Firdaus Bin Mohd Ali Kanabathi.

Penolong Pegawai Perubatan U41,

Jabatan Kardiologi, Hospital Sultanah BahiyahAlor Setar, Kedah Darul Aman.

ANALYZING THE 12 LEAD ECG

1) Rate.

2) Rhythm.

3) P Wave.

4) PR Interval.

5) QRS Complex.

6) ST Segment. (J Point)

7) P-QRS Relationship.

8) T Wave.

9) Q-T Interval.

10) Axis (12 Lead ECG) .

11) Conclusion/diagnosis of ECG.

Before Analyzing the ecg ensure:

1) Correct Patient (name,date, and time).

2) Standardization (1mv).

3) Speed (25mm).

4) Chest Lead can see the R wave progression (small to tall R wave). S wave progression (deep to small S wave).

5) -ve aways from heart.

6) +ve direct to heart.

Rate.

1) Note the ventricular regularity & measure ventricular rate.(If normal).

i) Count the no of big squares between the same point on 2 consecutive R wave & divide into 300.

eg. 5 big squares between RR interval

HR = 300 ÷ 5 = 60bpm

HR = 300 ÷ 4 = 75bpm

• 1 large box or 5mm = 0.5mv.

• 1 large box or 5mm = 20second.

• 1 small box or 5mm = 0.04second.

2. Measure the distance between 2 QRS with the caliper at the same point (RR interval).

i) Lift the caliper to the edge of the strip.

ii) Place the 1st caliper point on a heavy line.

iii) Count the second caliper point to determine the number of small squares & divide into 1500.

Eg. HR = 1500 ÷ 23 (small box) = 65bpm

HR = 1500 ÷ 21 = 71.4 0r 71bpm

3. Ruler 6 inches method.

i) Count the number of R wave in a 6 second ( 6 inches) strips.

ii) Multiplying it by 10

Eg. 6 R wave in 6 inches strip (start 0cm on P wave).

HR = 6 x 10 = 60bpm or 7 x 10 = 70bpm

6 Inch Ruler

Rhythm

1. Regular / irregular with caliper / edge of paper. RR interval difference ½ small squares or < 3small squares – consider regular rhythm.

2. If irregular rhythm.

i) Total irregular eg. Atrial fibrillation, MAT or Atrial flutter with variable block.

ii) Follow a pattern eg. Bigeminal PVC. (sinus with sinus, pvc with pvc).

Regular or Irregular?

P wave1) Atrial activity / atrial depo. Duration > 0.08sec

2) P wave present / absent?

3) Observe it’s:

- Shape (3 morphology) small ,round and upright.

- Height P Wave.

- Width P Wave.

- P Wave +ve, -ve, biphasic, peaked, notched.

PR Interval1) Width is 0.12sec to 0.20sec2) Measure pr interval to evaluate conduction through

atrium, AV junction & bundle of his and bundle branches.

i) Measure from beginning of P wave to onset of 1st

ventricular deflection.(If no Q wave, can measure R wave).

ii) Multiply no of small squares by 0.04sec.iii) IS the measurement normal/shorter/prolonged?

Eg. PR Interval = 4smallsquares x 0.04sec = 0.16sec

3) Shorter PR is WpW syndrome, prolonged PR is raletedto AV Block.

QRS COMPLEX

1) Thin, tall, and narrow.

2) Q wave is 1st negative ventricular deflection.

3) R wave is 1st positive ventricular deflection.

4) S wave is 2nd negative ventricular deflection.

5) Width is 0.08sec to 0.12sec (within 3 small square). Should be narrow QRS.

6. Height is <20mm (R wave).

E.g. i) Height = 7 square box x 0.1mv = 0.7mv

ii) Height = 7 square box x 1mm = 7mm

7. To analyze the length & sequence of ventricular depolarization.

8) Measure from onset of 1st ventricular deflection from baseline to end of last ventricular deflection that return to baseline. (Width).

9) Multiply the no of small squares by 0.04sec.

- (Is it normal, broad) or constant/variable with consistent pattern (completely variable).

- Is it appearance of QRS similar for all complexes & present at constant level? (shape & regularity).

10) Examine QRS deflection upward (+)/inverted (-).

11) Is the Q wave is present?- Is it a physiological or pahological Q wave?

(according the depth & width of Q wave) - Physiological Q wave width is less than 0.04sec

and Q wave depth less than 25% compare with R wave is physiological.

- If pathological Q wave width is more than 0.04sec and Q wave depth is more than 25% compare with R wave.

12) Tall R wave indicate ventricular hypertrophy:- Tall R wave seen in V1 usually:E.g RVH, RBBB, True Posterior MI, WpW type A and Dextrocardia/variant.

ST SEGMENT1) ST normal is isoelectric line & same level with

PR interval.

2) ST segment elevate more than 1mm above baseline. E.g ACS, Aneurysm and pericarditis.

3) ST segment depress more than 1mm. E.g ACS (myocardial ischaemia or injury).

P – QRS RELATIONSHIP

1) P wave precedes each QRS. (P coming 1st and followed by QRS). 1:1 AV Nodal conduction or 1:1 relationship.

T WAVE.1) Observe it’s (shape,height,witdh).

2) The T wave morphology upright/inverted or flat.

3) Normal T wave upright (+ve). If inverted usually myocardial ischemia (deep, inverted & symmetrical T wave is subendocardialinfarction. Mostly in chest lead.

4) Tall, peak and narrow = hyperkalaemia.

QT INTERVAL1) Measure QT interval & calculate QTC using

bazette’s formula.i) QTC = √ QT ∕ RR interval (in second)

QTc = QT√RR

ii) Normal Qtc interval is 0.35sec to 0.45seciii) No Q wave. Take R wave.

QT = 10smsq x 0.04sec= 0.4

RR = 21smsq x 0.04sec= 0.8

10smsq X 0.04sec

√ 21smsq X 0.04sec

= 0.04sec

√ 0.84sec

= 0.436sec.

= 0.43sec.

√

11smsq X 0.04sec√22smsq X 0.04sec

= 0.44sec√ 1.0sec

= 0.44sec.

AXIS1) Look at lead I and AVF.2) Normal axis deviation:

i) Lead I is +ve.ii) Lead AVF is +ve.

1) Left Axis deviation:i) Lead I is +ve.

ii) Lead AVF is –ve.4) Right axis deviation:

i) Lead I is –ve.ii) Lead is +ve.

5) No man’s land:i) Lead I is –ve.

ii) Lead AVF is –ve.

Normal Axis Deviation is -30 till +110

Left Axis Deviation.

Right Axis Deviation.

No Man’s Land.

How About This Ecg?