Cardiovascular System
Ischemic heart disease
Troponin rises at 3–6 hours and peaks near 24 hours; a single early normal value does not exclude myocardial infarction. ST elevation in contiguous leads localizes: II/III/aVF inferior (RCA), V1–V4 anterior (LAD), I/aVL/V5–V6 lateral (circumflex). Inferior infarction may produce bradycardia or AV block and right ventricular involvement - avoid nitrates and aggressive diuresis when preload dependence is suspected. Mechanical complications at 3–5 days: papillary muscle rupture (abrupt mitral regurgitation, new murmur, flash pulmonary edema), ventricular septal defect (harsh holosystolic murmur with thrill), and free wall rupture (tamponade, pulseless electrical activity). Pericarditis shows diffuse ST elevation with PR depression and positional pain; Dressler syndrome occurs weeks later.
Murmurs
Aortic stenosis: crescendo-decrescendo systolic murmur radiating to the carotids with delayed upstroke and low-volume pulse. Hypertrophic cardiomyopathy: harsh systolic murmur that increases with Valsalva and decreases with squatting. Mitral regurgitation: holosystolic murmur to the axilla. Mitral stenosis: opening snap with a diastolic rumble. Aortic regurgitation: early diastolic decrescendo murmur with bounding pulses.
Heart failure and shock
HFrEF: reduced ejection fraction, eccentric hypertrophy, benefit from beta-blockers, ACE inhibitors or ARNI, mineralocorticoid antagonists, and SGLT2 inhibitors. HFpEF: stiff ventricle; treat risk factors and congestion. Shock categories: hypovolemic, cardiogenic, distributive (septic, neurogenic), and obstructive (tamponade, tension pneumothorax, massive pulmonary embolism).
Arrhythmias
Atrial fibrillation is irregularly irregular without P waves; rate control and anticoagulation by stroke risk score. Atrial flutter shows sawtooth waves, often with 2:1 block. First-degree AV block is PR prolongation; Mobitz I shows progressive PR lengthening; Mobitz II shows fixed dropped beats; third-degree shows complete dissociation. Torsades de pointes follows QT prolongation and is treated with magnesium.
Rule of thumb
Hypotension with distended neck veins and clear lungs suggests an obstructive cause - decompress or image before giving fluid.