Here is an example of how to calculate the risk of angioplasty/stent in a patient with stable coronary artery disease. Stable CAD is occurs when cholesterol buildup in the heart arteries regularly causes chest pain or other symptoms (like shortness of breath) at a given level of exercise or emotional intensity. And the symptom promptly resolves when the stress of exercise or emotion goes away.
The other type of coronary artery disease is the Acute Coronary Syndrome (ACS) in which symptoms can occur at rest or with increasing frequency or with decreasing stress and is due to blood clot inside a heart artery occurring on top of an area of cholesterol buildup. I’ll go over ACS in upcoming articles on risk estimation.
The patient is a 60 year old women with stable coronary artery disease (also called stable ischemic heart disease—SIHD). She gets chest pain whenever she walks too fast or too far. She is on the maximum amount of medicine to control her chest pain symptoms but they aren’t giving her enough relief. The angina chest pain is interfering with her ability to enjoy life.
She has had a coronary angiogram. It showed severe narrowing from cholesterol buildup in one of the heart arteries (the left circumflex). This narrowing, the doctor felt, was clearly causing her heart symptoms. Her left main coronary artery (the artery that gives rise to the left anterior descending artery and the left circumflex artery) showed no blockage. The left anterior descending artery also showed no significant blockages.
She had a resting echocardiogram and it showed her heart had normal pumping ability at rest (a normal ejection fraction). She had a normal resting EKG and her resting echocardiogram showed the walls of her heart moved normally (she had no wall motion abnormalities). These two facts suggested that she had no heart muscle damage, that is, she had never had a heart attack.
She decides to have a balloon angioplasty/stent to relieve her symptoms of angina. To estimate the risk of the procedure, she and her doctor decide to use the NCDR CathPCI risk score
They go to the article Contemporary Mortality Risk Prediction for Percutaneous Coronary Intervention: Results From 588,398 Procedures in the National Cardiovascular Data Registry published in 2010 in the Journal of the American College of Cardiology available online at:http://content.onlinejacc.org/cgi/reprint/55/18/1923.pdf.
They use Table 4 in the article (on p 1929), the CathPCI risk score. There are a series of eight questions to be answered and each answer receives a point value. All the points are added up and then a risk of inpatient mortality is estimated based on the total number of points.
Our patient is 60 years old (4 points). She is not in cardiogenic shock (0 points). She has never had congestive heart failure (0 points). She does not have peripheral vascular disease (0 points). She does not have chronic lung disease (0 points). Her glomerular filtration rate (gfr) which is a measure of kidney function is mildly abnormal [between 60 and 90] (6 points). Her NYHA functional class is I (0 points). Her PCI status is elective and she has never had an ST elevation myocardial infarction (0 points).
So her total point score is 10 points which corresponds to a risk of dying in the hospital of 0.1%.
There are other risks that must be considered. There is the risk of bleeding from the two antiplatelet medicines that she must take to decrease the risk in-stent thrombosis which if it occurs has a very high death rate. She and her doctors consider these risks and she goes home to think about her decision.
Take a look at the CathPCI Risk Score system in Table 4 of the article at: http://content.onlinejacc.org/cgi/reprint/55/18/1923.pdf.