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Ann Thorac Surg 1995;60:678-680
© 1995 The Society of Thoracic Surgeons
Divisions of Pediatric Cardiology and Pediatric Cardiothoracic Surgery, Duke University Medical Center, Durham, North Carolina
Accepted for publication March 4, 1995.
Abstract
Background. Intraoperative transesophageal echocardiography provides the surgical team with important guidance during operations for congenital heart disease. Doppler echocardiography adds hemodynamic information to that provided by two-dimensional imaging. Here we describe intraoperative pulmonary vein Doppler echocardiography after operation involving the left atrium.
Methods. Intraoperative two-dimensional and pulsed-wave Doppler echocardiography of pulmonary veins were performed after surgical repair of anomalous pulmonary venous return in 4 patients.
Results. In 3 patients, intraoperative pulmonary vein Doppler findings were suggestive of obstruction. The surgical repair was thought to be excellent, and there was no obstruction apparent anatomically or clinically. No further intervention was performed, and all patients recovered uneventfully. No pulmonary venous obstruction was noted on follow-up two-dimensional echocardiography, and follow-up pulmonary vein Doppler echocardiography showed the expected pattern.
Conclusions. An obstructive pattern in the pulmonary vein Doppler was seen in 3 of 4 patients studied immediately after repair of anomalous pulmonary venous return. No obstruction, however, was manifest then or subsequently. The abnormal Doppler pattern, thus, is not indicative of pulmonary venous obstruction. We propose that acute postoperative changes in left atrial volume and compliance and acute postoperative tissue changes in the left atrium explain the abnormal pulmonary vein Doppler patterns observed.
Intraoperative transesophageal echocardiography (TEE) has become important in surgery for congenital heart disease because it provides the surgical team with an assessment of the adequacy of the repair in regard to the anatomic correction as well as the postoperative hemodynamics. Pulmonary venous flow patterns as assessed by Doppler echocardiography allow assessment of left heart hemodynamics and have been applied using intraoperative TEE [1]. Because pulmonary venous flow reflects left atrial (LA) hemodynamics, intraoperative assessment of pulmonary venous flow patterns using pulmonary venous Doppler echocardiography after left atrial operations may offer the operative team an immediate assessment of the adequacy of the repair.
Since June 1993, we have performed intraoperative TEE on 7 patients during operation for total anomalous pulmonary venous connection (TAPVC) or cor triatriatum. Four of these patients had intraoperative assessment of pulmonary venous flow by Doppler, and in 3, abnormal Doppler flow patterns were observed. These patterns were suggestive of obstruction to pulmonary venous drainage, but there was no clinical or two-dimensional echocardiographic evidence of such obstruction either intraoperatively or postoperatively. The pulmonary venous flow pattern returned to the expected pattern postoperatively in all 3 patients. We present the cases of these 3 patients and offer an explanation for the observed phenomenon.
Patients and Methods
Patient 1
The first patient was seen at 14 months of age with congestive heart failure. Evaluation by echocardiography and cardiac catheterization revealed cor triatriatum sinister with severe obstruction to pulmonary venous return and partial anomalous pulmonary venous connection with the left pulmonary veins draining to the superior vena cava by a levoatriocardinal vein to the innominate vein. At operation, the levoatriocardinal vein was ligated, and the LA membrane was resected.
After the repair and the discontinuation of cardiopulmonary bypass, TEE showed wide patency from the pulmonary veins across the area previously occupied by the membrane. Though there was no hemodynamic evidence of pulmonary venous obstruction, the spectral Doppler tracing showed a continuous gradient at this site (Fig 1
). The patient had an uneventful postoperative recovery and had no clinical evidence of pulmonary venous obstruction. Follow-up echocardiography at 4 weeks postoperatively showed the expected normal spectral Doppler tracing at the same area (see Fig 1).
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After the repair and the discontinuation of cardiopulmonary bypass, TEE showed wide patency of the anastomosis of the pulmonary venous confluence to the left atrium. This region had a diameter of 8.8 mm and an area of 2.3 cm2/m2, assuming the region had an elliptic shape; such a venous–atrial anastomosis area has been associated with long-term obstruction-free survival [2]. The spectral Doppler tracing obtained in this region, however, demonstrated abnormal monophasic flow. This was suggestive of obstruction to pulmonary venous drainage, but there were no clinical signs of obstruction. The patient had an uneventful postoperative recovery and had no signs of pulmonary venous obstruction. Follow-up echocardiography at 1 week postoperatively showed the expected normal pulmonary venous flow pattern.
Patient 3
The third patient was seen at 3 weeks of age with pulmonary edema and in shock. After resuscitation, a diagnosis of TAPVR (infradiaphragmatic) with obstruction at the level of the hepatic veins was made, and the patient underwent urgent repair. After the repair and the discontinuation of cardiopulmonary bypass, TEE showed wide patency of the anastomosis of the pulmonary venous confluence to the left atrium. The spectral Doppler tracing of the pulmonary veins, however, revealed a continuous gradient (Fig 2). This again was suggestive of obstruction to pulmonary venous drainage, but there were no clinical signs of obstruction.
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). Both intraoperative and postoperative pulmonary venous Doppler patterns show the effect of respiration on the pattern of pulmonary venous flow. Although the velocity of flow is affected by the respiratory cycle, the pattern of flow is not. Thus the intraoperative findings were not confounded by mechanical ventilation or by spontaneous respiration. Comment
All 3 cases presented a discrepancy between pulmonary venous Doppler findings and clinical courses of the patients. The intraoperative pulmonary venous Doppler findings were suggestive of pulmonary venous obstruction, but no such obstruction was manifest clinically. This apparent paradox may be explained by the determinants of pulmonary venous flow.
Phasic pulmonary venous forward flow occurs during ventricular systole and ventricular diastole, and pulmonary venous flow reversal often occurs during atrial systole. The systolic flow is itself often biphasic; thus, four phases of pulmonary venous flow have been described and are demonstrated in Figures 1 and 2. All four phases are not consistently demonstrated in clinical studies, but biphasic (systolic and diastolic) flow is always seen in sinus rhythm, and systolic flow is most often the dominant flow [3].
Pulmonary venous systolic flow occurs as a result of LA relaxation (early phase) and the downward movement of the mitral valve annulus during ventricular systole (late phase) [4]. Left atrial relaxation depends on prior LA contraction and is influenced by LA pressure and compliance; thus, the primary determinants of this systolic flow are LA function (contraction and subsequent relaxation), LA pressure and compliance, and left ventricular systolic function. In contrast, during diastole, the left atrium acts as a simple conduit between the pulmonary veins and the left ventricle. Thus, the primary determinants of pulmonary venous diastolic flow are left ventricular compliance and relaxation [5].
Changes in LA function, pressure, and compliance, then, are reflected in altered pulmonary venous systolic flow. It is conceivable that surgical procedures involving suture lines or baffles in the left atrium or adding increased volume to a previously small left atrium would, by increasing LA pressure and decreasing LA compliance, alter pulmonary venous systolic flow. This has indeed been demonstrated after a TAPVR operation and after an atrial switch operation for transposition of the great arteries. After the latter, the proportion of systolic to diastolic pulmonary venous flow is decreased by atrial baffling and further decreased if pericardium and not native atrial tissue is used in constructing the baffle [6]. After TAPVR repair, the normal systolic predominance of pulmonary venous flow is replaced with a predominance of flow in diastole [7]. This phenomenon was demonstrated in our patients in the follow-up echocardiograms.
It is also conceivable that the acute addition of volume to a poorly compliant left atrium exacerbated by acute postoperative tissue changes that occur after TAPVR repair might result in a more precipitous rise in LA pressure than would similar chronic changes. Indeed, it has been suggested that acute and chronic changes in LA hemodynamics may have different effects on pulmonary venous flow [8].
We hypothesize that such acute intraoperative changes may have accounted for the abnormal pulmonary venous Doppler patterns we report. This hypothesis is supported by the fact that the patterns returned to the expected patterns shortly postoperatively. These findings will require confirmation, as we believe this is the first report of intraoperative pulmonary venous Doppler after LA operations.
The case reports presented here should serve as a caution to the surgeon, echocardiographer, and anesthesiologist involved in the interpretation of intraoperative echocardiograms. In these patients, though the pulmonary venous Doppler echocardiography suggested possible obstruction, the anastomoses were widely patent by two-dimensional imaging and the patients were doing well hemodynamically. No further intervention was performed, and the patients recovered uneventfully. As was done in these patients, the surgical team must integrate clinical information with Doppler echocardiographic information in the interpretation of intraoperative TEE studies.
Footnotes
Presented at the Sixth International Symposium on Echocardiography in Cardiac Surgery, Washington, DC, Nov 9-11, 1994.
Address reprint requests to Dr Li, Duke University Medical Center, PO Box 31172, Durham, NC 27710.
References
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