What the two ECGs show (21:05 and 21:06, heart rate 36 and 33)

• Very slow, regular, wide-complex rhythm. The QRS is 123 to 126 ms. The machine reads P and PR as 0, so no P waves are being detected.
• ST elevation in II, III and aVF. This is inferior STEMI, probably a right coronary artery occlusion. The machine also flags peaked T waves in the same leads.
• Reciprocal ST depression in I, aVL and V1 to V3. The V1 to V3 depression suggests posterior wall involvement.
• Third-degree AV block with a ventricular escape rhythm (machine read, first tracing). The second tracing is read as RBBB-like morphology.
• The machine label "marked sinus bradycardia" conflicts with its own P = 0 and the block reading. I would trust the block reading over that label.

Two things to check

1. Hyperkalemia or BRASH. Peaked T waves, absent P waves, a widened QRS and a slow rate can all come from high potassium. This is especially likely if the patient has renal failure or takes a beta blocker or AV nodal drug. Harrison's describes the ECG sequence as peaked T waves, then loss of P waves, then a wide QRS. Check potassium now, because it is quickly treatable and changes the prognosis.
2. Wide versus narrow escape. In inferior MI the block is usually at the AV node, with a narrow and fairly stable escape. Harrison's describes this as often reversible (Harrison's 22E, "AV Block in the setting of myocardial ischemia"). A wide escape at about 33 to 36 per minute is less reassuring. It means either a lower escape focus, or a conduction problem such as the RBBB, or hyperkalemia.

Survival data

• Swiss AMIS Plus registry (about 50,000 AMI patients, 2026 study):
  • In-hospital mortality was 15% with high-grade AV block on admission, versus 4.9% without.
  • The block predicted death more strongly in anterior MI than in non-anterior MI.
  • Block that appeared during the hospital stay carried a higher mortality (20%).
• French ORBI registry (6,662 STEMI patients, 2016 study):
  • Mortality was 18% with block on admission, versus 4.5% without.
  • After adjustment, the block was not an independent predictor of death.
  • The real drivers were age, cardiac arrest, anterior location, cardiogenic shock, ventricular arrhythmias, mechanical complications and failure to reperfuse.
• Inferior MI specifically. Heart block here is often transient and usually resolves in days. Harrison's also notes that post-discharge mortality is markedly lower after inferior than anterior infarction with AV block.

What gives the best chance of survival

• Reperfusion. Activate the cath lab for primary PCI as soon as possible. If PCI is not available within the guideline time window, use thrombolysis.
• Rate support.
  • Try atropine 0.5 to 1 mg IV. It works better for AV nodal block than for infranodal block.
  • Have transcutaneous pacing pads on now.
  • Use a temporary transvenous pacemaker if the rate stays slow, the patient is unstable, or the escape rhythm is wide and unreliable. A rate of 33 to 36 with a wide QRS fits that description.
  • Dopamine or adrenaline infusion can bridge to pacing.
• Hyperkalemia. If potassium is high, give IV calcium, insulin with glucose, and salbutamol, and consider dialysis. Do this before or alongside pacing, since high potassium makes pacing capture unreliable.
• Right ventricular infarct. Obtain right-sided leads (V4R). If the RV is involved, give IV fluids and avoid nitrates and diuretics.
• Avoid beta blockers, verapamil, diltiazem and other AV nodal blockers.
• Monitoring. Watch continuously for ventricular arrhythmias, shock and arrest.

Realistic outlook

• Best case (about 85 to 90% survival or better). The patient is conscious with adequate blood pressure, reaches PCI quickly, has a reversible cause treated, and is paced when needed.
• Worse prognosis. Cardiogenic shock, cardiac arrest, right ventricular failure, a late presentation with no reperfusion, severe untreated hyperkalemia, or a block that persists beyond about 2 weeks and needs a permanent pacemaker.