Heart and vessels
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The incidence of aortic valve prolapse and aortic regurgitation (AR) among Chinese with ventricular septal defect (VSD) has not been studied, and controversies still exist regarding optimal surgical treatment and timing of operation for this condition. A prospective study of 332 consecutive patients with VSD showed that aortic valve prolapse and AR occurred in 43 (11.9%) patients. Valve lesions occurred more commonly among patients with subpulmonic VSD (28.0%) than with subaortic VSD (8.8%) (P less than 0.005). ⋯ Surgical closure of the subpulmonic VSD may restore the prolapsed valve to normal. Closure of the subaortic VSD has little effect. Valvuloplasty in subaortic VSD may palliate AR, but in all probability cannot restore valve competency.
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A theoretical analysis of the step response in the closed cardiovascular system induced by a sudden shift of the right cardiac output curve predicted that if the relations of the right heart output (COr) and the total systemic capillary flow (CFs) to the systemic venous pressure (Psv) are linear, then the time course of Psv change will become monoexponential with a time constant T given by T = Csv/(Gr + Gs), where Csv is the systemic vein compliance and Gr and Gs are the conductances of the transient COr-Psv and CFs-Psv relationships. A similar prediction was obtained for the time constant T of the pulmonary vein pressure (Ppv) response to the step change in the left cardiac output (COl) curve, pulmonary vein compliance (Cpv) and the conductances of the COl curve, and the pulmonary capillary flow (CFp) curve against Ppv. The actual Psv or Ppv changes following sudden alteration of the COr or COl curve by inflation and deflation of the balloon in the right or left atrium revealed monoexponential time courses. ⋯ A similar linearity of the dynamic CFp-Ppv relationship was suggested from their steady-state curves. The values of Csv calculated from the experimental data were 1.70 +/- 0.12 ml/mmHg/kg body wt in 11 curves and those of Cpv were 0.13 +/- 0.03 ml/mmHg/kg in 15 curves. These results are mostly consistent with those previously reported.