Revista chilena de cardiología
On-line version ISSN 0718-8560
ORELLANA A, Mirta et al. Increased Q-T interval in different electrocardiographic patterns: a remote recording electrocardiographic study. Rev Chil Cardiol [online]. 2009, vol.28, n.4, pp. 349-356. ISSN 0718-8560. doi: 10.4067/S0718-85602009000300002.
Background. Increased Q-T interval has been identified as a risk factor for ventricular arrhythmia including normal subjects. Aim. To establish the prevalence of an increased QTc in normal electrocardiograms (N) an in those with complete bundle branch block (RBBB or LBBB) or left ventricular hypertrophy (L VH). Method. D1, aVL, V5 and V6 leads were analyzed; a > 440ms QTC agreed upon by 2 observers was considered prolonged. Results: anincreased QTc was observed in 16%> of 8459 N subjects, 51.5%> of subjects with LBBB and 25% of those with RBBB. Among subjects with LVH, 28% of those with voltage only criteria for LVH and 29% of those with ST-T changes but no voltage critería hadincreased QTc. In contrast, 42%> of patients with LVH exhibiting both diagnostic critería hadincreased QTc. In 7.6%> of LVH subjects withincreased QTc, this interval was >500ms, which broke down as follows: LVH by voltage criteria alone 4.7%>, ST-T changes alone 7.9% > and LVH with both voltage and ST-T critería 8.3%>. In patients with complete bundle branch block, the duration of the QRS interval was not related to QTc. Conclusion. A prolonged QTc is a frequent finding in normal ECGs, much more so in subjects with LVH associated to voltage and ST-T critería. The prognostic impact of a prolonged QTc in patients with complete bundle branch block deserves further study.
Keywords : Increased Q-T interval; left ventricular hypertrophy; bundle branch block.