Hi Dniraaj,
Presently, most of the insurance companies are providing pre-existing disease cover from and onwards 4th Year of the policy inception.
It is also observed that some of the insurers are not willing to grant policy for persons having pre-existing disease.
However, according to market report, Star Health Insurance Co. Ltd. can grant cover, but then in your case, your father would have to wait at least 4 years for enjoying re-imbursement for heart related disease.
But remember you would be required to continously renew that policy without break (i.e. renew the same before expiry).
In case of any further assistance, please get in touch with the administrator of this forum, Mr. Devanand Agarwala, he would certainly guide you as he has been doing in other cases.