Read the investigation.

The earliest sign. Look for narrow-based, symmetrically peaked T waves — often taller than the R wave — best seen in the precordial leads (V2–V4). A normal T wave is asymmetric with a gentle upslope; a tented T is sharp and “you could prick your finger on it.”

Reference · serum K⁺ 3.5–5.2 mmol/L. Peaked T waves typically emerge around 5.5–6.5 mmol/L.

As potassium climbs, atrial depolarisation slows: P waves flatten and widen, the PR interval stretches, and conduction through the AV node lags. The atria are the first chambers to fall silent.

Reference · PR 120–200 ms (3–5 small squares). Beyond 200 ms is first-degree block.

Ventricular conduction slows and the QRS widens, often into bizarre, non-specific shapes that don’t fit a normal bundle-branch pattern. A widening QRS in the right clinical context is a red flag to treat now, not to watch.

Reference · QRS < 120 ms (under 3 small squares). Broadening here is metabolic, not structural.

The broad QRS merges with the T wave into a smooth sine wave: the pattern on the rhythm strip at the foot of this ECG. This is a pre-arrest rhythm and a medical emergency: give IV calcium immediately.

Management · IV calcium gluconate/chloride first to stabilise the myocardium (it does not lower K⁺), then insulin–dextrose ± salbutamol to shift, then removal.

Fluid floods the alveoli around the hila in a symmetric bat-wing distribution: the dominant sign on this film. Air bronchograms may appear. It clears from the periphery inwards as the patient improves.

Look · medial two-thirds of both lungs, sparing the outer costophrenic zones early.

Short, horizontal septal lines reaching the pleural surface at the lung bases: thickened interlobular septa from interstitial fluid. Subtle, but they mark the shift from interstitial to alveolar oedema.

Look · peripheral lung near the costophrenic angles; each line is ≤ 2 cm and touches the pleura.

A cardiothoracic ratio above 0.5 points to chronic strain on the heart. Measure it only on a PA film. A portable AP projection like this one magnifies the heart, so defer the call to a dedicated PA film (below).

Reference · CTR = widest heart ÷ widest thorax, < 0.5 on PA. Not valid on AP/portable.

Rising left-atrial pressure redistributes blood to the apices: upper-zone vessels become as prominent as, or larger than, the lower-zone vessels: cephalisation. Often the earliest sign, visible before frank oedema.

Normal (erect) · lower-zone vessels are larger. Diversion reverses that ratio.

Transudative fluid blunts the costophrenic angles, often right > left, with a meniscus on an erect film. The last of the five to appear and the last to clear.

Look · sharp costophrenic angles are normal; a blunted, curved angle marks fluid.