Pulmonary Fibrosis (PF), or lung fibrosis is an umbrella term which covers many different lung conditions that involve scarring of the lungs. The most common type of pulmonary fibrosis is idiopathic pulmonary fibrosis (IPF). Patients with IPF have been known to suffer various cardiac complications with this lung condition – in other words, a lot of people diagnosed with IPF experience problems related to their heart as well.¹

So, what exactly is it about pulmonary fibrosis that can affect our heart health too? The lungs and heart are strongly connected in their roles in keeping our bodies alive and healthy. If we explore what happens to the lungs in pulmonary fibrosis, we start to see how this can also impact the heart.

What is pulmonary fibrosis? 

Essentially, pulmonary fibrosis means ‘lung scarring’ – with pulmonary meaning lungs and fibrosis meaning scarring. The term refers to a family of 200 different lung diseases, which is in turn part of a larger family of lung diseases called interstitial lung diseases. Interstitial lung diseases (ILDs) are diseases which involve inflammation and/or scarring of the lungs. However, not all ILDs involve scarring, which is what makes pulmonary fibrosis different. 

Inside your lungs are tiny air sacs called alveoli, and their job is to move oxygen from the lungs into the bloodstream. However, when somebody has pulmonary fibrosis, the walls of the alveoli – which are usually thin – become thicker and scarred, making it harder for the oxygen to move from them into the bloodstream. This lower level of oxygen circulating in the bloodstream, along with the thick scar tissue itself, means that people with PF struggle with shortness of breath, particularly during exercise. 

Many things can cause pulmonary fibrosis, like smoking, but most of the time the cause is unknown. In this event, it is referred to as idiopathic pulmonary fibrosis (IPF) and this is the most common type of interstitial lung disease. It is most prevalent in people around the ages of 70 to 75 years old and is rarely seen in anyone under the age of 50.²

Common symptoms of idiopathic pulmonary fibrosis

According to the NHS, common symptoms of IPF can include: 

• Fatigue
• A dry cough that doesn’t go away
• Shortness of breath 
• Swollen, rounded fingertips (referred to as clubbed fingers)
• Weight loss and/or loss of appetite 

Treatment for idiopathic pulmonary fibrosis

Unfortunately, there is currently no known cure for IPF, though there are treatment options which can slow the progression of the disease. 

The impact on heart health 

Aside from the fact that there is no cure, another major concern for IPF patients can be complications of the disease that affect heart health. Studies have shown that cardiovascular disease (heart disease) is more prevalent among people with IPF than those without.¹ In fact, there are certain heart conditions that are known as common complications for IPF patients. 

Coronary artery disease (CAD) 

Coronary artery disease (CAD) occurs when atherosclerosis affects the arteries which supply the heart with blood. Atherosclerosis is when fatty deposits build up inside arteries, causing them to narrow and restrict the blood that can flow through them. So in CAD, the heart’s blood supply is reduced. Unlike other lung conditions which do not involve scarring, it has been proven that CAD is strongly linked with pulmonary fibrosis.² In fact, it is the second leading cause of death in patients with IPF.³ 

For the time being, there is currently a lack of evidence as to why this is the case. However, what we do know is that pulmonary fibrosis and atherosclerosis have many similarities in the way they present and develop, and it is thought that they are linked by a causal relationship – i.e. one is causing the other.² 

This may be evidenced by the fact that both IPF patients and atherosclerosis patients usually have higher levels of the same immune mediators – cells produced as an immune response. Essentially, it appears that cells produced in response to IPF are similar to those produced in response to CAD.

In addition, a common symptom of IPF referred to as ‘finger clubbing’ involves the process of new vessels being generated from existing ones, and the growth of fibrous (scar) tissue, both of which are also observed in atherosclerosis.² 

It is also thought that hypoxia – low levels of oxygen in your body – caused by pulmonary fibrosis can worsen angina, which is the chest pain often felt with CAD.⁴

Pulmonary hypertension 

Another common heart-related complication of IPF is pulmonary hypertension (PH) - high blood pressure in the pulmonary arteries which supply blood to the lungs. Although the data on how many IPF patients also have PH is limited due to how difficult it can be to diagnose it, the ARTEMIS-IPF trial revealed that clinically stable IPF patients appeared to progressively develop PH.⁵

Whereas data from UNOS has shown that in patients with severe IPF (to the extent that they are awaiting a lung transplant) PH appears to be much more prevalent.⁶ Therefore, it is clear that the more severe the IPF, the more prevalent the PH. 

So why can IPF cause PH? As pulmonary fibrosis advances, more and more of the normal lung tissue is replaced by thicker scar tissue. This means that the lung’s blood vessels (the pulmonary arteries) are less capable of carrying blood to the lungs, and this can lead to high blood pressure (hypertension) in these arteries. 

Right-sided heart failure

The main consequence of PH is right-sided heart failure.⁷ This is because the high blood pressure in the pulmonary arteries (caused by the effects of the scar tissue in IPF) means that it is much harder for the right side of your heart to pump blood to the lungs.

So, whilst right-sided heart failure is not directly linked to IPF, it is a common complication since many IPF patients suffer from PH which can then lead to it. 

Arrhythmias

It is also common for patients with IPF to experience heart arrhythmias, with the most common type being atrial fibrillation.⁸ Arrhythmias are irregular heartbeats, and in the case of atrial fibrillation, it is usually an abnormally fast heart rate. 

As with PH and IPF, it is thought that the changes to the lung’s blood vessels that occur from the lack of oxygen experienced in IPF could serve as triggers for arrhythmias. Furthermore, the overload that the right side of the heart experiences in the case of PH can cause it to change structure/shape, and this can further increase somebody’s risk of arrhythmias like atrial fibrillation.

Chronic inflammation from IPF has been associated with a higher level of cytokines (signalling proteins) which can also act as triggers for arrhythmias. 

Preferential attention to the lungs vs the heart 

Another theory as to why IPF can have a harmful impact on heart health, is simply that patients with IPF may be receiving a lot of attention to their lung problems, and therefore not much to any heart problems they may have – potentially missing warning signs or symptoms from the heart. This was even supported by a study that found that patients with IPF were less likely to receive statins and beta blockers, two medications that treat issues involving the heart.¹

The bottom line on pulmonary fibrosis and heart health 

Essentially, pulmonary fibrosis has a large impact on the health of the lungs – by thickening the lung tissue and scarring it, it significantly reduces the lungs’ job of moving oxygen around the body. The lungs and heart both work together to do this, so it is no surprise that if the lungs are in poor health, it is likely the heart will suffer too. Whilst the research is still limited, it is certainly evident that patients suffering from IPF are at a higher risk of developing heart problems too, and should be closely monitored for them. 

Summary

• Pulmonary fibrosis is a condition which causes thickening and scarring of the lung tissue
• This means the lungs cannot move oxygen into the bloodstream very well
• The effects of PF can affect heart health in various ways
• Coronary artery diseases are more likely in IPF patients 
• Pulmonary hypertension (high blood pressure in the lung’s blood vessels) can be a result of the thickening/scarring 
• This can also lead to right-sided heart failure 
• Arrhythmias are also common in IPF patients 
• Another explanation for heart health issues from IPF could be a lack of attention to the heart vs the lungs