Retrospective Cohort Study of Additional Procedures and Transplant-Free Survival for Patients With Functionally Single Ventricle Disease Undergoing Staged Palliation in England and Wales.

BACKGROUND: Reinterventions may influence the outcomes of children with functionally single-ventricle (f-SV) congenital heart disease. METHODS AND RESULTS: We undertook a retrospective cohort study of children starting treatment for f-SV between 2000 and 2018 in England, using the national procedure registry. Patients were categorized based on whether they survived free of transplant beyond 1 year of age. Among patients who had transplant-free survival beyond 1 year of age, we explored the relationship between reinterventions in infancy and the outcomes of survival and Fontan completion, adjusting for complexity. Of 3307 patients with f-SV, 909 (27.5%), had no follow-up beyond 1 year of age, among whom 323 (35.3%) had ≥1 reinterventions in infancy. A total of 2398 (72.5%) patients with f-SV had transplant-free survival beyond 1 year of age, among whom 756 (31.5%) had ≥1 reinterventions in infancy. The 5-year transplant-free survival and cumulative incidence of Fontan, among those who survived infancy, were 93.4% (95% CI, 92.4%-94.4%) and 79.3% (95% CI, 77.4%-81.2%), respectively. Both survival and Fontan completion were similar for those with a single reintervention and those who had no reinterventions. Patients who had >1 additional surgery (adjusted hazard ratio, 3.93 [95% CI, 1.87-8.27] P<0.001) had higher adjusted risk of mortality. Patients who had >1 additional interventional catheter (adjusted subdistribution hazard ratio, 0.71 [95% CI, 0.52-0.96] P=0.03) had a lower likelihood of achieving Fontan. CONCLUSIONS: Among children with f-SV, the occurrence of >1 reintervention in the first year of life, especially surgical reinterventions, was associated with poorer prognosis later in childhood.

Congenitally Corrected Transposition of the Great Arteries in Utero: Morphological Spectrum, Outcomes and Pitfalls in Fetal Diagnosis.

Congenitally corrected transposition of the great arteries (ccTGA) is a rare malformation with diverse morphology. We assessed features of fetuses with ccTGA and evaluated neonatal and pediatric outcomes. This was a retrospective review of fetuses with ccTGA at Birmingham Women's and Children's Hospital born from 2005 to 2019. Of thirty-six fetuses identified, six had unavailable prenatal data, one was postnatally diagnosed with isomerism and 29 fetuses were evaluated. ccTGA without associated cardiac lesions was found in 28% (8/29), ccTGA with significant VSD in 31% (9/29), ccTGA with pulmonary obstruction in 24% (7/29) and ccTGA with complex anomalies in 17% (5/29). Tricuspid regurgitation (TR) was observed in 17% (5/29) and heart block (HB) in 10% (3/29) prenatally. Six, that is 21% underwent genetic testing of which one was abnormal. Five extra-cardiac anomalies were reported prenatally and postnatally. Pregnancy was discontinued in five, of which two had moderate TR. There were thirty-one liveborn. Coarctation of the aorta was found in five postnatally but not suspected prenatally. In one, pulmonary stenosis was underestimated; otherwise, prenatal morphology was confirmed. Cardiac interventions were performed in 77% (24/31) liveborn with 39% (12/31) undergoing neonatal intervention. Overall, 6/31 liveborn died including all three with prenatal heart block and one with TR. Estimated survival for all liveborn at 1, 5 and 10 years was 87% (95% CI 76-100%), 83% (95% CI 72-98%) and 80% (95% CI 66-96%) respectively. Accurate prenatal diagnosis of ccTGA is critical for counseling. Early outcomes are favorable with 77% of liveborn undergoing surgery. Fetuses with prenatal diagnosis of complex associated abnormalities, HB and TR appear to do less well.

Fetal single ventricle journey to first postnatal procedure: a multicentre UK cohort study.

OBJECTIVES: UK single ventricle (SV) palliation outcomes after first postnatal procedure (FPP) are well documented. However, survival determinants from fetal diagnosis to FPP are lacking. To better inform parental-fetal counselling, we examined factors favouring survival at two large UK centres. DESIGN: Retrospective multicentre cohort study. SETTING: Two UK congenital cardiac centres: Leeds and Birmingham. PATIENTS: SV fetal diagnoses from 2015 to 2021. MAIN OUTCOME MEASURES: Survival from fetal diagnosis with intention to treat (ITT) to birth and then FPP. Maternal, fetal and neonatal risk factors were assessed. RESULTS: There were 666 fetal SV diagnoses with 414 (62%) ITT. Of ITT, 381 (92%) were live births and 337 (81%) underwent FPP. Survival (ITT) to FPP was notably reduced for severe Ebstein's 14/22 (63.6%), unbalanced atrioventricular septal defect 32/45 (71%), indeterminate SV 3/4 (75%), mitral atresia 8/10 (80%) and hypoplastic left heart syndrome 127/156 (81.4%). Biventricular pathway was undertaken in five (1%). After multivariable adjustment, prenatal risk factors for mortality were increasing maternal age (OR 1.05, 95% CI 1.0 to 1.1), non-white ethnicity (OR 2.6, 95% CI 1.4 to 4.8), extracardiac anomaly (OR 6.34, 95% CI 1.8 to 22.7) and hydrops (OR 7.39, 95% CI 1.2 to 45.1). Postnatally, prematurity was significantly associated with mortality (OR 6.3, 95% CI 2.3 to 16.8). CONCLUSIONS: Around 20% of ITT fetuses diagnosed with SV will not reach FPP. Risk varies according to the cardiac lesion and is significantly influenced by the presence of an extracardiac anomaly, fetal hydrops, ethnicity, increasing maternal age and gestation at birth. These data highlight the need for fetal preprocedure data to be used in conjunction with procedural outcomes for fetal counselling.

Medium-term Outcome of Prenatally Diagnosed Hypoplastic Left-Heart Syndrome and Impact of a Restrictive Atrial Septum Diagnosed in-utero.

OBJECTIVE: Surgical outcome data differs from overall outcomes of prenatally diagnosed fetuses with hypoplastic left heart syndrome (HLHS). Our aim was to describe outcome of prenatally diagnosed fetuses with this anomaly. METHODS: Retrospective review of prenatally diagnosed classical HLHS at a tertiary hospital over a 13-year period, estimated due dates 01/08/2006 to 31/12/2019. HLHS-variants and ventricular disproportion were excluded. RESULTS: 203 fetuses were identified with outcome information available for 201. There were extra-cardiac abnormalities in 8% (16/203), with genetic variants in 14% of those tested (17/122). There were 55 (27%) terminations of pregnancy, 5 (2%) intrauterine deaths and 10 (5%) babies had prenatally planned compassionate care. There was intention to treat (ITT) in the remaining 131/201(65%). Of these, there were 8 neonatal deaths before intervention, two patients had surgery in other centers. Of the other 121 patients, Norwood procedure performed in 113 (93%), initial hybrid in 7 (6%), and 1 had palliative coarctation stenting. Survival for the ITT group from birth at 6-months, 1-year and 5-years was 70%, 65%, 62% respectively. Altogether of the initial 201 prenatally diagnosed fetuses, 80 patients (40%) are currently alive. A restrictive atrial septum (RAS) is an important sub-category associated with death, HR 2.61, 95%CI 1.34-5.05, p = 0.005, with only 5/29 patients still alive. CONCLUSION: Medium-term outcomes of prenatally diagnosed HLHS have improved however it should be noted that almost 40% do not get to surgical palliation, which is vital to those doing fetal counselling. There remains significant mortality particularly in fetuses with in-utero diagnosed RAS.

Outcomes of the arterial switch for transposition during infancy using a standardized approach over 30 years.

OBJECTIVES: The aim of this study was to describe the early and late outcomes of the arterial switch for transposition. METHODS: A single-centre retrospective cohort study was conducted to assess the early and late outcomes of arterial switch performed during infancy using a standardized institutional approach between 1988 and 2018, compared by morphological groups. RESULTS: A total of 749 consecutive patients undergoing arterial switch during infancy were included, 464 (61.9%) with intact septum, 163 (21.8%) with isolated ventricular septal defect and 122 (16.3%) with complex transposition with associated lesions, including 67 (8.9%) with Taussig-Bing anomaly. There were 34 early deaths [4.5%, 95% confidence interval (CI) 3.1-6.1] with only 10 (2.6%) early deaths since 2000. Complex morphology (odds ratio 11.44, 95% CI 4.76-27.43) and intramural coronary artery (odds ratio 5.17, 95% CI 1.61-15.91) were identified as the most important risk factors for 90-day mortality. Overall survival was 92.7% (95% CI 90.8-94.6) at 5 years and 91.9% (95% CI 89.9-94.1) at 20 years; in hospital survivors, there were 15 (2.1%) late deaths during a median follow-up of 13.7 years. Cumulative incidence of surgical or catheter reintervention was 16.0% (95% CI 14.5-17.5) at 5 years and 22.7% (95% CI 21.0-24.0) at 20 years; early and late reinterventions were more common in the complex group, with no difference between the other groups. CONCLUSIONS: Using a standardized approach, the arterial switch can be performed with low early mortality, moderate rates of reintervention and excellent long-term survival. Concomitant lesions were the most important risk factor for early death and were associated with increased risk of late reintervention.

Long-term survival and center volume for functionally single-ventricle congenital heart disease in England and Wales.

OBJECTIVES: Long-term survival is an important metric for health care evaluation, especially in functionally single-ventricle (f-SV) congenital heart disease (CHD). This study's aim was to evaluate the relationship between center volume and long-term survival in f-SV CHD within the centralized health care service of England and Wales. METHODS: This was a retrospective cohort study of children born with f-SV CHD between 2000 and 2018, using the national CHD procedure registry, with survival ascertained in 2020. RESULTS: Of 56,039 patients, 3293 (5.9%) had f-SV CHD. Median age at first intervention was 7 days (interquartile range [IQR], 4, 27), and median follow-up time was 7.6 years (IQR, 1.0, 13.3). The largest diagnostic subcategories were hypoplastic left heart syndrome, 1276 (38.8%); tricuspid atresia, 440 (13.4%); and double-inlet left ventricle, 322 (9.8%). The survival rate at 1 year and 5 years was 76.8% (95% confidence interval [CI], 75.3%-78.2%) and 72.1% (95% CI, 70.6%-73.7%), respectively. The unadjusted hazard ratio for each 5 additional patients with f-SV starting treatment per center per year was 1.04 (95% CI, 1.02-1.06), P < .001. However, after adjustment for significant risk factors (diagnostic subcategory; antenatal diagnosis; younger age, low weight, acquired comorbidity, increased severity of illness at first procedure), the hazard ratio for f-SV center volume was 1.01 (95% CI, 0.99-1.04) P = .28. There was strong evidence that patients with more complex f-SV (hypoplastic left heart syndrome, Norwood pathway) were treated at centers with greater f-SV case volume (P < .001). CONCLUSIONS: After adjustment for case mix, there was no evidence that f-SV center volume was linked to longer-term survival in the centralized health service provided by the 10 children's cardiac centers in England and Wales.

Pulmonary artery banding: still a role for staged bi-ventricular repair of intracardiac shunts?

OBJECTIVES: Although pulmonary artery banding remains a useful palliation in bi-ventricular shunting lesions, single-stage repair holds several advantages. We investigate outcomes of the former approach in high-risk patients. METHODS: Retrospective cohort study including all pulmonary artery banding procedures over 9 years, excluding single ventricle physiology and left ventricular training. RESULTS: Banding was performed in 125 patients at a median age of 41 days (2-294) and weight of 3.4 kg (1.8-7.32). Staged repair was undertaken for significant co-morbidity in 81 (64.8%) and anatomical complexity in 44 (35.2%). The median hospital stay was 14 days (interquartile range 8-33.5) and 14 patients (11.2%) required anatomical repair before discharge. Nine patients died during the initial admission (hospital mortality 7.2 %) and five following discharge (inter-stage mortality 4.8%). Of 105 banded patients who survived, 19 (18.1%) needed inter-stage re-admission and 18 (14.4%) required unplanned re-intervention. Full repair was performed in 93 (74.4%) at a median age of 13 months (3.1-49.9) and weight of 8.5 kg (3.08-16.8). Prior banding, 54% were below the 0.4th weight centile, but only 28% remained so at repair. Post-repair, 5/93 (5.4%) developed heart block requiring permanent pacemaker, and 11/93 (11.8%) required unplanned re-intervention. The post-repair mortality (including repairs during the initial admission) was 6/93 (6.5%), with overall mortality of the staged approach 13.6% (17/125). CONCLUSIONS: In a cohort with a high incidence of co-morbidity, pulmonary artery banding is associated with a significant risk of re-intervention and mortality. Weight gain improves after banding, but heart block, re-intervention, and mortality remain frequent following repair.

Management of prenatally detected vascular rings: a United Kingdom national survey.

OBJECTIVE: To investigate UK variability in prenatal and postnatal management strategy of right aortic arch and double aortic arch (RAA/DAA). METHODS: Online surveys were sent to senior physicians (consultants) of the National Fetal Cardiology Working Group regarding prenatal diagnosis, counselling, and perinatal management of antenatally diagnosed RAA/DAA and to the British Congenital Cardiovascular Association regarding postnatal management strategies. RESULTS: There were 28 prenatal and 90 postnatal surveys completed. Prenatally, there was consensus for potential associated chromosomal/genetic anomalies, but there was variation in the risk quoted. Confidence in defining aortic arch morphology was reported by 43% (12/28) of fetal cardiologists. There was variation in what was felt to be possible symptoms/signs of a compressive vascular ring, postnatal investigation, postnatal management, follow-up duration of asymptomatic patients, and indications for surgical intervention. CONCLUSION: This study has highlighted important areas for future research: improving accuracy of prenatal diagnosis, clarification of potential symptoms, optimal investigation strategies, and indications for surgery.

Congenitally Malformed Hearts: Aspects of Teaching and Research Involving Medical Students.

To appreciate congenital heart disease fully, a detailed understanding of the anatomical presentation, as well as the physiology, is required. This is often introduced at an advanced stage of training. Professor Anderson has been influential in the Clinical Anatomy Intercalated BSc programme at the University of Birmingham, in particular in his teaching on Sequential Segmental Analysis. This article describes the experiences of the latest cohort of students on this programme, who undertook varying research projects using the Birmingham Cardiac Archive, with the guidance of Professor Anderson. The projects outlined include various aspects of isomerism, encompassing both the cardiac and abdominal manifestations, as well as details of congenitally corrected transposition of the great arteries and prenatally diagnosed right aortic arch and double arch. These studies all aimed to increase the knowledge base of their respective cardiac malformations and provide a basis for further research.

The Diagnostic Yield of Prenatal Genetic Technologies in Congenital Heart Disease: A Prospective Cohort Study.

INTRODUCTION: The objective was to evaluate: (i) the proportion of prenatally diagnosed congenital heart disease (CHD) associated with an abnormal quantitative fluorescence-PCR (QF-PCR), chromosome microarray (CMA), and exome sequencing (ES) result; and (ii) the diagnostic yield of these technologies based on CHD category and presence of extra-cardiac anomalies (ECAs). METHODS: This prospective cohort study was set across 12 UK foetal medicine centres. All cases underwent QF-PCR, CMA, and ES, and the diagnostic yield in n = 147 cases of prenatally diagnosed CHD was assessed. RESULTS: In 34.7% (n = 51/147), a genetic diagnosis was obtained. Using a stepwise testing strategy, the diagnostic yield for QF-PCR, CMA, and ES was 15.6% (n = 23/147), 13.7% (n = 17/124), and 10.2% (n = 11/107), respectively. Abnormal QF-PCR/shunt (septal) defects 31.4% (n = 11/35), p = 0.046, and abnormal CMA/conotruncal anomalies 22.7% (n = 10/44), p = 0.04, had significant associations. Monogenic variants were commonest in complex CHD 36.4% (n = 4/11). Multisystem CHD had a greater diagnostic yield overall compared to isolated OR 2.41 (95% CI, 1.1-5.1), particularly in association with brain and gastrointestinal tract anomalies. The proportion of variants of uncertain significance was 4.7% (n = 5/107) with ES, with none in the CMA group. CONCLUSION: In the era of prenatal ES, there remains an important role for QF-PCR and CMA. Identification of monogenic pathologic variants further allows delineation of prognosis in CHD.

Morphology of vascular ring arch anomalies influences prognosis and management.

OBJECTIVE: This study aimed to explore the anatomical features of aortic arch anomalies associated with vascular rings, hoping to identify those which may increase the risk of symptomatic presentation and surgical intervention. METHODS: This was a retrospective observational study at a single cardiac unit. Individuals diagnosed with an aortic arch anomaly, either isolated or non-isolated, between June 2014 and September 2018 were included. The morphology of the aortic arch was established via analysis of postnatal echocardiography, CT or MRI scans. CT and magnetic resonance studies were evaluated for the presence of a Kommerell diverticulum in those with aberrant vessels. Case notes were reviewed for relevant clinical data. RESULTS: Of those with aberrant subclavian arteries, 24/79 (30.4%) were shown to have a Kommerell diverticulum. Additional forms of congenital heart disease were present in 133/227 (58.6%) individuals. Surgical division of the vascular ring was performed in 30/227 (13.2%), most commonly in the setting of a double aortic arch (70.8%). In those with aberrant subclavian arteries, no children without a Kommerell diverticulum were referred for surgery. In those with a Kommerell diverticulum confirmed on imaging, 11/24 underwent surgery. CONCLUSION: Individuals with a double aortic arch, or an aberrant subclavian artery arising from a Kommerell diverticulum, have the highest requirement for surgical intervention, especially in isolated anomalies. These individuals should remain under monitoring. The subjective nature of symptoms remains problematic. Longitudinal research is required further to understand the natural history of vascular rings and how it links to morphology.

EDUCATIONAL SERIES IN CONGENITAL HEART DISEASE: Prenatal diagnosis of congenital heart disease.

This review article will guide the reader through the background of prenatal screening for congenital heart disease. The reader will be given insight into the normal screening views, common abnormalities, risk stratification of lesions and also recent advances in prenatal cardiology.

Total anomalous pulmonary venous connection: outcome of postoperative pulmonary venous obstruction.

OBJECTIVE: Pulmonary venous obstruction (PVO) is an important cause of late mortality in total anomalous pulmonary venous connection (TAPVC). We aimed to describe current practices for the management of postoperative PVO and the efficacy of the different interventional procedures. METHODS: We conducted a retrospective international collaborative population-based study involving 19 pediatric cardiac centers in the United Kingdom, Ireland, and Sweden. Patients with TAPVC born between January 1, 1998, and December 31, 2004, were identified. Patients with functionally univentricular circulation or atrial isomerism were excluded. All available data and images were reviewed. RESULTS: Of 406 patients undergoing repair of TAPVC, 71 (17.5%) had postoperative PVO. The diagnosis was made within 6 months of surgery in 59 (83%) of the 71 patients. In 12, serial imaging documented change in appearance of the pulmonary veins. Good-sized pulmonary veins can progress to diffusely small veins and rarely atresia. Patients presenting after 6 months had less severe disease; all are alive at most recent follow-up. Fifty-six (13.8%) of 406 patients underwent intervention for postoperative PVO: 44 had surgical treatment and 12 had an initial catheter intervention. One half underwent 1 or more reinterventions. Three-year survival for patients with postoperative PVO was 58.7% (95% confidence intervals, 46.2%-69.2%) with a trend that those having a surgical strategy did better (P = .083). Risk factors for death included earlier presentation after TAPVC repair, diffusely small pulmonary veins at presentation of postoperative PVO, and an increased number of lung segments affected by obstruction. CONCLUSIONS: Postoperative PVO tends to appear in the first 6 months after TAPVC repair and can be progressive. Early intervention for PVO may be indicated before irreversible secondary changes occur.

Total anomalous pulmonary venous connection: morphology and outcome from an international population-based study.

BACKGROUND: late mortality after repair of total anomalous pulmonary venous connection is frequently associated with pulmonary venous obstruction (PVO). We aimed to describe the morphological spectrum of total anomalous pulmonary venous connection and identify risk factors for death and postoperative PVO. METHODS AND RESULTS: we conducted a retrospective, international, collaborative, population-based study involving all 19 pediatric cardiac centers in the United Kingdom, Ireland, and Sweden. All infants with total anomalous pulmonary venous connection born between 1998 and 2004 were identified. Cases with functionally univentricular circulations or atrial isomerism were excluded. All available data and imaging were reviewed. Of 422 live-born cases, 205 (48.6%) had supracardiac, 110 (26.1%) had infracardiac, 67 (15.9%) had cardiac, and 37 (8.8%) had mixed connections. There were 2 cases (0.5%) of common pulmonary vein atresia. Some patients had extremely hypoplastic veins or, rarely, discrete stenosis of the individual veins. Sixty (14.2%) had associated cardiac anomalies. Sixteen died before intervention. Three-year survival for surgically treated patients was 85.2% (95% confidence interval 81.3% to 88.4%). Risk factors for death in multivariable analysis comprised earlier age at surgery, hypoplastic/stenotic pulmonary veins, associated complex cardiac lesions, postoperative pulmonary hypertension, and postoperative PVO. Sixty (14.8%) of the 406 patients undergoing total anomalous pulmonary venous connection repair had postoperative PVO that required reintervention. Three-year survival after initial surgery for patients with postoperative PVO was 58.7% (95% confidence interval 46.2% to 69.2%). Risk factors for postoperative PVO comprised preoperative hypoplastic/stenotic pulmonary veins and absence of a common confluence. CONCLUSIONS: preoperative clinical and morphological features are important risk factors for postoperative PVO and survival.

Prenatal identification of the pulmonary arterial supply in tetralogy of Fallot with pulmonary atresia.

OBJECTIVE: To define the patterns of flow of blood to the lungs in fetuses with tetralogy of Fallot and pulmonary atresia. BACKGROUND: In this condition, supply of blood to the lungs is provided via an arterial duct or systemic-to-pulmonary collateral arteries, or very rarely through other conduits such as coronary arterial fistulas or an aortopulmonary window. The intrapericardial pulmonary arteries vary in size, and may be absent. These variables influence the prognosis and management. METHODS: We carried out a retrospective review of cases from a tertiary service for fetal cardiology, identifying all cases of tetralogy of Fallot with pulmonary atresia diagnosed antenatally between January, 1997, and April, 2006. We established pre- and postnatal outcomes, and compared the prenatal diagnosis with postnatal or autopsy findings. RESULTS: Of 6587 fetuses scanned during this period, 11 were diagnosed as having tetralogy of Fallot with pulmonary atresia and no other cardiac defect. In 5, arterial flow to the lungs was via an arterial duct, and in the other 6, the main identified source of flow was systemic-to-pulmonary collateral arteries. Of the latter 6 pregnancies, 4 were terminated, along with 3 of the 5 with ductal supply. The presence of systemic-to-pulmonary collateral arteries was confirmed at postmortem examination in 3 instances, and in the two delivered neonates, in neither of whom was an infusion of prostaglandin commenced. CONCLUSION: The patterns of pulmonary flow can be identified prenatally in the setting of tetralogy with pulmonary atresia. Supply through systemic-to-pulmonary collateral arteries impacts on counselling, introducing uncertainty regarding postnatal surgical management.

Total anomalous pulmonary venous connection to the supradiaphragmatic inferior vena cava.

Total anomalous pulmonary venous connection to the inferior vena cava is a rare form of total anomalous pulmonary venous connection infrequently described in the literature. We report two cases where the pulmonary venous connection was to the supradiaphragmatic portion of the inferior vena cava. In both patients, preoperative echocardiography findings were misleading, which suggested a cardiac type of total anomalous pulmonary venous connection.

PR interval: a comparison of electrical and mechanical methods in the fetus.

BACKGROUND: Mechanical surrogates are used to assess fetal cardiac electrical activity. AIMS: To compare electrical PR interval measured using non-invasive fetal electrocardiography (fECG) with mechanical atrioventricular (AV) interval using Doppler. STUDY DESIGN AND SUBJECTS: Prospective study of 55 recordings made in 50 human fetuses. Those with structural heart defects, second degree or complete heart block were excluded. OUTCOME MEASURES: Mechanical AV interval was measured from the onset of mitral A wave to onset of aortic ejection. Electrical PR interval was measured from a coherent averaged signal obtained using non-invasive fECG recorded from the maternal abdomen. Wilcoxon signed rank test was used to compare both methods. Agreement between AV and PR intervals was assessed using linear regression and by Bland-Altman plots. Bland-Altman analysis assessed inter-observer and intra-observer variability. RESULTS: There was no significant difference in the heart rates of the 55 paired traces measured consecutively using both methods (p<0.35). AV interval was longer than PR (median [range] 116 [96-169] vs. 102 [75-143] ms; p<0.001), with mean difference -16.47 ms (95% Confidence Interval -43.43, 10.44), reflecting the increased proportion of the cardiac cycle measured. Using fECG, PR inter-observer and intra-observer mean differences were 0.4 ms (CI -7.29, 8.09) and 0.7 ms (CI -3.22, 4.62) respectively. R values for inter and intra-observer studies were 0.95 and 0.99 respectively. Using Doppler methods, AV inter-observer and intra-observer mean differences were -2.69 ms, (CI -15.33, 9.95) and 0.92 ms, (CI -9.41, 11.26) respectively. R values for AV measurements were 0.93 for inter-observer and 0.96 for intra-observer variation. CONCLUSIONS: Non-invasive fECG is a robust tool to measure the PR interval with narrow limits of agreement.