Detecting a Heart Attack with an EKG

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  • 0:04 Heart Attack: Definition
  • 0:27 EKG: Definition
  • 1:40 Clinical Manifestations
  • 2:30 Acute Coronary Syndrome
  • 3:10 Analyzing an EKG
  • 5:46 Lesson Summary
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Lesson Transcript
Instructor: Anne Vaz

Anne has worked as a nurse for 14 years and is a Family Nurse Practitioner.

This lesson will describe how to recognize a heart attack on an EKG. You will also learn how to identify which wall of the heart is affected based on the location of the changes in EKG leads.

Heart Attack: Definition

Let's say that you're stuck in traffic and cars are backed up as far as you can see. It turns out there's an accident blocking traffic lanes. This is similar to what happens during a heart attack, also known as a myocardial infarction (MI). Blood flow to the heart muscle is occluded (or obstructed), leading to a loss of blood supply (ischemia) and the death of heart tissue.

EKG: Definition

An EKG is the mainstay of the initial testing done for chest pain. An EKG displays the heart's electrical activity as a wave. When a patient suffers a myocardial infarction, it can often but not always be seen on an EKG. A myocardial infarction is always an emergency. Not treating an MI can lead to death. Time is muscle, which means that for every minute that the blood flow to the heart muscle is obstructed, there's an increase in damage to the heart muscle. Early identification and treatment can save lives. Therefore, it's important to know how to identify a myocardial infarction on an EKG.

Let's review some of the basics for reading an EKG:

The P wave represents atrial depolarization or atrial contraction. The QRS complex represents ventricular depolarization or ventricular contraction. The ST segment begins at the end of the QRS complex and extends until the beginning of the T wave. The J point is the junction between the end of the QRS complex and the beginning of the ST segment. The T wave represents ventricular repolarization or ventricular relaxation.

Clinical Manifestations

Have you ever watched a television show that takes place in a medical setting? When someone comes into the emergency room with chest pain, the doctors do an EKG, perform blood tests, put in an IV line, and connect the patient to a heart monitor. This is similar to what happens when a patient experiencing chest pain comes into a real emergency room, minus their dramatic music. In this type of situation, doctors and nurses are like detectives, trying to determine what's causing the symptoms the patient is having.

Let's review some of the clinical manifestations of a myocardial infarction:

  • Chest discomfort or pain radiating down the jaw, left arm, shoulder, and neck
  • An ache, burning sensation, pain, or pressure in the chest
  • Profuse sweating
  • Shortness of breath
  • Dizziness
  • Nausea
  • Fatigue

Acute Coronary Syndrome

Acute coronary syndrome (ACS) is a spectrum of symptoms that indicate myocardial ischemia or reduced oxygenation of the heart muscle. It includes unstable angina, ST elevation MI (STEMI), and non-ST elevation MI (non-STEMI).

When dealing with ACS, the first step is to get an EKG, followed by obtaining blood work for cardiac markers. The EKG helps determine if the patient has a STEMI. If there's no ST elevation, cardiac markers help identify a non-STEMI. If both the EKG and the cardiac markers are negative, then the patient has unstable angina.

Analyzing an EKG

Let's say you're working in triage in an emergency room. The next patient you see is experiencing chest pain, shortness of breath, profuse sweating, and nausea. These are symptoms of a possible myocardial infarction, so it's important to get an EKG and have it read by a medical doctor, nurse practitioner, or physician's assistant within 10 minutes of the patient presenting to you (remember, time is muscle). Now it's time to analyze the EKG.

If you notice an ST elevation and the presence of new Q waves when compared to an old EKG, there's a high probability of a myocardial infarction.

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