Ch. 2 ECG Flashcards
Basic contractile unit of the heart
myofibril
SA Node
@ RA/SVC
- controlled by ANS (symp/para)
- at P wave
AV Node
@ interior intra-atrial septum- relays signal from atrium to ventricle
- during P-R= isoelectric line
EKG Times
- P wave= 0.8-1.2
- QRS= .8-.1
- T wave= .2
- PR= .12-.2
- ST= .12-.15
Elevated vs Depressed S-T
Elevated ST= myocardial injury
Depressed ST= acute MI/ischemic
Inverted vs Peaked T wave
Inverted= ischemia Peaked= high K
Deep QRS
necrosis
Node BPM
SA= 60-100 AV= 40-60 Perkinje= 20-40
Brady < 60
Tachy >100
U wave
due to low K/Ca, or perkinje repol
PAC
Premature Atrial Contraction
-early P wave, QRS/Twave= normal
Atrial Tachycardia
Pwave overlaps with Wave, rhythm regular with narrow QRS (bpm= 120-150)
-aka paroxysmal supraventricular tachycardia (PSVT)
Atrial Flutter
Pwave= bidirectional** and saw-toothed*
2: 1 ratio Atrial:Ventricle
- atrial 250-350 bpm
Atrial Fibrillation
irregular ventricular response (AV node)***
- high atrial impulses
- ventricular response
1) rapid- 100 bpm
2) mod- 60-100
3) slow- <60
AV Block
1st: P-R > .2 sec
2nd (intermittent)= some signals fail to present QRS
3rd (complete block)= no impulse hit AV nod= no vent depol from AV node- random impulses though the ventricle conduction
PVC
Premature Ventricle Contraction= No P wave, wide QRS, followed by pause
1) Bigminy= every sinus beat followed by PVC
2) Trigeminy= every 2 sinus beats followed by PVC
3) Couplet= 2 consecutive PVCs
Ventricular Tachycardia
ventricle rate > 20-50 bpm, QRS >100
Ventricular Fibrillation
starts with short run of VT
-ventricle quivers= no contration
ANS effects on SA node
1) sympathetic= norepinephrine= increase HR, contraction
2) parasympathetic= acetylcholine= decrease HR, CO, perph resistance
- works on prejunctional to lower nori release
- works on post junctional muscarinic receptors= lower beta adrenergic receptors
Chemoreceptors and Baroreceptors
@carotid and arctic bodies
- chemo= stimulated by low O2, high CO2, low pH
- baroreceptors= controls HR, BP, and lesser inotrophy
Exercise and Hemorrhage do what do ANS
increase sympathetic, lower para
incase BP, HR
Adrenergic, muscarinic, and nicotinic receptors
adrenergic= symp (alpha and beta) muscarinic/nicotinic= para