principles of ECG

Question 1

ecg?

Answer 1

leads are elctrods which meaure the diference in electrical potential betwee either:

1. two different points on the body (bipolar leads)
2. one point on the body and a virtual reference point with zero eelctrical potenial, located in the center of the heart (unipolar leads)

12 lead - 3 standard limb, 3 augmented limb, 6 precordial leads

Question 2

axis

Answer 2

normal -30 to 90

-30 to -90 left axis deviation

+90 to +180 right axis deviation

Question 3

qrs complex

Answer 3

tall - hypertroph

small - fat/fluid/ air/ infiltration/damage

Question 4

st

Answer 4

elevation - infarct, aneurysm, pericarditis

depresed - ischemia, digoxin, strain

Question 5

simus bradycardia?

Answer 5

vagal stimulation, sleep, SA node dysfunction/ischemia, beta blockers, digoxin, raised intracranail pressure

Question 6

atrial flutter?

Answer 6

Aetiology : atrial disease/dilatation, ischaemia,
ventricular disease/dysfunction, valve disease,
pericarditis COPD

Question 7

supreventricular tachycardia?

Answer 7

Definition: Rapid regular heartbeat .
• Aetiology:
Commonly due to an abnormal atrioventricular accessory pathway
or a reentry pathway (short circuit) within or adjacent to AV Node
• ECG Characteristics:
Rate: 150-250 min. Rhythm: regular.
P Wave: Absent or retrograde.
PR Interval: N/A.
QRS Complex: Normal (unless aberrant conduction).

Question 8

unifocal PVC’s?

Answer 8

•electrolyte imbalances, (K+, Mg+), hypoxia, ischemia,
medication toxicity, ischaemia/infarction

every beat is a pvc

bigeminal - every other beat is a PVC

trigeminal PVC - every 3rd beat is a PVC.

coupled- couples PVC

triplet - triplet PVC

A premature ventricular contraction (PVC), also known as a premature ventricular complex, ventricular premature contraction (or complex or complexes) (VPC), ventricular premature beat (VPB), or extrasystole, is a relatively common event where the heartbeat is initiated by Purkinje fibres in the ventricles rather than by the sinoatrial node, the normal heartbeat initiator. The electrical events of the heart detected by the electrocardiogram allow a PVC to be easily distinguished from a normal heart beat.
A PVC may be perceived as a “skipped beat” or felt as palpitations in the chest. In a normal heartbeat, the ventricles contract after the atria have helped to fill them by contracting; in this way the ventricles can pump a maximized amount of blood both to the lungs and to the rest of the body. In a PVC, the ventricles contract first and before the atria have optimally filled the ventricles with blood, which means that circulation is inefficient. However, single beat PVC arrhythmias do not usually pose a danger and can be asymptomatic in healthy individuals.[1]

Question 9

ventricular tachycardia?

Answer 9

Definition:
A rapid often deadly rhythm originating from the
ventricles.
Typically rapid wide QRS complex (>0.12s),
often very wide and bizarre with indeterminate
axis.

Question 10

ventricular fibrillation?

Answer 10

Definition:
Multiple foci of activity. Disorganized, chaotic rhythm.
Pulseless, no blood pressure.
Fatal without immediate intervention.
• Causes:
myocardial ischemia/infarction, cardiomyopathy,
trauma, drug toxicity, hypoxia, electrolyte imbalance.
• ECG Characteristics:
Rate: No apparent rate. Rhythm: Fibrillatory waves.
P Waves and QRS Complex: none.

Question 11

heart blocks?

Answer 11

1
st
degree
• 2
nd
Degree Mobitz Type I (Wenkebach
Mobitz Type II
• 3
rd
Degree/Complete

Question 12

mobitz - type 1 wankebach?

Answer 12

Some but not all P-waves followed by QRS
• Progressive increase in PR before dropped QRS
• Block typically located in AV node

Question 13

mobitz type II

Answer 13

Some but not all P-waves followed by QRS
• Consistent PR interval when QRS conducted
• Relationship P and dropped QRS complexes may
be consistent (e.g. 2:1 etc) or variable (occasional)
• Block typically located in His Bundle

Question 14

different axis’s?

Answer 14

Question 15

how to work out axis

Answer 15

1. Examine the QRS complex in leads I and aVF to determine
   if they are predominantly positive or predominantly
   negative. The combination should place the axis into one
   of the 4 quadrants below.

2.In the event that LAD is present, examine lead II to
determine if this deviation is pathologic. If the QRS in II is
predominantly positive, the LAD is non-pathologic (in other
words, the axis is normal). If it is predominantly negative, it
is pathologic.

Question 16

axis for equiphasic?

Answer 16

1. Determine which lead contains the most equiphasic QRS
   complex. The fact that the QRS complex in this lead is
   equally positive and negative indicates that the net
   electrical vector (i.e. overall QRS axis) is perpendicular
   to the axis of this particular lead.
2. Examine the QRS complex in whichever lead lies 90°
   away from the lead identified in step 1. If the QRS
   complex in this second lead is predominantly positive,
   than the axis of this lead is approximately the same as
   the net QRS axis. If the QRS complex is predominantly
   negative, than the net QRS axis lies 180° from the axis
   of this lead.

Question 17

atrial enlargement?

Answer 17

?Wide (≥3mm) ?Tall (≥2.5mm)
• Right atrial enlargement
– P wave amplitude >2.5 mm in II and/or >1.5 mm in V1
• Left atrial enlargement
– P wave duration > 0.12s in frontal plane (usually lead II)
– P wave double hump
in inferior leads

Question 18

qt formular?

Answer 18

QT Interval (QTc < 0.40 sec)
– Bazett’s Formula: QTc = (QT)/SqRoot RR
– Poor Man’s Guide to upper limits of QT:
– For HR = 70 bpm QT<0.40 sec
– for every 10 bpm increase above 70subtract 0.02 sec,
– for every 10 bpm decrease below 70 add 0.02 sec

Question 19

lvh with strain?

Answer 19

Sokolow Voltage(SV1+RV5>35mm) + Asymmetrical T-inversion (Subtle)

Question 20

inferior MI? RV infarct?

Answer 20

Consider Right Sided Chest Leads or V4R