Post on 22-Dec-2015
Claude Monet: French Impressionist“Japanese Bridge”
Cardiac Cardiac ElectrophysiologyElectrophysiology
ECG in DiagnosisECG in Diagnosis
Wagner:
Chapter 1:3-23
What is an ECG?What is an ECG?
Recording: (“gram”)Electrical Activity: (“electro”)Generated by heart cells:
(“cardio”)That reach the body surface
EElectroCCardioGGram
What Does an ECG What Does an ECG Measure?Measure?Voltage: Vertical axis
Summation of electrical activity of the total number of cardiac cells
Higher voltage ~ more mass12-Leads give 3-D “image”
Time: Horizontal axisHeart Rate and RhythmLead II or V5-V6 usually
I aVF V1
II
III
aVL
aVR
II
V2
V3
V4
V5
V6
**Limb LeadsLimb Leads: I, II, III, aVF, aVL, aVR: I, II, III, aVF, aVL, aVR
**Chest Leads: Chest Leads: V1 – V6V1 – V6
What Can ECG Diagnose?What Can ECG Diagnose?
Electrical impulse formation and conduction problems
Cardiac HypertrophyMyocardial Ischemia/InfarctMetabolic Problems:
Potassium, calcium and drug toxicity
ECG and CADECG and CAD Ischemic Cascade:1. Hypoxia = Anaerobic ATP
and lactic acidosis2. Ventricles “stiffen” diastolic fill3. Reduced SV and EF ( CO)4.4. ECG Waveform ChangesECG Waveform Changes5.5. Potentially Lethal Potentially Lethal
ArrhythmiasArrhythmias
Electrophysiology Electrophysiology ReviewReview
Myocardial Action PotentialMyocardial Action Potential
mV
-100
+40
0
4
0
1 2
3
4
ECG
AP
AP AP ECG ECG Measured in the
Cardiac Cell
Resting Potential = -90mV
Depolarization = Phase 0
Repolarization = Phase 3
Measured at the Skin Surface
Resting Potential = Isoelectric Line
Depolarization = +/- deflection
Repolarization = “T-Wave”
Myocardial Action PotentialMyocardial Action Potential
mV
-100
+40
0
4
0
1 2
3
4
ECG
AP
ECG BasicsECG Basics
ECG graphs:1 mm squares5 mm squares
Paper Speed:25 mm/sec standard
Voltage Calibration: 10 mm/mV standard
ECG Paper: ECG Paper: Dimensions5 mm
1 mm
0.1 mV
0.04 sec
0.2 sec
Speed = rate
Voltage ~Mass
Cardiac CycleCardiac Cycle: ECG WAVESNormal ECG
formation / conduction: P Wave: Atrial
depolarization/contractionQRS Waves: Ventricular
depolarization/contractionT Wave: Ventricular Repolarization
ECG: Cardiac CycleECG: Cardiac Cycle
Cardiac Cycle Basics:Cardiac Cycle Basics:Begins with SA Node
depolarizationP – P = 1 CycleHeart rate (pulse) is determined
by ventricle depolarization/contraction
R – R = 1 heart beat
Calculating Heart Rates from ECG’s: Step OneSinus Rhythm: Each QRS
complex is preceded by P waveNSR: Within the intrinsic rate of
the SA Node: 60-100 bpmTachycardia: >100 bpmBradycardia: < 60 bpm
Step Two: Step Two: Count the number of small
squares between R – R waves (X):
Divide 1500 by X:Rate = 1500 / X
Example: X = 20 1500 / 20 =75 Rate = 75 bpm
Why “1500 / X”?Why “1500 / X”?
Paper Speed: 25 mm/ sec60 seconds / minute60 X 25 = 1500 mm / minute
Activity 1: Cardiac Cycle Activity 1: Cardiac Cycle Identification and RatesIdentification and RatesDraw and Label ECG
representing one cardiac cycle (see page 18)
Identify the Mechanical Events coinciding with the ECG Wave forms and intervals
Calculate the heart rates for the sample rhythm strips