What is Lateral Wall Myocardial Infarction (Heart Attack)?
In August 2018, leading global heart health organizations from Europe, the United States, and around the world came together to release a new definition of what constitutes a heart attack, also known as Myocardial Infarction (MI). According to this unified definition, detecting whether a heart attack has occurred involves looking for changes in a specific heart protein called cardiac Troponin (cTn). This protein will rise or fall if there’s a heart attack, and at least one measurement must be above a certain level. Additionally, at least one of the following signs must be present:
1. Heart attack symptoms
2. New signs of poor blood flow to the heart on an EKG
3. Certain EKG wave patterns that suggest damage
4. New motion abnormality or lost function in a section of the heart seen in an imaging test
5. Finding a clot in the heart vessels only during a special x-ray test.
Heart attacks can be further grouped based on the EKG findings and where the poor blood flow is located. The left main pumping chamber wall gets its blood supply from the main front artery (LAD) and left side branch artery (LCx). The left pumping chamber wall and back wall together make the free-wall, a common site for rupture after a heart attack. Rarely, there can be a heart attack that only affects the side wall of the pumping chamber, usually as part of a heart attack that covers many areas, such as front-sideways, back-sideways, and bottom-sideways. Blockage of a branch of the LCx or a diagonal artery branch can cause a heart attack only involving the side of the heart.
What Causes Lateral Wall Myocardial Infarction (Heart Attack)?
Isolated LMI, like other forms of acute heart attacks, is typically caused by the sudden rupture of fatty deposits in the heart vessels. This rupture leads to the formation of a blood clot in the LCx or one of its branches, blocking blood flow and causing a heart attack. It’s common for LAD, another blood vessel, to be involved, causing a heart attack in the front and side area of the heart.
People who have had certain stents implanted and don’t take their medication properly can develop a narrowing of the stents, leading to a heart attack. There are also rare instances where patients have a heart attack despite their coronary arteries not being blocked, a condition known as MINOCA. The occurrence of MINOCA is estimated to be around 6% according to a 2015 study.
There are several causes for MINOCA including:
- Spasms in the coronary artery
- Spontaneous tears in the coronary artery, also known as SCAD
- Coronary artery embolism (blockade of a coronary artery by foreign substances or blood clots), which can be caused by conditions like atrial myxoma, irregular heartbeats, valvular heart infections, rheumatic valve disease, and mitral stenosis
- Autoimmune conditions such as Takayasu arteritis
- Myocardial bridging, where a part of a coronary artery dips into and underneath the heart muscle and then comes back out again
Risk Factors and Frequency for Lateral Wall Myocardial Infarction (Heart Attack)
Recent updates show a decrease in the occurrence of ST-elevation myocardial infarction (STEMI), a specific type of heart attack, and an increase in non-ST-elevated heart attacks (NSTEMI). It’s been noted that between 25% and 40% of heart attack patients have this STEMI type, and out of those, 23% have diabetes. Research also shows that, of patients suffering from STEMI, 13.4% experience a left-side heart attack.
People with certain risk factors are more likely to have a left-side heart attack. These factors include:
- Age
- Family history
- Obesity
- Smoking
- High blood pressure (hypertension)
- Unhealthy cholesterol levels (dyslipidemia)
- Diabetes
- Alcohol use
Signs and Symptoms of Lateral Wall Myocardial Infarction (Heart Attack)
Heart attacks, also known as myocardial infarctions (MIs), usually cause similar symptoms regardless of where they occur in the heart. The most common symptoms include chest pain on the left side that can spread to the arm or neck, trouble breathing, feeling nauseous or vomiting, a racing heartbeat, breaking out in a cold sweat, and feeling tired. Some people who have had heart attacks before might recognize these symptoms and get medical help faster. However, some heart attacks, known as silent MIs, happen without causing any symptoms. In fact, up to 23% of heart attacks could be silent.
If a healthcare professional thinks a patient might be experiencing a heart attack, they’ll perform a detailed examination of the patient’s history and symptoms. Details about the chest pain, like when it started, what makes it worse or better, and where the pain is felt, can help make a diagnosis. The doctor may also look for indications of high cholesterol levels, such as visible fatty deposits on the skin, known as xanthoma, and yellow patches on the eyelids, known as xanthelasma.
During the physical examination, the doctor may also notice signs like a patient breaking out in a cold sweat, abnormal heart sounds, heart murmurs or swelling in the neck veins, indicating an increased risk of a heart attack.
Testing for Lateral Wall Myocardial Infarction (Heart Attack)
If you’re suspected of having a sudden blockage in a heart artery, the medical term for which is acute LMI, doctors will quickly run two types of tests. One is an electrocardiogram (ECG), which measures the electrical activity in your heart, and the other is a test for a protein called troponin that your heart releases when it’s injured.
The ECG can help doctors identify what’s happening in your heart by showing distinct patterns. Some of the patterns doctors might see include:
* ST-Elevated LMI: Which shows an increase in ST measurement in certain leads of an ECG, along with a decrease in other leads.
* High lateral STEMI: This pattern is often caused by a blockage in a specific artery of the heart and can result in changes in various leads.
* Old LMI: This shows deep and broad Q waves in particular ECG leads.
* Inferolateral STEMI or Anterolateral STEMI: These patterns are usually indicative of blockages in different arteries of the heart.
If your troponin levels are normal and your ECG doesn’t provide a clear diagnosis, doctors might use an echocardiogram next. This is an ultrasound of your heart that can help check for damage by looking at its movements. Although this test is highly sensitive, it doesn’t always correctly identify a blockage.
If you get a normal echocardiogram result but your doctor still thinks there’s a fair chance you could have a heart blockage, they might recommend a stress test. This measures how your heart responds to exertion. However, the most definitive test for diagnosing a heart artery blockage is a coronary angiogram, which involves using dye and special x-rays to show the insides of your coronary arteries.
Treatment Options for Lateral Wall Myocardial Infarction (Heart Attack)
For patients who have a type of heart attack known as left main coronary artery infarction (LMI) that presents as ST-segment elevation myocardial infarction (STEMI), immediate treatment is crucial. Studies have shown that quickly restoring blood flow in the heart tends to produce better patient outcomes. The preferred treatment procedure is percutaneous intervention (PCI), a minimally invasive procedure to open blocked coronary arteries. It has proven to be more effective than thrombolytic therapy, a treatment that dissolves blood clots.
The American College of Cardiology and the American Heart Association recommend that the time from a patient’s arrival at the hospital to receiving PCI should ideally be under 90 minutes at a facility equipped to perform the procedure, and less than 120 minutes at a facility that doesn’t have PCI capabilities.
The treatment protocol includes antiplatelet therapy, which works to prevent blood clots from forming. This therapy includes the use of aspirin, coupled with either a P2Y12 inhibitor (such as Clopidogrel, Ticagrelor, Prasugrel) or a Glycoprotein IIb/IIIa inhibitor, both before and after PCI. Additional medications like beta-blockers (Metoprolol, Carvedolol, Bisoprolol) and high-intensity statins (like Rosuvastatin) have also been found to help decrease the risk of death in these cases.
If a patient goes into shock or experiences a heart valve rupture following the heart attack, they may require a mechanical support device like an intra-aortic balloon pump (IABP) after the PCI procedure.
Relief of symptoms during treatment can also involve the use of Morphine for pain relief, supplemental oxygen for patients with low oxygen levels, and nitrates (such as nitroglycerin) to alleviate chest pain.
For LMI patients presenting as NSTEMI, or non-ST-segment elevation myocardial infarction, initial standard treatment involves administering oxygen (if the patient’s oxygen saturation levels are low), beta-blockers, and a statin. Antithrombotic therapy that includes antiplatelet medications (aspirin and a P2Y12 inhibitor) and anticoagulants like heparin should be initiated as soon as possible. In contrast with STEMI, thrombolytic therapy isn’t indicated for patients with NSTEMI. However, early restoration of blood flow, like for STEMI, also leads to improved outcomes in NSTEMI cases.
Patients with left main artery occlusions are generally recommended to continue long-term therapy with aspirin, beta-blockers, and high-potency statins.
What else can Lateral Wall Myocardial Infarction (Heart Attack) be?
When a patient comes in with chest pain, there are several different conditions that a doctor will consider as potential causes:
- Acute pericarditis (inflammation of the tissue around the heart)
- Acute gastritis (sudden stomach inflammation)
- Peptic ulcer disease (stomach or intestine sores)
- Aortic dissection (tearing in the large blood vessel branching off the heart)
- Esophagitis (swelling of the food pipe)
- Cardiac tamponade (fluid in the pericardium, the sac around the heart)
- Costochondritis (inflammation of chest cartilage)
- Myocarditis (inflammation of the heart muscle)
- Pneumonia (lung infection)
- Pneumothorax (collapsed lung)
- Prinzmetal’s angina (chest pain due to coronary artery spasm)
- Pulmonary embolism (a blood clot in the lung)
- Cocaine induced vasospasm (narrowing of the blood vessels caused by cocaine use)
The doctor’s primary job is to evaluate these different possibilities through proper testing to come up with the correct diagnosis.
What to expect with Lateral Wall Myocardial Infarction (Heart Attack)
LMI generally has positive outcomes. The well-being of patients with severe types of heart attacks known as STEMI and NSTEMI has improved over the last decade. It has been reported that there’s a slightly increased risk of a certain type of heart rhythm disorder in patients presenting with heart attacks affecting the front or side of the heart.
The prognosis tends to be worse for patients who show life-threatening complications like irregular heartbeats, sudden cardiac arrest, rupture of the heart muscle, and shock caused by poor blood flow. Using the TIMI scores to categorize one’s risk can help identify patients who are more likely to have a higher in-hospital mortality rate.
The 30-day mortality rates are 13% with medical treatment alone for STEMI patients. But, it decreases to 6-7% with optimal clot-dissolving therapy and further reduces to 3-5% if a procedure to open blocked coronary arteries is carried out within 2 hours of reaching the hospital. Interestingly, there’s an even lower 2% risk of death for patients with NSTEMI after 30-days when compared to STEMI.
Possible Complications When Diagnosed with Lateral Wall Myocardial Infarction (Heart Attack)
- Rupture of the left ventricular free wall
- Pericarditis (a condition where the tissue around the heart is inflamed)
- Dressler Syndrome (a post-heart attack syndrome)
- Ventricular aneurysm (a bulge in the wall of heart’s ventricle)
- Acute mitral regurgitation (a leaky heart valve condition)
- Left ventricular thrombus (a blood clot in the left ventricle of the heart)
- Congestive heart failure (a condition in which the heart is not able to pump enough blood to meet the body’s needs)
- Ventricular fibrillation (a severe disturbance in heart rhythm)
- Ventricular tachycardia (a rapid heart rate that starts in the heart’s lower chambers)
- Sudden cardiac arrest (an unexpected loss of heart function)
- Cardiogenic shock (a severe decrease in cardiac output)
- Complications related to PCI (a procedure to open blocked coronary arteries)
Preventing Lateral Wall Myocardial Infarction (Heart Attack)
Educating patients is key to avoiding another heart attack in the future. Steps like quitting smoking, losing weight, sticking to prescribed medication, and changing diet have all been proven to improve heart health overall. It’s also helpful to keep blood pressure, sugar, and cholesterol levels under control to lower the risk of problems after a heart attack. We encourage heart attack patients to take part in heart rehabilitation programs. These programs can improve how the heart works and better control the heart rate.
