<![CDATA[<B>Adjustable pulmonary trunk banding</B>: <B>comparison of two methods of acute subpulmonary ventricle hypertrophy</B>]]>

Abstract

Bandagem ajustável do tronco pulmonar: comparação de dois métodos de hipertrofia aguda do ventrículo subpulmonarAdjustable pulmonary trunk banding: comparison of two methods of acute subpulmonary ventricle hypertrophy Abstract Objective: This study compares ventricular hypertrophy induced by continuous versus intermittent systolic overload of the pulmonary ventricle (RV) of young goats.Methods: Three groups of seven goats were used (control, continuous, and intermittent). Systolic overload was maintained for 96 hours in the continuous group, while the intermittent group suffered four 12-hour periods of systolic overload, alternating with 12-hour resting periods. Echocardiographic and hemodynamic evaluations were performed every day. The animals were then killed for myocardial water content and weight evaluation.Results: Both study groups achieved significant increases in RV mass (p<0.05). However, significant increases of the septum mass were observed only in the Intermittent Group (p<0.05). A greater increase in the RV wall thickness was observed in the Intermittent Group (p<0.05). There was a significant difference in RV diastolic volume between the two groups (p= 0.01), with a greater RV dilation in the Continuous Group after 24 hours of continuous overload (p< 419ASSAD, RS ET AL -Adjustable pulmonary trunk banding: comparison of two methods of acute subpulmonary ventricle hypertrophy Braz J Cardiovasc Surg 2006; 21(4): 418-428 INTRODUCTIONThe concept of rapid preparation of the left ventricular (LV) was introduced by the group from Boston in 1989 to treat transposition of the great arteries (TGA) after the neonatal period. Retraining of the subpulmonary ventricle was obtained in a mean time of nine days and after this Jatene's operation was performed [1]. These authors achieved good preliminary results, however, they were not reproduced in other centers due to high morbimortality. One of the greatest limitations of this technical approach is related to the lack of adjustability of the pulmonary trunk (PT) banding. The degree of PT banding may be inadequate or imprecise and can cause an important acute systolic overload of the LV [2,3].Heart hypertrophy is the main adaptive response of a heart submitted to physiological or pathological overload. It is interesting to note that the acquisition of LV mass during physical conditioning of athletes who practice swimming for example, reaches a peak in about only one week of training. Then the LV mass remains relatively constant [4] In an attempt to improve the rapid hypertrophic process without causing injury to the myocardium of the subpulmonary ventricle, we tried to find an analogy between the physiological hypertrophic processes in static-type exercises and intermittent PT banding, where periods of systolic overload are alternated with periods of subpulmonary ventricle relaxation.We formed a hypothesis that the subpulmonary ventricle, submitted to the gradual and progressive systolic overload alternated with periods of relaxation, could cause a more benefici...

Sobrecarga sistólica intermitente promove melhor desempenho miocárdico em animais adultos

“…The 33% increase observed in the RV free wall thickness in the Intermittent group corresponded to about 25% of the increase found in the study of young animals, corroborating the findings of a smaller increase in ventricular mass in adult animals, over a longer time of hypertrophic stimulus 15 . The most evident RV free wall thickness appeared as early as in the second week and remained constant thereafter.…”

“…Although it has been subjected to a smaller area of systolic overload, the Intermittent group was found to be more likely to gain ventricular mass, which was approximately 75% of the gain observed in young animals subjected to the same systolic overload protocol, but with a training time seven times smaller 15 . That corroborates the differences found between infants and adults in ventricular preparation studies, with great variability in time and increased risk of early and late ventricular failure in adults [25][26][27] .…”

“…We performed left thoracotomy in the 4 th intercostal space and implanted intracath catheters 17G (BD, Juiz de Fora, MG) in the descending thoracic aorta (Ao), at the outflow of the RV and in the pulmonary trunk (PT), as described previously 15 . Then, the PT was dissected to implant PB.…”

“…As in the Conventional group, the basal pressures of RV, PT and Ao were recorded with the animal conscious, immobilized on a special stretcher and the device completely deflated. After reading the basal pressures, the adjustable banding device was inflated with 0.9% saline in order to reach an RV systolic pressure of approximately 70% of systemic systolic pressure, provided that it did not cause a decrease of systolic pressure of more than 10%, as described in previous studies 15,17,18 . Then, the pressures were measured again.…”

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

“…It has been demonstrated in a young animal model that intermittent systolic overload, in agreement with athletic philosophy, has promoted more prominent hypertrophy, compared with continuous systolic overload. 2,3 However, these studies assessed global right ventricular (RV) systolic function only at rest, without showing any significant differences between the systolic overload protocols.…”