Novel Method for Evaluating Tricuspid Valve Function after Tricuspid Valve Detachment in the Repair of Perimembranous Ventricular Septal Defects

Abstract

Tricuspid valve detachment has been used for decades in the repair of type II ventricular septal defects (VSDs); however, the procedure can damage the tricuspid valve and conduction system.

We retrospectively reviewed 177 consecutive type II VSD repairs performed at our hospital from 1997 through 2004. Patients were included if they had symptoms, pulmonary hypertension, or a Qp/Qs ratio >1.5: 86 underwent tricuspid valve detachment (TVD group) and 84 underwent VSD repair without this detachment (non-TVD group).

There was no significant difference between groups in age, body weight, VSD size, Qp/Qs ratio, follow-up duration, or incidence of residual shunting. Cross-clamp times (109.6 ± 42.6 vs 92.2 ± 38.1 min) and cardiopulmonary bypass times (155.1 ± 53.8 vs 137 ± 47 min) were longer in the TVD group. No patients developed tricuspid stenosis or heart block. After excluding patients who underwent tricuspid repair, we found similar grades of postoperative tricuspid regurgitation in both groups. In applying our novel criterion (last postoperative regurgitation grade minus preoperative regurgitation grade) to evaluate changes between preoperative and postoperative tricuspid regurgitation, we found significant deterioration in the non-TVD group (P=0.018). Had conventional evaluation methods been used, severity in the groups would not have differed significantly. Our method enables additional evaluation of late tricuspid function in individual patients.

Tricuspid valve detachment is safe for type II VSD repair and has no adverse effect on late tricuspid valve function. In addition, we recommend the interrupted-suture technique for leaflet reattachment.

Currently, the transatrial approach for repairing type II (perimembranous) ventricular septal defects (VSDs) is routine. However, in some patients, this approach can result in suboptimal repair, with residual shunting or tricuspid valve damage. To circumvent this, tricuspid valve detachment (TVD) was introduced by Hudspeth and colleagues.¹ Since then, authors have reported the usefulness and advantages of this technique for improving the exposure of the entire circumference of the type II VSD and improving postoperative tricuspid valve function.^2,3 However, no studies have investigated long-term changes between preoperative and postoperative tricuspid valve function on a patient-by-patient basis after TVD in the repair of type II VSDs. We evaluated the effect of TVD on long-term changes in postoperative tricuspid regurgitation (TR) in patients who underwent repair of type II VSDs.

Patients and Methods

We retrospectively reviewed repairs of type II VSDs that were performed at our hospital from March 1997 through November 2004. This study was approved by the Institutional Review Board of Kaohsiung Chang Gung Memorial Hospital. In total, 177 consecutive patients with type II VSD (with symptoms, pulmonary hypertension, or Qp/Qs ratio >1.5) underwent transatrial surgical correction. Seven cases lost to follow-up were excluded. Of the remaining 170 patients, 86 (50.6%) underwent VSD repair with TVD (the TVD group) and 84 (49.4%) underwent repair without TVD (the non-TVD group). The endpoint of data collection for this study was 31 May 2008.

Of the 170 patients, 97 were male. Because our department's protocol is medical therapy for infants with minimal shunts, the absence of symptoms, or pulmonary hypertension, the average age at operation in this series was older than typical: 82.3 months (range, 1–522 mo; median, 18 mo). The patients' average body weight was 20.3 kg (range, 2–95 kg; median, 10 kg). Thirty-five patients (20.6%) also underwent tricuspid valve repair (anterior commissural plication only) if more than a moderate degree of TR was identified by means of preoperative 2-dimensional echocardiography. In one patient (TVD group), the preoperative degree of TR fluctuated between mild and moderate.

All patients underwent standard cardiac catheterization preoperatively. The Qp/Qs (left-to-right shunt) ratio was calculated by means of the Fick principle (mean ratio, 2.1 ± 1.2). Ventricular septal defect size (mean, 11.9 ± 7.1 mm) was measured while each patient was under intraoperative cardioplegic cardiac arrest. The classification of the type II VSDs was also confirmed at surgery, in accordance with the nomenclature for VSDs reviewed by The Society of Thoracic Surgeons in 2000 (VSD Hierarchy Level 3 definition).⁴

Operative Procedure

Surgical repair was performed by either of 2 surgeons (JPC or CLK). Each VSD was repaired through a right atriotomy with use of bicaval cannulation and mild hypothermic cardioplegic cardiac arrest. In the non-TVD group, the septal leaflet and subvalvular apparatus of the tricuspid valve were retracted laterally and through the tricuspid valve orifice, and the VSD was patched. In the TVD group, the septal leaflet of the tricuspid valve was detached circumferentially, and the VSD was repaired through the orifice created between the tricuspid annulus and the detached leaflet. In both groups, the VSD was repaired with a piece of knitted Dacron patch and pledgeted polypropylene interrupted horizontal mattress sutures.

Tricuspid Valve Detachment: Indication and Procedures

Our indications for TVD were compatible with those described by Sasson and colleagues.³ When the VSD margin was difficult to identify, especially in patients with a high position of the defect with outlet extension (n=52, 60.4%), septal leaflet aneurysm formation (n=12, 14%), or tricuspid chordal straddling (n=22, 25.6%), TVD was performed by creating an incision 1 mm inside and parallel to the tricuspid annulus for detaching the septal leaflet. Radial-type TVD was not performed, in order to avoid a rigid vertical suture line that would restrict the septal leaflet. After VSD repair, the leaflet was reattached to the annulus with interrupted sutures.

Analysis of Tricuspid Regurgitation

Four pediatric cardiologists (blinded to the study) performed annual transthoracic color-flow Doppler echocardiographic grading of the TR in all 170 patients, until the endpoint of data collection. The severity of TR was evaluated semiquantitatively, by color-Doppler jet area-to-right atrial area ratio, with scores of 0 (no TR), 1 (trivial, <10%), 2 (mild, 11%–20%), 3 (moderate, 21%–50%), and 4 (severe, >50%). Right ventricular systolic pressure was calculated from the TR jet velocity.⁵ The follow-up period was 11 years (mean, 81.5 ± 25.2 mo). Change in TR was defined as the last postoperative TR grade minus preoperative TR grade. This novel method enabled an analysis of the degree of TR in each patient and the direction of change.

Statistical Analysis

Statistical analysis was performed with use of SPSS for Windows software, version 13.0 (SPSS Inc., part of IBM Corporation; Armonk, NY). The estimated rates of freedom from worsening of TR were determined by the Kaplan-Meier product-limit method with 95% confidence intervals (CIs). Continuous variables acquired from the clinical characteristics were expressed as mean ± SD and were compared with use of the Mann-Whitney test. The χ² analysis was used for comparisons between categorical variables. A 2-tailed P value <0.05 was considered statistically significant.

Results

There were no significant differences between the groups in age, sex, body weight, VSD size, Qp/Qs ratio, follow-up duration, incidence of tricuspid repair, or residual shunting. The cross-clamp and cardiopulmonary bypass times were longer in the TVD group (Table I). The distribution of the type II VSD classifications in the groups was not significantly different (Table II).

Table I. Characteristics of the Groups

Table II. Distribution of Type II VSDs

No patient had postoperative tricuspid stenosis or heart block. During follow-up, severe TR developed in 2 patients in the non-TVD group. In the analysis of TR grades and changes, patients who underwent tricuspid repair were excluded, in order to avoid tricuspid repair-related confounding factors. There were no statistically significant differences between the groups in preoperative and postoperative TR grades (Table III). However, the TVD group had significantly less TR progression (P=0.018) (Table IV). The Kaplan-Meier curve, which compared the 2 groups for freedom from significant worsening of TR change over time, also showed a significant difference (P=0.045) (Fig. 1). The calculated freedom from significant worsening of TR change at 10 years was 69.8% in the TVD group (95% CI, 53.3%–86.3%) and 19.3% in the non-TVD group (95% CI, 3.9%–34.7%).

Table III. Grades of Preoperative and Postoperative TR

Table IV. Tricuspid Regurgitation Changes in the Groups

Fig. 1 The Kaplan-Meier curve comparing the 2 groups for freedom from significant worsening of tricuspid regurgitation (TR) over time (after excluding the patients who received tricuspid repair) shows a significant difference (P=0.045).

Discussion

In this study, we devised and applied a new criterion—subtracting preoperative TR grade from the last postoperative TR grade—to evaluate the change between preoperative and postoperative TR on a patient-by-patient basis. This criterion revealed significant deterioration of tricuspid function in our non-TVD group (P=0.018). Had the conventional evaluation method been used, the severity of preoperative and postoperative TR in our 2 groups would not have differed significantly. We believe that this additional criterion yields a new evaluation option for late tricuspid function.

Successful transatrial repair of type II VSDs requires optimal exposure of the perimembranous septal region to prevent residual shunting, heart block, and damage to the tricuspid septal leaflet and subvalvular apparatus.^2,3 Tricuspid valve detachment was introduced in the early 1960s as an adjunctive technique for the transatrial repair of type II VSDs when exposure was difficult.¹ However, this technique was not popular initially because of misgivings about damage to the tricuspid leaflet and conduction system. In 1981, Frenckner and colleagues⁶ applied TVD in 27 patients with satisfactory results. However, the idea of using TVD liberally was still controversial. As the technique evolved, its usefulness and advantages were reported; and by the 1990s, TVD was being used in 20% to 44% of patients for VSD repair (Table V).2,3,6–13

Table V. Reported Incidences of Applied TVD

In TVD, long-term tricuspid valve function is the chief concern. Gaynor and colleagues⁹ reported that no patient in their TVD group had postoperative TR that exceeded mild; conversely, 6 patients (4.4%) in their non-TVD group had greater-than-mild TR. Others reported similar outcomes in regard to postoperative TR in their TVD and non-TVD groups.^10,11,13 Of note, Sasson and colleagues³ sought to establish indications for TVD in the closure of type II VSDs. These involved preoperative echocardiographic criteria applied to newly developed TR in 3 groups of patients and consideration of whether the tricuspid valve should be detached during VSD repair when at least one criterion was fulfilled. In that study, 53.1% of patients had at least one echocardiographic criterion, but only 22.9% underwent repair with TVD. More postoperative sequelae developed in the 30.2% of patients who did not undergo TVD. Hence, we are able to hypothesize that, just as in our study, approximately 50% of all VSD patients will meet at least one criterion for TVD and should be strongly considered as candidates for the procedure.

Our patients who underwent TVD tended to fulfill the criteria advocated by Sasson and colleagues.³ In these difficult cases, the VSD margins were obscure, and the tricuspid valve tended to exhibit chordal straddling or aneurysmal deformity. Therefore, when we applied TVD, these additional conditions could be corrected concomitantly, resulting in better long-term tricuspid valve function in our TVD group. The incidences of intraoperative tricuspid repair with anterior commissural plication for patients with more-than-moderate preoperative TR were statistically insignificant between our TVD and non-TVD groups (23.3% vs 17.9%; P = 0.383). Accordingly, we conclude that this factor did not affect the analysis of postoperative TR change.

Of some note is the higher incidence of residual VSD in our TVD group. However, considering the higher reported residual-VSD incidence of 7.4% in this challenging patient population that required TVD,³ the residual-VSD incidence of 5.8% in our TVD group seems to be fairly acceptable.

In our study, all detached tricuspid valves were reattached with interrupted sutures while the patients were under cardioplegic cardiac arrest, to avoid damaging fragile leaflet tissue. As a result, the cross-clamp and on-pump times were both prolonged by 40 minutes. Although it is the fashion to use running sutures to reattach the leaflets, Tatebe and colleagues⁸ had negative experiences when they used running sutures to reattach tricuspid leaflets in small infants and patients with Down syndrome. We believe that using running sutures can result in purse-string-type valvular distortion and also in restricted tricuspid valve growth in young patients.

In conclusion, our study shows that TVD is a safe technique for difficult perimembranous VSD repair, and that TVD has no adverse effect on late tricuspid valve function. Using the interrupted-suture technique for leaflet reattachment is recommended, to avoid leaflet distortion and growth restriction.