This strip shows a second-degree AV block. During most of the strip, 2:1 conduction is present. At the beginning, however, two consecutive p waves are conducted, revealing progressive prolongation of the PR interval. This usually represents a Type I , or nodal, block: progressive refractoriness of the AV node. However, the wide QRS ( possibly left bundle branch block), and the fact that the non-conducted p waves are "out in the open" where they should have conducted, points to Type II - an intermi
Sinus bradycardia. This strip meets the criteria of: regular rhythm, rate less than 60 bpm (40 bpm in this case), regular P waves before every QRS. Sinus bradycardia can have many causes from a completely normal variation to a malfunction of the sinus node. In some cases, enhanced parasympathetic tone causes sinus bradycardia. Well-conditioned athletes typically have sinus bradycardia. Treatment depends upon the cause and the patient's response to the rate. If the rate does not cause hemodynamic impairment, treatment may not be necessary.
This strip offers several good teaching opportunities. If it were a 12-lead ECG, no doubt it would be a bonanza! First, there is sinus tachycardia at a rate of about 138 per minute. The P waves are all alike and regular. The T waves are tall and narrow, with a sharp peak. This is often a transient sign of hyperkalemia, and should be investigated with serum electrolyte tests and with a 12-lead ECG. In addition, the baseline shows a wandering type of artifact.
This Lead II rhythm strip is from a nine-year-old girl being monitored for an outpatient surgical procedure. She has no known heart disease. Her heart rate is 110 per minute. The PR interval is .12 seconds (120 ms), the QRS is upright and narrow at .06 seconds (60 ms), and the rhythm is regular.
This ECG rhythm strip has all the hallmarks of atrial fibrillation: the rhythm is irregularly irregular and there are no P waves. The rate is about 150 beats per minute. There is no P wave because the atria are being irregularly depolarized by many ectopic pacemakers at once, causing the atria to "quiver". This patient has new-onset atrial fib, and has been medicated with a calcium channel blocker. The rate shows signs of slowing, but has not reached the target rate for this patient of less than 80 bpm.
This strip was taken from a patient at rest. It shows a regular tachycardia with a slightly-widened QRS complex at about .10 seconds duration. It is somewhat difficult to evaluate the baseline for P waves or flutter waves. We ALWAYS recommend multi-lead assessment for such evaluation. The P waves (or flutter waves) here have a sharp point, and can be easily "marched out", with a rate of about 300 per minute.
This rhythm strip is recorded in two simultaneous leads, which is always preferable to one single lead. It is a good example of atrial fibrillation with a rapid ventricular response. Atrial fib that has not been treated will usually have a rapid ventricular rate. This reflects the ability of the AV node to conduct a tachycardia, within limits. The natural slow conduction of the AV node allows it to act as a "filter", preventing the huge numbers of impulses generated by the atrial fibrillation from reaching the ventricles.
This rhythm strip offers two leads taken at the same time, Lead II and Lead V1. The Lead II strip may not look "typical" to a beginning student, because the sinus beats are very small and biphasic. This is due to an axis shift, which cannot be evaluated without more leads.
This is a good teaching strip on many levels. At the BASIC level, we see a strip that clearly meets all the criteria for sinus tachycardia: a regular rhythm over 100/min. with P waves that look normal and all look alike. The rate is 110 per minute. The PR interval is just at the upper limits of normal at .20 second, or 200 ms. The QRS complex is within normal limits, but slightly wide at .10 seconds.
This strip shows an underlying sinus bradycardia with a rate less than 40/min. There is one "premature" beat, which can be considered to be ectopic, because it interrupts an otherwise regular rhythm. The interesting thing is that the premature beat is not terribly early - it is about 740 ms from the previous beat. If all the beats were spaced like this, the heart rate would be about 84/min. There is probably an element of "escape" here, in that the ectopic beat is able to express itself due to the slow rate.
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