Circulation
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Comparative Study
Pulsatility improves hemodynamics during fetal bypass. Experimental comparative study of pulsatile versus steady flow.
The main advantage of pulsatile flow compared with steady flow during cardiopulmonary bypass is to prevent a rise in systemic vascular resistances. We hypothesized that pulsatile flow could overcome the progressive rise in peripheral and placental vascular resistances observed during fetal bypass and leading to progressive irreversible hypoxemia. ⋯ The data suggest that pulsatile flow for 30 minutes of bypass in a fetal lamb preparation temporarily prevents the progressive hypoxemia observed under steady-flow bypass. Pulsatile flow allows higher pump flow through a significant decrease in systemic vascular resistances. Individual organ blood flow, including placenta, was significantly higher under pulsatile bypass. With technical improvements in the design of pulsatile devices adapted to more physiological beat rates, pulsatility may become a valuable adjunct to overcome placental dysfunction observed during experimental fetal cardiac surgery.
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Although retrograde warm continuous cardioplegia (RWCC) has been recently advocated as a method of myocardial preservation during cardiac surgery, scant data exist on the effects of RWCC on right ventricular function. However, previous data have clearly shown that retrograde cardioplegia is poorly distributed to the right ventricle and interventricular septum. This experiment was performed to analyze functional preservation of the right ventricle after RWCC. ⋯ RWCC may be harmful to the right ventricle and should be used with caution, particularly in patients with preexisting RV hypertrophy.
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Dynamic cardiomyoplasty remains a promising but poorly understood surgical modality for selected patients with dilated cardiomyopathy. Despite encouraging clinical results, objective evidence of enhanced ventricular function using traditional indexes (cardiac output, ejection fraction, and dP/dt) has been difficult to document after cardiomyoplasty. Several investigators have suggested that cardiomyoplasty acts partly by unloading the left ventricle. These indexes all depend somewhat on loading conditions, however, and might not detect such an interaction. The time-varying elastance model provides an index of contractility, Emax, that is relatively insensitive to changes in loading conditions. We applied this model to study the effect of right latissimus dorsi cardiomyoplasty on left ventricular function in an acute canine model. ⋯ These results show that, in this acute canine model, right latissimus dorsi cardiomyoplasty significantly improves left ventricular function while decreasing left ventricular volumes. The results are consistent with the theory that cardiomyoplasty increases contractility while unloading the ventricle by decreasing end-diastolic volume. This increase in Emax despite inconsistent changes in other indexes underlies the importance of using load-insensitive indexes of ventricular function when studying cardiomyoplasty.