Tuesday, June 3, 2008

ecg made easy.

This is first of a set of articles on ecg which i am going to post to make u understand basics and help u interpret even the toughest of ecgs.

Today we start with introduction:

first know the difference b/w electrocardiogram & electrocardiograph- 

electrocardiogram:electro, because it is related to electrical activity, cardio, Greek for heart, gram, a Greek root meaning "to write"800px-12leadECG1

  electrocardiograph:instrument used to record . 

NK_Cardiofax electrocardiograph1

basics:Electrical waves cause the heart muscle to pump. These waves pass through the body and can be measured at electrodes (electrical contacts) attached to the skin. Electrodes on different sides of the heart measure the activity of different parts of the heart muscle. An ECG displays the voltage between pairs of these electrodes, and the muscle activity that they measure, from different directions. This display indicates the overall rhythm of the heart, and weaknesses in different parts of the heart muscle. It is the best way to measure and diagnose abnormal rhythms of the heart, particularly abnormal rhythms caused by damage to the conductive tissue that carries electrical signals, or abnormal rhythms caused by levels of dissolved salts (electrolytes), such as potassium, that are too high or low.

note:ecg does not record all the hearts electrical activity.the electrodes placed on surface of body record only currents that are transmitted to area of electrode placement.therefore there are actually "silent areas" of heart.the ecg records only currents produced by working heart muscle.
for example-1.ecg is not sensitive enough to record depolarisation of pacemaker cells in sinus node

      2.the conventional ecg does not detect the spread of stimuli through AV junction-this is recorded using a special apparatus & special electrode placed in heart {His bundle electrogram }


3.conduction:fastest through purkinje fibres

                        slowest:AV node{because it allows ventricles time  to fill with blood before signal for cardiac contraction arrives}

left bundle

that's for today, in the next topic we will deal with basic ecg waves & ecg leads.

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