EKG monitoring Flashcards
What cells generate the electrical potential recorded in the EKG monitor
Myocardial cells
Best lead placement to read dysrhythmias
Lead II
What occurs during systole?
Mitral and tricuspid valve close
Aortic & pulmonic valve open
What occurs during diastole?
Aortic & pulmonic valves close
Tricuspid & mitral valve open
What does the P wave represent
Atrial depolarization
What is a normal PR interval?
0.08 - 0.20
What happens during the QRS on an EKG?
Ventricular depolarization
What is a normal QRS interval?
What can cause an abnormal interval?
0.08 - 0.12
Prolonged in HF & Cardiomyopathy
What does the T wave represent on an ECG? And what is a normal measurement?
Ventricular repolarization
- 0.4 sec
What can cause EKG artifact in the OR
- Patient movement
- Electrocautery use
- Nearby currents
- Surgeon manipulation
What EKG interpretation represents Ischemia?
Flat or down sloping ST depression exceeding 1 mm
- especially w/ T wave inversion
ST elevation w/ peaked T waves
What conditions can you not accurately read ST interpretations?
- Wolf Parkinson White (WPW)
- Pacemakers
- Digoxin therapy
- Bundle Branch Block
True or False:
ECGs can be normal when something awful is happening.
True.
ECGs aren’t fool proof.
If you think the patient is experiencing angina from the history, but the ECG is normal, put in a consult.
How many leads must show ST depression to confirm angina
2 or more consecutive leads to confidently say it is a case of angina.
If you manually have to set up your ECG monitor, what do you always want to check? And what is the setting?
- ST Segment
- ECG must be set that a 1 mV signal results in a deflection of 10 mm on a strip monitor.
Purpose of analyzing the ST Segment
- Allows for early detection of ischemia
- Increases sensitivity of ischemia detection
- Doesn’t require additional practitioner skill/vigilance
- May help diagnose intraoperative myocardial ischemia
ST depression = ?
Ischemia
- The ST segment (flat area between the QRS & the T wave) sinks lower than the baseline
ST elevation = ?
Injury
- in the inferior leads = greater than 1 small square
- in the limb leads (V1-6) = greater than 2 small squares
Where does ST elevation most commonly occur?
Can occur anywhere in the heart.
- More commonly in the antero-septal or the inferior regions of the ECG
- Need to see in 2 or more consecutive leads
What is more important in your assessment than an EKG by itself?
The patient’s history & a change on the ECG is more important than an EKG by itself.
- Serial EKGs are better than one. They interpret what the heart is doing in that exact moment.
What do Q waves represent?
Scarring/ infarction
Ischemic tissue is negatively charged = an inversion on the ECG
Q waves = > 1mm in width & > 1/3 total height of the QRS
If a STEMI w/ ST elevation is seen in leads II, III, and aVF what reciprocal changes would you see?
ST depression in Lead I and aVL
- Reciprocal changes are mirror image changes that occur when 2 electrodes view the same MI from the opposite angle
What are hemodynamic changes of a Right-sided MI? And why?
Lower Blood Pressures (systolic < 140 mmHg)
- decreased RV contractility = decreased LV preload
What should you withhold during a Right-sided MI?
Nitroglycerin
- Patient is already experiencing peripheral edema, JVD, hypoxemia, and hypotension from the RV not contracting, decreasing blood flow from the venous system to the lungs.
What should you look for in a Posterior MI
Look for ST-depression & larger than normal R waves in Leads V1 and V2
How do you distinguish Pericarditis on an EKG?
Global ST-elevation in every lead of the 12-lead
Left Coronary Artery Main supplies ?
- Circumflex artery
- Left Circumflex artery
- Left Anterior Descending artery
- Left Anterior interventricular artery
What Leads represent the Lateral Circumflex?
Lead I & aVL
What leads will represent Inferior RCA
Lead II, III, & aVF
What Lead will represent Septal LAD
V1 & V2
What leads will represent an Anterior & Distal LAD?
V3 & V4
What leads represent the Lateral side?
V5 & V6
What is a Normal QRS axis on an EKG?
Normal axis = 0 to + 90 (or -20 to + 100)
- Right axis = overly positive
- Left axis = overly negative
What leads do you look at for QRS deflection & axis deviation?
Look at the QRS in Lead I & aVF
If the QRS in Lead 1 is negative/downward and the QRS in aVF is positive/upward what would you interpret this as?
Right axis deviation
If the QRS in Lead 1 is positive/upward and the aVF is negative/downward what would you interpret this as?
Left axis deviation
If your patient has a left axis deviation what might be some clinical diagnoses to expect?
- Left Bundle Branch Block
- Left ventricular hypertrophy
- Pregnancy
- Ascites
- Abdominal tumors
Anything pushing up against the heart
Why do you care about an axis deviation?
It could mean a lot of things:
- Infarct
- Hypertrophy
- Conduction delay
- Abnormal anatomy
What might a Right axis deviation depict clinically?
- Right bundle branch block
- Right ventricular hypertrophic
- Emphysema
What lead is the only one to deflect negatively in normal tissue?
- aVR
Do not use this lead to diagnose
How does the R wave progress in leads V1 - V6
Progressively get more positive.
V1 & V2 are downward deflections
V3 & V4 are half & half “transitional” or “biphasic”
V5 & V6 are upward deflections (primarily positive)
Reasons for poor R wave progression ? (V leads)
- Anterior myocardial infarction
- Left bundle branch block
- Wolf parkinson white
- Right ventricular hypertrophy
- Left ventricular hypertrophy
How to calculate the rate on an ECG strip?
2 Methods:
- Count QRS in a 6 sec strip and multiply by 10
- Count the number of small boxes between QRS peaks & divide this number INTO 1500
Reasons for a prolonged QT (9):
- Drugs (Na Ch blockers)
- Antipsychotics
- Hypomagnesemia
- Hypocalcemia
- Hypokalemia
- Hypothermia
- AMI
- Congenital
- Increased ICP
- Can lead to Torsades de Pointes = Fatal
What are 7 steps to reading an EKG?
- Regular or irregular
- Rate
- P wave presence and regularity
- P to QRS ratio
- QRS width
- PR interval
- QT interval
