Dr Cathal Breen, Cardiac & Vascular Physiology Theme Lead at The Physiological Society and Senior Lecturer in Physiology & HCPC registered Clinical Scientist, Ulster University, UK
A degree in Clinical Cardiac Physiology, led to years studying cardiac physiology. To deepen my understanding of heart health and function, I have done research exploring cardiac electrophysiology (science of elucidating, diagnosing and treating the electrical activities of the heart); epicardial adipose tissue associations with atrial fibrillation; and Heart Failure with preserved Ejection Fraction (HFpEF) diagnosis and treatment.
As a Health and Care Professions Council (HCPC) regulated Clinical Scientist, I routinely detect and diagnose abnormal heart rhythms and evaluate heart structure and function in people referred to hospital cardiology departments. My work involves using sophisticated technology and my role is to determine the cause of a person’s cardiac symptoms and refer them for treatments. Now that we can detect our heart rhythms using personalised mobile phone and accessories there is a real opportunity to detect arrhythmias faster and mitigate side effects sooner.
How an irregular heartbeat can affect the heart’s performance
Disturbances to the normal heartbeat are called arrhythmias, with Atrial Fibrillation (AF) the most common sustained cardiac arrhythmia seen in cardiovascular departments, occurring in 1–2% of the general population (Camm et al., 2010).
AF is associated with increased risk of death, stroke, heart failure and hospitalisation. The risk of stroke is particularly high, with one in five of all strokes attributed to this arrhythmia (Bairapareddy, et al., 2018, Camm et al 2010). This is because blood can pool within the atrial appendages of the heart and coagulate resulting in a blood clot.
The AF heart rhythm impairs the coordination of atrial contraction and is caused by other heart conditions, such as high blood pressure (hypertension), atherosclerosis (thickening and hardening of the arteries) and heart valve disease.
Who is most at risk?
AF tends to occur in people with respiratory health conditions, such as pneumonia, asthma and chronic obstructive pulmonary disease (COPD). However, AF can sometimes affect people who are physically fit, including athletes. It can also be triggered by drinking excessive amounts of alcohol, drinking lots of caffeine and taking drugs, particularly amphetamines or cocaine.
Obesity is increasingly recognised as a major factor of AF. My work specifically investigates epicardial adipose tissue (EAT) as a possible cause of and modifiable target to treat this arrhythmia.
Studying the fat around the heart
Although body mass index and other clinical measures are useful indications of obesity, much recent interest has focused on epicardial fat (EAT). A distinct adipose tissue (body fat) depot located mainly around the epicardial coronary vessels and is also present on the myocardial surface from which it can extend into the heart to be interspersed with the myocardial muscle fibres (Wong, et al., 2017).
Epicardial fat serves several important functions for the heart, including a protective role where it buffers the coronary artery (which transports oxygen rick blood to the heart muscle) against torsion caused by pressure waves when the heart and arteries contract. Epicardial fat also offsets rapid changes in the width of the blood vessels maintaining their normal diameter to allow blood to flow easily (Rabkin & Campbell, 2015).
Too much heart fat and the risk of AF
A growing body of data from epidemiological and clinical studies has demonstrated that excess epicardial fat is consistently associated with the presence, severity, and recurrence of AF across a range of clinical settings.
Evidence from science and translational studies has also suggested that arrhythmogenic mechanisms may involve adipocyte infiltration, pro-fibrotic, and pro-inflammatory paracrine effects, oxidative stress, and other pathways (Wong, et al., 2017).
Improving public health
A current treatment for AF is cardiac ablation, a procedure that uses long flexible tubes called catheters, which are inserted into blood vessels into the heart to block irregular electrical signals. We are observing the levels of EAT in participants referred to this procedure and their success rate following cardiac ablation, by measuring the EAT thickness and volumes using CT images.
With increasing awareness of the association between EAT and AF, we are proposing to validate a new marker of risk for developing AF. I am working to develop a treatment plan to target the EAT risk factor. My aim is to evaluate the prevalence of atrial fibrillation and epicardial fat thickness in overweight populations. I will review and analysis the published literature on EAT and AF incidence, aerobic training and nutrition directives to reduce EAT. I will then use the results to design a physical activity programme to specifically reduce EAT.
Cathal is the new Cardiac & Vascular Physiology Theme Lead at The Physiological Society. Find out more about this role and what he hopes to achieve.