Since they are American, I understand that you have the best feeling with US doctors. That said, I would highly recommend to see some cardiologist in South Africa or Western Europe (UK, Ireland, France, Belgium, Netherlands, Germany, Austria, Switzerland, Denmark, Sweden, Norway, Finland, ...). They know their business as well and they are quicker and cheaper to reach. I would assume that each one of them is fluently enough in English as well. If it is that urgent, then I would take the next real good doctor - regardless where he is.