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Sumario Vol. 42 - Nº 2 Abril - Junio 2013

Impact of Additional Flow on the Indication
of Total Cavopulmonary Shunt

Alfredo M. Naranjo Ugalde, Eugenio Selman-Housein Sosa,
Adel González Morejón, Luis E. Marcano Sanz,
Eutivides Aguilera Sanchez, Maritza Oliva Pérez

Cardiocentro Pediátrico William Soler. La Habana, Cuba.
Calle 1ra 3607. Playa Habana 11300. Cuba.
Correo electrónico

The authors declare not having a conflict of interest.
 


Print version Imprimir sólo la columna central

 

SUMMARY

Bidirectional cavopulmonary shunt (BCPS), or bidirectional Glenn shunt, has frequently been performed as a primary palliation or intermediate step before the final Fontan-type repair in patients with univentricular heart syndrome. There are some controversies regarding the usefulness of leaving additional pulmonary blood flow. The aim was to evaluate the influence of this strategy on follow-up and timing for Total cavopulmonary connection in patients with univentricular hearts. A series of 43 patients with ages ranging from two to five years oldwere studied across 10 years, 70% received Glenn operation;the most frequent indication was Univentricular Heart. Criteria for antegrade flow from native pulmonary stenosis or banding in 21 patients was transoperative oxygen partial blood pressure about 50 with mean artery pulmonary pressure less than 15 mmHG. Patients without accessory antegrade pulmonary flow received Fontan operation earlier that those who received accessory flow. Time free or reintervention for Fontan operation and pulmonary arteries branches development is related with pulmonary accessory antegrade flow in patients with univentricular heart.

Key words: Univentricular. Fontan.Cavopulmonary connection.
Rev Fed Arg Cardiol. 2013; 42(2): 113-118

 

 

INTRODUCTION
Surgical strategies have varied after 40 years in patients in whom it is not possible to keep a biventricular physiology. The separation in these hearts of the systemic and the pulmonary circulation is made by connecting the systemic venous return to the pulmonary artery tree, through cavopulmonary derivations or Fontan-like surgeries [1,2-4].

In patients with risk of total cavopulmonary derivation (TCPD) functioning or with effective pulmonary flow decreased after partial derivation (PCPD) by bidirectional Glenn or Hemi-Fontan operation [5], the contribution of additional flow through the pulmonary artery trunk (PAT) or Blalock – Taussig shunt (BTS), could be an alternative to favor the growth of branches or even a permanent option [6-9]. This flow should be regulated, so that ventricular overload, atrioventricular valve incompetence or pulmonary pressures may not increase [10].

In Cuba, BTS was used first in 1990. We set out to identify how beneficial it could be to leave a patent PAT and to identify how much it may modify the need for TCPD in a greater or lesser term and its possible impact on the growth of pulmonary branches.

Objectives
To describe the hemogasometric development in patients operated with additional flow by Pulmonary Artery after partial cavopulmonary derivation.

To identify if there is a relation between the additional pulmonary flow in the partial cavopulmonary derivation, the growth of pulmonary branches and the free period of reintervention for total cavopulmonary derivation.


MATERIAL AND METHODS
An observational, prospective, cohort study was made in a series of patients that were operated with bidirectional cavopulmonary derivation (BCVD) between January 1990 and December 1997, at the Cardiocentro Pediátrico William Soler (CPWS). Patients with diagnosis of associated Pulmonary Atresia (PA) and patients in whom the follow-up could not reach at least five years after the PCPD were excluded.

They were divided into two groups, those in whom BTS (open PAT) was left, and those without it (closed PAT). The criterion for BTS was obtaining by native pulmonary stenosis or pulmonary artery cerclage, pressures measured in the transoperative of the PCPD of less than 16 mmHg, with no gradient between superior vena cava (SVC) and PAT, with oxyhemoglobin (HbO2) close to 85 mmHg and partial blood pressure of oxygen (PO2) 45-50 mmHg.

They were grouped according to the main diagnosis. The variables collected were age, hemogasometric indicators, partial blood pressure of oxygen (PO2), arterial saturation of hemoglobin (HbO2), hematocrit (Htc). The times of observation were the preoperative of BCVD, the immediate postoperative, one year after the BCVD, the preoperative of the TCPD and the final time of the investigation with an average time of follow-up of 125.9 months (±37.32). The diameter of the pulmonary branches was measured by echocardiography in the preoperative of the partial derivation, after a year of the operation, in the preoperative of the total derivation or at the end of the period of study and the difference was found between the means of the values at the extreme moments. The dates in which the BCPD and the TCPD were made were gathered, as the time between them in months.

A database in SPSS 11.5 was made for the statistical processing. The association was tested by the chi square test of independence. For the comparison of the continuous variables, the T test was made for the matched and independent samples. The time of evolution was estimated between bidirectional cavopulmonary anastomosis (BCPA) and total cavopulmonary anastomosis (TCPA) and the time free from reintervention until December 2011. The probability of not undergoing reintervention at a given time was estimated by the Kaplan Meier method. The groups were compared in regard to the survival curves by the Log Rank test, with a significance level lower than 0.05.

To perform this investigation we had the approval by the Scientific Council and the Committee on Ethics of the Cardiocentro Pediátrico William Soler. The principles of the Helsinki Declaration about biomedical investigation in human beings were followed [11].


RESULTS
There were 43 BCPD performed in an equal number of patients without PA, 60.5% of the male gender. In 24 patients, native pulmonary stenosis was left or pulmonary artery cerclage was made. In 19, PAT was resected or ligated (Table 1).

Table 1. Diagnosis and option of additional flow

 

BTS
n

No BTS
n

total
n

p

TA

6

5

11

0,66

TGV

6

3

9

0,15

SV

7

6

13

0,69

RVDO

5

5

10

1

Total

24

19

43

 

TA: Tricuspid atresia. TGV: Transposition of great vessels. SV: Single ventricle. DORV: Double outletright ventricle. BTS: Blalock Taussig shunt.

 

There were three in-hospital deaths, which represented 6.97% of mortality. Two of the deceased people did not have BTS. There was no statistical relation between mortality and BTS.

Single Ventricle (SV) was the most frequent diagnosis (30.2%) followed by Tricuspid Atresia (TA), Double Outlet Right Ventricle (DORV), and complex Transposition of the Great Vessels (TGV) (Table 1). The youngest patient had 8 months of age. Seventy percent of the patients underwent PCPD between 2 and 5 years of age, 7% before the 2 years of age. The average of the age of undergoing BCPD was 2.47 years (0.6-14).

The changes in partial blood pressure of oxygen in the postoperative (p=0.04) and at a year of the operation (p=0.0004) showed a statistical relation with the procedure. Oxygen saturation in hemoglobin showed changes related to the option of pulmonary flow in the immediate postoperative (p=0.001). The hematocrit decreased in the postoperative for both groups, increased at a year in regard to the immediate postoperative. There was no significant variation in the hematocrit related to the pulmonary flow option. All the parameters showed significant changes in the postoperative with respect to the preoperative and at a year after the operation in regard to the immediate postoperative (Table 2).

Table 2. Averages of hemogasometric parameters according to additional flow option

BTS /
Time

PO2 (mmHg)
Averages (±SD)

p

Hbo2 (%)
Averages(±SD)

p

Hct (%)
Averages (±SD)

BTS

No BTS

BTS

No BTS

BTS

No BTS

Preoperative

36,64 (7,2)

32,56 (6,8)

 

67.06 (5,8)

61,95(9,1

 

46,65 (2,3)

55,14 (4,2)

Postoperative

49,62(4,6)

46,26 (5,4)

*

86,66 (4,2)

80,24 (6,3)

*

38,90(3,5)

36,71(3,3)

One year after operation

43,12 (3,8)

48,1(2,8)

*

80,52 (5,7)

 80,53 (5,2)

 

41,25 (5,5)

41,21(7,2)

P<0.05; PO2: Partial blood pressure of oxygen; HbO2: Oxygen saturation of hemoglobin; Hct: Hematocrit; BTS: Blalock Taussig shunt.

 

A significant variation was shown in the diameter of the right pulmonary branches related to the contribution of the additional flow through PAT (p=0.04). The average of the increase of left branches was also greater in the group with additional flow (Table 3).

Table 3. Variation of diameter of pulmonary branches according to option of additional flow.

Pulmonary branches

Glenn w/o accessory flow.
Averages(±SD) (mm)

Glenn with accessory flow.
Averages(±SD) (mm)

 

Right

1,30(±2,14)

2,84(±3,44)

p=0,039

Left

1,06(±1,72)

1,54(±2,84)

p=0,465

 

As Table 4 shows, TCPD was made in 24 patients, in 40% of those that survived PCPD with BTS, 13 patients. In 11 (72%), with closed PAT, the cavopulmonary derivation was completed (p=0.84), RR=1.03 CI (0.62 to 1.71).

Table 4. Performance of total cavopulmonary derivation according to additional flow

 

TCPD.
n(%)
No TCPD.
n(%)

n Total
(%)

BTS 13 (40%) 9 (60%)

22 (100%)

No BTS

11 (72%)

7 (28%)

18 (100%)

Total

24 (55%)

16 (45%)

40 (100%)

P=0.84;  RR=1.03;  CI (0.62 to 1.71); TCPD: Total cavopulmonary derivation;
BTS:
Blalock Taussig shunt.

 

The interval in months between BCPD and TCPA was greater, although not significant for the group with BTS (p=0.69). The time in which the patients with BTS lived without requiring TCPD did not show significant differences in regard to the group without BTS (p=0.86) either. The averages in the time of follow-up were similar for all the patients (Table 5).

Table 5. Relation between time without total cavopulmonary derivation and additional flow

 

Interval in months BCPD-TCPD
n=24
Average (±SD)

Time in months only with BCPD.
n=16
Average (±SD)

Time of average evolution. Months
n=40
Average (±SD)

 

BTS

68.15 (±40,58)

186.11 (±32,73)

127.1 (±36,65)

No BTS

60.55 (±51,63)

188.88 (±24,38)

124.7 (±38)

Total

64.35 (±46,1)

187.49 (±28,5)

125.9 (±37,32)

p

0.69

0.86

 

BCPD: Bidirectional cavopulmonary derivation; TCPD: Total cavopulmonary derivation.

 

Perioperative mortality in this series, at the time of the Fontan surgery was 8.3%, one of the deceased patients with BTS (Figure 1). Four patients, two with BTS, died without total derivation. From the 12 patients in our series that did not receive TCPD, seven have patent PAT.

Figure 1. Distribution of the sample according to surgical option and result

BCPD: Bidirectional cavopulmonary derivation; TCPD:  Total cavopulmonary derivation; BTS: Blalock Taussig shunt.

 

Figure 2 shows the time free from TCPD in relation to the option of BTS in the interval studied. There were no significant differences in the long run, at the time of performance of TCPD associated to additional pulmonary flow (p=0.63).

Figure 2. Period free from completion of cavopulmonary derivation according to additional pulmonary artery flow

 


DISCUSSION
The pulsatile contribution of the flow through PAT with native stenosis or pulmonary artery cerclage has been used along with BCPD as an alternative to improve oxygenation, without affecting the aim of decreasing the volume overload into the single ventricle [7,10]. The decision is often arbitrary and its repercussions, have not been explored enough in our area.

In this review, the rate of indication of BCPD was lower that the one mentioned in some publications [8,10,12,13], which may be due to those being multicenter studies or with greater population care areas, regardless of the period studied. The SV was as in other works, the most frequent one [8,10]. BCPD was described as an alternative for TA [14. The progressive volume discharge, in two stages, the resulting remodeling of the ventricular geometry, a better oxygenation and diastolic function of the single ventricle justify the extent of its application in other complex heart diseases with single-ventricle pathophysiology [5,15,16].

Age is a risk factor for the success of BCPD [17,18]. There were few reports of BPCA in newborn babies and small infants [12,19]; the increase in pulmonary vascular pressure forces to find a source of additional flow as a consequence of low oxygen saturations. On the other hand, the ratio of SVC/IVC return flow is inversely proportional to age. If the indication is delayed, cyanosis will show a poor effective pulmonary venous flow and will induce to complete the CPD in a shorter term. Although the ages of indication in our work are similar to those of other studies [8], others indicate the first derivation with a lower average age [13,19].

In the first months of age, there is an increase in intra-acinar arteries; during the first year of life the new arterial branches develop, accompanying the alveolar arborizations. The pulsatile pulmonary flow may determine the growth of the more distal branching, improving the exchange, HbO2 and the endothelial function [7,20].

The parameters measured in our investigation showed significant changes related to the BTS option, which at first we thought would show clinical consequences proving that BCPD with BTS could be a definitive option for some patients. Calvaruso [8], in a series of 273 patients with an average follow-up of five years, presented 7.03% of patients with BCPD with supplementary flow as a definitive procedure, because these patients were in high risk, with satisfactory results.

Mainwaring et al [21], in 92 patients, 42 with BTS, reported three perioperative deaths, two of them with open PAT, the morbidity was higher in the group with BTS. Although he concluded that morbi-mortality is lower in those in whom the additional flow is removed, he supports what other authors propose [8,22] that the additional flow protects against the regression of pulmonary artery diameters, improves ventricular post-load and HbO2. This modifies the need to complete TCPD and allows a greater period of acceptable clinical conditions. Tan [19] mentions that from 29 patients with additional flow, in 9 TCPD was completed as average after 2 years since BCPA. Berdat [10] reports TCPD around 36 months after performing Glenn operation in 36% of the group without BTS and close to 50 months in 30% with BTS. Although the percentage of patients without BTS that was operated to complete the cavopulmonary derivation was greater (Table 4), there does not seem to be a greater risk of needing TCPD related to the existence or not of additional flow, a fact contrary to what was expected by this team at the time of introducing the BTS variant.

In this series, the average of the time interval between the partial and total derivation was greater in the group with BTS, but without significant differences, which does not show the advantage of BTS in regard todelaying the time of facing the patients to the known morbidity of TCPD (Tables 4 and 5).

The benefit is shown, as an intermediary of BCPA with BTS, which may determine a greater time of evolution free from a second intervention. BTS does not represent an additional risk for morbi-mortality and TCPD [22,23,24], although the ideal condition for some is still the absence of BTS and the early indication of TCPA [13].

Although in the comparison of the curves of the time free from a second intervention, we did not find significance, there was a difference in the first five years after the partial derivation.

Between 60 and 70% of the patients with additional flow were free from a second intervention after the five years of the partial derivation. Calvaruso [8] reports in a multicenter study that 70% of the patients were free from Fontan surgery after seven years of partial derivation.

The growth of the pulmonary branches in relation to the option of additional flow was shown, although the difference in the measurements of the right branch was remarkable in comparison to the left one. Kinetics studies of the single-ventricle circulation suggest preferential flows in Glenn surgery toward the right territory [25]. Although the additional flow could be preferential to one pulmonary artery territory or another, this study lacks an evaluation to be able to justify the difference found. In patients with branches of boundary dimensions for the indication of cavopulmonary derivation, the association of trasnpulmonary anterograde flow would be justified to evaluate its growth to complete the cavopulmonary derivation, even when some authors have not found a relation between these and the evolution in the long term [26].

of BTS in BCPD; but do not reinforce the definitive option for these patients in whom the clinical conditions seem to deteriorate to the extent of requiring TCPD before 10 years elapsing since the first one, which compels us to reconsider whether BCPD with BTS could be a definitive option for some patient [18]. Nevertheless, it should be considered an option in patients in risk to avoid facing them early with the morbidity associated [27] to circulation with total cavopulmonary derivation.


CONCLUSIONS
Bidirectional cavopulmonary derivation (BCPD) shows its usefulness in the improvement of PO2, HbO2 at the year of the operation in relation to the preoperative period.

The additional flow through the pulmonary artery trunk favors the growth of pulmonary branches.

The patients with BCPD and additional flow through the pulmonary artery have less probabilities of undergoing reintervention in the first 5 years of evolution for total derivation, than those with closed pulmonary artery trunk.

The Bidirectional Cavopulmonary Derivation with additional flow through the pulmonary artery is not a definitive option for most of the patients with single ventricle heart.

 

 

REFERENCES

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