Prevalence of asystole during tilt test-induced vasovagal syncope may depend on test methodology

This review addresses tilt-testing methodology by searching the literature which reports timing of asystole and loss of consciousness (LOC). Despite the Italian protocol being the most widely adopted, its stipulations are not always followed to the letter of the European Society of Cardiology guidelines. The discrepancies permit reassessment of the incidence of asystole when tilt-down is early, impending syncope, compared with late, established LOC. Asystole is uncommon with early tilt down and diminishes with increasing age. However, if LOC is established as test-end, asystole is more common, and it is age-independent. Thus, the implications are that asystole is commonly under-diagnosed by early tilt-down. The prevalence of asystolic responses observed using the Italian protocol with a rigorous tilt down time is numerically close to that observed during spontaneous attacks by electrocardiogram loop recorder. Recently, tilt-testing has been questioned as to its validity but, in selection of pacemaker therapy in older highly symptomatic vasovagal syncope patients, the occurrence of asystole has been shown to be an effective guide for treatment. The use of head-up tilt test as an indication for cardiac pacing therapy requires pursuing the test until complete LOC. This review offers explanations for the findings and their applicability to practice. A novel interpretation is offered to explain why pacing induced earlier may combat vasodepression by raising the heart rate when sufficient blood remains in the heart.

Deconditioning does not explain orthostatic intolerance in ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome)

BACKGROUND

Orthostatic intolerance (OI) is a frequent finding in individuals with myalgic encephalomyelitis /chronic fatigue syndrome (ME/CFS). Published studies have proposed that deconditioning is an important pathophysiological mechanism in various forms of OI, including postural orthostatic tachycardia syndrome (POTS), however conflicting opinions exist. Deconditioning can be classified objectively using the predicted peak oxygen consumption (VO₂) values from cardiopulmonary exercise testing (CPET). Therefore, if deconditioning is an important contributor to OI symptomatology, one would expect a relation between the degree of reduction in peak VO₂during CPET and the degree of reduction in CBF during head-up tilt testing (HUT).

METHODS AND RESULTS

In 22 healthy controls and 199 ME/CFS patients were included. Deconditioning was classified by the CPET response as follows: %peak VO₂ ≥ 85% = no deconditioning, %peak VO₂ 65-85% = mild deconditioning, and %peak VO₂ < 65% = severe deconditioning. HC had higher oxygen consumption at the ventilatory threshold and at peak exercise as compared to ME/CFS patients (p ranging between 0.001 and < 0.0001). Although ME/CFS patients had significantly greater CBF reduction than HC (p < 0.0001), there were no differences in CBF reduction among ME/CFS patients with no, mild, or severe deconditioning. We classified the hemodynamic response to HUT into three categories: those with a normal heart rate and blood pressure response, postural orthostatic tachycardia syndrome, or orthostatic hypotension. No difference in the degree of CBF reduction was shown in those three groups.

CONCLUSION

This study shows that in ME/CFS patients orthostatic intolerance is not caused by deconditioning as defined on cardiopulmonary exercise testing. An abnormal high decline in cerebral blood flow during orthostatic stress was present in all ME/CFS patients regardless of their %peak VO₂ results on cardiopulmonary exercise testing.

The clinical characteristics of situational syncope in children and adults undergoing head-up tilt testing

OBJECTIVE

Situational syncope is a subtype of neurally mediated syncope and associated with specific circumstances. This paper is to assess the clinical characteristics and underlying causes of situational syncope.

METHODS

This is a retrospective study of patients who underwent head-up tilt testing (HUTT). Medical records including age at HUTT, gender, number of syncopal episodes, family history of syncope, triggers before the syncopal episode, position during the syncopal episode and the responses to HUTT were reviewed.

RESULTS

Among 3140 patients, 354 patients (mean age 28.3 ± 16.6 years old, with 184 males and 170 females) were diagnosed with situational syncope. The causes of situational syncope included micturition (50.85%), defecation (15.82%), bathing (10.45%), swallowing (6.50%), cough (4.80%), post-dinner (3.95%), singing (3.11%), teeth brushing (2.26%), and hair grooming (2.26%). Patients with syncope triggered by micturition, cough, post-dinner were more likely to be men, while those caused by bathing, swallowing, singing, teeth brushing and hair grooming were more likely to be women. 34.75% of patients with situational syncope were between the ages of 10-19 years old, and 20.34% were between the ages of 40-49 years old. 74.01% of situational syncopal events occurred in an upright position. 47.74% of patients had positive responses to HUTT.

CONCLUSIONS

These findings show that micturition was the most common cause of situational syncope in both children and adults. There were significant gender and age differences among situational syncope triggered by different causes. Most of situational syncope occurred in the upright position and nearly half of the patients had positive responses to HUTT.

POLYMORPHISMS IN β-ADRENERGIC RECEPTORS ARE ASSOCIATED WITH INCREASED RISK TO HAVE A POSITIVE HEAD-UP TILT TABLE TEST IN PATIENTS WITH VASOVAGAL SYNCOPE

Background

Vasovagal syncope (VVS) is a frequent clinical condition in which a genetic background seems to be implicated. Considering that the adrenergic receptors (ARs) may play a role in VVS, the present study has as principal aim to determine if the α- and β-AR (ADRA and ADRB) gene polymorphisms are associated with an increased risk to have a positive head-up tilt table (HUTT) test in patients with VVS. Methods: Nine polymorphisms in the ADRA1A (rs1048101, rs1383914, rs574584, and rs573542), ADRB1 (rs1801252 and rs1801253), ADRB2 (rs1042713 and rs1042714), and ADRB3 (rs4994) genes were analyzed using the 5' exonuclease TaqMan genotyping assay in a group of 134 patients with VVS.

Results

Under different models, the rs1801252 (OR = 8.63, 95% CI: 0.95-78.72, P_recessive = 0.02), rs1042713 (OR = 1.94, 95% CI: 1.02-3.66, P_additive = 0.04), and rs4994 (OR = 2.46, 95% CI: 1.01-6.01, P_dominant = 0.042 and OR = 2.62, 95% CI: 1.04-6.63, P_{over-dominant} = 0.03) polymorphisms were associated with increased risk for a positive HUTT. All models were adjusted for statistically significant covariates.

Conclusion

These results suggest that some polymorphisms of the β-AR genes could contribute to a positive tilt test in patients with VVS.

Syncope as a health risk for soldiers - influence of medical history and clinical findings on the sensitivity of head-up tilt table testing

BACKGROUND

Syncope is a relevant health problem in military environments. Reliable diagnosis is challenging. Tilt table testing is an important tool for syncope diagnosis. The aim of this study was to determine whether signs such as prodromal symptoms, co-morbidity, frequency of syncopal events, body length, body mass index, and electrocardiography abnormalities can be used to predict the success of tilt table testing at diagnosing syncope.

METHODS

Data from 100 patients with histories of syncope or pre-syncope, who were diagnosed using head-up tilt table testing, were retrospectively analyzed in a cross-sectional analysis. The diagnostic procedure was based upon a modified version of the Westminster protocol without any pharmacological provocation.

RESULTS

Patients showing pathological reaction patterns during tilt table testing suffered from prodromal symptoms, such as dizziness and sweating, significantly more often. The patients reported more injuries resulting from syncopal events and more previous syncopal events, and the prevalence of co-morbidity was greater among patients presenting negative findings during tilt testing. An asthenic-leptosomal physique was not confirmed as a risk factor for syncopal events as is the case for idiopathic arterial hypotension. However, patients with pathological reaction patterns during tilt table testing were significantly taller. This finding was detected for both females and males. No significant predictors were found in the electrocardiogram (ECG) patterns of patients showing syncope during tilt table testing.

CONCLUSIONS

Frequency of prior syncope and prodromal symptoms, and increased body length with an otherwise good state of health influence the predictive value of tilt table testing for syncope diagnosis. In particular, if these factors are present, tilt table testing should be considered part of the diagnostic algorithm for soldiers with recurrent syncope.

P-wave voltage and peaking on electrocardiogram in patients undergoing head-up tilt testing for history of syncope

BACKGROUND

Only scanty data are available in the literature on P-wave (PW) morphology at ECG in patients with history of vasovagal syncope undergoing diagnostic functional testing. In this study, we evaluated resting and head-up tilt testing (HUTT) related changes in PW voltage (PWV) and duration (PVD) and their relationship with triggered syncope.

METHODS

55 patients, mean aged 41 ± 19 y (35 F), without patent heart disease or neuropathy, underwent potentiated HUTT according to the Italian protocol. Heart rate (HR), blood pressure (BP), PR-interval, PWV and PWD were measured at rest, 15 min from passive position (15-min) and after nitroglycerine (peak-HR). PW peaking (PWP) was calculated as percent increase in PWV than baseline values. Patients were divided into 2 groups based on tilt-positive (group-A) or negative (group-B) response.

RESULTS

20 patients (36%) entered the group-A, whereas 35 (64%) the group-B. Higher PWV was observed at baseline in group-A (0.147 ± 0.034 mV vs 0.114 ± 0.036 mV in group-B, p=0.001), with no differences in the remaining ECG measurements. BP was lower in group-A than in B, both at 15-min and peak-HR. HUTT-related PWP in lead II (the most significant among all inferior leads) was 31 ± 30% in group-A vs 95 ± 54% in group-B (p<0.0001) at 15-min, and 52 ± 44% vs 112±72% at peak-HR, respectively (p=0.002). 75% of patients with PWP ≤ 50% experienced HUTT-triggered syncope, vs 5% of those with PWP ≥ 100% (p<0.0001).

CONCLUSIONS

This study shows a potential relationship between HUTT-triggered syncope and low or absent PWP, suggesting a role for atrial chamber functional involvement in the mechanisms underlying the vasovagal syncope.

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.