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Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. GETUG-13 established that switching patients with poor-prognosis nonseminomatous germ-cell tumors with an unfavorable marker decline to intensified chemotherapy resulted in improved outcomes. Here, we report the GETUG-13 long-term efficacy and toxicity. Two hundred and sixty-three patients with International Germ Cell Cancer Consensus Group poor prognosis received one cycle of bleomycin, etoposide, and cisplatin (BEP): 51 with a favorable tumor marker decline continued with three cycles of BEP (Fav-BEP) and 203 with an unfavorable decline were randomly treated with three BEP (Unfav-BEP) cycles or a dose-dense regimen (Unfav-dose-dense; two cycles of paclitaxel-BEP-oxaliplatin + two cycles of cisplatin, ifosfamide, and bleomycin). The median follow-up was 7.1 years (range, 0.3-13.3). Five-year progression-free survival (PFS) rates were 58.9% in the Unfav-dose-dense arm and 46.7% in the Unfav-BEP arm (hazard ratio [HR], 0.65 [95% CI, 0.44 to 0.97]; P = .036). Five-year overall survival rates were 70.9% and 61.3% (HR, 0.74 [95% CI, 0.46 to 1.20]; P = .22). Side effects evolved favorably, with only three patients in the Unfav-dose-dense arm reporting grade 3 motor neurotoxicity at 1 year and no reported toxicity over grade 1 after year 2. Salvage high-dose chemotherapy plus a stem-cell transplant was used in 8% in the Unfav-dose-dense arm and 17% in the Unfav-BEP arm ( P = .035). Long-term outcomes suggest a sustained benefit of intensified chemotherapy in terms of PFS and numerically better survival, with a minimal toxicity and reduced use of salvage high-dose chemotherapy plus stem-cell transplant.

Background: Probiotics could decrease irinotecan-induced diarrhea due to the reduction of intestinal beta-d-glucuronidase activity. This study included a combined analysis of two clinical trials aimed to determine the effectiveness of the probiotics in the prophylaxis of irinotecan-induced diarrhea in metastatic colorectal cancer (CRC) patients., Methods: This combined analysis included 46 patients with CRC enrolled in the Probio-SK-003 (NCT01410955) and 233 patients from Probio-SK-005 (NCT02819960) starting a new line of irinotecan-based therapy with identical eligibility criteria. Patients were randomized in a ratio 1:1 to probiotic formulas vs. placebo administered for 12 and 6 weeks, respectively. Due to the different durations of study treatments, only the first 6 weeks of therapy were used for analysis., Results: In total, 279 patients were randomized, including 142 patients in the placebo and 137 participants in the probiotic arm. Administration of probiotics did not significantly reduce the incidence of grade 3/4 diarrhea compared to placebo (placebo 12.7% vs. probiotics 6.6%, p = 0.11). Neither the overall incidence of diarrhea (placebo 48.6% vs. probiotics 41.6%, p = 0.28) nor the incidence of enterocolitis (placebo 4.2% vs. probiotics 0.7%, p = 0.12) was different in the placebo vs. probiotic arm. However, subgroup analysis revealed that patients with a colostomy who received a placebo had a significantly higher incidence of any diarrhea (placebo 51.2% vs. probiotics 25.7%, p = 0.028) and grade 3/4 diarrhea (placebo 14.6% vs. probiotics 0.0%, p = 0.03) compared to the probiotic arm., Conclusions: This combined analysis suggests that probiotics could be beneficial in the prevention of irinotecan-induced diarrhea in colorectal cancer patients with colostomy., Competing Interests: RD is employed by S&D Pharma. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Mego, Kasperova, Chovanec, Danis, Reckova, Bystricky, Konkolovsky, Jurisova, Porsok, Vaclav, Wagnerova, Stresko, Brezinova, Sutekova, Ciernikova, Svetlovska and Drgona.)

Background: Colorectal cancer (CRC) is an ideal disease for screening due to known and detectable precursor lesions and slow progression from benign adenoma to invasive cancer. The introduction of organized population-based screening programs reduces the burden of colorectal cancer and increases the quality of the screening process with a more favorable harm to benefit ratio compared to opportunistic screening., Methods: The study used the microsimulation screening analysis-colon simulation model for the estimation of the effect of various factors on cancer incidence and mortality. The model simulated the Slovakian population from 2018 to 2050. Study includes the analysis of two screening strategies the fecal immunochemical test (FIT) every 2 years and annual FIT. Cost-effectiveness parameters were evaluated comparing each simulated screening scenario with no screening., Results: Compared to no screening, the biennial FIT would detect 29 600 CRC cases and annual FIT 37 800 CRC cases. Mortality due to CRC showed benefits for both strategies with 17,38% reduction in biennial FIT and 24,67% reduction in annual FIT approach. Both screening programs were more costly as well as more effective compared to no screening. The ICER for biennial FIT strategy was 1776 EUR per 1 QALY and for the annual FIT 3991 EUR per 1 QALY., Conclusions: In summary, this is the first cost-effectiveness analysis focusing on multiple national CRC screening strategies in Slovakia. Both strategies demonstrated cost-effectiveness compared to no screening. However, for optimal population-based programmatic screening strategy, the policymakers should also consider human resources availability, acceptability of screening test among the population or additional resources including the screening funding., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background Patients with multiple relapsed/refractory germ cell tumours (GCTs) have an extremely poor prognosis. PARP (poly-ADP-ribose polymerase) is overexpressed in GCTs compared to normal testes, and PARP overexpression is an early event in GCT development. This study aimed to determine the efficacy and toxicity of gemcitabine, carboplatin and the PARP inhibitor veliparib in patients with multiple relapsed/refractory GCTs. Methods Fifteen patients with multiple relapsed/refractory GCTs were enrolled in this phase II study from October 2016 to October 2020. Gemcitabine was administered at a dose of 800 mg/m2 on days 1 and 8 every 3 weeks; carboplatin at a target AUC of 4 on day 1 every 3 weeks; and veliparib at a dose of 250 mg b.i.d. throughout. The primary end point was 12-month progression-free survival (PFS). Results The median number of treatment cycles was 4 (range 2-8). Twelve-month PFS was achieved in 1 (6.7 %) patient. The median PFS was 3.1 months (95 % CI 2.2-3.9), and the median overall survival was 10.5 months (95 % CI 8.9-11.1). Partial remission was achieved in 4 (26.7 %) patients, and disease stabilization was observed in 5 (33.3 %) patients. A favourable response was achieved in 3 (20.0 %) patients. Treatment was well tolerated; however, 11 (73.3 %) patients experienced grade 3/4 neutropenia, 10 (66.7 %) experienced thrombocytopenia, 5 (33.3 %) anaemia and 2 (13.3 %) febrile neutropenia. Conclusions This study failed to achieve its primary endpoint, and our data suggest limited efficacy of gemcitabine, carboplatin and veliparib for multiple relapsed/refractory GCTs. ClinicalTrials.gov Identifier: NCT02860819, registered August 9, 2016., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Germ cell tumors represent highly curable disease even in metastatic stage. However, poor-risk patients with an unfavorable serum tumor marker (STM) decline after the first cycle of chemotherapy represent a subgroup with dismal prognosis, with approximately 50% cure rate using bleomycin, etoposide, and cisplatin (BEP)., Objective: The aim of this study was to determine the efficacy and safety of paclitaxel, ifosfamide, and cisplatin (TIP) in this patient population., Design Setting and Participants: This was an open-labeled, nonrandomized, single-center phase II trial to study the efficacy and toxicity of TIP in the first-line treatment of germ cell tumor patients with an unfavorable decline of STMs. Nineteen patients with a poor prognosis according to the International Germ Cell Cancer Collaboration Group classification and an unfavorable STM decline after the first cycle of chemotherapy were included in this phase II study (NCT02414685). The treatment regimen consisted of paclitaxel 250 mg/m 2 on day 1, ifosfamide 1200 mg/m 2 on days 1-5, and cisplatin 20 mg/m 2 on days 1-5, totally for four cycles., Outcome Measurements and Statistical Analysis: The primary endpoint was complete response (CR) rate. An optimal Simon two-stage design was used with a type I error of 5% and study power of 80%. If fewer than six CRs to study therapy have been observed among the first 19 patients, the study was to be terminated., Results and Limitations: A CR was achieved in four (21.1%) patients; therefore, the study was terminated in the first stage. A favorable response rate (CR or partial remission with negative tumor markers) was observed in 14 (78.9%) patients. At a median follow-up period of 35.2 mo (range, 5.6-62.1 mo), ten (52.6%) patients experienced disease progression and eight patients (42.1%) died. The 2-yr progression-free and overall survival was 41.2% (95% confidence interval [CI] 16.8-65.7) and 72.7% (95% CI 48.9-96.4), respectively. TIP was well tolerated, and no unexpected toxicity was observed. No informative biomarkers, including miR-371a-3p was identified., Conclusions: Treatment modification from the BEP to the TIP regimen in patients with an unfavorable STM decline after the first cycle of chemotherapy was not associated with improved outcome, and four cycles of BEP remain the standard treatment option in this patient population., Patient Summary: Poor-risk patients with an unfavorable serum tumor marker decline after the first cycle of chemotherapy represent a subgroup with dismal prognosis, with an approximately 50% cure rate using bleomycin, etoposide, and cisplatin (BEP). Treatment modification from the BEP regimen to the paclitaxel, ifosfamide, and cisplatin regimen in patients with an unfavorable serum tumor marker decline after the first cycle of chemotherapy was not associated with improved outcome, and four cycles of BEP remain the standard treatment option in this patient population., (© 2021 The Author(s).)

Background: The GETUG 13 phase III trial tested personalised chemotherapy based on tumour marker decline in patients with poor-prognosis germ-cell tumour (GCT) and demonstrated that a dose-dense regimen improves progression-free survival in patients with an unfavourable decline. We investigated the pattern of relapse for patients included in GETUG 13., Methods: We conducted an analysis of relapse events in patients from GETUG 13. Baseline procedures before inclusion in the trial comprised a thoraco-abdomino-pelvic computed tomography scan and a magnetic resonance imaging of the brain., Results: With a median follow-up of 4.1 years (0.3; 8.8 years), a progression event was observed in 109/254 patients (43%). First event consisted in a marker progression only in 47 patients (43%), a radiographic progression only in 35 patients (32%), a mix progression on both markers and imaging in 12 patients (11%) and death in 15 patients (14%). In patients with radiographic progression only, brain was the predominant site (n = 19/35, 54%). Among patients with unfavourable decline who experienced a radiographic progression (as first and subsequent progression event, n = 58), brain was a site of progression in 28 patients (48%): 12/30 (40%) in patients treated with cisplatin, bleomycin and etoposide and 16/28 (57%) in those treated with dose-dense chemotherapy., Conclusions: Brain metastases develop often, early and frequently as the only site of relapse in the course of poor-prognosis GCT. This raises the question of early detection and optimal treatment of brain metastases in these patients, e.g. by integrating a systematic brain MRI after 2-3 months of chemotherapy., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Roma (Gypsies) constitute one of the largest ethnic minorities in Slovakia. Some reports have supported a higher prevalence of communicable diseases in Roma but data on cancer prevalence in Roma is absent. The aim of this study was to compare differences in the incidence and pathological characteristics of breast cancer between Roma and non-Roma in Slovakia., Patients and Methods: Roma and non-Roma breast cancer patients were identified using the Slovak HER2 Registry. The database from the last Census of Slovakia in 2011 was matched by gender, date of birth, and residency with the HER2 Registry from 2011 to 2013. Based on the match, Roma and non-Roma breast cancer patients were identified., Results: Thirty-two and 5,775 women with breast cancer were identified as Roma and non-Roma, resp. The age-standardized breast cancer incidence rate was 2.12 times higher for non-Roma than for Roma patients (36 vs. 17 per 100,000 people). Roma patients were younger than non-Roma patients (median 49 vs. 61 years; p = 0.00001). Roma patients had more hormone receptor negative (34.4% vs. 18.1%; p = 0.03) and triple negative tumors (28.1% vs. 12.3%; p = 0.01) than non-Roma, and these differences remained statistically significant in multivariate analysis., Conclusion: For the first time, this study has revealed that the incidence and biological characteristics of breast cancer are different between Roma and non-Roma. Our data suggests that Roma patients are younger at diagnosis, have a lower age-standardized breast cancer incidence rate, and have more aggressive tumors than non-Roma.

Background: Roma (Gypsies) constitute the largest ethnic minority in Slovakia. Although some studies have reported a higher prevalence of communicable diseases in Roma, there have been no studies on cancer prevalence in Roma. The aim of this study was to compare differences in age at diagnosis, oncological diagnoses, and stage between Roma and non-Roma patients registered at a single oncology outpatient department in Eastern Slovakia where substantial numbers of Roma patients are treated., Patients and Methods: Roma and non-Roma cancer patients were identified based on the judgement of both the treating physician and nurse. Age at diagnosis, oncology diagnoses, and disease stage were compared between Roma and non-Roma patients., Results: Thirty Roma and 702 non-Roma cancer patients were identified. The age distribution at diagnosis was not statistically different between Roma and non-Roma for both male and female patients. A statistically significant difference was detected in the number of Roma men having lung cancer (risk ratio - RR 0.19; 95% CI 0.13-0.35; p < 0.01), and more Roma women had kidney cancer (RR 0.16; 95% CI 0.05-0.69; p = 0.01). There were numerically more Roma patients diagnosed with TNM stage IV disease. Significantly more Roma men were diagnosed with stage IV disease than with stage I-III disease., Conclusion: The data suggest that differences in cancer type exist between Roma and non-Roma patients. Larger population--based studies directed at analyzing for differences between Roma and non-Roma cancer patients are warranted.Key words: Roma - neoplasms - histology - stage.

Background: Testicular germ cell tumors (TGCTs) represent a highly curable disease; however, a small proportion of patients develop disease recurrence. Loss of the tumor-suppressor gene phosphatase and tensin homolog marks the transition from intratubular germ cell neoplasia to invasive GCT and is correlated with disease progression. Inactivation of phosphatase and tensin homolog is associated with deregulation of the PI3K/Akt pathway and increased mammalian target of rapamycin signaling. This study aimed to determine the efficacy and toxicity of a mammalian target of rapamycin inhibitor, everolimus, in patients with refractory TGCTs., Methods: From December 2011 to February 2015, 15 patients with refractory GCTs were enrolled in the phase II study. All patients were pretreated with at least 2 cisplatin-based therapies; 4 tumors (26.7%) were absolutely refractory to cisplatin and 9 patients (60.0%) had visceral nonpulmonary metastases. Everolimus was administered at a dose of 10mg daily until progression or unacceptable toxicity. The primary end point was the objective response rate, according to Response Evaluation Criteria in Solid Tumors., Results: No objective response was observed, but 6 patients (40.0%) achieved 12-week progression-free survival. During a median follow-up period of 3.6 months (range: 1-35.1mo), all patients experienced disease progression and 11 patients (80.0%) died. Median progression-free survival was 1.7 months (95% CI: 1.1-4.0mo) and median overall survival was 3.6 months (95% CI: 2.0-11.0mo)., Conclusions: This study failed to achieve its primary end point and our data suggest limited efficacy of everolimus against unselected heavily pretreated refractory TGCTs., Condensed Abstract: Everolimus showed limited efficacy in unselected heavily pretreated refractory TGCTs. Prolonged disease stabilization could be achieved in selected patients., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: Diarrhea is one of the dose limiting toxicity of irinotecan. SN-38 is main irinotecan metabolite responsible for diarrhea development, which is excreted in glucuronidated form into the intestine. This study aimed to determine the effectiveness of the probiotics in the prevention of irinotecan induced diarrhea due to reduction of intestinal beta-d-glucuronidase activity., Methods: Between January 2011 and December 2013, 46 patients with colorectal cancer starting a new line of irinotecan based therapy were included. Patients were randomized 1:1 to probiotics (PRO) or placebo (PLA). Probiotic formula Colon Dophilus™, was administered at a dose of 10×10(9)CFU of bacteria tid, orally for 12 weeks of chemotherapy. The study was prematurely terminated due to slow accrual, when 46 of 220 planned patients were accrued., Results: Twenty-three patients were randomized to PRO and 23 patients to PLA. Administration of probiotics compared to placebo led to a reduction in the incidence of severe diarrhea of grade 3 or 4 (0% for PRO vs. 17.4% for PLA, p=0.11), as well as reduction of the overall incidence of diarrhea (39.1% for PRO vs. 60.9% for PLA, p=0.24) and incidence of enterocolitis (0% for PRO vs. 8.7% for PLA). Patients on PRO used less antidiarrheal drugs compared to PLA. There was no infection caused by probiotic strains recorded., Conclusions: Administration of probiotics in patients with colorectal cancer treated with irinotecan-based chemotherapy is safe and could lead to a reduction in the incidence and severity of gastrointestinal toxicity., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background: Poor prognosis germ-cell tumours are only cured in about half of patients. We aimed to assess whether treatment intensification based on an early tumour marker decline will improve progression-free survival for patients with germ-cell tumours., Methods: In this phase 3, multicentre, randomised trial, patients were enrolled from France (20 centres), USA (one centre), and Slovakia (one centre). Patients were eligible if they were older than 16 years, had evidence of testicular, retroperitoneal, or mediastinal non-seminomatous germ cell tumours based on histological findings or clinical evidence and highly elevated serum human chorionic gonadotropin or alfa-fetoprotein concentrations that matched International Germ Cell Cancer Consensus Group poor prognosis criteria. After one cycle of BEP (intravenous cisplatin [20 mg/m(2) per day for 5 days], etoposide [100 mg/m(2) per day for 5 days], and intramuscular or intravenous bleomycin [30 mg per day on days 1, 8, and 15]), patients' human chorionic gonadotropin and alfa-fetoprotein concentrations were measured at day 18-21. Patients with a favourable decline in human chorionic gonadotropin and alfa-fetoprotein continued BEP (Fav-BEP group) for 3 additonal cycles, whereas patients with an unfavourable decline were randomly assigned (1:1) to receive either BEP (Unfav-BEP group) or a dose-dense regimen (Unfav-dose-dense group), consisting of intravenous paclitaxel (175 mg/m(2) over 3 h on day 1) before BEP plus intravenous oxaliplatin (130 mg/m(2) over 3 h on day 10; two cycles), followed by intravenous cisplatin (100 mg/m(2) over 2 h on day 1), intravenous ifosfamide (2 g/m(2) over 3 h on days 10, 12, and 14), plus mesna (500 mg/m(2) at 0, 3, 7 and 11 h), and bleomycin (25 units per day, by continuous infusion for 5 days on days 10-14; two cycles), with granulocyte-colony stimulating factor (lenograstim) support. Centrally blocked computer-generated randomisation stratified by centre was used. The primary endpoint was progression-free survival and the efficacy analysis was done in the intention-to-treat population. The planned trial accrual was completed in May, 2012, and follow-up is ongoing. This study is registered with ClinicalTrials.gov, number NCT00104676., Findings: Between Nov 28, 2003, and May 16, 2012, 263 patients were enrolled and 254 were available for tumour marker assessment. Of these 51 (20%) had a favourable marker assessment, and 203 (80%) had an unfavourable tumour marker decline; 105 were randomly assigned to the Unfav-dose-dense group and 98 to the Unfav-BEP group. 3-year progression-free survival was 59% (95% CI 49-68) in the Unfav-dose-dense group versus 48% (38-59) in the Unfav-BEP group (HR 0·66, 95% CI 0·44-1·00, p=0·05). 3-year progression-free survival was 70% (95% CI 57-81) in the Fav-BEP group (HR 0·66, 95% CI 0·49-0·88, p=0·01 for progression-free survival compared with the Unfav-BEP group). More grade 3-4 neurotoxic events (seven [7%] vs one [1%]) and haematotoxic events occurred in the Unfav-dose-dense group compared with in the Unfav-BEP group; there was no difference in grade 1-2 febrile neutropenia (18 [17%] vs 18 [18%]) or toxic deaths (one [1%] in both groups). Salvage high-dose chemotherapy plus a stem-cell transplant was required in six (6%) patients in the Unfav-dose-dense group and 16 (16%) in the Unfav-BEP group., Interpretation: Personalised treatment with chemotherapy intensification reduces the risk of progression or death in patients with poor prognosis germ-cell tumours and an unfavourable tumour marker decline., Funding: Institut National du Cancer (Programme Hospitalier de Recherche Clinique)., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Backgrounds: Small cell carcinoma (SCC) is characterised by high metastatic potential and the possibility to metastasize to practically any tissue. Small cell carcinoma of the ovary (SCCO) has a very poor prognosis and patients usually die within one year of the initial diagnosis. Breast metastases from SCCO are extremely rare., Case: We present a 67-year-old female patient with SCCO who initially presented with bone and bilateral breast metastases. Considering the clinical presentation, the patient's age, the absence of hypercalcemia and histological characteristics, a diagnosis of pulmonary type SCCO was made. There was no tumour present in the lungs at the time of the initial diagnosis and thus we ruled out pulmonary SCC., Results: Initially, the patient was treated with radiotherapy of the bone lesion and systemic chemotherapy (etoposide with carboplatin) with the result of partial remission. Then, radical abdominal surgery was performed. Six months later she was diagnosed with progressive disease in the bone, soft tissue including the breast as well as new lesions in the right kidney, pelvis and lungs. She was treated with 2nd line chemotherapy (topotecan with cisplatin) with the result of progressive disease. Because of mediastinal lymphadenopathy, which was causing tracheobronchial compression, radiotherapy was administered with a good palliative outcome. Nine months later, multiple brain metastases were diagnosed and she was treated with whole brain radiotherapy. Shortly after brain irradiation, her status deteriorated rapidly and she died two years after her initial SCCO diagnosis., Conclusion: Extrapulmonary small cell carcinoma is a clinicopathological entity distinct from pulmonary small cell carcinoma. It is very rare and therefore there is very little information available regarding treatment of this disease. In contrast to experience in the treatment of pulmonary small cell cancers, prolonged survival is not common.

Early serum tumor marker decline (STMD) during chemotherapy was shown to predict survival in patients with poor prognosis non-seminomatous germ cell tumors (GCT) in the first line. The aim of the study was to assess the prognostic value of STMD in relapsed GCT;s patients. From January 1995 to December 2007, all patients treated for GCT s with salvage therapy at the National Cancer Institute of Slovakia were identified from the tumor registry database and screened retrospectively for serum AFP and betaHCG level at the time of relapse. STMD rate was calculated for each patient and each tumor marker with an abnormal marker value at baseline and each tumor marker M (HCG or AFP) using only two values: the baseline value (M0) and the value obtained after one cycle of chemotherapy (day 21 value; M1). The decline rate was calculated using a logarithmic transformation, and it was expressed as a theoretical number of weeks necessary to normalization that was called predicted time to normalization. Decline rates were classified into "favorable" or "unfavorable". Totally, 75 patients were identified, 39 had favourable (group A) and 36 unfavorable (group B) STMD. The 2-year and 5-year PFS rates were 61% and 58% for group A and 17% and 7% group B (p<0.00001). Of all the baseline characteristics that were included in the Cox model, STMD was the most important predictor of PFS and OS. We suggest that STMD is strong independent prognostic factor in GCT patients treated with salvage chemotherapy. Prospective studies of different approaches in this patient's population based on STMD are warranted.

Specialized conduction tissues mediate coordinated propagation of electrical activity through the adult vertebrate heart. Following activation of the atria, the activation wave is slowed down in the atrioventricular canal or node, after which it spreads rapidly into the left and right ventricles via the His-Purkinje system (HPS). This results in the ventricles being activated from the apex toward the base, which is a hallmark of HPS function. The development of mature HPS function follows significant phases of cardiac morphogenesis. Initially, the cardiac impulse propagates in a slow, linear, and isotropic fashion from the sinus venosus at the most caudal portion of the tubular heart. Although the speed of impulse propagation gradually increases as it travels toward the anterior regions of the heart tube, the actual sequence of ventricular activation in the looped heart proceeds in the same direction as blood flow. Eventually, the immature base-to-apex sequence of ventricular activation undergoes an apparent reversal, changing to the mature apex-to-base pattern. Using an optical mapping approach, we demonstrate that the timing of this last transition shows striking dependence on hemodynamic loading of the ventricle, being accelerated by pressure overload and delayed in left ventricular hypoplasia. Comparison of chick and mammalian hearts revealed some striking similarities as well as key differences in the timing of such events during cardiac organogenesis.

The specialized conduction tissue network mediates coordinated propagation of electrical activity through the adult vertebrate heart. Following activation of the atria, the activation wave is slowed down in the atrioventricular canal or node, then spreads rapidly into the left and right ventricles via the His-Purkinje system (HPS). This results in the ventricle being activated from the apex toward the base and is thought to represent HPS function. The development of mature HPS function in embryogenesis follows significant phases of cardiac morphogenesis. Initially, cardiac impulse propagates in a slow, linear, and isotropic fashion from the sinus venosus at the most caudal portion of the tubular heart. Although the speed of impulse propagation gradually increases, ventricular activation in the looped heart still follows the direction of blood flow. Eventually, the immature base-to-apex sequence of ventricular activation undergoes an apparent reversal, maturing to apex-to-base pattern. The embryonic chick heart has been studied intensively by both electrophysiological and morphological techniques, and the morphology of its conduction system (which is similar to mammals) is well characterized. One interesting but seldom studied feature is the anterior septal branch (ASB), which came sharply to focus (together with the rest of the ventricular conduction system) in our birthdating studies. Using an optical mapping approach, we show that ASB serves to activate ventricular surface between stages 16 and 25, predating the functionality of the His bundle/bundle branches. Heart morphogenesis and conduction system formation are thus linked, and studying the abnormal activation patterns could further our understanding of pathogenesis of congenital heart disease., (copyright 2004 Wiley-Liss, Inc.)

Impulse-conducting Purkinje fibers differentiate from myocytes during embryogenesis. The conversion of contractile myocytes into conduction cells is induced by the stretch/pressure-induced factor, endothelin (ET). Active ET is produced via proteolytic processing from its precursor by ET-converting enzyme 1 (ECE1) and triggers signaling by binding to its receptors. In the embryonic chick heart, ET receptors are expressed by all myocytes, but ECE1 is predominantly expressed in endothelial cells of coronary arteries and endocardium along which Purkinje fiber recruitment from myocytes takes place. Furthermore, co-expression of exogenous ECE1 and ET-precursor in the embryonic heart is sufficient to ectopically convert cardiomyocytes into Purkinje fibers. Thus, localized expression of ECE1 defines the site of Purkinje fiber recruitment in embryonic myocardium. However, it is not known how ECE1 expression is regulated in the embryonic heart. The unique expression pattern of ECE1 in the embryonic heart suggests that blood flow-induced stress/stretch may play a role in patterning ECE1 expression and subsequent induction of Purkinje fiber differentiation. We show that gadolinium, an antagonist for stretch-activated cation channels, downregulates the expression of ECE1 and a conduction cell marker, Cx40, in ventricular chambers, concurrently with delayed maturation of a ventricular conduction pathway. Conversely, pressure-overload in the ventricle by conotruncal banding results in a significant expansion of endocardial ECE1 expression and Cx40-positive putative Purkinje fibers. Coincident with this, an excitation pattern typical of the mature heart is precociously established. These in vivo data suggest that biomechanical forces acting on, and created by, the cardiovascular system during embryogenesis play a crucial role in Purkinje fiber induction and patterning.

Patterns of DNA synthesis in the developing mouse heart between ED7.5-18.5 were studied by a combination of thymidine and bromodeoxyuridine labeling techniques. From earliest stages, we found zones of slow myocyte proliferation at both the venous and arterial poles of the heart, as well as in the atrioventricular region. The labeling index was distinctly higher in nonmyocardial populations (endocardium, epicardium, and cardiac cushions). Ventricular trabeculae showed lower proliferative activity than the ventricular compact layer after their appearance at ED9.5. Low labeling was observed in the pectinate muscles of the atria from ED11.5. The His bundle, bundle branches, and Purkinje fiber network likewise were distinguished by their lack of labeling. Thymidine birthdating (label dilution) showed that the cells in these emerging components of the cardiac conduction system terminally differentiated between ED8.5-13.5. These patterns of slowed proliferation correlate well with those in other species, and can serve as a useful marker for the forming conduction system., (Copyright 2003 Wiley-Liss, Inc.)

The His-Purkinje system (HPS) is a network of conduction cells responsible for coordinating the contraction of the ventricles. Earlier studies using bipolar electrodes indicated that the functional maturation of the HPS in the chick embryo is marked by a topological shift in the sequence of activation of the ventricle. Namely, at around the completion of septation, an immature base-to-apex sequence of ventricular activation was reported to convert to the apex-to-base pattern characteristic of the mature heart. Previously, we have proposed that hemodynamics and/or mechanical conditioning may be key epigenetic factors in development of the HPS. We thus hypothesized that the timing of the topological shift marking maturation of the conduction system is sensitive to variation in hemodynamic load. Spatiotemporal patterns of ventricular activation (as revealed by high-speed imaging of fluorescent voltage-sensitive dye) were mapped in chick hearts over normal development, and following procedures previously characterized as causing increased (conotruncal banding, CTB) or reduced (left atrial ligation, LAL) hemodynamic loading of the embryonic heart. The results revealed that the timing of the shift to mature activation displays striking plasticity. CTB led to precocious emergence of mature HPS function relative to controls whereas LAL was associated with delayed conversion to apical initiation. The results from our study indicate a critical role for biophysical factors in differentiation of specialized cardiac tissues and provide the basis of a new model for studies of the molecular mechanisms involved in induction and patterning of the HPS in vivo.

Zebrafish and Xenopus have become popular model organisms for studying vertebrate development of many organ systems, including the heart. However, it is not clear whether the single ventricular hearts of these species possess any equivalent of the specialized ventricular conduction system found in higher vertebrates. Isolated hearts of adult zebrafish (Danio rerio) and African toads (Xenopus laevis) were stained with voltage-sensitive dye and optically mapped in spontaneous and paced rhythms followed by histological examination focusing on myocardial continuity between the atrium and the ventricle. Spread of the excitation wave through the atria was uniform with average activation times of 20 +/- 2 and 50 +/- 2 ms for zebrafish and Xenopus toads, respectively. After a delay of 47 +/- 8 and 414 +/- 16 ms, the ventricle became activated first in the apical region. Ectopic ventricular activation was propagated significantly more slowly (total ventricular activation times: 24 +/- 3 vs. 14 +/- 2 ms in zebrafish and 74 +/- 14 vs. 35 +/- 9 ms in Xenopus). Although we did not observe any histologically defined tracts of specialized conduction cells within the ventricle, there were trabecular bands with prominent polysialic acid-neural cell adhesion molecule staining forming direct myocardial continuity between the atrioventricular canal and the apex of the ventricle; i.e., the site of the epicardial breakthrough. We thus conclude that these hearts are able to achieve the apex-to-base ventricular activation pattern observed in higher vertebrates in the apparent absence of differentiated conduction fascicles, suggesting that the ventricular trabeculae serve as a functional equivalent of the His-Purkinje system.

We review here the evolution and development of the earliest components of the cardiac pacemaking and conduction system (PCS) and the turnover or persistence of such cells into old age in the adult vertebrate heart. Heart rate is paced by upstream foci of cardiac muscle near the future sinoatrial junction even before contraction begins. As the tubular heart loops, directional blood flow is maintained through coordinated sphincter function in the forming atrioventricular (AV) canal and outflow segments. Propagation of initially peristaltoid contraction along and between these segments appears to be influenced by physical conditioning and orientation of inner muscle layers as well as by their slow relaxation; all characteristic of definitive conduction tissue. As classical elements of the mature conduction system emerge, such inner 'contour fibres' maintain muscular and electrical continuity between atrial and ventricular compartments. Elements of such primordial architecture are visible also in histological and optical electrical study of fish and frog hearts. In the maturing chick heart, cells within core conducting tissues retain early thymidine labels from the tubular heart stage into adult life, dividing only slowly, if at all. Preliminary evidence from mammals suggest similar function and kinetics for these 'oldest, toughest' cells in the hearts of all vertebrates.