Baroreflex Sensitivity in Patients With Vasovagal Syncope

Thomson, Helen L.; Wright, Kate; Frenneaux, Michael

doi:10.1161/01.cir.95.2.395

Cited by 87 publications

(65 citation statements)

References 29 publications

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“…On contrary, TPR did not change signifi cantly by assuming an upright position in HUT positive patients (1550.1 ± 576.3 vs 1741.9 ± 738.4 dyne.s/cm 5 , p = 0.90) nor in HUT negative patients (1642.7 ± 702 vs 1783.9 ± 695.5 dyne.s/cm 5 , p = 0.37) BRS decreased signifi cantly in the fi rst 5 minutes of HUT in both group of patients (HUT positive group: 9.0 ± 4.7 vs 5.6 ± 3.0, p < 0.0001, HUT negative group 8.5 ± 5.1 vs 6.2 ± 2.8, p < 0.0001) HUT There were no signifi cant differences in hemodynamic values and BRS during passive HUT between HUT positive and HUT negative patients (Tab. 2).Similarly, no signifi cant differences between HUT positive and HUT negative group were present during early phase (0-5 minutes) of nitroglycerine-stimulated HUT (Tab.…”

Section: Resultsmentioning

confidence: 85%

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Reduced baroreflex sensitivity in patients with vasovagal syncope

Mitro¹,

Šimurda²,

Evin³

et al. 2015

BLL

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OBJECTIVES: The evidence is confl icting regarding the role of barorefl ex in patients with vasovagal syncope. The aim of the study was to measure barorefl ex sensitivity (BRS) and hemodynamic parameters during head up tilt test (HUT) with nitroglycerine stimulation. METHODS: Nitroglycerine stimulated HUT was performed in 51 patients with the history of recurrent syncope (mean age 46± 19 years, 18 men, 23 women). Cardiac output (CO), stroke volume (SV), left-ventricular ejection time (LVET) and total peripheral resistance (TPR) were assessed during HUT by volume-clamp method using a beat-to-beat photopletysmography. Spontaneous BRS sensitivity was computed using a sequential BRS calculation. RESULTS: HUT was positive after nitroglycerine administration in 28 patients and negative in 23 patients. BRS was lower at the time of syncope in HUT positive group compared to end-test values in HUT negative group (0.54±0.27 vs 0.72±0.35, p = 0. 03). At the time of syncope, CO was signifi cantly lower in HUT positive patients compared to HUT negative patients (2.6±1.4 vs 4.3±1.4 l/min, p < 0.0001), similarly as SV (34.7±14.7 vs 49.2±19 ml, p=0.005 ). LVET was signifi cantly higher in syncopal patients (282.27±26.2 vs 240.5±58.8 ms, p=0.002) and TPR did not differ between two groups. CONCLUSIONS: Reduced BRS may contribute to the development of the vasovagal syncope by inability to adequately counteract hypotension resulting from decreased cardiac output at the time of syncope (Tab. 3, Ref. 18). Text in PDF www.elis.sk.

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Section: Resultsmentioning

confidence: 85%

“…Reduced arterial barorefl ex sensitivity was reported in patients suffering from vasovagal syncope in some studies (1,3,4), whereas another studies did not found differences in barorefl ex sensitivity in these subjects (5). In some reports, an increased baroreceptor refl ex gain was observed in fainting subjects (6, 7).…”

Section: Introductionmentioning

confidence: 97%

Reduced baroreflex sensitivity in patients with vasovagal syncope

Mitro¹,

Šimurda²,

Evin³

et al. 2015

BLL

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“…30 Additionally, diminished vascular resistance responses during orthostatic challenges have been shown in many patients with neurally mediated syncope well before the onset of syncope. 13,[31][32][33] It has also been reported that administration of midodrine (␣ 1 -agonist drug) at the end of bed rest significantly ameliorated the excessive decreases in blood pressure and presyncope during a provocative tilt test 34 and that enhancement of sympathetic tone by yohimbine (an ␣ 2 -antagonist) markedly improved orthostatic tolerance in patients with neurally mediated syncope. 35 Taken together, these results indicate that vasoconstrictor capacity may be a contributor to the individual variability in orthostatic intolerance.…”

Section: Individual Variability In Orthostatic Intolerancementioning

confidence: 95%

Vasoconstrictor Reserve and Sympathetic Neural Control of Orthostasis

2004

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Background-We tested the hypothesis that individual variability in orthostatic tolerance is dependent on the degree of neural and vasomotor reserve available for vasoconstriction. Methods and Results-Muscle sympathetic nerve activity (MSNA) and hemodynamics were measured in 12 healthy young volunteers during 60°head-up tilt (HUT), followed by a cold pressor test (CPT) in HUT. Orthostatic tolerance was determined by progressive lower-body negative pressure (LBNP) to presyncope. The same protocols were performed randomly in normovolemic and hypovolemic conditions. We found that mean arterial pressure increased and stroke volume decreased, whereas heart rate (HR), MSNA, and total peripheral resistance (TPR) increased during HUT (all PϽ0.01). Application of the CPT in HUT did not increase HR or decrease stroke volume further but elevated mean arterial pressure (PϽ0.01) and increased MSNA and TPR in some subjects. There was a positive correlation between the time to presyncope from Ϫ50 mm Hg LBNP (equivalent to 60°HUT alone) and the changes in MSNA produced by the CPT under both conditions (rϭ0.442, Pϭ0.039). Those who had greater increases in MSNA had greater increases in TPR during the CPT and longer time to presyncope (both PϽ0.05). One subject had dramatic increases in MSNA but small increases in TPR during the CPT, which indicates a disassociation between sympathetic activity and the increase in peripheral vascular resistance. Conclusions-These results support our hypothesis and suggest that vasoconstrictor capability is a contributor to orthostatic tolerance in humans. Vasoconstrictor reserve therefore may be one mechanism underlying individual variability in orthostatic intolerance.

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“…Important neural control mechanisms known to be altered in patients with syncope, such as high-and lowpressure baroreceptor reflex control of heart rate, 13,14,33 were not directly addressed.…”

Section: Limitations Of the Studymentioning

confidence: 99%

Cardiac Autonomic Patterns Preceding Occasional Vasovagal Reactions in Healthy Humans

et al. 1998

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Background-The wide range of clinical presentation of orthostatic vasovagal syncope suggests different underlying changes in the cardiac autonomic modulation. Methods and Results-To evaluate the beat-by-beat modifications in the neural control of heart period preceding a syncopal event, we studied RR interval variability in 22 healthy subjects who experienced fainting for the first time during a 90°head-up tilt and in 22 control subjects by means of time-variant power spectral analysis. Sympathetic and vagal modulations to the sinoatrial node were assessed by the normalized power of the low-frequency (LF, Ϸ0.1-Hz) and high-frequency (HF, Ϸ0.25-Hz) oscillatory components of RR variability. When the patients were supine, no differences were observed in the hemodynamic and spectral parameters of the 2 groups. During the tilt procedure, RR, LF NU , and HF NU (NUϭnormalized units) values were relatively stable in control subjects. During early tilt (T 1 ), subjects with syncope had reduced RR intervals compared with control subjects. In 13 subjects with syncope, RR decreased while LF NU and LF/HF increased in the last minute of tilt before syncope (T 2 ). Conversely, in the remaining 9 fainters, LF NU and LF/HF decreased from T 1 to T 2 and HF NU increased slightly. Conclusions-Two different patterns may be recognized in the cardiac autonomic changes preceding an occasional vasovagal event, namely, one characterized by a progressive increase of the marker of cardiac sympathetic modulation up to the onset of syncope, the other by a sympathetic inhibition with an impending vagal predominance. The recognition of different pathophysiological mechanisms in fainters may have important therapeutic implications.

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Baroreflex Sensitivity in Patients With Vasovagal Syncope

Cited by 87 publications

References 29 publications

Reduced baroreflex sensitivity in patients with vasovagal syncope

Reduced baroreflex sensitivity in patients with vasovagal syncope

Vasoconstrictor Reserve and Sympathetic Neural Control of Orthostasis

Cardiac Autonomic Patterns Preceding Occasional Vasovagal Reactions in Healthy Humans

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