Emerging truths about Early repolarisation syndrome !
Posted Aug 06 2009 10:35pm
Early repolarisation syndrome, (Also called ERS) is a common ECG observation among general population.It is diagnosed when ST elevation occurs with concavity upwards in anterior chest leads and inferior leads or both. The exact incidence is variable (Up to 2%). It forms an important variant in young males .Females form a minority with this finding.
The ST segment instead of staying at baseline drift superiorly .The descending limb of qrs , ie the S wave is prematurely interrupted as it travels downhill before reaching the baseline , the ST segment is inscribed resulting in a elevated ST segment.
What is the mechanism ?
ST segment represents the major part of ventricular repolarisation. The ionic channel responsible forthis current is K+ efflux from the cells. The potassium channel opening determines the speed with which replorisation happens. The kinetics K+ channels are greatly dependent on genetic inheritance (As do long qt syndromes) .The high degree of variance of ST morphology in normal population is attributed to potassium channel heterogeneity.
Is ERS a benign entity ?
For long . . .we believed so ! now evidence indicates it may not be . . .
The importance of ERS not lies in it’s ECG appearance , the fact that , it occurs in a critical time of cardiac cycle makes it a potential threat. We know ST segment encloses the electrically unstable QT interval .Any alteration in it’s morphology can trigger a electrical heterogeneity. In fact there is some truth in the observation ERS prolongs the QT interval when compared to controls.
Haissagure has elegantly studied this issue in NEJM and provided evidence ERS may have a strong propensity for ventriculaarrhytmias (Read below)
But , there is no need to panic , ERS is still considered benign, but waht is posible is persons with this abnormality could be prone for primary VF when confronted with a episode of ischemia.
What is exercise response in ERS patients?
One of the following can occur.
ST segment normalises
ST segment normalisation is the expected response. Some believed the resting ST elevation tend to prevent the true ST depression in times of ischemia . Often , classical ischemic ST depression can occur in patients with CAD.
The most tricky finding is fluctuation in ST segment magnitude with reference to vagal tone, heart rate can occur.This can mimic a coronary syndrome , and enzyme levels are necessary to rule out .
1.Haïssaguerre M, Derval N, Sacher F et al. Sudden cardiac arrest associated with early repolarization. N Engl J Med, 2008; 358: 20632065.
2. Early repolarization syndrome: Is it always benign? International Journal of Cardiology, Volume 114, Issue 3, Pages 390-392 K. Letsas, M. Efremidis, L. Pappas, G. Gavrielatos, V. Markou, A. Sideris, F. Kardaras