'My Apple Watch saved my life - when it detected my heart failure as I tried Couch to 5k'

Niamh Cassidy took up running in the summer of 2023, trying the Couch to 5k running plan to join her partner who ran marathons. Despite being an avid gym-goer, Niamh said she could not run more than 1km without feeling breathless.

The 25-year-old said she got notifications on her Apple watch alerting her of her high heart rate and went to hospital when her dad noticed how tired she got while running.

After wearing a heart monitor for a week, she was diagnosed with tachycardia, a condition causing the heart to beat faster than normal. But after experiencing chest pains, palpitations, and breathlessness even when brushing her teeth, she returned to hospital and had to be treated for mild heart failure.

Only two weeks after her shocking diagnosis, Niamh got pregnant with her first child, leaving her scared for her baby's life. Her condition meant she had to undergo an emergency C-section to give birth to her daughter Mable in April 2025 as doctors detected worrying heart rates for her and her baby.

The new mum credits her Apple watch for saving her baby's life too - though her ongoing heart condition means she can 'no longer do what an average 25-year-old can do'.

Niamh, from Manchester, said: "I genuinely really thank my Apple watch for a lot of things, I ignored it at first but I wish I had called the doctors when it gave me the first notification. If it wasn't for my Apple watch I never would have known anything was wrong."

Niamh's watch began giving her worrying alerts on her heart back in 2023 when she had a personal trainer but she didn't take much notice of it at first.

Niamh said: "There were a few times my apple watch would give me an alert and say my heart rate was too high, saying I had low cardiovascular fitness. I didn't really take notice of it and took up running.

"I was doing the Couch to 5k and the furthest I could run was 1k before feeling like I was going to collapse. I went for a run with my dad and my dad was 55 at the time. He said, 'alright, heart rate check' and we had only done a five-minute warm-up and my heart rate was already at 170.

"He spoke to the doctors on my behalf and they told me to go straight to A&E. They said I needed to do some tests. I was keeping track of my own heart rate with my Apple watch for a while whilst I was waiting for the monitors. I did find any form of cardio really tiring but I just thought that was just me being unfit and I was a little bit overweight. I never took it seriously."

Doctors said she had a high heart rate but reportedly put it down to tachycardia and said she could keep training.

Niamh said: "I started getting chest pains, palpitations, breathlessness, but everything was put down on tachycardia. It was every day, even running up the stairs, I found little things like brushing my teeth really hard. In November 2024, I got an appointment with the heart failure department and thought that was a bit weird.”

While being treated for mild heart failure, Niamh found out she was pregnant.

Despite having a relatively smooth pregnancy, Niamh was still out of breath 'all the time' and had her heart rate monitored.

In the end she needed an emergency C-section as her own heart rate went very high while her baby's dropped - leaving doctors worried. Niamh said she feared for her daughter's life and considers herself lucky to have known about her condition prior to her pregnancy. A few months after the birth of her daughter, Niamh was diagnosed with dilated cardiomyopathy, a condition that causes part of her heart to swell.

The intensive support practitioner said she feels frustrated as she cannot do what a normal 25-year-old can, or do activities like walking with other mums.

Niamh said: "I was scared for her more than I was scared for me. I was frustrated my heart was letting me down in that situation. I felt like I wasn't fit enough to give birth, I had hyped up myself that I was going to be fine. That's just not the way it went. It was upsetting. I was definitely lucky to know about my condition prior to this, the hospital had emailed my cardiologist.

"I came out of my newborn bubble and started getting out of the house more, and even getting off the floor I found gave me lots of palpitations. I was very concerned because now I have a little human relying on me. It's frustrating, especially now I have Mabel. There's things like a mum's group that go for walks and I can't join because I walk a lot slower and get out of breath. I find it quite embarrassing that I can't keep up.

"I can do a short distance. I can do it a bit longer at a very slow speed. I don't drink anymore, I'll have a very odd glass of wine but cut out all my drinking. I can't do what your average 25-year-old can do but there's things I can do and I focus on the things I can do."

WHAT IS HEART FAILURE? (Info from NHS)

Heart failure means that the heart is unable to pump blood around the body properly. It usually happens because the heart has become too weak or stiff.

WHAT IS DILATED CARDIOMYOPATHY? (Info from NHS)

Cardiomyopathy is a general term for diseases of the heart muscle, where the walls of the heart chambers have become stretched, thickened or stiff. This affects the heart's ability to pump blood around the body.