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It is normal to have a narrow QS and rSr' patterns in V 1, and this is also the case for qRs and R patterns in V 5 and V 6. The transition zone is where the QRS complex changes from predominantly negative to predominantly positive (R/S ratio becoming >1), and this usually occurs at V 3 or V 4.
Precordial concordance, also known as QRS concordance is when all precordial leads on an electrocardiogram are either positive (positive concordance) or negative (negative concordance). [1]
In lead V 1, the QRS complex is often entirely negative (QS morphology), although a small initial R wave may be seen (rS morphology). 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.
To determine a true LAD, examine QRS in lead II. If the QRS complex is positive in lead II, then this is a normal axis. On the other hand, if QRS complex is negative in lead II, then this is a LAD. Another method of determining LAD is called the Isoelectric lead, which allows for a more precise estimation of the QRS axis. [3]
ST elevation ≥1 mm in a lead with a positive QRS complex (i.e.: concordance) - 5 points; concordant ST depression ≥1 mm in lead V1, V2, or V3 - 3 points; ST elevation ≥5 mm in a lead with a negative (discordant) QRS complex - 2 points; ≥3 points = 90% specificity of STEMI (sensitivity of 36%) [2]
This refers to the appearance of leads I and II. If the QRS complex is negative in lead I and positive in lead II, the QRS complexes appear to be "reaching" to touch each other. This signifies right axis deviation. Conversely, if the QRS complex is positive in lead I and negative in lead II the leads have the appearance of "leaving" each other.
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A shortcut for determining if the QRS axis is normal is if the QRS complex is mostly positive in lead I and lead II (or lead I and aVF if +90° is the upper limit of normal). [59] The normal QRS axis is generally down and to the left, following the anatomical orientation of the heart within the chest. An abnormal axis suggests a change in the ...