Review of Normal ECG

00:01 Hello, I'm Joseph Alpert.

00:03 And in this talk, we are going to go over the EKG changes that occur with myocardial infarction.

00:10 This is one of the most important uses for the electrocardiogram.

00:13 Early recognition of myocardial infarction enables effective therapy for example; reopening a blocked coronary artery to occur which markedly improves the survivability of the patient.

00:26 So again, let's just have a little review.

00:29 Remember that the electrocardiogram shows the electrical depolarization of the heart.

00:35 It's a simple, cheap, easy task often done in offices and hospitals everywhere.

00:40 It's almost always the first cardiac test that's done.

00:44 It's accurate for ischemia and acute myocardial infarction; that is a heart attack.

00:49 It's also quite accurate on ventricular hypertrophy; that is enlargement of the ventricle muscle and also for arrhythmias.

00:57 And remember, there are many nonspecific and non-diagnostic patterns which is why one has to practice a lot to recognize when something on the electrocardiogram doesn't mean anything.

01:07 An acute myocardial infarction is a heart attack.

01:10 It causes changes on the electrocardiogram in the T waves, in the ST segment and with the development of Q waves.

01:19 Q waves that were not present in the normal ECG that developed during a myocardial infarct represent literally holes in the heart.

01:27 That is electrical holes where there's no viable myocardial cells left. Remember this diagram? This is the normal electrocardiographic complex.

01:38 Notice in yellow, the P wave, usually three little boxes are less in duration and then a - then a short segment between the P wave and the QRS.

01:47 The entire yellow and orange section is referred to as the PR segment on the electrocardiogram.

01:53 In gray, the QRS complex; that's ventricular depolarization.

01:58 Then we have an ST segment that's usually flat, followed by a T wave which is the repolarization wave of the heart as it resets itself for the next beat.

02:07 And the U wave sometimes occurs very often in patients with low blood potassium.

02:13 Here is a normal sinus rhythm. Notice, we've talked about this in earlier slides and in earlier lectures.

02:21 The P wave comes just before the QRS and it is less than five little boxes from the beginning of the P wave to the beginning of the QRS.

02:31 And these are normal ECG complexes, nice narrow QRS.

02:35 And you've seen this normal ECG before.

02:40 This is somebody with nice, normal progression of the R waves across the precordium from almost a tiny R wave in lead V1 to a dominant R wave in V4, 5 and 6 as it goes over the left ventricle.

02:55 And also, the axis is normal with the maximum R wave in lead II.

03:00 And the T waves are all up right, it's a nice, normal ECG.