Sensible calories. There is no special cardiac diet for rapid weight loss. I would recommend watching calorie intake with a balanced diet. Rapid wight loss can be harmful.
Difficult. Rapid weight loss is difficult, and potentially dangerous. Additionally, if you lose weight slowly, you are more likely to maintain weight loss. If your heart condition is such that quick weight loss is needed, it may require an intensive special program, carefully monitored, and under a physician's care.