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.
!!!!!!!
P/ PR analysis
- The P wave and PR interval have to be measured at
least with a three-channel device - The exact P wave duration is the distance from P
wave start in any lead to the last end of the P wave
also in any lead. - The PR interval measurement is the distance from
the earliest onset of the P wave in any lead (in this
case, lead III) to the earliest onset of the QRS
complex in any lead (in this case, also in lead III). - Abnormalities of Atrial Repolarization
The atrial repolarization wave (ST-Ta) usually has a
polarity opposed to the P wave and is not visible
because it is hidden within the QRS complex. In cases
of great sympathetic overdrive in normal individuals, an
ST-Ta depression may be seen
QRS analysis (I)
- The QRS complex corresponds to ventricular depolarization.
Its morphology varies in the different leads. - 1th deflection may be: negative = Q wave
pozitive = R wave - 2th deflection negative = S wave
- following waves: positive = R’, R”; negative = S’, S”
- q, Q, r, R, s, S aspect– depend on wave amplitude
- QRS interpretation:
• duration
• amplitude (voltage)
• general aspect (morphology) of waves -
• transition zone in chest lead
• time of onset of intrinsecoid deflection
• electrical axis
• Q wave presence
+ SLIDE 21 (SOS)
QRS analysis (II)
QRS Duration : — abnormalities —> Intraventricular Conduction Delays or Defects
“QRS duration traditionally is set at less than 120 milliseconds, measured in the lead with the widest QRS complex. Recent epidemiologic studies have suggested that the median QRS duration may be shorter, as low as 100 milliseconds in men and 92 milliseconds in women”
50 -100 ms in standard lead (narrow QRS)
- 110 – 120 milisec. - Ventricular Hypertrophy
- minor BBB (bundle brunch block)
120 milisec. (wide)– intraventricular Block, BBB – bundle branch block
Left Anterior Fascicular Block
- QRS axis:−45 and −90 degrees
- qR pattern in lead aVL
- QRS duration < 120 msec
- Time to peak R wave in aVL TOID ≥ 45 msec
Left Posterior Fascicular Block
- QRS axis between +90 and +180 degrees
- rS pattern in leads I and aVL with qR patterns in leads III, aVF
- QRS duration < 120 msec
QRS analysis
Intraventricular Conduction Delays or Defects
Common Diagnostic Criteria for Bundle Branch Blocks
Complete Left Bundle Branch Block
• QRS duration ≥ 120 msec with midfinal slurring
• Broad, notched, or slurred R waves in leads I, aVL, V5, and V6
• Small or absent initial r waves in leads V1 and V2 followed by deep
S waves
• Absent septal q waves in leads I, V5, and V6
• Prolonged TOID >60 msec in V5 and V6
QRS analysis
Intraventricular Conduction Delays or Defects
Common Diagnostic Criteria for Bundle Branch Blocks
Complete Right Bundle Branch Block
• QRS duration ≥ 120 msec
• rsr′, rsR′, or rSR′, patterns in leads V1 and V2
• S waves in leads I and V6 ≥ 40 msec wide
• Normal TOID in V5 and V6 but > 50 msec in V1
+ SLIDE 23
QRS analysis
Intraventricular Conduction Delays or Defects
Trifascicular Blocks
1. RBBB alternating with the block of one of two left bundle branch divisions
The most frequent features are as follows:
1. RBBB alternating with the block of one of two left bundle branch divisions
! • Once the block of three fascicles has been confirmed
by an ECG (RBBB alternating with superoanterior and
inferoposterior fascicle blocks), a pacemaker should be implanted as soon as possible because the patient may suddenly develop a paroxysmal AV block
QRS analysis
Intraventricular Conduction Delays or Defects
Trifascicular Blocks
2. Bifascicular blocks with a long PR segment.
Note that a long PR segment may also be caused by a block at a proximal location (bundle of His); thus, electrophysiologic studies are required to confirm their occurrence
QRS Voltage (amplitude) influenced by:
- position + electrodes contact,
- thorax size, emphysema, etc.
- pathological condition
•QRS pattern: morphology
slide 26
•Electrical axis of the QRS
describes the mean orientation of the
QRS vector with reference to the six
frontal plane leads.
• Time of onset of intinsecoid
deflection (TOID)
- V1-V2 < 0.035 sec.
- V5-V6 < 0.045 sec.
Q wave
slide 28 • Normal Q in D1, aVL, V5, V6, aVF Amplitude q < 2 mm Duration = 30 msec. maximum • Pathological Q Amplitude > 1/4 R from the same lead Duration > 40 msec. absence of delta wave in WPW ~ q Q presence (D2, D3, aVF, V1-V3) in patients with LBBB Inspiration disappearance of positional q in inferior lead
ST segment Analysis- Izoelectric line is TP segment
- Distance between S wave and beginning of T wave
- emergence from QRS = J point
- analysis of 2 elements :
• Translation from the isoelectric line - Permitted ST elevation : < 1 mm D1-D3, ≤ 2 mm V1-V2
Pathological:= subepicardial injury (> 1 mm D1-D3, >2 mm V1-V2) - Permitted ST depression: < 0,5 mm Secondary to: ventricular
- hypertrophy, BBB, WPW
Pathological > 0.5 mm subendocardial injury
• Shape: linear, curved slightly to the slope of T wave
Pathological= perfect horizontally line: supposition of mioc. ischemia
+ slide 29 (SOS)
T wave Analysis
The ST-T wave reflects activity during the plateau phase (the ST segment) and the later repolarization phases (the T wave) of the cardiac action potential. - T wave Represents ventricular repolarization - same orientation as QRS complex - positive: D1, D2, V3, V6 - negative: aVR - amplitude aprox. 1/3 of R - shape – asymmetrical - smooth ascending slope - abrupt descending slope, rounded top \+ SLIDE 30 (SOS)
U wave analysis
• Small rounded, upright wave following T wave
• Usually less than 0.1 mV in amplitude
• Same orientation as T wave, Positive except aVR
• The U wave is largest in the leads V2 and V3 and is most often seen at slow heart rates
• Best seen V3
• If amplified with same polarity → hipopotasemia
• “Electrophysiologic basis is uncertain. Suggestions include delayed repolarization in areas of the ventricle that undergo late mechanical relaxation,
late repolarization of the Purkinje fibers, and long action potentials of
(putative) midmyocardial M cells. “
• If negative → ischemia (subtle sign )
→ left ventricular (LV) strain in hypertension (HTN)
+ SLIDE 31 (SOS)
QT interval analysis
epresents total ventricular systolic activity Variability - determined by heart rate → correction formula = Bazett QTc - affected by: catecholamine, sex, age circadian pattern, sleep Pathology: QT prolongation QTc > 440 milisec. Is prolonged Long QT - idiopathic / acquired Prone to malign arrhythmia (torsade de points, VT; syncope, SCD) \+ SLIDE 32 (SOS)
PATHOLOGICAL
Findings on Electrocardiography
ATRIAL ENLARGEMENT
- P wave changes (atrial depolarization)
RA enlargement
• hypervoltage > 3 mm • morphologic P changes in V1, V2, D2, D3, aVF • P axis modification • P pulmonary - symmetrical - sharp, like a tent = RA Dilation
LA enlargement
• P wave- left axis deviation • P wave- morphological changes (wave 2nd part) in D1, aVL, V5, V6, indirect V1,V2 mitral P - duration > 110 msec. - slurred - P negative in V1, V2 asynchronism AD-AS > 20 msec.
RA + LA enlargement
• depend on each dominance
• P wave changes
duration > 110 msec.
hypervoltage > 3 mm, especially in standard lead
hypervoltage both deflections +/ - V1, V2
LV ENLARGEMENT + LV criteria
Anatomy/physiopathology:
- ventricular hypertrophy = thickening of the wall
- cavitaty dilatation
- LV strain (forced LV)
LVH Criteria
Sokolow – Lyon Index : R (V5/V6) + S (V1/V2) >35 mm (3.5 mV)
Romhilt – Estes Score
Ecg characteristics of LV hyperthrophy
• QRS amplitude - Direct view – R > 25 (35) mm - V5,V6 – R > 13 mm - aVL – R > 15 mm - D1 - Indirect view - S > 2 mV - V1,V2 • duration QRS ≥ 120 –130 msec. • secondary ST-T changes D1, aVL,V5, V6 •TAID duration = 60 msec V5, V6
RV enlargement/hypertrophy
- inverted aspect of normal Ecg: • R in V1, V2 • S in V5, V6 - clockwise rotation \+ slide 38,39 (sos)
ISCHEMIC HEART DISEASE (IHD)
ECG pattern in IHD:
- Ischemia → pathological T wave
- Injury → pathological ST segment
- Necrosis → pathological Q wave
Ischemia
• T wave – changed polarity to QRS
- symmetrical
- deviated electric axis
Injury ( ro: Leziune)
• subepicardial = ST segment elevation diagnostic & treatment criteria de for STEMI • subendocardical = ST segment depression
Necrosis
pathological Q wave
• duration > 0.04 sec.
• width > 1/3 of R in the same lead
ST elevation Myocardial Infarction
STEMI
ECG
- Necrosis N
- Injury L
- Ischemia I
+ SLIDE 43,44 (SOS)
Non ST elevation MI (NSTEMI)
ECG variants - subendocardical ischemia = most frequent - ST depression - T wave = negative Deep Persistent - QT prolongation - subepicardical ischemia - positive, symmetrical T wave - without Q wave
! ! In NSTEMI ECG criteria cannot be single
diagnostic tool
