Table 1.

Score system for estimate of risk of a compound for relative TdP risk using the isolated rabbit left ventricular wedge preparation^a

Score	Difference in QT interval (%)	Tp-e/QT ratio (%)	Phase 2 EAD
−1	<−5	<−5
0	−5–<10	−5–<10
1	10–<20	10–<20
2	20–<30	20–<30	±EAD
3	>30	>30
4			EAD without R on T
6			EAD with R on T
8			TdP

^aPoints for the QT interval, the T_p-e/QT ratio, and phase 2 EAD are provided (7). The maximal score is 14, and the minimum is −2. Basic cycle lengths (BCLs) are 2,000 ms. EAD, early after depolarization; ±EAD, equivocal EAD from endocardial action potential at a BCL of 2,000 ms when the QT interval is >30%; TdP, torsade de pointes; T_p-e, interval between the end (e) and the peak (p) of the T wave; QT, QT interval.