Resilience of the Eastern African electricity sector to climate driven changes in hydropower generation.

Notwithstanding current heavy dependence on gas-fired electricity generation in the Eastern African Power Pool (EAPP), hydropower is expected to play an essential role in improving electricity access in the region. Expansion planning of electricity infrastructure is critical to support investment and maintaining balanced consumer electricity prices. Variations in water availability due to a changing climate could leave hydro infrastructure stranded or result in underutilization of available resources. In this study, we develop a framework consisting of long-term models for electricity supply and water systems management, to assess the vulnerability of potential expansion plans to the effects of climate change. We find that the most resilient EAPP rollout strategy corresponds to a plan optimised for a slightly wetter climate compared to historical trends. This study demonstrates that failing to climate-proof infrastructure investments can result in significant electricity price fluctuations in selected countries (Uganda & Tanzania) while others, such as Egypt, are less vulnerable.

Temporary sympathectomy in chronic refractory angina: a randomised, double-blind, placebo-controlled trial.

BACKGROUND: Temporary sympathectomy by injection of bupivacaine at the site of the left stellate ganglion is used in the management of refractory angina at several UK centres. Although patients frequently report significant reduction in symptoms, efficacy has not been established by double-blind, randomised placebo-controlled trial (RCT). OBJECTIVE: To investigate the efficacy of the procedure for the first time by a double-blind RCT. METHODS: Consecutive patients referred to the authors' National Health Service (NHS) angina centre who were candidates for temporary sympathectomy were invited to participate in a trial. A total of 65 patients were randomised to receive either bupivacaine or saline injections. Identical syringes were prepared remotely, blinding patients and staff from randomisation. Cardiac autonomic function was measured 3 hours pre- and post-injection using new heart rate variability (HRV) analyses. Angina episodes were recorded contemporaneously by patients in study diaries in the 7-day periods pre- and post-injection. RESULTS: In 51 patients suitable for analysis, no significant differences between the active and placebo groups were found in patient-recorded frequency or intensity of angina episodes pre- and post-injection. However, across both groups combined, a significant difference was found in the frequency of angina episodes pre- and post-injection. CONCLUSION: The reduction in frequency of angina episodes produced by this procedure may not be due to drug pharmacology. It may be a placebo response or due to the mechanical effects of the injection of fluid. There is a need for further work using a larger patient cohort considering both mechanical and psychological factors.

Clinical implications of QRS duration and QT peak prolongation in patients with suspected coronary disease referred for elective cardiac catheterization.

BACKGROUND: The electrocardiogram (ECG) remains a simple, universally available, and prognostically powerful investigation in heart failure, and acute coronary syndromes. We sought to assess the prognostic utility of clinical, angiographic, and simple ECG parameters in a large cohort of patients undergoing elective cardiac catheterization (CC) for known or suspected coronary artery disease. METHODS: Consecutive consenting patients undergoing CC for coronary disease were enrolled at a single tertiary center. Patient data, drug therapy, catheter reports, and ECG recordings were prospectively recorded in a validated electronic archive. The primary outcome measure was death or nonfatal myocardial infarction (MI) over 1 year or until percutaneous or cardiac surgical intervention. Independent prognostic markers were identified using the Cox proportional hazard model. RESULTS: A total of 682 individuals were recruited of whom 17(2.5%) died or suffered a nonfatal MI in 1 year. In multivariate analysis QRS duration (ms) (HR 1.03 95% CI 1.01-1.05, P = 0.003), extent of coronary disease (HR 2.01 95% CI 1.24-3.58, P = 0.006), and prolonged corrected QT peak interval in lead I (HR 1.02 95% CI 1.00-1.03, P = 0.044) were independently associated with death or nonfatal MI. Receiver-operator characteristic (ROC) analysis for the multivariate model against the primary end point yielded an area under the curve of 0.759 (95% CI 0.660-0.858), P < 0.001. CONCLUSIONS: QRS duration and QT peak are independently associated with increased risk of death or nonfatal MI in stable patients attending for coronary angiography.

A brief cognitive-behavioral intervention reduces hospital admissions in refractory angina patients.

Chronic refractory angina is an increasingly prevalent, complex chronic pain condition, which results in frequent hospitalization for chest pain. We have previously shown that a novel outpatient cognitive-behavioral chronic disease management program (CB-CDMP) improves angina status and quality of life in such patients. In the present study of 271 chronic refractory angina patients enrolled in our CB-CDMP, total hospital admissions were reduced from 2.40 admissions per patient per year to 1.78 admissions per patient per year (P<0.001). The rising trend of total hospital bed day occupancy prior to enrollment fell from 15.48 days per patient per year to a stable 10.34 days per patient per year (P<0.001). There were 32 recorded myocardial infarctions prior to enrollment compared to eight in the year following enrollment (14% vs. 2.3%, P<0.001) and overall mortality was lower that comparable groups treated with surgery. This study shows that educating patients and demystifying angina using a brief outpatient CB-CDMP produces an immediate and sustained reduction in hospital admission costs that represents a major potential health care saving. This benefit accrues in addition to the known effects of CB-CDMP on symptoms and quality of life. These data suggest that a CB-CDMP approach to symptom palliation represents a low cost alternative to palliative revascularization.

Spectral analysis, death and coronary anatomy following cardiac catheterisation.

OBJECTIVE: To establish the associations and prognostic utility of angiographic, clinical and HRV parameters in a large cohort of patients undergoing diagnostic cardiac catheterisation (CC). METHODS: Patients undergoing CC as elective day cases were enrolled at a single tertiary center from September 2001 to January 2003. Patient data, serum biochemistry, current drug therapy, catheter reports and five minute high resolution electrocardiograph (ECG) recordings were prospectively recorded and validated in an electronic archive. ECG recordings were used to generate time domain (SDNN (standard deviation of NN intervals)) and spectral HRV parameters (low frequency (LF) and high frequency (HF) power). Significant associations between dichotomized HRV variables and covariates were investigated using binary logistic regression. The independent prognostic ability of clinical markers was evaluated using the Cox proportional hazard model. RESULTS: 841 consecutive consenting patients of mean age 61+/-10 years were recruited into the study with a mean follow-up period of 690+/-436 days. In multivariate analysis decreasing LF spectral power was independently associated with proximal right coronary stenosis OR (odds ratio)=1.65 (95% CI=1.16-2.36), P=0.006 and to all cause mortality OR=5.01 (95% CI=1.47-17.01), P=0.010. Increasing LF power was also independently associated with normal coronary angiograms in patients investigated suspected coronary disease without a confirmed prior history of a coronary ischaemic event OR=2.16 (95% CI=1.26-3.73), P=0.002. CONCLUSIONS: Reduced LF power independently predicts all cause mortality in a large cohort of patients receiving medical therapy after elective CC. LF power was also independently associated with >75% proximal RCA stenosis.

Heart rate turbulence and death due to cardiac decompensation in patients with chronic heart failure.

BACKGROUND: As treatment strategies for patients with chronic heart failure (HF) become more sophisticated, identifying patients at high risk of death and predicting mode of death is important. The aim of this study was to explore the potential utility of heart rate turbulence (HRT) to identify patients with HF at high risk of death. METHODS AND RESULTS: In a prospective study, 553 ambulant outpatients age 63+/-10 with symptoms of HF and evidence of cardiac dysfunction were recruited. All patients underwent 24-h Holter ECG recordings, which were analysed for arrhythmias, heart rate variability and HRT a measurement that is thought to quantify cardiac autonomic regulatory mechanisms. Baseline chest radiograph, biochemistry and 12-lead electrocardiograms were also obtained. In patients with HRT measurements at 5 years follow up, 146 patients had died, 59 due to decompensated HF. Independent predictors of death from decompensated HF at 5-year follow up (Cox proportional hazard model) were HRT slope (HR for 10% increment 0.84, 95% CI 0.77-0.91), serum sodium (HR for 10% increment 0.75, 95% CI 0.62-0.91) and serum creatinine (for 10% increment HR 1.14, 95% CI 1.08-1.19) all P<0.01. These 3 variables combined had excellent discrimination between patients dying of decompensated HF and other patients, C-statistic=0.82. CONCLUSIONS: In patients with mild-to-moderate HF, HRT slope is an independent predictor of death due to decompensated HF. HRT may have the potential to help tailor therapy in this patient group.