Electrocardiogram(ECG, EKG)

I mentioned earlier that every bed in the ER had EKG machine next to it.

The EKG has a wide array of uses:

• Determine whether the heart is performing normally or suffering from abnormalities (eg. extra or skipped heartbeats - cardiac arrhythmia).
• May indicate acute or previous damage to heart muscle (heart attacks) or ischaemia of heart muscle (angina).
• Can be used for detecting potassium, calcium, magnesium and other electrolyte disturbances.
• Allows the detection of conduction abnormalities (heart blocks and in bundle branch blocks).
• As a screening tool for ischaemic heart disease during an exercise tolerance test.
• Can provide information on the physical condition of the heart (eg: left ventricular hypertrophy, mitral stenosis).
• Can suggest non-cardiac disease (e.g. pulmonary embolism, hypothermia)

An EKG is constructed by measuring electrical potential between various points of the body using a galvanometer. Leads I, II and III are measured over the limbs: I is from the right to the left arm, II is from the right arm to the left leg and III is from the left arm to the left leg. From this, the imaginary point V is constructed, which is located centrally in the chest above the heart. The other nine leads are derived from potential between this point and the three limb leads (aVR, aVL and aVF) and the six precordial leads (V_1-6).

EKG gives a reading that looks like this:



One doctor told me that this showed the rate of heart as well as its rhythm and that peak size also matched the intensity of the signal that travels from SA node to Purkinje fibers. He showed me two examples of abnormal heart reading. One was VT which looked like this:



Three or more ventricular extrasystoles are a bad sign, and are termed ventricular tachycardia (VT). There is usually severe underlying myocardial disease. Sustained VT (more than about 30 beats) often degenerates into ventricular fibrillation, resulting in death. Ventricular Fibrillation is where too many signal arrives too fast(and irregular rhythm) for the heart muscles to respond. It produces an EKG reading that looks like:



At this point, doctors are free to shock the patient to wake his ass up. If the patient decides that he'd rather stay lazy, soon the peaks will disappear.