Cardio II Flashcards
Corresponds to atrial depolarization in the ECG
P Wave
Corresponds to ventricular depolarization in the ECG
QRS complex
Corresponds to ventricular repolarization in the ECG
T wave
Conduction of Cardiac AP through AV node
PR Interval
Correlates with Phase 2/Plateau of Cardiac AP
ST segment
Isoelectric points
PR Segment
ST Segment
Stimulates AV node which increases conduction velocity and decreases PR interval
Sympathetic NS
B2 receptors
- Shorter Phase 4 = Faster AP
Type of Heart block where all atrial impulses reach the ventricles but PR INTERVAL IS LONG
1st Degree AV Block
Type of Heart block where not all impulses are conducted to ventricles:
Ventricular rate < atrial rate
Or P Wave not always followed by QRS
2nd Degree AV Block
Complete AV Block with P and QRS waves independent from each other causing atrioventricular dissociation
3rd Degree AV Block
Sporadically occurring block with constant PR Intervals before a block occurs
Mobitz Type II
(-) Wenckebach phenomenon
ECG shows gradual increase of PR interval before a block occurs
Mobitz Type I
(+) Wenckebach phenomenon
Systemic diseases that can cause 3rd Degree AV Blocks
Amyloidosis
Sarcoidosis
SLE
3rd Degree AV block causes:
Fainting/syncope
Worsening exercise intolerance
**Due to cerebral ischemia
ECG findings in Hypokalemia
- Increased amplitude and width of P wave
- QT prolongation
- ST depression
- Flat/inverted T wave
- Prominent u wave
ECG findings in Hyperkalemia
- Low P wave
- Tall T wave
ECG Findings in Hypocalcemia
- Prolonged QT interval
Hypocalcemia is associated with
Long QT syndrome which can cause sudden fainting and sudden death
Torsades de Pointes which can cause ventricular arrhythmias/ventricular fibrillation
Which drug class causes Torsades de Pointes?
Macrolides
ECG finding in Hypercalcemia
Shortened QT interval
ECG finding in Q-wave infarct or Transmural Infarct
ST Segment Elevation
ECG finding in non Q-wave infarct or Subendocardial Infarct
ST Segment Depression
Cardiac Stable RMP
-90mV
Phases of Cardiac AP
Phase 0, 1, 2, 3, 4
Phases of Cardiac SA Node AP
Phase 4, 0, 3
Phase 4 = Unstable RMP
Phase 0 = Depolarization - Ca influx
Phase 3 = Repolarization - K efflux
Sequence of Cardiac pacemakers
SA Node > AV Node > Bundle of His > Purkinje Fibers
Master Pacemaker that exerts overdrive suppression on other pacemakers
SA Node
Latent Pacemakers
AV Node, Bundle of His, Purkinje Fibers
When latent pacemakers assume pacemaking activity
Ectopic Pacemaker
Intrinsic rate of Phase 4
SA Node: 70-80 beats/min
AV Node: 40-60 beats/min
Bundle of His: 40 beats/min
Purkinje Fibers: 15-20 beats/min
Pacemaker with slowest conduction velocity
AV Node at 0.01-0.05 m/sec
Pacemaker with duration of cycles
SA Node
Pacemaker with fastest conduction velocity
Purkine Fibers at 2-4 m/sec
Responsible for slow Na influx during Phase 4 of SA Node AP
If or slow, funny Na channels
What triggers If channels?
K efflux of Phase 3 which causes automaticity and pacemaking activity
**phase 3 always causes phase 4
What causes AV Nodal conduction delay?
Fibrous tissue with less gap junctions causes delay in transmission of conduction which allows adequate time for ventricular filling
Changes in CONTRACTILITY
Inotropic effect
Changes in RELAXATION
Lusitropic effect
Changes in HEART RATE
CHronotripic effecy
Changes in CONDUCTION VELOCITY
Dromotropic effect
Intropes affect
Ventricular contraction and stroke volume
Chromotropes affect
SA Node (HR)
Dromotropes affect
AV Node (Conduction Velocity)
Dromotropes are affected vg
Inward calcium current
B1 stimulation of the heart will cause
Stronger, briefer and more frequent contractions
+ inotrope
+ lusitrope
+ chronotrope
Myocardial contractility is best correlated with intracellular concentration of
Calcium