Prevalence and prognostic significance of long QT interval in patients with acute coronary syndrome: review of the literature

Background Sympathetic hyperactivity is linked with several adverse cardiovascular events in patients with acute coronary syndrome (ACS). Sympathetic activity increases early in the process of ischemia through 2 mechanisms. One originates from the central nervous system and leads to enhanced sympathetic activity. The other mechanism originates at the infarct zone and leads to B receptor up-regulation and catecholamine supersensitivity. Nevertheless, sympathetic hyperactivity accompanied by an underlying myocardial structural damage is likely to increase the ventricular repolarization duration measured as QT interval on the body surface electrocardiogram. Purpose The aims of the current review of the literature were to examine the physiological processes underlying the use of long QT interval as a risk prediction tool in patients with ACS and to critically review and critique the existing evidence related to this matter. Conclusion The available evidence is contradictory and includes serious limitations in design and QT measurement and correction. Until accurate and reliable data are available, it is difficult to determine the additional clinical value and prognostic significance of long QT interval in patients with ACS beyond that in other patients. Clinical implications Long QT interval is not uncommon among patients with ACS. Automated continuous QT interval monitoring is superior to manual QT interval measurement with the standard 10-second electrocardiogram. Optimum care for patients with ACS requires nurses to keep monitoring the QT interval several days after the initial event.