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The E.C.G - a non-invasive way in measuring the electrical signals of the heart.

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E.C.G Introduction The E.C.G is a non-invasive way in measuring the electrical signals of the heart. The heart is only attached at the aorta (vena cava), and comprises of 2 electrically isolated chambers these being the atria and the ventricular chambers this is where propagation of electrical impulses spread, (however in diseased hearts this may not be the case). The heart is suspended in liquid, which conducts electricity, and the E.C.G is extremely useful in diagnosing patients who may suffer with a heart disease such as, mitrale stenosis, Ischemia and acute myocardial infarction. The E.C.G can graphically records conduction abnormalities, the rate at which the heart is contracting, rhythm disturbances and the magnitude of the heart chambers. The E.C.G can also be used in determining the physical effects and strains on the heart during exercise, breathing and resting etc. ECG is also able to detect thus measure the changes of potentials that are transmitted through the body. An electrode refers to the physical wires of the ECG whereas the lead refers to the electrical view of the heart. The standard limb Lead I, is positive on the left arm and negative on the right arm. Lead II, is positive on the left leg and negative on the right arm and lead III, is negative on the left arm and positive on the right leg. ...read more.


an increase in sodium ions inside the cell inside the cell is now positive and the threshold has been reached. The 'T' ECG defection represents the ventricular repolarisation, which follows after the ventricular has depolarised. The Potassium (K+) ion channel inside the membrane opens and K+ flood out of the cell it is at this point that electrical balance is restored. The 'ST' segment on an ECG is electrically neutral; also a 'U' wave ECG defection sometimes may be seen on an ECG trace after a 'T' wave and it is believed that this may represent a late repolarisation of the Purkinje fibres, which are situated in the ventricles. Some patients can develop chest pains within the first 2 minutes or so of exercise, the extra workload on the heart is measured by metabolic equivalents (METs). A diagnostic for ECG exercise-achieved testing is arrhythmia irritation and/or where a patient complains of symptoms, such as sudden chest pains. " After only 2 minutes and 24 seconds of exercise (according to Bruce protocol), the patient developed chest pain and electrocardiography showed marked ischaemic changes (maximum 3 mm ST segment depression in lead V6)". BMJ 2003;326:1027-1030 ( 10 May ) Clinical review ABC of interventional cardiology. The changes during exercise in a 'normal' ECG trace show the measurements of the 'P' wave increases in height and the measurements of the 'T' ...read more.


This gave and axis of approximately 89 0. This was repeated for the cardiac axis number 2 this was also worked out and gave 930. Therefore it was determined that the axis for this ECG trace is 89 + 93 =182, 182/2 = 91 (or equals an amount between 890 - 93 0). Discussion The subjects were not known to suffer or had suffered from any heart abnormalities however this was not confirmed. During exercise the body is moving i.e. when walking or running on a treadmill therefore it is quite possible this movement could wrongly detect a false-positive arrhythmia, or cyclic artefacts. These sequences can occur during exercise testing because when the body moves so does the heart. The quality of the electrodes can also be taken into consideration i.e. if 1 or more of the electrodes is inadequate. Filtering, filters are good because the get do away with interference however; filters can cut out the subjects signalling. A better method could be to filter the relevant electrodes by a band pass filter and the obtained results transformed to absolute values. Different heart rates in different people can be linked to fitness and whether the person is a smoker as opposed to non-smoker. Variation in heart rate is linked to breathing therefore as a person inhales the heart rate varies, this is possibly a reason as to why when subject 1 was resting within a period of about 10 minutes his heart rate was fluctuating. ...read more.

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