ST Segment in ECG

Cellular electrophysiological changes Hypotoxic conditions lead to diminished intracellular concentration of ATP => loss ATP  Loss ATP => No Na/K ATPase pump => No K influx and Na out

ST Segment in ECG

THL

I Action potential

II Heart Conduction

III Cellular electrophysiological changes

 Hypotoxic conditions lead to diminished intracellular

concentration of ATP => loss ATP

 Loss ATP => No Na/K ATPase pump => No K influx and Na outflux => DEPOLARIZATION because of no hyperpolarization curents

 Loss ATP => No Na/K ATPase pump => More K in extracellular concentration => membrane DEPOLARIZATION

 Loss ATP => Open K - ATP Channel => outward of movement of K => More HYPERPOLARIZATION => Membrane DEPOLARIZATION

 DEPOLARIZATION leads to inactive fasting Na – Chanel (phase 0)

=> Decrease conduction velocity => ARRHYTHMIA

IV T wave abnormalities

T waves usually positive in almost leads

cause the double negavetive in direction and charge

sbubendocardial ischemia cells have a

shorter duration of action potential => Earlier

onset of repolarization => Repolarization

waves travels towards recording electrodes

=> Inverted T waves

V Electrocardiogram ST segment changes

 Subendocardial ischemia = ST depresstion = Partial occlusion

 Transmural ischemia = ST elevation = Total occlusion

Subendocardial ischemia = ST depresstion = Partial occlusion

Subendocardial ischemia = ST

depresstion = Partial occlusion

 DEPOLARIZATION ISCHEMIC SUBENDOCARDIUM => electrical current

travels toward the recording electrode => BASALINE VOLTAGE ( which is

normal isoelectric = 0mV) elevated => RED LINE No.1

 The whole ventricular DEPOLARIZATION => 0mV like normal => RED LINE No.2

 REPOLARIZATION => Voltage remains positive in resting stage => RED LINE

No.3

Transmural ischemia = ST elevation = Total occlusion

Transmural ischemia = ST elevation =

Total occlusion

 The ischemic region and subsequent infarcted tissue spans the entire thickness

of the muscle wall from endocardium to epicardium Occurs when ventrical is at rest and repolarized

 DEPOLARIZATION ISCHEMIC SUBENDOCARDIUM => electrical current

travels away the recording electrode => BASALINE VOLTAGE ( which is

normal isoelectric = 0mV) depressed => RED LINE No.1

 The whole ventricular DEPOLARIZATION => 0mV like normal => RED LINE No.2

 REPOLARIZATION => Voltage remains negative in resting stage => RED

LINE No.3

How to read an ECG

 Rate

 Rhythm

 Axis

 Hypertrophy

 Infarction

Thank you very much

 THL