Syncope

Syncope is common, and difficult to investigate because by definition, the patient has recovered from the event! It is summarised here. There are five main causes to consider:

1. Neurocardiogenic or vasovagal (emotional, situational or orthostatic triggers)
2. Cardiac
3. Orthostatic
4. Neurological / psychiatric (5%). Neurological causes of syncope include basilar artery migraine, vestibular dysfunction and vertebrobasilar ischaemia. Psychiatric syncope is a recognised syndrome consisting of syncopal episodes found in anxiety, depression and conversion disorder that resolve with treatment of the psychiatric disorder.
5. Essential (no cause found -35-50%).

These will all be covered in turn, and separately. There are scoring systems used to help risk-stratify syncope (very important).  I do like EM Basic's quick approach:

Syncope + headache= subarachnoid or intracranial hemorrhage

Syncope + neuro deficit= stroke/TIA or intracranial bleed

Syncope + confusion= seizure

Syncope + chest pain= MI, PE, or aortic dissection

Syncope + back/abdominal pain in older patient= abdominal aortic aneurysm (AAA)

Syncope + positive HCG= ectopic pregnancy

Young with Syncope R/O: Structural heart prob HOCM Elect (brugada, prolonged QT, arrhythmia) Hypoglycaemia CNS insult Abnormal Lytes #FOAMed
— Meshal AlBassam (@meshal_albassam) March 16, 2014

OESIL (Osservatorio Epidemiologico della Sincope nel Lazio) Score

• age over 65 years;
• previous history of cardiovascular disease;
• syncope without prodrome and
• abnormal ECG

The score predicts 12 month mortality which rises from under 1% for patients with no risk factors to over 50% in patients with all 4 risk factors. I've never seen this used in clinical practice, or heard of it.

The San Francisco Rule
The San Francisco rule identifies high risk patients based on the presence of the following factors:

• History of congestive cardiac failure
• Haematocrit < 30%
• Abnormal ECG
• Complaint of shortness of breath
• Systolic Blood Pressure < 90 mm Hg

The presence of any factor is considered sufficient for the patient to be high risk.The rule is 98% sensitive and 56% specific to predict adverse events.

The EGSYS (derived from patients enrolled in the Evaluation of Guidelines in SYncope Study 2 trial) Score

Predictor	Score
Palpitations preceding syncope	4
Syncope during effort	3
Heart disease/ abnormal ECG	3
Syncope while supine	2
Precipitating/ predisposing factors	-1
Autonomic prodromes	-1

This specifically identified cardiac syncope with a score of 3 or more being 99% sensitive and 65% specific for identifying cardiac syncope (positive and negative predictive values 33% and 99%). Again, I've never seen this used in clinical practice.

Investigations
A completely normal ECG makes a cardiac cause of syncope other than transient arrhythmia unlikely.

Echocardiography should be performed in any patient with a cardiac murmur and to diagnose and quantify suspected heart failure. If aortic stenosis is suspected, echocardiography should be performed urgently.
Carotid sinus massage for 5 to 10 seconds with continuous ECG and blood pressure monitoring can be used to diagnose carotid sinus syndrome. It is considered positive if it produces a drop in systolic blood pressure of 50 mm Hg or a period of asystole of 3 seconds.
Ambulatory 24 hour ECG recording may be considered in patients with a high pre-test probability of arrhythmia.
Tilt table testing is not used much any more

@drsuneet @SergioPinski @MGKatz036 To me, tilts worthless in eval of syncope. Not reproducible and high false pos/neg rates.
— Westby Fisher, MD (@doctorwes) April 6, 2014

Management
Think about all causes - 18% of patients with syncope in one study had more than one cause.

Driving - consider whether the patient should refrain from driving

Other guidelines can be found here.

Orthostatic Syncope

Orthostatic syncope (10%) is defined as an orthostatic drop of >20mm systolic blood pressure or >10 mm diastolic blood pressure. This may be due to absolute volume depletion from dehydration or haemorrhage or to venodilatation caused by medications or autonomic insufficiency (eg as occurs in Parkinson’s Disease). It is NOT the same as reflex syncope caused by orthostatic stresses, although the clinical presentation is very similar.

Pathophysiology
Sympathetic activity is chronically impaired, so vasoconstriction can't happen. This means when you stand, the BP falls.

Clinical Features
Syncope is one symptom, others include dizziness/ lightheadedness, pre-syncope; weakness, fatigue, lethargy;palpitations, sweating; (iv) visual disturbances (including blurring, enhanced brightness, tunnel vision); hearing disturbances (including impaired hearing, crackles, and tinnitus); and pain in the neck (occipital/paracervical and shoulder region), low back pain, or precordial pain.

Cardiac Causes of Syncope

There are lots of cardiac causes of syncope, and they account for 10 - 30% of syncopal episodes. Cardiac causes include: arrhythmias, cardiac failure, ventricular dysfunction (eg. hypertrophic obstructive cardiomyopathy HOCM) and valvular heart disease.

Arrhythmias
The most common cardiac causes of syncope, and the arrhythmia should be treated.
Bradycardias - Mobitz II and complete AV block are most likely to cause syncope.
Tachycardias - Narrow and Broad
Sick sinus syndrome - the sinoatrial node is damaged,because of either abnormal automaticity or sinoatrial conduction abnormalities.Syncope is due to long pauses caused by sinus arrest or sinoatrial block and a failure of escape mechanism. It is a completely different pathogenesis to carotid sinus syndrome. It is more likely to happen in people >65 years old, with ischaemic heart disease risk factors. ECGs can show many things, including sinus bradycardia.

Arrhythmia related syncope can be diagnosed on ECG in the presence of:
    Sinus bradycardia rate under 40 bpm
    Mobitz II second degree block or above
    Alternating right and left bundle branch block
    Ventricular tachycardia or rapid supraventricular tachycardia
    Pacemaker malfunction

Cardiac Failure
This will be diagnosed as normal.

Ventricular Dysfunction
The ECG needs careful scrutiny.

Valvular Problems
Aortic stenosis needs excluding. What better summary than the one from The Calgary Guide here. 

Reflex syncope

This is one of the most common causes of syncope, estimated at 35-50%, and about 30% of people have survived at least one faint - and many more will have witnessed fainting! Vasovagal syncope is the "common faint" but it can be difficult to differentiate "faints" from other causes of syncope.

Reflex syncope is neurally modulated and can be split into three main groups:
- Vasovagal (emotional eg Blood and orthostatic stress)
- Situational (cough, sneeze, defaecation, micturition, post-exercise, post-prandial)
- Carotid sinus syncope

Signs and Symptoms
Transient loss of consciousness
Jerky movements similar to a seizure
May be associated with palpitations, blurred vision, and feelings of nausea, warmth and light-headedness prior to the syncope episode, and patients are more likely to have had previous syncopal episodes.

Pathophysiology
This arises from an initial increase in sympathetic outflow followed by a rebound reduction in sympathetic activity leaving unopposed parasympathetic activity causing vasodilatation, bradycardia and hypotension.
In other word, you get worried about something, so get the flight or fight response. This then stops, and the unopposed activity makes you collapse. 

Investigations
Look for carotid sinus hypersensitivity in any patient older than 40. A ventricular pause lasting >3 seconds or fall in BP of 50mmHg defines carotid sinus hypersensitivity.


Treatment
Exercises to improve blood flow
Driving - no restriction