Author Correction: Mapping the world's free-flowing rivers.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Mapping the world's free-flowing rivers.

Free-flowing rivers (FFRs) support diverse, complex and dynamic ecosystems globally, providing important societal and economic services. Infrastructure development threatens the ecosystem processes, biodiversity and services that these rivers support. Here we assess the connectivity status of 12 million kilometres of rivers globally and identify those that remain free-flowing in their entire length. Only 37 per cent of rivers longer than 1,000 kilometres remain free-flowing over their entire length and 23 per cent flow uninterrupted to the ocean. Very long FFRs are largely restricted to remote regions of the Arctic and of the Amazon and Congo basins. In densely populated areas only few very long rivers remain free-flowing, such as the Irrawaddy and Salween. Dams and reservoirs and their up- and downstream propagation of fragmentation and flow regulation are the leading contributors to the loss of river connectivity. By applying a new method to quantify riverine connectivity and map FFRs, we provide a foundation for concerted global and national strategies to maintain or restore them.

Maximizing patient benefit from cardiac resynchronization therapy with the addition of structured exercise training: a randomized controlled study.

OBJECTIVES: We evaluated the benefits of additional exercise training after cardiac resynchronization therapy (CRT). BACKGROUND: Cardiac resynchronization therapy results in improved morbidity and mortality in appropriate patients. We hypothesized that a structured exercise training program in addition to CRT would maximize the improvements in exercise capacity, symptoms, and quality of life (QOL). METHODS: Fifty patients referred for CRT were recruited. Patients were assessed before and 3 and 6 months after CRT. Functional class and QOL scores were recorded, and exercise tests were performed with hemodynamic measurements. Peak lower limb skeletal muscle torque was measured during extension, and echocardiography was undertaken at each visit. At 3 months, patients were randomized with a simple sealed envelope method to exercise training (n = 25) or control group (n = 25). The exercise group underwent an exercise program consisting of 3 visits/week for 3 months. Paired sample t tests were used to look for in-group differences and independent sample t tests for between-group differences. RESULTS: Three months after CRT there were significant improvements in all functional, exercise hemodynamic, and echocardiographic measures. After randomization the exercise group showed further significant improvements in functional, exercise hemodynamic, and QOL measures compared with the control group. There were also significant in-group improvements in peak skeletal muscle function and ejection fraction that did not reach statistical significance on intergroup analysis. CONCLUSIONS: Exercise training leads to further improvements in exercise capacity, hemodynamic measures, and QOL in addition to the improvements seen after CRT. Therefore, exercise training allows maximal benefit to be attained after CRT.

Incremental prognostic value of changes in B-type natriuretic peptide in heart failure.

PURPOSE: B-type natriuretic peptide is one of the most sensitive and specific biohumoral markers of heart failure. We hypothesized that B-type natriuretic peptide changes during treatment of heart failure may provide independent information on disease progression and outcome in patients enrolled in the Val-HeFT trial. METHODS: Patients were divided into four groups according to concentrations of B-type natriuretic peptide at baseline versus 4 months (n = 3740) or 12 months (n = 3343), with respect to the baseline median (97 pg/mL): low-->low (stable below median, 44%-46%), high-->high (stable above median, 32%-37%), high-->low (above to below median, 12%-14%), and low-->high (below to above median, 6%-9%). Cox multivariate regression analysis was used to assess the risk of death and morbidity, with adjustment for baseline B-type natriuretic peptide concentrations. RESULTS: Patients who improved their B-type natriuretic peptide at 4 months (high-->low) had a similar risk for mortality (hazard ratio = 1.191, 95% confidence interval [CI] 0.870-1.631, P =.2746) compared with the low-->low patients. Conversely, patients who worsened in their B-type natriuretic peptide (low-->high) had a risk for mortality (hazard ratio 2.578, CI, 1.861-3.571, P <.0001) higher than patients in the low-->low group, and indistinguishable from the high-->high group. Worsening of B-type natriuretic peptide (low-->high) was associated with 0.03 cm/m2 increase in left ventricular end-diastolic diameter, whereas it decreased by 0.10 cm/m2 in high-->low and low-->low groups (P <.001). CONCLUSIONS: Changes in B-type natriuretic peptide over time with respect to a threshold value of 97 pg/mL convey an independent and additional prognostic value compared with a single determination of B-type natriuretic peptide in a large population of patients with chronic symptomatic heart failure and might be helpful in the management of these patients.