Is there a significant transmural gradient in repolarization time in the intact heart? Cellular basis of the T wave: a century of controversy.

The ECG is one of the oldest and most versatile noninvasive cardiac diagnostic tests. It has remained in use essentially in its original form despite dramatic advances in cardiac electrophysiology. In May 1887, Augustus Desiré Waller recorded the first human Electrogram using a primitive instrument called a Libbmann capillary electrometer. It had 2 deflections corresponding to ventricular depolarization and repolarization.1 In 1903, Willem Einthoven invented the String Galvanometer—a more sophisticated voltage recording instrument and recorded an Elektrokardiogramm with 5 deflections that he named PQRST.2