Syncope Group Research Articles

Influence of respiratory instability during neurocardiogenic presyncope on cerebrovascular and cardiovascular dynamics

Objective:To analyse the influence of breathing activity on cerebrovascular dynamics during presyncope.Design:Retrospective study.Setting:University hospital.Patients:38 subjects developing neurocardiogenic syncope (syncope group), and 61 age-matched control subjects with negative tilt.Interventions:Middle cerebral artery...

Abstract 2640: Clinical Characteristics and Risk Stratification in Symptomatic and Asymptomatic Patients with Brugada Syndrome - Multi-center Study in Japan-

Background Neither the clinical characteristics nor risk stratification of symptomatic and asymptomatic patients with Brugada syndrome have been clearly determined. We compared clinical and ECG characteristics of symptomatic and asymptomatic patients with Brugada syndrome to identify new markers for distinguishing high- from low-risk patients. Methods A total of 216 consecutive individuals with Brugada syndrome (mean age 52±14 years, 197 males) were enrolled in the Japan Idiopathic Ventricular Fibrillation Study (J-IVFS). Clinical and ECG characteristics were compared among 3 groups of patients: VF group; patients with aborted sudden death and documented VF (N=34), Syncope (Sy) group; patients with syncope without documented VF (N=70), and Asymptomatic (As) group; subjects without symptoms (N=112). Comparisons were made among the 3 groups as well as between the symptomatic (VF/Sy) and asymptomatic (As) groups. Short-term prognosis was also compared among the 3 groups, and between the VF/Sy and As groups. Results 1) Clinical characteristics: incidence of past history of AF was significantly higher in the VF and Sy groups than in the AS group (26, 26, and 12 %, respectively; [p=0.04]), though no other clinical parameters differed among the groups. 2) On resting 12-lead ECG, r-J interval (interval from QRS onset to J point) in lead V2 and QRS duration in lead V6 were highest in the VF group (104, 98, and 92 msec in V2 [p<0.001]; 106, 103, and 94 msec in V6 [p<0.0001], respectively, VF vs. Sy vs. As). 3) Positive late potential and inducibility of VF by EPS did not differ in incidence among the 3 groups. 4) Clinical follow-up: during a mean follow-up of 36±16 months, incidence of cardiac events (sudden death and/or VF) was higher in the VF/Sy groups than in the As group (29, 8, and 0 %, respectively [p<0.001]). Multivariate analysis showed that the frequencies of r-J interval ≥ 90 msec in lead V2 and QRS duration ≥ 90 msec in lead V6 were significantly higher in patients with cardiac events (p=0.02, 0.02, respectively). Conclusions In symptomatic patients, prolonged ventricular depolarization in precordial leads of the ECG was prominent in the VF group, and this sign can be used to distinguish high- from low-risk patients with Brugada syndrome.

Abstract 94: Difference of Clinical Characteristics of Sudden Cardiac Arrest and Syncope Related to Coronary Vasospasm

Patients with coronary vasospasm generally have a good prognosis although lethal arrhythmia can result in sudden cardiac arrest (SCA) or syncope. Clinical predictors of SCA related to coronary vasospasm were not clear. We investigated the differences of clinical characteristics and outcome of pts with SCA and syncope related to coronary vasospasm. Method and results; Out of consecutive 47 pts with coronary vasospasm, pts presented SCA(n=13) and syncope(n=26) were enrolled in the study. Pts complicated with 5 idiopathic VF/VT and 3 neurally-mediated syncope were excluded. All pts had a normal LV function except 1 pt with ACS. One pt had coronary artery disease. SCA was experienced during first cardiac event in 77% of SCA group, whereas syncope in 31% of syncope group (p=0.04, as shown in Table ). In SCA group, 2 pts resulted in hospital death after DC-resistant VF, 1 pt died suddenly at home after medical-refractory angina. ICD was implanted in 3 survivors. Ca channel blockers were administered in all pts of each group. After discharge of hospital, during a follow-up period of 3.7±4.1yrs, survivors of SCA group did not experience any additional arrhythmic events and all pts of syncope group were alive while 1 pt had recurrent syncope. Conclusion; Coronary vasospasm can results in SCA during a first cardiac event. The prognosis of the survivors and pts with a history of syncope may be favorable under good medical control of spasm.

Síncope em pacientes com extra-sístoles de via de saída de ventrículo direito e sem cardiopatia estrutural aparente

Study the prevalence of neurocardiogenic etiology in patients with unexplained syncope and ventricular premature beats, with right ventricle outflow tract morphology (RVOT) and no apparent structural cardiopathy. Ninety patients (66 women, mean age 40.2 +/- 16.95 years of age) with monomorphic premature beats originated at RVOT were evaluated prospectively. Fifty-four patients reported syncopes or near-syncopes associated to palpitations or not; twenty-seven presented palpitations with no pre-syncope or syncope, and nine were asymptomatic. All patients were submitted to echocardiogram, high resolution ECG and cardiac MRI to rule out structural cardiopathy, to exertion test to rule out adrenergic dependent ventricular tachycardia, and ECG prolonged outpatient monitoring (Holter and symptomatic events monitor) to correlate symptoms and ventricular arrhythmias. Investigation on the susceptibility to neurocardiogenic syncope was evaluated by Tilt Table Test (TTT). Groups were compared regarding gender, age, premature beats frequency and complexity, at exertion or not, TTT results and clinical course. In the syncope and pre-syncope groups, TTT was positive for 38% of cases, and in groups with palpitations and assymptomatics, it was positive for 11% (p = 0.0257). After recommendations and treatment of neurocardiogenic syncope, 85% of syncope and pre-syncope patients and positive TTT was asymptomatic along the 40-month follow-up. Two patients with syncope and negative TTT presented spontaneous, sustained ventricular tachycardia during clinic course. The prevalence of neurocardiogenic syncope in patients with idiopathic RVOT premature beats is high. Patients with recurrent, unexplained syncope and idiopathic VE must be kept under investigation.

Hemodynamic, autonomic and neurohormonal behaviour of familial amyloidotic polyneuropathy and neurally mediated syncope patients during supine and orthostatic stress

Orthostatic intolerance (OI) syndromes are frequent and share symptoms like dizziness and orthostatic syncope. Their pathophysiology however seems to be different. The aim of our work was to evaluate autonomic and hemodynamic behaviour in patients with familial amyloidotic polyneuropathy and neurally mediated syncope in supine position and after acute orthostatic passive stress. We studied 12 patients with autonomic failure (group A), 12 patients with neurally mediated syncope (group B) and 16 aged matched normal controls (group C), in supine position and during the first 10 min of head-up tilt test (HUTT). Beat-by-beat blood pressure and heart rate were continuously monitored and digitised at 500 Hz. The baroreceptor alfa-index gain (vagal reflex-BRG), high frequency of RR variability (HFRR, vagal tonus) and low frequency of systolic arterial pressure variability (LFSAP, sympathetic tone) were calculated. Catecholamines, plasma brain (BNP) and atrial natriuretic (ANP) peptides were also measured. Hemodynamic data were derived and calculated by the non-invasive modelflow method. During supine position, cardiac output (CO) and stroke volume (SV) were similar in all groups. Mean arterial pressure (MAP) and BNP were higher in group A. Noradrenaline (NOR), BRG, HFRR and LFSAP were extremely low in this group. BRG and adrenaline (ADR) were higher in group B than in controls. Within the first 10 min of HUTT, there was a huge drop of CO, SV and MAP in group A, maintenance of very low levels of neurohormones and lack of autonomic function. HR, LFSAP and ADR had a higher rise at HUTT in group B compared with controls ( p < 0.01) but a significant decrease of BRG was noted ( p < 0.05). ANP or BNP did not change with tilt in any group. Different orthostatic intolerance syndromes may show important hormonal, autonomic and hemodynamic differences during supine rest and enhanced after passive orthostatism.

Heart Rate Variability During Sleep in Patients with Vasovagal Syncope

There are a few studies showing no significant heart rate variability (HRV) over a 24-hour period in vasovagal syncope (VVS) patients, but no research has examined HRV and its sympathetic and parasympathetic components during rapid eye movement (REM) and non-REM sleep. The authors hypothesized that REM sleep might be a critical state in which VVS patients would show abnormal responses. To analyze the sympathetic and parasympathetic components of HRV during REM and SWS in patients with VVS compared to normal subjects, and in patients with positive HUTT compared to negative ones. Thirty-seven VVS patients and 20 normal age-matched controls were submitted to polysomnography with 24-hour Holter monitoring to assess HRV. Time and frequency domain techniques were carefully performed for 24 hours and during Stages 3 and 4 of REM and non-REM sleep. Variation of sympathetic activity index (VSAI) was defined as the difference in the low frequency (LF) component of HRV between REM and Stages 3 and 4 of non-REM sleep. An analysis of variance was performed to compare patients and controls; patients with positive and negative head-up tilt testing. The LF component was lower in syncope compared to normal patients (1,769.54 +/- 1,738.17, 3,225.37 +/- 2,585.05, respectively, P = 0.03). There was a significant decrease in VSAI in the syncope group compared to the control group (-539.39 +/- 1,930.78, 1,268.10 +/- 2,420.20, respectively, P = 0.01). The other sleep variables analyzed including very LF, high frequency, low frequency/high frequency and time domain parameters did not reach statistical significance. Syncope patients also showed an increase in slow wave sleep (28.2 +/- 10.5, 19.7 +/- 7.8, P = 0.01). VVS patients exhibited sympathetic suppression during REM sleep. Possible mechanisms are discussed in this article.

Low-frequency oscillation of sympathetic nerve activity decreases during development of tilt-induced syncope preceding sympathetic withdrawal and bradycardia

Sympathetic activation during orthostatic stress is accompanied by a marked increase in low-frequency (LF, approximately 0.1-Hz) oscillation of sympathetic nerve activity (SNA) when arterial pressure (AP) is well maintained. However, LF oscillation of SNA during development of orthostatic neurally mediated syncope remains unknown. Ten healthy subjects who developed head-up tilt (HUT)-induced syncope and 10 age-matched nonsyncopal controls were studied. Nonstationary time-dependent changes in calf muscle SNA (MSNA, microneurography), R-R interval, and AP (finger photoplethysmography) variability during a 15-min 60 degrees HUT test were assessed using complex demodulation. In both groups, HUT during the first 5 min increased heart rate, magnitude of MSNA, LF and respiratory high-frequency (HF) amplitudes of MSNA variability, and LF and HF amplitudes of AP variability but decreased HF amplitude of R-R interval variability (index of cardiac vagal nerve activity). In the nonsyncopal group, these changes were sustained throughout HUT. In the syncopal group, systolic AP decreased from 100 to 60 s before onset of syncope; LF amplitude of MSNA variability decreased, whereas magnitude of MSNA and LF amplitude of AP variability remained elevated. From 60 s before onset of syncope, MSNA and heart rate decreased, index of cardiac vagal nerve activity increased, and AP further decreased to the level at syncope. LF oscillation of MSNA variability decreased during development of orthostatic neurally mediated syncope, preceding sympathetic withdrawal, bradycardia, and severe hypotension, to the level at syncope.

Long-term survival of Japanese patients transported to an emergency department Because of syncope

Study objectiveCardiovascular disease mortality is affected by ethnic differences and is lower in Japan than in Western countries. Although patients with cardiac syncope have significantly higher mortality than patients with noncardiac syncope in Western countries, no such phenomenon has been described in Japan. The aim of this study is to clarify the long-term mortality of patients with syncope who are brought to an emergency department (ED) in Japan. MethodsThis retrospective observational study was conducted on patients treated in the ED of Keio University Hospital in Tokyo. Nine hundred twelve consecutive patients who presented with syncope were identified. The patients were classified into 2 groups according to the cause of syncope: cardiac syncope and noncardiac syncope. Follow-up information about mortality was obtained from mailed questionnaires and medical records. Mortality data were analyzed using the actuarial life-table method and a Cox proportional hazards model. ResultsFollow-up information was obtained for 715 patients. The median follow-up period was 38 months, during which 63 patients died. At 5 years, the 23.1% (95% confidence interval [CI] 12.7% to 33.4%) mortality of the patients with cardiac syncope was significantly higher than the 8.2% (95% CI 5.5% to 10.9%) mortality of the patients with noncardiac syncope (P<.0001). The incidence of cardiac death among the patients with cardiac syncope was 17.2% (95% CI 7.8% to 26.5%) compared with 0.9% (95% CI 0% to 1.8%) in the noncardiac syncope group (P<.0001). Cardiac syncope was an independent predictor of overall mortality and cardiac mortality (relative risk 2.81 [95% CI 1.53 to 5.16], 18.74 [95% CI 5.90 to 59.52]). ConclusionCardiac syncope is associated with higher mortality than noncardiac syncope in this Japanese patient population.

Effects of Tilt Test and Beta-Ad re nergic Stimulation on the QT Interval in Normal Children and Pediatric Patients With Unexplained Syncope

In normal children, any procedure that increases heart rate, such as the tilt test, may shorten the QT interval. The effect of the tilt test on QT interval in children with syncope remains unknown. We analyzed the response of RR and QT intervals during a tilt test in 3 groups of children: 28 healthy children (group 1), 26 with syncope of unknown etiology and negative tilt test results (group 2), and 17 with vasovagal syncope (group 3). During the tilt test, RR and QT intervals were significantly shortened in groups 1 and 2. In group 3, RR interval was lengthened during syncope whereas the QT interval remained constant. QT interval lengthening during the tilt test is not a characteristic finding in normal children or in children with vasovagal syncope.

The usefulness of carotid sinus massage in different patient groups.

to determine the positive yield of carotid sinus massage in different patient groups: unexplained syncope, falls, dizziness and controls. observational study. teaching hospital. we studied consecutive patients over the age of 60 years referred to the 'falls clinic' with a history of unexplained syncope, unexplained falls and unexplained dizziness. We also studied asymptomatic control subjects recruited from a general practice register aged 60 years and over. All patients and control subjects underwent a full clinical assessment (comprehensive history and detailed clinical examination including supine and erect blood pressure measurements) and 12-lead electrocardiography. We performed carotid sinus massage in the supine position for 5 seconds separately on both sides followed by repeating the procedure in the upright positions using a motorised tilt table. Heart rate and blood pressure were recorded using a cardiac monitor and digital plethysmography respectively. The test was considered positive if carotid sinus massage produced asystole with more than a 3 second pause (cardioinhibitory type of carotid sinus syndrome), or a fall in systolic blood pressure of more than 50 mmHg in the absence of significant cardioinhibition (vasodepressor type of carotid sinus syndrome) or where there was evidence of both vasodepressor and cardio-inhibition as above (mixed type). we studied 44 asymptomatic control subjects and 221 symptomatic patients (130 with unexplained syncope, 41 with unexplained falls and 50 with unexplained dizziness). In the overall symptomatic patient group, the positive yield (any type of carotid sinus syndrome) was 17.6% (95% CI = 12.7-22.5). The positive yield in men (26.3% (95% CI = 16.4-36.2)) was twice that in women (13.1% (95% CI = 7.6-18.6)) (P = 0.014). Overall any type of carotid sinus syndrome was present in 22.3% (n = 29) of the syncope group, 17.1% (n = 7) in the unexplained fallers group and 6% (n = 3) in the dizziness group. We also found that no women with unexplained dizziness had a positive carotid sinus massage test. None of the controls demonstrated a positive response. None of the subjects suffered any complications during or after the test. the positive yield of carotid sinus massage in symptomatic patients was 17.6% with the yield in men being twice that in women. None of the asymptomatic control subjects demonstrated a positive response. The yields in unexplained syncope and unexplained falls patients were around 4-fold and 3-fold higher respectively than in unexplained dizziness patients. The positive yield in women with unexplained dizziness (without a definite history of syncope and falls) is zero. Hence, carotid sinus massage in older adults should particularly be targeted at patients with unexplained syncope and unexplained falls.

Transient loss of consciousness as reason for admission to primary health care emergency room

Scand J Prim Health Sci 2002;20:000-000. ISSN 0281-3432 Objective - To study the occurrence and main causes of transient loss of consciousness in primary health care. Design - A 4-month prospective survey. Setting - Primary health care emergency room of the City of Tampere, Finland. Subjects - Consecutive patients, aged over 15 years, admitted to the emergency room. Main outcome measures - The overall prevalence of loss of consciousness divided into three subgroups: seizure, syncope and uncertain, and their distribution by gender and age. The prevalence of epilepsy, coronary heart disease and alcohol abuse among these diagnostic subgroups. Results - Of all emergency room visits, 1.2% were for loss of consciousness. Of these, 53% were diagnosed as seizures, 33% as syncope attacks and 14% as uncertain. In the seizure group, 75% of patients were men and 67% had a history of alcohol abuse. In the syncope group, 44% of patients had coronary heart disease and 68% were women. Conclusion - Loss of consciousness is a fairly frequent problem for the primary health care emergency room. A history of alcohol abuse is commonly associated with seizures.

Catecholamine response during haemodynamically stable upright posture in individuals with and without tilt-table induced vasovagal syncope.

Changes in circulating catecholamine concentrations during vasovagal faints have been the subject of considerable study. However, whether catecholamines are part of the triggering mechanism, or principally reflect attempted compensation for an evolving circulatory crisis is unknown. To address this issue, we determined whether the circulating catecholamine response to upright posture differs among patients with and without inducible vasovagal faints at a time when there is no detectable haemodynamic compromise. Blood samples for measurement of adrenaline and noradrenaline (Norepi) concentrations were obtained in the baseline state, and at both 2-3 min and 4-6 min of upright posture in 22 patients undergoing head-up tilt-table testing for evaluation of syncope of unknown cause. In 11 individuals tilt-testing induced syncope at >5 min head-up posture (Group 1). In 11 other individuals tilt testing did not result in syncope (Group 2). Supine arterial catecholamine levels were comparable in the two groups. However, adrenaline concentrations during upright posture tended to be greater at 2-3 min and were significantly greater at 4-6 min in Group 1 than in Group 2 (P< 0.01). These differences occurred in the absence of significant intergroup differences in mean arterial pressure or cardiac cycle lengths. Norepi concentrations also increased in both groups, but without significant differences. Circulating adrenaline concentrations in posturally induced vasovagal faints rise more rapidly in vasovagal fainters than in comparably posturally stressed non-fainters, and were significantly greater in fainters prior to either detectable haemodynamic compromise or diminution of circulating Norepi levels. These findings suggest that a premonitory rise in adrenaline concentrations occurs in vasovagal fainters unassociated with an evolving circulatory crisis.

Comparison of hemodynamic adaptation to orthostatic stress in patients with hypertrophic cardiomyopathy with or without syncope and in vasovagal syncope

This study was designed to investigate whether, in patients with hypertrophic cardiomyopathy (HC), tilt-induced volume unloading triggers a peripheral reflex similar to that seen in patients with a history of vasovagal syncope or rather acts through an intrinsic cardiac mechanism secondary to diastolic dysfunction. Thirty-seven patients with HC (10 with and 27 without a history of syncope), 10 patients with vasovagal syncope, and 9 controls underwent 70° head-up tilt for 45 minutes during continuous radionuclide monitoring of left ventricular function. We focused on the initial 5 minutes into the tilt test, well before symptoms occurred, to exclude that the observed hemodynamic changes were the consequence rather than the cause of syncope. HC patients with previous syncope and vasovagal patients experienced significant hypotension after the initial 5 minutes of tilt. Only HC patients with a history of syncope had a significant decrease in cardiac output, which began at the initial stage of the test. Systemic vascular resistance decreased in vasovagal patients, but increased in the HC syncopal group. Baseline peak filling rate was lower (2.4 ± 0.5 vs 3.3 ± 1.1 stroke counts/s, p = 0.03) and a “pseudonormal” or a restrictive pattern of left ventricular filling was more frequent (70% vs 26%, p = 0.02) in HC patients with than without a history of syncope. Thus, significant hypotension or frank syncope during orthostatic stress in HC patients with a history of syncope is due to an early decrease in cardiac output, which occurs well before the onset of symptoms; such impaired hemodynamic adaptation seems to be related to diastolic dysfunction.

Implantable defibrillator event rates in patients with idiopathic dilated cardiomyopathy, nonsustained ventricular tachycardia on Holter and a left ventricular ejection fraction below 30%

ObjectivesThis study investigated the incidence of appropriate implantable cardioverter defibrillator (ICD) interventions for ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients with idiopathic dilated cardiomyopathy (IDC) and nonsustained VT in the presence of a left ventricular ejection fraction below 30%, versus in patients with syncope and patients with a history of VT or VF. BackgroundTo date, only limited information is available about the prophylactic use of ICDs in patients with IDC. MethodsFrom January 1993 to July 2000, 101 patients with IDC underwent implantation of ICDs with electrogram storage capability at our institution. Patients were placed into one of three groups according to their clinical presentation: asymptomatic or mildly symptomatic nonsustained VT in the presence of a left ventricular ejection fraction ≤30% (49 patients, prophylactic group), unexplained syncope or near syncope (26 patients, syncope group) and a history of sustained VT or VF (26 patients, VT/VF group). ResultsDuring 36 ± 22 months follow-up, 18 of 49 patients (37%) in the prophylactic group received appropriate shocks for VT or VF, compared with 8 of 26 patients (31%) in the syncope group and with 9 of 26 patients (35%) of the VT/VF group. Multivariate Cox analysis of baseline clinical variables identified left ventricular ejection fraction, atrial fibrillation and a history of sustained VT or VF as predictors for appropriate ICD interventions during follow-up. ConclusionPatients with IDC and prophylactic ICD implantation for nonsustained VT in the presence of a left ventricular ejection fraction ≤30% had an incidence of appropriate ICD interventions similar to that of patients with a history of syncope or sustained VT or VF. These findings indicate that ICDs may have a role in not only secondary but also primary prevention of sudden death in IDC.

Prevalence and prognostic significance of psychiatric disorders in patients evaluated for recurrent unexplained syncope

We aimed to assess the psychiatric profile and prognostic value of psychiatric disorders (PDs) in patients presenting with unexplained syncope. Forty patients with recurrent unexplained syncope referred for head-up tilt testing were compared with age- and sex-matched patients free of known chronic PDs referred for arrhythmia. All patients underwent a semistandardized psychiatry questionnaire (Mini-International Neuropsychiatric Interview) to assess their profile. Additional stress coping was performed to study adaptational processes to stressful situations. After tilt testing and psychiatric evaluation, a drug-free follow-up was performed in patients with syncope. Of the 80 patients who referred to the psychiatric interview, 40 had evidence of at least 1 psychiatric disorder. They were 26 patients (65%) in the syncope group and 14 patients (35%) in the control group (p = 0.01). Detailed analysis revealed a more frequent subprofile of anxiety and panic disorders in patients with syncope than in controls (30% vs 12% and 20% vs 10%, respectively), whereas the subprofile of depression was similar in both groups. Moreover, those with syncope were more likely to have a high anxiety index (25 ± 5 vs 22 ± 4, p = 0.004), and were more prone to avoidance-oriented coping strategies when experiencing undesirable life events than controls. Considering syncope patients, no difference could be found between the 25 with a positive tilt test and the 15 with a negative tilt test with respect to the number of syncopal episodes and psychiatric profile. After a 3-year drug-free follow-up, 15 patients (37.5%) had at least 1 recurrent syncope. The recurrence rate was similar in patients with positive and negative head-up tilt test results (9 of 25 vs 6 of 15, respectively). In contrast, the syncopal recurrence rate was higher in patients who fulfilled criteria for affective disorders (13 of 26 vs 2 of 14, 95% confidence interval 1.09 to 2.55, relative risk 1.7, p = 0.04). Thus, patients with recurrent unexplained syncope are more anxious and are more prone to panic disorders and avoidance-oriented coping strategies than control patients with arrhythmia. The presence of a psychiatric disorder is associated with an increased risk of recurrence. The outcome of such patients may be improved with recognition and treatment of PDs.

Population and survival characteristics of cats with hypertrophic cardiomyopathy: 260 cases (1990-1999).

To determine current population characteristics of, clinical findings in, and survival times for cats with hypertrophic cardiomyopathy (HCM). Retrospective study. 260 cats with HCM. Information was obtained from the medical records. Cats were classified into 1 of 4 clinical groups (congestive heart failure [CHF] group, arterial thromboembolism [ATE] group, syncope group, or cats without clinical signs [subclinical group]) on the basis of the primary clinical signs at the initial examination. 120 cats were classified in the CHF group, 43 in the ATE group, 10 in the syncope group, and 87 in the subclinical group. Antecedent events that may have precipitated CHF included i.v. fluid administration, anesthesia, surgery, and recent corticosteroid administration. Median survival time was 709 days (range, 2 to 4,418 days) for cats that survived > 24 hours. Cats in the subclinical group lived the longest (median survival time, 1,129 days; range, 2 to 3,778 days), followed by cats in the syncope group (654 days; range, 28 to 1,505 days), cats in the CHF group (563 days; range, 2 to 4,418 days), and cats in the ATE group (184 days; range, 2 to 2,278 days). Causes of death included ATE (n = 56), CHF (49), sudden death (13), and noncardiac causes (27). In univariate analyses, survival time was negatively correlated with left atrial size, age, right ventricular enlargement, and thoracentesis. Cats with systolic anterior motion of the mitral valve lived longer than cats without this echocardiographic finding. In multivariate analyses, only age and left atrial size remained significant predictors of survival time. Although overall survival time for cats with HCM was similar to earlier reports, survival times for cats with CHF or ATE were longer than previously reported.

Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope

Background Because of its episodic behavior, the correlation of spontaneous syncope with an abnormal finding can be considered a reference standard. Methods and Results We inserted an implantable loop recorder in 111 patients with syncope, absence of significant structural heart disease, and a normal ECG; tilt-testing was negative in 82 (isolated syncope) and positive in 29 (tilt-positive). The patients had had ≥3 episodes of syncope in the previous 2 years and were followed up for 3 to 15 months. Results were similar in the isolated syncope group and the tilt-positive group: syncope recurred in 28 (34%) and 10 patients (34%), respectively, and electrocardiographic correlation was found in 24 (23%) and 8 (28%) patients, respectively. The most frequent finding, which was recorded in 46% and 62% of patients, respectively, was one or more prolonged asystolic pauses, mainly due to sinus arrest, preceded for a few minutes by progressive bradycardia or progressive tachycardia-bradycardia. Bradycardia without pa...

Mechanism of Syncope in Patients With Isolated Syncope and in Patients With Tilt-Positive Syncope

Because of its episodic behavior, the correlation of spontaneous syncope with an abnormal finding can be considered a reference standard. We inserted an implantable loop recorder in 111 patients with syncope, absence of significant structural heart disease, and a normal ECG; tilt-testing was negative in 82 (isolated syncope) and positive in 29 (tilt-positive). The patients had had >/=3 episodes of syncope in the previous 2 years and were followed up for 3 to 15 months. Results were similar in the isolated syncope group and the tilt-positive group: syncope recurred in 28 (34%) and 10 patients (34%), respectively, and electrocardiographic correlation was found in 24 (23%) and 8 (28%) patients, respectively. The most frequent finding, which was recorded in 46% and 62% of patients, respectively, was one or more prolonged asystolic pauses, mainly due to sinus arrest, preceded for a few minutes by progressive bradycardia or progressive tachycardia-bradycardia. Bradycardia without pauses was observed in 8% and 12% of cases, respectively. The remaining patients had normal sinus rhythm or sinus tachycardia, except for one, who had ectopic atrial tachycardia. In the tilt-positive group, an asystolic syncope was also recorded when the type of response to tilt-testing was vasodepressor or mixed. Presyncopal episodes were never characterized by asystolic pauses; normal sinus rhythm was the most frequent finding. Homogeneous findings were observed during syncope. In most patients, the likely cause was neurally-mediated, and the most frequent mechanism was a bradycardic reflex. In the other cases, a normal sinus rhythm was frequently recorded. Presyncope was not an accurate surrogate for syncope in establishing a diagnosis.

Comparison of event rates and survival in patients with unexplained syncope without documented ventricular tachyarrhythmias versus patients with documented sustained ventricular tachyarrhythmias both treated with implantable cardioverter-defibrillators

Patients with unexplained syncope and inducible ventricular tachyarrhythmias during electrophysiologic testing have an increased cardiac mortality rate. We compared event rates and survival of 178 patients with unexplained syncope and no documented ventricular arrhythmias (syncope group) versus 568 patients with documented sustained ventricular tachycardia (VT) or fibrillation (VF) (VT/VF group) treated, as part of a lead (Ventritex TVL) investigation, with similar implantable cardioverter-defibrillators (ICDs) capable of extensive data storage. The 2 groups shared similar clinical characteristics. The mean follow-up was 11 months for the syncope group and 14 months for the VT/VF group. The mean time from device implantation to first appropriate therapy was similar in the 2 groups (109 ± 140 vs 93 ± 131 days, p = 0.40). Actuarial probability of appropriate ICD therapy was 49% and 55% at 1 and 2 years, respectively, in syncope group and 49% and 58% in VT/VF group (p = 0.57). Recurrent syncope was associated with ventricular tachyarrhythmias in 85% and 92% of the syncope group and VT/VF group, respectively (p = 0.54). At 2 years, actuarial survival was 91% in the syncope group and 93% in VT/VF group (p = 0.85). We conclude that patients treated with ICD with unexplained syncope and induced VT/VF have an equally high incidence of appropriate ICD therapy and low mortality compared with similar patients with documented VT/VF. These findings, plus the high association between recurrent syncope and ventricular arrhythmias, indicate that VT/VF are likely etiologies in selected patients with unexplained syncope and support ICD therapy in such cases.

Implantable defibrillator event rates in patients with unexplained syncope and inducible sustained ventricular tachyarrhythmias: A comparison with patients known to have sustained ventricular tachycardia

OBJECTIVESTo assess the clinical significance of inducible ventricular tachyarrhythmias among patients with unexplained syncope.BACKGROUNDInduction of sustained ventricular arrhythmias at electrophysiology study in patients with unexplained syncope and structural heart disease is usually assigned diagnostic significance. However, the true frequency of subsequent spontaneous ventricular tachyarrhythmias in the absence of antiarrhythmic medications is unknown.METHODSIn a retrospective case-control study, the incidence of implantable cardiac defibrillator (ICD) therapies for sustained ventricular arrhythmias among patients with unexplained syncope or near syncope (syncope group, n = 22) was compared with that of a control group of patients (n = 32) with clinically documented sustained ventricular tachycardia (VT). Sustained ventricular arrhythmias were inducible in both groups and neither group received antiarrhythmic medications. All ICDs had stored electrograms or RR intervals. Clinical variables were similar between groups except that congestive cardiac failure was more common in the syncope group.RESULTSKaplan-Meier analysis of the time to first appropriate ICD therapy for syncope and control groups produced overlapping curves (p = 0.9), with 57 ± 11% and 50 ± 9%, respectively, receiving ICD therapy by one year. In both groups, the induced arrhythmia was significantly faster than spontaneous arrhythmias, but the cycle lengths of induced and spontaneous arrhythmias were positively correlated (R = 0.6, p < 0.0001). During follow-up, three cardiac transplantations and seven deaths occurred in the syncope group, and two transplantations and five deaths occurred in the control group (36-month survival without transplant 52 ± 11% and 83 ± 7%, respectively, p = 0.03).CONCLUSIONSIn patients with unexplained syncope, structural heart disease and inducible sustained ventricular arrhythmias, spontaneous sustained ventricular arrhythmias occur commonly and at a similar rate to patients with documented sustained VT. Thus, electrophysiologic testing in unexplained syncope can identify those at risk of potentially life-threatening tachyarrhythmias, and aggressive treatment of these patients is warranted.