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H Suga

Publications and source records attributed to H Suga.

At least 235 records · Page 13Linked to original sources
PubMed1988

Efficiencies from consumed O2 and pressure-volume area to work of in situ dog heart.

We studied the efficiencies from oxygen consumption (VO2) to external mechanical work (EW), from VO2 to the systolic pressure-volume area (PVA), and from PVA to EW, and the effects of cardiac output and contractility index (Emax) on these efficiencies in the left ventricle of open-chest, right-heart-bypassed dogs. PVA is an intermediate form of energy between VO2 and EW. PVA, EW, and Emax were determined by an abrupt occlusion of the ascending aorta. The right-heart bypass allowed us to collect all coronary venous return for VO2 measurement. The EW/VO2 efficiency ranged between 4 and 21%, the PVA/VO2 efficiency ranged between 5 and 27%, and the EW/PVA efficiency ranged between 60 and 95%. At a given Emax, EW/PVA efficiency was independent of cardiac output, but PVA/VO2 and EW/VO2 efficiencies increased with cardiac output. An increase in Emax by dobutamine increased EW/PVA efficiency, but decreased PVA/VO2 and EW/VO2 efficiencies. We could theoretically account for these changes in EW/PVA, PVA/VO2, and EW/VO2 efficiencies of the in situ heart by the VO2-PVA relation and its dependence on Emax that we had observed.

Animals↗
PubMed1987

Reduction of arginine-vasopressin in the cerebral cortex in Alzheimer type senile dementia.

Arginine-vasopressin (AVP) concentrations in five cortical areas were measured post mortem in nine patients with senile dementia of Alzheimer's type (SDAT), and compared with the control group of comparable ages. In SDAT patients, AVP was significantly reduced in Brodmann areas 4, 7 and 10 (p less than 0.05). In areas 17 and 22, the detectability and the mean concentrations of AVP were also lower than those of control patients, although not significantly.

Aged↗
PubMed1987

Transient vs. steady end-systolic pressure-volume relation in dog left ventricle.

We compared transient slope of end-systolic pressure-volume line (T-Emax) with steady Emax (S-Emax) in isolated cross-circulated canine left ventricles. T-Emax is the slope of the end-systolic pressure-volume line (ESPVL) determined from the last steady-state ejecting contraction (SEC) and the first transient isovolumic contraction produced by end-diastolic volume clamp. S-Emax is the slope of ESPVL determined from five steady-state contractions by linear regression analysis. We obtained three T-Emax values in the same contractile state by changing ejection fraction (EF) of SEC to three levels (range 14-58%) from the same end-diastolic volume. T-Emax variably increased with EF in any contractile state. The ratios of the three T-Emax values to the same S-Emax value was 1.08 +/- 0.04 (11 ventricles, means +/- SE) for high EF, 0.87 +/- 0.06 for middle EF, and 0.69 +/- 0.07 for low EF in control contractile state. These ratios decreased under epinephrine and increased under propranolol. We conclude that T-Emax depends not only on EF but also on contractile state in isolated dog left ventricles.

Animals↗
PubMed1987

Prospective prediction of O2 consumption from pressure-volume area in dog hearts.

Systolic pressure-volume area (PVA) is the area circumscribed by the end-systolic pressure-volume (PV) line, the end-diastolic PV curve, and the systolic PV trajectory of the ventricle. PVA represents the total mechanical energy generated by ventricular contraction. Myocardial O2 consumption (VO2) linearly correlates with PVA under different pre- and afterloads in the dog left ventricle. The linear VO2-PVA relation parallel shifts with changes in contractility index Emax. We have retrospectively obtained VO2 = A X PVA + B . Emax + C, where A, B, and C are regression coefficients. We used this equation to prospectively predict VO2 from measured PVA and Emax in a new group of dog left ventricles. Coefficient of determination (CD) of measured VO2 from predicted VO2 was 0.86 +/- 0.09 (SD) in individual hearts, but decreased to 0.72 when data of the five hearts were pooled. These prospective CDs in individual hearts and all hearts were smaller than retrospective CDs in the individual hearts (0.90 +/- 0.06). Inter-individual variations of A,B, and C caused the lower prospective predictability.

Animals↗
PubMed1987

Relation between oxygen consumption and pressure-volume area of in situ dog heart.

We studied the relation between O2 consumption (VO2) and the systolic pressure-volume area (PVA) in the left ventricle of open-chest dogs. PVA and the slope (Emax) of the end-systolic pressure-volume line were determined by an abrupt occlusion of the ascending aorta. VO2 linearly correlated with PVA in control contractile state, where Emax was 15.8 +/- 4.4 (SD) mmHg/ml with intact reflexes and 11.5 +/- 1.2 mmHg/ml with blocked reflexes. Emax and the VO2 axis intercept of the VO2-PVA line were greater in the in situ heart than in the excised cross-circulated dog heart in our previous study. Enhancement of contractile state by dobutamine increased Emax by 60-80% and shifted the VO2-PVA line upward, increasing the VO2 axis intercept by 38% with intact reflexes and by 79% with blocked reflexes. The slope had a tendency to increase with dobutamine, but the increase was statistically insignificant. We conclude that PVA and Emax obtained by the aortic-occlusion method can account for changes in VO2 with changes in loading conditions and contractility in an in situ dog heart.

Animals↗
PubMed1987

Left ventricular O2 consumption and pressure-volume area in puppies.

We studied the relation between O2 consumption (VO2) and systolic pressure-volume (PV) area (PVA) in the left ventricles of eight puppies (2-4 mo old). PVA is the area circumscribed by the end-systolic and end-diastolic PV curves and systolic PV trajectory. We assumed PVA to represent the total mechanical energy generated by ventricular contraction. We produced isovolumic contractions at different volumes in the left ventricles isolated and cross-circulated with adult dogs. VO2 closely correlated with PVA in each of control contractile state, an enhanced contractile state with epinephrine, and a depressed contractile state with propranolol in each heart. The slope of the regression line of VO2 on PVA was not significantly affected by epinephrine and propranolol. The regression line shifted upward with epinephrine and downward with propranolol. These characteristics of the puppy's VO2-PVA relation were comparable to those of the adult dog. These results suggest that similar relations hold between myocardial mechanics and energetics in both the puppy and adult dog despite the differences in the heart size and contractile properties.

Animals↗
PubMed1987

Force-time integral decreases with ejection despite constant oxygen consumption and pressure-volume area in dog left ventricle.

We have shown that systolic pressure-volume area (PVA), which is equivalent to the total mechanical energy generated by ventricular contraction, correlates linearly with myocardial oxygen consumption, VO2, in canine left ventricle. Systolic force-time integral, FTI, also correlates with VO2. In this study, stroke volume was increased from 0 (isovolumic) in isolated cross-circulated canine left ventricle in a stable contractile state while keeping PVA constant with a servo pump. Ventricular total force was calculated from ventricular pressure and volume by the force-equilibrium equation and was integrated from the end of diastole to the end of systole as identified with the time of Emax to yield FTI. Under the conditions of constant PVA, FTI significantly (p less than 0.001) decreased by 10 +/- 7% and 25 +/- 8% with increases in stroke volume from 0 to 8 +/- 4 ml and 17 +/- 3 ml and in ejection fraction from 0 to 0.24 +/- 0.10 and 0.61 +/- 0.05, respectively, while VO2 and Emax remained constant. Therefore, we conclude that in a stable contractile state, it is possible to keep PVA constant even when stroke volume and ejection fraction are varied and that under such conditions, FTI no longer predicts VO2. PVA remains a reliable predictor of VO2 regardless of ventricular loading conditions.

Animals↗
PubMed1987

Quantitative evaluation of left ventricular regional work from wall tension-regional area loop in canine heart.

We evaluated left ventricular (LV) regional work from a wall tension-regional area (T-A) loop using sonomicrometers in the excised cross-circulated canine left ventricle connected to a volume servo pump. Regional work assessed from a T-A loop closely agreed with the predicted value calculated from LV stroke work and percent regional area under conditions of the control state, dobutamine infusion, and global ischemia. In addition, globally integrated regional work over the entire ischemic and non-ischemic zones agreed closely with LV stroke work either before or after coronary occlusion. These results indicate that LV regional work can be assessed reliably from the T-A loop in both normal and regionally ischemic hearts. Regional work correlated linearly with end-diastolic regional area, indicating a regional Frank-Starling relation, and the slope of this relationship increased with dobutamine infusion and decreased with global ischemia. The correlation between regional work and LV stroke work was also linear and the regression line was the same during the control state and global ischemia, indicating a constant relationship between the work of a specific wall region and LV stroke work regardless of global changes in contractile state. However, after regional ischemia, this regression line apparently shifted downward because T-A loops in the ischemic region were extremely deformed and regional work markedly decreased. From these results, we conclude that T-A loops are a reliable and useful means of assessing regional contractile performance of the LV.

Animals↗
PubMed1987

Intact chordae tendineae increase ventricular volume measurement error by the balloon method.

We assessed the accuracy of the intraventricular balloon method of left ventricular volume measurement with all chordae tendineae intact and then severed. The space between the endocardium and the balloon is the source of the volume measurement error. We assessed the volume errors at different intra-balloon pressures between 50 and 250 mmHg, using formalin fixed canine left ventricles. The volume error with all chordae tendineae intact was significantly greater than with all chordae tendineae severed at any balloon pressure. The difference of the volume errors under these two conditions amounted to 1.9-3.3 ml regardless of intra-balloon pressures. We visually confirmed that this difference predominantly originated from the space behind the tense chordae tendineae.

Animals↗
PubMed1987

Dissociation of pressure-rate product from myocardial oxygen consumption in dog.

Although the pressure-rate product (double product; DP) is generally recognized as a good index of myocardial oxygen consumption (VO2), catecholamines are reported to change the VO2-DP relationship. However, the separate influences of chronotropism and inotropism on the VO2-DP relation have not been studied. Therefore, we examined these influences in anesthetized open-chest dogs by cardiac pacing and dobutamine infusion. We observed two different VO2-DP lines under the separate chronotropic and inotropic changes. We interpreted such VO2-DP relations by the concept of the pressure-volume area (PVA). PVA is a measure of total mechanical energy for ventricular contraction and is a specific area in the ventricular pressure-volume (P-V) diagram circumscribed by the end-systolic and end-diastolic P-V relation curves and the systolic segment of the P-V trajectory. The empirical VO2-PVA relation that had been obtained in our previous studies reasonably simulated the dissociation of DP from VO2 under separate changes in chronotropism and inotropism.

Animals↗
PubMed1986

Cardiac oxygen consumption and systolic pressure volume area.

Since we found that the total mechanical energy generated by ventricular contraction could be represented by a specific area (PVA) in the pressure-volume diagram, we have been studying the correlation between myocardial oxygen consumption (VO2) per beat and PVA in dog left ventricles. VO2 was found to be closely and linearly correlated with PVA under a variety of loading, heart rate, and contractile conditions. The regression of VO2 on PVA was given by VO2 = A X PVA + B.A was 1.8 X 10(-5) ml O2/(mm Hg ml) on the average and was relatively constant despite the changes in loading, heart rate, and contractile conditions. B was 0.02 ml O2/beat/100 g on the average in control contractile state and was relatively constant despite the changes in loading and heart rate conditions. However, B increased by 50-80% with 70-80% increases in Emax by epinephrine or calcium infused into the coronary circulation. After both VO2 and PVA were expressed in J/beat/100 g, the inverse of the slope coefficient A indicated that the energy conversion efficiency of PVA from the excess VO2 above the VO2 of the mechanically unloaded contraction was relatively constant at 40%, independent of the loading, heart rate, and contractile conditions.

Animals↗
PubMed1986

Reconsideration of normalization of Emax for heart size.

We previously proposed Emax Vd as a normalized form of Emax for heart size relatively independent of wall volume Vm, where Emax is the slope of the end-systolic pressure-volume line and Vd is its volume axis intercept. When Emax Vd remains constant, average circumferential stress for a specified average circumferential strain in the ventricular wall also remains relatively constant, despite changes in Vd/Vm around its normal value. Because accurate determination of Vd is difficult and stress for a given Emax Vd changes slightly with Vd/Vm, we investigated whether Vd could be replaced with Vm in a normalized Emax in this analysis. As the result, we obtained a function of Vd/Vm as the coefficient by which to multiply Emax Vd or Emax Vm to yield stress for a specified strain. Using this coefficient, one can easily calculate stress for any strain from Emax, Vd, and Vm in order to compare myocardial contractility among left ventricles of different sizes. The present study confirms the importance of Vd as an indispensable reference volume for normalization of Emax, as well as the low sensitivity of Emax Vd as a normalized Emax to changes in Vd/Vm. Only when Vd/Vm remains constant is Emax Vm proportional to Emax Vd and can replace Emax Vd.

Blood Pressure↗
PubMed1986

Left ventricular regional work from wall tension-area loop in canine heart.

To quantitatively evaluate left ventricular (LV) regional work, LV pressure-volume relation and wall tension-regional area (TA) relation were analyzed in the excised cross-circulated left ventricle connected to a volume servo pump system. Wall tension was calculated using Laplace's law for a spherical model, and regional area was determined from orthogonal segment lengths measured with pairs of ultrasonic crystals. Data were obtained by changing LV end-diastolic volume or stroke volume before and after dobutamine infusion and before and after global ischemia. Regional work, assessed from the area within a TA loop during one cardiac cycle, correlated well with simultaneously obtained LV stroke work under all of the above experimental conditions (r = 0.90 +/- 0.09 to 0.97 +/- 0.02), and the linear regression line was not altered by changes in stroke volume, end-diastolic volume, or contractile state. Furthermore, measured regional work (RWm) proved to agree closely with the predicted value (RWp) calculated from LV stroke work and regional area [RWm = 0.91 RWp - 0.69 (mmHg . ml), r = 0.93]. Thus we conclude that TA relation may be useful for quantitative evaluation of regional work of the LV wall.

Animals↗
PubMed1986

Peak isovolumic pressure-volume relation of puppy left ventricle.

We studied peak isovolumic pressure-volume (PV) relation of the left ventricle in 3-mo-old mongrel puppies. A puppy heart was excised and cross circulated with an adult dog. Left ventricular pressure and volume were measured with a water-filled balloon. Peak isovolumic PV curve in control contractile state was convex upward, reaching a maximum pressure of 130 mmHg. Epinephrine (0.6 microgram/min intracoronary) shifted the curve leftward and up to a maximum pressure of 160 mmHg. Propranolol (0.8 mg intracoronary) shifted it rightward and down to a maximum pressure of 110 mmHg. These PV curves were reasonably fitted by an asymptotic equation: P = A (1 - exp[-B (V - Vd)]), where V was normalized volume for 100 g left ventricle and Vd (6 ml/100 g) was V at which peak pressure was zero. A and B are regression coefficients. A was 149, 169, and 120 mmHg, and B was 0.16, 0.19, and 0.06 ml, respectively, in control, enhanced, and depressed contractile states. These changes in A and B were statistically significant. We conclude that the puppy left ventricular peak isovolumic PV curve is convex upward and shifts sensitively with inotropic changes.

Animals↗
PubMed1986

Assessment of slope of end-systolic pressure-volume line of in situ dog heart.

The purpose of this study was to establish a new method of assessment of the slope (Emax) of the end-systolic pressure-volume line (ESPVL) of the in situ heart. In anesthetized open-chest dogs, an isovolumic contraction was produced by an aortic occlusion after steady-state ejecting contractions in the left ventricle. We plotted ventricular pressure measured with a catheter-tip manometer against time integral of aortic flow measured with an electromagnetic flowmeter of the last ejecting and the first isovolumic contraction, assuming the same end-diastolic volume. ESPVL was drawn from the peak isovolumic pressure-volume point tangential to the left upper corner of the +/- 3.0 (SE) mmHg/ml (n = 9 dogs) in control run and was increased by 59 +/- 19% under isoproterenol and decreased by 47 +/- 9% after propranolol. Emax was little changed by atrial pacing. We conclude that Emax by this aortic occlusion method is useful for assessment of left ventricular contractility of the in situ dog heart.

Animals↗