Pacemaker for Vasovagal Syncope: Good for the Few
M. BRIGNOLE
The decision to implant a pacemaker needs to be kept in the clinical context of a benign condition which frequently affects young patients. Thus, cardiac pacing should be limited as the last-resort choice to a very selected small proportion of patients affected by severe vasovagal syncope. How to select these patients still remains partly uncertain.
Background
The term ‘vasovagal syncope’ refers to a reflex response that, when triggered, gives rise to vasodilation and bradycardia, although the contribution of both of these to systemic hypotension and cerebral hypoperfusion may differ con- siderably. It is valuable to assess the relative contribution of cardioinhibition and vasodepression before embarking on treatment as there are different therapeutic strategies for the two entities. The triggering events may vary considerably over time in any individual patient. ‘Classical’ vasovagal syn- cope is mediated by emotional or orthostatic stress and can be diagnosed by history taking. ‘Non-classical’ presentations are frequent, and these forms are diagnosed by minor clinical criteria, exclusion of other causes of syncope (absence of structural heart disease), and positive response to tilt testing or carotid sinus massage. Examples of non-classical vasovagal syncope include episodes without clear triggering events or premonitory signs.
Criteria for Selection of Patients
In general, initial ‘treatment’ of all forms of neurally-mediated reflex syn- cope consists of reassurance as to the benign nature of the syndrome, educa-
Department of Cardiology and Arrythmologic Centre, Ospedali del Tigullio, Lavagna (Genua), Italy
tion regarding avoidance of triggering events and predisposing factors, recognition of premonitory symptoms and manoeuvres to abort the episode, and avoidance of volume depletion and prolonged upright posture. The above measures are sufficient for the vast majority of patients affected by vasovagal syncope. Additional treatment may be necessary in the high risk or high frequency settings defined by the ESC Task Force on Syncope [1]
when syncope:
- is very frequent, e.g. alters the quality of life
- is recurrent and unpredictable (absence of premonitory symptoms) and exposes patients to ‘high risk’ of trauma
- occurs during participation in a ‘high risk’ activity (e.g. driving, machine operator, flying, competitive athletics, etc.).
Among these settings, cardiac pacing may be reserved for those patients with cardioinhibitory vasovagal syncope with a frequency of more than five attacks per year or severe physical injury or accident and age above 40 years [1]. In order to limit the vasodepressor component of the vasovagal reflex, dual-chamber pacemakers with rate hysteresis features are usually preferred, although formal comparison studies among modes of pacing have not yet been performed.
Results from Randomised Controlled Trials
Pacing for vasovagal syncope has been the subject of five major multicentre randomised controlled trials [2–6], of which three gave positive and two gave negative results. Putting together the results of the five trials, 318 patients were evaluated; syncope recurred in 21% (33/156) of the paced patients and in 44% (72/162) of non-paced patients (P < 0.000). However, all the studies have weaknesses, and further follow-up studies addressing many of these limitations (particularly the pre-implant selection criteria for patients who might benefit from pacemaker therapy) need to be completed before pacing can be considered an established therapy.
Future Perspectives
It seems that pacing therapy might be effective in some but not in all patients. This is not surprising if we consider that pacing is probably effica- cious for asystolic reflex but has no role in combating hypotension, which is frequently the dominant reflex in vasovagal syncope. How to stratify the patients is still uncertain. A recent study using the implantable loop recorder as reference standard [7] showed that only about half of the patients had an asystolic pause recorded at the time of spontaneous syncope which might
310 M. Brignole
eventually benefit from a pacemaker. In the other patients a pacemaker is unlikely to be effective. The role of the implantable loop recorder for select- ing patients who may benefit from cardiac pacing is actually under evalua- tion.
A widely used method for selecting patients suitable for cardiac pacing is the finding of a cardioinhibitory form of syncope during tilt testing.
However, recent data showed that the mechanism of tilt-induced syncope was frequently different from that of the spontaneous syncope recorded with the Implantable Loop Recorder [7]. These data show that the use of tilt test- ing for assessing the effectiveness of different treatments has important limi- tations and its use is now disregarded in the ESC Guidelines [1].
References
1. Brignole M, Alboni P, Benditt D et al (2004) Guidelines on management (diagnosis and treatment) of syncope. Update 2004 – Executive summary and recommenda- tions. Eur Heart J 25:2054–2072
2. Connolly SJ, Sheldon R, Roberts RS et al (1999) The North American vasovagal pacemaker study (VPS): a randomised trial of permanent cardiac pacing for the prevention of vasovagal syncope. J Am Coll Cardiol 33:16–20
3. Sutton R, Brignole M, Menozzi C et al (2000) Dual-chamber pacing in treatment of neurally-mediated tilt-positive cardioinhibitory syncope. Pacemaker versus no the- rapy: a multicentre randomized study. Circulation 102:294–299
4. Ammirati F, Colivicchi F, Santini M (2001) Permanent cardiac pacing versus medi- cal treatment for the prevention of recurrent vasovagal syncope. A multicenter, randomized, controlled trial. Circulation 104:52–57
5. Connolly SJ, Sheldon R, Thorpe KE et al (2003) Pacemaker therapy for prevention of syncope in patients with recurrent severe vasovagal syncope: Second Vasovagal Pacemaker Study (VPS II). JAMA 289:2224–2229
6. Giada F, Raviele A, Menozzi C et al (2003) The vasovagal syncope and pacing trial (Synpace). A randomized placebo-controlled study of permanent pacing for treat- ment of recurrent vasovagal syncope. PACE 26:1016 (abstract)
7. Moya A, Brignole M, Menozzi C et al (2001) Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope. Circulation 104:1261–1267 311 Pacemaker for Vasovagal Syncope: Good for the Few
