The right answer is Electrocardiography (or Electrocardiogram).
In a typical plot, one can notice five characteristic waves. They are called P, Q, R, S and T. The illustration below shows what a normal electrocardiogram looks like:
* the P wave marks the depolarization during the contraction of the atria;
* the PR interval indicates the time required to transmit the electrical impulse of the sinus node of the atria to the ventricular muscles;
* the QRS complex marks depolarization and ventricular contraction;
* the QT interval corresponds to the global ventricular repolarization;
* T wave refers to the end of ventricular repolarization.