WK 2: Dysrhythmias

Question 1

What is Dysrhythmia?

Answer 1

• Abnormal cardiac rhythms are termed dysrhythmias.
• Prompt assessment of dysrhythmias and the patient’s response to the rhythm is critical.

Question 2

What is ECG monitoring?

Answer 2

· Graphic tracing of electrical impulses produced by the heart
· Waveforms of ECG represent activity of charged ions across membranes of myocardial cells.

Question 3

What is the significance of lead placement?

Answer 3

Limb leads I, II, and III: These bipolar leads are located on the extremities.

Limb leads aVR, aVL, and aVF: These unipolar leads use the centre of the heart as their negative electrode.

Placement for the unipolar chest leads: V1, fourth intercostal space at the right sternal border; V2, fourth intercostal space at the left sternal border; V3, halfway between V2 and V4; V4, fifth intercostal space at the left midclavicular line; V5, fifth intercostal space at the l

Question 4

Cardiac action potential

Answer 4

P Wave: representing atrial depolarization

QRS complex: QRS complex representing ventricular depolarization

T wave: T wave representing ventricular repolarization

ST segment: represents the time period in which the ventricles are completely depolarized.

Question 5

What is Sinus bradycardia

Answer 5

· Sinus node fires <60 bpm
· Normal rhythm in aerobically trained athletes and during sleep

Question 6

What is Sinus tachycardia

Answer 6

· Discharge rate from the sinus node is increased as a result of vagal inhibition and is >100 bpm.
· HR: 140bpm = Tachycardia
· Regular Rhythm - Sinus

Question 7

What is Premature atrial contraction

Answer 7

· Contraction originating from ectopic focus in atrium in location other than sinoatrial (SA) node
· Travels across atria by abnormal pathway, creating distorted P wave
· May be stopped, delayed, or conducted normally at the atrioventricular (AV) node
· Changes in the P wave

Question 8

Premature atrial contraction ECG findings

Answer 8

HR: 120bpm
Irregular rhythm
QRS: are different
P wave: some are smaller and shorter

Question 9

Causes of Premature atrial contraction

Answer 9

· Emotional stress, physical fatigue
· Use of caffeine, tobacco, alcohol
· Hypoxia
· Electrolyte imbalances
· Hyperthyroidism, chronic obstructive pulmonary disease (COPD), heart disease including coronary artery disease (CAD) and valvular disease

Question 10

Clinical significance of Premature atrial contraction

Answer 10

· Isolated PACs are not significant in persons with healthy hearts.
· In persons with heart disease, may be warning of more serious dysrhythmia

Question 11

What is Atrial flutter

Answer 11

· Atrial tachydysrhythmia identified by recurring, regular, sawtooth-shaped flutter waves
Originates from a single ectopic focus

Question 12

ECG findings of Aflutter

Answer 12

• Flutter waves - between each QRS
• P wave: unclear

Question 13

Clinical significance of Atrial flutter

Answer 13

• High ventricular rates (>100) and loss of the atrial “kick” can decrease CO and precipitate HF
• Risk for stroke due to risk of thrombus formation in the atria
  Warfarin (Coumadin) is given to prevent stroke in patients with atrial flutter of longer than 48 hours duration.

Question 14

Causes of Atrial flutter

Answer 14

§ CAD
§ Hypertension
§ Mitral valve disorders
§ Pulmonary embolus
§ Chronic lung disease
§ Cor pulmonale
§ Cardiomyopathy
§ Hyperthyroidism
Medications: digoxin, quinidine, epinephrine

Question 15

What is Atrial Fibrillation

Answer 15

· Total disorganization of atrial electrical activity due to multiple ectopic foci, resulting in loss of effective atrial contraction
· Most common dysrhythmia
· Prevalence increases with age
· The dysrhythmia may be chronic or intermittent. Atrial fibrillation is the most common dysrhythmia in Canada. with 1 to 2% of the population living with atrial fibrillation.

Question 16

ECG Findings of Atrial Fibrillation

Answer 16

§ Irregular rhythm
No p waves

Question 17

Clinical Significance of Atrial Fibrillation

Answer 17

· Can result in decrease in CO due to ineffective atrial contractions (loss of atrial kick) and rapid ventricular response
· Thrombi may form in the atria as a result of blood stasis.
· An embolus may develop and travel to the brain, causing a stroke.
· Overall risk of stroke increases three to five times greater with atrial fibrillation.
Medications: blood thinners

Question 18

Causes of Atrial Fibrillation

Answer 18

· Rheumatic heart disease
· CAD
· Cardiomyopathy
· Hypertension
· HF
Pericarditis

Question 19

What is Ventricular tachycardia?

Answer 19

· Run of three or more PVCs
· Monomorphic, polymorphic, sustained, and nonsustained
Considered life-threatening because of decreased CO and the possibility of deterioration to ventricular fibrillation

Question 20

Clinical significance of is Ventricular tachycardia

Answer 20

· VT can be stable (patient has a pulse) or unstable (patient is pulseless).
· Sustained VT: severe decrease in CO
§ Hypotension
§ Pulmonary edema
§ Decreased cerebral blood flow
§ Cardiopulmonary arrest
§ Treatment for VT must be rapid.
§ May recur if prophylactic treatment is not initiated
Ventricular fibrillation may develop.

Question 21

Causes of is Ventricular tachycardia

Answer 21

· MI
· CAD
· Electrolyte imbalances
· Cardiomyopathy
· Mitral valve prolapse
· Long QT syndrome
· Digitalis toxicity
· Central nervous system disorders
This dysrhythmia can be seen in patients who have no evidence of cardiac disease.

Question 22

What is Ventricular Fibrillation

Answer 22

· Severe derangement of the heart rhythm characterized on ECG by irregular undulations of varying contour and amplitude
No effective contraction or CO occurs.

Question 23

ECG findings of Ventricular Fibrillation

Answer 23

· No clear definition in any waves.
Varied rhythm

Question 24

Clinical significance for Ventricular Fibrillation

Answer 24

· Unresponsive, pulseless, and apneic state
If not treated rapidly, death will result.

Question 25

Causes of Ventricular Fibrillation

Answer 25

· Acute MI, CAD, cardiomyopathy
· May occur during cardiac pacing or cardiac catheterization
· May occur with coronary reperfusion after fibrinolytic therapy
· Accidental electric shock
· Hyperkalemia
· Hypoxia
· Acidosis
Drug toxicity

Question 26

Management of Ventricular Fibrillation

Answer 26

· Assessment of circulation, airway, and breathing (CAB)
· Immediate initiation of cardiopulmonary resuscitation (CPR) and advanced cardiac life support (ACLS) measures with the use of defibrillation and definitive medication therapy

Question 27

ECG changes in Acute Coronary Syndrome

Answer 27

· Definitive ECG changes occur in response to ischemia, injury, or infarction of myocardial cells.
§ Changes seen in the leads that face the area of involvement
The leads facing opposite the area involved in ACS often demonstrate reciprocal (opposite) ECG changes. Additionally, the pattern of ECG changes among the 12 leads provides information on the coronary artery involved in ACS.

Question 28

ST depression in Acute Coronary Syndrome

Answer 28

· ST segment depression is significant if it is at least 1 mm (one small box) below the isoelectric line.
· The isoelectric line is flat and represents those normal times in the cardiac cycle when the ECG is not recording any electrical activity in the heart. These times are as follows: (1) from the end of the P wave to the start of the QRS complex, (2) the entire ST segment, and (3) from the end of the T wave to the start of the next P wave.
· Changes occur in response to the electrical disturbance in myocardial cells due to inadequate supply of oxygen.
Once treated (adequate blood flow is restored), ECG changes resolve and ECG returns to baseline.

Question 29

ST elevation in Acute Coronary Syndrome

Answer 29

· ST-segment elevation is significant if >1 mm above the isoelectric line.
§ If treatment is prompt and effective, may avoid infarction
§ If serum cardiac markers are present, an ST-segment–elevation myocardial infarction (STEMI) has occurred.

Question 30

T wave changes in Acute Coronary Syndrome

Answer 30

· T-wave inversion related to infarction occurs within hours and may persist for months

Question 31

Pathological Q wave in Acute Coronary Syndrome

Answer 31

• A pathological Q wave indicates that at least half the thickness of the heart wall is involved.
• Referred to as a Q-wave MI
• Pathological Q wave may be present indefinitely