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Parry SW. Should We Ever Pace for Carotid Sinus Syndrome? Front Cardiovasc Med 2020; 7:44. [PMID: 32391383 PMCID: PMC7188762 DOI: 10.3389/fcvm.2020.00044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 03/06/2020] [Indexed: 12/16/2022] Open
Abstract
Carotid sinus syndrome has been associated with transient loss of consciousness for millennia, and while steeped in cardiovascular lore, there is little in the way of solid evidence to guide its main treatment modality, permanent cardiac pacing. This article reviews the history of the condition in the context of its contemporary understanding before examining three key concepts in the consideration of what constitutes a manageable disease: first, is there a pathophysiologic rationale for the disease (in this case carotid sinus syndrome)? Second, is there a good diagnostic test that will identify it reliably? And finally, is there a convincingly evidence-based treatment for the disease? Relevant literature is reviewed, and recommendations made in how we view pacing in the context of this intriguingly opaque condition.
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Affiliation(s)
- Steve W Parry
- Newcastle University Institute of Ageing, Newcastle University, Newcastle upon Tyne, United Kingdom
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Finucane C, Kenny RA, Boyle G. Cardioinhibitory Carotid Sinus Syndrome - a mathematical model. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:2059-62. [PMID: 26736692 DOI: 10.1109/embc.2015.7318792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Carotid sinus massage (CSM) is a simple clinical test for stimulating the carotid sinus reflex. During CSM, firm longitudinal massage is applied at the point of maximal pulsation over the carotid bifurcation resulting in relative bradycardia. CSM is used to diagnose Cardioinhibitory Carotid Sinus Syndrome (CICSS). CICSS is an age-related disorder, characterized by profound symptomatic cardioinhibition (> 3 seconds pause) following CSM. CICSS prevalence increases with age and is responsible for 1 to 20% of all pacemaker implantations per year. Treatment options for CSS are limited and much debate still remains around its underlying etiology. In this paper we present a first computer simulation of carotid sinus massage (CSM) in older adults and demonstrate its ability to simulate normal heart rate responses to CSM. Importantly we demonstrate that our mathematical model requires inclusion of model elements to simulate autonomic control of perinodal T-cell activity in order to replicate the profound cardioinhibitory response observed in CICSS. Our model findings implicate CSS as a candidate biomarker of biological aging and frailty.
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Tan MP, Murray A, Hawkins T, Chadwick TJ, Kerr SRJ, Parry SW. Cardiac Iodine-123-Meta-Iodo-Benzylguanidine Uptake in Carotid Sinus Hypersensitivity. PLoS One 2015; 10:e0126241. [PMID: 26057525 PMCID: PMC4461270 DOI: 10.1371/journal.pone.0126241] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 03/18/2015] [Indexed: 01/08/2023] Open
Abstract
Background Carotid sinus syndrome is the association of carotid sinus hypersensitivity with syncope, unexplained falls and drop attacks in generally older people. We evaluated cardiac sympathetic innervation in this disorder in individuals with carotid sinus syndrome, asymptomatic carotid sinus hypersensitivity and controls without carotid sinus hypersensitivity. Methods Consecutive patients diagnosed with carotid sinus syndrome at a specialist falls and syncope unit were recruited. Asymptomatic carotid sinus hypersensitivity and non-carotid sinus hypersensitivity control participants recruited from a community-dwelling cohort. Cardiac sympathetic innervation was determined using Iodine-123-metaiodobenzylguanidine (123-I-MIBG) scanning. Heart to mediastinal uptake ratio (H:M) were determined for early and late uptake on planar scintigraphy at 20 minutes and 3 hours following intravenous injection of 123-I-MIBG. Results Forty-two subjects: carotid sinus syndrome (n = 21), asymptomatic carotid sinus hypersensitivity (n = 12) and no carotid sinus hypersensitivity (n = 9) were included. Compared to the non- carotid sinus hypersensitivity control group, the carotid sinus syndrome group had significantly higher early H:M (estimated mean difference, B = 0.40; 95% confidence interval, CI = 0.13 to 0.67, p = 0.005) and late H:M (B = 0.32; 95%CI = 0.03 to 0.62, p = 0.032). There was, however, no significant difference in early H:M (p = 0.326) or late H:M (p = 0.351) between the asymptomatic carotid sinus hypersensitivity group and non- carotid sinus hypersensitivity controls. Conclusions Cardiac sympathetic neuronal activity is increased relative to age-matched controls in individuals with carotid sinus syndrome but not those with asymptomatic carotid sinus hypersensitivity. Blood pressure and heart rate measurements alone may therefore represent an over simplification in the assessment for carotid sinus syndrome and the relative increase in cardiac sympathetic innervation provides additional clues to understanding the mechanisms behind the symptomatic presentation of carotid sinus hypersensitivity.
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Affiliation(s)
- Maw Pin Tan
- Ageing and Age-Associated Disorders Research Group, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Alan Murray
- Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom
| | - Terry Hawkins
- Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom
| | - Thomas J. Chadwick
- Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Simon R. J. Kerr
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- Falls and Syncope Service, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Steve W. Parry
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- Falls and Syncope Service, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
- * E-mail:
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Krediet CTP, Parry SW, Jardine DL, Benditt DG, Brignole M, Wieling W. The history of diagnosing carotid sinus hypersensitivity: why are the current criteria too sensitive? Europace 2010; 13:14-22. [DOI: 10.1093/europace/euq409] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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Tan MP, Kenny RAM, Chadwick TJ, Kerr SRJ, Parry SW. Carotid sinus hypersensitivity: disease state or clinical sign of ageing? Insights from a controlled study of autonomic function in symptomatic and asymptomatic subjects. Europace 2010; 12:1630-6. [DOI: 10.1093/europace/euq317] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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Finucane C, Boyle G, Fan CW, Hade D, Byrne L, Kenny RA. Mayer wave activity in vasodepressor carotid sinus hypersensitivity. Europace 2010; 12:247-53. [DOI: 10.1093/europace/eup385] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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Shepherd JT, Mancia G. Reflex control of the human cardiovascular system. Rev Physiol Biochem Pharmacol 2006; 105:1-99. [PMID: 3541137 DOI: 10.1007/bfb0034497] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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van Vliet BN, Montani JP. Baroreflex stabilization of the double product. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H1679-89. [PMID: 10564120 DOI: 10.1152/ajpheart.1999.277.5.h1679] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether the baroreflex control of heart rate (HR) stabilizes the product of arterial pressure (P(A)) and HR, called the double product (DP), an indirect indicator of left ventricular oxygen consumption. During pharmacological increases and decreases of P(A) in conscious rabbits, the mean (+/-SE) rate of change of the DP with respect to P(A) (dDP/dP(A)) was -88 +/- 36 and -20 +/- 36 DP units/mmHg, respectively. Regression analysis of all peak responses obtained in individual rats produced a dDP/dP(A) value of 15 +/- 16 DP units/mmHg. These estimates were significantly less than the dDP/dP(A) value predicted if HR were constant (184 +/- 7 DP units/mmHg) and were not significantly different from zero. We also compared values of baroreflex sensitivity (BRS) from the literature with those calculated to provide ideal stabilization of the DP. BRS values were significantly correlated with the calculated ideal values (R = 0.95; n = 14). BRS averaged 128 +/- 24% of the ideal value in all species and 148 +/- 28% in mammals and birds. Our results suggest that stabilization of the DP is a common consequence of the baroreflex control of heart rate.
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Affiliation(s)
- B N van Vliet
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3V6.
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Morillo CA, Camacho ME, Wood MA, Gilligan DM, Ellenbogen KA. Diagnostic utility of mechanical, pharmacological and orthostatic stimulation of the carotid sinus in patients with unexplained syncope. J Am Coll Cardiol 1999; 34:1587-94. [PMID: 10551710 DOI: 10.1016/s0735-1097(99)00365-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
OBJECTIVES The purpose of the present study was to systematically evaluate the diagnostic utility of mechanical, pharmacological and orthostatic stimulation of the carotid sinus in a consecutive series of patients with recurrent unexplained syncope. BACKGROUND Carotid sinus hypersensitivity (CSH) is an infrequently recognized cause of recurrent unexplained syncope usually diagnosed by carotid sinus massage (CSM) in the supine position. The diagnostic utility of systematic assessment of mechanical, pharmacological and orthostatic stimulation of the carotid sinus has not been clearly established. METHODS Eighty consecutive patients (63 +/- 12 years) with a history of recurrent unexplained syncope (mean episodes: 6 +/- 3); 30 age-matched controls (65 +/- 14 years) and 16 patients (59 +/- 12 years) with syncope not related to CSH were studied. Pharmacological stimulation of the carotid sinus was achieved by randomly administering bolus injections of nitroprusside and phenylephrine. Mechanical stimulation of the carotid sinus was performed by CSM applied for 5 s in the supine position and after 2 min at 60 degrees. A 60 degree low-dose isoproterenol head-up tilt test (HUTT) was also performed for a total duration of 30 min. RESULTS Carotid sinus hypersensitivity was elicited by CSM in the supine position in seven (8.7%) patients, two (6.6%) controls and one (6.3%) patient with syncope unrelated to CSH, compared with 48 (60%) patients, two (6.6%) controls and one (6.3%) syncope unrelated to CSH patient after 60 degree HUTT, increasing the diagnostic yield by 51%. Baroreceptor gain was significantly reduced in the CSH group. Head-up tilt test was positive in 12 (25%) patients with CSH, two (6.6%) controls and two (12%) with documented syncope but not positive in any of the patients in which syncope remained unexplained. Diagnostic accuracy was enhanced by 38% (31% supine vs. 69% upright) when CSM was performed at 60 degrees. CONCLUSIONS CSH was documented in 68% of patients, 8.7% in the supine position and 60% in the upright position. Sensitivity was increased by 51%, and diagnostic accuracy was enhanced by 38% by performing CSM in the upright position. Decreased baroreceptor gain was documented and may play a role in the pathophysiology of CSH.
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Affiliation(s)
- C A Morillo
- Department of Cardiology, Fundación Cardiovascular del Oriente Colombiano, Bucaramanga, Colombia
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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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Munro NC, McIntosh S, Lawson J, Morley CA, Sutton R, Kenny RA. Incidence of complications after carotid sinus massage in older patients with syncope. J Am Geriatr Soc 1994; 42:1248-51. [PMID: 7983286 DOI: 10.1111/j.1532-5415.1994.tb06505.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE To review the incidence of neurological complications occurring after carotid sinus massage performed for diagnostic purposes. DESIGN Case review and comparison with previously published work. SETTING Syncope Clinic, Royal Victoria Infirmary, Newcastle-upon-Tyne, and Chelsea and Westminster Hospital, London. PARTICIPANTS Patients undergoing investigation of dizziness, syncope, or unexplained falls. METHODS Carotid sinus massage performed for 5 seconds in both supine and erect postures, both before and after atropine. Contraindications to carotid sinus massage were the presence of carotid bruits, recent myocardial or cerebral ischemia, or previous ventricular tachyarrhythmias. RESULTS Two cases of neurological complications were reported from a total of 500 patients (2000 massage episodes) investigated in one center, giving an incidence of 0.1%. Combining this data with another center performing investigations in a similar fashion, seven neurological complications arose from a total of 5000 massage episodes, an incidence of 0.14%. Reported complications were pyramidal signs in five cases and visual field defects in two. Pyramidal weakness persisted in one case with a pre-existing stroke on the same side, and a visual field loss was permanent in one. CONCLUSIONS Neurological complications following carotid sinus massage for diagnosis of the carotid sinus syndrome are uncommon and usually transient. Contraindications to carotid sinus massage should be respected and the standardized technique used.
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Affiliation(s)
- N C Munro
- Cardiovascular Investigation Unit, Royal Victoria Infirmary, Newcastle-upon-Tyne, London, UK
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Kenny RA, McIntosh SJ, Wynne H. Pattern of inhibition of parasympathetic activity in response to incremental bolus doses of atropine in carotid sinus hypersensitivity. Clin Auton Res 1994; 4:63-6. [PMID: 8054839 DOI: 10.1007/bf01828840] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Patients with established reproducible cardioinhibitory carotid sinus hypersensitivity were studied to define the dose of atropine required to abolish the heart rate slowing in response to carotid sinus massage, the heart rate response to the Valsalva manoeuvre and salivary gland flow. Bolus doses of intravenous atropine were given to a cumulative dose of 700 mcg. Cardioinhibition was abolished in all patients with a total dose of 700 mcg. The heart rate ratio during the Valsalva manoeuvre did not vary significantly. The decline in salivary gland flow was evident earliest, at a dose of 75 mcg. In clinical studies, 700 mcg of atropine will abolish the diagnostic cardioinhibitory response to carotid sinus message in patients with the syndrome. This may not prevent syncope, as could occur in the key frequent vasodepressor form of carotid sinus hypersensitivity syndrome.
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Affiliation(s)
- R A Kenny
- Department of Medicine and Geriatric Medicine, Royal Victoria Infirmary, Newcastle upon Tyne, UK
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McIntosh SJ, Lawson J, Kenny RA. Clinical characteristics of vasodepressor, cardioinhibitory, and mixed carotid sinus syndrome in the elderly. Am J Med 1993; 95:203-8. [PMID: 8356984 DOI: 10.1016/0002-9343(93)90261-m] [Citation(s) in RCA: 162] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PURPOSE Carotid sinus syndrome (CSS) is frequently overlooked as a cause of syncope in the elderly. It is diagnosed when carotid sinus massage (CSM) produces asystole exceeding 3 seconds (cardioinhibitory CSS), a reduction in systolic blood pressure exceeding 50 mm Hg independent of heart rate slowing (vasodepressor CSS), or a combination of the two (mixed CSS). Most published data pertain to the cardioinhibitory subtype. The recent availability of noninvasive phasic blood pressure monitoring has allowed accurate routine assessment of the vasodepressor response to CSM. The aim of this study was to assess the clinical characteristics of vasodepressor, cardioinhibitory, and mixed CSS. PATIENTS AND METHODS CSM was carried out on 132 consecutive patients over 65 years referred for investigation of dizziness, falls, or syncope. Massage was performed both supine and upright with continuous electrocardiographic and phasic blood pressure monitoring. Patients exhibiting greater than 1.5-second asystole were given 600 micrograms of intravenous atropine to abolish heart rate slowing and allow assessment of the pure vasodepressor response. RESULTS Carotid sinus hypersensitivity was documented in 64 patients (mean age 81 +/- 7 years, 31 male). The response was vasodepressor in 37%, cardioinhibitory in 29%, and mixed in 34%. Thirty-six patients had recurrent syncope, 17 presented with unexplained falls, and the remainder had dizziness alone. Symptoms had been present for a median of 24 months, and the median number of syncopal episodes was four. Twenty-five percent had sustained a fracture and, of these, 93% had not experienced a prodrome. Head movement precipitated symptoms in 47% and vagal stimuli in 73%. Episodes were unwitnessed in two thirds of patients. Twelve patients who presented with falls denied syncope but had witnessed loss of consciousness during CSM. Mean cardioinhibition was 5 +/- 2 seconds and mean vasodepression 61 +/- 9 mm Hg. The blood pressure nadir occurred rapidly at 18 +/- 3 seconds after massage, and baseline values were regained at 30 +/- 6 seconds. The clinical characteristics of patients with vasodepressor, cardioinhibitory, and mixed responses were similar. CONCLUSION CSS is an underdiagnosed cause of dizziness, falls, and syncope in the elderly. The vasodepressor form occurs more frequently than previously reported and has clinical characteristics similar to those of the cardioinhibitory and mixed subtypes. Elderly patients with this condition may deny syncope and present with recurrent unexplained falls. CSM, ideally with noninvasive phasic blood pressure monitoring, should be routinely performed in elderly patients with unexplained bradycardic or hypotensive symptoms.
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Affiliation(s)
- S J McIntosh
- Department of Medicine/Geriatric Medicine, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
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da Costa D, McIntosh S, Kenny RA. Benefits of fludrocortisone in the treatment of symptomatic vasodepressor carotid sinus syndrome. Heart 1993; 69:308-10. [PMID: 8489861 PMCID: PMC1025042 DOI: 10.1136/hrt.69.4.308] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
OBJECTIVE To assess treatment with fludrocortisone in vasodepressor carotid sinus syndrome. PATIENTS AND METHODS Eleven patients, mean (SD) age 83 (5) years, with daily dizzy episodes and a median of five (range two to 20) syncopal episodes over a median of one year were studied. All had vasodepressor carotid sinus syndrome (> 50 mm Hg fall in systolic blood pressure during carotid sinus massage independent of bradycardia). Carotid sinus massage was carried out while the patient was supine and upright (tilt table) before and after 600 micrograms intravenous atropine. Phasic heart rate and blood pressure recordings were monitored throughout. The study was repeated after 100 micrograms of fludrocortisone daily by mouth for two weeks. Patients continued to take fludrocortisone for a six month follow up period. RESULTS Baseline systolic blood pressure was (mean (SD)) 169 (31) mm Hg and the RR interval was 770 (150) ms. After carotid sinus massage, systolic blood pressure fell to 113 (27) mm Hg (p < 0.01) and RR was 1060 (210) ms (NS). The vasodepressor response was 56 (12) mm Hg. Baseline systolic blood pressure after two weeks of fludrocortisone treatment was 171 (37) mm Hg (NS); but the fall in systolic blood pressure during carotid sinus massage was significantly reduced (32 (14) mm Hg; p < 0.01). At six months follow up, two patients complained of intermittent dizziness and no patients had syncope. CONCLUSION Fludrocortisone effectively reduces the vasodepressor response and relieves the symptoms of vasodepressor carotid sinus syndrome.
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Affiliation(s)
- D da Costa
- Department of Medicine and Geriatric Medicine, Royal Victoria Infirmary, Newcastle upon Tyne
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Schafers RF, Elliott HL, Meredith PA, Miller SH, Reid JL. Studies with abanoquil (UK-52,046) a novel quinoline alpha 1-adrenoceptor antagonist: II. Duration of action, pharmacokinetics and concentration-effect relationships in normotensive subjects. Br J Clin Pharmacol 1991; 32:605-10. [PMID: 1683250 PMCID: PMC1368638 DOI: 10.1111/j.1365-2125.1991.tb03959.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
1. This study further examines the quinoline-derivative abanoquil with particular respect to the duration of its alpha 1-adrenoceptor antagonist activity and its concentration-effect relationship following a single intravenous bolus dose of 0.5 micrograms kg-1 in young, normotensive males. 2. alpha 1-adrenoceptor antagonism (as assessed by phenylephrine pressor responses) was detectable for up to 12 h post dosing: at 12 h there was a significant 1.5-fold rightward shift (95% CI: 2.2 to 1.1) of the pressor dose-response curve for diastolic blood pressure. 3. Despite evidence of substantial alpha 1-adrenoceptor antagonism abanoquil had no significant effect on blood pressure, supine and erect, but there were small and statistically significant increments in heart rate. 4. The degree of alpha 1-adrenoceptor antagonism was related to whole blood concentrations abanoquil: the PD-ratios of phenylephrine pressor responses performed at 1, 6, and 12 h post dosing were significantly correlated with log drug concentrations (r = 0.57 for systolic (P less than 0.05) and r = 0.78 for diastolic blood pressure (P less than 0.005). 5. In conclusion, abanoquil produced significant alpha 1-adrenoceptor antagonism which was related to circulating drug concentrations. The absence of other significant cardiovascular effects suggests that abanoquil warrants further clinical study as an antiarrhythmic agent.
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Affiliation(s)
- R F Schafers
- University Department of Medicine and Therapeutics, Stobhill General Hospital, Glasgow
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Baig MW, Kaye GC, Perrins EJ. Can central neuropeptides be implicated in carotid sinus reflex hypersensitivity? Med Hypotheses 1989; 28:255-9. [PMID: 2739593 DOI: 10.1016/0306-9877(89)90079-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Carotid sinus reflex hypersensitivity involves profound and intermittent changes in heart rate and blood pressure associated with symptoms of dizziness and syncope. This involves a reflex arc in which the main defect is believed to lie within the central nervous system. The discovery of classical and peptidergic neurotransmitters within the same neurone, and the presence of these peptides within the central nervous system raises the possibility that carotid sinus reflex hypersensitivity may be related to an abnormality of peptide distribution or function.
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Affiliation(s)
- M W Baig
- Department of Medical Cardiology, General Infirmary, Leeds, England, U.K
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