💗 Cardiac & ECG
ECG Basics & Rhythm Interpretation
Essential ECG components, normal sinus rhythm criteria, and common arrhythmia patterns.
📊
ECG Components
| Test / Parameter | Normal Range | Clinical Notes |
|---|---|---|
| P wave | <0.12 sec, <2.5mm | Atrial depolarization. Absent: AFib, junctional. |
| PR interval | 0.12–0.20 sec | AV node delay. Prolonged: 1st degree AV block. |
| QRS complex | 0.06–0.12 sec | Ventricular depolarization. Wide: ventricular origin, BBB. |
| QT interval | <0.44 sec (M) <0.46 sec (F) | Ventricular repolarization. Prolonged: torsades risk. |
| ST segment | Isoelectric | Elevation: STEMI. Depression: ischemia. Peaked T: hyperkalemia. |
✅
Normal Sinus Rhythm
| Test / Parameter | Normal Range | Clinical Notes |
|---|---|---|
| Rate | 60–100 bpm | Regular rate. |
| Rhythm | Regular | Equal R-R intervals. |
| P wave | 1:1 with QRS | Every QRS preceded by P wave. |
| PR interval | 0.12–0.20 sec | Normal conduction through AV node. |
| QRS | <0.12 sec | Narrow — normal ventricular conduction. |
⚡
Common Arrhythmias
| Test / Parameter | Normal Range | Clinical Notes |
|---|---|---|
| Sinus Tach | HR >100, normal P | Causes: fever, pain, anxiety, hypovolemia, hyperthyroid. |
| Sinus Brady | HR <60, normal P | Causes: athlete, medications, hypothyroid, heart block. |
| AFib | Irregular, no P waves | Stroke risk. Anticoagulate. Rate or rhythm control. |
| AFlutter | Sawtooth P waves | Atrial rate 250–350. Ventricular rate variable. |
| SVT | HR 150–250, narrow QRS | Vagal maneuvers, adenosine 6mg IV push. |
| VTach | Wide QRS, regular | Stable: amiodarone. Unstable: synchronized cardioversion. |
| VFib | Chaotic, no pattern | DEFIBRILLATE immediately. CPR + epinephrine + amiodarone. |
| Asystole | Flatline | CPR + epinephrine. Do NOT defibrillate. |
🚧
Heart Blocks
| Test / Parameter | Normal Range | Clinical Notes |
|---|---|---|
| 1st Degree | PR >0.20 sec | All P waves conducted. Usually benign, monitor. |
| 2nd Degree Type I (Wenckebach) | PR progressively prolongs until dropped beat | Usually benign. Monitor. |
| 2nd Degree Type II | Dropped beats without PR prolongation | Often needs pacemaker. Can progress to 3rd degree. |
| 3rd Degree (Complete) | P and QRS independent | Medical emergency. Pacemaker required. Atropine may not help. |
🫀
STEMI Localization
| Test / Parameter | Normal Range | Clinical Notes |
|---|---|---|
| Inferior MI | ST elevation II, III, aVF | Right coronary artery. Check for RV involvement. |
| Anterior MI | ST elevation V1–V4 | LAD. High mortality. Monitor for complications. |
| Lateral MI | ST elevation I, aVL, V5–V6 | Circumflex. Less common. |
| Posterior MI | ST depression V1–V3 (mirror) | Right coronary or circumflex. Use V7–V9. |
ECGEKGarrhythmiasinus rhythmheart blockscardiac
← Back to All Cheat Sheets
