Adenosine Testing to DEtermine the Need for Pacing Therapy
Adenosine Testing to DEtermine the Need for Pacing Therapy
The purpose of this study is to determine whether or not the intravenous adenosine test
 readily identifies patients with unexplained syncope who would benefit from permanent
 pacemaker implantation.
The investigation of syncope (transient loss of consciousness with loss of postural tone,
 collapse and spontaneous recovery) varies widely, is often lengthy and frequently expensive.
 The intravenous adenosine test has been used in the investigation of syncope and is cheap,
 safe and free of serious side effects. However, it is unclear what diagnosis the test
 unearths. There is some evidence that the test readily identifies bradycardia pacing
 indications.

 In this study we plan to perform the adenosine test and implant a pacemaker should the test
 be positive. In half of the patients we will turn the pacemaker "on" and in the other half
 the pacemaker "off". The groups will swap over after six months. During this time we will
 assess the number of syncopal episodes. Also, in those who have a negative adenosine test we
 will implant a loop recorder to try to discover the cause of syncope.
Inclusion Criteria:

 -  Episode of syncope

 -  Patient has provided written informed consent for participation in the study prior to
 any study specific procedures

 -  Male or female

 -  Age > 40 years

 -  No cause of syncope clearly identified on clinical examination, lying and standing
 blood pressure measurements and standard 12 lead ECG.

 Exclusion Criteria:

 -  Asthma or chronic obstructive pulmonary disease

 -  Severe coronary disease (myocardial infarction within 3 months, known coronary
 stenosis >70%, NYHA heart failure or angina symptoms Class III or IV)

 -  Known severe cerebrovascular disease or known significant internal carotid artery
 stenosis (>70%)

 -  Prolonged corrected QT interval

 -  Unablated accessory pathway

 -  Pregnancy or lactation

 -  Use of dipyridamole or any rate-limiting medication that cannot be safely discontinued

 -  Hypertrophic cardiomyopathy

 -  Cardiac transplantation

 -  Concurrent participation in another investigational study or trial

 -  Inability to give informed consent; carer/proxy assent will be allowed in this study

 -  Cause of syncope established from initial clinical history and examination, lying and
 standing blood pressure and ECG