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An Apple smartwatch application helped save the life of a US man who was later diagnosed with a life-threatening blood clot by warning him about a rise in heart rate.

James Green, a 28-year-old podcaster and former MTV employee living in New York, first described his ordeal on Twitter, saying that a health-monitoring application called "HeartWatch" alerted him to the fact his heart rate had spiked significantly.

He tweeted: "Never thought a stupid lil wrist computer I bought 2 years ago would save my life. Saw my rate go up, ended up being a pulmonary embolism."

In a second update he added: "Shout out to @HeartWatchApp, y'all made a helluva thing."

The application measures and captures personal health data via the smartwatch's sensors. It lets users keep a close eye on their daily heart rates and live pulse.

In this case it helped to predict a pulmonary embolism – a blocked blood vessel in the lungs.

Green, who said he had a pulmonary embolism in the past, told The Telegraph that his doctor found it "would have been fatal" if he didn't find the issue in time.

He said: "I got an alert from HeartWatch that my heart rate was continually above my resting heart rate of 54, even when I was just sitting at my desk.

"That, along with other symptoms I was having, was enough data I needed to act on it, and realise it wasn't a panic attack, that it was something more."

His doctors performed the necessary scans and he was put on a blood thinner.

"It was the data I needed to prove this wasn't just a panic attack," he told The Telegraph. "It helped me get the ball rolling." His story resonated with many commenters on Twitter.

"Incredibly glad that you're ok and we're able to catch it," one commenter wrote. Another tweeted: "Thanks for sharing your story. I'm happy that you are back at home."

The official Twitter profile for the HeartWatch app wrote to Green after he tagged it in one update. It responded: "Thanks! Also wow! This is so fantastic that you are ok. Humbled to have played a part. Wishing you a rapid recovery [and] best of future health."

The creator of the platform, 50-year-old David Walsh, said it was "truly heartwarming" to learn that his iOS application had helped to save lives.

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