Scale-dependent impact of land management on above- and belowground biodiversity

Land management is known to have consequences for biodiversity; however, our synthetic understanding of its effects is limited due to highly variable results across studies, which vary in the focal taxa and spatial grain considered, as well as the response variables reported. Such synthetic knowledge is necessary for management of agroecosystems for high diversity and function.To fill this knowledge gap, we investigated the importance of scale-dependent effects of land management (LM) (pastures vs. meadows), on plant and soil microbe diversity (fungi and bacteria) across 5 study sites in Central Germany. Analyses included diversity partitioning of species richness and related biodiversity components (i.e., density of individuals, species-abundance distribution, and spatial aggregation) at two spatial grains (α- and γ-scale, 1 m2 and 16 km2, respectively).Our results show scale-dependent patterns in response to LM to be the norm rather than the exception and highlight the importance of measuring species richness and its underlying components at multiple spatial grains.Our outcomes provide new insight to the complexity of scale-dependent responses within and across taxonomic groups. They suggest that, despite close associations between taxa, LM responses are not easily extrapolated across multiple spatial grains and taxa. Responses of biodiversity to LM are often driven by changes to evenness and spatial aggregation, rather than by changes in individual density. High-site specificity of LM effects might be due to a variety of context-specific factors, such as historic land management, identity of grazers, and grazing regime. Synthesis and applications: Our results suggest that links between taxa are not necessarily strong enough to allow for generalization of biodiversity patterns. These findings highlight the importance of considering multiple taxa and spatial grains when investigating LM responses, while promoting management practices that do the same and are tailored to local and regional conditions.

Resumption of driving after life-threatening ventricular tachyarrhythmia

BACKGROUND

Although the privilege of driving must be respected, it may be necessary to restrict driving when it poses a threat to others. The risks associated with allowing patients with life-threatening ventricular tachyarrhythmias to drive have not been quantified.

METHODS

The Antiarrhythmics versus Implantable Defibrillators (AVID) trial compared antiarrhythmic-drug therapy with the implantation of defibrillators in patients resuscitated from near-fatal ventricular arrhythmias. In the current study, we sent patients who participated in the AVID trial a questionnaire, to be completed anonymously, requesting information about driving habits and experiences.

RESULTS

The questionnaire was returned by 758 of 909 patients (83 percent). Of these, 627 patients drove during the year before their index episode of ventricular tachyarrhythmia. A total of 57 percent of these patients resumed driving within 3 months after randomization in the AVID trial, 78 percent within 6 months, and 88 percent within 12 months. While driving, 2 percent had a syncopal episode, 11 percent had dizziness or palpitations that necessitated stopping the vehicle, 22 percent had dizziness or palpitations that did not necessitate stopping the vehicle, and 8 percent of the 295 patients with an implantable cardioverter-defibrillator received a shock. Fifty patients reported having at least 1 accident, for a total of 55 accidents during 1619 patient-years of follow-up after the resumption of driving (3.4 percent per patient-year). Only 11 percent of these accidents were preceded by symptoms of possible arrhythmia (0.4 percent per patient-year).

CONCLUSIONS

Most patients with ventricular tachyarrhythmias resume driving early. Although it is common for them to have symptoms of possible arrhythmia while driving, accidents are uncommon and occur with a frequency that is lower than the annual accident rate of 7.1 percent in the general driving population of the United States.

The effect of psychological intervention on patients' long-term adjustment to the ICD: a prospective study

This study prospectively examined the role of cognitive behavioral therapy (CBT) in (1) alleviating psychological and somatic distress, and (2) lowering arrhythmic events requiring shocks. Forty-nine of 61 consecutive patients were randomized into therapy (CBT, n = 25) or no therapy (NT, n = 24) and completed a battery of self-report questionnaires at baseline and at 9-month follow-up. CBT was administered at preimplant, predischarge, and at seven routine follow-up visits. Patients were 65 +/- 10 years old, 65% were men, and 92% Caucasian. Eighteen (72%) CBT patients and 18 (75%) NT patients were retained at follow-up. Compared to CBT patients, NT patients reported higher levels of depression (P = 0.046), more anxiety (P = 0.013), more psychological distress (P = 0.015), poorer overall adjustment (P = 0.009), and poorer sexual functioning (P = 0.003). Mean number of shocks did not differ between the CBT and NT groups (2.85 vs 2.30, respectively); however, more patients in the CBT group (61%) than the NT group (33%) received shocks (P = 0.070). At follow-up, a subgroup analysis revealed that the significant differences observed between the CBT and NT groups were attributable to the patients who received shocks in both groups. In conclusion, CBT was associated with decreased depression, decreased anxiety, and increased adjustment for ICD recipients, particularly among those patients receiving shocks. CBT can be administered effectively at routine follow-up visits or transtelephonically with little added inconvenience to the ICD recipient.

Beta-blocker use and survival in patients with ventricular fibrillation or symptomatic ventricular tachycardia: the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial

OBJECTIVES

To evaluate whether use of beta-adrenergic blocking agents, alone or in combination with specific antiarrhythmic therapy, is associated with improved survival in persons with ventricular fibrillation (VF) or symptomatic ventricular tachycardia (VT).

BACKGROUND

The ability of beta-blockers to alter the mortality of patients with VF or VT receiving contemporary medical management is not well defined.

METHODS

Survival of 1,016 randomized and 2,101 eligible, nonrandomized patients with VF or symptomatic VT followed in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial through December 31, 1996 was assessed using Cox proportional hazards analysis.

RESULTS

The 817 (28%) patients discharged from hospital receiving beta-blockers had less ventricular dysfunction, fewer symptoms of heart failure and a different pattern of medication use compared with patients not receiving beta-blockers. Before adjustment for important prognostic variables, beta-blockade was not significantly associated with survival in randomized or in eligible, nonrandomized patients treated with specific antiarrhythmic therapy. After adjustment, beta-blockade remained unrelated to survival in randomized or in eligible, nonrandomized patients treated with amiodarone alone (n = 1142; adjusted relative risk [RR] = 0.96; 95% confidence interval [CI] 0.64-1.45; p = 0.85) or a defibrillator alone (n = 1347; adjusted RR = 0.88; 95% CI 0.55 to 1.40; p = 0.58). In contrast, beta-blockade was independently associated with improved survival in eligible, nonrandomized patients who were not treated with specific antiarrhythmic therapy (n = 412; adjusted RR = 0.47; 95% CI 0.25 to 0.88; p = 0.018).

CONCLUSIONS

Beta-blocker use was independently associated with improved survival in patients with VF or symptomatic VT who were not treated with specific antiarrhythmic therapy, but a protective effect was not prominent in patients already receiving amiodarone or a defibrillator.

Flecainide acetate: critical care administration guidelines

Flecainide may play an important role in the treatment of ventricular arrhythmias because of its convenient dosing regimen and high rate of efficacy in controlling ventricular ectopic activity. In stable patients with normal or mildly reduced left ventricular function, flecainide has proved to be promising. In those patients with severe left ventricular dysfunction, lethal arrhythmias, and preexisting conduction system disease, caution must be exercised.

Effectiveness and safety of oral verapamil to control exercise-induced tachycardia in patients with atrial fibrillation receiving digitalis

The safety and efficacy of oral verapamil to control exercise tachycardia in 27 patients with atrial fibrillation and 3 with atrial flutter receiving digitalis was evaluated in a double-blind, randomized, crossover study. The heart rate in patients who received verapamil compared with placebo group was lower at rest (mean 69 +/- 13 versus 87 +/- 20 beats/min, p less than 0.01), as was the degree of tachycardia at the end of 3 minutes of a standardized exercise test (104 +/- 14 versus 136 +/- 23 beats/min, p less than 0.01). Doses of verapamil required to achieve suppression of tachycardia were 240 mg/day in 18 patients, 320 mg/day in 6 patients, and 480 mg/day in 3 patients. Only 3 patients complained of adverse effects from verapamil during the double-blind phase of the study. Two patients were discontinued from the study because of adverse reactions. No clinically significant changes during verapamil therapy were observed on the electrocardiogram, chest roentgenogram, echocardiogram or in the laboratory evaluation. Digoxin blood levels were higher in patients who received concomitant verapamil compared with placebo (1.23 +/- 0.59 versus 0.85 +/- 0.46 ng/ml, p less than 0.01), but no patient had signs or symptoms of digitalis toxicity. Thus, oral verapamil given in addition to digitalis is a safe and effective agent in the treatment of patients with chronic atrial fibrillation or flutter to decrease exercise-induced tachycardia.