RESULTS Haemodynamic results Haemodynamic parameters are presented in Table 1. There was no significant difference between ventricular pressure, LV dP/dt or heart rate between groups. There was a significantly higher transvalvular pressure loss within both groups with the force transducers in situ corresponding to a mild stenosis. However, there was no significant difference in transvalvular pressure with the force transducers implanted between the 2 groups. The double-ring procedure itself caused a significant increase in transvalvular pressure loss compared with a single ring (double ring: 33 ± 17 mmHg; single ring: 21 ± 7 mmHg, P = 0.04). All pigs had no or trivial aortic insufficiency at any time during the procedure. Table 1: Haemodynamic parameters in the 2 groups with and without force transducers Parameter With force transducers Without force transducers Single ring Double ring P-value Single ring Double ring P-value HR (min−1) 87 ± 15 101 ± 15 NS 108 ± 18 102 ± 19 NS LVP max (mmHg) 106 ± 14 110 ± 14 NS 87 ± 11 99 ± 15 NS TvP max (mmHg) 38 ± 14 43 ± 17 0.04 21 ± 7 33 ± 17 0.04 LV dP/dt max (mmHg/s) 1833 ± 432 1778 ± 416 NS 1589 ± 429 1675 ± 442 NS Total ECC time (min) 276 ± 36 Cross-clamp time (min) 149 ± 12 All data are presented as mean ± standard deviation. ECC: extracorporeal circulation; HR: heart rate; LVP: left ventricular pressure; Max: maximum; LV dP/dt: time derivative of left ventricular pressure; TvP: transvalvular pressure; NS: non-significant. Force results Segmental force results for the aortic annulus and STJ from MS–MD are presented in Fig. 4 and summarized in Table 2. The total force acting in the STJ from MS–MD was significantly reduced in the double-ring group compared with the single-ring group from 1.7 ± 0.6 to 0.04 ± 1.1 N (P = 0.001). There was no significant difference in the total force at the aortic annulus (single ring: 6.7 ± 3.3 N; double ring: 6.6 ± 2.2 N, P = 0.94), nor any difference in the segmental forces in the aortic annulus. In the STJ, there was a reduced force in the RN and LR segments, but not in the LN segment after double ring compared with single ring. There was a significantly higher force in the LR segment compared with the 2 other segments in the aortic annulus within each group. In the STJ, there was no significant difference in force between segments within each group. Figure 4: Segmental force for each of the 3 segments (LN, RN, LR) for single and double ring (mid-systole–mid-diastole). (A) Level of the annulus. (B) Level of the STJ (mean ± standard deviation). LN: left/non-coronary segment; LR: left/right-coronary segment; RN: right/non-coronary segment; STJ: Sinotubular junction. Table 2: Segmental force at the level of the annulus and STJ from MD to MS for both groups Force (N) Single ring Double ring P-value between groups Annulus LN segment 0.7 ± 1.4 0.6 ± 1.0 NS Annulus RN segment 1.3 ± 1.0 1.3 ± 1.0 NS Annulus LR segment 4.3 ± 1.5 4.2 ± 1.1 NS STJ LN segment 0.2 ± 0.3 0.1 ± 0.3 NS STJ RN segment 0.7 ± 0.6 0.0 ± 0.3 0.001 STJ LR segment 0.8 ± 0.7 0.0 ± 0.9 0.041 All data are presented as mean ± standard deviation. LN: left/non-coronary segment; LR: left/right-coronary segment; MD: mid-diastole; MS: mid-systole; NS: non-significant; RN: right/non-coronary segment; STJ: Sinotubular junction. Geometrical results Geometrical results are summarized in Table 3. Area and circumference for the annulus and STJ are presented in Fig. 5A and B. Area and circumference in the double-ring group compared with the single-ring group were significantly reduced at the STJ but not in the annulus. We found significantly reduced expansibility in the STJ with double ring compared with single ring, but no difference in the annulus was observed between the groups. Figure 5: (A and B) Area at 4 defined time points (ED, MS, ES, MD) throughout the cardiac cycle for single and double rings at the annulus and STJ. (C and D) Cross-sectional diameters NC–LR, RC–LN and LC–RN at 4 defined time points throughout the cardiac cycle for single and double rings at the annulus and STJ (mean ± standard deviation). ED: end-diastole; ES: end-systole; LC: left coronary sinus; LN: left/non-coronary segment; LR: left/right-coronary segment; MD: mid-diastole; MS: mid-systole; NC: non-coronary sinus; RC: right coronary sinus; RN: right/non-coronary segment; STJ: sinotubular junction. Table 3: Area, circumference, segmental distance and cross-sectional diameters at the annulus and STJ for both groups Parameter Single ring Double ring P-value between groups Max Min Change % Max Min Change % Max Min Change % Annulus area (mm2) 320.9 ± 40.5 286.2 ± 33.5 12.1 ± 3.8 321.3 ± 38.8 282.8 ± 34.7 13.7 ± 5.5 NS NS NS Annulus circumference (mm) 70.8 ± 3.8 67.2 ± 3.5 5.4 ± 1.1 71.6 ± 3.9 67.6 ± 3.5 6.0 ± 2.0 NS NS NS STJ area (mm2) 234.8 ± 37.6 201.8 ± 36.5 16.9 ± 6.4 147.5 ± 31.8 136.6 ± 30.7 8.2 ± 3.1 <0.001 <0.001 0.001 STJ circumference (mm) 60.4 ± 4.9 56.5 ± 5.2 7.0 ± 3.1 49.3 ± 5.5 47.5 ± 5.5 4.1 ± 1.8 <0.001 <0.001 0.02 Annulus left/non-segment (mm) 22.1 ± 2.2 20.6 ± 1.9 6.9 ± 2.8 22.1 ± 2.5 20.5 ± 1.9 7.7 ± 3.2 NS NS NS Annulus right/non-segment (mm) 20.1 ± 2.3 18.7 ± 1.9 7.6 ± 1.6 21.2 ± 3.7 19.6 ± 3.4 8.2 ± 3.6 NS NS NS Annulus left/right segment (mm) 28.9 ± 3.9 27.4 ± 3.7 5.5 ± 2.0 28.6 ± 4.0 26.9 ± 4.0 6.5 ± 2.4 NS NS NS STJ left/non-segment (mm) 19.4 ± 2.4 18.3 ± 2.3 6.4 ± 3.6 17.1 ± 2.3 16.4 ± 2.3 4.7 ± 1.4 NS NS NS STJ right/non-segment (mm) 19.6 ± 2.9 18.1 ± 3.0 8.2 ± 3.4 15.1 ± 3.5 14.4 ± 3.4 4.8 ± 1.8 0.005 0.02 0.01 STJ left/right segment (mm) 21.4 ± 2.0 19.9 ± 1.8 7.4 ± 3.9 17.1 ± 2.2 16.3 ± 2.0 4.9 ± 3.0 <0.001 <0.001 NS Annulus crystal NC–LR (crystal 1–4) 25.8 ± 1.5 23.3 ± 1.4 10.4 ± 3.2 25.6 ± 1.6 23.1 ± 1.4 11.0 ± 3.5 NS NS NS Annulus crystal RC–LN (crystal 2–5) 18.8 ± 2.9 16.4 ± 2.4 14.6 ± 3.6 19.3 ± 3.0 16.8 ± 2.6 14.8 ± 4.0 NS NS NS Annulus crystal LC–RN (crystal 3–6) 22.7 ± 2.2 21.5 ± 2.3 5.8 ± 2.8 22.0 ± 1.9 20.3 ± 1.7 8.0 ± 3.1 NS NS NS STJ crystal NC–LR (crystal 7–10) 20.3 ± 1.8 18.7 ± 1.6 8.6 ± 3.5 15.8 ± 1.7 15.2 ± 1.7 4.1 ± 1.9 <0.001 <0.001 0.001 STJ crystal RC–LN (crystal 8–11) 17.8 ± 1.3 16.4 ± 1.2 8.8 ± 3.6 13.5 ± 2.3 12.9 ± 2.3 5.1 ± 2.5 <0.001 <0.001 0.009 STJ crystal LC–RN (crystal 9–12) 18.7 ± 2.1 17.6 ± 2.1 6.6 ± 3.9 15.4 ± 1.6 14.6 ± 1.8 5.7 ± 2.4 <0.001 0.001 NS All data are presented as mean ± standard deviation. Crystals 1–12 representing sonomicrometry crystals. LC: left coronary sinus; LN: left/non-coronary segment; LR: left/right-coronary segment; Max: maximum; Min: minimum; NC: non-coronary sinus; NS: non-significant; RC: right coronary sinus; RN: right/non-coronary segment; STJ: sinotubular junction. Both in the aortic annulus and the STJ, there was no significant difference between segment expansion within each group. All 3 segments were reduced with double ring compared with single ring at the STJ, however, only significantly for the RN segment. In the aortic annulus, there was no difference between the length and expansion of the segments between the 2 groups. The cross-sectional diameters in the annulus and STJ are presented at 4 defined time points throughout the cardiac cycle in Fig. 5C and D. At the STJ, the largest cross-sectional diameter was the NC–LR segment in both the single- and double-ring groups. The expansion in cross-sectional diameters at the STJ was not statistically different between the 3 segments within each group. In the aortic annulus, the largest cross-sectional diameter was also the NC–LR segment in both groups. However, the expansion was different within both groups with the largest expansion at the right coronary sinus to LN and the smallest expansion at the left coronary sinus to RN. The shape of the aortic annulus was oval and remained unchanged after single ring and double ring [20], and the shape was more circular at MD compared with MS. In the STJ, the shape was primarily circular at both MS and MD in the single-ring group, but became more oval after the double ring. However, the sphericity in the STJ was maintained throughout the cardiac cycle in each group, thus there was no change in shape configuration within each group.