Electrocardiograph ecg waves and segments p wave qrs

Electrocardiograph
ECG – waves and segments
P- wave
QRS – wave
T- wave
PR - interval
QRS - interval
QT- interval
PQ – segment
ST – segment
SA node must depolarize
Ventricular
Depolarization
QT intervial tells us about the action potential of the myocyte

Summary

Disorders
Most problems caused by disjunction of electrical
system
Arrhythmia – abnormal cardiac rhythm
1. Heart Block (varies in degrees) – failure in
conduction system
2. Atrial flutter – extra beats of the atrial
muscle
3. Premature ventricular contractions (PVC’s) –
extra beat
4. Ventricular fibrillation – electrical signals
arrive at ventricular myocytes at different
times
5. Myocardial infarction
6. Long QT
7. Electrolyte disturbances

•
Heart Block – electrical
signal disrupted between
atria and ventricles
i. First degree
ii. Second degree
iii. Third degree
(complete)
Disorders

Electrocardiograph
•
Nodal Rhythm – no SA node input , AV node
pacemaker – 50 bpm
Which wave is
missing?

•
Atrial Flutter: rapid heart beat (tachycardia)
250-300 bpm

2:1 QRS usually present (QRS max out at
250 bpm)
•
Atrial Fibrillation: rapid heart beat (tachycardia)
300-500 bpm
Disorders

•
PVC’s (extrasystole) – usually originate in left
ventricle
i. Inverted, misshapen QRS wave
Disorders

•
Ventricular fibrillation– erratic firing of
ventricular myocytes, unsynchronized
contraction
Disorders

•
Myocardial Infarction (MI)
i. ST elevation
ii. T- wave inversion
Disorders

•
Long QT syndrome
i. Ion channel mutations (K
+
, Ca
2+
, Na
+
)
ii. Leads to ventricular tachycardia, and death
Disorders
Longer to repolarize
Na or Ca stays on
K doesn’t turn on

•
Changes in Plasma K
+
: most relevant
electrolyte disturbance
Disorders
Hyperkalemia leads to death