Heart Structure Overview
Cardiac Conducting System Flow
ECG Waves Reference Table
| Wave | Electrical Event | Mechanical Consequence | Visible? |
|---|---|---|---|
| P wave | Atrial depolarization | Atrial contraction (systole) | Yes |
| PR interval | AVN conduction delay | (none — transition) | Yes (flat line) |
| QRS complex | Ventricular depolarization | Ventricular contraction | Yes |
| Atrial repolarization | Atrial recovery | Atrial relaxation | NO — hidden within QRS |
| T wave | Ventricular repolarization | Ventricular relaxation | Yes |
Cardiac Cycle Phase Summary
| Phase | Duration | AV Valves | Semilunar Valves | Net Blood Movement |
|---|---|---|---|---|
| Atrial Systole | 0.1 s | Open | Closed | Atria → Ventricles |
| Isovolumetric Contraction | Brief | Closed | Closed | None (pressure builds) |
| Ventricular Ejection | ~0.25 s | Closed | Open | Ventricles → Arteries |
| Joint Diastole | 0.4 s | Open | Closed | Veins → Atria → Ventricles |
Normal vs. Abnormal Values at a Glance
| Parameter | Normal | Abnormal Low | Abnormal High |
|---|---|---|---|
| BP (systolic/diastolic) | 120/80 mmHg | Hypotension (<90/60) | Hypertension (>140/90) |
| Heart rate | 60-100 bpm | Bradycardia (<60) | Tachycardia (>100) |
| RBC count (male) | 5-5.5 million/ | Anaemia | Polycythaemia |
| Platelet count | 1.5-3.5 lakh/ | Thrombocytopenia | Thrombocytosis |
| Cardiac output | ~5 L/min | Heart failure | Exercise physiology |