Effect of altered loading conditions during haemodialysis on left ventricular filling pattern

Changes in the circulating volume associated with haemodialysis result in modification of left ventricular loading conditions. To determine the influence of haemodialysis on Doppler indices of left ventricular filling, 12 patients (mean age 40.8 ±2.7 (SEM) years) with renal insufficiency but without overt heart disease were studied by Doppler-echocardiography immediately before and after haemodialysis. Haemodialysis resulted in a decrease in body weight from 68.0±3.8 kg to 65.0 ±3.7 kg (P< 0.01). Heart rate and blood pressure did not change significantly during haemodialysis. Left ventricular diastolic dimension (M-mode) decreased from 53.5±1.1 mm to 49.5±1.9 mm (P < 0.05), whereas the shortening fraction did not change. Haemodialysis elicited marked changes in the early diastolic rapid filling wave (E wave) recorded by pulsed Doppler at the level of the mitral annulus. Peak velocity of the early rapid filling phase (peak E) decreased significantly from 95.3 ± 8.2 cm .s−1 to 63.0 ±5.7cm .s−1 (P< 0.001) and mid-diastolic deceleration of transmitral velocity decreased from 437.3 ±54.2 cm . s−2 to 239.7 ±54.4 cm . s−2 (P<0.01). The peak filling velocity during atrial contraction (peak A) did not change (79.7 ±6.3 cm .s−1 vs 74.1±4.7 cm.s−1;P=NS). The ratio peak E/peak A decreasedfrom 1.19±0.06 to 0.85 ± 0.04 (P < 0.01) during haemodialysis. The results provide further evidence for the pronounced preload-dependence of Doppler indices of left ventricular diastolic functio

White matter lesions in watershed territories studied with MRI and parenchymography: a comparative study

Brain aging affects an increasing segment of the population and the role of chronic cerebrovascular disease is considered to be one of the main parameters involved. For this purpose we compared retrospectively MRI data with digitized subtraction angiography (DSA) data in a group of 50 patients focusing onto the watershed area of the carotid artery vascular territories. In order to evaluate the presence of white matter lesions (WML) in the hemispheric watershed areas, coronal fluid-attenuated inversion-recovery or axial T2 weighted MRI images of patients with symptomatic cerebrovascular insufficiency areas were compared with the capillary phase of DSA studies in anterior-posterior projection. Presence of cerebrovascular occlusive disease was evaluated on DSA using North American symptomatic carotid endarterectomy trial criteria and including evaluation of collateral vascular supply. Pathological MRI findings in the region of the watershed territories correlated overall in 66% of cases with a defect or delayed filling on DSA. In the case of asymmetrical MRI findings, there was a pathological finding of the capillary phase in the watershed area in 92% of DSA studies. Hypoperfusion in the capillary phase of the watershed area as seen on DSA correlated with the stenosis degree of the concerned carotid artery. Our findings suggest that asymmetrical findings of WML in the watershed areas as seen on MRI are caused by hemodynamic effect and a differentiation between small vessel disease and a consequence of distant stenosis may be possible under such condition

The effect of insulin on cardiac autonomic balance predicts weight reduction after gastric bypass

Aims/hypothesis: The aim of this study was to assess the predictive role of autonomic reactivity in body weight loss induced by gastric bypass. Methods: A group of 22 morbidly obese subjects, who were due to undergo a gastric bypass, were submitted, before surgery, to a euglycaemic-hyperinsulinaemic clamp, during which a continuous recording of the ECG was performed. The effect of insulin on cardiac autonomic balance was evaluated by performing power spectral analysis of heart rate variability. The low-to-high frequency ratio was calculated before and during the clamp and its modifications were expressed as % delta low-to-high frequency ratio (%Δ L: H). Results: Preoperative %Δ L: H showed a significant (p=0.0009, r 2=0.43), positive relationship to the reduction of body weight, measured 1 year after surgery and expressed as % excess weight loss (% EWL). Preoperative BMI was also significantly (p=0.0009, r 2=0.43) negatively related to the 12-month % EWL. In a multiple regression analysis, %Δ L: H remained a significant (p=0.003), independent predictor of body weight loss, even when preoperative BMI or age, % fat mass, insulinaemia and glucose disposal were taken into account. Conclusions/interpretation: The best correction of excess body weight was achieved by those obese subjects who had a preserved capacity to shift their cardiac autonomic balance towards a sympathetic prevalence in response to an euglycaemic-hyperinsulinaemic clamp. Further studies are needed to elucidate the mechanisms through which the autonomic nervous system influences weight reductio

Heart rate variability: Measurement and emerging use in critical care medicine

Variation in the time interval between consecutive R wave peaks of the QRS complex has long been recognised. Measurement of this RR interval is used to derive heart rate variability. Heart rate variability is thought to reflect modulation of automaticity of the sinus node by the sympathetic and parasympathetic components of the autonomic nervous system. The clinical application of heart rate variability in determining prognosis post myocardial infarction and the risk of sudden cardiac death is well recognised. More recently, analysis of heart rate variability has found utility in predicting foetal deterioration, deterioration due to sepsis and impending multiorgan dysfunction syndrome in critically unwell adults. Moreover, reductions in heart rate variability have been associated with increased mortality in patients admitted to the intensive care unit. It is hypothesised that heart rate variability reflects and quantifies the neural regulation of organ systems such as the cardiovascular and respiratory systems. In disease states, it is thought that there is an ‘uncoupling’ of organ systems, leading to alterations in ‘inter-organ communication’ and a clinically detectable reduction in heart rate variability. Despite the increasing evidence of the utility of measuring heart rate variability, there remains debate as to the methodology that best represents clinically relevant outcomes. With continuing advances in technology, our understanding of the physiology responsible for heart rate variability evolves. In this article, we review the current understanding of the physiological basis of heart rate variability and the methods available for its measurement. Finally, we review the emerging use of heart rate variability analysis in intensive care medicine and conditions in which heart rate variability has shown promise as a potential physiomarker of disease

Prevalence, Clinical Staging and Risk for Blood-Borne Transmission of Chagas Disease among Latin American Migrants in Geneva, Switzerland

Chagas disease, a parasitic disease caused by Trypanosoma cruzi, is a leading cause of cardiac and digestive tract disorders in Mexico, Central and South America. An increasing number of cases have recently been reported in North America and Europe due to international human migration, but data outside Latin America remains scarce. This study showed that Chagas disease is an emerging health problem in Switzerland, affecting a substantial proportion of Latin American migrants (13%). Persons at increased risk of infection were Bolivian, older than 35 years or had a mother infected with T. cruzi. Early signs of cardiac or digestive tract disease were found in one out of six infected patients. The risk of local transmission by blood transfusion or organ transplant was illustrated by the frequent willingness expressed by patients to donate blood or organs in Switzerland. The authors recommend the screening of persons at risk of infection and the diffusion of appropriate information to the medical community to increase awareness of this emerging health problem. Considering that affected persons frequently lack health insurance in Switzerland, a facilitated access to medical care is an important step towards better recognition and management of Chagas disease

Differences in Heart Rate Variability Associated with Long-Term Exposure to NO2

BACKGROUND: Heart rate variability (HRV), a measure of cardiac autonomic tone, has been associated with cardiovascular morbidity and mortality. Short-term studies have shown that subjects exposed to higher traffic-associated air pollutant levels have lower HRV. OBJECTIVE: Our objective was to investigate the effect of long-term exposure to nitrogen dioxide on HRV in the Swiss cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA). METHODS: We recorded 24-hr electrocardiograms in randomly selected SAPALDIA participants >or= 50 years of age. Other examinations included an interview investigating health status and measurements of blood pressure, body height, and weight. Annual exposure to NO2 at the address of residence was predicted by hybrid models (i.e., a combination of dispersion predictions, land-use, and meteorologic parameters). We estimated the association between NO2 and HRV in multivariable linear regression models. Complete data for analyses were available for 1,408 subjects. RESULTS: For women, but not for men, each 10-microg/m3 increment in 1-year averaged NO2 level was associated with a decrement of 3% (95% CI, -4 to -1) for the standard deviation of all normal-to-normal RR intervals (SDNN), -6% (95% CI, -11 to -1) for nighttime low frequency (LF), and -5% (95% CI, -9 to 0) for nighttime LF/high-frequency (HF) ratio. We saw no significant effect for 24-hr total power (TP), HF, LF, or LF/HF or for nighttime SDNN, TP, or HF. In subjects with self-reported cardiovascular problems, SDNN decreased by 4% (95% CI, -8 to -1) per 10-microg/m3 increase in NO2. CONCLUSIONS: There is some evidence that long-term exposure to NO2 is associated with cardiac autonomic dysfunction in elderly women and in subjects with cardiovascular disease

ADARRI:a novel method to detect spurious R-peaks in the electrocardiogram for heart rate variability analysis in the intensive care unit

We developed a simple and fully automated method for detecting artifacts in the R-R interval (RRI) time series of the ECG that is tailored to the intensive care unit (ICU) setting. From ECG recordings of 50 adult ICU-subjects we selected 60 epochs with valid R-peak detections and 60 epochs containing artifacts leading to missed or false positive R-peak detections. Next, we calculated the absolute value of the difference between two adjacent RRIs (adRRI), and obtained the empirical probability distributions of adRRI values for valid R-peaks and artifacts. From these, we calculated an optimal threshold for separating adRRI values arising from artifact versus non-artefactual data. We compared the performance of our method with the methods of Berntson and Clifford on the same data. We identified 257,458 R-peak detections, of which 235,644 (91.5%) were true detections and 21,814 (8.5%) arose from artifacts. Our method showed superior performance for detecting artifacts with sensitivity 100%, specificity 99%, precision 99%, positive likelihood ratio of 100 and negative likelihood ratio <0.001 compared to Berntson’s and Clifford’s method with a sensitivity, specificity, precision and positive and negative likelihood ratio of 99%, 78%, 82%, 4.5, 0.013 for Berntson’s method and 55%, 98%, 96%, 27.5, 0.460 for Clifford’s method, respectively. A novel algorithm using a patient-independent threshold derived from the distribution of adRRI values in ICU ECG data identifies artifacts accurately, and outperforms two other methods in common use. Furthermore, the threshold was calculated based on real data from critically ill patients and the algorithm is easy to implement

Heart Rate Variability and Atria Function in Children at Late Follow-Up Evaluation After Atrioventricular Node Slow-Pathway Radiofrequency Ablation

This study was designed to assess the changes in the conductive system, autonomic dysfunction, and global and regional function of the atria and ventricles in children late after slow-pathway radiofrequency ablation (RFA). The study enrolled 22 children, who has successfully undergone RFA 2 to 5 years previously (RFA group) and 20 healthy children (control group). Electrophysiologic study was performed for the RFA group. Holter monitoring and echocardiography were performed for all the children. At a late follow-up assessment, the RFA children were free of paroxysms, whereas 8 of the 22 children (36%) reported transient palpitations. Both mean and maximal heart rates (HR) were significantly increased, whereas indices of HR variability (% of succesive normal sinus RR intervals exceeding 50 ms [pNN50], root mean square of the succesive normal sinus RR interval difference [rMSSD], high-frequency component [HFC]) were significantly decreased in the RFA group compared with preablation and control data. Left atrial (LA) and right atrial (RA) volumes were significantly higher, and atria deformation indices were significantly lower in the RFA group. Correlations were found between the mean HR and the volumes of LA (r = 0.477; p < 0.001) and RA (r = 0.512; p < 0.001). A negative correlation between the maximal LA volume and the longitudinal strain rate (SR) during relaxation (r = –0.476; p = 0.03) and a positive correlation between the minimal LA volume and both longitudinal SR (r = 0.361; p = 0.03) and strain (ε) (r = 0.375; p = 0.024) during contraction were shown. These data suggest a possible link between atrial dysfunction and the hyperadrenergic state after RFA