of AV conduction. Progressive lengthening of the PR interval until a beat is “dropped” (P wave not followed by a QRS complex). Usually asymptomatic and rarely progressive to third-degree AV block

17

Describe Mobitz Type II (Hay) second degree AV block. What EKG findings are associated with it and what progress does it make?

Sudden, unpredictable loss of AV conduction. Dropped beats (QRS intervals) not preceded by a change in the length of PR intervals. It is often described as the ratio of P waves to QRS complexes, with a 2:1 block most commonly seen. Often progresses to third-degree AV block and may require prophylactic pacing

18

What is third degree AV block? Discuss the EKG pattern and treatment.

Failure of any impulses to be conducted from atria to ventricles. Atria and ventricles beat independently of each other (AV dissociation), in which ventricles are depolarized by AV nodal or ventricular escape rhythm. As a result, both P waves and QRS complexes are present, but there is no relationship between P waves and QRS complexes. Atrial rate is faster than ventricular rate; usually treated with a pacemaker.

19

What is Wolff-Parkinson-White syndrome and what does it cause electrically?

congenital abnormality where a muscle remnant makes an electrical connection between the atrium and the ventricle; this results in pre-mature excitation of the ventricle through a non-decrementally conducting pathway, changing the pattern of the QRS (has a characteristic delta wave on ECG); May result in a reentry current, leading to supraventricular tachycardia.

20

4 requirements for Wolff-Parkinson White

1. Short P-R interval (< 120 ms) 2. Normal P wave vector (to exclude junctional rhythm) 3. Presence of a delta wave, slurring or notching of the first portion of the QRS complex 4. QRS duration greater than 100 ms

21

What is a Bundle Branch Block (BBB)?

Bundle Branch Block: When a bundle branch or fascicle becomes injured (by underlying heart disease, myocardial infarction, or cardiac surgery), it may cease to conduct electrical impulses appropriately.

22

What does a BBB do to the electrical pathway?

This results in altered pathways for ventricular depolarization. Since the electrical impulse can no longer use the preferred pathway across the bundle branch, it may move instead through muscle fibers in a way that both slows the electrical movement and changes the directional propagation of the impulses.

23

Effect of BBB on the heart's activity?

As a result, there is a loss of ventricular synchrony, ventricular depolarization is prolonged, and there may be a corresponding drop in cardiac output. (The affected ventricle depolarizes much more slowly)

24

What does an atrial flutter do and why?

Atrial Flutter: causes an anatomic reentry (macroreentry) due to the tricuspid annulus presenting as the obstacle

25

What in exact terms is an Atrial flutter and what does the EKG look like?

Regular, rapid (250-350/min) arrhythmia originating from the atria. ECG shows a rapid succession of identical, back-to-back atrial depolarization waves, giving a “sawtooth” appearance. Not all atrial impulses are transmitted to ventricles because the AV node is in refractory period.

26

Electrical result of an atrial fibrillation

Atrial fibrillation - irregularly irregular, rapid (350-600/min) impulses from multiple atrial foci depolarize the atria. Chaotic and erratic baseline with no discrete P waves and irregularly spaced QRS complexes.

27

Anatomical result of atrial fibrillation

Associated with right and left atrial enlargement. Atrial contraction is ineffective, causing decreased cardiac output and atrial stasis, and therefore predisposes for emboli formation and subsequent stroke.

28

Treatment for atrial fibrillation

warfarin

29

Electrical pattern for ventricular fibrillation

rapid, irregular ventricular depolarization due to impulses that originate from multiple ectopic ventricular foci. Completely erratic rhythm with no identifiable waves.

30

Treatment for ventricular fibrillation

Fatal arrhythmia without immediate defibrillation.

31

Describe how cell injury, resulting in a less negative resting potential, alters ionic events in depolarization and repolarization.

Will result in different speeds of conduction, which may lead to fibrillation and possible tachycardia or bradycardia (usually more negative and less negative respectively)

32

What type of AV block is this? How do you know?

Mobitz 1: progressive lengthening of the PR interval until a beat is “dropped” (more P waves than QRS waves)

33

What type of AV block is this? How do you know?

First: prolonged PR interval seen

34

What type of AV block is this? How do you know?

Third Degree:  complete heart block, atrial rate is greater than the ventricular, no relationship between the two chambers. PR constantly changing without altering ventricular rhythm.

35

What type of AV block is this? How do you know?

Mobitz 2: dropped beats that are not preceded by a change in the length of the PR interval; usually seen as 2:1 block, meaning that there are 2 or more P waves for every QRS response. May see increased QRS length (indicative of total heart disease