Chapter 20 - The Heart - ECG/EKG Flashcards
What does ECG stand for?
Electrocardiogram
the electrical events in the heart are powerful enough to be detected by ____ on the surface of the body
electrode
Clinicians can use an ECG to assess the performance of which 3 things?
-a specific nodal
-conducting components
-contractile components
Briefly explain the 5 steps of impulse conduction through the heart
- SA node activity begins and atrial activation begins
- The stimulus spreads across the atrial surfaces and reaches the AV node
- 100msec delay at the AV node to allow for atrial contraction
4.impulse travels towards the interventricular septum within the AV bundle, to the bundle branches, to the Purkinje fibers, and then through the moderator band the impulse travels to the papillary muscles of the right ventricle
- The impulse is distributed by the Purkinje fibers throughout the ventricular myocardium. Atrial contraction is complete and ventricular contraction begins
Step 1 — SA node activity and atrial activation – represents what on the ECG?
nothing. just a flat line
Step 2 – The stimulus spreads across the atrial surfaces and reaches the AV node — what does this step represent on the ECG?
the p wave – smallest wave
Step 3 — there is a 100msec delay to allow for atrial contraction to begin – what is this step represented by on the ECG?
P-R interval. flat line
step 4 – the impulse travels along interventricular septum to the bundle branches, Purkinje fibers, and to the papillary muscles by way of the moderator band — what is this step represented by on the EKG?
The Q wave —- downwards wave. Ventricular depolarization begins
Step 5 – Atrial contraction is complete and ventricular contraction begins – what is this represented by on the ECG?
the QRS complex — completion of ventricular depolarization
the small P wave accompanies the…
depolarization of the atria
What does the T wave represent on an EKG?
Occurs after the ventricles contract
indicates when the ventricles have repolarized after contracting
the QRS complex appears as the ventricles…
depolarize. complex, strong signal
the ventricles begin contracting shortly after the peak of the ___ wave
R
why is atrial repolarization not apparent on an ECG?
because it occurs while the ventricles are depolarizing and the QRS complex masks this electrical event
Explain the P-R interval
extends from the start of atrial depolarization to the start of the QRS complex (ventricular depolarization)
