Getting an ECG feels routine, but staring at those squiggly lines on the report leaves most puzzled—what do they really say about your heart? This simple 10-second test traces electrical impulses powering every beat, flagging issues from skipped rhythms to silent blockages. In India, where heart disease strikes young due to stress and diets, mastering basics empowers you to ask smart questions.
ECG Basics: The Heart’s Electrical Story
Your heart beats 100,000 times daily via timed electrical waves from sinus node pacemaker. ECG captures this via 12 leads (views) from chest/limbs electrodes. Paper speed 25mm/sec, 1 small square=0.04sec, large=0.2sec. Rhythm strips show cycles. Normal sinus: regular 60-100 bpm.
India costs ₹200-500; 24hr Holter ₹3k tracks irregularities.
P Wave: Atrial Kickoff
P wave kicks depolarization—right then left atria contract, filling ventricles. Normal: upright leads I/II/aVF, 0.08-0.11sec wide, <2.5mm tall. Precedes every QRS. Absent? Atrial fib chaos. Tall/peaked? Right atrial enlarge (lung issues). Notched wide? Left atrial (mitral valve). Inverted? Ectopic focus.
PR interval (P start-QRS start) 0.12-0.20sec conduction delay AV node. Short WPW bypass, long 1st block.
QRS Complex: Ventricular Power Surge
QRS ventricular depolarization—septum left-right, apex up. Narrow <0.12sec normal conduction. Wide >0.12 bundle branch block/ventricular origin. Q small initial negative I/II/V5-6 normal septal. Pathologic deep/wide old infarct. R tall V leads voltage. S deep right precordials.
Amplitude criteria hypertrophy: tall R left ventricle strain. Axis normal -30 to +90; left deviation LVH, right RVH/pulm embolism.
ST Segment and T Wave: Recharge Phase
ST segment flat/equiline post-QRS to T start. Elevation >1mm acute MI STEMI emergency. Depression ischemia/strain. T upright repolarization most leads. Inverted ischemia/hypertrophy/electrolytes. Peaked hyperK, flat hypoK. QT 0.36-0.44sec corrected QTc heart rate (Bazett formula). Long torsades risk.
U wave occasional post-T hypokalemia.
Common Abnormal Patterns
Sinus brady <60 athletes, tachy >100 fever/thyroid. AFib no P irregular RR fibrillatory baseline stroke risk. VT wide bizarre rapid life-threatening. Blocks: 2nd Mobitz dropped beats, 3rd complete no relation P-QRS. LVH criteria Sokolow voltage+strain.
India young MI ST elevation common smoker diabetics.
Rate Rhythm Calculation
Rate 300/large boxes RR interval or 1500/small. Irregular average 30sec strip x6. Calipers check regularity.
Clinical Context Matters
Single ECG snapshot; compare priors. Symptoms chest pain? Troponin echo follow. Normal athletes high voltage. Women thinner leads variants. Consult cardiologist interprets holistically.
Table: Normal Values
| Component | Normal Range | Abnormal Example |
| Rate | 60-100 bpm | Tachy >100 |
| PR | 0.12-0.20s | Long 1st block |
| QRS | <0.12s | Wide LBBB |
| QTc | <440ms men | Long arrhythmia risk |
Abnormal ECG Next Steps India
Abnormal? Echo function, stress test ischemia, Holter palpitations. TMT ₹2k, angiogram ₹20k. Lifestyle quits smoking cuts risk 50%.
FAQ
- What does absent P waves on ECG mean?
Absent P waves with irregular RR intervals indicate atrial fibrillation, where atria quiver ineffectively raising stroke risk 5x untreated; anticoagulation often needed alongside rate control.
- ST elevation on ECG—emergency?
Yes, >1-2mm convex ST elevation in contiguous leads signals STEMI heart attack; immediate cath lab reperfusion within 90 minutes saves myocardium, per guidelines.
- Wide QRS complex significance?
QRS >0.12sec suggests bundle branch block delaying conduction or ventricular rhythm; left common hypertension, right lung disease—echo assesses underlying structure