Truths and myths in heart disease: heart facts

IF you have chest pain and are suspected to have heart disease, what are some of the truths and fallacies that you should be aware of? Sieving through the mountain of information and professional guidelines may leave you confused and bewildered.

Let us filter through the information and find the pearls of truth among commonly asked questions to help us have a healthy heart.

After my abnormal treadmill test, I underwent a heart nuclear scan with injection of radioisotopes and am now absolutely sure that I have no heart artery disease

Myth: The nuclear scan assesses the heart muscle's blood flow (myocardial perfusion) which involves injection of radioisotopes and the result is normal. You can be 100 per cent sure your heart arteries are not blocked.

Truth: These heart radioisotope scans include Thallium scan, MIBI scan, Tetrofosmin scan and Rubidium PET CT scan. Even if there is 100 per cent occlusion of one major heart artery, as long as the other heart arteries are able to provide adequate cross flow, the scan can be completely normal.

In addition, these isotopes circulate throughout the body, exposing the entire body to radiation. The radiation dose exposure is based on certain assumptions that the isotope will be passed out of the body within a certain time period.

However, no one can really be certain how long it takes for the isotope to be completely cleared from the body. In 2011, two patients who had undergone a Rubidium PET CT scan were found to have high radiation in their bodies more than one month post-scan.

The US Food and Drug Administration (FDA) released an advisory stating that these two patients had excessive radiation exposure of approximately 90 millisieverts or mSv (the sievert is the unit used to measure the health effect of ionising radiation on the human body) as compared to the US Nuclear Regulatory Commission estimated annual natural radiation exposure per person of about 3.1 mSv.

Having a discussion with your doctor about potential radiation exposure for the nuclear scan test that you have been recommended, especially if you are young, will be helpful in your decision making process.

I have chest pain and risk factors and the only way to rule out the presence of heart artery disease completely is to do an invasive coronary angiography, which involves the insertion of plastic tubings into my heart under X-ray guidance to visualise the arteries

Myth: Invasive coronary angiography (ICA), which involves the insertion of a plastic catheter into the heart via the wrist or groin artery, is the only safe and accurate manner to diagnose the presence of significant blockage of the heart arteries.

Truth: There are other non-invasive and safer ways to visualise the heart arteries without inserting tubes into the arteries.

If you undergo an ICA, there is a higher chance of finding normal or minor disease than significant disease. Data from the USA registry on ICA published by Patel in New England Journal of Medicine show that about 40 per cent of the patients undergoing ICA show normal arteries and about two-thirds show minor disease. ICA carries real risks.

There are at least six prospective studies that have demonstrated that ICA is associated with 5 to 22 per cent incidence of minor "silent" strokes which can be detected on magnetic resonance imaging (MRI) of the brain. Hence, over the years, there have been many studies to look for safer alternatives which can be performed non-invasively.

There is substantial date to show that a safer alternative to ICA is computed tomography angiography (CTA) scan of the heart arteries as it is safer, less costly, has lower radiation dose, does not require hospitalisation, can provide three-dimensional images, can be completed in a few seconds and carries no risk of stroke or death.

In 2020, the Journal of the American College of Cardiology (JACC) published a report, Current Evidence and Recommendations for Coronary CTA First in Evaluation of Stable Coronary Artery Disease that reflected expert consensus of attendees at the American College of Cardiology (ACC) Summit on Technology Advances in Coronary Computed Tomography Angiography, held in September 2019.

The statement outlines data that for patients who do not have known CAD, the detection of CAD should change from detection of a myocardial perfusion abnormality to detection of coronary atherosclerosis through a CTA-first strategy.

The current European Society of Cardiology guidelines advocate the use of CTA as an initial test for assessment of stable chest pain. The United Kingdom in 2016 had already implemented this approach in their National Health System.

Hence, if you have chest pain and risk factors, CTA of the heart arteries is currently the non-invasive test of choice which can determine the presence of heart artery blockage safely and accurately.

Another method to visualise the heart arteries non-invasively is MRI scan of heart arteries. This technique carries no risk of X-ray radiation and does not require any injection. It is especially useful for young people where X-ray radiation should be avoided. However, this test is not readily available as there are few centres that are able to provide this service.

Blood thinning medication must be taken forever after stenting of heart arteries

Myth: After opening of heart arteries with cylindrical meshes (stents), blood-thinning medication must be taken for the rest of the patient's life. There is a risk that clots can form in the metallic stents if blood-thinning medication is stopped.

Unfortunately, if there is a need for surgery, blood-thinning medication must be stopped and hence, there will be a real risk of stent clotting.

Truth: Not all stents are the same. Those who need to have stents implanted into the heart arteries should seriously consider opting for stents which will enable them to stop their blood-thinning medication.

Bioresorbable stents can be completely absorbed by the body in about one year. After one year post-stenting, it is possible to stop blood-thinning medication if there is no strong indication to continue blood thinners for other medical reasons.

Newer generation stents have thin metallic struts that can be covered by a new layer of cells within months. Once the metallic mesh is completely covered by a new lining of cells, blood-thinning medication can potentially be stopped. This is an important consideration for those who had an increased predisposition to bleeding and for those who are at risk of falls.

A study published in November 2015 in the Catheterisation and Cardiovascular Interventions journal reported that at six months, about 97 per cent of the area of the platinum chromium stent with absorbable polymer ("Synergy" stent by Boston Scientific, US) was covered by a new lining of cells. Hence, there is a very high likelihood of complete coverage of the stents by the end of one year.

Generally, the newer generation thin strut stents demonstrate early coverage of the stent surface by the lining of the blood vessels within months and early cessation of the blood thinning medication due to bleeding have rarely resulted in complications.

Make the best decisions for your future.

Here is a checklist to help you make the decisions you will not regret:

• Consider getting your heart checked if you are experiencing shortness of breath or if you have multiple risk factors for heart disease, which includes high cholesterol levels, diabetes mellitus, high blood pressure and smoking.
• When doing a heart check, tests that allow heart artery visualisation are the most accurate for determining heart artery blockage.
• Always consider a non-invasive test first.
• Based on the current guidelines, CTA of the heart arteries is a recommended test of choice if you have chest pain, rather than doing an invasive coronary angiography.
• When undergoing a test that involves X-ray radiation, opt for a test that has relatively lower radiation dose and for women of child-bearing age, wherever possible, avoid radioisotope tests that will expose the entire body to radiation.
• Finally, if you need to have stents for heart arteries, do seriously consider newer generation stents so that should you need to stop blood thinning medication as a result of surgery or bleeding, you can do so safely.

This article is produced on alternate Saturdays in collaboration with Royal Healthcare Heart, Stroke & Cancer Centre