NASVAL-SVT: Nasal Swab Versus Modified Valsalva for Supraventricular Tachycardia

Summary

Supraventricular tachycardia (SVT) is a common heart rhythm disorder seen in emergency departments, causing a rapid heartbeat (typically 150-250 beats per minute). The current best non-drug treatment, the modified Valsalva maneuver (mVM), successfully restores normal rhythm in about 43% of cases. When these maneuvers fail, intravenous adenosine is used, which, while effective, can cause brief but distressing side effects such as chest tightness, shortness of breath, and intense anxiety. During the COVID-19 pandemic, some patients briefly fainted during nasal swab collection. This happens because inserting a swab into the back of the nasal cavity (nasopharynx) stimulates the trigeminal nerve, which then activates the vagus nerve and slows the heart - a phenomenon called the trigeminocardiac (or nasocardiac) reflex. One published case report described a patient whose SVT was terminated within 10 seconds using a nasal swab. This study compares the nasal swab technique with the modified Valsalva maneuver in patients presenting to the emergency department with SVT. Patients are randomly assigned to one of two groups. The primary outcome is whether a normal heart rhythm is restored within 1 minute of the procedure. Patient comfort and satisfaction are also measured. The study is conducted in two phases. The first (pilot) phase (30 patients per group) will assess whether the study can be successfully conducted and collect data to finalize the required sample size. The second (main) phase will use the pilot phase's actual data to determine the final number of participants needed.

Eligibility

Inclusion Criteria:

* Age 18 years or older
* Electrocardiographically confirmed supraventricular tachycardia (SVT): narrow QRS complex (≤120 ms), regular rhythm, rapid ventricular rate, documented on 12-lead ECG or continuous cardiac monitoring
* Hemodynamic stability, defined as ALL of the following simultaneously present:
* Systolic blood pressure ≥90 mmHg
* Diastolic blood pressure ≥60 mmHg
* Alert and oriented mental status (GCS 15)
* No signs of acute end-organ dysfunction
* Ability and willingness to provide written informed consent

Exclusion Criteria:

* Age younger than 18 years
* Pregnancy (known or suspected)
* Inability to confirm SVT diagnosis by ECG criteria
* Delta wave or pre-excitation pattern on ECG (Wolff-Parkinson-White syndrome or asymptomatic pre-excitation) - due to risk of ventricular fibrillation with vagal maneuvers
* Wide QRS tachycardia (QRS ≥120 ms) where ventricular tachycardia cannot be excluded
* Absolute contraindication to modified Valsalva maneuver (inability to assume supine position or passive leg elevation)
* Contraindication to nasal swab (nasal surgery within 30 days, active epistaxis, visible nasal polyp or mass)
* Hemodynamic instability requiring immediate synchronized cardioversion
* Prior enrollment in this study (re-presentation with SVT)
* Refusal to participate

Conditions5

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