Does a negative treadmill test mean that there is no heart disease?

IF you are in your early 30s and have a negative treadmill test, does it mean that you have absolutely no heart disease? Well, the answer is not so simple. Mr A was 32 years old and had been seen annually together with his parents since his late 20s. Given his father's history of coronary artery disease and his extremely high levels of "bad" or low density lipoprotein (LDL) cholesterol, his parents wanted him assessed for heart artery disease.

In terms of risk assessment, in the latest 2013 American College of Cardiology and American Heart Association Practice Guidelines on the Assessment of Cardiovascular Risk, the risk calculator is meant for those between the ages of 40 and 79 years, and is not meant to be extrapolated to those below the age of 40.

The authors of the guidelines remind us that: "These guidelines are meant to define practices that meet the needs of patients in most circumstances and are not a replacement for clinical judgment.

"The ultimate decision about care of a particular patient must be made by the healthcare provider and patient in light of the circumstances presented by that patient. As a result, situations might arise in which deviations from these guidelines may be appropriate."

Hence, experience and clinical judgment are important in managing young people with a strong family history of heart disease.

Severe but painless heart disease

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Despite his youth, given his risk factors, he was given an annual treadmill exercise test and was put on cholesterol lowering medication. He passed his treadmill test with flying colours, having achieved a high level of exercise (stage 5 of Bruce Protocol) with no chest pain and no abnormal findings.

He returned three months later complaining of recent onset of chest pain which he described as "severe chest tightness" and "shortness of breath. Despite the absence of evidence of a heart attack from blood tests or electrocardiogram (ECG), and his recent negative treadmill stress test, his risk factor profile and his recent symptoms warranted further investigation.

A computed tomography (CT) scan of his heart arteries was performed and this showed that of his three major heart arteries, two had 100 per cent occlusion and the remaining one had diffuse severe 90 per cent diameter narrowing. Not unexpectedly, the patient was shocked by the revelation.

Although Mr A had complete occlusion of two heart arteries and severe narrowing of the third artery, he did extremely well for his recent treadmill test, had normal heart function and had no symptoms till recently.

Studies which looked at young patients with acute heart events such as a heart attack (Gulf Race-2 study, Genesis Praxy study and Virgo study) showed that 6.5 per cent to 21 per cent of the patients with acute heart attacks did not have typical chest pain symptoms.

Know your risk

If we go by the body of knowledge available to us at present, most doctors will not perform further testing if a treadmill test is negative, especially if the patient was able to achieve high levels of exercise.

It is a known fact that if you take a hundred patients with significant narrowing of one major heart artery and put them on a treadmill test, only about 60 per cent will have an abnormal result - such is the limitation of treadmill testing.

How then do we avoid the risk of sudden death in patients such as Mr A who did not have typical chest pain symptoms until a very late stage despite having very severe life-threatening heart disease?

The first step is to assess your own risk profile. If there is a history of parents having developed significant heart artery disease by the time they are middle-aged and if the patient has severely elevated levels of LDL cholesterol (>190 mg/dl), this will put the individual at very high risk of developing heart artery disease.

If the person is a chronic smoker, has poorly controlled diabetes mellitus or uncontrolled high blood pressure, the risk will increase significantly.

In these patients, even if they do not have typical exertional chest pain symptoms and even if their treadmill test was negative, they should not engage in endurance sports or participate in competitive sports unless a confirmatory test is able to demonstrate without a shadow of a doubt that there is no significant narrowing of the heart arteries.

Atypical symptoms

Secondly, it is important to recognise atypical symptoms which may suggest that a heart event is impending. In the Virgo study published in Circulation journal by Lichtman, those who did not have classical symptoms during a heart attack commonly described the symptoms as indigestion, stress, anxiety or muscle pain. Hence, if you experience recent onset of recurrent symptoms of this nature in the context of a high risk profile, seek advice from your doctors.

Choosing a confirmatory test

Thirdly, if a confirmatory test is required, which test will provide a definitive result as to the status of your heart artery? In the context of a person with high risk profile and a negative functional test such as treadmill testing, it may not be useful to select another functional test such as stress echocardiography (ultrasound assessment of the heart function under stress conditions) or myocardial nuclear perfusion testing (injection of radioactive isotopes to see the distribution in the heart muscle at rest and after stress).

Both these tests do not allow visualisation of the heart arteries and can be negative even in the context of a complete occlusion of a heart artery. In addition, these studies are extremely operator dependent, not to mention the high radiation dose associated with myocardial nuclear perfusion scan.

The other category of tests will be anatomical tests which will allow imaging and visualisation of the heart arteries. The main non-invasive test used to visualise heart arteries is CT scan of heart arteries or CT coronary angiography ( CTCA).

In recognition of the numerous trials that have been performed to establish the usefulness and reliability of CTCA as a first-line examination, the latest European Society of Cardiology guidelines recommend the use of CTCA as an initial test to rule out or establish the diagnosis of blocked heart arteries in symptomatic patients. In the United Kingdom, using CTCA as the first line test for the diagnosis of heart artery blockage in those with chest pain has become the standard of care for those presenting to hospitals with chest pain.

In highly experienced centres, the CT scan of the heart artery can be performed with a low radiation dose and interpreted with high accuracy. Another option is the use of magnetic resonance imaging (MRI) to scan the heart arteries.

This technique is particularly useful for the young as it does not involve any X-rays and requires no injection. However, there are very few centres which have experience with this technique and hence this test is not readily available.

Unusual warning symptoms

The fourth point to remember is that there may be tell-tale symptoms that may alert you to seek medical advice to avoid sudden death. Other than blocked heart arteries, sudden death often occurs as a result of a life-threatening abnormal heart rhythm causing the heart to stop or "seize up".

This abnormal heart rhythm can arise as a result of blocked heart arteries or underlying muscle or electrical abnormalities in the heart. In a Danish study published by Glinge in Circulation on those 35 years or younger who had unexplained sudden death, antecedent symptoms (>24 hours preceding death) and prodromal symptoms (

Hence, if there are unusual symptoms which have rarely occurred in the past, one may wish to seek medical advice especially if there is a strong family history of sudden death.

For the young ones who intend to embark on a vigorous physical exercise programme, do not assume that a negative treadmill test is a safe passport for intense physical exercise. It is wise to understand your risk profile, be alert for unusual symptoms and seek medical advice if you have a high risk profile before starting out on a strenuous physical exercise programme.

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