Mayo Clinic Study: Stress Test Anomalies Unmask More Than Just Heart Threats

The exercise stress test, commonly known as an electrocardiogram (ECG), is a treadmill exercise test that is one of the most familiar tests in medicine. These are common tests. According to a 2017 study published in the journal Circulation, over 2 million treadmill exercise tests with ECG were performed in the United States in 2016. The study also found that the number of tests has increased in recent years.

A 2020 study published in the journal Heart estimated that over 10 million treadmill exercise tests with ECG were performed globally in 2019. The study also found that the number of these tests performed is increasing in developed and developing countries.

The most common age groups for treadmill exercise tests with ECG are adults between 40 and 60. These are the ages at which people are most likely to develop heart disease. However, treadmill exercise tests with ECG can be performed on people of all ages, depending on an individual's risk factors for heart disease.

A recent Mayo Clinic study suggests that while the primary purpose of these tests is to diagnose coronary artery disease, anomalies such as decreased functional aerobic capacity can forecast deaths from non-cardiovascular causes, including cancer, in addition to those from cardiovascular-related conditions. The study appears in "Mayo Clinic Proceedings."

Noninvasive and Easily Available

The exercise stress test is a noninvasive and readily accessible procedure that yields vital diagnostic insights. Beyond the ECG readings, the test generates data on functional aerobic capacity, heart rate recovery, and the chronotropic index — a standardized metric indicating heart rate during exercise, which factors in age, resting heart rate, and fitness level.

Thomas Allison, Ph.D., M.P.H., director of Mayo Clinic's Integrated Stress Testing Center and the study's senior author, says that more than just cardiac issues were observed.

In our exercise testing cohort, non-cardiovascular deaths were more frequently observed than cardiovascular deaths. Though this was a cardiac stress test, we found that cancer was the leading cause of death, at 38%, whereas only 19% of deaths were cardiovascular. Exercise test results including low exercise capacity, low peak heart rate, and a slow recovery of the heart rate after exercise test were associated with increased mortality.

The research analyzed 13,382 patients who had no prior cardiovascular conditions or other significant illnesses and had undergone exercise tests at the Mayo Clinic from 1993 to 2010. They were then monitored for an average span of 12.7 years. Based on the results, clinicians are advised to consider not just the ECG outcomes but also exercise test data, including reduced functional aerobic capacity, low chronotropic index, and irregular heart rate recovery.

Dr. Allison says patients should be encouraged to increase their physical activity if these results are atypical, even if the ECG results show no significant cardiovascular-related risk.

Heart Issues Top Concern of Doctors When Ordering Stress Test

Generally, heart-related issues are the reasons these exercise stress tests are performed:

• To diagnose heart disease
• To assess the severity of heart disease
• To monitor the effectiveness of heart disease treatment
• To assess a person's risk of developing heart disease
• To clear a person for participation in sports or other physical activities

Exercise stress tests, such as the ones conducted at the Mayo Clinic, serve a dual purpose: diagnosing coronary artery disease and evaluating other indicators that might predict various health outcomes. The outcomes of these tests can provide a wealth of information critical for tailoring individual treatment plans.

One key metric derived from these tests is functional aerobic capacity. This measures how effectively the heart, lungs, and muscles work together to use oxygen, and it can be a strong predictor of overall cardiovascular health. 

A lower functional aerobic capacity can be an early warning sign of potential cardiovascular problems in the future. If this capacity is found to be reduced, it might suggest that the patient's heart isn't pumping blood as efficiently as it should or that their lungs aren't effectively transferring oxygen into the bloodstream.

Another significant metric is the chronotropic index. This gauges how the heart rate responds to increased physical activity. A lower chronotropic index could indicate that the heart isn't reacting as it should to the demands of exercise. This could be due to issues with the heart's electrical system or could indicate other underlying heart conditions.

Abnormal heart rate recovery is yet another critical factor. After exercising, the heart rate should gradually decrease back to its resting rate. If it remains elevated, it might suggest that the heart is under undue stress or that there are issues with the autonomic nervous system, which regulates heart rate.

Given these potential outcomes, doctors often recommend a range of interventions. For those with decreased functional aerobic capacity, a regimen of monitored physical activity might be prescribed to improve cardiovascular fitness. Patients with a low chronotropic index might be further evaluated for arrhythmias or other heart conditions, leading to treatments ranging from medications to procedures like pacemaker implantation. And for those with abnormal heart rate recovery, further diagnostic tests might be conducted to delve deeper into potential causes.

Ultimately, the recommendations hinge on the individual's specific test results and overall health profile. What remains consistent is the emphasis on early detection and proactive intervention, underscoring the importance of such tests in preventative care.

Aging and the Heart

Aging is a natural process that affects every organ and system in the human body, and the cardiovascular system is no exception. As individuals grow older, various structural and functional changes in the heart and blood vessels can increase the risk of developing heart-related issues. While some age-related cardiovascular changes are inevitable, understanding them can help manage and mitigate potential complications.

One of the most common age-related changes is the thickening and stiffening of the heart's walls, particularly in the left ventricle, which can reduce the heart's ability to fill with and pump out blood efficiently. This condition, known as left ventricular hypertrophy, can lead to heart failure if not addressed. Moreover, aging can lead to the calcification of heart valves, especially the aortic valve, affecting its function and leading to conditions like aortic stenosis. Additionally, the heart's electrical system, responsible for maintaining a regular heartbeat, can undergo changes with age, leading to arrhythmias such as atrial fibrillation.

Aging also affects the blood vessels. Arteries may become less elastic and more rigid, a condition known as arteriosclerosis, which can increase blood pressure and strain the heart. The buildup of fatty deposits on the inner walls of arteries, or atherosclerosis, can restrict blood flow and lead to angina, heart attacks, or strokes. Furthermore, age-related changes in the body's hormonal balance and other factors like chronic inflammation can contribute to these vascular changes. While aging is inevitable, adopting a heart-healthy lifestyle—including regular exercise, a balanced diet, and regular check-ups—can significantly reduce the risk of heart-related issues in older adults.

Long-Term Care and Heart Issues

As heart-related conditions stemming from aging progress, they can severely compromise an individual's independence and overall quality of life. Conditions like heart failure, severe arrhythmias, or post-stroke complications often require constant monitoring, medication management, and assistance with daily activities. 

In some cases, the aftermath of a heart attack or stroke can result in reduced mobility, cognitive impairment, or the need for rehabilitation services. These challenges might necessitate modifications in the home environment, the use of mobility aids, or even the implementation of specialized care routines, which can be overwhelming for families to manage on their own.

The repercussions of these cardiovascular conditions frequently lead to the need for long-term care. This can manifest in various forms, ranging from home health care services to assist with daily tasks and medical needs to admission into assisted living facilities or nursing homes. 

In these situations, long-term care offers a safe environment where medical and personal needs are addressed, reducing the risks of complications and hospital readmissions. Additionally, as managing heart-related issues often requires a multi-disciplinary approach, long-term care settings can provide access to a range of health professionals, including therapists, nutritionists, and specialized nurses, ensuring comprehensive care for affected individuals.

The problem for some people is most long-term care is not covered by traditional health insurance or Medicare. Long-Term Care Insurance will provide coverage, but someone cannot purchase a policy once they require care. Usually, you purchase an LTC policy in your 40s or 50s when your health is still fairly good. Medicaid will only provide benefits for those with little or no income and assets.