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Effects of asynchronous electrical activation on local blood flow and pump work in the left ventricular subepicardial layers
,J Mel Cell Cardiol
23 (Supplement
V) (1991)
P55
MECHANICAL RESTITUTION CURVE IN FOUR MODELS OF CARDIAC HYPERTROPHY IN THE RAT Roberto Bottinelli, Monica Canepari, Carlo Reggiani, Lucia Ricciardi. Institute of Human Physiology, University of Pavia, Pavia, Italy. Ventricular hypertrophy was induced in male adult Wistar rats according to four pro tocols: pressure overload produced by a metal clip on the abdominal aorta (CLIP), swim ming (90 minlday for 8 weeks, SW), hyperthyroidism (200 pg/Kg BW T3/day for 2 weeks, 300 pg/Kg BW/day for 2 weeks (ISO). All treatments resulted inamar T3) > isoproterenol ked cardiac hypertrophy: the increase of HW/BW ranged from 39% to 51% compared to age matched controls. Mechanical restitution curve (MRC) was determinedinthincardiac prep arations (papillary muscles or trabeculae) from right (T3, SW, ISO) or left (CLIP) vet tricles of hypertrophic and control hearts at 12 stimuli/min, 26”C, as previously described (Poggesi et al., Circ. Res. 1987,65,142-151). In IS0 cardiac preparations both the first phase (test interval up to 1 set) and the second (up to 100 set) of the NRC were the same as in controls, whereas in both T3 and SW the first phase was steeper and the second flatter. In CLIP the first phase was less steep than in controls, while no difference was present in the second one. These results provide a basis to investigate cardiac plasticity in relation to the hemodynamical load imposed.
P56
EFFECTS OF ASYNCHRONOUS ELEXXRICALACTIVAT1ON ON LOCAL ULOOD FLOW AND PUMP WORK IN THE LEFT VENTRICULAR SUBEPICARDIAL LAYERS Tammo Delhaas, Theo Arts’, Frits W Prinzcn, and Robert S Rcneman. Dcpts. of Physiology and Biophysics*, Cardiovascular Research Institute Maastricht, University oI Limburg, Maastricht, The Netherlands. We tested the hypothesis that asynchronous electrical activation ol the left vcntriclc (LV) causes similar redistributions of local subepicardial blood flow (BF) and pump work (PW). In 5 open-chest dogs BF (microspheres) and PW in 16 regions of the LV ant&or wall were measured aCtcr 15 min ol sinus rhythm or right ventricular outflow tract pacing (synchronous and asynchronous activation, rcspectivcly). PW was estimated Irom the lime integral of local tiber stress (or) and strain rate (bet) during ventricular ejection. Local CI
was measured, using optical markers attached to the epicardial surface and recorded on video. or during ejection was calculated as: or = P,-v(l+3Vc/Vw), in which P._“, Vc and VW are LV pressure, cavity and wall volume, respectively. Local V w was calculated using: 1) global LV radius, measured with 4 inductive coils sutured to the LV in a tetrahedic conliguration; 2) local epicardial surface area. VW was measured post-mortem. cc, BF and PW (table)
were significantly (p
synchronous
early activated than in late activated regions. We conclude that asynchronous activation causes similar rcdistributions of local blood flow and pump work. (Supported by NWO)
mean -C SD -0.10 -c 0.02 2392 + 4.48 2.46 + 0.44 7.12 +_ 0.64
fiber strain max. fiber stress (kPa) pump work (kJ/m”.beat) blood flow (I/m3.beat)
P57 THE EFFECT OF HYPERTENSION
late
early mean -0.05 17.81 1.47 6.18
2 2 -C -+ rt
SD 0.02 5.37 0.52 0.43
mean +- SD -0.15 r 0.02 16.37 f 5.53 2.71 t 0.79 7.62 + 1.30
ON LEFT VENTRICULAR FUNCTION IN CONSCIOUS DIABETIC RATS. Schenk J.. H&den R.A.. McNeil1 J.H. Facultv of Pharmaceutical Sciences. The Universitv of British Columbia. Vanco&er, B.C., Canada. V&T 123. We investigated the effect of deoxycorticosterone acetate (DOCA)-induced hypertension on the rate of left ventricular contraction (+dP/dt) in male Sprague Dawle rats injected with the diabetogenic a ent streptozotocin SlZ; 65 mg/kg) or 0.9% saline (C r; N). Seven days later injections of D8 CA (25 mg/kg; S.C.\ or DOCA vehicle were initiated. Rats were catheterized and hemodynamic measurements made after 5 weeks of treatment. Systolic BP in the CON group (n=i 1) was 132?5 mmHg, 13526 mmHg in the STZ group (n-7). 17925 mmHg in the DOCA-CON group (n=9), and 16327 mmHg in the DOCA-ST2 group n=7). CON group +dP/dt was 5650+230 mmHg/s, SE! was 57402210 mmH Is. The D CA-CON +dP/dt (7190%290 mmHg/s) was not significantly different from the D8 CA-STZ (621 6 Ok450 mmHg/s) group. In conclusion, contractile function as determined by +dP/dt was not reduced in conscious diabetic animals during the presence or absence of hypertension induced by 5 weeks of DOCA treatment. (This work was supported by the B.C. and Yukon Heart and Stroke foundation.) 5.75
23 (Supplement
V) (1991)
P55
MECHANICAL RESTITUTION CURVE IN FOUR MODELS OF CARDIAC HYPERTROPHY IN THE RAT Roberto Bottinelli, Monica Canepari, Carlo Reggiani, Lucia Ricciardi. Institute of Human Physiology, University of Pavia, Pavia, Italy. Ventricular hypertrophy was induced in male adult Wistar rats according to four pro tocols: pressure overload produced by a metal clip on the abdominal aorta (CLIP), swim ming (90 minlday for 8 weeks, SW), hyperthyroidism (200 pg/Kg BW T3/day for 2 weeks, 300 pg/Kg BW/day for 2 weeks (ISO). All treatments resulted inamar T3) > isoproterenol ked cardiac hypertrophy: the increase of HW/BW ranged from 39% to 51% compared to age matched controls. Mechanical restitution curve (MRC) was determinedinthincardiac prep arations (papillary muscles or trabeculae) from right (T3, SW, ISO) or left (CLIP) vet tricles of hypertrophic and control hearts at 12 stimuli/min, 26”C, as previously described (Poggesi et al., Circ. Res. 1987,65,142-151). In IS0 cardiac preparations both the first phase (test interval up to 1 set) and the second (up to 100 set) of the NRC were the same as in controls, whereas in both T3 and SW the first phase was steeper and the second flatter. In CLIP the first phase was less steep than in controls, while no difference was present in the second one. These results provide a basis to investigate cardiac plasticity in relation to the hemodynamical load imposed.
P56
EFFECTS OF ASYNCHRONOUS ELEXXRICALACTIVAT1ON ON LOCAL ULOOD FLOW AND PUMP WORK IN THE LEFT VENTRICULAR SUBEPICARDIAL LAYERS Tammo Delhaas, Theo Arts’, Frits W Prinzcn, and Robert S Rcneman. Dcpts. of Physiology and Biophysics*, Cardiovascular Research Institute Maastricht, University oI Limburg, Maastricht, The Netherlands. We tested the hypothesis that asynchronous electrical activation ol the left vcntriclc (LV) causes similar redistributions of local subepicardial blood flow (BF) and pump work (PW). In 5 open-chest dogs BF (microspheres) and PW in 16 regions of the LV ant&or wall were measured aCtcr 15 min ol sinus rhythm or right ventricular outflow tract pacing (synchronous and asynchronous activation, rcspectivcly). PW was estimated Irom the lime integral of local tiber stress (or) and strain rate (bet) during ventricular ejection. Local CI
was measured, using optical markers attached to the epicardial surface and recorded on video. or during ejection was calculated as: or = P,-v(l+3Vc/Vw), in which P._“, Vc and VW are LV pressure, cavity and wall volume, respectively. Local V w was calculated using: 1) global LV radius, measured with 4 inductive coils sutured to the LV in a tetrahedic conliguration; 2) local epicardial surface area. VW was measured post-mortem. cc, BF and PW (table)
were significantly (p
synchronous
early activated than in late activated regions. We conclude that asynchronous activation causes similar rcdistributions of local blood flow and pump work. (Supported by NWO)
mean -C SD -0.10 -c 0.02 2392 + 4.48 2.46 + 0.44 7.12 +_ 0.64
fiber strain max. fiber stress (kPa) pump work (kJ/m”.beat) blood flow (I/m3.beat)
P57 THE EFFECT OF HYPERTENSION
late
early mean -0.05 17.81 1.47 6.18
2 2 -C -+ rt
SD 0.02 5.37 0.52 0.43
mean +- SD -0.15 r 0.02 16.37 f 5.53 2.71 t 0.79 7.62 + 1.30
ON LEFT VENTRICULAR FUNCTION IN CONSCIOUS DIABETIC RATS. Schenk J.. H&den R.A.. McNeil1 J.H. Facultv of Pharmaceutical Sciences. The Universitv of British Columbia. Vanco&er, B.C., Canada. V&T 123. We investigated the effect of deoxycorticosterone acetate (DOCA)-induced hypertension on the rate of left ventricular contraction (+dP/dt) in male Sprague Dawle rats injected with the diabetogenic a ent streptozotocin SlZ; 65 mg/kg) or 0.9% saline (C r; N). Seven days later injections of D8 CA (25 mg/kg; S.C.\ or DOCA vehicle were initiated. Rats were catheterized and hemodynamic measurements made after 5 weeks of treatment. Systolic BP in the CON group (n=i 1) was 132?5 mmHg, 13526 mmHg in the STZ group (n-7). 17925 mmHg in the DOCA-CON group (n=9), and 16327 mmHg in the DOCA-ST2 group n=7). CON group +dP/dt was 5650+230 mmHg/s, SE! was 57402210 mmH Is. The D CA-CON +dP/dt (7190%290 mmHg/s) was not significantly different from the D8 CA-STZ (621 6 Ok450 mmHg/s) group. In conclusion, contractile function as determined by +dP/dt was not reduced in conscious diabetic animals during the presence or absence of hypertension induced by 5 weeks of DOCA treatment. (This work was supported by the B.C. and Yukon Heart and Stroke foundation.) 5.75