Yup heart surgery is probably completely and utterly out of...

Yup heart surgery is probably completely and utterly out of reach of the majority of the population. Market size? Maybe a rough guide would be to apply the incidence/prevalence of CHD in the population that has private health insurance (going by the above link, thats about 5% of the population or 66 million have private health insurance).

Using the figures used by other posters:

Number of private health insured = 66 million
Population growth = 2% x 66 million = 1.3 million p.a.
Incidence of CHD = 1% x 1.3 million = 13,200 p.a.
Number of operations = 25% x 13,200 = 3,300 p.a.

The country in itself wont be a company maker but its another market to add to the list and for sure over time a progressively larger segment of the population in India will join the ranks of those that can afford proper healthcare.