Katja M. Gist

Learning Curve for Zero-Fluoroscopy Catheter Ablation of AVNRT: Early versus Late Experience

Introduction/Background:  Three‐dimensional catheter navigation systems are being utilized more frequently to minimize or eliminate fluoroscopy during catheter ablation. We reviewed our learning curve for a zero‐fluoroscopy approach over a 32‐month period.

Acute Success of Cryoablation of Left‐Sided Accessory Pathways: A Single Institution Study

Objective: To compare the acute success and recurrence rate of cryoablation for left‐sided accessory pathways (AP) with controls who underwent radiofrequency ablation (RFA) at the same institution.

Cardiac findings and long-term thromboembolic outcomes following pulmonary embolism in children: a combined retrospective-prospective inception cohort study

In paediatric pulmonary embolism, cardiac findings and thromboembolic outcomes are poorly defined. We conducted a mixed retrospective-prospective cohort study of paediatric pulmonary embolism at the Childrens Hospital Colorado between March, 2006 and January, 2011. A total of 58 consecutive children - age less than or equal to 21 years - with acute pulmonary embolism were enrolled. Data collection included clinical and laboratory characteristics, treatments, serial echocardiographic and electrocardiographic findings, and outcomes of pulmonary embolism non-resolution and recurrence. The median age was 16.5 years ranging from 0 to 21 years. The most prevalent clinical risk factors were oral contraceptive pill use (52% of female patients), presence of a non-infectious inflammatory condition (21%), and trauma (21%). Thrombophilias included heterozygous factor V Leiden in 21%; antiphospholipid antibody syndrome was established in 31% overall. Proximal pulmonary artery involvement was present in 34%. At presentation, nearly half of the patients had hypoxaemia and 37% had tachycardia. The classic electrocardiographic finding of S1Q3T3 was present in 12% acutely; tricuspid regurgitation greater than 3 metres per second, septal flattening, and right ventricular dilation were each present on acute echocardiogram in 25%. Nearly all patients received therapeutic anticoagulation, with initial systemic tissue plasminogen activator administered in 16% for occlusive iliofemoral deep venous thrombosis and/or massive pulmonary embolism. Pulmonary embolism resolution was observed in 82% by 6 months. Recurrent pulmonary embolism occurred in 9%. There were no pulmonary embolism-related deaths. Right ventricular dysfunction was rare in follow-up. These data indicate that acute heart strain is common, but chronic cardiac dysfunction is rare, following aggressive management of acute pulmonary embolism in children.

Tachyarrhythmia Following Norwood Operation A Single-Center Experience

Background: The purpose of this study was to characterize tachyarrhythmias in children following the Norwood procedure. Methods: This is a single-center retrospective study including all children who underwent stage I Norwood procedure (n = 98; January 2003-September 2011). The primary outcome measure is the development of tachyarrhythmia during hospitalization after the Norwood procedure. Secondary aims include quantification of mortality in patients with tachyarrhythmias and evaluation of potential risk factors for the development of tachyarrhythmia. Results: Tachyarrhythmia occurred in 33 (34%) of 98 patients. The median time to onset of tachyarrhythmia was ten days (0-47 days). Tachyarrhythmia conferred no increase in overall mortality (P = .45), including operative mortality (P = .37) or interstage mortality (P = 1.00). There was no significant difference in the incidence of arrhythmia based on demographic, anatomic, or surgical variables, including shunt type (P = .23) except that patients with tachyarrhythmias were slightly larger (median weight 3.2 kg) at the time of stage I than those without tachyarrhythmia (median weight 2.93 kg; P = .02]. The odds of arrhythmia in males were 8.7 times higher than that in females (95% confidence interval 2.9-31.3; P < .0001). Conclusions: Postoperative tachyarrhythmia is common, occurring in 34% of patients after the Norwood operation. Onset of tachyarrhythmia occurred later after the Norwood operation than reported previously, and male gender is a risk factor. Further studies to elucidate the etiology and the timing of tachyarrhythmias after the Norwood procedure are necessary.

Assessment of the Relationship Between Contegra Conduit Size and Early Valvar Insufficiency

BACKGROUND Contegra bovine jugular vein (BJV) conduit results vary widely, and little attention has been directed at assessment of early conduit insufficiency. Conduit insufficiency is graded subjectively, and criteria vary. Several studies have used branch pulmonary artery flow reversal (BPAFR) to define severe conduit insufficiency. BJV valves are larger than human pulmonary valves of similar diameter. We hypothesize that anatomic differences between BJV and human pulmonary valves limit the use of BPAFR in the evaluation of BJV competence. Our purposes were to (1) assess the prevalence of early and 6-month BJV conduit insufficiency in our patients, (2) determine if conduit size affects BJV competence, and (3) determine if BPAFR is a specific discriminator of severe conduit insufficiency. METHODS We reviewed 135 BJV conduits. One cardiologist blinded to original reports reviewed postoperative and 6-month echocardiograms. Conduits were grouped by size: group 1, 12 to 14 mm (n=51), and group 2, 16 to 22 mm (n=84). Moderate or greater insufficiency was considered clinically significant. RESULTS Early conduit insufficiency was common in group 1 (37%) and rare in group 2 (5%, p<0.0001). After excluding conduits with significant insufficiency, BPAFR occurred in 18% (group 1, 27%; group 2, 13%; p=0.02). At follow-up, insufficiency worsened in group 1 but was stable in group 2. CONCLUSIONS Early conduit insufficiency is common and worsens with follow-up in small BJVs. Conduit insufficiency is limited in larger sizes and remains stable. BJV exhibits BPAFR commonly in the absence of significant conduit insufficiency. BPAFR should not be used as a primary criterion for grading insufficiency in BJV conduits.

A Decline in Intraoperative Renal Near-Infrared Spectroscopy Is Associated With Adverse Outcomes in Children Following Cardiac Surgery.

Objectives: Renal near-infrared spectroscopy is known to be predictive of acute kidney injury in children following cardiac surgery using a series of complex equations and area under the curve. This study was performed to determine if a greater than or equal to 20% reduction in renal near-infrared spectroscopy for 20 consecutive minutes intraoperatively or within the first 24 postoperative hours is associated with 1) acute kidney injury, 2) increased acute kidney injury biomarkers, or 3) other adverse clinical outcomes in children following cardiac surgery. Design: Prospective single center observational study. Setting: Pediatric cardiac ICU. Patients: Children less than or equal to age 4 years who underwent cardiac surgery with the use of cardiopulmonary bypass during the study period (June 2011–July 2012). Interventions: None. Measurements and Main Results: A reduction in near-infrared spectroscopy was not associated with acute kidney injury. Nine of 12 patients (75%) with a reduction in renal near-infrared spectroscopy did not develop acute kidney injury. The remaining three patients had mild acute kidney injury (pediatric Risk, Injury, Failure, Loss, End stage-Risk). A reduction in renal near-infrared spectroscopy was associated with the following adverse clinical outcomes: 1) a longer duration of mechanical ventilation (p = 0.05), 2) longer intensive care length of stay (p = 0.05), and 3) longer hospital length of stay (p < 0.01). A decline in renal near-infrared spectroscopy in combination with an increase in serum interleukin-6 and serum interleukin-8 was associated with a longer intensive care length of stay, and the addition of urine interleukin-18 to this was associated with a longer hospital length of stay. Conclusions: In this cohort, the rate of acute kidney injury was much lower than anticipated thereby limiting the evaluation of a reduction in renal near-infrared spectroscopy as a predictor of acute kidney injury. A greater than or equal to 20% reduction in renal near-infrared spectroscopy was significantly associated with adverse outcomes in children following cardiac surgery. The addition of specific biomarkers to the model was predictive of worse outcomes in these patients. Thus, real-time evaluation of renal near-infrared spectroscopy using the specific levels of change of a 20% reduction for 20 minutes may be useful in predicting prolonged mechanical ventilation and other adverse outcomes in children undergoing cardiac surgery.

Improving acute kidney injury diagnostics using predictive analytics.

Purpose of reviewAcute kidney injury (AKI) is a multifactorial syndrome affecting an alarming proportion of hospitalized patients. Although early recognition may expedite management, the ability to identify patients at-risk and those suffering real-time injury is inconsistent. The review will summarize the recent reports describing advancements in the area of AKI epidemiology, specifically focusing on risk scoring and predictive analytics. Recent findingsIn the critical care population, the primary underlying factors limiting prediction models include an inability to properly account for patient heterogeneity and underperforming metrics used to assess kidney function. Severity of illness scores demonstrate limited AKI predictive performance. Recent evidence suggests traditional methods for detecting AKI may be leveraged and ultimately replaced by newer, more sophisticated analytical tools capable of prediction and identification: risk stratification, novel AKI biomarkers, and clinical information systems. Additionally, the utility of novel biomarkers may be optimized through targeting using patient context, and may provide more granular information about the injury phenotype. Finally, manipulation of the electronic health record allows for real-time recognition of injury. SummaryIntegrating a high-functioning clinical information system with risk stratification methodology and novel biomarker yields a predictive analytic model for AKI diagnostics.

Milrinone Dosing Issues in Critically Ill Children With Kidney Injury: A Review.

Abstract: Milrinone is an inotropic drug used in a variety of clinical settings in adults and children. The efficacy of milrinone in pediatric low–cardiac output syndrome after cardiac surgery is reported. Its primary route of removal from the body is through the kidney as unchanged drug in the urine. Milrinone is not known to be efficiently removed by extracorporeal dialytic therapies and thus has the potential to cause serious adverse effects and potentially worsens renal function in patients experiencing acute kidney injury (AKI). AKI is an important public health issue that is associated with increased morbidity, mortality, and cost. It is a known risk factor for the development of chronic kidney disease. There are no specific therapies to mitigate AKI once it has developed, and interventions are focused on supportive care and dose adjustment of medications. Estimating glomerular filtration rate based on height and serum creatinine is the most commonly used clinical method for assessing kidney function and modification of medication doses. The purpose of this review is to discuss our current understanding of milrinone pharmacokinetics and pharmacodynamics in children with AKI and to describe the potential use of urinary biomarkers to guide therapeutic decision making for milrinone dosing.

Retrospective Evaluation of Milrinone Pharmacokinetics in Children With Kidney Injury.

Objectives: Milrinone is an inotropic agent with vasodilating properties used in the treatment of ventricular dysfunction. Milrinone is predominantly eliminated by the kidneys and accumulates in the setting of acute kidney injury (AKI). The purpose of this study was to evaluate milrinone pharmacokinetics in children with AKI with or without continuous renal replacement therapy (CRRT). Methods: Retrospective collection of milrinone therapeutic drug monitoring data in patients with AKI, including those requiring CRRT, through chart review from January 2008 to March 2014. Pharmacokinetic (PK) data were analyzed by Bayesian estimation using a pediatric population PK model (MW/Pharm). Clearance estimates were allometrically scaled to body weight. Results: Data on 11 patients were available for analysis. Three patients required CRRT. Milrinone concentrations during continuous infusion varied 30-fold and ranged from 44 to 1343 ng/mL. Of the 33 samples obtained in 11 patients, 24 were outside the target range (72.7%), with 16 (48.5%) above and 8 (24.2%) below. Patients with AKI had significantly lower milrinone clearance (4.72 ± 2.26 L/h per 70 kg) compared with published data in patients without AKI. There was large between-patient variability in milrinone clearance (range: 2.91–13.6 L/h per 70 kg). Clearance in patients on CRRT ranged from 2.8 to 7.19 L/h per 70 kg. A significant correlation between milrinone clearance and estimated creatinine clearance was observed (r2 = 0.70, P = 0.0097). Allometrically scaled milrinone clearance was lower in the youngest patients (younger than 2 years), suggestive of ongoing renal maturation and existing AKI. Conclusions: Pediatric patients with AKI have significantly lower milrinone clearance compared with published data in patients without AKI. Large variability was noted in milrinone concentrations, and they were frequently outside the target range. The large between-patient variability in milrinone concentrations suggests that dosing regimens should be individualized in this population of critically ill patients. Evaluation of PK model–based milrinone dose optimization and the use of biomarkers as predictors of changes in clearance warrant further study.

Fluid Management With Peritoneal Dialysis After Pediatric Cardiac Surgery

Children who undergo cardiac surgery with cardiopulmonary bypass are a unique population at high risk for postoperative acute kidney injury (AKI) and fluid overload. Fluid management is important in the postoperative care of these children as fluid overload is associated with increased morbidity and mortality. Peritoneal dialysis catheters are an important tool in the armamentarium of a cardiac intensivist and are used for passive drainage for fluid removal or dialysis for electrolyte and uremia control in AKI. Prophylactic placement of a peritoneal catheter is a safe method of fluid removal that is associated with few major complications. Early initiation of peritoneal dialysis has been associated with improved clinical markers and outcomes such as early achievement of a negative fluid balance, lower vasoactive medication needs, shorter duration of mechanical ventilation, and decreased mortality. In this review, we discuss the safety and potential benefits of peritoneal catheters for dialysis or passive drainage in children following cardiopulmonary bypass.