ELECTROCARDIOGRAPHY

Wednesday, 18 March 2015

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.

Tuesday, 6 May 2014

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)

Thursday, 20 March 2014

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)

ECG INTERPRETATION HALLMARK OF THE TRAINING PART 2

3.T wave

The T wave indicates the repolarisation of the ventricles.

Follows the QRS complex. Take note of T waves which have a 1.downward (negative) deflection ischemic changes indicates or 2. tall, pointed peaksT waves- indicates hyperkalemia

Sometimes we see a U wave.
4.The U-wave is a small upright, rounded bump. When observed, it follows the T-wave.indicates Late repolarisation of the ventricles.

STEP 4.INTERVALS

I -PR INTERVAL

The PR Interval indicates AV conduction time.

The interval is from where the P wave begins till the beginning of the QRS complex.

Count the small boxes to determine PR Intervals.

Normal PR interval is 0.12 to 0.20 seconds (3 to 5 small boxes)

This interval shortens with increased heart rate.

Evaluate if PR Intervals are constant or varying across the EKG strip.

If they vary, determine if the variations are a steady lengthening until the point where an expected QRS does not appear.

PR Interval questions to address:

Does the PR-Interval fall within the norm of 0.12-0.20 seconds/120-200 ms?

Is the PR-Interval constant across the ECG tracing?

II-QT INTERVAL

The QT interval represents the time of ventricular activity including both depolarization and repolarisation. Measured from the beginning of the QRS complex to the end of the T wave.

Normal, the QT interval is 0.36 to 0.44 seconds (9-11 boxes). The QT interval will vary with patient gender, age and heart rate.

Criteria-Another guideline is that normal QT Intervals is less than half of the R-R Interval for heart rates below 100 bpm.

Abnormalities associated.-LONG QT SYNDROME.

ECG INTERPRETATION -HALLMARK OF THE TRAINING PART 1

7 STEP METHOD OF ECG INTERPRETATION

The following steps are required for interpretation of an ECG.
1.Rhythm
2.Rate
3.Waveforms- P ,QRS complex, T wave.
4.Intervals,-PR, and R-R
5. Heart axis
6. ST Segment
7.Abnormalities- e.g Hypertrophy, AV blocks,pericardial effusion

1.The Rhythm.
There are 3 main types of rhythms.
1.sinus rhythm- .there is evidence of P waves on the ECG strip indicating the source as sinoatrial node.
Lead 2 (THE GOLDEN LEAD) is ideal in determining presence of P waves.
Absence P waves would suggest-
ATRIAL FIBRILLATION,
ATRIAL FLUTTER.
2.AV junctional rhythm- evident when sinoatrial node fails and hence the AV node takes over the pacing mechanism of the heart.
Common with patients with AV block. 2nd and 3rd Degree AV blocks
QRS COMPLEXES ARE BROAD AND WIDE>120ms

3.Idio-ventricular rhythm-The origin being the purkinje system of fibres.
This is an emergency with patients being in ICU.
Very low voltage and wide QRS complexes

2.The Rate.
Expressed in Bpm ( beats per minute)
The easiest and fastest way to calculate the rate is to use two R waves on the ECG strip.
Using a factor of 1500 divide it by the number of small boxes in between the two R waves.
Ideal in ICU EMERGENCY CASES.

Other ways exist such as -
Counting NUMBER OF R WAVES OF 6 SECOND STRIP OF AN ECG STRIP AND MULTIPLYING THE NUMBER BY A FACTOR OF 10.

The 300 METHOD is inaccurate and I don't advice you to use it.It involves dividing the factor of 300 by the number of large boxes in between 2 R waves.

3.THE WAVEFORMS
1.The P WAVE.-Indicates atrial contraction/DEPOLARISATION.
A normal P wave is upright /POSITIVE in Lead 2.

The P wave represents atrial depolarization. In normal ECGs the P-wave preceeds the QRS complex. It looks like a small bump upwards from the baseline. The amplitude is normally 0.05 to 0.25mV (0.5 to 2.5 small boxes). Normal duration is 0.06-0.11 seconds (1.5 to 2.75 small boxes). The shape of a P-wave is usually smooth and rounded.
P Wave illustration

ASK YOURSELF P-wave questions:

Are they present?

Do they occur regularly?

Is there one P-wave for each QRS complex?

Are the P-Waves smooth, rounded, and upright?

Do all P-Waves have similar shapes?

2.QRS COMPLEX
The QRS complex indicates ventricular depolarization. Depolarization triggers contraction of the ventricles.
Because of the larger tissue mass, the QRS complex is larger than the P wave. .

In this step, measure the QRS interval from the end of the PR interval to the end of the S wave. Normal QRS interval is 0.08 to 0.12 seconds/60-120 ms (2 to 3 boxes).

ASK YOURSELF QRS questions:

Does the QRS interval fall within the range of 0.08-0.12 seconds?

Are the QRS complexes similar in appearance across the ECG tracing?

Tuesday, 28 January 2014

How to perform a good ECG .

PART 2-LEAD PLACEMENT

1.The first thing is get acquitted with lead placement.
2. Know the ECG machine and its controls.

Lead placement.
There are 12 leads during the recording of an ECG.
-6 chest leads- V1-V6
-6 Limb leads-.aVR, aVL, aVF, 1,2,3.

(3 limb leads are created by virtue of placing 3 limb leads- aVR, aVF, aVL and hence are known as imaginary leads.)

LIMB LEAD PLACEMENT.

-Let the patient lie supine on a couch, bed.
-Clean the electrode sites using some alcohol and cotton wool (swab)
-Put the limb electrodes on the inner aspect while having applied some gel to achieve good conductance.

USIPlace the limb leads appropriately.
They are color coded and marked for easy identification
The N -Neutral is the ground electrode placed on the right foot.

CHEST LEAD PLACEMENT

V1 -4th intercostal space on the right 1cm from the sternum

V2 -4th intercostal space on the left 1cm from the sternum.

V3 -Between V2 and V3

V4 -5th intercostal space mid-clavicular line.

V5 -5th intercostal space anterior axillary line.

V6 -5th intercostal space mid axillary line.

COMMON MISTAKE- is counting from the clavicle as your first rib.

Performance of a good ECG.

1. The ECG waves must be visible and clear.
The ECG waves such as the P ,QRS complex ,T waves must be visible on the ECG paper.
This makes it easier in identifying any pathological waveforms present.

2.Artifact free.
minimal or no artifact must be present.
Types of artifacts -
-Muscle artifacts obscure the identification of P waves.
-Respiratory artifacts as the patient breths in and out.
-Electrical artifacts from the mains.-Turn on the notch rejection filter at 50/60 Hz
-Baseline wander artifact caused by movement of the leads.
-Movement artifacts.- the patient ought to be still.

3.Patient data must be included.

In summary.

1.Prepare electrocardiography machine for use	-Check ECG machine is in good working order connect it to power.

2. Prepare client for ECG procedure	-Reassure the patient the procedure is safe and the reason for it. -Record client information -Review client medical history

3. Attach ECG electrodes	-Maintain the client's privacy and dignity throughout procedure -Complete preparation of client's skin for electrode placement as required -Position the client correctly and comfortably and place electrodes in accordance with client's needs and current standards -Attach leads correctly and double check lead placement

4. Produce an ECG tracing by printing

-Produce trace and check for interference, wandering baseline and amplitude

Make sure the waves are visible with no artifacts.

-Repeat trace if interference , increased amplitude or wandering baseline is identified

-Identify and action abnormal ECG patterns which require immediate medical attention

-Forward trace to cardiologist or requesting medical officer for reading

-Record test details according to department and organisation procedures



	5. Complete ECG procedure. -Remove ECG leads and electrodes from client -Refer the patient appropriately. -Clean ECG leads and electrodes on completion of procedure in accordance with infection control guidelines OR -Dispose of disposable ECG electrodes and other materials in accordance with waste management procedures. -Store ECG machine as required making sure there is no entanglement or kinks of the leads.This will increase the longevity of your machine as well as of electrodes.

Thursday, 16 January 2014

ORIGIN OF ECG WAVES- Conduction System of the Heart

ORIGIN OF ECG WAVES AND CONDUCTION SYSTEM OF THE HEART.
The (heart) cardiac muscle is able to :
1. Contract
2. Generate its own impulse/ electrical activity - automaticity
3. be excitable as the heart muscle responds to an appropriate amount of stimuli and generate an action potential---an electrical pulse that spreads across the entire heart.This knowledge is applied in (CPR) cardiopulmonary resuscitation.

4 Conduct or transfer the action potential from muscle cell to muscle cell originating at the sino-atrial (SA) node---the pacemaker of the heart.

An action potential from the SA node travels through the heart at a rate of 0.8 to 1 meter per second

The heart has primary and secondary sites for electrical generation.
1,The sino-atrial node.The primary source of the cardiac impulse or electrical power.
Located on the right atrium at the junction of the opening of the superior vena cava.
The others below are considered as secondary.
2.The atrioventricular node.
3. The Bundle of HIS
4.RIGHT AND LEFT BUNDLE branches
5.PURKINJE FIBERS
N/b The BACHMAN'S BUNDLE is responsible for the spread of the impulse to the left atrium for uniform atria contraction during systole.

The electrical impulse moves from the sino- atrial node via the AV node, bundle of HIS, bundle branches down to the purkinje system of fibers.
This is known as the conductivity system of the heart.
This important activity is responsible for the contraction of the heart and to initiate a heart beat.

T

ECG WAVES.

FROM THE LAST POST WE IDENTIFIED THE ECG WAVES AND THEIR MEANING.

What is an ECG?
Electrocardiography as its known involves recording electrical potential originating from the heart. These potentials cause the heart muscle to contract and pump blood to the body via the aorta and to the lungs for oxygenation via the pulmonary artery.
These activities can be recorded on an ECG paper in form of waves.
These waves are as follows:
1.P wave represents atrial contraction.
2.QRS complex represents ventricular contraction.
3.T wave represents. ventricular relaxation
4.U wave though not common.- late ventricular relaxation

The identification of these waves is very important