The number of AF patients that are prime targets for AF catheter-based ablative therapy through a primary Pulmonary Vein Isolation procedure (PVI) using PRI products are derived by two adjustments to the AF patient population.

Given current AF management practices of antiarrhythmic drugs, approximately 50% of the AF population is not adequately treated by drug-based therapies.

PRI estimates that 15% of the AF population may not be indicated for catheter-based ablation therapy. This adjustment includes those patients in very poor health due to underlying heart disease, extreme age or other factors. It also includes patients that will receive surgical treatment of AF as an adjunct to open heart surgery being performed for some other therapeutic purpose (such as coronary artery bypass graft or mitral valve replacement).

After the above judgmental adjustments, there are approximately 3.1 million prime PVI patients in the economically developed world of which 900,000 are in the US and including the US. We estimate that the overall potential market for PVI products is estimated at $2.7 billion in the US and $8.4 billion worldwide (including the US).

In a relevant study, the Medtech Insight Report announced in November, 2002 projected AF sales of non-drug products in 2010 of over $4.0 billion. Drug therapy was projected to add $1.1 billion. The market for PVI products is an important subset of the overall AF market. The size of the future market is dependent on the rate of penetration of the existing backlog of patients and the rate of continued growth in AF prevalence and incidence.