Questioning Guidelines in the ECG Puzzler.
I have been teaching this content for 25 years and would define the above measurements as follows: (1) tachycardia is greater than 100/min; (2) normal PR interval is equal to or less than 0.11 seconds; (3) wide QRS complex duration is equal to or greater than 0.12 seconds; (4) NSVT rate is 3 or more complexes at a rate greater than 100/min (all tachycardia rhythms minimally fall under this definition); (5) as for ventricular tachycardia with positive QRS, in [V.sub.1] the width greater than 0.14 seconds is a ventricular tachycardia characteristic; with a negative QRS in [V.sub.1], the width equal to or greater than 0.16 is a characteristic of ventricular tachycardia. (1)
There are so many more points to be made related to ECG characteristics of ventricular tachycardia that do not appear in this article, including but not limited to axis, capture and fusion complexes, previous ECG characteristics, and the 4 signs of ventricular tachycardia, which apply if QRS is greater than 0.14 seconds in [V.sub.1] and/or [V.sub.2]. These 4 signs are (1) wide R (>0.04 seconds) in [V.sub.1] and/or [V.sub.2], (2) slurred S (notched) downstroke in [V.sub.1] and/or [V.sub.2], (3) delayed S nadir (>0.06 seconds) in [V.sub.1] and/or [V.sub.2], and (4) q wave in [V.sub.6] when the complex is mainly negative in [V.sub.1]. Opposite polarity doesn't always diagnose the rhythm as ventricular tachycardia.
Also, it is troubling that the authors close the article with "it is important to rule out cardiac disease in this patient before he is discharged, by means of resting 12-lead ECG, serum biomarkers, echocardiography, and so on." I find the phrase "and so on" a little disconcerting. This patient probably should receive serial ECGs (not just one), serial cardiac markers, risk assessment, and, at the very least, noninvasive testing including a stress test and perhaps a percutaneous coronary intervention.
Sandra Walden, MS, BSN, RN
(1.) Marriott HJL, Conover MB. Advanced Concepts in Arrhythmias. St. Louis, Mo: Mosby: 1998.
My colleague and I use AACN's "9 features" (those that appear in the ECG Puzzler column) in a basic ECG course we teach to nurses working in the intensive care and telehealth units in our hospital. However, we've been wondering about some discrepancies in the column. The first deals with heart rate. Although the ECG Puzzler states that "normal" heart rate is "60-90 beats per minute," the literature (including AACN's literature) states that a normal rate is 60 to 100/min.
The second problem is with PR interval. According to the ECG Puzzler, a short PR interval is one that is less than 0.08 seconds. However, the literature seems to disagree on this measurement, instead suggesting that a short PR interval is less than 0.12 seconds.
The next point is about QTc and T waves. We would suggest that both of these features could include a check box that reads "cannot determine" for cases in which neither is discernible because of distortion.
Similarly, ST segments could include a check box that reads "flat," because this has been identified as an abnormality of concern in the literature.
Michele Kilbourne, RN, CCRN
Chris Sorenson, RN, MSN, CCRN
Mary G. Carey and Michele M. Pelter reply:
Our thanks to these authors for their letters. First let's deal with points the letters have in common.
Yes, it's true that sinus rhythm historically has been defined as 60 to 100/min. However, physiologically and clinically speaking, sinus rhythm in the resting adult is specifically 44 to 84/min for men and 50 to 90/min for women. (1,2)
As for the PR interval, it is normally between 0.12 and 0.20 seconds; therefore, we've made a correction to the column beginning with this issue. A QRS duration greater than 0.12 seconds does suggest an intraventricular conduction delay. However, given that it is often difficult to determine exactly where the QRS begins and ends, precise measurements are difficult to ensure. And so, to improve the specificity of identifying a wide QRS in the ECG Puzzler column, the criterion of "greater than 0.12 seconds" (3 small boxes) has been applied.
We concur with Ms Walden that tachycardia is greater than 100/min rather than 120/min. We also agree that there are numerous characteristics of ventricular tachycardia easily applied to a resting 12-lead ECG (eg, QRS axis). Ms Walden is not incorrect in her assessment, but the 4 signs of ventricular tachycardia she outlines are correct only with a particular ECG waveform; for the ECG waveform in our example, Ms Walden's criteria are not helpful. Also, our overall interpretation was not incorrect; that is, we called it ventricular tachycardia. Because our column only provided a short dual-lead ECG strip typically found in clinical practice, many additional ECG criteria cannot be applied. It is for this reason that we focus on criteria that can be applied, such as QRS width and morphology.
We agree that it is important for the patient to have a cardiac evaluation--that is why we introduced the final paragraph with the word however in italics to emphasize the point. A comprehensive list of possible cardiac procedures (eg, resting ECG, serial ECG, Holter ECG, serum biomarkers, C-reactive protein level, echocardiography, stress test, angiogram, computed tomography scan, magnetic resonance images) is beyond the scope of the ECG Puzzler column. For the sake of brevity, then, we simply used "and so on."
The letter from Kilbourne and Sorenson raises 2 other points. Yes, "cannot determine" is not a fixed option for measures of QTc and T wave, but depending on the scenario presented in the ECG Puzzler we have added it as an option. Although notable, "flat" ST segments are nondiagnostic; in other words, they do not definitively identify a diagnosis. Given that the focus of our column is clinical, however, we prioritized true ST-segment deviation that meets diagnostic criteria.
(1.) Yang XS, Beck G J, Wilkoff BL. Redefining normal sinus heart rate [abstract 749-1]. J Am Coll Cardiol. February 1995:193A.
(2.) Palatini P. Need for a revision of the normal limits of resting heart rate. Hypertension. 1999;33(2):622-625.
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|Title Annotation:||LETTERS TO THE EDITORS|
|Author:||Pelter, Michele M.|
|Publication:||American Journal of Critical Care|
|Date:||Jan 1, 2007|
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