Real-time measurement of tricuspid valve annular area for annuloplasty. Experimental study

We used real-time measurement of the tricuspid valve annular area in anesthetized dogs to study the optimal size of the annular area for annuloplasty. During control conditions, the maximum tricuspid annular area appeared at the onset of ventricular systole. The minimum tricuspid annular area appeared between the ventricular isovolumic relaxation phase and the early ventricular filling phase. The maximum annular area varied in seven dogs between 2.18 and 3.10 cm2, and the minimum annular area ranged between 1.68 and 2.45 cm2. In regular sinus rhythm (heart rates 97 to 120 beats/min), the maximal decreases in tricuspid annular area during one cardiac cycle ranged from 14.3% to 23.6% of the maximum size. When the tricuspid annular area after the annuloplasty was kept larger than the minimum area that was observed during the cardiac cycle in the control study, cardiac output and right atrial pressure remained unchanged, as a result of unobstructed ventricular filling. On the other hand, when the annular area was reduced to smaller than the minimum area seen in the control study, a decrease in cardiac output and an elevation of right atrial pressure ensued. These findings suggest that the tricuspid annular area can be safely decreased by annuloplasty to the minimum area seen in the control study without causing a reduction of cardiac output or an elevation of right atrial pressure.