Rosen & Barkin's 5-Minute Emergency Medicine Consult (594 page)

• Symptomatic prolonged QT
  
• Syncope
  
• Cardiac dysrhythmia
  
• Possible cardiac or ischemic event
  
• Metabolic abnormality
  

Asymptomatic prolonged QT in consultation with cardiology

Follow-up recommended in all patients with a new diagnosis of prolonged QT

• Suspect prolonged QT in patients with syncope
  
• Prolonged QT is an independent risk factor for sudden cardiac death.
  
• Correct electrolyte abnormalities and discontinue offending drugs in those with prolonged QT.
  
• Magnesium sulfate followed by pacing for torsades de pointes.
  

• Chugh SS, Reinier K, Singh T, et al. Determinants of prolonged QT interval and their contribution to sudden death risk in coronary artery disease: The Oregon sudden unexpected death study.
  Circulation
  . 2009;119:663–670.
  
• John RM, Tedrow UB, Koplan BA, et al. Ventricular arrhythmias and sudden cardiac death.
  Lancet
  . 2012;380(9852):1520–1529.
  
• Kannankeril P, Roden DM, Darbar D. Drug-induced long QT syndrome.
  Pharmacol Rev
  . 2010;62(4):760–781.
  
• Mikesell CE, Atkinson DE, Rachman BR. Prolonged QT syndrome and sedation: A case report and a review of the literature.
  Pediatr Emerg Care
  . 2011;27(2):129–131.
  
• Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 guidelines for management of patients With ventricular arrhythmias and the prevention of sudden cardiac death-executive summary: A report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death).
  J Am Coll Cardiol
  . 2006;48:1064.
  

See Also (Topic, Algorithm, Electronic Media Element)

www.QTDrugs.org

CODES

426.82 Long QT syndrome

BASICS

CNS infectious disease of mammals caused by the rabies virus:

• Highest case fatality rate of any known infectious disease
  

• Epidemiology:
  
  • 30,000–70,000 people die/yr worldwide
    
  • Especially common in Southeast Asia, Philippines, Africa, South America, and Indian subcontinent
    
  • US has 2–3 human cases per year.
    
  • Most clinical cases in US from foreign travel and bat exposures
    
  • Raccoons, skunks, foxes, bats, dogs, woodchucks, groundhogs are reservoirs.
    
  • In US bats are the most common reservoir while abroad dogs are more common.
    
  • Squirrels, rats, mice, hamsters, guinea pigs, gerbils, chipmunks, and rabbits can also be infected but there has never been a reported case of human transmission.
    
• Pathophysiology:
  
  • Negative-stranded RNA genome, family Rhabdoviridae, genus Lyssavirus
    
  • Mode of transmission:
    
    • Contact with infected saliva of host
      
    • Bite: Most common
      
    • Nonbite: Saliva or bat aerosol exposure to an open wound or mucous membrane
      
    • Transplant procedures are the only well-documented person-to-person transmission
      
    • Not considered a transmission risk: Petting rabid animal or contact with the blood, urine, or feces of a rabid animal
      
  • Progression after infection:
    
    • Virus multiplies in local tissue and is taken up into muscle through n-acetylcholine receptors.
      
    • Virus enters peripheral nerves and is transported to CNS via retrograde axoplasmic flow at ~1--4 inches per day
      
    • Once in CNS, rapid replication and dissemination cause encephalitis.
      
    • Centrifugal spread of virus to peripheral nerves, including salivary glands
      

DIAGNOSIS

• Once a patient exhibits clinical signs course is almost universally fatal.
  
• 5 stages: Incubation, prodrome, encephalitis, coma, death (or recovery):
  
  • Incubation: 1–3 mo (range 10 days to 1 yr):
    
    • Virus amplifies in peripheral tissues
      
    • Time depends on amount inoculated and proximity to CNS, thus shorter incubation for head or neck bites
      
  • Prodrome: 1–7 days:
    
    • Nonspecific symptoms: Fever, headache, malaise, myalgias, anorexia, sore throat, nausea, and vomiting
      
    • Paresthesias or fasciculations around bite site give clue to diagnosis.
      
  • Encephalitis (classic form): 2–7 days:
    
    • Anxiety, agitation, hallucinations, confusion or delirium, muscle spasms, opisthotonos, and seizure
      
    • Aerophobia (pathognomonic): Pharyngeal spasm from draft of air
      
    • Hydrophobia (pathognomonic): Violent involuntary muscle contraction of diaphragm, pharyngeal, laryngeal, and accessory respiratory muscles when attempting to swallow (seen in up to half of cases)
      
    • Dysrhythmias, myocarditis, autonomic instability, and fevers
      
    • Brainstem involvement: Diplopia, facial paralysis
      
  • Coma:
    
    • Apnea from respiratory center involvement, vascular collapse, flaccid paralysis, adult respiratory distress syndrome, syndrome of inappropriate diuretic hormone
      
    • Most die within 2 wk
      
  • Death (or recovery):
    
    • Almost universally fatal if no pre- or postexposure prophylaxis (PEP) given
      
    • Rare case reports of survival without prophylaxis
      
    • Known survivors have some residual neurologic deficits
      
• 3 manifestations of disease:
  
  • Classic or encephalitic rabies accounts for ∼80% of cases. See above.
    
  • Paralytic rabies (∼20%): Ascending paralysis mimicking Guillain–Barré syndrome
    
  • Atypical rabies (<1%): Seen with bat-associated rabies. Characterized by neuropathic pain, sensory or motor deficits, choreiform movements, myoclonus, and seizures
    

• Bite wound or other known exposure
  
• Bat found in room with person unable to give history (e.g., child or intoxicated): Assume exposure
  
• Travel to endemic areas with associated dog exposure
  
• Rabid animals more likely to attack unprovoked. Any handling of the animal prior to bite is considered a provoked attack.
  

• Fever
  
• A bat bite wound often not visible on exam
  
• Altered mental status, seizures, encephalopathy
  
• Percussion myoedema: Muscle mounds at percussion site
  
• Autonomic manifestations: Dilated pupils, perspiration, hypersalivation, orthostatic hypotension
  

• Saliva:
  
  • Rabies RNA by reverse transcription polymerase chain reaction (RT-PCR)
    
  • Virus isolation in cell culture
    
• Serum:
  
  • Rabies antibodies are diagnostic only if not vaccinated.
    
  • Earliest positive, day 6
    
• CSF:
  
  • Mildly elevated WBC and protein, normal glucose
    
  • Virus isolation
    
  • Rabies antibodies in CSF are diagnostic, even if immunized.
    

• CBC: May have leukocytosis
  
• Electrolytes, BUN, creatinine, glucose
  
• Blood cultures/urinalysis:
  
  • Search for other infection/illness
    
• Neck biopsy: RT-PCR, immunofluorescent staining for viral antigen
  

• CT head: Usually normal but may show cerebral edema, evaluate for other causes of symptoms
  
• Chest radiograph: Other infectious etiologies
  

Lumbar puncture

• Other causes of encephalitis:
  
  • Herpesviruses: HSV1, VZV
    
  • Enterovirus (Coxsackie, echovirus, poliovirus)
    
  • Arboviruses (West Nile, eastern/western equine encephalitis, St. Louis)
    
• Tetanus
  
• Delirium tremens
  
• Psychosis
  
• Paralytic form:
  
  • GBS
    
  • Polio
    
  • Tick-bite paralysis
    
  • Immune-mediated polyneuritis
    
  • Botulism
    

TREATMENT