Introduction

The term “gut microbiome” refers to a collection of bacteria and microorganisms in the gut tube which have evolved to form a symbiotic relationship with the host - in this case, humans.¹ The gut microbiome has a number of physiological functions such as supporting the immune response, strengthening the gut and fighting off pathogens,¹ however if disrupted - for example, by autoimmune conditions - it could cause problems in our gut and systemically.¹ 

A heart can become enlarged - known as cardiomegaly - for a variety of reasons, such as pathological conditions, autoimmune and toxins. Potential causes cardiomegaly include:³

• viral infections such as HIV and Chagas
• some types of heart disease, such as coronary heart disease and valve disease
• immune types of myocarditis (i.e eosinophilic myocarditis)

Some examples of toxins, such as cocaine and alcohol, can enlarge your heart, as can pregnancy - although pregnancy often only enlarges it in the short-term.³

An enlarged heart has a range of symptoms, such as chest pain, shortness of breath, arrhythmia, palpitations and dizziness.⁴ Although an enlarged heart is often a sign that there is another condition affecting your heart, which will need to be addressed, it will be giving patients symptoms that reduce their quality of life. Therefore, it is important to find therapeutic strategies to deal with cardiomegaly. 

This article will describe the role of the gut microbiome in helping patients with an enlarged heart.

The Gut-Heart Axis

Although cardiovascular disease (CVD) is a well-researched field of medicine, the mortality rate for patients with CVD is expected to grow exponentially due to the changes in lifestyle and increased life expectancy.⁵ One of the newer areas of research to look for new therapies concerns the change in ratio of Firmicutes to Bacteroidetes  and the imbalanced levels of gut metabolites, short-chain fatty acids and trimethylamine N-oxide.⁵ These have been found to have a strong correlation with CVD. Short-chain fatty acids (SCFAs) and trimethylamine N-oxide (TMAO) are overproduced in an imbalanced gut and enter the bloodstream, influencing the function of proteins at different sites, which can have both good and negative effects.⁵ 

One study found that SCFAs and TMAO had specific roles in the gut-cardiac axis.⁶ SCFAs were found to regulate blood pressure and lipid metabolism.⁶ They were also found to be crucial in reducing cardiac ischaemic injury.⁶ One specific fatty acid, butyrate, was associated with decreased risk of atherosclerosis due to its anti-inflammatory properties.⁶ On the other hand, the same study found TMAO to be linked to higher risks of cardiovascular disease.⁶ Raised levels of TMAO were associated with thrombosis, atherosclerosis and myocardial infarction.⁶

Overall, although we do not know the role of all the microorganisms in the gut and how they affect the heart, good advancements in research have been made and a definite link between the gut microbiome and the heart has been identified. This means that, potentially, gut microorganisms could have therapeutic roles for patients with a number of heart conditions, such as an enlarged heart. 

The Gut Micriobiome’s Influence On Enlarged Hearts

The gut microbiome can influence patients with enlarged hearts in many ways, some negative and some positive.

Negative Effects

To start off, an imbalance in the bacteria of the gut - known as dysbiosis - can kickstart chronic inflammation in the body.⁷ Inflammation has been identified as a major risk factor for cardiovascular disease and conditions that lead to an enlarged heart, such as hypertension.⁷ Dysbiosis also compromises the gut barrier, allowing dangerous substances such lipopolysaccharides to enter the bloodstream.⁷ This can lead to more stress on the heart, exacerbating the cardiomegaly and potentially making it worse.

Another negative effect of the gut microbiome on enlarged hearts is the disrupted metabolism of key nutrients. The gut microbiome metabolises substances such as fats and sugars, which are essential to the body in a number of ways.⁸ If this function is disrupted in any way, it could lead to an altered lipid profile, raised cholesterol and insulin resistance, which are all factors that can make an enlarged heart and its underlying disease worse.⁸ 

Positive Effects

However, the gut microbiome can also have positive effects in the overall health of patients with enlarged hearts. As previously mentioned, short-chain fatty acids can be extremely beneficial for heart health. They can either raise or decrease blood pressure,⁶ which can be beneficial if the cardiomegaly is being caused by hypertension. They can decrease cardiac inflammation and regulate the inflammation caused by atherosclerosis.⁶ SCFAs can also regulate the immune response in heart failure and preserve the gut’s health.⁹ 

Another positive influence of the gut microbiome in patients with enlarged hearts is the potential therapeutic approaches that come from the role the gut-microbiome plays in cardiac health. Prebiotics and probiotics may help reduce inflammation and lower blood pressure, both of which would benefit patients with cardiomegaly.¹⁰ Probiotics have also been found to lower the risk of cardiovascular heart disease by improving the levels of a few cardiac markers.¹⁰

Another potential therapeutic effect of this gut-heart axis in patients with enlarged axis is a faecal microbiome transplant. This is still experimental, but it could reset the gut microbiome and therefore halt the excessive production of TMAO and other harmful substances. Recently, a faecal microbiome transplant (FMT) was carried out on an animal model to treat cardiovascular disease,¹¹ and recent human trials showed encouraging results for the reduction of CVD after FMT.¹¹ This could have good implications for patients with enlarged hearts to relieve their symptoms and the pathologies causing their cardiomegaly.

Foods to Eat to Improve Your Gut’s Microbiome

Eating a balanced diet can help maintain one’s gut microbiome healthy, and thus avoid the overproduction of microorganisms that will disrupt the gut-heart axis and your health, in general. Some foods which are especially good to eat to maintain a balanced gut microbiome will be discussed now.

A diet rich in high-fibre foods - such as brown rice, fruits, lentils and vegetables - affects the type and amount of microbiota in the bowel.¹² As a result of the fermentation of fibres when they are digested, short-chain fatty acids are produced, which are then able to have their beneficial effects on the heart.¹² 

Another group of nutrients that releases SCFAs are “prebiotics” fibres, found in foods such as garlic, onion, artichokes, leeks and asparagus.¹² However, a sudden high intake of these fibres can cause flatulence and bloating.¹² 

A last group of foods that is beneficial to your gut microbiome are “probiotics” foods, which contain live bacteria that are beneficial to your gut.¹² These foods are yoghurt, kefir, pickled vegetables, kimchi and miso.¹²

FAQs

How is an enlarged heart treated?

Currently, this depends on the underlying condition causing the enlargement, and it may include a mixture of surgery, medications and lifestyle modifications. 

How can I improve my gut microbiome?

Eating a balanced diet with a good amount of fibres.

How many microbes are in the human body?

Approximately 39 trillion.¹³ 

Summary

This article explored the various roles the gut microbiome plays in relation to the heart, as there is a well-established gut-heart axis. The gut microbiome has been shown to influence cardiovascular disease by either causing, worsening, or alleviating it—effects that can, in some cases, lead to cardiomegaly. The gut microbiome can make the symptoms of an enlarged heart better or worse depending on its many interactions, such as the production of TMAO, SCFAs and the process of gut dysbiosis. However, the gut microbiome can also have potential therapeutic strategies to improve the symptoms and overall health of patients with enlarged hearts.