5 - EKG Introduction Flashcards
A _______ wave of depolarizion within the myocytes flows toward the _______ electrode.
This will record as a ______ on the EKG.
Positive, Positive
Positive
The ________ is the heart’s dominant pacemaker.
In what direction does the wave of depolarization spread from this location?
SA Node
Spread in all directions (pebble dropped in pool of water)
P Wave
Each depolarization wave emitted by the SA Node as it spreads to both atria, represents simultaneous contraction of the atria
What valves does blood flow through when a P Wave is produced?
Atrioventricular (AV)
Mitral
TRicuspid (R Atrium - R Ventricle)
What valve controls flow from the right ventricle to the polmonary circulation?
What vessel does this flow through?
Pulmonary Valve
Pulmonary Artery
What valve separates the Left Atrium and the Left Ventricle?
What valve separates the Left Ventricle and Systemic Circulation? What Vessel is this?
MitraL Valve
Aortic Valve, Ascending Aorta
MitraL is on the Left side
What directly follows the P Wave on an EKG?
A brief flatline, or pause which allows the atria to empty completely before ventricles contract
Depolarization slows as it progresses from SA - AV Node
What is the major ion for slow conduction through AV Node?
Ca2+
What ions are key for the fast conduction from the His Bundle Branches through the Purkinje fibers?
Fast Na+ ions
Depolarization of the _______ along terminal filaments of Purkinje fibers produces what on the EKG?
Entire ventricular myocardium
QRS Complex
How does the conduction of purkinje fibers spread within the myocardium?
From endocardium to epicardium
What EKG complex represents the beginning of ventricular contraction?
QRS Complex
Q Wave
R Wave
Are Q Waves always present on EKGs?
First downward wave of the QRS Complex (Q)
First upward wave of the QRS Complex (R)
No, Q Wave is OFTEN ABSENT on EKG
If there is any upward deflection in a QRS complex, what type of wave is it?
R Wave
By definition, a Q Wave is the first downward wave of a QRS Complex; if it goes UPWARD it is NOT a Q Wave
S Wave
The downward wave (S) preceded by an upward wave (R)
What is a QS Wave?
A negative “V”
The downward portion is the Q
Upward is the S
An R would be positive
What is the horizontal baseline immediately following QRS Wave on EKG?
What is the broad hump following this?
What does this entire area represent?
Plateau Phase - ST Segment
T Wave
Ventricular Repolarization
What does an abnormal (elevated/depressed) ST Segment usually represent?
Imminent pathological problems
T Wave
Final “rapid” phase of ventricular repolarization, during which ventricular repolarization occurs quickly and effectively
What is the principle ion for repolarization?
K+ ions leaving myocytes
Through what EKG periods does systole (contraction) occur?
What is significant about this range?
Clinical implications?
Begins with QRS through end of T Wave
QT Interval
Clinical: Lonq QT Syndrome rapid ventricular rhythms
QTc Intervals
General rule of thumb?
QT Intervals are corrected for heart rate
Normal: QT Interval < 0.5 R-to-R Interval
Key Ions:
Calcium
Potassium
Sodium
Calcium - Myocyte contraction
Potassium- Myocyte repolarization
Sodium - Cell to Cell depolarization (Exception: AV node depends on slow Ca2+ ions)
Standard time scale on EKG graph?
X - axis
Small square = 0.04 seconds
Large square = 0.2 seconds
