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Kujawski S, Buszko K, Cudnoch-Jędrzejewska A, Słomko J, Jakovljevic DG, Newton JL, Zalewski P. The impact of total sleep deprivation upon supine and head up tilt hemodynamics using non-linear analysis in firefighters. Biomed Signal Process Control 2021. [DOI: 10.1016/j.bspc.2021.102989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Yamaguchi Y, Mizumaki K, Nishida K, Sakamoto T, Nakatani Y, Kataoka N, Kinugawa K, Inoue H. Vasovagal syncope is associated with poor prognosis in patients with left ventricular dysfunction. Heart Vessels 2017; 33:421-426. [PMID: 29110073 DOI: 10.1007/s00380-017-1078-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 11/01/2017] [Indexed: 11/29/2022]
Abstract
Vasovagal syncope (VVS) is known to have a benign prognosis and be associated with enhanced contraction and activation of the left ventricular (LV) mechanoreceptors. However, a little is known about VVS in patients with LV dysfunction. The present study aimed to investigate the prevalence and prognosis of VVS in patients with LV dysfunction. We enrolled 368 patients with unexplained syncope. In 7 of these patients, LV ejection fraction was lower than 40%. The results of a head-up tilt test (HUT) and the recurrence of syncope were compared between these 7 patients with LV dysfunction and the remaining patients. Positive HUT was obtained in the 6 patients (86%) with LV dysfunction; this rate tended to be higher as compared with normal cardiac function (192/361, 53%, P = 0.069). In patients with LV dysfunction, response in HUT was mostly vasodepressor type (62%); however, most of HUT responses were mixed type in patients with normal LV function (67%). Among patients with positive HUT, the recurrent rate of syncope after HUT was higher in those with LV dysfunction than in those with normal LV function (67 vs. 21%, P = 0.008). VVS in patients with LV dysfunction may be refractory to treatment and could be associated with poor prognosis.
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Affiliation(s)
- Yoshiaki Yamaguchi
- The Second Department of Internal Medicine, Graduate School of Medicine, University of Toyama, Toyama, 930-0194, Japan
| | - Koichi Mizumaki
- Alpen Murotani Clinic, 275 Higashiiwase, Toyama, 931-8358, Japan.
| | - Kunihiro Nishida
- The Second Department of Internal Medicine, Graduate School of Medicine, University of Toyama, Toyama, 930-0194, Japan
| | - Tamotsu Sakamoto
- The Second Department of Internal Medicine, Graduate School of Medicine, University of Toyama, Toyama, 930-0194, Japan
| | - Yosuke Nakatani
- The Second Department of Internal Medicine, Graduate School of Medicine, University of Toyama, Toyama, 930-0194, Japan
| | - Naoya Kataoka
- The Second Department of Internal Medicine, Graduate School of Medicine, University of Toyama, Toyama, 930-0194, Japan
| | - Koichiro Kinugawa
- The Second Department of Internal Medicine, Graduate School of Medicine, University of Toyama, Toyama, 930-0194, Japan
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Lindenberger M, Länne T. Slower lower limb blood pooling in young women with orthostatic intolerance. Exp Physiol 2015; 100:2-11. [PMID: 25557726 DOI: 10.1113/expphysiol.2014.082867] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 10/20/2014] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Orthostatic stress is mostly caused by venous blood pooling in the lower limbs. Venous distension elicits sympathetic responses, and increased distension speed enhances the cardiovascular response. We examine whether lower limb blood pooling rate during lower body negative pressure is linked to orthostatic intolerance. What is the main finding and its importance? A similar amount of blood was pooled in the lower limb, but at a slower rate in women who developed signs of orthostatic intolerance. The difference in blood pooling rate increased with orthostatic stress and was most prominent at a presyncope-inducing level of lower body negative pressure. The findings have implications for the pathophysiology as well as treatment of orthostatic intolerance. Vasovagal syncope is common in young women, but its aetiology remains elusive. Orthostatic stress-induced lower limb blood pooling is linked with central hypovolaemia and baroreceptor unloading. Venous distension in the arm elicits a sympathetic response, which is enhanced with more rapid distension. Our aim was to study both the amount and the speed of lower limb pooling during orthostatic stress and its effects on compensatory mechanisms to maintain cardiovascular homeostasis in women with orthostatic intolerance. Twenty-seven healthy women, aged 20-27 years, were subjected to a lower body negative pressure (LBNP) of 11-44 mmHg. Five women developed symptoms of vasovagal syncope (orthostatic intolerant) and were compared with the remaining women, who tolerated LBNP well (orthostatic tolerant). Lower limb blood pooling, blood flow and compensatory mobilization of venous capacitance blood were measured. Lower body negative pressure induced equal lower limb blood pooling in both groups, but at a slower rate in orthostatic intolerant women (e.g. time to 50% of total blood pooling, orthostatic intolerant 44 ± 7 s and orthostatic tolerant 26 ± 2 s; P < 0.001). At presyncope-inducing LBNP, the mobilization of venous capacitance blood was both reduced (P < 0.05) and much slower in orthostatic intolerant women (P = 0.0007). Orthostatic intolerant women elicited blunted arterial vasoconstriction at low-grade LBNP, activating only cardiopulmonary baroreceptors, while orthostatic tolerant women responded with apparent vasoconstriction (P < 0.0001). In conclusion, slower lower limb blood pooling could contribute to orthostatic intolerance in women. Mobilization of venous capacitance blood from the peripheral to the central circulation was both slower and decreased; furthermore, reduced cardiopulmonary baroreceptor sensitivity was found in women who developed orthostatic intolerance. Further studies including women who experience syncope in daily life are needed.
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Affiliation(s)
- Marcus Lindenberger
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Department of Cardiology, County Council of Östergötland, Linköping, Sweden
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Goel R, Caracciolo G, Wilansky S, Scott LR, Narula J, Sengupta PP. Effect of head-up tilt-table testing on left ventricular longitudinal strain in patients with neurocardiogenic syncope. Am J Cardiol 2013; 112:1252-7. [PMID: 23932189 DOI: 10.1016/j.amjcard.2013.06.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 06/11/2013] [Accepted: 06/11/2013] [Indexed: 10/26/2022]
Abstract
Recent studies have shown conflicting data regarding left ventricular (LV) function in patients with neurocardiogenic syncope, with some investigators reporting a marked decrease in LV end-systolic wall stress and stress-corrected fractional shortening. We sought to determine the characteristics of resting LV deformation in patients with neurocardiogenic syncope by selective motion tracking of subendocardial and subepicardial regions using speckle tracking echocardiography. We assessed resting LV function in 82 patients undergoing head-up tilt-table (HUTT) testing. Patients were divided into 3 groups based on a positive HUTT test with associated co-morbid conditions (n = 30), no associated co-morbid conditions (n = 30), or negative HUTT results (n = 22). LV longitudinal, circumferential, and radial strains were obtained by speckle tracking echocardiography of subendocardial and subepicardial regions in each group and compared with resting LV deformation in 20 healthy control subjects. Compared with endocardial longitudinal strain in control subjects, that in patients with positive HUTT results was attenuated, irrespective of co-morbid conditions (p <0.05). Circumferential and radial strains did not differ among groups. On multivariate logistic regression analysis, endocardial longitudinal strain was an independent predictor (odds ratio, 1.16; p = 0.01) of positive HUTT test results. In conclusion, resting LV longitudinal strain is attenuated in patients with positive HUTT test results. Overall, these results may suggest that an increase in resting LV contractility is not a prerequisite for development of neurocardiogenic syncope.
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Karataş Z, Alp H, Sap F, Altın H, Baysal T, Karaarslan S. Usability of QTc dispersion for the prediction of orthostatic intolerance syndromes. Eur J Paediatr Neurol 2012; 16:469-74. [PMID: 22226850 DOI: 10.1016/j.ejpn.2011.12.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 12/09/2011] [Accepted: 12/18/2011] [Indexed: 11/25/2022]
Abstract
BACKGROUND Syncope is defined as transient loss of consciousness and muscle tone, usually of short duration. Noncardiac causes of syncope are classified as orthostatic intolerance syndromes (OIS). QT and QTc (corrected QT) dispersions are the measurements of myocardial instability and show predisposition to arrhythmias. In this study; clinical findings, QT and QTc dispersions of the patients who were diagnosed as OIS were evaluated retrospectively. Also, the aim of the study is to clarify the association of clinical characteristics of unexplained syncope with the outcome of the QT and QTc dispersions in children. METHODS We designed a retrospective study including 152 children and adolescents who had repeated unexplained syncope or presyncope between June 2002 and August 2010. Head-up Tilt table test (HUTT) were performed for all patients. Control group consisted of 67 healthy children. The QT and QTc dispersions were measured from the 12 ECG leads. RESULTS Eighty-four (55.2%) patients had positive and 68 (44.8%) had negative response to HUTT. QT and QTc dispersions were significantly higher in HUTT-positive group than in negative (p < 0.01, p < 0.001 respectively). Also, QTc dispersion was significantly higher in both vasovagal syncope and postural orthostatic tachycardia syndrome groups than in HUTT-negative group (p < 0.001, p < 0.05 respectively). Specifity and sensitivity of QTc dispersion for predicting positive HUTT are 76.5% and 59.5% respectively. The positive predictive value of the test calculated as 75.8%. CONCLUSIONS These results revealed that we can use QTc dispersion measurement as a noninvasive electrocardiographic test to evaluate OIS for predicting positive result before performing HUTT.
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Affiliation(s)
- Zehra Karataş
- Selcuk University Meram, Department of Pediatric Cardiology, Beysehir Yolu, Meram, Konya, Turkey.
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Roessler A, Goswami N, Haditsch B, Hinghofer-Szalkay H. Modulation of plasma adrenomedullin by epinephrine infusion during head up tilt. Eur J Appl Physiol 2011; 111:531-7. [PMID: 20924597 DOI: 10.1007/s00421-010-1668-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2010] [Indexed: 02/07/2023]
Abstract
We investigated whether head up tilt (HUT) with and without simultaneous epinephrine infusion modulate plasma adrenomedullin. We studied eight healthy male volunteers, using two 5 min 70° HUT trials: control (saline infusion) and intervention (epinephrine infusion, titrated to a dose which increased supine systolic pressure by 20% above resting values). Protocols were randomized and separated by 2 weeks. Cardiac function and systolic time intervals, recorded using a phonocardiograph microphone, included left ventricular ejection time (LVET), pre-ejection period (PEP), PEP/LVET and electromechanical systole (QS2). Compared to saline infusion, epinephrine increased supine adrenomedullin (3.2 ± 0.8 pmol/l, i.e., mean ± SEM, respectively), heart rate (HR) (+11.3 ± 2.6 bpm), systolic pressure (+18.4 ± 2.6 mmHg) but decreased supine LVET, LVET corrected for HR (LVETi) and QS2-time (all p = 0.004). Despite similar HUT induced thoracic fluid shifts, reflected by similar thoracic impedance changes, HUT-induced adrenomedullin increases were minimal in epinephrine-supplemented men in comparison to controls (+8% vs. 42%). During HUT, epinephrine infusion decreased only the LVET (p = 0.039). Our findings confirm that short-term HUT increases plasma adrenomedullin. They further suggest that with increased supine epinephrine levels (epinephrine infusion clamping systolic arterial pressure at 120% control level), supine cardiac performance rises to a level similar to that during HUT, while adrenomedullin is still elevated with HUT. This might be in accordance with a 'dampening' role of adrenomedullin during catecholaminergic cardiovascular stimulation. As epinephrine is used as a drug to treat cardiac arrest and ventricular arrhythmias, our results may have important clinical/emergency resuscitation applications.
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Affiliation(s)
- Andreas Roessler
- Institute of Physiology, Center of Physiological Medicine, Medical University of Graz, Harrachgasse 21/5, 8010, Graz, Austria
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Affiliation(s)
- Elan Hekier
- Division of Pulmonary and Critical Care Medicine, University of California, San Diego School of Medicine, La Jolla, CA.
| | - Jess Mandel
- Division of Pulmonary and Critical Care Medicine, University of California, San Diego School of Medicine, La Jolla, CA
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Folino AF, Russo G, Porta A, Buja G, Cerutti S, Iliceto S. Autonomic modulation and cardiac contractility in vasovagal syncope. Int J Cardiol 2008; 139:248-53. [PMID: 19049848 DOI: 10.1016/j.ijcard.2008.10.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Revised: 08/12/2008] [Accepted: 10/12/2008] [Indexed: 11/17/2022]
Abstract
BACKGROUND Previous studies proposed as one of the main mechanisms involved in neurally mediated syncope, the stimulation of ventricular mechanoreceptors as the final trigger for vagal discharge. OBJECTIVES This study aimed to verify the presence of a sympathetic driven increase of cardiac contractility before vasovagal syncope. METHODS We studied 23 patients with recurrent syncope. All underwent a 60 ° tilt with pharmacologic challenge (sublingual spray nitrate). Two conditions were used to assess autonomic activity by heart rate variability analysis: in a supine position after 5 min of rest and after 15 min of tilt. Simultaneously, cardiac contractility was quantified by tissue-Doppler echocardiography at the base of the free walls of left ventricle. The peak myocardial velocities during systole (Sw) and late diastole (Aw) were considered. RESULTS Passive tilt induced a significant increase of the low frequency component (LF) as well as a decrease of the high frequency component (HF) in positive patients (LF: from 49 ± 18 to 65 ± 18 nu, p<0.05; HF: from 41 ± 21 to 26 ± 16 nu, p<0.05). Tissue-Doppler showed a similar increase in Sw in both positive and negative patients but showed a significant decrease of Aw in syncopal subjects (p<0.005). CONCLUSIONS Our results do not show an increase in ventricular contractility before tilt-induced syncope, or in presence of a valuable increase of sympathetic activity. Instead, we observe a reduction of atrial contractility, which may be a contributory component in the pathogenesis of vasovagal syncope.
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Tan MP, Parry SW. Vasovagal Syncope in the Older Patient. J Am Coll Cardiol 2008; 51:599-606. [DOI: 10.1016/j.jacc.2007.11.025] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2007] [Revised: 11/08/2007] [Accepted: 11/12/2007] [Indexed: 01/14/2023]
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Saito F, Imai S, Tanaka N, Tanaka H, Suzuki K, Takase H, Aoyama H, Matsudaira K, Ebuchi T, Akamine Y, Takahashi N, Sugino K, Kanmatsuse K, Yagi H, Kushiro T. Basic autonomic nervous function in patients with neurocardiogenic syncope. Clin Exp Hypertens 2007; 29:165-73. [PMID: 17497343 DOI: 10.1080/10641960701361569] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Basic autonomic nervous function was evaluated in patients with neurocardiogenic syncope (NCS). Atropine, isoproterenol, propranolol, phenylephrine, and phentolamine were administered successively, and parasympathetic nerve activity and beta- (and alpha-) activity, sensitivity, and secretion of the sympathetic nerve were determined in patients with NCS and control subjects. In patients with NCS, beta- and alpha- sensitivity were higher and beta-activity and beta- and alpha-secretion lower than in control subjects. In patients with NCS, the increased basic beta-sensitivity may contribute to induce strong cardiac contractions and augment ventricular mechanoreceptor response, and a compensatory state against diminished neuronal sympathetic activity is suggested by the increased alpha-sensitivity.
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Affiliation(s)
- Fumio Saito
- Department of Cardiology, Surugadai Nihon University Hospital, Tokyo, Japan.
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Funakami Y, Hata T, Itoh E, Itano S. Effects of some beta-adrenoceptor antagonists on orthostatic hypotension in repeatedly cold- (SART-) stressed rats. Biol Pharm Bull 2007; 30:303-8. [PMID: 17268070 DOI: 10.1248/bpb.30.303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Rats stressed by specific alternation of rhythm in temperature (SART) show various symptoms of disautonomia, increased pulse rates, continuous hypotension, and severe orthostatic hypotension (OH) when they are subjected to postural change. The OH symptoms are improved by muscarinic M2-receptor blockers. In the present study, effects of beta-adrenoceptor blocking agents on OH in SART-stressed rats were investigated. Anesthetized rats were restrained on a board in the supine position, and direct blood pressure and ECG were measured automatically using Fluclet Jr.2. Postural change was performed by raising the rat's head up to a 60 degrees angle for 4 min. Unstressed rats treated with hexamethonium showed large decrease in blood pressure, small reflex from the bottom of pressure and decreased tachycardia reflex, whereas isoproterenol showed little changes. In SART-stressed rats, isoproterenol alleviated the decrease in blood pressure in postural change, brought large reflex from the bottom of pressure and increased tachycardia reflex, whereas hexamethonium had little changes. Propranolol and atenolol induced the similar changes as those seen by hexamethonium. ICI-118,551, a selective beta2-adrenoceptor antagonist showed large reflex from the bottom of pressure and increased tachycardia reflex in stressed rats, whereas little changes in unstressed rats. In conclusion, it was suggested that the hypotension in OH manifestation time of rats reflects the state of peripheral blood vessels, and beta1-adrenoceptors played a role in compensatory tachycardia reflex and beta2-adrenoceptors in blood pressure reflex. The circulatory regulation in SART-stressed rats seems to be poorly functioning in nervous reflex in postural changes.
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Affiliation(s)
- Yoshinori Funakami
- Department of Pharmacology, Faculty of Pharmacy, Kinki University, Higashi-Osaka, Japan.
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Sato Y, Ichihashi K, Kikuchi Y, Shiraishi H, Momoi MY. Autonomic Function in Adolescents with Orthostatic Dysregulation Measured by Heart Rate Variability. Hypertens Res 2007; 30:601-5. [PMID: 17785927 DOI: 10.1291/hypres.30.601] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We evaluated the responses of autonomic nervous system to transient positional changes and daily changes in orthostatic dysregulation (OD) patients in order to clarify the mechanisms underlying the appearance of symptoms. The control group consisted of 16 healthy adolescents (8 males and 8 females), and the OD group consisted of 25 adolescents (13 males and 12 females). Each subject underwent continuous electrocardiographic monitoring during the head-up tilt test, followed by electrocardiographic monitoring for 24 h. Low frequency power (LF) and high frequency power (HF) were calculated as indices of autonomic function. During 0-5 min in the standing position in the tilt test, HF was higher in the OD group than in the control group (180+/-110 ms(2) vs. 42.6+/-54.1 ms(2); p<0.05). The LF/HF ratio during standing for 15-20 min was higher in OD patients than in the controls (4.75+/-3.45 vs. 1.67+/-1.21; p<0.05). The 24 h analysis showed that HF during sleep was significantly lower in the OD patients than in the controls (516+/-290 ms(2) vs. 1,290+/-429 ms(2); p<0.05); the LF/HF ratios were consistently higher in the OD patients than in the controls (4.13+/-3.41 and 2.92+/-2.00 vs. 2.46+/-0.89 and 1.35+/-1.54 in waking and sleeping states, respectively; p<0.05). This study showed that OD patients have less variability of the parasympathetic nervous system as well as hyperactivity of the sympathetic nervous system. This autonomic dysfunction is responsible for the symptoms of OD.
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Affiliation(s)
- Yuko Sato
- Department of Pediatrics, Jichi Medical University School of Medicine, Yakushiji, Shimotsuke, Japan.
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Folino AF, Russo G, Porta A, Buja G, Cerutti S, Iliceto S. Modulations of autonomic activity leading to tilt-mediated syncope. Int J Cardiol 2006; 120:102-7. [PMID: 17141893 DOI: 10.1016/j.ijcard.2006.03.093] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Revised: 03/20/2006] [Accepted: 03/25/2006] [Indexed: 10/23/2022]
Abstract
BACKGROUND Vasovagal syncope (VVS) results from a complex interaction among afferent vagal and sympathetic signals, cortical modulation and bulbar integration. The aim of our study was to evaluate the modifications of autonomic activity during Upright Tilt Test (UTT) in patients with unexplained syncope, and to correlate these changes with the specific cardiovascular reactions induced. METHODS AND RESULTS We studied 90 patients with a mean age of 44+/-17 yrs. Frequency domain analysis of heart rate variability (HRV) (normalized units) was performed on 2 periods of 300 beats: at baseline and after 5 min of 60 degrees tilt. UTT was positive in 56 patients (62%). The responses were cardioinhibitory in 8, vasodepressive in 15, mixed in 33. Baseline LF and HF components did not show significant difference between subjects with positive or negative test (HF: 39+/-21 versus 41+/-22; LF: 50+/-22 versus 49+/-23). HRV during UTT showed similar changes in patients with positive or negative test. However, subjects with mixed or cardioinhibitory reactions were characterized by a relevant increase of LF during UTT (from 47+/-23 to 66+/-21), whereas the others by a non-significant decrease of the same component (from 57+/-19 to 51+/-31). CONCLUSIONS Patients developing a reflex cardioinhibitory reaction during UTT were characterized by an increase of sympathetic activity during the test, that might represent an essential factor to induce a stronger vagal reaction on the sinus node. On the contrary, in subjects with vasodepressive reactions an inadequate enhancement of the sympathetic drive, probably causing a failure of peripheral vasoconstriction, was evidenced.
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Evrengul H, Tavli V, Evrengul H, Tavli T, Dursunoglu D. Spectral and time-domain analyses of heart-rate variability during head-upright tilt-table testing in children with neurally mediated syncope. Pediatr Cardiol 2006; 27:670-8. [PMID: 17072674 DOI: 10.1007/s00246-003-0598-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2003] [Accepted: 10/02/2003] [Indexed: 12/01/2022]
Abstract
Neurocardiac syncope (NS) is a common cause of syncope in children. The mechanism, though related to abnormalities in autonomic function, has not been fully elucidated, particularly in pediatric patients. This study assessed the heart-rate variability (HRV) response to head-upright tilt-table test (HUT) in children with NS and normal volunteers. Spectral and time-domain analysis of HRV was used to assess changes in autonomic function in 27 children (9 male, mean age 12.3 +/- 1.6 years) with a history of at least one episode of syncope and positive passive HUT and 27 age-matched normal volunteers with negative passive HUT before and during postural tilt and to attempt to relate such changes to specific types of hemodynamic response to tilt. Frequency-domain measurements of the high-(HF) and low-(LF) frequency bands and the ratio LF/HF were derived from Holter recordings and computed by fast Fourier analysis for 5-min intervals. Time-domain measurements of the SDNN, SDNNI, SDANN, RMSSD, and triangular index were derived from 24-h Holter recordings. There were no significant differences between clinical characteristics, time-domain, and basal frequency domain parameters of the groups. Mean values of LF and LF/HF ratio was increased and HF was decreased significantly in response to tilt in both patient and control groups. Mean values of LF and LF/HF ratio were higher and HF was lower compared to controls immediately after tilt. LF and LF/HF ratio showed a statistically significant decrease and a significant increase in HF during syncope in patients. The three subgroups of patients had similar patterns of changes in autonomic activity. The results of this study show that although the basal autonomic function was similar to that of the control group, patients with NS have a different pattern of response to the HUT. In our study, patients with NS demonstrated an exaggerated response to the HUT. This exaggerated response may be the factor that activates the pathological reflexes of NS. The pathological mechanism leading to NS appears to be independent of the specific type of hemodynamic response to HUT.
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Affiliation(s)
- Harun Evrengul
- Pamukkale University School of Medicine, Denizli, Turkey.
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Fucà G, Dinelli M, Suzzani P, Scarfò S, Tassinari F, Alboni P. The venous system is the main determinant of hypotension in patients with vasovagal syncope. ACTA ACUST UNITED AC 2006; 8:839-45. [PMID: 16916860 DOI: 10.1093/europace/eul095] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
AIMS In patients with vasovagal syncope (VVS), a neural reflex appears the main determinant of hypotension leading to loss of consciousness; whether hypotension is mainly due to involvement of the arterial system or the venous system remains a debated issue. The aim of the present study was to assess which of these two systems is responsible for the fall in blood pressure (BP) in patients with VVS; to this end, a haemodynamic study was carried out not only before and during loss of consciousness but also during the recovery phase. METHODS AND RESULTS Beat-to-beat recordings of heart rate (HR), BP (volume-clamp method) and stroke volume (SV) (modelflow method), cardiac output (CO), and total peripheral resistance (TPR) were made at rest, during unmedicated tilt testing (TT) and recovery from loss of consciousness in 18 patients with a history of syncope (age 45+/-23 years) and positive response to TT. Blood pressure showed a significant fall during prodromal symptoms and a further fall at the beginning of loss of consciousness, together with a fall in SV, CO, and HR, and a slight, but significant, increase in TPR. At the beginning of recovery, BP showed a significant increase and a further increase 5 min later, together with an increase in SV, CO, and HR without significant changes in TPR. CONCLUSION These results suggest that in VVS the fall in BP is mainly caused by reduced venous return to the heart. The arterial system does not appear to be the main determinant of the fall of BP; however, the system appears unable to make the appropriate compensatory changes.
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Affiliation(s)
- Giuseppe Fucà
- Division of Cardiology, Ospedale Civile, 44042 Cento (Fe), Italy
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Mizumaki K, Fujiki A, Sakabe M, Nishida K, Sugao M, Tsuneda T, Nagasawa H, Inoue H. Dynamic changes in the QT-R-R relationship during head-up tilt test in patients with vasovagal syncope. Ann Noninvasive Electrocardiol 2005; 10:16-24. [PMID: 15649233 PMCID: PMC6932693 DOI: 10.1111/j.1542-474x.2005.00587.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND QT interval is influenced by preceding R-R intervals and autonomic nervous tone. Changes in QT intervals during vasovagal reflex might reflect autonomic modulation of ventricular repolarization; however, this issue has not been fully elucidated. This study aimed to evaluate dynamic response of QT interval to transient changes in R-R interval during vasovagal syncope (VVS) induced by head-up tilt test. METHODS Eighteen patients with VVS and 18 age-and sex-matched controls were studied. All patients with VVS had a positive mixed-type response to head-up tilt and all controls had a negative response. CM5-lead digital electrocardiogram (ECG) was recorded and QT intervals were analyzed using Holter ECG analyzer. Using scatter plots of consecutive QT and the preceding R-R intervals, QT-R-R relations during tilt-up and tilt-back or during vasovagal reflex were independently fitted to an exponential curve: QT (second) = A + B x exp[k x R-R (second)]. RESULTS During the tilt-up, A, B, and k did not differ between patients with VVS and controls. During the tilt back, k showed equivalent positive value compared to the tilt-up (4.1 +/- 1.3 vs -4.6 +/- 0.9) in controls. However, k remained negative (-1.3 +/- 1.5) during vasovagal reflex in patients with VVS. In six patients, in whom metoprolol was effective in eliminating VVS, QT-R-R relationship during the tilt-back became similar to that in controls. CONCLUSIONS In patients with VVS, hysteresis of the QT-R-R relation is similarly shown during tilt-up as in controls, whereas this hysteresis is no longer evident and failure of QT prolongation is observed during VVS.
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Affiliation(s)
- Koichi Mizumaki
- Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama, Japan.
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17
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Kochiadakis GE, Papadimitriou EA, Marketou ME, Chrysostomakis SI, Simantirakis EN, Vardas PE. Autonomic Nervous System Changes in Vasovagal Syncope:. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2004; 27:1371-7. [PMID: 15511246 DOI: 10.1111/j.1540-8159.2004.00641.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spectral analysis of heart rate variability was used to compare the changes in autonomic function during tilting in young and older patients with vasovagal syncope. Twenty-four young (age 28 +/- 8 years) and 31 older (56 +/- 5 years) patients with unexplained syncope and a positive tilt test and 25 controls (age 48 +/- 12 years) were included in the study. Frequency-domain measurements of the low (LF) (0.06-0.15 Hz) and high (HF) (0.15-0.40 Hz) frequency bands and the ratio of LF to HF were computed from Holter recordings for 4-minute intervals before and immediately after tilting and just before the end in all groups. Syncopal patients showed a different pattern of response to tilting from controls in all spectral indexes. Young and older patients showed the same pattern of changes in all measurements, even though certain differences were observed. The LF after tilting reduced more in the older (-20 +/- 7% vs -14 +/- 5%, P < 0.001), while HF reduced more in young patients (-17 +/- 8% vs -8 +/- 3%, P < 0.001). Young patients showed mainly a cardioinhibitory type (71%) of response whereas a vasodepressor type response predominated (68%) in the older patients. The autonomic nervous system appears to play an important role in the pathophysiological mechanism of vasovagal syncope. This role is similar in young and in older patients and this should be taken into account in the therapeutic approach to the condition. Specific differences between age groups may be related to the type of vasovagal syncope.
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18
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Suwa S, Sumiyoshi M, Mineda Y, Ohta H, Kojima S, Nakata Y. Vasovagal Response Induced by a Low Dose of Isoproterenol Infusion Before Tilting-up. Circ J 2004; 68:876-7. [PMID: 15329512 DOI: 10.1253/circj.68.876] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A 56 year-old man was referred to hospital for evaluation of syncopal episodes. During head-up tilt testing, his symptom was reproduced, associated with bradycardia and hypotension, by a low dose of isoproterenol (0.02 microg. kg (-1). min(-1)) infusion in the supine position before tilting-up. Isoproterenol infusion can provoke a vasovagal response without tilting. Careful observation of the patient's hemodynamics is mandatory not only during tilting, but also in the supine position before tilting-up.
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Affiliation(s)
- Satoru Suwa
- Department of Cardiology, Juntendo University Izunagaoka Hospital, Shizuoka, Japan
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19
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Freeman R. Chapter 37 Assessment of cardiovascular autonomic function. ACTA ACUST UNITED AC 2004; 57:369-75. [PMID: 16106635 DOI: 10.1016/s1567-424x(09)70373-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- Roy Freeman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
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20
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Koyama S, Sato N, Nagashima K, Aizawa H, Kawamura Y, Hasebe N, Iwasaki H, Kikuchi K. Effects of right stellate ganglion block on the autonomic nervous function of the heart: a study using the head-up tilt test. Circ J 2002; 66:645-8. [PMID: 12135131 DOI: 10.1253/circj.66.645] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The effect of peripheral sympathetic block on the autonomic nerve function of the heart was studied using the head-up tilt test (HUTT) and right stellate ganglion block (RSGB). Blood pressure (BP), heart rate (HR) and the parameters of power spectral analysis of HR variability recorded during the HUTT were measured in 8 patients with chronic pain syndrome before and after RSGB. In the control state, the mean HR and the LF/HF component recorded during HUTT significantly increased whereas the HF component markedly decreased. Conversely, the mean HR and LF/HF and HF components during HUTT did not significantly alter after the RSGB procedure. There were no significant differences between the BP values before and after RSGB. These results suggest that RSGB suppresses cardiac sympathetic function without significantly affecting BP and thus may be a safe and effective therapy for the chronic pain syndrome.
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Affiliation(s)
- Satoshi Koyama
- First Department of Medicine, Asahikawa Medical College, Japan.
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21
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Takase B, Hosaka H, Kitamura K, Uehata A, Satomura K, Isojima K, Kosuda S, Kusano S, Kurita A, Ohsuzu F. The repeatability of left ventricular volume assessment by a new ambulatory radionuclide monitoring system during head-up tilt. JAPANESE HEART JOURNAL 2001; 42:749-58. [PMID: 11933924 DOI: 10.1536/jhj.42.749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The precise measurement of changes in left ventricular volume is important to elucidate the mechanisms of neurally mediated syncope. This study was conducted to determine whether or not a brand-new ambulatory radionuclide monitoring system (C-VEST system) can be clinically used to easily and precisely measure left ventricular volume and function in tilt testing. To assess the repeatability of the C-VEST system, 12 healthy volunteers (mean age 24+/-4 years old) underwent 20 minute head-up tilt testing and we measured the temporal changes in left ventricular volume and ejection fraction twice a day (first and second studies). To investigate the changes in the C-VEST measurements and the detector position in the first and second studies, tilt testing was performed with an 80-degree passive tilt, which is the same as the standard procedure used in diagnosing neurally mediated syncope. The coefficient of repeatability for both the C-VEST and detector position was well within the clinical range (coefficient of repeatability in left ventricular volume ranged from 1.7 to 2.8; coefficient of repeatability in the detector position ranged from 2.3 to 3.1). Precise evaluation of the left ventricular volume can be achieved by an ambulatory radionuclide monitoring system in tilt testing.
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Affiliation(s)
- B Takase
- National Defense Medical College, Internal Medicine-1, Saitama, Tokorozawa, Japan
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22
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Boh-Oka S, Ohmori H, Kawabe T, Tutiyama Y, Shimamoto Y, Shioji S, Obana M, Satani O, Wanaka Y, Hamada M, Baba A, Tsuda K, Hano T, Nishio I. Neurally mediated syncope and cardiac beta-adrenergic receptor function. J Cardiovasc Pharmacol 2001; 38 Suppl 1:S75-9. [PMID: 11811365 DOI: 10.1097/00005344-200110001-00016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
To evaluate the mechanism of neurally mediated syncope (NMS), we investigated basal autonomic nerve function using a conventional pharmacological method and [123I]-metaiodobenzyl-guanidine (MIBG) single photon emission computed tomography (SPECT). Nine patients with NMS, whose syncope was induced by head-up tilt test with or without isoproterenol, underwent [123I]-MIBG SPECT. Eight of nine NMS patients showed reduced myocardial uptake (two patients, diffuse; four patients, anteroseptal and inferior; one patient, anteroseptal; one patient, inferior). In the study of pharmacological autonomic nervous function test, atropine sulfate (atr.) (0.04 mg/kg), isoproterenol (isp.) (5 x 10(-3) microg/kg/min), propranolol (prop.) (0.2 mg/kg), phenylephrine (phenyl.) (0.4 microg/kg/min), and phentolamine (phent.) (0.2 mg/kg) were successively administered to patients with NMS (n = 5) and control subjects (n = 5). The heart rate (HR) after atr. and prop., and systolic blood pressure (SBP) after phent. were defined as intrinsic HR (IHR) and intrinsic SBP (ISBP). Parasympathetic activity (increase in HR by atr.), beta-sympathetic tone (HR after atr. minus IHR), beta-sensitivity (change in HR by 1 microg isp./kg/min), beta-secretion (beta-tone/beta-sensitivity), alpha-sympathetic tone (SBP before phenyl. minus ISBP), alpha-sensitivity (change in SBP by 1 microg phenyl./kg/min) and alpha-secretion (alpha-tone/alpha-sensitivity) were also calculated. The beta-secretion was decreased (0.0027+/-0.0008 versus 0.0060+/-0.0004 microg/kg/min/isp.; p < 0.05), while the beta-sensitivity was increased (5850+/-947 versus 3150+/-292 beats/microg/kg/min isp.; p < 0.05) in NMS compared with control subjects. In the other indexes, there were no significant differences between two groups. The results of the present study suggest that increased beta-sensitivity may contribute hypercontraction of left ventricles, which might partially explain the mechanism of NMS.
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Affiliation(s)
- S Boh-Oka
- Department of Medicine, Wakayama Medical University, Japan.
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23
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Shen WK, Low PA, Rea RF, Lohse CM, Hodge DO, Hammill SC. Distinct hemodynamic profiles in patients with vasovagal syncope: a heterogeneous population. J Am Coll Cardiol 2000; 35:1470-7. [PMID: 10807449 DOI: 10.1016/s0735-1097(00)00567-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The objective was to investigate mechanisms of vasovagal syncope by identifying laboratory techniques that characterize cardiovascular profiles in patients with vasovagal syncope. BACKGROUND The triggering mechanisms of vasovagal syncope are complex. The patient population is likely heterogeneous. We hypothesized that distinct hemodynamic profiles are definable with provocative maneuvers. METHODS Three groups of subjects were matched for age and gender: 16 patients with a history of syncope and an inducible vasovagal response during passive tilt table testing (70 degrees, 45 min, group I), 16 with a history of syncope, negative passive tilt table testing but positive isoproterenol tilt table testing (0.05 microg/kg per min, 70 degrees, 10 min, group II), and 16 control subjects. Beat-to-beat hemodynamic functions were determined noninvasively by photo-plethysmography and impedance cardiography. RESULTS At baseline, hemodynamic functions were not different among the three groups (supine). In response to tilt before any symptoms developed, total peripheral resistance decreased 9% +/- 14% in group I from baseline supine to tilt position but increased 27% +/- 18% in group II and 28% +/- 17% in controls (p < 0.001). Responses to isoproterenol were not significantly different between group II and controls in supine position. In response to tilt during isoproterenol infusion before any symptoms developed, total peripheral resistance decreased 24% +/- 20% in group II and increased 20% +/- 48% in controls (p = 0.002). CONCLUSIONS Group I patients may have impaired ability to increase vascular resistance during orthostatic stress. The inability to overcome isoproterenol-induced vasodilatation during tilt is important in triggering a vasovagal response in group II patients. These data suggest that the population with vasovagal response is heterogeneous. Distinct hemodynamic profiles in response to various provocative maneuvers are definable with noninvasive, continuous monitoring techniques.
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Affiliation(s)
- W K Shen
- Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA
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24
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Lazzeri C, La Villa G, Barletta G, Franchi F. 24-hour heart rate variability in patients with vasovagal syncope. Pacing Clin Electrophysiol 2000; 23:463-8. [PMID: 10793435 DOI: 10.1111/j.1540-8159.2000.tb00828.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Since alterations in the autonomic nervous system are thought to play a major role in the pathogenesis of vasovagal syncope, we characterized the chronic autonomic profile of 44 patients with syncope and 20 healthy subjects by means of heart rate variability using 24-hour Holter recordings (time- and frequency-domain indexes), and evaluated whether the different types of responses to tilting (vasodepressive versus cardioinhibitory) could be associated with different cardiac autonomic patterns. Twenty-three patients exhibited a positive response to tilting, which was vasodepressive in 11 patients and cardioinhibitory in 12 patients. All vasodepressive patients had a standard deviation of the averages of NN (SDANN) intervals in all 5-minute segments lower than 100 ms. Patients with vasodepressive syncope also had significantly lower values of RMSSD (the 24-hour square root of the mean of the sum of the squares of differences between adjacent normal RR intervals) than those with cardioinhibitory response, and lacked the day-night rhythm of the low frequency/high frequency ratio. However, only SDANN values correctly identified patients with vasodepressive response to tilting. We conclude that (1) the population of patients with vasovagal syncope is heterogeneous, (2) patients with vasodepressive syncope have a peculiar chronic autonomic profile as assessed by 24-hour heart rate variability analysis, and (3) the evaluation of the autonomic profile in 24-hour Holter recordings could be of value in the diagnosis of patients with syncope.
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Affiliation(s)
- C Lazzeri
- Department of Internal Medicine, University of Florence School of Medicine, Italy
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25
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Koga T, Kaseda S, Miyazaki N, Kawazoe N, Abe I, Sadoshima S, Onoyama K. Neurally mediated syncope induced by lung cancer--a case report. Angiology 2000; 51:263-7. [PMID: 10744016 DOI: 10.1177/000331970005100312] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The authors present hemodynamic and autonomic features of recurrent and episodic neurally mediated syncope in a man with lung cancer involving afferent vagus. He revealed extreme hypotension with bradycardia occurring during sitting or standing. A head-up tilt test also induced syncope. However, syncope attacks no longer occurred 2 weeks after admission. Alternatively, the paralyses of the left recurrent laryngeal nerve and the left phrenic nerve developed. It is suggested that the lung cancer involved upper rootlets of the left vagus and caused transient hypersensitivity of baroreceptor function that resulted in neurally mediated syncope.
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Affiliation(s)
- T Koga
- Division of Cardiology, Nippon Steel Yawata Memorial Hospital, Kitakyushu, Japan
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26
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Liu JE, Hahn RT, Stein KM, Markowitz SM, Okin PM, Devereux RB, Lerman BB. Left ventricular geometry and function preceding neurally mediated syncope. Circulation 2000; 101:777-83. [PMID: 10683352 DOI: 10.1161/01.cir.101.7.777] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Neurally mediated syncope has been associated with increased left ventricular (LV) fractional shortening (FS) during tilt testing, which is consistent with the hypothesis that the stimulation of LV mechanoreceptors leads to reflex hypotension and/or bradycardia. However, FS does not represent true LV contractility because of its dependence on afterload and preload. METHODS AND RESULTS To elucidate the role of increased contractility in the mediation of neurally mediated syncope, we compared echocardiographic measures of LV performance corrected for end-systolic stress (ESS) in 21 patients (13 women and 8 men) with unexplained syncope who had either positive (n=10) or negative (n=11) responses to a tilt-table test. Two-dimensional echocardiographic LV imaging was performed at baseline and during the initial 5 minutes of upright tilt. In the supine position, both groups had similar LV end-diastolic volume indexes, stroke volumes, FS, circumferential ESS, and afterload-independent measures of LV performance (stress-corrected midwall and FS). However, after 5 minutes of upright tilt, patients who subsequently had a positive test had a lower stroke volume, lower stress-corrected midwall shortening, and endocardial FS. The tilt-positive group also had a greater fall in ESS and FS early during upright tilt. CONCLUSIONS Reduced ESS, LV volume, and chamber function during initial upright tilt are associated with a subsequent positive tilt response in patients with unexplained syncope. These data suggest that if paradoxic activation of LV mechanoreceptors has a role in mediating neurally mediated syncope, it is not triggered by LV hypercontractility or increased systolic wall stress during the initial period of upright tilt.
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Affiliation(s)
- J E Liu
- Department of Medicine, Division of Cardiology, The New York Hospital-Cornell Medical Center, New York, NY 10021, USA
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27
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Nakagawa M, Takahashi N, Iwao T, Yonemochi H, Ooie T, Hara M, Saikawa T, Ito M. Evaluation of autonomic influences on QT dispersion using the head-up tilt test in healthy subjects. Pacing Clin Electrophysiol 1999; 22:1158-63. [PMID: 10461291 DOI: 10.1111/j.1540-8159.1999.tb00595.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Our objective was to examine the autonomic influence on QT interval dispersion using the head-up tilt test in healthy subjects. RR and QT intervals, heart rate variability, and plasma norepinephrine concentration were measured in the supine position and tilting to 70 degrees for 20 minutes using a footboard support in 15 healthy male volunteers (mean age +/- SD: 28.0 +/- 4.5 years). The rate-corrected QT interval (QTc) was calculated using Bazett's formula, and QT and QTc dispersions were defined as the maximum minus minimum values for the QT and QTc, respectively, from the 12-lead ECG. Spectral analysis of the heart rate variability generated values for the low- and high-frequency powers (LF and HF) and their ratio (LF/HF). Compared with values obtained in the supine position, tilting significantly increased QT (P < 0.05) and QTc dispersion (P < 0.01), the LF/HF ratio (P < 0.0001), and plasma norepinephrine concentration (P < 0.0001), and significantly decreased HF (P < 0.0001). QTc dispersion was positively correlated with the LF/HF ratio and plasma norepinephrine concentration, and negatively correlated with HF. These results suggest that head-up tilt testing increases QT dispersion by increasing sympathetic tone and/or decreasing vagal tone in healthy subjects.
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Affiliation(s)
- M Nakagawa
- Department of Laboratory Medicine, Oita Medical University, Japan
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28
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Burklow TR, Moak JP, Bailey JJ, Makhlouf FT. Neurally mediated cardiac syncope: autonomic modulation after normal saline infusion. J Am Coll Cardiol 1999; 33:2059-66. [PMID: 10362214 DOI: 10.1016/s0735-1097(99)00133-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVES This study assessed the heart variability response to orthostatic stress during tilt table testing before and after normal saline administration. BACKGROUND The efficacy of sodium chloride and mineralocortoid in the treatment of neurally mediated cardiac syncope is attributed to intravascular volume expansion; however, their modulation of autonomic nervous system activity has not been evaluated. METHODS Heart rate variability analysis was performed on 12 adolescents with a history of syncope or presyncope (mean age 15.2+/-0.7 years) during tilt table testing. Subjects were upright 80 degrees for 30 min or until syncope. After normal saline administration, the patient was returned upright for 30 min. Heart rate variability analysis data were analyzed by an autoregression model (Burg method). RESULTS All subjects reproducibly developed syncope during control tilt table testing; median time to syncope was 9.4+/-2.1 min. After normal saline infusion, none of the subjects developed syncope after 30 min upright. In the control tilt, there was an initial increase followed by a progressive decrease in low frequency power until syncope. Repeat tilt after normal saline administration demonstrates that low frequency power increased but the magnitude of initial change was blunted when compared with control. In addition, low frequency power increased during normal saline tilt sequence compared with the control tilt, during which it decreased. CONCLUSIONS Normal saline blunted low frequency power stimulation and prevented paradoxical low frequency power (sympathetic) withdrawal. Increasing intravascular volume with normal saline alters autonomic responses that may trigger neurally mediated syncope reflexes.
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Affiliation(s)
- T R Burklow
- Department of Cardiology, Children's National Medical Center, Washington, DC 20010, USA
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29
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Lagi A, Cencetti S, Fattorini L, Tamburini C. Age-related changes of cardiac parasympathetic modulation after vasovagal syncope. Am J Cardiol 1999; 83:977-80, A10. [PMID: 10190425 DOI: 10.1016/s0002-9149(98)01044-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The time-domain analysis of 24-hour electrocardiographic recordings showed that vagal modulation of heart rate is reduced within 48 hours from vasovagal syncope. However, patients with recent vasovagal syncope can be differentiated from healthy subjects only up to the age of 40 years with this analysis, because this parasympathetic modulation physiologically decreases with increasing age.
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Affiliation(s)
- A Lagi
- Department of Internal Medicine, Santa Maria Nuova Hospital, Florence, Italy.
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30
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Pérez-Paredes M, Picó-Aracil F, Fuentes-Jiménez T, Sánchez-Villanueva JG, Expósito-Ordoñez E, Gonzálvez-Ortega M, González-Caballero E, Nicolás-Garcia F, Nuño de la Rosa JA, Ruiz-Ros JA, Ruipérez-Abizanda JA. Role of endogenous opioids in syncope induced by head-up tilt test and its relationship with isoproterenol-dependent and isoproterenol-independent neurally-mediated syncope. Int J Cardiol 1998; 67:211-8. [PMID: 9894701 DOI: 10.1016/s0167-5273(98)00220-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This study was designed to evaluate the role of endogenous opioids in neurally-mediated syncope. Head-up tilt test was performed on 35 patients with syncope of unknown origin. Plasma beta-endorphin was measured (1) at baseline, (2) at the end of tilt test or at time of syncope, (3) 15 min before isoproterenol-test, (4) at the end of the isoproterenol-test or at time of syncope. Subjects with a positive tilt testing showed a larger rise in plasma beta-endorphin concentrations at time of syncope (baseline 13.7+/-8.0 vs. syncope 41.4+/-26.4 pmol l(-1); P<0.01). On the contrary, patients with a positive isoproterenol-test showed no rise in plasma beta-endorphin levels (baseline 7.9+/-3.6 vs. syncope 7.4+/-2.7 pmol l(-1); P=ns). Patients with a passive negative tilt test (baseline 6.7+/-2.8 vs. end of test 7.0+/-3.3 pmol l(-1); P=ns) and negative isoproterenol tilt test (baseline 7.4+/-3.8 vs. end of test 8.1+/-3.4 pmol l(-1); P=ns) showed no changes in beta-endorphin concentrations. To further examine the efficacy of i.v. naloxone to prevent syncope, 10 patients were randomized to naloxone (0.02 mg/kg) or placebo. Second head-up tilt testing was negative in 1/5 patients with naloxone and in 2/5 patients with placebo. We conclude that, (1) endogenous opioids seem to be involved in vasovagal syncope induced by baseline head-up tilt test, (2) changes in plasma beta-endorphin concentrations show significant differences between patients who have isoproterenol-dependent and isoproterenol-independent syncope, this finding might occur in the setting of different pathophysiologic mechanisms, and (3) intravenous naloxone at a dose of 0.02 mg/kg was not superior to placebo in order to prevent positive responses to baseline tilt test.
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Affiliation(s)
- M Pérez-Paredes
- Cardiology Unit, University Hospital Morales Meseguer, Murcia, Spain.
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31
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Wang CH, Cherng WJ, Hung MJ. Diagnostic value of dobutamine echocardiography in patients with angina-like symptoms preceding syncope. Int J Cardiol 1998; 67:147-53. [PMID: 9891948 DOI: 10.1016/s0167-5273(98)00168-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Dobutamine echocardiography was performed in 55 patients with syncope which was clinically suspected to be angina-related. We evaluated the value of using a single test, dobutamine echocardiography, in differentiating real ischemia-related from vasovagal syncope which was diagnosed by a tilt test. During testing, supraventricular arrhythmia was provoked in four (7.2%) patients. Dobutamine echocardiography identified all of six (10.9%) patients (sensitivity 100%), who were found with significant coronary stenosis by coronary angiograms. The etiology of syncope in the remaining 45 patients was investigated further by tilt testing, the findings of hypotension and bradycardia during which were compared head to head with those of dobutamine echocardiography. Tilt testing diagnosed vasovagal syncope in 31 patients, in whom only 19 (61.3%) patients developed vasovagal reflex during dobutamine echocardiography. Conclusively, dobutamine echocardiography had a high sensitivity in identifying syncope related to myocardial ischemia in patients with coronary stenosis, but a low sensitivity (61.3%), high specificity (90.5%) and high positive predictive value (81.8%) in detecting the syncope patients with angina caused by vasovagal effect.
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Affiliation(s)
- C H Wang
- Department of Medicine, Chang Gung Medical College, Chang Gung Memorial Hospital, Keelung, Taiwan, ROC
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Furlan R, Piazza S, Dell'Orto S, Barbic F, Bianchi A, Mainardi L, Cerutti S, Pagani M, Malliani A. Cardiac autonomic patterns preceding occasional vasovagal reactions in healthy humans. Circulation 1998; 98:1756-61. [PMID: 9788830 DOI: 10.1161/01.cir.98.17.1756] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
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 degrees 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, approximately 0.1-Hz) and high-frequency (HF, approximately 0.25-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, LFNU, and HFNU (NU=normalized units) values were relatively stable in control subjects. During early tilt (T1), subjects with syncope had reduced RR intervals compared with control subjects. In 13 subjects with syncope, RR decreased while LFNU and LF/HF increased in the last minute of tilt before syncope (T2). Conversely, in the remaining 9 fainters, LFNU and LF/HF decreased from T1 to T2 and HFNU 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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Affiliation(s)
- R Furlan
- Centro Ricerche Cardiovascolari, CNR; Medicina Interna II e Medicina Interna III, Università di Milano, Italy
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Kochiadakis GE, Kanoupakis EM, Rombola AT, Igoumenidis NE, Chlouverakis GI, Vardas PE. Reproducibility of tilt table testing in patients with vasovagal syncope and its relation to variations in autonomic nervous system activity. Pacing Clin Electrophysiol 1998; 21:1069-76. [PMID: 9604238 DOI: 10.1111/j.1540-8159.1998.tb00152.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To assess the variability of head-up tilt table testing, 35 patients with vasovagal syncope, shown by a positive tilt table test, underwent a second test 1 week later. Also, on the day before each test, spectral and time-domain indexes of heart rate variability were derived from Holter recordings to examine the stability of autonomous nervous system activity in these patients. Fifteen healthy volunteers served as a control group and also underwent two tilt table tests with prior Holter monitoring. Twenty-one (60%) of the 35 patients had a second positive test. None of the patients in the control group experienced syncope during either of the tests. The heart rate variability measures in the control group varied slightly from 1 day to the other, in contrast to the syncopal patients, where only low frequency spectral power and the mean of all 5-minute standard deviations of RR intervals showed comparable behavior. The indexes which reflect parasympathetic activity exhibited significant fluctuations in the syncopal patients. These fluctuations were due entirely to the patients who did not reproduce the outcome of the tilt table test, where high parasympathetic tone was associated with the positive test and normal parasympathetic tone with the negative test. In contrast, the patients with two positive tests had high parasympathetic tone during both test periods, with low individual variability. In conclusion, patients with vasovagal syncope show variations in vagal autonomic tone and appear to be more prone to syncope when their parasympathetic tone is elevated.
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Affiliation(s)
- G E Kochiadakis
- Cardiology Department, University Hospital of Heraklion, Crete, Greece
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Kochiadakis GE, Kanoupakis EM, Igoumenidis NE, Marketou ME, Solomou MC, Vardas PE. Spectral analysis of heart rate variability during tilt-table testing in patients with vasovagal syncope. Int J Cardiol 1998; 64:185-94. [PMID: 9688438 DOI: 10.1016/s0167-5273(98)00039-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Spectral analysis of heart rate variability was used to assess changes in autonomic function in 44 patients with vasovagal syndrome and 20 normal controls before and during postural tilt and to attempt to relate such changes to specific types of haemodynamic response to tilt. Frequency domain measurements of the high (HF) and low (LF) frequency bands and the ratio LF/HF were derived from Holter recordings, computed by Fast Fourier Analysis for 4 min intervals immediately before tilt testing, immediately after tilting and just before the end of the test. In the syncopal patients the mean values of LF and HF decreased significantly in response to tilting, while the LF/HF ratio remained constant. All parameters showed a statistically significant increase just before the onset of syncope. In the control group there was an increase in the LF and LF/HF ratio and a decrease in the HF immediately after tilting. The three subgroups of patients had similar patterns of changes in autonomic activity. The results of this study show that syncopal patients have a different pattern of response to the tilting test. The pathological mechanism leading to vasovagal syncope appears to be independent of the specific type of haemodynamic response to tilt testing.
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Affiliation(s)
- G E Kochiadakis
- Cardiology Department, University Hospital of Heraklion, Crete, Greece.
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Shen WK, Fenton AM, Lohse CM, Bailey KR, Low PA, Hammill SC. Hemodynamic analysis during isoproterenol-induced vasovagal syncope. Am J Cardiol 1997; 80:817-22. [PMID: 9315603 DOI: 10.1016/s0002-9149(97)00529-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An isoproterenol-mediated increase in cardiomotor tone and a decrease in afterload contribute to the induction of vasovagal syncope. Contrary to conventional belief, a significant decrease in preload is not observed immediately before isoproterenol-induced syncope.
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Affiliation(s)
- W K Shen
- Department of Neurology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA
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Kochiadakis GE, Rombola AT, Kanoupakis EM, Simantirakis EN, Chlouverakis GI, Vardas PE. Assessment of autonomic function at rest and during tilt testing in patients with vasovagal syncope. Am Heart J 1997; 134:459-66. [PMID: 9327703 DOI: 10.1016/s0002-8703(97)70082-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This study evaluated autonomic nervous system function in 30 patients with syncope and a positive tilt test result, 20 with a negative test result, and 20 healthy controls. Indexes of heart rate variability were measured during the intervals immediately before and after tilt, while all subjects were asymptomatic, and over a 24-hour period. There were no significant differences among the groups in any of the indexes of heart rate variability over the 24-hour period. In patients with a positive tilt result, tilting caused a decrease in low-frequency (LF) and high-frequency (HF) bands, although the LF/HF ratio did not significantly change. In patients with a negative tilt result there was a decrease in the HF band but no other significant changes. In the controls there was an increase in the LF band and LF/HF ratio and a decrease in the HF band. Our findings showed that patients with vasovagal syncope have no chronic differences from normal subjects in autonomic nervous system activity, but that these patients respond differently to the orthostatic stimulus.
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Affiliation(s)
- G E Kochiadakis
- Cardiology Department, University Hospital of Heraklion, Crete, Greece
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Sumiyoshi M, Nakata Y, Mineda Y. Paroxysmal atrioventricular block induced during head-up tilt testing in an apparently healthy man. J Cardiovasc Electrophysiol 1997; 8:561-4. [PMID: 9160232 DOI: 10.1111/j.1540-8167.1997.tb00824.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Prolonged asystole during head-up tilt testing has been reported, but the occurrence of paroxysmal AV block appears to be rare. METHODS AND RESULTS A 25-year-old man with no history of syncope underwent head-up tilt testing. After 11 minutes of 80 degrees tilting, he developed syncope with paroxysmal AV block and asystole lasting 10.5 seconds. However, this response was not reproduced during a subsequent tilt test 4 weeks later. Treadmill exercise testing and Holter monitoring showed no abnormalities. Power spectral analysis of heart rate variability revealed a marked increase in sympathetic activity several minutes before the induction of paroxysmal AV block. CONCLUSION We report a case of paroxysmal AV block that occurred during head-up tilt testing but did not recur on a subsequent test in an apparently healthy young man.
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Affiliation(s)
- M Sumiyoshi
- Department of Cardiology, Juntendo University Izunagaoka Hospital, Shizuoka, Japan
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Abstract
The current knowledge regarding the pathophysiologic basis of the vasodepressor response was reviewed. The balance of evidence indicates that the mechanoreceptor hypothesis seems unlikely to be the sole afferent alteration that leads to the vasodepressor response. Alternative afferent mechanisms should include neurohumoral mediated sympathoinhibition triggered by opioid mechanisms as well as impaired endothelial and NO responses to orthostatic stress in susceptible individuals. It is possible that impaired cardiovagal and sympathetic outflow control of arterial baroreceptors is enhanced by the aforementioned mechanisms. The role of central sympathoinhibition and vagal excitation triggered directly from pathways within the temporal lobe or triggered by alterations in regional cerebral blood flow should be considered as potential alternative mechanisms. Efferent autonomic outflow during vasodepressor syncope include sympathetic neural outflow withdrawal in addition to activation of parasympathetic outflow to the heart and abdominal viscera. Further human research is needed to understand the underlying mechanisms that result in the described neural and vascular responses.
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Affiliation(s)
- C A Morillo
- Department of Medicine, Universidad Industrial de Santander, Colombia
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Abstract
Head-up tilt testing has become a valuable and widely accepted diagnostic tool for evaluation of patients with vasovagal syncope. This test has afforded clinical researchers the opportunity to focus on the hemodynamic, humoral, and neural changes that accompany syncope. We review the animal and clinical studies that provide insight into the possible pathophysiological mechanisms involved in vasovagal syncope. Hemodynamic measurements in patients with vasovagal syncope suggest that a relative decrease in ventricular size and increase in cardiac contractility may be seen in many patients with vasovagal syncope. Patients with vasovagal syncope have also demonstrated numerous "exaggerated" neurohumoral responses to syncope. Differential changes in plasma levels of epinephrine, renin, endothelin, vasopressin, cortisol, prolactin, beta endorphins, and substance P have been reported by some investigators either prior to or during a syncopal episode in patients with vasovagal syncope. The precise pathophysiological significance of these measurements is unknown at the present time. Measurements of autonomic tone may be accomplished indirectly with analysis of heart rate variability or baroreflex slope, or directly by sympathetic neural recordings of the peroneal nerve. We have demonstrated decreased baroreflex slopes in patients with vasovagal syncope. Using microneurography, we and others have demonstrated decreased sympathetic nerve activity occurring 11 +/- 3 seconds prior to syncope during head-up tilt table testing. A variety of other abnormal reflexes, including blunted forearm blood flow responses during exercise, have been demonstrated by others. These observations suggest that pacing instituted after the event may not be as helpful as the use of a hemodynamic sensor that will result in the initiation of pacing prior to sympathetic withdrawal or modify the decrease in sympathetic tone that occurs prior to syncope.
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Affiliation(s)
- K A Ellenbogen
- Department of Medicine, Medical College of Virginia, Richmond 23298-0053, USA.
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Abstract
BACKGROUND In the present study, we tested the hypothesis that baroreflex sensitivity is reduced in patients with vasovagal syncope compared with normal control subjects. METHODS AND RESULTS We investigated 30 patients with vasovagal syncope (mean age, 43.6 +/- 16.7 years; 14 men and 16 women) and 32 normal control subjects (mean age, 41.8 +/- 17.0 years; 24 men and 8 women). Cardiopulmonary baroreceptor sensitivity was assessed by measuring the change in forearm vascular resistance during subhypotensive lower body negative pressure (LBNP). Carotid baroreflex sensitivity was assessed by measuring the change in RR interval during the manipulation of carotid transmural pressure. Phenylephrine baroreceptor sensitivity was assessed on the basis of the linear regression slope of the RR interval versus systolic blood pressure during the increment in blood pressure after intravenous administration of phenylephrine. In patients with vasovagal syncope, during the application of -10 mm Hg LBNP, forearm vascular resistance decreased by 0.7 +/- 11.6 U versus an increase of 8.3 +/- 6.2 U in control subjects (P = .002). Phenylephrine baroreceptor sensitivity was 11 +/- 7 ms/mm Hg in patients versus 14 +/- 6 ms/mm Hg in control subjects (P = NS). Carotid baroreflex sensitivity was 4 +/- 6 versus 4 +/- 2 ms/mm Hg in patients and control subjects, respectively (P = NS). CONCLUSIONS In patients with vasovagal syncope, during the application of subhypotensive LBNP, there is impaired forearm vasoconstriction or paradoxical forearm vasodilation. This suggests impaired cardiopulmonary baroreceptor inactivation or paradoxical activation of these receptors and is consistent with reduced cardiopulmonary baroreceptor sensitivity.
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Affiliation(s)
- H L Thomson
- Department of Medicine, University of Queensland, Royal Brisoane Hospital, Australia
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Jaeger FJ, Pinski SL, Trohman RG, Fouad-Tarazi FM. Paradoxical failure of QT prolongation during cardioinhibitory neurocardiogenic syncope. Am J Cardiol 1997; 79:100-2. [PMID: 9024751 DOI: 10.1016/s0002-9149(96)00690-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
QT modulation was explored in 31 patients with cardioinhibitory neurocardiogenic syncope. Despite a marked in increase in RR intervals, the QT interval remained stable.
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Affiliation(s)
- F J Jaeger
- Department of Cardiology, The Cleveland Clinic Foundation, Ohio 44195, USA
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Novak V, Honos G, Schondorf R. Is the heart "empty' at syncope? JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1996; 60:83-92. [PMID: 8884700 DOI: 10.1016/0165-1838(96)00040-9] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Neurally-mediated syncope (NMS) is thought to be reflexly triggered by vagal cardiac ventricular afferents that are activated by impaired cardiac filling. If this hypothesis is true then maneuvers that increase venous pooling should progressively diminish cardiac volume triggering syncope once a threshold decrease in cardiac filling is reached. Beat-to-beat recordings of heart rate, blood pressure (Finapres) and stroke volume (impedance cardiograph) were made at rest and during head-up tilt (80 degrees) in twenty controls and in fourteen patients with recurrent NMS (group 1). Hemodynamic profiles of controls and group 1 were compared. In eleven additional patients with NMS (group 2) we measured cardiac chamber volume from apical two or four-chamber views or stroke volume from Doppler measurements of the left ventricular outflow tract at rest and during tilt. Baseline values and initial response to head-up tilt of controls and group 1 patients were similar. A small negative trend in blood pressure and total peripheral resistance was present for at least 250 s before the onset of syncope. Stroke volume remained stable during this presyncopal period and increased at syncope. The profile of stroke volume changes using impedance cardiography mirrored those obtained using Doppler (5 subjects). Reliable echocardiographic measurements of cardiac chamber size were obtained in five subjects and did not change during tilt, presyncope or syncope. These data show that there is no significant decrease in cardiac volume before syncope that could serve as a trigger of syncope.
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Affiliation(s)
- V Novak
- Autonomic Reflex Laboratory Department of Neurology, McGill University, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec, Canada
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