Enhanced dispersion of atrial refractoriness as an electrophysiological substrate for vulnerability to atrial fibrillation in patients with paroxysmal atrial fibrillation.

Atrial electrical remodeling plays a part in recurrence of atrial fibrillation (AF). It has been related to an increase in heterogeneity of atrial refractoriness that facilitates the occurrence of multiple reentry wavelets and vulnerability to AF. AIM: To examine the relationship between dispersion of atrial refractoriness (Disp_A) and vulnerability to AF induction (A_Vuln) in patients with clinical paroxysmal AF (PAF). METHODS: Thirty-six patients (22 male; age 55+/-13 years) with > or =1 year of history of PAF (no underlying structural heart disease--n=20, systemic hypertension--n=14, mitral valve prolapse--n=1, surgically corrected pulmonary stenosis--n=1), underwent electrophysiological study (EPS) while off medication. The atrial effective refractory period (AERP) was assessed at five different sites--high (HRA) and low (LRA) lateral right atrium, high interatrial septum (IAS), proximal (pCS) and distal (dCS) coronary sinus--during a cycle length of 600 ms. AERP was taken as the longest S1-S2 interval that failed to initiate a propagation response. Disp_A was calculated as the difference between the longest and shortest AERP. A_Vuln was defined as the ability to induce AF with 1-2 extrastimuli or with incremental atrial pacing (600-300 ms) from the HRA or dCS. The EPS included analysis of focal electrical activity based on the presence of supraventricular ectopic beats (spontaneous or with provocative maneuvers). The patients were divided into group A--AF inducible (n=25) and group B--AF not inducible (n=11). Disp_A was analyzed to determine any association with A_Vuln. Disp_A and A_Vuln were also examined in those patients with documented repetitive focal activity. Logistic regression was used to determine any association of the following variables with A_Vuln: age, systemic hypertension, left ventricular hypertrophy, left atrial size, left ventricular function, duration of PAF, documented atrial flutter/tachycardia and Disp_A. RESULTS: There were no significant differences between the groups with regard to clinical characteristics and echocardiographic data. AF was inducible in 71% of the patients and noninducible in 29%. Group A had greater Disp_A compared to group B (105+/-78 ms vs. 49+/-20 ms; p=0.01). Disp_A was >40 ms in 50% of the patients without A_Vuln and in 91% of those with A_Vuln (p=0.05). Focal activity was demonstrated in 14 cases (39%), 57% of them with A_Vuln. Disp_A was 56+/-23 ms in this group and 92+/-78 ms in the others (p=0.07). Using logistic regression, the only predictor of A_Vuln was Disp_A (p=0.05). CONCLUSION: In patients with paroxysmal AF, Disp_A is a major determinant of A_Vuln. Nevertheless, the degree of nonuniformity of AERP appears to be less important as an electrophysiological substrate for AF due to focal activation.     

Characteristics of Acute Asthma Patients Attended Frequently Compared with Those Attended Only Occasionally in an Emergency Department

Asthma patients that depend on emergency department (ED) services are generally considered to have extremely poor disease control and prognosis. It is important to identify characteristics related to poor disease control and frequent visits to the ED to apply appropriate clinical management. This study comprised a cross-sectional survey of consecutive patients with asthma exacerbation (age ≥12 years) presenting at the adult ED of a large, tertiary care, university-affiliated hospital over a 2-month period. The frequent visitors (FV) were defined by ≥3 visits to the ED in the preceding year, and the occasional visitors (OV) by ≤2 visits. Eighty-six patients (61 females and 25 males) were included in the study (mean age 38 ± 18 years). Of these patients, 51.2% were FV and 48.8% were OV. Sixty-nine percent had annual income lower than A$3000 and 66.3% had ≤8 years of the formal education. Only 18.6% had used inhaled corticosteroids, 79.1% identified the asthma attack severity, 70.9% increased or initiated inhaled β-agonist, 20.9% increased or initiated steroid therapy, and 55.8% had an asthma action plan for attack. The number of hospital admissions in past year (OR 4.3, P = .02), use of home nebulizer (OR 3.6, P = .05) and the lack of a written asthma action plan (OR 3.3, P = .03) were independently associated with frequent visits to the ED. We conclude that a substantial proportion of the patients that visit the ED are FV. These patients are more likely to have hospital admission in the past year, to use a home nebulizer, and to lack a written asthma action plan. They should be considered the most important target for asthma education.     

The dynamics of oral contraceptive use in the Netherlands 1990–1993

Data from an ongoing series of surveys on contraceptive use in the Netherlands were analyzed with respect to the percentages of oral contraceptive (OC) users who annually started use, discontinued use or switched to another OC type. The surveys had been conducted between 1990 and 1993 among samples of women aged 15–49 who belonged to a survey panel. Response rates of the surveys were 89–90% and the sample sizes ranged from 4560 to 4621 women. The assessed OC use rates reflected those of the Dutch population reasonably well. Of all respondents who had used OCs during the 12 months prior to the surveys, 12–15% discontinued use within this period, mainly in order to get pregnant, 12–16% were starters and 9–14% switchers. Of all starters 37% switched to another OC type within the first 12 months after starting. Switching was mainly related to the experience of perceived side-effects and wishes for better cycle control. The results highlighted the relevance of closely monitoring the individual woman's satisfaction with her OC. Since OC use appeared in many cases to be characterized by an active seeking for the most acceptable OC type, a wide range of OC types available and the development and introduction of new types is highly relevant for tailoring contraceptive use to individual needs.

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Resumen Se analizaron los datos de una serie de estudios que se están efectuando con respecto al uso de anticonceptivos en los Países Bajos a fin de determinar los porcentajes de usuarias de anticonceptivos orales (AO) que habían comenzado a utilizar, dejado de utilizar o pasado a otro tipo de AO, anualmente. Los estudios se habían efectuado entre 1990 y 1993 con muestras de mujeres de 15 a 49 años que formaban parte de un panel de estudio. Las tasas de respuesta de los estudios fueron del 89–90% y los tamaños de las muestras estuvieron comprendidos entre 4.560 y 4.621 mujeres. Las tasas de uso de AO evaluadas reflejaron las de la población holandesa razonablemente bien. De todas las encuestadas que habían utilizado AO durante los 12 meses anteriores a los estudios, el 12–15% dejó de utilizarlos dentro de este período, principalmente a fin de quedar embarazada, el 12–16% recién comenzaba a utilizarlos y el 9–14% había cambiado a otro tipo de AO. De todas las que recién comenzaban a utilizarlos, el 37% pasó a otro tipo de AO dentro de los 12 meses de iniciado su uso. El cambio se relacionaba principalmente con la experiencia de los efectos secundarios percibidos y el deseo de un mejor control del ciclo. Los resultados destacaron la importancia de una monitorización estrecha de la satisfacción individual de la usuaria con respecto a su AO. Dado que la utilización de AO pareció en muchos casos caracterizarse por la búsqueda activa del tipo más aceptable de AO, una amplia gama disponible de tipos de AO y el desarrollo y la introducción de nuevos tipos son aspectos que revisten gran importancia en la adaptación del uso de anticonceptivos a las necesidades individuales.

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Resumé Les données provenant d'une série en cours d'enquêtes sur l'utilisation des contraceptifs aux Pays-Bas ont été analysées du point de vue des pourcentages des utilisatrices de contraceptifs oraux (CO) qui ont, pendant chaque année, commencé à les utiliser, les ont abandonnés ou sont passées à un autre type de CO. Les enquêtes ont été menées entre 1990 et 1993 parmi des échantillons de femmes âgées de 15 à 49 ans qui constituaient la population étudiée. Les pourcentages de réponses aux enquêtes se sont élevés à 89–90% pour un échantillonnage allant de 4560 à 4621 femmes. Les pourcentages d'utilisation de CO évalués reflétaient assez bien ceux de la population néerlandaise en général. Parmi toutes ces femmes qui avaient utilisé les CO durant les 12 mois précédant l'enquête, 12–15% avaient cessé au cours de cette même période, en général pour avoir un enfant, 12–16% avaient commencé à les utiliser et 9–14% avaient changé de type de CO. Parmi toutes celles qui avaient commencé, 37% ont changé de produit au cours des 12 premiers mois. Le choix d'un autre type de CO étail essentiellement lié à des effets secondaires ressentis et au désir de mieux régler le cycle menstruel. Les résultats mettent en évidence combien il est important de suivre de près dans quelle mesure les femmes sont individuellement satisfaites du CO qu'elles adoptent. Etand donné que l'utilisation des Co semble, dans beaucoup ce cas, être caractérisée par une recherche active du type de CO le plus acceptable, le choix possible dans toute une gamme de CO, ainsi que la mise au point et l'introduction de nouveaux types, permettent remarquablement bien d'adapter l'utilisation des contraceptifs aux besoins individuels.

     

The 1989 report of the North American Pediatric Renal Transplant Cooperative Study

This report of the North American Pediatric Transplant Cooperative Study summarizes data contributed by 57 participating centers on 754 children with 761 transplants from 1 January 1989 to 16 February 1989. Data collection was initiated in October 1987 and follow-up of all patients is ongoing. Transplant frequency increased with age; 24% of the patients were less than 5 years, with 7% being under 2 years. Common frequent diagnoses were: aplastic/dysplastic kidneys (18%), obstructive uropathy (16%), and focal segmental glomerulosclerosis (12%). Preemptive transplant, i.e., transplantation without prior maintenance dialysis, was performed in 21% of the patients. Dialytic modalities pretransplant were peritoneal dialysis in 42% and hemodialysis in 25%. Bilateral nephrectomy was reported in 29%. Live-donor sources accounted for 42% of the transplants. Among cadaveric donors, 41% of the donors were under 11 years old. During the first post-transplant month, maintenance therapy was used similarly for live-donor and cadaver source transplants, with prednisone, cyclosporine, and azathioprine used in 93%, 83%, and 81%, respectively. Triple therapy with prednisone, cyclosporine, and azathioprine was used in 78%, 75%, and 75% of functioning cadaver source transplants at 6 months, 12 months, and 18 months as opposed to 60%, 63%, and 54% for live-donor procedures, with single-drug therapy being uncommon. Rehospitalization during months 1–5 occurred in 62% of the patients, with treatment of rejection and infection being the main causes. Additionally, 9% were hospitalized for hypertension. During months 6–12 and 12–17, 30% and 28% of the patients with functioning grafts were rehospitalized. Times to first rejection differed significantly for cadaver and live-donor transplants. The median time to the first rejection was 36 days for cadaver transplants and 156 days for live-donor transplants. Overall, 57% of treated rejections were completely reversible although the complete reversal rate decreased to 37% for four or more rejections. One hundred and fifty-two graft failures had occurred at the time of writing, with a 1-year graft survival estimate of 0.88 for live-donor and 0.71 for cadaver source transplants. In addition to donor source, recipient age is a significant prognostic factor for graft survival. Among cadaver donors, decreasing donor age is associated with a decreasing probability of graft survival. Thirty-five deaths have occurred; 16 attributed to infection and 19 to other causes. The current 1-year survival estimate is 0.94. There have been 9 malignancies.A list of all participating centers and the names of the investigators is printed on pages 552–553     

Endothelial Vascular Function in Hypertensive Patients After Renin—Angiotensin System Blockad

It is unclear whether single and combined pharmacologic inhibition of the renin-angiotensin-aldosterone system have similar effects on endothelial function and blood pressure (BP). The authors evaluated 63 hypertensive patients divided into 4 groups (hydrochlorothiazide 25 mg/d; irbesartan [IRBE] 150 mg/d; quinapril [QUIN] 20 mg/d; or IRBE 150 mg/d + QUIN 20 mg/d) and 25 healthy normotensive subjects (normal) followed for 12 weeks. Endothelium-dependent dysfunction measured as flow-mediated dilation at Weeks 0 and 12 were: normal, 11.5%±2.4% vs 13.5%±2.0%; hydrochlorothiazide, 7.3%±2.0% vs 12.8%±3.1%; QUIN, 7.2%±2.8% vs 13.2%±2.1%; IRBE, 7.1%±2.8% vs 13.0%±2.9%; and IRBE + QUIN, 7.5%±1.9% vs 12.8%±3.0%. Nitroglycerin-mediated responses were: normal, 26.0%±1.9% vs 24.0%±2.5%; hydrochlorothiazide, 17.0%±2.2% vs 18.3%±2.6%; QUIN, 17.8%±3.2% vs 23.4%±3.0%; IRBE, 16.8%±3.6% vs 24.7%±2.0%; and IRBE + QUIN, 17.3%±3.0% vs 25.1%±2.5%. Antihypertensive therapy restored BP to normal and improved the endothelium-dependent and -independent dysfunction after renin-angiotensin-aldosterone system blockade. In a further finding, the combined effect of angiotensin-converting enzyme inhibition and angiotensin II type 1 receptor blockade was not superior to the action of either of these treatments separately.