Encarta:

tracciato = (here) tracing, diagram

diagram

.....

2. chart: a chart or graph that illustrates something such as a statistical trend

3. mathematical drawing: a line drawing that presents mathematical information

Cardiac Cycle
Electrocardiogram Diagram

(thereｴs a photo here )

The electrocardiogram (ECG) is an indirect measure of the electrical activity of the heart. The activity can be measured by placing leads on the surface of the skin. The ECG is made up of five points P, Q, R, S and T. The points are grouped together to represent important electrical events in the heart. A normal healthy hearts ecg is represented by 3 distinct waves;
the P wave,
the QRS complex and
the T wave.

The P wave represents atrial depolarization followed by atrial contraction. The QRS complex represents ventricular depolarization followed by ventricular ejection. The T wave represents ventricular repolarization.
Other than the three mentioned above there are other significant pieces to the ecg:
The PR segment is the AV nodal delay. The ST segment is the time it takes for the ventricles to contract and empty. The TP interval is the time during which the ventricles are relaxing and filling.

http://artsci.shu.edu/biology/Student Pages/Kyle Keenan/hear...

Cardiovascular
... 7. Diagram an electrocardiogram tracing that shows the three normally
recognizable waves and intervals. Explain what each represents. ...
www.park.edu/csanders/courses/bi212/cardiovascular.htm

HTH

Good luck.

D.