FIG. 7.29 The heart. The heart and major blood vessels viewed from the front (anterior). Inset shows the relationship of the heart to other structures in the thoracic cavity. (From Patton KT, Thibodeau GA: The human body in health & disease, ed 6, St Louis, 2014, Mosby.)
FIG. 7.31 Conduction system of the heart. Specialized cardiac muscle cells (yellow) in the wall of the heart rapidly conduct an electrical impulse throughout the myocardium. The signal is initiated by the sinoatrial (SA) node (pacemaker) and spreads to the rest of the atrial myocardium and to the atrioventricular (AV) node. The AV node then initiates a signal that is conducted through the ventricular myocardium by way of the AV bundle (of His) and Purkinje fibers. Labels for parts of the heart’s conduction system are highlighted in red. (From Patton KT, Thibodeau GA: The human body in health & disease, ed 6, St Louis, 2014, Mosby.)
• This surgery is usually chosen when a significant disparity in size exists between a donor’s small heart and a recipient’s large one.
Bronchoscopy
• This invasive procedure is used for the diagnosis, evaluation, and treatment of various conditions. Examples include:
• Retrieval of foreign objects from the bronchus in pediatric patients
• Laser guidance in the treatment of endobronchial tumors
• Postoperative evaluation of transplanted lungs
• Because the bronchoscope is inserted through the mouth but there is no wound, the procedure is categorized in wound classification V (unclassified).
• Foreign bodies lodge more easily in the right bronchus because it’s wider and straighter than the left one.
• A rigid bronchoscope is employed in pediatric patients to remove foreign bodies. This instrument, with its larger diameter and hollow working channel, can be used in ways that the pediatric flexible bronchoscope cannot:
• It facilitates the passage of various grasping devices and other instruments.
• It permits suctioning of clotted blood, foreign bodies, and thick secretions.
FIG. 7.32 Cardiopulmonary bypass circuit. Venous blood is drained by gravity from the right atrium or venae cavae into an oxygenator that incorporates a blood reservoir and a heat exchanger, which warms or cools the blood as needed. The ventilating gas flowing into the oxygenator removes carbon dioxide and adds oxygen to the blood. Saturated blood leaves the oxygenator and is pumped from the reservoir into the arterial system by the use of a roller pump. Filters and monitors are incorporated into the circuit. Additional roller pumps are used to suction shed blood from the pericardial well and the intracardiac chambers (cardiotomy suckers); the blood is returned to the cardiotomy reservoir. Another roller pump is used to vent air and blood through a right superior pulmonary venous catheter that is inserted into the left ventricle. (From Buxton B et al: Ischemic heart disease surgical management, London, 1999, Mosby.)
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