Experts are urging individuals to be vigilant for the subtle, often-missed symptoms of pulmonary embolism, a deadly blood clot condition that tragically claimed the life of Hollywood actress Catherine O’Hara. The acclaimed Home Alone and Schitt’s Creek star passed away last month at the age of 71, with a coroner’s report detailing her admission to hospital struggling to breathe before succumbing to a blood clot in her lungs.

Pulmonary embolism is a life-threatening condition responsible for nearly 3,000 deaths in Britain annually. Despite its severity, many patients remain unaware of its early signs, according to Professor Rasha Al-Lamee, a distinguished cardiologist at Imperial College London. Professor Al-Lamee also highlights several factors that elevate the risk of developing a pulmonary embolism and outlines simple preventative measures.

A pulmonary embolism occurs when a blood clot lodges in the arteries of the lungs, obstructing blood flow, straining the heart, and depriving the body of vital oxygen. These clots frequently originate as deep-vein thrombosis (DVT), forming in the veins of the leg or pelvis. DVT often manifests as pain, swelling, and tenderness, particularly in the calf, as noted by Professor Al-Lamee. However, the symptoms of an embolism vary significantly depending on its severity.

A severe pulmonary embolism, where a large clot completely blocks blood flow in the lungs, typically presents unmistakable symptoms. Professor Al-Lamee explains, ‘If a patient is suffering from a large pulmonary embolism they will experience sharp chest pain, a racing heart and can feel really unwell, alongside breathlessness.’ In some critical instances, patients may exhibit bluish lips or fingernails, or an overwhelming sense of anxiety or impending doom. The tragic case of actress Emily Chesterton, 30, in 2023 underscores the dangers of misdiagnosis; she died of a pulmonary embolism after an NHS worker mistook her symptoms – calf pain, a swollen and hot leg, and shortness of breath – for anxiety. A coroner concluded that her life could have been saved with prompt A&E treatment for the condition.

Treatment for pulmonary embolism primarily involves anti-clotting medications to reduce the size of the blockage. In extreme cases, surgical removal of the clot from the lungs may be necessary. Research indicates that severe embolisms can be fatal within an hour, or even minutes, and even with rapid treatment, survival is not guaranteed; approximately half of patients experiencing a large pulmonary embolism die.

Professor Al-Lamee cautions that smaller embolisms, where blood flow is not entirely blocked, can be equally perilous. While not immediately deadly, these smaller clots are frequently missed because their symptoms are mistaken for less severe conditions. Without intervention, these clots can persist, grow larger, and eventually lead to a complete blockage of blood flow. Data reveals that around 400 patients in the UK die annually due to misdiagnosed pulmonary embolisms. ‘Smaller embolisms can recur over a period of time and patients often first notice a reduction in their ability to exercise, breathlessness, fatigue and sometimes blood-stained phlegm,’ says Professor Al-Lamee, emphasizing why these smaller clots are difficult to detect.

Certain individuals face a higher risk of pulmonary embolisms and must therefore be more alert to early warning signs. Professor Al-Lamee identifies cancer as a significant risk factor, increasing the chance of a deadly lung clot by six times, as cancer cells can make blood ‘stickier’ and more prone to clotting. This factor likely contributed to Ms. O’Hara’s death, as her death certificate revealed she was battling rectal cancer, a fact she kept private during her lifetime. Professor Al-Lamee stated, ‘In Catherine O’Hara’s case this was likely the underlying cause of her embolism.’ Other common risk factors include pregnancy, smoking, obesity, and recent surgery.

To mitigate the risk of pulmonary embolism, Professor Al-Lamee stresses the importance of lifestyle changes such as losing weight and quitting smoking. Crucially, extended periods of immobility, such as long plane journeys, significantly increase the chances of developing deep vein thrombosis in the leg, which can then travel to the lungs. Professor Al-Lamee advises, ‘This is why when on a long haul flight it is important to wear compression socks and make sure you go for regular walks as this reduces the risk.’