EKG questions - negatively deflected QRS?

Aliakey · Mar 31, 2013

I've tried a couple of different browsers, but as of the time I write this, your strip is not being displayed (errors in the link?).

Are you seeing predominately-negative complexes like those shown in leads II and III in this image below?

In short though, you may find a predominately-negative QRS complex to be a normal finding in certain leads (such as aVR or V1). Or, it may suggest the presence of a new or chronic condition, which is why serial ECGs are so important. Changes in the axis also depend heavily on whether certain leads are predominantly negative or positive. A pathological left axis would have a predominately-negative lead II and III (like what you see in the image above), and I'd want to search more with the other leads or increase my concern if the patient is symptomatic.

For example, a patient with a more predominately-negative QRS in lead II should have you looking for a qR complex in the leads I and aVL and also an rS pattern in leads II, III, and aVF (inferior leads). You are looking at a possible left anterior fascicular block in this case, which may be normal for an older patient with a chronic history of hypertension and coronary artery disease, or a younger patient with a cardiomyopathy of sorts. Or, in about 5% of cases, this can suggest an inferior myocardial infarction (usually if supported with signs/symptoms or other ECG changes).

Without knowing which leads are involved, its hard to say whether the negative orientation is normal. Could also be something that is a face-slapper :facepalm: , like incorrect lead placement (for example, the normally-negative QRS of lead aVR is positive... may be a lead switch).

Since I have no affiliations with this site, I hope it's okay to post this link to EMS 12-Lead: : Site Index : | EMS 12-Lead

This site offers a wealth of practical ECG interpretation information geared towards paramedics (since we can't really consult a cardiologist in the field before initiating treatments ), but obviously great information for anyone learning 12-lead interpretation.

Hope it helps!

nurseprnRN, BSN, RN · Mar 31, 2013

Are you looking at the same leads?

Thought experiment here:

You are at your favorite baseball diamond. You are holding a piece of plexiglas in front of you, and you have a wax crayon in your dominant hand. You will be drawing lines on it based on what you see on the other side of it. Ready?

You are sitting in the stands between home plate and first base. The pitcher throws the ball to the catcher. You follow its progress and draw the line on the plexiglas as you see it go. The line goes from...? Correct, a long line, going from your right to your left, dropping down a bit with gravity.

Through the miracle of time travel, you are now on the other side of the diamond, between third base and home. The pitcher throws the same pitch. Where do you draw your line? Correct-- the ball appears to go a long way from left to right, again dropping down a bit with gravity. Same pathway, different vantage point, different crayon tracing on the plexiglas.

OK, now you are sitting right behind the pitcher. Same pitch, coming straight at you. When you trace its path on your plexiglas, what does the line look like? NOT right-to-left, because it's coming straight towards you, so you draw a very short line from the center of the plexiglas, where you see the pitch leaving the pitcher's hand, dropping a little bit to account for the gravity as it settles into the pitcher's mitt.

Last, you could even pretend you were in the grass between the pitcher's mound and the plate, and seeing the ball coming by. Your line would rise as the ball approached you, and then fall as it went past you.

In EKG-land, the electrical impulse traveling through the heart's anatomical conduction system is that ball. The different lines you have drawn on your plexiglas are the picture of that impulse as seen from many different vantage points. Why bother? Because it's important to see the path clearly as it moves about the heart. Some leads "see" the P wave better than others. Other leads, because of their vantage point, show the QRS upright or downgoing. Depending on where the lead is, it might show derangements in conduction better, like a bundle branch that's damaged (bundle branch block). So the derangements in some leads specifically tell you about how the conduction goes through specific areas of the myocardium, with the understanding that abnormal conduction (an abnormal line) means something wrong in the muscle.

That may be why you are getting confused-- you might not see the P wave in one lead and wonder where it is. There's (probably) still conduction from the SA node to the AV node, but you're looking from behind the plate, not from first base, so you don't see its movement so well. You might be looking at the QRS from second base, where it's normal to see it moving away from you.

I hope that helps some. I love baseball. :)