A mobile phone alarm killed a 17-year-old girl who had an undiagnosed heart condition, her father said yesterday.

Kasia Ber died in bed at her parents home in Horden, Co Durham, on December 28 last year. 

Subsequent tests showed she was suffering the genetic disorder Long QT syndrome, which can be treated with beta blockers. 

Her 45-year-old father John said yesterday: "There are different varieties of it.  The one my daughter had was triggered by sudden noises, such as a mobile phone ringing and that is what happened to her. 

"The mobile phone went of and that's what we think brought the attack on." 

An inquest in Hartlepool on Thursday heard evidence from Kasia's boyfriend Scott Wheatley, saying the alarm went off at 7am. 

In written evidence, he said: "Kasia said my name and she was shaking slightly. 

"I held her to comfort her and then I realised she had stopped breathing." 

Coroner Malcolm Donnelly recorded a narrative verdict that the teenager died as a result of an undiagnosed genetic condition.  The cause of death was congenital fatal ventricular arrhythmia brought on by Long QT syndrome. 

Mr Ber, a shift supervisor, wanted the coroner to recommend that young people should be screened for heart defects. 

The family is raising money, and awareness, for the Cardiac Risk in the Young (CRY) charity, in memory of Kasia. 

"She was absolutely beautiful, so bubbly and full of fun," he said. 

She was perfectly fit and healthy, outwardly, but she was not screened. 

"We want to get young people screened." 

Kasia sought medical help for breathlessness in the days before she died and was diagnosed as having stress. 

Mr Ber's 42-year-old wife Diane also has the condition, but only found out after her daughter's death.  Their son Christopher, 15, has been tested and given the all-clear.