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.
