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Once the balloon catheter is placed, inappropriate handling of the catheter may result in trapping of the catheter at the atrial septum or in the pulmonary vein, or migration of the catheter into the atrial appendage. This usually occurs during the next attempts to cross the mitral valve after the catheter is withdrawn to the left atrium. As alluded to in the previous section, an initial deep placement of the catheter circumvents the above mentioned problems. I. AVOIDING LEFT ATRIAL APPENDAGE (Figure 4) Left atrial appendage thrombus may be unsuspected when PTMC candidates are screened only with insensitive transthoracic echocardiography. To minimize the risk of inadvertent thrombus dislodgement and systemic embolism, the anterolateral appendage region must be avoided. During balloon catheter manipulation performed under a 30° right anterior oblique fluoroscopic view, the catheter in the left atrium should always be kept to the left of the pigtail catheter preplaced in the left ventricle (Figure 4). After the precautions detailed below have become rote, it may be possible to perform PTMC safely even in the presence of left atrial appendage thrombi proven by transesophageal echocardiography [1, 2]. Our previous study of PTMC under intraoperative biplane transesophageal echocardiography in a limited number of patients showed that contact of the guide wire or balloon catheter with the appendage can indeed be avoided [1]. Furthermore, in a more recent study extending the former observation, the feasibility and safety of Inoue PTMC were confirmed in a large number of patients with left atrial appendage thrombi [2]. By preventing the balloon catheter from entering the appendage, we were able to avoid systemic embolization in these patients. The alternatives are either to subject patients with appendage thrombi to mitral valve surgery, or to defer PTMC for stable patients until resolution of the thrombi after warfarin treatment [1]. References:
First crossing (Figure 4, upper panel) As previously mentioned, deep placement of the balloon catheter in the left atrium keeps it from flipping into the appendage during the first crossing of the mitral valve. Withdrawing catheter from left ventricle (Figure 4, lower panel) After each balloon inflation procedure, in order to exert better control over the catheter tip and to prevent it from encroaching on the left atrial appendage, the stylet is advanced halfway into the balloon segment, and a slight clockwise twist to the stylet is applied as the catheter is withdrawn back to the left atrium. The balloon catheter, with its tip thus directed posteriorly, can then be safely pulled to the atrium by cautiously withdrawing the catheter and the stylet in steps. The catheter, however, should not be withdrawn too far during the process (see CATHETER ENTRAPMENT AT ATRIAL SEPTUM, below). The stylet is then removed entirely from the catheter for left atrial pressure measurement, leaving the deflated balloon segment pointing vertically. Again, during hemodynamic measurements, care should be exercised to avoid accidentally pushing the catheter forward into the appendage. Subsequent crossings The catheter, after having been withdrawn from the left ventricle, stands fairly straight up without looping. Thus, for the next crossings of the mitral valve, extra care is needed to keep the catheter to the left of the pigtail catheter. The stylet is carefully inserted to the catheter tip to bend the catheter downwards into a generous arch with the distal catheter segment oriented more vertically. Then a counterclockwise twist to the stylet is made, and the catheter is slowly withdrawn to direct the partially inflated balloon towards the mitral valve (see PTMC Procedures). It should be noted that the catheter has a propensity to enter the left atrial appendage if the catheter is more horizontally oriented and the stylet is pulled back too vigorously during a failed crossing attempt. To avoid this, a catheter loop should be made after reinserting the stylet as noted above, and the stylet should not be withdrawn too much during any manipulation in the left atrium, including during withdrawal of the catheter from the ventricle after each balloon inflation-deflation cycle. II. CATHETER ENTRAPMENT AT ATRIAL SEPTUM When the septal puncture site is thick and tough, the catheter may be entrapped by the septum, thereby making manipulations difficult during attempts at crossing the mitral valve. The operator should be alert to the possibility of this entrapment when marked resistance is encountered at the septum during septal puncture. This vexing problem usually does not occur during the first crossing of the valve because, as alluded to earlier, the catheter is already deeply placed and coiled in the left atrium. However, entrapment may occur during subsequent valve crossing attempts, when it becomes necessary to advance the catheter, which has been inadvertently withdrawn too far back into the atrium after valvular dilatation and caught at the thick septum. If the catheter cannot be advanced with the stylet inserted all the way to the catheter tip, a clockwise twist is applied to the stylet, directing the catheter tip posterolaterally to align it more or less perpendicular to the septal plane. The catheter may then be advanced forward together with the stylet. If even this approach fails, the coiled-tip guide wire should be reinserted to facilitate deep placement of the catheter in the left atrium. III. CATHETER ENTRAPMENT IN PULMONARY VEIN Entrapment of the balloon catheter usually does not occur during the first crossing of the valve because, as alluded to earlier, the catheter is already deeply placed and coiled in the left atrium. However, the entrapment may occur during subsequent crossings. This is recognized by the lack of free motion of the distal catheter when attempting to advance the catheter or when the stylet is rotated. |
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©
2002-2003 Dr. Jui-Sung Hung. All Rights Reserved.
Questions or Comments? Email shung@pipeline.com. |
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