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An R wave follows as an upward deflection, and the S wave is any downward deflection after the R wave. The T wave follows the S wave, and in some cases, an additional U wave follows the T wave. To measure the QRS interval start at the end of the PR interval (or beginning of the Q wave) to the end of the S wave.
There are 6 different sinus arrhythmia. [1] [2]A normal heart should have a normal sinus rhythm, this rhythm can be identified by a ventricular rate of 60-100 bpm, at a regular rate, with a normal PR interval (0.12 to 0.20 second) and a normal QRS complex (0.12 second and less).
In the lateral leads (I, aVL, V 5-V 6) the QRS complexes are usually predominantly positive with a slow upstroke last >60ms to the R-wave peak. [4] Notching may be seen in these leads but this is not universal. The small Q-waves that are usually seen in the lateral leads are absent in LBBB. [4]
A Sgarbossa score of ≥3 was specific but not sensitive (36%) in the validation sample in the original report. [2] A subsequent meta-analysis of 10 studies consisting of 1614 patients showed that a Sgarbossa score of ≥3 had a specificity of 98% and sensitivity of 20%. [4] The sensitivity may increase if serial or previous ECGs are available. [5]
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. An abnormally long or abnormally short QT interval is associated with an increased risk of developing abnormal heart rhythms and sudden cardiac death.
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rS pattern (small r, deep S) in the inferior leads II, III, and aVF; Delayed intrinsicoid deflection in lead aVL (> 0.045 s) LAFB cannot be diagnosed when a prior inferior wall myocardial infarction (IMI) is evident on the ECG. IMI can also cause extreme left-axis deviation, but will manifest with Q-waves in the inferior leads II, III, and aVF.
Rule 9: There is no Q wave or only a small q (<0.04 seconds in width) in I, II and V2 to V6. Rule 10: The T wave is upright in I II and V2 to V6. The end of the T wave should not drop below the isoelectric baseline. Rule 11: Does the deepest S wave in V1 plus the tallest R wave in V5 or V6 equal >35 mm? Rule 12: Is there an Epsilon wave?