Hospitals and clinics accumulate a huge amount of patient data over the years. These data provide a basis for the analysis of risk factors for many diseases. For example,we can predict the level of heart attack to find patterns associated with heart disease. One of the major topics in data mining research is the discovery of interesting patterns in data. From the introduction of frequent itemset mining and association rules, the pattern explosion was acknowledged: at high frequency thresholds only common knowledge is revealed, while at low thresholds prohibitively many patterns are returned. A majority of areas related to medical services such as prediction of effectiveness of surgical procedures, medical tests, medication, and the discovery of relationships among clinical and diagnosis data also make use of Data Mining methodologies [1].