What is Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)?
An acute ST-elevation myocardial infarction (STEMI) is a medical emergency that involves damage or death of heart muscle tissue. This occurs due to a lack of blood supply to the heart. The 2018 clinical definition of a heart attack, also known as myocardial infarction (MI), requires confirmation of heart injury through abnormal heart-related biological markers. This is a complex condition involving reduced blood supply to the heart, changes in the heart’s electrical activity (as seen on an EKG), and chest pain.
What Causes Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)?
An ST-elevation myocardial infarction, or heart attack, happens when one or more of the arteries supplying blood to the heart get blocked. The blockage is usually due to rupture of plaque, erosion, fissuring, or dissection of these arteries, leading to a blockage-causing thrombus, also known as a blood clot. Risk factors for this type of heart attack include high levels of unhealthy lipids in your blood, diabetes, high blood pressure, smoking and a family history of coronary artery disease.
Heart attacks can be categorized from Type 1 to Type 5 based on the cause and development mechanisms. Type 1 heart attack is caused by a blockage due to a rupture of plaque in an artery. This type typically includes patients with ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation MI (NSTEMI).
Type 2 is the most common type of heart attack seen in medical settings. It’s caused by an imbalance between the demand of the heart muscle for oxygen and the supply of oxygen the blocked arteries can provide. This imbalance can be due to various factors such as a stable obstruction in the artery, quick heart rate, lack of oxygen, or stress. In some cases, the presence of a stable artery block is not necessary. Other potential causes of type 2 include spasms in the coronary artery, a blood clot in the artery, and spontaneous dissection or tear of the artery’s innermost layer.
Type 3 relate to cardiac arrests where the person does not survive long enough to show markers of a heart attack in their blood. Types 4 and 5 are associated with medical procedures trying to improve blood flow to the heart, such as Percutaneous Coronary Intervention (PCI) or Coronary Artery Bypass Grafting (CABG).
Risk Factors and Frequency for Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)
Every year, there are about 550,000 new cases of heart attacks, known as myocardial infarction (MI), and 200,000 repeat occurrences in the United States. In 2013, close to 117,000 people passed away from a heart attack in the U.S., with men making up 57% of these cases and women 43%. The average age for the first heart attack is around 65 for men and 72 for women. About 38% of patients who come to the hospital with symptoms of a heart attack have a specific type of this condition called an ST-elevation myocardial infarction.
- Each year in the U.S., there are approximately 550,000 new heart attack cases and 200,000 repeat cases.
- In 2013, nearly 117,000 U.S. people died from a heart attack. Of these, 57% were men and 43% were women.
- The average age for experiencing a first heart attack is usually 65 for men and 72 for women.
- About 38% of patients going to the hospital with heart attack symptoms have a specific form called ST-elevation myocardial infarction.
Signs and Symptoms of Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)
Before conducting an ECG (Electrocardiogram) and checking for troponins (proteins that indicate heart damage), a patient’s history and physical exam are the only initial clues to diagnosing a myocardial infarction, also known as a heart attack. During the early stages of evaluation, doctors typically focus on examining the patient physically and taking a brief health history. This usually involves asking about the nature of the patient’s pain, any related symptoms, whether they have any risk factors or a history of heart disease, and recent drug use.
Risk factors that can increase the chances of an ST-elevation myocardial infarction (a severe type of heart attack) include age, gender, family record of early-onset coronary artery disease, tobacco use, abnormal blood lipid levels (dyslipidemia), diabetes, high blood pressure, excess belly fat, a lack of physical activity, a diet low in fruits and vegetables, and psychosocial stress. Using cocaine can also lead to a heart attack, regardless of these other risk factors.
In addition, having known congenital (present from birth) abnormalities can also be a useful piece of information when diagnosing.
Testing for Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)
If a person suddenly experiences chest pain, the first steps a doctor will take is to perform an electrocardiogram (ECG) and a troponin blood test. The purpose of these tests is to identify any signs that suggest the person might be having a type of heart attack called ST-elevation myocardial infarction (STEMI).
The American College of Cardiology and other major heart health organizations have defined certain criteria on the ECG readout that indicate a STEMI. These criteria involve measurements of small changes in the ECG pattern, specifically in the up-and-down “ST-segment” of the ECG readout. If there are new increases in the ST-segment in specific patterns across two leads (or connected points), it can suggest a STEMI. The exact amount of increase that is considered significant depends on the patient’s age, sex, and the specific ECG lead.
For people who already have a certain type of heart conduction issue called a left bundle branch block, additional ECG criteria, known as Sgarbossa’s criteria, are used. These additional criteria look at other patterns of the ST-segment in relation to other parts of the ECG readout, to help determine if a heart attack is happening.
Treatment Options for Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)
When a diagnosis of acute heart attack (formally known as ST-elevation myocardial infarction) is made, it’s important to start by setting up an intravenous line and beginning heart monitoring. If the patient has low oxygen levels or is at risk of having low oxygen levels, oxygen therapy is recommended. However, recent studies suggest that oxygen therapy might not benefit patients who have normal oxygen levels.
If the patient is in a hospital that is equipped to do so, a procedure called percutaneous coronary intervention (PCI) should be performed within 90 minutes of the patient arriving. In cases where the patient needs to be transferred to a suitable hospital, this procedure should take place within 120 minutes.
Suppose the medical team can’t carry out the PCI procedure within the first 120 minutes. In that case, a different treatment called fibrinolytic therapy should be started within 30 minutes of the patient getting to the hospital. This is to ensure other conditions that can show the same symptoms as a heart attack, such as a torn aorta or a lung blood clot, are not the actual cause of the symptoms.
All heart attack patients should quickly be put on a course of medication that includes a beta blocker, high intensity statin, aspirin, and a P2Y12 inhibitor, with only a few exceptions. Nitroglycerin can help reduce chest pain, but it should be avoided if the patient has taken certain types of medication in the last 24 hours or if their heart attack affected the right side of their heart. Morphine, which can be used for further pain relief, should only be used conservatively as it may potentially have negative effects.
The choice of P2Y inhibiting antiplatelet medication is based on whether the patient underwent PCI or fibrinolytic therapy. Ticagrelor and prasugrel are generally preferred for patients who underwent PCI, whereas clopidogrel is typically used for patients receiving fibrinolytic therapy. However, medical professionals should also take note of any relative contraindications to P2Y12 inhibitors. For instance, prasugrel is not recommended for patients with a history of transient ischemic attack and stroke.
Alongside these medications, anticoagulation treatment should also be started with drugs such as unfractionated heparin, low-molecular-weight heparin, bivalirudin, or fondaparinux.
What else can Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes) be?
Other health issues that can cause a spike in the ST-segment (a part of the heart’s electrical activity visible on an EKG) can include:
- Myocarditis (Inflammation and damage to the heart muscle)
- Pericarditis (Inflammation of the tissue surrounding the heart)
- Stress cardiomyopathy, also known as Takotsubo (A condition where heart muscles weaken due to severe stress)
- Benign Early Repolarization (A condition often seen in younger people and athletes where the heart beats in a certain abnormal pattern but isn’t usually dangerous)
- Acute vasospasm (A sudden tightening of the muscles within the arteries of the heart)
- Spontaneous coronary artery dissection (A rare condition where a tear occurs in the heart’s blood vessels)
- Left bundle branch block (A condition where the heart’s electrical impulses are delayed or blocked)
- Channelopathies (Disorders due to flaws in the proteins that form the body’s channels for ions)
- Electrolyte abnormalities (This occurs when mineral levels in the body are too high or too low)
What to expect with Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)
The chance of dying within 30 days for patients suffering from a specific type of heart attack, known as “ST-elevation myocardial infarction,” ranges from 2.5% to 10%. The TIMI risk score is often used to predict this 30-day mortality rate. This system assigns different points based on several factors:
- being over 75 years old (3 points) or between 64 to 74 years old (2 points),
- having diabetes, hypertension, or having had chest pain related to the heart in the past (1 point),
- having a blood pressure lower than 100 mm Hg (3 points),
- having a heart rate faster than 100 beats per minute (2 points),
- falling under the Killip class II to IV, which are classifications of heart failure (2 points),
- weighing less than 150 lbs (1 point).
The higher the score, the higher the risk of dying within the first month after the heart attack.
Possible Complications When Diagnosed with Acute ST-Elevation Myocardial Infarction (Heart Attack with ECG Changes)
There are three severe complications of a heart attack that could be life-threatening. These are the rupture of the ventricular free wall, the rupture of the interventricular septum, and sudden severe mitral regurgitation.
The ventricular free wall rupture usually occurs within five days in half the cases and within two weeks in 90% of the cases. This usually results in more than 80% of patients passing away.
The rupture of the interventricular septum is reported approximately half as much as the ventricular wall rupture and usually occurs three to five days post-attack. This also results in over 70% mortality. However, timely surgery can reduce the death rate in both conditions.
Sudden mitral regurgitation after a heart attack is usually caused by the displacement, stretching, or rupture of the chordae or papillary muscles in the heart due to lack of oxygen. Severe mitral regurgitation in heart attacks where the ST segment of the ECG is elevated is usually associated with a survival rate of 24% after 30 days.
The major life-threatening complications of a heart attack include:
- Ventricular free wall rupture
- Interventricular septum rupture
- Acute mitral regurgitation