It would be great for the patient if you are very attractive, it would make him feel great.
If you are average, wait 2 weeks after he is released from hospital.
Open heart surgery is no picnic for the patient,
I would suggest not putting any stress on the patient.
If you are a teen or a kid, forget it, wait till patient is recovered.
Some hospitals no longer allow visitors unless they are in the immediate family, or on the patients list of allowed visitors.
Make sure you are spottlessly clean, open heart patients are a higher risk for infection.
Do send a small flower gift and a box of fresh high quality chocalates.