What is an ECG? An ECG is a paper or digital recording of the electrical signals in the heart. It is also called an electrocardiogram or an EKG. The ECG is used to determine heart rate, heart rhythm and other information regarding the heart's condition. ECGs are used to help diagnose heart arrhythmias, heart attacks, pacemaker function and heart failure.
ECG can be analyzed by studying components of the waveform. These waveform components indicate cardiac electrical activity.
The first upward of the ECG tracing is the P wave. It indicates atrial contraction.
The QRS complex begins with Q, a small downward deflection, followed by a larger upwards deflection, a peak (R); and then a downwards S wave. This QRS complex indicates ventricular depolarization and contraction.
Finally, the T wave, which is normally a smaller upwards waveform, representing ventricular re-polarization.