Unit III (9-13)- The Heart Flashcards
Parasympathetic innervation of the heart is provided by what nerves
Vagus nerve
Pre-ganglionic fibers of of the recurrent laryngeal n.
Sympathetic innervation of the heart is provided by what nerves
Cardiac nerves that originate from the cervicothoracic/middle and 1st few thoracic ganglion
What mechanical event is represented by a P-wave?
Atrial depolarization
What mechanical event is represented by a QRS complex?
Ventricular depolarization
What mechanical event is represented by a T wave?
Ventricular repolarization
What mechanical event is represented by a QT interval?
Ventricular contraction and relaxation
What mechanical event is represented by a PR interval?
Atrial contraction and relaxation
What does S1 sound represent?
Lub - Closure of mitral and tricuspid valves
Usually occurs at the end of QRS complex
What does S2 sound represent?
Dub - Closure of semilunar valves
Usually occurs at the end of T wave
What does S3 sound represent?
Early ventricular filling
What does S4 sound represent?
Atrial contraction
At what stage of the cardiac cycle do gallop sounds occur?
Diastole
low frequency in dogs; higher frequency in cats
What pathology is usually associated with S3 sounds?
DCM
What pathology is usually associated with S4 sounds?
HCM
pushing blood into a stiff non compliant ventricle
What do systolic clicks represent?
Primary AV valve prolapse
(usually higher amplitude, just as loud or louder than S1 and S2) would occur between S1 and S2
What do split sounds represent?
Delay between closure and opening of valves
S1 - Mitral and tricuspid valves
S2 - semilunar valves
ECG paper speed of 25mm/sec
1 small box = ___
0.04 seconds
ECG paper speed of 50mm/sec
1 small box = ___
0.02 seconds
ECG paper speed of 25mm/sec
30 big boxes x ____ = beats per pen
10
ECG paper speed of 50mm/sec
30 big boxes x ____ = beats per pen
20
What are the ECG characteristics of sinus block? sinus arrest?
Abrupt pause in rhythm
Block - 2x longer than the previous R-R interval
Arrest - more than 2x longer than previous R-R interval
What are the ECG characteristics of atrial standstill?
No P waves
What diseases are associated with atrial standstill?
Hyperkalemia
Atrial fibrosis - english springer spaniels, old english sheepdogs
What are the ECG characteristics of 1st degree AV block?
Prolonged P-R interval
There is a P for every QRS
What are the causes of 1st degree AV block?
increased vagal tone - resting and digestion
What are the ECG characteristics of 2nd degree AV block Type 1?
Gradually prolonged PR interval
P without QRS complex
What is the cause of 2nd degree AV block Type I?
High vagal tone
What are the ECG characteristics of 2nd degree AV block Type 2?
Fixed P-R interval
P without a QRS
What are the causes of 2nd degree AV block Type 2?
AV nodal disease (myocarditis, tumors, age related fibrosis)
more likely to go into 3rd degree AV block
What are the ECG characteristics of 3rd degree AV block?
Complete dissociation between P and QRS complex
What is the mechanism behind atrial tachycardia?
increased automaticity of ectopic foci with re-entry
What are the ECG characteristics of atrial tachycardia?
Abnormal P wave morphology
Normal QRS complex with regular R-R interval
What is the mechanism behind atrial fibrillation?
Micro-reentry
What are the ECG characteristics of atrial fibrillation?
No P waves
Irregularly irregular of R-R interval
Normal QRS complex
What is the mechanism behind atrial flutter?
Macro-reentry
What are the ECG characteristics of atrial flutter?
Flutter waves - saw tooth appearance to the baseline
Regular R-R interval
Normal QRS complex
A VPC with positive deflection originates from what side?
Right
A VPC with negative deflection originates from what side?
Left
