Diagnosis and natural history of syncope and the role of invasive electrophysiologic testing

Syncope in Patients with Organic Heart Disease

Patients with syncope and organic heart disease remain a small but important subset of those patients who experience transient loss of consciousness. These patients require thoughtful and complete evaluation in an attempt to better understand the mechanism of syncope and its relationship to the underlying disease, and to diagnose and treat both properly. The goal is to reduce the risk of further syncope, to improve long-term outcomes with respect to arrhythmic and total mortality, and to improve patients' quality of life.

Sudden death risk in syncope: the role of the implantable cardioverter defibrillator

Syncope is generally benign but when it is due to an underlying cardiovascular condition, the prognosis can be guarded. Patients with syncope may be at risk of dying suddenly from a ventricular arrhythmia especially if the collapse is caused by a poorly-tolerated, self-terminating, ventricular tachycardia (VT). If a similar VT recurs, and persists, it could initiate cardiac arrest, leading to sudden cardiac death. However, distinguishing which patient with syncope may benefit most from implantable cardioverter defibrillator (ICD) therapy, which can stop life-threatening and poorly tolerated VT, thereby preventing sudden cardiac death, remains an ongoing challenge. Careful assessment of the patient's underlying cardiovascular conditions, scrupulous attention to historical detail to assess potential causes for syncope, and risk stratification based upon clinical characteristics and short and long-term risks can help. This review focuses on the sudden death risk in patients with syncope and explores the role of the ICD to treat ventricular arrhythmias, prevent symptoms, and prevent death.

Psychogenic syncope? A cautionary note

INTRODUCTION

In some patients with recurrent syncope, the etiology may remain unclear despite extensive evaluation. These patients may sometimes be labeled as having a "psychogenic" cause for their syncope.

METHODS

We report on three patients with recurrent unexplained syncope (despite extensive evaluation) who were labeled as having a psychogenic cause for their events. In each patient following placement of an implantable loop recorder, their syncopal events were found to be due to periods of prolonged asystole and/or complete heart block. One patient had prolonged asystole for 44 seconds. In each patient, episodes of syncope were eliminated following permanent pacemaker implantation.

CONCLUSION

We conclude that physicians should exercise great caution before labeling any patient's syncope as psychogenic and that prolonged monitoring may be necessary to exclude a potential cardiac rhythm-related etiology.

Utility of implantable loop recorders for diagnosing unexplained syncope in clinical practice

BACKGROUND

Establishing a symptom-rhythm correlation in patients with unexplained syncope is complicated because of its sporadic, infrequent, and unpredictable nature. Prolonged monitoring with an implantable loop recorder (ILR) allows the recording of electrocardiogram (ECG) data from a spontaneous syncopal event.

HYPOTHESIS

The aim of this study was to evaluate the usefulness of the ILR for the diagnosis of syncope of unknown origin after conventional management in clinical practice.

METHODS

We reviewed the results with ILR implantation in patients with syncope of unknown origin after conventional management in the cardiology department at HU Marques de Valdecilla (Santander, Cantabria, Spain).

RESULTS

One hundred and forty patients (age 64 +/- 16 y; 86 male [62%]) with syncope of unknown etiology after conventional work-up underwent prolonged monitoring with an ILR from September 1998 to February 2006; 46 patients (33%) had structural heart disease. During a mean follow-up of 346 +/- 160 d, 51 patients (36.5%) had recurrent syncope with diagnostic ECG recording. An arrhythmic cause for syncope was found in 33 of them (64.5%), with bradycardia present in 27 (53%) and tachycardia in 6 (11%). There were no sudden deaths, and 1 patient suffered a complication related to a recurrence of syncope.

CONCLUSION

Long-time experience with the ILR confirmed the utility of this device in the diagnosis of unexplained syncope in clinical practice. Most of these patients had syncope of arrhythmogenic etiology that could be successfully treated. This strategy of prolonged monitoring is safe even in patients with structural heart disease.

The use of monitoring strategies in patients with unexplained syncope

Syncope is a complex clinical syndrome with multiple etiologies that can be very difficult to diagnose. The major obstacles to diagnosis are the periodic and unpredictable nature of events and the high spontaneous remission rate. Short-term electrocardiographic monitoring is often unproductive in patients when initial non-invasive testing is negative, particularly when a paroxysmal arrhythmia is suspected. The external and implantable loop recorders extend the ability to monitor cardiac patients, enhancing the diagnostic yield to as high as 85% in difficult to diagnose syncope. Several recent studies suggest that prolonged monitoring with an implantable loop recorder has a role in patients with syncope and conduction disturbances, negative tilt testing, unexplained seizures and may be superior to conventional testing with tilt and electrophysiologic studies in selected patients.

Use of the implantable loop recorder in evaluation of patients with unexplained syncope

Syncope is a complex symptom with multiple potential etiologies that can be difficult to establish. The major obstacles to diagnosis are the periodic and unpredictable nature of events and the high spontaneous remission rate. Short-term ECG monitoring often is unproductive when initial noninvasive testing is negative due to the low probability of recurrence during the brief monitoring period. Implantable loop recorders extend the ability to monitor cardiac patients, enhancing the diagnostic yield to as high as 85% in difficult to diagnose syncope. Several recent studies suggest that prolonged monitoring with an implantable loop recorder has a role in patients with syncope and conduction disturbances, negative tilt testing, and unexplained seizures, and may be superior to conventional testing with tilt and electrophysiologic studies.

Cost implications of testing strategy in patients with syncope: randomized assessment of syncope trial

OBJECTIVES

We sought to assess the cost implications of two investigation strategies in patients with unexplained syncope.

BACKGROUND

Establishing a diagnosis in patients with unexplained syncope is complicated by infrequent and unpredictable events. The cost-effectiveness of immediate, prolonged monitoring as an alternative to conventional diagnostic strategies has not been studied.

METHODS

Sixty patients (age 66 +/- 14 years; 33 males) with unexplained syncope and LV ejection fraction >35% were randomized to conventional testing with an external loop recorder, tilt and electrophysiologic (EP) testing, or prolonged monitoring with an implantable loop recorder with one-year monitoring. If patients remained undiagnosed after their assigned strategy, they were offered a crossover to the alternate strategy. Cost analysis of the two testing strategies was performed.

RESULTS

Fourteen of 30 patients who were being monitored were diagnosed at a cost of 2,731 Canadian dollars +/- 285 Canadian dollars per patient and 5,852 Canadian dollars +/- 610 Canadian dollars per diagnosis. In contrast, only six of 30 conventional patients were diagnosed (20% vs. 47%, p = 0.029), at a cost of 1,683 Canadian dollars +/- 505 Canadian dollars per patient (p < 0.0001) and 8,414 Canadian dollars +/- 2,527 Canadian dollars per diagnosis (p < 0.0001). After crossover, a diagnosis was obtained in 1 of 5 patients undergoing conventional testing, compared with 8 of 21 patients who completed monitoring (20% vs. 38%, p = 0.44). Overall, a strategy of monitoring followed by tilt and EP testing was associated with a diagnostic yield of 50%, at a cost of 2,937 Canadian dollars +/- 579 Canadian dollars per patient and 5,875 Canadian dollars +/- 1,159 Canadian dollars per diagnosis. Conventional testing followed by monitoring was associated with a diagnostic yield of 47%, at a greater cost of 3,683 Canadian dollars +/- 1,490 Canadian dollars per patient (p = 0.013) and a greater cost per diagnosis (7,891 Canadian dollars +/- 3,193 Canadian dollars, p = 0.002).

CONCLUSIONS

A strategy of primary monitoring is more cost-effective than conventional testing in establishing a diagnosis in recurrent unexplained syncope.

Evaluating elderly patients with syncope

Age-related physiologic changes together with high prevalence of chronic illness and the use of multiple medications predispose older adults to syncope. The causes of many of these patients' syncope are unexplained and most remained symptomatic. A thoughtful diagnostic strategy is essential to pinpoint the cause in each patient. The initial assessment includes a comprehensive medical history, preferably with an eye witness account, and a thorough physical examination. The decision for further diagnostic tests often depends on whether there is evidence of underlying structural heart disease. In the absence of heart disease, tilt table testing and the related autonomic function testing are usually most productive. Various cardiac studies will be more appropriate for those with suspected structural heart disease. A cause of syncope can only be concluded if there is a sufficiently strong correlation between syncopal symptoms and the detected abnormalities on investigations. A strategic evaluation of syncope of the elderly subjects should allow a correct diagnosis and appropriate management.

When is intracardiac electrophysiologic evaluation indicated in the older or very elderly patient? Complications rates and data

The use of invasive EPS and catheter ablation is well established for many cardiac rhythm disorders. Because of the high prevalence of arrhythmias, which often are tolerated poorly in the elderly, and the increased frequency of adverse effects of pharmacologic therapy in this population, the potential for benefit from invasive EPS and catheter ablation is great. The notion that elderly patients are at increased risk of complications from invasive EPS is not borne out by available data. Therefore, the suitability of this form of diagnostic and therapeutic approach should be based on the assessment of the individual patient and the clinical context, while taking into consideration patient-specific risks, goals, and expectations in adopting an invasive strategy.

Costs and utility of tests in the evaluation of the pediatric patients with syncope

New diagnostic tests have markedly improved the ability to establish a cause of syncope in pediatric patients, but at a substantial cost. The goal of syncope evaluation should be to diagnose treatable causes and identify patients at high risk for sudden death. The diagnostic utility of commonly used tests is reviewed. Although there are limited data on the application of specific diagnostic tests in the child with syncope, most tests have a low yield in unselected patients. A more directed approach to testing, based on the results of history, physical examination and the electrocardiogram is likely to result in significant cost reduction while still identifying patients with life threatening disorders. Validation of such an approach awaits prospective evaluation.

Randomized assessment of syncope trial: conventional diagnostic testing versus a prolonged monitoring strategy

BACKGROUND

Establishing a diagnosis in patients with unexplained syncope is complicated by infrequent and unpredictable events. Prolonged monitoring may be an alternative strategy to conventional testing with short-term monitoring and provocative tilt and electrophysiological testing.

METHODS AND RESULTS

Sixty patients (aged 66+/-14 years, 33 male) with unexplained syncope were randomized to "conventional" testing with an external loop recorder and tilt and electrophysiological testing or to prolonged monitoring with an implantable loop recorder with 1 year of monitoring. If patients remained undiagnosed after their assigned strategy, they were offered crossover to the alternate strategy. A diagnosis was obtained in 14 of 27 patients randomized to prolonged monitoring compared with 6 of 30 patients undergoing conventional testing (52% versus 20%, P=0.012). Crossover was associated with a diagnosis in 1 of 6 patients undergoing conventional testing compared with 8 of 13 patients who completed monitoring (17% versus 62%, P=0.069). Overall, prolonged monitoring was more likely to result in a diagnosis than was conventional testing (55% versus 19%, P=0.0014). Bradycardia was detected in 14 patients undergoing monitoring compared with 3 patients undergoing conventional testing (40% versus 8%, P=0.005).

CONCLUSIONS

A prolonged monitoring strategy is more likely to provide a diagnosis than conventional testing in patients with unexplained syncope. Consideration should be given to earlier implementation of a monitoring strategy.

Diagnostic evaluation and management of patients with syncope

This article focuses on the evaluation of patients with syncope, a symptom not a disease. Syncope is a transient loss of consciousness associated with loss of postural tone with spontaneous recovery. The authors discuss the utility of an indications for different diagnostic tests, the indications for hospital admission, and the management of patients with certain known causes of syncope, including vasovagal and arrhythmic.

The costs of recurrent syncope of unknown origin in elderly patients

Although syncope has been shown to reduce quality-of-life, its impact on resource costs has not been documented. The objective of this study was to quantify the annual medical costs of caring for elderly patients with syncope, especially recurrent syncope of unknown origin. Administrative data from the Health Care Financing Administration were obtained on 7,959 Medicare patients who had at least one inpatient admission with a diagnosis of syncope in 1993. The costs of any inpatient admissions, outpatient procedures, or physician visits with an ICD-CM-9 diagnosis for syncope were summed for a 365-day period from the date of the initial hospitalization for syncope. Patients who had at least two hospitalizations with admission and discharge diagnosis of syncope were deemed to have recurrent syncope of uncertain origin. To better estimate syncope costs for those whose syncope costs could have been attributed to other diagnoses, a regression analysis was performed including variables representing the most frequent secondary diagnoses. The average annual costs of those who were admitted with syncope but who were discharged with another diagnosis was $4,942 in 1993. The average annual cost of patients with recurrent syncope deemed to be of unknown origin was $5,165. For those patients with secondary diagnoses of atherosclerosis, urinary tract infections, or hypokalemia, the annual costs of syncope averaged $6,820, $7,013, or $7,949, respectively.

The effect of intravenous procainamide on the HV interval at electrophysiologic study

The His bundle electrogram recorded at electrophysiologic study clearly differentiates atrioventricular (AV) node disease from distal conduction system disease. The distal conduction system may be tested further by infusing procainamide (10-15 mg/kg) intravenously. High-grade distal AV block or prolongation of the HV interval <80 ms was defined as an abnormal response to this test. We retrospectively reviewed the medical records of 79 patients who underwent electrophysiologic study with intravenous procainamide. An abnormal response to procainamide was observed in only 3% of 37 patients with a normal baseline HV (</= ms), in 48% of 27 patients with mild HV prolongation (56 to 70 ms), and in all 15 patients with moderate HV prolongation (<70 ms) (P <0.0001 for the trend). Procainamide induced high-grade AV block in 4 of 28 patients (14%) studied for syncope and in 1 of 51 patients (2%) studied for ventricular tachycardia. Syncope as the indication for electrophysiologic study (P = 0.05) and left bundle branch block morphology (P = 0.03) were predictors of high-grade AV block; baseline HV and QTc intervals were significantly prolonged in patients who developed AV block with procainamide. We identified a strong linear correlation (R = 0.85) between post-drug and baseline HV intervals, with a regression slope of 1.17 +/- 0.09 and an intercept (+/- standard error) of 5.8 +/- 5.0 ms. This linear response to procainamide and published prospective studies support pacing syncope patients with baseline HV <70 ms. Therefore, procainamide infusion during the electrophysiologic study of patients with undifferentiated syncope should be reserved for those with mild HV prolongation from approximately 55 to 70 ms.

Contribution of head-up tilt testing and ATP testing in assessing the mechanisms of vasovagal syndrome: preliminary results and potential therapeutic implications

BACKGROUND

In patients with vasovagal syndrome, head-up tilt testing may reproduce symptoms generally associated with vasodepression. Recent research suggests ATP testing identifies patients with abnormal vagal cardiac inhibition. This preliminary study examined the joint contribution of both tests in identifying underlying mechanisms in the general population with vasovagal syndrome.

METHODS AND RESULTS

Both tests were performed in random order during 1 session and outside of predominant sympathetic periods in 72 patients hospitalized for syncope (n=56) or presyncope (n=16) for whom no cardiac or extracardiac cause was found. For passive and isoproterenol-provocative tilt testing by standard protocol, reproduction of symptoms defined a positive test. The ATP test consisted of injecting ATP 20 mg IV at bedside, continuously monitoring ECG and blood pressure; a vagal cardiac pause >10 seconds defined a positive test. For most patients (64%), >/=1 test was positive. Of the 41 patients (57%) with a positive tilt test (either passive or provoked by isoproterenol), 32% had cardiac disease; none had significant bradycardia (<50 bpm). Of the 8 patients (11%) with a positive ATP test, 62% had cardiac disease; the probability of a positive result increased with age (P=0.015). Both tests were positive in 3 patients and negative in 26 patients; the tilt and ATP test results were uncorrelated (P=0.28).

CONCLUSIONS

Results suggest tilt and ATP tests individually and jointly determine the mechanism of vasovagal symptoms in most patients and that vagal cardiac inhibition increases with age.

The high cost of syncope: cost implications of a new insertable loop recorder in the investigation of recurrent syncope

BACKGROUND

Patients with recurrent syncope frequently undergo extensive investigations that consume significant health care resources. Recent advances in long-term monitoring techniques have enhanced diagnostic yield in patients with infrequent symptoms. There is little information on the relative cost-effective profile of the investigative tools used in patients with syncope.

METHODS

Two methods to determine health care costs in patients with syncope were used. In the first, health care resource utilization was determined in 24 patients with recurrent unexplained syncope and negative investigations who underwent insertion of the implantable loop recorder (ILR) during a pilot study of the feasibility of the device. The costs of investigations before, during, and after ILR implantation in each patient were calculated on the basis of median charges for an index investigation and a regression analysis of 1018 US Medicare hospital claims for syncope from 1993. Charges were converted to costs using a cost-to-charge ratio of 0.64. The second method was based on estimated costs per diagnosis and published diagnostic yields of 6 commonly applied tests in patients with syncope. A cohort simulation using theoretic models of 100 patients undergoing investigation for syncope was created to compare the diagnostic yield and cost per diagnosis of various diagnostic cascades.

RESULTS

In the pilot study, the cost of investigation of syncope in the 2 years before ILR insertion was $7584 per patient. After the ILR was inserted, a diagnosis was obtained in 21 of 24 patients (diagnostic yield 88%). The cost of therapy was $2452, followed by a reduction in cost of care to $596 over 30 +/- 10 months of follow-up. In the second method, the diagnostic yield of individual tests ranged from 3% for echocardiography to 88% for the ILR. The cost per diagnosis obtained ranged from $529 for the external loop recorder to $73,260 for electrophysiologic testing in patients without structural heart disease. An approach to syncope similar to that of the ILR pilot study resulted in a cost per diagnosis of $3193 and a diagnostic yield of 98%. Performance of echocardiography in half of the patients and electrophysiologic testing only in the presence of structural heart disease reduced the cost to $2494 and retained a diagnostic yield of 98%.

CONCLUSIONS

The cost of investigation of syncope is high. The ILR may reduce health care resource utilization by providing a diagnosis permitting definitive therapy. The cost per diagnosis profile of current diagnostic tests commonly used in patients with syncope is highly variable. A cost-effective approach to diagnosing this disorder can retain a high diagnostic yield with a reduction in resource utilization compared with a conventional approach.

Clinical significance of syncope in the electrophysiologic study versus electrocardiographic monitoring (ESVEM) trial. The ESVEM Investigators

BACKGROUND

Syncope may portend risk of death, but which patients with syncope are at high risk remains unclear.

OBJECTIVE

The ESVEM trial, a multicenter randomized prospective trial, provided the opportunity to compare mortality rates of patients enrolled with syncope to those enrolled with spontaneous ventricular arrhythmias.

METHODS

Patients enrolled in the ESVEM trial presenting with syncope alone (25 patients) or in combination with ventricular tachycardia (24 patients) were compared with patients with spontaneous ventricular tachycardia alone (332 patients) or ventricular fibrillation (105 patients). All patients had ventricular tachyarrhythmias induced at electrophysiology testing of >/=10 premature ventricular complexes per hour on Holter monitor.

RESULTS

Of all patients randomly assigned, arrhythmic death and total mortality rates were the same for those with syncope alone, with ventricular tachycardia and syncope, with ventricular tachycardia alone, or with ventricular fibrillation. At 1 year, arrhythmic and total mortality rate for all patients was 21% and 24%, respectively; for patients with syncope alone, 30% and 29%, respectively (P = NS). At 4 years, arrhythmic death and total mortality rate for all patients was 33% and 42%, respectively; for patients with syncope alone, 37% and 42%, respectively (P = NS).

CONCLUSION

Syncope, associated with induced ventricular tachyarrhythmias at electrophysiologic testing, indicates high risk for death, similar to that of patients with documented spontaneous ventricular tachyarrhythmias.

Effects of age on outcome of tilt-table testing

Although neurally mediated syncope is thought to be common in the young and rare in the elderly, there are few data evaluating the effects of age on the outcome of tilt-table testing (TTT), especially in patients aged > or =80 years. We examined the results of TTT in 352 subjects with unexplained syncope including 133 patients >65 years of age and 43 patients >80 years of age. The average age was 54 +/- 20.8 years (range 11 to 99) and 51% were men. The TTT protocol included at least 45 minutes of upright tilt in the drug-free state with or without repeat TTT with isoproterenol or 15 minutes of upright tilt in the drug-free state followed by repeat TTT with isoproterenol. One hundred sixty-four subjects (47%) had a positive TTT. As expected, there was an age-related decline in positive TTT. A high proportion of elderly patients with unexplained syncope had a positive TTT (37% of patients aged > or =65, and 23% patients aged > or =80). Thus, TTT is a useful diagnostic test in patients aged > or =65 years with unexplained syncope.

Use of an extended monitoring strategy in patients with problematic syncope. Reveal Investigators

BACKGROUND

The conventional investigation of patients who present with syncope involves short-term ECG monitoring or provocative testing with head-up tilt and electrophysiological testing. A symptom-rhythm correlation is often difficult to obtain during spontaneous syncope because of its sporadic, infrequent, and unpredictable nature.

METHODS AND RESULTS

We used a prolonged monitoring strategy to determine the cause of syncope in 85 patients (age, 59+/-18 years; 44 men) with recurrent undiagnosed syncope with an implantable loop recorder capable of cardiac monitoring for up to 18 months. During a mean of 10.5+/-4.0 months of follow-up, symptoms recurred in 58 patients (68%) 71+/-79 days (2.3+/-2.6 months) after implantable loop recorder insertion. An arrhythmia was detected in 42% of patients who recorded a rhythm during recurrent symptoms, with bradycardia present in 18 and tachycardia in 3. Five of the 18 bradycardic patients and 2 additional sinus rhythm patients received a clinical diagnosis of neurally mediated syncope. Patients who experienced presyncope were much less likely to record an arrhythmia during symptoms compared with recurrence of syncope (24% versus 70%, P=0.0005). There were no adverse events associated with recurrent symptoms, and there were no sudden deaths. Inability to freeze after an event occurred in 8 patients, and pocket infection occurred in 3.

CONCLUSIONS

The strategy of prolonged monitoring is effective and safe in patients with problematic syncope.

[Patients with structural heart disease, syncope of unknown etiology and inducible ventricular arrhythmias treated with implantable defibrillators]

OBJECTIVES

This study evaluates the hypothesis that in patients with syncope of unknown origin and heart anomalies, inducible ventricular arrhythmias are specific arrhythmias and therefore should be treated as such.

BACKGROUND

Although syncope is a frequent clinical entity, the evaluation and treatment of patients with syncope without a clear etiology still remains undefined. Many patients with syncope of undetermined origin undergo invasive electrophysiologic evaluation. Abnormalities of the sinus node, prolongation of conduction times or inducible arrhythmias found during these evaluations are usually assumed to be the cause of syncope, and are consequently treated. However, whether tachyarrhythmias are truly the cause of syncope, and whether treatment of these tachyarrhythmias can prevent recurrent syncope and arrhythmic death, is unknown.

PATIENTS AND METHODS

An electrophysiological study was performed on 160 patients with structural heart disease and syncope of unknown origin. In 23 out of the 160 patients (16%), programmed electrical stimulation induced sustained ventricular arrhythmias. In 18 out of the 23 patients an automatic defibrillator was implanted and they form the study group.

RESULTS

In these 18 patients, programmed ventricular stimulation induced sustained monomorphic ventricular tachycardia in 12, sustained polymorphic ventricular tachycardia in 2 and ventricular fibrillation in 4. During a mean follow-up of 14 months, 9 patients received 81 appropriate therapies from the device (53 because of ventricular tachycardia and 23 because of ventricular fibrillation). The probability of appropriate therapy was 100% at 1 year follow-up. There were no episodes of sudden death and 1 patient died of congestive heart failure.

CONCLUSIONS

In patients with syncope of undetermined origin, heart disease and inducible ventricular tachyarrhythmias treated with a implantable cardioverter defibrillator, there is a high incidence of appropriate therapies. Our results support the practice of using implantable cardioverter defibrillators in patients with syncope of unknown origin, heart disease and inducible ventricular arrhythmias.

Can adenosine 5'-triphosphate be used to select treatment in severe vasovagal syndrome?

BACKGROUND

Selection of treatment in vasovagal syndrome should be guided by the mechanism of symptoms. This study determined whether a simple drug test may assess one mechanism.

METHODS AND RESULTS

To identify patients at risk of severe cardioinhibitory response of vagal origin, we infused 20 mg ATP into 316 patients hospitalized for recurrent syncope (n=195) or presyncope (n=121) of unknown origin and into normal subjects (n=51). We then assessed the ECG and clinical responses to the drug, recommended therapy, and followed up the subjects chronically. A cardiac pause > 10 seconds was seen in only 3 normal subjects (6%). Therefore, a pause < or = 10 seconds yielded the approximately 95th percentile of the normal range. ATP provoked a pause > 10 seconds in 130 symptomatic patients (41%) and a pause < or = 10 seconds in 186 symptomatic patients (59%). Thus, symptomatic patients with pauses > 10 seconds were proposed for pacemaker implantation; all other patients and normal subjects were simply monitored. Among long-pause patients with follow-up, the observed recurrence rate for the 104 with pacemakers was one-third that for the 21 who were only monitored (P<.0001). Among followed-up short-pause patients, the rate in the 153 monitored-only patients did not differ from the 20 implanted patients (P=.432).

CONCLUSIONS

The vagal effect of ATP may identify the subgroup of patients at high risk of severe cardioinhibitory response of vagal origin who likely will benefit from pacemaker therapy. This fast, uncomplicated test should be considered for further use in screening patients with vasovagal syndrome.

Maturation of the sensed electrogram amplitude over time in a new subcutaneous implantable loop recorder

The cause of recurrent syncope may be difficult to determine if the diagnosis is not established from initial noninvasive and invasive testing. Eighteen patients with recurrent syncope and negative tilt table and electrophysiological testing underwent implantation of a left pectoral subcutaneous loop recorder. This device "freezes" the preceding 7.5 or 15 minute rhythm strip after magnet application after spontaneous syncope. Baseline and follow-up electrograms were routinely recorded, and patients were followed until syncope recurred. Three patients had syncope within 1 month of implantation and were excluded from this report. Implantation electrogram amplitude was 250 +/- 124 microV and increased to 291 +/- 114 microV at 2-3 months, and increased further to 353 +/- 167 microV at 4-6 months (P < 0.001, ANOVA). Syncope recurred in 14 of the 15 patients. An arrhythmic basis for syncope was established (n = 7) or excluded (n = 7) in every patient who had recurrent syncope. All syncopal episodes were associated with diagnostic sensed electrograms. The increase in sensed electrogram amplitude over time suggests a maturation of the device-tissue interface. These results support the long-term viability of this implantable monitoring technique.

Value and limitations of noninvasive assessment of syncope

The noninvasive assessment of patients who present with syncope is based on a thorough, complete history and physical examination. The history requires close attention to precipitating events and the description of the spell. Often, patients are poor historians with regard to symptoms leading up to and following the episode of syncope. Therefore, it is important to interview individuals who observed the spell to improve the accuracy of the history and sort out whether or not the spell was due to cardiogenic syncope, vasodepressor syncope, or a neurologic disorder. Carotid sinus massage is a useful procedure that can be performed during the routine physical examination, identifying patients who are at increased risk for carotid sinus syncope because of hypersensitivity of the carotid sinus. The clinician must be careful to attribute the clinical syncope to carotid sinus hypersensitivity only when the spell induced at the time of carotid massage reproduces the clinical spell. Routine laboratory tests are commonly performed, although the blood tests rarely yield information to confirm the cause of syncope. The routine ECG is often helpful identifying abnormalities of rhythm, conduction, or morphology that give a clue as to the cause for the patient's syncope. The most helpful aspect of ECG recording is to obtain a recording during an episode of syncope when exact correlation can be made between the ECG findings and the patient's symptoms. Recording the ECG during the spell can be achieved using 24-hour ambulatory monitoring, an event recorder, or a memory loop recorder. Twenty-four-hour ambulatory monitoring is useful in patients who have frequent spells that would be expected to be recorded during 1 or 2 days of monitoring. These individuals need to have a non-life-threatening spell and therefore be safe to evaluate as an outpatient. The event recorder and loop memory recorder have proved extremely helpful in evaluating spells that occur too infrequently to be recorded by 24-hour or 48-hour ambulatory monitoring. The nature of these recording devices does require that the patient or a companion be able to activate the monitor at the time of symptoms. If a patient experiences syncope but is unable to activate the device, the important information as to what the rhythm was doing at the time of symptoms is lost. The implantable loop recorder should prove to be uniquely advantageous by allowing extended ECG recording with the device activated by the patient or companion recording 20 minutes before and 4 minutes after device activation. Signal-averaged electrocardiography is most helpful in assessing patients with ischemic heart disease with a substrate capable of supporting a reentrant ventricular arrhythmia. This test should be used in combination with other historical or laboratory predictors of arrhythmic events such as history of myocardial infarction or abnormal ventricular function assessed by echocardiography. In this setting, the signal-averaged ECG helps to identify patients at increased risk for ventricular tachycardia as the cause of syncope who thus may benefit from electrophysiologic testing.

Value and limitations of electrophysical testing for syncope

Syncope is by definition a transient event, and its cause has usually resolved by the time the patient is examined. Electrophysiologic testing provides a method for assessing a patient's risk for future arrhythmias based on the known sensitivity and specificity of the analyses of sinus node function, atrioventricular conduction, and responses to programmed atrial and ventricular stimulation. Interpretation of these data must always be made in the context of the patient's total clinical situation.

Recurrent syncope. Experience with an implantable loop recorder

The cause of recurrent syncope is often difficult to determine when initial laboratory investigations are negative. Advances in implantable monitoring technology permit long-term monitoring of the electrocardiogram in patients with recurrent undiagnosed syncope. A pilot device implanted in the left pectoral region established the cardiac rhythm during syncope in all 20 of 24 patients who developed syncope during follow-up. The cause was arrhythmic in 10 and nonarrhythmic in 10. Therapy resulted in resolution of symptoms in 17 of 20 patients. The implantable loop recorder is a promising diagnostic tool for investigation of syncope.

High incidence of appropriate implantable cardioverter-defibrillator therapy in patients with syncope of unknown etiology and inducible ventricular arrhythmias

OBJECTIVES

This study evaluates the hypothesis that in patients with syncope of unknown origin, inducible ventricular arrhythmias are specific arrhythmias and therefore should be appropriately treated.

BACKGROUND

Although syncope is a common clinical entity, the evaluation and treatment of patients with syncope without a clear etiology are not well defined. Many patients with syncope of undetermined origin undergo invasive electrophysiologic evaluation. Abnormalities of the sinus node, prolongation of conduction times or inducible arrhythmias found at these evaluations are usually assumed to be the cause of syncope and are therefore treated. However, whether tachyarrhythmias are truly the cause of syncope, and whether treatment of these tachyarrhythmias can prevent recurrent syncope and arrhythmic death, is unknown.

METHODS

This study included 50 consecutive patients with syncope of undetermined origin, ventricular tachyarrhythmias at electrophysiologic evaluation and treatment with an implantable cardioverter-defibrillator.

RESULTS

Ventricular stimulation led to sustained monomorphic ventricular tachycardia in 36 patients, nonsustained ventricular tachycardia in 5 and ventricular fibrillation in 9. Over a 23 +/- 15-month (mean +/- SD) follow-up period, 18 patients received appropriate implantable cardioverter-defibrillator shock. Actuarial probability of appropriate therapy was 22% at 1 year and 50% at 3 years. Recurrent syncope was seen in five patients, three of whom had appropriate defibrillatory detections at the time of syncope. Four patients died (sudden death in one, congestive heart failure in two).

CONCLUSIONS

In patients with syncope of undetermined origin and inducible ventricular tachyarrhythmias, appropriate implantable cardioverter-defibrillator therapy is common at follow-up. Sudden cardiac death is uncommon. This low incidence of sudden cardiac death and high incidence of appropriate defibrillator therapy support the current practice of using implantable cardioverter-defibrillators in patients with syncope of unknown origin and inducible ventricular arrhythmias.

Is syncope a risk factor for poor outcomes? Comparison of patients with and without syncope

OBJECTIVE

To determine whether syncope, independent of underlying comorbidities, is associated with increased mortality or other cardiovascular outcomes.

PATIENTS AND METHODS

A prospective cohort study of patients with syncope and a group of patients without syncope matched with respect to age, gender, site of care (inpatient/ outpatient) and a cardiac disease index at an urban university medical center. Overall mortality, cardiac mortality, cardiovascular outcomes, and occurrence of syncope within 1 year of study enrollment were compared between the groups with Kaplan-Meier rates and Mantel-Cox statistics.

RESULTS

The characteristics of 470 patients with syncope and the matched patients without syncope were similar except that the patients without syncope had more cardiac diseases than those with syncope (P = 0.002). Patients with and without syncope had similar rates of 1-year overall mortality (9% versus 11%, P = 0.29) and cardiac mortality (3% versus 6%, P = 0.08). In multivariate analyses, syncope was not a significant predictor of overall or cardiac mortality, but male gender, age > 55 years, and congestive heart failure were. One-year rates for other cardiovascular outcomes (myocardial infarction, congestive heart failure, cardiac arrest with survival, and cerebrovascular events) in patients with syncope were similar to those in patients without syncope (P > or = 0.2 for all comparisons). Patients with syncope had a 20.2% recurrence rate in 1 year as compared with a 2.1% rate for new syncope in patients without prior syncope (P < 0.00001).

CONCLUSIONS

Syncope itself is not a risk factor for increased overall and cardiac mortality or cardiovascular events. Underlying heart diseases are risk factors for mortality regardless of whether the patient has syncope or not. The major focus of the evaluation of patients with syncope should be to identify and treat underlying heart diseases.

Significance and prevalence of inducible atrial tachyarrhythmias in patients undergoing electrophysiologic study for presyncope or syncope

The purpose of the study was to report the prevalence of inducible supraventricular tachyarrhythmias (SVTA) in 827 consecutive patients aged 17 to 90 years who did not have spontaneous documented SVTA and who had unexplained presyncope and/or syncope. The electrophysiologic study (EPS) included programmed atrial and ventricular stimulation up to two extrastimuli at three cycle lengths, and the study of sino-atrial and AV conduction. The results were as follows. EPS was normal in 386 patients. Inducible junctional tachycardia or atrial flutter and fibrillation was the only finding in 187 patients (23%). In the remaining patients we found ventricular tachycardia in 103 (12%), heart block in 67 (8%), sick sinus syndrome in 56 (7%) and increased vagal tone in 28 (3%). The presence of an underlying heart disease (47%) and salvos of atrial premature beats on Holter monitoring (39%) were significantly correlated with the induction of SVTA. However, the comparison with similar groups without syncope indicates that only the induction of SVTA in patients with hypertrophic cardiomyopathy and mitral valve prolapse was significantly correlated with the history of syncope. In patients without heart disease or with prior myocardial infarction or decreased left ventricular function, the induction of SVTA, which is not associated with hypotension in the supine position, could require an induction after head-up tilting, because of the lack of specificity of programmed stimulation in these patients. Programmed atrial stimulation should be systematically performed in patients with unexplained syncope, in particular in those with hypertropic cardiomyopathy and mitral valve prolapse, who require a specific treatment, if a SVTA is induced. In other patients the results of programmed atrial stimulation should be interpreted cautiously.

The etiology of syncope in patients with negative tilt table and electrophysiological testing

BACKGROUND

Patients with syncope of unknown etiology after negative noninvasive and electrophysiological testing may suffer from recurrent disability. Syncopal episodes are often too infrequent and unpredictable for detection by conventional ambulatory monitoring techniques.

METHODS AND RESULTS

A long-term subcutaneous monitoring device was implanted in patients with negative ambulatory monitoring, tilt table and electrophysiological testing to establish cardiac rhythm during spontaneous syncope. Sixteen patients aged 57 +/- 19 years with a mean of 8.4 +/- 4.4 previous episodes of syncope underwent device implantation. Fifteen patients (94%) had recurrent syncope 4.4 +/- 4.2 months after implantation. The remaining patient has not had recurrent syncope and continues to be followed. A diagnosis was obtained in every patient who had recurrent episode. Syncope was secondary to sinus arrest in 5, atrioventricular block in 2, ventricular tachycardia in 1, supraventricular tachycardia in 1, and nonarrhythmic in 6. Successful therapy was implemented in all 15 patients, without recurrence of syncope during 13.0 +/- 8.4 months of follow-up.

CONCLUSIONS

Unexplained syncope in patients with negative investigations has a broad spectrum of etiologies, the most common of which is bradycardia. An implantable long-term monitoring device is useful for establishing a diagnosis when symptoms are recurrent but too infrequent for conventional monitoring techniques.

Workup and management of patients with syncope

Syncope accounts for approximately 1% to 6% of hospital admissions and 3% of emergency room visits. Syncope is defined as a sudden transient loss of consciousness associated with a loss of postural tone with spontaneous recovery. Patients should not require electrical or chemical cardioversion to regain consciousness. Syncope must be clinically differentiated from other states of altered consciousness, such as dizziness, vertigo, seizures, coma, and nacrolepsy.

Electrophysiologic study in chronic Chagas' heart disease

Cardiac arrhythmias are common in chagasic patients. Electrophysiologic study is an invasive procedure for the investigation of sinus node function, atrioventricular node conduction and intraventricular (His-Purkinje) conduction and the mechanism of tachycardias. It is useful in elucidating syncope, dizziness and tachycardiac palpitations that remain unexplained by non-invasive diagnostic methods. It is fundamental in directing non-pharmacological therapy, especially in "sudden death" survivors. Chagasic patients may benefit from electrophysiologic study after a critical clinical evaluation.

A placebo-controlled trial of intravenous and oral disopyramide for prevention of neurally mediated syncope induced by head-up tilt

OBJECTIVES

A double-blind randomized trial was designed to determine the efficacy of intravenous and oral disopyramide phosphate in preventing neurally mediated syncope induced by a head-up tilt test.

BACKGROUND

Neurally mediated syncope is a frequent cause of syncope and may be induced by head-up tilt testing. Recent uncontrolled trials have suggested that disopyramide may be an effective therapy in patients with neurally mediated syncope.

METHODS

Twenty-two consecutive patients with recurrent neurally mediated syncope and two or more successive positive head-up tilt test responses were randomly allocated to receive either intravenous disopyramide or placebo. Head-up tilt testing at 60 degrees was performed for 15 min. If presyncope or syncope was not provoked, isoproterenol infusion was started at a rate of 1 microgram/min and the rate gradually increased until a 25% increase in heart rate was achieved. Eleven patients were subsequently randomized in crossover fashion to receive oral disopyramide (800 mg/day) or placebo during 1 week. The primary end point was prevention of syncope or presyncope provoked by head-up tilt testing.

RESULTS

Head-up tilt test results were positive for syncope in 12 (75%) of 16 patients receiving intravenous placebo and in 12 (60%) of 20 patients receiving disopyramide (p = 0.55 Fisher exact test, 95% confidence interval [CI] -14% to 40%). In the intravenous phase, complete crossover was achieved in 15 patients. Head-up tilt test results during this phase were positive in 13 patients (87%) receiving placebo and in 12 patients (80%) receiving disopyramide (p = 0.50 Fisher exact test, 95% CI -19% to 32%) and were positive in all patients receiving their initially randomized drug or placebo. In the oral phase, head-up tilt results were positive in only two patients (18%) assigned to placebo and in three patients (27%) receiving disopyramide (p = 0.54 Fisher exact test, 95% CI -42% to 24%). A mean follow-up time of 29 +/- 8 months was obtained in 21 of the 22 patients. Syncope recurred in 3 (27%) of the 11 patients receiving disopyramide and 3 (30%) of the 10 patients not treated pharmacologically (p > 0.05).

CONCLUSIONS

Intravenous disopyramide was ineffective for the prevention of neurally mediated syncope provoked by head-up tilt testing. No significant effect was observed after oral therapy with disopyramide. There was a striking decrease in the incidence of positive tilt test results over time regardless of intervention, thus discouraging the use of head-up tilt as the single method of assessing therapeutic efficacy. Recurrence of syncope after the investigative protocol was infrequent over long-term follow-up regardless of treatment group.

Invasive electrophysiologic evaluation in octogenarians: is age a limiting factor?

To assess the indications, diagnostic yield, and incidence of complications of electrophysiologic testing in the elderly we reviewed our experience with 60 procedures in 45 patients aged > or = 80 years (range 80 to 92 years, mean age 83) undergoing full electrophysiologic evaluation in our laboratory over the past 7 years. The yield of inducible ventricular tachycardia (31%), supraventricular tachycardia (4%), and previously unsuspected conduction abnormalities significant enough to warrant permanent pacemaker implantation (9%), together with the low incidence of complications (1 patient had a deep venous thrombosis and femoral artery pseudoaneurysm, representing an incidence of 2.2% of patients undergoing studies or 3.3% incidence of complications per procedure), suggest that invasive electrophysiologic procedures in the elderly can provide useful information at a complication rate comparable with that of younger patients.

Current usefulness of the signal-averaged electrocardiogram

Signal-averaged electrocardiography is a relatively simple, noninvasive technique by which valuable information can be gained to help in the management of patients with cardiovascular disease. The presence of late potentials on the SAECG is a good marker for the presence of an arrhythmogenic substrate that is believed to be the source of ventricular tachycardia in patients with coronary artery disease. The value of the detection of late potentials has been studied best after myocardial infarction, when the absence of late potentials makes the occurrence of an arrhythmic event very unlikely. The positive predictive value for an arrhythmic event to occur in the presence of late potentials is low, however, comparable to the predictive value of decreased left ventricular function, complex ventricular ectopy, or abnormal autonomic tone. This appears to have its explanation in the complex pathophysiology behind the occurrence of arrhythmic events. Improved accuracy for the SAECG is achieved when the result of the test is interpreted with consideration of the presence or absence of other predictive markers. A thorough understanding of the signal-averaged electrocardiogram makes optimal clinical use of the information gained from this easily acquired test possible.

[Transient loss of consciousness in an internal medicine unit. Study of the initial evaluation and medium-term outcome]

The authors report the results of a study concerning 90 patients admitted to an Internal Medicine Unit for transient loss of consciousness. The cause of this event was found in 74 cases (82%), including 73 where the initial evaluation had been simple, consisting of physical examination, electrolytogram, blood glucose level, electrocardiogram and test for postural hypotension. Patients and physicians reported different frequencies of recurrence (17 and 51% respectively) and complications (27 and 96% respectively). Recurrences were usually multiple and appeared soon after the initial event. A 4% mortality rate was recorded over 21 months, but only one death was due to a cardiovascular cause. No death was observed in the group of patients without initial aetiological diagnosis. Apart from cardiac syncopes, the consequences of transient loss of consciousness seem to be psychological rather than physical. A simple initial evaluation is often sufficient.

The diagnosis of syncope in the elderly

Given a group of individuals presenting with syncope, the use of the standard diagnostic maneuvers will yield a diagnosis for approximately half. Promising new diagnostic tests offer the prospect of more efficient diagnostic pathways and treatments and demonstrate the need for better clinical trials before they are adopted.

Selection of patients for programmed ventricular stimulation: a clinical decision-making model based on multivariate analysis of clinical variables

OBJECTIVE

This study was conducted to assess the utility of clinical variables in predicting the inducibility of sustained ventricular arrhythmias in a heterogeneous group of patients undergoing programmed ventricular stimulation.

METHODS

Variables were considered in a simulated chronologic order to determine the incremental information added by the signal-averaged electrocardiogram (ECG) and left ventricular ejection fraction. All patients undergoing baseline programmed ventricular stimulation for induction of ventricular tachyarrhythmia during a 30-month period were included in the study. Fourteen historical, ECG, signal-averaged ECG and left ventricular wall motion variables were evaluated for their ability in predicting inducibility of a sustained ventricular arrhythmia, a "positive" event, at programmed ventricular stimulation.

RESULTS

On univariate analysis of the clinical variables, comparison between patients with positive or negative results showed significant differences in 10 of the 14 clinical variables: major cardiac diagnosis, history of ventricular tachycardia, myocardial infarction by history or ECG, all five signal-averaged ECG variables, left ventricular ejection fraction and presence of left ventricular aneurysm. On multivariate analysis, five independent variables were determined to be important: history of ventricular tachycardia, historical or ECG evidence of myocardial infarction, history of loss of consciousness, filtered QRS duration on the signal-averaged ECG and left ventricular ejection fraction. However, with sequential multivariate analysis, a model based only on historical and conventional ECG data was found to do as well as a model that included signal-averaged ECG and left ventricular ejection fraction data.

CONCLUSIONS

Routinely available noninvasive historical, ECG, signal-averaged ECG and left ventricular wall motion variables can be used to accurately predict the outcome of programmed ventricular stimulation. The majority of the predictive power was obtained with the routine model, using only historical and ECG data. The signal-averaged ECG and left ventricular wall motion analysis added no significant incremental information.

Long-term outcome in symptomatic carotid sinus hypersensitivity

Between 1982 and 1988, we observed 312 patients who were affected by syncope or presyncope and whose spontaneous symptoms could be reproduced by means of carotid sinus massage (CSH); no other definite cause of syncope could be identified. The clinical outcome during a 2- to 8-year follow-up period (mean 44 +/- 24 months) was assessed in 262 of them (mean age, 71 +/- 11 years; 183 men) and was compared with that of a group of 55 patients who were affected by unexplained syncope (control patients) who were matched 4:1 for age and sex with CSH patients. CSH patients had an overall mortality rate of 7.3 per 100 person-years (cardiovascular, 66%; sudden death, 9%); overall predicted cumulative survival rates at 1, 3, 5, and 7 years were 92%, 80%, 66% and 53%. Survival was similar in control patients; mortality rate was 5.8 per 100 person-years (cardiovascular, 82%; sudden death, 18%); cumulative survival rates at 1, 3, 5, and 7 years were 85%, 80%, 73%, and 69%. Standardized mortality rate of the general population with similar age and sex distribution, as calculated by means of Italian Istituto Centrale di Statistica death-rate data (1987 edition) was 8 per 100 person-years. Of 13 clinical variables, age, sex, abnormal electrocardiogram, and heart failure (but not CSH type or related arrhythmias) were independently linked to mortality in CSH patients (Cox model). In the vasodepressor form of CSH, patients were younger than those with other forms of CSH and the percentage of women was higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid sinus massage, eyeball compression, and head-up tilt test in patients with syncope of uncertain origin and in healthy control subjects

To verify the role of abnormal neural mechanisms in unexplained syncopes, we evaluated the results of carotid sinus massage (CSM), eyeball compression (EBC), and head-up tilt test (HUT) in the basal state (B) and during isoproterenol infusion (ISO) in: (1) 100 consecutive patients affected by syncope which, despite careful cardiovascular and neurologic examination, was of uncertain origin (age 60 +/- 18 years; 54 men) and (2) 25 healthy subjects matched 4:1 with the patients of the previous group. All the patients underwent CSM and EBC in the supine and standing position for 10 seconds and HUT at 60 degrees for 60 minutes; if HUT-B was negative (68 cases), it was repeated during ISO (1 to 5 micrograms/min) infusion. In the patients with uncertain syncope, spontaneous symptoms were fully reproduced in 49%, 16%, 32%, and 16% of cases respectively by means of CSM, EBC, HUT, and HUT-ISO; overall positivity for at least one test was observed in 79% of cases. The results of CSM, EBC, or HUT-ISO were linked to age, sex, and underlying heart disease. In the healthy subjects, syncope was induced by CSM, EBC, HUT, and HUT-ISO in one case each; overall positivity was 16%. In conclusion, neural reflex induction tests reproduced spontaneous symptoms in most patients affected by uncertain syncope, while they evoked normal responses in most healthy subjects. Therefore on the basis of results of induction tests, the diagnosis of neurally mediated syncope can be ascribed to most patients affected by syncope of uncertain origin.