Tissue Doppler Em and instantaneous end-diastolic stiffness: validation against pressure-volume loops in patients undergoing coronary artery bypass surgery Connelly KA¹ ² ³, Royse AG 4 , Royse CR 4 ¹University of Melbourne Department of Medicine, St. Vincent’s Hospital, Victoria, Australia, ² Cardiac Investigation Unit, St Vincent’s Hospital Melbourne, Victoria Australia ³ St Michael’s Hospital Department of Medicine, University of Toronto. 4 Human Cardiovascular Research Laboratory, University of Melbourne Background ｾ Transoesophageal echocardiography (TOE) assessment of cardiac function has now become routine for patients undergoing coronary artery bypass surgery (CABG) ｾ TOE measures of diastolic function demonstrate dependence upon loading conditions, which may vary as a result of anaesthesia, blood loss or cardiopulmonary bypass. ｾ Tissue Doppler imaging early lateral basal wall relaxation velocities (Peak E’) along with instantaneous end diastolic stiffness (IEDS) have emerged as promising indices of cardiac diastolic function which demonstrate minimal load independence. Aim ｾ To evaluate TOE indices of diastolic function against load insensitive techniques obtained using pressure volume (PV) loop analysis across different loading conditions . Methods ｾ10 patients referred for CABG were enrolled in the study. Haemodynamic measurements and TOE was performed as routine. Pulsed wave tissue Doppler of the lateral basal wall was used to assess Peak E’. IEDS was calculated via the following equations: IEDS = 100*log10(PCWP)/EDA (mmHg/cm² ) Pulsed wave Doppler at the mitral leaflet tips was used to assess the “E:A ratio”. Pulsed wave Doppler of pulmonary vein flow was measured in the right upper pulmonary vein. ｾPV loops: A combined dual-field 12 segment conductance and micromanometer pressure catheter was placed into the left ventricle. IVC compression was performed by the surgeon. The slope of the EDPVR, Tau and dP/dt min were calculated from steady state loops and after preload reduction using dedicated CFL 512 software. Measurement protocol: All measurements were acquired at each time point below, with atrial pacing at 70 bpm. 1. Baseline: after the Y-graft was completed and aortic cannular inserted. 2. Reduced preload: blood was drawn into the cardiopulmonary bypass circuit to reduce MAP by 15 mmHg. 3. Increased Afterload: blood was returned and metaraminol 0.25 mg boluses were injected to raise the MAP >20 mmHg above baseline. 4. Increased Heart Rate: the atrial pacemaker was increased to 100 bpm, or 30 bpm above baseline. 5. Post CPB: Following weaning from CPB. Discussion ｾ The principle finding of this study was that IEDS demonstrated little change across loading conditions, whilst Em varied significantly with increased heart rate. dP/dt min varied considerably across altered loading conditions, demonstrating load dependence. Results: The protocol was completed in 10 patients, although unsatisfactory PV loop data prevented analysis in one individual. ｾ3 patients had a baseline EF less than 40%. There were no complications as a result of catheter placement. Post CABG hospital stay was uncomplicated in all patients. Variable Mean ± SD Range Age (yr) 59 ± 9 49-73 Male sex (%) 66 - EF (%) 43 ± 13 28-66 CPB time (min) 81 ± 21 59-121 Aortic cross clamp time (min) 60 ± 25 29-102 Duration of surgery (min) 308 ± 55 260-445 Grafts (n) 3.2 ± 1 2-5 CPB = cardiopulmonary bypass Results: (cont) ｾLoading conditions were altered significantly with the haemodynamic protocol. Reducing preload resulted in a 29% reduction in EDV, a 21% reduction in ESP and a 26% reduction in CO. Increasing afterload altered systolic blood pressure and MAP by 16 and 33% respectively. Rapid atrial pacing reduced EDV by 20%. (Table 2) Results: (cont) Steady state pressure volume loops, patient 4. 0 20 40 60 80 100 120 140 160 0 50 100 150 200 LV Volume (mL) LV Pressure (mmH g ) Baseline Reduced preload Increased afterload Pacing Figure 1: Steady state pressure volume loops at differing loading conditions Figure 2: Graphs demonstrating absolute movement of index (from baseline) of diastolic function across different loading conditions. A represents the slope of the EDPVR, B: dP/dt min, C: IEDS, D: Tissue Doppler Em, E: Tau. There is a clear trend towards increased Em with increased heart rate (p <0.05), whilst dP/dt min demonstrates marked variability across the 9 patients studied. (P<0.001). EDPVR and Tau demonstrate only small changes across the loading conditions studied. Table 2: Effect of loading conditions upon haemodynamic variables. Table 1: Baseline characteristics. Acknowledgements I would like to thank Karen Groves, the NHF Australia and Pfizer CVL grants for the support of this project. Variable: Baseline Reduced Preload Increased Afterload Increased HR Post Bypass P P’ Heart rate; Beats.min -1 75 (3) 74 (3) 75 (3) 100 (4) 80 (7) <0.001 <0.001 CI; L.min. m 2 3.31 (0.5) 2.45 (0.43) 3.51 (0.50) 3.35 (0.39) 3.34 (0.82) 0.001 0.005 EDP; mmHg 15.9 (2.4) 12.8 (2.6) 21 (3.1) 16 (1.7) 24 (4.5) <0.001 <0.001 ESP; mmHg 115 (12) 91 (8.5) 147 (7) 125 (11) 106 (15) <0.001 <0.001 EDV; ml 183 (34) 129 (38) 203 (51) 146 (18) 169 (36) 0.009 0.018 PCWP; mmHg 13.6 (2.4) 8.6 (2.2) 14.7 (4) 11.6 (1.6) 16 (4.1) 0.004 0.016 RAP mmHg 8.8 (1.8) 5.9 (1.5) 8.7 (1.8) 11.6 (1.5) 8.3 (3.1) 0.008 0.024 SVRI; dynes/cm.s -5 /m -2 2259(477) 2538(348) 2849(371) 2621(516) 1799(630) 0.009 0.018 Variable: Baseline Reduced Preload Increased Afterload Increased HR Post Bypass P P´ dP/dtmin (mmHg/sec -1 ) 1160 (143) 920 (113) 1479 (156) 1333 (170) 1045 (234) <0.001 <0.001 Tau (mmHg) 50.3 (2.5) 54.9 (1.3) 49 (3.5) 47.4 (3.2) 52 (7) 0.073 0.146 EDPVR slope (mmHg) 0.16 (0.06) 0.13 (0.06) 0.18 (0.06) 0.17 (0.1) 0.2 (0.12) 0.479 0.479 Variable: Baseline Reduced Preload Increased Afterload Increased HR Post Bypass P P’ Peak E wave (cm/s) 58 (14.2) 52 (15.4) 86 (14) 67 (16.2) 66 (13.7) 0.04 0.28 Peak A wave (cm/s) 64 (7.2) 55 (7.60 79 (9.8) - 53 (9.8) 0.317 0.951 E/A ratio 0.92 (0.36) 0.93 (0.21) 0.93 (0.22) - 1.1 (0.2) 0.213 >0.99 PVS (cm/s) 48 (10.8) 42 (11.6) 39 (12.1) 38 (5.4) 42 (8.6) 0.469 0.938 PVD (cm/s) 34 (18) 33 (11) 42 (15) 39 (9.6) 44 (10.5) 0.306 >0.99 Em (cm/s) 9.4 (2.1) 8.2 (2.2) 9.2 (1.1) 14.3 (4.2) 8.4 (0.96) 0.001 0.008 Am (cm/s) 9.6 (2.3) 10.4 (1.5) 11.3 (2.0) 8.5 (2.5) 8.6 (1.6) 0.523 0.523 IEDS 9.1 (0.9) 9.1 (0.7) 8.7 (1.1) 10.1 (1.2) 9.2 (1.6) 0.232 >0.99 Conclusion ｾ Instantaneous end–diastolic stiffness and tissue Doppler Peak Em are promising indexes of diastolic function in patients undergoing rapidly changing loading conditions, though caution should be used in interpreting Peak Em when large changes in heart rate occurs. Slope of the End diastolic pressure volume relationship -0.6 -0.4 -0.2 0 0.2 0.4 0.6 Baseline Preload Reduction Increased Afterload Increased Heart rate Post Bypass mmHg dP/dt min -800 -600 -400 -200 0 200 400 600 800 Baseline Preload Reduction Increased Afterload Increased Heart rate Post Bypass mmHg/sec-1 Instantaneous end-diastolic stiffness -10 -8 -6 -4 -2 0 2 4 6 8 10 Baseline Preload Reduction Increased Afterload Increased Heart rate Post Bypass mmHg/cm² Tissue Doppler Em -20 -15 -10 -5 0 5 10 15 20 Baseline Preload Reduction Increased Afterload Increased Heart rate Post Bypass cm/s Tau -20 -15 -10 -5 0 5 10 15 20 Baseline Preload Reduction Increased Afterload Increased Heart rate Post Bypass mmHg