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CVD quiz 4

Terms in this set (14)

ECG or EKG
electrocardiogram
-look at 12 pictures of the heart
-4 pics in a row 1, row 2, and row 3
-then the last row can show you if there is an arrhythmia (each cycle is exactly the same (the spacing) you are in a rhythmic state (a complete cardiac cycle))
-you get about 3 secs in each image
-horizontal questions always answered in seconds
-vertical questions always answered in mm
graph paper - voltage
1 of the tiny boxes is 1mm in height and 1 mm in width
-so a box is 5mm x 5mm
graph paper - time
moving piece of graph paper at 25 mm/sec
-tiny box represents 0.04 seconds
-look at it from a horizontal view now, 5 big boxes represent 1 sec, 1 big box is 0.2 secs
phases of the resting ECG
-first thing you see is the P wave which is the depolarization of the atrias
-the three waves involved in the next part are the QRS waves, which is ventricular depolarization
-the Q wave deflecting downwards from baseline (always down)
-the R wave deflecting up from the baseline (always up)
-the S wave downward deflecting part of the wave after the R wave
the electrocardiogram: waves and intervals
-PR interval: horizontal measurement, beginning of the P wave all the way to the beginning of the Q or R wave, hence PR interval, described in seconds

-QRS interval: beginning of the Q wave all the way to the S wave, horizontal seconds number for that one

QT interval: begins at the Q wave and ends at the end of the T wave, horizontal number given in seconds
the electrocardiogram: waves and segments
ST segment is from the S wave to the beginning of the T wave, very important part
-not a time thing
rate
heart rate, paper moving at 25 mm/sec
-every heavy line = 300, 150, 100, 75, 60, 50
-5 heavy lines = 1 sec
-rate > 100 = tachycardia
-rate < 60 = bradycardia

-every set of boxes, 5 little ones
-going to look for one of those waves at that end right on the line
the electrocardiogram: electrical vectors
-a vector describes both magnitude and direction
-as it relates to magnitude, if the vectors are facing in the same direction, you can add them together to get unit c
-vectors always have a head and a tail
-add tail of vector a to head of vector b and you get a summation of vector c
the electrocardiogram: electrical vectors
-describes activity through right and left bundle branches: septal depolarization vector
-you can add all of these vectors together and get an overall summation of the activity of the heart
-a typically healthy heart without any hypertrophy, the overall summation of vectors is 60 degrees of overall axis
-if we had left ventricular hypertrophy: more muscle in the left side so it creates a larger vector and it is going to shift it up
-magnitude directly related to muscle mass
the electrocardiogram: mean electrical axis
-the MEA refers to the direction of the QRS complex (or, more specifically, to the R-wave)
-the grand vector
the electrocardiogram: electrical vectors round 2
-tail and head run parallel
-if it's running parallel, it will have a large upright magnitude
-but if the overall vector was exactly perpendicular to lead I, no signal or very small signal, diphasic signal, because the vector is running perpendicular to the axis
-what would the wave signal look like if the vector pointed left: large downward deflection, it is parallel and opposite
-parallel vectors always big and upward (running parallel from - to + of lead I)
-if the tails line up and the heads line up, the waves are going to be large
-vectors have to run parallel to be large, when they are perpendicular waves are very small if you can even see them, diphasic signal
the electrocardiogram: leads and axes
-lead 1: left arm to right arm, 0 degrees
-lead 2: left shoulder to right leg, 60 degrees
-lead 3: left shoulder to left hip, 120 degrees

-aVR: -150 degrees
-aVL: -30 degrees
-aVF: 90 degrees
the electrocardiogram: leads and axes
-aVR: augmented voltage right arm, has it's positive in the right shoulder
-aVL: augmented voltage left arm, has it's positive at the left shoulder
-aVF: augmented voltage foot, has it's positive at the foot or leg

-which of these 6 leads in the picture is the tallest of the allest? lead 2, so what is the axis of the heart? 60 degrees b/c that's where lead 2 falls on the pinwheel

-if lead 1 and lead 2 were the same height, the axis would be at 30 degrees, it the middle of lead 1 at 0 degrees and lead 2 at 60 degrees
mean electrical axis determination
-normal MEA: QRS is positive (or zero) in I, II, or aVF, and is negative in aVR
-right axis deviation (RAD): QRS is negative in I, positive in aVR
-left axis deviation (LAD): QRS is negative in III, aVF, and II

-if your axis spills out to beyond 90 degrees and you are in between 90 and 180, you are in right axis deviation, you can be put there if you have tight ventricular hypertrophy, the muscle will build up and the vector will shift the axis of the heart, you can't have this, go back and check it
-left ventricular hypertrophy will put you into LAD, too much left ventricular muscle mass
-positive aVL and positive aVF means you are in the bottom right quadrant (optimal quadrant)
-negative lead I and positive aVF puts you in RAD
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