Term
| what are vectors? in the heart? |
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Definition
• Energy that can be measured in direction and quantity
• Myocardium depolarizes in many directions at the same time
• Vectors are the average of the directional forces moving through the heart and translated as wave patterns on the ECG |
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Term
| 3 basic laws of electrocardiography |
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Definition
needed to understand the appearance of the waveform in each lead
• Law 1: Depolarization that approaches a surface electrode records a positive (upward) deflection
• Law 2: Depolarization that moves away from a surface electrode records a negative (downward) deflection
• Law 3: Depolarization that is perpendicular to an electrode will record an equiphasic deflection |
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Term
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Definition
• The average direction of the myocardium depolarization is termed the electrical axis
• It is the sum of the six extremity leads on the frontal plane
• “Mean QRS axis” |
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Term
| average vector in a "normal" heart |
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Definition
• In a “normal” heart, the average vector is downward, slightly to the left, and slightly posterior
• I, II, and aVF have mainly a “+” deflection |
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Term
| picture of chest with leads and angles |
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Definition
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Term
| easiest way to determine the axis |
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Definition
• LAD exists if SII>RII and/or tall R wave in lead I and a deep S wave in lead III
• RAD exists if RIII>RII and/or lead I has an rS wave |
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Term
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Definition
| • As the neonate grows, the mean QRS vector rotates from right anterior to left posterior |
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