[Diagnostic accuracy of a protocol in the evaluation of unexplained syncope]. / Rendimiento diagnóstico de un protocolo de estudio del síncope de causa no aparente.

INTRODUCTION AND OBJECTIVES: To assess the diagnostic capacity of a protocol to study syncope of unknown cause in which electrophysiological studies and tilting table tests are selectively used. PATIENTS AND METHODS: The study was performed in 137 consecutive patients (94 men and 43 women, with a mean age of 57.6+/-18.3 years) with syncope of unknown cause after the initial clinical evaluation, who were divided into two groups. Group A consisted of 77 patients meeting any of the following criteria: a) presence of structural heart disease; b) abnormal ECG; c) presence of significant non-symptomatic arrhythmia in the Holter recording, and d) presence of paroxysmal palpitations. These patients initially underwent an electrophysiological study. Group B consisted of 60 patients not meeting any of the above criteria, who were initially submitted to tilting table tests.Results. In group A, the electrophysiological study was positive in 43 patients (55%). In group B, the tilting test was positive in 41 patients (68%). Among patients in group A with a negative study, 20 (59%) were submitted to the tilting table test, with positive results in 7 cases (35%). Five patients from group B with a negative tilting test underwent the electrophysiological study, which was negative in all of them. Overall, a positive diagnosis was achieved in 91 of 137 patients (66%). CONCLUSIONS: In patients with syncope of a non-apparent cause in the initial assessment, selective use of electrophysiological studies or tilting table tests, guided by clinical criteria, allows for a positive diagnosis in over 60% of the cases. Our results suggest that the tilting table test should be performed in cases of group A with a negative electrophysiological study.

[The tilt-table test: is it essential for adequate treatment of vasovagal syncope? Arguments against]. / Test de mesa basculante: es imprescindible para el tratamiento adecuado del síncope vasovagal? Argumentos en contra.

The knowledge about vasovagal syncope has hugely grown since its initial description by Lewis in 1932. Nevertheless some critical gaps remain, affecting specially to the patient management. There are not enough data about the natural history of the process and, because of that, no useful markers are known to identify patients who need or would benefit from a specific treatment. A diagnostic test with a sensibility/specificity relationship good enough to be a diagnostic gold standard is lacking. Although tilt-table test can be helpful in diagnosis, its sensitivity is, nowadays, unknown. Available data about reproducibility of tilt test are scarce and sometimes contradictory, specially with positive tilt test results. Should the lack of reproducibility of positive results found by some authors be confirmed, the usefulness of serial tilt tests in selecting treatment would be seriously affected. No evidence about the existence of an effective treatment for vasovagal syncope has been published yet, not either about the advantage of an specific strategy in selecting it. Therefore, tilt test has not been proved to be a more useful tool in selecting therapy for patients with vasovagal syncope.

[Auricular fibrillation and stroke in patients with sick sinus syndromeusing permanent pacemakers]. / Fibrilación auricular y accidente vascular encefálico en pacientes con enfermedad del nodo sinusal portadores de marcapasos definitivos.

INTRODUCTION AND OBJECTIVES: Since physiological pacing systems have become available, a debate has raged about the merits of atrial versus ventricular pacing in the sick sinus syndrome. The goal of this retrospective report was to study the long term incidence and the independent predictors for atrial fibrillation and stroke in 153 paced patients with sick sinus syndrome, adjusting for differences in baseline clinical variables with multivariate analysis. METHOD AND RESULTS: From 1980 to 1994, we implanted 32 dualchamber, 33 atrial, and 88 ventricular pacemakers to treat patients with sick sinus syndrome. After a maximum follow-up of 177 months (median 30 months for paroxismal atrial fibrillation, 45 months for chronic atrial fibrillation and 43,5 months for stroke) the actuarial incidence of paroximal atrial fibrillation was 7.8% at 1 year, 29% at 5 years and 42% at 10 years. The actuarial incidence of chronic atrial fibrillation was 1.3% at 1 year, 9.8% at 5 years and 22% at 10 years. Independent predictors for paroxismal AF from Cox's model was history of atrial tachyarrhythmias (p < 0.0001), chronic obstructive pulmonary disease (p = 0,006) and age (> 70 years-old) (p = 0.035). Only a history of atrial tachyarrhythmias before pacemaker implant was an independent predictor for chronic atrial fibrillation (p < 0.0001). The odd ratio for paroxismal atrial fibrillation in patients with previous atrial tachyarrhythmias and chronic atrial fibrillation were 6 (2.8-12) and 4 (1.6-9.7) (95% confiance limits). Actuarial incidence of stroke was 3% at 1 year, 10% at 5 years and 14% at 10 years. Independent predictors for stroke were history of peripheral vascular disease (p = 0.033) and hypertensive cardiomyopathy (p = 0.015). Development of paroxysmal and chronic atrial fibrillation during the follow-up were higher in patients with stroke (p < 0.001 and p < 0.05). CONCLUSIONS: Development of atrial fibrillation and stroke in paced patients with sick sinus syndrome are strongly determined by clinical variables. Preimplant paroxysmal atrial tachyarrhythmias is the most important predictor for atrial fibrillation in the follow-up.

[50 hz alternating current as a cause of inhibition of monopolar ventricular pacemakers]. / Corriente alterna de 50 Hz como causa de inhibición de marcapasos ventriculares monopolares.

It is not well established the importance of 50 Hz alternating current (AC) (that supplies most of house appliances) as a source of inappropriate inhibition of today cardiac pacemakers (PM). This problem has been studied in 58 consecutive patients permanently paced (VVI unipolar) for AV block with 27 different PM models from 11 manufacturers. Under ECG monitoring, 50 Hz AC was applied through a pair of electrodes set at both patient's wrists using a battery powered external source, with voltage ranging between 0 and 45 V. Inappropriate inhibition was considered if PM pauses longer than twice the programmed escape interval of the PM were observed during interference. This happened in 46 patients (79.3%), with PM from all 11 manufacturers, with voltages ranging from 3 to 28 V. In each case, inhibition was seen with a narrow voltage window between no interference detection and interference reversion of the PM. Only 3 patients (5.2%) referred perception of electrical current during the study. Three of the patients studied had complained, prior to the study, about dizziness or presyncope related to touching electrical devices and in all of them inappropriate inhibition was observed during interference. We conclude that: 1) it is possible to demonstrate inappropriate inhibition caused by 50 Hz AC galvanic interference in a high percentage of unipolar PM; 2) This inhibition occurs at current levels that in most cases are not sensed by the cutaneous nerves, and 3) although the problem seems to have little clinical significance it should be investigated in paced patients with symptoms attributable to inappropriate inhibition of their PM.

[Syncope: epidemiological characteristics of a hospital series]. / Síncope: características epidemiológicas de una serie hospitalaria.

Three hundred hospital patients with syncope (193 males and 107 females, mean age 61 +/- 17 years) were prospectively evaluated with a standard protocol. Associated diseases were found in 76.7% of cases. The incidence of heart diseases was 50.8% in males vs 32.7% in females (p less than 0.003). The cause of syncope was diagnosed in 250 patients (84%). The diagnosis was made at initial evaluation in 101 patients (group A); in the remaining patients (group B), no diagnosis was made in 25% (16.6% of the overall series) despite a wide array of investigations. Syncope due to arrhythmia was diagnosed in 57.6% (group A: 91.1% group B: 40.7; p less than 0.0001); cardiac syncope not due to arrhythmia was diagnosed in 4%, and other types of syncope in 21.6% (group A; 6.9%; group B: 29.1%; p less than 0.0001). It is concluded that a) the hospital population of patients with syncope represents a subgroup of advanced age and a high incidence of associated diseases; b) one third of patients were diagnosed at the initial evaluation, whereas in 25% of the remaining ones no diagnosis was obtained, and c) in these patients, arrhythmia is the most likely cause of syncope.