Usefulness of speckle tracking echocardiography and biomarkers for detecting acute cellular rejection after heart transplantation.

BACKGROUND: Acute cellular rejection (ACR) is a major complication after heart transplantation. Endomyocardial biopsy (EMB) remains the gold standard for its diagnosis, but it has concerning complications. We evaluated the usefulness of speckle tracking echocardiography (STE) and biomarkers for detecting ACR after heart transplantation. METHODS: We prospectively studied 60 transplant patients with normal left and right ventricular systolic function who underwent EMB for surveillance 6 months after transplantation. Sixty age- and sex-matched healthy individuals constituted the control group. Conventional echocardiographic parameters, left ventricular global longitudinal, radial and circumferential strain (LV-GLS, LV-GRS and LV-GCS, respectively), left ventricular systolic twist (LV-twist) and right ventricular free wall longitudinal strain (RV-FWLS) were analyzed just before the procedure. We also measured biomarkers at the same moment. RESULTS: Among the 60 studied patients, 17 (28%) had severe ACR (grade ≥ 2R), and 43 (72%) had no significant ACR (grade 0 - 1R). The absolute values of LV-GLS, LV-twist and RV-FWLS were lower in transplant patients with ACR degree ≥ 2 R than in those without ACR (12.5% ± 2.9% vs 14.8% ± 2.3%, p=0.002; 13.9° ± 4.8° vs 17.1° ± 3.2°, p=0.048; 16.6% ± 2.9% vs 21.4%± 3.2%, p < 0.001; respectively), while no differences were observed between the LV-GRS or LV-GCS. All of these parameters were lower in the transplant group without ACR than in the nontransplant control group, except for the LV-twist. Cardiac troponin I levels were significantly higher in patients with significant ACR than in patients without significant ACR [0.19 ng/mL (0.09-1.31) vs 0.05 ng/mL (0.01-0.18), p=0.007]. The combination of troponin with LV-GLS, RV-FWLS and LV-Twist had an area under curve for the detection of ACR of 0.80 (0.68-0.92), 0.89 (0.81-0.93) and 0.79 (0.66-0.92), respectively. CONCLUSION: Heart transplant patients have altered left ventricular dynamics compared with control individuals. The combination of troponin with strain parameters had higher accuracy for the detection of ACR than the isolated variables and this association might select patients with a higher risk for ACR who will benefit from an EMB procedure in the first year after heart transplantation.

Relation of mitral valve morphology to surgical repair results in patients with mitral valve prolapse: A three-dimensional transesophageal echocardiography study.

BACKGROUND: The identification of predictors of mitral valve (MV) repair results is important for quality improvement in cardiac surgery. The aim of this study was to evaluate the relationship between MV morphological quantification by three-dimensional (3D) transesophageal echocardiography and mitral repair results. METHODS: Fifty-four patients with MV prolapse who were submitted to surgical repair were divided into 2 groups according to their postoperative mitral regurgitation (MR) degree (group 1, grade 0-I MR; group 2, ≥grade II MR). Morphological parameters related to the mitral ring, dimension of leaflets and prolapse, coaptation line, distance from papillary muscles to the leaflet border and valve angles were analyzed by 3D MV quantification. Cardiac remodeling and MR quantitative parameters were also evaluated. RESULTS: There was no correlation between 3D MV quantification and surgical results; a multivariate analysis did not show an association between morphological parameters and surgical outcome. The distance from the posteromedial papillary muscle to the leaflet border was higher (P = .038) in patients with ≥grade II postoperative MR. The left atrial diameter, left ventricular end-systolic diameter, left ventricular end-diastolic and end-systolic volumes were larger in patients with a significant residual MR (P < .05). CONCLUSION: Three-dimensional MV quantification did not predict the postoperative MR grade; however, the distance from the posteromedial papillary muscles to the leaflet border may be related to suboptimal repair results. Furthermore, excessive cardiac remodeling was related to postoperative MR ≥ grade II, what could suggest a potential benefit of early surgical treatment.

Evaluation of cardiac masses by real-time perfusion imaging echocardiography.

BACKGROUND: Diagnosis of cardiac masses is still challenging by echocardiography and distinguishing tumors from thrombi has important therapeutical implications. We sought to determine the diagnostic value of real-time perfusion echocardiography (RTPE) for cardiac masses characterization. METHODS: We prospectively studied 86 patients, 23 with malignant tumors (MT), 26 with benign tumors (BT), 33 with thrombi and 6 with pseudotumors who underwent RTPE. Mass perfusion was analyzed qualitatively and blood flow volume (A), blood flow velocity (ß), and microvascular blood flow (A x ß) were determined by quantitative RTPE. RESULTS: Logistic regression models showed that the probability of having a tumor increased by 15.8 times with a peripheral qualitative perfusion pattern, and 34.5 times with a central perfusion pattern, in comparison with the absence of perfusion. Using quantitative RTPE analysis, thrombi group had parameters of blood flow lower than tumor group. A values for thrombi, MT, and BT were 0.1 dB (0.01-0.22), 2.78 dB (1-7) and 2.58 dB (1.44-5), respectively; p < 0.05, while A x ß values were 0.0 dB/s(-1) (0.01-0.14), 2.00 dB/s(-1) (1-6), and 1.18 dB/s(-1) (0.52-3), respectively; p < 0.05. At peak dipyridamole stress, MT had greater microvascular blood volume than BT [A = 4.18 dB (2.14-7.93) versus A = 2.04 dB (1.09-3.55); p < 0.05], but no difference in blood flow [Axß = 2.46 dB/s(-1) (1.42-4.59) versus Axß = 1.55 dB/s [1] (0.51-4.08); p = NS]. An A value >3.28 dB at peak dipyridamole stress predicted MT (AUC = 0.75) and conferred 5.8-times higher chance of being MT rather than BT. CONCLUSION: RTPE demonstrated that cardiac tumors have greater microvascular blood volume and regional blood flow when compared with thrombi. Dipyridamole stress was useful in differentiating MT from BT.

Reversible pulmonary trunk banding: Myocardial vascular endothelial growth factor expression in young goats submitted to ventricular retraining.

BACKGROUND: Ventricle retraining has been extensively studied by our laboratory. Previous studies have demonstrated that intermittent overload causes a more efficient ventricular hypertrophy. The adaptive mechanisms involved in the ventricle retraining are not completely established. This study assessed vascular endothelial growth factor (VEGF) expression in the ventricles of goats submitted to systolic overload. METHODS: Twenty-one young goats were divided into 3 groups (7 animals each): control, 96-hour continuous systolic overload, and intermittent systolic overload (four 12-hour periods of systolic overload paired with 12-hour resting period). During the 96-hour protocol, systolic overload was adjusted to achieve a right ventricular (RV) / aortic pressure ratio of 0.7. Hemodynamic evaluations were performed daily before and after systolic overload. Echocardiograms were obtained preoperatively and at protocol end to measure cardiac masses thickness. At study end, the animals were killed for morphologic evaluation and immunohistochemical assessment of VEGF expression. RESULTS: RV-trained groups developed hypertrophy of RV and septal masses, confirmed by increased weight and thickness, as expected. In the study groups, there was a small but significantly increased water content of the RV and septum compared with those in the control group (p<0.002). VEGF expression in the RV myocardium was greater in the intermittent group (2.89% ± 0.41%) than in the continuous (1.80% ± 0.19%) and control (1.43% ± 0.18%) groups (p<0.023). CONCLUSIONS: Intermittent systolic overload promotes greater upregulation of VEGF expression in the subpulmonary ventricle, an adaptation that provides a mechanism for increased myocardial perfusion during the rapid myocardial hypertrophy of young goats.

Assessment of a new experimental model of isolated right ventricular failure.

We assessed a new experimental model of isolated right ventricular (RV) failure, achieved by means of intramyocardial injection of ethanol. RV dysfunction was induced in 13 mongrel dogs via multiple injections of 96% ethanol (total dose 1 mL/kg), all over the inlet and trabecular RV free walls. Hemodynamic and metabolic parameters were evaluated at baseline, after ethanol injection, and on the 14th postoperative day (POD). Echocardiographic parameters were evaluated at baseline, on the sixth POD, and on the 13th POD. The animals were then euthanized for histopathological analysis of the hearts. There was a 15.4% mortality rate. We noticed a decrease in pulmonary blood flow right after RV failure (P = 0.0018), as well as during reoperation on the 14th POD (P = 0.002). The induced RV dysfunction caused an increase in venous lactate levels immediately after ethanol injection and on the 14th POD (P < 0.0003). The echocardiogram revealed a decrease in the RV ejection fraction on the sixth and 13th PODs (P = 0.0001). There was an increased RV end-diastolic volume on the sixth (P = 0.0001) and 13th PODs (P = 0.0084). The right ventricle showed a 74% +/- 0.06% transmural infarction area, with necrotic lesions aged 14 days. Intramyocardial ethanol injection has allowed the creation of a reproducible and inexpensive model of RV failure. The hemodynamic, metabolic, and echocardiographic parameters assessed at different protocol times are compatible with severe RV failure. This model may be useful in understanding the pathophysiology of isolated right-sided heart failure, as well as in the assessment of ventricular assist devices.

Group A Streptococcus Adsorbed Vaccine: Repeated Intramuscular Dose Toxicity Test in Minipigs.

Streptococcus pyogenes infection continues to be a worldwide public health problem causing various diseases in humans and plays an important role in the pathogenesis of rheumatic fever and rheumatic heart disease. We developed a vaccine candidate to prevent S. pyogenes infections, identified as StreptInCor, that presented promising results in mouse models. A certified and independent laboratory conducted two repeated intramuscular dose toxicity tests (28 days, four weekly injections). The first test, composed of four experimental groups treated with 0 (vehicle), 50, 100 or 200 µg/500 µL StreptInCor, did not show significant alterations in clinical, hematological, biochemical or anatomopathological parameters related to the administration of StreptInCor. In addition to the parameters mentioned above, we evaluated the cardiac function and valves of animals by echocardiography before and after administration of 200 µg/500 µL StreptInCor versus placebo. We did not observe any changes related to StreptInCor administration, including changes in cardiac function and valves in animals, after receiving the highest dose of this vaccine candidate. The results obtained in the two repeated intramuscular dose toxicity tests showed that this vaccine formulation did not induce harmful effects to the tissues and organs studied, indicating that the candidate vaccine is well tolerated in minipigs.

Reversible pulmonary trunk banding VIII: Intermittent overload causes harmless hypertrophy in adult goat.

BACKGROUND: Traditional pulmonary artery banding (PAB) is not always suitable for mature subpulmonary ventricle retraining. We sought to assess in detail the myocardial morphologic adaptations of two different protocols for inducing right ventricular (RV) hypertrophy in an adult animal model. METHODS: Eighteen adult goats were distributed into three groups: sham (no systolic overload), traditional (continuous systolic overload), and intermittent (daily 12-hour systolic overload). Systolic overload was adjusted to achieve a 0.7 RV-to-aortic pressure ratio. All animals underwent weekly echocardiographic studies, and hemodynamic evaluations were performed 3 times a week. After 4 weeks, the animals were humanely killed for morphologic assessment. RESULTS: A 37.2% increase was observed in the RV wall thickness of the intermittent group (p<0.05), but no significant echocardiographic changes were observed in the other two groups. The intermittent and traditional groups had a 55.7% and 36.7% increase in RV mass, respectively, compared with the sham group (p<0.05). No differences were observed in myocardial water content of the three groups (p=0.27). RV myocardial fiber and nuclei diameters were increased in the intermittent group compared with the sham group (p<0.05). The area of collagen deposition in the RV interstitium was increased 98% in traditional group compared with the sham group (p<0.05). No significant cellular proliferation occurred in any group. CONCLUSIONS: This study suggests that a more effective and harmless hypertrophy can be achieved in adult animals using intermittent PAB compared with the traditional approach.

Reversible pulmonary trunk banding: VII. Stress echocardiographic assessment of rapid ventricular hypertrophy in young goats.

BACKGROUND: Ventricle retraining with abrupt systolic overload can cause myocardial edema and necrosis, followed by late ventricular failure. Intermittent systolic overload could minimize the inadequacy of conventional pulmonary artery banding. The present study compared ventricle function under dobutamine stress in 2 protocols of systolic overload in young goats. METHODS: Nineteen young goats were divided into 3 groups: sham (n = 7; no systolic pressure overload), continuous (n = 6; systolic overload maintained for 96 hours), and intermittent (n = 6; 4 periods of 12-hour systolic overload, paired with a 12-hour resting period). Echocardiographic and hemodynamic evaluations were performed daily. The myocardial performance index and ejection fraction were evaluated at rest and during dobutamine stress. The goats were then killed for morphologic evaluation. RESULTS: The intermittent group underwent less systolic overload than the continuous group (P < .05). Nevertheless, both groups had increased right ventricular and septal masses compared with the sham group (P < .0002). Echocardiography revealed a major increase in right ventricular wall thickness in the intermittent group (+64.8% ± 23.37%) compared with the continuous group (+43.9% ± 19.26%; P = .015). Only the continuous group remained with significant right ventricular dilation throughout the protocol (P < .001). The intermittent group had a significantly better myocardial performance index at the end of the protocol, under resting and dobutamine infusion, compared with the continuous group (P < .012). CONCLUSIONS: Both systolic overload protocols have induced rapid right ventricular hypertrophy. However, only the intermittent group had better preservation of right ventricular function at the end of the protocol, both at rest and during dobutamine infusion.

Reversible pulmonary trunk banding. VI: Glucose-6-phosphate dehydrogenase activity in rapid ventricular hypertrophy in young goats.

OBJECTIVE: Increased myocardial glucose-6-phosphate dehydrogenase (G6PD) activity occurs in heart failure. This study compared G6PD activity in 2 protocols of right ventricle (RV) systolic overload in young goats. METHODS: Twenty-seven goats were separated into 3 groups: sham (no overload), continuous (continuous systolic overload), and intermittent (four 12-hour periods of systolic overload paired with a 12-hour resting period). During a 96-hour protocol, systolic overload was adjusted to achieve a 0.7 RV/aortic pressure ratio. Echocardiographic and hemodynamic evaluations were performed before and after systolic overload every day postoperatively. After the study period, the animals were humanely killed for morphologic and G6PD tissue activity assessment. RESULTS: A 92.1% and 46.5% increase occurred in RV and septal mass, respectively, in the intermittent group compared with the sham group; continuous systolic overload resulted in a 37.2% increase in septal mass. A worsening RV myocardial performance index occurred in the continuous group at 72 hours and 96 hours, compared with the sham (P < .039) and intermittent groups at the end of the protocol (P < .001). Compared with the sham group, RV G6PD activity was elevated 130.1% in the continuous group (P = .012) and 39.8% in the intermittent group (P = .764). CONCLUSIONS: Continuous systolic overload for ventricle retraining causes RV dysfunction and upregulation of myocardial G6PD activity, which can elevate levels of free radicals by NADPH oxidase, an important mechanism in the pathophysiology of heart failure. Intermittent systolic overload promotes a more efficient RV hypertrophy, with better preservation of myocardial performance and and less exposure to hypertrophic triggers.

Intermittent systolic overload promotes better myocardial performance in adult animals.

BACKGROUND: Corrected transposition of great arteries often evolves with right ventricular dysfunction. The ventricular preparation for anatomic correction in adult patients has produced disappointing results. OBJECTIVE: To assess right ventricular hypertrophy (RV) induced by conventional and intermittent pulmonary banding (PB) in adult animals. METHODS: Nineteen adult goats were divided into three groups: conventional (six animals), intermittent (six animals) and control (seven animals). The Conventional group underwent fixed PB with cardiac tape, while the intermittent group received PB adjustable device, which generated systolic overload for 12 hours, alternated with 12 hours of rest of RV. The pressures of the RV, pulmonary artery and aorta were measured throughout the study. Echocardiography was performed weekly. After four weeks, the animals were euthanized for morphological evaluation of the ventricles. The Control group was put to euthanasia for analysis at baseline. RESULTS: Pressure overload was lower in the intermittent group (p = 0.001), compared to the conventional group. There was an increase in the thickness of the RV of the Intermittent group measured by echocardiography compared to their baseline values (p < 0.05). The myocardial performance index in the RV group was better in the Intermittent group (p = 0.024), compared to the Conventional group. The groups stimulated showed increased muscle mass compared to the Control group (p = 0.001). There was no difference in myocardial water content. CONCLUSION: The intermittent BP developed hypertrophy of better performance, suggesting this protocol as the preferred method of ventricular preparation.

Reversible pulmonary trunk banding III: assessment of myocardial adaptive mechanisms-contribution of cell proliferation.

OBJECTIVES: Rapid ventricular conditioning induced by pulmonary artery banding has been recommended for patients with transposition of the great arteries who have lost the chance for the arterial switch operation or whose systemic (right) ventricle failed after the atrial switch. The present study was designed to experimentally evaluate 2 types of pulmonary artery banding (continuous and intermittent) and verify histologically the changes (hypertrophy or hyperplasia or both) of cardiomyocytes and vascular and interstitial cells from the stimulated ventricle beyond the neonatal period. METHODS: Twenty-one goats, 30 to 60 days old, were divided into 3 groups, each comprising 7 animals, as follows: control group (no surgical procedure); continuously stimulated group (systolic overload maintained for 96 hours); and intermittently stimulated group (4 periods of 12-hour systolic overload, alternated with a resting period of 12 hours). The animals were then killed for histologic and immunohistochemical analysis of the hearts. Murine monoclonal antibody Ki-67 was used as a proliferation cell marker. Myocardial collagen area fraction was determined by Sirius red staining. RESULTS: For both stimulated groups, a significant increase occurred in right ventricular cardiomyocytes and respective nuclei diameters compared with the controls (P < .05). The number of Ki-67-positive cardiomyocytes and interstitial/vessel cells from the right ventricle was augmented in both trained groups in relation to the left ventricle (P < .05). There was no significant difference in the right ventricular collagen area fraction from both trained groups compared with controls. CONCLUSIONS: Irrespective of the shorter training time (periods of overload intercalated with resting), the intermittent stimulation regimen was able to produce a similar training of the subpulmonary ventricle compared with the continuous stimulation regarding mass acquisition, cell hypertrophy, and hyperplasia.

Sobrecarga sistólica intermitente promove melhor desempenho miocárdico em animais adultos / Intermittent systolic overload promotes better myocardial performance in adult animals / Sobrecarga sistólica intermitente promueve mejor desempeño miocárdico en animales adultos

FUNDAMENTO: A transposição corrigida das grandes artérias frequentemente evolui com disfunção ventricular direita. O preparo ventricular para a correção anatômica em pacientes adultos apresenta resultados desapontadores. OBJETIVO: Analisar a hipertrofia do ventrículo direito (VD) induzida por dois tipos de bandagem pulmonar (BP), convencional e intermitente em animais adultos. MÉTODOS: Dezenove cabras adultas foram divididas em três grupos: Convencional (seis animais), Intermitente (seis animais) e Controle (sete animais). O grupo Convencional foi submetido à BP fixa com fita cardíaca, enquanto no grupo Intermitente foi usado dispositivo de BP ajustável, que gerava sobrecarga sistólica por 12 horas, alternada com 12 horas de descanso do VD. As pressões de VD, tronco pulmonar e aorta foram medidas durante todo o estudo. Ecocardiograma foi realizado semanalmente. Após quatro semanas, os animais foram eutanasiados para avaliação morfológica dos ventrículos. O grupo Controle foi submetido a eutanásia para análise em condições basais. RESULTADOS: A sobrecarga pressórica foi menor no grupo Intermitente (p=0,001), comparada ao grupo Convencional. Houve aumento na espessura do VD do grupo Intermitente, medida pelo ecocardiograma, comparado ao seu momento basal (p<0,05). O índice de performance miocárdica do VD foi melhor no grupo Intermitente (p=0,024), comparado ao Convencional. Os grupos estimulados apresentaram aumento da massa muscular em comparação ao grupo Controle (p=0,001). Não houve diferença no conteúdo de água miocárdica. CONCLUSÃO: A BP intermitente desenvolveu hipertrofia de melhor desempenho funcional, sugerindo este protocolo como método preferencial de preparo ventricular.

BACKGROUND: Corrected transposition of great arteries often evolves with right ventricular dysfunction. The ventricular preparation for anatomic correction in adult patients has produced disappointing results. OBJECTIVE: To assess right ventricular hypertrophy (RV) induced by conventional and intermittent pulmonary banding (PB) in adult animals. METHODS: Nineteen adult goats were divided into three groups: conventional (six animals), intermittent (six animals) and control (seven animals). The Conventional group underwent fixed PB with cardiac tape, while the intermittent group received PB adjustable device, which generated systolic overload for 12 hours, alternated with 12 hours of rest of RV. The pressures of the RV, pulmonary artery and aorta were measured throughout the study. Echocardiography was performed weekly. After four weeks, the animals were euthanized for morphological evaluation of the ventricles. The Control group was put to euthanasia for analysis at baseline. RESULTS: Pressure overload was lower in the intermittent group (p = 0.001), compared to the conventional group. There was an increase in the thickness of the RV of the Intermittent group measured by echocardiography compared to their baseline values (p < 0.05). The myocardial performance index in the RV group was better in the Intermittent group (p = 0.024), compared to the Conventional group. The groups stimulated showed increased muscle mass compared to the Control group (p = 0.001). There was no difference in myocardial water content. CONCLUSION: The intermittent BP developed hypertrophy of better performance, suggesting this protocol as the preferred method of ventricular preparation.

FUNDAMENTO: La transposición corregida de las grandes arterias frecuentemente evoluciona con disfunción ventricular derecha. La preparación ventricular para la corrección anatómica en pacientes adultos presenta resultados desalentadores. OBJETIVO: Analizar la hipertrofia del ventrículo derecho (VD) inducida por dos tipos de vendaje pulmonar (VP), convencional e intermitente en animales adultos. MÉTODOS: Diecinueve cabras adultas fueron divididas en tres grupos: Convencional (seis animales), Intermitente (seis animales) y Control (siete animales). El grupo Convencional fue sometido al VP fijo con cinta cardíaca, mientras que en el grupo Intermitente fue usado dispositivo de VP ajustable, que generaba sobrecarga sistólica por 12 horas, alternada con 12 horas de descanso del VD. Las presiones de VD, tronco pulmonar y aorta fueron medidas durante todo el estudio. Ecocardiograma fue realizado semanalmente. Después de cuatro semanas, los animales fueron eutanasiados para evaluación morfológica de los ventrículos. El grupo Control fue sometido a eutanasia para análisis en condiciones basales. RESULTADOS: La sobrecarga presórica fue menor en el grupo Intermitente (p=0,001), comparada al grupo Convencional. Hubo aumento en el espesor del VD del grupo Intermitente, medida por el ecocardiograma, comparado a su momento basal (p<0,05). El índice de performance miocárdica del VD fue mejor en el grupo Intermitente (p=0,024), comparado al Convencional. Los grupos estimulados presentaron aumento de la masa muscular en comparación al grupo Control (p=0,001). No hubo diferencia en el contenido de agua miocárdica. CONCLUSIÓN: EL VP intermitente desarrolló hipertrofia de mejor desempeño funcional, sugiriendo este protocolo como método preferencial de preparación ventricular.

Outflow occlusion for circulatory arrest in dogs / "Outfow occlusion" para parada circulatória em cães

The purpose of this study was to evaluate the possibility of producing circulatory arrest by occlusion of the pulmonary trunk as an alternative to the venous inflow occlusion through the left hemithorax. Eight healthy mongrel dogs were divided in two groups. Group I underwent 4 minutes of outflow occlusion and Group II was submitted to 8 minutes of circulatory arrest. Outflow occlusion was performed through left thoracotomy and pericardiotomy by passing a Rumel tourniquet around the pulmonary trunk. Physical examination, electrocardiography, echocardiography, blood gas analyses, hemodynamic, and oxygen transport variables were obtained before and after the procedure. The dogs from Group I did not have any clinical, electrocardiographic, echocardiographic, or hemo-dynamic abnormalities after anesthetic recover. In the Group II, only one dog survived, which had no clinical, electrocardiographic, or echocardiographic abnormalities. In this last dog, just after releasing the occlusion, it was detected increases in the following parameters: heart rate (HR), systolic, diastolic and mean arterial blood pressure (SAP; DAP; MAP), pulmonary artery pressure (PAP), pulmonary wedge pressure (PWP), central venous pressure (CVP), cardiac output (CO), systolic index (SI), cardiac index (CI), left and right ventricular stroke work (LVSW; RVSW), oxygen delivery index (DO2), oxygen consumption index (VO2), and oxygen extraction (O2 ext). Moreover, the oxygen content of arterial and mixed venous blood (CaO2; CvO2), and the arterial and mixed venous partial pressure of oxygen (PaO2; PvO2) were decreased 5 minutes after circulatory arrest. Outflow occlusion is a feasible surgical procedure for period of 4 minutes of circulatory arrest.

O objetivo deste estudo foi avaliar a possibilidade de se produzir uma parada circulatória pela oclusão do tronco pulmonar, como alternativa ao "inflow occlusion", pelo hemitórax esquerdo. Oito cães sem raça definida foram divididos em dois grupos. O Grupo I foi submetido a quatro minutos de parada circulatória e o Grupo II, a 8 minutos de parada. Realizou-se o "outflow occlusion" por meio de toracotomia intercostal esquerda e pericardiotomia, passando-se um torniquete de Rumel ao redor do tronco pulmonar. Foram realizados exame físico, eletrocardiografia, ecocardiografia, hemogasometria, avaliação hemodinâmica e cálculo de variáveis de transporte de oxigênio, antes e após o procedimento. Os cães do Grupo I não sofreram alterações clínicas, eletrocardiográficas, ecocardiográficas e hemodinâmicas após a recuperação anestésica. No Grupo II, apenas um animal sobreviveu, sem apresentar alterações clínicas, eletrocardiográficas e ecocardiográficas. Neste cão, após a liberação do torniquete, houve aumento nas seguintes variáveis: freqüência cardíaca, pressões arteriais sistólica, média e diastólica, pressão arterial pulmonar, pressão da artéria pulmonar ocluída, pressão venosa central, débito cardíaco, índice sistólico, índice cardíaco, trabalho ventricular esquerdo e direito, índice de transporte de oxigênio, índice de consumo de oxigênio e taxa de extração de oxigênio. O conteúdo de oxigênio arterial e venoso misto e a pressão parcial de oxigênio arterial e venosa mista diminuíram, cinco minutos após a parada circulatória. Concluiu-se que o "outflow occlusion" é um procedimento viável para a realização de parada circulatória por um período de quatro minutos.