==Change in rhythm==
Example: new atrial fibrillation. Atrial fibrillation occurs in ten percent of elderly people (>70 year) without clinical symptoms. Therefore atrial fibrillation in acute
dyspnoic patients does not prove atrial fibrillation induced cardiac decompensation. Also other causes (e.g. cardiac ischemia, pneumonia) should be considered. Previous ECG registrations could provide additional information.
Example: bradycardia. New
sinusbradycardia of 50 beats per minute (bpm) may cause dizziness , however, long existing bradycardias are often without symptoms. Therefore it is important to know about someones normal frequency.
An increase in PQ time may be seen in elderly patients, but may also be caused by the use of medication or by ischemia. Broadening of the QRS complex may be caused by medication or ischemia. An increase in QTc time may be caused by medication, but may also be
heridetary. Comparison of previous made ECG registration with new registration may provide the clue.
Ischemia may cause a change in the heart axis,
however a deviated heart axis caused by left anterior fascicular block may be present for years already (and will remain for the rest of life). Again, a previous ECG differentiates between old and new changes.
Hallmark of the comparison between old and new ECG are pathological Q's. New
pathologische Q's provide evidence for the occurence of a myocardial infarction in the mean time.
==Increase R wave==
'''Decrease''' of the R wave may
a a sign of occured infarction. Tamponade, cardiomyopathy and increased bodysize also decrease the R wave.
'''Increase''' of the R wave indicates
hypertrofia of the left ventricle (leads V5-V6), or a posterior infarction (V2-V3) or a loss of body weight.
==the ST segment==
New elevation of the ST segment indicates
a acute myocardial infarction. Chronic elevation of the ST segment may be caused by cardiac aneurysmata and long existing (several weeks) of pericarditis.
top inversion is caused by ischemia, disturbances in electrolytes and stress. Often no distinction can be made between these causes. T top inversion indicates that something is possible wrong , however further investigation is needed.