Acute Pericarditis
Diffuse inflammation of the pericardial sac roughens its two layers so they rub together with every heartbeat, producing sharp pain that worsens lying flat and eases leaning forward, with widespread ECG changes because the injury current spreads across the whole heart rather than one coronary territory.
First principles
Diffuse inflammation, not a territorial injury
Acute pericarditis is inflammation involving the whole pericardial surface: most often viral in the UK, but also seen post-myocardial infarction (Dressler's syndrome), in uraemia, autoimmune disease, tuberculosis or malignancy. Unlike ischaemic heart disease, which damages a single coronary territory, pericarditis affects the entire pericardial sac, and this difference in distribution explains almost every distinguishing feature from a myocardial infarction.
Educational content pending clinical review. Not medical advice.