Chapter 4 - Overview of electrocardiography

Question 1

what is the J point on the ECG

Answer 1

junction point between end of QRS complex and S-T

Question 2

describe the part of the cardiac cycle that is occurring during the ST segment on ECG. what phase of the cardiac myocyte action potential does this represent?

Answer 2

period between ventricular depolarization and depolarization - phase 2

Question 3

when measuring to QT interval, do you use the start or end of the T wave?

Answer 3

end - you are measuring from the onset of depolarization to completion of repolarization

Question 4

is an AV junctional rhythm classified as being supraventricular or ventricular?

Answer 4

supraventricular

Question 5

how many premature ectopic complexes are required to constitute a tachycardia?

Answer 5

3 or more

Question 6

list 8 causes of sinus bradycardia

Answer 6

hypothermia, hypothyroidism, brainstem disease, increased ICP, carotid pressure, ocular pressure, athletic heart, before/after cardiac arrest, drugs (tranquilizers, anaesthetics, beta blockers, calcium channel blockers, digoxin etc), severe metabolic disease (uraemia, hyperkalemia), sinus node disease, other causes of high vagal tone (lower airway, pharyngeal or GI obstruction)

Question 7

list 8 causes of sinus tachycardia

Answer 7

hyperthermia/fever, hyperthyroidism, anemia/hypoxia, heart failure, shock, hypotension, sepsis, anxiety/fear, excitement, exercise, pain, drugs (anticholinergics, sympathomimetics), toxicities (chocolate, hexachlorophene), electric shock, other causes of high sympathetic tone

Question 8

name two causes of abnormal QRS configuration with a supraventricular rhythm

Answer 8

intraventricular conduction disturbance
ventricular enlargement
bundle branch block

Question 9

ventricular escape rhythm speed

Question 10

difference between type 1 and type 2 2nd degree AV block

Answer 10

type 1 = progressive lengthening of PR interval before drop, usually d.t. AV node disorder or high vagal tone
type 2 = consistent PR interval before drop, usually d.t. lower AV conduction abnormalities (bundle of His, bundle branches)

Question 11

describe the appearance of a typical ECG in a dog with sinoatrial block

Answer 11

interval between P waves is a multiple of normal P to P interval - conduction failure between SA node and surrounding atrial muscle causes failure of atrial depolarisation. difficult to differentiate from sinus arrest on ECG