Female sex workers population size estimation in Rwanda using a three-source capture-recapture method.

Establishing accurate population size estimates (PSE) is important for prioritising and planning provision of services. Multiple source capture-recapture sampling method increases PSE accuracy and reliability. In August 2018, the three-source capture-recapture (3S-CRC) method was employed with a stringent assumption of sample independence to estimate the number of female sex workers (FSW) in Rwanda. Using Rwanda 2017 FSW hotspots mapping data, street and venue-based FSW were sampled at the sector level of each province and tagged with two unique gifts. Each capture was completed within one week to minimise FSW migration between provinces and recall bias. The three captures had 1042, 1204 and 1488 FSW. There were 111 FSW recaptured between captures 1 and 2; 237 between captures 2 and 3; 203 between captures 1 and 3 and 46 captured in all three. The PSE for street and venue-based FSW in Rwanda lies within 95% credible set: 8328-22 806 with corresponding median of 13 716 FSW. The 3S-CRC technique was low-cost and relatively easy to use for PSE in hard-to-reach populations. This estimate provides the basis for determining the denominators to assess HIV programme performance towards FSW and epidemic control and warrants further PSE for home- and cyber-based FSW in Rwanda.

Use of a Plasmodium vivax genetic barcode for genomic surveillance and parasite tracking in Sri Lanka.

BACKGROUND: Sri Lanka was certified as a malaria-free nation in 2016; however, imported malaria cases continue to be reported. Evidence-based information on the genetic structure/diversity of the parasite populations is useful to understand the population history, assess the trends in transmission patterns, as well as to predict threatening phenotypes that may be introduced and spread in parasite populations disrupting elimination programmes. This study used a previously developed Plasmodium vivax single nucleotide polymorphism (SNP) barcode to evaluate the population dynamics of P. vivax parasite isolates from Sri Lanka and to assess the ability of the SNP barcode for tracking the parasites to its origin. METHODS: A total of 51 P. vivax samples collected during 2005-2011, mainly from three provinces of the country, were genotyped for 40 previously identified P. vivax SNPs using a high-resolution melting (HRM), single-nucleotide barcode method. Minor allele frequencies, linkage disequilibrium, pair-wise FST values, and complexity of infection (COI) were evaluated to determine the genetic diversity. Structure analysis was carried out using STRUCTURE software (Version 2.3.4) and SNP barcode was used to identify the genetic diversity of the local parasite populations collected from different years. Principal component analysis (PCA) was used to determine the clustering according to global geographic regions. RESULTS: The proportion of multi-clone infections was significantly higher in isolates collected during an infection outbreak in year 2007. The minor allele frequencies of the SNPs changed dramatically from year to year. Significant linkage was observed in sample sub-sets from years 2005 and 2007. The majority of the isolates from 2007 consisted of at least two genetically distinct parasite strains. The overall percentage of multi-clone infections for the entire parasite sample was 39.21%. Analysis using STRUCTURE software (Version 2.3.4) revealed the high genetic diversity of the sample sub-set from year 2007. In-silico analysis of these data with those available from other global geographical regions using PCA showed distinct clustering of parasite isolates according to geography, demonstrating the usefulness of the barcode in determining an isolate to be indigenous. CONCLUSIONS: Plasmodium vivax parasite isolates collected during a disease outbreak in year 2007 were more genetically diverse compared to those collected from other years. In-silico analysis using the 40 SNP barcode is a useful tool to track the origin of an isolate of uncertain origin, especially to differentiate indigenous from imported cases. However, an extended barcode with more SNPs may be needed to distinguish highly clonal populations within the country.

Improving recognition and management of acute kidney injury.

Acute kidney injury (AKI) is currently suboptimally recognised and managed in the UK, despite its association with significant patient morbidity, mortality and consequent implications for healthcare economics. Our prospective study, performed in a large urban London hospital, demonstrated that the introduction of a specially designed care bundle can significantly improve documentation of baseline creatinine, assessment and optimisation of fluid status, performance of urine dip, withholding of nephrotoxic drugs, appropriate monitoring of urine output, prescription of renal drug doses, and appropriate consideration of a renal ultrasound and urinary protein-creatinine ratio. Improved compliance of appropriate investigations and initial treatments translated to decreased requirement for intensive care admission and a trend towards shorter length of stays.

Seasonal variation in the management and outcomes of cardiac arrest complicating acute myocardial infarction.

BACKGROUND: There are limited data on the influence of seasons on the outcomes of acute myocardial infarction-cardiac arrest (AMI-CA). AIM: To evaluate the outcomes of AMI-CA by seasons in the United States. DESIGN: Retrospective cohort study. METHODS: Using the National Inpatient Sample from 2000 to 2017, adult (>18 years) admissions with AMI-CA were identified. Seasons were defined by the month of admission as spring, summer, fall and winter. The outcomes of interest were prevalence of AMI-CA, in-hospital mortality, use of coronary angiography, percutaneous coronary intervention (PCI), hospital length of stay, hospitalization costs and discharge disposition. RESULTS: Of the 10 880 856 AMI admissions, 546 334 (5.0%) were complicated by CA, with a higher prevalence in fall and winter (5.1% each) compared to summer (5.0%) and spring (4.9%). Baseline characteristics of AMI-CA admissions admitted in various seasons were largely similar. Compared to AMI-CA admissions in spring, summer and fall, AMI-CA admissions in winter had slightly lower rates of coronary angiography (63.3-64.3% vs. 61.4%) and PCI (47.2-48.4% vs. 45.6%). Compared to those admitted in the spring, adjusted in-hospital mortality was higher for winter {46.8% vs. 44.2%; odds ratio (OR) 1.08 [95% confidence interval (CI) 1.06-1.10]; P < 0.001}, lower for summer [43% vs. 44.2%; OR 0.97 (95% CI 0.95-0.98); P < 0.001] and comparable for fall [44.4% vs. 44.2%; OR 1.01 (95% CI 0.99-1.03); P = 0.31] AMI-CA admissions. Length of hospital stay, total hospitalization charges and discharge dispositions for AMI-CA admissions were comparable across the seasons. CONCLUSIONS: AMI-CA admissions in the winter were associated with lower rates of coronary angiography and PCI, and higher rates of in-hospital mortality compared to the other seasons.

Transport and magnetotransport studies on Sol-Gel grown nanostructured La0.7Pb0.3MnO3 manganites.

Sol-Gel synthesis offers relatively inexpensive scale processing of mixed oxide materials with a good control over the stoichiometry and morphology which helps to tailor the required materials on atomic scale to suit specific applications. Nanophasic polycrystalline samples of La0.7Pb0.3MnO3 (LPMO) manganites having perovskite type structure synthesized by novel Sol-Gel technique using acetate precursor route were sintered at various temperatures in the range 950-1150 degrees C for studying the effect of grain size modifications on their structural, transport and magnetotransport properties. X-ray diffraction (XRD) studies show that the samples exhibit rhombohedral structure crystallizing in space group R-3C. Microstructural investigations using Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM) measurements reveal the observation of secondary grain growth behavior starting in the sample sintered at 1000 degrees C. The d.c. four probe resistivity measurements with and without applied magnetic field in the temperature range of 2-380 K, show the effect of secondary grain growth on the magnetoresistance (MR) behavior of LPMO manganites. The microstructural studies show the atomic scale engineering at nanoscale which is reflected in the improvement of surface to volume ratio (D(-1)) which in turn modifies the physical properties of samples under investigation. All the samples exhibit resistivity minima at approximately 30 K which can be explained in terms of e-e interaction at 0 Tesla field. There is a correlation between the parameters derived from e-e scattering model and the secondary grain growth present in the samples. The results of the microstructural and MR measurements on the nanostructured LPMO manganites have been discussed in detail.

Factors influencing medical student self-competence to provide weight management services.

This study aimed to identify factors associated with high obesity care self-competence among US medical students. The authors performed a cross-sectional analysis of 2014 survey data on fourth year medical students collected online as part of the Medical Student Cognitive Habits and Growth Evaluation Study (CHANGES). Independent variables included quality and quantity of interaction with patients and peers with obesity; hours of communication and partnership skills training; negative remarks against patients with obesity by supervising physicians, and witnessed discrimination against patients with obesity. The dependent variable was self-competence in providing obesity care. Of 5823 students invited to participate, 3689 (63%) responded and were included in our analyses. Most students were white (65%), half were women and 42% had high self-competence in caring for patients with obesity. Factors associated with high self-competence included increased interaction with peers with obesity (39% vs. 49%, P < 0.001) and increased partnership skills training (32% vs. 61%, P < 0.001). Increased partnership skills training and quantity of interactions with peers with obesity were associated with high student self-competence in providing obesity-related care to patients. Medical schools might consider increasing partnership skills training to improve students' preparedness and skill in performing obesity-related care.

Grain size dependent transport and magnetoresistance behavior of chemical solution deposition grown nanostructured La0.7Sr0.3MnO3 manganite films.

Grain-size dependence of electronic transport and magnetoresistance (MR) properties of nanostructured La0.7Sr0.3MnO3 (LSMO) manganite thin films on LaAlO3 (100) single crystal substrates prepared using Chemical Solution Deposition (CSD) technique have been studied. The LSMO thin films were annealed at temperatures in the range of 700-1000 degrees C for different time intervals [6 h and 12 h] and crystallized as singlephase LSMO. Microstructural studies carried out using AFM show a marginal increase in the grain-size from 50 to 90 nm as the temperature was varied from 700 degrees C to 1000 degrees C respectively. It has been observed that the insulator-metal transition (T(p)) and MR depend on the grain size. In zero applied field, resistivity reduction is approximately 10(3) at 5 K for the films annealed at 700 degrees C [T(p) approximately 341 K] and 1000 degrees C [T(p) approximately 373 K]. MR versus H isotherms reveal that MR enhances in the vicinity of T(p) but decreases at low temperatures. The results obtained from the electronic and magnetotransport studies are in good agreement with the change in surface morphology of the films studied, which shows that the randomly distributed domains are composed of faceted grains. Synthesizing conditions, annealing temperature and time control the growth and alignment of grains into the domains, which cause better conduction at grain interface.

Detection and classification of leprosy: future needs and strategies.

This paper focuses on the obstacles and dilemmas in detection and classification of leprosy cases and suggested strategies for the same. This review attempts to raise some cardinal issues within leprosy diagnosis and the need for capacity building at clinical and field level in light of research conducted. It also recommends strategies to overcome these obstacles.

Differential regulation of right and left ventricular beta-adrenergic receptors in newborn lambs with experimental cyanotic heart disease.

To determine whether chronic hypoxemia secondary to an intracardiac right-to-left shunt alters regulation of the myocardial beta-adrenergic receptor/adenylate cyclase system, we produced chronic hypoxemia in nine newborn lambs by creating right ventricular outflow obstruction and an atrial septal defect. Oxygen saturation was reduced to 65-74% for 2 wk. Eight lambs served as normoxemic controls. beta-receptor density (Bmax) and ligand affinity (KD) were determined with the radio-ligand [125I]iodocyanopindolol and adenylate cyclase activity determined during stimulation with isoproterenol, sodium fluoride (NaF), and forskolin. During chronic hypoxemia, Bmax decreased 45% (hypoxemic, 180.6 +/- 31.5 vs. control, 330.5 +/- 60.1 fmol/mg) in the left ventricle (exposed to hypoxemia alone) but was unchanged in the right ventricle (exposed to hypoxemia and pressure overload). KD was not different from control in either ventricle. Left ventricular isoproterenol-stimulated adenylate cyclase activity was decreased by 39% (30.0 +/- 4.3% increase vs. 44.1 +/- 9.5% increase) whereas right ventricular adenylate cyclase activity was unchanged. Stimulation of adenylate cyclase with NaF or forskolin was not different from control in either ventricle. Circulating epinephrine was increased fourfold whereas circulating and myocardial norepinephrine were unchanged. These data demonstrate a down-regulation of the left ventricular beta-adrenergic receptor/adenylate cyclase system during chronic hypoxemia secondary to an intracardiac right-to-left shunt.

Efficient nonviral transfection of dendritic cells and their use for in vivo immunization.

Immunization with dendritic cells (DCs) transfected with genes encoding tumor-associated antigens (TAAs) is a highly promising approach to cancer immunotherapy. We have developed a system, using complexes of plasmid DNA expression constructs with the cationic peptide CL22, that transfects human monocyte-derived DCs much more efficiently than alternative nonviral agents. After CL22 transfection, DCs expressing antigens stimulated autologous T cells in vitro and elicited primary immune responses in syngeneic mice, in an antigen-specific manner. Injection of CL22-transfected DCs expressing a TAA, but not DCs pulsed with a TAA-derived peptide, protected mice from lethal challenge with tumor cells in an aggressive model of melanoma. The CL22 system is a fast and efficient alternative to viral vectors for engineering DCs for use in immunotherapy and research.

Health Professionals' perceptions of insurance coverage for weight loss services.

Objective: To examine health professionals' (HPs) perceptions of top challenges and solutions in obesity care, and whether these perceptions differ by patient-panel income level. Methods: A 2014 national cross-sectional survey of HPs in nutrition, nursing, behavioural or mental health, exercise and pharmacy was analysed. The dependent variables were identification of insurance coverage for their services as a top (1) challenge or (2) solution for obesity care. The independent variable was self-reported income distribution of HPs' patient panels, which was dichotomized as 'lower-income' if 'mostly low income' or 'higher-income' if 'mostly not low income/evenly split between low-income and not low-income'. Multivariate logistic regression with survey weights was used. Results: Among 450 HPs, mean age was 44.9 years; 86% were women; 44% had lower-income panels. Overall, 25% of HPs endorsed insurance coverage as a current challenge, and 58% viewed improved coverage as a solution. HPs with lower and higher-income patient panels were similarly likely to identify coverage as a challenge (28% vs. 20%, p = 0.33) and benefits expansion as a solution (47% vs. 64%, p = 0.08). Conclusions: Most HPs perceive insurance coverage for their services to benefit patient weight loss. While the Affordable Care Act expands obesity counselling coverage to many lower-income patients, legislation increasing access to benefits for all patients regardless of insurance type may be beneficial.

An unusual source of Burkholderia cepacia outbreak in a neonatal intensive care unit.

During a two-month period, seven preterm infants in our neonatal intensive care unit (NICU) were found to have sepsis with Burkholderia cepacia demonstrated by blood culture. A complete environmental investigation was conducted to identify the source of infection. Caffeine citrate was found to be the source of this organism. The offending drug was immediately withdrawn from the NICU and the hospital pharmacy, and local authorities were informed. All seven babies were discharged with no infection-related morbidities.

A systematic review of commercial weight loss programmes' effect on glycemic outcomes among overweight and obese adults with and without type 2 diabetes mellitus.

OBJECTIVE: We examined the glycemic benefits of commercial weight loss programmes as compared with control/education or counselling among overweight and obese adults with and without type 2 diabetes mellitus (T2DM). METHODS: We searched MEDLINE, Cochrane Database of Systematic Reviews, and references cited by individual programmes. We included randomized controlled trials of ≥12 weeks duration. Two reviewers extracted information on study design, population characteristics, interventions, and mean changes in haemoglobin A1c and glucose. RESULTS: We included 18 randomized controlled trials. Few trials occurred among individuals with T2DM. In this population, Jenny Craig reduced A1c at least 0.4% more than counselling at 12 months, Nutrisystem significantly reduced A1c 0.3% more than counselling at 6 months, and OPTIFAST reduced A1c 0.3% more than counselling at 6 months. Among individuals without T2DM, few studies evaluated glycemic outcomes, and when reported, most did not show substantial reductions. DISCUSSION: Few trials have examined whether commercial weight loss programmes result in glycemic benefits for their participants, particularly among overweight and obese individuals without T2DM. Jenny Craig, Nutrisystem and OPTIFAST show promising glycemic lowering benefits for patients with T2DM, although additional studies are needed to confirm these conclusions. © 2016 World Obesity.

Vein of marshall cannulation for the analysis of electrical activity in patients with focal atrial fibrillation.

BACKGROUND: Whether or not the muscle bundle within the ligament of Marshall (LOM) can serve as the origin of focal atrial fibrillation (AF) is unknown. METHODS AND RESULTS: A total of 28 consecutive patients with paroxysmal AF underwent balloon-occlusion coronary sinus angiograms to identify the vein of Marshall (VOM). Attempts were then made to advance a 1.5-French electrophysiological catheter into the VOM via the coronary sinus orifice. In 17 of the 28 patients (10 of 17 were men aged 38+/-15 years), cannulation was successful. Double potentials were registered in 8 of these 17 patients. The first potential corresponded with local left atrial activation. The second potential was shorter and narrower than the first. The sequence of activation in the second potential in the VOM was proximal to distal. In 6 patients with direct VOM recordings, we documented that the origin of AF was in the muscle bundle within the LOM. Radiofrequency catheter ablation aimed at the insertion site of the VOM successfully terminated AF in 4 of these 6 patients. CONCLUSIONS: (1) It is possible to cannulate and to record electrical potentials from the VOM. (2) The characteristics of the double potentials within the VOM suggest that the second potential is from the muscle bundle (Marshall bundle) within the LOM. (3) The Marshall bundle may be the origin of focal AF in some patients.

Mechanism of procainamide-induced prevention of spontaneous wave break during ventricular fibrillation. Insight into the maintenance of fibrillation wave fronts.

BACKGROUND: Ventricular fibrillation (VF) is maintained by 2 mechanisms: first by reentry formation and second by spontaneous wave break or wave splitting. We hypothesized that spontaneous wave break results from a critical shortening of the action potential duration (APD) during VF and that its prevention by procainamide eliminates spontaneous wave break. METHODS AND RESULTS: The endocardial surfaces of 7 isolated, perfused swine right ventricles were mapped with a 3.2x3.8 cm plaque with 477 bipolar electrodes. Activation pattern during VF was visualized dynamically while simultaneously recording epicardial action potentials with a glass microelectrode. APD restitution curves were constructed during VF (dynamic) and during S(1)S(2) protocols. At baseline, VF was maintained by 5.3+/-1 wavelets. Procainamide (PA) at 10 microgram/mL decreased the number of wavelets to 3.5+/-1 (P<0.05). At baseline VF was maintained by spontaneous wave break and by new reentrant wave front formation. PA eliminated spontaneous wave break during VF while having no effect on reentry formation. PA increased the cycle length of the VF (148.5+/-41.2 ms vs 81+/-10 ms, P<0.01) and the core area of the reentry from 5.8 to 14.5 mm(2) (P<0.05). Dynamic APD restitution curve during VF showed that PA eliminated the initiation of activation with APDs shorter than 30 ms. The effects of PA on cellular properties and wave front dynamics were reversed during 60 minutes of drug-free perfusion. CONCLUSIONS: Critically short APDs during VF promote spontaneous wave break. Their elimination with PA, however, maintains VF by generating new reentrant wave front.

Relation between ligament of Marshall and adrenergic atrial tachyarrhythmia.

BACKGROUND: The mechanism of the adrenergic atrial tachyarrhythmia is unclear. We hypothesize that the ligament of Marshall (LOM) is sensitive to adrenergic stimulation and may serve as a source of the adrenergic atrial tachyarrhythmia. METHODS AND RESULTS: We performed computerized mapping studies in isolated-perfused canine left atrial tissues from normal dogs (n=9) and from dogs with chronic atrial fibrillation (AF) induced by 10 to 41 weeks of rapid pacing (n=3). Before isoproterenol, spontaneous activity occurred in only one normal tissue (cycle length, CL >1300 ms). During isoproterenol infusion, automatic rhythm was induced in both normal tissues (CL=578+/-172 ms) and AF tissues (CL=255+/-29 ms, P<0.05). The origin of spontaneous activity was mapped to the LOM. In the AF tissues, but not the normal tissues, we observed the transition from rapid automatic activity to multiple wavelet AF. Ablation of the LOM terminated the spontaneous activity and prevented AF. Immunocytochemical studies of the LOM revealed muscle tracts surrounded by tyrosine hydroxylase-positive (sympathetic) nerves. CONCLUSIONS: We conclude that the LOM is richly innervated by sympathetic nerves and serves as a source of isoproterenol-sensitive focal automatic activity in normal canine atrium. The sensitivity to isoproterenol is upregulated after long-term rapid pacing and may contribute to the development of AF in this model.

Pulmonary veins and ligament of Marshall as sources of rapid activations in a canine model of sustained atrial fibrillation.

BACKGROUND: In dogs, chronic rapid pacing may result in sustained atrial fibrillation (AF). However, activation patterns in pacing-induced sustained AF are unclear. METHODS AND RESULTS: We induced sustained AF (>48 hours) in 6 dogs by rapid pacing for 139+/-84 days. We then performed computerized atrial epicardial mappings and recorded the activations in the ligament of Marshall (LOM) and the pulmonary veins (PVs). During AF, mean activation cycle length in the right atrial free wall (126+/-17 ms) was significantly longer than that in the left atrial free wall (96+/-5 ms, P:=0.006). In addition, mean activation cycle length in the left atrial free wall was significantly longer than that in the LOM (84+/-5 ms, P:<0.001), the left inferior PV (81+/-4 ms, P:=0.001), and the left superior PV (85+/-7 ms, P:=0.003). Similarly, the dominant frequency was highest in the LOM and the PVs (range 11.2 to 13.3 Hz), followed by the left and right atria (P:<0.001). In all dogs studied, rapid and complicated electrograms were consistently observed at the LOM and the PVs. During AF, both wandering wavelets and organized reentry were present. There were more wave fronts in the left atrium than in the right atrium (P:<0.001). CONCLUSIONS: In chronic pacing-induced sustained AF, the LOM and the PVs are the sources of rapid activations. The mechanism by which the left atrium activates faster and has more wave fronts than the right atrium may relate to the fact that the left atrium is closer to the sources of rapid activations.

Nerve sprouting and sympathetic hyperinnervation in a canine model of atrial fibrillation produced by prolonged right atrial pacing.

BACKGROUND: Long-term rapid atrial pacing may result in atrial fibrillation (AF) in dogs. Whether there is histological evidence for neural remodeling is unclear. METHOD AND RESULTS: We performed rapid right atrial pacing in 6 dogs for 111+/-76 days to induce sustained AF. Tissues from 6 healthy dogs were used as controls. Immunocytochemical staining of cardiac nerves was performed using anti-growth-associated protein 43 (GAP43) and anti-tyrosine hydroxylase (TH) antibodies. In dogs with AF, the density of GAP43-positive and TH-positive nerves in the right atrium was 470+/-406 and 231+/-126 per mm(2), respectively, which was significantly (P:<0.001) higher than the nerve density in control tissues (25+/-32 and 88+/-40 per mm(2), respectively). The density of GAP43-positive and TH-positive nerves in the atrial septum was 317+/-36 and 155+/-85 per mm(2), respectively, and was significantly (P:<0.001) higher than the nerve density in control tissues (9+/-13 and 30+/-7 per mm(2), respectively). Similarly, the density of GAP43-positive and TH-positive nerves in the left atrium of dogs with AF was 119+/-61 and 91+/-40 per mm(2), respectively, which was significantly (P:<0.001) higher than the nerve density in control tissues (10+/-15 and 38+/-39 per mm(2), respectively). Furthermore, in dogs with AF, the right atrium had a significantly higher nerve density than the left atrium. Microscopic examinations revealed an inhomogeneous distribution of cardiac nerves within each sampling site. CONCLUSIONS: Significant nerve sprouting and sympathetic hyperinnervation are present in a canine model of sustained AF produced by prolonged right atrial pacing. The magnitude of nerve sprouting and hyperinnervation was higher in the right atrium than in the left atrium.

Role of papillary muscle in the generation and maintenance of reentry during ventricular tachycardia and fibrillation in isolated swine right ventricle.

BACKGROUND: The role of papillary muscle (PM) in the generation and maintenance of reentry is unclear. METHODS AND RESULTS: Computerized mapping (477 bipolar electrodes, 1.6-mm resolution) was performed in fibrillating right ventricles (RVs) of swine in vitro. During ventricular fibrillation (VF), reentrant wave fronts often transiently anchored to the PM. Tissue mass reduction was then performed in 10 RVs until VF converted to ventricular tachycardia (VT). In an additional 6 RVs, procainamide infusion converted VF to VT. Maps showed that 77% (34 of 44) of all VT episodes were associated with a single reentrant wave front anchored to the PM. Purkinje fiber potentials preceded the local myocardial activation, and these potentials were recorded mostly around the PM. When PM was trimmed to the level of endocardium (n = 4), sustained VT was no longer inducible. Transmembrane potential recordings (n = 5) at the PM revealed full action potential during pacing, without evidence of ischemia. Computer simulation studies confirmed the role of PM as a spiral wave anchoring site that stabilized wave conduction. CONCLUSIONS: We conclude that PM is important in the generation and maintenance of reentry during VT and VF.

Calculation of volume flow rate by the proximal isovelocity surface area method: simplified approach using color Doppler zero baseline shift.

OBJECTIVES: The goal of this study was to develop an accurate, simplified proximal isovelocity surface area (PISA) method for calculating volume flow rate using lower blue-red interface velocity produced by a color Doppler zero baseline shift technique. BACKGROUND: The Doppler color proximal isovelocity surface area method has been shown to be accurate for calculating the volume flow rate (Q) across a narrowed orifice by the formula Q = PISA x Blue-red interface velocity. A hemispheric model is generally used to calculate proximal isovelocity surface area (PISA = 2 pi a2, where a = the radius corresponding to the blue-red interface velocity). Although a hemispheric model is simple, requiring measurement of one radius, it may underestimate the actual volume flow rate because, in the general case, the shape of a proximal isovelocity surface area is hemielliptic. Although a hemielliptic model is generally more accurate for calculating proximal isovelocity surface area, it is more complex, requiring measurement of two orthogonal radii. METHODS: Sixteen in vitro constant flow model studies were performed using planar circular orifices (diameter range 6 to 16 mm). The blue-red interface velocity was changed from 3 to 54 cm/s using color Doppler zero baseline shift. RESULTS: 1) With decreasing blue-red interface velocity, the size of the proximal isovelocity surface area was increased, and its shape changed from hemielliptic to hemispheric. 2) With the blue-red interface velocity in the range 11 to 15 cm/s, the proximal isovelocity surface area became nearly hemispheric; however, it was difficult to determine the blue-red interface radius at a blue-red interface velocity < 10 cm/s because of interface fluctuations. 3) Calculated volume flow rate using the hemispheric proximal isovelocity surface area model with a single radius was relatively accurate at a blue-red interface velocity of 11 to 15 cm/s (mean percent difference from actual volume flow rate was -3.6%). CONCLUSIONS: Because the shape of the proximal isovelocity surface area is nearly hemispheric at a blue-red interface velocity of 11 to 15 cm/s, volume flow rate can be accurately calculated in this proximal isovelocity surface area interface velocity range (produced by zero baseline shift) by measuring a single-interface radius. This approach should be clinically useful for calculating the volume flow rate across stenotic and regurgitant valves and across shunt defects.