By
Ernest Madu, MD, FACC and Paul Edwards, MD, FACC
Consultant Cardiologists, Heart Institute of the Caribbean (HIC) and HIC Heart Hospital
Dr. Madu is a main TED Speaker whose TED talk has been translated into 19 languages, seen, and shared by more than 500 thousand viewers. He has received the Distinguished Cardiologist Award, the highest award from the American College of Cardiology and has been named among the 100 most influential people in healthcare and among the 30 most influential in Public Health. Dr. Madu is also a recipient of the Global Health Champion Award from the University of Pennsylvania. Dr. Madu was past CEO of HIC and is currently the Chairman of IHS Holdings Ltd, an asset management company with interests in the USA, Africa, and the Caribbean. Correspondence to [email protected] or call 876-906-2107
One of the more frequent questions that patients have is “What is my risk of getting cardiovascular disease?” We are all familiar with anecdotal stories of a 40-year-old man with no known health problems who dies suddenly of a heart attack or who suddenly experiences a disabling stroke. Ever since the dawn of medicine, we have been able to associate some element of risk or medical conditions with poor outcome over time. For example, an obese individual with normal blood pressure today has a 70% chance of developing hypertension over the following 10 years. A middle-aged individual with an elevated blood sugar early in the morning has a 5-6% risk yearly of going on to develop Type 2 diabetes. It turns out that for many diseases, there are often numerous factors that contribute to disease development and progression. As medical knowledge has advanced there are diseases for which we have an increasing body of knowledge in terms of causes and contributory factors. This knowledge has allowed us to begin to predict risk of disease over time.
Atherosclerotic Cardiovascular Disease
In the realm of cardiovascular disease, atherosclerotic cardiovascular disease is currently the most common on a worldwide basis and in most countries, including Jamaica, it is the leading cause of death. Atherosclerosis refers to the laying down of cholesterol in the walls of various arteries in the body. This process results in deficiency of blood flow to various organ systems resulting in clinical disease. The organs most often affected are the heart, the brain, the kidneys, and the lower limbs; with clinical impact being most pronounced for the heart “heart attack” and the brain “stroke”. These events can be fatal or non-fatal. They can also occur in the absence of prior symptoms with the first clinical event being a fatal heart attack or a fatal or disabling stroke. Given the impact of atherosclerotic disease on society it has been an area that has generated much research interest over the past 100years.
Risk Factors
Over time it has become clear that certain conditions and behaviors increase the risk of atherosclerosis. These include hypertension, diabetes, abnormal cholesterol, cigarette smoking, family history, genetics, age, sex, obesity, diet, exercise, chronic inflammatory conditions etc. It has also become clear that for most patients who present with clinical atherosclerotic disease they tend to have several risk factors often acting in concert. Given this, if one is to try to estimate an individual or population risk profile one must consider as many risk factors as possible and to see how they impact each other and the risk of disease. We are beginning to realize that often, the finding of one risk factor means that others are present as well. For example, patients with type 2 diabetes tend to have hypertension, abnormal cholesterol, and obesity. It has also been found that patient with one risk factor will often have increased risk from a second risk factor when compared to an individual with no risk factor. It should also be noted that although we are better able to assess risk from atherosclerotic cardiovascular disease there are many areas of cardiovascular medicine for which we do not have reliable ways of predicting risk of developing disease over time. These would include congestive heart failure, valvular heart disease, arrhythmias (abnormal heart rhythm), and congenital heart disease.
Disease Risk Prediction
Currently tools exist that allow us to estimate 10-year risk and lifetime risk of atherosclerotic cardiovascular disease (Usually defined as heart attack, stroke, or cardiovascular death) in middle aged and older adults. The methodology involves assessing risk factors and using a mathematical model to convert the presence of these risk factors into a numerical level of risk. A patient can be thought of as low risk if they have a 10-year risk of <5.0-7.5%, High risk if the 10-year risk is >20% or intermediate risk between 7.5 to 20%
Risk Scores
This data is usually obtained from large studies looking at individuals with no history of cardiac disease and assessing their risk factors at baseline. These patients are then followed over time and the incidence of various events are noted e.g., myocardial infarction, stroke, cardiovascular death etc. At the end of the study one can look at which baseline conditions were related to disease outcome. One of the first large studies using risk factors to predict cardiac risk was the Framingham Study which was started in 1948 in the Framingham County of Massachusetts. The Framingham risk score was one of the first prediction tools used to estimate the 10-year risk of developing cardiac disease. Other prediction tools have been developed over time including the American Heart Association/American College of Cardiology Pooled Cohort Equations, the SCORE charts in Europe and on a world-wide basis the WHO risk prediction models which have data for the Caribbean region.
The WHO risk prediction models were developed in response to the fact that most of the early prediction models were developed mostly in the rich developed countries whose populations, baseline cardiac risk and prevalence of risk factors differed markedly from less developed countries. Given this, prediction models obtained from these more developed nations could not be reliably applied to many low- and middle-income countries. The WHO risk prediction tools are geographically divided into 21 regions worldwide with local data being used to inform risk prediction. Data from the Caribbean region is used to predict outcome for our patients. Patient data required include age, sex, presence of smoking, diabetes, systolic blood pressure and total cholesterol. The output is a 10-year risk of cardiovascular disease including fatal and non-fatal stroke and coronary heart disease.
How do risk scores apply to you?
From the point of view on an individual patient, how is this number useful? It turns out that many of our patients are unaware of their level of risk. It is a common finding that if patient feel well and has no limitations in their day-to-day life, they feel as if there is no way that they could have significant cardiovascular disease. To take an example of a 55-year-old diabetic man who has no symptoms but who has a total cholesterol of 5.4, a systolic blood pressure of 170mmHg and is currently a smoker. Despite the absence of symptoms, his 10-year risk of cardiovascular disease is >30% and he certainly would benefit from aggressive risk factor management. This would include stopping smoking, good control of his hypertension and blood cholesterol, dietary and lifestyle measures. In a patient such as this there would be a low threshold for testing for evidence of cardiac or cerebrovascular disease.
From a medical point of view the identification of patients at high or intermediate risk allows us to target patients who would get greater benefit from aggressive treatment, testing and intervention with the potential for better outcomes and health care savings at a system level. Patients who are at higher levels of risk benefit more from medical intervention than patients at low risk. This has been codified in the latest American and European recommendations for the treatment of hypertension and hyperlipidemia. A patient with a high 10-year cardiovascular risk (>20%) is treated earlier and more aggressively than a patient who has a risk that is less than 5%.
As responsible individuals, it behooves us to understand our underlying medical conditions. It is reasonable to periodically have your blood pressure, blood sugar and cholesterol levels evaluated. We would recommend that everyone try to follow a heart healthy diet, exercise regularly and avoid high risk behaviors including smoking and drinking alcohol to excess. If possible, we should avoid weight gain and attempt to keep our body weight normal.
If there is concern of risk for cardiovascular disease in the future, then seeing one of our HIC Cardiologists will allow risk assessment and early treatment as needed to lower the risk of future cardiovascular disease.
