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Lecture 2
Intro to EKG/ECG
| Question | Answer |
|---|---|
| What is an ECG? | graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin |
| Types of ECG | resting, stress/exercise, resting 12 lead, 12 lead, holter |
| What can it tell us? | heart rate, cardiac output, life threatening arrhythmia, setting up for arrhythmia |
| Physiology Step 1 | action potential originates in SA node and then spreads to both the atrial nodes via the internal tracts and the atrial tissues |
| Physiology Step 2 | the AP passes to the AV node and to the ventricle through bundles of His and Purkinje fibers |
| Physiology Step 3 | It spreads very quickly through a common bundle of the His, then to the right and left bundle branches to the Purkinje fibers, and finally to the ventricle tissues from the endocardium to the epicardium |
| The Electrocardiogram | three standard limb leads (lead I, II, III) for continuous monitoring |
| The Electrocardiogram | a 12 lead ECG provides detailed information about the heart's conduction system = records activity from 12 separate angles; electrical snapshot of a part of the heart |
| Electrode Placement | predetermined spots; usually adhesive with gel center (white, black, green, red) |
| The Leads: two main groups | Limb leads (I, II, III, aVL, aVF); precordial leads (chest leads; V1 to V6) |
| Limb Leads | Einthoven's theory=every time the heart contracts, electrical energy is emitted |
| Limb Leads: lead I=____; lead II=____, lead III=____ | attached to right and left arms, runs between right arm and left leg, runs between left arm and left leg |
| Limb Leads | leads I, II, III are bipolar leads; contain a positive and negative pole; measure the difference in electrical potential |
| Limb Leads: augmented voltage (aV) leads are created using _____. Leads aVR, aVL, aVF = combine two limb leads and use the other lead as the other ____ | four limb electrodes; pole |
| 12 lead ECG Placement | white = right wrist, green = right ankle, black=left wrist, red=left ankle |
| Precordial leads | V1 to V6; unipolar, referenced against a calculated point; depict the heart in the horizontal plane; must be placed correctly and consistently |
| Contiguous leads | leads that view geographically similar areas of the myocardium; useful for localizing areas of ischemia, injury, or infarction |
| Right sided leads | used to evaluate the electrical of the right ventricle; precordial leads are placed on the right anterior thorax |
| ECG Concepts | baseline represents electrical silence in the myocardium = 0, up =positive; down = negative |
| ECG Concepts: electrical impulse moving toward a positive electrode produces a deflection ___baseline | above |
| ECG Concepts: electrical impulse moving toward a negative electrode produces a deflection ___baseline | below |
| ECG Concepts: biphasic waves = waveforms with ____ and ____components | positive, negative |
| ECG Paper**: one 1mm box =___second. one large box =____second | graph paper moves past stylus at 25 mm/s; 0.04 second, 0.20 second |
| ECG Paper**: vertical axis=____. standard amplitude calibration=___mm/mV | amplitude; 10 |
| ECG Components | correspond to electrical events in the heart |
| ECG Components: P wave =____ | represents atrial depolarization/atrial contraction; smooth, round, upright shape; normal duration of less than 0.12 seconds; amplitude(height) less than 2.5mm tall |
| ECG Components: PR interval (PRI) | represents the time required for an impulse to transverse the atria and AV junction; normal duration of 0.12 to 0.20 seconds |
| ECG Components: QRS complex | three waveforms representing ventricular depolarization; from beginning of Q wave to end of S wave; narrow in healthy people, less than 0.12 seconds; indicates that impulse has proceeded normally; |
| ECG Components: QRS complex | Q wave=first negative deflection; R wave=first upward deflection; S wave=downward deflection after the R wave |
| ECG Components: QRS complex J point | where QRS complex ends and ST segments begins; end of depolarization and beginning of depolarization |
| ECG Components: ST segment=____ | begins at J point and ends at T wave; used to diagnose a heart attack |
| ECG Components: T wave | represents ventricular depolarization; should be asymmetric; less than half overall QRS complex height; oriented in same direction as QRS complex; |
| ECG Components: T wave | very large=may indicate myocardial ischemia, injury, and infarction; tall, pointed (peaked): may indicate hyperkalemia (excessive potassium in blood); deeply inverted: acute CNS events, such as intracranial hemorrhage/massive stroke |
| ECG Components: QT interval | represents all electrical activity of one completed ventricular cycle; it begins at onset of Q wave; ends at T wave; normally lasts 390-460ms; long QT intervals can lead to ventricular dysrhythmias/sudden cardiac arrest |
| ECG Components: PR interval | time of measurement; something wrong with heart |
| Do I have a P wave? | do/is it present and upright? do they have the same morphology? do I have a P for every QRS? Do I have a QRS for every P wave? What's my PR interval? |
| QRS wide or narrow | QRS interval? |
| QT and ___interval? Rate and ___? ST segments on ___? | QTC. regularity. baseline |
| Approach to Dysrhythmia Interpretation | identify the waves (P-QRS-T), measure the PRI, measure the QRS duration, determine rhythm regularity, measure the heart rate |
| Rhythm Regularity | measure the distance between R waves. Regular=the distance between R waves is the same |
| Rhythm Regularity: irregularly irregular= no two R waves ____ | equal |
| Rhythm Regularity: regularly irregular=R waves irregular but follow a ____ | pattern |
| Determining Heart Rate: 6 second method | count the number of QRS complexes in a 6 second strip and multiply by 10 |
| Determining Heart Rate: 10 second method | a full 12 lead ECG is 10 seconds long |
| Determining Heart Rate: sequence method | find R wave; count off above sequence until next R wave. if the interval spans fewer than 3 boxes, the rate is greater than 100. if it's more than 4 boxes, the rate is less than 60 |
| Determining Heart Rate: 1,500 method | count the number of small boxes between any two QRS complexes. divide by 1,500 |
| Rhythms Originating at the AV Junction | The AV junction will take over if the SA node fails; rhythms of AV junction origin are known as junctional rhythms =have inverted or missing P waves; an impulse generated in the AV junction travels down into the ventricles and up toward the SA node |
| Rhythms Originating at the AV Junction 3 possibilities | 1)upside down P wave immediately followed by QRS complex 2)smaller inverted P wave hidden within QRS complex 3)inverted P wave after the QRS complex. rates of 40-60 beats/min |
| Rhythms Originating at the AV Junction junctional escape rhythm | occurs when the SA node does not function = the AV node becomes the pacemaker; most common with significant SA node problems; treatment usually an implanted pacemaker |
| Rhythms Originating at the AV Junction accelerated junction rhythm | present with a rate exceeding 60 beats/min but less than 100 beats/min; regular rhythm, little variation between R-R intervals |
| Rhythms Originating at the AV Junction junctional tachycardia | junctional rhythm rate higher than 100 beats/min; regular rhythm, little variation between R-R intervals |
| Rhythms Originating in the Ventricles | ventricles may become the pacemaker if the AV junction does not take over after the SA node fails = wide QRS complexes and missing P waves; intrinsic firing rate of ventricles 20-40 BPM |
| Rhythms Originating in the Ventricles idioventricular rhythm | occurs when SA and VA nodes fail; may or may not result in a palpable pulse |
| Rhythms Originating in the Ventricles accelerated idioventricular rhythm (AIVR) | occurs when an IVR exceeds; 40 beats/min but less than 100 beats/min |
| Rhythms Originating in the Ventricles | fibrillation, tachycardia, asystole |
| Pulseless Electrical Activity | organized cardiac rhythm not accompanied by a detectable pulse; can look like anything |
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