RESUMO
The atrioventricular (AV) node is permanently damaged in approximately 3 percent of congenital heart surgery operations, requiring implantation of a permanent pacemaker. Improvements in pacemaker design and in alternative treatment modalities require an effective in vivo model of complete heart block (CHB) before testing can be performed in humans. Such a model should enable accurate, reliable, and detectable induction of the surgical pathology. Through our laboratorys efforts in developing a tissue engineering therapy for CHB, we describe here an improved in vivo model for inducing chronic AV block. The method employs a right thoracotomy in the adult rabbit, from which the right atrial appendage may be retracted to expose an access channel for the AV node. A novel injection device was designed, which both physically restricts needle depth and provides electrical information via electrocardiogram interface. This combination of features provides real-time guidance to the researcher for confirming contact with the AV node, and documents its ablation upon formalin injection. While all animals tested could be induced to acute AV block, those with ECG guidance were more likely to maintain chronic heart block >12 h. Our model enables the researcher to reproduce both CHB and the associated peripheral fibrosis that would be present in an open congenital heart surgery, and which would inevitably impact the design and utility of a tissue engineered AV node replacement.
Assuntos
Animais , Feminino , Coelhos , Nó Atrioventricular/cirurgia , Ablação por Cateter/métodos , Bloqueio Cardíaco/cirurgia , Toracotomia/métodos , Modelos Animais de Doenças , Eletrocardiografia , Fluoroscopia , Bloqueio Cardíaco/etiologiaRESUMO
The atrioventricular (AV) node is permanently damaged in approximately 3% of congenital heart surgery operations, requiring implantation of a permanent pacemaker. Improvements in pacemaker design and in alternative treatment modalities require an effective in vivo model of complete heart block (CHB) before testing can be performed in humans. Such a model should enable accurate, reliable, and detectable induction of the surgical pathology. Through our laboratory's efforts in developing a tissue engineering therapy for CHB, we describe here an improved in vivo model for inducing chronic AV block. The method employs a right thoracotomy in the adult rabbit, from which the right atrial appendage may be retracted to expose an access channel for the AV node. A novel injection device was designed, which both physically restricts needle depth and provides electrical information via electrocardiogram interface. This combination of features provides real-time guidance to the researcher for confirming contact with the AV node, and documents its ablation upon formalin injection. While all animals tested could be induced to acute AV block, those with ECG guidance were more likely to maintain chronic heart block >12 h. Our model enables the researcher to reproduce both CHB and the associated peripheral fibrosis that would be present in an open congenital heart surgery, and which would inevitably impact the design and utility of a tissue engineered AV node replacement.
Assuntos
Nó Atrioventricular/cirurgia , Ablação por Cateter/métodos , Bloqueio Cardíaco/cirurgia , Toracotomia/métodos , Animais , Modelos Animais de Doenças , Eletrocardiografia , Feminino , Fluoroscopia , Bloqueio Cardíaco/etiologia , CoelhosRESUMO
Endotracheal intubation is not without complications, among the most serious of these being misplacement of the endotracheal (ET) tube. Unrecognized esophageal placement is a lethal complication, but even when placed in the trachea, ET tubes can be displaced distally and enter a mainstem bronchus. Correct positioning of an ET tube is usually defined as the placement of the tube within the trachea approximately 5 cm above the carina. Chest x-ray is the most common and a reliable method of demonstrating correct positioning, particularly in ICU patients. Using transillumination by means of a flexible stylet (lightwand), we investigated whether transillumination could position an ET tube consistently within 5 +/- 2 cm of the carina. Ten human cadavers of varied weight and body habitus were intubated under direct vision and 10 ml of a radiopaque dye was injected down the tube as a marker for the carina. A premeasured flexible lighted stylet was then inserted into the inplace tube so that the bulb was positioned at the tube's distal opening. The brightest transilluminated glow produced by the bulb was then positioned at the sternal notch. A chest x-ray was taken and the distance of the tube tip from the carina was calculated. In each case the tube tip could be placed consistently at a level 5 +/- 1 cm from the carina by observing the maximal transilluminated glow at the sternal notch. We conclude that transillumination of the neck using a flexible lighted stylet can accurately and consistently position an ET tube at an appropriate distance above the carina.(ABSTRACT TRUNCATED AT 250 WORDS)