Complex systems and the technology of variability analysis

Characteristic patterns of variation over time, namely rhythms, represent a defining feature of complex systems, one that is synonymous with life. Despite the intrinsic dynamic, interdependent and nonlinear relationships of their parts, complex biological systems exhibit robust systemic stability. Applied to critical care, it is the systemic properties of the host response to a physiological insult that manifest as health or illness and determine outcome in our patients. Variability analysis provides a novel technology with which to evaluate the overall properties of a complex system. This review highlights the means by which we scientifically measure variation, including analyses of overall variation (time domain analysis, frequency distribution, spectral power), frequency contribution (spectral analysis), scale invariant (fractal) behaviour (detrended fluctuation and power law analysis) and regularity (approximate and multiscale entropy). Each technique is presented with a definition, interpretation, clinical application, advantages, limitations and summary of its calculation. The ubiquitous association between altered variability and illness is highlighted, followed by an analysis of how variability analysis may significantly improve prognostication of severity of illness and guide therapeutic intervention in critically ill patients

Diaphragmatic eventration

In general, diaphragmatic eventration (DE) is defined as abnormal elevation of all (or a portion of) an attenuated (but otherwise intact) diaphragmatic leaf [1]. The term “eventration” was used first by Becklard in 1829 (through Petit probably described the condition in 1970). Bingham described plication of the diaphragm in 1954 [2, 3]. Based on etiopathogenesis, DE may be classified as “congenital” or “acquired” even though the clinical features and principles of management are similar for both forms

Multiple valve disease

Multiple valvular heart disease is a highly prevalent condition. Whereas the burden of rheumatic heart disease is decreasing, degenerative etiologies are becoming increasingly prevalent in industrialized regions. Hemodynamic interactions may impact both the clinical expression and the diagnosis of each singular lesion, and the clinician should be aware of its specific diagnostic pitfalls. There is currently little if any evidence-based management strategy. Patients should be followed by a Heart Valve Team in the setting of heart valve clinics, using a “case by case” therapeutic strategy. In addition to the severity of each singular lesion, clinical and imaging factors should be considered, including the individual risk profile, the increased morbidity associated with multiple prostheses, and the natural history of each valvular lesion if left untreated. Advances in transcatheter valve therapies are likely to change the therapeutic paradigm, but these approaches still require prospective validation before gaining wide acceptance.SCOPUS: ch.binfo:eu-repo/semantics/publishe

A review of outcome following valve surgery for rheumatic heart disease in Australia

Background: Globally, rheumatic heart disease (RHD) remains an important cause of heart disease. In Australia it particularly affects younger Indigenous and older non-Indigenous Australians. Despite its impact there is limited understanding of the factors influencing outcome following surgery for RHD. Methods: The Australian and New Zealand Society of Cardiac and Thoracic Surgeons Cardiac Surgery Database was analysed to assess outcomes following surgical procedures for RHD and non-RHD valvular disease. The association with demographics, co-morbidities, pre-operative status, valve(s) affected and operative procedure was evaluated. Results: Outcome of 1384 RHD and 15843 non-RHD valve procedures was analysed. RHD patients had longer ventilation, experienced fewer strokes and had more readmissions to hospital and anticoagulant complications. Mortality following RHD surgery at 30 days was 3.1 % (95 % CI 2.2 – 4.3), 5 years 15.3 % (11.7 – 19.5) and 10 years 25.0 % (10.7 – 44.9). Mortality following non-RHD surgery at 30 days was 4.3 % (95 % CI 3.9 - 4.6), 5 years 17.6 % (16.4 - 18.9) and 10 years 39.4 % (33.0 - 46.1). Factors independently associated with poorer longer term survival following RHD surgery included older age (OR1.03/additional year, 95 % CI 1.01 – 1.05), concomitant diabetes (OR 1.7, 95 % CI 1.1 – 2.5) and chronic kidney disease (1.9, 1.2 – 2.9), longer invasive ventilation time (OR 1.7 if greater than median value, 1.1– 2.9) and prolonged stay in hospital (1.02/additional day, 1.01 – 1.03). Survival in Indigenous Australians was comparable to that seen in non-Indigenous Australians.Conclusion: In a large prospective cohort study we have demonstrated survival following RHD valve surgery in Australia is comparable to earlier studies. Patients with diabetes and chronic kidney disease, were at particular risk of poorer long-term survival. Unlike earlier studies we did not find pre-existing atrial fibrillation, being an Indigenous Australian or the nature of the underlying valve lesion were independent predictors of survival