ECG PRIMER / Intro to EKG lecture
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| A dysfunction in refractoriness will lead to what cardiac adbnormality? | fibrillation. Due to cardiac cells all firing at different times.
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| What is slowest conducting point of the heart? | The AV node ~ 1.5 seconds. This prevents atria and ventricles from contracting simultaniously, allowing time for ventricular filling.
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| What is represented by the P wave. How should it look? | The P wave represents atrial depolarization. It should be upright and slightly rounded.
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| What is the Ta wave. | The Ta wave represents atrial REpolarization. It is opposite to the P wave, but is usually not visible because it normally coincides with the QRS complex.
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| What is represented by the QRS wave. | Ventricular depolarization
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| What is represented by the T wave? How should t look? | Ventricular REpolarization. It is normally upright and rounded
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| What is the U wave. How should it look, | The U wave is sometimes seen after the T wave. It is thought to relate to the events of the late repolarization of the ventricles. It should be small and in the same direction as the T wave.
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| What is the difference between and interval and a segment | Intervals contain waves, while segments are the lines between the waves (ie ST segment)
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| What does the PR interval represent? | The time from the beginning of the P wave to the beginning of the QRS complex. It represents the time interval between the depolarization of the atria and the spread of depolariztion up to and including the AV node.
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| It represents the time interval between the depolarization of the atria and the spread of depolariztion up to and including the AV node. | PR interval
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| What does the PR segment represent? | Represents the period of time between the P wave and the QRS complex. (should be called PQ segment!)
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| Represents the period of time between the P wave and the QRS complex. | PR segment
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| What does the ST segment represent? | The distance between the end of the QRS complex (j point) and the beginnng of the T wave. This is a sensitive indicator of myocardial ischemia or injury (MI)
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| This is a sensitive indicator of myocardial ischemia or injury (MI) | ST segment
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| What is represented by the QT interval? | The time from the beginning of the QRS complex to the end of the T wave. It represents both ventricular depolarization AND repolarization.
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| It represents both ventricular depolarization AND repolarization. | QT interval.
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| What is ventricular activation time? | The time from the beginning of the QRS complex to the peak of the R wave. It represents the time necessary for the depolarization wave to travel from the inner surface of the heart (endocardium) to the outer surface of the heart (epicardium)
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| It represents the time required for the depolarization wave to travel from the endocardium to the epicardium. | Ventricular activation time. (beginning of QRS complex to peak of R wave... should be called a QR interval)
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| Describe the Q, R, and S, waves in terms of positive or negative deflection | Q wave: always negative. R wave: always positive. S wave: always negative.
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| Normal value: P wave = | <.12 seconds **< 3 small boxes** (3 small boxes is .12 seconds)
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| Normal value: PR interval = | .12-.20 seconds **< 1 large box**
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| Normal value: QRS interval = | <.12 seconds **<3 small boxes**
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| Normal value: QT interval = | Varies with HR should be < 1/2 R-R interval
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| Normal value: QTc interval = | .33-.47 seconds ** QT/SQRT(RR interval ** QTc is QT corrected for HR
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| 1 small box = (what time interval?) | .04 seconds
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| 1 large box = (what time interval?) | .2 seconds
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| 1 small box vertically represents what voltage? | 1mV
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| How is HR calculated from EKG? | **300/ # of big squares** Count each large box from one QRS to the next as 300, 150, 100, 75, 60, 50, 42. So 5 large boxes = 60 BPM
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| What is the standard paper speed of an EKG | 25mm/sec (300 big squares per minute)
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| Each small box is how large? | 1 MM
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| Normal value: ST segment = | at rest: < or = 1 mm depression/elevation. At exercise: < or = 2 mm depression/elevation.
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| Describe the EKG appearance of a first degree AV block? | PR>.20 seconds (1 big box)
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| Describe the EKG appearance of a second degree AV block: Mobitz I | Mobitz I = Progressive increase in PR interval followed by a P wave w/o a QRS
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| Describe the EKG appearance of a second degree AV block: Mobitz II | Mobitz II: Constant PR interval then P wave without a QRS
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| Describe the EKG appearance of a third degree AV block | P waves not related to QRS... atrial rate faster than ventricular rate
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| Describe the EKG appearance of sick sinus syndrome | Pause without a Q wave.
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| What is the criteria for a right axis deviation? | RAD = > +120 degrees
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| What is the criteria for a left axis deviation? | LAD = < -30 degrees
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| What is the normal range for axis? | 0 to 90 degrees
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| Rule of thumb for determining if athere is a left or right axis deviation... | If AvF is negative it's a LAD (<0 degrees). If 1 is negative then it's a RAD (>90). Net positive QRS = Positive lead
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| A left axis deviation (LAD) may represent what pathology? | Inferior MI, LVH, LAHB
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| A Right axis deviation (RAD) may represent what pathology? | RVH, RPHB *NORMAL IN CHILDREN*
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| Hypokalemia commonly results in what ECG finding? | a prominent U wave. Although this is not diagnostic of hypokalemia, it may explain a ECG finding in a pt that is hypokalemic.
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