Arrhythmias

Question 1

One type of arrhythmia is an irregular rhythm, usually caused by multiple, active automaticity sites which are often parasystolic. What does it mean to be parasystolic?

Answer 1

Insensitive to overdrive suppression

Question 2

One type of arrhythmia is an irregular rhythm, usually caused by multiple, active automaticity sites which are often parasystolic. What are the 3 main types of irregular rhythms?

Answer 2

Wandering pacemaker

Multifocal atrial tachycardia (MAT)

Atrial fibrillation

Question 3

Etiology of wandering pacemaker

Answer 3

Produced by pacemaker activity wandering from SA node to nearby atrial automaticity foci

Question 4

EKG changes with wandering pacemaker

Answer 4

Produces cycle length variation and variation in P’ shape

Overall rate is in normal range

Question 5

What type of arrhythmia mimics a wandering pacemaker, but with a rate >100bpm?

Answer 5

Multifocal atrial tachycardia

[see varying P’ shape, atrial rate exceeds 100, irregular ventricular rhythm]

Question 6

Multifocal atrial tachycardia is found in pts with what conditions?

Answer 6

Primarily COPD or digitalis toxicity

[overall association with lung disease includes COPD, pneumonia, ventilator theophylline; also associated with beta agonists, electrolyte abnormalities like hypokalemia, hypomagnesemia, sepsis]

Question 7

Arrythmia caused by continuous, rapid firing of multiple atrial automaticity foci in which no single impulse depolarizes the atria completely and only the occasional, random atrial depolarization reaches the AV node to be conducted to the ventricles

Answer 7

Atrial fibrillation

Question 8

“______” refers to a beat or rhythm response of an automaticity focus to a pause in pacemaking activity

Answer 8

Escape

[i.e., an escape rhythm = automaticity focus escapes overdrive suppression to pace at its inherent rate; escape beat = automaticity focus transiently escapes overdrive suppression to emit one beat]

Question 9

A ____ escape rhythm becomes the dominant pacemaker after sinus arrest, with an inherent range of _____-_____

Answer 9

Atrial; 60-80

Question 10

A junctional escape rhythm (aka idiojunctional rhythm) occurs after sinus arrest AND failure of atrial automaticity foci; or if there is a complete conduction block in the proximal AV node. What is the inherent range of this type of escape rhythm, and what other changes are seen on ECG?

Answer 10

Inherent range 40-60

Produces a series of lone QRS complexes, may produce retrograde atrial depolarization —> inverted P’ waves with upright QRS

[note that inverted P’ wave may be before, after, or buried within QRS]

Question 11

Inherent rate and circumstances in which you might see a ventricular escape rhythm (aka idioventricular rhythm)

Answer 11

Inherent rate = 20-40

Occurs with complete conduction block in ventricular system BELOW the AV node; or total failure of SA node and all automaticity foci above the ventricles

[this is RARE — and referred to as downward displacement of the pacemaker]

Question 12

Specific ventricular escape rhythm in which pacing is so slow that pt loses consciousness and you must constantly maintain/monitor their airway

Answer 12

Stokes Adams Syndrome

Question 13

Upon transient sinus block of one pacemaking stimulus from the SA node, if the pause is sufficient enough, you may see an atrial _____ _____

Answer 13

Escape beat

Question 14

ECG finding associated with atrial escape beat

Answer 14

P’ wave that is different shape/appearance than others; the SA node then quickly resumes pacing and tracing returns to normal

Question 15

If the SA node misses one pacing cycle, and there is no atrial focal response, the result is a junctional escape beat. What is the resulting change on ECG?

Answer 15

There may bay retrograde atrial depolarization, resulting in inverted P’ before or after QRS

Question 16

If the SA node and all atrial and junctional foci fail, there may be a resulting ventricular escape beat. What usually causes this?

Answer 16

Burst of parasympathetic activity, which depresses SA node, atrial, and junctional foci, leaving ventricular foci to respond

Question 17

Premature beats occur when there is an irritable focus that spontaneously fires a single stimulus. What are some potential causes of irritable atrial or junctional foci?

Answer 17

Epinephrine from adrenals
Sympathetic stimulation (or decreased parasympathetic stim)
Caffiene, amphetamines, cocaine, other stimulants
Beta 1 agonists
Excess digitalis
Toxins
Ethanol
Hyperthyroid
Stretch
O2 (to some extent)

Question 18

ECG findings with premature atrial beats

Answer 18

P’ wave earlier than expected (appears different from sinus-generated P) — will be upright when focus is close to SA node, inverted when further away

The SA node then resets to continue pacing one cycle length from premature stimulus (requires that dominant center is depolarized by premature beat)

Question 19

Why might you see slightly widened QRS following a premature atrial beat?

Answer 19

Aberrant ventricular conduction because the ventricles were still partially refractory when the premature beat occurred

Question 20

Why might you see a dropped QRS following a premature atrial beat? What ECG finding does this mimic?

Answer 20

If premature atrial beat is not conducted through AV node, may see dropped QRS; mimics heart block

Question 21

What is it called when you see a premature atrial beat coupled to the end of each normal cycle?

Answer 21

Atrial bigeminy

[atrial trigeminy is coupled to the end of every 2 cycles]

Question 22

What causes a premature junctional beat? What is seen on ECG?

Answer 22

AV junction spontaneously fires stimulus that depolarizes ventricles and sometimes retrograde to atria (inverted P’)

Often see widened QRS because ventricles are still partially refractory

AV junctional bigeminy (PJB after each normal cycle); AV junctional trigeminy (PJB after every 2 cycles)

Question 23

Which automaticity foci are considered the most sensitive to O2?

Answer 23

Ventricular automaticity foci - when they sense low O2 they emit a premature ventricular beat (may occur with airway obstruction, absence of air d/t things like drowning, minimal oxygenation at lungs, reduced cardiac output, poor coronary blood supply, etc.)

Question 24

Other than low O2, what are some causes of premature ventricular beats?

Answer 24

Hypokalemia
Mitral valve prolapse
Stretch
Myocarditis
Sometimes beta 1 agonists

Question 25

Premature ventricular beats usually occur early in the cycle, and are easily recognized by what characteristics on ECG?

Answer 25

Great width and amplitude of QRS, usually opposite the polarity of the other QRS complexes Premature ventricular beats do NOT depolarize the SA node, so SA node continues pacing on schedule, but the ventricles are refractory d/t extra beat so a pause is seen ST-T wave moves in opposite direction of QRS Can also see bigeminy or trigeminy Can be unifocal (QRS’s appear uniform) or multifocal (multiple QRS morphologies present)

Question 26

____+ premature ventricular beats in a minute is considered pathologic

Answer 26

Six

Question 27

______ ______ = premature ventricular contractions coupled to a long series of normal cycles (dual rhythm with pacing from 2 sources)

Answer 27

Ventricular parasystole

Question 28

Condition characterized by a run of 3+ PVCs in rapid succession (rate of 120-200), usually regular with wide QRS

Answer 28

Ventricular tachycardia [sustained V-tach when >30 seconds]

Question 29

If a PVC falles on a ____ wave, it potentiates ischemia in something called ______ phenomenon, which may result in dangerous arrhythmias

Answer 29

T; R on T

Question 30

Tachyarrhythmias are rapid rhythms originating in very irritable automaticity foci. What are the 3 types of tachyarrhythmias and their associated rates?

Answer 30

Paroxysmal tachycardia = 150-250 bpm Flutter = 250-350 bpm Fibrillation = 350-450 bpm

Question 31

Paroxysmal atrial tachycardia and paroxysmal junctional tachycardia can not typically be distinguished, and are usually treated the same way anyway, so they can generally be referred to using what blanket term?

Answer 31

Paroxysmal Supraventricular Tachycardia

Question 32

ECG findings with paroxysmal supraventricular tachycardia

Answer 32

P’ waves that appear different from normal P waves, otherwise normal P’-QRS-T cycles; when paroxysmal junctional tachycardia may see retrograde atrial depolarization with inverted P’ before, after, or buried in QRS May see widened QRS d/t aberrant ventricular conduction (aka still refractory)

Question 33

ECG findings with paroxysmal atrial tachycardia with AV block

Answer 33

Rapid rate, spiked P’ waves 2:1 ratio of P’:QRS

Question 34

What should you suspect as the etiology for paroxysmal atrial tachycardia with AV block?

Answer 34

Digitalis excess or toxicity

Question 35

Paroxysmal junctional tachycardia may lead to AV nodal re-entry tachycardia (AVNRT). What does that mean?

Answer 35

Continuous re-entry circuit develops (including AV node and lower atria) and rapidly paces the atria and ventricles; No P waves are seen Mechanism: 1. Premature atrial impulse enters slow path but is blocked at the fast path 2. Impulse is conducted forward through slow path 3. Ventricles activated in synchrony 4. Impulse is conducted backward through fast path 5. Impulse activates atria retrogradely and re-enters slow path

Question 36

Characteristic ECG pattern of paroxysmal ventricular tachycardia

Answer 36

Enormous, consecutive PVC-like complexes SA node is still pacing, but it will be buried in the tracing Signs of AV dissociation or extreme right axis deviation are also characteristic

Question 37

Paroxysmal ventricular tachycardia is most likely to occur in what pt populations?

Answer 37

Elderly pts with ischemia of ventricles

Question 38

Type of polymorphic ventricular tachycardia, characterized by shifting sinusoidal waves on EKG; can lead to ventricular fibrillation

Answer 38

Torsades de pointes

Question 39

Causes of Torsade de Pointes

Answer 39

``` Hypokalemia K+ channel blockers Congenital abnormalities (long QT syndrome) ```

Question 40

Arrhythmia characterized by “sawtooth” appearance on ECG representing atrial depolarization

Answer 40

Atrial flutter

Question 41

_____ maneuvers increase ____ node refractoriness allowing fewer flutters to be conducted to ventricles and may help to reduce symptoms associated with atrial flutter

Answer 41

Vagal; AV

Question 42

______ flutter produces a series of smooth sine waves, rarely self resolves, and almost always precedes a deadly arrhythmia

Answer 42

Ventricular flutter (deadly arrhythmia it leads to is ventricular fibrillation)

Question 43

What usually triggers Afib?

Answer 43

Usually initiated by parasystolic foci in the pulmonary vein ostia of the LA

Question 44

ECG appearance of Afib; what leads are best to identify it?

Answer 44

Appears as wavy baseline without identifiable P or P’ waves; QRS response is not regular and may be fast or slow “Irregularly irregular” Best Leads = II, III, aVF

Question 45

Condition characterized by totally erratic EKG without identifiable waves with gradually diminishing amplitude as the heart fails

Answer 45

Ventricular fibrillation

Question 46

Most common type of ventricular pre-excitation syndrome

Answer 46

Wolff-Parkinson-White syndrome

Question 47

WPW is characterized by abnormal fast accessory condition pathway from the atria to the ventricle (bundle of ____) which bypasses the rate-slowing AV node; thus the ventricles begin to partially depolarize earlier, leading to characteristic _____ wave with ______ QRS and _____ PR interval

Answer 47

Kent; delta; widened; shortened

Question 48

WPW may result in re-entry circuit, leading to _____ ____

Answer 48

Supraventricular tachycardia

Question 49

Condition in which AV node is bypassed by extension of the anterior internodal tract; absence of conduction delay in AV node allows “James” bundle to conduct atrial depolarization directly to the His bundle without delay

Answer 49

Lown-Ganong-Levine syndrome

Question 50

Lown-ganong-levine syndrome allows atrial conduction be transmitted directly to the His bundle without delay. This may lead to what complication?

Answer 50

Rapid atrial arrhythmias like atrial flutter

Question 51

Autosomal dominant disorder leading to increased risk of ventricular tachyarrhythmias and SCD, most common in asian males

Answer 51

Brugada syndrome

Question 52

ECG findings associated with Brugada syndrome

Answer 52

RBBB with ST elevation in V1, V2, V3 [these pts need pacemakers/ICD]

Question 53

Condition characterized by stenosed anterior descending coronary artery in which angioplasty is necessary to prevent impending MI

Answer 53

Wellens syndrome

Question 54

Long QT syndrome predisposes to dangerous ventricular arrhythmias. What defines a QT segment as long?

Answer 54

A long QT segment exceeds 1/2 the cardiac cycle

Question 55

What typically causes long QT syndrome? What is the major complication of concern?

Answer 55

Typically caused by ion channel defects, but can also be drug-induced (class IA and class III antiarrhythmics, abx like macrolides, antipsychotics like haloperidol, antidepressants like TCAs, anti-emetics like odansetron) Major complication of concern is increased risk of SCD d/t torsade de pointes

Question 56

COPD is associated with ______ hypertrophy, ____ axis deviation, and ______ (arrhythmia)

Answer 56

RV; Right; MAT

Question 57

ECG findings with pulmonary embolus

Answer 57

[tachycardia, non-specific ST-T changes] Large S wave in lead I ST depression in lead II Large Q wave in lead III (with T wave inversion in V1-4) Transient RBBB

Question 58

ECG findings in moderate to severe hyperkalemia

Answer 58

Moderate —> peaked T wave, wide flat P wave, wide QRS Severe —> No P waves, QRS more widened May see increased PR interval

Question 59

ECG findings in hypokalemia

Answer 59

U waves Increased QT interval Flat or inverted T wave

Question 60

ECG findings in hypercalcemia

Answer 60

Short QT

Question 61

ECG findings in hypocalcemia

Answer 61

Prolonged QT

Question 62

Medical conditions/situations associated with bradycardia

Answer 62

Normal people, healthy athletes, physiologic components to sleep, fright, carotid sinus massage, carotid hypersensitivity, ocular pressure (glaucoma), obstructive jaundice (effect of bile salts on SAN), sliding hiatal hernia, valsalva maneuver diseases of atrium or SAN — CAD, inflammation, invasive neoplasm, cardiomyopathy, muscular dystrophy, amyloidosis Drugs like digitalis, quinidine, HTN drugs like clonidine, methyldopa, reserpine, beta blockers Acute inferior MI (d/t increased vagal tone), ischemia, acidosis, SSS, convalescence from digitalis toxicity

Question 63

What is the most common cause of an unexplained pause on ECG?

Answer 63

Nonconducted premature atrial contraction (PAC)

Question 64

What med is given in sinus bradycardia if HR is <45-50 with hemodynamic compromise/unstable acute situations?

Answer 64

Atropine can also give epinephrine, isoproterenol, or pacemaker [note side effects = urinary retention, abdominal distention]

Question 65

______ = property of a cardiac cell to depolarize spontaneously during phase 4 of AP/leads to generation of an impulse

Answer 65

Automaticity

Question 66

Treatment of PACs

Answer 66

Only if symptomatic — look to reverse the cause (stress, alcohol, tobacco, coffee, COPD, CAD) Can give beta blockers — metoprolol

Question 67

Tx for MAT

Answer 67

Focus on underlying cause IV verapamil (calcium channel blockers)

Question 68

Treatment for AVNRT (SVT)

Answer 68

Adenosine (try valsalva first to slow HR); can also give diltiazem, beta blocker, or shock if needed

Question 69

Treatment of PVCs

Answer 69

If stable, do nothing If symptomatic or in setting of ACS — give metoprolol If unstable (in setting of MI, acidosis, etc.), give antiarrhythmic like amiodarone, lidocaine, procainamide, etc.

Question 70

Fusion beats in the setting of ventricular tachycardia are characteristic of ______ syndrome

Answer 70

Dressler

Question 71

A 63 y/o man has been in the ED for 1.5 hours with hx of CP. EKG reveals changes consistent with anterior AMI. The pt suddenly becomes cool, clammy, and confused with systolic BP of 70. EKG at that time reveals ventricular tachycardia. What do you do?

Answer 71

Cardioversion required d/t sudden change in status

Question 72

Tx for Vfib

Answer 72

CPR, defibrillation

Question 73

Torsade de pointes tx

Answer 73

MgSO4 Overdrive pacing Isoproternol

Question 74

If the clinical vignette ever mentions cancer or malignancy, the first electrolyte that should come to mind is _____

Answer 74

Calcium [hypercalcemia is associated with malignancy, look for short QT interval and/or short ST segment on ECG]

Question 75

What change in pH reduces the threshold for VF?

Answer 75

Acidosis

Question 76

ECG findings in hypothermia

Answer 76

Bradycardia and J wave (Osborne wave)

Question 77

ECG changes with cor pulmonale

Answer 77

Tall, pointed P waves [p-pulmonale]

Question 78

ECG changes with cerebral hemorrhage

Answer 78

Impressive ST-T changes [tall T waves, inverted wide T waves, etc.]

Question 79

Whenever you see widespread flattening or mild inversion of T waves without associated ST segment displacement, always think of __________

Answer 79

Hypothyroidism

Question 80

Whenever you see widespread flattening or mild inversion of T waves without associated ST segment displacement, always consider hypothyroidism. The other most constant ECG finding in myxedema (severe hypothyroid) is low voltage of the ________. Sinus bradycardia is less often seen.

Answer 80

QRS complex