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EKG Interpretation
Technology
Question | Answer |
---|---|
What is ECG | ECG record electrical potentials generated by myocardial cells |
ECG allows the detection of | Dysrhythmias Myocardial ischemia conduction abnormalities pacemaker malfunction electrolyte disturbances |
Why use ECG | In the beginning..observations of electrical activity (hopefully normal) Recognition of intraoperative myocardial ischemia Follow the proper functioning of indwelling pacing devices. |
How it works | The ECG measure voltage between a positive and a negative lead over time The changes are graphed over time at a specific standard rate (25mm/sec) Vectures that travel towards the positive lead show positive deflections in the lead being measured |
The Normal ECG cycle | SA node reigns as the dominant "Pacemaker pf the heart". Proceeds first through the right then left atria (p wave). Three ways to the AV node! (pause). Dep slowly (ST segment and the T wav. The T-Wa represents the largely uncancelled poten dif of vent rep |
ECG Operational Therory | The elect currents in the heart are low (mV,and mcA!). Electrodes should be placed over clean bony prominences if poss. Shave hair off, max contact and minimize resistance (if poss). However they spread All over d body. can be measure on surface any site |
ECG Operational Theory cont. | Standard Bipolar leads (I,II,III) content to form a triangle. Routed through a resistance circuit (5K Ohms standard0 The center (central terminal/ZERO potential points0 forms a virtual "common" electrode. |
What is Goldbergers modification ( ECG operating theory) | Augmented limb leads (aVL, aVR, aVF) measure ACTUAL potential --- Tehy measure WITHOUT resistance circuit in the line. Produces larger ECG deflection. |
Continuation of ECG Operational Theory | The precorial lead system places the EXPLORING electrode around the thorax while the neutral electrode remains in the one of the standard limb leads. Indicated by letter V 1-6 |
Leads V 1 - 6 are placed | 1,2 - Right chest leads 3,4 - Septal (usually over the intraventricular septum) 5,6 - Lateral (left chest leads) |
Where do the leads go anyway? | RA - Right shoulder ( trying to avoid thick muscle) LA - Left shoulder ( trying to avoid thick muscle) LL _ Left lower abdomen ( traditionally on left lateral calf) RL - Any convenient location (traditionally on Left lateral calf) |
Where do the other leads go | V1 - Fourth ICS right of sternal border V2 - Fourth ICS left of sternal border V3 - Equal distance between V2 and V4 V4 - MCL at fifth ICS V5 - Horizontal to V4 on AAL V6 - Horizontal to V5 or MAL |
3 Leads starts with Basics | Consists of three bipolar leads (l,ll,lll) REquires the operator to switch between leads Advantages -Convenience & Simplicity in operation ( generally a good picture of the physiologic P wave) Disadvantage -Poor ischemic monitoring sensitivity (narro |
3 Leads kick it up a notch | A few modification can be employed to overcome the limitation of the 3 lead system In general the goal is to maximize the detection of atrial arrhythmias, anterior myocardial ischemia, and used competently and correctly, just as sensitive as a 5 lead sys |
More on 3 lead kick it up a notch | Central subclavicular lead (CS5) -Particularly suited for anterior myoc ischemia detection -If a unipolar precordial lead is unavailable, the CS% is the Best and easiest alternative. |
3 Leads kick it up a notch (Central Back Lead(CSB) | Best for supraventricular arrythmia detection because the P wave is 90% larger than V5. R wave may have increased amplitude and ST segment changes exaggerated |
More with Kick it up a notch | -LA <= lll + LL MCL1 |
Central Subclavian | The right arm (RA) electrode is placed under the right calvicle, the left arm (LA) electrode is placed in the V5 position, and the left leg electrode is in the usual position to serve as a ground. |
What does lead l do | Lead l is selected for detection of anterior wall ischemia |
What does Lead ll do | Lead ll can be selected for monitoring inferior wall ischemia or for the detection of arrhythmias. If a a unipolar precordial electrode is unavailable, the CS5 bipolar lead is the best and easiest alternative to a true V5 lead for monitoring MI. |
How do you obtain CB5 | CB5 is obtained by placing the RA elecrode over the center of the right scapular and LA electrode in the V5 position. The lead selector swithc should be on lead 1 is great for SV arrhythmias and ischemia |
5 Leads kick it up another notch | Adds the augmented and precordial leads Allows for enhanced ability for detection of myocardial ischemia Allows for simultanueos multi lead analysis ( not simultaneous predcordial) |
5 Leads Invasive ! (THE ULTIMATE) | Intra cardiac Esophageal (enjanced atrial arrhythmia dectedtion Edontracheal Mainly used inpatient where skin lead placement is not practical Not practical, but can be very sensitive indicators if placed correctly |
ECG Recording | ECG paper standards -paper moves at 25 mm/sec -small squares in the grid 1 mm x 1mm -Horizontal= .04 seconds -Vertical = 1mm =.1mV(10mm = 1mV) |
My ECG HZ | Degradation in shielding lets 60 Hz cycle intoe the picture. Muscle movement Radio frequency ( RF) (800-2k Hz) Bovi interference (.1 -10 Hz) |
On to Practical application | Assess the patient, use the monitor accordingly Atrial arrhythmia or AV dysrhthmia detection myocardial ischemia |
Myocardial Ischemia Review | Three levels of dection T wave changes St segment changes Development of Q waves |
T Waves | Normally a positive asymmetrical weave Upright in l,ll,V3-6 (variable in others) can be up to 10 mm in precordial, 5 mm in limb leads. Changes in T wave baseline can indicate ischemia ( non specific changes) |
ST Segment Chamges | Changes here reflect more significant injury (or infarction). Degree of depression measured 60 ms from the J point and measured to isoelectric in mm |
Anterior Wall MI | Leads showing elevations are : V3, V4 with lead depression. Artery affected is (Left Anterior Descending LAD) |
Anteroseptal WAll MI | Leads showing elevations are : V1,V2,V3, and V4 with no lead depression. Artery affected will be Left Anterior Descending (LAD) |
Anterolateral Wall MI | Leads showing elevation are :V3-V6, I, aVL. Lead showing depressions are leads ll, lll, and aVF. The artery affecte are Left anterior Descending (LAD), Circumflex (LCX) or obtuse marginal. |
Inferior Wall MI | Leads showing elevation l, lll, aVF. with lead showing depressions on l, aVL. the artery affected are Right Coronary Artery (RCA), or Circumflex (LCX). |
Lateral Wall MI | Lead showing elevations are l, aVL, V5-6. Leads showing depressions are ll, lll, and aVF. The artery affected are Circumflex (LCX), or obtuse marginal. |
Septal Wall MI | Leads showing elevations are V1 and V2. With no lead showing depression. The artery affected is Left anterior Descending ( LAD) |
MI Review | Awake pt, commonly (but not always) manifests as angina, but your pt is asleep. -Quantitative Data- Horizontal or downsloping ST-segment depression of 0.1mV. St-seg ele of 0.1 mV in a non-Q wave lead. Slow upsloping ST-seg depr. of 0.2 mV ( all measu f |
Slowly upsloping St-segment depression of 0.2 mV ( all measeure from 60 to 80 m sec after the j point is a part of quantitative data for MI review. ( true or false) | true |
ECG Interpretation (Follow a rigorous method) | What is the heart rate (brady-normal-tachy) Is the rhythm regular? (sinus vs fib flutter block) is there a P wave? is it appearing regularly Is there a P wave before each QRS complex ( sinus clues) Is the Pr interval normal and constant? (1st degree b |
ECG interpretation continued | Is there a path Q wave(25-33% of the ht of the R and >0.04 sec) (MI history). Is the QRS duration normal (Junctional vs BBB) Is the ST segment normal (ischemia/injury,infarction) Is the T-wave normal and properly config (injury).Is there a U W + elec i |
ECG Interpretation-Bare minimum | Follow a rigus method- What is the rate Is the rhythm regular Axis normal is there evidence of hypertrophy is there evidence of infarction or ischemia |
Basic rhythms to interpret | NSR 1-3 degree AV blocks SB VF ST VT Sinus Arrythmia VPB AF APB Afib RBBB LBBB |