A Short PR and a Slurred Upstroke on a Pre-Employment ECG: Systematic Interpretation of Ventricular Pre-Excitation in an Asymptomatic 22-Year-Old and the Next Step for Risk
[Student Name]
University of Phoenix
NRP/571: Advanced Health Assessment II and Clinical Procedures
Week 1 Assignment
[Instructor Name]
[Date]
The patient is a composite written for a model paper.
Mr. T., a 22-year-old applying to a fire academy, needs medical clearance including a resting ECG. He has no palpitations, fainting, chest pain or exercise intolerance, and no family history of sudden death. His examination is normal. The ECG computer reads "abnormal ECG." This paper interprets the tracing systematically and explains the next step.
A Systematic Read
The AHA recommendations for standardization and interpretation of the ECG emphasize a consistent approach to measuring intervals and describing waveforms (Kligfield et al., 2007). I read in a fixed order and do not accept the computer's statement until my own read is complete.
Rate: 72 beats per minute, regular.
Rhythm: sinus, with a P wave before each QRS, upright in leads I and II.
Axis: normal, about +60 degrees.
PR interval: 100 milliseconds, short (normal 120 to 200).
QRS: 120 milliseconds, widened, with a slurred, slowly rising initial upstroke in leads I, aVL and V4 to V6.
ST segments and T waves: T waves inverted in leads III and aVF, with ST-T changes opposite in direction to the initial QRS deflection.
QT interval: corrected QT 430 milliseconds, normal.
The computer said abnormal; the fixed-order read said why, and why is what decides the next step.
The Interpretation
Short PR, delta wave and wide QRS form the classic triad of ventricular pre-excitation. The ST-T changes are secondary to abnormal depolarization and do not indicate ischemia. In a person without symptoms of tachycardia, this is called a pre-excitation pattern; if he had had documented tachyarrhythmias, it would be called Wolff-Parkinson-White syndrome.
The Mechanism
Normally, the AV node delays conduction from atria to ventricles, producing the PR interval. An accessory pathway, a strand of conducting tissue across the AV groove, bypasses this delay. Part of the ventricle is activated early and slowly through ordinary muscle, creating the delta wave, while the rest is activated normally through the AV node, completing the QRS. The resulting QRS is a fusion of the two.
Why It Matters
Most people with a pre-excitation pattern never have problems. The concern is that if atrial fibrillation develops, the accessory pathway may conduct atrial impulses to the ventricles much faster than the AV node would, potentially triggering ventricular fibrillation. The PACES/HRS consensus statement on asymptomatic young patients with a WPW pattern notes that sudden death is rare but can be the first manifestation, and recommends risk stratification to identify pathways capable of rapid conduction (Cohen et al., 2012).
Risk Stratification
The consensus statement describes noninvasive risk stratification, particularly exercise stress testing: abrupt and complete loss of pre-excitation at higher heart rates suggests a pathway with a long refractory period, which is less able to conduct rapidly and indicates lower risk (Cohen et al., 2012). If pre-excitation persists or the result is unclear, an electrophysiology study can measure the pathway's properties directly, and catheter ablation can eliminate the pathway, often with high success. The ACC/AHA/HRS guideline for supraventricular tachycardia also addresses evaluation of asymptomatic pre-excitation (Page et al., 2016).
My Plan
I refer Mr. T. to cardiology for an exercise stress test and consideration of an electrophysiology study. Because firefighting involves extreme exertion and his safety and that of others depends on him, clearance should await this evaluation. I explain this to him without alarm, noting that the finding is not uncommon, is usually harmless and, if needed, is often curable.
Why Not Trust the Computer
Automated interpretation is useful for measuring intervals but frequently mislabels complex patterns. A pre-excitation pattern may be read as bundle branch block, prior infarction or nonspecific abnormality, because the delta wave can mimic Q waves and the secondary ST-T changes can mimic ischemia. A clinician who accepts the computer's label without reading the tracing may order the wrong tests or miss the real finding.
Distinguishing It From Other Wide QRS Patterns
Bundle branch block also widens the QRS but with a normal PR interval and without a delta wave. Pre-excitation can also produce Q waves that mimic old infarction, especially in inferior leads, as the accessory pathway's location changes the initial vector. The short PR interval is the clue that separates pre-excitation from these mimics.
Locating the Pathway
The pattern of delta wave polarity across the leads can suggest where the accessory pathway lies, left or right, anterior or posterior. This matters to the electrophysiologist planning ablation, though it does not change the primary care decision to refer.
Explaining It to Mr. T.
I show Mr. T. the tracing and point to the short PR interval and the slurred upstroke, explaining that he has an extra electrical connection in his heart that most people with this pattern never notice. I tell him the plan is to learn whether his connection could ever conduct dangerously fast, and that if it could, it can usually be removed with a catheter procedure.
His Family
Pre-excitation is usually sporadic, though familial forms exist. I ask about relatives with palpitations or early unexplained deaths; there are none, and routine screening of relatives is not necessary.
Drugs to Avoid
Until evaluation is complete, I tell him that if he ever has a fast, irregular heartbeat, he should seek emergency care and inform clinicians of his ECG, because drugs that block the AV node, such as some calcium channel blockers or digoxin, can be dangerous in pre-excited atrial fibrillation.
Why the Rate of Conduction Matters
The danger in pre-excitation depends on how quickly the accessory pathway can conduct. A pathway that can conduct only slowly offers little risk even during atrial fibrillation. Measuring this property, noninvasively through exercise testing or directly in an electrophysiology study, is the purpose of risk stratification (Cohen et al., 2012).
His Work Clearance Letter
I write a brief letter to the fire academy stating that clearance is pending cardiology evaluation of an ECG finding, without detailing the diagnosis, and that a final decision will follow.
Exercise Stress Testing Details
During the exercise test, the cardiologist will watch whether the delta wave disappears suddenly as the heart rate rises. A sudden, complete loss suggests the pathway cannot conduct at high rates, while gradual loss is less informative (Cohen et al., 2012).
Timeline
I ask cardiology for an appointment within four weeks so that his academy start date is not delayed unnecessarily.
Documentation
The note records each measured interval, the interpretation, the reason for referral and the conversation, with a copy of the tracing sent to cardiology.
Conclusion
A systematic read of Mr. T.'s ECG found a short PR interval, delta waves and a widened QRS with secondary ST-T changes, the pattern of ventricular pre-excitation. Although he is asymptomatic and the risk is low, the rare possibility of rapid conduction during atrial fibrillation justifies risk stratification under the PACES/HRS consensus before clearance for a physically demanding job.
References
Cohen, M. I., Triedman, J. K., Cannon, B. C., Davis, A. M., Drago, F., Janousek, J., Klein, G. J., Law, I. H., Morady, F. J., Paul, T., Perry, J. C., Sanatani, S., & Tanel, R. E. (2012). PACES/HRS expert consensus statement on the management of the asymptomatic young patient with a Wolff-Parkinson-White (WPW, ventricular preexcitation) electrocardiographic pattern. Heart Rhythm, 9(6), 1006-1024. https://doi.org/10.1016/j.hrthm.2012.03.050
Kligfield, P., Gettes, L. S., Bailey, J. J., Childers, R., Deal, B. J., Hancock, E. W., van Herpen, G., Kors, J. A., Macfarlane, P., Mirvis, D. M., Pahlm, O., Rautaharju, P., & Wagner, G. S. (2007). Recommendations for the standardization and interpretation of the electrocardiogram: Part I: The electrocardiogram and its technology. Circulation, 115(10), 1306-1324. https://doi.org/10.1161/CIRCULATIONAHA.106.180200
Page, R. L., Joglar, J. A., Caldwell, M. A., Calkins, H., Conti, J. B., Deal, B. J., Estes, N. A. M., III, Field, M. E., Goldberger, Z. D., Hammill, S. C., Indik, J. H., Lindsay, B. D., Olshansky, B., Russo, A. M., Shen, W.-K., Tracy, C. M., & Al-Khatib, S. M. (2016). 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation, 133(14), e506-e574. https://doi.org/10.1161/CIR.0000000000000311
How this NRP 571 Week 1 example is structured
The NRP/571 Week 1 work usually asks for systematic 12-lead ECG interpretation. This paper works through the tracing in a fixed order, names the finding only after every element is read, explains why it matters and states the next step, which is the part of interpretation that protects the patient. Students search this week as NRP 571 Week 1, NRP571 Wk 1 or NRP/571 Wk 1; all three are the same assignment.
NRP/571 Week 1 questions, answered
What does NRP/571 Week 1 usually ask for?
Many sections ask students to interpret a 12-lead ECG systematically and state the clinical next step.
What is ventricular pre-excitation?
Early activation of part of the ventricles through an accessory pathway that bypasses the AV node, producing a short PR interval, a slurred initial QRS upstroke called a delta wave and a widened QRS.
Is asymptomatic pre-excitation dangerous?
Usually not, but rarely atrial fibrillation can conduct rapidly over the accessory pathway and cause ventricular fibrillation. Risk stratification identifies pathways that could conduct dangerously fast.
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