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Ann Thorac Surg 1996;62:630
© 1996 The Society of Thoracic Surgeons
Cardiothoracic Surgeons of New Haven, PC, 2 Church St S, Suite 507, New Haven, CT 06519
To the Editor:
We read with interest the report by Salerno and associates [1] regarding the role of mechanical problems with the right coronary artery as an etiologic factor in causing right ventricular (RV) failure during aortic valve operation. It is of course axiomatic that unexpected and in particular regional myocardial dysfunction after a cardiac operation may be due to mechanical coronary obstruction. Such obstruction should obviously be considered and repaired, particularly in patients undergoing complex proximal aortic operations as in several patients in their series.
We believe that a more clinically significant cause of unexplained RV failure after "true" open heart operations such as aortic or mitral valve repair or replacement, cardiac transplantation, and even occasionally coronary artery bypass grafting is air embolization down the right coronary artery.
Transesophageal echocardiography has shown retained intracardiac air in as many as 73% of valvular surgical patients, and retained intracardiac air has been implicated in myocardial infarction, usually in the inferior wall, after valve operations [2, 3]. For this reason, almost as a routine on all valvular operations we choose to nick a small, anterior RV acute marginal branch with a no. 11 blade before discontinuation of cardiopulmonary bypass. Escaping air bubbles are commonly seen, with a rapidly visualized improvement in RV function. In addition, we have occasionally observed cases in which weaning from cardiopulmonary bypass was difficult, and significant and rapid improvement was seen after this maneuver. The defect is closed with a fine figure-of-8 suture of polypropylene, which is tied after no further air is seen to escape. We have not observed any untoward complications of this simple technique, as applied in several hundred cases.
It is of interest that in patient 2 in the series reported by Salerno and associates, RV failure with what appeared to be a patent vein graft to the posterior descending artery was successfully treated by addition of a graft to the acute marginal branch of the RV on the beating heart. We would suggest that perhaps deairing occurred through the open arteriotomy and may explain the good outcome seen in this case.
We also noted that in the 2 cases described in detail by Salerno and associates, RV dysfunction occurred 15 minutes after coming off of cardiopulmonary bypass and at chest closure. The routine use of transesophageal echocardiography has demonstrated air bubbles in the left heart at such time after cardiopulmonary bypass. Anatomic problems with the right coronary artery will more likely prevent successful separation of the patient from cardiopulmonary bypass rather than cause deterioration 10 to 15 minutes later or upon chest closure.
Although mechanical coronary obstruction should always be considered and treated, we believe that Salerno and associates' recommendation for blind, empiric bypass to the right coronary artery in unexplained postcardiotomy RV dysfunction is probably not warranted until the simple method that we have suggested has been tried.
References
Division of Cardiothoracic Surgery, University at Buffalo, The Buffalo General Hospital, 100 High St, Buffalo, NY 14203
To the Editor:
We agree with Drs Passik and Hashim regarding air retention in the left ventricular cavity during valvular operations. Its sequelae have been diminished by techniques used to evacuate air and by transesophageal echocardiography to confirm its elimination at the time of weaning from cardiopulmonary bypass. Most of the patients in our report had transesophageal echocardiographic monitoring, and in none of them did air appear to be causative of right ventricular failure. As a matter of fact, a mechanical problem was confirmed at autopsy in 1 patient and was either suspected or confirmed in the other patients who survived. The technique described by Drs Passik and Hashim further ensures that air is totally eliminated from the right coronary artery during valvular operations. We therefore agree that these measures are indicated as an initial step before proceeding to a more aggressive approach, such as by bypassing the right coronary artery, as described in our article. We still believe, however, that no patient undergoing an aortic valvular procedure should be allowed to be in severe right ventricular failure at the end of the procedure without having the right coronary artery bypassed.
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