Early Cerebral Hypoperfusion in Patients with Orthostatic Intolerance Without Tachycardia During Head-Up Tilt Test is Independent of Vasovagal Response.

BACKGROUND: Cerebral hypoperfusion before syncope has been shown in patients with chronic orthostatic intolerance (OI) without tachycardia, but it is unknown if an initial decrease of cerebral blood flow velocity (CBFv) could be related to the vasovagal response (VVR) to head-up tilt test (HUTT). OBJECTIVE: The objective of the study was to compare cardiovascular, cerebrovascular, and autonomic variables during HUTT in OI patients with or without a VVR. METHODS: We included 74 subjects (58% female, mean age 33 ± 12 years) who underwent a 30-min HUTT and were divided into three groups: OI with VVR positive (VVR+), OI without VVR negative (VVR-), and asymptomatic healthy subjects with negative HUTT (control group). Cardiovascular, cerebrovascular, and autonomic variables were assessed beat-to-beat during HUTT with a Task Force monitor and a trans-cranial Doppler. Mean values were evaluated at baseline and throughout the first 10 min of tilting. RESULTS: Cardiovascular variables were similar in the three groups. Systolic, diastolic, and mean CBFv were similar in VVR+ and VVR-, but both groups had lower CBFv than the control group. Systolic and diastolic CBFv decreased from baseline since min 1 in VVR+ and VVR- and since min 5 in the control group. The mean CBFv had a significant decrease since min 1 compared to baseline in all groups. Spectral indices of heart rate and blood pressure variability showed a similar autonomic response to HUTT in all groups. CONCLUSION: Patients with chronic OI without tachycardia have early postural cerebral hypoperfusion, regardless of the VVR during HUTT.

Paced breathing can prevent vasovagal syncope during head-up tilt testing.

BACKGROUND: Clinical experience suggests that, through the control of heart rate, paced breathing may prevent syncope. OBJECTIVE: To assess the effect of metronome-paced breathing (0.2 Hz) on the outcome of head-up tilt test (HUT) in patients with vasovagal syncope. PATIENTS AND METHODS: Ten patients (two men), mean +/- SD age 18.4 +/- 5.1 years, with a positive HUT with spontaneous breathing and no evidence of cardiovascular or neurological disease, were exposed to a second HUT under metronome-paced breathing (0.2 Hz). Continuous electrocardiographic recordings were obtained during the two tests, and heart rate variability was analyzed off-line. RESULTS: During HUT with metronome-paced breathing, only one of the 10 patients developed bradycardia, hypotension and syncope (P<0.01, Wilcoxon). Compared with HUT with spontaneous breathing, HUT with paced breathing induced a larger increase in the heart rate in the first minute of tilt (4 +/- 6 beats/min versus 16 +/- 12 beats/min, P<0.05). CONCLUSIONS: The results show that paced breathing can prevent vasovagal syncope induced by HUT. This finding suggests that respiratory training could be useful to prevent vasovagal syncope.

Cerebrovascular blood flow during the near syncopal phase of head-up tilt test: a comparative study in different types of neurally mediated syncope.

AIMS: This study analyses the changes in cerebral blood flow (CBF) velocity occurring in the near syncopal phase of head-up tilt test (HUT) to determine whether their appearance during the premonitory symptoms permits the differentiation of the different types of haemodynamic response. METHODS AND RESULTS: Six hundred and nineteen patients aged 35.9 +/- 16.4 with a prior history of syncope (55%) or presyncope (45%) were studied. Head-up tilt test was positive in 585 patients. The test was interrupted before syncope, once hypotension was evident and CBF changed. A vasovagal reaction (VVR) was observed in 245 patients. They had a 59% fall in diastolic CBF velocity, whereas systolic CBF velocity decreased by 12%. Postural orthostatic tachycardia syndrome (POTS) was observed in 82, systolic and diastolic CBF velocity decreased 44 and 60%, respectively. A similar response was observed in 258 patients with the orthostatic intolerance (OI) pattern. No significant changes were observed in the negative group. CONCLUSION: Patients with VVR had changes in CBF velocity, which are different from those presented by patients with POTS and OI pattern. Cerebral blood flow monitoring is useful to increase the yield of HUT and may allow early interruption before syncope occurs, reducing patient discomfort.

Mecanismo da síncope em nadadoras de elite / Mechanisms of syncope in female elite swimmers

Os atletas podem ter baixa tolerância ao ortostatismo. O mecanismo envolvido ainda não é bem conhecido. Nossa hipótese se baseia em que as mulheres nadadoras de alta performance desmaiam facilmente durante o teste de inclinação, tilt test (TT), provavelmente devido a um pobre controle barorreflexo. A frequencia cardíaca e as variabilidades da pressão arterial diastólica, a sensibilidade barorreflexa, a hemdinâmica cardíaca e a velocidade do fluxo cerebral foram analisadas durante o TT em um grupo de 8 mulheres...