There are also a number of possible major complications that may occur. These are uncommon. However, your overall health will play an important part in the complication rate of this procedure. For example, the average risk of having a heart attack during cardiac catheterization is 5 out of 10,000 patients. In seriously ill patients, the risk increases to greater than 10 in 10,000 patients. In healthier patients, the risk decreases to 1 in 10,000 patients.