Approach to syncope: Clinical sciences

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. 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. 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. 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. 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. If you have these findings, you can diagnose cardiogenic syncope due to a vascular disorder.