syncope, lightheadedness) caused by CSH manifesting during activities of daily life that put pressure on the carotid sinus (eg, turning the neck, looking upward). When CSS manifests as syncope it is called carotid sinus syncope. (See 'Clinical manifestations' above.) Prevalence CSH is a commonly observed physical finding but an uncommon cause of symptoms (as in CSS). CSS is a relative rare cause of syncope, accounting for approximately 1 percent of syncope cases. Older individuals and males are more likely to have an abnormal CSH response even if they do not have CSS. Clinical presentation The most common presenting symptoms of CSS are lightheadedness/presyncope, syncope, and otherwise unexplained falls. Although a clear relationship between neck movements and symptom episodes is rarely established, a history of syncope following accidental manipulation of the carotid sinuses should be sought. (See 'Clinical manifestations' above.) When to perform CSM to diagnose CSS In patients over age 50 with syncope or presyncope of unknown etiology despite an initial evaluation (see "Syncope in adults: Clinical manifestations and initial diagnostic evaluation"), we recommend performing CSM to evaluate for possible CSS. However, false positive results are common in older adults, so other potential causes of syncope or collapse should be excluded ( algorithm 1). (See 'Diagnostic evaluation' above and 'When to perform CSM' above.) Although a history of pressure in the region of the carotid sinuses prior to syncope or presence of a risk factor for CSS raises the index of suspicion, absence of these features does not exclude CSS, so the indication for CSM to assess for CSS is broad. Contraindications to CSM CSM should be avoided in patients at risk for stroke due to carotid artery disease, including those with prior transient ischemic attack (TIA) or stroke https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 13/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate within the past three months, clinically significant carotid stenosis, or carotid bruit. (See 'Contraindications to CSM' above.) Abnormal responses to CSM Criteria for a positive (ie, abnormal) response to CSM are controversial, ranging from stringent criteria that are more specific to less specific criteria that are more sensitive. The test is most diagnostic for CSS when stringent criteria are met with reproduction of symptoms (see 'Criteria for abnormal responses' above): Stringent criteria A HR pause of 6 s or a fall in systolic BP to <60 mmHg lasting for 6 s. Less specific criteria a HR pause >3 s or a fall in systolic BP of 50 mmHg. Types of abnormal responses An abnormal response to CSM may be cardioinhibitory (greater than normal decline in HR), vasodilatory (greater than normal fall in BP) or mixed (greater than normal fall in HR and BP). (See 'Types of abnormal responses' above.) General management (See 'Approach to management' above and 'General management' above.) For CSH Patients with isolated CSH who remain asymptomatic require no specific therapy other than counselling to avoid movements or positions that may accidentally stimulate the carotid baroreceptors. For CSS General measures include education regarding CSS risks, applicable driving restrictions, and treatment options. Pharmacologic therapy is an option for patients with a vasodilatory response to CSM. (See 'General management' above.) Permanent pacing For patients with recurrent syncope diagnosed with CSS (by either stringent or less specific criteria) with a cardioinhibitory or "mixed" response to CSM resulting in asystole for more than three to six seconds, we suggest permanent cardiac pacemaker implantation (Grade 2C). The certainty of a beneficial response is highest for patients meeting stringent criteria for CSS, including reproduction of symptoms with CSM. (See 'Permanent pacing' above.) ACKNOWLEDGMENT The editorial staff at UpToDate acknowledges Brian Olshansky, MD, who contributed to earlier versions of this topic review. https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 14/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Thomas JE. Hyperactive carotid sinus reflex and carotid sinus syncope. Mayo Clin Proc 1969; 44:127. 2. Kerr SR, Pearce MS, Brayne C, et al. Carotid sinus hypersensitivity in asymptomatic older persons: implications for diagnosis of syncope and falls. Arch Intern Med 2006; 166:515. 3. Sullivan RM, Olshansky B. Carotid sinus hypersensitivity: disease state or clinical sign of ageing? The need for hard endpoints. Europace 2010; 12:1516. 4. Tan MP, Kenny RA, Chadwick TJ, et al. 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. 5. Krediet CT, Parry SW, Jardine DL, et al. The history of diagnosing carotid sinus hypersensitivity: why are the current criteria too sensitive? Europace 2011; 13:14. 6. Volkmann H, Schnerch B, K hnert H. Diagnostic value of carotid sinus hypersensitivity. Pacing Clin Electrophysiol 1990; 13:2065. 7. Brignole M, Menozzi C, Gianfranchi L, et al. Carotid sinus massage, eyeball compression, and head-up tilt test in patients with syncope of uncertain origin and in healthy control subjects. Am Heart J 1991; 122:1644. 8. Alboni P, Brignole M, Menozzi C, et al. Diagnostic value of history in patients with syncope with or without heart disease. J Am Coll Cardiol 2001; 37:1921. 9. 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. 10. Shen WK, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society. J Am Coll Cardiol 2017. 11. Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J 2018; 39:1883. 12. Pasquier M, Clair M, Pruvot E, et al. Carotid Sinus Massage. N Engl J Med 2017; 377:e21. 13. Morillo CA, Camacho ME, Wood MA, et al. Diagnostic utility of mechanical, pharmacological and orthostatic stimulation of the carotid sinus in patients with unexplained syncope. J Am Coll Cardiol 1999; 34:1587. https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 15/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate 14. Parry SW, Richardson DA, O'Shea D, et al. Diagnosis of carotid sinus hypersensitivity in older adults: carotid sinus massage in the upright position is essential. Heart 2000; 83:22. 15. Waxman MB, Wald RW, Sharma AD, et al. Vagal techniques for termination of paroxysmal supraventricular tachycardia. Am J Cardiol 1980; 46:655. 16. Sutton R. Carotid sinus syndrome: Progress in understanding and management. Glob Cardiol Sci Pract 2014; 2014:1. 17. Menozzi C, Brignole M, Lolli G, et al. Follow-up of asystolic episodes in patients with cardioinhibitory, neurally mediated syncope and VVI pacemaker. Am J Cardiol 1993; 72:1152. 18. Wieling W, Thijs RD, van Dijk N, et al. Symptoms and signs of syncope: a review of the link between physiology and clinical clues. Brain 2009; 132:2630. 19. Epstein AE, Miles WM, Benditt DG, et al. Personal and public safety issues related to arrhythmias that may affect consciousness: implications for regulation and physician recommendations. A medical/scientific statement from the American Heart Association and the North American Society of Pacing and Electrophysiology. Circulation 1996; 94:1147. 20. Moore A, Watts M, Sheehy T, et al. Treatment of vasodepressor carotid sinus syndrome with midodrine: a randomized, controlled pilot study. J Am Geriatr Soc 2005; 53:114. 21. Almquist A, Gornick C, Benson W Jr, et al. Carotid sinus hypersensitivity: evaluation of the vasodepressor component. Circulation 1985; 71:927. 22. Maggi R, Menozzi C, Brignole M, et al. Cardioinhibitory carotid sinus hypersensitivity predicts an asystolic mechanism of spontaneous neurally mediated syncope. Europace 2007; 9:563. 23. Brignole M, Menozzi C, Lolli G, et al. Long-term outcome of paced and nonpaced patients with severe carotid sinus syndrome. Am J Cardiol 1992; 69:1039. 24. Claesson JE, Kristensson BE, Edvardsson N, W hrborg P. Less syncope and milder symptoms in patients treated with pacing for induced cardioinhibitory carotid sinus syndrome: a randomized study. Europace 2007; 9:932. 25. Kenny RA, Richardson DA, Steen N, et al. Carotid sinus syndrome: a modifiable risk factor for nonaccidental falls in older adults (SAFE PACE). J Am Coll Cardiol 2001; 38:1491. 26. Ryan DJ, Nick S, Colette SM, Roseanne K. Carotid sinus syndrome, should we pace? A multicentre, randomised control trial (Safepace 2). Heart 2010; 96:347. 27. McLeod CJ, Trusty JM, Jenkins SM, et al. Method of pacing does not affect the recurrence of syncope in carotid sinus syndrome. Pacing Clin Electrophysiol 2012; 35:827. Topic 1071 Version 30.0 https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 16/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate GRAPHICS Anatomy of the carotid sinus The carotid sinus is located at the base of the internal carotid artery just superior to its bifurcation from the external carotid artery. Graphic 139405 Version 1.0 https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 17/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate Algorithm for syncope/collapse This algorithm poses key questions about a collapse episode, including whether and when LOC occurred. However, in the absence of a credible witness, information about such episodes is often limited, as the affected individual may not have accurate recall of the event. Some causes have more than one possible type of presentation. LOC: loss of consciousness; BLS: basic life support; ACLS: advanced cardiac life support; SAH: subarachnoid hemorrhage; TIA: transient ischemic attack. This includes actual LOC as well as apparent LOC. Accidental falls without LOC often have multiple causes, including gait, posture, or balance impairment, environmental hazard, vertigo, focal seizure, TIA, stroke, and presyncope. These conditions result in apparent transient LOC, although consciousness may be preserved. https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 18/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate Other causes of collapse may cause secondary head trauma. Most TIAs and strokes are not associated with LOC. An SAH may cause transient or prolonged LOC. A rare cause of LOC is a brainstem stroke. Graphic 131146 Version 1.0 https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 19/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate Recommendations for resuming driving after syncope Condition Symptom-free waiting time* OH 1 month [1] VVS, no syncope in prior year No restriction [2] VVS, 1 to 6 syncope per year 1 month [1,2] VVS, >6 syncope per year Not fit to drive until symptoms resolved Situational syncope other than cough syncope 1 month Cough syncope, untreated Not fit to drive Cough syncope, treated with cough suppression 1 month [1] Carotid sinus syncope, untreated Not fit to drive Carotid sinus syncope, treated with permanent 1 week [1] pacemaker [1] Syncope due to nonreflex bradycardia, untreated Not fit to drive Syncope due to nonreflex bradycardia, treated with [1,3] permanent pacemaker 1 week [1] Syncope due to SVT, untreated Not fit to drive [1] Syncope due to SVT, pharmacologically suppressed 1 month [1] Syncope due to SVT, treated with ablation 1 week Syncope with LVEF <35% and a presumed arrhythmic [4,5] etiology without an ICD Not fit to drive Syncope with LVEF <35% and presumed arrhythmic etiology with an ICD 3 months [6,7] Syncope presumed due to VT/VF, structural heart disease, and LVEF 35%, untreated Not fit to drive Syncope presumed due to VT/VF, structural heart disease, and LVEF 35%, treated with an ICD and guideline-directed drug therapy 3 months [6,7] Syncope presumed due to VT with a genetic cause, Not fit to drive untreated Syncope presumed due to VT with a genetic cause, treated 3 months with an ICD or guideline-directed drug therapy Syncope presumed due to a nonstructural heart disease VT, Not fit to drive such as RVOT or LVOT, untreated https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 20/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate Syncope presumed due to a nonstructural heart disease VT, 3 months such as RVOT or LVOT, treated successfully with ablation or suppressed pharmacologically [1] Syncope of undetermined etiology 1 month OH: orthostatic hypotension; VVS: vasovagal syncope; SVT: supraventricular tachycardia; LVEF: left ventricular ejection fraction; ICD: implantable cardioverter-defibrillator; VT: ventricular tachycardia; VF: ventricular fibrillation; RVOT: right ventricular outflow tract; LVOT: left ventricular outflow tract. It may be prudent to wait and observe for this time without a syncope spell before resuming driving. References: 1. Epstein AE, Miles WM, Benditt DG, et al. Personal and public safety issues related to arrhythmias that may a ect consciousness: implications for regulation and physician recommendations. A medical/scienti c statement from the American Heart Association and the North American Society of Pacing and Electrophysiology. Circulation 1996; 94:1147-66. 2. Tan VH, Ritchie D, Maxey C, et al. Prospective assessment of the risk of vasovagal syncope during driving. JACC Clin Electrophysiol 2016; 2:203. 3. Epstein AE, DiMarco JP, Ellenbogen KA, et al. 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2013; 61:e6. 4. B nsch D, Brunn J, Castrucci M, et al. Syncope in patients with an implantable cardioverter-de brillator: incidence, prediction and implications for driving restrictions. J Am Coll Cardiol 1998; 31:608. 5. Antonelli D, Peres D, Freedberg NA, et al. Incidence of postdischarge symptomatic paroxysmal atrial brillation in patients who underwent coronary artery bypass graft: long-term follow-up. Pacing Clin Electrophysiol 2004; 27:365. 6. Thijssen J, Borle s CJ, van Rees JB, et al. Driving restrictions after implantable cardioverter de brillator implantation: an evidence-based approach. Eur Heart J 2011; 32:2678. 7. Vijgen J, Botto G, Camm J, et al. Consensus statement of the European Heart Rhythm Association: updated recommendations for driving by patients with implantable cardioverter de brillators. Europace 2009; 11:1097. Reproduced from: Shen W-K, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope. J Am Coll Cardiol 2017. Table used with the permission of Elsevier Inc. All rights reserved. Graphic 113080 Version 2.0 https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 21/22 7/6/23, 2:38 PM Carotid sinus hypersensitivity and carotid sinus syndrome - UpToDate Contributor Disclosures David Benditt, MD Equity Ownership/Stock Options: Medtronic [Pacemakers/event recorders and defibrillators]. Grant/Research/Clinical Trial Support: Medtronic [Pacemakers/event recorders and defibrillators]; St Jude Medical [Pacemakers/event recorders and defibrillators]. Consultant/Advisory Boards: Medtronic [Pacemakers/event recorders and defibrillators]; Zoll [Pacemakers/event recorders and defibrillators]. Other Financial Interest: Advanced CPR Solutions [Outside director]. All of the relevant financial relationships listed have been mitigated. Peter Kowey, MD, FACC, FAHA, FHRS Equity Ownership/Stock Options: VuMedi [Arrhythmias]. Consultant/Advisory Boards: Abbvie [Arrhythmias]; Acesion Pharma [Arrhythmias]; Allergan [Arrhythmias, cardiac safety of non-cardiac drugs]; Anthos [Anticoagulants]; Boehringer-Ingelheim [Arrhythmias]; Bristol-Meyers-Squibb [Arrhythmias]; Daiichi Sankyo [Arrhythmias]; Gilead [Arrhythmias]; Huya [Arrhythmias]; InCarda Therapeutics [Arrhythmias]; INSTA [Arrhythmias]; Johnson & Johnson [Arrhythmias]; Medtronic [Arrhythmias]; Milestone [Arrhythmias]; Novartis [Arrhythmias, cardiac safety of non-cardiac drugs]; Pfizer [Arrhythmias]; Sanofi [Arrhythmias]; Takeda [Arrhythmias]. All of the relevant financial relationships listed have been mitigated. Susan B Yeon, MD, JD, FACC No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/carotid-sinus-hypersensitivity-and-carotid-sinus-syndrome/print 22/22