THE QT INTERVAL... March 07 2018

This month’s blog is about a topic that has been of immense interest to me my entire career: the QT Interval.  My first exposure to the QT interval was as a CCU bedside nurse, and our practice at that time was to assess the QT interval on all patients that were started on anti-arrhythmic medication. Then, as a research nurse in Cardiovascular and Diabetic clinical trials, I noticed a shift in the FDA and Health Canada when they made it mandatory in their Phase II and III Clinical Trials to measure the QT interval before starting on the study medication and periodically throughout the clinical trial. The importance of QT interval measurement became more apparent to these federal agencies because of all the known drug-to-drug interactions and, more importantly, because of the unknown drug-to-drug interactions.

For over 20 years, I have been asking participants at the Rhythm and ECG courses that I teach how often they measure the QT interval and in which patients. In 2008, my initial research on the practice of routine QT interval measurement was published in the Canadian Association of Critical Care Nursing, and my findings were that of 180 nurses working with patients on cardiac monitors/telemetry, only 30% of nurses reported that they always measure the QT interval when performing their rhythm assessment. More impressively, 45% reported they only sometimes measure this interval and 25% reported they never measure this interval.

So, ten years after this research was published, has practice changed? I would hope so. Given FDA and Health Canada’s increased awareness, increased knowledge of drug-to-drug interactions, and technology where electronic medical records are available among health care interdisciplinary teams allowing for a more-thorough assessment of the patient’s polypharmacy regime, one would feel safe to assume that the routine measurement of the QT interval was common practice to all who assess rhythms and ECGs. However, I am still polling my participants and still frequently seeing less than 40% acknowledge that they look at the QT interval with every patient and every rhythm strip analysis. I believe a practice gap continues to exist and I would really like to re-evaluate this issue again and address areas where we can focus on improving this gap.

I have many questions: how many nurses in critical care routinely measure QT interval? How many nurses in the Emergency Department routinely measure this interval? What about the nurses working on Telemetry? And, lastly, what about staff working with the patient who is pre-hospital or in out-patient clinics? How have guidelines and recommendations changed over the past ten years and what are the current guidelines?

Starting in April, I will be incorporating an assessment tool in my ECG and Rhythm workshops that will ask those meeting certain criteria, to answer a series of questions addressing their practice of rhythm interpretation specific to the QT interval. I am looking forward to readdressing this topic and getting some facts on what is really happening out there.  I’ll keep you posted on my findings.