Endothelial function and peripheral vasomotion in the brachial artery in neurally mediated syncope

Clinical features and response at head-up tilt test of patients with situational syncope

OBJECTIVE

The study compared clinical characteristics and response at head-up tilt test (HUTT) between situational (SS) and vasovagal syncope (VVS).

METHODS

Consecutive patients who underwent nitroglycerin-potentiated HUTT were retrospectively dichotomised into two groups: those with a history of SS and those with a history of VVS. The patients with SS were further subdivided into patients with SS alone and with SS and at least one episode of VVS.

RESULTS

1285 patients were enrolled: 246 (19.1%) had SS (SS alone in 121 and SS+VVS in 125). Patients with SS were older (48.8±20.0 vs 44.4±19.1, p=0.007) and more frequently male (57.3% vs 47.7%, p=0.001). At multivariable analysis, smoking habit (OR 2.28; p<0.0001), history of traumatic syncope (OR 2.29; p=0.0001) and ACE inhibitors/angiotensin II receptor blockers (OR 4.74; p<0.0001) were independently associated with SS. HUTT was positive in 175 (71.1%) patients with SS and in 737 (70.9%) patients with VVS (p=0.9). Patients with SS showed more mixed (42.3% vs 32.0%, p=0.002) and vasodepressor forms (10.6% vs 6.1%, p=0.01) and less cardioinhibitory responses compared with others (18.3% vs 32.8%, p<0.0001).

CONCLUSIONS

Compared with VVS, patients with SS have different clinical characteristics and a higher prevalence of hypotensive drugs leading to hypotensive susceptibility. The positivity rate of HUTT is high and similar to that of VVS, although patients with SS show a higher prevalence of hypotensive responses.

The clinical presentation of syncope influences the head-up tilt test responses

INTRODUCTION

Little is still known about the positivity rate of nitroglycerin (NTG) potentiated head-up tilt test (HUTT) according to the history-based clinical features of syncope. The study aimed to compare the HUTT positivity rate and type of responses in patients with classical and non-classical vasovagal syncope (VVS).

MATERIALS AND METHODS

We retrospectively evaluated all consecutive patients who underwent NTG-potentiated HUTT for VVS. The study population was dichotomized into classical and non-classical VVS.

RESULTS

A total of 1285 VVS patients (45± 19.1 years; 49.6% male) were enrolled: 627 (48.8%) had a history of classical VVS and 658 (51.2%) of non-classical VVS. HUTT was positive in 866 (67.4%) patients. The positivity rate was significantly higher in patients with classical compared to those with non-classical VVS (81.5% vs 54%; P< 0.0001). Cardioinhibitory response showed similar total positivity rate (27.6% vs 31%; P= 0.17), but higher relative prevalence among positive tests (57.7% vs 33.9%, P< 0.0001) in patients with non-classical VVS. At multivariable analysis, classical reflex syncope, male sex, history of traumatic syncope and use of diuretics were independent predictors of HUTT positivity.

CONCLUSION

The clinical presentation of syncope influences the overall HUTT positivity rate and the type of responses. Cardioinhibitory response and traumatic syncope are more likely in patients with non-classical VVS.

Cardioinhibitory syncope with asystole during nitroglycerin potentiated head up tilt test: prevalence and clinical predictors

Aims

The aim of our study was to evaluate the prevalence and clinical predictors of cardioinhibitory (CI) responses with asystole at the nitroglycerin (NTG)-potentiated head-up tilt test (HUTT) in patients with a history of syncope admitted to a tertiary referral syncope unit.

Methods

We retrospectively evaluated all consecutive patients who underwent NTG-potentiated HUTT for suspected reflex syncope at our institution from March 1 2017 to May 1 2020. The prevalence of HUTT-induced CI syncope was assessed. Univariate and multivariate analyses were performed to test the association of asystolic response to HUTT with a set of clinical covariates.

Results

We enrolled 1285 patients (45 ± 19.1 years; 49.6% male); 368 (28.6%) showed HUTT-induced CI response with asystole. A multivariate analysis revealed that the following factors were independently associated with HUTT-induced CI syncope: male sex (OR 1.48; ConInt 1.14–1.92; P = 0.003), smoking (OR 2.22; ConInt 1.56–3.115; P < 0.001), traumatic syncope (OR: 2.81; ConInt 1.79–4.42; P < 0.001), situational syncope (OR 0.45; ConInt 0.27–0.73; P = 0.002), and the use of diuretics (OR 9.94; ConInt 3.83–25.76; P < 0.001).

Conclusions

The cardioinhibitory syncope with asystole induced by NTG-potentiated HUTT is more frequent than previously reported. The male gender, smoking habit, history of traumatic syncope, and use of diuretics were independent predictors of HUTT-induced CI responses. Conversely, the history of situational syncope seems to reduce this probability.

Serum Asymmetric Dimethylarginine Levels in Patients with Vasovagal Syncope

Background and Objectives: Vasovagal syncope (VVS) is the most common cause of syncope and has multiple pathophysiological mechanisms. Asymmetric dimethylarginine (ADMA) is the major inhibitor of nitric oxide (NO). In this study, we aimed to investigate the relationship between plasma ADMA levels and syncope during the head-up tilt (HUT) test. Materials and Methods: Overall, 97 patients were included in this study. They were above 18 years of age and were admitted to our clinic with the complaint of at least one episode of syncope consistent with VVS. The HUT test was performed in all patients. Patients were divided into the following two groups based on the HUT test results: group 1 included 57 patients with a positive HUT test and group 2 included 35 patients with a negative HUT test. Blood samples were taken before and immediately after the HUT test to measure ADMA levels. Results: No significant intergroup differences were observed concerning gender and age (female gender 68% vs 60%; mean age 24.85 ± 4.01 vs 25.62 ± 3.54 years, respectively, for groups 1 and 2). ADMA values were similar between groups 1 and 2 before the HUT test [ADMA of 958 (544–1418) vs 951 (519–1269); p = 0.794]. In the negative HUT group, no significant differences were observed in ADMA levels before and after the HUT test [ADMA of 951 (519–1269) vs 951 (519–1566); p = 0.764]. However, in the positive HUT group, ADMA levels were significantly decreased following the HUT test [pretest ADMA of 958 (544–1418) vs post-test ADMA of 115 (67–198); p < 0.001]. Conclusion: ADMA levels significantly decreased after the HUT test in patients with VVS.

Reactive Vasodilation Predicts Mortality in Primary Systemic Light-Chain Amyloidosis

Supplemental Digital Content is available in the text.

Cardiac involvement and hypotension dominate the prognosis of light-chain amyloidosis (AL). Evidence suggests that there is also peripheral vascular involvement in AL but its prognostic significance is unknown.

Endothelial Function and Cardiovascular Autonomic Activity in Neurally Mediated Syncope

OBJECTIVES

The aim of this study was to investigate endothelial function and cardiovascular autonomic activity in patients with neurally mediated syncope (NMS).

METHODS

Patients with a typical history of NMS were divided according to the result of a head-up tilt (HUT) test. There were 25 patients each in the HUT-positive (HUT+), HUT-negative (HUT-) and control groups. Flow-mediated dilation (FMD) and 24-hour ambulatory electrocardiography (AECG) were performed before the HUT tests.

RESULTS

The HUT+ group had a significantly higher FMD than that of the HUT- group and the control group (8.8 ± 3.3 vs. 6.4 ± 2.9%, p = 0.006, and 8.8 ± 3.3 vs. 5.7 ± 2.2%, p = 0.001, respectively). On a 24-hour AECG, the parasympathetic indexes of time domain, such as rMSSD and the pNN50, were significantly higher in the HUT+ group than in the HUT- group (39.0 ± 9.6 vs. 31.6 ± 9.6 ms, p = 0.016, and 16.5 ± 8.1 vs. 10.2 ± 7.2%, p = 0.002, respectively) and the control group (39.0 ± 9.6 vs. 28.9 ± 9.6%, p = 0.001 and 16.5 ± 8.1 vs. 8.7 ± 6.7%, p = 0.001, respectively). High-frequency spectra (parasympathetic activity) of the frequency domain showed similar results.

CONCLUSIONS

Not only parasympathetic activity, but also endothelial function may affect the results of HUT tests in patients with NMS.

Endothelial dysfunction state in migraine headache and neutrally mediated syncope in children and young adults

Background:

Recent evidences have supported migraine headache and neurally mediated syncope as the especial types of endotheliopathies. To determine endothelial function in patients with migraine headache or those with neurally mediated syncope, the present study was conducted.

Materials and Methods:

This cross-sectional study was performed on 93 consecutive patients aged 5-20 years in four groups; neurally mediated syncope, migraine, both neurally mediated syncope and migraine, and control groups. All subjects were tested for basic biophysical and biochemical features including age, gender, body mass index, systolic, and diastolic blood pressures, intima-media thickness (IMT) and flow-mediated dilation (FMD), blood hemoglobin, fasting blood glucose, lipid profile, intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM), and E-selectin.

Results:

The mean levels of VCAM and ICAM were significantly higher in all groups when compared to control group (P < 0.05). FMD was significantly higher in syncope, migraine, and syncope and migraine groups than in the control group (P < 0.05). Furthermore, mean IMT was significantly lower in migraine and also in syncope and migraine groups than in syncope group and control group (P < 0.05). Examining the association between IMT and other baseline parameters showed positive association of IMT with systolic and diastolic blood pressures.

Conclusion:

Endothelial dysfunction is seen in both migraine headache and neurally mediated syncope. Changes in endothelial functional indices are also dependent on the blood pressure.

Erythrocytic hydrogen sulfide production is increased in children with vasovagal syncope

OBJECTIVES

To explore the differences in erythrocyte hydrogen sulfide (H2S) production in children with vasovagal syncope (VVS).

STUDY DESIGN

A total of 54 children including 27 with VVS, aged 6-16 years (mean age 11.3 ± 3.3 years), and 27 healthy children, aged 3-17 years (mean age 10.4 ± 1.8 years) were included in the study. Children with VVS had symptoms of dizziness, pallor, blurred vision, nausea, and some had syncope. Erythrocyte H2S production was measured by a sulphur-sensitive electrode. Flow-mediated dilation (FMD) of brachial artery was measured for each patient by vascular ultrasound.

RESULTS

H2S production from erythrocytes was significantly increased in the children with VVS compared with controls (P < .01). The erythrocytic H2S production in the VVS-vasoinhibitory subgroup was obviously higher than that in VVS-cardioinhibitory (P < .05) and VVS-mixed inhibitory subgroups (P < .05). FMD in the VVS-vasoinhibitory subgroup was greater than that in the VVS-cardioinhibitory (P < .05) and the VVS-mixed subgroups (P < .05). The erythrocytic H2S production had a positive linear correlation with FMD in children with VVS (P < .05).

CONCLUSIONS

Increased erythrocyte H2S production may be involved in the pathogenesis of VVS in children.

An increased endothelial-independent vasodilation is the hallmark of the neurally mediated syncope

BACKGROUND

The neurally mediated syncope (NMS) is sustained by complex cardiac and vascular reflexes, acting on and amplified by central autonomic loops, resulting in bradycardia and hypotension.

HYPOTHESIS

Our aim was to assess whether the pathophysiology of NMS is also related to an abnormal peripheral vasoreactivity.

METHODS

We evaluated by ultrasound the flow-mediated vasodilation (FMD) and the nitrate-mediated dilation (NMD) in 17 patients with NMS, induced by drug-free tilt test in 6 subjects and by nitrate-potentiated tilt test in the other 11 cases; the syncope was classified as vasodepressive (VD) in 8 cases, cardioinhibitory (CI) in 7, and mixed in 2.

RESULTS

The FMD was not different from controls (10.2 ± 4.5 vs 11.4 ± 3.9, P = ns), with normal recovery times; the NMD was greater in fainting subjects than in controls (26.7 ± 7.3 vs 19.0 ± 3.6, P < 0.05), with higher values in VD than in CI syncope (31.1 ± 7.0 vs 23.1 ± 5.0, P = ns); compared to controls, subjects with NMS showed normal recovery times after FMD but longer recovery times after nitrate administration (13.0 ± 5.6 vs 6.3 ± 0.7 minutes, P < 0.05).

CONCLUSIONS

The evaluation of endothelial function supports evidence that NMS is characterized by a marked and sustained endothelial-independent vasodilation, in the presence of a normal FMD; vascular hyperreactivity in response to nitrate administration is particularly overt in vasodepressive syncope and can explain the high rate of responses to nitrate administration during tilt test.

Role of nitric oxide in young patients with vasovagal syncope

AIMS

Nitric oxide (NO) formed in the vascular endothelium produces, among other effects, a strong vasodilation. In order to evaluate the possible role of NO in hypotension induced by head-up tilt test (HUT), we measured plasma levels of its metabolites, nitrites and nitrates (NOx), during the test.

METHODS AND RESULTS

Twelve patients with vasovagal syncope and positive HUT [HUT(+)] (mean age: 23+/-5 years) and 13 healthy volunteers with negative HUT (controls) (mean age: 24+/-5 years) were included. Venous blood samples were obtained during the baseline stage for biochemical measurements. Plasma values of NOx were obtained under baseline conditions (T0), at the end of the HUT (T1), and 15 min after the end of the HUT (T2). The baseline biochemical values as well as haemodynamic parameters were similar in HUT(+) patients and controls. NOx plasma values (in micromol/L) were as follows [HUT(+) vs. controls]: T0: 5.7+/-1.6 vs. 8.8+/-4.7 (P=0.05), T1: 6.1+/-3.2 vs. 8.5+/-3.6 (P=NS), and T2: 6.1+/-3 vs. 10.2+/-8.9 (P=NS). The NOx levels were directly correlated with the insulin levels (Spearman's R=0.53, P=0.008).

CONCLUSION

Baseline plasma levels of NOx were significantly lower in HUT(+) patients than in controls. However, since the expected increase in NOx values during HUT-induced syncope was not observed, the possible role of NO in vasovagal hypotension is uncertain.

Increased flow-mediated vasodilation in cirrhotic patients with ascites: relationship with renal resistive index

BACKGROUND

Peripheral vasodilation is the key factor in the development of hyperdynamic circulation, sodium retention and functional renal failure in patients with cirrhosis. Brachial artery flow-mediated dilation (FMD) after transient vascular occlusion is a non-invasive method to assess the shear stress-induced arterial vasodilation.

AIMS

To evaluate FMD in cirrhotic patients with and without ascites and to assess the relationship between FMD and intrarenal resistances.

METHODS

Flow-mediated dilation was determined in 32 cirrhotic patients (22 with ascites) and 12 healthy controls and correlated with the intrarenal resistive index (RI) assessed by Doppler exploration.

RESULTS

Basal diameter of the brachial artery was similar in healthy controls and in cirrhotic patients, whereas FMD was significantly higher in patients with cirrhosis and ascites [29.5% (range 10.3-50%)] than in pre-ascitic patients [17.3% (range 2.4-48.5%)] and healthy control subjects [11.6% (range 5.1-17.8%)] (P<0.001). Intrarenal RI was significantly higher in patients with cirrhosis than in healthy subjects, and a direct relationship existed between FMD and intrarenal RI (r=0.66; P<0.00001).

CONCLUSIONS

These findings in vivo demonstrate that cirrhotic patients with ascites have an enhanced shear stress-induced peripheral vasodilation, which is closely related to intrarenal vasoconstriction.

Vasodilation in vasovagal syncope and the effect of water ingestion

Abnormal (increased, but also decreased) vasodilative responses have been observed in patients with vasovagal syncope (VVS). The objective was to assess reactive vasodilation in supine patients with VVS and its relation to severity of the syndrome. Reactive vasodilation was also assessed after a simple therapeutic intervention (water drinking). Thirty-four patients were studied, all with recurrent VVS and a recent positive head-up tilt test result. Seventeen matched healthy subjects served as controls. Venous occlusion plethysmography was used to assess forearm blood flow (FBF) and forearm vascular resistance resistance (1) at rest and (2) during reactive hyperemia. Clinical severity of the syndrome was related to the intensity and duration of the vasodilative reflex. The same plethysmographic measurements were repeated 60 minutes after drinking 500 ml of water. Before water drinking, no difference was observed between groups in baseline measurements. However, duration of hyperemia was longer in patients (p <0.05) and was related to the duration of the previous positive tilt test (r = -0.69, p <0.05) and total number of each patient's symptomatic vasovagal episodes (r = 0.49, p <0.05). After water ingestion, baseline FBF decreased in patients (p <0.05) and remained stable in controls. In patients, duration of hyperemia decreased to normal values. Hyperemic FBF remained similar between groups. In conclusion, increased reactive vasodilative reflexes were observed in patients with VVS. They seemed to be of significant pathophysiologic significance. Water drinking can normalize them for >or=60 minutes.

Pulse wave analysis during supine rest may identify subjects with recurrent vasovagal syncope

In the present study, we studied whether analysis of the FAP (finger arterial pressure) waveform during supine rest discriminates subjects with recurrent VVS (vasovagal syncope) from healthy controls. Signal-averaged FAP waveforms (Finapres) were obtained in 32 head-up tilt-test-positive subjects with recurrent VVS (35±13 years) and in 32 sex- and age-matched healthy controls. The DT (time delay) between the systolic and diastolic peaks of the FAP waveform was measured and large artery SI (stiffness index) was calculated as a ratio of body height and DT. VVS patients had significantly shorter DT compared with controls (303±31 compared with 329±18 ms; P<0.001) and higher SI (5.79±0.70 compared with 5.20±0.36 m/s; P<0.001). The differences were independent of heart rate and blood pressure. SI >5.45 m/s identified subjects with syncope with a sensitivity of 72% and a specificity of 84%. Age-corrected DT (cDT=DT+age−350) identified subjects with syncope with a sensitivity of 75% and a specificity of 84%. Combined use of cDT <0 ms and SI >5.45 m/s increased sensitivity and specificity to 81% and 96% respectively. The discriminative power of FAP descriptors improved further when younger subjects were excluded. In subjects aged >30 years (median age), the combination of cDT and SI identified subjects with syncope with a sensitivity of 93% and a specificity of 100%. These results suggest that FAP descriptors during supine rest might be useful in the diagnosis of VVS in middle-aged subjects.

Flow-mediated vasodilation: a diagnostic instrument, or an experimental tool?

Brachial arterial flow-mediated dilation (FMD), assessed by high-resolution ultrasonography, reflects endothelium-dependent vasodilator function. FMD is diminished in patients with atherosclerosis and with coronary risk factors, and improves with risk-reduction therapy. Therefore, the measurement of FMD can be a good prognostic instrument in preventive cardiology, is useful to predict short-term postoperative cardiovascular events in a high-risk population and to assess long-term cardiovascular risk in a lower risk population, and is an excellent experimental tool to detect changes in endothelial function after new therapeutic interventions. In this review article, the pathophysiology of FMD, based on reactive hyperemia, is extensively discussed. Furthermore, an overview is given of the actual clinical indications of FMD measurement.

Assessment of flow-mediated vasodilatation (FMD) of the brachial artery: effects of technical aspects of the FMD measurement on the FMD response

AIMS

The ability to assess endothelial function non-invasively with B-mode ultrasound has lead to its widespread application in a variety of studies. However, the absolute values obtained using this approach vary considerably across studies. We studied whether technical aspects of the methodology can explain the wide variety in absolute values across studies.

METHODS AND RESULTS

A literature search was performed to identify published reports on flow-mediated vasodilatation (FMD) of the brachial artery published between 1992 and 2001. Information on type of equipment (wall track/B-mode), location of the measurement (antecubital fossa/upper arm), occlusion site (lower/upper arm), occlusion duration (min), and occlusion pressure was extracted. Patient characteristics were also extracted. For the healthy populations, mean FMD varied from 0.20 to 19.2%; for the coronary heart disease (CHD) patients FMD varied from -1.3 to 14%; for subjects with diabetes mellitus FMD varied from 0.75 to 12%. Compared with occlusion at the upper arm, lower arm occlusion was related to decreased FMD (mean difference in FMD -2.47%; 95% CI 0.55-4.39). An occlusion duration of > or =4.5 min was related to an increased FMD compared with an occlusion time of < or =4 min (mean difference 1.30%; 95% CI 0.35-2.46). These findings were adjusted for other technical aspects of the methodology and for differences in risk factors between populations.

CONCLUSION

Mean FMD differs widely between studies. There is a great overlap between populations (healthy, CHD, diabetics). Our findings suggest that the technical aspects of the measurements, the location, and the duration of the occlusion may explain some of these differences, whereas type of equipment, location of the measurement, and occlusion pressure do not.