Pt. II At the Heart of It All

2,838,240,000. This is about the number of times your heart will beat throughout your lifetime if you live to be 75 years of age. Millions of coordinated pulses delivering oxygenated blood throughout 100,000 miles (laid end to end) of vascular infrastructure. The muscular aorta, the main life line providing nourishing blood down the vascular tree – to oxygen-hungry capillary beds which nourish tissues responsible for me writing this very sentence. The adaptive miracles of skeletal muscle pumps and one-way valves permit optimal flow through our body despite gravity and upright posture. We’ve developed mechanisms to restrict blood to non-essential organs while we exercise so we can deliver it to areas that need it the most, a concept we like to give the fancy name “functional sympatholysis.”

Luckily, we have developed the methods and mechanisms to understand the integrated physiology and pathophysiology of our unique cardiovascular system. This wasn’t always the case. Ancient Egyptians had no conception of a circulatory system – largely considering the heart a “standalone” organ – believing the heart to be the center of intelligence and life itself. Many ancient philosophers and medical scholars held this belief as well –  and from them we gained the concepts of the “four humors” and ideas of emotions originating from the heart. These beliefs still have a foothold in our modern culture – be it through poems, songs, and our emotions. The cultural idea of feelings such as love and sadness originating “from the heart” have not been discarded – but we are knowledgeable enough now to know the difference between mere rhetoric and hard physiological fact.

We now know that diseases of the cardiovascular system arise not from defects in the balance of bodily humors – but rather from conditions such as plaque buildup in the arteries (atherosclerosis), high blood pressure due to of aging, poor diets, environmental toxins, or stiffening and loss of elasticity in the blood vessels.

This Ultrasound Machine is Probably Worth More Than My Degree

Stiffening of the blood vessels and their subsequent (dys)function is largely what we are currently study in the Integrative Cardiovascular Physiology Lab (ICPL). One of our aims is to understand the processes and lifestyle factors first, better associated with arterial stiffening. While diet and age play their respective roles, so do apparently unrelated diseases such as obesity and diabetes. Many individuals have comorbid (present along with one another) conditions such as obesity and diabetes – which may exacerbate the risks of cardiovascular disease. Vascular stiffening is the result disease interplay with complex biochemical and mechanical processes that change the ability of the body to circulate blood effectively and efficiently; so, one can see how this can lead to further complications later in life. A quality life depends on a quality delivery system.

This is where we can intervene. Using knowledge of the mechanisms involved in vascular stiffening, our lab tests and develops interventions that may counteract deleterious effects of aging, diet, and disease on our vasculature. Our favorite? Exercise.

Aerobic exercise is a well-known intervention to prevent vascular stiffening, lower blood pressure, and improve overall cardiovascular fitness with aging and other diseases. What is more, we now know that aerobic exercise started later in life can reverse vascular stiffening and improve the function of the endothelium. Cardiovascular disease does not represent an end-point for which there is not cure. Currently, we are studying whether high intensity interval training (HIIT) can be more effective than a traditional (more moderate intensity) aerobic exercise training condition. HIIT is time efficient – making it more enjoyable for many people – which is why it has become so popular in the literature and the media.  The reason for HIIT being more beneficial than moderate aerobic exercise lies in its ability to (and this is what we are testing) enhance the amount of blood flow during a particular exercise session, leading to enhanced adaptations in the blood vessels and cardiovascular system.

To measure improvements, we rely on non-invasive ultrasound imaging of the arteries to study structure and function. We can study transmission of blood pressure waveforms throughout various sections of the arterial tree in order to gain insight into how an intervention affected vessel elasticity. More invasive measures of blood parameters are also key to gaining a more molecular understanding of what is going on in the body in response to exercise training. Nobody said understanding physiology was simple.

An Ultrasound Image of the Brachial Artery

For me, the attractiveness in studying cardiovascular physiology lies in fact that in every one of us, there is a beating heart, networks of blood vessels, all with similar physiology – working to keep us alive during times of sedentarism as well as stress. This system is integral, and it is fascinating. My desire is that, the more I learn about mechanisms of dysfunction, the more I can build upon and develop ways to help people live to their most optimal state of function. The paradigm that aging is synonymous with disease is slowly being discarded in favor of an active and healthy model. Preventable diseases such as diabetes and obesity, we now know, can favorably respond to intervention. It is my hope that our lab produces quality research in this area and advances the discussion on cardiovascular health into areas currently unexplored.

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