What is Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)?
Acute coronary syndrome (ACS) is a serious heart condition that can be broken down into three categories: ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina. ACS can lead to severe health issues and even death, so it’s critical to diagnose and treat it quickly. This article won’t cover STEMI; instead, we’ll focus on NSTEMI and unstable angina. These two are quite similar, with the main difference being that NSTEMI involves positive cardiac biomarkers, which indicate heart muscle damage. Let’s take a closer look at how NSTEMI presents itself, how it’s diagnosed, and how to manage it.
What Causes Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)?
Non-ST Segment Elevation Myocardial Infarction (NSTEMI) can occur due to a variety of reasons. These can range from lifestyle factors like tobacco use and lack of exercise, to health conditions such as high blood pressure, high cholesterol levels, and diabetes. Obesity and having a familial history of heart disease can also contribute to the onset of NSTEMI.
Risk Factors and Frequency for Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
The average age at which people in the United States first experience Acute Coronary Syndrome (ACS) is 68 years. More men than women have this condition, with a ratio of 3:2. Every year in the US, there are over 780,000 cases of ACS. Of these, about 70% are diagnosed as having Non-ST Elevation Myocardial Infarction (NSTEMI), a type of heart attack.
Signs and Symptoms of Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
NSTEMI, or non-ST-elevation myocardial infarction, usually presents itself with a pain in the chest that feels like pressure. It typically happens during rest or light activity and lasts for more than 10 minutes. The pain might spread to the arms, neck, or jaw. Some people might also experience shortness of breath, nausea, vomiting, fainting, fatigue, or excessive sweating. It’s not uncommon for people to also just feel an unexplained shortness of breath, with or without other symptoms. Factors that might put some people at higher risk of this condition include being male, being older, having a family history of heart disease, having diabetes, having a personal history of heart disease, and having kidney problems.
Some people might experience atypical symptoms—examples include stabbing or chest pain when breathing, pain in the upper belly or abdomen, indigestion, and shortness of breath. While most people with this condition will present typical symptoms, certain groups are more likely to exhibit atypical presentations, including people over the age of 75, women, and those with diabetes, kidney problems, or dementia.
The physical examination for ACS and NSTEMI typically doesn’t yield specific results. Back pain might suggest an aortic dissection, and pericardial friction rub could indicate pericarditis, both as alternative causes for a patient’s chest pain. However, there is no definitive physical exam finding that can confirm ACS as the most likely diagnosis. If signs of heart failure are present, there might be an increased concern for ACS, but these signs aren’t specific to ACS either.
Testing for Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
If you come to the hospital with chest pain and there’s a concern you might have Acute coronary syndrome (ACS), a condition where the blood supply to the heart is blocked, some specific tests can help the doctors figure out what’s going on. They’ll initially look at your medical history, conduct a physical examination, and perform an electrocardiogram (ECG) test as soon as possible. The ECG measures the electrical activity of your heart and can help identify any unusual patterns.
However, just because an ECG appears normal, this doesn’t mean you don’t have ACS or Non-ST-Elevation myocardial infarction (NSTEMI), which is a type of heart attack. Sometimes, the ECG may show signs that point towards a more serious type of heart attack called STEMI. Any changes in the ECG, such as ST elevation, ST depression or new T wave inversions, warrant closer observation. The ECG test might need to be repeated at particular periods or if your symptoms come back.
Another crucial part of the evaluation is a biomarker test called cardiac troponin. It’s preferred because it’s incredibly specific and sensitive, meaning it can detect heart damage early on in the disease. These troponin levels can rise in the first 2 to 4 hours after symptoms start, especially with new high sensitivity methods of testing. The larger the heart attack or ‘infarct,’ the higher these levels will be. If you’re truly having heart issues, by about 6 hours, this test will typically show elevation and can effectively identify the problem. If the levels haven’t risen by then, most likely, there isn’t a heart attack.
Several risk calculators and scores help determine the likelihood of having ACS. They need to be applied carefully and in conjunction with the doctor’s judgment as none can confirm the diagnosis outright. These include the TIMI risk score, GRACE risk score, Sanchis score, Vancouver rule, HEART score, HEARTS3 score, and Hess prediction rule. The HEART score has become popular in the Emergency Department for assessing patients.
Finally, a diagnosis of NSTEMI is given to patients who show symptoms of ACS, have elevated troponin levels without the typical ECG changes for a STEMI. Unstable angina and NSTEMI are differentiated mainly by whether there has been a noticeable increase in troponin levels.
Treatment Options for Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
When a patient is first suspected of having Acute Coronary Syndrome (ACS), it’s important to take steps to reduce the risk of heart damage and prevent death. Oxygen, aspirin, and nitrates may be given before the condition is confirmed.
However, giving oxygen to all patients was once common practice, but new findings indicate that this could do more harm than good in patients who do not generally need extra oxygen. Nowadays, oxygen is administered to patients only if they have an oxygen level less than 90%, they are finding it hard to breathe, or they exhibit other signs of not having enough oxygen (hypoxemia).
When it comes to aspirin, unless a patient has a reason not to take it, every patient suspected of having ACS should be given a chewable, non-coated 324 mg tablet. If a patient can’t take aspirin, an alternative medication is prasugrel (60 mg, taken orally).
If a patient is still experiencing symptoms, nitroglycerin (0.4 mg under the tongue) can be given every 5 minutes up to three times, or until the pain subsides. However, certain circumstances may prevent the use of nitroglycerin, such as if the patient has recently taken a specific type of drug (phosphodiesterase inhibitors) or if they have low blood pressure. Nitroglycerin must be used very cautiously in patients who may have an infarct on the right side of their heart. If a patient keeps showing signs of heart failure or high blood pressure, then continuous nitroglycerin administered directly into the vein could be considered.
Sometimes, patients display symptoms suggestive of ACS, but initial tests (like ECGs or troponin tests) don’t show any evidence of the condition. In such cases, these patients may be closely monitored with repeated ECGs and troponin tests every 3 to 6 hours. Additionally, they may be asked to perform certain exercises (like a treadmill stress test) or have imaging of the heart performed. If ACS is ruled out, patients at low risk are often allowed to leave the hospital but advised to continue testing in an outpatient setting.
If a type of heart attack called NSTEMI is diagnosed or strongly suspected, an anti-clotting medicine should be given, although the specific regimen can vary and should be supervised by a heart specialist. If a minimally invasive procedure (percutaneous intervention) is being considered, this could impact the choice of anti-clotting treatment. The use of different drugs may be considered, including heparin, enoxaparin, bivalirudin, fondaparinux, and combinations of antiplatelet drugs. However, medicine to break down blood clots (fibrinolytic therapies) shouldn’t be used for NSTEMI.
If a patient is diagnosed with NSTEMI, they should be admitted to a unit specialized in heart care for further management. Within 24 hours of diagnosis, a medication called a Beta-blocker should be started unless the patient has a reason not to take it, like heart failure, low blood pressure, heart conduction problems, or a reactive airway disease. ACE Inhibitors are advisable if a patient has a poor heart pump function (an ejection fraction less than 40%), high blood pressure, diabetes, or chronic kidney disease. High-dose statins are given for managing cholesterol.
The need for further testing and treatment options is determined on a case-by-case basis. This could include invasive strategies such as diagnostic angiography and intervention, or more conservative approaches. The specific strategy chosen often depends on the individual patient and the hospital’s protocols.
What else can Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes) be?
There are several medical conditions that can cause chest pain. These conditions can also lead to changes in your electrocardiogram (ECG) results and an increase in a protein called troponin in your blood. These conditions may include:
- Myocarditis (inflammation of your heart muscle)
- Pericarditis (inflammation of the sac that surrounds your heart)
- Pulmonary embolism (a blood clot in your lungs)
- Left ventricular aneurysm (a weak spot in the wall of your heart’s main pumping chamber)
- Prinzmetal angina (a type of chest pain caused by spasms in your heart’s arteries)
- Anxiety disorders
- Aortic stenosis (narrowing of the heart valve)
- Hypertensive emergency (a severe increase in blood pressure that can lead to a stroke)
What to expect with Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
Patients who come to the hospital with NSTEMI, a type of heart attack, typically have a better survival rate after six months compared to those diagnosed with unstable angina, a condition that could lead to a heart attack. However, this rate can change based on certain factors. These include how much the heart disease marker called troponin has increased, as well as other health issues the patient may have. Such health issues can include the seriousness of diabetes, whether they have peripheral vascular disease (a condition that affects blood circulation), kidney issues, or dementia.
Possible Complications When Diagnosed with Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
NSTEMI, a type of heart attack, can cause complications due to the disease’s impact on the entire body, rather than due to specific structural issues in the heart, seen in another kind of heart attack called STEMI. A weakened heart muscle that doesn’t contract properly might be noticed, but it’s less likely to see left ventricle bulging pockets (aneurysms) or malfunctioning heart valve muscles (papillary muscle dysfunction). Serious cases might suffer from fluid accumulation in the lungs because the heart is not pumping blood efficiently. Poor blood flow can also lead to other issues like kidney problems.
Common Complications of NSTEMI:
- Weakened heart muscle that doesn’t contract properly
- Less likely occurrence of left ventricle bulging pockets (aneurysms)
- Rare malfunctioning heart valve muscles (papillary muscle dysfunction)
- Fluid accumulation in the lungs in severe cases
- Other issues due to poor blood flow, like kidney problems
Preventing Non–ST-Segment Elevation Myocardial Infarction (Heart Attack without ECG Changes)
Patients who have experienced a non-ST elevation myocardial infarction or NSTEMI need detailed advice on sticking to their medications and changing their lifestyle to prevent future such medical episodes and improve their overall health and life expectancy. They must quit smoking. it is also strongly recommended that they receive proper counseling from their healthcare provider to help them quit smoking.
