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Assessment of calf muscle pump in patients with primary varicose veins of the lower limbs by air plethysmography

Abstracts

OBJECTIVE: This article aims at assessing the influence of calf muscle vein reflux (suraland genicular veins) on calf muscle pump function in patients with primary varicose veins of the lower limbs. METHODS: Cross-sectional and prospective study assessing 120 patients divided into two groups (60 subjects each) by physical examination, duplex scan and air plethysmography. The first group showed calf muscle venous reflux, whereas the second group presented absence of reflux. Both groups were examined by air plethysmography to verify calf pump function through measurement of ejection fraction, residual volume fraction, ejected volume and venous filling index in both limbs. RESULTS: In the group of patients with reflux, ejection fraction indexes lower than 60% (p < 0.001) were found in 82.3% (left leg) and 74.6% (right leg) of cases. Levels of residual volume fraction greater than 60% were identified in 62.5% (left leg, p= 0.015) and in 86.7% (right leg, p = 0.014) of assessed cases. There was no statistically significant variation concerning the venous filling index between groups with or without reflux, with p= 0.140 in both legs. Of all patients, 63.6% had calf vein reflux (left leg) and 61.8% (right leg) had ejection volume greater than 150 mL (p = 0.001). CONCLUSIONS: The calf pump function decreased in both lower limbs, due to presence of calf muscle vein reflux (genicular and sural veins).

Air plethysmography; calf pump function; varicose veins; gastrocnemius and soleal veins; duplex scan


OBJETIVO:Avaliar a influência do refluxo das veias musculares da panturrilha (surais e geniculares) na função da bomba muscular da panturrilha em pacientes com varizes primárias nos membros inferiores. MÉTODOS: Estudo transversal prospectivo, no qual os pacientes foram avaliados por meio de exame físico, mapeamento dúplexe pletismografia a ar. Foram selecionados 120 pacientes divididos em dois grupos (60 indivíduos em cada). O primeiro grupo apresentava refluxo das veias musculares da panturrilha e o segundo grupo apresentava ausência de refluxo. Cada grupo foi analisado com pletismografia a ar para estudo da função da bomba da panturrilha. As variáveis estudadas foram fração de ejeção, fração do volume residual, volume ejetado e índice de enchimento venoso para membro inferior direito e esquerdo. RESULTADOS: No grupo com refluxo, índices de fração de ejeção abaixo de 60% (com p < 0,001) foram encontrados em 82,3% (em perna esquerda) e em 74,6% (em perna direita) dos casos. Índices de fração do volume residual acima de 60% foram identificados em 62,5% (em perna esquerda, p = 0,015) e em 86,7% (em perna direita, p = 0,014) dos casos avaliados. Não houve variação estatisticamente significativa para o índice de enchimento venoso entre os grupos com e sem refluxo, com p = 0,140 e p = 0,140 para pernas esquerda e direita, respectivamente. Foram encontrados 63,6% dos pacientes com refluxo das veias da panturrilha (em perna esquerda), e 61,8% (em perna direita) com volume ejetado acima de 150 mL (p = 0,001). CONCLUSÕES: Houve alteração da bomba muscular da panturrilha, levando a uma diminuição de sua função, em ambos os membros inferiores por conseqüência da presença do refluxo das veias musculares da panturrilha (geniculares e surais).

Pletismografia a ar; bomba muscular da panturrilha; varizes; veias gastrocnêmias e soleares; mapeamento dúplex


ORIGINAL ARTICLE

Assessment of calf muscle pump in patients with primary varicose veins of the lower limbs by air plethysmography

André de Araújo SacchiI; Aldemar Araújo CastroII; Guilherme Benjamin Brandão PittaIII; Fausto Miranda JuniorIV

I

IIMSc. Assistant professor, Department of Social Medicine, Universidade Estadual de Ciências da Saúde de Alagoas/Escola de Ciências Médicas de Alagoas (UNCISAL/ECMAL), Maceió, AL, Brazil

IIIPhD. Associate professor, Department of Surgery, UNCISAL/ECMAL, Maceió, AL, Brazil

IVFull professor of Vascular Surgery, Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil

Correspondence Correspondence:André de Araujo Sacchi Rua Cônego Pequeno 615, Bairro Prata CEP 58101–343 – Campina Grande, PB Tel.:(83) 3321.2442, (83) 3321.1976, (38) 9913.0509 Email: aasacchi@uol.com.br

ABSTRACT

OBJECTIVE: This article aims at assessing the influence of calf muscle vein reflux (sural and genicular veins) on calf muscle pump function in patients with primary varicose veins of the lower limbs.

METHODS: Cross–sectional and prospective study assessing 120 patients divided into two groups (60 subjects each) by physical examination, duplex scan and air plethysmography. The first group showed calf muscle venous reflux, whereas the second group presented absence of reflux. Both groups were examined by air plethysmography to verify calf pump function through measurement of ejection fraction, residual volume fraction, ejected volume and venous filling index in both limbs.

RESULTS: In the group of patients with reflux, ejection fraction indexes lower than 60% (p < 0.001) were found in 82.3% (left leg) and 74.6% (right leg) of cases. Levels of residual volume fraction greater than 60% were identified in 62.5% (left leg, p = 0.015) and in 86.7% (right leg, p = 0.014) of assessed cases. There was no statistically significant variation concerning the venous filling index between groups with or without reflux, with p = 0.140 in both legs. Of all patients, 63.6% had calf vein reflux (left leg) and 61.8% (right leg) had ejection volume greater than 150 mL (p = 0.001).

CONCLUSIONS: The calf pump function decreased in both lower limbs, due to presence of calf muscle vein reflux (genicular and sural veins).

Keywords: Air plethysmography, calf pump function, varicose veins, gastrocnemius and soleal veins, duplex scan.

Introduction

Varicose veins are the most common manifestation of chronic venous insufficiency.1 It is believed that they originate from the abnormal distensibility of the venous wall. Previous studies have already suggested that veins in patients with varicosities were more distensible than veins in normal patients,2 indicating a likely systemic base for this abnormality. Varicose veins usually start at the site where superficial veins communicate with deep veins, especially at the saphenofemoral and saphenopopliteal junctions and in the perforating vein systems, due to valve insufficiency. Primary varicose veins result from venous dilatation without patent thrombosis, whereas secondary varicose veins are caused by valve damage as a consequence of deep venous thrombosis in which recanalization of the obstruction leads to incompetence of deep and perforating veins. A deficient venous drainage not only leads to increased venous pressure, but also to transmural pressure in capillaries and venules, producing skin changes, fluid exudation, edema and deficiency in tissue nutrition, which favors inflammatory and infectious processes, thromboses and tissue necrosis leading to lipodermatosclerosis and to occasional ulcers.3 Causes of reflux in the deep venous system may have a post–thrombotic origin, but can also be idiopathic. Descending phlebography showed, in cases of idiopathic origin, that the reflux resulted from thick valve cusps, agenesia or valve aplasia.4.5

Through a detailed clinical history, we can identify signs and symptoms that will provide us important information as to origin, extension and severity of the venous problem, as well as identify other possible associated diseases.

Noninvasive (and even invasive) complementary examinations may be requested with the aim of confirming clinical evaluation. The classical tourniquet test can provide information about likely sites of reflux from the deep to the superficial system, but presents difficulties in interpretation when there are nonprominent varicose veins. This test does not identify whether there is obstruction or reflux in the deep venous system either.

Since history and clinical examination do not always indicate the nature and extension of abnormalities reported by patients, noninvasive examinations have been developed to better investigate these factors.6.7 Such examinations are characterized by qualitative and quantitative assessments of venous hemodynamics and provide answers to most questions found in daily clinical practice.8 They can be used, for example, to find out whether there is dysfunction in the calf muscle pump and to determine the extension and severity of the obstruction and venous reflux.

This study aims at studying the effect caused by venous reflux of calf veins in patients with primary varicose veins, using air plethysmography.

Methods

In April and May 2004, 120 patients were consecutively assessed, in a total of 240 lower limbs. After clinical evaluation, the patients were submitted to color duplex ultrasonography, being divided into two groups of 60 patients. The first group presented reflux in calf muscle veins (sural and genicular veins), whereas the second group did not present reflux in these veins. Criterion for reflux was retrograde venous reflux persisting for 0.5 second or more after compression or Valsalva's maneuver.9–11 After groups were identified, the patients were consecutively and quantitatively assessed using air plethysmography. We used the examination protocol described by Nicolaides12 to perform this examination. All the patients were symptomatic and were classified between C2 and C4 according to clinical, etiologic, anatomical and physiopathological (CEAP) classification (Table 1).13 They did not present another concomitant disease in venous and arterial systems that could interfere with results.

CEAP classification

The patients who were included in the study signed a consent form, according to Norm 196/96 and Norm 251/97 of the National Health Council, as well as to the Helsinki Declaration VI and to the Nuremberg Code. The study was approved by the Research Ethics Committee of Universidade Estadual de Ciências da Saúde de Alagoas/Escola de Ciências Médicas de Alagoas (UNCISAL/ECMAL), Maceió, AL, Brazil.

Duplex scan

All patients were assessed by duplex scan, using high–frequency (7.5 or 10 MHz) B–mode (bidimensional image) linear probes. We used pulsed Doppler (venous flow) and color ultrasonography to study primary truck varicose veins. The device used was the HP Image Point Multispeciality Ultrasound System, by Hewlett Packard, 1999.

Each patient was initially studied in a supine position, with external rotation and slight leg flexion. The examination was started at the inguinal crease level, performing cross–sectional scans to study patency and to assess venous diameters under segmental compression throughout the whole extremity. Next, a longitudinal scan was performed to study wave pattern and flow characteristics, assessing responses to respiratory movements (inspiration and expiration), to distal compression and to Valsalva's maneuver.

The study of the internal and external saphenous veins was carried out with the patient standing erect, using 10–MHz transducers. Saphenofemoral and saphenopopliteal junctions and tributaries of the aortic arch, including assessment of perforating veins.

Infragenicular segments (fibular, anterior and posterior tibial veins), as well as calf veins (sural and genicular), were studied in their whole extension and submitted to segmental compressions, in longitudinal and cross–sectional sections, being assessed according to the main following topics: patency, compressibility, texture, diameter and flow characteristics.

Air plethysmography

After duplex scan, all patients were submitted to analysis of calf muscle pump function through air plethysmography using the device SDV 3000 (Angiotec), with computer–automated gauging, manufactured in Brazil.

To perform the examination, the laboratory temperature was maintained between 22 and 24 °C. The examination bed was placed at a height of 55 cm to facilitate changing from supine to standing position.

The plethysmograph is a device connected to a computer and a 35–cm polyurethane air cuff with capacity of approximately 5 liters.

The examination is performed with the patient in a supine position, elevating the leg at 45 ° and with the knee slightly flexed for vein drainage. The foot is placed on a 20–cm support.

The pneumatic cuff is placed on the patient's leg from the knee to the ankle, not exceeding the leg limits, thus allowing good cuff contact with the skin. It promotes a minimal occlusion of superficial leg veins.

The device is then automatically gauged. Care should be taken to avoid the cuff from being in contact with the support for foot elevation or with the examination table, so that there are no problems in device reading. After an electronic command, the cuff is automatically inflated until selected pressure of 6 mmHg, and the data are transmitted to the pressure transducer, located in the device, amplifying the signal and registering it as a graph in the computer screen.

A basal volume value is obtained and then the patient is requested to stand up aided by the examiner, standing on the unassessed limb.

The patient uses a walker for hand support. The graph shows elevation in the curve corresponding to increased venous blood volume in the leg. The graph curve reaches a maximum peak, forming a plateau, indicating that veins are full. The difference between initial and plateau volume represents functional venous volume (VV).

Next, the patient is requested to stand with both feet on the ground and to perform a movement of plantar flexion, causing contraction of calf muscles, then returning to initial position (rest). Decrease observed in the graph curve corresponds to ejected volume (EV), resulting from calf muscle contraction.

After this movement, a new plateau is reached (usually more elevated than the initial plateau) and the patient is requested to perform 10 movements of plantar flexion in a velocity of one movement per second. Decreased volume is also recorded. Residual volume (RV) is calculated based on final basal value in relation to remaining volume at the end of movements.

After plantar flexions are over, the patient is requested to return to initial rest position and relaxation of the assessed leg until reaching a new plateau of venous filling. After leveling, with the aid of the examiner, the patient returns to supine position on the examination table with the foot on the support, and total limb emptying is recorded, shown by a graph leveling corresponding to final volume (FV) (Figure 1).


Volume/time graph is seen on the computer screen. After the graph is created, the software cursor is used to perform markings corresponding to initial zero volume, VV, minimal EV, refilling volume (ReV), minimal residual volume (RVmin) and final volume. The software automatically marks the time spent to reach 90% of venous volume (90% VV).

After these markings are on the graph, the computer automatically processes the calculations for: venous filling index (VFI), ejection fraction (EF) and residual volume fraction (RVF), which are shown on the computer screen.

VFI is the variation produced in the limb divided by the corresponding time, in seconds, from supine to standing position. It is calculated using the following formula: VFI = 90% x VV/VFT90, expressed in mL/s.

We study the calf pump function using the data obtained from the variables EF and RVF.

EF provides the idea of venous reflux during physical activity and the changes that result in less ejected blood. EF is the percentage of ejected total venous volume in a single contraction of the calf muscle, being calculated using the formula: EF = (EV/VV) x 100.

RVF is linearly correlated to walking venous pressure, but it is noninvasively measured using the formula: RVF = (RV/VV) x 100.14

Statistical analysis

In statistical analysis, we used hypothesis test (chi–square test), odds ratio and confidence intervals for variables EF (right and left), RVF (right and left) and EV (right and left). For descriptive analysis, we used tables with absolute frequencies and percentages for assessed variables. We also used a technique of multivariate analysis for frequencies, correspondence analysis, to determine the influence diagram between frequencies of reflux, EF (right and left) and RVF (right and left) and EV (right and left).

Type I error (significance level = a) was set in 5%. Therefore, if p < 0.05, null hypothesis is rejected and the result is considered significant.

Calculations were performed using the software SPSS 8.0 for Windows, Chicago, 1995.

Results

Of the patients assessed, 10.8% (13/120) were male and 89.2% (107/102) were female. Mean age was 35 years (±3 years). In the group of patients with reflux in sural and genicular veins, three patients (5%) were classified as C2, 20 (33.3%) as C3 and 37 (61.6%) as C4. In the group without reflux, 42 (70%) patients were classified as C2, 17 (28.3%) as C3 and one (1.6%) as C4 (Table 1).

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In our sample, we verified that the chi–square test showed association between venous reflux in calf muscle veins and EF > 60%, independent of assessed side.

Among the patients who presented EF > 60% in the left lower limb, 15.5% (9/58) had reflux in the left calf muscle veins, assessed using color–flow Doppler ultrasonography, whereas 84.5% (49/58) did not present that reflux. On the other hand, among those who had EF < 60% in the left calf, most (82.3%, i.e., 51/66 had reflux, opposed to 17.7% (11/66), who did not have reflux, as can be seen in Table 2.

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When the left side was assessed, the chi–square test showed significant association between reflux and EF (Table 2), with likely presence of reflux in the group with left EF under 60% (with 82.3%). Odds ratio showed that an individual with left EF higher than 60% has 25 (1/0.04) times less chances of having reflux in calf veins. Such information is based on the fact that this risk is within an interval lower than 1, i.e., between 0.015 and 0.104, with 95% confidence interval.

The same occurred with the right lower limb in relation to the EF. Among the patients who had EF > 60%, a minority (28.8%, i.e., 10/53) had reflux in calf veins, whereas most patients (71.2%, i.e., 43/53) did not have reflux. Regarding the patients with EF < 60%, most patients (74.6%, i.e., 50/67) had reflux, and the others (25.4%, i.e., 17/67) had no reflux (Table 2).

Chi–square test showed significant association between reflux and EF of the left leg. Reflux was more prevalent in the group with EF of the right leg below 60%. Odds ratio showed that individuals with EF of the right leg below 60% have 12.5 (1/0.08) times more chances of presenting reflux, and this risk could be between 0.033 and 0.191, with 95% confidence interval.

When assessing RVF of the left leg, we found 28.8% (15/52) of reflux in calf veins with values below 35%, and 62.5% (10/16) of reflux with values above 60%. In the group without reflux, there were 71.2% (37/52) below 35%, and 37.5% (6/16) above 60% (Table 2).

Chi–square value 5.96 (with p value = 0.015) showed an association between RVF of the left leg and reflux, that is, these factors have an influence on each other. Odds ratio showed that there is approximately 4 times (exact 4.11) more chances of reflux when RVF of the left leg is above 60%. This is a significant result.

The same was observed for the right lower limb. In this group, in which there was RVF < 35%, 29.2% (14/48) had reflux and 70.8% (34/48) had no reflux in soleal and gastrocnemial veins. However, for RVF values above 60%, 86.7% (13/15) had reflux, opposed to 13.3% (2/15) who did not have reflux (Table 2).

Chi–square value of 1.68 (with p value = 0.140) showed that the RVF of the right leg and reflux are dependent, i.e., they are associated. Odds ratio showed that there are 2 times (exact 1.75) more chances of not having reflux when RVF of the right leg is low (below 35%). This is not a significant result.

VFI was assessed in both groups. In the left leg, indexes above 2 mL/s occurred in limb with reflux in 39.3% (11/28) and in limb without reflux in 60.7% (17/28) of cases. Among indexes lower than 2 mL/s, 53.3% (49/92) presented reflux and 46.7% (43/92) did not present reflux in calf veins (Table 3).

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According to the data presented, there was no significant association between VFI of the left leg and occurrence of reflux. Chi–square test showed that the occurrence of reflux presented equal proportion in groups above and below 2 mL/s. Odds ratio of 0.57 showed that occurrence of reflux was equal in individuals with high or low VFI.

In the same analysis, but for the right leg, 41.9% (13/31) had reflux and 58.1% (18/31) did not have reflux in calf veins in indexes above 2 mL/s. Similarly, for indexes below 2 mL/s, 52.8% (47/89) had reflux and 47.2% (42/89) did not have reflux (Table 3). Therefore, there was no significant association between VFI of the right leg and occurrence of reflux. Chi–square test showed that the occurrence of reflux presented equal proportion in groups above and below 2 mL/s. Odds ratio of 0.57 showed that the occurrence of reflux was statistically identical in groups with VFI above and below 2 mL/s.

The variable EV was also assessed. For the left leg, 25.6% (11/43) of occurrences with EV between 50 and 150 mL had reflux in calf veins, and 74.4% (32/43) had no reflux. On the other hand, among patients who presented EV above 150 mL,

63.6% (49/77) had reflux and 36.4% (28/77) had no reflux (Table 3). Thus, chi–square test showed that the observed data presented statistical evidence of an association between EV of the left leg and reflux. Odds ratio showed that there are 5 times more chances of occurring reflux with EV between 50 and 150 mL.

In the right leg, 29.5% (13/44) of the patients with EV between 50 and 150 mL had reflux in calf veins, whereas 70.5% (31/44) had no reflux. For the group with EV above 150 mL, 61.8% (47/76) had reflux, whereas 38.2% (29/76) had no reflux in sural and genicular veins (Table 3). In Table 3, chi–square test showed that the data observed did not present statistical evidence of association between EV and reflux. Odds ration showed that there are 3.9 times more chances of occurring reflux with EV between 50 to 150 mL, and this odds ratio showed that its 95% confidence interval was higher than unit risk (the interval is above 1).

Figure 2 refers to the result of the multivariate technique for correspondence analysis applied to the data grouped in Table 2, concerning the 120 patients under investigation.


The factors that are closest to reflux are EF below 60% and RVF above 35%.

The patients with EF below 60% are more likely to have reflux in calf veins, whereas the group of patients with EV in the left and right legs above normal volume is more likely to have dilatation of calf veins.

Discussion

Air plethysmography7 and duplex scan8,15 are currently the tools with the highest possibility of measuring absolute volumetric variation and visualization of veins in situ and noninvasively. They are simple, noninvasive and reproducible methods to assess venous hemodynamics of lower limbs.3,5 The data assessed using air plethysmography are quantitative both for valve reflux and for calf muscle pump function, whereas duplex scan16 assesses the same data, but shows anatomical details qualitatively and in segments with reflux and obstruction.17

Differently from the duplex scan, which is an examiner–dependent examination, air plethysmography can be performed by qualified people trained to use the equipment, besides being an examination depending more on the patient than on the examiner, since any variation in posture (such as, for example, a more marked muscle contracture or a partial foot flexion) will change the graph. If the graph is altered, final absolute values are compromised and, consequently, the graph will be incorrectly marked, resulting in misinterpretation, which does not represent the physiopathological reality of the assessed individual. For that reason, every patient who presents any deformity or difficulty in flexing his/her feet will have their examination compromised, and will not be able to finish it. Some patients have difficulty including in understanding the exercises proposed during the examination. When climbing down the examination table, some patients often stand on both feet, causing partial venous emptying of the calf.

For some patients, the examination can be tiring. In cases in which venous filling is slower, the patient should remain standing on one leg only, using only the hands for support, for a longer time, and may present muscle pains and not wait for the end of the examination. In addition, older patients and those with rheumatic, musculoskeletal or heart disease have more difficulty in performing the examination.

Since the examination table has a standardized height of around 55 cm, patients with heights over 1.80 m or below 1.50 m present some difficulty in leaving the examination table without changing the plethysmographic curve.

There is a reproducibility of measures expressed in percentages for VFI, EF and RVF, all having a variation coefficient lower than 10%.18 Our results demonstrate that there is no significant relationship between VFI and reflux in calf veins, since, in the left leg, 60.7% of the patients who had VFI above 2 mL/s had no reflux. Nicolaides12 found VFI above 2 mL/s associated with reduced EF with values below 60%,19 presenting significant signs of venous reflux, and those patients had a potential for developing ulcers in lower limbs.20

The results obtained by those authors demonstrate the development of venous insufficiency8 by alteration in absolute values in symptomatic patients, but with no evident clinical manifestation.12

Venous hypertension is manifested through signs and symptoms that have already been well established by other authors.21,22 There seems to be a disagreement because, in our study, even with no external signs that could raise suspicion of venous hypertension, RFV (which, for some authors,16,21 is related with walking venous pressure) occurred in 86.7% of the patients who presented levels above 60%, and this information is statistically relevant. However, there is agreement with the literature as to the fact that EV does not present statistically significant differences for both genders.23 Although venous compliance is altered due to reflux, there is no influence on venous hemodynamics.24

Air plethysmography allows a complete analysis of venous hemodynamics of the whole limb,25 which can be added to the data obtained by duplex scan, which allows the analysis of abnormalities in individualized veins.8

In venous insufficiency at an early stage, there are cases in which clinical signs do not present direct correspondence with the symptoms reported by patients.22 For these cases, air plethysmography26 plays a major role in the identification, quantification and differentiation of early stages of venous insufficiency. A well indicated examination offers valuable information that could guide the treatment, as well as its follow–up.

The variations found throughout the treatment will quantitatively identify the target points to be achieved and what should be changed in terms of therapeutic approach, promoting a prognosis that is closer to reality and providing more comfort and less anxiety to physicians and patients. Air plethysmography is an examination whose technical applicability is simple, being a noninvasive and low–cost examination that presents important results in the evolution and follow–up of patients with venous diseases.

Therefore, it is concluded that, when there is reflux in calf veins as a primary result of venous insufficiency, hemodynamics of venous reflux will be affected by contraction of calf muscle pump. In case there are no other clinical characteristics to justify presented symptoms and after discarding diseases of varied nature, we found responses in calf muscle pump insufficiency initially caused by structural changes of its veins. However, we should not stop here. Although the data presented in this study have their significance, there is much to be investigated, there is much to be discovered.

References

Manuscript received November 6, 2006, accepted January 30, 2007.

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  • Correspondence:

    André de Araujo Sacchi
    Rua Cônego Pequeno 615, Bairro Prata
    CEP 58101–343 – Campina Grande, PB
    Tel.:(83) 3321.2442, (83) 3321.1976, (38) 9913.0509
    Email:
  • Publication Dates

    • Publication in this collection
      19 July 2007
    • Date of issue
      Mar 2007

    History

    • Accepted
      30 Jan 2007
    • Received
      06 Nov 2006
    Sociedade Brasileira de Angiologia e de Cirurgia Vascular (SBACV) Rua Estela, 515, bloco E, conj. 21, Vila Mariana, CEP04011-002 - São Paulo, SP, Tel.: (11) 5084.3482 / 5084.2853 - Porto Alegre - RS - Brazil
    E-mail: secretaria@sbacv.org.br