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Pathologic Q waves occur when the electrical signal passes through stunned or scarred heart muscle; as such, they are usually markers of previous myocardial infarctions, with subsequent fibrosis. A pathologic Q wave is defined as having a deflection amplitude of 25% or more of the subsequent R wave, or being > 0.04 s (40 ms) in width and > 2 mm ...
Following infarction, ventricular aneurysm can develop, which leads to persistent ST elevation, loss of S wave, and T wave inversion. [1] Weakening of the electrical activity of the cardiac muscles causes the decrease in height of the R wave in those leads facing it. In opposing leads, it manifests as Q wave. However, Q waves may be found in ...
The presence of a short PR interval and a delta wave (Wolff-Parkinson-White syndrome) is an indication of the existence of ventricular pre-excitation. [1] Significant left ventricular hypertrophy with deep septal Q waves in I, L, and V4 through V6 may indicate hypertrophic obstructive cardiomyopathy. [1]
Over a period of hours, a pathologic Q wave may appear and the T wave will invert. Over a period of days the ST elevation will resolve. Pathologic Q waves generally will remain permanently. [72] The coronary artery that has been occluded can be identified in an STEMI based on the location of ST elevation.
Specifically, an increase in Q wave size, abnormalities in the P wave, as well as giant inverted T waves, are indicative of significant concentric hypertrophy. [13] Specific changes in repolarization and depolarization events are indicative of different underlying causes of hypertrophy and can assist in the appropriate management of the condition.
A mnemonic can be used for some causes of ST depression, namely DEPRESSED ST: [citation needed]. D - Drooping valve (mitral valve prolapse) E - Enlargement of the left ventricle P - Potassium loss R - Reciprocal ST depression (e.g. inferior wall MI) E - Encephalon hemorrhage S - Subendocardial infarct S - Subendocardial ischemia E - Embolism (pulmonary) D - Dilated cardiomyopathy S - Shock T ...
The algorithm takes particularly into consideration the possibility of a false detection of T waves. If a potential QRS falls up to a 160 ms window after the refractory period from the last correctly detected QRS complex, the algorithm evaluates if it could be a T wave with particular high amplitude.
The QT interval is a measurement made on an electrocardiogram used to assess some of the electrical properties of the heart.It is calculated as the time from the start of the Q wave to the end of the T wave, and approximates to the time taken from when the cardiac ventricles start to contract to when they finish relaxing.