| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Ann Thorac Surg 1995;60:665-668
© 1995 The Society of Thoracic Surgeons
Division of Cardiology, Departments of Medicine and Thoracic and Cardiovascular Surgery, Winthrop-University Hospital, Mineola, New York and School of Medicine, Health Sciences Center, SUNY at Stony Brook, Stony Brook, New York
Accepted for publication March 21, 1995.
Abstract
Background. Echocardiography can detect aortic regurgitation (AR) that may interfere with the adequate delivery of cardioplegia solution to the myocardium during cardiac operation. When aware of this lesion, the surgeon can modify the operative technique accordingly. We sought to evaluate the ability of intraoperative transesophageal echocardiography to detect AR and to correlate the severity of the lesion with the need for retrograde cardioplegia administration.
Methods. Eighty-four consecutive patients undergoing coronary artery bypass grafting were evaluated. When AR was noted by intraoperative transesophageal echocardiography, a cannula was placed in the coronary sinus for possible retrograde cardioplegia administration. The surgeon was unaware of the severity of AR. After operation, the severity of AR was quantitated using the ratio of the regurgitation jet width to the left ventricular outflow tract diameter.
Results. The AR patients who required retrograde cardioplegia had a significantly higher ratio of regurgitation jet width to left ventricular outflow tract diameter than those AR patients who did not (0.36 ± 0.06 versus 0.19 ± 0.06, p < 0.005).
Conclusions. Transesophageal echocardiography can provide accurate information regarding the presence and severity of AR. The calculated severity of AR on transesophageal echocardiography is associated with the need for retrograde cardioplegia administration.
Echoardiography is a sensitive and specific technique for the diagnosis of aortic regurgitation (AR) [1–5]. In a younger population, the prevalence of AR is 33% [6, 7], whereas it is as common as 53% in apparently healthy individuals aged more than 60 years and 78% in those more than 70 years [8]. Frequently, AR is clinically unsuspected [1, 2].
An awareness of AR is important to the cardiac surgeon because of its implications for cardioplegia administration. Incompetence of the aortic valve may result in significant amounts of solution entering the left ventricle
causing distention and subsequent left ventricular dysfunction. Aortic regurgitation can result in inadequate cardioplegia delivery to the myocardium and ischemic injury from inadequate protection. If the presence of AR is known in advance, the cardiac surgeon can take necessary steps to avoid the occurrence of these problems. These steps may include surveillance for cardiac distention, use of left ventricular venting, and the administration of retrograde cardioplegia through the coronary sinus. Retrograde cardioplegia administration is more complex and carries potential risks [9–12]. Therefore, its use should be restricted to patients in whom antegrade cardioplegia is inadequate. Retrograde cannulation, however, must be performed before aortic cross clamping.
When transesophageal echocardiography (TEE) is used for purposes of left ventricular monitoring, Doppler interrogation of the heart is an accurate method for the detection and quantification of regurgitation jets.
The purpose of this study is to determine whether there is a relationship between the calculated severity of AR as determined by TEE, the adequacy of antegrade cardioplegia, and the need for retrograde cardioplegia.
Material and Methods
Surgical Technique and Transesophageal Echocardiography Monitoring
In our institution, if no contraindications exist, cardiac surgical patients routinely undergo intraoperative TEE monitoring. The study group consisted of patients undergoing coronary artery bypass grafting only and those undergoing valvular operation were excluded. After the induction of general anesthesia, a 5.0-MHz monoplane transesophageal echocardiographic probe (Hewlett Packard, Andover, MA) was inserted under direct visualization. As part of the cardiac evaluation, pulse wave and color flow Doppler interrogation of the left ventricular outflow tract (LVOT) was performed to assess aortic valve competency.
Aortic regurgitation was defined as a turbulent diastolic jet in the LVOT. When AR was noted by TEE, the surgeon was made aware only of its presence, but not its severity. In all such patients, a retrograde cardioplegia cannula (Retroplegia, Research Medical Co, Salt Lake City, UT) was placed. Antegrade administration of cardioplegia was always first attempted by way of the aortic root at 4°C delivered at a pressure of 200 mm Hg as monitored at the cardiopulmonary bypass roller pump head. Aortic root pressure, degree of left ventricular (LV) distention, and rate of fall of septal temperature were assessed by the surgeon. Retrograde cardioplegia was administered only in those patients where (1) aortic root pressure was maintained inadequately as judged by clinical evaluation of aortic root filling and distention; (2) significant LV distention occurred as assessed by the degree and rapidity of LV filling; and (3) septal hypothermia was difficult to achieve or inadequate (target less than 15°C in less than 3 minutes with less than 1 L of cardioplegia solution). The surgeon was blinded to the severity of AR at the time of evaluation of cardioplegia administration.
Quantification of the regurgitation severity was performed after operation by calculating the jet width to LVOT diameter ratio [13]. The maximal AR jet was visualized in the standard five-chamber view of the LVOT [14] and the width of the jet and the maximal LVOT diameter were measured and averaged for at least two cardiac cycles (Fig 1
) [15]. The echocardiographer was unaware of the method of cardioplegia administration.
|
2 or Fisher's exact test if the cell sizes were small. Results
Eighty-four consecutive patients were studied. Eighteen (21%) were noted to have AR by intraoperative TEE. There were 38 patients with a history of hypertension among the 66 patients with no AR and 12 of 18 patients with AR had hypertension (p = not significant [NS]). The average age of the patient with AR was 65.6 ± 9.4 years. For those without AR, the average age was 62.5 ± 9.1 years (p = NS). There were no significant differences in sex.
The observed AR had a calculated jet width to LVOT diameter ratio ranging from 0.10 to 0.47, with an average of 0.28 ± 0.11 (95% CI 0.24 to 0.34). Ten of the 18 (56%) patients with AR received retrograde cardioplegia. In patients who did not require retrograde cardioplegia the ratio was 0.19 ± 0.06 (95% CI 0.14 to 0.24). In patients who did require retrograde cardioplegia, however, the ratio was 0.36 ± 0.06 (95% CI 0.32 to 0.41) (p < 0.005) (Fig 2).
|
A history of hypertension was present in 7 of the 10 patients requiring retrograde cardioplegia and in 5 of 8 patients where antegrade was adequate (p = NS).
Comment
The presence of AR is important to the cardiac surgeon. We found this lesion to be present in 21% of patients without clinically suspected AR undergoing coronary artery bypass grafting. There was no association noted with age, sex, or history of hypertension.
If TEE can predict inadequate antegrade cardioplegia, a retrograde cannula can be placed early during operation. This would facilitate retrograde cardioplegia administration, thus avoiding myocardial damage attributable to suboptimal myocardial preservation. Conversely, if TEE can predict adequate antegrade cardioplegia, the added effort and morbidity of retrograde cannula placement could be reserved for only those patients likely to benefit from retrograde cardioplegia.
Our results show that the severity of AR as assessed by TEE interrogation of the LVOT is associated with inadequate cardioplegia administration. In 10 of 11 patients where the jet widthAu: jet width or jet diameter? see fig 2
to LVOT diameter ratio was 0.25 or greater by TEE, retrograde cardioplegia was necessary. Antegrade cardioplegia administration was satisfactory for ratios less than 0.25.
Of the factors used to evaluate the adequacy of antegrade cardioplegia, only the ability to achieve septal cooling may be influenced by entities other than AR. The development of LV distention and inability to maintain aortic root pressure as markers of inadequate antegrade cardioplegia are solely determined by AR. In severe coronary artery disease, delivery of cardioplegia to areas of the myocardium supplied by stenotic vessels is at best nonhomogeneous and at worst, inadequate [16, 17]. Thus, left main or LAD disease may lead to inadequate septal cooling in the absence of AR. We did not find any difference in the distribution of LAD stenosis or occlusion or left main disease between the groups of patients who did or did not require retrograde cardioplegia.
A limitation of this study is that LV distention during antegrade cardioplegia administration was based on a subjective assessment by the surgeon. In addition, no set criteria are available to determine when aortic root pressure is poorly maintained. The surgeon, however, was unaware of the calculated severity of AR and therefore, this information could not have biased the clinical assessment of the adequacy of antegrade cardioplegia.
Another possible limitation of the study is the lack of data on blood pressure, heart rate, and LV pressure at the time of AR imaging. Because the calculation of severity of regurgitation may be affected by these factors [18, 19], our measurements may be applicable only in a limited range of hemodynamic states. The influence of these variables needs further study.
Patients with a history of hypertension may be more prone to the development of AR possibly attributable to stretching of the aortic root or annulus [20]. Nevertheless, we did not find this or other clinical variables to be predictors for the presence of AR or need for retrograde cardioplegia.
In summary, TEE can provide an assessment of AR which may be useful in determining operative strategy for myocardial preservation in coronary bypass procedures. Transesophageal echocardiography imaging may identify a significant number of patients at risk of perioperative myocardial dysfunction on the basis of inadequate myocardial preservation and further prospective studies should be considered.
Acknowledgments
Supported in part by the Margaret S. Winthrop Fund.
We thank Richard M. Steingart, MD, for his critical review of this work.
Footnotes
Presented at the Sixth International Symposium on Echocardiography in Cardiac Surgery, Washington, DC, Nov 9–11, 1994. Received the Doppler Award for best paper presented at the symposium.
Address reprint requests to Dr Zeldis, Division of Cardiology, Winthrop-University Hospital, 259 First St, Mineola, NY 11501.
References
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 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 |
