Drugs grouped by the job they do
Cardiology has dozens of medicines, but they fall into a handful of jobs. Some keep blood flowing freely so clots do not block a vessel — that is antiplatelet agents and anticoagulants. Some lighten the heart's workload by relaxing arteries or slowing the heart down — ACE inhibitors, ARBs, calcium channel blockers, beta-blockers and nitrates. Some remove extra fluid so a struggling pump is not overloaded — the loop diuretics. Some steady an unruly rhythm — the antiarrhythmic drugs. And some change the long-term chemistry of the blood vessels, like statins lowering cholesterol.
Notice that one heart problem usually needs several of these jobs at once. After a heart attack a person may take an antiplatelet to protect the stent, a beta-blocker to calm the heart, an ACE inhibitor to protect the left ventricle, and a statin to cool the atherosclerosis. Each pill does a different job; together they form a strategy.
Two big levers: flow and load
Two ideas unlock most of cardiology pharmacology. The first is flow: blood must reach the heart muscle and the rest of the body, and it must not clot where it shouldn't. The second is load: the heart is a pump, and how hard it must work depends on the pressure it pushes against (afterload), how full it is before each beat (preload), and how fast it beats (heart rate). Many heart drugs work simply by turning one of these dials down.
- Flow problems (a clot blocking an artery): reach for antiplatelets, anticoagulants, and sometimes clot-busting thrombolysis.
- Too much load (high blood pressure, an enlarged heart): relax the arteries with ACE inhibitors, ARBs or calcium channel blockers; slow the heart with beta-blockers.
- Too much fluid (a congested, failing pump): drain it with a loop diuretic so the lungs and legs are not waterlogged.
- A bad rhythm (too fast, too irregular): steady it with an antiarrhythmic or rate-slowing drug.