Hey!
The answer to your query should be wholly dependent upon your interest. If you find your interest more in cardiology , then go for cardiac care otherwise operation theatre , provided these are the two only options.
Now if interest isn't a major factor here , then if choosing money as the factor , you should go for operation theatre as it has the potential to offer you more salary than cardiac care.
Below i am mentioning all the important aspects related to both the courses:
B.Sc Cardiac Care Technology

Duration: 3 years
Course Fees Range: Rs 1,000 tp Rs 4 Lakhs
Top Job Profiles: Cardiovascular Technologist, Cardiologist, Medical Sonographer etc
Average Starting Salary: 20,000 INR to INR 2 Lakhs

Top Colleges:
Christian medical College
Geentanjali medical College and Hospital
Rajiv Gandhi Paramedical Institute
MGMHIS
JIPMER


BScOperation Theatre

Duration: 3 years

Average Course Fees: Rs 50,000 to Rs 10 lakhs

Top Job Positions:Lecturer, OT Technician,Consultant,Anaesthectic Consultant,Lab Technician etc.

Salary Range: Rs 2 lakhs to Rs 10 Lakhs

Top Colleges:

SGT University

Christian Medical College

NIMS

Government Medical College

University of Technology