Syncope and Loss of Consciousness of Unknown Etiology

Question 1

Major ddx for LOC of unknown etiology

Answer 1

• Syncope
  
  • Arrhythmia/cardiogenic
  • Neurocardiogenic
  • Vasovagal
• Seizure
• TIA
• Vertigo
• Cardiac outflow obstruction (aortic stenosis, HOCM)
• Neurovascular perfusion defect (carotid stenosis, fibromuscular dysplasia)

Question 2

Sick sinus syndrome

Answer 2

• Dysfunction of the SA node leading to cardiogenic syncope
• Often due to senescence of the SA node and surrounding atrial myocardium
• Diagnosis:
  
  • Made based on history and ECG findings
  • Holter monitor is generally required to rule out other arrhythmias, as SSS is a diagnosis of exclusion
  • ECG findings are often nonspecific and vague. No true arrhythmias, but generally inappropriately bradycardic in response to low blood pressure with infrequent sinus pauses.Tachycardia-bradycardia may also be seen.
• Treatment:
  
  • Temporizing external pacing may be required
  • Definitive treatment is permanent pacemaker

Question 3

Tilt-table testing

Answer 3

• Evaluates how the body regulates blood pressure in response to changes in posture
• Things that are monitored:
  
  • ECG
  • Continuous blood pressure monitoring
• Pharmacologic agents may be used to stress the system

Question 4

Exercise-induced syncope

Answer 4

Worrisome for cardiac outflow obstruction, particularly HOCM or aortic stenosis

Question 5

Neurocardiogenic/vasovagal syncope

Answer 5

• Mechanism:
  
  • Thought to result from decreased venous return to heart, leading to increased HR and contractility due to carotid sinus baroreceptors (repsond to low pressure), followed by activation of parasympathetic left ventricular baroreceptors (respond to high pressure), resulting in hypotension with paradoxical bradycardia
• Often precipitated by an unpleasant physical or emotional stimulus (pain, blood, GI discomfort)
• Diagnosis: Clinical
• Treatment: Supportive (hydration, pressure stockings). Identification and avoidance of triggers.

Question 6

Risk factors for adverse outcome within 1 week of syncopal event

Answer 6

• Cardiovsacular:
  
  • Abnormal ECG, CHF, SBP < 90 mmHg, or Hx cardiovascular disease
• Pulmonary:
  
  • Dyspnea or Hx pulmonary disease
• Hematocrit < 30%
• Lack of prodrome
• Age > 65 years
  
  • Note: This is important to remember because it changes management, so it IS worth knowing

Question 7

High-risk syncope patient management

Answer 7

Admit for inpatient workup including continuous telemetry, echocardiography, carotid ultrasound, and stress test

If they have a negative workup, they may be discharged on an implantable loop recorder (NOT Holter monitor)

Question 8

Low-risk syncope patient management

Answer 8

Follow up on an outpatient basis.

May use Holter monitor/implantable loop recorder or tilt-table test as an outpatient, depending on clinical suspicion.

Question 9

Difference between a Holter monitor and an implantable loop recorder.

Answer 9

Holter monitor is intended for ~24-48 hour monitoring.

Implantable loop recorder is intended for more chronic monitoring.

Question 10

Treatment of orthostatic hypotension

Answer 10

• Conservative:
  
  • Volume resuscitation
  • Compression stockings
  • Avoiding BP-reducing medications
  • Correction of electrolyte imbalances
• Persistent:
  
  • Midodrine
  • Fludricortisone
  • Droxipoda

Question 11

Droxipoda

Answer 11

• Norepinephrine-pro drug recently FDA approved for treatment of neurogenic orthostatic hypotension

Question 12

Indications for permanent pacing

Answer 12

• Heart block
• Sick sinus syndrome
• Symptomatic bradyarrhythmias refractory to medical therapy

Question 13

The single most important feature for differentiating a seizure from syncope

Answer 13

Presence of absence of a post-ictal state