Figure 1.

A) The cardiac sequelae of blockade of the HERG channel. Blockade of the HERG channel results in prolongation (in red) of the cardiac action potential leading to early after depolarizations (not shown). QT interval prolongation occurs secondary to these changes and ultimately leads to torsade de pointes (TdP). In the example above the TdP degenerates to ventricular fibrillation (VF). B) Summary of the potential areas of concern where significant impact can be made to the observed QT interval data, including the algorithm used for ECG recordings, the technique selected to correct measurement bias, the nature of the disease that influence ECG values, and various other covariates that can impact the recordings (modified from Totterman [68])