Partial 4 - Cardiac Arrhythmias

Question 1

Four EKG characteristics of normal sinus rhythm

Answer 1

Regular narrow-complex
HR is between 60-100bpm
Each QRS complex is proceeded by a P wave
P wave is upright in lead II and downgoing in lead aVR

Question 2

Mechanism of arrhytmogenesis include

Answer 2

Altered impulse formation

Altered impulse conduction

Question 3

Altered impulse formation include

Answer 3

Increased automaticity which lead to tachyarrhythmias or decreased automaticity which leads to bradyarrhythmia’s.

Question 4

Altered impulse conduction include

Answer 4

Reentry (Arrhythmia caused by not completed circuit) which lead to tachyarrhythmia, or Conduction blocks which leads to Bradyarrhythmia’s

Question 5

Increased automaticity includes

Answer 5

Sinus tachycardia
Ectopic atrial tachycardia
Junctional tachycardia

Question 6

Mechanism of reentry

Answer 6

There are two electrical pathways that make up reentry loop. We have one pathway (β-pathway) which has fast conduction and long refractory time, and one (α-pathway) with slow conduction with short refractory time (time it takes to conduct another signal). Reentry can be recognized on EKG due to the abrupt onset and termination of arrhythmia. The P wave of the first beat of the arrhythmia is different from the remaining beats of the arrhythmia.

Question 7

AV nodal reentrant tachycardia (AVNRT)

Answer 7

It occurs when a re-entrant circuit forms within or just next to the atrioventricular node. AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia

Question 8

AV reentrant tachycardia (AVRT)

Answer 8

There are two types of AVRT; Orthodromic meaning that the impulse travels in the same direction as normal conduction, and antidromic which means that the conduction travels in opposite direction of normal conduction-

Question 9

AVRT is most commonly associated with

Answer 9

Wolff–Parkinson–White syndrome

Question 10

Atrial flutter is mostly caused by

Answer 10

a large reentrant circuit in the wall of the right atrium

Question 11

EKG characteristics in atrial flutter include

Answer 11

A) sawtooth flutter waves at rate between 250-350 (300) bpm
(B) Flutter waves have constant amplitude, duration and morphology throughout the cardiac cycle
(C) There is usually a 2:1 or 4:1 block at the AV node, resulting in ventricular rates of either 150 or 75 bpm.

Question 12

Atrial Fibrillation

Answer 12

is an abnormal heart rhythm characterized by rapid and irregular beating of the atria

Question 13

Atrial Fibrillation is caused by

Answer 13

numerous wavelets of depolarization spreading throughout the atria simultaneously, leading to an absence of coordinated atrial contraction.

Question 14

Atrial Fibrillation may lead to

Answer 14

Hemodynamic compromise
Systemic embolization
Symptoms (Palpitions, exercise intolerance, shortness of breath)

Question 15

EKG characteristics in atrial fibrillation

Answer 15

Absent P waves
Presence of fine “fibrillatory” waves which vary in amplitude and morphology
Narrow QRS
Irregular ventricular response

Question 16

AV-block deifinition

Answer 16

Heart block describes a type of arrhythmia that happens when the electrical signal gets held up and delayed, or blocked entirely at some point along the conduction system. These delays usually happen because of some sort of damage or fibrosis to the electrical conduction system.

Question 17

Causes of AV block

Answer 17

Lev`s disease (idiopathic fibrosis)

IHD (ending with MI and scars).

Question 18

First degree AV block

Answer 18

When signals is delayed but still makes its way to the ventricles. There is prolongation of PR interval more then 200 ms (normal 120-200 ms). There are usually no symptoms

Question 19

First degree AV block EKG characteristics

Answer 19

Prolongation of the PR interval, which is constant

All P waves are conducted

Question 20

Second degree AV block Type 1

Answer 20

Type 1 (Mobitz 1 or Wenckebach), happens when the PR interval becomes progressively longer with each beat until a P-wave is blocked completely and not conducted (disappears after some cycles), whereas RR interval actually shortens. All P waves are still conducted, and the signal reaches the ventricles.

There are usually no symptoms, but sometimes symptoms such as lightheadness, dizziness and syncope is seen.

Question 21

Second degree AV block Type 2

Answer 21

In Type 2 (Mobitz II) is where there is constant PR interval (does not become longer) with intermittent failure to conduct that occurs randomly. A lot of times a ratio for the overall number of beats conducted to not-conducted is given, like 2:1 Mobitz II AV block.

Most people feel symptoms like, fatigue, dyspnea, chest pain, and syncope

Question 22

Third degree AV block

Answer 22

Third degree AV block describes when the signal is completely blocked when moving from atria to the ventricles, every time. So even though atria go with 60 bpm, none of the signals make it down to the ventricles, and the ventricles, and the ventricles struggle along with escape beats at very slow rates, probably closer to 30 bpm

This type of AV block will often cause dizziness, syncope, angina and heart failure

Question 23

Third degree AV block EKG characteristics

Answer 23

No relationship between P waves and QRS complexes
Relatively constant PP intervals and RR intervals
Greater number of P waves than QRS complexes

Question 24

The conduction system of the heart is influenced by

Answer 24

Direct neural inputs (vagal stimulation)
Adrenergic agents (epinephrine)
Hypoxia
Potassium concentrations (hyperkalemia can block signal transmission altogether)

Question 25

What is the most common cause of rhythm disorders?

Answer 25

Ischemic injury

Question 26

Sinus bradycardia EKG

Answer 26

Every QRS is narrow and proceeded by P wave.

Question 27

Causes of sinus bradycardia

Answer 27

Normal aging 15-25% of Acute MI especially those affecting inferior wall Hypothyroidism and inflitrative diseases (sarcoid, amyloid) Hypothermia and hyperkalemia SLE, and collagen vascular diseases Situations such as micturition and coughing Drugs such as beta-blockers, digoxin, CCBs

Question 28

Sinus tachycardia EKG

Answer 28

Often difficult to distinguish between P and T waves

Question 29

Causes of Sinus tachycardia

Answer 29

``` Fever Hyperthyroidism Effective volume depletion Anxiety Pheochromocytoma Sepsis Anemia Exposure to stimulants (nicotine, caffeine) Hypotension and shock Pulmonary embolism Acute coronary ischemia and MI Chronic pulmonary disease Hypoxia ```

Question 30

Sick sinus syndrome

Answer 30

Its a sinus dysfunction which result in bradycardia. It often results from tachy-brady syndrome where a burst of atrial tachycardia is then followed by a long, symptomatic sinus arrest.

Question 31

Sick sinus syndrome is due to

Answer 31

Sinus fibrosis S node atherosclerosis Inflammation such as RA Congenital and aquired heart disease and after surgery Hypothyroidism or hypothermia or even drugs such a digoxin

Question 32

Paroxysmal supraventricular tachycardia

Answer 32

It is a type of short-circuit arrhythmia which may result from AVNRT, or from an accessory pathway, which may occur as part of Wolff-parkingson-White syndrome

Question 33

Atrial Fibrillation causes

Answer 33

``` Hypertension Hyperthyroidism CHF and CAD Mitral and tricuspid valve disease Hypertrophic cardiomyopathy COPD Obstructive sleep apnea Caffeine Digitalis/Digoxin Congenital (ASD) atrial septal defect ```

Question 34

Premature atrial contraction

Answer 34

Its when the atria contract early due to depolarization from an ectopic focus. It is usually benign and there is no treatment

Question 35

Premature ventricular contraction

Answer 35

These are very common and is abnormal heartbeats that originate in the ventricles and show up as tall and wide QRS complexes on ECG. They are usually asymptomatic

Question 36

Premature ventricular contraction causes

Answer 36

Abnormal automaticity | Reentry

Question 37

Non-sustained ventricular tachycardia

Answer 37

It is ventricular tachycardia that stops by itself within 30 seconds

Question 38

Sudden Cardia Death definition

Answer 38

a natural, unexpected death occuring within 1 hour of the onset of symptoms