| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ann Thorac Surg 2001;72:S2218-S2219
© 2001 The Society of Thoracic Surgeons
a Department of Surgery, University of Kentucky, MN264 University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536, USA
e-mail: mentzer{at}pop.uky.edu
I want to compliment Dr Al-Tabbaa on his fine presentation and congratulate him on his work in this area. It is clear from his presentation that intraoperative echocardiography can be extremely helpful to both the surgeon and anesthesiologist in diagnosing and assessing myocardial injury. This, in turn, can help the surgical team strategize on how best to minimize postischemic ventricular dysfunction.
The problem of postoperative myocardial injury after heart surgery should not be underestimated. Heart surgery is now one of the most commonly performed operations in the United States. In 1998 alone, it is estimated that more than 730,000 surgical procedures were performed. Of these, more than 70% of the operations involved some form of myocardial revascularization. It is quite likely that in the next 2 to 3 years, over 1 million heart operations will be performed annually. If, as suggested by Dr Mangano and his colleagues, 10% of coronary artery bypass surgery patients may experience a serious cardiac complication, eg, infarction, heart failure, or death, this means that a considerable number of patients are at risk. The economic impact is not inconsequential, as well. The cost of the morbidity and mortality associated with many of these complications has been estimated to approach 2 billion dollars. Thus, while the Centers for Medicaid and Medicare Services (CMS) and other managed care organizations may be interested in reducing medical errors for altruistic reasons, there are also fiscal reasons why the Department of Health and Human Services is interested in reducing postoperative complications after heart surgery. Although one approach may be simply not to operate on high-risk patients, this would deny access to appropriate health care for a specific subset of patients. A better long-term strategy is to utilize and develop new methodologies that make surgery for high-risk patients safer.
Myocardial injury after cardiac surgery can be divided into two basic categories: (1) reversible injury, and (2) irreversible injury. Myocardial stunning, an example of reversible injury, may occur in as many as 80% of the patients. It can result in mild, moderate, or even severe ventricular dysfunction, the latter occurring in 15% to 20% of high-risk patients. While myocardial stunning, in general, may not be associated with a high mortality, it certainly can contribute to a prolonged hospital stay and aggravate existing co-morbidities. In those patients with limited myocardial reserve, it may actually lead to death. With respect to irreversible myocardial injury, ie, infarction, the incidence of some degree of necrosis may be as high as 5% to 7%.
Currently, 30-day mortality for low-risk patients undergoing coronary artery bypass surgery is reported to range between 1% and 3%. It is curious, though, that there has been a tendency to not address the question as to why low-risk coronary artery bypass mortality is not zero. Despite all the new technologies and methodologies that have been introduced to limit perioperative ischemia, this mortality rate has changed little over the past 10 to 15 years. This is due, in part, to our lack of understanding of the basic mechanisms underlying the etiology of myocardial stunning and infarction, and we have not fully utilized existing technologies like intraoperative echocardiography and continuous online monitoring of intracardiac pH.
Now, I would like to share with you an intraoperative transesophageal echocardiogram (TEE) that was obtained during an aortic valve replacement (AVR) operation. This echo is an excellent example of how TEE can provide important, timely, new information that can be critical to the success of an operation. The patient presented with the diagnosis of acute valvular endocarditis and was scheduled to undergo an AVR. Intraoperative TEE was used to evaluate the extent of the disease and the overall contractile status of the heart. The TEE revealed severe aortic regurgitation and the presence of a large vegetation that prolapsed into the left ventricle during diastole. Despite the severe regurgitation, the patient was in normal sinus rhythm and left ventricular function was normal. After placing the patient on cardiopulmonary bypass, the aorta was cross-clamped and cold blood cardioplegia was administered first antegrade to arrest the heart, and then retrograde through the coronary sinus to maximize myocardial protection. Following valve replacement and removal of the aortic cross clamp, the beating state of the heart was restored. The TEE showed a normally functioning St. Jude valve prosthesis and normal ventricular function indicating that myocardial protection had been satisfactory. After weaning the patient from cardiopulmonary bypass (within 5 to 7 minutes), the TEE showed gradual deterioration in global left ventricular function; this progressed to marked hypocontractility over the course of several minutes. The early echo findings preceded any hemodynamic evidence of heart failure or the appearance of electrocardiographic abnormalities. The ECG did demonstrate significant ST-segment elevation shortly after the decision was made to place the patient back on cardiopulmonary bypass and reexamine the mechanical prosthesis. Upon inspection, there was no evidence of thrombus formation, but it appeared that the valve ring encroached upon and partially occluded the ostium of the left main coronary artery. The 23 mm prosthesis was replaced with the 21 mm prosthesis and the patient was successfully weaned from cardiopulmonary bypass. At this time, the TEE showed normal ventricular function with a normal ejection fraction. The ECG was normal, as well. In this case, the TEE clearly contributed important new information in a timely manner that helped the surgeon to intervene, thus preventing both reversible and irreversible myocardial injury.
In closing, I want to again congratulate Dr Amer Al-Tabbaa on a superb and enlightening presentation. Clearly, intraoperative transesophageal echocardiography can play a valuable role in the management of patients undergoing heart surgery. When used in conjunction with other techniques such as intracardiac pH monitoring, it may well be that we can look forward to a time when we can prevent myocardial injury after heart surgery altogether.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
