Week 12 Handout EKG

Question 1

What is a 12-Lead EKG?

Answer 1

A non-invasive diagnostic tool that records the electrical activity of the heart from 12 different angles. It helps guide decision-making in preoperative, intraoperative, and critical care settings.

Question 2

What can a 12-Lead EKG identify?

Answer 2

It can identify arrhythmias (e.g., atrial fibrillation, ventricular tachycardia, heart blocks), detect ischemia or MI (STEMI vs. NSTEMI), assess conduction defects (e.g., bundle branch blocks, WPW), and evaluate electrolyte imbalances (e.g., hyperkalemia, hypocalcemia).

Question 3

When should EKG be used?

Answer 3

Use EKG in patients with suspected heart disease, electrolyte disturbances, or during perioperative cardiac evaluation.

Question 4

What are the limitations of EKG?

Answer 4

Can yield false positives or misreadings due to incorrect electrode placement, patient movement (artifact), or non-cardiac causes of changes (e.g., pericarditis, electrolyte imbalance).

Question 5

What is the first step in EKG interpretation?

Answer 5

Determine the rate.

Question 6

How do you assess the rhythm in EKG interpretation?

Answer 6

Is it regular or irregular? Use calipers or measure R-R intervals and look for patterns like atrial fibrillation, flutter, or heart block.

Question 7

What should you analyze about the P wave?

Answer 7

Check if P waves are present and upright in Lead II, and if there is one P for every QRS, suggesting sinus rhythm.

Question 8

What is the normal range for PR interval?

Answer 8

The PR interval should be between 0.12 and 0.20 seconds.

Question 9

What does a wide QRS complex suggest?

Answer 9

A wide QRS complex (>0.12 sec) suggests bundle branch block, ventricular rhythm, or hyperkalemia.

Question 10

How do you check for axis deviation?

Answer 10

Check Leads I and aVF: Both positive = normal axis; I positive, aVF negative = left axis deviation; I negative, aVF positive = right axis deviation.

Question 11

What should the ST segment look like?

Answer 11

The ST segment should be isoelectric (flat). Elevation or depression suggests ischemia or infarction.

Question 12

What is the normal appearance of T waves?

Answer 12

T waves should be upright in most leads except aVR and V1. Peaked T waves suggest hyperkalemia, while inverted T waves suggest ischemia.

Question 13

What is the significance of the QT interval?

Answer 13

The QT interval should be < ½ the R-R interval. QTc > 440 ms (men), > 460 ms (women) indicates prolonged QT and risk of torsades.

Question 14

What indicates pathologic Q waves?

Answer 14

Pathologic Q waves are a sign of prior MI, defined as 0.04 sec wide and >25% of QRS height.

Question 15

What patterns should be looked for in EKG?

Answer 15

Look for inferior (II, III, aVF), anterior (V1–V4), lateral (I, aVL, V5–V6), and posterior (ST depression in V1–V3) patterns.

Question 16

What should be included in the final impression of EKG?

Answer 16

Summarize rate and rhythm, axis, intervals, ischemia/infarction, and abnormal findings (blocks, hypertrophy, electrolyte signs).

Question 17

What is the mnemonic for EKG interpretation steps?

Answer 17

The mnemonic is ‘R-R-P-P-Q-Q-A-S-T-Q-Q-P-S’ for Rate, Rhythm, P wave, PR interval, QRS, QRS Axis, ST, T wave, QT, Q waves, Patterns, Summary.

Question 18

What is the lead placement technique for limb leads?

Answer 18

Limb leads: I, II, III, aVR, aVL, aVF on extremities.

Question 19

What are the special considerations for EKG?

Answer 19

Leads V3–V5 are most sensitive for detecting ischemia. EKG alone does not reliably predict perioperative cardiac events.

Question 20

What are the lead groupings by coronary territory?

Answer 20

Inferior leads (II, III, aVF): RCA; Lateral leads (I, aVL, V5, V6): LCx; Anterior leads (V3, V4): LAD; Septal leads (V1, V2): LAD (proximal).

Question 21

What defines normal axis deviation?

Answer 21

Normal axis is –30° to +90°.

Question 22

What indicates left axis deviation?

Answer 22

Left axis deviation (LAD) is more negative than –30° (e.g., left anterior fascicular block).

Question 23

What indicates right axis deviation?

Answer 23

Right axis deviation (RAD) is more positive than +90° (e.g., right heart strain, pulmonary disease).

Question 24

What are the characteristics of a normal EKG?

Answer 24

P wave before every QRS, PR interval 0.12–0.20 sec, QRS duration <0.12 sec, ST segment is isoelectric (flat).

Question 25

What are the signs of STEMI?

Answer 25

ST elevation in two or more contiguous leads, reciprocal ST depression, and later development of Q waves.

Question 26

What are the signs of NSTEMI?

Answer 26

ST depression or T wave inversion with positive troponins.

Question 27

What are the cardiac effects of volatile anesthetics?

Answer 27

Volatile agents can decrease myocardial contractility and cause dose-dependent hypotension, increasing the risk of arrhythmias, especially with preexisting conduction abnormalities.

Question 28

Which of the following statements about ECG lead selection are correct? (Select all that apply) A. Lead II is commonly used for arrhythmia detection. B. Lead V5 is optimal for detecting ischemia in the anterior and lateral walls. C. A modified V5 lead can be achieved using a 3-lead system. D. The standard 3-lead system provides the most comprehensive ischemia monitoring. E. The best ECG lead for ischemia detection is always Lead I.

Answer 28

Correct Answers: • A,B,C Rationales: • Lead II aligns with the heart’s electrical axis, providing the best P-wave visibility, making it ideal for detecting arrhythmias. • Lead V5 is positioned over the 5th intercostal space at the anterior axillary line, making it highly sensitive for ischemia detection in the anterior and lateral walls of the heart. • In a 3-lead system, the LA electrode can be repositioned to the V5 location to provide better ischemia monitoring (CS5 configuration). • The 3-lead system is primarily used for basic arrhythmia detection, while 5-lead ECG provides better ischemia monitoring due to additional precordial lead placement. • Lead I is not the most sensitive for ischemia. Instead, Lead V4 and V5 are more effective for detecting ischemic changes.

Question 29

What are common causes of ECG artifacts? (Select all that apply) A. Patient movement B. Electrocautery interference C. Faulty electrodes D. Low heart rate E. 60-Hz electrical interference

Answer 29

Correct Answers: • A,B,C,E Rationales: • Patient movement can create motion artifacts, leading to false readings on the ECG. • Electrical signals from surgical cautery can disrupt ECG signals, creating artifacts. • Poor electrode contact, dried gel, or disconnected leads can cause erratic readings. • Alternating current (AC) devices operating at 60 Hz (in the U.S.) or 50 Hz (in other regions) can cause interference in ECG readings.

Question 30

How can ECG signal quality be improved? (Select all that apply) A. Ensuring proper electrode placement B. Using conductive gel to lower skin resistance C. Positioning lead wires parallel to power cords D. Selecting an appropriate filter setting for motion artifacts E. Avoiding the use of a precordial lead

Answer 30

Correct Answers: • A,B,D Rationales: • Correct placement prevents signal distortion and improves lead accuracy. • Conductive gel enhances electrical conduction between the skin and electrode, reducing impedance. • Lead wires should be positioned perpendicularly to power cords to minimize 60- Hz interference. • Using low-pass or notch filters can help reduce motion artifacts while preserving key ECG features. • Precordial leads (e.g., V4, V5) enhance ischemia detection, so avoiding them would reduce diagnostic accuracy.

Question 31

Which ECG lead combination provides the highest sensitivity for detecting myocardial ischemia? A. Lead I and Lead II B. Lead II and Lead III C. Lead II and Lead V5 D. Lead V1 and Lead V4

Answer 31

Correct Answer: C Rationales: • Lead II is best for arrhythmia detection, while Lead V5 is most sensitive for anterior and lateral wall ischemia. • Studies show that monitoring Lead II + V5 can detect up to 85% of ischemic episodes.

Question 32

What is the primary function of the 3-lead ECG system in anesthesia? A. Continuous ischemia monitoring B. Basic arrhythmia detection C. Comprehensive cardiac assessment D. Diagnosing complex conduction abnormalities

Answer 32

Correct Answer: B Rationales: • 3-lead ECG is mainly used for basic rhythm monitoring (arrhythmia detection). • 5-lead or 12-lead ECG is needed for more detailed ischemia or conduction abnormality analysis. • Comprehensive cardiac assessment requires a full 12-lead ECG.

Question 33

A 62-year-old male with a history of hypertension and diabetes is scheduled for an elective laparoscopic cholecystectomy. During preoperative evaluation, he reports experiencing exertional chest discomfort over the past few weeks. A preoperative ECG shows 1.5 mm ST- segment depression in leads V4 and V5, recorded 80 msec after the J-point. What is the most likely cause of this ECG finding, and what should be the next step in management? A. Normal variant, proceed with surgery without further testing B. Myocardial ischemia, consider further cardiac evaluation C. Electrolyte imbalance, check potassium and calcium levels D. Pericarditis, look for PR segment depression

Answer 33

Correct Answer: B Rationales: • ST-segment depression (>1 mm, 80 msec after J-point) is a strong indicator of myocardial ischemia, especially when seen in leads V4-V5 (which reflect the anterior/lateral walls). • Patients with exertional chest discomfort and risk factors (HTN, DM) should be further evaluated before proceeding with elective surgery.