Tilt Testing Remains a Valuable Asset

Richard Sutton; Artur Fedorowski; Brian Olshansky; J. Gert van Dijk; Haruhiko Abe; Michele Brignole; Frederik de Lange; Rose Anne Kenny; Phang Boon Lim; Angel Moya; Stuart D. Rosen; Vincenzo Russo; Julian M. Stewart; Roland D. Thijs; David G. Benditt

Disclosures

Eur Heart J. 2021;42(17):1654-1660. 

In This Article

Pros and Cons of Tilt Testing

Since its clinical introduction, the utility of TT has not been without criticism, as discussed above in light of Kulkarni et al.'s[9] opinion. It must be re-emphasized that TT is supported by evidence-based professional society practice guidelines.[10,11] Furthermore, guidelines strongly emphasize that such testing is not necessary when the clinical history is clear-cut.[10,11]

Mortality is not an issue in most patients who undergo TT. The typical TT candidate is in a low-to-intermediate risk category, in whom a diagnosis is needed but has not been revealed at initial assessment by clinical history, physical examination including orthostatic blood pressure measurement and 12-lead ECG.[10,11,25–27] TT is one means of reaching a diagnosis when not yet made; TT has almost no risks except rare, transient, atrial fibrillation, and very rare, prolonged, self-terminating asystole.[10] TT demands detailed and thoughtful analysis of available data including that previously collected at initial clinical assessment where history from the patient and eyewitnesses of spontaneous syncope/collapse play the most important part.

Tilt-test reproducibility and estimated specificity and sensitivity are summarised in the recent European guidelines.[10] It should be reiterated that there is no gold standard with which TT can be compared, although the follow-up expert review committee in FAST is a step towards.[25] Reproducibility of positive tests is reduced in second tests and further in third tests to 80% positives in each.[15] The decreasing positivity may be explained by the patient being aware of the unpleasantness of outcome, attempting in any way to avoid it. Leg movement is one obvious way. However, in severely affected VVS patients, reproducibility is high. This disadvantage of TT is rarely a clinical problem as repeat testing is seldom necessary.

False-positive outcomes occur with TT just as with any medical test, with a rate, expressed in terms of specificity and sensitivity,[5] that is comparable with many widely used medical tests, such as exercise testing in daily cardiology practice. A positive TT in those who have never experienced syncope may be revealing a 'hypotensive susceptibility',[5] which could manifest as syncope later in life. False negatives also occur but are over-ridden by the history. Analysis of the literature shows that TT has acceptable sensitivity and specificity,[10] which should be distinguished from the positivity rate.[5,21] It is, however, less good in the most difficult cases, which also applies widely in medicine.[5] However, TT allows patients to confirm similarity, or its absence, of induced to spontaneous symptoms. The difficulty in some cases may be attributed to the overlap of a common reflex with another important condition, such as hypertrophic cardiomyopathy.

Tilt testing to monitor the effects of therapy is not recommended by European[10] or North American[11] practice guidelines. Nevertheless, TT can be useful, particularly in post-pacing syncope recurrence in severe VVS[33–38] when combined with other cardiovascular autonomic tests such as carotid sinus massage.[10,36] TT can help in pacemaker therapy selection[12] and predict syncope recurrence after pacing; positive tilts pre-pacing are associated with a much higher recurrence rate than negative tilts with similarly positive ILR observations of VVS.[5,34–37] An explanation may be that 'hypotensive susceptibility' is present even when dominated by cardioinhibition. Another may be that timing of development of hypotension ahead of bradycardia is very important[39] but impossible to determine from ILR/insertable cardiac monitors (ICMs), which are yet unable to record blood pressure. TT may also have utility in reprogramming pacemakers after syncope recurrence, although this has not been widely adopted.[40]

Although TT may not be necessary to secure a diagnosis, it can serve to teach patients about prodromes so they can learn to invoke preventive measures, notably physical counter-measures, to abort subsequent episodes.[10,41] Tilt provocation of symptoms can, thus, be an educational tool and is recommended by ESC guidelines as a class IIB indication.[10]

In the case of treatment selection, pacing using the closed-loop system offers stimulation earlier in the vasovagal reflex than awaiting bradycardia and, thus, a potentially effective therapy requiring consideration.[12,42,43] However, if evidence from TT shows syncope due to hypotension preceding marked bradycardia by minutes, this may alter treatment strategy avoiding unnecessary pacemaker implantation.[39] These issues have been reviewed in detail.[43] Recent studies of TT methodology have provided greater insight into the sequence of haemodynamic events during VVS and may permit more appropriate application of pacing systems.[39,44,45] The impact of reducing venous return and stroke volume during evolving VVS seems to be key to understanding the utility and limitations of pacing intervention.[44]

To summarize, TT has many pros in terms of its diagnostic, educational, patient reassurance and choice of pacing therapy with few cons other than being a lengthy procedure; importantly, it has virtually no risks. In contrast, active standing is really valuable only in immediate/classical OH. In delayed OH, it cannot replace tilt on grounds of haemodynamics and tolerability (Table 1).

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