On Monday, Aug. 19th 2013 it was really hot in Fresno CA, 110 to be exact. I am 58yrs old, with a pacemaker, enlarged heart (right side). I was delivering mail from my vehicle. Trucks are aluminum & usually 15 degrees hotter inside than outside. I was drinking lots of water, also a cup of iced Sierra Mist. After eating half a sandwich w/chips I continued on my route. I started experiencing an increase in my pulse rate. My head felt like it wanted to explode, my right ear had pressure. I'm 5'4 & weigh about 196.I wasn't perspiring but still drinking lots of water. The urge to urinate more frequent than usual. I worked over 14hrs that day, 8am to 810pm. I went home exhausted. The next morning reported at 7am feeling tired as usual. Began to case mail but in 45minutes started to experience dizziness, like vertigo. I went to the doctor, my blood pressure was 150/ .Today its Wednesday head exploding feeling returning & still feel very tired. Could this be due to the heat & not treated my symptoms when they first started?