The QTc interval: An Essential Tool in Every Clinician's Toolbox

By Dr. Payal Kohli, MD, FACC

I was utterly horrified. I stood by the young man's bedside, paralyzed to do anything but stare at the rhythmic Torsades de pointes on the monitor ahead of me. It is a scene I replay in my mind often.

It started with a young man who presented with hypokalemia from toxin-mediated diarrhea. The severe hypokalemia had triggered polymorphic VT arrest due to prolonged QTc interval. Once his potassium was repleted, his underlying QTc revealed that he probably had underlying long QT syndrome, which had until then remained undiagnosed. The story doesn't end there, however. Due to his "VT arrest", he was subsequently loaded with intravenous amiodarone in the emergency room. The result was the longest QTc I have ever seen in my cardiology career.

I have always had profound respect for the QTc interval. It is a truly understated interval that we sometimes neglect while interpreting ECG. And yet, this "vulnerable period" of cardiac repolarization is perhaps one of the most important parts of the cardiac electrical cycle. A PVC during this period, or prolonging of this period, can take an otherwise structurally normal heart and stop it in an instant. I always knew the prognostic power of the QTc, but that day, I think I truly appreciated how important this interval is and how it can literally mean the difference between life and death.

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Dr. Payal Kohli, MD, FACC is a top graduate of MIT and Harvard Medical School (magna cum laude) and, as a practicing noninvasive cardiologist, is the managing partner of Cherry Creek Heart in Denver, Colorado.

The opinions, beliefs and viewpoints expressed in this article are solely those of the author and do not necessarily reflect the opinions, beliefs and viewpoints of GE Healthcare or The EKG Guy.