There are an estimated 5 million emergency department visits each year in the United States for chest pain. Annually, greater than 800,000 people experience an acute MI; 27% die, and most do so before reaching the hospital. With percutaneous coronary intervention (PCI) and stenting, antithrombotic pharmacological therapy, and use of adjunctive medical treatment, the in-hospital mortality of STEMI has reached a low of 7%. This number in the 1970’s approached 30%. There has been a considerable decline in mortality with newer methods, procedures, medications, and protocol changes that have been evidence based modification.
The mechanics of a myocardial infarction:
An AMI occurs when there is an abrupt reduction in myocardial blood flow usually by plaque rupture within a coronary artery which exposes the blood to thrombogenic/clot forming lipids and leads to a violent cascade of events resulting in the activation of platelet and clotting factors. The coronary plaques that are most prone to rupture are those with a rich lipid core and thin fibrous cap. Other rare causes of MI include coronary artery embolism from a valvular vegetation or intracardiac thrombi, cocaine use, coronary artery dissection, hypotension, and anemia.
Risk Factors for an AMI:
Risk factors for an MI fall into three general categories: nonmodifiable, modifiable. Nonmodifiable risk factors include age, sex, and family history. Modifiable risk factors include smoking, alcohol intake, physical inactivity, poor diet, hypertension, type 2 diabetes, dyslipidemias, and the metabolic syndrome. Other risk factors such as C-reactive protein (CRP), fibrinogen, coronary artery calcification (CAC), homocysteine, lipoprotein(a), and small, dense low-density lipoprotein (LDL). Landmark studies have been conducted such as The Framingham Heart Study which led to the development of a coronary risk estimate using the major risk factors to estimate the 10-year cardiovascular risk. Primary prevention of an acute MI is aimed at reducing the modifiable risk factors. This is typically accomplished with regular doctors’ visits, development of a structured healthcare routine with screening of BP, cholesterol, and regular activity.
The presenting symptoms are usually described as a heavy, squeezing, tightness, crushing, and sometimes stabbing or burning pain. In some Asian cultures, the symptoms may manifest as trouble swallowing or a choking sensation. Referred pain can be seen epigastrum, shoulders, arms, back (interscapular region), lower jaw, and neck. Radiation to both arms is a stronger predictor of acute MI. There is a large number of patients that either have a blunted pain response or no pain at all. About 20% of patients (diabetic, elderly, postoperative, or female) do not have chest pain. AMI patients should always be educated to remember their presenting symptoms and be able to recognize them if they should recur and alert a caregiver or healthcare provider.paragraph here.
- Manish Bansal