Genetic mutations and phenotype characteristics in peripheral vascular malformations: A systematic review

Vascular malformations (VMs) are clinically diverse with regard to the vessel type, anatomical location, tissue involvement and size. Consequently, symptoms and disease impact differ significantly. Diverse causative mutations in more and more genes are discovered and play a major role in the development of VMs. However, the relationship between the underlying causative mutations and the highly variable phenotype of VMs is not yet fully understood. In this systematic review, we aimed to provide an overview of known causative mutations in genes in VMs and discuss associations between the causative mutations and clinical phenotypes. PubMed and EMBASE libraries were systematically searched on November 9th, 2022 for randomized controlled trials and observational studies reporting causative mutations in at least five patients with peripheral venous, lymphatic, arteriovenous and combined malformations. Study quality was assessed with the Newcastle-Ottawa Scale. Data were extracted on patient and VM characteristics, molecular sequencing method and results of molecular analysis. In total, 5667 articles were found of which 69 studies were included, reporting molecular analysis in a total of 4261 patients and 1686 (40%) patients with peripheral VMs a causative mutation was detected. In conclusion, this systematic review provides a comprehensive overview of causative germline and somatic mutations in various genes and associated phenotypes in peripheral VMs. With these findings, we attempt to better understand how the underlying causative mutations in various genes contribute to the highly variable clinical characteristics of VMs. Our study shows that some causative mutations lead to a uniform phenotype, while other causal variants lead to more varying phenotypes. By contrast, distinct causative mutations may lead to similar phenotypes and result in almost indistinguishable VMs. VMs are currently classified based on clinical and histopathology features, however, the findings of this systematic review suggest a larger role for genotype in current diagnostics and classification.

Development, behaviour and sensory processing in Marshall-Smith syndrome and Malan syndrome: phenotype comparison in two related syndromes

BACKGROUND

Ultrarare Marshall-Smith and Malan syndromes, caused by changes of the gene nuclear factor I X (NFIX), are characterised by intellectual disability (ID) and behavioural problems, although questions remain. Here, development and behaviour are studied and compared in a cross-sectional study, and results are presented with genetic findings.

METHODS

Behavioural phenotypes are compared of eight individuals with Marshall-Smith syndrome (three male individuals) and seven with Malan syndrome (four male individuals). Long-term follow-up assessment of cognition and adaptive behaviour was possible in three individuals with Marshall-Smith syndrome.

RESULTS

Marshall-Smith syndrome individuals have more severe ID, less adaptive behaviour, more impaired speech and less reciprocal interaction compared with individuals with Malan syndrome. Sensory processing difficulties occur in both syndromes. Follow-up measurement of cognition and adaptive behaviour in Marshall-Smith syndrome shows different individual learning curves over time.

CONCLUSIONS

Results show significant between and within syndrome variability. Different NFIX variants underlie distinct clinical phenotypes leading to separate entities. Cognitive, adaptive and sensory impairments are common in both syndromes and increase the risk of challenging behaviour. This study highlights the value of considering behaviour within developmental and environmental context. To improve quality of life, adaptations to environment and treatment are suggested to create a better person-environment fit.

A genome-wide DNA methylation signature for SETD1B-related syndrome

SETD1B is a component of a histone methyltransferase complex that specifically methylates Lys-4 of histone H3 (H3K4) and is responsible for the epigenetic control of chromatin structure and gene expression. De novo microdeletions encompassing this gene as well as de novo missense mutations were previously linked to syndromic intellectual disability (ID). Here, we identify a specific hypermethylation signature associated with loss of function mutations in the SETD1B gene which may be used as an epigenetic marker supporting the diagnosis of syndromic SETD1B-related diseases. We demonstrate the clinical utility of this unique epi-signature by reclassifying previously identified SETD1B VUS (variant of uncertain significance) in two patients.

Genome-wide methylation profiling of Beckwith-Wiedemann syndrome patients without molecular confirmation after routine diagnostics

Beckwith-Wiedemann syndrome (BWS) is caused due to the disturbance of imprinted genes at chromosome 11p15. The molecular confirmation of this syndrome is possible in approximately 85% of the cases, whereas in the remaining 15% of the cases, the underlying defect remains unclear. The goal of our research was to identify new epigenetic loci related to BWS. We studied a group of 25 patients clinically diagnosed with BWS but without molecular conformation after DNA diagnostics and performed a whole genome methylation analysis using the HumanMethylation450 Array (Illumina).We found hypermethylation throughout the methylome in two BWS patients. The hypermethylated sites in these patients overlapped and included both non-imprinted and imprinted regions. This finding was not previously described in any BWS-diagnosed patient.Furthermore, one BWS patient exhibited aberrant methylation in four maternally methylated regions-IGF1R, NHP2L1, L3MBTL, and ZDBF2-that overlapped with the differentially methylated regions found in BWS patients with multi-locus imprinting disturbance (MLID). This finding suggests that the BWS phenotype can result from MLID without detectable methylation defects in the primarily disease-associated loci (11p15). Another patient manifested small but significant aberrant methylation in disease-associated loci at 11p near H19, possibly confirming the diagnosis in this patient.

Influence of the 20-week anomaly scan on prenatal diagnosis and management of fetal facial clefts

OBJECTIVE

To investigate trends in prenatal diagnosis and termination of pregnancy rates in cases of fetal cleft lip with or without cleft palate (CL ± P), before and after the introduction in The Netherlands of the 20-week anomaly scan in 2007, and to assess the accuracy of this scan for the diagnosis of facial clefts.

METHODS

This was a retrospective cohort study of consecutive cases of CL ± P diagnosed in 2001-2010 in the referral region of the Academic Medical Centre. Cases diagnosed prenatally were identified from the hospital's database. These data, grouped according to the periods before and after the introduction of the routine 20-week anomaly scan, were compared with data of all cases managed by the multidisciplinary cleft team, which services the same region, to identify cases of CL ± P that were not seen prenatally.

RESULTS

We identified 123 cases of CL ± P diagnosed prenatally, of which 76% (93/123) were diagnosed before 24 weeks. In one case, the CL ± P was not confirmed after birth. There were 46 cases with associated structural anomalies and 76 isolated cases. The median gestational age at diagnosis decreased by 2 weeks after 2007 (P = 0.02). The proportion of isolated clefts detected prenatally increased significantly after 2007 (P < 0.0001), whereas the proportion of associated clefts remained stable over the years (P = 0.426). The overall detection rate of CL ± P increased from 43% before 2007 to 86% after 2007 (P < 0.0001), without an increase in terminations of pregnancy.

CONCLUSION

Introduction of the routine fetal anomaly scan has decreased the gestational age at diagnosis of CL ± P and has increased the proportion diagnosed prenatally, without a significant change in the number of terminations of pregnancy.

X-linked congenital ptosis and associated intellectual disability, short stature, microcephaly, cleft palate, digital and genital abnormalities define novel Xq25q26 duplication syndrome

Submicroscopic duplications along the long arm of the X-chromosome with known phenotypic consequences are relatively rare events. The clinical features resulting from such duplications are various, though they often include intellectual disability, microcephaly, short stature, hypotonia, hypogonadism and feeding difficulties. Female carriers are often phenotypically normal or show a similar but milder phenotype, as in most cases the X-chromosome harbouring the duplication is subject to inactivation. Xq28, which includes MECP2 is the major locus for submicroscopic X-chromosome duplications, whereas duplications in Xq25 and Xq26 have been reported in only a few cases. Using genome-wide array platforms we identified overlapping interstitial Xq25q26 duplications ranging from 0.2 to 4.76 Mb in eight unrelated families with in total five affected males and seven affected females. All affected males shared a common phenotype with intrauterine- and postnatal growth retardation and feeding difficulties in childhood. Three had microcephaly and two out of five suffered from epilepsy. In addition, three males had a distinct facial appearance with congenital bilateral ptosis and large protruding ears and two of them showed a cleft palate. The affected females had various clinical symptoms similar to that of the males with congenital bilateral ptosis in three families as most remarkable feature. Comparison of the gene content of the individual duplications with the respective phenotypes suggested three critical regions with candidate genes (AIFM1, RAB33A, GPC3 and IGSF1) for the common phenotypes, including candidate loci for congenital bilateral ptosis, small head circumference, short stature, genital and digital defects.

Surgical treatment of macroglossia in patients with Beckwith-Wiedemann syndrome: a 20-year experience and review of the literature

Macroglossia is observed in the majority of paediatric patients diagnosed with Beckwith-Wiedemann syndrome and surgical treatment may be indicated. A 20-year retrospective study was performed to evaluate all patients with Beckwith-Wiedemann syndrome who underwent tongue reduction surgery at the authors' institution. A literature review was performed. Surgical treatment was indicated and carried out in 23 patients with a yearly average varying from 0 to 3 subjects. The mean follow-up time was 7 years. Primary indications for surgical treatment of macroglossia included significant tongue protrusion in 30% (n=7), and a combination of clinical problems in 70% (n=16). In all cases, the procedure was performed by the same surgeon using an anterior, V-shaped, wedge resection technique. Two patients had direct postoperative complications. No recurrence of macroglossia was observed in this study. Reported clinical outcome during follow-up demonstrated a satisfactory resting tongue position in all patients. Review of the literature demonstrated variability in surgical indications and techniques, and postoperative outcome. The results of this study indicate that the anterior wedge resection is a simple, effective and safe technique in the surgical treatment of paediatric patients, diagnosed with Beckwith-Wiedemann syndrome, suffering from macroglossia.

Enlarged nuchal translucency in chromosomally normal fetuses: strong association with orofacial clefts

OBJECTIVES

The aim of this study was to investigate whether there is an association between enlarged nuchal translucency (NT) and orofacial clefts.

METHODS

The pregnancy outcome of women who underwent an NT measurement between January 2000 and November 2008 was reviewed. All orofacial clefts detected prenatally and postnatally in karyotypically normal fetuses/infants were reviewed and a distinction was made between isolated defects and clefts as part of multiple congenital anomalies (associated).

RESULTS

The cohort included 8638 fetuses. The NT was enlarged in 746 (8.6%). The karyotype was normal in 8347 fetuses, including 513 of the fetuses with an enlarged NT. Isolated or associated cleft lip, with or without cleft palate (CL/P), or cleft palate (CP) were diagnosed in 18 chromosomally normal fetuses (an incidence of 2.2 per 1000). In eight of these cases the NT was normal (8/7834; an incidence of 1.0 per 1000) and in the remaining 10 it was enlarged (10/513; an incidence of 19.5 per 1000). CL/P and CP were isolated or associated in three and seven of the chromosomally normal fetuses with an enlarged NT, respectively. Euploid fetuses with an enlarged NT had a relative risk for any clefts of 19 and a relative risk for isolated or associated clefts of 8 and 53, respectively (P < 0.001).

CONCLUSIONS

Chromosomally normal fetuses with an enlarged NT have an increased risk of orofacial clefts. CL/P and CP are, in these fetuses, mostly associated findings, frequently part of a genetic syndrome. A detailed ultrasound examination with special attention given to the orofacial area is indicated in these fetuses.

Phenotype and genotype in 17 patients with Goltz-Gorlin syndrome

BACKGROUND

Goltz-Gorlin syndrome or focal dermal hypoplasia is a highly variable, X-linked dominant syndrome with abnormalities of ectodermal and mesodermal origin. In 2007, mutations in the PORCN gene were found to be causative in Goltz-Gorlin syndrome.

METHOD

A series of 17 patients with Goltz-Gorlin syndrome is reported on, and their phenotype and genotype are described.

RESULTS

In 14 patients (13 females and one male), a PORCN mutation was found. Mutations included nonsense (n = 5), frameshift (n = 2), aberrant splicing (n = 2) and missense (n = 5) mutations. No genotype-phenotype correlation was found. All patients with the classical features of the syndrome had a detectable mutation. In three females with atypical signs, no mutation was found. The male patient had classical features and showed mosaicism for a PORCN nonsense mutation in fibroblasts. Two affected sisters had a mutation not detectable in their parents, supporting germline mosaicism. Their father had undergone radiation for testicular cancer in the past. Two classically affected females had three severely affected female fetuses which all had midline thoracic and abdominal wall defects, resembling the pentalogy of Cantrell and the limb-body wall complex. Thoracic and abdominal wall defects were also present in two surviving patients. PORCN mutations can possibly cause pentalogy of Cantrell and limb-body wall complexes as well. Therefore, particularly in cases with limb defects, it seems useful to search for these.

CONCLUSIONS

PORCN mutations can be found in all classically affected cases of Goltz-Gorlin syndrome, including males. Somatic and germline mosaicism occur. There is no evident genotype-phenotype correlation.

Increased tumour risk for BWS patients correlates with aberrant H19 and not KCNQ1OT1 methylation: occurrence of KCNQ1OT1 hypomethylation in familial cases of BWS

Beckwith-Wiedemann syndrome (BWS) is an overgrowth malformation syndrome that maps to human chromosome 11p15.5, a region that harbours a number of imprinted genes. We studied the methylation status of H19 and KCNQ1OT1 (LIT1/KvDMR1) in a large series of BWS patients. Different patient groups were identified: group I patients (20%) with uniparental disomy and hence aberrant methylation of H19 and KCNQ1OT1; group II patients (7%) with a BWS imprinting centre 1 (BWSIC1) defect causing aberrant methylation of H19 only; group III patients (55%) with a BWS imprinting centre 2 (BWSIC2) defect causing aberrant methylation of KCNQ1OT1 only; and group IV patients (18%) with normal methylation patterns for both H19 and KCNQ1OT1. BWS patients have an increased risk of developing childhood tumours. In our patient group, out of 31 patients (group III) with KCNQ1OT1 demethylation only, none developed a tumour. However, tumours were found in 33% of patients with H19 hypermethylation (group I and II) and in 20% of patients with no detectable genetic defect (group IV). All four familial cases of BWS showed reduced methylation of KCNQ1OT1, suggesting that in these cases the imprinting switch mechanism is disturbed.

Intrauterine fetal death due to Farber disease: case report

We report a case of Farber disease in a fetus who died in utero at a gestational age of 29 weeks. Macroscopic examination showed moderate postmortem changes in a microcephalic female fetus (46,XX) with mild internal hydrops, two vessels in the umbilical cord, and a moderately enlarged, relatively well-preserved spleen. Microscopic examination showed foamy cells in the spleen. Electron microscopic examination revealed the presence of Farber bodies within these foamy cells. Enzyme studies of the fetus were not possible because all tissues were formalin fixed. Lipids were extracted from formalin-fixed tissues and increased levels of ceramide and the presence of hydroxyceramide in tissue of the spleen, liver, and lung were found. Glucosylceramide was not increased excluding saposin-precursor-deficiency. Because of these findings, both parents were tested for acid ceramidase activity in their leukocytes. They both had markedly reduced enzyme activity consistent with heterozygosity for Farber disease. To the best of our knowledge, this is the first published case of Farber disease in Dutch nonconsanguineous parents.

RET and GDNF gene scanning in Hirschsprung patients using two dual denaturing gel systems

Hirschsprung disease (HSCR) is a congenital disorder characterised by intestinal obstruction due to an absence of intramural ganglia along variable lengths of the intestine. RET is the major gene involved in HSCR. Mutations in the GDNF gene, and encoding one of the RET ligands, either alone or in combination with RET mutations, can also cause HSCR, as can mutations in four other genes (EDN3, EDNRB, ECE1, and SOX10). The rare mutations in the latter four genes, however, are more or less restricted to HSCR associated with specific phenotypes. We have developed a novel comprehensive mutation detection system to analyse all but three amplicons of the RET and GDNF genes, based on denaturing gradient gel electrophoresis. We make use of two urea-formamide gradients on top of each other, allowing mutation detection over a broad range of melting temperatures. For the three remaining (GC-rich) PCR fragments we use a combination of DGGE and constant denaturing gel electrophoresis (CDGE). These two dual gel systems substantially facilitate mutation scanning of RET and GDNF, and may also serve as a model to develop mutation detection systems for other disease genes. In a screening of 95 HSCR patients, RET mutations were found in nine out of 17 familial cases (53%), all containing long segment HSCR. In 11 of 78 sporadic cases (14%), none had long segment HSCR. Only one GDNF mutation was found, in a sporadic case.

RET and GDNF gene scanning in Hirschsprung patients using two dual denaturing gel systems

Hirschsprung disease (HSCR) is a congenital disorder characterised by intestinal obstruction due to an absence of intramural ganglia along variable lengths of the intestine. RET is the major gene involved in HSCR. Mutations in the GDNF gene, and encoding one of the RET ligands, either alone or in combination with RET mutations, can also cause HSCR, as can mutations in four other genes (EDN3, EDNRB, ECE1, and SOX10). The rare mutations in the latter four genes, however, are more or less restricted to HSCR associated with specific phenotypes. We have developed a novel comprehensive mutation detection system to analyse all but three amplicons of the RET and GDNF genes, based on denaturing gradient gel electrophoresis. We make use of two urea-formamide gradients on top of each other, allowing mutation detection over a broad range of melting temperatures. For the three remaining (GC-rich) PCR fragments we use a combination of DGGE and constant denaturing gel electrophoresis (CDGE). These two dual gel systems substantially facilitate mutation scanning of RET and GDNF, and may also serve as a model to develop mutation detection systems for other disease genes. In a screening of 95 HSCR patients, RET mutations were found in nine out of 17 familial cases (53%), all containing long segment HSCR. In 11 of 78 sporadic cases (14%), none had long segment HSCR. Only one GDNF mutation was found, in a sporadic case.

Interstitial deletion of the long arm of chromosome 2: a clinically recognizable microdeletion syndrome?

We report on a boy with an interstitial deletion of the long arm of chromosome 2 with breakpoints in chromosome bands q23 and q24.3. Main features were low-set and malformed ears, digital anomalies and congenital heart defects, which have also been reported in most of the previously described cases. A comparison of the features of the present patient with those in previously reported cases suggests the deletion 2q23q24 to be a clinically recognizable syndrome.

[Genes and genetics in Hirschsprung's disease]

Hirschsprung's disease (HSCR) is a congenital disorder characterized by intestinal obstruction due to the absence of intramural ganglia along variable lengths of the colon. Occurrence among family members and recurrence risks among siblings are indications for involvement of genetic predispositions. Mutations have been discovered in five different susceptibility genes. One of the most important findings is the detection of specific mutations in the so-called RET gene, which can also be responsible for the multiple endocrine neoplasia type 2A (MEN2A) syndrome. HSCR patients with such specific mutations run an increased risk of developing MEN type 2A related tumours.

Laparoscopic rectosigmoid colpopoiesis: does it benefit our transsexual patients?

When inversion of the combined penile and scrotal skin flaps for vaginoplasty in male-to-female transsexuals has not led to functional results, rectosigmoid colpopoiesis offers an immediate solution to a complicated and difficult problem. However, open colocolpopoiesis involves major surgery, and it may be associated with substantial extended morbidity and hospitalization, short- and long-term unfavorable results, and extensive scarring of the abdomen. To reduce this associated morbidity, we employ a laparoscopically assisted approach and a total laparoscopic rectosigmoid colpopoiesis. This procedure has been performed safely in the series presented herein, with no apparent compromise in the adequacy of the dissections. We conclude that our patients benefited from this procedure, and we advocate considering a total or partial laparoscopic approach whenever secondary rectosigmoid colpopoiesis is indicated in male-to-female transsexuals.

Oncological implications of RET gene mutations in Hirschsprung's disease

BACKGROUND

Germline mutations of the RET proto-oncogene identical to those found in the tumour predisposition syndrome multiple endocrine neoplasia type 2A (MEN2A), were detected in 2.5-5% of sporadic and familial cases of Hirschsprung's disease. Some patients with Hirschsprung's disease may therefore be exposed to a highly increased risk of tumours.

AIMS

To define clinical use of RET gene testing in Hirschsprung's disease and related patient management from an oncological point of view.

METHODS

Sixty patients with Hirschsprung's disease were screened for RET mutations. In three, MEN2A type RET mutations were detected. Case reports for these three patients are presented.

RESULTS AND CONCLUSIONS

Only 22 families or sporadic patients with Hirschsprung's disease and MEN2A type RET mutations have been reported. Therefore, it is difficult to predict tumour risk for patients with familial or sporadic Hirschsprung's disease, and their relatives, who carry these mutations. For these mutation carriers, periodic screening for tumours as in MEN2A is advised, but prophylactic thyroidectomy is offered hesitantly. RET gene testing in familial or sporadic Hirschsprung's disease is not recommended at present outside a complete clinical research setting. In combined MEN2A/Hirschsprung's disease families RET gene testing, tumour screening, and prophylactic thyroidectomy are indicated as in MEN2A.

EEC syndrome and genitourinary anomalies: an update

We report on a large family with the ectrodactyly, ectodermal dysplasia, clefting (EEC) syndrome. The clinical manifestations in this family show great variability. Specific genitourinary anomalies were found. The propositus with micturition problems is discussed in detail. A dysplastic bladder epithelium might be the cause of these problems. A remarkable improvement of the complaints was achieved upon treatment with synthetic sulfonated glycosaminoglycans.

[Consensus inflammatory intestinal diseases in children: ulcerative colitis and Crohn disease. Work Group Academic Medical Center, Amsterdam]

Members of different societies, including Paediatrics, Gastroenterology, Clinical Chemistry, Radiology and Pathology, involved in the treatment of children with inflammatory bowel disease (IBD) reached consensus during 12 meetings about definition, clinical and diagnostic work-up as well as initial treatment options in paediatric IBD. On the basis of history and physical examination a distinction is made between colitis-like or Crohn-like appearance. Further laboratory investigations are required in the presence of malnutrition, extraintestinal manifestations or growth retardation. Pathology plays an important part in the final diagnosis. Special attention is given to pubertal staging and height measurements as routine aspects of the treatment of children with IBD.

Further characterization of the 5'-flanking region of the rat lactase-phlorizin hydrolase gene

The lactase-phlorizin hydrolase gene is widely used as a marker of intestinal differentiation. Recent evidence demonstrating that transcription plays a major role in the regulation of this gene suggests that study of the 5'-flanking region will allow an understanding of how the expression of this gene is controlled. However, sequence, restriction, and primer extension analysis of a rat genomic clone has revealed that previously published data are incomplete. In the present study, we used a directed sequencing strategy to carefully analyze this region. Our expanded analysis of the 5'-flanking region of the lactase-phlorizin hydrolase gene should facilitate future studies of its structure and function.

[Pregnancy during residency]

The number of female residents in the Netherlands has steadily increased in recent years. Due to the increased time on waiting lists to enter residency programmes and to the increased duration of training, female residents will be older during their residencies. This will probably result in an increased number of pregnancies during residencies. A questionnaire regarding pregnancy during residency was sent to 191 residents in two university hospitals in the Netherlands. The response rate was 74.3%. Fifty percent of the male and only 19% of the female residents had children. No negative effects of a pregnancy on their training were experienced or anticipated by the residents. However, a negative effect on the functioning of the department was expected. No formal provisions, like replacements were available and many solutions to replace pregnant colleagues depended on the flexibility of the colleagues. The wish to have children was high and equally distributed among male and female residents, 92% and 96%, resp. Given the difficulty to seek a permanent position and to have children after residency, the choice of many female residents will be to have their children during residency. This increase in number of pregnancies requires anticipation of the residency programme directors. They should take the lead in proposing adequate regulations.

A method for analysis of the local atrial evoked response for determination of atrial capture in permanent pacing systems

We developed a method for detection and analysis of the local atrial evoked response. Eleven patients undergoing permanent dual chamber pacemaker implantations for standard clinical indications were included in the study. Using a pacing system emulator, charge balancing using a variable triphasic stimulus waveform to reduce polarization artifact amplitude was performed first. This could not be completed in one patient because of a poor signal-to-noise ratio. Subsequent analysis of the local atrial evoked response in the remaining ten patients showed the typical signal to be a biphasic waveform with an initial negative deflection followed by a positive deflection nearly equal in amplitude. The mean amplitude of the atrial evoked response was 3.1 +/- 1.4 mV, while the intrinsic P wave amplitude in these same patients averaged 5.6 +/- 3.0 mV. The summed evoked response, a parameter that is directly proportional to the area of the signal, was used to determine atrial pacing threshold. The median atrial pacing threshold determined by the algorithm was 1.00 V. There was no instance of failure to detect loss of capture, nor was loss of capture inaccurately determined when there was still successful atrial pacing. Atrial capture in permanent pacing systems can thus be determined using an algorithm to record and analyze the local atrial evoked response. This method could potentially be useful in the automatic determination of atrial pacing threshold.

Detection of ventricular tachycardia using scanning correlation analysis

Cross correlation is an accurate method for distinguishing normal sinus rhythm (NSR) from ventricular arrhythmias. The computational demands of the method, however, have prohibited development of an implantable device using correlation. In this study, temporal data compression prior to correlation analysis was used to reduce the total number of computations. Unipolar and bipolar intracardiac electrograms of NSR and 23 episodes of ventricular tachycardia (VT) from 23 patients were obtained from a right ventricular apex electrode catheter during routine electrophysiology studies. The data were filtered (1-11 Hz), digitized (250 samples/sec) and temporally compressed to 50 samples/sec. Data compression removed four out of every five samples by only saving the sample with the maximum excursion from the last saved sample. The average squared correlation coefficient (r2) was computed for the NSR and VT episodes using each patient's NSR waveform as a template. In all 23 patients, the r2 values showed large separation between NSR versus VT in both unipolar (0.93 +/- 0.05 vs 0.20 +/- 0.16, P less than 0.005) and bipolar (0.91 +/- 0.07 vs 0.17 +/- 0.11, P less than 0.005) electrode configurations using template lengths of 80% the intrinsic interval (avg +/- SD). Narrow templates (40% intrinsic interval or less) often resulted in multiple r2 peaks during each heart cycle and degraded the r2 separation (n = 10, P less than 0.005). High pass filtering at 3 Hz also degraded the r2 separation (n = 10, P less than 0.05). Standard noncompressed correlations indicated that data compression had negligible effects on the results. Thus, a computationally efficient cross correlation method was found to be a reliable detector of VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Tachyarrhythmia therapy utilizing electrical stimulation: a review

The review is structured in such a way as to fall naturally into four main sections. These are as follows: clinical overview of the common mechanisms leading to the generation of tachyarrhythmias; commonly used sensing techniques and algorithms for the detection of tachyarrhythmias; electrical stimulation algorithms used to terminate many of the rhythms; existing implantable devices and a brief look at the future. The clinical overview introduces the reader unfamiliar with tachyarrhythmias to such mechanisms as sinus tachycardia, supraventricular tachycardias (SVTs), ventricular tachycardia, 'torsade de pointes', and ventricular fibrillation. SVT includes paroxysmal SVT, atrial flutter, atrial tachycardia and junctional tachycardia (enhanced automaticity). Also there is a brief introduction to alternative therapies (drugs, surgery etc.) The sensing techniques section covers input signal processing to enable the R wave to be adequately detected; while the tachycardia detection algorithms section discusses such areas as simple rate detect, rate of change of rate detect, stability of rate, the so-called probability density function technique and some other more complex detection algorithms. The section on electrical stimulation algorithms used for tachycardia therapy discusses burst pacing techniques, special cases such as automatically decrementing bursts and automatically incrementing bursts, defibrillation shock therapy (since fibrillation is a form of tachyarrhythmia) and several other more complex algorithms. The review finishes up with a discussion of current implantable antitachy pacemakers and defibrillators. There is also a speculative look at the future to enable the reader to obtain a full picture.