Efficacy of Adenosine as Compared to Verapamil in Paroxysmal Supraventricular Tachycardia (pSVT) Patients

Supraventricular tachycardia (SVT) is a term widely used to describe tachycardial dysrhythmias, paroxysmal SVT (PSVT) is a narrow term including only AV nodal re-entrant tachycardia (AVNRT) and atrioventricular re-entrant tachycardia (AVRT), both of which can cause discomfort and, in some cases, life-threatening symptoms. The incidence of PSVT is approximately 1 in 300 and this prevalence increases with age.

Maneuvers that increase vagus activity have been used to terminate PSVT. Vagal maneuvers reduce the rate of stimulation of the sinus node, slow the rate of delivery to the atrioventricular node, and prolong the refractory period. Vagal-maneuver techniques include carotid sinus massage, the diving reflex, the oculocardiac reflex, and Valsalva maneuvers. Because vagal maneuvers are a non-invasive technique, recent guidelines recommend them as a first-line treatment before medical intervention to terminate PSVT.

Since the 17th century, the Valsalva maneuver (VM) has been used in daily practice and aims to challenge the individual with forced expiration while the glottis is closed, or exhalation to raise the mercury column in tubing of standard manometer to 40 mmHg. In clinical practice, VM has varied success rates (5-20%) in terminating PSVT. It has been found that the patient's posture is an important factor affecting the success of VM. In addition, several studies and case reports have shown that VM with simple, safe modifications (modified VM) is more effective in terminating PSVT. These modifications include pressing the epigastric zone or abdomen for 10 seconds after VM; changing position quickly, such as from being seated to supine; or lifting the feet at a 45-degree angle just after the VM.

Efficacy of SVM in restoring sinus rhythm is less than 25% while of Modified Valsalva maneuver (MVM)) has showed higher efficacy (> 40%).6 However, few studies have evaluated the success rate of modified VM. Therefore, the present randomized controlled study aimed to detect whether modified VM is more effective than standard VM in terminating PSVT.

Inclusion criteria

• Stable SVT (not requiring cardioversion, fully conscious, maintaining systolic blood pressure of >90mmHg)
• Alert enough and able to give consent
• Able to lie flat and non-painful legs during passive leg raising

Exclusion criteria

• Unstable SVT (Semiconscious, drowsy, breathless, systolic BP <90mmHg)
• Not able to give consent
• Orthopnea causing inability to lie flat
• Atrial fibrillation/atrial flutter
• Recent MI (within last 7 days)
• Ongoing ischemia as indicated by chest pain or ST segment depression/elevation in ECG
• Aortic stenosis
• All trimesters of pregnancy