STEP 4 .INTERVALS IN ECG INTERPRETATION

•PR interval- 120-200 ms

•Shows how fast impulse travels from SA node to AV node.

•QT INTERVAL

•<440 ms

•Shows the duration for a complete ventricular systole and diastole.

STEP 3 . QRS AXIS IN ECG INTERPRETATION.

•Normal  axis -30 to +90 degrees for all standard limb leads.

Have a positive R wave recording

•Left axis deviation. Limb leads 1 +VE

•11- VE

•RIGHT axis deviation 1 –ve and 11 +ve

•Normal QRS DURATION -80-120 ms

STEP 1 +2 RHYTHM AND RATE IN ECG interpretation.

RATE
•1500 method

•1500/no of small squares  between 2 R waves.

• most accurate method.

RYHTHM 

•Sinus rhythm -SA node

•AV junctional rhythm -AV node.

•Idioventricular rhythm- purkinje in origin.

THE 7 STEP PLAN FOR ECG INTERPRETATION.

 INTERPRETATION OF ECG
Always follow a consistent 7 step plan  and  you wont get lost.

•1.Rhythm

•2.Rate

•3. QRS Axis and duration.

•4. Interval

•5.Wave morphology.

•6.ST segment

•7. Check for any abnormality.

COMMON ECG FINDINGS IN KENYA.

CLINICAL APPLICATION.

 1. Hypertension.

The common feature is left ventricular hypertrophy.
Based on R wave voltage across the chest leads.

Left Ventricular Hypertrophy (LVH)

General ECG features include:

• ≥ QRS amplitude (voltage criteria; i.e., tall R-waves in LV leads, deep S-waves in RV leads)
• Widened QRS/T angle (i.e., left ventricular strain pattern, or ST-T oriented opposite to QRS direction)
• LEFT AXIS DEVIATION  QRS axis 

Please consider the patient's history and the anti-hypertensive medication.
Measure the patients blood pressure and indicate on the report.
Other Voltage Criteria for LVH:

• Limb-lead voltage criteria:
  • R in aVL ≥ 11 mm or, if left axis deviation, R in aVL ≥ 13 mm plus S in III ≥ 15 mm
  • R in I + S in III > 25 mm
• Chest-lead voltage criteria:
  • S in V1 + R in V5 or V6 ≥ 35 mm
  •  
  •  
    

	ECG report

Sinus rhythm with HR 68bpm.Left Ventricular Hypertrophy.

Notice the high R wave in V4/V5  overshooting AND CAUSING OVERLAP.

BP 150/90mmHg

The LVH Criteria.V1 + R in V5 or V6 ≥ 35 mm

other criteria used.

CORNELL Voltage Criteria for LVH (sensitivity = 22%, specificity = 95%) S in V3 + R in aVL > 24 mm (men) S in V3 + R in aVL > 20 mm (women)

STEP 6;ST SEGMENT ABNORMALITIES

STEP 6 :ST SEGMENT
The ST segment represents the early part of ventricular repolarization.
The ST segment is the line that from the end of the QRS complex to beginning of the T wave. 

Normal ST segment is flat/ isoelectric, 
 
GIVES IMPORTANT INFORMATION ON THE CORONARY BLOOD SUPPLY TO THE HEART VIA THE CORONARY ARTERIES.

1.ST SEGMENT ELEVATION-suggests myocardial infarction due to blocked coronary arteries causing a dead/necrosis to a specific segment of the heart.

2.ST SEGMENT  DEPRESSION- Suggests myocardial ischemia due to a partially blocked coronary artery causing a poor perfusion of oxygen to the heart muscle/myocardium.

PLEASE DON'T MISS TO DIAGNOSE THESE ST SEGMENT ABNORMALITIES.
YOU MIGHT LOOSE YOUR PATIENT.

ALERT THE CONSULTANT CARDIOLOGIST/PHYSICIAN FOR ACTION.
URGENT CORONARY ANGIOGRAPHY WOULD BE REQUIRED.

ECG INTERPREATATION HALLMARK OF TRAINING: HEART AXIS

5.IMPORTANT STEP :ECG HEART AXIS
Indicates the direction of the average electrical depolarization with an arrow (vector). This is the heart axis.
A change of the heart axis or an extreme deviation can be an indication of pathology.
To determine the heart axis you look at the LIMB leads only (not chest leads V1-V6).
  On leads I, II, and AVF you can make a good estimate of the heart axis.

 An important concept in determining the heart axis is the fact
-electricity flow towards a lead yields a positive deflection in the electric recording of that lead.

YOU remember the the EINTHOVENS TRIANGLE -

• Positive  QRS deflection in lead I: the electrical activity is directed to the left (of the patient)
• Positive QRS deflection in lead AVF: the electrical activity is directed down.                                                                                             Clinical application
  
• • A left heart axis is present when the QRS in lead I is positive and negative in II and AVF. (between -30 and -90 degrees)
  • A right heart axis is present when lead I is negative and AVF /II positive. (between +90 and +180)
  • An extreme heart axis is present when both I and AVF/II are negative. (axis between +180 and -90 degrees) 
    

    Left axis deviation

    
    

    

    Left heart axis
    
    

    

    Left anterior hemiblock
    
    Causes of left axis deviation include:
    
  • Normal variation (physiologic, often with age)
  • Mechanical shifts, such as expiration, high diaphragm (pregnancy, ascites, abdominal tumor)
  • Left ventricular hypertrophy
  • Left bundle branch block
  • left anterior fascicular block
  • Congenital heart disease (e.g. atrial septal defect)
  • Emphysema
  • Hyperkalemia
  • Ventricular ectopic rhythms
  • Preexcitation syndromes
  • Inferior myocardial infarction
  • Pacemaker rhythm 
  
  

  Right axis deviation

  
  

  

  Right heart axis deviation
  
  Causes of right axis deviation include:
  
• Normal variation (vertical heart with an axis of 90º)
• Mechanical shifts, such as inspiration and emphysema
• Right ventricular hypertrophy
• Right bundle branch block
• Left posterior fascicular block
• Dextrocardia- heart in the right position
• Ventricular ectopic rhythms
• Preexcitation syndromes
• Lateral wall myocardial infarction
• Right ventricular load, for example Pulmonary Embolism or Cor Pulmonale (as in COPD)

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