cardiac physiology interview Watch
I'd also suggest looking over the basics of which parts form a basic ECG reading, different job roles within cardiac physiology and what you expect your be doing there, and think about how you'd respond to am aggressive patient, and to someone refusing a clinically urgent test
Read up on current advances in cardiac tech and treatment e.g. New Scientist, and always remember to link anything you write about back to the profession. You could discuss how cardiac physiology allows you to apply science directly to human health and see the outcomes often immediately.
Remember to discuss any experience you have also. Even if you have no direct healthcare experience, working with members of the public or team members in a job or school/hobby role will allow you to discuss if you like interacting with people, which again you can link back to choosing a science role that requires you to work with patients, rather than in a traditional lab setting.
The most important I'd say, is show an interest in the science and people interactions, the NHS, and why specifically cardiac physiology. Hope this helps