Short PR interval

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vendhan Ramanujam M.B.B.S [2]

Overview

PR interval below its normal interval of 0.10 to 0.21 seconds is called as short PR interval. Although short PR interval may be a normal variant, it has also been noted in numerous clinical conditions like cardiomyopathy, mitral valve prolapse, Duchenne's muscular dystrophy, Pompe disease, Fabry disease etc. It is also seen in number of electrophysiological disorders including preexcitation syndrome, premature atrial beats, AV junctional rhythms and isorhythmic AV dissociation.

Pathophysiology

Clinical conditions

Short PR interval in most of the clinical conditions is due to the preexcitation and ectopics arising from dilated atria.

Electrophysiological disorders

The two subsets of preexcitation syndrome, Lown-Ganong-Levine syndrome and Wolff-Parkinson-White syndrome are associated with short PR interval due to bypass tracts that bypass the AV node, directly connecting the atria with the ventricle.

The possibilities for short PR interval in LGL syndrome are faster AV nodal conduction due to the rapidly conducting fibers within the AV node or rapid conduction through Brechenmacher fibers that bypass the AV node connecting atria with bundle of His or the conduction through the accessory pathway James fibers that connect atria with low AV node.
Short PR interval in WPW syndrome results from an accessory pathway, the bundle of Kent that directly connects the atria to the ventricles, bypassing the AV node.

The difference between both is that LGL syndrome has a normal QRS complex following ventricular activation via the normal conduction pathway (His Purkinje system) and WPW syndrome has a wide QRS complex due to the combined early ventricular activation via the abnormal accessory pathway and terminal ventricular activation via the normal conduction system.

Premature atrial beats arising close to the AV node (low atrial ectopics) activate the atria retrogradely, producing an inverted P wave with a relatively short PR interval.
In AV junctional rhythms with retrograde atrial activation the retrograde P waves occur before the QRS complex shortening the PR interval. Negative P waves in leads II, III and aVF point towards this diagnosis.
In isorhythmic AV dissociation P waves are dissociated from QRS complex but both their rates are similar resulting in P waves marching back and forth across the QRS complex creating an appearance of sinus P wave with a short PR interval.

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

Common Causes

Causes by Organ System

Cardiovascular	Congenital heart disease, congestive heart failure, coronary heart disease, dilated cardiomyopathy, Ebstein’s anomaly, hypertensive heart disease, hypertrophic cardiomyopathy, ischemic heart disease, junctional tachycardia, Lown-Ganong-Levine syndrome, Mahaim fiber tachycardia, mitral regurgitation, mitral stenosis, mitral valve prolapse, myocardial infarction, myocarditis, obstructive sleep apnea, pericarditis, restrictive cardiomyopathy, rheumatic fever, sustained ventricular tachycardia, valvular heart disease, Wolff-Parkinson-White syndrome
Chemical/Poisoning	No underlying causes
Dental	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	5-fluorouracil, aminophylline, amiodarone, amlodipine, amphetamines, beta blockers, carbamazepine, cimetidine, clonidine, digoxin, diltiazem, dobutamine, ephedrine, flumazenil, guanethidine, isoproterenol, lithium, methyldopa, phenylephrine, reserpine, salbutamol, sympathomimetic agents, tacrolimus, theophylline, thiazides, verapamil
Ear Nose Throat	No underlying causes
Endocrine	Cushing's syndrome, diabetic ketoacidosis, hypothyroidism, pheochromocytoma, thyrotoxicosis
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	Duchenne's muscular dystrophy, Emery-Dreifuss muscular dystrophy, Fabry disease, Friedreich ataxia, glycogen storage disease II, hemochromatosis, LQT type 4, Pompe disease
Hematologic	No underlying causes
Iatrogenic	Cardioversion, pacemaker malfunction, permanent pacemaker
Infectious Disease	Chagas disease, diphtheria, leptospirosis, Lyme disease, pneumonia, rheumatic fever, salmonella, trichinosis
Musculoskeletal/Orthopedic	Duchenne's muscular dystrophy, Emery-Dreifuss muscular dystrophy
Neurologic	Friedreich ataxia
Nutritional/Metabolic	Diabetic ketoacidosis, Fabry disease, glycogen storage disease II, hypocalcemia, hypokalemia, hypomagnesemia, Pompe disease
Obstetric/Gynecologic	No underlying causes
Oncologic	No underlying causes
Ophthalmologic	No underlying causes
Overdose/Toxicity	Cannabis, cocaine, digoxin, grayanotoxin
Psychiatric	No underlying causes
Pulmonary	Acute respiratory failure, chronic obstructive pulmonary disease, obstructive sleep apnea, pneumonia, pulmonary embolism
Renal/Electrolyte	Chronic renal failure
Rheumatology/Immunology/Allergy	Scleroderma
Sexual	No underlying causes
Trauma	No underlying causes
Urologic	No underlying causes
Miscellaneous	Idiopathic

Causes in Alphabetical Order

References

↑ MacKenzie, R. (2005). "Short PR interval". J Insur Med. 37 (2): 145–52. PMID 16060547.
↑ Perloff, JK. (1984). "Cardiac rhythm and conduction in Duchenne's muscular dystrophy: a prospective study of 20 patients". J Am Coll Cardiol. 3 (5): 1263–8. PMID 6707378. Unknown parameter |month= ignored (help)
↑ Efthimiou, J.; McLelland, J.; Betteridge, DJ. (1986). "Short PR intervals and tachyarrhythmias in Fabry's disease". Postgrad Med J. 62 (726): 285–7. PMID 3086855. Unknown parameter |month= ignored (help)
↑ Huang, SK.; Rosenberg, MJ.; Denes, P. (1984). "Short PR interval and narrow QRS complex associated with pheochromocytoma: electrophysiologic observations". J Am Coll Cardiol. 3 (3): 872–5. PMID 6693659. Unknown parameter |month= ignored (help)
↑ Castellanos, A.; Castillo, CA.; Agha, AS.; Tessler, M. (1971). "His bundle electrograms in patients with short P-R intervals, narrow QRS complexes, and paroxysmal tachycardias". Circulation. 43 (5): 667–78. PMID 5578843. Unknown parameter |month= ignored (help)

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[MacKenzie-2005-1] MacKenzie, R. (2005). "Short PR interval". J Insur Med. 37 (2): 145–52. PMID 16060547.

[Perloff-1984-2] Perloff, JK. (1984). "Cardiac rhythm and conduction in Duchenne's muscular dystrophy: a prospective study of 20 patients". J Am Coll Cardiol. 3 (5): 1263–8. PMID 6707378. Unknown parameter |month= ignored (help)

[Efthimiou-1986-3] Efthimiou, J.; McLelland, J.; Betteridge, DJ. (1986). "Short PR intervals and tachyarrhythmias in Fabry's disease". Postgrad Med J. 62 (726): 285–7. PMID 3086855. Unknown parameter |month= ignored (help)

[Huang-1984-4] Huang, SK.; Rosenberg, MJ.; Denes, P. (1984). "Short PR interval and narrow QRS complex associated with pheochromocytoma: electrophysiologic observations". J Am Coll Cardiol. 3 (3): 872–5. PMID 6693659. Unknown parameter |month= ignored (help)

[Castellanos-1971-5] Castellanos, A.; Castillo, CA.; Agha, AS.; Tessler, M. (1971). "His bundle electrograms in patients with short P-R intervals, narrow QRS complexes, and paroxysmal tachycardias". Circulation. 43 (5): 667–78. PMID 5578843. Unknown parameter |month= ignored (help)

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