p.35 抽出テキスト

....................................................................................................................................................................... chamber pacemaker with closed-loop stimulation compared with 21 (46%) patients who had received a sham pacemaker programmed off (P=0.0001).

Adding video recording to tilt testing, Saal et al.205 recently showed, in patients with asystole, that asystole occurred 3 s before syncope or later in one-third of patients, in whom cardioinhibition was too late to have primarily caused syncope; in the other two-thirds of asystolic tilt responses, the cause must have been mainly cardioinhibition or a combination of cardioinhibition and vasodepression. The clinical presentation is probably as important as tilt test positivity when selecting patients who can benefit from cardiac pacing. The SUP 2 study population was characterized by higher mean age, history of recurrent syncope beginning in middle or older age, and frequent injuries, probably due to presentation without warning.292

Owing to the contrasting results of the randomized trials, the estimated benefit of dual-chamber pacing in cardioinhibitory tilt-positive patients is weak. Divergence of opinion exists among experts. Further research is very likely to have an important impact on recommendations. Conversely, there is strong consensus that pacing cannot be offered to patients with non-cardioinhibitory tilt-positive response, and further tests (e.g. ILR) are warranted to document the mechanism of the spontaneous reflex.

5.2.6.4 Evidence from trials in patients with adenosine-sensitive syncope Under this term, classified as a non-classical form of reflex syncope in Table 3, different clinical conditions are included, which have a supposed role of adenosine in the genesis of syncope in common. A new clinical entity, called idiopathic AV block, has recently been described in patients with a long history of syncope and in whom paroxysmal AV block could be recorded at the time of syncope recurrence.5 These patients had an otherwise normal heart and no sign of conduction disease on ECG and EPS; they had very low plasma adenosine levels and a high induction rate of transient complete heart block during exogenous injections of adenosine. No syncope recurrence was observed after permanent cardiac pacing over very long periods of follow-up and there was no permanent AV block. Similarly, the entity of ‘low-adenosine syncope’ has recently been described in patients who have an otherwise unexplained syncope with sudden onset without prodrome, a normal heart, and normal ECG.4 The clinical, laboratory, and biological features of these patients are similar to those observed in patients affected by idiopathic paroxysmal AV block. Unlike in VVS, tilt testing is usually negative.4,226 No syncope recurrence was observed after permanent cardiac pacing in 10 patients who had ECG documentation of asystolic pause due to sinus arrest or AV block.286 In a small multicentre trial227 performed in 80 highly selected elderly patients with unexplained unpredictable syncope who had a positive response to intravenous injection of a bolus of 20 mg of ATP, dual-chamber cardiac pacing significantly reduced the 2-year syncope recurrence rate from 69% in the control group to 23% in the active group.

There is weak evidence that dual-chamber cardiac pacing may be useful in reducing recurrences of syncope in patients with the clinical features of adenosine-sensitive syncope. The documentation of possible bradyarrhythmia in spontaneous syncope remains the preferred eligibility criterion for pacing.

5.2.6.5 Choice of pacing mode In CSS, a few small controlled studies304,305 and one registry306 showed that dual-chamber pacing is better than the single chamber ventricular mode in counteracting BP fall during CSM and in preventing symptom recurrences. Even if the quality of evidence is weak, dual-chamber pacing is widely preferred in clinical practice. In patients with VVS, dual-chamber pacing was used mostly with a rate drop response feature that instituted rapid dual-chamber pacing if the device detected a rapid decrease in HR. A comparison between dual-chamber closed-loop stimulation and conventional dual-chamber pacing has been performed by means of a crossover design in two small studies; these studies showed fewer syncope recurrences with closed-loop stimulation, both in the acute setting during repeated tilt testing307 and during 18-month clinical follow-up.308

5.2.6.6 Selection of patients for pacing and proposed algorithm The fact that pacing is effective does not mean that it is always necessary. In patients with reflex syncope, cardiac pacing should be the last choice and should only be considered in highly selected patients, i.e. those >_40 years of age (mostly >60 years), affected by severe forms of reflex syncope with frequent recurrences associated with a high risk of injury, often due to the lack of prodrome.186 While there is growing scepticism over the diagnostic accuracy of tilt testing for syncope diagnosis, emerging evidence supports the use of tilt testing for the assessment of reflex hypotensive susceptibility132, which may be considered to identify patients with an associated hypotensive response who would be less likely to respond to permanent cardiac pacing (see section 4.2.2.2). In a meta-analysis309 of individual patient data from four studies performed in patients with asystolic reflex syncope documented by an ILR, the estimated 3-year recurrence rate of syncope was 2% (95% CI ± 4%) in tilt-negative patients and 33% (95% CI ± 20%) in tilt-positive patients; a positive tilt test response was the only significant predictor of syncope recurrence with a hazard ratio of 4.3. Patients with hypotensive susceptibility should need measures directed to counteract hypotensive susceptibility in addition to cardiac pacing, e.g. the discontinuation/reduction of hypotensive drugs and the administration of fludrocortisone or midodrine. The algorithm shown in Figure 11 has recently been prospectively validated in a multicentre pragmatic study, which showed a low recurrence rate of syncope with pacing of 9% at 1 year and 15% at 2 years, significantly lower than the 22% and 37%, respectively, observed in unpaced controls.186 Downloaded from academic.oup.com/eurheartj/article/39/21/1883/4939241 by guest on 07 October 2026