Health Imaging has a good overview
of the current state of affairs on information systems for diagnostic
cardiology, including a list of 16 of the leading vendors.

Cardiology presents special challenges when compared to other
diagnostic departments. In many hospitals cardiology modalities are
located in different departments, and some diagnostic modalities are
dual-use, presenting the challenge of supporting both radiology
RIS/PACS and a cardiology information system (CIS). The breadth of
modalites and variety of data, from arrhythmia analysis to pressures to
images -- many with their own mini information systems and archives --
adds considerable complexity.

Unlike most radiologists who are employed by and work within a
traditional healthcare, cardiologists primarily have practices outside
of a hospital and are on the move between two, three or four different
healthcare facilities and their own main offices. That situation can
create two problems: A patient's test and imaging results are scattered
throughout a facility among the different cardiac subspecialties, such
as nuclear medicine, echocardiography and electrocardiography; and,
because the cardiologist is not at the facility full-time, he or she
may not have the influence to affect a change in that process.

Fewer than 15% of U.S. hospitals have adopted cardiology information
systems, and significant market growth is expected in the next 5 years.
This situation has already started some consolidation in the market.

For a look at the future of cardiology, see Health Imaging's article, Sneak Peek: Cardiology Department 2010.