Autonomic responses to orthostatic stress in head-up tilt testing: Relationship to test-induced prolonged asystole

Background: Prolonged asystole is sometimes an extreme manifestation of neurally mediated syncope. Hypothesis: To investigate the mechanism of head-up tilt testing-induced prolonged (life-threatening) cardiac asystole, we measured temporal changes in frequency domain heart rate variability indices in 25 patients with syncope of undetermined etiology. Methods: Head-up tilt testing (80°) was performed in 25 patients for up to 40 min or until asystole or syncope occurred. Three patients (Group 1; 37 ±13 years, 1 man, 2 women) had an episode of prolonged cardiac asystole (≥ 10 s) during testing, necessitating cardiopulmonary resuscitation. Syncope, but no asystole, was induced in 10 patients (Group 2; 48 ± 31 years, 6 men, 4 women), and 12 patients (Group 3; 55 ± 20 years, 5 men, 7 women) failed to show asystole or syncope during testing. Power spectra of low (0.04–0.15 Hz) and high (0.15–0.40 Hz) frequency, and total (0.01–1.00 Hz) frequency spectra were measured in consecutive 2 min segments throughout the test. Results: Maximally changed values in heart rate, systolic blood pressure, and heart rate variability indices during testing were compared among the three groups (maximally changed values did not include the values during tilt-induced symptoms). High frequency spectra in Groups 2 and 3, but not in Group 1, decreased during the test. High frequency spectra, low frequency spectra, and total spectra in Group 1 were significantly higher than those in Groups 2 and 3 during testing. In Group 1 patients, findings at test-induced asystole were consistent with exaggerated sympathetic and concurrent persistent parasympathetic activity. Conclusion: Unusual autonomic responses to orthostatic stress can cause prolonged asystole, and this autonomic nerve dysregulation may relate to asystolic episodes associated with cardiovascular collapse.     

Fludrocortisone in Pediatric Vasovagal Syncope: A Retrospective,Single-Center Observational Study

Background and PurposeThe purpose of this study was to determine the effect of fludrocortisone in patients with pediatric vasovagal syncope (VVS).MethodsThis retrospective observational single-tertiary-center study based on chart reviews included 74 patients who were newly diagnosed with VVS in the head-up tilt-table test (HUTT). Some of the patients had been treated with fludrocortisone. All patients were assessed using a brain and cardiac workup before treatment to rule out the syncope being due to other causes, which resulted in seven of them being excluded: two for epilepsy and five for brain pathologies. The remaining 67 patients were analyzed. The effect of fludrocortisone was evaluated based on the results of a follow-up HUTT, with a response to the treatment considered to be present if there was a negative change at the follow-up HUTT. Univariate logistic regression were used for statistical analyses, with the criterion for significance being p<0.05.ResultsThere were no significant differences in the characteristic of the patients between the no-medication (n=39) and fludrocortisone (n=28) groups, including age, sex, and duration of treatment. The recurrence rate of syncopal or presyncopal events was significantly lower in the fludrocortisone group (39.3%, 11 of 28) than in the no-medication group (64.1%, 25 of 39) (p=0.044), as was the rate of negative change at the follow-up HUTT: 57.1% (16 of 28) and 28.2% (11 of 39), respectively (p=0.017).ConclusionsOur findings suggest that fludrocortisone is more effective than no medication in pediatric patients with VVS.     

Comparison of provocative tests for unexplained syncope: isoprenaline and glyceryl trinitrate for diagnosing vasovagal syncope.

AIMS: To compare the sensitivity, specificity and adverse event profile of glyceryl trinitrate head-up tilt with isoprenaline head-up tilt in the diagnosis of vasovagal syncope in patients with unexplained syncope and healthy controls. METHODS AND RESULTS: Forty-eight patients with unexplained syncope and negative passive head-up tilt at 70 degrees for 40 min, and 14 healthy controls underwent glyceryl trinitrate head-up tilt and isoprenaline head-up tilt (maximum dose 5 microg x min(-1)) one week apart in random order. Outcome measures were production of symptoms (syncope, pre-syncope) with development of hypotension. In those with negative passive head-up tilt, the sensitivity of glyceryl trinitrate for diagnosing vasovagal syncope was 48% and the specificity was 71%. Glyceryl trinitrate was well tolerated. Isoprenaline sensitivity was 21% with specificity 64%. Side-effects prevented completion of the test in 68%. Commonest adverse events were the development of hypertension or tachycardia and intolerable flushing or nausea. CONCLUSIONS: Glyceryl trinitrate head-up tilt is as effective as isoprenaline head-up tilt as a provocative agent for vasovagal syncope and has a lower incidence of adverse events.     

A comparison of non-invasive continuous finger blood pressure measurement (Finapres) with intra-arterial pressure during prolonged head-up tilt

Simultaneous intra-radial and non-invasive (Finapres, Ohmeda)blood pressures were compared during prolonged head-up tilt,in eight patients (mean age 49 years) with malignant vasovagalsyncope. Twelve tilts were performed, of which eight resultedin vasovagal syncope. The mean bias (difference between Finapresand intra-arterial pressures) for systolic pressure was +0.7mmHg (standard deviation 11.3 mmHg) and for diastolic pressurewas +5.4 mmHg (standard deviation 7 mmHg). The within-tilt precision(standard deviation of the bias) of the non-invasive measurementsvaried between 2.9–12.4 mmHg (median 4.5 mmHg) for systoliccomparisons, and 1.6–8.4 mmHg (median 4.4 mmHg) for diastoliccomparisons. In all but one tilt highly significant positiveincreases in both systolic (median 7.1 mmHg) and diastolic bias(median 81 mmHg) occurred on tilt with respect to resting pre-tiltlevels. Independent of the absolute level of agreement, thenon-invasive measurements followed changes in intra-arterialpressure closely, with 89% of beat-to-beat changes in systolicpressure, and 95% of beat-to-beat changes in diastolic pressurefollowed to within ±2 mmHg. This study suggests thatthe Finapres is well suited for use during diagnostic tilt testing,demonstrating an acceptable within-tilt precision and closelyfollowing pressure changes during vasovagal syncope.     

Recurrencia y mortalidad a largo plazo de los pacientes con síncope no cardiogénico

Introduction and objectivesThere are no in-depth studies of the long-term outcome of patients with syncope after exclusion of cardiac etiology. We therefore analyzed the long-term outcome of this population.MethodsFor 147 months, we included all patients with syncope referred to our syncope unit after exclusion of a cardiac cause.ResultsWe included 589 consecutive patients. There were 313 (53.1%) women, and the median age was 52 [34-66] years. Of these, 405 (68.8%) were diagnosed with vasovagal syncope (VVS), 65 (11%) with orthostatic hypotension syncope (OHS), and 119 (20.2%) with syncope of unknown etiology (SUE). During a median follow-up of 52 [28-89] months, 220 (37.4%) had recurrences (21.7% ≥ 2 recurrences), and 39 died (6.6%). Syncope recurred in 41% of patients with VVS, 35.4% with OHS, and 25.2% with SUE (P = .006). In the Cox multivariate analysis, recurrence was correlated with age (P = .002), female sex (P < .0001), and the number of previous episodes (< 5 vs ≥ 5; P < .0001). Death occurred in 15 (3.5%) patients with VVS, 11 (16.9%) with OHS, and 13 (10.9%) with SUE (P = .001). In the multivariate analysis, death was associated with age (P = .0001), diabetes (P = .007), and diagnosis of OHS (P = .026) and SUE (P = .020).ConclusionsIn patients with noncardiac syncope, the recurrence rate after 52 months of follow-up was 37.4% and mortality was 6.6% per year. Recurrence was higher in patients with a neuromedial profile and mortality was higher in patients with a nonneuromedial profile.Full English text available from:www.revespcardiol.org/en     

血管迷走性晕厥的诊断治疗手段及评价

血管迷走性晕厥(VVS)的诊断主要依靠详细的病史询问和体格检查,并排除其他类型的晕厥。目前认为直立倾斜试验(HUT)是诊断VVS的“金标准”。HUT检查阴性的部分所谓不明原因晕厥的VVS病人可通过植入性心电记录仪进行诊断。偶发VVS不需要特别处理,复发性VVS及部分特殊人群才需要进一步的诊治。目前VVS尚无有效的根治方法,其治疗以预防发作为主,包括患者教育、一般治疗、药物治疗(β-受体阻滞剂、盐皮质激素、抗胆碱能药物、选择性5-羟色胺重吸收抑制剂、α-受体激动剂)及起搏器治疗等几个方面。     

一平苏对血管迷走性晕厥疗效观察

目的观察一平苏对血管迷走性晕厥的疗效。方法对86例倾斜试验阳性晕厥患者给予一平苏2.5mg/d,3月后复查倾斜试验并随访。结果除7例有咳嗷或其他原因退出试验外,余79例倾斜试验阴转率为75.95%。服药期间无一例发生晕厥。治疗前卧位血压为121/73mmHg,治疗后为120/76mmHg,P>0.05。心率在治疗前后分别为68±13和70±13/min,两者无显著性差异。结论一平苏可以作为治疗血管迷走性晕厥的有效药物,副作用少,对正常血压和心率无影响。