Evaluation of the Valsalva Assist Device to Treat SVT

The Valsalva Assist Device (VAD) is a simple hand held device, designed to assist in the physical treatment of a common, fast heart rhythm disorder called supraventricular tachycardia (SVT). This treatment, called the Valsalva manoeuvre (VM), is a safe, physical technique involving a forced exhalation against resistance (like that required to blow up a balloon). This causes a reflex slowing of the heart and can correct attacks of SVT (cardioversion). It is an internationally recommended initial treatment but previously has had a low success rate (5-27%) and patients often have to be taken to hospital for drug treatment. Recent hospital research has demonstrated that a VM carried out using a certain level of strain pressure(40mmHg) measured with a blood pressure manometer, combined with a simple postural modification (the modified VM) gives a far better chance of success (43%) and avoids the need for drug treatment. More practical methods of generating this strain such as blowing on an empty syringe have been used but are unreliable. The Valsalva Assist Device (VAD) has been designed to provide the correct resistance and is packaged with instructions for the modified VM. Attacks of SVT frequently occur without warning in otherwise healthy people. Patients are often initially seen by ambulance staff and so the use of the VAD therefore represents an opportunity to provide ambulance clinicians with instructions for the modified VM and a means to deliver the correct strain in one, easy to use device. The investigators plan to test use of the device in patients with an attack of SVT and attended by paramedics or other pre-hospital practitioner, compared to current recommended practice. This project will provide important feasibility and recruitment data for a definitive trial, assessing the performance of the VAD on SVT cardioversion and conveyance (transfer to hospital) rates.