The simple idea
- Dilated cardiomyopathy — the ventricle becomes big and floppy and can't squeeze well. Causes include genes, alcohol, some cancer drugs, viral infections, and pregnancy (peripartum cardiomyopathy).
- Restrictive cardiomyopathy — the muscle becomes stiff, so the heart can't fill properly, even though it may squeeze fine. A classic cause is amyloid, an abnormal protein deposited in the muscle.
- Myocarditis — the muscle is inflamed, often after a virus. It can cause chest pain, breathlessness or an irregular heartbeat.