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Ann Thorac Surg 1999;68:1705-1712
© 1999 The Society of Thoracic Surgeons
a Escorts Heart Institute and Research Centre, New Delhi, India
Address reprint requests to Dr. Iyer, Department of Pediatric and Congenital Heart Surgery, Escorts Heart Institute and Research Centre, Okhla Rd, New Delhi 110025, India
e-mail: iyerks{at}hotmail.com
Presented at the Thirty-fifth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 25–27, 1999.
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Abstract |
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Methods. Since October 1995, 166 patients of ToF underwent transatrial repair. Postbypass residual RVOTO was assessed by surgeon’s subjective impression, direct intracardiac pressure measurements, and intraoperative echocardiography (IOE). RVOTO was labeled "significant" whenever it exceeded a gradient of 40 mm Hg on IOE or right ventricular to left ventricular pressure ratio (pRV/LV) exceeded 0.85. Further, on IOE, significant RVOTO was defined "fixed", if there was no change in RVOT dimensions during the cardiac cycle, along with the presence of anatomic substrate for obstruction, and "dynamic" if RVOT dimensions increased appreciably in diastole. Postoperative course and follow-up echocardiograms of all patients were analyzed.
Results. Significant RVOTO was detected in 58 (35%) patients (mean gradient 54 mm Hg). Seven (12%) of them with fixed obstruction (mean 46 mm Hg) underwent immediate surgical revision, while the remaining 51 patients with mean gradient of 78 mm Hg (including 10 patients with pRV/LV ratio of 
1.0) with dynamic obstruction did not undergo revision. There were six (3.6%) early deaths. Operative mortality and postoperative morbidity were not related to higher residual gradients, although the first 15 such patients had longer intensive care stay and inotropic support, in which this was done electively. On follow-up (mean 18.5 months), outflow gradients declined sharply (mean 16 mm Hg) irrespective of the severity of intraoperative gradients (p < 0.001). There were no reoperations or late deaths.
Conclusions. This study shows that: 1) existing parameters for immediate revision of residual RVOTO possibly need to be reviewed; 2) intraoperative echocardiography helps in differentiating "fixed" from "dynamic" obstruction and helps obviate needless revisions; and 3) dynamic RVOT gradients decline significantly irrespective of their severity after transatrial repair of ToF.
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Introduction |
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Many published reports, including ours, attest to the fact that a high intraoperative RVOT gradient falls significantly in the majority of the patients [7, 10–12]. However, it does remain high or becomes higher in some patients, necessitating reoperation despite the fact that similar surgical techniques and operative guidelines have been used [11, 13, 14]. It is possible that in these cases the amount of resection of right ventricular outflow tract muscle could have been inadequate, but there would have been no way to confirm this impression.
The recent introduction of intraoperative echo may obviate this disadvantage, and in patients with high residual gradients may actively disclose the cause of obstruction and help the surgeon to better assess the adequacy of anatomic repair and intervene appropriately [15, 16].
This current study was therefore conducted at the Escorts Heart Institute and Research Centre, New Delhi, India, with the objective of reviewing existing guidelines for the management of significant residual RVOTO, and to elucidate findings on routine intraoperative echocardiography that would differentiate those patients requiring immediate revision from those who do not.
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Material and methods |
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Seven patients had had previous repair of ToF performed at other centers and now required complete revision for significant residual defects. Four of them had required placement of transannular patch at the time of first correction. Two of these 4 with transannular correction required pulmonary valve replacement (1 had developed severe left pulmonary artery origin stenosis) and 4 (including these 2) also required RVOT pseudoaneurysmorraphy.
One patient of ToF with pulmonary atresia had a pulmonary circulation dependent on a single coronary artery, which terminated as a coronary to main pulmonary artery (MPA) fistula, after giving off the myocardial branches. He required closure of fistula and right ventricle (RV) to pulmonary artery (PA) valve conduit along with repair of ToF. A 3-year-old girl, who had ToF and infective endocarditis unresponsive to medical treatment, was found to have large vegetations obstructing the MPA, which were excised successfully before correction. Other associated defects are detailed in Table 1.
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First, right atrium (RA) was opened and anatomy was discerned. Infundibular resection was then performed transatrially in all the cases and, if required, it was completed through a pulmonary arteriotomy in patients who required a pulmonary valvotomy (n = 45). Adequacy of RVOTO resection was determined by sizing the RVOT with Hegar dilators to appropriate diameters based on Rowlatt’s table for minimal acceptable pulmonary artery size [17]. If the annulus was found to be inadequate, the pulmonary arteriotomy was extended into the RVOT for a short distance (n = 74). The VSD was closed with a Dacron patch using a combination of interrupted pledgetted and continuous sutures transatrially in all the cases. All atrial communications were closed. In 6 of 7 patients with pulmonary atresia, right ventricle to pulmonary continuity was established by mobilizing the stump of MPA and anastomosing it to the right ventriculotomy. The anterior wall was then reconstructed with glutaraldehyde-treated autologous pericardial patch with a monocusp pericardial valve. In the seventh patient, a RV to PA valved conduit was required due to a dilated tortuous coronary artery running across RVOT-PA junction. In 3 patients of ToF with absent pulmonary syndrome, a monocusp valve was fashioned from the anterior pulmonary artery wall. Direct intracardiac pressures were taken after discontinuation of CPB and stabilization of hemodynamics. Other procedures performed for associated lesions are detailed in Table 1.
Introperative echocardiography (IOE)
Pre-CPB IOE was performed only in cases where preoperative transthoracic echocardiograms or angiograms were deficient. Post-CPB IOE was performed in all patients. Ninety patients underwent transoesophageal echocardiography (TEE), while in 70 patients, epicardial echocardiography was performed. Three patients underwent epicardial echocardiography with a pediatric TEE probe because of inadequate visualization of the RVOT with the conventional transthoracic probe placed epicardially. In another 3 patients, where the heart was displaced leftwards, IOE was performed transthoracically after removing the sternal retractor and filling the pericardial cavity with normal saline. Generally speaking, the decision to choose one of the modes of IOE mostly depended upon the size of the patient and availability of the probe at that time. Additionally, epicardial echo gave more reliable visualization of the RVOT in comparison with TEE, especially in patients less than 15 kg in weight. All patients were imaged with an 2500 Sonos echocardiography machine (Hewlett-Packard Co, Andover, MA). For TEE, a pediatric biplane transducer probe was used in patients less than 15 kg body weight, while in patients with body weight more than 15 kg, an adult multiplane probe was used. For epicardial echocardiography, a 7.5/5.5-MHz transducer probe was used.
The following parameters were evaluated and graded in the manner described by Stumper, Papagiannis, and their colleagues [18, 19] with some modifications: (1) presence of any residual VSD; (2) presence of residual RVOT obstruction; (3) right and left ventricular function; and (4) presence of tricuspid regurgitation. A residual VSD was graded as: (1) small (color flow width at the spectrum < 3 mm; well-defined turbulence into the right ventricular cavity); (2) moderate (color flow jet width 3 to 5 mm; substantial RV turbulence); and (3) large (color flow jet width > 5 mm; turbulence in RV and pulmonary artery). When two or more residual defects were detected in the same patient, they were counted as one and graded according to the largest one to avoid confusion. Residual RVOT obstruction was graded as: (1) none: no anatomic narrowing, minimal turbulence by color flow; RVOT gradient less than 20 mm Hg; (2) mild to moderate: anatomic narrowing, turbulent flow; RVOT gradient less than 40 mm Hg; and (3) severe or significant; discrete narrowing; severe turbulence; gradient more than 40 mm Hg.
The RVOTO was considered "fixed" if it appeared to be discrete and did not change in dimensions during the cardiac cycle. The presence of localized muscle band or increased echogenicity suggestive of residual fibrous tissue also favored a "fixed" obstruction. The RVOTO was considered to be "dynamic" variety if it appeared to be diffuse and if there was a definite increase in dimensions during diastole.
Ventricular dysfunction
Ventricular dysfunction was graded visually as none, mild to moderate, or severe. The presence of RV dysfunction prompted exclusion of a "fixed" RVOTO.
Postoperative course
All patients remained in the intensive care unit until ventilatory and inotropic support was withdrawn. Postoperative parameters recorded and analyzed for all patients were: intensive care unit and hospital stays; duration of inotrope infusion and mechanical ventilation; presence of pleural effusions or ascites; and any other complication including arrhythmias and reexplorations. Postoperative duration of decongestive therapy was noted in all the patients.
Transthoracic echocardiograms (TThE)
TThE were performed at discharge (predischarge) and subsequently at 3-month follow-up interval in those with significant gradients, and their findings were compared with those of immediate post-CPB study. In the others, it was performed routinely between 6 and 12 months of follow-up.
Statistical analysis
Statistical analysis of continuous variables were analyzed with two-sample t test, if the variances of the groups were equal. Otherwise, the Mann-Whitney U test was used. Paired t test was used for comparing the paired observations.
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Results |
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Post-CPB echocardiography was performed in all cases. In 58 (35%) patients, RVOT gradient was found to be equal to or more than 40 mm Hg on IOE. Seven (12%) of them were revised for fixed gradient. The cause of RVOTO in these patients was residual hypertrophied trabeculae (6 patients) and/or restrictive RVOT-PA junction despite a transannular patch (5 patients). Revision was performed in the form of additional infundibular resection (6 patient), and extension or addition of transannular pericardial patch (5 patients). Postrevision gradients came down to a mean of 48 ± 21.2 mm Hg from a prerevision mean of 78 ± 17.7 mm Hg. However, 2 patients still had a postrevision IOE gradient of greater than 50 mm Hg, but now it was dynamic, and so was considered acceptable.
In the remaining 51 patients with RVOT gradient of more than 40 mm Hg, obstruction was found to be dynamic on IOE. All but 1 left the operating room without any revision. One patient with absent pulmonary valve required immediate revision for severe pulmonary regurgitation (PR) due to noncoaptation of monocusp valve placed at RVOT-PA junction. Modification and plication of overlying pericardial patch resulted in significant reduction of PR. Direct intraoperative pressure gradient was significantly correlated with IOE residual gradient (Pearson correlation = 0.9). There were 10 patients with a small residual VSD, none of whom required revision.
Immediate postoperative complications are described in Table 2. There were no complications related to IOE. There were six (3.6%) early deaths. One patient died of massive cerebrovascular hemorrhage on zero postoperative day. She had a preoperative hematocrit of 65%. The second patient died of septicemia on the 20th postoperative day. This particular patient was 3.5 months old and had ToF with pulmonary atresia and bifurcation stenosis. Postoperatively, he had a severe cyanotic spell and cardiac arrest in the ward. He was resuscitated and taken for emergency correction due to persistent hypercyanosis. The third patient died of multiorgan failure after fulminant hepatitis 7 days after the surgery. The fourth patient had obtundation of the sensorium presumably after intraoperative global cerebral ischemia. She had a stable cardiac status but died on the 30th postoperative day after aspiration into the lung during feeding. The fifth patient died of unexplained resistant malignant ventricular arrhythmias, which she developed on the third postoperative day. She had been extubated on the first postoperative day and was hemodynamically stable. The last patient had required intraoperative revision and died of persistent intractable biventricular failure on the seventh postoperative day.
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When patients who had higher intraoperative gradients (whether fixed or dynamic) were compared with those without higher gradient, their periods of mechanical ventilation and decongestive therapy were similar (Pearson correlation = 0.5), but ICU stay and inotrope requirement were marginally higher (Table 3). In part, this was due to the fact that the initial patients with high residual gradients were electively observed in the ICU for a longer duration for fear of complications.
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RVOT obstruction
There was significant fall in RVOT gradients on predischarge echocardiograms (54 ± 15.4 to 31.5 ± 14.7 mm Hg, p < 0.005). A further significant fall in gradients was noticed at a mean follow-up of 18.5 ± 8.3 months (21 ± 8.8 mm Hg, p < 0.05). The fall was sharper in patients with gradients greater than 40 mm Hg as compared with patients with gradients less than 40 mm Hg (Table 5). Decongestive medications were tapered off routinely over 8 to 12 weeks in all the patients, irrespective of their IOE gradients. Furthermore, there was a significant fall in IOE gradients of fixed and dynamic RVOTO on predischarge and follow-up echocardiograms (Table 5)
One patient on follow-up echocardiogram was found to have developed significant LPA and RPA origin restenosis with a total RVOT gradient of 50 mm Hg. He had required a transannular pericardial patch extending across LPA origin. His intraoperative and predischarge echocardiogram showed relatively mild LPA stenosis with a total RVOT gradient of 36. He is awaiting reintervention for branch PA stenosis. There were 9 patients (7 transannular) with asymptomatic moderate PR. Four of these patients were those operated for TOF with absent pulmonary valve syndrome, and in whom no monocusp valve was used.
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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In ToF, the RVOT is formed inferolaterally by the aortic root and infundibular septum and superiolaterally by thick muscular free wall of RV, with numerous fibro muscular bands tethering the infundibular septum. After transatrial correction, the RVOT becomes elliptical and tends to clamp itself between the infundibular septum and thinned-out free wall of the RVOT in systole, while in diastole, the free wall relaxes and moves away to reveal the true lumen of the RVOT. The hypercontractile state, which exists in the immediate postbypass period, usually as a result of inotropes and hypovolemia, tends to exaggerate this systolic clamping of the RVOT. Significant systolic gradients may thus be generated in the postbypass period even in the presence of an adequate RVOT. This can be well documented by IOE, and we labeled such gradients as "dynamic" (Figs 1A, 1B). In the course of time, remodeling of the RVOT occurs. The free wall of the RV then tends to become stretched out and less hypercontractile, and hence the RVOT gradients fall. In transventricular repair, the ellipsoidal RVOT is broken at the free wall by the noncontractile patch, which does not contract in systole. Thus, systolic gradients in this form of repair are not expected. However, over the course of time, remodeling of the RVOT tends to produce redundancy of the outflow patch, resulting in progressive increase in pulmonary regurgitation (PR) and RV dysfunction. This difference in the two approaches underscores the superiority of the transatrial over the transventricular approach. Thus, the transatrial approach strikes a fine balance between adequate relief of RVOTO and preservation of RV function.
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To circumvent this problem, we feel a combination of parameters should be used, which includes: (1) surgeons impression of degree of resection, including the ability to pass an adequate sized Hegar dilator across the RVOT; (2) post-op RV/LV pressure ratio; (3) the impression on intraoperative echocardiography as to whether the increased gradients are as a result of a "fixed" or "dynamic" obstruction; and (4) hemodynamic stability. Using these criterion, our experience showed that although 58 (35%) of the patients had significant residual RVOT obstruction after transatrial repair, 51 (88%) of these did not require revision because the nature of obstruction was judged to be of "dynamic" variety (even though the RV/LV ratio was greater than 1.0 in 10 patients).
All these patients fared well in the immediate postoperative period, and on follow-up echocardiography, their residual outflow gradients decreased significantly well below 25 mm Hg. This is in agreement with findings of other authors [7, 10–12, 23]. In the 7 patients who underwent surgical revision, their postoperative outflow gradients reduced to below 20 mm Hg with good RV function on follow-up TThEs.
Thus, the presence of significant dynamic residual gradients at the end of surgery was not found to increase postoperative morbidity or mortality in our series as long as they were of dynamic nature, further emphasizing that these gradients may be safely accepted without subjecting the patient to unnecessary surgical revision.
Of the 6 patients who died, only 1 had a cardiac death resulting from biventricular failure. He had had a revision of the outflow patch on the table, and the residual gradient in the postoperative period was only 30 mm Hg. Four deaths were related to noncardiac causes. Nonetheless, none of them had an RVOT gradient in excess of 40 mm Hg on IOE. Likewise, a comparison of postmorbidity patterns did not reveal any significant differences between those with gradients less than 40 and those over 40 mm Hg.
Besides outflow gradients and nature of obstruction, the RV function also needs to be taken into account [24]. Patients with significant post-CPB RV dysfunction appeared to be more likely to have "fixed" rather than "dynamic" obstruction.
Thus, we propose that where significant outflow obstruction is found by IOE or by direct pressure measurement, surgical revision is indicated only in those patients who have "fixed" obstruction based on IOE. It should be stressed that RVOT turbulence by itself (cause by dynamic obstruction) is not necessarily an indication of significant residual obstruction and should not encourage revision. It was common for such patients with turbulent RV flow or dynamic obstruction to have acceptable right to left ventricular function and to do well over the immediate postoperative and intermediate follow-up period. In the early postoperative period, it was found that early morbidity was significantly higher in patients who required a transannular patch at the RVOT (p 
0.05 to 0.005). ICU and hospital stays, duration of dopamine infusion, frequency of pleural and peritoneal effusions, and duration of decongestive medicines were all significantly higher in this particular group of patients in comparison with patients who either underwent transatrial with or without transpulmonary correction or who had had higher IOE RVOT gradients.
We conclude that in patients who undergo transatrial repair of ToF, two forms of RVOT obstruction can be identified postoperatively by intraoperative echocardiography. Only patients with "fixed" form of obstruction need immediate surgical revision. Higher gradient with "dynamic" form of obstruction need not be surgically revised, and this does not increase surgical morbidity in the immediate postoperative period. On follow-up, the high gradients normalized in all such cases. Thus, intraoperative echocardiography correctly identifies the anatomic substrate for residual gradients and helps obviate unnecessary surgical revision in patients of ToF undergoing transatrial repair.
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Acknowledgments |
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References |
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This article has been cited by other articles:
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  B. Airan, S. K. Choudhary, H. V. J. Kumar, S. Talwar, J. Dhareshwar, R. Juneja, S. S. Kothari, A. Saxena, and P. Venugopal Total transatrial correction of tetralogy of fallot: no outflow patch technique. Ann. Thorac. Surg., October 1, 2006; 82(4): 1316 - 1321. [Abstract] [Full Text] [PDF]
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