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Heroin Addiction and Related Clinical Problems: 2009, 11, 4 (pages: 5 - 10)

QT Interval

Caldarola P., Cuonzo M.

Summary: The electrocardiogram records the electrical activity of the heart, the depolarization and repolarization of the atria and ventricles. Deflections are all shown by the single features of the electrocardiogram: the P wave, the QRS complex, the T wave, the U wave, the PR interval and the QT. The QT interval represents the entire electrical activity of the left ventricle: it begins with the onset of ventricular depolarization (start of the Q wave) and is completed when ventricular repolarization ends (at the end of the T wave). Measurement of the QT interval is important because of the useful information it provides on the electrical activity of the heart; the length of the interval depends on various pathophysiological conditions, changes in electrolyte concentration, and the pharmacological action of toxic substances.