Managing Syncope and Indications for Pediatric Cardiology Referral

Autonomic dysfunction/dysautonomia is an umbrella term describing a condition where there is altered function in one or more components of the autonomic nervous system that negatively affects health. We think of it as a term for the overall “thermostat” of the body that has some dysfunction in regulation related to the autonomic nervous system in pre-syncopal patients, including heart rate, blood pressure, and temperature. Dysfunction in autonomic regulation can also include digestion, sweat gland function, urinary function, and sexual function.

“About one-third to half the population faints at some point in their lifetime” (Shen et al., 2017). Heat exhaustion, severe emotional stress, significant dehydration, straining in the bathroom, seeing blood, needles including blood draws and vaccinations, severe pain, and fear can all cause a syncopal event that would be considered “expected” for the conditions. Conditions can be mixed that make fainting more likely to occur such as taking a hot shower after recovering from influenza when they were not drinking or eating enough for a few days.

upon standing from a sitting or supine position. At that time, a drop in systolic blood pressure by ≥20 mmHg and/or a decrease in diastolic blood pressure by ≥10 mmHg within the first 3 minutes of standing (Boris et al., 2022). Creating a data dictionary for pediatric autonomic disorders. Clinical Autonomic Research. https://doi.org/10.1007/s10286-023-00923-3). A delayed OH is when the blood pressure drops after 5 minutes and can be a sign of vasodepressor response in children. It is normal to see an increase in heart rate as compensation for the drop in blood pressure

If a patient is 18 years old or younger, POTS in noted when there is a 40-point increase in heart rate from supine to sitting or to standing or a heart rate at least 120 bpm upon standing for 10 minutes with no orthostatic hypotension. A patient needs to have reported symptoms with this change in heart rate as well, including lightheadedness, dizziness, nausea, diaphoresis, headache, fatigue, and other autonomic dysfunction symptoms (Boris et al., 2022). Symptoms need to be occurring for 3 months or greater to equate a POTS diagnosis. If symptoms have occurred for less than 3 months, a more appropriate diagnosis is orthostatic intolerance.

Orthostatic intolerance includes symptoms like dizziness, lightheadedness, headache, palpitations, and vision changes when in an upright position that resolve while seated or supine. There should be no changes in orthostatic blood pressures or heart rates, or OH or POTS is a more appropriate diagnosis.

IST is a heart rate consistently greater than 100 bpm at rest or greater than 90 bpm on average over 24 hours. A patient is also reporting symptoms including palpitations, dyspnea, or dizziness. If there are no symptoms, then it’s not IST syndrome. Chronic deconditioning can lead to elevated baseline heart rates which can confound the diagnosis.

Conversion disorder (functional neurologic symptom disorder) is characterized by neurologic symptoms, such as weakness, abnormal movements, or nonepileptic seizures, which involve abnormal nervous system functioning rather than structural disease. [DSM 5, American Psychiatric Association, 2013]. In our pediatric cardiology practice, we have identified conversion disorder at times associated with syncopal symptoms. We coordinate with psychiatry when this is suspected. Anxiety, especially when associated with panic attacks, can cause elevated heart rates, tingling of the perioral area and of the extremities (fingers, hands, feet, etc).

Post-exertional syncope that is non-pathologic can occur when exercise is stopped suddenly and there is a reduction in “lower extremity muscle pumping...that results in less cardiac venous return and cardiac output.” A normal variant that is not pathologic can commonly be seen in runners at the end of a race in track and cross country when they suddenly stop exerting themselves. Meaningful drops in blood pressure immediately after exertion have been recorded since 1898 (Tipton, 2011). Patients with baseline hypertension are more susceptible to it. Exertion while dehydrated or on hot days and/or on humid days worsens symptoms.