Heart Chambers
The four chambers of the heart are arranged with the right side receiving deoxygenated blood and pumping it to the lungs, and the left side receiving oxygenated blood and pumping it to the systemic circulation. Wall thickness reflects the pressure each chamber generates.
✦ The Mnemonic
"Returning Blood Fills Left: Rightward, Pulmonary, Left Atrium, Left Ventricle"
Right atrium → Right ventricle → Pulmonary circulation → Left atrium → Left ventricle → Systemic
Clinical Breakdown
Wall thickness reflects workload: LV:RV ratio is approximately 3:1. In pulmonary hypertension, the RV hypertrophies and the interventricular septum can bow leftward — reducing LV filling (D-sign on echo). In severe pulmonary hypertension, RV failure leads to right heart failure with peripheral oedema, hepatomegaly, and raised JVP.
The left atrial appendage (LAA) is the most common site of thrombus formation in atrial fibrillation — the appendage is a blind-ending pouch with sluggish flow. LAA thrombus is the source of the majority of cardioembolic strokes. TOE (transoesophageal echo) is more sensitive than TTE for detecting LAA thrombus before cardioversion.
Cardiac tamponade: pericardial effusion compresses all chambers. Beck's triad: hypotension, raised JVP (distended neck veins), muffled heart sounds. Pulsus paradoxus (drop in systolic BP >10 mmHg on inspiration) is the key examination finding. Urgent pericardiocentesis is lifesaving.
⭐ Clinical Pearl
Eisenmenger syndrome: a left-to-right shunt (VSD, ASD, PDA) causes pulmonary hypertension over years. Eventually pulmonary pressure exceeds systemic, reversing the shunt to right-to-left — causing central cyanosis, polycythaemia, and clubbing. At this stage the shunt cannot be surgically corrected. Prevention (early repair of the defect) is the only cure.