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.
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
Systolic blood pressure ≥90 mmHg
Diastolic blood pressure ≥60 mmHg
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
Parallel
Nasopharyngeal Swab Insertion
Procedure/SurgeryA standard nasopharyngeal swab (approximately 15 cm flexible nylon-tipped swab, sterile) is inserted through the right nostril (left if anatomically impeded), directed parallel to the nasal septum along the nasal floor (posteriorly, not superiorly), and advanced until mild resistance is felt at the nasopharyngeal vault. The swab is held in this position for 10 seconds with optional gentle rotation, then slowly withdrawn. The procedure is performed with the patient in a 45-degree semi-recumbent position under continuous cardiac monitoring (ECG, SpO2, NIBP). T=0 is defined as the moment the swab is fully withdrawn. The procedure is performed once; failure leads to rescue therapy (intravenous adenosine) without a second attempt.
Modified Valsalva Maneuver (REVERT Protocol)
Procedure/SurgeryThe modified Valsalva maneuver is performed per the REVERT protocol. The patient, seated at 45 degrees, performs a forced expiration for 15 seconds into the barrel of a 10 mL syringe (aiming to push the plunger back, targeting an expiratory pressure of≥40 mmHg). Immediately upon completion, the patient is rapidly repositioned supine, and both legs are passively elevated to 45 degrees for 15 seconds, then returned to the semi-recumbent position. Total maneuver duration is approximately 30 seconds. T=0 is defined as the moment the patient returns to the semi-recumbent position. The procedure is performed once; failure leads to rescue therapy (intravenous adenosine) without a second attempt.
Sinus Rhythm Conversion Rate at 1 Minute
Proportion of participants who convert to sinus rhythm within 1 minute of procedure completion (T=60 seconds), as assessed by continuous 12-lead ECG monitoring. T=0 is defined as the moment the intervention is completed (swab withdrawn / patient returned to semi-recumbent position after leg raise). Rhythm is independently verified by two investigators reviewing the ECG rhythm strip recording. Conversion is defined as a dichotomous outcome: yes (sinus rhythm confirmed at T=60 seconds) or no.
Sinus Rhythm Conversion Rate at 5 Minutes
Proportion of participants who convert to sinus rhythm within 5 minutes of procedure completion, assessed by continuous ECG monitoring.
Adverse Events Profile
Incidence and nature of adverse events including but not limited to epistaxis, vasovagal syncope, significant bradycardia (heart rate \<40 bpm), hypotension, and respiratory distress, documented on a structured adverse event checklist.
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