Swallow (deglutition) syncope: An evaluation of swallowing-induced heart rate and hemodynamic changes in affected patients and control subjects.

BACKGROUND: Syncope triggered by swallowing is a well-known but uncommon condition that has been the focus of case reports but is otherwise largely unstudied. To better understand swallow syncope we examined heart rate (HR) and blood pressure (BP) changes during swallowing in clinically suspected swallow syncope patients and asymptomatic control subjects. METHODS: The study population comprised four individuals with a history suggesting swallow syncope (three men, 53 ± 14.9 years) and 15 (nine men, 46 ± 17.1 years, P = NS vs patients) asymptomatic volunteer control subjects. Studies in all individuals comprised noninvasive beat-to-beat HR and BP measurement during swallowing 150 mL of cold liquid while standing. Additional tests in swallow syncope patients included: active standing, Valsalva maneuver, carotid sinus massage (CSM), and head-up tilt (HUT). RESULTS: Swallowing resulted in a greater decrease of both HR (-22 ± 22.1 vs -3 ± 11.7 beats/minute [bpm]; P = 0.045) and BP (-22 ± 17.4 vs - 2 ± 11.8; P = 0.036) in swallow syncope patients than in controls. Further, in swallow syncope patients the time to lowest HR and BP differed (9 ± 5.5 vs 19 ± 7.2 seconds; P = 0.02), suggesting that both cardioinhibitory (CI) and vasodepressor (VD) mechanisms are present but operate independently. Other autonomic studies were normal in swallow syncope patients except for CSM pause more than 3 seconds in two patients. CONCLUSION: Swallow syncope is associated with transient and temporally independent CI and VD features, consistent with reflex syncope. Potentially, a swallowing test during autonomic evaluation may be useful to unmask relative magnitudes of CI and VD responses, thereby facilitating treatment strategy decisions.

ECG electrode reversals: An opportunity to learn from mistakes.

An ECG with an "odd" appearance may raise the suspicion that ECG recording electrodes may have been reversed. Odd appearances include unexpected Q-waves or R-waves, markedly isoelectric leads, and abrupt changes from previous ECGs. A few examples of ECG electrode reversal provide the opportunity to review some fundamental principles of ECG recording. Some ECG electrode reversals will invert the QRS complex recorded in a lead. Other ECG leads may be affected in a manner that initially may seem unexpected. These patterns may be understood upon reviewing the genesis of the "unipolar" leads, particularly the "augmented" leads. Recording an ECG between electrodes placed on the two legs will produce a nearly isoelectric tracing. Elucidation of electrode reversals is often less difficult than it seems, may present an enjoyable intellectual challenge, and provides insight into the process of ECG recording.

Ambulatory diagnostic ECG monitoring for syncope and collapse: An assessment of clinical practice in the United States.

INTRODUCTION: Diagnostic ambulatory electrocardiogram (AECG) monitoring is widely used for evaluating syncope and collapse, and practice guidelines provide recommendations regarding optimal AECG device selection. However, whether physicians utilize AECGs in accordance with the pertinent guidelines is unclear. This study assessed utilization of AECG monitoring systems for syncope and collapse diagnosis by physicians in the United States. METHODS AND RESULTS: A quantitative survey was undertaken of physicians comprising multiple specialties (emergency department, n = 35; primary care, n = 35; hospitalists, n = 30; neurologists, n = 30; nonimplanting, n = 34, and implanting-cardiologists, n = 35). Depending on specialty, respondents reported that neural-reflex and orthostatic causes accounted for 17-23%, cardiac causes for 12-20%, and "neurological causes" (specifically psychogenic pseudo-syncope/pseudo-seizures and acute cerebrovascular conditions) for 7-12% of their syncope/collapse cases. The choice of AECG technology varied by specialty. Thus, despite patients having daily symptoms, 25% of respondents chose an AECG technology other than a Holter-type monitor. Conversely, when monitoring for infrequent events (e.g., less than monthly), 12-18% indicated that they would choose a 24- to 48-hour Holter, 20-34% would choose either a conventional event recorder or a mobile cardiac telemetry system, and only 53-65% would select an insertable cardiac monitor. CONCLUSIONS: In evaluation of syncope/collapse, most U.S. clinicians across specialties use AECGs appropriately, but in a substantial minority there remains discordance between choice of AECG technology and guideline-based recommendations.

Cardiac pauses in competitive athletes: a systematic review examining the basis of current practice recommendations.

AIMS: It is generally recommended that individuals aspiring to competitive sports should undergo pre-participation cardiovascular assessment, particularly including arrhythmia risk evaluation. In regard to bradyarrhythmias, the 36th Bethesda Conference suggested that asymptomatic cardiac pauses ≤3 s are 'probably of no significance', whereas longer 'symptomatic' pauses may be abnormal. This study focused on assessing the evidence for the '3 s' threshold. METHODS: A systematic literature search was undertaken including Embase (1980-) and Ovid Medline (1950-). The following MeSH terms were used in the database searches: Cardiac.mp & pause.mp. Additionally, pertinent publications found by review of citation lists of identified publications were examined. Individuals with reversible causes of bradyarrhythmia (e.g. drugs) were excluded. RESULTS: The study population comprised 194 individuals with cardiac pauses of 1.35-30 s. In 120 athletes, specific records for pause durations were provided, but it was not always clear whether pauses occurred at rest. Among these 120 athletes, 106 had pauses ≤3 s, of whom 92 were asymptomatic and 14 were symptomatic. Fourteen athletes had pauses >3 s, of whom nine were asymptomatic and five were symptomatic. There were no deaths during follow-up (7.46 ± 5.1 years). With respect to symptoms, the ≤3 s threshold had a low-positive predictive value (35.7%) and low sensitivity (26.3%), but good negative predictive value (86.7%) and specificity (91%). CONCLUSION: While the evidence is not incontrovertible, the 3 s pause threshold does not adequately discriminate between potentially asymptomatic and symptomatic competitive athletes, and alone should not be used to exclude potential competitors.

R-wave sensing in an implantable cardiac monitor without ECG-based preimplant mapping: results from a multicenter clinical trial.

INTRODUCTION: Reducing the form factor of an implantable cardiac monitor (ICM) may simplify device implant. This study evaluated R-wave sensing at a range of electrode distances and a preferred device implant location without mapping. METHODS: Patients scheduled for a Medtronic Reveal® ICM implant (Medtronic Inc., Minneapolis, MN, USA) underwent a preimplant pocket recording using a diagnostic recording catheter. The ICM implant location was left to the discretion of the implanting physician, but a "recommended" position spanned the V2 -V3 electrocardiogram electrode location in an oblique 45° angle. R-wave amplitudes were analyzed from ICM follow-up. RESULTS: Seventeen of 41 subjects (15 male, age 57 ± 16 years) had the maximum surface-filtered R-wave at the recommended location. Fourteen patients underwent diagnostic recording across the range of electrode spacing. There was a strong correlation between the R-wave amplitude and electrode distance (r(2) = 0.97, P < 0.001) with an increase of 29 µV per 2.5 mm. Comparing normalized R-wave distributions between the recommended ICM implant group (Group 1, n = 19) and the remaining patients (Group 2, n = 7), the proportion of ICM R-wave counts of amplitude 0.25-1.2 mV was higher (79% vs 46%, P < 0.05). Of 17 patients in Group 1 who had ≥ 1-month ICM follow-up (79 ± 45 days), no sensing-related false arrhythmia detection was found in 16 (93%) patients. CONCLUSIONS: The subcutaneous R-wave amplitude correlates with electrode spacing in the implant zone of ICM patients. Implant locations at the V2 -V3 position at a 45° angle offer an adequate R wave for sensing. Preimplant mapping to achieve acceptable R-wave amplitude may not be necessary.

The prevalence of sinus rhythm in patients with "permanent" atrial fibrillation.

BACKGROUND: The term "permanent" atrial fibrillation (AF) is generally used to describe the rhythm status of patients for whom cardioversion has failed or attempts to restore normal sinus rhythm (NSR) have ceased. However, the rhythm status of such patients is typically assessed by symptoms or intermittent monitoring, and therefore categorization may be imprecise. METHODS: We evaluated the presence of NSR among patients who were identified by their physicians as having permanent AF and who underwent prior insertion of a cardiac rhythm management device in the OMNI study. Patients with a dual- or triple-chamber device (pacemaker, implantable cardiac defibrillator, or cardiac resynchronization therapy) and ≥30 days of device data were studied. We tabulated the percentage of follow-up days spent entirely in NSR, entirely in AF, or in both NSR and AF. RESULTS: A total of 69 patients met inclusion criteria and were followed for 767 ± 479 days. More than 73% of patients experienced ≥1 entire day in NSR. On average, 38.2% of days were spent entirely in NSR, 11.8% of days were spent in a combination of NSR and AF, and only 50.0% of days were spent entirely in AF. The median daily AF burden during follow-up was 14.6 [1.1-23.7] hours/day. CONCLUSIONS: NSR is common in many device patients thought to have permanent AF, suggesting that continuous arrhythmia monitoring could be useful in identifying permanent AF patients who may benefit from renewed rhythm control efforts. Alternatively, some permanent AF patients undergoing atrioventricular nodal ablation may benefit from dual-chamber devices due to likely periods of NSR.

Ambulatory ECG monitoring for syncope and collapse in United States, Europe, and Japan: The patients' viewpoint.

BACKGROUND: Practice guidelines provide clinicians direction for the selection of ambulatory ECG (AECG) monitors in the evaluation of syncope/collapse. However, whether patients' understand differences among AECG systems is unknown. METHODS AND RESULTS: A survey was conducted of USA (n = 99), United Kingdom (UK)/Germany (D) (n = 75) and Japan (n = 40) syncope/collapse patients who underwent diagnostic AECG monitoring. Responses were quantitated using a Likert-like 7-point scale (mean ± SD) or percent of patients indicating a Top 2 box (T2B) for a particular AECG attribute. Patient ages and diagnosed etiologies of syncope/collapse were similar across geographies. Patients were queried on AECG attributes including the ability to detect arrhythmic/cardiac causes of collapse, instructions received, ease of use, and cost. Patient perception of the diagnostic capabilities and ease of use did not differ significantly among the AECG technologies; however, USA patients had a more favorable overall view of ICM/ILRs (T2B: 42.4%) than did UK/D (T2B: 28%) or Japan (T2B: 17.5%) patients. Similarly, US patient rankings for education received regarding device choice and operation tended to be higher than UK/D or Japan patients; nevertheless, at their best, the Likert scores were low (approximately 4.7-6.0) suggesting need for education improvement. Finally, both US and UK/D patients were similarly concerned with ICM costs (T2B, 31% vs 20% for Japan). CONCLUSIONS: Patients across several geographies have a similar but imperfect understanding of AECG technologies. Given more detailed education the patient is likely to be a more effective partner with the clinician in establishing a potential symptom-arrhythmia correlation.

Neurohormones in the Pathophysiology of Vasovagal Syncope in Adults.

Vasovagal syncope (VVS) is the most common cause of syncope across all age groups. Nonetheless, despite its clinical importance and considerable research effort over many years, the pathophysiology of VVS remains incompletely understood. In this regard, numerous studies have been undertaken in an attempt to improve insight into the evolution of VVS episodes and many of these studies have examined neurohormonal changes that occur during the progression of VVS events primarily using the head-up tilt table testing model. In this regard, the most consistent finding is a marked increase in epinephrine (Epi) spillover into the circulation beginning at an early stage as VVS evolves. Reported alterations of circulating norepinephrine (NE), on the other hand, have been more variable. Plasma concentrations of other vasoactive agents have been reported to exhibit more variable changes during a VVS event, and for the most part change somewhat later, but in some instances the changes are quite marked. The neurohormones that have drawn the most attention include arginine vasopressin [AVP], adrenomedullin, to a lesser extent brain and atrial natriuretic peptides (BNP, ANP), opioids, endothelin-1 (ET-1) and serotonin. However, whether some or all of these diverse agents contribute directly to VVS pathophysiology or are principally a compensatory response to an evolving hemodynamic crisis is as yet uncertain. The goal of this communication is to summarize key reported neurohumoral findings in VVS, and endeavor to ascertain how they may contribute to observed hemodynamic alterations during VVS.

An unyielding valve leading to venous spasm during pacemaker implantation: a case report.

BACKGROUND: Subclavian venous spasm is an uncommon complication during permanent pacemaker implantation. The exact aetiology of subclavian venous spasm is not clear but has been suggested to be due to either mechanical irritation of the vein during needle puncture or due to chemical irritation from contrast injection. Here, we report a case of an unyielding subclavian vein valve that impeded guidewire advancement and the repeated guidewire manipulation led to venous spasm. CASE SUMMARY: A 45-year-old woman with a history of surgical repair of Tetrology of Fallot in childhood presented with symptomatic bifascicular block and underwent a permanent pacemaker implantation. A subclavian venogram done prior to the procedure showed a prominent valve in the distal portion of the vein. Following venous puncture, guidewire advancement was impeded by the prominent valve. The resulting guidewire manipulation led to subclavian venous spasm necessitating a medial subclavian venous puncture and access. DISCUSSION: Prolonged mechanical irritation of the vein during pacemaker implantation may lead to venous spasm impeding pacemaker implantation. Early identification of an impeding valve and obtaining access medial to the valve may help prevent this uncommon complication.

Increased impedance to inspiration ameliorates hemodynamic changes associated with movement to upright posture in orthostatic hypotension: a randomized blinded pilot study.

BACKGROUND: Movement to upright posture may result in marked drop of blood pressure with susceptibility to injury from syncope and falls in patients with orthostatic hypotension. OBJECTIVE: The purpose of this study was to determine if increasing negative intrathoracic pressure by using an inspiratory impedance threshold device before change of posture diminishes blood pressure fall by enhancing venous return. METHODS: Eighteen healthy subjects and 22 orthostatic hypotension patients were randomized to either an active (impedance 7 cmH2O) or sham (no inspiratory impedance) impedance threshold device. Arterial blood pressure, heart rate, and estimated stroke volume and total peripheral resistance were recorded in the supine and upright postures using a noninvasive finger arterial blood pressure monitor. After a rest period, the alternate impedance threshold device (sham or active) was tested in each individual. RESULTS: Compared with the sham impedance threshold device test, the active impedance threshold device resulted in significant reduction in the magnitude of upright posture-induced fall in blood pressure and a greater increase of total peripheral resistance after standing in both healthy subjects and orthostatic hypotension patients. Stroke volume was not measurably altered. Among all subjects who exhibited a postural blood pressure drop >10 mmHg on the day of study, active impedance threshold device treatment consistently blunted blood pressure fall during the initial 100 seconds after standing (<0.04). Induced orthostatic symptoms were less severe with the active impedance threshold device both at onset of upright posture and during 30 seconds of standing. CONCLUSION: Enhancing impedance to inspiration may prove useful as adjunctive therapy for diminishing symptoms associated with movement to upright posture in individuals with orthostatic hypotension.

Arrhythmias in Patients with Cardiac Implantable Electrical Devices after Implantation of a Left Ventricular Assist Device.

Utilization of continuous-flow left ventricular assist devices (CF-LVADs) for advanced heart failure is increasing, and the role of cardiac implantable electrical devices (CIED) is unclear. Prior studies of the incidence of arrhythmias and shocks are frequently limited by ascertainment. One hundred and seventy-eight patients were examined with a previous CIED who were implanted with a CF-LVAD. Medical history, medications, and CIED data from device interrogations were gathered. A cardiac surgery control group (n = 38) was obtained to control for surgical factors. Several clinically significant events increased after LVAD implantation: treated-zone ventricular arrhythmias (VA; p < 0.01), monitored-zone VA (p < 0.01), antitachycardia pacing (ATP)-terminated episodes (p < 0.01), and shocks (p = 0.01), although administered shocks later decreased (p < 0.01). Presence of a preimplant VA was associated with postoperative VA (odds ratio [OR]: 4.31; confidence interval [CI]: 1.5-12.3, p < 0.01). Relative to cardiac surgery, LVAD patients experienced more perioperative events (i.e., monitored VAs and shocks, p < 0.01 and p = 0.04). Neither implantable cardioverter defibrillator (ICD) shocks before implant nor early or late postimplant arrhythmias or shocks predicted survival (p = 0.07, p = 0.55, and p = 0.55). Our experience demonstrates time-dependent effects on clinically significant arrhythmias after LVAD implantation, including evidence that early LVAD-related arrhythmias may be caused by the unique arrhythmogenic effects of VAD implant.

Blunted Chronotropic Response to Hypotension in Cough Syncope.

OBJECTIVES: This study compared hemodynamic and chronotropic responses to cough in cough syncope (CS) patients to those in control subjects. BACKGROUND: Cough syncope is an uncommon form of situational fainting variously attributed to both reflex and mechanical causes. We hypothesized that if baroreflex responses contribute to CS, post-cough hypotension should be associated with cardioinhibition comparable to that observed in other reflex faints. METHODS: The study population consisted of 8 CS patients (group 1), 21 patients with vasovagal syncope (group 2), and 6 patients with nonvertiginous "lightheadedness" (group 3). Testing with patients seated included volitional coughing that achieved a transient blood pressure (BP) of ≥200 mm Hg. Beat-to-beat blood pressure (systolic blood pressure [SBP]) before cough, minimum cough-induced SBP and heart rate (HR) (beats/min) after cough, and HR change during cough-induced hypotension were recorded, along with SBP recovery time from SBP nadir after cough. RESULTS: Compared to controls, cough-induced SBP drop was greater in CS patients (CS patients: -48 ± 13.1 mm Hg vs. -29 ± 11.2 mm Hg for group 2 controls; p = 0.005; or -25 ± 10 mm Hg in group 3 controls; p = 0.02), and recovery time was longer (CS: 46 ± 19 s vs. 11 ± 3.6 s in group 1 controls; p = 0.002; or 12 ± 5 s in group 3 controls; p = 0.01). Furthermore, despite greater induced hypotension, post-cough chronotropic response was less in CS patients (+15% above baseline rate) than in either group 2 (+31% above baseline rate; p < 0.001) or group 3 (+28%; p = 0.01) controls. CONCLUSIONS: In CS patients, post-cough chronotropic response is blunted compared to that in controls despite greater cough-induced hypotension favoring baroreflex cardioinhibition contribution to the pathophysiology of cough syncope.

Usefulness of Atrial Fibrillation as a Marker for Adverse Cardiovascular Outcomes in Both Primary and Secondary Prevention in Patients With Implantable Cardioverter-Defibrillators.

Whether the risk factors for cardiovascular (CV) outcomes are different in primary versus secondary prevention implantable cardioverter-defibrillator (ICD) patients is unclear. We sought to identify predictors of CV outcomes in ICD recipients for primary (G1) versus secondary prevention (G2). Consecutive patients who had ICD implanted during August 2005 to December 2009 were included. The primary outcome was a composite of appropriate shock, acute coronary syndrome, ischemic stroke, coronary revascularization, heart failure exacerbation, CV hospitalization, or all-cause death. We used Cox proportional hazards model and a stepwise selection method to fit the most parsimonious model to predict the primary outcome in all patients and separately for G1 and G2 patients. We followed 223 (184 G1 and 39 G2, mean age 61 years) patients through December 31, 2012; 141 (63.2%) developed the primary outcome. In all patients, atrial fibrillation (AF; hazard ratio 6.72, 95% CI 4.20 to 10.75; p <0.001), use of antiarrhythmic drug (1.55, 1.02 to 2.36; p = 0.04), and lower estimated glomerular filtration rate (0.99, 0.98 to 0.997; p = 0.01) were associated with increased risk of the primary outcome; the attributable risks were 21.6%, 16.0%, and 15.9%, respectively. In G1, AF, hypertension, and lower estimated glomerular filtration rate were associated with increased risk, whereas in G2, AF, use of antiarrhythmic drug, and nonischemic cardiomyopathy were associated with increased risk. In conclusion, although risk factors are different for primary and secondary prevention patients, AF is a strong and consistent risk factor for adverse outcomes in both populations.

Comparison of ventricular arrhythmia frequency in patients with ischemic cardiomyopathy versus nonischemic cardiomyopathy treated with implantable cardioverter defibrillators.

Implantable cardioverter defibrillators have been shown to provide similar survival benefits for patients who have left ventricular dysfunction due to ischemic heart disease and for subsets of patients who have nonischemic cardiomyopathy. Findings in this study extend these observations by showing that patients who have ischemic or nonischemic heart disease and receive implantable cardioverter defibrillators not only have comparable mortality rates but also similar tachyarrhythmia frequencies during follow-up; further, mortality and tachyarrhythmia outcomes are independent of initial arrhythmia indication.

Effect of cough on heart rate and blood pressure in patients with "cough syncope".

BACKGROUND: "Cough syncope" is uncommon, and its mechanism remains controversial. OBJECTIVES: This study evaluated susceptibility to cough-triggered neural reflex hypotension-bradycardia among cough syncope patients. We hypothesized that individuals with cough syncope would manifest not only more profound cough-triggered hypotension than do other fainters but also an inappropriate chronotropic response accompanying cough-induced hypotension, thereby supporting the notion that a neural reflex hypotension-bradycardia contributes to the condition. METHODS/RESULTS: Three patient groups were studied. Group 1 patients (n = 9) had "cough syncope." The remaining patients had recurrent faints of other causes: group 2 (n = 13) had a positive head-up tilt test, and group 3 (n = 18) had a negative tilt test. With cough, group 1 patients exhibited a greater drop in systolic pressure (-51 +/- 19.3 mmHg) than did either group 2 (-23 +/- 11.1 mmHg, P < .04) or group 3 patients (-28 +/- 12.4 mmHg, P < .05). Recovery time to normalization of systolic pressure was greater in group 1 (25 +/- 9.1 seconds) than in group 2 or 3 (8 +/- 2.7 seconds and 9 +/- 6.1 seconds, respectively, both P < .01 vs group 1). The expected positive chronotropic response accompanying cough-induced hypotension was diminished in group 1 patients (0.16 +/- 0.21 bpm/mmHg) compared with that in either group 2 (0.74 +/- 0.60 bpm/mmHg, P < .05 vs group 1) or group 3 (0.33 +/- 0.15 bpm/mmHg, P = .06 vs group 1). CONCLUSION: Cough syncope patients not only exhibit more pronounced hypotension in response to cough than other fainters, but they also manifest an inappropriate cough-triggered blood pressure-heart rate relationship. These findings argue in favor of the importance of a neurally mediated reflex contribution to symptomatic hypotension in cough syncope.

Time course of appropriate implantable cardioverter-defibrillator therapy and implications for guideline-based driving restrictions.

BACKGROUND: American Heart Association/Heart Rhythm Society recommendations restrict driving in implantable cardioverter-defibrillator patients for 6 months after implant for secondary prevention or primary prevention with an appropriate therapy (antitachycardia pacing or shock) for ventricular arrhythmias (VA). OBJECTIVE: The purpose of this study was to analyze implantable cardioverter-defibrillator therapy data to inform guideline recommendations on driving. METHODS: The OMNI Registry was queried for VA and assessed for the time course of appropriate therapies. A blind events committee adjudicated events. The Kaplan-Meier method was used to estimate event rates. A 7-day blanking period was used for each event of interest. RESULTS: A total of 2262 patients (mean age 67 ± 12 years; mean left ventricular ejection fraction 28%) were enrolled; 1659 (73%) were men, and 1666 (74%) were implanted for primary prevention. Overall, 628 of 2255 patients (28%) received ≥1 appropriate therapy. The probability of receiving a subsequent appropriate therapy increased and occurred in a shorter time interval with each appropriate therapy. At 6 months, the likelihood of receiving a shock when the first VA was terminated by shock (30.0%) was 3 times the risk when the first VA was terminated by antitachycardia pacing (9.9%). CONCLUSION: Each appropriate VA therapy is associated with an increased risk of a subsequent event that occurs, on average, in a time frame shorter than current guideline-based restrictions. A differential risk of shock is noted in those receiving antitachycardia pacing vs shock for the first appropriate VA. These findings may help to inform future clinical guideline and practice decisions related to driving.

Comparison of catecholamine response during tilt-table-induced vasovagal syncope in patients <35 to those >65 years of age.

This study compared alterations in arterial catecholamine concentrations associated with tilt-induced vasovagal syncope that differed in older (>65 years) and younger patients (<35 years). Older patients with tilt-positive tests tended to exhibit higher baseline epinephrine (E) concentrations and lesser E surge before development of syncope than younger patients (<35 years), whereas both groups manifested comparable norepinephrine (NE) responsiveness.

Comparison of automatic and patient-activated arrhythmia recordings by implantable loop recorders in the evaluation of syncope.

The implantable loop recorder (ILR) has become an important tool for evaluating patients with recurrent syncope. Second generation ILRs have the ability to record events either automatically (auto activated) or by manual activation (patient activated). In an attempt to evaluate the relative utility of the auto-activation feature, this study stratified ILR events based on a grading system designed to classify detected arrhythmias in terms of the likelihood that they provide a diagnostic basis for syncope. Data from 50 patients (27 men, mean age 64 +/- 22 years) who underwent ILR implantation for investigation of recurrent syncope were assessed. The arrhythmia syncope grading system used 5 levels, ranging from grade 0 (rhythm recorded during syncope) to grade IV (rhythm unlikely to provide a diagnostic basis for syncope). Thirty-six patients (72%) demonstrated > or =1 auto-activated or patient-activated recording during a follow-up of 14.3 +/- 7.9 months. Of the total of 529 recordings, 223 (194 after auto activation [86.9%]) from 30 patients showed a rhythm abnormality. Auto activation was more effective for documenting arrhythmias that were recorded during syncope or those with highest probability of providing a syncope diagnosis (grade 0 or I arrhythmias: auto activated, 19 patients, patient activated, 3 patients). Times from ILR implantation to first grade 0 and grade I arrhythmias were 13.4 and 7.8 months, respectively. The ILR auto-activation feature proved effective in providing a high probability basis for syncope (196 arrhythmia recordings [87.1%] in 27 patients) and enhanced the diagnostic effectiveness of the device compared with patient activation alone (29 arrhythmia recordings [12.9%] in 6 patients).