EKG Flashcards
Ecg Definition
- The ECG is a linear recording of the electrical activity of the heart that repeats over time, taken from outside the body by surface electrodes.
- electrical activity recorded via electrodes are transcribed on to graph papeUsual method to explore the heart
- Useful tool of diagnostic of different cardiac disorders
- It remains a fundamental method to assess the heart’s electrical activity
- introduced more than 100 years ago by Willem Einthoven (describe utility of string galvanometer in 1901)
- It is old but not obsolete
- Less expensive, Accessible
Clinical Tip:
Patients should be treated according to their
symptoms, not merely their ECG.
Ecg paper
Marked with vertical and horizontal lines Vertical lines mark : - duration that depends on running speed (At 25 mm / sec: 1mm = 40 msec = 0.4 seconds) - The horizontal lines mark amplitude (voltage) configuration (+ / -) and Standard Calibration Signal (Gain) 1 mV = 1 cm 0.1 mV = 0.1 cm = 1 mm ECG paper divided into small 1 mm, and large 5mm squares 1 large square = 5 small squares ECG paper runs at 25 mm per sec 1 small square = 1/25 = 0.04 sec =40 ms 1 large square = 1/5 = 0.2 sec = 200 ms 5 large squares = 1 sec 300 large squares = 1 min
Technical Problems
Environmental Conditions
• Temperature ~20o (! Below → Parasitic waves)
• SKIN: degreasing (alcohol / ether), hair removal
• Lack of access electrodes → amputation / gypsum
• Contact solution should be Ecg gel / Saline solution)
• Ground →Isolation of the bed
Conditions of registration
• Correct positioning electrodes (solid plan, firm skin contact)
• Checking standard calibration (gain) !
• Set recording speed:
Standard 25 mm / s or
• 10 mm/ s → Rapid arrhythmias
• 50 mm/s → Morphology analysis
Information about the patient
Should be noted on the ECG 1. Identity data (Name, Sex, Age) 2. Symptoms : eg "in pain" 3. Drug therapy 4. If the device does not automatically, register • Record speed • Date • Time
Ecg clasification
Standard (conventional) Ecg (surface Ecg)
24 hours recording ECG (Holter)
Computerized ECG
Exercise ECG test - while the patient is doing a standardized effort
& immediately after (recovery)
Recording Electrodes and Leads Systems
The 12 conventional ECG leads record the difference in potential between electrodes placed on the surface of the body.
Electrodes are located on extremities and on the chest
The standard resting ECG is performed using 12 leads:
─ 3 standard limb leads (leads I, II, and III)
─ 6 precordial leads (leads V1 through V6)
─ 3 augmented limb leads (leads aVR, aVL, and aVF)
The limb leads record potentials transmitted onto the frontal plane, and the chest leads record potentials transmitted onto the horizontal plane
Electrode Placement
SLIDE 7 ,8 ,9 ,10
ECG analysis
- Heart Rhythm
- Heart rate
- Electric axis
- P wave analysis
- P-R / P-Q interval Analysis
- QRS and S-T segment Analysis
- T wave Analysis
- U wave analysis
- Q-T interval duration
ecg analysis
slide 12
Rhythm
Rhythm can be normal sinus rhythm or ectopic rhythm.
Sinus rhythm produces
− positive P waves in leads I, II, aVF, and V2 to V6
− Positive or positive/negative waves in III and V1
− positive or negative/positive waves in aVL
− Negative P waves in aVR
Rhythm check for :
• recognizable periodicity or pattern Description = Regular / irregular - depending on P wave in lead II & aVR ♥ regular Sinus Rhythm / jonctional / idioventricular ♥ irregular without p wave: AFib → with p wave: SR with premature beat
Normal Sinus Rhythm
P wave positive in lead II negative in lead aVR Heart rate 60-100 bpm Constant PP (constant RR) Constant PR (normal range)
Heart rate
Methods
- 1. 1500 R-R distance - 2. 300 / 150 / 100 / 75 / 60 / 50 / 43 / 37 / 33 / 30 (300 : 5 = 60 sec =1 min) regular rhythm: • count the number of large graph boxes between two R waves. • divide that number into 300 (300 : 5 = 60 bpm)
Electrical Axis (QRS axis)
- The electrical axis is the total sum of all electrical currents
- it is QRS complex axis
- tool: Einthoven triangle & hexaaxial system
- visual method : electrical impulse is
maximum in the parallel lead
Minimum in the lead perpendicular on it (or echidifazic) - bisector method - exact determination
♥ 0 (- 30) + 90o = normal axis
♥ +90 + 180o = right axis deviation
♥ [–30–45]
[-45–90o]= moderate and marked left axis deviation
♥ izoelectric cpx. all leads indeterminate axis
P wave analysis
P wave characteristics
slide 17
- Positive in II si I
- Negative aVR
- Best seen in D II, V1
- Biphasic in V1, usually
- Amplitude 2 - 3 mm (< 2.5 small squares)
- Duration → 80 – 120 msec (< 3 small squares)
- Small rounded, upright (positive)
- atrial repolarization = Tp, hidden in QRS complex
1th ½ - RA depolarization
2th ½ - LA depolarization
Atrial Depolarization = First wave seen on Ecg
P wave pathological changes
• inverted P inferior atrial depolarization
• ↑ P amplitudine Atrial hypertrophy / dilatation
• ↑ P duration dilated LA
• P absent, regularly rhythm junction rhythm, SA block
• P biphasic, the 2th ½ negative in V1 LA dilated
• P bifid, duration > 120 ms mitral P
amplit. D1>D3
• P amplitude > 2.5mm pulmonary P
sharp peak, D3>D1
PR (P-Q) Interval and Segment analysis (I)
PR interval is the distance from the beginning
of the P wave to the beginning of the QRS complex
= time from P to Q / R (Measures time during which
a depolarization wave travels from the atria to
the ventricles)
normal duration range from 120- 200 ms
- depend on Heart rate (HR)→ PR decrease when HR increase)
- depend on age (up to 0.22 second in the elderly
And < 0.12 sec in the newborn)
• P-R > 200 msec. = AV-Block
• P-R < 120 sec. = preexcitation syndromes
+ delta wave + wide QRS = WPW syndrome
+ narrow QRS = short P-R syndrome(LGL)
• Reduced P-R → suppression of parasympathetic tone at effort
• Increased P-R during tachycardia reflect - conduction disturbances or - digitalis effect
PR (P-Q) Interval and Segment analysis (II)
The PR segment is the distance from the end of the P wave to the QRS onset and is usually isoelectric.
**Sympathetic overdrive may cause a descent in PR segment that forms part of an arch of circumference
together with an ascendant ST segment
**In pericarditis and diseases affecting the atrial myocardium, as in atrial infarction, PR segment in lead II is depressed or, more frequently, an elevated PR segment in lead VR may be seen.
