List six causes of left atrial enlargement.

1. Aortic valve stenosis or insufficiency
2. Mitral valve stenosis or insufficiency
3. Intracardiac shunts, such as VSD and PDA
4. Left ventricular failure
5. Cardiac restriction
6. Diastolic dysfunction (e.g., as a result of hypertrophic cardiomyopathy, old age, hypertension)