ECG stands for electrocardiogram, which is a test that measures the electrical activity of the heart. It is widely used in clinical practice to diagnose a range of heart conditions such as arrhythmias, ischemia, and myocardial infarctions.
EKG is simply an alternative abbreviation for the same test. The term “EKG” is derived from the German word "Elektrokardiogramm". The use of "K" in EKG helps to avoid confusion with EEG, which stands for electroencephalogram (a test used to measure brain activity).
In essence, both ECG and EKG refer to the same diagnostic procedure. The choice of abbreviation largely depends on regional preferences and historical context. In many parts of the world, especially in the United States, the term EKG is used to prevent mix-ups with other similarly abbreviated tests.