Cardiology across continents: an interactive, case-based learning series.

Heart University [https://www.heartuniversity.org/] is a free educational website providing structured training curricula with knowledge-based testing and access to webinars and conference recordings for practicing and in-training providers of paediatric and congenital cardiac care. To date, there are over 15,000 registered website users from over 140 countries on Heart University, with over 2,000 training modules and/or recorded educational videos. Heart University has developed an "asynchronous" educational lecture series entitled "Pediatric and Congenital Cardiac Care in Resource-Limited Settings." This recorded lecture series is specifically focused on topics relevant to practicing paediatric and/or congenital cardiac care in low-resource settings.A relatively new initiative, "Cardiology Across Continents," supplements the existing educational resources for providers of paediatric and/or congenital cardiac care in low-income countries and lower-middle-income countries by providing an additional live, interactive, case-based forum. Sessions occur every 1-2 months and focus on challenging cases from diagnostic or management perspective with a view to promote collaboration between partnered institutions. "Cardiology Across Continents" is an expanding initiative that facilitates learning and collaboration between clinicians across varied practice settings via interactive case discussions. We welcome trainees and providers of paediatric and congenital cardiac care to join the sessions and invite any insight that can enhance learning for clinicians around the world. This manuscript describes "Cardiology Across Continents" and discusses the development, history, current status, and future plans of Heart University.

Early triage echocardiography to predict outcomes in patients admitted with COVID-19: a multicenter study.

INTRODUCTION: Cardiac involvement seems to impact prognosis of COVID-19, especially in critically ill patients. We aimed to assess the prognostic value of right ventricular (RV) and left ventricular (LV) dysfunction, evaluated by bedside triage echocardiography (echo), in patients admitted to emergency departments (ED) in the US with COVID-19. We also assessed the feasibility of using cloud imaging for sharing and interpreting echocardiograms. METHODS: Patients admitted to three reference EDs with confirmed COVID-19 underwent triage echo within 72 h of symptom onset with remote interpretation. Clinical and laboratory data, as well as COVID-19 symptoms, were collected. The association between echo variables, demographics and clinical data with all-cause hospital mortality and intensive care unit (ICU) admission was assessed using logistic regression. RESULTS: Three hundred ninety-nine patients were enrolled, 41% women, with a mean age of 62±16 years. Mean oxygen saturation on presentation was 92.3± 9.2%. Compared to in-hospital survivors, non-survivors were older, had lower oxygen saturation on presentation, were more likely to have a chronic condition and had lower LV ejection fraction (50.3±19.7% vs. 58.0±13.6%) (P < .05). In the cohort, 101 (25%) patients had moderate/severe LV dysfunction, 131 (33%) had moderate/severe RV dysfunction. Advanced age and lower oxygen saturation were independently associated with death and ICU admission. LV and RV function, or other echo variables, were not independent predictors of outcomes. CONCLUSION: In patients admitted with COVID-19 undergoing early echo triage, the independent predictors of death and ICU admission were age and oxygen saturation. The inclusion of echo variables did not improve prediction of unfavorable outcomes.

Transcatheter Closure of a Coronary Artery Fistula in a Neonate with Tetralogy of Fallot.

Coronary artery-to-pulmonary artery fistulae are a not uncommon finding in patients with Tetralogy of Fallot (TOF) and collateral-dependent pulmonary blood flow. Management for these fistulae is often primary surgical ligation or unifocalization at the time of complete repair, dependent on the presence of dual blood flow to the involved areas. We present the case of a 32-week premature boy weighing 1.79 kg with TOF, confluent branch pulmonary arteries, major aortopulmonary collaterals, and right coronary artery to main pulmonary artery fistula. The patient demonstrated evidence of coronary steal into the pulmonary vasculature with an elevation in the troponin level without hemodynamic instability, and subsequently underwent successful transcatheter occlusion of the fistula via right common carotid access using a Medtronic 3Q microvascular plug. This case demonstrates the realistic potential for early coronary steal in this physiology and possibility of transcatheter therapy even in a small neonate.

Atrial Reservoir Strain is Associated with Decreased Cardiac Index and Adverse Outcomes Post Fontan Operation.

Fontan patients rely on atrial function for diastolic filling and to augment cardiac output. Emerging data suggests that diminished atrial function is predictive of poor outcomes in adults but studies evaluating the association between atrial mechanics in Fontan patients and outcomes are lacking. We sought to assess atrial function in Fontan patients using speckle tracking echocardiography to determine whether atrial function is associated with invasive hemodynamics and clinical outcomes. Single-center review of Fontan patients receiving both catheterization and echocardiogram from 2012-2017. Atrial reservoir, conduit and pump global longitudinal strain and strain rate were assessed by speckle tracking echocardiography. The primary outcome was a composite of all adverse clinical outcomes including cardiac hospitalizations, transplant and death. Eighty-three Fontan patients at a median age of 14.2 years (IQR 8.6, 21.7) at time of echocardiogram were included. Increased atrial reservoir strain (p = 0.04), atrial emptying fraction (p = 0.04) and atrial fractional area change (p = 0.04), were associated with higher cardiac index at baseline. There were no associations between atrial strain and systemic ventricular end diastolic pressure (EDP) at catheterization. Reservoir strain was inversely associated with the composite clinical outcome on multivariable Cox proportional hazard analysis (HR 0.96, p = 0.03). Reduced atrial function is associated with reduced cardiac index, but is not directly associated with ventricular EDP in Fontan patients. Reservoir strain is associated with an excess of adverse clinical outcomes in Fontan patients.

Epicardial Implantation of a Micra™ Pacemaker in a Premature Neonate with Congenital Complete Heart Block.

Pacemaker implantation in neonates can be challenging due to their small size. Even pulse generators adapted for pediatric patients, such as the Microny device (Abbott, Chicago, IL, USA), are proportionately large in comparison to the size of the smallest newborns. Due to anatomic considerations, such as small vascular and ventricular sizes, leadless pacemakers and transvenous implantation in the youngest neonatal population remain unsuitable. Even so, the desire for leadless devices has prompted the industry to create the smallest pacemakers available. Adapting the smaller Micra™ transcatheter leadless pacing system (Medtronic, Minneapolis, MN, USA) for an epicardial pacing application may be advantageous to the smallest patients. This case illustrates the use of a Micra™ device modified with a header block to serve as the pulse generator in a ventricular epicardial pacing system for a 1-day-old, 2.68-kg patient with complete heart block.

Prosapia bicincta (Hemiptera: Cercopidae) abundance, plant associations, and impacts on groundcover in Hawai'i Island rangelands.

The twolined spittlebug, Prosapia bicincta (Say), is a major economic pest of forage grass and turfgrass. Prosapia bicincta was first detected in rangelands on Hawai'i Island in 2016 and has since spread to an estimated 72,000 ha in the North and South Kona districts. This study aimed to quantify P. bicincta abundance, plant associations, and impacts on groundcover over time. Monthly surveys of P. bicincta nymphs and adults were conducted from February 2018 to September 2022 along 17 established 100-m transects at 4 ranches located in Kona, Hawai'i Island, spanning an elevation gradient from 519 to 1,874 m above sea level (a.s.l.). Monitoring revealed P. bicincta occurs from 519 to 1,679 m a.s.l., primarily in Kikuyu grass (Cenchrus clandestinus (Hochst. ex Chiov.)) Morrone (Poales: Poaceae) pastures. Peaks in P. bicincta abundance coincided with the wet season, with most activity occurring from April to October and little to no activity between November and March. Mid elevation (1,000-1,300 m) transects had significantly higher mean P. bicincta abundance (126 nymphs/m2) relative to low (500-999 m) (64 nymphs/m2) and high elevations (>1,300 m) (20 nymphs/m2). Sites with the highest abundance of P. bicincta were also associated with the greatest decrease in mean grass cover (30%) and were replaced by forbs, bare ground, and shrubs. Grasses accounted for 72% of the total P. bicincta detections, with the remaining plants comprised of legumes (16%), sedges (6%), and forbs (6%). Twenty new P. bicincta plant associations were found. This information will help improve the effectiveness of management to suppress populations below economic thresholds.

Host plant resistance of cool-season (C3) turfgrasses to above- and belowground feeding by Tipula paludosa (Diptera: Tipulidae).

Feeding on above- and belowground plant tissues by Tipula paludosa Meigen during the period of rapid growth from second to forth instars is highly damaging to cool-season (C3) turfgrasses. It may be possible to reduce this damage by identifying grass genotypes that increase host plant protection. This study examined the impacts of plant genotype, endophyte infection, and plant ontogeny on host plant and insect responses during whole-plant feeding by T. paludosa. A series of no-choice greenhouse trials were conducted with third instar crane flies to determine 1) host plant tolerance in terms of reductions to above- and belowground plant biomass, 2) antixenosis resistance impacting insect behavior (emigration), and 3) antibiosis resistance impacting insect growth. Results showed that insect infestation level was the primary factor influencing plant biomass reductions. Belowground tissues were more tolerant to feeding than were aboveground tissues, with tall fescues, Festuca arundinacea Schreber, being most resistant to aboveground biomass reduction. Host plant associations with intercellular fungal endophytes (E+) decreased insect weight gain and decreased insect movement, but did not increase host plant tolerance. Plant ontogeny affected this response with insect weight gain significantly decreased on young (28 d) growth E+ grasses but not on old (90 d) growth E+ grasses, however. Host plant genotype and plant ontogeny can have significant impacts to host plant tolerance and insect physiology for T. paludosa larva. Furthermore, plant-endophyte associations have apparent sublethal effects that impact insect fitness and may further enhance host plant protection.

Occult Diastolic Dysfunction and Adverse Clinical Outcomes in Adolescents and Young Adults With Fontan Circulation.

Background In Fontan circulation, diastolic dysfunction portends a worse clinical outcome but may be concealed during routine assessment. Invasive evaluation with rapid volume expansion (RVE) can identify patients with occult diastolic dysfunction (ODD). We sought to evaluate the association between ODD and adverse clinical outcomes at medium-term follow-up. Methods and Results We conducted a single-center observational study of patients with Fontan circulation who underwent clinical catheterization with RVE from 2012 to 2017. ODD was defined as post-RVE end-diastolic pressure ≥15 mm Hg. A composite adverse clinical outcome included mortality, cardiac transplant, ventricular assist device, plastic bronchitis, protein-losing enteropathy, arrhythmia, stroke/thrombus, or cardiac-related hospital admission. Proportional hazards regression was used to compare the ODD-positive and ODD-negative groups for risk of the composite adverse clinical outcome. Eighty-nine patients with Fontan circulation (47% female patients) were included at a median age of 14 years. ODD was identified in 31%. Fontan duration was longer in the ODD group (P=0.001). The composite adverse clinical outcome occurred more frequently in the ODD group (52 versus 26%, P=0.03) during a median follow-up duration of 2.9 years after catheterization. ODD (hazard ratio [HR], 2.68 [95% CI, 1.28-5.66]; P=0.02) and Fontan duration (HR, 1.07 [95% CI, 1.02-1.12]; P=0.003) were associated with the composite adverse clinical outcome. When stratified by Fontan duration, ODD remained significantly associated with the hazard of adverse clinical outcomes in patients with a Fontan duration ≥10 years (HR, 2.57 [95% CI, 1.03-6.57]; P=0.04). Conclusions Cardiac catheterization with rapid volume expansion reveals a significant incidence of ODD, which relates to Fontan duration. ODD is associated with an increased hazard of adverse clinical outcomes during medium-term follow-up, especially in patients with longer Fontan duration. ODD may portend a worse prognosis in Fontan circulation.

The Use of Artificial Intelligence Guidance for Rheumatic Heart Disease Screening by Novices.

INTRODUCTION: A novel technology utilizing artificial intelligence (AI) to provide real-time image-acquisition guidance, enabling novices to obtain diagnostic echocardiographic images, holds promise to expand the reach of echo screening for rheumatic heart disease (RHD). We evaluated the ability of nonexperts to obtain diagnostic-quality images in patients with RHD using AI guidance with color Doppler. METHODS: Novice providers without prior ultrasound experience underwent a 1-day training curriculum to complete a 7-view screening protocol using AI guidance in Kampala, Uganda. All trainees then scanned 8 to 10 volunteer patients using AI guidance, half RHD and half normal. The same patients were scanned by 2 expert sonographers without the use of AI guidance. Images were evaluated by expert blinded cardiologists to assess (1) diagnostic quality to determine presence/absence of RHD and (2) valvular function and (3) to assign an American College of Emergency Physicians score of 1 to 5 for each view. RESULTS: Thirty-six novice participants scanned a total of 50 patients, resulting in a total of 462 echocardiogram studies, 362 obtained by nonexperts using AI guidance and 100 obtained by expert sonographers without AI guidance. Novice images enabled diagnostic interpretation in >90% of studies for presence/absence of RHD, abnormal MV morphology, and mitral regurgitation (vs 99% by experts, P ≤ .001). Images were less diagnostic for aortic valve disease (79% for aortic regurgitation, 50% for aortic stenosis, vs 99% and 91% by experts, P < .001). The American College of Emergency Physicians scores of nonexpert images were highest in the parasternal long-axis images (mean, 3.45; 81% ≥ 3) compared with lower scores for apical 4-chamber (mean, 3.20; 74% ≥ 3) and apical 5-chamber images (mean, 2.43; 38% ≥ 3). CONCLUSIONS: Artificial intelligence guidance with color Doppler is feasible to enable RHD screening by nonexperts, performing significantly better for assessment of the mitral than aortic valve. Further refinement is needed to optimize acquisition of color Doppler apical views.

Patent Ductus Arteriosus Stent Versus Surgical Aortopulmonary Shunt for Initial Palliation of Cyanotic Congenital Heart Disease with Ductal-Dependent Pulmonary Blood Flow: A Systematic Review and Meta-Analysis.

Background In patients with ductal-dependent pulmonary blood flow, initial palliation includes catheter-based patent ductus arteriosus (PDA) stent or surgical aortopulmonary shunt (APS). This meta-analysis aimed to compare outcomes between PDA stent and APS. Methods and Results A comprehensive literature search yielded six retrospective observational studies. Pooled adjusted hazard ratios (HR) were included to control for covariates and assess time to event analysis. Of 757 patients, 243 (32.1%) underwent PDA stent and 514 (67.9%) underwent APS. Pulmonary atresia with intact ventricular septum and expected biventricular repair were more common with PDA stent compared with APS (39.6% versus 21.2%, P<0.001 and 57.9% versus 46.6%, P=0.007, respectively). There was no statistically significant difference in mortality between PDA stent and APS (HR, 0.71; [95% CI, 0.26-1.93]; P=0.50). PDA stent was associated with lower risk of postprocedural complications (odds ratio [OR], 0.45; [95% CI, 0.25-0.81]; P=0.008), mechanical circulatory support (OR, 0.27; [95% CI, 0.09-0.79]; P=0.02), and shorter intensive care unit length of stay (-4.03 days; [95% CI, -5.99 to -2.07]; P<0.001), hospital length of stay (-5.54 days; [95% CI, -9.20 to -1.88]; P=0.003), and duration of mechanical ventilation (-3.41 days; [95% CI, -5.29 to -1.52]; P<0.001). There was no difference in pulmonary artery growth or hazard of unplanned reintereventions. Conclusions PDA stent has a similar hazard of mortality compared with APS. Benefits to PDA stent include shorter duration of mechanical ventilation, shorter hospital length of stay, and fewer complications. Differences in patient characteristics exist with more patients with pulmonary atresia with intact ventricular septum and expected biventricular repair undergoing PDA stent.

Metatranscriptomic Sequencing of Winter and Spring Planktonic Communities from Lake Erie, a Laurentian Great Lake.

Previous reports suggest planktonic and under-ice winter microbial communities in Lake Erie are dominated by diatoms. Here, we report the assembled metatranscriptomes of 79 Lake Erie surface water microbial communities spanning both the winter (28 samples) and spring (51 samples) months over spatial, temporal, and climatic gradients in 2019 through 2020.

First record of the scarab beetle, Phyllophaga lissopyge from South America, with descriptions of adult seasonal activity and male response to sex attractants.

Phyllophaga lissopyge (Bates) (Coleoptera: Scarabaeidae: Melolonthinae) is reported for the first time from South America. Male sex pheromone response is described for P. lissopyge and two other co-occurring Phyllophaga species. Adults of P. lissopyge and P. menetriesi (Blanchard) flew to traps baited with methyl 2-(methylthio) benzoate whereas adults of P. obsoleta (Blanchard) flew irregularly to four different pheromone compounds. Adult seasonal activity is described from males captures in Rionegro, Antioquia, Colombia.

Timing of Repair in Tetralogy of Fallot: Effects on Outcomes and Myocardial Health.

Early complete repair of tetralogy of Fallot (ToF) prior to 1 year of age has been demonstrated to be safe and has survival benefits over late repair. The age at repair of ToF affects long-term outcomes. This may largely be related to preserved, or comparatively better, myocardial health. Most studies advocate for an age of repair between 3 and 6 months and certainly below the age of 1 year. Patients with severe right ventricular outflow tract obstruction represent an exception to this rule and may require neonatal repair or surgical and catheter-based palliation before surgery. Older age at repair beyond the first birthday leads to unfavorable right ventricular remodeling with increased right ventricular stiffness and hypertrophy and is associated with increased long-term ventricular tachycardia and all-cause mortality. In this article, we review the short- and long-term benefits of early repair, with a focus on long-term morbidity. In conclusion, we emphasize the importance of myocardial health and the relationship to early repair and advocate for the use of magnetic resonance imaging in adult patients with repaired ToF to detect myocardial fibrosis.

Hepatic Steatosis in Patients With Single Ventricle and a Fontan Circulation.

Background Hepatic steatosis, caused by nonalcoholic fatty liver disease, is a leading cause of chronic liver disease. The interplay between hepatic steatosis and the development of liver disease following the Fontan procedure is not well understood. This study examined the prevalence and associations of hepatic steatosis in patients with a Fontan circulation. Methods and Results This was a single-center retrospective study of 95 patients with a Fontan circulation with liver magnetic resonance imaging performed between 2012 and 2019. The average age at magnetic resonance imaging was 21.5±8.5 years. The percent liver fat signal was determined using magnetic resonance chemical shift-encoded proton density fat fraction imaging. Hepatic steatosis was defined as liver fat ≥5% and was present in 10.5% of the cohort. The presence of hepatic steatosis was associated with higher body mass index (29±4 versus 24±6 kg/m2, P=0.006), a higher frequency of obesity (50% versus 12%, P=0.015), lower high-density lipoprotein cholesterol (35±9 versus 43±14 mg/dL, P=0.050), and greater subcutaneous fat thickness (2.6±0.7 versus 1.8±1.0 cm, P=0.043). There was no association between hepatic steatosis and cardiovascular imaging or hemodynamic variables from cardiac catheterization. Conclusions Risk factors for hepatic steatosis in patients with Fontan circulation include obesity and dyslipidemia, similar to what is seen in the general population. Fontan hemodynamics were not associated with hepatic steatosis.

Sex pheromone of the scarab beetle Phyllophaga (Phytalus) georgiana (horn).

The sex pheromone of Phyllophaga (Phytalus) georgiana was characterized as valine methyl ester, tentatively the L-enantiomer. This is the first sex pheromone identified from the Phyllophaga subgenus Phytalus. The pheromone was extracted from female glands, the active component isolated by coupled gas chromatography-electroantennogram detection analysis, characterized by mass spectrometry, and shown to be active in field tests. The seasonal flight pattern was determined for P. georgiana as well as for three other species, P. anxia (both northern and southern genitalic forms), P. gracilis, and P. postrema. The latter three species were captured in traps baited with L-isoleucine methyl ester.

Invasive Tipula (Diptera: Tipulidae) in turfgrass of the northeast United States: geographic distribution and local incidence three years after detection.

Two species of invasive crane flies are damaging pests of turfgrass in the Great Lakes region after their inadvertent introduction and establishment. In New York, where Tipula paludosa Meigen and Tipula oleracea L. (Diptera: Tipulidae) were first detected in 2004, baseline data on the extent of establishment is needed to monitor range expansion, make predictions about pest status, and guide management efforts. The incidence of both species was therefore addressed at two spatial scales to ascertain how widespread they were across the state and across sites of recent local establishment. Based on divergent natural history, T. oleracea was predicted to be more widespread both geographically and locally than T. paludosa. To delimit the current area of occurrence, surveys were conducted from 2004 to 2006. T. paludosa was detected in four counties and T. oleracea in 12 counties. In western New York, T. oleracea was established in more than a six-fold greater area than T. paludosa. T. oleracea was additionally detected on Long Island, shown to be a geographically disjunct area of establishment. To measure local incidence, putting greens and tee boxes were scouted on golf courses. Contrary to predictions, 56-97 and 22-56% of those surfaces were already infested by T. paludosa and T. oleracea, respectively, within one or two seasons after initial detection. Because damage thresholds are relatively high, scouting for the insect, rather than its injury, will promote earlier detection. Given the impact of invasive Tipula across diverse turf habitats, continued range expansion will have serious repercussions for regional turfgrass management.

Patterns of variation in the seasonal dynamics of Listronotus maculicollis (Coleoptera: Curculionidae) populations on golf course turf.

Listronotus maculicollis (Kirby) is a burgeoning pest of Poa annua L. in the northeast United States. To develop an understanding of its spatial and temporal association with golf course landscapes, we described the patterns of variation in certain population parameters across site (Fayetteville and Ithaca, NY), year (2004-2006), and management habitat (fairway, intermediaterough, rough). In weekly surveys along fairway transects, we sampled larvae (identified to instar) by soil core extraction and adults (identified to sex and maturation)by hand collection. Five instars were confirmed based on head capsule width measurements; there was no overlap among instars. Sex ratio was significantly male-skewed on the rough versus the fairway. Insect load, a measure of population size based on cumulative insect-days, varied from 3.0- to 18.5-fold across sites and years and averaged 8.7- and 8.0-fold greater on the fairway than rough for larvae and adults, respectively. Visual assessment of stage-specific population fluctuation curves revealed no divergence in adult males and females, i.e., no evidence of protandry. Variation was greater by year than by site in terms of overall shape of the fluctuation curves, relative abundance of overwintered to spring and summer adults, population synchrony, and number of generations (two to three). Evidence of bimodal spring generations showed that early season population synchrony may be linked to the pattern of adults transitioning from overwintering to developmental habitats. The magnitude of variation in population dynamics underscores the relevance of decision-making strategies and has implications for improving both the spatial and temporal targeting of intervention tactics.

Application timing and efficacy of alternatives for the insecticidal control of Tipula paludosa Meigen (Diptera: Tipulidae), a new invasive pest of turf in the northeastern United States.

BACKGROUND: Two invasive crane flies, Tipula paludosa Meigen and Tipula oleracea L. (Diptera: Tipulidae), were detected in New York State for the first time in 2004. Both are damaging pests of turfgrass and other horticultural systems in North America where establishment has already been documented. To develop management recommendations for the Northeast and define opportunities for preventive (autumn) and curative (spring) control, four insecticide trials targeting T. paludosa larvae were conducted over a 2 year period. RESULTS: The most efficacious (>or=70% control in both trials) products against early instars in autumn were bifenthrin, carbaryl, chlorantraniliprole, clothianidin and trichlorfon. Results varied for azadirachtin, Beauveria bassiana, cyfluthrin, dinotefuran, imidacloprid, imidacloprid + bifenthrin and indoxacarb. Clothianidin and dinotefuran were most efficacious against fourth instars in spring; results varied for imidacloprid, indoxacarb and trichlorfon. CONCLUSION: Several insecticides offer alternatives for preventive and curative control of T. paludosa, but, because there is little overlap with application windows for scarab larvae pests, management may entail an entirely new insecticide treatment window, implying new economic and environmental burdens to the turfgrass industry. Moreover, curtailing the impact and spread of these invasives may be severely hampered because the best performing alternatives (clothianidin, dinotefuran) are not registered in New York.

Cardiac memory: an under-recognised cause of deep T wave inversion in a patient presenting with chest pain.

T wave inversion (TWI) has many differential diagnoses with acute myocardial ischaemia being the highest on the list of potential causes. Cardiac T wave memory is a benign, under-recognised and clinically important phenomenon seen after periods of altered ventricular conduction. After normal ventricular conduction is restored, the T wave 'remembers' and mirrors the direction of the wide QRS complex. Therefore, negative T waves are seen in leads that had negative wide QRS complexes. We describe the case of a 60-year-old truck driver with chest pain, deep TWI and traditional cardiovascular risk factors. After ruling out significant myocardial ischaemia, it was crucial to determine the cause of his T wave changes to provide reassurance and provide commercial license medical clearance. While it is currently a diagnosis of exclusion, it remains an important clinical entity for clinicians to recognise to provide an explanation for certain T wave changes to avoid future unnecessary cardiac testing.

Fluid velocity based simulation of hydraulic fracture: a penny shaped model-part I: the numerical algorithm.

In the first part of this paper, a universal fluid velocity based algorithm for simulating hydraulic fracture with leak-off, previously demonstrated for the PKN and KGD models, is extended to obtain solutions for a penny-shaped crack. The numerical scheme is capable of dealing with both the viscosity and toughness dominated regimes, with the fracture being driven by a power-law fluid. The computational approach utilizes two dependent variables; the fracture aperture and the reduced fluid velocity. The latter allows for the application of a local condition of the Stefan type (the speed equation) to trace the fracture front. The obtained numerical solutions are carefully tested using various methods, and are shown to achieve a high level of accuracy.