Lecture 4 8/22/24 Flashcards
What is the use of electrocardiography?
clarify disorders of rate and rhythm
What is the limitation of electrocardiography?
inaccurate method for detection of cardiac chamber enlargement
What does it mean for cardiomyocytes to be excitable?
electrochemical gradient is maintained across the cell membrane
What is an action potential?
stimulation of cardiomyocytes resulting in a momentary reversal of trans-membrane potential
Why are specialized conduction cells such as the SA and AV nodes referred to as pacemaker cells?
they exhibit automaticity and can depolarize spontaneously
Why are the working cardiomyocytes considered to exhibit excitability, but not automaticity?
they do not spontaneously depolarize, but can be stimulated to do so
What are the characteristics of the fibrous skeleton of the heart?
-electrically isolates the atria and ventricles
-AV bundle penetrates the fibrous skeleton
What are the two main characteristics of heart function that are discerned from ECG?
-rate
-rhythm
When is an ECG indicated?
when the heart rate is inappropriately fast, slow, or irregular
What do the waves on an ECG correspond to?
P wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
How does the QRS complex appear when ventricular activation is normal?
-rapid
-narrow
-typically upright/positive
Which clinical signs can be caused by arrhythmias?
-syncope
-low cardiac output
-sudden cardiac death
What is an arrhythmia?
any deviation from regular sinus rhythm (all RR intervals being the same)
What can cause the development of a tachyarrhythmia?
-structural cardiac disease
-extra-cardiac disease
What are the steps to take when assessing ECG?
-is heart rate normal?
-is rhythm regular?
-are there consistent PR intervals?
