Visceral sensitization in postural tachycardia syndrome

Abstract

Both psychogenicity and organicity have been asserted in postural tachycardia syndrome (PoTS). We studied the genesis of palpitations to dissect the biologic nature of PoTS. Eleven PoTS patients and 10 control subjects were asked to discriminate types of palpitations when supine and in response to two sympathetic stimuli [Valsalva maneuver (VM) and 10-min head-up tilt (HUT)] and one vagolytic stimulus (atropine administration). Participants rated the 10 items of the somatosensory amplification scale to assess symptom exaggeration. Their time-dependent heartbeat counts were compared against EKG data to study ability to perceive heartbeat. Maximal heart rate increase (mean ± SE) over baseline (bpm) did not differ statistically between patients and controls (VM, 39.3 ± 4.7 versus 28.9 ± 3.9, respectively; p = 0.11; HUT, 42.4 ± 4.2 versus 34.7 ± 2.6, respectively; p = 0.14; and atropine, 47.8 ± 2.5 versus 52.0 ± 2.1, respectively; p = 0.22). Palpitations were more frequent in patients at baseline (55 versus 0 %, p = 0.006) and with VM (82 versus 10 %, p = 0.001) and HUT (64 versus 0 %, p = 0.002), but not with atropine (64 versus 60 %, respectively; p = 0.86). Patients discriminated more types of palpitations than did controls (seven versus three types). No difference was observed in somatosensory amplification or heartbeat perception. Palpitations were independent of tachycardia and were predominantly sympathetically mediated. The lack of somatosensory amplification militated against psychogenicity. PoTS patients were not superior in detecting peripheral cardiac sensation. However, patients were superior in discriminating palpitations qualitatively in response to individual stimuli, suggesting central visceral sensitization. Explanation of the nature of symptoms and pharmacologic management may be of therapeutic benefit.