Module 2: ECG Equipment & Lead Placement
What is an ECG Machine / Types of ECG Machines
English:
An Electrocardiogram (ECG or EKG) machine records the electrical activity of the heart. There are several types:
Resting ECG machines – standard 12‑lead ECG for resting patient.
Holter monitors – portable devices worn for 24‑48 hours to record continuous ECG.
Stress (Exercise) ECG – records ECG while patient exerts (treadmill or bicycle).
Telemetry/Monitoring ECG – continuous monitoring in hospital wards/ICU.
Portable / handheld ECGs – small devices, often 1‑lead or simplified versions.
Electrodes & Leads: Overview of 12‑Lead ECG
English:
Electrode: A sticky conductive pad that attaches to the skin, contains conductive gel.
Lead: A view or “perspective” of electrical activity derived from two electrodes (or one physical electrode vs. a reference). In 12‑lead ECG, 10 electrodes are placed but they produce 12 leads (views). EZ Med Learning+3Wikipedia+33D ECG Leads+3
Limb leads: RA (Right Arm), LA (Left Arm), RL (Right Leg), LL (Left Leg). These give leads I, II, III, and augmented leads (aVR, aVL, aVF).
Precordial (Chest) leads: V1, V2, V3, V4, V5, V6. They are placed at specific positions on chest to view horizontal plane of heart.
Proper Skin Preparation & Electrode Placement (Lead Placement)
English:
| Step | What to do / Why |
|---|---|
| Skin is clean, dry | Dirt, oil, sweat reduce electrode contact and cause artifacts. |
| Remove excess hair | Hair interferes with adhesion & signal quality. Use clipper, not razor if possible. |
| If skin oily or dirty, use alcohol swab; dry skin well. | Ensures better electrode contact. |
| Gentle abrasion if needed (light sandpaper / special pads) | Increases conductivity by removing dead skin cells. |
| Correct anatomical landmarks for chest leads: | |
| • V1: 4th intercostal space (ICS), right of sternum | |
| • V2: 4th ICS, left of sternum | |
| • V3: halfway between V2 and V4 | |
| • V4: 5th ICS, mid‑clavicular line (left) | |
| • V5: same horizontal level as V4, anterior axillary line | |
| • V6: same horizontal level as V4/V5, mid‑axillary line | |
| Limb electrodes: RA, LA, RL, LL placed on arms/legs or torso (depending on conditions) | Should avoid movement, thick muscles, joints. |
. Troubleshooting Poor Signal Quality
Common causes of poor ECG signal / distorted tracing and how to fix:
| Problem | Possible Cause(s) | Solution |
|---|---|---|
| Baseline wander (baseline shifting up/down) | Patient movement, breathing, poor pad adhesion | Ask patient to lie still; ensure arms/legs supported; retape electrodes; secure leads |
| AC (mains) interference / 50‑60 Hz noise | Nearby electrical devices, power cords close, poor grounding | Remove devices; ensure cables not crossing power lines; use proper grounding; ensure lead wires intact |
| Muscle (EMG) artifact | Shivering, muscle tension, tremors | Warm patient; support arms/legs; ask patient to relax; avoid placing leads over contracting muscles |
| Loose or dried electrode gel | Old electrodes, poor contact | Replace electrodes; ensure fresh conductive gel; press firmly onto skin |
| Poor skin prep (dirty, oily, hairy) | As above | Clean, dry, remove hair, gentle abrasion |
| Lead reversal (limb leads swapped) | Mislabelling / mis‑connection | Check color‑coding; ensure correct lead to correct electrode position; verify lead names on machine |
ECG ဘာလဲ၊ ECG ယန္တရားအမျိုးအစားများ
Electrocardiogram (ECG သို့မဟုတ် EKG) ဆိုသည်မှာ နှလုံး၏ လျှပ်စစ်လှုပ်ရှားမှုကို မှတ်တမ်းတင်သည်။ အမျိုးအစားများမှာ –
Resting ECG machine – လူနာအနားယူနေစဉ် 12‑lead ECG အသုံးပြုသည်။
Holter monitor – 24‑48 နာရီ ဆက်လက်စောင့်ကြည့်ရန် သယ်ဆောင်နိုင်သောစက်။
Stress (Exercise) ECG – လူနာအားကစားနေစဉ် ECG မှတ်တမ်းတင်သည်။
Telemetry / Monitoring ECG – ဆေးရုံဝါဒ / ICU တွင် များစွာအသုံးပြုသောဆက်လက်စောင့်ကြည့်စနစ်။
Portable / handheld ECGs – လူနာတစ်ယောက်နှင့်ပတ်သက်၍ 1‑lead သို့မဟုတ် ရိုးရှင်းသော ECG များ။
Electrode: အသားအေပေါ်တွင် ကပ်၍ ဓာတ်ကြောထဲက ဂျယ်ပါသော ကော်န်ဒတ်ပင်ချာနေသော pad ဖြစ်သည်။
Lead: နှလုံး၏ လျှပ်စစ်လှုပ်ရှားမှုကို electrode နှစ်ခု (သို့မဟုတ် reference electrode တစ်ခုနှင့် physical electrode တစ်ခု) မှတွက်ချက်၍ ရယူသော “အမြင်” သို့မဟုတ် "ကြည့်မြင်ချက်" ဖြစ်သည်။ 12‑lead ECG တွင် electrode 10 ခုတပ်သော်လည်း lead 12 ခုရပါသည်။ EZ Med Learning+3Wikipedia+33D ECG Leads+3
Limb leads: RA, LA, RL, LL leads I, II, III နှင့် aVR, aVL, aVF များ။
Precordial (ချယ်စ့်) leads: V1… V6 နှလုံး၏ အလျားတိုက် plane ကို ကြည့်ရန် chest ပေါ်တွင် တပ်သောနေရာများ။
Proper Skin Preparation & Electrode Placement (Lead Placement)
| အဆင့် | ပြုလုပ်ရမည့်အရာ / အကြောင်းအရင်း |
|---|
| အသားချေး၊ခြောက်ရှင်း၍ | ဖုန်၊ဆီ၊ခြစ်တို့ကြောင့် electrode ကောင်းစွာ မအပ်နိုင်ခြင်းနှင့် signal မှာ အသံအတု (artifact) ဖြစ်နိုင်သည်။ |
| များသောဆံပင် ဖယ်ရှားပါ | ဆံပင်က ကပ်လေးများ adhesion နှင့် signal ကိုလှည့်လှည့်ကျူးခံစေနိုင်သည်။ clipper သို့မဟုတ် hair cutter အသုံးပြုပါ၊ razor မှမျိုးကိုင်မသုံးရမည်။ |
| အသားအရေ ဆီဆန့်၊ သန့်ရှင်းစေဖို့ alcohol swab နှင့် swab ပြုလုပ်ပြီး ခြောက်သေစေပါ | electrode နှင့် အသားအဖြူ contact ကောင်းရန်။ |
| အကယ်လှဆုံး abrasion သက်သေအတိုင်း (သေးငယ်သော စက် / pad) | အသားပြားပျက်မှုအလွန်မရှိဘဲ dead skin cell ဖယ်ရှား၍ conductivity မြှင့်တင်ရန်။ |
| chest lead များအတွက် anatomical landmark မှန်ကန်စွာတပ်ပါ: |
| • V1: ၄‑ကြား intercostal space, စတားနမ်ရဲ့ ညာဘက် |
| • V2: ၄‑ကြား intercostal space, စတားနမ်၏ ဘယ်ဘက် |
| • V3: V2 နှင့် V4 ကြား အလယ်တွင် |
| • V4: ၅‑ကြား intercostal space, mid‑clavicular line ဘယ်ဘက် |
| • V5: V4 နှင့်တူသော အချင်းအလျား, anterior axillary line |
| • V6: V4/V5 နှင့်တူ horizontal အတန်း, mid‑axillary line |
| Limb electrode များ: RA, LA, RL, LL – သူလောင်း / ခြေ/တစ်ဘက်သားတို့တွင် တပ်ပါ | ရုပ်ပိုင်းဆိုင်ရာလှုပ်ရှားမှုမများနေပါစေ၊ ကြွက်သားထူသောနေရာများ၊ထုံးစံကုန်သောနေရာများ မသုံးသင့်။ |
Q: Why do we use 10 electrodes to get 12 leads in a 12‑lead ECG?
A: Because some leads are derived (augmented or virtual) from combinations of existing electrodes. The extra “views” are mathematically derived, so physically only 10 electrodes are needed. Wikipedia
Q: What happens if chest lead positions (V1‑V6) are placed incorrectly?
A: Misplacement can lead to waveform distortion, mimic disease (e.g. false signs of infarction), or make interpretation inaccurate.
Q: Can limb leads be placed on the torso instead of wrists/ankles?
A: Yes, sometimes limb leads are placed on the torso (near shoulders/hips) especially in infants, or to avoid movement; but must be consistent and documented so results are interpreted correctly.
Q: How often should electrodes be replaced / checked?
A: Replace electrodes if gel is dried, adhesive weak, or past expiration date. Check lead wires for damage before each use.
Q: What causes 50‑60 Hz interference and how can it be prevented?
A: Electrical noise from mains power, nearby devices; avoid crossing power cables, unplug unnecessary electrical devices, ensure machine is properly grounded.
Q: Is skin irritation a concern with repeated ECGs?
A: Yes. Use gentle prep, avoid harsh abrasion, use hypoallergenic electrodes if needed. Clean off adhesive carefully.
Q: In which scenario would you use a stress ECG instead of resting ECG?
A: When assessing for exercise‑induced ischemia, or chest pain with exertion; to see how heart performs under stress.
Q: What do ‘artifact’ and ‘baseline wander’ mean in ECG tracing?
A: Artifact = unwanted signals (muscle tremor, movement, loose leads); baseline wander = slow drift of baseline up/down, often due to respiration or movement.
Q: How to choose type of ECG machine (resting vs Holter vs telemetry)?
A: Depends on purpose: single snapshot vs continuous monitoring; setting (clinic vs hospital vs ambulatory); patient condition.
Q: What to do if patient has chest hair or prosthetics that make chest pad placement difficult?
A: Trim hair; use clipper; avoid pads over metal as much as possible; document placement location; adjust pads slightly if necessary, ensuring still as anatomically accurate as possible.
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