Diuretics: draining the flooded body
When the heart cannot keep up, fluid backs up — into the lungs as breathlessness, into the legs as swelling. Loop diuretics act on the kidney to flush out salt and the water that follows it, draining that excess. They are the fastest way to relieve the congestion of heart failure and pulmonary edema: a breathless patient can feel dramatically better within hours as the lungs dry out.
An important honesty: diuretics relieve symptoms of congestion superbly, but on their own they do not heal the underlying weak pump. That is why they are paired with the load-lightening, pump-protecting drugs from the previous guide. Because flushing out fluid also flushes out salts, the potassium is watched.
Nitrates for chest pain, statins for the long game
Nitrates relax blood vessels — especially the veins, which reduces the blood returning to the heart and so cuts the heart's workload and its oxygen need. A short-acting nitrate under the tongue can relieve an episode of angina within minutes; longer-acting forms help prevent attacks. Their honest limit: the body gets used to a steady level, so a daily nitrate-free window is usually built in to keep them working.
Statins play a completely different, slower game. They lower LDL cholesterol by blocking the liver's cholesterol-making enzyme, and — just as importantly — they stabilise [[atherosclerotic-plaque|atherosclerotic plaques]] so they are less likely to rupture and trigger a heart attack. You feel nothing day to day, but over years a statin meaningfully lowers the risk of heart attack and stroke. That is why they sit at the centre of both prevention and treatment after coronary disease is found.
Antiarrhythmics: steadying a heart out of order
Antiarrhythmic drugs work on the heart's electrical signalling — the action potential — to suppress abnormal beats and help restore an orderly rhythm. Amiodarone is the broad, powerful all-rounder, used in serious rhythms like ventricular tachycardia and stubborn atrial fibrillation; its trade-off is a long list of effects on the thyroid, lungs and liver, so it is monitored carefully. Digoxin, a much older drug, gently slows conduction through the AV node to help control the rate in atrial fibrillation and can give a modest squeeze to a failing heart.