A boy with a rare cardiac condition has been banned from laughing in case his chuckles trigger a fatal heart attack. Bradley Burhouse has a dangerously high heart rate and is on doctors' orders to keep calm to ensure his ticker doesn't beat any faster. The brave seven-year-old has stopped exercising and his mother has been told to make sure he doesn't laugh too hard in case his heart develops a severely abnormal heart rhythm, which can cause sudden death. He's not even allowed to play outside with his brothers Jack, 14, and Dalton, 12, and sister Maddison, 6. Bradley was diagnosed with ventricular tachycardia after he collapsed earlier this year. The rare condition in children means his resting heart rate is 120 to 200 beats per minute - at least twice as fast as the average person. Ventricular tachycardia is caused by faulty electrical signals in the lower heart chambers known as ventricles. These override the heart's normal rate and rhythm causing the ventricles to contract faster than normal. This causes the heart to pump out blood more quickly and the ventricles may not have enough time to fill up properly with blood. It can cause chest pain, dizziness and fainting fits. It can be corrected by a course of tablets or an operation but has also proved to be fatal in some child cases. If the condition worsens the heart can go into ventricular fibrillation, where the brain and muscles stop receiving blood from the heart. Bradley, from Huddersfield, West Yorks, will have a preliminary examination in the next few weeks before doctors decide what action to take. Mother Toni Burhouse, 34, said Bradley collapsed and was rushed to hospital in May this year after playing and joking around with his brother. She said: 'Now we have to be so careful that he doesn't get over excited. Even if he's laughing too hard we have to calm him down and make sure he doesn't get too worked up. 'I remember that he used to run up to me and say 'Mum my heart feels like it's going to jump out of my chest'. 'I'd always dismiss it and tell him it was only natural because he'd been running around. 'Then one day he was playing with his brother Dalton out in the field next to the house when he fell down. 'Dalton thought he had fallen and smacked his head so he helped him up and they came into the kitchen together. 'By this time Bradley was screaming in pain and then he was violently sick. My husband Simon rushed him to A&E and initially they thought he had a heart murmur. 'It was only when he had further checks that they discovered he had ventricular tachycardia.'