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ST segment depression and T-wave changes may be seen in patients with unstable angina; Depressed but upsloping ST segment generally rules out ischemia as a cause. Also, it can be a normal variant or artifacts, such as: Pseudo-ST-depression, which is a wandering baseline due to poor skin contact of the electrode [3]
An episode of chest pain in Wellens' syndrome is associated with ST elevation or depression and later progressed to T wave abnormality after chest pain subsided. T wave inversion less than 5 mm may still represents myocardial ischaemia, but is less severe than Wellens' syndrome. [5]
An upsloping, convex ST segment is highly predictive of a myocardial infarction (Pardee sign) while a concave ST elevation is less suggestive and can be found in other non-ischaemic causes. [1] Following infarction, ventricular aneurysm can develop, which leads to persistent ST elevation, loss of S wave, and T wave inversion.
In electrocardiography, the ST segment connects the QRS complex and the T wave and has a duration of 0.005 to 0.150 sec (5 to 150 ms). It starts at the J point (junction between the QRS complex and ST segment) and ends at the beginning of the T wave.
The hexaxial reference system is a diagram that is used to determine the heart's electrical axis in the frontal plane.. In electrocardiography, left axis deviation (LAD) is a condition wherein the mean electrical axis of ventricular contraction of the heart lies in a frontal plane direction between −30° and −90°.
[37] [38] It classically mimics ST-segment elevation myocardial infarction, and is characterised by acute onset of transient ventricular apical wall motion abnormalities (ballooning) accompanied by chest pain, shortness of breath, ST-segment elevation, T-wave inversion or QT-interval prolongation on ECG.
ST-T Abnormalities: ST-T vector opposite to QRS without digitalis; ST-T vector opposite to QRS with digitalis; 3 1 Negative terminal P mode in V 1 1 mm in depth and 0.04 sec in duration (indicates left atrial enlargement) 3 Left axis deviation (QRS of −30° or more) 2 QRS duration ≥0.09 sec 1 Delayed intrinsicoid deflection in V 5 or V 6 ...
IVCD can be caused by abnormalities in the structures of bundle of His, Purkinje fibers or ventricular myocardium. [5] [6] Nonspecific intraventricular conduction delay (NICD) is a delay with widened QRS complex but without a specific intraventricular block present. [7]