This ECG was obtained from a 24-year-old man who was seen in the Emergency Department for chest pain that was determined to be non-cardiac in origin. He had a fever and cough, with pain on inspiration. His vital signs were within normal range, and he appeared well-perfused. There was no complaint of dizziness or syncope.
So, what does his ECG show? The ECG should be interpreted in the context of the age and presentation of the patient. He is young, and has been healthy all his life. He is lean and reasonably fit.
The rhythm: the rate is 81 bpm, and the rhythm is regular. His P waves are upright in Leads I and II, and they are followed by QRS complexes. The rhythm is NORMAL SINUS RHYTHM.
Intervals: The PR interval is 137 ms (.137 seconds), and his QRS duration is 91 ms (0.9 seconds). His QTc is 404 ms. All are within normal range.
QRS frontal plane axis: Normal axis, at around 30 degrees. Lead II has the tallest QRS of the limb leads, which is an indication of axis in the normal range. When the electrical axis travels towards Lead II, we can expect Lead aVL to be small, or even biphasic.
R wave progression: There is normal R wave progression in the chest leads, with V1 having an rS pattern (mostly negative) and V6 having an Rs pattern – nearly 100% upright. Leads V2 through V5 progress from negative to positive in an orderly fashion, with the transition occurring in V3.
ST segments and T waves: There are very slight J point elevations in Leads I and aVL – almost unnoticeable. There are equally unimpressive ST depressions in Lead III. The shape of the ST segments is almost uniformly concave upward, or “smiling”, with Leads aVR, III, and V1 the only exceptions. There are very tiny U waves noticeable in Leads V2 and V3. There are T WAVE INVERSIONS in Leads III and V1 (right-sided leads), and of course, in aVR, which is a right-sided and superior lead. aVR should look like an upside-down mirror image of a combination of Leads I and II.
Interpretation: Young people - children, adolescents, and young adults – often have ECG features that would be concerning in older people, especially in those with cardiac symptoms. It is important to know what ECG findings might be seen as normal variants in young people. In this patient, the findings that might appear abnormal at first glance, but are normal variants, are:
* U waves
* T wave inversions in Leads III and V1.
* Slight ST elevation, or sometimes depression, in some leads. In young men, especially, ST elevation can even be pronounced without signifying cardiac injury. To read an interesting discussion on Early Repolarization Syndrome, click HERE.
There are many other findings you may see in young people, though not in this one:
* P wave changes such as bifid P waves in Lead II.
* Irregular rhythm – “sinus arrhythmia”.
* Tall voltages in left-sided chest leads. “LVH without the strain”.
* Incomplete and complete right bundle branch block.
This is a good ECG to use to remind your students to look at the whole picture – with patient presentation being very important!