Dr. Tobis was a leader in developing digital angiography for use in the cardiac catheterization laboratory. While at UC Irvine, Dr. Tobis performed the first digital left ventricular and coronary angiograms in the world. This work helped transform the cardiac catheterization laboratory from a film based procedure to a completely digital environment.

Dr. Tobis helped to develop one of the first mechanically rotating intravascular ultrasound (IVUS) imaging devices which aids our understanding of coronary pathophysiology and the mechanism of action of multiple devices used in interventional cardiology.

In collaboration with Antonio Colombo, IVUS technology helped to explain the high incidence of subacute thrombosis during the early experience with intracoronary stents. This led to the use of larger balloons and higher pressures with decreased subacute stent thrombosis and permitted a dramatic increase in the use of coronary stents for angioplasty.

He is the coauthor with Paul Yock of the textbook, "Intravascular Ultrasound Imaging" and with Antonio Colombo for "Techniques in Coronary Artery Stenting". His recent work has been devoted to understanding the role of patent foramen ovale (PFO) in relation to cryptogenic stroke, migraine headache, and orthodeoxia. He is a co-editor of a textbook on Patent Foramen Ovale. He is a consultant for Cardiac Dimensions, a start up company that has developed a percutaneous device for treating mitral regurgitation. He travels to Europe and Australia to proctor physicians how to perform this new procedure. He continues to work at UCLA seeing patients and doing procedures in the cardiac catheterization laboratory