By Dr. Mercola
Cardiac stress tests are sometimes used to make sure your heart works properly when put under stress.
Typically, you'll be asked to walk on a treadmill or ride a stationary bicycle to increase your heart rate until your heart is adequately stressed, then its function will be examined using an MRI or other imaging tests.
In cases where a person is unable to increase their heart rate via exercise, chemicals are sometimes used to simulate stress on your heart.
You need to be very careful when considering this type of heart test, known as a chemical cardiac stress test, as a new announcement from the US Food and Drug Administration (FDA) warns that the drugs used could actually trigger a heart attack and death.
Chemical Stress Tests Could Trigger Heart Attack, Death
The FDA's warning applies to two chemical stress test drugs called Lexiscan (regadenoson) and Adenoscan (adenosine). The injectable drugs dilate the arteries in your heart and increase blood flow, allowing doctors to check for areas of damage or low blood flow.
However, as blood flow increases, it naturally flows to healthy areas and may leave obstructed arteries with low blood flow, potentially triggering a heart attack.
Both drugs already contained a warning on their labels about the possible risk of heart attacks, but recent deaths reported to the FDA Adverse Event Reporting System (FAERS) database and in the medical literature1, 2 prompted updated recommendations for use.
The FDA now warns that people with symptoms of cardiovascular instability should not use the drugs, and cardiac resuscitation equipment and trained staff should be available before administering these medications.
The drugs are still on the market, however, which is why it's important that you're aware of the heart attack symptoms risk if you or a loved one is considering a chemical stress test. The FDA explained:3
"Lexiscan and Adenoscan cause blood to flow preferentially to the healthier, unblocked or unobstructed arteries, which can reduce blood flow in the obstructed artery. In some cases, this reduced blood flow can lead to a heart attack, which can be fatal."
Are There Other Ways to Check on Your Heart Health?
Yes, but they're not the conventional cholesterol tests your doctor may have ordered. If you've had your cholesterol levels checked, your doctor most likely tested your total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. But we now know those are not accurate predictors for cardiovascular disease risk.
A much more accurate predictor is testing your LDL particle number, as Chris Kresser, L.Ac, explains:
"To use an analogy: if you imagine your bloodstream's like a river, the LDL particles are like the boats that carry the cholesterol and fats around your body. The cholesterol and fats are like cargo in the boats.
Right now doctors are usually measuring the amount of cargo or cholesterol in the LDL particles. But what we should be measuring is the number of LDL particles, or the number of boats in the river, so to speak, because that's a much more accurate risk factor for heart disease."
There are several ways to test for your LDL particle number. Kresser recommends using the NMR LipoProfile, offered by a lab called Liposcience. The test uses FDA-approved technology for testing LDL particle number, and it's the test used in most of the scientific studies on LDL particles.
It's easy to get and all major labs offer it, including LabCorp and Quest. Most insurance policies cover the test as well. Best of all, even if your doctor were to refuse to order it, you can order it yourself via third-party intermediaries like Direct Labs, or you can order the test online, and get blood drawn locally.
If your levels come back high, it's time to figure out the underlying cause (which is not dietary cholesterol, as you may have been led to believe).
It's not the amount of cholesterol that is the main risk factor for heart disease, rather it's the number of cholesterol-carrying LDL particles, and, in particular, the small, dense (type B) particles that are linked to heart disease.
Also, what matters most is the quality of your lipoproteins. When oxidized (known as oxidized LDL or ox-LDL), these particles can cause direct damage to the lining of your arteries, contribute to plaque buildup and greatly increase your overall risk for heart disease.
When oxidative stress is high due to poor diet, insufficient exercise and sleep, and chronic stress, or when your antioxidant capacity is low (again usually because of a poor diet or smoking), then the accumulation of ox-LDL and associated arterial damage can occur.
The Real Underlying Causes of Heart Disease
If the primary cause of heart disease is not high cholesterol, then what is? Insulin and leptin resistance are the major culprits, as when this is present it causes an increase in small LDL particle number via several different mechanisms. While some genetic predisposition can play a role, insulin and leptin resistance is primarily caused by a combination of factors that are epidemic in our modern lifestyle:
- A diet high in processed and refined carbohydrates, sugars/fructose, refined flours, and industrial seed oils.
This is particularly relevant in lieu of the misleading public health advice, which suggests you replace healthful saturated fats with vegetable oils and grain carbohydrates. When you replace saturated fat with a higher carbohydrate intake, particularly refined carbohydrate, you exacerbate insulin resistance and obesity, increase triglycerides and small LDL particles, and reduce beneficial HDL cholesterol.
In a 2010 study published in the American Journal of Clinical Nutrition,4 the authors stated that dietary efforts to improve your cardiovascular disease risk should primarily emphasize the limitation of refined carbohydrate intake and weight reduction.
- Insufficient everyday physical activity, including exercise and non-exercise activity. Leading a sedentary lifestyle causes biochemical changes that predispose you to insulin and leptin resistance.
- Chronic sleep deprivation. Even one night of disturbed sleep can decrease your insulin sensitivity the next day and cause cravings and overeating.
- Environmental toxins. Exposure to BPA, for example, can disrupt your brain's regulation of your weight.
- Poor gut health. Imbalances in your gut flora (the bacteria that live in your gut) can predispose you to obesity and insulin and leptin resistance.
5 Other Essential Tests for Gauging Your Heart Disease Risk
There are several other tests that I recommend if you're unsure of your heart health. Again, not one of these is a conventional cholesterol test, but rather:
1. Fasting Insulin Level
Your fasting insulin level reflects how healthy your blood glucose levels are over time. Chronically elevated blood glucose leads to insulin resistance and numerous chronic diseases, including diabetes and heart disease.
Your fasting insulin level can be determined by a simple, inexpensive blood test. A normal fasting blood insulin level is below 5, but ideally you'll want it below 3. If your insulin level is higher than 3 to 5, the most effective way to optimize it is to reduce or eliminate all forms of dietary sugar, particularly fructose.
2. Cholesterol/HDL Ratio
The following two ratios are far better indicators of heart disease risk than total cholesterol alone:
- Your HDL/Cholesterol ratio: HDL (high-density lipoproteins) to total cholesterol percentage is a very good predictor of heart disease risk. Just divide your HDL number by your total cholesterol. Ideally, this number should exceed 24 percent; below 10 percent predicts an increased risk for heart disease.
- Your Triglyceride/HDL ratio: Divide your triglyceride number by your HDL. This ratio should ideally be below 2.
3. Serum Ferritin
Excess iron is a very potent oxidative stressor, causing dangerous free radicals that can damage your heart. Therefore, you should regularly check yourself for iron overload with a serum ferritin test. This blood test measures iron's carrier molecule—a protein called ferritin found inside your cells upon which the iron is stored. If your ferritin levels are low, it means your iron levels are also low, and vice versa. Use the following guidelines to interpret your serum ferritin level:
- The healthy range of serum ferritin is between 20 and 80 ng/ml
- The ideal serum ferritin range is 40 to 60 ng/ml
- Below 20, you are iron deficient; above 80, you have an iron surplus. Ferritin levels can go really high. I've seen levels over 1,000, but anything over 80 is likely to be a problem.
It is VITAL to appreciate that about one in five men and postmenopausal women have iron levels that are too high and are actually causing premature disease and death. If you or someone you love has triple digit ferritin levels you need to lower them ASAP.
The higher the number the worse it is, with numbers over 250-300 being particularly dangerous. Fortunately, there is a very simple way to lower it -- donate blood. If you have risk factors that prevent you from having your blood accepted for donation, you can have your doctor write you a prescription for a therapeutic phlebotomy.
4. Waist Size
Waist size provides a fairly accurate benchmark for predicting your risk of death from a heart attack and from other causes. Determining your waist size is easy. With a tape measure, measure the distance around the smallest area of your abdomen, below your rib cage and above your belly button. The following is a general guide for healthy waist circumference:
- Men: 37 to 40 inches is overweight; greater than 40 inches is obese
- Women: 31.5 to 34.6 inches is overweight; greater than 34.6 inches is obese
5. Vitamin D
People with lower blood levels of vitamin D may be more likely to die from heartdisease or stroke. The only way to determine whether you're within the therapeutic range is to regularly test your vitamin D levels. For more information, including an in-depth explanation of everything you need to know before you get tested, please see "Test Values and Treatment for Vitamin D Deficiency."
Heart Disease Prevention 101
Ideally, you'll take steps now to protect and nourish your heart so that you have no need for invasive and potentially deadly procedures like a chemical stress test. The INTERHEART study, which looked at heart disease risk factors in over 50 countries around the world, found that 90 percent of heart disease cases are completely preventable by modifying diet and lifestyle factors.5 Take control of your health, including your heart health, today by paying attention to these positive lifestyle changes for your heart:
- Diet: Shift toward a nutrient-dense-food-based diet with higher fat and lower carbohydrate intake, such as my nutrition plan
- Intermittent fasting is a powerful tool to lower your body fat and normalize your insulin and leptin resistance
- Make sure you're getting enough sleep
- Exercise regularly, and make sure to incorporate high-intensity interval exercises, as they are particularly effective for improving insulin and leptin sensitivity
- Avoid sitting too much, as that can have a direct adverse effect on insulin and leptin sensitivity
- Minimize your exposure to environmental toxins as much as possible
- Optimize your gut health by eating fermented foods, soluble fiber that enriches your beneficial gut flora, and avoid food toxins that harm your gut flora (i.e. sugar)
As you can see, the things you need to do to prevent heart disease are identical to what you would do to promote optimal health in general.