Endocardial pacing compared to epicardial left ventricle pacing and right ventricle pacing: A single-center long-term experience in a pediatric population

BACKGROUND AND AIMS

Pediatric pacing is usually performed as epicardial pacing in small children in need of pacemaker therapy. Epicardial pacing compared with transvenous pacing for pediatric complete atrioventricular block (CAVB) has different strengths and weaknesses. The epicardial left ventricular wall position of the lead has been considered superior, in terms of contraction pattern, compared to a transvenous right ventricular stimulation. We aimed to compare QRS duration and cardiac function before and after the switch from epicardial to transvenous pacing in a pediatric population.

METHODS

Pediatric patients with congenital or acquired CAVB, who underwent a switch from epicardial-to transvenous pacing at our center from 2005 to 2021, were identified through the national ICD- and Pacemaker Registry. Data regarding clinical status, ECG, and echocardiography before and after the switch and at last follow-up were collected.

RESULTS

We included 15 children. The median age at the switch was 6.7 (4.4-11.7) years with a median weight of 21 (15-39) Kg. The median QRS duration with the transvenous systems was 136 (128-152) ms vs. a QRS duration during epicardial stimulation of 150 (144-170) ms with a median difference in QRS duration of 14 (6-20) ms. Children with a post-surgical AV block had a broader QRS duration, both with epicardial and endocardial stimulation. Before the switch, there was one patient with impaired left ventricular function (LVF) but with normal left ventricular end-diastolic diameters. After the switch, one patient developed symptomatic LV dysfunction with the recovery of LVF at the last follow-up after being implanted with a cardiac resynchronization therapy device.

CONCLUSIONS

Our report of pediatric patients after switching from epicardial to transvenous pacing shows how transvenous pacing is not inferior to epicardial pacing in terms of QRS duration and no significant deterioration of cardiac function was detectable.

Cardiac response to water activities in children with Long QT syndrome type 1

BACKGROUND

Swimming is a genotype-specific trigger in long QT syndrome type 1 (LQT1).

OBJECTIVE

To examine the autonomic response to water activities in children and adolescents with LQT1.

METHODS

In this cross-sectional study, LQT1 patients were age and sex matched to one healthy control subject. Electrocardiograms (ECGs) were recorded during face immersion (FI), swimming, diving, and whole-body submersion (WBS). Heart rate (HR) and heart rate variability (HRV) was measured. The high frequency (HF) component of HRV was interpreted to reflect parasympathetic activity, while the low frequency (LF) component was interpreted as reflecting the combined influence of sympathetic and parasympathetic activity on autonomic nervous modulation of the heart.

RESULTS

Fifteen LQT1 patients (aged 7-19 years, all on beta-blocker therapy) and fifteen age and sex matched non-medicated controls were included. No significant ventricular arrhythmias were observed in the LQT1 population during the water activities. Out of these 15 matched pairs, 12 pairs managed to complete FI and WBS for more than 10 seconds and were subsequently included in HR and HRV analyses. In response to FI, the LQT1 group experienced a drop in HR of 48 bpm, compared to 67 bpm in the control group (p = 0.006). In response to WBS, HR decreased by 48 bpm in the LQT1 group and 70 bpm in the control group (p = 0.007). A significantly lower PTOT (p < 0.001) and HF (p = 0.011) component was observed before, during and after FI in LQT1 patients compared with the controls. Before, during and after WBS, a significantly lower total power (p < 0.001), LF (p = 0.002) and HF (p = 0.006) component was observed in the LQT1 patients.

CONCLUSION

A significantly lower HR decrease in response to water activities was observed in LQT1 subjects on beta-blocker therapy, compared to matched non-medicated controls. The data suggests an impaired parasympathetic response in LQT1 children and adolescents. An aberrant autonomic nervous system (ANS) response may cause an autonomic imbalance in this patient group.

Clinical presentation of calmodulin mutations: the International Calmodulinopathy Registry

AIMS

Calmodulinopathy due to mutations in any of the three CALM genes (CALM1-3) causes life-threatening arrhythmia syndromes, especially in young individuals. The International Calmodulinopathy Registry (ICalmR) aims to define and link the increasing complexity of the clinical presentation to the underlying molecular mechanisms.

METHODS AND RESULTS

The ICalmR is an international, collaborative, observational study, assembling and analysing clinical and genetic data on CALM-positive patients. The ICalmR has enrolled 140 subjects (median age 10.8 years [interquartile range 5-19]), 97 index cases and 43 family members. CALM-LQTS and CALM-CPVT are the prevalent phenotypes. Primary neurological manifestations, unrelated to post-anoxic sequelae, manifested in 20 patients. Calmodulinopathy remains associated with a high arrhythmic event rate (symptomatic patients, n = 103, 74%). However, compared with the original 2019 cohort, there was a reduced frequency and severity of all cardiac events (61% vs. 85%; P = .001) and sudden death (9% vs. 27%; P = .008). Data on therapy do not allow definitive recommendations. Cardiac structural abnormalities, either cardiomyopathy or congenital heart defects, are present in 30% of patients, mainly CALM-LQTS, and lethal cases of heart failure have occurred. The number of familial cases and of families with strikingly different phenotypes is increasing.

CONCLUSION

Calmodulinopathy has pleiotropic presentations, from channelopathy to syndromic forms. Clinical severity ranges from the early onset of life-threatening arrhythmias to the absence of symptoms, and the percentage of milder and familial forms is increasing. There are no hard data to guide therapy, and current management includes pharmacological and surgical antiadrenergic interventions with sodium channel blockers often accompanied by an implantable cardioverter-defibrillator.

Endocardial pacing compared to epicardial left ventricle pacing and right ventricle pacing: a single center long term experience in a pediatric population

Introduction

Complete atrioventricular block (CAVB), either congenital or post heart surgery, are the main indications for cardiac pacing in the pediatric population.

Epicardial pacing is preferred in small infants or for specific cardiac anomalies and some studies highlight a superior contraction pattern when pacing epicardially from the left ventricular apex region [1–3]. Endocardial pacing is more frequently used in children with a weight &gt;20 kg and is less invasive [4].

Paced QRS duration seems to be independently associated with ventricular dysfunction irrespective of location or age at device implantation [5].

Purpose

Describe the echocardiographic and electrocardiographic changes after switch from epicardial to transvenous pacing in a pediatric population with CAVB.

Methods

Children (0–18 years), who underwent a switch from left- (LV) or right ventricle (RV) epicardial pacing to transvenous pacing at our center, were retrospectively studied. Clinical, ECG- and echocardiographic parameters before and after the switch of the PM-system were collected as well as the most recent FU data. Left ventricular end-diastolic diameter (LVDD) and fractional shortening (FS) values were transformed to a body surface-related and age-related z-score (z), respectively.

Results

Fifteen patients with CAVB who received an epicardial pacemaker (60% congenital, 40% post-cardiac surgery) were converted to a transvenous system at our center (2005–2021). The median age at the switch was 6.8 (2–13) years with a median weight of 21 (9–62) kg. The epicardial lead location was more frequently the RV wall (60%) than the LV wall (40%). The RV outflow tract and interventricular septum were the most common locations (73%) for the endocardial leads. The mean QRS duration during epicardial stimulation was 150 (IQR 26) ms vs. a median QRS duration with the transvenous system of 136 (IQR 19) ms and a median delta QRS duration of 13ms. A detailed comparison between RV and LV epicardial pacing are reported in Figure 1. Children with post-surgical AV block had a broader median QRS duration, both with epicardial and endocardial stimulation. Before the switch, there was only one abnormal observation of FS less than −2 z with normal LVDD. At the last available follow-up (mean time 7 years), all the children had normal LVDD and only one had FS less than −2 z.

Conclusions

Our report of pediatric patients after switch from epi to endo pacing, shows good results in terms of QRS duration with no significant echocardiographic or clinical evidence of deterioration of the cardiac function. Due to the small sample size the results could serve as a hypothesis generator, but larger prospective studies are needed to evaluate the electrocardiographic and echocardiographic impact of transvenous - compared to epicardial pacing.

Funding Acknowledgement

Type of funding sources: None. Comparison of QRS duration

Pacing therapy in children with isolated complete atrioventricular block: a retrospective study of pacing system survival and pacing-related complications in a national cohort

AIMS

To evaluate pacing system survival and complications to pacemaker (PM) therapy in children with isolated complete atrioventricular block (CAVB).

METHODS AND RESULTS

We performed a nationwide retrospective study of children diagnosed before 15 years of age with isolated CAVB and PM treatment. Between 1983 and 2012, 127 patients underwent PM-implantations at 3.2 (0-17) [median (range)] years and were followed for 11 (0.6-19) years. An endocardial or epicardial PM system was implanted in 72 and 55 patients, respectively. A total of 306 pacing leads (76% steroid-eluting) were implanted. Pacing system survival was significantly affected by age, with a higher risk of a new intervention for children aged <1 month at first implantation. Lead survival of the steroid-eluting leads at 5 and 10 years was 90 and 81%, respectively, with no difference between epicardial and endocardial systems. Complications leading to revision of the pacing system occurred in 24% of the patients. Patients aged <1 month at first PM implantation had a five-fold increased risk for a complication to occur. Dividing the cohort according to year of first procedure showed that those who had their first implantation ≥2002 had fewer complications and also lead- and pacing system survival was better in the later cohort.

CONCLUSION

Pacing system survival and complications to PM therapy in young patients with isolated CAVB were significantly affected by age, with low age at PM implantation constituting a risk factor. Endocardial and epicardial pacing systems showed no significant differences in performance.

Comorbidity and long-term outcome in patients with congenital heart block and their siblings exposed to Ro/SSA autoantibodies in utero

Objective

Congenital heart block (CHB) may develop in fetuses of Ro/SSA autoantibody-positive women. Given the rarity of CHB, information on comorbidity and complications later in life is difficult to systematically collect for large groups of patients. We therefore used nation-wide healthcare registers to investigate comorbidity and outcomes in patients with CHB and their siblings.

Methods

Data from patients with CHB (n= 119) and their siblings (n= 128), all born to anti-Ro/SSA-positive mothers, and from matched healthy controls (n= 1,190) and their siblings (n= 1,071), were retrieved from the Swedish National Patient Register. Analyses were performed by Cox proportional hazard modelling.

Results

Individuals with CHB had a significantly increased risk of cardiovascular comorbidity, with cardiomyopathy and/or heart failure observed in 20 (16.8%) patients versus 3 (0.3%) controls, yielding a HR of 70.0 (95% CI 20.8 to 235.4), and with a HR for cerebral infarction of 39.9 (95% CI 4.5 to 357.3). Patients with CHB also had a higher risk of infections. Pacemaker treatment was associated with a decreased risk of cerebral infarction but increased risks of cardiomyopathy/heart failure and infection. The risk of systemic connective tissue disorder was also increased in patients with CHB (HR 11.8, 95% CI 4.0 to 11.8), and both patients with CHB and their siblings had an increased risk to develop any of 15 common autoimmune conditions (HR 5.7, 95% CI 2.83 to 11.69 and 3.6, 95% CI 1.7 to 8.0, respectively).

Conclusions

The data indicate an increased risk of several cardiovascular, infectious and autoimmune diseases in patients with CHB, with the latter risk shared by their siblings.

Sinus node dysfunction in patients with Fontan circulation: could heart rate variability be a predictor for pacemaker implantation?

Sinus node dysfunction (SND) causes significant morbidity in patients after Fontan surgery. Heart rate variability (HRV) reflects the autonomic regulation of the heart, and changes in HRV have been associated with SND in adults. We aimed to study whether changes in HRV could be detected in 24-h electrocardiographic (ECG) recordings in Fontan patients with SND. We compared HRV results from two patient groups; patients with Fontan circulation who later required a pacemaker due to severe SND (n = 12) and patients with Fontan circulation and SND, without indication for pacemaker treatment (n = 11), with two control groups; patients with Fontan circulation without SND (n = 90) and healthy controls (n = 66). The Poincaré plot index SD2 (representing changes in heart rate over 24-h) and the very low-frequency (VLF) HRV component were significantly higher in both SND groups, both compared with healthy controls and patients with Fontan circulation without SND. In SND patients with pacemakers, SD2 and VLF were slightly reduced compared to SND patients without pacemaker (p = 0.06). In conclusion, in Fontan patients with SND the HRV is significantly higher compared to healthy controls and Fontan patients without SND. However, in patients with severe SND requiring pacemaker, SD2 and VLF tended to be lower than in patients with SND without pacemaker, which could indicate a reduced diurnal HRV in addition to the severe bradycardia. This is a small study, but our results indicate that HRV analysis might be a useful method in the follow-up of Fontan patients regarding development of SND.

Cardiac Troponin T in Healthy Full-Term Infants

In this prospective cohort study of healthy full-term infants, we hypothesized that high-sensitivity cardiac troponin T (hs-cTnT) would be elevated in cord blood, compared with adult reference values, and that it would further increase over the first days of age. Cardiac troponin T has been shown to be significantly increased in healthy full-term newborns compared with adult reference values, but there is no established reference range. Most studies of cTnT in newborns have been performed before the introduction of high-sensitivity cTnT (hs-cTnT) assay. We conducted a study including 158 full-term newborns, at Stockholm South General Hospital. High-sensitivity cTnT was analyzed in umbilical cord blood and at 2-5 days of age. Median hs-cTnT (interquartile range) in cord blood was 34(26-44) ng/L; 99th percentile 88 ng/L. Median hs-cTnT at 2-5 days of age was 92(54-158) ng/L; 99th percentile 664 ng/L. We conclude that hs-cTnT is elevated in cord blood in healthy, full-term newborn infants compared with adult reference values, and that it increases significantly during the first days of life. Our findings further underline the need of caution when using hs-cTnT as a measurement of cardiac impact in newborns.

Doppler echocardiographic isovolumetric time intervals in diagnosis of fetal blocked atrial bigeminy and 2:1 atrioventricular block

OBJECTIVE

To distinguish between blocked atrial bigeminy (BB) and incomplete atrioventricular block with 2:1 conduction (2:1 AVB) can be very difficult, especially in the mid-term fetus. Making a correct diagnosis has important clinical implications, as their prognosis and management differ markedly. Our objective was to investigate whether analysis of isovolumetric time intervals could improve Doppler echocardiography in differentiating these conditions.

METHODS

Sixteen fetuses with sustained BB or isolated 2:1 AVB, diagnosed at our tertiary center from 2002 to 2012, were reviewed retrospectively. Doppler recordings of left ventricular in- and outflow, including mitral and aortic valve movements, were used to measure isovolumetric contraction (ICT) and relaxation (IRT) time intervals. ICT reference values obtained from 104 normal pregnancies were used for comparison.

RESULTS

Ten fetuses had BB and six 2:1 AVB. Five of the AVB cases were anti-Ro antibody positive and one had long QT syndrome (LQTS). ICT was systematically shorter in BB than in antibody-mediated 2:1 AVB. Nine of 10 cases with BB had an ICT below -2 SD and the five with antibody-mediated 2:1 AVB had values at or above +2 SD. All 15 fetuses with either BB or antibody-mediated AVB had an IRT of < 70 ms, as opposed to a markedly prolonged IRT (105 ms) in the LQTS case.

CONCLUSION

Measurement of ICT can improve the differential diagnosis between BB and antibody-mediated 2:1 AVB. Fetuses with BB or antibody-mediated AVB are unlikely to have IRT measurements exceeding 70 ms and, when this is observed, LQTS should be considered a more likely diagnosis.

The HLA locus contains novel foetal susceptibility alleles for congenital heart block with significant paternal influence

OBJECTIVE

The main aim of this study was to identify foetal susceptibility genes on chromosome six for Ro/SSA autoantibody-mediated congenital heart block.

SUBJECTS AND DESIGN

Single nucleotide polymorphism (SNP) genotyping of individuals in the Swedish Congenital Heart Block (CHB) study population was performed. Low-resolution HLA-A, -Cw and -DRB1 allele typing was carried out in 86 families comprising 339 individuals (86 Ro/SSA autoantibody-positive mothers, 71 fathers, 87 CHB index cases and 95 unaffected siblings).

RESULTS

A case-control comparison between index cases and population-based out-of-study controls (n = 1710) revealed association of CHB with 15 SNPs in the 6p21.3 MHC locus at a chromosome-wide significance of P < 2.59 × 10(-6) (OR 2.21-3.12). In a family-based analysis of association of SNP markers as well as distinct MHC class I and II alleles with CHB, HLA-DRB1*04 and HLA-Cw*05 variants were significantly more frequently transmitted to affected individuals (P < 0.03 and P < 0.05, respectively), whilst HLA-DRB1*13 and HLA-Cw*06 variants were significantly less often transmitted to affected children (P < 0.04 and P < 0.03). We further observed marked association of increased paternal (but not maternal) HLA-DRB1*04 transmission to affected offspring (P < 0.02).

CONCLUSIONS

HLA-DRB1*04 and HLA-Cw*05 were identified as novel foetal HLA allele variants that confer susceptibility to CHB in response to Ro/SSA autoantibody exposure, whilst DRB1*13 and Cw*06 emerged as protective alleles. Additionally, we demonstrated a paternal contribution to foetal susceptibility to CHB for the first time.

Long-term growth of children with autoantibody-mediated congenital heart block

AIM

To analyse growth of children with and without congenital heart block (CHB) born to anti-Ro/SSA positive mothers from birth to 18 years of age, using a population-based cohort of Swedish CHB patients.

METHODS

Medical records for siblings with (n = 72) and without (n = 60) CHB born 1973-2009 to anti-Ro/SSA positive mothers were retrieved from child healthcare centres and school health services and used to extract data on growth from birth to 18 years.

RESULTS

Compared with reference standards, children with CHB were retarded in weight by 0.75-1.0 SD from birth to 2-3 years of age. Thereafter, the CHB children started to catch up, reaching the reference standards at 9-11 years of age. Pacemaker treatment was not correlated with the catch-up in growth. Individuals with CHB were retarded in both weight and height from birth to 9-11 years of age when compared to siblings without CHB, who did not demonstrate restriction in these measurements.

CONCLUSION

Presence of CHB is a more important predictor of growth restriction than maternal rheumatic disease and foetal anti-Ro/SSA exposure. The restriction persists for several years after birth, despite pacemaker treatment, which highlights the importance of follow-up of children with CHB regarding nutrition and growth.

Progression to first-degree heart block in preschool children exposed in utero to maternal anti-SSA/Ro52 autoantibodies

AIMS

To study the children exposed in utero to maternal anti-SSA/Ro52 antibodies in terms of impaired atrioventricular (AV) conduction or disturbed myocardial performance, and to investigate the ability of prenatal Doppler to predict conduction abnormalities during childhood.

METHODS

Fifty-seven children exposed in utero to anti-SSA/Ro52 antibodies were grouped in accordance with (A) prolonged AV time intervals in utero by Doppler or (B) normal findings and examined by ECG, 24-hour ECG and echocardiography.

RESULTS

PR interval on ECG was longer in group A (n = 16) compared with that of group B (n = 41), 140 ± 24 ms vs. 121 ± 13 ms (p < 0.01). Six cases of 1°Atrioventricular block (AVB) developed in group A, giving an estimated prevalence of 10.5%, (95% confidence interval; 4.4-22.2%), progressing from normal sinus rhythm at 1 month of age. Prenatal Doppler predicted development of 1°AVB at follow-up with a sensitivity of 100%, Positive predictive value (PPV) 37.5%, LR+ 5.1, and Negative predictive value (NPV) 100%. Children in group A had a slightly higher myocardial performance index in flow and tissue Doppler imaging recordings.

CONCLUSIONS

Ten per cent of children exposed in utero to anti-SSA/Ro52, with a normal ECG at birth or 1 month of age, progressed to 1°AVB during preschool years. Cases at risk can be identified by prenatal Doppler echocardiography.

A population-based investigation of the autoantibody profile in mothers of children with atrioventricular block

The objective of the study was to investigate the antigen specificity and occurrence of individual autoantibodies in mothers of children diagnosed with atrioventricular (AV) block in a nation-wide setting. Patients with AV block detected before 15 years of age were identified using national quality registries as well as a network of pediatric and adult cardiologists and rheumatologists at the six university hospitals in Sweden. Patients with gross heart malformations, surgically or infectiously induced blocks were excluded. Blood samples were obtained from the mothers and maternal autoantibody profile, including the occurrence of antibodies against Ro52, Ro60, La, SmB, SmD, RNP-70k, RNP-A, RNP-C, CENP-C, Scl-70, Jo-1, ribosomal RNP and histones was investigated in 193 mothers of children with AV block by immunoblotting and ELISA. Autoantibody reactivity was detected in 48% (93/193) of the mothers of children with AV block. In autoantibody-positive mothers, the vast majority, 95% (88/93), had antibodies against Ro52, while 63% (59/93) had autoantibodies to Ro60 and 58% (54/93) had autoantibodies to La. In addition, 13% (12/93) of the autoantibody-positive mothers had antibodies to other investigated antigens besides Ro52, Ro60 and La, and of these anti-histone antibodies were most commonly represented, detected in 8% (7/93) of the mothers. In conclusion, this Swedish population-based study confirms that maternal autoantibodies may associate with heart block in the child. Further, our data demonstrate a dominant role of Ro52 antibodies in association with AV block.

Isolated Atrioventricular Block in the Fetus

Background—

Isolated complete atrioventricular block in the fetus is a rare but potentially lethal condition in which the effect of steroid treatment on outcome is unclear. The objective of this work was to study risk factors associated with death and the influence of steroid treatment on outcome.

Methods and Results—

We studied 175 fetuses diagnosed with second- or third-degree atrioventricular block (2000–2007) retrospectively in a multinational, multicenter setting. In 80% of 162 pregnancies with documented antibody status, atrioventricular block was associated with maternal anti-Ro/SSA antibodies. Sixty-seven cases (38%) were treated with fluorinated corticosteroids for a median of 10 weeks (1–21 weeks). Ninety-one percent were alive at birth, and survival in the neonatal period was 93%, similar in steroid-treated and untreated fetuses, regardless of degree of block and/or presence of anti-Ro/SSA. Variables associated with death were gestational age <20 weeks, ventricular rate ≤50 bpm, fetal hydrops, and impaired left ventricular function at diagnosis. The presence of ≥1 of these variables was associated with a 10-fold increase in mortality before birth and a 6-fold increase in the neonatal period independently of treatment. Except for a lower gestational age at diagnosis in treated than untreated (23.4±2.9 versus 24.9±4.9 weeks; P =0.02), risk factors were distributed equally between treatment groups. Two-thirds of survivors had a pacemaker by 1 year of age; 8 children developed cardiomyopathy.

Conclusions—

Risk factors associated with a poor outcome were gestation <20 weeks, ventricular rate ≤50 bpm, hydrops, and impaired left ventricular function. No significant effect of treatment with fluorinated corticosteroids was seen.

Development of heart block in children of SSA/SSB-autoantibody-positive women is associated with maternal age and displays a season-of-birth pattern

OBJECTIVE

Congenital heart block may develop in the fetuses of Ro/SSA-positive and La/SSB-positive mothers. Recurrence rates of only 10-20% despite persisting maternal antibodies indicate that additional factors are critical for the establishment of heart block. The authors investigated the influence of other maternal and fetal factors on heart block development in a Swedish population-based cohort.

METHODS

The influence of fetal gender, maternal age, parity and time of birth on heart block development was analysed in 145 families, including Ro/La-positive (n=190) and Ro/La-negative (n=165) pregnancies.

RESULTS

There was a recurrence rate of 12.1% in Ro/La-positive women, and no recurrence in Ro/La-negative women. Fetal gender and parity did not influence the development of heart block in either group. Maternal age in Ro/La-positive pregnancies with a child affected by heart block was, however, significantly higher than in pregnancies resulting in babies without heart block (p<0.05).Seasonal timing of pregnancy influenced the outcome. Gestational susceptibility weeks 18-24 occurring during January-March correlated with a higher proportion of children with heart block and lower vitamin D levels during the same period in a representative sample of Swedish women and a corresponding higher proportion of children with heart block born in the summer (p<0.02). Maternal age or seasonal timing of pregnancy did not affect the outcome in Ro/La-negative pregnancies.

CONCLUSION

This study identifies maternal age and seasonal timing of pregnancy as novel risk factors for heart block development in children of Ro/La-positive women. These observations may be useful for counselling when pregnancy is considered.

Mechanisms in fetal bradyarrhythmia: 65 cases in a single center analyzed by Doppler flow echocardiographic techniques

OBJECTIVE

Fetal bradyarrhythmias have various underlying mechanisms. As blocked atrial bigeminy (BB) generally resolves spontaneously, but incomplete atrioventricular block (AVB) might respond to steroid treatment, correct diagnosis is of major importance. Our objectives were to assess the underlying mechanisms in fetal bradyarrhythmia and the accuracy of Doppler techniques in differentiating between them.

METHODS

Seventy-eight patients referred to our tertiary center between 1990 and 2007 for evaluation of fetal bradycardia were analyzed retrospectively. Besides Doppler recordings from the mitral valve/aorta, superior vena cava/aorta and pulmonary vein/peripheral pulmonary artery, we used recordings from the pulmonary trunk and ductus venosus. We calculated the ratio of the time interval between conducted and consecutive blocked atrial contractions divided by the interval between two conducted atrial beats (a(cb) /a(cc) ), to analyze more meticulously the atrial rhythm in BB and second-degree AVB.

RESULTS

Fetal bradycardia ( ≤ 110 bpm) was confirmed in 65 of the 78 referred cases. Twenty-five had AVB (of which 20 were complete AVB), 29 had BB (of which 23 were intermittent) and 11 had sinus bradycardia. The bradyarrhythmic mechanism was identified correctly in all but one fetus with an atrial ectopic rhythm. Heart rates < 65 bpm were not seen in fetuses diagnosed with BB and rates < 60 bpm were seen only in cases with complete AVB, but heart rate did not distinguish between BB and AVB in the 60-75 bpm range. The a(cb) /a(cc) ratio clearly differentiated between fetsues with BB and those with second-degree AVB, including during midgestation, when it was difficult to distinguish these fetuses.

CONCLUSIONS

Using Doppler flow recordings, the mechanism causing fetal bradycardia can be clarified. In most cases this can be accomplished by visual validation only, and meticulous measurements are needed mainly to distinguish midterm fetuses with BB from those with second-degree AVB.

Molecular Detection of Persistent Francisella tularensis Subspecies holarctica in Natural Waters

Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia.

Anti-Ro52/SSA antibody-exposed fetuses with prolonged atrioventricular time intervals show signs of decreased cardiac performance

OBJECTIVE

To investigate if anti-Ro/SSA antibody-exposed fetuses with prolonged atrioventricular (AV) time intervals also have prolongation of the isovolumetric contraction time (ICT).

METHODS

Seventy-eight anti-Ro/SSA (including 70 anti-Ro52) antibody-exposed fetuses at risk for congenital heart block (CHB) were followed weekly, between 18 and 24 weeks of gestation, with two Doppler echocardiographic methods designed to detect signs of first-degree AV block. One of these AV time measurements, using hemodynamic events from the mitral valve and aortic outflow as indirect markers of atrial and ventricular depolarization (MV-Ao), was also used to calculate a time interval representing an early phase of systolic cardiac performance, i.e. the ICT. Two hundred and eighty-four women with normal pregnancies served as controls for AV time intervals and another 106 were used to establish an ICT reference range.

RESULTS

Strong positive relationships were found between ICT and MV-Ao time intervals (r = 0.91, P < 0.001), as well as between ICT and time intervals obtained from the superior vena cava and aorta (r = 0.85, P < 0.001). The ICT was estimated to contribute more than 50% of the total AV time prolongation. Abnormal AV time and ICT intervals were only seen in anti-Ro52 positive pregnancies.

CONCLUSIONS

The ICT is an important contributor to prolongation of AV time intervals. This observation suggests that anti-Ro52/SSA antibody-exposed fetal hearts have not only disturbed electrical conduction but also decreased mechanical performance. Moreover, our findings have implications for the interpretation of AV time intervals used for surveillance of fetuses at risk for developing CHB.

Transcriptional profiling of the peripheral blood response during tularemia

Tularemia is a febrile disease caused by the highly contagious bacterium Francisella tularensis. We undertook an analysis of the transcriptional response in peripheral blood during the course of ulceroglandular tularemia by use of Affymetrix microarrays comprising 14,500 genes. Samples were obtained from seven individuals at five occasions during 2 weeks after the first hospital visit and convalescent samples 3 months later. In total, 265 genes were differentially expressed, 95 of which at more than one time point. The differential expression was verified with real-time quantitative polymerase chain reaction for 36 genes (R(2)=0.590). The most prominent changes were noted in samples drawn on days 2-3 and a considerable proportion of the upregulated genes appeared to represent an interferon-gamma-induced response and also a proapoptotic response. Genes involved in the generation of innate and acquired immune responses were found to be downregulated, presumably a pathogen-induced event. A logistic regression analysis revealed that seven genes were good predictors of the early phase of tularemia. This is the first description of the transcriptional host response to ulceroglandular tularemia and the study has identified gene subsets relevant to the pathogenesis of the disease and subsets that may serve as early diagnostic biomarkers.

[Tricuspid valve stenosis--an serious complication to Port-a-cath]

Tricuspid valve stenosis and occlusion of superior vena cava are severe complications to Port-a-cath. In a child with SLE, symptoms started to develop about five to seven years after Port-a-cath insertion and cyclophosphamid injections. The patient developed hepatomegaly with abdominal and venous distension. Open heart surgery was necessary to remove the catheter. At operation it was found that the catheter was placed adjacent and through the tricuspid valve. The valve was severely stenosed with thrombus formation. The catheter and thrombus were removed, commissurotomy and bicuspidization of the valve and chordeal replacement performed to achieve an acceptable functional result. The superior vena cava was repaired with a pericardial patch. Retrospective analyses of the echocardiograms and chest x-rays show that the catheter was nearly related to the tricuspid valve and with the tip in the right ventricle. In such circumstances it is recommended with early withdrawal of the catheter, and in patients with immunological disease the indwelling time should be considered and limited.

Mode-coupling theory and polynomial fitting functions: a complex-plane representation of dielectric data on polymers

Recently, it has been shown that the higher-order A3 and A4 scenarios of the mode-coupling theory (MCT) are in many cases capable of providing a good description of the complicated dielectric spectra often encountered in polymeric systems. In this paper, more data from dielectric measurements on poly(ethylene terephthalate), poly(vinylidene fluoride), Nylon-66, poly(chlorotrifluoroethylene) (PCTFE), and the polymer gel system poly(acrylonitrile)-ethylene carbonate-propylene carbonate are evaluated within the A4 scenario of the MCT. For all these systems, very good agreement is found between the theoretical and experimental spectra. The data analysis is demonstrated to be facilitated considerably by plotting the data in the complex plane whereby the elliptic functions derived from the theory for the frequency-dependent dielectric function can be replaced by polynomials. For PCTFE, the scaling behavior predicted by the MCT could be verified and the temperature dependences of the extracted scaling parameters were found to be consistent with theory.