Author: Theresa George, DO (EM Resident Physician, Drexel University College of Medicine, @_DOctorG_) // Edited by: Alex Koyfman, MD (EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital, @EMHighAK) and Brit Long, MD (@long_brit, EM Chief Resident at SAUSHEC, USAF)
You’re in the middle of an overnight shift when the nurse hands you an ECG of a young female with chest pain that has been intermittent over the past week.
What’s the abnormality?
Answer: Short PR segment
What are the big things you should consider when you see this?
|Clinical condition||ECG characteristics|
|Wolff-Parkinson-White syndrome||Short PR, slurred upstroke to a broad QRS (delta wave)|
|Lown-Ganong-Levine syndrome||Short PR with normal QRS and no delta wave|
|AV nodal (junctional) rhythm||Short PR with abnormal or entirely absent p wave (retrograde p wave)|
- Other conditions in which you may see a shortened PR interval: ectopic atrial rhythm, hypertrophic cardiomyopathy, Ebstein’s anomaly, tricuspid atresia, corrected transposition of great vessels, mitral valve prolapse, Duchenne’s muscular dystrophy, Pompe’s disease, Fabry’s disease.4
- We thought that this was most likely Lown-Ganong-Levine syndrome (LGL).
- What is LGL?
- Lown-Ganong-Levine syndrome, like Wolff-Parkinson-White syndrome, is a preexcitation syndrome involving the presence of what is thought to be an accessory pathway between the atria and ventricles.1,8 However, a definitive accessory pathway has yet to be identified, in contrast to the bundle of Kent in WPW syndrome. Because the accessory pathway is thought to conduct electrical impulses faster than the normal pathway, a shortened PR interval, usually less than 120 ms, is observed. It also means that there is a viable re-entrant circuit, making patients with this syndrome susceptible to re-entry tachydysrhythmias.9 In contrast to WPW syndrome, LGL features a normal QRS and there is no delta wave. As you might imagine, this makes it harder to pick up, and one can easily miss this finding on ECG. Other criteria for LGL syndrome include tachycardia.3,5,6
- In the absence of both a shortened PR interval and tachycardia, patients are generally thought to fall into a category of “normal variants” with enhanced AV nodal conduction.7
- No studies to date have identified decreased survival or increased risk of sudden death in patients with LGL.3
- Approximately 70% of patients with LGL are women and they usually present in their early thirties.3,5
- How is LGL diagnosed?
- ECG, Holter monitor, echocardiogram to rule out structural disease.
- Ultimately, this is a diagnosis confirmed in the electrophysiology lab.2,3
- What should we do with these patients?
- In the acute setting, a standard workup for tachycardia is indicated i.e. ECG, lytes, TSH. In patients who have dyspnea, a chest X-ray should be obtained.
- To treat the tachycardia, vagal maneuvers can be tried first and if these fail to break the tachycardia, adenosine can be used. Treatment should be based on the cause of tachycardia.3
- Hospitalization is warranted in cases of hemodynamic instability.3
- Patients will require follow up with a cardiologist, despite the fact that long term management is difficult. There is no pathway to ablate but patients can be counseled on avoiding certain triggers like alcohol and coffee. Beta blockers may be used to slow AV nodal conduction. You can use non dihydropyridine calcium channel blockers to treat acute episodes of SVT, but do not use verapamil in conjunction with beta blockers, which can cause complete heart block.3 Permanent pacemaker implantation is a last resort option.2
- “Lown-Ganong-Levine Syndrome.” LITFL Life in the Fast Lane Medical Blog. Web. 5 Nov. 2015.
- “A Glimpse into the Rare Find of Lown-Ganong-Levine Syndrome.” EP Lab Digest. 1 Feb. 2015. Web. 5 Nov. 2015.
- “Lown-Ganong-Levine Syndrome: Background, Pathophysiology, Epidemiology.” Medscape. Web. 5 Nov. 2015.
- MacKenzie, MD, Ross. “Short PR Interval.” Journal of Insurance Medicine 37 (2005): 145-52. Web. 5 Nov. 2015.
- Lown B, Ganong WF, Levine SA. The syndrome of short P-R interval, normal QRS complex and paroxysmal rapid heart action. Circulation. 1952 May. 5(5):693-706.
- Moller P. Letter: Criteria for the LGL syndrome. Am Heart J. 1976 Apr. 91(4):539-41.
- Jackman WM, Prystowsky EN, Naccarelli GV, et al. Reevaluation of enhanced atrioventricular nodal conduction: evidence to suggest a continuum of normal atrioventricular nodal physiology. Circulation. 1983 Feb. 67(2):441-8.
- Josephson ME, Kastor JA. Supraventricular tachycardia in Lown-Ganong-Levine syndrome: atrionodal versus intranodal reentry. Am J Cardiol. 1977 Oct. 40(4):521-7.
- Benditt DG, Pritchett LC, Smith WM, et al. Characteristics of atrioventricular conduction and the spectrum of arrhythmias in lown-ganong-levine syndrome. Circulation. 1978 Mar. 57(3):454-65.