49-year-old (female) with chest pain

00:03 A 49 year old female is brought to the emergency room at 4 AM by her husband, complaining of crushing pain in her chest located behind her sternum and radiating to the left arm.

00:15 She is overweight and has a history of diabetes.

00:19 Myocardial infarction is suspected.

00:21 An ECG is performed which reveals ST segment elevation and T-wave inversion in leads II, III and aVF.

00:30 Which of the following is the most probable diagnosis? Answer choice (A) - inferior wall myocardial infarction or MI Answer choice (B) - lateral wall MI Answer choice (C) - posterior wall MI Answer choice (D) - anteroseptal MI or Answer choice (E) - right ventricular MI Now take a moment to come to a conclusion yourself before we go through the answers together.

01:00 Okay, let's tackle this question together.

01:02 First thing we have to determine is what subject are we talking about with this question? Well, we're concerning the heart the pathology of the heart, so this is cardiovascular pathology.

01:11 Now this is a 2-step question.

01:13 The first thing we have to do is determine what is the diagnosis.

01:17 And this case, I mean it looks like a myocardial infarction but the second step is to determine where in the heart are we gonna localize where the lesion is? And the stem is absolutely required in this case because we need it to help determine the diagnosis but also then we need the ECG results to localize the lesion in the heart.

01:36 Now let's start with the first step in this question in our walkthrough which is determining wether myocardial infarction is the most likely diagnosis.

01:44 Well this patient absolutely has risk factors for ischemic heart disease.

01:48 She has both obesity and diabetes.

01:51 Now this patient also presents with a very typical clinical presentation for an acute myocardial infarction.

01:59 She has crushing substernal chest pain, some patients will even say they feel like an elephant sitting on their chest and the pain is substernal, and in this case it's radiating to her left arm, very classic for a traditional or typical MI Now we also see that the patient has ST elevation and T wave inversion which is also typical of an acute myocardial infarction on the EKG.

02:26 Now that we think the diagnosis is a myocardial infarction, we need to be able to look at the EKG and then determine where in the heart we see the lesion.

02:35 Well the question stem says that there is ST segment elevation and T wave inversion in leads II, III, and aVF.

02:43 Now this is the inferior wall of the heart, so thus the answer in this case is answer choice (A) - an inferior wall myocardial infarction.`` Now let's refer to the image for this question as it is an extremely high-yield image and vital for every student to know.

02:59 It is absolutely critical as a doctor, that you can look at an EKG and quickly be able to determine what type of pathology we're looking at and where in the heart you see that pathology.

03:11 And if you look at how the location of the MI by EKG leads is set up in the diagram, you'll see 12 boxes.

03:18 And this is set up just like a clinical 12 lead EKG where each leads corresponds to a certain section on the heart Now if you look, leads II, III and aVF are our inferior leads.

03:30 leads V5, V6, I and aVL are lateral leads.

03:35 V1, V2 are septal and V3 and V4 anterior.

03:39 It is absolutely vital that you simply memorize this and put it to memory, ingrain it in your head because this information is not only vital to USMLE exam but it's also vital to basic clinical practice.

03:53 And as you can see above the images of the heart, it dictates where you have the different lateral, inferior and anterior segments of the heart and also the septal wall.

04:04 Now let's go through some high-yield facts regarding an acute myocardial infarction and also lcoalization of an acute myocardial infarction.

04:13 Now typical clinical symptoms that one can see with a patient presenting with an acute myocardial infarction include severe crushing substernal chest pain that can radiate to the left arm or into the jaw, and the pain can often be associated with sweating, nausea and even shortness of breath.

04:30 An important risk factors for patients with an acute MI, are smoking, obesity, hyperlipidemia, hypertension and diabetes.

04:39 And general changes that you can see in an ECG includes ST segment elevation and T wave inversion, or you can have what is called a STEMI which is ST segment elevation myocardial infarction.

04:53 Now when looking at a EKG, it's extremely important to be able to localize where we have different localization within the heart.

05:02 And very important to understand, V1-V2 are your septals, V3 and V4 anterior, V5, V6, I and aVL are lateral and II,III and aVF are inferior - absolutely vital information for localizing a myocardial infarction.