ECG Flashcards
The instrument used for recording electric activity of heart is …., paper obtained is ….. & speed of paper moving is …..
Electrocardiograph
Electricardiogram
25 mm/sec
Uses & importance of ECG
- Anatomical orientation of heart
- Relative sizes of atria & ventricles
- Heart rate & regularity
- The pacemaker & path taken by AP
- Mscle status esp ventricles.
Mention abnormalities diagnosed by ECG
Dysrhythmias, myocardial ischemia & infarction, electrolyte disturnbance & influence of drugs (digitalis)
P wave represents ….., the ascending limb is for ….., while the descending is for …… , its duration is …..
Atrial depolarization
Right atrial depolarization
Left atrial depolarization
0.1 sec
Q wave represents ….. from …to….
Depolarization of ventricular septum , left to right
R wave represents ………, while S wave represents ……
Activation of ventricular mycodium (mainly left) from endocardial to epicardial surfaces.
Depolarization of the posterior & posterobasal portion of left ventricle & pulmonary conus
The start of isoelectric line after QRS is called …..
J point
T wave represents ….., its duration is …..
Ventricular repolarization
0.16-0.25 sec
GR: In ventricles, epicardium is repolarized before endocardium
Because the high intraventricular pressure presses on subendocardial blood vessels leading to partial ischemia, which delays repolarization in the endocardiak myocardial cells.
GR: Venticular re & depolarization are both upwardly deflected
Because de. is from endocardium to epicardium, while re. is from epicardium to endocardium.
U wave may represent ……., it is promininet in …
Slow repolarization of papillary & Purkinje fibers
Hypokalemia
GR: QRS amplitude is greater than P amplitude
Due to larger & thicker ventricular wall compared to atrial
GR: Duration of QRS is shorter than P complex
Due to presence of rapidly conducting Purkinje fibers in the ventricles.
GR: Atrial repoalrization is not recorded by ECG
It is buried in the QRS complex
PR interval respresents ….
Its duration is ….
Prolongation indicates …..
The time for atrial depolarization (plateau) plus the time for conduction through the AV node
0.12-0.21 sec
An abnormality of the conduction pathway through the AV node
QRS duration represents ….
Its duration is …..
Its prolongation indicates ….
Intraventricular conduction
0.04-0.08 sec
Ventricular hypertrophy and ventricular ectopic focus de. depends on cell-to-cell conduction
Q-T interval indicates …..
Its duration is ……
Ventricular electrical systole, measure for ARP
0.34 TO 0.43 sec
GR: ST segment is isoelectric
Because it represents a time when the entire ventricular myocardium is depolarized
ST interval is elevated in cases of …..
Myocardial ischemia
…… represents the true isoelectric line of ECG
T-P segment
The right leg is connected to …. Because …..
Ground
It acts as an electrical earth to discount other electric currents not produced by the heart preventing interference
A negative electrode is always placed on ….., a positive electrode is always placed on …..
Right arm
Left leg
State Einthoven’s law
The magnitude of any deflection in lead II is equal to the summation of the magnitude of the same deflection in lead I and in lead III.
Einthoven’s law detects …..
Abnormal physical connection
Mention the role of augmented limb leads
They record the potential difference between an exploring electrode on RA, LA or LL respectively and an electrode obtained by connecting the other two limbs
aVR = VR - (VL+VF)/2
Mention the position of precordial leads
V1 : 4th intercistal space left of sternum
V2 : 4th intercistal space right of sternum
V3: between V2 & V4
V4: 5th intercostal space left midclavicular
V5: 5th intercostal space left ant axillary line
V6: 5th intercostal space midaxillary line
The normal direction of vector is ….
Average is …..
-30 to +110 degrees
+60 degrees
Mention causes of left & right axis deviation.
L: 1. Short obese individuals, anatomical shift to left 2. Left ventricular hyoertrophy 3. Left bundle branch block 4. Right ventricular extrasystole R: opposite
Enumerate mechanisms of arrhythmias
- Disorders of impulse formation
a. Altered normal automaticity
b. Triggered activity - Disorders of impulse conduction (eg, reentry)
Mention factors determining firing rate
Maximum diastolic potential
Threshold potential
Slope of phase 4 depolarization
Mention conditions in which myocardial cells can exhibit automaticity properties
Conditions that drive the maximum diastolic potential towards the threshold potential (i.e. increased excitability such as hyperkalemia & catecholamine excess).
Define afterpolarization
Membrane potential oscillation that occur during or immediately following a preceding AP which acts as a trigger.
Mention the cause of afterdepolarization and its effect if exaggerated
Caused by a variety of conditions that raise diastolic intracellular IC Ca conc which can trigger a new AP if they reach the stimulation threshold.
(eg, in ischemia due to decreased activity of active Ca uptake)
Describe acceleration-induced block.
Impulses are blocked at high rates of incomplete recovery of refractoriness. When an impulse arrives & tissue that is still refractory , it will not be conducted (blocked).
Mention proposed reasons for deceleration-dependant block
- The reduced excitability and reduced AP amplitude due to calcium channels blockers, beta blocker or digitalis.
- Degenerative processes (ischemia, infarction or mechanical injury)
Describe anatomic reentry
When the impulse arrives to an area of unidirectional block (area of obtacle) it will stimulate it but connot pass. Slow (necessary) conduction of the de. wave on the other side will reach the the area of obstacle and can re-excite it, it has recovered. Therefore, this area will stimulate other areas and act as ectopic focus.
Mention causes & characteristics of AF
C: multiple ectopic foci in atrium, reentry in atrium
CCC: atrial rate: 350-500 bpm, vr: 100-150 bpm, completely irregular due to physiologic AV block, so some of the pulse waves are not transmitted to the peripheral arteries with large variation CO & BP. Atrial pumping power is lost with no contribution of atrial systole, the atrial contraction appears as bag of worms.
Describe ECG picture of AF
P wave is absent repaced by F waves
P-R interval is irregular
Normal QRS & T wave
QRS are irregularly spaced with variable RR interval, this is because the impulses are transmitted to ventricles whenever the AV node can conduct the depolarization process, so ventricular contraction shows irregular irregularity.
Treatment of atrial fibrillation
- Cardioversion
- Digoxin to increase AV refractory period
- Anticoagulant
PAT, Af & AF can cause symptoms of ……
Heart failure
Causes & characteristics of PVT
C: ectopic focus in ventricle, circus movement in ventricle. Can be cause by ischemic damage or touching endocardium by intracardiac catheter
CCC: Atrial rate is normal, vr = 150-250 bpm, v filling & v pumping & cardiac output are decreased
Describe ECG picture of PVT
Absent P wave, QRS is slurred, notched & wide bec of aberrant conduction in ven, direction of T wave is opposite QRS complex.
Mention treatment of PVT
Cardioversion, treatment affecting vagal tone in ineffective.
Mention causes of ventricular fibrillation
Ventricular ectopic foci Ventricular circus movement These may be caused by Myocardial ischemia Electric shock Ectopic focus during vulnerable period, a diseased heart is particulary susceptible to develop this arrhythmiabif stimulated in the vulnerable period which correspnds to the last part of repolarization from middle of T wave when some fiber are still depolarized, some partially repolarized & some completely repolarized.
Mention CCC of ventricular fibrillation & ECG
Absent coordination of heart beat
Ventricular contraction is totally ineffective, twitching movements, bag if worms
Peripheral pulse disappears
Cardiac output falls to zero
ECG: low voltage, very irregular, undulating waves of varying frequency and amplitude, without any distinguishable rhythm
Treatment of ventricular fibrillation
Electric defibrillaltion (cardioversion) The heart is exposed to an electric current with a very high voltage, aiming to make the whole ventricle muscle fibers depolarize & repolarize together.
Mention the name of accessory bundle in WPW syndrome & describe conduction of impulse in it.
Accessory bundle or bundle of Kent
Accessory bundle: anomalous conduction with no delay thus causes early ventricular depolarization, in ECG, gives short PR segment & delta wave.
AV conduction, normal conducation with AV nodal delay responsible for remainder of QRS
Describe the ECG of WPW
Normal P wave, short PR, slurred upstroke of QRS
Mention cause & ECG of SA block
Increased vagal tone
Absent P, QRS & T waves
Causes of AV block
- AV node ischemia
- AV node compression by scar tissue
- Septal infarction
- Injury of bundle of His during surgical correction of septal defect
- Myocarditis due to diphtheria or rheumatic fever
ECG picture of first degree heart block
Abnormally Proplonged PR interval, normal QRS & T waves, ratio of P:QRS is 1:1
ECG picture of 2nd degree heart block
PR interval maybe normal, P:QRS may be 2:1 or 3:1, normal QRS & T wave
Describe Wenckebach phenomemon
Type of 2nd degree heart block, there is progressive lengthening of PR interval till a beat is dropped, then followed by a beat with normal PR interval.
In complete heart block the ventricles follow …..
A focus developed in the bundle of His
ECG picture of complete heart block
P waves at 70 bmp, QRS at 40 bpm, P waves & QRS complexes are not related to each other.
Write a short note on Stock-Adams syndrome
Sometimes the idioventricular rhythm is very slow 15-20 bpm, so there are periods of Asystole for minute or more leading to cerebral ischemia causing dizziness & fainting.
Describe ECG picture of bundle branch block
Wide prolonged QRS with two peaks, axis deviation towards affected side, T wave us opposite to main QRS deflection.
Enumerate abnormalities of ECG IN MI
- ST segment elevation
- T wave inversion
- Deep Q wave
Write a short note on ST elevation in MI
Heart damage causes part of the tissue to be always partially or completely depolarized which causes flow of current between pathological & normal tissue, current of injury. This appears as ST elevation which is actually depression which represents the true isoelectric line. It subsides in few days.
Write a short note on T wave inversion in MI
Mild ischemia/acute infarction
Repolarization is particularly sensitive in epicardium in case of ischemia, leading to reversal of direction of repolarization.
Reversible with regain of blood flow.
Write a short note on deep Q wave in MI
The dead muscle is replaced by fibrous tissue which acts as an electrical window, being itself electrically silent. Thus the electrodes pick up the negativity of ventricular septum & Q wave will appear much larger in size. It will remain for life as a sign of old MI.
ECG picture of hypokalemia
Prolongation of PR interval, low voltage T wave (T wave inversion), prominent U wave.
ECG picture of hyperkalemia & CCC
Tall peaked T wave
AV nodal block, reentry phenomenon, inc ectopic activity, ventricular fibrillation.
GR: In PAN, QRS & T wave are normal while in PVN QRS is bizzare & T wave is inverted.
In PAN, the impulse is conducted to ventricles via normal pathway
In PVN, impulse is conducted to ventricles slowly & abnormally from cell to cell, also the depolarization occurs in one direction so waves of the ventricles do not neutralize each other, T wave is inverted because the slow conduction of impulse causes the first area depolarzied to be the first area repolarized.
GR: PR interval is shoretend in PAN
Beacuse usually the beat originates near to AV node
Compare P wave in in PAN & PVN
A: abnormal, inverted or absent
V: absent
Mention underlying cause of extrasystoles
Due to development of ectopic focus that results in a beat that occuts before expected normal sinus beat.
Describe ECG picture of AV nodal rhythm
- Bradycardia
- Inverted P wave & may be absent
- Short PR interval as AV is closer to ventricles
- Normal QRS & T wave as ventricles are stimulated by normal pathway
Mention cases in which fever is associated with bradycardia & why?
Typhoid & diphtheria
Effect of toxins on the heart
Mention causes & ECG picture of respiratory sinus rhythm
C: during inspiration, the stretch receptors of lung send impulses via vagus which inhibit cardio-inhibitory center, leading to rising of HR, while during expiration vagal tone is restored.
ECG: RR interval is shortened during inspiration & lengthened during ex
Normal QRS & T wave
Diagnosis criteria of normal sinus rhythm
- Positive P wave in lead II
- Negative P wave in aVR
- HR = 60-100 bmp at rest
Mention causes & ECG picture of sinus tachycardia
C: increased symp activity, fever & hyperthyroidism (^metablosim of SAN)
ECG: inc HR, short RR interval, normal P, QRS & T waves
Causes & characteristics of atrial flutter
Causes: single ectopic focus in heart or circus movement in atrium
CCC:
atrial rate = 250-350 bpm, vr= 125-175 as a result of physiological AV block
Atrial pumping is still efficient
ECG: abnormal closely packed and repeated P waves giving rise to P wave pattern
Normal QRS & T wave
QRS:P = 1:2 OR 1:3
Mention lines of treatment if PSVT
- Increasing vagal tone (carotid sinus massage, occulo-cardiac reflex, induction of vomitting, valsalva maneuver)
- Cardioversion
- Antiarrhythmic drugs
- Radiofrequency catheter ablation
Describe characteristics of paroxysmal nodal tachy.
Atrial & vent rate = 140-220 bpm, atrial pumping is efficient
ECG: abnormal or inverted P wave, normal QRS & T wave, short PR interval
Mention causes of paroxysmal nodal tachy
- Ectopic focus in AV node
2. Circus movement AV bypass tract
Causes of Paroxysmal atrial tachycardia
- An single ectopic focus in atrium
2. Circus movement in atrium
Mention causes of ectopic tachycardias
- An abnormal ectopic focus that discharges at a rate higher than SAN thus supressing it.
- Reentry phenomenon (more common)
Compare complete & incomplete compensatory pause with respect to duration
C: the duration of the two PP intervals around PVC are equal to the duration of two normal sinus PP intervals
IC: the duration of the two PP intervals around PAC are less than the duration of two normal sinus PP intervals
GR: Premature beat can cause pulsus deficit
As it arises earlier thatvthe normal SA node beat, thus decreasing the ventricular filling & consequently the stroke volume.
GR: Occurence of post-extrasystolic potentiation
Because of long diastolic period and increased ventricular filling
GR: SAN rhythm is reset in PAN but not PVN
In PAN, because the ectopic focus in the atrium can depolarize the SAN itself, suppressing SAN rhythm.
In PVN, the ectopic focus in the ventricle cannot depolarize the SAN, as there is no retrograde conduction
Compensatory pause in PVN is ……, while in PAN it is …..
Complete
Inomplete
Mention causes & ECG picture of sinus bradycardia
C: increased vagal tone, regulation of high BP, hypothyroidism & BB
ECG: Dec HR, prolonged RR, Normal P & QRS waves
Mention characteristics of paroxysmal atrial tachy.
Atrial & vent rate = 140-220 bpm, atrial pumping is efficient
ECG: abnormal or inverted P wave, normal QRS & T wave
