What is the difference between invasive and non invasive cardiologist?

Non-invasive cardiologists provide expertise in the detection and treatment of Heart disease. Non-invasive cardiology involves tests to evaluate and diagnose disorders of the heart. A person with a history of heart disease, chest pain with unknown cause or valvular heart disease may be referred for non-invasive evaluation

[From: http://www.catholicmedicalcenter.org/Programs/Non-Invasive-Cardiology.aspx] Invasive cardiology is a special aspect of cardiology that uses invasive procedures to treat heart disease. These procedures generally require insertion of instruments through the skin and into the body to treat a problem - thus the term "invasive." Many of the procedures done in this exciting field can be lifesaving.

[From: http://www.personalmd.com/news/invasivecardio_81900.shtml] Hope this helps. There is plentiful more information in the links provided if you plan to deeply anylize these terms.