As per the guidelines of MCI, a person who have completed MBBS/BDS/BHMS/BAMS etc which are medical courses, are only eligible to practice in India as a medical practitioner if they have clinical license issued by MCI.

As a result, after PhD in Cardiac Care Technology you can treat patients or become a clinical practitioner. Although, you can be a Assistant Professor in Medical colleges as well as paramedical colleges. Also you can become the chief cardiac care technologist in private hospitals as well as Government hospitals.

I hope this answer provides you some insight. Wish you a great eve!