Intranasal dexmedetomidine for transthoracic echocardiography in infants with shunt-dependent single ventricle heart disease.

OBJECTIVES: We investigated the efficacy and complication profile of intranasal dexmedetomidine for transthoracic echocardiography sedation in patients with single ventricle physiology and shunt-dependent pulmonary blood flow during the high-risk interstage period. METHODS: A single-centre, retrospective review identified interstage infants who received dexmedetomidine for echocardiography sedation. Baseline and procedural vitals were reported. Significant adverse events related to sedation were defined as an escalation in care or need for any additional/increased inotropic support to maintain pre-procedural haemodynamics. Minor adverse events were defined as changes from baseline haemodynamics that resolved without intervention. To assess whether sedation was adequate, echocardiogram reports were reviewed for completeness. RESULTS: From September to December 2020, five interstage patients (age 29-69 days) were sedated with 3 mcg/kg intranasal dexmedetomidine. The median sedation onset time and duration time was 24 minutes (range 12-43 minutes) and 60 minutes (range 33-60 minutes), respectively. Sedation was deemed adequate in all patients as complete echocardiograms were accomplished without a rescue dose. When compared to baseline, three (60%) patients had a >10% reduction in heart rate, one (20%) patient had a >10% reduction in oxygen saturations, and one (20%) patient had a >30% decrease in blood pressure. Amongst all patients, no significant complications occurred and haemodynamic changes from baseline did not result in need for intervention or interruption of study. CONCLUSIONS: Intranasal dexmedetomidine may be a reasonable option for echocardiography sedation in infants with shunt-dependent single ventricle heart disease, and further investigation is warranted to ensure efficacy and safety in an outpatient setting.

Intranasal dexmedetomidine: the ideal drug for sedation in the pediatric echo lab?

BACKGROUND: Intranasal dexmedetomidine is an attractive option for procedural sedation in pediatrics due to ease of administration and its relatively short half-life. This study sought to compare the safety and efficacy of intranasal dexmedetomidine to a historical cohort of pediatric patients sedated using chloral hydrate in a pediatric echo lab. METHODS: Chart review was performed to compare patients sedated between September, 2017 and October, 2019 using chloral hydrate and intranasal dexmedetomidine. Vital signs, time to sedation, duration of sedation, need for second dose of medication, rate of failed sedation, and impact on vital signs were compared between groups. Subgroup analysis was performed for those with complex and cyanotic heart disease. RESULTS: Chloral hydrate was used in 356 patients and intranasal dexmedetomidine in 376. Patient age, complexity of heart disease, and duration of sedation were similar. Rates of failed sedation were very low and similar. Average heart rate and minimum heart rate were lower for those receiving intranasal dexmedetomidine than chloral hydrate. Impact on vital signs was similar for those with complex and cyanotic heart disease. No adverse events occurred in either group. CONCLUSIONS: Sedation with intranasal dexmedetomidine is comparable to chloral hydrate in regards to safety and efficacy for children requiring echocardiography. Consistent with the mechanism of action, patients receiving intranasal dexmedetomidine have a lower heart rate without morbidity.

A novel faculty development tool for writing a letter of recommendation.

OBJECTIVE: Based on a national survey of program directors we developed a letter of recommendation (LOR) scoring rubric (SR) to assess LORs submitted to a pediatric residency program. The objective was to use the SR to analyze: the consistency of LOR ratings across raters and LOR components that contributed to impression of the LOR and candidate. METHODS: We graded 30 LORs submitted to a pediatric residency program that were evenly distributed based on final rank by our program. The SR contained 3 sections (letter features, phrases, and applicant abilities) and 2 questions about the quality of the LOR (LORQ) and impression of the candidate (IC) after reading the LOR on a 5-point Likert scale. Inter-rater reliability was calculated with intraclass correlation coefficients (ICC(2,1)). Pearson (r) correlations and stepwise multivariate linear regression modeling predicted LORQ and IC. Mean scores of phrases, features, and applicant abilities were analyzed with ANOVA and Bonferroni correction. RESULTS: Phrases (ICC(2,1) = 0.82, p<0.001)) and features (ICC(2,1) = 0.60, p<0.001)) were rated consistently, while applicant abilities were not (ICC(2,1) = 0.28, p<0.001)). For features, LORQ (R2 = 0.75, p<0.001) and IC (R2 = 0.58, p<0.001) were best predicated by: writing about candidates' abilities, strength of recommendation, and depth of interaction with the applicant. For abilities, LORQ (R2 = 0.47, p<0.001) and IC (R2 = 0.51, p<0.001) were best predicted by: clinical reasoning, leadership, and communication skills (0.2). There were significant differences for phrases and features (p<0.05). CONCLUSIONS: The SR was consistent across raters and correlates with impression of LORQ and IC. This rubric has potential as a faculty development tool for writing LORS.

Echocardiography vs cardiac magnetic resonance imaging assessment of the systemic right ventricle for patients with d-transposition of the great arteries status post atrial switch.

OBJECTIVE: Patients with Dextro-transposition of the great arteries status post atrial switch (dTGA s/p atrial switch) are "at-risk" for systemic right ventricular (RV) dysfunction. Due to complex RV geometry, echocardiography (Echo) does not allow accurate determination of ejection fraction (EF), but cardiac magnetic resonance imaging (CMR) allows quantitative right ventricular assessment. Measures of ventricular deformation may be precursors to global ventricular dysfunction. The primary aim of this study was to characterize imaging and clinical findings for adult patients with dTGA s/p atrial switch. DESIGN: This was a retrospective cohort study of patients with dTGA s/p atrial switch operation (February 1966 to August 1988) with CMR performed at Children's Hospital of Wisconsin (from September 2005 to May 2015). Eligible patients had clinic visit, Echo, and exercise stress test within 1 year of CMR. RESULTS: This study enrolled twenty-seven patients (16 males, 11 females) with dTGA s/p atrial switch (18 with Mustard operation and 9 with Senning operation; median age 30 years; 74% New York Heart Association class 1 and 26% class 2). Seventy-four percentage had normal RV systolic function (RV EF >45% by CMR). No correlation was observed between Echo strain data and clinical status (EF, exercise endurance, VO2 max, or New York Heart Association class). Cardiac magnetic resonance imaging RV global circumferential strain GCS and RV EF had moderate negative correlation (r = -0.65, P < .001). Global circumferential strain was significantly different for those with RV EF above and below 45%, while global peak longitudinal strain (GLS) was not. Patients had reduced CMR myocardial strain values compared with healthy controls. CONCLUSIONS: Reduced RV CMR GCS (for those with RV EF <45%) suggests that CMR evaluation may enhance early detection of detrimental changes in the systemic RV myocardium.

Implementation of Quality-of-Life Assessment Increases Referrals for Intervention in Patients with Tetralogy of Fallot.

Mortality from surgical repair of tetralogy of Fallot (TOF) has decreased dramatically over the last several decades. Despite excellent surgical outcomes, studies reveal that patients with TOF continue to have decreased physical functioning, academic difficulties, and psychosocial impairments. We hypothesized that administering a validated quality-of-life assessment to patients with TOF during routine cardiology follow-up visits would help identify deficits and increase referrals to appropriate interventional programs. Between May 2017 and November 2018, TOF patients (5-20 years) and/or their families completed a standardized quality-of-life assessment (PedsQL 4.0) during cardiology clinic visits. Providers were encouraged to refer patients with abnormal PedsQL 4.0 scores to appropriate services including cardiovascular rehabilitation, psychological evaluation, neurodevelopmental testing, and school intervention. Referrals for the intervention group were compared to those of a control group using χ2 analysis. The PedsQL 4.0 was completed by 79 patients at 90 clinic visits. At least one abnormal PedsQL 4.0 score was identified in 58% (52/90) of patient encounters, and of those 52 encounters, 38% (20/52) received at least one referral for intervention. The most commonly placed referrals were for neurodevelopmental testing (16) and school intervention (11). When comparing the number of referrals from the intervention group to those of the control group, referrals to all intervention services were statistically significant (p < 0.05). Our quality improvement initiative successfully utilized a quality-of-life assessment to detect deficits and subsequently increased the number of referrals to intervention services. Future studies will address barriers that prevent completion of the PedsQL and assess how interventions impact quality-of-life scores.

Pediatric, Surgery, and Internal Medicine Program Director Interpretations of Letters of Recommendation.

PURPOSE: Literature describing program director (PD) perceptions of letters of recommendation (LORs) and "code" used by letter writers is limited. In 2016, a survey instrument was distributed nationally to pediatric PDs asking them to rate their interpretations of components of LORs. The results confirmed that letter phrases convey code, but these results were not known to be generalizable outside of pediatrics. The purpose of this study was to expand the survey to surgery and internal medicine (IM) PDs looking for areas of agreement or variation between the 3 specialties. METHOD: The survey was sent nationally to surgery and IM PDs asking them to rate LORs in 3 areas on a 5-point Likert scale: 14 commonly used phrases, 13 letter features, and 10 applicant abilities. The LOR phrases were grouped using principal component analysis (PCA). Mean scores of components were analyzed with repeated-measures analysis of variance. RESULTS: Response rates: pediatrics 43% (486 of 1079), surgery 55% (151 of 277), and IM 42% (170 of 408). PCA generated groups of positive, neutral, and negative phrases with moderate to strong correlation with each other for all 3 specialties. There were significant differences between the mean Likert scores of the positive, neutral, and negative groups of phrases for all 3 specialties (all P < .001). "Showed improvement" was rated the most negative phrase by all 3 specialties. CONCLUSIONS: Key elements of LORs include distinct phrases depicting different degrees of endorsement of candidates. Pediatric, surgery, and IM PDs interpret letter components differently.

Proximal Arch in Left Thoracotomy Repair of Neonatal and Infant Coarctation-How Small Is Too Small?

BACKGROUND: We sought to evaluate the relationship between proximal arch hypoplasia and reintervention for left thoracotomy repair of coarctation of the aorta. METHODS: This was a retrospective review of 153 consecutive neonates and infants undergoing left thoracotomy and extended end-to-end repair of coarctation from January 1, 2000, to January 1, 2014, at a single center with exclusion of single ventricle-palliated patients. Primary outcome was reintervention evaluated with respect to five definitions of proximal arch hypoplasia. RESULTS: Median follow-up was 7.2 years. Reintervention occurred in eight (5.2%) patients, with 50% of patients undergoing re-intervention in the first six months after their index operation. Using Kaplan-Meier analysis and log-rank test, with hypoplasia defined by weight, hypoplasia was not associated with increased reintervention for arch size < patient weight (in kilograms; P = .24) or for arch size < patient weight (in kilograms) +1 (P = .02, higher freedom from reintervention in hypoplasia group). For each of the five comparison groups, freedom from reintervention was similar between the groups with and without proximal arch hypoplasia: (1) z-score < -2 versus ≥-2 (P = .72), (2) z-score < -3 versus ≥-3 (P = .95), and (3) z-score < -4 versus ≥-4 (P = .17). CONCLUSION: In our cohort of patients with left thoracotomy and extended end-to-end repair of coarctation, proximal arch hypoplasia, defined by various weight-based or z-score thresholds, was not associated with reintervention. While this may imply value to a more liberal use of thoracotomy, confirmation requires longer term follow-up with a more comprehensive evaluation of the patients and their arches.

Chest tube removal algorithm is associated with decreased chest tube duration in pediatric cardiac surgical patients.

OBJECTIVE: Management of chest tubes in adult and pediatric patients is highly variable. There are no published guidelines for pediatric cardiac surgical patients. Our center undertook a quality improvement project aimed at reducing chest tube duration and length of stay in postsurgical pediatric cardiac patients. METHODS: A work group identified 2 opportunities for reducing chest tube duration: standardizing removal criteria and increasing frequency of assessment for removal. An algorithm was created, and chest tube assessments were increased to twice daily. All postsurgical cardiac patients were managed according to the algorithm. Outcome measure reporting was limited to patients age 1 month to 18 years with a biventricular surgical procedure. Outcome measures included chest tube duration, cardiac intensive care unit and hospital length of stay, and cost of hospitalization. Process measure was documentation of chest tube assessments. The balancing measure was chest tube reinsertions. RESULTS: Between April 2016 and July 2018, 126 patients aged 1 month to 18 years underwent a biventricular surgical procedure. Mean chest tube duration decreased from 61 to 47 hours. Cardiac intensive care unit length of stay decreased from 141 hours to 89 hours, hospital length of stay decreased from 266 to 156 hours, and average hospitalization cost decreased from $75,881 to $48,118. There was no increase in chest tube reinsertions. CONCLUSIONS: Implementation of a chest tube removal algorithm for pediatric cardiac surgery patients resulted in decreased chest tube duration and was associated with decreased length of stay and costs without an increase in reinsertions. More significant impact may be attainable with more aggressive approach to removal.

Dear Program Director: Deciphering Letters of Recommendation.

BACKGROUND: Letters of recommendation (LORs) are an important part of applications for residency and fellowship programs. Despite anecdotal use of a "code" in LORs, research on program director (PD) perceptions of the value of these documents is sparse. OBJECTIVE: We analyzed PD interpretations of LOR components and discriminated between perceived levels of applicant recommendations. METHODS: We conducted a cross-sectional, descriptive study of pediatrics residency and fellowship PDs. We developed a survey asking PDs to rate 3 aspects of LORs: 13 letter features, 10 applicant abilities, and 11 commonly used phrases, using a 5-point Likert scale. The 11 phrases were grouped using principal component analysis. Mean scores of components were analyzed with repeated-measures analysis of variance. Median Likert score differences between groups were analyzed with Mann-Whitney U tests. RESULTS: Our survey had a 43% response rate (468 of 1079). "I give my highest recommendation" was rated the most positive phrase, while "showed improvement" was rated the most negative. Principal component analysis generated 3 groups of phrases with moderate to strong correlation with each other. The mean Likert score for each group from the PD rating was calculated. Positive phrases had a mean (SD) of 4.4 (0.4), neutral phrases 3.4 (0.5), and negative phrases 2.6 (0.6). There was a significant difference among all 3 pairs of mean scores (all P < .001). CONCLUSIONS: Commonly used phrases in LORs were interpreted consistently by PDs and influenced their impressions of candidates. Key elements of LORs include distinct phrases depicting different degrees of endorsement.

Single-Stage Repair of Coarctation of the Aorta and Ventricular Septal Defect: A Comparison of Surgical Strategies and Resource Utilization.

BACKGROUND: We sought to compare clinical outcomes and resource utilization for two surgical approaches for single-stage repair of coarctation of the aorta and ventricular septal defect (VSD). METHODS: This was a retrospective chart review of 21 consecutive neonates and infants undergoing single-stage repair of coarctation of the aorta and VSD. Group 1 included 13 patients with both arch repair and VSD repair completed via sternotomy. Group 2 included eight patients with off-pump arch repair via left thoracotomy followed by repositioning and VSD repair via sternotomy. Primary clinical outcome was arch reintervention. Secondary outcomes included various measures of resource utilization. RESULTS: Group 1 patients demonstrated younger age at repair (median of 10 days vs 57 days for group 2; P = .05) and lower proximal arch z scores (-4.2 vs -2.3 for group 2; P = .003). Arch reintervention occurred in 0 of 8 patients in group 2 and 1 (7.7%) of 13 patients in group 1 ( P = nonsignificant). Group 2 was associated with lower total charges (US$68,301 vs US$211,723 for group 1; P = .0007), shorter length of stay (8 days vs 23 days for group 1; P = .004), and shorter duration of postoperative mechanical ventilation (0.5 days vs 4.0 days for group 1; P = .0008). Group 2 was also associated with shorter total cardiopulmonary bypass time (86 minutes vs 201 minutes for group 1; P = .0009). CONCLUSION: Single-stage two-incision repair of coarctation and VSD in appropriately selected patients may be associated with higher value of care. Confirmation of this finding will require further study based on larger numbers of patients.

Transplacental treatment of fetal tachycardia: A systematic review and meta-analysis.

OBJECTIVE: Multiple transplacental medications can be used to treat fetal tachycardia. We sought to perform a systematic review and meta-analysis to determine whether digoxin, flecainide, or sotalol was the most efficacious therapy for converting fetal tachycardia to sinus rhythm. METHOD: We performed a systematic review and meta-analysis to compare digoxin, flecainide, or sotalol as first-line therapy for fetal tachycardia. Studies were identified by a search of PubMed (Medline), Web of Science, and Scopus. RESULTS: There were 21 studies included. Flecainide (OR: 1.4, 95% CI: 1.1-2.0, I2  = 60%, P = 0.03) and sotalol (OR:1.4, 95% CI:1.1-2.0, I2  = 30%, P = 0.02) were superior to digoxin for conversion of fetal tachycardia to sinus rhythm. In those with hydrops, the benefit over digoxin was more notable for both flecainide (OR: 5.0, 95% CI: 2.5-10.0, I2  = 0%, P < 0.001) and sotalol (OR: 2.5, 95% CI: 1.7-5.0, I2  = 0%, P < 0.001). When limited to atrioventricular reentrant tachycardia, flecainide was superior to digoxin (OR:1.7, 95% CI:1.1-3.3, I2  = 62%, P = 0.03) and sotalol (OR:1.3, 95% CI:1.1-1.7, I2  = 0%, P = 0.01). CONCLUSION: Digoxin should not be first-line therapy for fetal tachycardia, particularly in the presence of hydrops fetalis. Flecainide should be the first-line therapy of choice in atrioventricular reentrant tachycardia. Further study may identify further sub-populations responding differently.

Quantitative echocardiographic measures in the assessment of single ventricle function post-Fontan: Incorporation into routine clinical practice.

BACKGROUND: Quantitative echocardiographic measurements of single ventricular (SV) function have not been incorporated into routine clinical practice. METHODS: A clinical protocol, which included quantitative measurements of SV deformation (global circumferential and longitudinal strain and strain rate), standard deviation of time to peak systolic strain, myocardial performance index (MPI), dP/dT from an atrioventricular valve regurgitant jet, and superior mesenteric artery resistance index, was instituted for all patients with a history of Fontan procedure undergoing echocardiography. All measures were performed real time during clinically indicated studies and were included in clinical reports. RESULTS: A total of 100 consecutive patients (mean age = 11.95±6.8 years, range 17 months-31.3 years) completed the protocol between September 1, 2014 to April 29, 2015. Deformation measures were completed in 100% of the studies, MPI in 93%, dP/dT in 55%, and superior mesenteric artery Doppler in 82%. The studies were reviewed to assess for efficiency in completing the protocol. The average time for image acquisition was 27.4±8.8 (range 10-62 minutes). The average time to perform deformation measures was 10.8±5.5 minutes (range 5-35 minutes) and time from beginning of imaging to report completion was 53.4±13.7 minutes (range 27-107 minutes). There was excellent inter-observer reliability when deformation indices were blindly repeated. Patients with a single left ventricle had significantly higher circumferential strain and strain rate, longitudinal strain and strain rate, and dP/dT compared to a single right ventricle. There were no differences in quantitative indices of ventricular function between patients <10 vs. >10 years post-Fontan. CONCLUSION: Advanced quantitative assessment of SV function post-Fontan can be consistently and efficiently performed real time during clinically indicated echocardiograms with excellent reliability.

Regional Implementation of a Pediatric Cardiology Syncope Algorithm Using Standardized Clinical Assessment and Management Plans (SCAMPS) Methodology.

BACKGROUND: Pediatric syncope is common. Cardiac causes are rarely found. We describe and assess a pragmatic approach to these patients first seen by a pediatric cardiologist in the New England region, using Standardized Clinical Assessment and Management Plans (SCAMPs). METHODS AND RESULTS: Ambulatory patients aged 7 to 21 years initially seen for syncope at participating New England Congenital Cardiology Association practices over a 2.5-year period were evaluated using a SCAMP. Findings were iteratively analyzed and the care pathway was revised. The vast majority (85%) of the 1254 patients had typical syncope. A minority had exercise-related or more problematic symptoms. Guideline-defined testing identified one patient with cardiac syncope. Syncope Severity Scores correlated well between physician and patient perceived symptoms. Orthostatic vital signs were of limited use. Largely incidental findings were seen in 10% of ECGs and 11% of echocardiograms. The 10% returning for follow-up, by design, reported more significant symptoms, but did not have newly recognized cardiac disease. Iterative analysis helped refine the approach. CONCLUSIONS: SCAMP methodology confirmed that the vast majority of children referred to the outpatient pediatric cardiology setting had typical low-severity neurally mediated syncope that could be effectively evaluated in a single visit using minimal resources. A simple scoring system can help triage patients into treatment categories. Prespecified criteria permitted the effective diagnosis of the single patient with a clear cardiac etiology. Patients with higher syncope scores still have a very low risk of cardiac disease, but may warrant attention.

Impact of initial norwood shunt type on right ventricular deformation: the single ventricle reconstruction trial.

BACKGROUND: The Single Ventricle Reconstruction trial demonstrated a transplantation-free survival advantage at 12-month follow-up for patients with right ventricle-pulmonary artery shunts (RVPAS) with the Norwood procedure compared with modified Blalock-Taussig shunts but similar survival and decreased global right ventricular (RV) function on longer term follow-up. The impact of the required ventriculotomy for the RVPAS remains unknown. The aim of this study was to compare echocardiography-derived RV deformation indices after stage 2 procedures in survivors with single RV anomalies enrolled in the Single Ventricle Reconstruction trial. METHODS: Global and regional RV systolic longitudinal and circumferential strain and strain rate, ejection fraction, and short-axis percentage fractional area change were all derived by speckle-tracking echocardiography from protocol echocardiograms obtained at 14.3 ± 1.2 months. Student t tests or Wilcoxon rank sum tests were used to compare groups. RESULTS: The cohort included 275 subjects (129 in the modified Blalock-Taussig shunt group and 146 in the RVPAS group). Longitudinal deformation could be quantified in 214 subjects (78%) and circumferential measures in 182 subjects (66%). RV ejection fraction and percentage fractional area change did not differ between groups. There were no significant differences between groups for global or regional longitudinal deformation. Circumferential indices showed abnormalities in deformation in the RVPAS group, with decreased global circumferential strain (P = .05), strain rate (P = .09), and anterior regional strain rate (P = .07) that approached statistical significance. CONCLUSIONS: RV myocardial deformation at 14 months, after stage 2 procedures, was not significantly altered by the type of initial shunt placed. However, abnormal trends were appreciated in circumferential deformation for the RVPAS group in the area of ventriculotomy that may represent early myocardial dysfunction. These data provide a basis for longer term RV deformation assessment in survivors after Norwood procedures.

Multicenter study comparing shunt type in the norwood procedure for single-ventricle lesions: three-dimensional echocardiographic analysis.

BACKGROUND: The Pediatric Heart Network's Single Ventricle Reconstruction (SVR) trial randomized infants with single right ventricles (RVs) undergoing a Norwood procedure to a modified Blalock-Taussig or RV-to-pulmonary artery shunt. This report compares RV parameters in the 2 groups using 3-dimensional echocardiography. METHODS AND RESULTS: Three-dimensional echocardiography studies were obtained at 10 of 15 SVR centers. Of the 549 subjects, 314 underwent 3-dimensional echocardiography studies at 1 to 4 time points (pre-Norwood, post-Norwood, pre-stage II, and 14 months) for a total of 757 3-dimensional echocardiography studies. Of these, 565 (75%) were acceptable for analysis. RV volume, mass, mass:volume ratio, ejection fraction, and severity of tricuspid regurgitation did not differ by shunt type. RV volumes and mass did not change after the Norwood, but increased from pre-Norwood to pre-stage II (end-diastolic volume [milliliters]/body surface area [BSA](1.3), end-systolic volume [milliliters]/BSA(1.3), and mass [grams]/BSA(1.3) mean difference [95% confidence interval]=25.0 [8.7-41.3], 19.3 [8.3-30.4], and 17.9 [7.3-28.5], then decreased by 14 months (end-diastolic volume/BSA(1.3), end-systolic volume/BSA(1.3), and mass/BSA(1.3) mean difference [95% confidence interval]=-24.4 [-35.0 to -13.7], -9.8 [-17.9 to -1.7], and -15.3 [-22.0 to -8.6]. Ejection fraction decreased from pre-Norwood to pre-stage II (mean difference [95% confidence interval]=-3.7 [-6.9 to -0.5]), but did not decrease further by 14 months. CONCLUSIONS: We found no statistically significant differences between study groups in 3-dimensional echocardiography measures of RV size and function, or magnitude of tricuspid regurgitation. Volume unloading was seen after stage II, as expected, but ejection fraction did not improve. This study provides insights into the remodeling of the operated univentricular RV in infancy.

MRI validated echocardiographic technique to measure total cardiac volume: a tool for donor-recipient size matching in pediatric heart transplantation.

Our aim is to develop and validate an accurate method for estimating TCV using standard echocardiographic imaging that can be easily employed to aid in donor-recipient size matching in pediatric heart transplantation. Thirty patients who underwent Echo and cardiac magnetic resonance imaging (cMRI) were identified. TCV was measured on cMRI. TCV was determined echocardiographically by two methods: a volume measurement using the modified Simpson's method on a four-chamber view of the heart; and a calculated volume measurement which assumed a true-elliptical shape of the heart. These two methods where compared with the value obtained by cMRI using the concordance correlation coefficient (CCC). TCV by method 1 correlated well with cMRI (CCC = 0.98%, CI = 0.97, 0.99). TCV by method 2 had a CCC = 0.90 (CI = 0.9464, 0.9716) when compared to cMRI. Left ventricular end-diastolic volume (LVEDV) also correlated as a predictor of TCV in patients with structurally normal hearts and could be described by the equation: TCV = 6.6 (LVEDV) + 12 (R(2)  = 0.97). Echocardiographic assessment of TCV for recipients and their potential donors is a simple process and can be prospectively applied as part of donor evaluation.

Evaluation of myocardial mechanics in the fetus by velocity vector imaging.

There are limited data on the properties of fetal myocardium with only a small number of Doppler tissue imaging-based studies published. We evaluated the feasibility of using velocity vector imaging, a novel technique for analyzing 2-dimensional images offline, to study myocardial mechanics in the normal fetal heart at different of gestational ages. A single 2-dimensional 4-chamber image of the heart was interrogated offline using velocity vector imaging software. Longitudinal velocity, strain, and strain rate were measured in the right ventricular free wall, ventricular septum, and left ventricular free wall. Images from 24 of 27 (89%) were successfully analyzed. The systolic and diastolic longitudinal velocities increased with gestational age in all myocardial segments analyzed (r = 0.56-0.78, P < .05). Systolic strain and strain rate were not found to have significant correlation with gestational age in any of the wall segments. This implies that increasing velocities during normal gestation are the result of somatic growth rather than changes in myocardial contractility.