A novel germline mutation in the aryl hydrocarbon receptor-interacting protein (AIP) gene in an Italian family with gigantism

PURPOSE

Acromegaly usually occurs as a sporadic disease, but it may be a part of familial pituitary tumor syndromes in rare cases. Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene have been associated with a predisposition to familial isolated pituitary adenoma. The aim of the present study was to evaluate the AIP gene in a patient with gigantism and in her relatives.

METHODS

Direct sequencing of AIP gene was performed in fourteen members of the family, spanning among three generations.

RESULTS

The index case was an 18-year-old woman with gigantism due to an invasive GH-secreting pituitary adenoma and a concomitant tall-cell variant of papillary thyroid carcinoma. A novel germline mutation in the AIP gene (c.685C>T, p.Q229X) was identified in the proband and in two members of her family, who did not present clinical features of acromegaly or other pituitary disorders. Eleven subjects had no mutation in the AIP gene. Two members of the family with clinical features of acromegaly refused either the genetic or the biochemical evaluation. The Q229X mutation was predicted to generate a truncated AIP protein, lacking the last two tetratricopeptide repeat domains and the final C-terminal α-7 helix.

CONCLUSIONS

We identified a new AIP germline mutation predicted to produce a truncated AIP protein, lacking its biological properties due to the disruption of the C-terminus binding sites for both the chaperones and the client proteins of AIP.

Combined ACL reconstruction and closing-wedge HTO for varus angulated ACL-deficient knees

PURPOSE

To report the medium-term clinical and radiographic outcomes of a group of patients who underwent anterior cruciate ligament (ACL) surgery combined with high tibial osteotomy (HTO) for varus-related early medial osteoarthritis (OA) and ACL deficiency knee.

METHODS

Thirty-two patients underwent single-bundle over-the-top ACL reconstruction or revision surgery and a concomitant closing-wedge lateral HTO. The mean age at surgery was 40.1 ± 8.1 years. Evaluation at a mean of 6.5 ± 2.7 years of follow-up consisted of subjective and objective IKDC, Tegner Activity Level, EQ-5D, VAS for pain and AP laxity assessment with KT-1000 arthrometer. Limb alignment and OA changes were evaluated on radiographs.

RESULTS

All scores significantly improved from pre-operative status to final follow-up. KT-1000 evaluation showed a mean side-to-side difference of 2.2 ± 1.0 mm. Two patients were considered as failures. The mean correction of the limb alignment was 5.6° ± 2.8°. Posterior tibial slope decreased at a mean of 1.2° ± 0.9°. At final follow-up, the mechanical axes crossed the medial-lateral length of tibial plateau at a mean of 56 ± 23 %, with only 1 patient (3 %) presenting severe varus alignment. OA progression was recorded only on the medial compartment (p = 0.0230), with severe medial OA in 22 % of the patients. No patients underwent osteotomy revision, ACL revision, UKA or TKA.

CONCLUSIONS

The described technique allowed patients with medial OA, varus alignment and chronic ACL deficiency to restore knee laxity, correct alignment and resume a recreational level of activity at 6.5 years of follow-up.

Ectopic expression of FSH receptor isoforms in neoplastic but not in endothelial cells from pancreatic neuroendocrine tumors

FSH receptor (FSHR) expression is restricted to gonads, where it drives FSH-dependent cell differentiation; in addition, FSHR plays an important role in the regulation of ovarian angiogenesis. Recently, FHSR expression has been shown in blood vessels of various tumors. However, pancreatic neuroendocrine tumors (p-NET), which have high-degree blood supply, were not included in that study. The aim of this study was to evaluate FSHR expression in p-NET. FSHR expression was evaluated in tumor samples from 30 patients with p-NET by immunohistochemistry and Western blot; fluorescence microscopy was used to localize FSHR in specific cells from tissue samples. von Willebrand factor (vWF) and chromograninA (chrA) was used as blood vessel and NET cells marker, respectively, to co-localize FSHR. FSHR expression was detected in all p-NET by immunohistochemistry. Western blot confirmed FSHR expression on p- NET although different FSHR isoforms, ranging from 240 kD to 55 kD were found in the samples studied. Surprisingly, FSHR co-localized with chrA but not with vWF, suggesting that neoplastic cells of neuroendocrine origin rather than blood vessels expressed FSHR. No relationship was found between degree of FSHR expression and histology of p-NET. FSHR may be aberrantly expressed in neoplastic cells from p-NET and not in tumor blood vessels; however, its biological significance as well as its clinical relevance remains to be elucidated.

The mechanisms of nadroparin-mediated inhibition of proliferation of two human lung cancer cell lines

OBJECTIVES

Clinical data suggest that heparin treatment improves survival of lung cancer patients, but the mechanisms involved are not fully understood. We investigated whether low molecular weight heparin nadroparin, directly affects lung cancer cell population growth in conventionally cultured cell lines.

MATERIALS AND METHODS

A549 and CALU1 cells' viability was assessed by MTT and trypan blue exclusion assays. Cell proliferation was assessed using 5-bromo-2-deoxyuridine incorporation. Apoptosis and cell-cycle distribution were analysed by flow cytometry; cyclin B1, Cdk1, p-Cdk1 Cdc25C, p-Cdc25C and p21 expressions were analysed by western blotting. mRNA levels were analysed by real time RT-PCR.

RESULTS

Nadroparin inhibited cell proliferation by 30% in both cell lines; it affected the cell cycle in A549, but not in CALU-1 cells, inducing arrest in the G(2) /M phase. Nadroparin in A549 culture inhibited cyclin B1, Cdk1, Cdc25C and p-Cdc25C, while levels of p-Cdk1 were elevated; p21 expression was not altered. Dalteparin caused a similar reduction in A549 cell population growth; however, it did not alter cyclin B1 expression as expected, based on previous reports. Fondaparinux caused minimal inhibition of A549 cell population growth and no effect on either cell cycle or cyclin B1 expression.

CONCLUSIONS

Nadroparin inhibited proliferation of A549 cells by inducing G(2) /M phase cell-cycle arrest that was dependent on the Cdc25C pathway, whereas CALU-1 cell proliferation was halted by as yet not elucidated modes.

[Implementing clinical pathways: some practical notes]

The traditional biomedical paradigm is no longer a guarantee of quality for health care, facing increasingly difficult challenges caused by chronic diseases and increasingly fragmented resources that current healthcare systems are dealing with. Health care organizations, considered to be the most complex enterprises of the modern era, must be able to focus on the flow of patients, integrating primary and secondary care through tools such as the Integrated Care Pathways (ICP). This brief discussion attempts to define the ICP its purposes, the elements that characterize it, its limitations and the mechanisms to push for a successful implementation. In order to highlight the elements and basic steps for the creation of an ICP, the authors have compared five different clinical pathways, whose implementation they have contributed to. The comparison was made using two grids: the first showing the essential elements for the definition of lCP and the second one with features that can facilitate their effectiveness. The conclusions of the work show what, pursuing the construction of a pathway, we must never forget: to analyze the gap between the clinical-care activities performed and the theoretical framework provided by the evidence; to see the barriers to change that may impede the implementation; to involve all actors in the system, with particular attention to patients and their associations, and finally to provide a plan for information and education, addressed to health professionals and patients as well.

Effect of rosiglitazone on serum IGF-I concentrations in uncontrolled acromegalic patients under conventional medical therapy: results from a pilot phase 2 study

OBJECTIVE

Current therapies for acromegaly are unsatisfactory for some patients. High-dose thiazolidinediones have been reported to reduce serum GH levels in animal models of acromegaly. The objective of the study was to evaluate the effect of increasing doses of rosiglitazone on serum GH and IGF-I concentrations in acromegalic patients.

DESIGN

Phase 2 clinical trial.

PATIENTS AND METHODS

Five consecutive patients with active and uncontrolled acromegaly under conventional medical therapies were treated with increasing doses of rosiglitazone [4 mg/day every month, starting from 8 up to 20 mg/day] added to previous medical therapies for acromegaly.

RESULTS

Mean serum IGF-I concentrations decreased from 547 ± 91 to 265 ± 126 μg/l (p<0,001) during rosiglitazone treatment: 4 patients had normal serum IGF-I concentrations, and a patient had lowered serum IGF-I values, although still abnormal, at the end of the study. On the contrary, serum GH concentrations did not significantly changed during rosiglitazone therapy as well as other pituitary hormones. No relevant side effects of rosiglitazone were observed during the study period. Quantitative real time PCR and Western blotting showed that rosiglitazone lowered GH-dependent hepatic generation of IGF-I in HepG2 cell line.

CONCLUSIONS

Rosiglitazone reduces serum IGF-I concentrations in patients with uncontrolled acromegaly under conventional medical therapies, likely acting on the GH-dependent hepatic synthesis of IGF-I. Large studies are necessary to confirm the role of rosiglitazone as an adjunctive therapy for uncontrolled acromegalic patients under conventional medical therapies.

Somatostatin analogues do not affect calcium metabolism in patients with acromegaly and primary hyperparathyroidism [corrected] due to MEN 1-like syndrome

Patients with clinical features of MEN 1 without mutations in the menin gene fulfill the criteria of MEN1-like syndrome. Primary hyperparathyroidism (PHP) is the most frequent clinical finding in both syndromes and is usually treated by surgery. However, PHP has been reported to respond to somatostatin analogues (SSA) in MEN 1 patients. 7 patients with PHP in the context of MEN 1-like syndrome (and absence of mutations in the menin gene) were enrolled in the study and treated with SSA for 6 months for the non-PHP disease before parathyroidectomy. Serum ionized calcium, phosphorus, and PTH concentrations, and 24-h urinary calcium and phosphorus excretion were measured before and after SSA therapy. Mean serum ionized calcium, phosphorus, and PTH concentrations did not significantly change after a 6-month course with SSA. SSA scintigraphy did not reveal uptake in the neck region corresponding to the parathyroid adenoma identified at surgery and confirmed at histology. However, immunohistochemistry revealed SS-type 2A receptor in parathyroid tissue samples of 6 out of 7 patients. SSA therapy does not affect calcium-phosphorus metabolism in patients with MEN 1-like syndrome, suggesting that the drug has no role in controlling PHP in these subset of patients.

Effects of cyclotronic ion resonance on human metabolic processes: a clinical trial and one case report

We studied the effects of ion cyclotron resonance (Seqex) magnetic therapy on the blood of thirty two healthy volunteers. They received 15 treatments each 27 minutes in length, distributed over 5 weeks. The concentrations of two blood components, malondialdehyde (MDA) and cholesterol were measured in each subject, immediately before and immediately after the 15 treatments as well as one month after the final treatment. Highly significant reductions in MDA concentrations, averaging 53.8% were noted just after the 15 treatments, tending to return to the original concentrations one month later. The effect on HDL and LDL cholesterol levels were not significant. The implication of this work is that this type of therapy may be useful in dealing with oxidative stress.

Uptake of amiodarone by thyroidal and non-thyroidal cell lines

Amiodarone perturbs thyroid function, causing overt hypothyroidism or hyperthyroidism in 15% of patients. Changes in thyroid function are likely due, at least in part, to amiodarone and/or desethylamiodarone (DEA) concentration into the thyroid gland, but mechanisms whereby the drug uptake occurred are not known. Thyroidal (FRTL-5) or non-thyroidal [Chinese hamster ovary wild-type (CHOwt) or CHO stably transfected with NIS (CHO-NIS)] cells were exposed to 10 microM amiodarone or DEA. Cellular content of both drugs was measured by HPLC and normalized by protein concentration. Cellular concentration of the two drugs was higher in FRTL-5 (mean +/- SD 17.2 +/- 1.2 microg/mg protein of amiodarone and 18.9 +/- 0.7 microg/mg protein of DEA) than in CHO-NIS and CHOwt cells (10.8 +/- 0.8 microg/mg protein and 12.8 +/- 0.2 microg/mg protein, respectively, of amiodarone (p < 0.004); 11.9 +/- 0.1 microg/mg protein and 11 +/- 0.2 microg/mg protein, respectively, of DEA (p < 0.0002). DEA concentration was higher than that of amiodarone in all cell lines (p < 0.002). Differences between FRTL-5 and CHO cell lines were not dependent on TSH: in fact, cellular content of either drug did not change in the presence or absence of TSH in the culture medium. NIS did not intervene in amiodarone or DEA entry into thyroid cells, since amiodarone and DEA content was the same in CHOwt and CHO-NIS cells; in addition, KClO4 inhibited NIS function, but had no effect on drug uptake by the cells. At variance, 80 microM DEA reduced 125I uptake by CHO-NIS cells by 40% at 30 min without affecting cell viability. In conclusion, mechanisms whereby amiodarone is taken up by thyroid cells remain largely unknown, but the two main factors involved in thyroid-specific cellular transport, ie, NIS and TSH, seem to be excluded.

Peroxisome proliferator-activated receptor (PPAR)gamma is highly expressed in normal human pituitary gland

OBJECTIVE

Expression of peroxisome proliferator-activated receptor (PPAR)gamma in normal pituitary seems to be restricted to ACTH-secreting cells. The aim of the study was to evaluate the expression of PPARgamma in normal human pituitary tissue and to study its localization in the pituitary secreting cells.

MATERIALS AND METHODS

Normal pituitary tissue samples were obtained form 11 patients with non-secreting adenoma who underwent surgical excision of the tumor. Expression of PPARgamma was evaluated by immunostaining and western blotting; localization of PPARgamma in each pituitary secreting cell lineage was evaluated by double immunofluorescence using confocal microscopy. Pituitary non-functioning adenomas served as Controls.

RESULTS

PPARgamma was highly expressed in all pituitary samples with a (mean +/- SD) 81 +/- 6.5% of stained cells; expression of PPARgamma was confirmed by western blotting. Non-functioning pituitary adenomas had 74 +/- 11% PPARgamma positive cells. Expression of PPARy was either in cytoplasm or nuclei. In addition, treatment of GH3 cells, with a PPARgamma ligand was associated with traslocation of the receptor from cytoplasm into the nucleus. Double immunostaining revealed that every pituitary secreting cell (GH, TSH, LH, FSH, PRL and ACTH) had PPARgamma expressed.

DISCUSSION

The present study demonstrated that PPARgamma is highly expressed in every normal pituitary secreting cell lineage. It can translocate into the nucleus by ligand binding; however, its role in pituitary hormone regulation remains to be elucidated.

Mutations in the SLC26A4 (pendrin) gene in patients with sensorineural deafness and enlarged vestibular aqueduct

Pendred syndrome and the enlarged vestibular aqueduct (EVA) are considered phenotypic variations of the same entity due to mutations in the SLC26A4 (pendrin) gene. Pendred syndrome consists in sensorineural deafness, goiter and impaired thyroid hormone synthesis while in EVA thyroid function seems to be preserved. The aim of this study was to evaluate thyroid function and morphology and to look for mutations in the SLC26A4 gene in patients presented with EVA. Among 57 consecutive patients with sensorineural deafness 15 with EVA, as assessed by magnetic resonance imaging (MRI), were identified and studied. A complete evaluation of thyroid function including thyroid echography and perchlorate discharge test was carried out in all patients with EVA; all exons of the SLC26A4 gene were amplified from peripheral leukocytes and directly sequenced, using specific intronic primers. Out of 15 patients with EVA, goiter was present in 8 (53%), hypothyroidism in 7 (47%), increased serum thyroglobulin levels in 8 (53%) and a positive perchlorate discharge test in 10 (67%). Nine alleles of the SLC26A4 gene were mutated: 2 novel mutations (L465W and G497R) and 4 already known mutations (T410M, R409H, T505N and IVS1001+1G>A) were found. Four subjects were compound heterozygous and 1 heterozygous (G497R/wt). All patients harbouring mutations in the SLC26A4 gene had goiter and a positive perchlorate discharge test: 3 were slightly hypothyroid and 2 euthyroid. The remaining 10 patients had no mutations in the SLC26A4 gene: 4 of them were hypothyroid, 2 with goiter and positive perchlorate discharge test, 2 without goiter and with negative perchlorate discharge test. Two patients without mutations were euthyroid with positive perchlorate discharge test. Patients with mutations in the SLC26A4 gene had larger thyroid volume (p<0.002), higher serum thyroglobulin (Tg) levels (p<0.002) and greater radioiodine discharge after perchlorate (p=0.09) than patients without mutations. The results of the present study lend support to the concept that all patients with mutated SLC26A4 gene have abnormalities of thyroid function tests.

Colonic polyps of acromegalic patients are not associated with mutations of the peroxisome proliferator activated receptor gamma gene

Peroxisome proliferator activated receptor (PPAR)gamma plays a pivotal role in regulating adipocyte differentiation and metabolism, but also has an antiproliferative effect in several tissues, including colonic mucosa, where it is highly expressed. Loss-of-function mutations have been reported in about 10% of sporadic primary colon cancer. Acromegalic patients have an increased prevalence of colonic neoplasms and lower PPARgamma levels in the colonic mucosa. Thus, PPARgamma may act as a tumor suppressor gene, and its reduced expression or loss-of-function mutations may contribute to tumorigenesis. In this study the expression and mutations of the PPARgamma gene in the colonic polyps and mucosa outside polyps were investigated in 10 acromegalic and 17 non-acromegalic patients. PPARgamma expression was evaluated by RT-PCR. PPARgamma was expressed in each sample, but expression appeared to be lower in polyps than in mucosa outside polyps from either acromegalic or non-acromegalic patients. All exons of the PPARgamma gene were directly sequenced after PCR amplification: no mutations were found either in acromegalic or in non-acromegalic patients. In conclusion, the results of this preliminary study suggest that the lower expression of PPARgamma rather than somatic mutations of this gene is involved in colonic tumorigenesis.

Effects of a mixture of polychlorinated biphenyls (Aroclor 1254) on the transcriptional activity of thyroid hormone receptor

Polychlorinated biphenyls (PCBs) are environmental contaminants which may affect thyroid function. PCBs may reduce serum thyroid hormone (TH) concentrations by either displacing T4 from TH transport proteins or increasing its hepatic metabolism. The reduced serum T4 causes neurological and growth defects in animals exposed to PCBs during the perinatal period, which can partially be reverted by T4 administration. In addition to a hypothyroid-like syndrome, a direct action of PCBs on TH-sensitive genes has been postulated. In the present study the effects of Aroclor 1254 (ARO), a mixture of PCBs, on transcription of TH-dependent genes were investigated. A reporter plasmid containing the TH-responsive element (TRE) of malic enzyme (ME) gene was used in transient transfections to assess the responsiveness to ARO. ARO (10 microM) reduced the CAT activity by about 50% and competed with T3 to reduce the induction of transcription. Cotransfection of TH receptor (TR) and a wild type TRE was required to reveal ARO inhibitiry effect, which was abolished by a mock reaction not containing TR or by a mutated TRE. ARO reduced the 125I-T3 binding to TR by 30%, but did not affect the interaction of TR with a 32P-labeled TRE in gel shift assay. ARO is likely to produce a conformational change in in vitro translated TR, leading to its increased proteolysis by trypsin. These results demonstrate that ARO interacts with TR, thereby affecting the transcription of TH-sensitive genes, and provide a molecular basis to further explain the complex effects of PCBs on TH disruption.

Desethylamiodarone antagonizes the effect of thyroid hormone at the molecular level

OBJECTIVE

To evaluate the molecular mechanisms of the inhibitory effects of amiodarone and its active metabolite, desethylamiodarone (DEA) on thyroid hormone action.

MATERIALS AND METHODS

The reporter construct ME-TRE-TK-CAT or TSHbeta-TRE-TK-CAT, containing the nucleotide sequence of the thyroid hormone response element (TRE) of either malic enzyme (ME) or TSHbeta genes, thymidine kinase (TK) and chloramphenicol acetyltransferase (CAT) was transiently transfected with RSV-TRbeta into NIH3T3 cells. Gel mobility shift assay (EMSA) was performed using labelled synthetic oligonucleotides containing the ME-TRE and in vitro translated thyroid hormone receptor (TR)beta.

RESULTS

Addition of 1 micromol/l T4 or T3 to the culture medium increased the basal level of ME-TRE-TK-CAT by 4.5- and 12.5-fold respectively. Amiodarone or DEA (1 micromol/l) increased CAT activity by 1.4- and 3.4-fold respectively. Combination of DEA with T4 or T3 increased CAT activity by 9.4- and 18.9-fold respectively. These data suggested that DEA, but not amiodarone, had a synergistic effect with thyroid hormone on ME-TRE, rather than the postulated inhibitory action; we supposed that this was due to overexpression of the transfected TR into the cells. When the amount of RSV-TRbeta was reduced until it was present in a limited amount, allowing competition between thyroid hormone and the drug, addition of 1 micromol/l DEA decreased the T3-dependent expression of the reporter gene by 50%. The inhibitory effect of DEA was partially due to a reduced binding of TR to ME-TRE, as assessed by EMSA. DEA activated the TR-dependent down-regulation by the negative TSH-TRE, although at low level (35% of the down-regulation produced by T3), whereas amiodarone was ineffective. Addition of 1 micromol/l DEA to T3-containing medium reduced the T3-TR-mediated down-regulation of TSH-TRE to 55%.

CONCLUSIONS

Our results demonstrate that DEA, but not amiodarone, exerts a direct, although weak, effect on genes that are regulated by thyroid hormone. High concentrations of DEA antagonize the action of T3 at the molecular level, interacting with TR and reducing its binding to TREs. This effect may contribute to the hypothyroid-like effect observed in peripheral tissues of patients receiving amiodarone treatment.

A novel mutation in the pendrin gene associated with Pendred's syndrome

OBJECTIVE

Pendred's syndrome is an autosomal recessive disorder characterized by goitre, sensorineural deafness and iodide organification defect. It is one of the most frequent causes of congenital deafness, accounting for about 10% of hereditary hearing loss. It is caused by mutations in the pendrin (PDS) gene, a 21 exon gene located on chromosome 7. The aim of this study was to examine an Italian family affected with Pendred's syndrome at the molecular level.

PATIENTS

Thirteen subjects belonging to a family from Southern Italy were evaluated for the clinical and genetic features of Pendred's syndrome.

MEASUREMENTS

Exons 2-21 of the PDS gene were amplified from peripheral leucocytes by the polymerase chain reaction; mutation analysis was performed by single strand conformation polymorphism, direct sequencing and restriction analysis.

RESULTS

The index patient had the classical triad of the syndrome and harboured two mutations in the PDS gene in the form of compound heterozygosity. He was found to be heterozygous for a cytosine to adenosine mutation at nucleotide 1523 in exon 13 and for a IVS 1001 + 1G --> A mutation. The former is a novel mutation which results in a change of 508 threonine to asparagine in the putative eleventh transmembrane domain. The latter mutation in the donor splice site has already been described in other patients and is thought to lead to aberrant splicing and premature protein truncation. Three subjects who were heterozygous for one mutation had normal phenotypes. Two subjects had sensorineural deafness and were heterozygous for a single mutation. Goitre was found only in patients with Pendred's syndrome and was absent in all other individuals, albeit residing in an iodine-deficient area.

CONCLUSIONS

We have identified a novel mutation in the pendrin gene causing Pendred's syndrome, and confirm that molecular analysis is a useful tool for a definitive diagnosis. This is particularly relevant in cases such as in the subjects of our family in which the clinical features might be misleading and other genetics factors might be responsible for deafness.

Pendrin does not increase sulfate uptake in mammalian COS-7 cells

Pendred's syndrome is characterized by goiter, sensorineural deafness and impaired iodide organification. It is one of the most frequent causes of congenital deafness accounting for about 10% of hereditary hearing loss. It is caused by mutations in the pendrin (PDS) gene, which was postulated to be a sulfate transporter, because of its homology with other genes. We tested sulfate transport in mammalian COS-7 cells that were transiently transfected with PDS cDNA. 35SO4 uptake increased in a time-dependent manner, but this phenomenon was similar in cells transfected with PDS and in mock-transfected cells (450 and 360 cpm/beta-gal units at 10 min, respectively; 38,250 and 31,000 cpm/beta-gal units, at 12 h, respectively). There was no significant increase in 35SO4 uptake using increasing amounts of PDS-containing plasmid (up to 12 microg per dish). These data indicate that pendrin is not a sulfate transporter. Additional functional studies on this protein are warranted to clarify its role in thyroid pathophysiology and inner ear development.

Left origin of the atrial esophageal signal as recorded in the pacing site

Clear atrial depolarizations from inside the esophagus have always been recorded in electrocardiology, but their precise origin is still under discussion. Though atrial signals are recorded along most of the esophagus, pacing of the atria is possible only in a short tract, probably where the esophagus is in contact with the posterior left atrium wall. In order to ascertain which portion of atria gives rise to the esophageal atrial signal recorded in the atrial pacing segment, we examined 37 patients with normal P waves on the standard ECG by inserting esophageal and endocavitary catheters. The interval between the earliest start of the P wave and the bipolar atrial deflection, was measured both through the esophagus (PA-Eso) and the Hisian region (PA-His) (the latest depolarization of interatrial septum). The former was longer than the latter (P < 0.001) in 36 of 37 patients, showing that the esophagus recorded atrial signal, at the site of effective pacing, originates outside the interatrial septum. As the atrial depolarization recorded through the esophagus is significantly delayed compared with the Hisian region recording, a pure left origin of the esophageal signal can be hypothesized. This is supported by the well-known delayed depolarization, during sinus rhythm, of the left atrium posterior wall compared with the right atrium and interatrial septum. Measuring the interval between the standard ECG P wave and atrial depolarization recorded through esophagus in the site of effective pacing, provides a reliable noninvasive estimate of interatrial time conduction.