para>Rare during pregnancy
ETIOLOGY AND PATHOPHYSIOLOGY
- Medications
- Digoxin (common)
- Calcium channel blockers
- ²-Blockers (e.g., sotalol)
- Clonidine
- Propafenone (Rythmol), a class IC antiarrhythmic
- Isoproterenol
- Other causes:
- Myocardial ischemia involving the AV node
- Degenerative (fibrosing) and infiltrative diseases involving the heart and its conduction system (e.g., Len ¨gre disease, systemic sclerosis, valvular disease, infective endocarditis, sarcoidosis)
- Degeneration of the AV node secondary to aging
- Neuromuscular diseases (e.g., myotonic muscular dystrophy or Kearns-Sayre syndrome)
- Postoperative cardiac damage
- The abrupt development of complete AV block, especially at His bundle level, may result in a prolonged period of asystole because of a slow and delayed response of the quiescent subsidiary (escape) ventricular pacemaker.
- Marked bradycardia secondary to AV conduction abnormality may lead to prolonged QT interval and paroxysmal torsades de pointes.
- Abrupt termination of tachyarrhythmia leading to precipitous decrease in heart rate.
- Degree of cerebral dysfunction related to duration of cardiac block and effect on cerebral circulation.
Genetics
- May be associated with complete congenital atrioventricular block (CCAVB)
- Of children with CCAVB, 40% experience syncopal episodes (2).
RISK FACTORS
- Use of the medications listed under "Etiology and Pathophysiology "
- Coronary artery disease
- Endocarditis and myocarditis
- Mitral/aortic valve disease
- History of previous AV nodal dysfunction/cardiac surgery
- Bundle-branch and/or fascicular block
- Acute myocardial infarction (MI) (especially acute right coronary artery occlusion)
- Amyloidosis
- Chagas disease
- Lyme disease
- Connective tissue diseases involving the heart (e.g., systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis)
- Hyperkalemia
- Acidosis
- Rheumatic fever
GENERAL PREVENTION
- Avoid negative chronotropic drugs (e.g., ²-blockers, calcium channel blockers, digoxin, clonidine) in at-risk patients.
- Prevention of cardiovascular disease through diet/exercise
COMMONLY ASSOCIATED CONDITIONS
- Myocardial ischemia/acute MI
- High-degree AV conduction abnormality
- Atrial standstill
- Right bundle-branch block (RBBB)
- CCAVB
- Systemic manifestations of connective tissue disease
- Sick sinus syndrome
- Neuromuscular disease
- Sudden death
- Heart failure
DIAGNOSIS
HISTORY
- History of predisposing factor/related conditions
- Angina
- Fatigue/exercise intolerance
- Dyspnea
- Altered sensorium/loss of consciousness unrelated to position/exertion
- Acute onset of syncopal/near-syncopal symptoms ( ± palpitations)
PHYSICAL EXAM
- Acute bradycardia
- Hypotension
- Pallor
- Reactive hyperemia with recovery
- Convulsions or seizure-like activity without postictal state
- Pulse <50 bpm
DIFFERENTIAL DIAGNOSIS
- Seizure
- Vertigo
- Transient ischemic attack
- Orthostatic hypotension
- Vasovagal syncope
- Hypoglycemia
- Neurocardiogenic syncope
- Cardiac arrhythmias
- Ventricular tachycardia
- Supraventricular tachycardia
- Reentrant tachycardia
- Wolff-Parkinson-White syndrome
- Sinus arrest
- Sinus exit block
- Sick sinus syndrome
- Transition from normal sinus rhythm to atrial fibrillation or vice versa
- Brugada syndrome
- Carotid sinus hypersensitivity
DIAGNOSTIC TESTS & INTERPRETATION
Initial Tests (lab, imaging)
- Cardiac enzymes (i.e., troponin-I)
- EEG with cardiac monitoring (to differentiate between syncope and seizure disorder) (3)
- ECG: partial/complete heart block at onset of symptoms with slow or no ventricular escape
- Bradycardia
- AV block 50 " 60%
- Sinoatrial block 30 " 40%
- Widened QRS, possibly of RBBB type, QTc >45 msec 4%
- Ventricular fibrillation/tachycardia <1%
- Marked ventricular slowing during sleep
- Wolf-Parkinson-White delta waves (infrequent)
- Serum digoxin level (other medication levels if appropriate)
- Thyroid-stimulating hormone level
- Hematocrit/hemoglobin
- Blood electrolyte levels (especially potassium)
- Transthoracic echocardiogram if cardiomyopathy/valvular disease is suspected
Follow-Up Tests & Special Considerations
- ECG, event monitor, or 24-hour Holter monitor
- Renal failure may lead to falsely elevated creatinine kinase.
Diagnostic Procedures/Other
- Coronary catheterization to rule out coronary ischemia if suspected
- Electrophysiologic testing to assess cardiac conduction system if ECG testing is ambiguous
- Tilt-table test to evaluate neurogenic etiology
- Myocardial biopsy if infiltrative disease suspected
Test Interpretation
- Myocardial ischemia
- Evidence of degenerative/infiltrative disease involving the AV node/His bundle
TREATMENT
GENERAL MEASURES
- Inpatient assessment in a monitored setting
- Continued treatment for prevention of future episodes in an ambulatory setting
- Cessation of precipitating medications
- Pacemaker implantation should be performed; oral medications are inferior therapy (4).
- Avoid: isoproterenol, digoxin, fosphenytoin, phenytoin
- Treat calcium channel blocker toxicity with calcium gluconate 60 mg/kg/dose over 5 minutes (max: 3,000 to 6,000 mg/dose) every 10 to 20 minutes; can repeat for 3 to 4 additional doses
- Treat ²-blockers toxicity with glucagon IV bolus 3 to 10 mg, then infuse at a rate of 2 to 5 mg/hr.
- For moderate ²-blocker or calcium channel blocker toxicity, consider high-dose insulin (with glucose) or vasopressor therapy (5).
- Symptomatic ²-blocker and calcium channel blocker toxicity should be admitted to the ICU for support and continuous cardiac monitoring (5).
- Blood pressure support for shock resulting from combined ²-blocker and calcium channel blocker toxicity with methylene blue bolus 1 mg/kg over 10 minutes, then infuse at 1 mg/kg/hr for 10 hours (5)
- Treat mixed or multidrug toxicity with lipid resuscitation therapy (Intralipid) or molecular absorbent recirculating system (5).
MEDICATION
First Line
- No medication currently is recommended for long-term treatment of symptomatic arrhythmias (6)[A].
- For symptomatic bradyarrhythmias (7)[C]
- Atropine 0.5 mg IV push to be given during the complete heart block with hypotension; may be repeated q3 " 5min with a maximum total dose of 3 mg; less likely to be effective if atrial rate is already adequate or in patients who have undergone cardiac transplantation
- Precautions: Doses of atropine sulfate of <0.5 mg may paradoxically result in further slowing of the heart rate.
- Contraindications: narrow-angle glaucoma, reflux esophagitis, obstructive GI disease, unstable cardiovascular status in acute hemorrhage or thyrotoxicosis, myasthenia gravis
- Correction of precipitating conditions (e.g., hypokalemia, acidosis)
Second Line
- For arrhythmias and heart block
- Ephedrine 5 to 25 mg IV push, titrate to patient response; repeat in 5 to 10 minutes if necessary; 25 to 50 mg IM or SC, range from 10 to 50 mg
- Precautions: hypertension and tachycardia; risk of serious adverse effects; caution in patients with cardiovascular disease, pregnancy, limited use in pediatric patients
- Contraindications: angle-closure glaucoma; should not be used if vasopressor drugs are contraindicated; known hypersensitivity to ephedrine
- Possible interactions: Concurrent use of certain monoamine oxidase inhibitors and catecholamines may result in increased hypertensive effects/hypertensive crisis; concurrent use of dopamine and epinephrine with cyclopropane/halogenated hydrocarbon anesthetic may sensitize the heart to the arrhythmic action of sympathomimetic drugs.
ISSUES FOR REFERRAL
Syncope requires frequent and close follow-up.
SURGERY/OTHER PROCEDURES
- Transthoracic pacing should be attempted as a temporizing device if a patient is bradycardic and hemodynamically unstable.
- Intracardiac pacing is the treatment of choice for patients with complete heart block and Stokes-Adams syncope (6)[A].
- Dual chamber may be more effective than single chamber pacing in AV block (8)[B].
- Transvenous pacing as interim measure to stabilize
- See 2012 American College of Cardiology/American Heart Association/Heart Rhythm Society focused update incorporated into the 2008 guidelines for device-based therapy of cardiac rhythm abnormalities for suggested intervention based on precipitating cause (9).
- Emergency insertion of a ventricular pacemaker is required when ventricular fibrillation/tachycardia is present.
INPATIENT CONSIDERATIONS
Admission Criteria/Initial Stabilization
Syncope in the setting of known AV node conduction abnormality or of an unknown cause. See first-line treatments to be used when intracardiac pacing is not available. External pacing may be life-saving.
IV Fluids
Use caution in patients with congestive heart failure.
Nursing
- Telemetry
- Out of bed with assist if patient has history of falls due to syncope
Discharge Criteria
Institution of proper treatment with resolution of symptoms
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
Routine follow-up with cardiologist
Patient Monitoring
- Routine pacemaker check if permanent pacemaker has been implanted
- Follow-up Holter and/or event monitoring for 2 weeks after causal medication has been discontinued
- Discontinuation of driving, heavy machinery operation; caution about fall risks
DIET
Regular
PATIENT EDUCATION
After the diagnosis has been made and a pacemaker has been implanted (if required), instruct patient regarding pacemaker guidelines.
PROGNOSIS
Excellent with proper institution of exogenous pacing; further symptoms are not expected.
COMPLICATIONS
- Sudden death (uncommon)
- Cerebral hypoxic damage and other end-organ damage with protracted bradycardia with hypotension
REFERENCES
11 Kojic EM, Hardarson T, Sigfusson N, et al. The prevalence and prognosis of third-degree atrioventricular conduction block: the Reykjavik study. J Intern Med. 1999;246(1):81 " 86.22 Vukomanovic V, Stajevic M, Kosutic J, et al. Age-related role of ambulatory electrocardiographic monitoring in risk stratification of patients with complete congenital atrioventricular block. Europace. 2007;9(2):88 " 93.33 D az-Castro O, Orizaola P, V ‘zquez S, et al. Images in cardiovascular medicine. "Stokes-Adams epilepsy " : sometimes we need the electroencephalogram. Circulation. 2005;112(8):e101 " e102.44 Sigurd B, Sand Έe E. Management of Stokes-Adams syndrome. Cardiology. 1990;77(3):195 " 208.55 Tomassoni AJ, Sanders S, Marcolini EG. Emergency department treatment of beta blocker and calcium-channel blocker poisoning. EM Critical Care. 2014:4:1 " 16.66 Epstein AE, Dimarco JP, Ellenbogen KA, et al. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: executive summary. Heart Rhythm. 2008;5(6):934 " 955.http://www.heart.org/HEARTORG/CPRAndECC/Science/Guidelines/2010-AHA-Guidelines-for-CPR-ECC_UCM_317311_SubHomePage.jsp. Accessed 2014.77 Dretzke J, Toff WD, Lip GY, et al. Dual chamber versus single chamber ventricular pacemakers for sick sinus syndrome and atrioventricular block. Cochrane Database Syst Rev. 2004;(2):CD003710.88 Epstein AE, DiMarco JP, Ellenbogen KA, et al. 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation. 2013;127(3):e283 " e352.
ADDITIONAL READING
- Bedford Laboratories. Ephedrine Sulfate Injection. USP (50 mg/mL) Prescribing Information. Bedford, OH: Bedford Laboratories; 1998.
- Elizari MV, Acunzo RS, Ferreiro M. Hemiblocks revisited. Circulation. 2007;115(9):1154 " 1163.
- Hood R. Syncope in the elderly. Clin Geriatr Med. 2007;23(2):351 " 361.
- Jensen G, Sigurd B, Sandoe E. Adams-Stokes seizures due to ventricular tachydysrhythmias in patients with heart block: prevalence and problems of management. Chest. 1975;67(1):43 " 48.
- McEvoy GK, ed. Ephedrine. In: AHFS Drug Information 2003. Bethesda, MD: American Society of Health " System Pharmacists; 2003:1235 " 1241.
- Vanden Hoek TL, Morrison LJ, Shuster M, et al. Part 12: cardiac arrest in special situations: 2010 American Heart Association Guidelines for cardioresuscitation and emergency cardiovascular care. Circulation. 2010;122(18)(Suppl 3):S829 " S861.
- You C, Chong C, Wang T, et al. Unrecognized paroxysmal ventricular standstill masquerading as epilepsy: a Stokes-Adams attack. Epileptic Disord. 2007;9(2):179 " 181.
CODES
ICD10
I45.9 Conduction disorder, unspecified
ICD9
426.9 Conduction disorder, unspecified
SNOMED
- Stokes-Adams attack (disorder)
- Stokes-Adams syndrome (disorder)
CLINICAL PEARLS
- Syncope due to Stokes-Adams attacks frequently can be confused for epilepsy.
- Stokes-Adams attacks usually require insertion of a pacemaker for definitive treatment unless due to a reversible condition, such as medication toxicity.
- External pacing may serve as a bridge until more definitive management can be accomplished.