Someone else may have a different opinion on this, but personally I don't think that an EKG and Echo scan are always enough to establish a heart problem. I believe that I had the very same thing happen to me three years ago. It was three months after a triple bypass and walking home from my local shops. I was suddenly gasping for air and fell to my knees. It also lasted just a few minutes and I felt much better again. Now, an angiogram revealed that my bypass vessels had completely closed up but collateral vessels had opened to compensate, forming a new natural bypass. My echo and EKG looked normal, blood tests were normal but an angiogram revealed a sorry state of a left coronary artery. So when people feel something like sudden shortness of breath and chest pains, it doesn't mean nothing has gone wrong simply because a few simple tests say so. They should take the matter seriously and determine the exact cause. A Carotid artery needs to be pretty blocked to notice any symptoms, there is one in either side of the neck and routes to the brain are numerous. If Carotid arteries are giving problems, the symptoms are usually much different to those described, usually passing out or lack of motor control.
I have to agree with Ed on this one. The symptoms he is describing are indusive of heart disease and the angiogram is a better look at the arteries from the inside. With carotid arteries becoming blocked there is more dizziness, visual disturbances and confusion. Like the symptoms of a stroke. Is there any particular reason the doctors are treating this as Lymes Disease?