White coat syndrome

Mechanism of conditioned reflex hypertension

White coat syndrome belongs to the group of neurogenic reflex hypertensions. It is based on a conditioned reflex reaction of the nervous system to a specific environment.

When a patient enters a medical facility or sees a doctor, they experience subconscious fear. This emotional trigger sets off a cascade of reactions:

• The vasomotor center (specifically its pressor region) is activated.
• The signal travels via efferent pathways to the peripheral vessels.
• Vasospasm of the vascular bed occurs.
• Blood pressure (BP) rises sharply.

Unlike unconditioned reflex disorders (for example, when the baroreflex fails, when receptors in the aortic arch and carotid sinus stop responding adequately to wall stretch), white coat hypertension is situational and not associated with organic baroreceptor damage.

Place in the classification of arterial hypertension

In modern clinical practice, this condition is officially termed isolated clinic hypertension.

The diagnosis is established when two conditions are met:

1. BP readings at a doctor's appointment are ≥140 mmHg for systolic and/or ≥90 mmHg for diastolic pressure.
2. Ambulatory blood pressure monitoring (ABPM) or home blood pressure monitoring (HBPM) values remain within normal limits.

Interestingly, there is a completely opposite condition — isolated ambulatory (masked) HTN. In this condition, the patient demonstrates perfect blood pressure in the doctor's office (less than 140/90 mmHg), but in everyday life, according to home measurements, suffers from elevated blood pressure.

Pseudoresistance: why treatment seems ineffective

White coat syndrome is often confused with resistant arterial hypertension. True resistance is diagnosed when the patient is adherent to treatment, takes three antihypertensive drugs in maximum doses (including a diuretic), secondary causes are excluded, and target figures are still not achieved.

The white coat effect creates pseudoresistance. The doctor sees high readings during the appointment, thinks the prescribed therapy is not working, and may mistakenly intensify treatment. To avoid such errors, the clinician must:

• Relies on home blood pressure measurement data.
• Ask the patient to keep a detailed blood pressure log.
• Exclude technical errors (such as a faulty tonometer or using an improperly sized cuff).
• Check other causes of false resistance: patient non-compliance, intake of sympathomimetics or non-steroidal anti-inflammatory drugs, alcohol abuse, or the presence of sleep apnea syndrome.

Related factors complicating diagnostics

In addition to emotional stress during the appointment, BP readings can be affected by other hidden factors that are important to consider when taking the anamnesis:

• Weight gain: a large body mass increases the surface area of the vascular bed, forcing the heart to work harder.
• Excess salt and fluid retention: volume overload due to dietary habits or glucocorticosteroid intake.
• Frequent changes in therapy: sometimes a patient visits different doctors, each of whom changes the treatment regimen to suit themselves, which prevents the drugs from accumulating the required effect and stabilizing hemodynamics.

Class and exam questions

What else to study on this topic

• Mechanisms of unconditioned reflex arterial hypertension and baroreflex function
• Centrogenic arterial hypertension: the role of brain structures
• Causes of true resistant hypertension and secondary HTN
• Impact of sleep apnea syndrome on the development of arterial hypertension
• Classification of blood pressure levels (optimal, normal, high normal)

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.