Avoidance of malignant arrhythmia caused by displacement of the right coronary artery ostium in surgical correction of supravalvular aortic stenosis.

Introduction

Supravalvular aortic stenosis (SVAS) is a complicated and severe congenital heart disease defined as a congenital obstructive narrowing of the aorta immediately above the aortic valve. SVAS was first described by Mencarelli[1] in 1930 but was not distinguished from other types of stenosis of the aortic orifice until the application of retrograde aortic catheterization in 1958.[2] The disease discussed in the present article is confined to stenosis immediately above the aortic valve; i.e., stenosis of the sinus. Simple aortic valve disease and coarctation of the ascending aorta and aortic arch are not within the scope of this article. To facilitate the discussion, the term “SVAS” is used to refer to all patients’ conditions in this study.

SVAS is characterized by two main pathophysiological changes. First, the difference in the pressure gradient between the left ventricle and aorta causes left ventricular hypertrophy; second, this difference in the pressure gradient leads to extension, tortuosity, and blood supply insufficiency of the coronary artery because of the adjacency of the coronary artery ostium to the proximal end of the stenosis. Patients with SVAS usually show obvious symptoms of angina pectoris beginning in childhood. By the age of 10 to 20 years, symptoms of left ventricular outflow tract obstruction (LVOTO) begin to appear; these symptoms may be related to the increased cardiac workload in childhood. In the absence of Williams syndrome, symptoms of SVAS are not obvious in infancy and early childhood; however, the detection rate by ultrasound is very high. SVAS progresses more rapidly and seriously than aortic stenosis, and many untreated patients die before adulthood. Therefore, early treatment of SVAS is crucial.

In clinical practice, surgical repair is the main treatment for SVAS. Common surgical techniques for repair of SVAS include McGoon’s technique (single-patch augmentation), Doty’s technique (bifurcated-patch aortoplasty), Brom’s technique (three-patch augmentation), and autologous slide aortoplasty. Research of patients who were followed up after SVAS repair indicated that all of these techniques had good long-term effects on survival, and no significant difference was found among the techniques.[3] However, one report indicated that the incidence of perioperative complications, especially serious malignant arrhythmia, perioperative reoperation, extracorporeal membrane oxygenation (ECMO) support, and reoperation, varies among these surgical techniques.[4] Assessments of these surgical methods are mixed. All four of these techniques have been used to treat SVAS in the clinical practice setting at Fuwai Hospital. No significant differences were found among the techniques with respect to eliminating the pressure gradient and relieving obstruction caused by primary diseases, but malignant arrhythmia, dependence on ECMO, and early postoperative death were commonly encountered in operations involving incision of the right coronary sinus. The complication rate significantly decreased after adjusting the size, shape, and position of the right coronary sinus patch. Therefore, we assume that displacement of the right coronary ostium may be the main cause of perioperative death or serious complications. During the surgery, the repair mesh of the right coronary sinus can be trimmed into a triangle instead of the traditional teardrop shape. This can reduce the displacement of the opening of the right coronary sinus and reduce the manifestations of right coronary ischemia, especially the occurrence of malignant arrhythmia, which is particularly important for reducing perioperative complications.

Methods

We retrospectively reviewed the data of consecutive patients who underwent surgical treatment of SVAS from 2008 to 2015 at the Children Heart Center of Fuwai Hospital. The patients underwent McGoon’s technique, Doty’s technique, Brom’s technique, or autologous slide aortoplasty. Rigorous preoperative examinations were performed for all patients undergoing surgical treatment. The surgical procedures were performed in the supine position with the patient under general anesthesia. A median sternotomy was performed, and routine extracorporeal circulation (ECC) was established. The aortic-pulmonary interval was extensively mobilized, and the patient was examined for extracardiac malformations during circulation. After examination of the characteristics and scope of the SVAS, a suitable surgical approach was chosen. The aorta was blocked when the body temperature dropped to 35°C. Ethical approval was obtained from the Ethics Committee of the Chinese Academy of Medical Sciences and Peking Union Medical College Fuwai Hospital. Informed consent for surgery was obtained from all patients and their family members.

Surgical techniques

In McGoon’s technique, a longitudinal incision was made parallel to the ascending aorta, and this incision was then extended down to the noncoronary sinus and up beyond the stenosing ring. A teardrop-shaped patch was inserted to widen and repair the sinus. The patch materials were autologous pericardium, autologous pericardium with an external polyester lining cloth, and an artificial vascular patch.

In Doty’s technique, a longitudinal incision was made in the ascending aorta, and this incision was then extended in an inverted Y shape separately into the noncoronary sinus and right coronary sinus. A corresponding Y-shaped patch was inserted, and the narrow part was widened. The incisions in the noncoronary sinus, right coronary sinus, and ascending aorta were then closed one after another. The patch materials were autologous pericardium, autologous pericardium with an external polyester lining cloth, and an artificial vascular patch.

In Brom’s technique, the ascending aorta was transected, and three longitudinal incisions were extended downward into the noncoronary sinus, right coronary sinus, and left coronary sinus, respectively. A patch was stitched into each of the three sinuses. The patch materials were autologous pericardium and an artificial vascular patch.

Finally, in autologous slide aortoplasty, the ascending aorta to aortic arch was extensively mobilized. The aorta was transected at the location of the stenosis, and the stenosing ring was excised. A longitudinal incision was made in the aortic sinus, and the free end of the ascending aorta was clipped corresponding to the shape of the aortic sinus incision and anastomosed to the aortic root.

Results

In total, 91 consecutive patients (65 male, 26 female) who underwent surgical treatment of SVAS were included in this study. The patients’ mean age was 10.0 ± 2.5 years (range, 3 months to 18 years), and eight patients were <1 year old. The patients’ mean weight was 14.5 ± 1.8 kg (range, 5 to 37 kg), and 48 patients weighed <15 kg. Preoperative examination revealed left ventricular hypertrophy in 85 (93.4%) patients, a mean ejection fraction of 71.18% ± 9.61%, a mean supravalvular aortic flow velocity of 4.30 ± 1.0 m/s, and a mean transvalvular aortic pressure gradient of 74.30 ± 35.67 mmHg. McGoon’s technique was performed in 29 patients (autologous pericardium, n = 22; autologous pericardium with an external polyester lining cloth, n = 3; artificial vascular patch, n = 4), Doty’s technique was performed in 47 patients (autologous pericardium, n = 30; autologous pericardium with an external polyester lining cloth, n = 7; artificial vascular patch, n = 10), Brom’s technique was performed in 12 patients (autologous pericardium, n = 7; artificial vascular patch, n = 5), and autologous slide aortoplasty was performed in 3 patients. Four deaths occurred in the perioperative period, but no late deaths occurred in the long-term follow-up. The mean intraoperative ECC time was 108.57 ± 64.17 minutes (<90 minutes in 44 patients), and the mean aortic clamping time was 70.73 ± 34.42 minutes (<60 minutes in 49 patients). Six patients required ECMO support postoperatively, and eight patients underwent reoperations. The mean mechanical ventilation time was 17.87 ± 46 hours (<12 hours in 69 patients), and the mean residence time in the intensive care unit (ICU) was 81.24 ± 197.42 hours (<24 hours in 41 patients).

Six patients experienced a delay of sternal closure and required ECMO support after surgery because of failed ECC weaning. Eight patients required a reoperation due to malignant arrhythmia or low cardiac output syndrome upon arrival in the pediatric ICU (PICU). Four perioperative deaths occurred. In the earliest death in 2008, failed ECC weaning occurred during the operation. The patient was barely weaned from ECC after having been continuously supported for >3 hours, and sternal closure was delayed. While staying in the PICU, the patient developed recurrent malignant arrhythmia and significant blood pressure fluctuation and was declared clinically dead within 24 hours. Thereafter, ECMO was more actively applied in cases of failed ECC weaning. The other three perioperative deaths are summarized as follows.

Preoperative ultrasound in a 1-year-old, 10-kg boy showed a transvalvular aortic pressure gradient of 100 mmHg, left ventricular end-diastolic diameter (LVED) of 20 mm, ventricular septal thickness of 18 mm, and pulmonary transvalvular pressure gradient of 70 mmHg. Intraoperative ultrasound revealed SVAS, supravalvular pulmonic stenosis, significant stenosis of the right ventricular outflow tract (RVOT), stenosis of the ostia of the left and right pulmonary arteries, and double ventricular hypertrophy. Histidine-tryptophan-ketoglutarate solution was used for myocardial protection during the operation. Doty’s technique was conducted to surgically repair the SVAS by widening the noncoronary sinus and right coronary sinus. The RVOT obstruction (RVOTO) was then dredged; the main pulmonary artery was remodeled; and the left and right pulmonary artery, main pulmonary artery, aortic sinotubular junction, and ascending aorta were respectively repaired and widened with glutaraldehyde-treated autologous pericardium. The abnormal muscle bundle of the RVOT was excised. The RVOT was repaired and widened with a bovine jugular vein patch. When ECC support was stopped after surgery, the right ventricle exhibited enlargement and weak systolic activity; however, the S-T segment in leads II, III, and AVF showed no significant change. The patient failed to be weaned from ECC because the measured aortic valve pressure difference and pulmonary valve pressure difference were small, and the stenosis was relieved completely. Therefore, ECMO was installed during the operation and the return to PICU was delayed. A large dosage of vasoactive drugs was used after surgery, and the patient developed recurrent ventricular tachycardia. S-T elevation was found in leads II, III, and AVF, and it was difficult to maintain his blood pressure. The patient died on postoperative day 11.

In another case, preoperative ultrasound in a 3-month-old, 5-kg boy revealed a transvalvular aortic pressure gradient of 110 mmHg and LVED 27 mm. The intraoperative exploration findings corresponded with the preoperative examination findings. Doty’s technique was used to repair the SVAS. Defibrillation of ventricular fibrillation was performed twice after circulation was restored, and sinus rhythm was restored by these two defibrillations. Weaning from ECC was successful. Ten hours after surgery, the patient’s blood pressure became difficult to maintain, and recurrent ventricular fibrillation and S-T elevation were observed in leads II, III, and AVF. Ultrasound showed that the pulmonary artery pressure was not high and the aortic valve pressure difference was small; however, the right ventricle was relatively full and the interventricular septum had shifted to the left. Emergency thoracotomy was performed, but ECMO support showed a poor effect and the patient finally died.

Another case of death involved an 8-month-old, 5-kg girl. Preoperative ultrasound revealed a transvalvular aortic pressure gradient of 70 mmHg and LVED of 18 mm. Intraoperative exploration showed supravalvular, ascending aortic, and aortic arch dysplasia. Doty’s technique was used to repair the SVAS. Ventricular fibrillation occurred during cardiac resuscitation and was reverted to sinus rhythm after two defibrillations. ECG showed no obvious abnormalities. One day after surgery, pleural effusion developed and the urine volume decreased; however, the urine volume increased after peritoneal dialysis. Two days after surgery, S-T elevation of leads II, III, and AVF gradually appeared, and recurrent ventricular tachycardia developed. Ultrasound showed a normal pulmonary arterial pressure and transvalvular aortic pressure gradient. Five days after surgery, recurrent ventricular fibrillation occurred, and the patient died after rescue.

We realized that after these complex deformities had been repaired, the transvalvular pressure gradient and other malformations were not the causes of early death. Therefore, we focused on determining the cause of the recurrent malignant arrhythmia. In later cases, we more closely observed the relationship between the shape of the right coronary artery sinus and the development of complications. In the next eight reoperations, we adjusted the size, location, and direction of the right coronary sinus patches and cut the patches into an inverted triangle shape (Figure 1). The symptoms of malignant arrhythmia and low cardiac output were substantially relieved, and no further deaths occurred. The mean mechanical ventilation time among all cases was 17.87 ± 46 hours (<12 hours in 69 patients), and the mean residence time in the ICU was 81.24 ± 197.42 hours (<24 hours in 41 patients). Follow-up continued for an average of 15 months. The mean aortic pressure was 9.31 ± 3.11 mmHg and the mean flow rate was 1.3 ± 0.71 m/s, and no deaths occurred among the patients who survived until discharge.

Figure 1.

Adjustment of right coronary sinus patch. (a) Supravalvular aortic stenosis before surgery. The dotted line indicates the location of the incision. (b) The right coronary artery was distorted with a traditional Y-shaped patch. (c) The right coronary artery remained undistorted with an asymmetrical (triangle-shaped) right coronary sinus patch

Discussion

SVAS is an obstructive disease involving a series of pathological changes, including abnormal thickening of the aortic wall and pulmonary artery wall. It is generally believed that the main pathological change involved in SVAS is sinotubular junction stenosis; however, other obstructions can also occur in the ascending aorta, aortic arch, innominate artery, or carotid artery.[5-13] The sinotubular junction plays an important role in maintaining the flexibility of the aorta in the systolic and diastolic periods. In SVAS, a hyperplastic ridge develops at the sinotubular junction, seriously affecting the function of both the sinotubular junction and aortic valve during systole.[8,14] This occurs because hypertrophy and hyperplasia of the aortic sinus lead to deformation of the aortic root, and the resultant fusion of the aortic valve leaflets with the supravalvular ridge of the aorta then damages the coronary artery ostium and influences the blood flow of the coronary artery. In addition, the high pressure of the supravalvular ridge of the aorta induces coronary ischemia and myocardial infarction. Related injuries then gradually appear, such as a double-orifice mitral valve, SVAS, coarctation of the aorta, and pulmonary artery stenosis. Thus, although the ridge is limited to the sinotubular junction, it can still affect the aortic valve, the tissue near the ascending aorta, or the ascending aorta itself. The primary abnormality is the prominent stenosing ring at the sinotubular junction. Other stenoses may also occur in the LVOT, ascending aorta, aortic arch, or pulmonary valve. SVAS is often complicated with Williams syndrome,[15,16] which is believed to be caused by a lack of elastin.[17] In a 38-year independent large-scale cohort study of 101 patients with SVAS, 14% of patients had the Williams syndrome phenotype or exhibited abnormal behavior.[10] In other reports, 28% to 39% of patients with SVAS also had Williams syndrome.[18-20] In the present study, however, the term “SVAS” only referred to stenosis of the aortic sinus. Only 4.39% of our patients were complicated with Williams syndrome; this might be explained by selection bias.

The primary objective of surgical treatment is to reduce LVOTO, remove the stenosing ring, and reduce the postoperative transvalvular pressure gradient. The initial surgical technique was performed only by expanding the stenotic ring to relieve the occlusion[21]; in other words, the incision of the aorta was closed immediately after excision of the stenosing ring.[13,22] Later surgical techniques mainly focused on restoring the morphology and structure of the aortic root through various repair methods.[18,23-25] SVAS repair methods have been substantially improved during the past 40 years. In 1961, McGoon et al.[26] inserted a teardrop-shaped patch into the longitudinal incision of the noncoronary sinus of the ascending aorta to expand the narrow part and thus relieve the occlusion along with excision of the narrow ridge. Doty et al.[27] and Delius et al.[7] reported more aggressive techniques. They extended the sinus space of the right coronary sinus and the noncoronal sinus by insertion of an inverted Y-shaped patch. Myers et al.[28] reported another technique in which they transected the aorta above the level of the stenosis; inserted three artificial patches into the coronary sinus, right coronary sinus, and left coronary sinus; and then respectively anastomosed the three ends to the ascending aorta. Chard and Cartmill[13] described a technique in which they extensively mobilized the ascending aorta, cut open the three sinuses, clipped the free end of the ascending aorta into a trident shape, and widened the sinuses. According to follow-up reports, these techniques did not show significant differences in enlarging the sinus space and reducing the transvalvular pressure gradient. Regardless of the technique used, a high long-term success rate is the main goal; however, early malignant arrhythmia and low cardiac output should be avoided. Among the 91 patients in the present study, 4 deaths occurred and all were caused by malignant arrhythmia. Owing to our lack of experience in the early stage, we attributed the malignant arrhythmia to the long operation time and resultant myocardial edema, poor heart function, and unsatisfactory effect of ECMO. Later, when we began using a right coronary sinus patch, neither postoperative malignant arrhythmia nor severe low cardiac conditions occurred regardless of the operation time or complications associated with other severe deformities. Therefore, we assume that the surgical restructuring of the aortic sinus may have squeezed the ostia of the coronary arteries and that a soft polyester patch is ineffective; when a large polyester patch is extruded, it will impact the right coronary artery and induce associated clinical symptoms. Besides the four deaths that occurred in this study, eight patients developed early malignant arrhythmia. Symptoms included unsuccessful ECC weaning during the operation; S-T segment elevation or depression in leads II, III, and AVF; arrhythmia; poor maintenance of blood pressure; the need for a large dosage of vasoactive drugs; and postoperative malignant arrhythmia without abnormal intraoperative electrocardiographic findings. ECMO showed a poor effect in emergency thoracotomy, but when the edge of the patch was pulled with a pair of tweezers, the S-T segment changed. When the right coronary artery patch was clamped to reduce the relative area of the patch, the S-T segment substantially reverted. We performed reoperations for these cases, re-cut the patches, or decreased the patch area (inverted triangle) before inserting the patch into the right coronary sinus and reopening the aorta. After successful cardiac resuscitation and achievement of stable hemodynamics, the chest was closed and the patients were returned to the ICU. No malignant ventricular arrhythmia or poor maintenance of blood pressure occurred. Right coronary sinus patches were used in the surgical procedures for all of these patients. In 2009, Cruz-Castañeda et al.[4] reported a case of postoperative refractory supraventricular arrhythmia and death due to lack of repair of a right coronary artery occlusion, while the other eight patients whose right coronary artery occlusion was relieved developed no arrhythmia. Therefore, we assume that at an early stage, if the patch inserted into the right coronary sinus to fully relieve the obstruction is too large, the right coronary artery ostium will be displaced, resulting in the development of folds in the right coronary artery ostium or proximal end and consequent hypoperfusion and corresponding changes. Thus, regardless of whether Doty’s technique or Brom’s technique is used, the right coronary sinus patch must be carefully clipped to avoid a large-sized patch. In McGoon’s technique, a too-large patch may also lead to sinus congestion and displacement of the right coronary artery ostium. We suggest that regardless of the surgical method used, the right coronary sinus patch should be shaped as an inverted triangle (Figure 1). In future clinical practice, we will continue to collect relevant data in an effort to quantitatively determine the optimal size of the patch inserted into the right coronary artery in patients of different ages and weights to avoid the early adverse events caused by displacement of the coronary artery ostium.