THE ELECTRICAL activity of the ventricular myocardium, ie, ventricular electrical systole, is assumed to begin with the Q wave of the ECG and end with the T wave.
The time between the end of the T and the beginning of the following Q wave, ie, the ventricular electrical diastole, is defined as the resting time of the ventricles.
The correlation between the QT interval and the heart cycle time has been suggested as a quadratic function by Bazett1 and Heggling and Holzmann,2 as a cubic one by Fridericia3 and Schlomka and Raab,4 as a linear one by Lombard and Cope5 and Adams.6
The statistical analyses performed by Sandera,7 Brambilla and Margaria,8 and Simonson9 on representative populations have recently confirmed the linear correlation: this is, as defined by Simonson and based on observations on nearly 1,000 subjects:
1. QT= (242.3+0.0003 years)+0.14 t±16msec where t is the heart cycle time.
I. BRAMBILLA, R. MARGARIA. The Components of Electrical Diastole and Systole Against the Heart Cycle Time. Arch Intern Med. 1966;117(1):70–73. doi:10.1001/archinte.1966.03870070084012