The vast majority of angina has an onset within 3-15 minutes, and this pain sensation tends to be dull and crushing rather than sharp. If the pain is very short-lived, less than 1 minute or a pinprick sensation for a few seconds, it is often not a symptom of angina. If the pain lasts longer than half an hour without clear relief, and improvement with medication is not obvious, it is important to be aware of whether it is no longer angina but an acute infarction. For the majority of patients it is around 3-15 minutes before an attack of angina really occurs. If the angina attack is more and more frequent, the duration is longer and longer, often suggests that there is a progression of coronary artery disease, which must be treated as soon as possible, to avoid angina pectoris develops into myocardial infarction.