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P WAVE represents depolarization of the atria
QRS COMPLEX correspond to the depolarization of the ventricles
T WAVE represents ventricular repolarization
LARGER SIZEOF THE QRS COMPLEX OVER SMALLER P WAVE caused by the greater muscle mass of the ventricles and hence greater number of cellular depolarizations
SMALL Q WAVE occurs during the activation of the septal fascicle and the depolarization of the interventricular sseptum
R WAVE SPIKE occurs when both ventricles are depolarizing at the same rate
ECG useful for the clinician in diagnosing heart attacks (MI), conduction abnormalities, arrhythmias, toxicity and electrolyte imbalances
Cardiac muscle contains 3 types of cells that are involved in synchronized contraction of the 4 chambers of the heart NODAL CELLS, SPECIALIZED CONDUCTING FIBERS, CONTRACTILE OR MYOCARDIAL CELLS
1. NODAL CELLS involved in generating the internal action potentials of the heart. They are localized in 2 areas of the heart, the SA and AV node.
2. SPECIALIZED CONDUCTING FIBERS allows for the quick transmission of the action potentials from one part of the chambers to another. AV bundle and the PURKINJE fibers
Nodal cells and specialized conducting fibers INTRINSIC CONDUCTION SYSTEM OF THE HEART
3. CONTRACTILE OR MYOCARDIAL CELLS makes up over 90 percet of the heart and is responsible for muscle contraction and the pumping of blood
ELECTRICAL AXIS OF THE HEART important for clinical diagnosis because it indicates the position of the heart in the thoracic cavity and hypertrophy of the chambers
ELECTRICAL AXIS RANGE nomally between -30 degrees and +90 degrees.
LEFT AXIS DEVIATION when the electrical axis is less than -30 degrees and can be caused by left ventricular hypertrophy, COPD, obesity, or an inferior myocardial infarction.
RIGHT AXIS DEVIATION when electrical axis is greater than +90 degrees and can be caused by right ventricular hypertrophy, an anterior-lateral myocardial infarction, pulmonary emboli, or normally occurs in tall thin adults
PR INTERVAL represents the time it takes electrical impulse to spread from the beginning of atria depolarization to the beginning of ventricular depolarization and is normally 0.12 to 0.20 seconds
PR INTERVAL calculated from the beginning of the P wave to the first Q wave deflection in the QRS complex.
PROLONGED PR INTERVAL may be caused by longer delay at the AV node, hypothyroidism, or various drugs.
SHORTEND PR INTERVAL suggests that the impulse has originated in areas other than the SA node.
PR SEGMENT is a component of the interval and is measured from the end of the P wave to ventricular depolarization.
PR INTERVAL if longer, AV node block
QRS DURATION the time it takes to complete depolarization within the ventricles.
QRS DURATION measured from the beginning of the Q wave to the end of the S wave and is normally between 0.08 to 0.11 seconds
QRS - prolonged prolonged time might suggest a bundle block or ventricular hypertrophy
QT INTERVAL is a measurement of the duration of the action potential and thus the refractory period in the ventricles and is calculated from the beginning fo the Q wave to the end of the T wave
QT INTERVAL changes with physical activity, calcium or potassium imbalances and various drugs.
ST SEGMENT part of the QRS interval and is measured from the end of the S wave to the beginning of the T wave. Represents the PLATEAU phase of the action potential
Created by: jekjes