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ABSTRACT Introduction: The aims of this study were to determine the incidence of severe and moderate primary graft dysfunction (PGD) in our center, to identify, retrospectively, donors’ and recipients’ risk factors for PGD development, and to evaluate the impact of PGD within 30 days after heart transplantation. Methods: Donors’ and recipients’ medical records of 64 consecutive adult cardiac transplantations performed between January 2016 and June 2017 were reviewed. The International Society for Heart and Lung Transplantation (ISHLT) criteria were used to diagnose moderate and severe PGD. Associations of risk factors for combined moderate/severe PGD were assessed with appropriate statistical analyses. Results: Sixty-four patients underwent heart transplantation in this period. Twelve recipients (18.7%) developed severe or moderate PGD. Development of PGD was associated with previous donor cardiopulmonary resuscitation and a history of prior heart surgery in the recipient (P=0.01 and P=0.02, respectively). The 30-day in hospital mortality was similar in both PGD and non-PGD patients. Conclusion: The use of the ISHLT criteria for PGD is important to identify potential risk factor. The development of PGD did not affect short-term survival in our study. More studies should be done to better understand the pathophysiology of PGD.

Abstract Introduction: The Technical Performance Score (TPS) was developed and subsequently refined at the Boston Children's Hospital. Our objective was to translate and validate its application in a developing country. Methods: The score was translated into the Portuguese language and approved by the TPS authors. Subsequently, we studied 1,030 surgeries from June 2018 to October 2020. TPS could not be assigned in 58 surgeries, and these were excluded. Surgical risk score was evaluated using Risk Adjustment in Congenital Heart Surgery (or RACHS-1). The impact of TPS on outcomes was studied using multivariable linear and logistic regression adjusting for important perioperative covariates. Results: Median age and weight were 2.2 (interquartile range [IQR] = 0.5-13) years and 10.8 (IQR = 5.6-40) kilograms, respectively. In-hospital mortality was 6.58% (n=64), and postoperative complications occurred in 19.7% (n=192) of the cases. TPS was categorized as 1 in 359 cases (37%), 2 in 464 (47.7%), and 3 in 149 (15.3%). Multivariable analysis identified TPS class 3 as a predictor of longer hospital stay (coefficient: 6.6; standard error: 2.2; P=0.003), higher number of complications (odds ratio [OR]: 1.84; 95% confidence interval [CI]: 1.1-3; P=0.01), and higher mortality (OR: 3.2; 95% CI: 1.4-7; P=0.004). Conclusion: TPS translated into the Portuguese language was validated and showed to be able to predict higher mortality, complication rate, and prolonged postoperative hospital stay in a high-volume Latin-American congenital heart surgery program. TPS is generalizable and can be used as an outcome assessment tool in resource diverse settings.

Abstract Introduction: Elevated neutrophil-lymphocyte ratio (NLR) has been associated with poorer outcomes in cyanotic patients undergoing single ventricle palliation. Little is known about this biomarker on patients with tetralogy of Fallot (TOF), the most common cyanotic congenital heart disease. Our objective is to study the impact of preoperative NLR on outcomes of TOF patients undergoing total repair. Methods: This retrospective study included 116 consecutive patients between January 2014 and December 2018. Preoperative NLR was measured from the last complete blood count test before the surgery. Using the cutoff value of 0.80, according to the receiver-operating characteristic (ROC) curve, the sample was divided into two groups (NLR < 0.80 and ≥ 0.80). The primary endpoint was hospital length of stay (LOS). Results: ROC curves showed that higher preoperative NLR was associated with longer hospital LOS, with an area under the curve of 0.801±0.040 (95% confidence interval 0.722 - 0.879; P

Abstract This study presents the method used for chest reconstruction and treatment of mediastinitis following cardiac surgery at the Heart Institute of the University of São Paulo Medical School. After infection control with antibiotic therapy associated with aggressive surgical debridement and negative pressure wound therapy, chest reconstruction is performed using flaps. The advantages and disadvantages of negative pressure wound therapy are discussed, as well as options for flap-based chest reconstruction according to the characteristics of the patient and sternum. Further studies are needed to provide evidence to support the decisions when facing this great challenge.

Abstract Introduction: The coronavirus disease 2019 (COVID-19) has negatively impacted healthcare services worldwide. We hypothesized that the pandemic would affect our case mix and mortality. Our objective was to study this impact. Methods: We retrospectively studied all patients who underwent congenital heart surgeries from March 21st to August 21st in 2019 and 2020 using the institutional electronic database. We compared demographic data, preoperative and postoperative length of stay (LOS), risk stratification using Risk Adjustment for Congenital Heart Surgery (RACHS) classification and outcomes in both periods. Results: We observed a 66.7% decrease in our surgical volume (285 × 95 patients). Patients operated in the pre-pandemic period were older (911.3 [174.8 - 5953.8] days-old) compared to the pandemic period (275 days-old; P

Abstract Introduction: The coronavirus disease 2019 (COVID-19) pandemic brought an unprecedented lack of control of what was to come. The intent of this document is to provide a balance of how much was ceased to be done for patients with aortic disease, to assess the mortality of these patients, and to show what happened to those who became COVID-19 positive during their hospitalization. Methods: From April 1st to July 31st 2020, the worst period of the pandemic in São Paulo, Brazil, the Institute’s aortic surgical patients operated on were evaluated and those were compared with patients operated during the same period in 2019. Results: In 2019, 88 surgeries were performed; most of them were elective (66 [75%]), 10 were urgent, and 12 were emergency surgeries. In 2020, during the COVID-19 pandemic, we operated on only 31 patients, being 74.2% non-elective surgeries (P

Abstract Introduction: Anemia and blood transfusion are risk factors for morbidity/mortality in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). The objective of this study is to analyze the association of blood transfusion with morbidity/mortality in patients undergoing coronary artery bypass grafting (CABG) under CPB in the state of São Paulo, Brazil. Methods: This is a retrospective analysis using the State of São Paulo Registry of Cardiovascular Surgery from November 2013 to August 2014. Blood transfusion was only considered during surgery or within six hours after surgery. Anemia was defined as hematocrit ≤ 37.5%. Patients < 18 years old were excluded. The sample was divided in four groups - Group I (851, no anemia), Group II (200, anemia without blood transfusion), Group III (181, no anemia and transfusion), and Group IV (258, anemia and transfusion). Results: A total of 1,490 patients were included; 639 (42.9%) were anemic and 439 (29.5%) underwent blood transfusion. Group II showed lower composite morbidity (odds ratio [OR] −0.05; confidence interval [CI] −0.27-0.17; P=0.81) than Group III (OR 0.41; CI 0.23-0.59; P=0.018) or Group IV (OR 0.54; CI 0.31-0.77; P=0.016). Group III was at greater risk of mortality (OR 0.73; CI 0.43-1.03; P=0.02) than Group II, which was exposed only to anemia (OR −0.13; CI −0.55-0.29; P=0.75), or Group IV (OR 0.29; CI −0.13-0.71; P=0.539). Conclusion: Anemia in patients undergoing CABG with CPB is bad, but blood transfusion can be worse, increasing at least 50% the risk for mortality and/or morbidity.

Abstract Introduction: The presence of mild to moderate pericardial effusion after cardiac surgery is common and oral medical therapy is usually able to treat it. Larger effusions are less frequent and surgical intervention is usually necessary. However, there are some rare cases of large effusions that are recurrent even after intervention and become challenging to treat. Methods: We describe the case of a patient submitted to coronary artery bypass grafting (CABG) without any intraoperative complications, who was regularly discharged from the hospital. She was referred to our emergency department twice after surgery with large pericardial effusion that was drained. Even after those two interventions and with adequate oral medication, the large effusion recurred. Results: During follow-up, the patient had her symptoms resolved, with no need for further hospital admission. Her echocardiograms after the last intervention showed no pericardial effusion. The present surgical technique demonstrated to be easy to perform, thus it should be considered as a treatment option for these rare cases of large and repetitive effusions, which do not respond to the traditional methods. Conclusions: In challenging cases of recurrent and large pericardial effusions, the pericardial-peritoneal window is an alternative surgical technique that brings clinical improvement and diminishes the risk of cardiac tamponade.

Abstract Since Barnard’s first heterotopic heart transplant in 1974, Copeland’s method has been the greatest contribution to heterotopic transplants but has the drawback of donor’s right ventricular atrophy. This new method proposes a modification in the anastomosis of the superior vena cava aiming to pre-serve donor’s right ventricular function by decompressing the pulmonary territory and reducing the pulmonary arterial pressure, as a biological ventricular assist device. Finally, a second intervention is proposed, where a “twist” is performed to place the donor’s heart in an orthotopic position after re-moval of the native heart. A pioneering research on this method received approval from the ethics committee of the Heart Institute of São Paulo. We believe that this method has the potential to im-prove quality of life in a selected group of patients.

Abstract Objective: To analyze the impact of vacuum-assisted venous drainage (VAVD) on arterial pump flow in a simulated pediatric cardiopulmonary bypass circuit utilizing a centrifugal pump (CP) with an external arterial filter. Methods: The simulation circuit consisted of a Quadrox-I Pediatric oxygenator, a Rotaflow CP (Maquet Cardiopulmonary AG, Rastatt, Germany), and a custom pediatric tubing set primed with Lactated Ringer's solution and packed red blood cells. Venous line pressure, reservoir pressure, and arterial flow were measured with VAVD turned off to record baseline values. Four other conditions were tested with progressively higher vacuum pressures (-20, -40, -60, and -80 mmHg) applied to the baseline cardiotomy pressure. An arterial filter was placed into the circuit and arterial flow was measured with the purge line in both open and closed positions. These trials were repeated at set arterial flow rates of 1500, 2000, and 2500 mL/min. Results: The use of progressively higher vacuum caused a reduction in effective arterial flow from 1490±0.00 to 590±0.00, from 2020±0.01 to 1220±0.00, and from 2490±0.0 to 1830±0.01 mL/min. Effective forward flow decreased with increased levels of VAVD. Conclusion: The use of VAVD reduces arterial flow when a CP is used as the main arterial pump. The reduction in the forward arterial flow increases as the vacuum level increases. The loss of forward flow is further reduced when the arterial filter purge line is kept in the recommended open position. An independent flow probe is essential to monitor pump flow during cardiopulmonary bypass.

Abstract Quadricuspid aortic valve (QAV) is a rare cardiac malformation. Many cases are incidentally diagnosed in aortic surgeries or autopsies and it usually appears as an isolated anomaly. The most widely classification used is the one by Hurwitz and Roberts[1], which divides 7 alphabetical subtypes based on the cusps size. The aim of this report is to describe three different anatomic presentations of this rare aortic valve anomaly.

Introdução: O modelo mais utilizado para predição de mortalidade em cirurgia cardíaca foi recentemente remodelado, mas dúvidas referentes à sua metodologia e desenvolvimento têm sido relatadas. Objetivo: O objetivo deste estudo foi avaliar o desempenho do EuroSCORE II na predição de mortalidade em pacientes submetidos a cirurgia de coronária e/ou valva na instituição. Métodos: Mil pacientes, operados consecutivamente de coronária e/ou valva, entre outubro de 2008 e julho de 2009, foram analisados. O desfecho de interesse foi mortalidade intra-hospitalar. A calibração foi realizada pela correlação entre mortalidade esperada e observada por meio do teste de Hosmer Lemeshow. A discriminação foi calculada pela área abaixo da curva ROC. O desempenho do EuroSCORE II foi comparado com os modelos EuroSCORE e InsCor (modelo local). Resultados: Na calibração, o teste de Hosmer Lemeshow foi inadequado para o EuroSCORE II (P=0,0003) e bom para os modelos EuroSCORE (P=0,593) e InsCor (P=0,184). No entanto, na discriminação, a área abaixo da curva ROC para o EuroSCORE II foi de 0,81 [IC 95% (0,76-0,85), P

INTRODUCTION: The descending branch of the lateral femoral circumflex artery is an option for coronary artery bypass grafting. OBJECTIVE: To evaluate the early patency and adaptation of lumen diameter using multidetector computed angiotomography. METHODS: Thirty-two patients were selected to undergo coronary artery bypass grafting using the descending branch of the lateral circumflex artery, the internal thoracic artery, and other grafts. Evaluations were carried out through high resolution computed tomography performed on the 7th and 90th postoperative day. Diameters of the descending branch of the lateral circumflex artery and the left internal thoracic artery were measured 3 cm before the distal anastomosis, in the middle portion, and 3 cm after the proximal anastomosis. Diameters were compared using paired t-test (P

OBJECTIVE: To report on our initial clinical experience of the utilization of a mechanical anastomotic device (MAD) to perform saphenous vein graft to aorta anastomosis. METHOD: Between June 2002 and May 2003, 17 patients, including 13 male, with a mean age of 64.4 ± 9.4 years, were selected for coronary artery bypass grafting using MAD. A total of 49 anastomoses, 19 arterial and 30 vein grafts, were performed with a mean of 2.9 ± 0.5 anastomoses per patient. Eleven (36.7%) vein-graft anastomoses were performed with conventional sutures and 19 (63.3%) using MAD. The clinical evolution, enzymatic and electrocardiographic alterations as well as an angiographic study were analyzed in the postoperative period. RESULTS: Of the 17 patients, the mechanical device was used on 16 (94.1%). Six (37.5%) patients were operated on under cardiopulmonary bypass with a mean time of 102.9 ± 16.9 minutes. The postoperative evolution was satisfactory in all patients. No patient presented with enzymatic, myocardial infarction or other ischemic electrocardiographic alterations in the immediate postoperative period. Early postoperative angiography was performed in 9 (52.9%) patients. The anastomoses of the left internal thoracic artery to left anterior descending artery were patent in all cases. Of the 15 saphenous vein grafts studied, 11 (73.3%) were performed using MAD, 9 (81.8%) of which were patent. All the 4 conventionally sutured vein anastomoses were patent. No hospital deaths occurred. In the late follow-up, 88.2% of the patients were free of cardiac-related events. CONCLUSIONS: MAD for vein graft-to-aorta anastomosis proved to be feasible, but a wider analysis of the benefits of its utilization regarding operative time, aggression to the patient, patency of the grafts and final cost are necessary.

OBJECTIVES: To evaluate the prognostic implications of myocardial creatine kinase and troponin I (cTn I) in blood samples from the coronary sinus of patients submitted to coronary artery bypass surgery both with and without ischemic preconditioning. METHODS: From October 1998 to May 1999, 35 patients with coronary artery disease who were submitted to coronary artery bypass surgery were studied. Samples containing creatine kinase and cTn I were obtained from the great cardiac vein during surgery at the onset of cardiopulmonary bypass, at the end of the first anastomosis, and at the end of cardiopulmonary bypass. In May 2002, 29 patients were evaluated in regards to the angina functional class, congestive heart failure, number of hospitalizations, myocardial infarction and death. There were 15 patients in the Preconditioned group and 14 in the Control group. Each group was subdivided into patients with and without cardiovascular symptoms. RESULTS: The Control and Preconditioned groups were not significantly different in relation to frequency of cardiovascular symptoms. There were progressive increases of the creatine kinase and cTn I levels at different Interval s of the study. The cTn I in the Preconditioned group was 1.21 ± 0.64 ng/mL and 3.19 ± 3.21 ng/mL in the Control group (pOBJETIVO: Avaliar a implicação prognóstica da dosagem da creatino-quinase miocárdica (CKMB) e Troponina I (cTn I) em amostras no seio coronariano, na evolução de pacientes submetidos a revascularização do miocárdio (RM), com e sem o pré-condicionamento isquêmico. MÉTODO: Entre outubro de 1998 e maio de 1999, 35 pacientes com insuficiência coronariana foram submetidos a RM foram estudados. No intra-operatório foram coletadas amostras do seio coronariano para dosagem de CKMB e cTn I. Os momentos de coleta foram: momento 1-no início da circulação extracorpórea (CEC), momento 2- após a primeira anastomose e momento 3- no final da CEC. Em maio de 2002, 29 pacientes foram avaliados quanto aos sintomas para classe funcional de angina e de insuficiência cardíaca congestiva, número de internações hospitalares, ocorrência de infarto agudo do miocárdio e morte. Os 29 pacientes estavam distribuídos em dois grupos: 15 no grupo pré-condicionamento e 14 no grupo controle. Cada grupo também foi subdividido em: pacientes com sintomas cardiovasculares e assintomáticos. RESULTADOS: Os grupos controle e pré-condicionado não apresentaram diferença estatística para a presença de sintomas cardiovasculares. Houve aumento progressivo nos valores de CKMB e cTn I nos diferentes momentos de coleta. A cTn I no grupo pré-condicionado foi de 1,21 +0,64 ng/ml e 3,19+ 3,21 ng/ml no grupo controle (p

OBJETIVO: Determinar os fatores preditores de má evolução nos pacientes submetidos a revascularização do miocárdio (RM) na fase aguda do infarto do miocárdio (IAM). CASUÍSTICA E MÉTODOS: No período de março de 1998 a novembro de 1999, 49 pacientes foram submetidos a RM na fase aguda do IAM. Foram excluídos pacientes portadores de complicações mecânicas do IAM e submetidos a procedimentos associados a RM. Os pacientes foram divididos em: Grupo I - 29 casos que não apresentaram complicações decorrentes do IAM e Grupo II - 20 casos com uma ou mais complicações. As complicações consideradas foram: isquemia recorrente (18 pacientes), insuficiência cardíaca congestiva (11), choque cardiogênico (9), hipotensão (7), reinfarto (4), taquicardia ventricular sustentada (4) e fibrilação ventricular (3). Os grupos foram considerados comparáveis em relação às características pré-operatórias, exceto pela idade mais avançada no grupo II. No intuito de identificar os fatores determinantes de pior prognóstico pós-operatório, foram correlacionadas e analisadas as características dos pacientes e as complicações do IAM, estudados pelo teste de variância e análise multivariada. RESULTADOS: A mortalidade global foi de 6,12% (3 pacientes), sendo somente no grupo II. A análise multivariada identificou como fatores preditores de mortalidade hospitalar a hipotensão arterial (p=0,045), o choque cardiogênico (p=0,001) e a fibrilação ventricular (p=0,012). CONCLUSÕES: A RM na fase aguda do IAM é um procedimento seguro em pacientes sem complicações, sem mortalidade operatória. A presença de complicações pré-operatórias como choque cardiogênico, fibrilação ventricular e hipotensão são considerados fatores de mau prognóstico nesta condição.

Diretrizes tradicionalmente são desenvolvidas por médicos para aumentar a qualidade dos cuidados ao paciente, podendo fornecer aos seus usuários informação médica valiosa, aumentando a objetividade na decisão médica. Este artigo aborda aspectos determinantes de diretrizes de boa qualidade, sobretudo os métodos de elaboração, discutindo fatores envolvidos em sua aplicabilidade como custos implicações éticas e legais.Traditionally, guidelines are developed by physicians to improve quality of health care, to provide practitioners with valuable medical information and to improve objectivity in medical decision making. Determinant aspects of good guidelines, mainly, development methods, discussing, applicability factors such as costs, ethical and legal implications are approached in this article.

Objetivo: Este estudo testa a hipótese de que curtos períodos de isquemia podem aumentar a proteção obtida pelo pinçamento intermitente da aorta. Métodos: No grupo controle (18), a operação foi realizada com hipotermia sistêmica a 32 ºC com pinçamento intermitente da aorta e uso de circulação extracorpórea (CEC). No segundo grupo, denominado de pré-condicionamento (17), foram acrescidos dois pinçamentos de 3 minutos da aorta com intervalo de 2 minutos de reperfusão entre eles, previamente ao pinçamento intermitente da forma convencional. CK-MB, troponina I, adenosina e lactato foram obtidos do seio ocoronário no início da circulação extracorpórea (1), ao final da segunda anastomose (2) e ao final da CEC (3). Resultados: Os níveis de CK-MB e troponina I apresentaram uma leve tendência a aumentar ao final da CEC no grupo controle, enquanto os de adenosina e lactato não apresentaram diferença. Conclusão: Concluímos que o pré-condicionamento isquêmico não promoveu melhora significante na proteção miocárdica.

OBJETIVO: Avaliar a evolução hemodinâmica imediata na revascularização do miocárdio com pinçamento intermitente da aorta, acrescido ou não de um protocolo de pré-condicionamento. CASUÍSTICA E MÉTODOS: Trinta e cinco pacientes submetidos à revascularização do miocárdio foram randomizados em 2 grupos. No grupo controle (18), o procedimento foi realizado com pinçamento intermitente da aorta; no segundo grupo (17), denominado pré-condicionamento, foram acrescidos 2 pinçamentos curtos da aorta, previamente ao pinçamento intermitente convencional. Foram obtidos a pressão arterial média (PAm), a pressão capilar pulmonar (PCP), o índice cardíaco (IC) e o índice de trabalho sistólico do VE (ITSVE) antes da circulação extracorpórea (1); antes da sutura esternal (2); com 6h (3); 12h (4); 18h (5) e 24h de pós-operatório (6), além da fração de ejeção (FEVE) por ecocardiograma nos momentos 1 e 2. RESULTADOS: Não houve diferença estatística entre os grupos, havendo um aumento do IC e FEVE após a revascularização. Todos os pacientes tiveram boa evolução clínica. CONCLUSÃO: O comportamento hemodinâmico foi semelhante nos dois grupos de pacientes.

O grande atrativo da Operação de Senning como descrita originalmente é a utilização das paredes do próprio átrio do paciente para a realização dos túneis venosos. A atrioseptostomia por balão, utilizada atualmente na grande maioria dos casos de transposição das grandes artérias (TGA), cria grandes comunicações interatriais. Com isso, é necessário a utilização de enxertos biológicos ou sintéticos (Dacron, Teflon e pericárdio bovino) na septação do átrio esquerdo. Doze crianças consecutivas, com idades de 5 meses a 4 anos (média = 20 meses), foram submetidas à Operação de Senning com a utilização de tecidos do próprio paciente. O diagnóstico era de TGA em 9, TGA com comunicação interventricular (CIV) em 1, TGA com estenose pulmonar valvar discreta em 1, TGA com justaposição das aurículas em 1 caso e todas as crianças foram submetidas à atrioseptostomia com balão no período neonatal. Em 5 casos foi utilizada a aurícula esquerda aberta e invertida para a septação interatrial, 1 com inversão e, em 5, inversão com abertura da aurícula esquerda e uso do próprio pericárdio in situ para a realização do túnel das veias pulmonares, devido às reduzidas dimensões do átrio direito (1 caso de justaposição das aurículas). O tempo de internação variou de 10 a 24 dias (média 15 dias), sendo que o período de pós-operatório variou de 7 a 22 dias (média 12 dias). Não houve óbitos no período de internação hospitalar. O seguimento no pós-operatório foi de 8 a 34 meses (média 23 meses) e todos os pacientes apresentaram boa evolução clínica. O ecocardiograma realizado no período de internação e no seguimento pós-operatório não evidenciou sinais de obstrução ao fluxo nos túneis intracardíacos. O uso de tecidos do próprio paciente in situ, com potencial possibilidade de crescimento, resgata a vantagem principal da técnica originalmente descrita por Senning.

Nas operações minimamente invasivas o uso de cânula de menor calibre facilita a realização dos procedimentos cirúrgicos, mas, por outro lado, a drenagem venosa pode ser prejudicada. O emprego de vácuo no reservatório venoso do oxigenador é uma maneira simples e de baixo custo na correção do problema. O objetivo deste trabalho é apresentar nossa experiência com um dispositivo que permite além da utilização do vácuo, a sua regulagem conforme a necessidade específica do paciente e cânula empregada. Esse dispositivo consiste de uma válvula reguladora de vácuo, um filtro para a retenção de líquidos do ar aspirado e um manômetro eletrônico de pressão negativa. Os testes de bancada evidenciaram eficiência e segurança na aplicação da pressão negativa no oxigenador até 250 mmHg em temperaturas de até 40oC. O estudo clínico consistiu, inicialmente, na aplicação em 11 pacientes com esternotomia total. Posteriormente, foi utilizado em esternotomias parciais para tratamento da doença isolada da valva aórtica em 5 casos (L invertido) e 4 casos de atriosseptoplastia. Esse dispositivo permitiu a utilização de cânulas de diâmetros menores que as cânulas únicas convencionais, variando de 32 a 26 Fr, com a utilização de pressões negativas de 62,40 ± 11,69 mmHg com drenagem venosa satisfatória, sem evidências indiretas de hemólise. O dispositivo por nós idealizado permitiu a drenagem venosa assistida com a utilização de vácuo de forma controlada, segura e eficiente.

Visando um melhor resultado estético pode-se optar por técnicas minimamente invasivas na correção cirúrgica das cardiopatias congênitas. Entre os acessos utilizados realizamos a esternotomia parcial em 20 pacientes pediátricos para correção de comunicação interatrial (CIA). Após análise deste grupo de pacientes concluímos tratar-se de técnica cirúrgica segura, de fácil execução e com ótimo resultado estético. Não ocorreram complicações específicas relacionadas ao acesso cirúrgico.A better cosmetic effect may result from minimally invasive techniques available for the surgical correction of congenital cardiopathies. Amongst the possible accesses for the correction of an interatrial communication, we selected a partial sternotomy which we performed in 20 pediatric patients. When analyzed, this group of patients demonstrated that this approach is a safe and easy one, and that the cosmetic result is very satisfactory. No complications specifically related to the surgical access were observed.

Com o advento de novas técnicas cirúrgicas para o tratamento das arritmias cardíacas, em especial da fibrilação atrial, como a cirurgia de Cox, o conhecimento das características e do trajeto das artérias coronárias atriais assumiu grande importância. O objetivo deste trabalho é o estudo desta circulação e a definição dos padrões de irrigação atrial. Para tanto, utilizamos 30 corações a fresco de indivíduos sem cardiopatia prévia, cujas artérias coronárias e ramos foram visibilizados através de injeção de resina vinílica corada com tinta laca preta, seguida de cuidadosa dissecção. Após avaliação macroscópica das peças, não foram encontrados padrões de irrigação uniforme dos átrios. Porém, a artéria do nó sinoatrial (ANSA), quando analisada isoladamente, revelou não apenas padrões de origem, como também padrões de trajeto. Foram descritos 7 padrões de origem e trajeto da ANSA, considerando-se pontos de referências da estrutura anatômica dos átrios. Os padrões descritos, diferente dos encontrados por outros autores, são de fácil interpretação e de aplicabilidade direta em técnicas cirúrgicas que abordam os átrios.Since the appearance of new surgical techniques such as Cox surgery employed for the treatment of cardiac arrhythmia, especially for atrial fibrillation, the knowledge of coronary artery characteristics and courses has been of increasing importance. The aim of this study was the analysis of this circulation and definition of atrial irrigation patterns. Hence, the coronary arteries of 30 normal human hearts were injected with colored resin and carefully dissected. After macroscopic evaluation of the hearts, no atrial irrigation patterns were found. However, when only the sinus atrial node was analyzed, it showed origin patterns as well as course patterns. Seven origin and route patterns of this artery are described, considering the anatomical structure of the atria as reference points. The described patterns, differently from others found in the literature, are easy to understand and apply in surgical techniques which deal with the atria.

A surgical experimental investigation is being carried out in an attempt to provide a viable alternative to the current approaches to cardiac resection of the left ventricular myocardium in cases of cardiomyopathies with dilated ventricle. The experiments are based upon the presence of anatomicosurgical segments in the dog's heart similar to those existing in the atria and ventricles of humans. So far three mongrel dogs (weight 15 kg) were submitted to cardiac catheterism to evaluate the anatomy of the coronary arteries and their branches, the function and cavity of the left ventricle (LV). A lateral thoracotomy on the left side was performed to expose the heart. Cardiopulmonary bypass (CPB) of each animal was established through the right atrium and the femoral artery (4 mg/kg Heparin, at 32°C, intermittent aorta cross-clamping). The left marginal artery and veins were ligated, causing an area of acute myocardial infarction, showing well-defined sharp limits. Such an area was then resected and the left ventricle was reconstructed. The animals were weaned from CPB, one dog having remained in a stable condition during a 7-day period of observation. The second was sacrificed after 4-day period of observation and the third dog died four hours after CPB owing to an excessive reduction of the LV chamber related to an anatomical variation. Pre and post operation transthoracic echocardiograms were obtained after undergoing cardiac catheterism. The echocardiogram revealed discrete mitral insufficiency, reduction of the diameter of the left ventricle with approximation of the papillary muscles, a dysfunction and an impressive reduction of the cavity of the left ventricle. Peri-sutural areas of infarction were not observed. The orientation given by the anatomicosurgical segmentation of the coronary circulation is an important alternative to the present surgical treatment of cardiomyopathies with dilated ventricle.Uma investigação experimental cirúrgica está sendo realizada, numa tentativa de fornecer uma alternativa viável às atuais abordagens para ressecção cardíaca do ventrículo esquerdo em casos de cardiomiopatias com dilatação ventricular. Os experimentos são baseados na presença de segmentos anatomocirúrgicos em corações de cães, similares aos existentes nos átrios e ventrículos humanos. Três cães (peso 15kg) foram submetidos a cateterismo cardíaco, para avaliar a anatomia das artérias coronárias e de seus ramos, a função e cavidade do ventrículo esquerdo (VE). Toracotomia lateral esquerda foi realizada para expôr o coração. Circulação extracorpórea (CEC) de cada animal foi estabelecida através do átrio direito e da artéria femoral (4 mg/kg Heparina, 32°C, clampeamento intermitente da aorta). Artéria e veias marginais esquerdas foram ligadas, causando uma área de infarto agudo do miocárdio, exibindo limites de corte bem definidos. Desta forma, uma área foi ressecada e o ventrículo esquerdo foi reconstruído. Os animais foram desconectados da CEC. Um cão permaneceu em condição estável durante um período de 7 dias de observação. O segundo foi sacrificado após 4 dias de observação e o terceiro cão morreu 4 horas após CEC, devido a uma redução excessiva da câmara do VE relacionada a uma variação anatômica. Os ecocardiogramas transtorácicos pré e pós-operatórios foram obtidos após cateterismo cardíaco. O ecocardiograma revelou insuficiência mitral discreta, redução do diâmetro do ventrículo esquerdo com aproximação dos músculos papilares, uma disfunção e uma redução significativa da cavidade do ventrículo esquerdo. Áreas peri-suturais de infarto não foram observadas. A orientação dada pela segmentação anatomocirúrgica da circulação coronariana é uma alternativa importante ao tratamento cirúrgico atual de cardiomiopatias com ventrículo dilatado.

São apresentados os resultados iniciais de pacientes submetidos à cirurgia de revascularização do miocárdio (RM), nos quais os enxertos venosos foram obtidos através de técnica minimamente invasiva. A técnica consiste na dissecção da veia safena através de incisões de 3 a 4 cm, repetidas a intervalos variáveis (de 8 a 14 cm) sobre o trajeto da veia cuja liberação é feita com auxílio de afastadores apropriados, ótica de iluminação e instrumental específico. A técnica permitiu a obtenção de segmentos de veia de 30 a 65 cm (média de 51,6 cm) através de 2 a 4 incisões na pele. O método foi usado com sucesso em 8 pacientes que receberam 25 enxertos venosos, além de enxertos arteriais. A evolução do membro inferior foi bastante em todos os pacientes, possibilitando deambulação precoce, redução da dor, edemas, hematomas e excelente efeito cosmético.

Objetivo: No sentido de associar os maiores benefícios da operação de revascularização do miocárdio tradicional com a utilização da anastomose da artéria interventricular anterior, com vários dos benefícios da angioplastia, alguns grupos têm começado a realizar a cirurgia de revascularização do miocárdio minimamente invasiva. O objetivo deste trabalho é o relato de nossa experiência inicial com essa abordagem técnica, especialmente com a utilização de videotoracoscopia (VDT) e do estabilizador de sutura (ES). Métodos: Foram operados 73 pacientes, sendo 51 do sexo masculino, com idades variando de 37 a 83 anos, com média de 61,2 anos, portadores de lesão isolada do ramo interventricular anterior acima de 80%. Foi utilizada intubação orotraqueal com sonda de duplo lume. O paciente foi colocado em decúbito lateral direito com 30 graus de rotação. A minitoracotomia anterior, com 8 a 10 cm de extensão, foi realizada no quarto espaço intercostal. Através dessa incisão foram colocados a ótica da videotoracoscopia e os instrumentos cirúrgicos. O pericárdio foi aberto longitudinalmente e reparado para facilitar a exposição do RIA. Não foi utilizada circulação extracorpórea e a freqüência cardíaca foi diminuída no momento da anastomose com o uso de betabloqueador endovenoso. Para a realização da anastomose ATI-RIA, foi utilizado torniquete proximal e distal, além de uso de CO2 para manter o campo operatório livre de sangue. Previamente ao fechamento dos torniquetes, foi feita a administração de 1,5 mg/kg de peso de heparina endovenosa. A anastomose da ATI com o RIA foi realizada com fio de Polipropilene 7-0. O ES, dispositivo metálico acoplado ao afastador foi utilizado na parede anterior do coração, nos últimos 15 casos, para reduzir a movimentação cardíaca, criando condições para uma anastomose mais segura. Resultados: Todos os pacientes apresentaram boa evolução pós-operatória, sem complicações isquêmicas, estando em condições de alta hospitalar entre 2 e 13 dias após reavaliação da operação (média de 4 dias). Cineangiocoronariografia pós-operatória foi realizada em 48 (65,7%) pacientes, sendo que 2 (4,2%) mostraram oclusão na anastomose e 1 (2,1%) oclusão pós anastomose. Os pacientes estão assintomáticos, com seguimento médio de um ano após a cirurgia. No pós-operatório tardio, ocorreram duas mortes: uma devido a pneumonia e a outra a provável tromboembolismo. Conclusões: A cirurgia de revascularização do miocárdio minimamente invasiva mostrou ser uma boa alternativa para determinado grupo de pacientes com insuficiência coronária. Torna possível a operação com melhor estética, menor custo e possibilita uma recuperação mais rápida do que a operação convencional. O uso da VDT e do ES constitui avanço que busca trazer maior apoio técnico ao procedimento.

Acute pulmonary edema is a serious event. Its occurrence in association with interrupted aortic arch and coronary heart disease is rare. Recently, an old patient developed cardiogenic shock and acute pulmonary edema due to acute coronary insufficiency, associated with interrupted aortic arch. The coronary angiography revealed occlusion of the right coronary artery and 95% obstruction in the left main coronary artery, associated with interruption of the descending aorta. Coronary artery bypass graft was performed, without extracorporeal circulation, to the anterior descending coronary artery. We discuss the initial management, given the seriousness of the case.

Os autores apresentam sua experiência com 385 pacientes, no período de 30 meses, que tiveram seu miocárdio revascularizado com o uso exclusivo de enxertos arteriais. Oito deles já haviam sido previamente revascularizados, 114 (29,6%) apresentavam lesão coronária unilateral, 118 (30,6%) biarterial e 153 (39,7%) pacientes tinham comprometimento em 3 ou mais artérias coronárias. A artéria torácica interna esquerda foi utilizada preferencialmente para o ramo interventricular anterior. A artéria coronária direita foi usada in situ para a coronária direita e seus ramos, ou como enxerto livre a partir da aorta ou ainda em "Y" artificial a partir da artéria torácica interna esquerda para ramos diagonais e marginais da coronária esquerda, num total de 108 (28,1%) pacientes. Foram também empregadas as artérias: radial em 215 (55,8%) pacientes, gastroepiplóica direita em 24 (6,3%) pacientes e a artéria epigástrica inferior em 4 (1,1%) pacientes. No total foram realizados 809 enxertos arteriais nesse grupo de pacientes, com 839 anastomoses com as artérias coronárias. Nos pacientes com lesão coronária triarterial a média de artérias revascularizadas foi de 3,2 por paciente. Não foram observados óbitos intra-operatórios. A mortalidade hospitalar foi de 7 (1,8%) pacientes, dos quais apenas 3 (42,8%) decorrentes de baixo débito cardíaco. Os autores destacam as vantagens do uso preferencial de enxertos arteriais na revascularização do miocárdio de grupos selecionados de pacientes, especialmente de faixa etária baixa. Essas conclusões baseiam-se na pequena incidência de morbimortalidade observada, além da reconhecida superioridade dos enxertos arteriais, especialmente da artéria torácica interna, patente a longo prazo e pela possibilidade de sua composição com os demais enxertos arteriais.The authors present their experience over a period of 30 months with 385 patients submitted to myocardial revascularization procedures using only arterial grafts. Eight patients had already been revascularized: 114 (29.6%) had lesions just in one coronary artery, 118 (30.6%) in two arteries and 153 (39.7%) in three or more arteries. The left internal thoracic artery was preferably used for bypassing the anterior interventricular branch. The right internal thoracic artery was used "in situ" for the right coronary artery and its branches or as a free graft from the aorta or even in artificial "Y" from the left internal thoracic artery to the diagonal and marginal branches of the left coronary artery. Other arteries such as the radial artery were used in 215 (55.8%). The right gastroepiploic artery in 24 (6.3%) and the inferior epigastric artery in 4 (1.1%) patients. Summing up, 809 arterial grafts were used in that group of patients and in 839 anastomoses to the coronary arteries. In patients with lesions in three coronary arteries the average of revascularized arteries was 3.2 for each patient. There were no intra-operative deaths. Seven (1.8%) patients died during their stay in the hospital but only 3 (42.8%) of them presented low cardiac output. The authors also emphasize the advantages of using just arterial grafts in a selected group of patients especially young ones. This conclusion is based on the low incidence of morbimortality observed in that group and also due to the well-known superiority of arterial grafts as the internal thoracic arteries which present a high percentage of patency over the years and also make possible a composition with other arterial grafts.

Abstract Introduction: Three-dimensional (3D) printing has become an affordable tool for assisting heart surgeons in the aorta endovascular field, both in surgical planning, education and training of residents and students. This technique permits the construction of physical prototypes from conventional medical images by converting the anatomical information into computer aided design (CAD) files. Objective: To present the 3D printing feature on developing prototypes leading to improved aortic endovascular surgical planning, as well as transcatheter aortic valve implantation, and mainly enabling training of the surgical procedure to be performed on patient's specific condition. Methods: Six 3D printed real scale prototypes were built representing different aortic diseases, taken from real patients, to simulate the correction of the disease with endoprosthesis deployment. Results: In the hybrid room, the 3D prototypes were examined under fluoroscopy, making it possible to obtain images that clearly delimited the walls of the aorta and its details. The endovascular simulation was then able to be performed, by correctly positioning the endoprosthesis, followed by its deployment. Conclusion: The 3D printing allowed the construction of aortic diseases realistic prototypes, offering a 3D view from the two-dimensional image of computed tomography (CT) angiography, allowing better surgical planning and surgeon training in the specific case beforehand.

Abstract Introduction: Donor shortage and organ allocation is the main problem in pediatric heart transplant. Mechanical circulatory support is known to increase waiting list survival, but it is not routinely used in pediatric programs in Latin America. Methods: All patients listed for heart transplant and supported by a mechanical circulatory support between January 2012 and March 2016 were included in this retrospective single-center study. The endpoints were mechanical circulatory support time, complications, heart transplant survival and discharge from the hospital. Results: Twenty-nine patients from our waiting list were assessed. Twelve (45%) patients were initially supported by extracorporeal membrane oxygenation (ECMO) and a centrifugal pump was implanted in 17 (55%) patients. Five patients initially supported by ECMO were bridged to another device. One was bridged to a centrifugal pump and four were bridged to Berlin Heart Excor®. Among the 29 supported patients, 18 (62%) managed to have a heart transplant. Thirty-day survival period after heart transplant was 56% (10 patients). Median support duration was 12 days (interquartile range [IQR] 4 - 26 days) per run and the waiting time for heart transplant was 9.5 days (IQR 2.5-25 days). Acute kidney injury was identified as a mortality predictor (OR=22.6 [CI=1.04-494.6]; P=0.04). Conclusion: Mechanical circulatory support was able to bridge most INTERMACS 1 and 2 pediatric patients to transplant with an acceptable complication rate. Acute renal failure increased mortality after mechanical circulatory support in our experience.

Abstract Introduction: Most risk stratification scores used in surgery do not include external and non-technical factors as predictors of morbidity and mortality. Objective: The present study aimed to translate and adapt transculturally the Brazilian version of the Disruptions in Surgery Index (DiSI) questionnaire, which was developed to capture the self-perception of each member of the surgical team regarding the disruptions that may contribute to error and obstruction of safe surgical flow. Methods: A universalist approach was adopted to evaluate the conceptual equivalence of items and semantics, which included the following stages: (1) translation of the questionnaire into Portuguese; (2) back translation into English; (3) panel of experts to draft the preliminary version; and (4) pre-test for evaluation of verbal comprehension by the target population of 43 professionals working in cardiothoracic surgery. Results: The questionnaire was translated into Portuguese and its final version with 29 items obtained 89.6% approval from the panel of experts. The target population evaluated all items as easy to understand. The mean overall clarity and verbal comprehension observed in the pre-test reached 4.48 ± 0.16 out of the maximum value of 5 on the psychometric Likert scale. Conclusion: Based on the methodology used, the experts' analysis and the results of the pre-test, it is concluded that the essential stages of translation and cross-cultural adaptation of DiSI to the Portuguese language were satisfactorily fulfilled in this study.

Abstract Objective: To analyze the inflammation resulting from myocardial revascularization techniques with and without cardiopulmonary bypass, based on ultrasensitive C-reactive protein (US-CRP) behavior. Methods: A prospective non-randomized clinical study with 136 patients was performed. Sixty-nine patients were enrolled for Group 1 (on-pump coronary artery bypass - ONCAB) and 67 patients were assigned to Group 2 (off-pump coronary artery bypass - OPCAB). All study participants had blood samples collected for analysis of glucose, triglycerides, creatinine, total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL) and creatinephosphokinase (CPK) in the preoperative period. The samples of creatinephosphokinase MB (CKMB), troponin I (TnI) and US-CRP were collected in the preoperative period and at 6, 12, 24, 36, 48 and 72 hours after surgery. We also analyzed the preoperative biological variables of each patient (age, smoking, diabetes mellitus, left coronary trunk lesion, body mass index, previous myocardial infarction, myocardial fibrosis). All angiographically documented patients with >70% proximal multiarterial stenosis and ischemia, documented by stress test or classification of stable angina (class II or III), according to the Canadian Cardiovascular Society, were included. Reoperations, combined surgeries, recent acute myocardial infarction, recent inflammatory disease, deep venous thrombosis or recent pulmonary thromboembolism, acute kidney injury or chronic kidney injury were not included. Results: Correlation values between the US-CRP curve and the ONCAB group, the treatment effect and the analyzed biological variables did not present expressive results. Laboratory variables were evaluated and did not correlate with the applied treatment (P>0.05). Conclusion: The changes in the US-CRP at each moment evaluated from the postoperative period did not show any significance in relation to the surgical technique applied.

Abstract Objective: To report the early results of the BYPASS project - the Brazilian registrY of adult Patient undergoing cArdiovaScular Surgery - a national, observational, prospective, and longitudinal follow-up registry, aiming to chart a profile of patients undergoing cardiovascular surgery in Brazil, assessing the data harvested from the initial 1,722 patients. Methods: Data collection involved institutions throughout the whole country, comprising 17 centers in 4 regions: Southeast (8), Northeast (5), South (3), and Center-West (1). The study population consists of patients over 18 years of age, and the types of operations recorded were: coronary artery bypass graft (CABG), mitral valve, aortic valve (either conventional or transcatheter), surgical correction of atrial fibrillation, cardiac transplantation, mechanical circulatory support and congenital heart diseases in adults. Results: 83.1% of patients came from the public health system (SUS), 9.6% from the supplemental (private insurance) healthcare systems; and 7.3% from private (out-of -pocket) clinic. Male patients comprised 66%, 30% were diabetics, 46% had dyslipidemia, 28% previously sustained a myocardial infarction, and 9.4% underwent prior cardiovascular surgery. Patients underwent coronary artery bypass surgery were 54.1% and 31.5% to valve surgery, either isolated or combined. The overall postoperative mortality up to the 7th postoperative day was 4%; for CABG was 2.6%, and for valve operations, 4.4%. Conclusion: This first report outlines the consecution of the Brazilian surgical cardiac database, intended to serve primarily as a tool for providing information for clinical improvement and patient safety and constitute a basis for production of research protocols.

Abstract Introduction: Coronary artery bypass grafting (CABG) is the most frequently performed heart surgery in Brazil. Recent international guidelines recommend that national societies establish a database on the practice and results of CABG. In anticipation of the recommendation, the BYPASS Registry was introduced in 2015. Objective: To analyze the profile, risk factors and outcomes of patients undergoing CABG in Brazil, as well as to examine the predominant surgical strategy, based on the data included in the BYPASS Registry. Methods: A cross-sectional study of 2292 patients undergoing CABG surgery and cataloged in the BYPASS Registry up to November 2018. Demographic data, clinical presentation, operative variables, and postoperative hospital outcomes were analyzed. Results: Patients referred to CABG in Brazil are predominantly male (71%), with prior myocardial infarction in 41.1% of cases, diabetes in 42.5%, and ejection fraction lower than 40% in 9.7%. The Heart Team indicated surgery in 32.9% of the cases. Most of the patients underwent cardiopulmonary bypass (87%), and cardioplegia was the strategy of myocardial protection chosen in 95.2% of the cases. The left internal thoracic artery was used as a graft in 91% of the cases; the right internal thoracic artery, in 5.6%; and the radial artery in 1.1%. The saphenous vein graft was used in 84.1% of the patients, being the only graft employed in 7.7% of the patients. The median number of coronary vessels treated was 3. Operative mortality was 2.8%, and the incidence of cerebrovascular accident was 1.2%. Conclusion: CABG data in Brazil provided by the BYPASS Registry analysis are representative of our national reality and practice. This database constitutes an important reference for indications and comparisons of therapeutic procedures, as well as to propose subsequent models to improve patient safety and the quality of surgical practice in the country.

Abstract Objective: Introduce the low-cost and easy to purchase simulator without biological material so that any institution may promote extensive cardiovascular surgery training both in a hospital setting and at home without large budgets. Methods: A transparent plastic box is placed in a wooden frame, which is held by the edges using elastic bands, with the bottom turned upwards, where an oval opening is made, "simulating" a thoracotomy. For basic exercises in the aorta, the model presented by our service in the 2015 Brazilian Congress of Cardiovascular Surgery: a silicone ice tray, where one can train to make aortic purse-string suture, aortotomy, aortorrhaphy and proximal and distal anastomoses. Simulators for the training of valve replacement and valvoplasty, atrial septal defect repair and aortic diseases were added. These simulators are based on sewage pipes obtained in construction material stores and the silicone trays and ethyl vinyl acetate tissue were obtained in utility stores, all of them at a very low cost. Results: The models were manufactured using inert materials easily found in regular stores and do not present contamination risk. They may be used in any environment and maybe stored without any difficulties. This training enabled young surgeons to familiarize and train different surgical techniques, including procedures for aortic diseases. In a subjective assessment, these surgeons reported that the training period led to improved surgical techniques in the surgical field. Conclusion: The model described in this protocol is effective and low-cost when compared to existing simulators, enabling a large array of cardiovascular surgery training.

Abstract Objective: To analyze the behavior of platelets after transcatheter valve-in-valve implantation for the treatment of degenerated bioprosthesis and how they correlate with adverse events upon follow-up. Methods: Retrospective analysis of 28 patients who received a valve-in-valve implant, 5 in aortic, 18 in mitral and 5 in tricuspid positions. Data were compared with 74 patients submitted to conventional redo valvular replacements during the same period, and both groups' platelet curves were analyzed. Statistical analysis was conducted using the IBM SPSS Statistics(r) 20 for Windows. Results: All patients in the valve-in-valve group developed thrombocytopenia, 25% presenting mild (50%. Conclusion: Although thrombocytopenia is an extremely common finding after valve-in-valve procedures, the degree of platelet count drop did not correlate with greater incidence of postoperative adverse outcomes in our study population.

Abstract Currently there is a progressive increase in the prevalence of diabetes in a referred for cardiovascular surgery. Benefits of glycemic management (< 180 mg/dL) in diabetic patients compared to patients without diabetes in perioperative cardiac surgery. The purpose of this study is to present recommendations based on international evidence and adapted to our clinical practice for the perioperative management of hyperglycemia in adult patients with and without diabetes undergoing cardiovascular surgery. This update is based on the latest current literature derived from articles and guidelines regarding perioperative management of diabetic patients to cardiovascular surgery.

Abstract Objective: Hemodilution is a concern in cardiopulmonary bypass (CPB). Using a smaller dual tubing rather than a single larger inner diameter (ID) tubing in the venous limb to decrease prime volume has been a standard practice. The purpose of this study is to evaluate these tubing options. Methods: Four different CPB circuits primed with blood (hematocrit 30%) were investigated. Two setups were used with two circuits for each one. In Setup I, a neonatal oxygenator was connected to dual 3/16" ID venous limbs (Circuit A) or to a single 1/4" ID venous limb (Circuit B); and in Setup II, a pediatric oxygenator was connected to dual 1/4" ID venous limbs (Circuit C) or a single 3/8" ID venous limb (Circuit D). Trials were conducted at arterial flow rates of 500 ml/min up to 1500 ml/min (Setup I) and up to 3000 ml/min (Setup II), at 36°C and 28°C. Results: Circuit B exhibited a higher venous flow rate than Circuit A, and Circuit D exhibited a higher venous flow rate than Circuit C, at both temperatures. Flow resistance was significantly higher in Circuits A and C than in Circuits B (P