Lead Placement Unlike leads I, II, III, the augmented leads utilize a central negative terminal. This virtual "electrode" is calculated by the EKG computer to measure vectors originating roughly at the center of the heart. -150 degrees
Lead Placement The negative electrode is the central termininal. The positive electrode is connected to the LEFT ARM. -30 degrees
Lead Placement The negative electrode is the central termininal. The positive electrode is connected to the LEFT LEG. +90 degrees
Lead Placement Super-imposing the augmented leads over Einthoven's triangle demonstrates the vector relationship.
Lead Placement These leads provide essental information used in localizing ischemic or infarcted tissue during a cardiac event.
Refractoriness Absolute refractory period Relative refractory period
Relative Refractory Period An impulse during the relative refractory period may cause a premature contraction. In this situation, the chambers are not filled completely. According to the Frank-Starling Law, this decreased preload will cause cardiac output to decrease.
Methodology of EKG Interpretation Always begin you analysis by asking the following questions: Is the rate fast or slow? Are the atrial and ventricular rates the same? Are the P-P interval and R-R interval regular or irregular? If the rhythm is irregular, is it consistent or irregular Irregularity? Is there a P-wave before each QRS? Is there a QRS before every P- wave? Are the P-waves and QRS complexes identical and normal in configuration? Are the P-R and QRS intervals within normal limits?
Sinus Rhythm Sinus Rhythms originate at the SA node travel through the entire conduction system without inhibition a conducted P-wave P-R interval between 0.12 and 0.20 seconds The QRS width should be 0.04 to 0.12 seconds and all QRS's are preceded by a P- wave