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Despite clinical importance of ventricular repolarisation, it remains difficult to analyse. Conventionally, quantification of the electrocardiographic ventricular repolarization is usually performed with reference to axis of the T wave and QT interval duration. A variety of factors can prolong the QT interval, such as drug effects, electrolyte imbalances, and myocardial ischemia. The biggest risk with prolongation of the QT interval is the development of torsades de pointes. Commonly accepted reference ranges for the electrocardiogram (ECG) have been in use, with little change, for many years. Populations throughout the world present several differences: age, ethnic compositions, and are exposed to different environmental factors. Recent studies have reported reference data for QT interval in healthy population and have evaluated the influence of age, gender, QRS duration and heart rate on this interval. In this review, we address several issues relative to the measurement, and interpretation of QT interval and its adjustment for rate, age, gender and QRS duration.

Aims: To assess whether a strategy of invasive management without stents in selected acute coronary syndrome (ACS) patients with a large thrombus burden (LTB) might be feasible and safe.\ud \ud Methods and results: We performed a prospective non-randomised observational cohort study of invasive treatment decisions guided by optical coherence tomography (OCT) in selected ACS patients with LTB. Among 852 ACS patients who had undergone invasive coronary angiography, 101 (11.8%) patients with large thrombus burden on initial angiography underwent thrombectomy to restore TIMI 3 flow without stenting. All of these patients then had repeat angiography with OCT (days 0-2 [Group 1], days 3-6 [Group 2] or days 7-30 [Group 3]). No adverse events occurred between the initial and second angiograms. Residual thrombus was detected in 68% of patients with OCT (respectively, 94%, 79% and 32% in Group 1, Group 2 and Group 3), and 20% of cases with angiography. Plaque rupture was detected by OCT in 65% of cases. Minimal lumen area was 2.81 mm2, 3.40 mm2 and 4.89 mm2 in Group 1, Group 2 and Group 3, respectively. Sixty-two percent of patients were stented (respectively, 76%, 61% and 50%). During a minimum follow-up period of 12 months in all patients, one non-fatal MI occurred and one PCI was performed for angina.\ud \ud Conclusions: Medical management without stents is safe and feasible in selected ACS patients with LTB. OCT revealed culprit lesion characteristics that were not disclosed by angiography and facilitated treatment decisions.