11.1 Introduction

The development of new drugs by the pharmaceutical industry is a costly and lengthy process, with the time from concept to final product typically lasting 10 years. Perhaps the most critical stage of this process is the phase one study, where the drug is administered to humans for the first time. During this stage each subject is carefully monitored for any unexpected adverse effects which may be brought about by the drug. Of particular interest is the ECG of the patient, which provides detailed information about the state of the patient's heart.

By examining the ECG signal in detail, it is possible to derive a number of informative measurements from the characteristic ECG waveform. These can then be used to assess the medical well-being of the patient, and more importantly, detect any potential side effects of the drug on the cardiac rhythm. The most important of these measurements is the QT interval. In particular, drug-induced prolongation of the QT interval (so called Long QT Syndrome) can result in a very fast, abnormal heart rhythm known as torsade de pointes. This rhythm can degenerate into ventricular fibrillation and hence lead to sudden cardiac death.

In practice, QT interval measurements are carried out manually by specially trained ECG analysts. This is an expensive and time-consuming process, which is susceptible to mistakes by the analysts and provides no associated degree of confidence (or accuracy) in the measurements. This problem was recently highlighted in the case of the...