RESUMEN
BACKGROUND: Nucleic acid testing is the major method used to monitor HIV viral load. Commercial systems based on real-time PCR assays are available for high-volume centralized laboratory testing, but they are not fully automated. OBJECTIVES AND STUDY DESIGN: We have compared the diagnostic performance of the Hologic Aptima HIV-1 Quant Dx assay (Aptima) (based on real-time TMA) on the Panther instrument, a fully-automated random access platform, to that of, the Roche Cobas Ampliprep Cobas TaqMan (CAP/CTM) HIV-1 version 2.0 (based on real-time PCR). RESULTS: Probit analysis of replicate dilutions of NIBSC WHO International HIV-1 Standard, gave LODs of 8.6 c/ml for Aptima and 15.2 c/ml for CAP/CTM. The agreement between the assays was excellent when measuring HIV RNA in a calibrated reference (κ=0.90, p<0.001) and good when measuring clinical samples (κ=0.62, p<0.001). The correlation among the samples quantified by the two methods was very good (r=0.95, p<0.001) and the mean difference between the values obtained with the two assays was 0.02 log c/ml for B and non-B subtypes. The vast majority of results showed <0.5 log variance between the two assays (89%); only one sample showed results that differed by over 1.0 log c/ml. CONCLUSION: The performance of the new fully automated Aptima assay is adequate for clinical monitoring of HIV-1 RNA during infections and treatment. The Aptima assay is well suited for routine laboratory use.
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Automatización de Laboratorios , Infecciones por VIH/virología , VIH-1/genética , VIH-1/aislamiento & purificación , Técnicas de Amplificación de Ácido Nucleico , ARN Viral/sangre , Infecciones por VIH/diagnóstico , Humanos , Límite de Detección , Técnicas de Amplificación de Ácido Nucleico/instrumentación , Técnicas de Amplificación de Ácido Nucleico/métodos , ARN Viral/genética , ARN Viral/aislamiento & purificación , Juego de Reactivos para Diagnóstico , Reacción en Cadena en Tiempo Real de la Polimerasa/instrumentación , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Carga ViralRESUMEN
BACKGROUND: Completely automated systems for monitoring CMV-DNA in plasma samples are now available. OBJECTIVES: Evaluate analytical and clinical performances of the VERIS™/MDx System CMV Assay(®). STUDY DESIGN: Analytical performance was assessed using quantified quality controls. Clinical performance was assessed by comparison with the COBAS(®) Ampliprep™/COBAS(®) Taqman CMV test using 169 plasma samples that had tested positive with the in-house technique in whole blood. RESULTS: The specificity of the VERIS™/MDx System CMV Assay(®) was 99% [CI 95%: 97.7-100]. Intra-assay reproducibilities were 0.03, 0.04, 0.05 and 0.04 log10IU/ml (means 2.78, 3.70, 4.64 and 5.60 log10IU/ml) for expected values of 2.70, 3.70, 4.70 and 5.70 log10IU/ml. The inter-assay reproducibilities were 0.12 and 0.08 (means 6.30 and 2.85 log10IU/ml) for expected values of 6.28 and 2.80 log10IU/ml. The lower limit of detection was 14.6IU/ml, and the assay was linear from 2.34 to 5.58 log10IU/ml. The results for the positive samples were concordant (r=0.71, p<0.0001; slope of Deming regression 0.79 [CI 95%: 0.56-1.57] and y-intercept 0.79 [CI 95%: 0.63-0.95]). The VERIS™/MDx System CMV Assay(®) detected 18 more positive samples than did the COBAS(®) Ampliprep™/COBAS(®) Taqman CMV test and the mean virus load were higher (0.41 log10IU/ml). Patient monitoring on 68 samples collected from 17 immunosuppressed patients showed similar trends between the two assays. As secondary question, virus loads detected by the VERIS™/MDx System CMV Assay(®) were compared to those of the in-house procedure on whole blood. The results were similar between the two assays (-0.09 log10IU/ml) as were the patient monitoring trends. CONCLUSION: The performances of the VERIS™/MDx System CMV Assay(®) facilitated its routine use in monitoring CMV-DNA loads in plasma samples.
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Automatización de Laboratorios/métodos , Infecciones por Citomegalovirus/virología , ADN Viral/sangre , Técnicas de Diagnóstico Molecular/métodos , Plasma/virología , Humanos , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
BACKGROUND: Lack of HIV RNA during antiretroviral therapy (ART) is regarded as a desirable outcome. Commercial assays of HIV virus load now need to detect virus RNA concentrations below 50 c/ml and several of them have claimed a limit of detection (LOD) of 20-45 c/ml. OBJECTIVES AND STUDY DESIGN: We have compared the performances of three commercial assays of HIV RNA, the Abbott RealTime HIV-1, the Qiagen Artus RG HIV-1 and the Roche Cobas Ampliprep Cobas TaqMan (CAPCTM) HIV-1 vs 2.0 using replicate of specimens with HIV-1 subtype B RNA concentrations of 20-200 c/ml. RESULTS: Despite fair-to-moderate agreement between the three assays, probit analysis showed that their LODs differed; they were 81, 65 and 18c/ml respectively. The CAPCTM HIV-1 vs 2.0 values were higher than those of the other two; the maximum difference was 0.26 log c/ml. By testing 20 replicate of each concentration, coefficients of variation were between 0.6% and 9.2% (Abbott RealTime HIV-1), 10.3% and 38% (Qiagen Artus RG HIV-1) and 5.2% and 13.1% (Roche CAPCTM HIV-1 vs 2.0). The three assays also differed in their reproducibility and linearity for virus loads of 50-200 c/ml. CONCLUSION: The analytical performances of commercial virus load assays differ. Direct comparisons of widely used commercial assays in clinical studies could help to identify the residual viremia that is clinically relevant for effective long term therapy.
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Infecciones por VIH/sangre , VIH-1/aislamiento & purificación , ARN Viral/sangre , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Carga Viral/métodos , Análisis de Varianza , Infecciones por VIH/diagnóstico , Infecciones por VIH/virología , VIH-1/clasificación , VIH-1/genética , Humanos , Límite de Detección , Modelos Lineales , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
The aim of the study was to evaluate the MagNA Pure 96™ nucleic acid extraction system using clinical respiratory specimens for identifying viruses by qualitative real-time PCR assays. Three extraction methods were tested, that is, the MagNA Pure LC™, the COBAS Ampliprep™, and the MagNA Pure 96™ with 10-fold dilutions of an influenza A(H1N1)pdm09 sample. Two hundred thirty-nine respiratory specimens, 35 throat swabs, 164 nasopharyngeal specimens, and 40 broncho-alveolar fluids, were extracted with the MagNA Pure 96™ and the COBAS Ampliprep™ instruments. Forty COBAS Ampliprep™ positive samples were also tested. Real-time PCRs were used to identify influenza A and influenza A(H1N1)pdm09, rhinovirus, enterovirus, adenovirus, varicella zoster virus, cytomegalovirus, and herpes simplex virus. Similar results were obtained on RNA extracted from dilutions of influenza A(H1N1)pdm09 with the three systems: the MagNA Pure LC™, the COBAS Ampliprep™, and the MagNA Pure 96™. Data from clinical respiratory specimens extracted with the MagNA Pure 96™ and COBAS Ampliprep™ instruments were in 98.5% in agreement (P < 0.0001) for influenza A and influenza A(H1N1)pdm09. Data for rhinovirus were in 97.3% agreement (P < 0.0001) and in 96.8% agreement for enterovirus. They were in 100% agreement for adenovirus. Data for cytomegalovirus and HSV1-2 were in 95.2% agreement (P < 0.0001). The MagNA Pure 96™ instrument is easy-to-use, reliable, and has a high throughput for extracting total nucleic acid from respiratory specimens. These extracts are suitable for molecular diagnosis with any type of real-time PCR assay.
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Automatización/métodos , Ácidos Nucleicos/aislamiento & purificación , Infecciones del Sistema Respiratorio/diagnóstico , Manejo de Especímenes/métodos , Virología/métodos , Virosis/diagnóstico , Virus/genética , Líquido del Lavado Bronquioalveolar/virología , Humanos , Técnicas de Diagnóstico Molecular/métodos , Nasofaringe/virología , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Infecciones del Sistema Respiratorio/virología , Sensibilidad y Especificidad , Virosis/virología , Virus/aislamiento & purificaciónRESUMEN
BACKGROUND: Rapid, high throughput extraction systems are needed to monitor viral infections in immunosuppressed patients. OBJECTIVES: Evaluate the performance of the MagNA Pure 96™ extraction system, and compare it to the COBAS Ampliprep™ for quantitative real-time PCR from whole blood samples. STUDY DESIGN: Compare the MagNA Pure LC™, COBAS Ampliprep™ and MagNA Pure 96™ using ten-fold dilutions of blood samples containing cytomegalovirus. Evaluate analytical performances of the MagNA Pure 96™ from test samples containing cytomegalovirus. Evaluate clinical performances from 209 blood samples collected prospectively, extracted with the COBAS Ampliprep™ and the MagNA Pure 96™ systems and tested for cytomegalovirus, Epstein-Barr, BK and JC viruses. RESULTS: All three extraction systems gave similar results with dilutions of a cytomegalovirus-positive sample. Analytical tests showed that the limit of detection was 500 copies/ml, specificity was 100%, with no cross-contamination. Quantification was linear from 3.0 to 6.0 log(10)copies/ml. Intra-assay variation was 8.3-0.9% and inter-assay variation 8.8-5.2%. Clinical specimens extracted with the MagNA Pure 96™ and COBAS Ampliprep™ instruments agreed well for cytomegalovirus (r=0.54; p=0.07), Epstein-Barr virus (0.69; p=0.0005) and BK virus (0.85; p=0.01). All 55 samples were negative for JC virus. Mean loads were similar for cytomegalovirus (0.17 log(10)copies/ml) and BK virus (-0.24 log(10)copies/ml) while that of Epstein-Barr virus was slightly lower (1.02 log(10)copies/ml). CONCLUSIONS: The MagNA Pure 96™ instrument is an easy-to-use, reliable high throughput platform for extracting nucleic acid from clinical whole blood specimens.
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Automatización/métodos , Virus ADN/aislamiento & purificación , ADN Viral/aislamiento & purificación , Huésped Inmunocomprometido , Infecciones Oportunistas/sangre , Reacción en Cadena en Tiempo Real de la Polimerasa/instrumentación , Citomegalovirus/genética , Citomegalovirus/aislamiento & purificación , Infecciones por Citomegalovirus/sangre , Infecciones por Citomegalovirus/virología , Infecciones por Virus ADN/sangre , Infecciones por Virus ADN/virología , Virus ADN/genética , ADN Viral/sangre , Humanos , Infecciones Oportunistas/virología , Juego de Reactivos para Diagnóstico , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Carga Viral/métodosRESUMEN
BACKGROUND: Automated HIV-1 RNA extraction and its quantification by real-time PCR assays provide improved sample processing and better analytical performances. The new Artus HIV-1 RealTime assay can be performed after automated extraction with the Qiagen Qiasymphony robot. OBJECTIVES AND STUDY DESIGN: To evaluate the sensitivity, reproducibility, linearity, ability to detect HIV-1 subtypes of the Qiagen Qiasymphony and RealTime Artus HIV-1 assay system and to compare with the Roche Cobas Ampliprep Cobas TaqMan assay, vs 2.0 (CAP/CTM; Roche Molecular Systems). RESULTS: The detection limit calculated by probit analysis was 65 c/ml using dilutions of a NIBSC. Assays of serially diluted clinical samples gave very good inter-assay and intra-assay reproducibilities (<10% CV) and linearity (2.2-6.5 log copies/ml). The results Artus™ HIV-1 and CAP/CTM assays provided very similar results: average difference=0.11 log copies/ml. The Artus™ titers for 18 (22%) of the 114 HIV-1 group M samples tested differed by over 0.5 log copies/ml from the CAP/CTM titers. The Artus™ values were lower than the CAP/CTM values in 83% of cases. Discrepant results were not associated with particular subtypes. CONCLUSION: The Artus™ HIV-1 assay reliably quantified the HIV RNA in clinical specimens. Analytical performances were good and it integrated well with the Qiasymphony automated RNA extraction procedure. It appears to be appropriate for monitoring therapy and the routine management of HIV-1 infections.
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Automatización/métodos , Infecciones por VIH/virología , VIH-1/aislamiento & purificación , Juego de Reactivos para Diagnóstico , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Carga Viral/métodos , VIH-1/genética , Humanos , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
There is considerable evidence that the loss of hepatitis C virus (HCV) RNA during the first 3 months of treatment with pegylated interferon plus ribavirin is a prognostic marker of response to therapy. Real-time polymerase chain reaction (PCR) assays for quantifying HCV RNA in plasma or serum are now commercially available. The extraction of HCV RNA can also be automated. This report analyses the performance of the COBAS Ampliprep-COBAS Taqman 48 (CAP/CTM) real-time PCR assay and compares this new test with the COBAS Amplicor HCV Monitor v 2.0 assay (CAM). CAP/CTM was 100% specific. The assay was linear across a wide range of HCV RNA concentrations without sample dilution. The intra-assay variation was 0.3-3.3% and the interassay variation was 1.5-6.7%. A total of 118 clinical samples with different HCV genotypes were assayed using both methods. The results obtained using the two methods were well correlated (r = 0.89, P < 0.001). The mean difference [CAP/CTM-CAM] was 0.17 log IU/ml and it was not influenced by the HCV genotype or by the subtype. It is concluded that the new CAP/CTM system is adequate for quantifying HCV RNA in clinical practice.
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Hepacivirus/genética , Hepacivirus/aislamiento & purificación , Reacción en Cadena de la Polimerasa , ARN Viral/análisis , ARN Viral/genética , Manejo de Especímenes/métodos , Automatización , Genotipo , Humanos , Modelos Lineales , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Manejo de Especímenes/instrumentaciónRESUMEN
BACKGROUND: Although the implantable cardioverter-defibrillator effectively prevents sudden cardiac death, patients are still prone to recurrence of ventricular tachyarrhythmias. Electrophysiologically guided surgery is the most effective modality in abolishing ventricular tachycardia, having a lower recurrence rate than pharmacologic therapy or catheter ablation. Return cycle mapping after entrainment has been shown to localize the central common pathway, which is the target region for ablation, without pacing at the pathway or recording the potentials from the pathway. METHODS: To determine the accuracy and usefulness of return cycle mapping in surgery for ventricular tachycardia, we cryoablated 8 morphologies of ventricular tachycardia induced in postinfarction dogs with the guidance of return cycle mapping. The ventricular tachycardia was entrained from 3 to 5 different epicardial sites at a paced cycle length 10 to 20 ms shorter than the ventricular tachycardia cycle length and the epicardium was mapped with 61 unipolar electrodes during cessation of entrainment to construct return cycle maps. The return cycle was determined by subtracting the first activation time from the second activation time after the last stimulus in each electrode location, and the maps were then displayed on a computer. RESULTS: The total analysis process was completed within 3 minutes by means of a computer with custom-made programs. The activation map during ventricular tachycardia did not localize the central common pathway in any morphology of ventricular tachycardia, because the pattern of activation was concentric and diastolic potentials were not recorded. Cryoablation of the region where the isotemporal lines of the return cycle equal to the ventricular tachycardia cycle length intersected resulted in termination of ventricular tachycardia in all morphologies. The intersection was 26 +/- 9 mm from the earliest activation site. Epicardial mapping with 253 electrodes during cryothermia showed that the region localized by return cycle mapping was the central common pathway sandwiched between the lines of conduction block and that the cryolesion connected the lines of block, blocked the rotating wave front, and resulted in termination of the ventricular tachycardia. CONCLUSION: Return cycle mapping provides an accurate and rapid means of localizing the central common pathway without the need for recording potentials from the pathway or pacing at the pathway in ablation for ventricular tachycardia.
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Criocirugía/métodos , Electrocardiografía/métodos , Infarto del Miocardio/complicaciones , Taquicardia Ventricular/cirugía , Animales , Mapeo del Potencial de Superficie Corporal/métodos , Perros , Femenino , Sistema de Conducción Cardíaco/fisiología , Masculino , Infarto del Miocardio/fisiopatología , Taquicardia Ventricular/fisiopatología , Función Ventricular Izquierda/fisiologíaRESUMEN
This study reports the comparative quantitative, morphological, and electrophysiological properties of two pacemaker cell types, spider and spindle-shaped cells, isolated from the rabbit sinoatrial node. Isolated nodal cells were studied with perforated and ruptured patch whole cell recording techniques. The basic spontaneous cycle length of the spider cells was 381 +/- 12 ms, and the basic spontaneous cycle length of the spindle cells was 456 +/- 17 ms (n = 12, P < 0.05). The spider cells had a more positive maximum diastolic potential (-54 +/- 1 mV) compared with the spindle cells (-68 +/- 1mV, P < 0.05). The overshoot and action potential amplitudes were also smaller in the spider cells. The hyperpolarization-activated inward (I(f)) current density, measured from their tail currents, was 15 +/- 1.3 pA/pF for the spider cells and 9 +/- 0.7 pA/pF for the spindle cells (P < 0.01). I(f) current activation voltage was more positive in the spider cells than the spindle cells. Isoproterenol (1 microM) decreased the spontaneous cycle length of the spider cells by 28 +/- 3% and the spindle cells by 20 +/- 1.5% (P < 0.05). Acetylcholine (0.5 microM) hyperpolarized the membrane potential of the spider cells to -86 +/- 0.7 mV and the spindle cells to -76 +/- 0.8 mV (P < 0.05). In summary, there are at least two distinct pacemaker cell types in the sinus node with different electrophysiological characteristics.
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Membrana Celular/fisiología , Nodo Sinoatrial/citología , Nodo Sinoatrial/fisiología , Acetilcolina/farmacología , Animales , Relojes Biológicos/fisiología , Cardiotónicos/farmacología , Tamaño de la Célula/fisiología , Femenino , Isoproterenol/farmacología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Técnicas de Placa-Clamp , Conejos , Vasodilatadores/farmacologíaRESUMEN
INTRODUCTION: Prior studies in isolated canine atria demonstrated that acetylcholine-induced reentrant atrial fibrillation (AF) was triggered by multifocal activity in the area of normal impulse origin (sinus node-crista terminalis). The aim of this study was to investigate the activation sequence in AF induced by vagal stimulation (VS) in intact dog hearts. METHODS AND RESULTS: VS (10 to 50 Hz, 1 msec, 15 V, 5-sec trains) induced single or multiple atrial premature depolarizations (APDs), and/or AF in 8 of 10 open chest dogs. Occurrence of APDs and AF increased with increasing VS intensity. Epicardial mapping (254 unipolar electrodes) of both atria showed that APDs as a rule emerged from ectopic sites, often from the right atrial appendage. Activation mapping of the first 10 cycles of AF showed that only a small number (<3 to 4) of unstable reentrant circuits were possible at the same moment. Moreover, most sustained VS-induced AFs were accounted for by a single leading stable reentrant circuit that activated the remainder of the atria. CONCLUSION: (1) Occurrence of vagally induced APDs and AF increases with increasing frequency of VS. (2) VS-induced focal ectopic APDs are widely distributed over the atria. (3) A single APD can be sufficient for initiation of reentrant AF. (4) Despite its high rate of sustained AF, it may be maintained by single stable reentrant circuit. (5) The atrial septum can play an important role in both the initiation and the maintenance of VS-induced AF.
Asunto(s)
Fibrilación Atrial/etiología , Nervio Vago/fisiología , Animales , Mapeo del Potencial de Superficie Corporal , Perros , Electrochoque , Tabiques Cardíacos/inervaciónRESUMEN
The Maze procedure was developed for the treatment of atrial fibrillation over a period of several years. Extensive experimental and clinical studies of the underlying electrophysiology of the arrhythmia were performed, and numerous surgical techniques and principles were tried before the Maze procedure was conceived. Few cardiac surgical procedures have undergone more extensive research and experimental trials before being applied clinically. This article gives a brief summary of the work leading up to the eventual Maze-III procedure that is now in clinical use.
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Fibrilación Atrial/cirugía , Procedimientos Quirúrgicos Cardíacos/métodos , Atrios Cardíacos/cirugía , Sistema de Conducción Cardíaco/cirugía , Animales , Fibrilación Atrial/fisiopatología , Electrocardiografía , Atrios Cardíacos/fisiopatología , Sistema de Conducción Cardíaco/fisiopatología , Frecuencia Cardíaca , Humanos , Resultado del TratamientoRESUMEN
BACKGROUND: The MAZE-III is the surgical treatment of choice for medically refractory atrial fibrillation. Although a number of nonsurgical techniques are evolving to duplicate the transmural atrial lesions of the MAZE-III, the surgical atriotomy remains the gold standard for conduction block. It was the objective of this study to surgically create the atrial incisions of the MAZE-III without the use of cardiopulmonary bypass. METHODS: A technique was developed to create and intersect the linear incisions of the MAZE-III on 10 beating canine hearts without the use of cardiopulmonary bypass using a "tunnel" of atrial tissue. The effectiveness of the procedure was tested by atrial burst pacing. RESULTS: This technique was successfully performed on 10 mongrel dogs without operative mortality. Preoperatively, sustained atrial fibrillation (>30 seconds) was induced in all animals. Postoperatively, all the animals remained in sinus rhythm even after burst pacing. CONCLUSIONS: In an experimental canine model, the MAZE-III can be performed on beating hearts without the assistance of cardiopulmonary bypass using a "tunnel" technique. This technique allows for the immediate assessment of electrophysiologic and mechanical function after the MAZE-III, or any other type of procedure using the "maze principle" and may find future application in the clinical arena.
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Fibrilación Atrial/cirugía , Procedimientos Quirúrgicos Cardíacos/métodos , Técnicas de Sutura , Animales , Perros , Estudios de Factibilidad , Hemostasis QuirúrgicaRESUMEN
BACKGROUND: The maze procedure cures atrial fibrillation; however, it isolates the pulmonary vein area and results in discordant activation in certain adjacent left atrial segments, which affects left atrial function. To preserve a more physiologic atrial transport function, we developed a new concept of surgical treatment for atrial fibrillation-the radial approach. The atrial incisions radiate from the sinus node toward the atrioventricular annular margins to allow a more physiologic atrial activation sequence and parallel the atrial coronary arteries to preserve blood supply to most atrial segments. METHODS: We examined the atrial coronary arteries and the activation sequence during sinus rhythm in normal canine hearts to design the atrial incisions according to the concept of a radial approach. RESULTS: The pattern of coronary artery distribution was centripetal, branching from the right coronary or left circumflex coronary artery at the right or left atrioventricular groove and spreading toward the sinus node. The endocardial mapping of the atria disclosed some important findings in designing the atrial incisions of the radial approach: the activation sequence at the left atrial septum and at the posterior left atrium between the pulmonary vein orifices. The atrial incisions were designed according to these findings. CONCLUSIONS: The radial approach may represent a more physiologic atrial transport function.
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Fibrilación Atrial/cirugía , Función Atrial , Animales , Fibrilación Atrial/fisiopatología , Procedimientos Quirúrgicos Cardíacos/métodos , Perros , Femenino , Atrios Cardíacos/inervación , Sistema de Conducción Cardíaco/fisiopatología , Humanos , MasculinoRESUMEN
BACKGROUND: In a previous study the atrial incisions that follow the concept of the radial approach were designed according to the activation sequence during sinus rhythm and the atrial coronary artery anatomy in normal dogs. The purpose of the present study was to determine whether the radial approach provides a more physiologic activation sequence and atrial transport function than the maze procedure. METHODS: Ten dogs that had undergone the radial approach (n = 5) or the maze procedure (n = 5) were studied 6 weeks postoperatively. Sinus node function and inducibility of atrial fibrillation were examined before and after operation. The atria were mapped endocardially with 212 electrodes, and atrial activation sequences during sinus rhythm and right atrial pacing were examined. Atrial transport function was assessed by transepicardial Doppler echocardiography. RESULTS: No dogs developed sinus node dysfunction postoperatively. Both the radial approach and the maze procedure equally prevented sustained atrial fibrillation. The atrial activation sequence was more synchronous after the radial approach than after the maze procedure. There was no electrically isolated region after the radial approach. The total activation time of the left atrium was significantly shorter after the radial approach than after the maze procedure (53.6+/-9.8 versus 70.5+/-9.6 ms, p<0.05). The ratio of peak flow velocity of the E wave to the A wave (peak E/A) of the transmitral Doppler flow was significantly smaller after the radial approach than after the maze procedure (1.7+/-0.4 versus 3.5+/-1.7, p<0.05). The atrial filling fraction of the transmitral Doppler flow was significantly larger after the radial approach than after the maze procedure (29.9%+/-7.3% versus 14.8%+/-5.0%, p<0.01). There was no significant difference in peak E/A and atrial filling fraction of the transtricuspid Doppler flow between the two procedures. CONCLUSIONS: The radial approach provides a more synchronous activation sequence and atrial transport function, and thus may represent a more physiologic alternative to the maze procedure as a surgical treatment for atrial fibrillation.
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Fibrilación Atrial/cirugía , Función Atrial , Atrios Cardíacos/inervación , Sistema de Conducción Cardíaco/fisiología , Gasto Cardíaco , Procedimientos Quirúrgicos Cardíacos/métodos , Ecocardiografía Doppler , Hemodinámica , HumanosRESUMEN
The objectives of this study were to explore the mechanisms of cardiac autonomic system (CAS) impairment and to assess whether warm blood cardioplegia can prevent the decrease of heart rate variability (HRV) after CPB. Twelve adult mongrel dogs were divided into two groups. One group received warm blood cardioplegia and maintained at a systemic temperature of 38 degrees C throughout the experiment (WB group). The other received cold crystalloid cardioplegia at 31 degrees C and topical hypothermia (CC group). Anesthesia was induced and maintained with sodium pentobarbital and isoflurane. The heart was exposed through a right thorectomy. CPB was established using a single right atrial cannula. The arterial cannula was placed in the right femoral artery. The crossclamp time for both groups was 30 minutes. Serum potassium levels were normalized throughout the study. Each animal's ECG was continuously recorded for 24 hours before surgery and for the first five postoperative days (POD) using a two-channel Holter monitor. The data were analyzed for heart rate variability (TP = total power, 0.01-1.00; LF = low frequency, 0.04-0.15; HF = high frequency, 0.15-0.40; LF/HF). There were no differences in the preoperative values. In both groups the TP, LF, and HF decreased, compared to control (P < 0.05), with CC group having significantly lower TP, LF and HF than the WB group (P < 0.05). The LF/HF did not change both between groups and between before- and after-CPB in each group (P > 0.05). The mean heart rate at 24 hours (MHR) increased in both groups, compared to control (P < 0.05), with CC group having a significantly higher MHR than WB group (P < 0.05). The data suggest that CPB, with warm blood or cold crystalloid cardioplegia does not disturb the balance of CAS, but it causes the decrease of HRV, and warm blood cardioplegia can not prevent the impairment of HRV.
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Sistema Nervioso Autónomo/fisiología , Soluciones Cardiopléjicas/farmacología , Frecuencia Cardíaca/fisiología , Corazón/inervación , Compuestos de Potasio/farmacología , Animales , Sangre , Puente Cardiopulmonar , Frío , Perros , Paro Cardíaco Inducido , Frecuencia Cardíaca/efectos de los fármacos , Calor , Distribución AleatoriaRESUMEN
The purpose of this study was to develop an animal model of atrial flutter (AFL) or fibrillation (AFB) and to determine precisely the pathway of atrial activation during arrhythmias induced by programmed stimulation. In 10 dogs, a shunt from the left subclavian artery to the left upper pulmonary vein was created to produce left atrial enlargement. Five months later, using programmed electrical stimulation, it was possible to induce 17 sustained atrial tachycardias in 9 of the 10 dogs, including 9 episodes of AFL caused by circus movement re-entry, 6 episodes of focal tachycardia, and 2 episodes of AFB. Short cycle length left atrial tachycardias caused by either circus movement or a focus did not propagate in a uniform 1:1 pattern to the right atrium (RA), resulting in RA dissociation. In these arrhythmias, complex wavefronts from both current and preceding left atrial cycles coexisted in the RA. Circus movement was associated with a spectrum of different re-entrant pathways with different path lengths. These differences in the path length were determined by various ways in which obstacles such as the superior vena cava and orifice of the right atrial appendage or pulmonary vein orifices were combined by contiguous areas of functional block.
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Fibrilación Atrial/fisiopatología , Aleteo Atrial/fisiopatología , Sistema de Conducción Cardíaco/fisiopatología , Animales , Modelos Animales de Enfermedad , Perros , ElectrofisiologíaRESUMEN
Electrical coupling of pacemaker cells at gap junctions appears to play an important role in sinus node function. Although the major cardiac gap junction protein, connexin43 (Cx43), is expressed abundantly in atrial and ventricular muscle, its expression in the sinus node has been a subject of controversy. The objectives of the present study were to determine whether Cx43 is expressed by sinus node myocytes, to characterize the spectrum of connexin expression phenotypes in sinus node pacemaker cells, and to define the spatial distribution of different connexin phenotypes in the intact sinus node. To fulfill these objectives, we performed high-resolution immunohistochemical analysis of disaggregated adult canine sinus node preparations. Using enhanced tissue preservation and antigen retrieval techniques, we also performed immunohistochemical studies on sections of intact canine sinus node tissue. Analysis of disaggregated sinus node preparations revealed three populations of pacemaker cells distinguished on the basis of connexin immunohistochemical phenotype: approximately 55% of cells expressed only connexin40 (Cx40); 30% to 35% of cells expressed Cx43, connexin45 (Cx45), and Cx40; and the remaining cells had no detectable connexin expression. In immunostained sections of intact sinus node, Cx43- and Cx45-positive cells were limited in their distribution and were observed in discrete bundles that appeared to abut atrial myocytes. In contrast, Cx40 immunoreactive signal was widely distributed in the sinus node region. These results indicate that subsets of pacemaker cells express distinct connexin phenotypes. Differential expression of connexins could create regions within the sinus node with different conduction properties, thereby contributing to the nonuniform conduction properties seen in this tissue.
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Uniones Comunicantes/química , Uniones Comunicantes/metabolismo , Nodo Sinoatrial/química , Nodo Sinoatrial/metabolismo , Animales , Especificidad de Anticuerpos , Conexinas/análisis , Conexinas/biosíntesis , Conexinas/inmunología , Perros , Técnica del Anticuerpo Fluorescente , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/fisiología , Proteína alfa-5 de Unión ComunicanteRESUMEN
BACKGROUND: The central common pathway, which is the target for ablation in reentrant ventricular tachycardia, can be localized by entrainment mapping techniques. However, localization of the pathway is not always possible because of the elevated pacing threshold and the low voltage and fractionated potentials at the pathway. We examined whether return cycle mapping after entrainment localizes the pathway without pacing at the pathway or recording the potentials from the pathway and determined the required electrode resolution to localize the pathway. METHODS AND RESULTS: Epicardial mapping was performed with 253 unipolar electrodes during and after entrainment of 13 morphologies of ventricular tachycardia that were induced in dogs 4 days after infarction. The return cycle was calculated by subtracting the first activation time from the second activation time after the last stimulus and the return cycle distribution map was constructed for each stimulation site. The return cycle isochrones equal to the ventricular tachycardia cycle length converged on the lines of conduction block irrespective of the stimulation site, and the central common pathway was localized at the region between the intersections of the return cycle isochrones after entrainment from different stimulation sites. The potentials from the central common pathway were not required to localize the pathway, and the mapping accuracy did not change with or without analysis of the potentials from the pathway. According to the correlation between the electrode resolution and the mapping accuracy, an interelectrode distance of 8.5 mm was estimated as sufficient resolution for successful tachycardia termination during radiofrequency ablation guided by return cycle mapping. CONCLUSIONS: Return cycle mapping after entrainment localizes the central common pathway without pacing at the pathway or recording the potentials from the pathway. This new mapping technique could improve the success rate of the ablative procedures.
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Electrocardiografía , Sistema de Conducción Cardíaco/fisiología , Taquicardia Ventricular/fisiopatología , Animales , Estimulación Cardíaca Artificial , Perros , Electrodos , Electrofisiología , Femenino , MasculinoRESUMEN
Atrial flutter (AFL) is a common problem in children who have undergone a Fontan operation for single ventricle physiology. Although this has been attributed to the atrial stretch inherent in the earlier forms of this operation, AFL has persisted in spite of a modification that minimizes atrial distension. Therefore, it was hypothesized that AFL following the modified Fontan procedure may result from anatomic barriers related to suture lines rather than from atrial stretch or hypertension. In a series of experiments performed in dogs under general anesthesia, the modified Fontan repair was simulated by placing only the suture line of the intra-atrial repair. No baffle was placed, thus avoiding any hemodynamic alterations. After closure of the atriotomy, 253 point unipolar atrial endocardial form-fitting electrodes were inserted through the mitral and tricuspid valves via bilateral ventriculotomies. Induction of AFL was attempted with atrial burst pacing and programmed extrastimulation, and activation sequence maps of subsequent reentry were generated from the endocardial electrodes. Atrial flutter was induced in all of 17 dogs, with a median cycle length of 177 +/- 31 ms. Activation sequence maps demonstrated conduction block along the crista terminalis corresponding to the free wall portion of the suture line. This created an isthmus between the suture line and tricuspid annulus, which appeared critical for sustaining AFL, although the circuit used both the septal and free wall surfaces of the right atrium. In seven dogs, a cryolesion was placed from the tricuspid annulus to the free wall segment of the suture line, terminating the AFL, in all seven. When the free wall segment of the suture line was moved 5 mm medial to the crista terminalis, AFL was induced in four of five dogs, but only in the presence of isoproterenol and at a shorter cycle length (136 +/- 8 ms, P < .001). Atrial flutter was not inducible, even with the addition of isoproterenol, in any of five dogs in which the suture line was placed 10 mm anterior to the crista terminalis and incorporated into closure of the atriotomy. This acute canine model of the modified Fontan operation demonstrates that conduction block from the free wall portion of the suture line creates an isthmus of tissue between the suture line and the tricuspid annulus. This is a sufficient substrate to produce AFL; no hemodynamic alteration is required. Injury to the crista terminalis is a significant risk factor in this model, which suggests that a modification of the suture line might reduce the incidence of AFL in patients following this operation.
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Aleteo Atrial/fisiopatología , Procedimiento de Fontan/efectos adversos , Animales , Aleteo Atrial/etiología , Aleteo Atrial/prevención & control , Estimulación Cardíaca Artificial , Perros , Electrocardiografía , Electrofisiología , Procedimiento de Fontan/métodos , Atrios Cardíacos/cirugía , Sistema de Conducción Cardíaco/fisiopatología , SuturasRESUMEN
The atria are anatomically complex three-dimensional (3-D) structures. Impulse propagation is dynamic and complex during both normal conduction and arrhythmia. Atria activation has traditionally been represented on two-dimensional surface maps, which have inherent inaccuracies and are difficult to interpret. Interactive computerized 3-D display facilitates interpretation of complex atrial activation sequence data obtained from form-fitting multipoint electrodes. Accordingly, the purpose of this article is to describe the application of 3-D form-fitting electrode molds to the 3-D mapping and display system developed in this laboratory for the study of complex cardiac arrhythmias. Computer generated 3-D surface models are created from a database of serial cross-sectional anatomical images. Points chosen on endocardial and epicardial surfaces in each cross-sectional image are processed to create polygons defining myocardial wall boundaries. The polygons from adjacent serial images are then combined, to create a 3-D surface model. The discrete anatomical locations of unit electrodes on multipoint electrode templates are then assigned in the proper position on the surface model. Computer analysis of simultaneous activation data from each unit electrode is performed based on parameters set by the user. Activation data from each unit electrode site are displayed on the computer surface model in a color spectrum correlating with a user-defined time scale. Activation sequence maps can be visualized as static isochrone maps, interval maps, or as dynamic maps at variable speeds, from any 3-D perspective. Thus, an interactive computerized 3-D display system is described, which allows anatomically superior analysis and interpretation of complex atrial arrhythmias.