Timing and Technique of Pulmonary Valve Replacement in the Patient With Tetralogy of Fallot

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1 Timing and Technique of Pulmonary Valve Replacement in the Patient With Tetralogy of Fallot James S. Tweddell, a,b Pippa Simpson, c Shun-Hwa Li, c Jennifer Dunham-Ingle, b Peter J. Bartz, b,d Michael G. Earing, b,d and Andrew N. Pelech b,d Residual right ventricular (RV) outflow tract pathology is universal among patients with repaired tetralogy of Fallot, and pulmonary regurgitation (PR) is also commonly present. Although tolerated in early life, by the second decade of life PR is associated with an increased risk of death because of ventricular arrhythmias. Pulmonary valve replacement (PVR) is a safe procedure that will eliminate PR, but timing and indications are evolving. Patients with arrhythmias or prolonged QRS duration are candidates for PVR. Patients with symptomatic exercise intolerance are likely to have improvement in symptoms and quality of life and should be offered PVR. Cardiac magnetic resonance has become an essential component of the management of the patient with tetralogy of Fallot with PR, and has identified the potential for and limitations of RV remodeling following PVR. Among patients with severe RV enlargement, particularly those with diminished RV or left ventricular function, there is an increased risk of adverse events and even asymptomatic patients with severe PR should be considered for PVR. Valve replacement is accomplished with homografts or heterografts, either stented bioprosthetic valves or valved conduits. In a retrospective analysis of the Children s Hospital of Wisconsin experience with PVR, there was no difference in survival or freedom from reintervention between heterografts and homografts. Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann 15: Elsevier Inc. All rights reserved. Introduction Fifty years have passed since the first repair of tetralogy of Fallot (TOF). By definition TOF includes hypoplasia of the right ventricular (RV) outflow tract (OT). As result, the individual with repaired TOF nearly always has residual RVOT pathology, most commonly pulmonary regurgitation (PR). Young patients appear to tolerate PR well, but as they reach adulthood the hemodynamic burden of chronic PR begins to have an impact on exercise tolerance and survival. Long-term studies of outcome of patients with TOF identify a change in the survival curve in the second decade following repair (Fig. 1). 1 The most common cause of mortality is sudden death; PR is strongly associated with late adverse events (Fig. 2). 2 a Department of Surgery, Division of Cardiothoracic Surgery, Medical College of Wisconsin, Milwaukee, WI. b Herma Heart Center, Children s Hospital of Wisconsin, Milwaukee, WI. c Children s Research Institute, Medical College of Wisconsin, Milwaukee, WI. d Department of Pediatrics, Section of Pediatric Cardiology, Medical College of Wisconsin, Milwaukee, WI. Address correspondence to James S. Tweddell, MD, Cardiothoracic Surgery, Children s Hospital of Wisconsin, 9000 West Wisconsin Ave, Milwaukee, WI 53226; jtweddell@chw.org. The pathophysiology by which chronic PR results in RV dysfunction may be analogous to the natural history of aortic regurgitation. 3 Early on, the RV is able to compensate for the increased regurgitant volume associated with severe PR. This compensation is characterized by an increase in end-diastolic volume with ventricular hypertrophy, resulting in maintenance of low RV filling pressures. Over time, however, the chronic volume load continues and the mass-to-volume ratio decreases, leading to increased filling pressures, and decline in the myocardial function. Presumably this process is at first reversible, but at some point irreversible ventricular dysfunction with fibrosis occurs. Compared with the left ventricle (LV) in the setting of chronic aortic valve regurgitation, the time course to development of RV dysfunction is prolonged. This is related to the different load conditions and coronary flow dynamics of the RV compared with the LV. Timing of Pulmonary Valve Replacement Surgical intervention for any pathology is considered when the benefits outweigh the risks and can favorably alter the natural history. Indications for pulmonary valve replacement /12/$-see front matter 2012 Elsevier Inc. All rights reserved. doi: /j.pcsu

2 28 J.S. Tweddell et al Figure 1 Long-term survival curve of 490 early survivors of repair of TOF. The curve shows two different phases that are distinct. The early, low-risk phase lasts 25 years; thereafter, the risk increases significantly. Mortality risk (r) per year, as a linearized number, is calculated for each phase. (Reprinted with permission. 1 ) Figure 2 Survival curve showing freedom from sudden death after repair of TOF comparing patients who had a transannular patch for RVOT reconstruction with those who did not during tetralogy repair. The risk of sudden death was significantly higher among patients with a transannular patch. Patients with a transannular patch would be anticipated to have significant PR. (Reprinted with permission. 2 ) Figure 3 Survival curves from a case control study comparing 77 patients who underwent PVR with 77 matched patients who did not undergo PVR. Survival was not improved among patients who underwent PVR. (Reprinted with permission. 4 ) (PVR) could potentially include objective indications such as decreased mortality, improved exercise tolerance as determined by formal exercise testing, and decreased arrhythmias. Other acceptable indications would include symptomatic relief and improved quality of life. The Impact of PVR on Mortality As stated above, sudden death is the most common cause of late death after repair of TOF. Ventricular tachycardia is the presumed mechanism of sudden death and is strongly associated with PR. The best studies evaluating the impact of PVR on mortality are retrospective case-controlled studies and do not show a clear benefit in terms of improved survival (Fig. 3). 4,5 It is likely that patients submitted to PVR were identified by clinicians as tolerating PR less well than those who did not undergo PVR. Whether these differences, apparent somehow to the physicians caring for the patients, were owing to anatomic or other individual factors not identified, and therefore not accounted for, in matched control patients are likely. Prospective randomized trials would be impractical because of the symptomatic benefit of PVR and the prolonged duration of observation (decades) necessary to identify a difference. Nevertheless, improved survival has not been a demonstrated benefit of PVR. The Impact of PVR on Symptoms and Exercise Tolerance Exercise intolerance is common among patients with repaired TOF; these individuals are frequently referred for PVR. Studies have shown a benefit in terms of NYHA classification pre- and post-pvr. 6,7 Following PVR, the majority of patients are in NYHA class I or II (Fig. 4). Patients with repaired TOF have diminished performance on formal exercise testing, but the impact of PVR is equivocal. 7-9 Eyskens and colleagues 8 evaluated 11 patients before and after PVR with formal exercise testing and demonstrated a significant improvement in anaerobic threshold. Tsang et al 9 evaluated 16 patients before and after PVR and found no improvement in maximal oxygen consumption. In a study of 71 patients, Frigiola and colleagues 7 could not demonstrate an improvement in peak oxygen consumption or anaerobic threshold; they did find an improvement in ventilatory response to carbon dioxide production at anaerobic threshold, but the importance and prognostic significance of this finding among patients with repaired TOF is as yet unclear. In total, the data suggest that patients with symptoms of exercise intolerance can anticipate improvement in symptoms following PVR, but as yet consistent improvement in formal exercise testing parameters have not been demonstrated. The Impact of PVR on Electrophysiologic End-Points The most common cause of death late after repair of TOF is sudden death, presumably caused by ventricular arrhythmias. Efforts have been made to identify electrophysiologic risk factors

3 Pulmonary valve replacement in the patient with TOF 29 Figure 4 NYHA functional class before and at last follow-up in patients undergoing PVR after TOF repair. (Reprinted with permission. 6 ) that would predict ventricular tachycardia and guide management strategies, including PVR. Prolonged QRS duration has been associated with sudden death and ventricular tachycardia In general, PVR results in a modest reduction of QRS duration. 14 In a study by Van Huysduynen et al, patients underwent PVR and the average QRS duration decreased from ms to ms early (6 to 12 months). The decrease in QRS duration correlated with the decrease in RV end-diastolic volume measured by MRI. In contrast, in a study by Therrien et al, 13 there was no change in the QRS duration following PVR at a mean follow-up of 4.7 years. PVR, however, did appear to have a stabilizing effect as the QRS duration of the control group made up of TOF patients who did not have PVR continued to prolong over a similar follow-up period. The more important question is whether PVR has an impact on the prevalence of arrhythmias. In a study from the group from Toronto, the presence of arrhythmias before PVR did not impact survival. 5,16 Among patients with supraventricular tachycardia, the addition of an arrhythmia procedure did result in improved freedom from arrhythmias among patients undergoing PVR. While improvement in arrhythmias or shortening of the QRS in any given patient is unpredictable, the association of PR, QRS prolongation, ventricular arrhythmias, and sudden death makes these electrophysiologic abnormalities reasonable indications for PVR. Improvement in Quality of Life as an Indication for PVR There is little data using validated quality-of-life instruments to measure the impact of PVR among patients with TOF. Not surprisingly, among patients with repaired TOF, decreased ventricular function and exercise capacity are associated with diminished quality of life. 17,18 As part of a study to investigate the benefits of RVOT remodeling on RV function following PVR, Geva and colleagues 19 measured quality of life in their study of 64 patients and found improvement in the physical and mental components in adults and the physical components of children s quality-of-life measures. Although these findings have not yet been confirmed by other investigators, improved quality of life appears to be an anticipated benefit of PVR. Cardiac Magnetic Resonance Measurements as an Indication for PVR The unique shape of the RV makes it difficult to determine volume and function using echocardiography. Cardiac magnetic resonance (CMR) can be used to obtain quantitative measures of RV volume and PR and has become an indispensable tool for imaging and functional assessment of the RV among patients with TOF and other forms of congenital heart disease. Furthermore, CMR is noninvasive and does not use ionizing radiation. CMR was first applied to congenital heart disease in By 1996, it was used to measure RV volume in repaired TOF. 17,20 Vliegen and colleagues 21 showed that PR was eliminated and RV volume was reduced following PVR. However, the authors noted that the RV did always decrease to normal size. 21 In 2005, Therrien and colleagues 22 showed that once the RV end-diastolic volume (RVEDV) reached 170 ml/m 2 and the RV end-systolic volume (RVESV) reached 85 ml/m 2 that remodeling to normal size following PVR was unlikely (Fig. 5). These findings were subsequently confirmed by others. 12,14,23 In addition to volumes, CMR can also provide additional data on ejection fraction of both the RV and LV. In a cross-sectional study, Knauth et al 24 examined 88 patients with repaired TOF by CMR. Median time between TOF repair and enrollment in the study was 20.7 years, and median follow-up was 4.2 years. During this Figure 5 The impact of PVR on RV end-diastolic (A) and RV end-systolic (B) volumes as determined by CMR. Among 17 patients, baseline CMR imaging studies were performed at a mean of 10 9 months before PVR and postoperative CMR imaging at a mean of months after PVR. Whereas volumes were reduced in all 17 patients after PVR those with a preoperative RV end-diastolic volume 170 ml/m 2 had a late RV end-diastolic volume within the normal range and those with a preoperative RV end-systolic volume 85 ml/m 2 had a late RV end-systolic volume within the normal range. Dashed horizontal line represents normal volume. (Reprinted with permission. 22 )

4 30 J.S. Tweddell et al d. Prolonged QRS: 140 ms e. Tachyarrhythmias attributable to RV volume overload 3. Other hemodynamically important indications for PVR a. RVOT obstruction and/or severe branch PS b. Moderate tricuspid regurgitation c. Residual shunt with Qp/Qs 1.5 d. In addition to an operation for aortic regurgitation and/or aortic root dilatation Figure 6 In this study, 88 patients with a median time from TOF repair of 20.7 years underwent CMR and were then followed for a median time of 4.2 years. The figure shows the probability of major adverse clinical outcomes (death, sustained ventricular tachycardia, or an increase in NYHA class to grade III or IV) based on multivariate logistic regression model containing RV end-diastolic volume (RVEDV) Z-score and RV ejection fraction (RVEF). (Reprinted with permission. 24 ) time, major adverse events were identified in 18 patients, including death, ventricular tachycardia, and worsening NYHA class. Predictors of poor outcome were RV enlargement (RVEDV z-score 7), decreased LV or RV ejection fraction and QRS 180 ms (Fig. 6). CMR has become indispensable in the management of patients with repaired TOF, and routine CMR follow-up is now commonly performed among patients with repaired TOF. Important interactions between the severity of PR, LV, and RV function have been identified. The degree of PR as determined by CMR correlates with RV dysfunction. Several investigators have found strong correlations between LV and RV function among patients with repaired TOF LV dysfunction occurs in approximately 20% of patients with repaired TOF, risk factors for LV dysfunction include duration of palliation with a shunt and, most importantly, RV function. 28 Of course, LV function is an important predictor of outcome and, in the study by Knauth and colleagues mentioned above, diminished LV ejection fraction was as strong a predictor of adverse events as RV dysfunction. 24 Therefore, among patients with severe PR and diminished RV function, the addition of LV dysfunction would be an additional indication for PVR. Indications for PVR Based on the evidence outlined above, indications for PVR among patients with repaired TOF and severe PR might reasonably include the following: 1. Symptomatic patients a. Symptoms of exercise intolerance attributable to moderate to severe PR and RV volume overload b. Syncope and other tachyarrhythmias 2. Asymptomatic patients a. RV dilatation: RVESV 80 ml/m 2, RVEDV 150 ml/m 2 (Z-score 4) b. Decreased RVEF or LVEF c. RVOT aneurysm The overall clinical condition of the patient must be taken into account, especially when considering PVR for the asymptomatic patient. These indications are consistent with those put forth by other authors, as well as the AHA/ACC Task Force on Adults with Congenital Heart Disease. 29,30 Technique of PVR PVR can be accomplished with a low mortality. The Society of Thoracic Surgeons Congenital Heart Database includes 1,326 PVRs and 1,402 operations to replace a RV-to-pulmonary artery conduit over the last 4 years, with hospital mortality of 0.7% and 1.0%, respectively. 31 Cheung and colleagues 14 performed a meta-analysis of studies reporting outcome of PVR after TOF repair and summarized the outcome of 15 studies including 595 patients. The pooled early mortality was 2.1% (1.1% to 4%). Most of the risk is related to resternotomy and the preoperative status of the patient. Careful preoperative planning can minimize risk. Old operative reports should be reviewed for observations on coronary anatomy, absence of thymus, and bilateral superior caval veins that are associated with a more prominent ascending aorta. The status of the atrial septal should be noted. Did the surgeon specifically close the atrial septal defect (ASD) or was it left open? If the status of the ASD was not specifically mentioned by the previous surgeon it should assumed to be open, unless echocardiography with a Valsalva maneuver and bubble study demonstrate that there is no communication. Preoperative imaging studies should be performed to confirm the coronary artery anatomy. In addition, the preoperative studies should be evaluated specifically to determine the risk of resternotomy. Are the RVOT, previous conduit, aorta, or right coronary in potential jeopardy from resternotomy? Femoral vessels cannot assume to be patent in an adult congenital heart disease patient. The vessels may have been sacrificed during previous cardiac catheterization or thrombosed as a consequence of vascular access. Ultrasound studies should be routinely performed to confirm patency of the femoral vessels. 32 Patients should have alternate cannulation sites identified and prepped into the field before resternotomy. In addition to the femoral vessels, the axillary artery can be used. However, if the patient had a previous Blalock-Taussig shunt, the patency of the subclavian artery should be confirmed. 33 The innominate artery has been described as an alternate cannulation site, but the course and position will be impacted by a right-sided aortic arch, which is common with TOF. 34 Resternotomy is undertaken with an oscillating saw. In general, our practice is to leave the poste-

5 Pulmonary valve replacement in the patient with TOF 31 rior periosteum intact and divide this layer with the electrocautery to avoid damage to underlying structures. If bleeding from the heart, most commonly the right atrium or right ventricle is encountered during resternotomy, the sternum should be reapproximated with towel clips and peripheral cannulation for cardiopulmonary bypass achieved before completing the sternotomy. If there is a known residual intracardiac shunt, Trendelenburg positioning and hypothermia to make cardiac contraction less effective may limit the potential for air embolism. Massive air embolism is a rare but potentially devastating complication. Because it is rare but treatable, a written protocol for management should be readily available in the operating room. Once resternotomy has been completed the pericardial contents are dissected out. We have found that it is sometimes easier for the surgeon to stand on the patient s left side. The dissection is begun on the diaphragmatic surface and continued along the right atrium, freeing up the inferior vena cava, right atrial free-wall, and superior vena cava. If possible, the aorta is separated from the pulmonary artery before initiating cardiopulmonary bypass. Single aortic and bicaval cannulation are routinely used. A variety of perfusion strategies have been used by many centers with excellent results, including empty beating perfusion, ventricular fibrillation, and aortic cross clamping with cardioplegia. We routinely use aortic cross-clamping and cardioplegia for at least the first portion of the PVR operation. An antegrade cardioplegia cannula is placed in the ascending aorta. After cardioplegia, the LV is vented through the aortic root. We use aortic cross-clamping and cardioplegic arrest as opposed to empty beating heart surgery for two reasons: to improve exposure and to eliminate the risk of air embolism. Because the ascending aorta of patients with TOF is larger than normal, exposure of the distal main pulmonary artery may be improved by decompression that is achieved with cross-clamping. In addition, the bloodless field and arrested heart make suturing the valve in place easier. Cross-clamping also decreases the risk for air embolism. Occasionally, residual, occult septal defects remain and can result in air embolism if the heart is allowed to beat while empty. In addition, the left atrial appendage may be adherent to the main and left pulmonary artery and entry into the left atrial appendage can occur and result in entry of air into the left side. Because the heart is empty, this entry into the left atrial appendage may go unnoticed until air is identified in the root vent. Ventricular fibrillation can be used, as an alternative to crossclamping, but a LV vent should be considered to minimize the risk of LV distension. If additional right-sided procedures are planned (such as patch arterioplasty of the branch pulmonary arteries and/or tricuspid valve repair), removal of the crossclamp may be reasonable to limit the ischemic time. However, the surgeon should be confident that the atrial septum and ventricular septum are intact. In addition, venting of the LV and head-down position may be considered. If additional procedures are necessary (eg, ASD closure, tricuspid valve repair, arrhythmia procedure, etc), these are carried out first. If aneurysmal dilatation of the RVOT is present, this is resected. Our current practice is to use a heterograft for PVR. For an individual with repaired TOF, we commonly use a stented bovine pericardial valve and most commonly implant a 29-mm valve (Fig. 7). Alternatively, a porcine valved conduit (most commonly 25 mm or 30 mm) is used if the situation calls for an RV-to-pulmonary artery conduit. Once the procedure is complete, the patient is placed in Trendelenburg position, deairing confirmed, and the cross-clamp is released. Transesophageal echo is routinely used to confirm de-airing before weaning from cardiopulmonary bypass and to make certain the repair is satisfactory. Milrinone may be useful for the patient with decreased RV function, but higher levels of inotropic support are rarely necessary. Complete hemostasis should be achieved before Figure 7 Surgical technique for PVR. A, A stented bioprosthetic valve is sewn into the orthotopic position in the RVOT. B, The RVOT is augmented with a patch as necessary to accommodate the valve.

6 32 J.S. Tweddell et al closure to minimize the risk of mediastinitis. Consideration should be given to placement of substernal Gore-Tex or other barrier to facilitate predictable resternotomy. Children s Hospital of Wisconsin Experience A retrospective analysis of experience with PVR among patients with TOF was approved by the Children s Hospital of Wisconsin Human Research Review Board and was conducted in accordance with all human research regulatory requirements. Between 1985 and 2010, 122 patients greater than 5 years of age underwent a first-time PVR following repair of TOF and variants including TOF with pulmonary stenosis, TOF with pulmonary atresia, double outlet right ventricle with normally related great arteries and pulmonary stenosis, and TOF with complete atrioventricular canal defect. The goal of the study was to determine the relative durability of homograft pulmonary valves with heterografts (either stented bioprosthetic valves or porcine valved conduits). Homograft valves were used in 83 patients; heterografts were used in 39 patients. Median age of those patients receiving a homograft was 12.5 years (interquartile range, 7.8, 15.9) and was significantly younger than those patients receiving heterografts with a median age was 18.9 years (interquartile range, 15.1, 36.0) (P.0001). There was one early death (0.8%, 1/122). There was no survival difference between homografts and heterografts (Fig. 8). The freedom from re-intervention was not different between homografts and heterografts (Fig. 9). Potential advantages of heterografts include lower cost and ready availability. Although not specifically analyzed in our study, other investigators have shown a low incidence of the development of PR among patients receiving heterografts. 35 For these reasons, we Figure 9 Freedom from reintervention and death among patients over 5 years of age undergoing PVR for TOF and variants. There was no significant difference in reintervention-free survival among patients receiving a homograft compared with a heterograft. consider heterograft valves to be the first choice among patients with TOF requiring PVR. Conclusions Patients with repaired TOF are at increased risk for death after the second decade. This risk is strongly related to PR and its sequelae. Those individuals with symptoms of exercise intolerance, arrhythmias, or prolonged QRS should be offered PVR. The application of CMR to patients with TOF has identified RV dilatation and RV dysfunction as associated with adverse events, and even among asymptomatic patients these might be considered indications for PVR. CMR has revolutionized the management of patients with TOF, but it is noteworthy that currently established CMR criteria for PVR identify thresholds that are associated with irreversible RV dilatation and dysfunction rather than criteria that ensure maintenance of RV function. Given the safety of PVR and increasing options for catheter-based PVR, as well as the increasing use of CMR for routine follow-up of patients with repaired TOF, the threshold for PVR is likely to continue to change. Figure 8 Survival of patients over 5 years of age undergoing PVR for TOF and variants. There was no significant difference in survival among patients receiving a homograft compared with a heterograft. References 1. Nollert G, Fischlein T, Bouterwek S, et al. Long-term survival in patients with repair of tetralogy of Fallot: 36-year follow-up of 490 survivors of the first year after surgical repair. J Am Coll Cardiol 1997;30: Gatzoulis MA, Balaji S, Webber SA, et al. Risk factors for arrhythmia and sudden cardiac death late after repair of tetralogy of Fallot: a multicentre study. Lancet 2000;356: Geva T, Sandweiss BM, Gauvreau K, et al. Factors associated with impaired clinical status in long-term survivors of tetralogy of Fallot repair evaluated by magnetic resonance imaging. J Am Coll Cardiol 2004;43: Harrild DM, Berul CI, Cecchin F, et al. Pulmonary valve replacement in tetralogy of Fallot: impact on survival and ventricular tachycardia. Circulation 2009;119:

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