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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.
MDCalc is a free online medical reference for healthcare professionals that provides point-of-care clinical decision-support tools, including medical calculators, scoring systems, and algorithms. [1] MDCalc is also a mobile and web app. [ 2 ] The decision-support tools are based on published clinical research, [ 3 ] and MDCalc’s content is ...
Corrected QT interval (QTc) The QT interval is measured from the beginning of the QRS complex to the end of the T wave. Acceptable ranges vary with heart rate, so it must be corrected to the QTc by dividing by the square root of the RR interval. A prolonged QTc interval is a risk factor for ventricular tachyarrhythmias and sudden death.
A medical calculator is a type of medical computer software, whose purpose is to allow easy calculation of various scores and indices, presenting the user with a friendly interface that hides the complexity of the formulas.
Qalculate! supports common mathematical functions and operations, multiple bases, autocompletion, complex numbers, infinite numbers, arrays and matrices, variables, mathematical and physical constants, user-defined functions, symbolic derivation and integration, solving of equations involving unknowns, uncertainty propagation using interval arithmetic, plotting using Gnuplot, unit and currency ...
T-wave alternans and prolonged QT interval in a male patient found to be in a narrow-complex tachycardia and ruled in for an acute myocardial infarction.Administered Ibutilide and converted to sinus rhythm but subsequently had an episode of Torsades de Pointes which required DC cardioversion back into sinus rhythm.
The T wave contains more information than the QT interval. The T wave can be described by its symmetry, skewness, slope of ascending and descending limbs, amplitude and subintervals like the T peak –T end interval. [1] In most leads, the T wave is positive. This is due to the repolarization of the membrane.
The value for a normal QT interval is similar in males and females from birth up to adolescence. During infancy, a normal QTc is defined as 400 ± 20 milliseconds. Before puberty, the 99th percentile of QTc values is 460 milliseconds. After puberty, this value increases to 470 milliseconds in males and 480 milliseconds in females. [citation needed]