Right ventricular performance during left ventricular unloading conditions: the contribution of the right ventricular free wall.

AIM: Right ventricular (RV) dysfunction is a significant complication following implantation of left ventricular assist device (LVAD). However, RV performance after LVAD implantation remains unclear. We have studied the effects of preload and afterload on RV performance under left ventricular (LV) unloading. METHODS: Six adult mongrel dogs were subjected to cardiopulmonary bypass. RV preload and afterload were independently regulated. Dynamic pressure-length analysis of RV free walls was performed using micromanometer catheter and sonomicrometric dimension transducers. Global RV systolic function was evaluated by the relationship between stroke volume vs. end-diastolic length (EDL) or end-diastolic pressure (EDP). We also examined the afterload dependency of RV performance at constant stroke volume. RESULTS: Stroke volume vs. EDP and stroke volume vs. EDL demonstrated a linear relationship (r(2) = 0.849 +/- 0.147 and 0.776 +/- 0.121, respectively). At constant stroke volume, RV systolic peak pressure vs. EDL or EDP were shown to have a linear relationship (r(2) = 0.906 +/- 0.050 vs. 0.909 +/- 0.047, respectively). CONCLUSION: The Frank-Starling relationship for RV performance was shown in this animal model. Without interventricular interaction, RV preload is dependent on RV afterload.

Characterization of soluble and microsomal adenosine 3',5'-monophosphate-dependent protein kinases from rabbit heart.

Cardiac microsomes contained an intrinsic adenosine 3',5'-monophosphate (cyclic AMP)-dependent protein kinase which stimulated phosphorylation of serine residue(s) of microsomal protein. The phosphorylated residues were associated with a microsomal protein component of 20,000 molecular weight as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Intrinsic phosphoprotein phosphatase activity of the microsomal membrane resulted in rapid dephosphorylation of these residues. Microsomes phosphorylated in the presence of cyclic AMP (10(-6) M) exhibited enhanced calcium uptake. We conclude that: 1) cardiac microsomes contain intrinsic cyclic AMP-dependent protein kinase(s) which phosphorylate a specific microsomal protein and phosphoprotein phosphatase(s) capable of dephosphorylating this protein, 2) phosphorylation of this protein enhances calcium uptake, 3) reversible phosphorylation of microsomal membrane may be an important mechanism for the regulation of calcium uptake of cardiac microsomes by cyclic AMP.