What Causes Chest Pain Followed By Blurred Vision And Dizziness?

I have a 12 yr old son. He s always been active. In April of last year, while running, he began to have shortness of breathe, blurred vision, difficulty standing and his face became flush. We sat him down and he slowly recovered after about 10 min. We took him to his physician the next day. They did blood work and chest x-rays. All came back clear. He saw a cardiologist and EKG and sono was done. All clear. Dr stated it was most likely due to dehydration. The following week while running he experienced the same issue but more severe to the point he past out and was taken by ambulance to the hospital. EKG, blood work and CT scan done. All clear again. Back to pediatrician. Saw cardiologist for a stress test and a halter monitor for 1 day. Pediatrician advised it could be asthma, but aside from that all clear. Visited a Neurologist and EEG was done. All clear. Pediatrician decided to put him on an inhaler. No issues until September. While running he began to experience chest pain. Took a min or two and he recovered with no major symptoms. A week later, while running, he began having sharp chest pains followed by blurred vision, numbness in arms and dizziness. Back to ER. All tests came up clear. Went to a pulmonologist and he stated there are no signs of asthma. Back to cardiologist and he stated it was most likely a case of reflex syncope. Had not had any more symptoms while running after that until about 3 weeks ago and then again the following week. Both occurred while he was running. Chest pain, followed by dizziness, limbs are cold and face is flush. Each episode has lasted about 5-10 min and then he fully recovers. Every time any issues have occurred have been while he s running. Mostly during a light to med jog. And doesn t occur every time he runs. He s had instances where he sprints 20-30 yds without issue. But times when he s jogging a few reps of about 20 ft and the symptoms begin.