Ann Thorac Surg 1998;66:2117-2118
© 1998 The Society of Thoracic Surgeons
How To Do It
Facile left ventricular deairing by administration of cardioplegia into the left ventricular vent
Steven R. Gundry, MDa
a Division of Cardiothoracic Surgery , Loma Linda University Medical Center, Loma Linda, California USA
Accepted for publication June 16, 1998.
Address reprint requests to Dr Gundry, Division of Cardiothoracic Surgery, Loma Linda University, CP21121, 11175 Campus St, Loma Linda, CA 92354
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Abstract
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De-airing of left heart structures during minimally invasive valve operations is often difficult. A method of using a left ventricular vent temporarily hooked to the cardioplegia cannula for facile left ventricular deairing is described. Routine use of this simple method coupled with transesophageal echocardiography monitoring simplifies the process of left ventricular deairing in minimally invasive or standard valvular operations.
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Introduction
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During most valvular heart operations, and occasionally during coronary artery bypass operations when veins are anastomosed to the ascending aorta under single cross-clamping, air is introduced into the left ventricle or the left atrium, or both. The consequences of this retrained air being ejected into the arterial bloodstream during subsequent cardiac systole are legend, including coronary and cerebral embolism. As such, numerous maneuvers exist to assure that most, if not all, air is removed from the left heart at the end of aortic cross-clamping or before full cardiac ejection ensues. These maneuvers may consist of vigorously shaking the heart, elevating and shaking the left ventricular (LV) apex, with or without placing a needle in the apex, holding venous blood while applying suction to the left ventricle or aortic root vents, inflating the lungs, and placing the patient in a head down position. Indeed, to some surgeons, so fearsome are the consequences of retained LV air that all of the above maneuvers are used in the course of routine valve operations.
Recently, less invasive approaches to aortic and mitral valve operations have been popularized, using either ministernotomies or various right thorax incisions to access the aorta or the left atrium. All of these incisions share a limited view of the left ventricle, and as such, many if not all of the deairing maneuvers in the surgeon’s armamentarium are of limited use. Although the use of transesophageal echocardiography has convinced us that deairing is easily accomplished during ministernotomies by shaking the entire patient or by compressing the left ventricle with sponge sticks or defibrillator paddles, we began applying a technique that we and other investigators have used to de-air the HeartMate LV assist device (Thermo Cardiosystems, Inc, Danville, MA) to deair the ventricle in valvular heart operations.
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Technique
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In our general practice of aortic valve operations, a LV vent is placed through the right superior pulmonary vein. In a number of ministernotomy operations, we have alternatively placed vents directly through the aortic annulus or through the dome of the left atrium. Similarly, in many mitral valve operations, a vent is placed through the right superior pulmonary vein or through the dome of the left atrium (Fig 1 ). The same is done using the ministernotomy. Once the aortic or mitral valves have been repaired or replaced, the aorta or left atriotomy is closed. Toward the end of this closure, the cardioplegia line is disconnected from the retrograde or antegrade cannula and either connected to the side port (if present) or held against the end of the LV or left atrial vent line, which is momentarily disconnected from its suction source. Alternatively, a vein graft extender tubing (Medtronic, DLP, Inc, Grand Rapids, MI) can be placed on the cardioplegia line at the time of initial hookup, so that the extender tubing is used to make the connection to the LV vent tubing. If desired, the crystalloid mixer of the cardioplegia setup can be turned off during this period so that straight blood is delivered. With the aorta vented or still partially opened, cardioplegia (or blood) is then delivered into the LV vent, allowing this to escape from the aorta. Gentle ventilation of the lungs with the perfusionist holding some venous return will also mobilize any pulmonary venous air trapped in the lungs. Progress in deairing can be monitored by transesophageal echocardiography; typical deairing maneuvers such as shaking the heart or patient can also be performed simultaneously. The cross-clamp is then removed and the LV vent returned to suction; once the heart has started to beat, additional blood can be delivered into the LV vent from the cardioplegia circuit to aid in ejection. Deairing maneuvers can still be applied once the heart is ejecting, but this is rarely necessary (1).
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Fig 1. Artists conception of " " vein graft extension attached to the cardioplegia line from the pump with one limb connected to the retrograde cardioplegia cannula. Other active limbs are connected to side port of the left ventricular (LV) vent. (Not illustrated is the possibility of a direct connection of the cardioplegia line to the end of the left ventricular vent).
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Comment
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Although the role that microbubbles of air escaping from the cardiac structures may play in creating intraoperative complications, there is full agreement that air emboli can cause temporary coronary and other arterial occlusions, with sometimes disastrous consequences. Eliminating air from poorly mobile structures, such as LV assist devices, led us and other investigators to use a side arm taken from the arterial line, which was then connected to the LV vent, to de-air the HeartMate LV assist device. In those patients, cardioplegia was sometimes not used during the HeartMate implantation, therefore another source of blood (ie, the arterial line) was needed. In the method we describe here, the blood cardioplegia line is already present on the field. Thus, no additional equipment is needed to add a new easily applied safety tool to cardiac operations. This is especially important in minimally invasive operations, where the ability to apply traditional deairing maneuvers may be limiting or frustrating. Coupled with transesophageal echocardiography, this method effectively eliminates deairing problems. We now use this method universally, regardless of whether a full or ministernotomy is used. With practice, we have also found this method to be an effective way of loading the left ventricle with controlled blood flow in the case of acute right ventricular infarction, providing effective LV ejection without taxing the right heart while coming off bypass.
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References
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Ream, AK. Cardiopulmonary bypass & circulatory support. In: Dudley H, Carter D, eds, St. Louis: CV Mosby, 1986:58–9.
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