Risk factors Several studies have proposed different risk factors for torsades de pointes. Among them, the most commonly encountered are female gender, advanced age, bradycardia, different metabolic disorders, and a number of therapeutic agents (Haverkamp, 2000) . The genderspecific preponderance in females to develop drug-induced torsades de pointes when treated with antiarrhythmic drugs or during spontaneous bradyarrhythmias is also well documented. In the general population, women have a

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... er corrected QT interval than men. www.intechopen.com Aspects of Pacemakers -Functions and Interactions in Cardiac and Non-Cardiac Indications 40 Several endocrine disorders as well as a number of electrolytic imbalances have been incriminated as torsades de pointes facilitators (hypothyroidism, mental anorexia, hypokalaemia, hypomagnesaemia, hypocalcaemia, acidosis). A great number of drugs are currently considered "torsadogenic". Almost all of these drugs have an IKr channel blocking effect, which explains QT interval prolongation. These agents belong to both "cardiotropic" and "non-cardiotropic" drugs (an exhaustive list is available on Internet at http://www.qtdrugs.org). Atrio-ventricular block -a piece in the puzzle The common element between atrio-ventricular block and torsades de pointes seems to be the presence of QT interval prolongation. Still, the association between atrio-ventricular block and QT interval prolongation is infrequent. Several studies have shown that this exact category of patients who present atrio-ventricular block induced -QT prolongation has the most elevated risk of developing torsades de pointes.