Key result
Oral glucose load alters T wave morphology in 100% of LQTS patients unlike healthy controls.
Why the study?
Does glucose-induced insulin secretion alter ventricular repolarization in patients with congenital long QT syndrome?
Case-Control (n=22)
Single-blind
Yes
Does glucose-induced insulin secretion alter ventricular repolarization in patients with congenital long QT syndrome?
Absolute Event Rate: 100% vs 0%
p-value: p=<0.00001
Glucose-induced insulin secretion significantly alters ventricular repolarization and increases QT dispersion in patients with congenital LQTS, potentially increasing their susceptibility to arrhythmias.
May warrant caution with glucose loads in LQTS; leaves open arrhythmia risk pending prospective validation.
To assess the role of insulin in ventricular repolarization in patients with congenital long QT syndrome (LQTS), an oral glucose tolerance (OGT) test was performed in 11 patients with LQTS and in 11 control cases without QT prolongation. Plasma glucose, potassium level and the immunoreactive insulin concentration (IRI) were measured, and the QT interval and T wave morphology on 12-lead ECG were analyzed during fasting and after glucose load. The LQTS group had a higher incidence of changes in T wave morphology, such as biphasic, bifid or notched T wave, after glucose load than the control group (11 of 11 patients [100%] vs 0 of 11 [0%]; p<0.00001). The T wave changes returned to baseline at 180 min after glucose load in 7 patients. The maximal QT interval and QT dispersion increased significantly and returned to baseline level in response to IRI after glucose load in LQTS, whereas the QT interval was unaffected in the control group. After glucose load, ventricular arrhythmias and T wave alternans were observed in 3 and 1 patients with LQTS, respectively, but none in the control group. The findings suggest that glucose-induced insulin secretion plays a role in inducing abnormalities and inhomogeneity of ventricular repolarization in patients with LQTS.
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Nishizaki et al. (2002) conducted a case-control in Congenital Long QT Syndrome (n=22). Oral glucose tolerance test vs. Healthy controls was evaluated on Changes in T wave morphology after glucose load (p=<0.00001). An oral glucose load induced distinct changes in T wave morphology in 100% of patients with congenital long QT syndrome compared to 0% of healthy controls (p<0.00001).
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