In case angina pectoris is ignored, and the disease is allowed to progress, the blockage in coronary arteries/or in its branches may go on increasing. The end-result of such a severe blockage in coronary arteries/branches would be that the blood supply of a part of heart muscle (supplied by the respective branch of coronary artery) may suddenly stop completely leading to severe damage / injury / necrosis / death of the affected portion of the heart muscle. However, the patient may directly go into the stage of heart attack without undergoing the stage of angina pectoris.

There may be only sudden spasm/narrowing/constriction of a coronary artery or its branches, either of a normal vessel or already involved coronary artery as a result of atherosclerosis. If the spasm is momentary, the patient may get only angina, but if it is a prolonged one, blood supply of a portion of heart muscle will suffer adversely, leading to a heart attack.

As regards clinical manifestations in a heart attack, the patient suddenly gets very severe pain in the centre of the chest (retrostemal) which may radiate to the left upper arm. In some cases, the pain may radiate to the back of the chest or towards the neck/lower jaw. In atypical cases, the pain may only be present in any of these areas i.e. back of the chest or the neck, etc.

Unlike the pain in angina, the pain in a heart attack is not relieved by rest, or by the administration of quick-acting coronary dilator drugs like glyceryl trinitrate. It may last more than half an hour, and may be accompanied by profuse sweating. The pain, truly speaking, may be highly unbearable, the worst the patient has ever suffered/experienced and may be only relieved by a strong analgesic/pain-killer. The patient may even get breathlessness/syncope/vertigo. Some patients may quickly go into shock called cardiogenic shock which becomes a grave emergency, and the patient may die if proper aid is not given. However, a patient may die even instantaneously if the heart attack is very severe. Hence, after the immediate first aid he should be shifted to the hospital. Such patients are treated in an intensive care unit (ICU) of the hospital. The sooner the patient is given aid, the lesser will be the damage to the heart. For this reason, in some of the places, there are mobile cardiac care units. The van, duly-equipped, reaches the place of emergency in no time, and the patient receives proper treatment in the van itself on the way to hospital. If some fatal complications occur on the way, they are also tackled right in the van. Many lives can be saved with such timely treatment.

Hence, early diagnosis as well as treatment is important to save the life of a patient in a case of a heart attack. One must bear in mind the solitary important warning signal to detect cases of heart attack, in most of the cases, that whenever there is pain in chest/difficulty in breathing/syncope (transitory unconsciousness)/vertigo (dizziness), especially in middle age, the physician should be consulted for an immediate check-up. Further, cases of stable/unstable angina pectoris may precede a heart attack and thus should be considered a most important early warning signal.