12 lead depression

firstinfamily, RN · Dec 5, 2014

The ST segment represents depolarization of ventricles and beginning of ventricular repolarization. Ideally it should be isometric, if ST is depressed when it is 0.5mm below the isometric line. ST depression can be associated with digoxin toxicity or myocardial ischemia. ST elevation is usually 1mm or more above the isometric line and associated with myocardial injury. Hope this helps. IT takes a lot of practice to read EKGs!!

akulahawkRN, ADN, RN, EMT-P · Dec 5, 2014

ST Depression can also reflect a reciprocal change, in effect showing you that there's an MI on the opposite side of the heart from where the lead is. There really quite a bit to learn about reading EKG's. I'm not bad at it, but there's much I still need to learn and get experience in before I consider myself even close to good at it.

macawake, MSN · Dec 5, 2014

What does a normal 12 lead with no st elevation but depression in some leads signify?

There's not enough information in your question to answer it properly. There can be many so different causes for ST segment depression.

In what leads is the depression noted? Is it a resting or stress ECG? Is the depressed ST segment horizontal, symmetric or asymmetric, upward or downward sloping? Does the patient have any symptoms indicative of a cardiac event/disease?

As already mentioned it can be reciprocal changes, a mirror image of an ST elevation on the "other" side of the heart. It can be digitalis effect, both at therapeutic (the med doesn't automatically have to be discontinued due to this, it's a normal effect) and toxic levels. (Toxic levels of digitalis will likely have other effects/cause arrhythmias since it increases intracellular potassium).

Repolarization abnormalitities can be the result of ventricular hypertrophy causing ST segment depression (and T wave inversion). Bundle branch blocks do too (but of course the rest of the ecg won't look normal).

Healthy women can sometimes have ST segment depression when taking a stress ECG (usually in lateral and inferior leads) of about 1 - 1.5 mm, not necessarily a sign of cardiac disease.

ECG's are complex and it's important to weigh in other symptoms the patients have and any medications they might be on. I don't know if I've managed to help answer your question, but I hope so.