Approach to syncope: Clinical sciences

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Introduction0:00–0:33

Syncope is a sudden, transient loss of consciousness triggered by a temporary decrease in cerebral perfusion. Based on the underlying cause, syncope can be categorized into several types.
These include cardiogenic syncope caused by heart-related issues, reflex-mediated syncope triggered by various stimuli like neck pressure, syncope due to orthostatic hypotension, and neurologic syncope, which is associated with neurological conditions.Now, if your patient presents with a chief concern suggesting syncope, perform an ABCDE assessment to determine if they are unstable or stable.

Unstable0:33–1:10

If unstable, stabilize the airway, breathing, and circulation, obtain IV access, and consider giving IV fluids. Next, put your patient on continuous vital sign monitoring including heart rate, blood pressure, and pulse oximetry, as well as cardiac telemetry.
Finally, if needed, provide supplemental oxygen.Okay, now that we’re done with unstable patients, let’s go back to the ABCDE assessment and take a look at stable ones.

Stable1:10–3:13

In this case, obtain a focused history and physical examination, as well as an ECG. Your patient, and ideally any witnesses present, will likely report a brief loss of consciousness and postural tone, typically lasting less than a minute.
You might also be able to uncover a clear trigger, like a sudden change in position, dehydration, exertion, strong emotional reaction, defecation, urination, or even coughing.
Additionally, your patient might report prodromal symptoms, typically lightheadedness, feeling warm or clammy, nausea, and visual changes.
During the physical exam, you might notice myoclonic jerks, which are non-rhythmic muscle twitches that may happen during a witnessed syncopal event, lasting less than 15 seconds.
With these findings, you can diagnose syncope!Now, here’s a clinical pearl to keep in mind! There are other causes of transient loss of consciousness that can mimic syncope.
One of these is hypoglycemia. So, remember to check a fingerstick blood glucose, especially if there’s a history of diabetes mellitus.
Other conditions that can mimic syncope include epileptic seizures and psychogenic pseudosyncope. However, there are key clinical differences that might give you a clue on how to differentiate them.
For example, while syncope has myoclonic jerks and quick recovery, epileptic seizures involve rhythmic activities and a longer post-ictal confusion period.
On the other hand, psychogenic pseudosyncope usually presents with a history of panic disorder or anxiety, and lacks post-ictal confusion.
Another important point is that epileptic seizures can be associated with tongue biting and incontinence, which are not typical in syncope or psychogenic pseudosyncope.Alright, once you diagnose syncope, your next step is to assess the underlying cause.

Cardiogenic Syncope3:13–4:48

Let’s start with cardiogenic syncope! These patients typically report chest pain, shortness of breath, or palpitations before the event.
Additionally, they could have been exerting themselves, or simply sitting or lying down before losing consciousness. In some cases, a person might have a history of cardiac disease or a family history of sudden cardiac death.
On the flip side, the physical exam often reveals an irregular rhythm, murmur, or the presence of an S3 or S4 gallop. Additionally, there could be rales, jugular venous distention, and lower extremity edema.
When it comes to ECG, it might reveal arrhythmias like sinus bradycardia, high-degree AV block, or ventricular or supraventricular tachycardia.
You might also notice a short or long QT interval or pre-excitation. Any of these findings should prompt you to consider cardiogenic syncope.
Here’s a clinical pearl! You should suspect cardiogenic syncope when someone has a significant injury, such as a jaw fracture, suggesting a completely sudden loss of consciousness with no prodrome.
These syncopal episodes are so sudden that the patients can't get themselves out of danger and therefore injure themselves.
In contrast, with vasovagal or orthostatic syncope, injuries are uncommon, since the prodrome usually gives people time to get to safety.To confirm the diagnosis, you need to investigate further with an echocardiogram.

Cardiogenic syncope due to structural heart disease4:48–5:28

You might also order a CT angiogram, an exercise stress test, an ambulatory ECG monitoring, or an electrophysiology or EP study.
If the echocardiogram reveals structural heart abnormalities like valvular heart disease, such as aortic or mitral stenosis; hypertrophic obstructive cardiomyopathy; a cardiac mass; or cardiac tamponade, diagnose cardiogenic syncope due to structural heart disease.On the other hand, the echocardiogram could reveal elevated pulmonary artery systolic pressure and right ventricular dysfunction, whereas a CT angiogram might show pulmonary embolism or aortic dissection.

Cardiogenic syncope due to a vascular disorder5:28–5:50

If you have these findings, you can diagnose cardiogenic syncope due to a vascular disorder.Lastly, if the echocardiogram shows a reduced ejection fraction or a wall motion abnormality; the exercise stress test induces an arrhythmia; or if the ambulatory ECG monitoring or EP study reveals an arrhythmia, diagnose cardiogenic syncope due to an arrhythmia.Here’s another clinical pearl!

Cardiogenic syncope due to arrhythmia5:50–6:46

Since cardiogenic syncope can be life-threatening, you should rule out cardiogenic causes first, especially when the underlying cause of syncope isn’t clear from the history and physical exam.
There are several risk prediction scores that help determine which patients need closer observation and further cardiac testing.
One such score is the Evaluation of Guidelines in Syncope Study score, or EGSYS score, which helps to predict whether cardiogenic syncope is likely, and the risk of mortality at 24 months.Now that we’re done with cardiogenic syncope, let’s move on to reflex-mediated syncope!

Reflex-mediated Syncope6:46–8:48

These patients typically report syncope when upright, but not with exertion. Usually, there’s an emotional or situational trigger, like witnessing an accident, prolonged standing, undergoing a medical procedure, or a physiologic process like defecation or cough.
Also, prior to losing consciousness, there are usually prodromal symptoms like lightheadedness, feeling warm or clammy, diaphoresis, nausea, and visual changes.
Lastly, these patients typically have no history of cardiac diseases. Additionally, the physical exam might reveal pallor or diaphoresis, especially if it’s conducted shortly after the event.
Otherwise, they typically have a normal cardiac and neurological exam with normal ECG findings. In such cases, you can diagnose reflex-mediated syncope!
Here’s a high-yield fact! Reflex-mediated syncope is the most common cause of syncope.
It happens when an increase in sympathetic activity triggers a reflex activation of vagal tone. This results in transient bradycardia and vasodilation, ultimately leading to cerebral hypoperfusion and transient loss of consciousness.Now, there are several types of reflex-mediated syncope; to determine which one your patient has, you should first assess the trigger.
If an emotional or environmental situation triggered the syncope, diagnose vasovagal syncope. On the other hand, if the trigger was cough, urination, defecation, or swallowing, diagnose situational syncope.
Finally, if neck movement or pressure was present, such as rapid head turning, shaving, or wearing a tight necktie, diagnose carotid sinus syndrome.Next up is orthostatic hypotension!

Orthostatic Hypotension8:48–9:48

These patients will typically report clues associated with volume depletion, such as vomiting, diarrhea, excessive sweating, or even blood loss.
Alternatively, they might be taking medications like diuretics, vasodilators, or anticholinergics, which can cause a similar effect.
Lastly, there could be a history of conditions associated with autonomic neuropathy, such as diabetes or Parkinson disease.
Next, the physical exam will reveal a drop in systolic blood pressure greater than 20 mmHg, a drop in diastolic blood pressure greater than 10 mmHg, or both when the patient goes from a supine or seated position to a standing position.
If you see these findings and there are no ECG abnormalities, diagnose orthostatic hypotension!Finally, let’s have a look at neurologic syncope.

Neurologic Syncope9:48–10:26

Your patient may report dizziness, vertigo, and sometimes double vision, called diplopia. The physical exam usually reveals ataxia and nystagmus, but in some cases, you might identify focal numbness and weakness.
If the ECG is normal, you should consider neurologic syncope. To confirm your suspicion, you need to order an imaging of the brain, such as a CT angiogram or MRI with angiogram.
If imaging reveals an abnormal finding, such as stroke, diagnose neurologic syncope.Alright, as a quick recap… Syncope refers to a sudden, transient loss of consciousness, triggered by a temporary decrease in cerebral perfusion.

Review10:26–11:13

Depending on the underlying cause, syncope can be categorized into several types. First, there is cardiogenic syncope caused by heart-related issues, such as structural heart diseases, vascular disorders, and arrhythmias.
Next, there is reflex-mediated syncope triggered by various stimuli, further divided into vasovagal syncope, situational syncope, and carotid sinus syndrome.
There is also syncope due to orthostatic hypotension, and lastly, neurologic syncope, which is associated with neurological conditions.