Director, Cardiovascular Division, NHO Osaka National Hospital, Osaka, Japan
Many people still die from acute Myocardial Infarction (MI) in this era of optimal medical therapy. Since majority of death occurs before hospitalisation, prevention strategy is important. Half of acute MI patients are known to experience pre-infarction angina in Japan, and treating them at this stage can save their lives.
Acute Myocardial Infarction (MI) is still a worldwide leading cause of death even in this era of optimal medical therapy including the use of statins. However, the mechanism for its onset has not been adequately clarified. Furthermore, the in-hospital mortality of those patients has decreased significantly according to the advance in the in-hospital treatment strategies including primary coronary intervention. Therefore, majority of death from acute MI these days occurs before hospitalisation, and thus a strategy to prevent MI onset should be improved.
Mechanism of acute MI onset
Formation of vulnerable coronary plaques is known to be accelerated by many risk factors such as diabetes mellitus, hypercholesterolemia, and smoking. The rupture of those vulnerable plaques is also known to induce thrombus formation in the coronary artery. However, since many silent plaque ruptures that did not cause acute MI and healed spontaneously have been detected by several clinical studies using intracoronary imaging, it is evident that the rupture of vulnerable plaque does not always cause MI and that majority of ruptured plaques may heal without causing MI. Among the ruptured plaques that cause acute MI, about half of them take <24hrs from plaque rupture to acute MI onset; however, the rest half take days to weeks to the onset of acute MI according to a clinical study that examined the age of thrombus at acute MI culprit by pathological method. During the enlargement process of intracoronary thrombus to the final step of coronary artery occlusion, the sub-occlusion of coronary artery may induce mild chest pain of short duration, i.e., unstable angina or pre-infarction angina. Therefore, this symptom of unstable angina can be a ‘preceding symptom of MI’.
Preceding symptom of MI
According to some registry of acute MI patients in Japan, about half of acute MI patients had this preceding symptom of MI, although they did not go to hospital or clinic at that time because they did not take the symptom serious or they did not think the symptom came from heart. If they had appropriate diagnosis and treatment of unstable angina at that time, they should not have suffered acute MI.
Prevention of acute MI by public education
Since about half of acute MI patients have pre-infarction angina in Japan, incidence of acute MI can be reduced into half by treating those patients with pre-infarction angina appropriately. To achieve this goal, Japanese Circulation Association started ‘STOP MI Campaign’ to let people know the fact that 1) acute MI is still highly lethal, 2) death occurs mainly before hospitalisation, and 3) MI can be prevented by treating appropriately at the time of ‘preceding symptom’. The preceding symptom of MI is a chest pain, chest oppression, chest discomfort, or heartburn that is a mild symptom of short duration within 10 minutes. The symptom may be repeated and may be worsened by effort. On the other hand, a symptom of too short duration within a minute or that induced by oppression or deep breathing may have a low probability of being preceding symptom of MI.
Public education is not easy
The web-site of ‘STOP MI Campaign’ was made. A mascot character Mie-chan (cat) was also made to make the campaign familiar to people. Some short movies to tell about acute MI and preceding symptom were made. Some model cities are now intensively performing the campaign in the city using posters, public lectures, newspaper, TV program and so on. Recently, mass communication such as TV and radio does not appear an effective tool to perform public education. Sending message through Social Networking Service may be an effective option to perform campaign. Education at high school or junior high school may also be an effective option, since the patients, who themselves do not take the symptom serious, often come to hospital being encouraged by their son or daughter.
Another difficulty is diagnosis
Since the preceding symptom of MI is relatively mild that people do not take it so serious. This is often the same for general practitioners. Electrocardiogram may be normal when they come to hospital, serum troponin may not be elevated, and echocardiogram may not show left ventricular asynergy, although coronary CT or angiography can detect the disease correctly. In my experience, a patient came to my outpatient clinic appealing a repeated mild chest discomfort of short duration. Coronary CT within a week and next visit to my clinic within 2 weeks were scheduled for him; however, he suffered acute MI within a few days.
Goal of STOP MI Campaign
The goal of campaign can be evaluated by the frequency of pre-infarction angina among the hospitalised acute MI patients. If it becomes 0 per cent, the goal is achieved. If all patients with unstable angina are appropriately and timely treated and never suffer acute MI, the goal of campaign is achieved. Nationwide incidence of acute MI would become half by this achievement.
Acute MI is still highly lethal and majority of death occurs before hospitalisation. However, many acute MI patients experience preceding symptom of MI, i.e., unstable angina. The preceding symptom of MI is a mild symptom of chest pain, chest oppression, chest discomfort, or heartburn of short duration that has never been experienced previously and is often repeated and worsens. Please do not miss the symptom and visit cardiologist immediately to save your life!