Heart, Lung and Circulation

Prediction of Pacemaker Requirement in Patients With Unexplained Syncope: The DROP Score

Published:March 31, 2022DOI:


      Implantable loop recorders (ILR) are increasingly utilised in the evaluation of unexplained syncope. However, they are expensive and do not protect against future syncope.


      To compare patients requiring permanent pacemaker (PPM) implantation during ILR follow-up with those without abnormalities detected on ILR in order to identify potential predictors of benefit from upfront pacing.


      We analysed 100 consecutive patients receiving ILR: Group 1 (n=50) underwent PPM insertion due to bradyarrhythmias detected on ILR; Group 2 (n=50) had no arrhythmias detected on ILR over >3 years follow-up. Baseline clinical characteristics, syncope history, electrocardiographic and echocardiographic parameters were assessed to identify predictors of ultimate requirement for pacing.


      Group 1 (64% male, median age 70.8 years; IQR 65.5–78.8) were older than Group 2 (58% male, median 60.2 years; IQR 44.0–73.0 p=0.001) and were less likely to have related historical factors such as overheating, posture and exercise (98% vs 70% p<0.001). PR interval was also longer in Group 1 (192±51 vs 169±23 p=0.006) with greater prevalence of distal conduction system disease (30% vs 4.3% p=0.002). Significant univariate predictors for PPM insertion were distal conduction disease (p=0.007), first degree atrioventricular (AV) block (p=0.003), absence of precipitating factors (p=0.004), and age >65 years (p=0.001). Injury sustained, recurrent syncope, history of atrial fibrillation (AF) or heart failure, left atrial (LA) size and left ventricular ejection fraction (LVEF) were not predictive. These significant predictors were incorporated into the DROP score1 (0–4). Using time-to-event analysis, no patients with a score of 0 progressed to pacing, while higher scores (3–4) strongly predicted pacing requirement (log-rank p<0.001).


      The DROP score may be helpful in identifying patients likely to benefit from upfront permanent pacemaker (PPM) insertion following unexplained syncope. Larger prospective studies are required to validate this tool.


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      1. 2018 ESC Guidelines for the diagnosis and management of syncope.
        Rev Esp Cardiol (Engl Ed). 2018; 71: 837
        • Sun B.C.
        • Emond J.A.
        • Camargo Jr., C.A.
        Direct medical costs of syncope-related hospitalizations in the United States.
        Am J Cardiol. 2005; 95: 668-671
        • Brignole M.
        • Menozzi C.
        • Bartoletti A.
        • Giada F.
        • Lagi A.
        • Ungar A.
        • et al.
        A new management of syncope: prospective systematic guideline-based evaluation of patients referred urgently to general hospitals.
        Eur Heart J. 2006; 27: 76-82
        • Quinn J.V.
        Yield of diagnostic tests in evaluating syncopal episodes in older patients--invited commentary.
        Arch Intern Med. 2009; 169: 1305-1306
        • Soteriades E.S.
        • Evans J.C.
        • Larson M.G.
        • Chen M.H.
        • Chen L.
        • Benjamin E.J.
        • et al.
        Incidence and prognosis of syncope.
        N Engl J Med. 2002; 347: 878-885
        • Krahn A.D.
        • Klein G.J.
        • Yee R.
        • Skanes A.C.
        Detection of asymptomatic arrhythmias in unexplained syncope.
        Am Heart J. 2004; 148: 326-332
        • Sun B.C.
        • Mangione C.M.
        • Merchant G.
        • Weiss T.
        • Shlamovitz G.Z.
        • Zargaraff G.
        • et al.
        External validation of the San Francisco Syncope Rule.
        Ann Emerg Med. 2007; 49 (420-427, 7 e1-4)
        • Saccilotto R.T.
        • Nickel C.H.
        • Bucher H.C.
        • Steyerberg E.W.
        • Bingisser R.
        • Koller M.T.
        San Francisco Syncope Rule to predict short-term serious outcomes: a systematic review.
        CMAJ. 2011; 183: E1116-E1126
        • Quinn J.
        • McDermott D.
        • Stiell I.
        • Kohn M.
        • Wells G.
        Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes.
        Ann Emerg Med. 2006; 47: 448-454
        • de Sousa Bispo J.
        • Azevedo P.
        • Mota T.
        • Fernandes R.
        • Guedes J.
        • Candeias R.
        • et al.
        EGSYS score for the prediction of cardiac etiology in syncope: Is it useful in an outpatient setting?.
        Rev Port Cardiol. 2020; 39: 255-261
        • Thiruganasambandamoorthy V.
        • Kwong K.
        • Wells G.A.
        • Sivilotti M.L.A.
        • Mukarram M.
        • Rowe B.H.
        • et al.
        Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope.
        CMAJ. 2016; 188: E289-E298
        • Thiruganasambandamoorthy V.
        • Sivilotti M.L.A.
        • Le Sage N.
        • Yan J.W.
        • Huang P.
        • Hegdekar M.
        • et al.
        Multicenter emergency department validation of the Canadian Syncope Risk Score.
        JAMA Intern Med. 2020; 180: 737-744
        • Del Rosso A.
        • Ungar A.
        • Maggi R.
        • Giada F.
        • Petix N.R.
        • De Santo T.
        • et al.
        Clinical predictors of cardiac syncope at initial evaluation in patients referred urgently to a general hospital: the EGSYS score.
        Heart. 2008; 94: 1620-1626
        • Palmisano P.
        • Accogli M.
        • Zaccaria M.
        • Luzzi G.
        • Nacci F.
        • Anaclerio M.
        • et al.
        Predictive factors for pacemaker implantation in patients receiving an implantable loop recorder for syncope remained unexplained after an extensive cardiac and neurological workup.
        Int J Cardiol. 2013; 168: 3450-3457
        • Del Rosso A.
        • Alboni P.
        • Brignole M.
        • Menozzi C.
        • Raviele A.
        Relation of clinical presentation of syncope to the age of patients.
        Am J Cardiol. 2005; 96: 1431-1435
        • Kenny R.A.
        Syncope in the elderly: diagnosis, evaluation, and treatment.
        J Cardiovasc Electrophysiol. 2003; 14: S74-S77
        • Goyal P.
        • Rich M.W.
        Electrophysiology and heart rhythm disorders in older adults.
        J Geriatr Cardiol. 2016; 13: 645-651
        • Sud S.
        • Klein G.J.
        • Skanes A.C.
        • Gula L.J.
        • Yee R.
        • Krahn A.D.
        Predicting the cause of syncope from clinical history in patients undergoing prolonged monitoring.
        Heart Rhythm. 2009; 6: 238-243
        • Brignole M.
        • Menozzi C.
        • Maggi R.
        • Solano A.
        • Donateo P.
        • Bottoni N.
        • et al.
        The usage and diagnostic yield of the implantable loop-recorder in detection of the mechanism of syncope and in guiding effective antiarrhythmic therapy in older people.
        Europace. 2005; 7: 273-279
        • Roca-Luque I.
        • Francisco-Pascual J.
        • Oristrell G.
        • Rodriguez-Garcia J.
        • Santos-Ortega A.
        • Martin-Sanchez G.
        • et al.
        Syncope, conduction disturbance, and negative electrophysiological test: Predictive factors and risk score to predict pacemaker implantation during follow-up.
        Heart Rhythm. 2019; 16: 905-912
        • Da Costa A.
        • Gulian J.L.
        • Romeyer-Bouchard C.
        • Messier M.
        • Zarqane N.
        • Samuel B.
        • et al.
        Clinical predictors of cardiac events in patients with isolated syncope and negative electrophysiologic study.
        Int J Cardiol. 2006; 109: 28-33
        • Furukawa T.
        • Hachiya H.
        • Isobe M.
        • Hirao K.
        Is head injury characteristic of arrhythmic syncope?.
        J Arrhythm. 2013; 29: 217-220
        • Ahmed N.
        • Frontera A.
        • Carpenter A.
        • Cataldo S.
        • Connolly G.M.
        • Fasiolo M.
        • et al.
        Clinical predictors of pacemaker implantation in patients with syncope receiving implantable loop recorder with or without ECG conduction abnormalities.
        Pacing Clin Electrophysiol. 2015; 38: 934-941
        • D'Ascenzo F.
        • Biondi-Zoccai G.
        • Reed M.J.
        • Gabayan G.Z.
        • Suzuki M.
        • Costantino G.
        • et al.
        Incidence, etiology and predictors of adverse outcomes in 43,315 patients presenting to the Emergency Department with syncope: an international meta-analysis.
        Int J Cardiol. 2013; 167: 57-62
        • Sule S.
        • Palaniswamy C.
        • Aronow W.S.
        • Ahn C.
        • Peterson S.J.
        • Adapa S.
        • et al.
        Etiology of syncope in patients hospitalized with syncope and predictors of mortality and rehospitalization for syncope at 27-month follow-up.
        Clin Cardiol. 2011; 34: 35-38
        • Puppala V.K.
        • Dickinson O.
        • Benditt D.G.
        Syncope: classification and risk stratification.
        J Cardiol. 2014; 63: 171-177
        • Rivera-Lopez R.
        • Cabrera-Ramos M.
        • Jordan-Martinez L.
        • Jimenez-Jaimez J.
        • Macias-Ruiz R.
        • Aguilar-Alonso E.
        • et al.
        Syncope and bifascicular block in the absence of structural heart disease.
        Sci Rep. 2020; 10: 8139
        • Krahn A.D.
        • Morillo C.A.
        • Kus T.
        • Manns B.
        • Rose S.
        • Brignole M.
        • et al.
        Empiric pacemaker compared with a monitoring strategy in patients with syncope and bifascicular conduction block--rationale and design of the Syncope: Pacing or Recording in ThE Later Years (SPRITELY) study.
        Europace. 2012; 14: 1044-1048
        • Kusumoto F.M.
        • Schoenfeld M.H.
        • Barrett C.
        • Edgerton J.R.
        • Ellenbogen K.A.
        • Gold M.R.
        • et al.
        2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society.
        Circulation. 2019; 140: e382-e482
        • Brignole M.
        • Auricchio A.
        • Baron-Esquivias G.
        • Bordachar P.
        • Boriani G.
        • Breithardt O.A.
        • et al.
        2013 ESC Guidelines on Cardiac Pacing And Cardiac Resynchronization Therapy: The Task Force on Cardiac Pacing And Resynchronization Therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA).
        Eur Heart J. 2013; 34: 2281-2329
        • Solbiati M.
        • Costantino G.
        • Casazza G.
        • Dipaola F.
        • Galli A.
        • Furlan R.
        • et al.
        Implantable loop recorder versus conventional diagnostic workup for unexplained recurrent syncope.
        The Cochrane Database of Systematic Reviews. 2016; 4: CD011637