Download Physiology Objectives 4

Physiology Objectives 4
1.
Dipole: a separation of charge between which current can flow
Picture of heart with depolarization wave, vectors, and ECG correlates:
2.
Leads (- to +) and ECG dipole conventions:
I (RA to LA):
II (RA to LL):
III (LA to LL):
aVF (virtual to LL):
aVL (virtual to LA):
aVR (virtual to RA):
V1:
V2 (virtual to floor (90o)):
V3:
V4:
V5:
V6 (virtual to RA (0o)):
3.
ECG with waves and intervals labeled:
Wave: an event that starts and ends at 0 volts
 P wave: 0.05-0.10 sec
 Q wave: first negative event before R wave
 R wave: first positive wave of ventricular depolarization
 S wave: first negative event after R wave
 T wave: 0.15 sec
Segment: an event that begins at one wave and stops before the next
 ST segment: 0.10 sec
 TQ segment: 0.60 sec
o Note: recall that this is a segment because the Q and T
waves are in the ventricle while the P wave is in the atrium!
Interval: an event that includes a segment and one or more waves
 PR interval: 0.12-0.20 sec
 QT interval: 0.31 sec
Complex: an event that includes more than one wave with no segments
 QRS complex: 0.06-0.10 sec
4.
ECG with timing of activation through heart:
5.
Given data, determine axis of depolarization: Draw perpendicular lines from
the heads of leads I, II, and III. These lines will intersect and form a triangle. The
vector from the origin to the center of the newly drawn triangle is the axis of
depolarization.
6.
1o heart block: P wave conduction to AV node is long
a.
PR interval longer than 0.20 sec
2o heart block: some P wave conduction to AV node does not occur
a.
Mobitz type I: PR intervals of increasing length until reset when a
P wave is not followed by a QRS complex
b.
Mobitz type II: multiple P waves followed by a single QRS
complex; named in ratios (X P waves followed by a QRS complex
is called X:1 block)
o
3 heart block: no P wave conduction to AV node
a.
Large QRS complexes not associated with P waves
Conditions needed for reentrant arrythmia: a divergent pathway and a
unidirectional block; this causes reentrant arrythmia because the wave of
depolarization can complete a circuit around the divergent path