Carotid sinus syncope
Carotid sinus hypersensitivity was defined in the 1930s. The definition included the following in respons to carotid sinus massage for 5-10s:
- asystole for more than 3s (cardio-inhibitory type) or
- systolic blood pressure fall of 50 mmHg (vasodepressor type)
- or both (mixed type)
Carotid sinus hypersensitivity is almost exclusively diagnosed in patients over 50 years of age.
In the older literature the clinical presentations of this disorder are reported to be heterogeneous. In the vasodepressor type patients would be likely to have a prodromal pattern as in classical vasovagal syncope, whereas the cardio-inhibitory type could occur without warning and present as a clinical Adams-Stokes attack. In the latter, on regaining consciousness typically there is a facial flush (FRANKE & BRACHARZ, 1956). However even under standardized laboratory conditions both types often can not be distinguished on clinical grounds.
Triggers
The prevalence of spontaneous carotid sinus syndrome induced by every-day manipulations like wearing a tight collar, shaving, head turning or stretching the neck is unknown, but likely to be rare, since its occurrence is reported as only 1% of causes of syncope in clinical settings (for review see (Colman et al., 2004a)). However in a series of 33 cases of carotid sinus hypersensitivity (among a total of 130 consecutive syncope patients) head-turning as a trigger was reported in 52% of the cases (Kenny & Traynor, 1991). Most syncopal episodes attributed to carotid sinus hypersensitivity after laboratory testing occur apparently spontaneously.
Epidemiology
The prevalence of carotid sinus hypersensitivity (i.e. a positive test in a syncope patient without a typical history of loss of consciousness following neck manipulation) in the general population is between 1 and 25%, occurring primarily in older patients, with a strongly positive correlation with age (Humm & Mathias, 2006). However since the reflex can also be triggered in otherwise healthy elderly without a history compatible with the carotid sinus syndrome (i.e. falls, dizziness and light-headedness) (Humm & Mathias, 2006;Kerr et al., 2006) the true clinical importance of carotid sinus hypersensitivity remains unclear.
Treatment
Cardiac pacing is the therapy of choice in syncope patients with documented asystole (>3 s) in response to carotid sinus massage, or on ambulatory ECG recording (Kenny et al., 2001). The vasodepressor type is likely to benefit from general orthostatic tolerance enhancing measures such as salt and volume loading, and there is some evidence that fludrocortisone may be effective (Hussain et al., 1996). However up to date there are no large scale clinical trials confirming this.