Head-up tilt test with isoproterenol provocation in syncope of unknown origin

Head-up tilt testing for diagnosing vasovagal syncope: a meta-analysis

BACKGROUND

A systematic evaluation focused on sensitivity and specificity of head-up tilt testing (HUT) for diagnosing vasovagal syncope has not been previously performed. We conducted a meta-analysis of studies comparing HUT outcome between patients with syncope of unknown origin and control subjects without previous syncope.

METHODS

We searched Pubmed and Embase databases for all English-only articles concerning case-control studies estimating the diagnostic yield of HUT, and selected 55 articles, published before March 2012, including 4361 patients and 1791 controls. The influence of age, test duration, tilt angle, and nitroglycerine or isoproterenol stimulation on tilt testing outcome was analyzed.

RESULTS

Head-up tilt testing demonstrated to have a good overall ability to discriminate between symptomatic patients and asymptomatic controls with an area under the summary receiver-operating characteristics curve of 0.84 and an adjusted diagnostic odds ratio of 12.15 (p<0.001). A significant inverse relationship between sensitivity and specificity of tilt testing for each study was observed (p<0.001). At multivariate analysis, advancing age and a 60° tilt angle showed a significant effect in reducing sensitivity and increasing specificity of the test. Nitroglycerine significantly raised tilt testing sensitivity by maintaining a similar specificity in comparison to isoproterenol.

CONCLUSIONS

The results from this meta-analysis show the high overall performance of HUT for diagnosing vasovagal syncope. Our findings provide useful information for evaluating clinical and instrumental parameters together with pharmacological stressors influencing HUT accuracy. This could allow the drawing of tilt testing protocols tailored on the diagnostic needs of each patient with unexplained syncope.

Diagnostic value of dobutamine echocardiography in patients with angina-like symptoms preceding syncope

Dobutamine echocardiography was performed in 55 patients with syncope which was clinically suspected to be angina-related. We evaluated the value of using a single test, dobutamine echocardiography, in differentiating real ischemia-related from vasovagal syncope which was diagnosed by a tilt test. During testing, supraventricular arrhythmia was provoked in four (7.2%) patients. Dobutamine echocardiography identified all of six (10.9%) patients (sensitivity 100%), who were found with significant coronary stenosis by coronary angiograms. The etiology of syncope in the remaining 45 patients was investigated further by tilt testing, the findings of hypotension and bradycardia during which were compared head to head with those of dobutamine echocardiography. Tilt testing diagnosed vasovagal syncope in 31 patients, in whom only 19 (61.3%) patients developed vasovagal reflex during dobutamine echocardiography. Conclusively, dobutamine echocardiography had a high sensitivity in identifying syncope related to myocardial ischemia in patients with coronary stenosis, but a low sensitivity (61.3%), high specificity (90.5%) and high positive predictive value (81.8%) in detecting the syncope patients with angina caused by vasovagal effect.