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H Yaku

Publications and source records attributed to H Yaku.

At least 91 records · Page 5Linked to original sources
PubMed1991

Equivalent heart rate during ventricular fibrillation in the dog heart: mechanoenergetic analysis.

We propose equivalent heart rate (eHR) as an estimate of the frequency of contractions of individual myocytes in a fibrillating ventricle by analyzing mechanics and energetics of the ventricle. Using the isolated, cross-circulated dog heart preparation, we determined eHR in two different ways. First, we obtained eHR (eHR1) from myocardial O2 consumption (Vo2)-equivalent pressure-volume area (ePVA) data points during ventricular fibrillation (VF) by utilizing the Vo2-pressure-volume area (PVA) relation in the beating state. PVA is the area surrounded by the end-systolic and end-diastolic pressure-volume relations and the systolic pressure-volume trajectory in the pressure-volume diagram. PVA has been shown to represent the total mechanical energy generated by each contraction. We have recently proposed ePVA as a measure of the total mechanical energy generated by single contractions of all individual asynchronously contracting myocytes in a fibrillating ventricle. ePVA is the area surrounded by the horizontal line at the VF pressure and the end-systolic and end-diastolic pressure-volume relations in the beating state. Second, we measured Vo2 in beating state at various heart rates and Vo2 during VF under a mechanically unloaded condition. By comparing these fibrillating and beating Vo2 values, we determined eHR (eHR2) for the fibrillating state. eHR1 was 216 +/- 27 beats/min and eHR2 was 223 +/- 26 beats/min. These two values were not significantly different. We conclude that the average frequency of contractions of individual myocytes in a fibrillating ventricle is equivalent approximately to 220 beats/min in terms of ventricular energetics.

Animals↗
PubMed1990

Force-time integral does not improve predictability of cardiac O2 consumption from pressure-volume area (PVA) in dog left ventricle.

We have proposed the systolic pressure-volume area (PVA) as a measure of the total mechanical energy generated by ventricular contraction, and we found a closely linear correlation between PVA and cardiac oxygen consumption (VO2). Although the force-time integral (FTI) has long been considered to be the most reliable correlate of cardiac oxygen consumption (VO2), we have already shown that VO2 remained constant although FTI was changed while PVA was kept constant in the excised, cross-circulated dog left ventricle. This means that PVA is superior to FTI as a predictor of VO2. In the present study, we studied whether a linear addition of FTI to PVA could improve the prediction of VO2 from PVA in isovolumic and ejecting contractions with different afterload pressures in the same type of dog left ventricle preparation. Although left ventricular VO2 was always closely correlated with either PVA (r = 0.967, mean after z-transformation) or FTI (mean r = 0.925), multiple regression analysis indicated that PVA alone accounted for as much as 94% (mean) of the variance of VO2 and that FTI linearly added to PVA accounted for an additional few percent of the variance (statistically significant in less than half the cases). We conclude that the addition of FTI to PVA does not improve the predictability of VO2 from PVA in ordinary contractions.

Animals↗
PubMed1990

Simulation of mechanoenergetics of asynchronously contracting ventricle.

We simulated mechanoenergetics of ventricular asynchronous contraction using a model comprising two compartmentalized asynchronous time-varying elastic elements, E1 and E2. Their elastances [e1(t) and e2(t)] waxed and waned cyclically with a variable time lag (tau). The pressure-volume area (PVA1 or PVA2) circumscribed by the maximum (emax) and minimum e1(t) or e2(t) lines and the contracting pressure-volume trajectory of E1 or E2 quantifies the mechanical energy generated by a contraction of E1 or E2. Similarly, the PVA circumscribed by the resultant Emax (ventricular contractility index) line, the end-diastolic pressure-volume (P-V) line, and the systolic P-V trajectory quantifies the mechanical energy of the entire ventricle. PVA of the ventricle is equal to the sum of PVA1 and PVA2. We found that Emax decreased with increases in tau despite constant emax, and hence ventricular PVA decreased with increases in tau. This simulation helps us to better understand the mechanism of decreased oxygen consumption with increasing ventricular asynchrony reported in the literature.

Animals↗
PubMed1990

New method to determine oxygen cost for contractility.

We developed a new method to determine the oxygen cost for myocardial contractility and applied it to epinephrine in the excised cross-circulated dog heart. We utilized the relation between myocardial oxygen consumption (VO2) and the systolic pressure-volume area (PVA) which represents the total mechanical energy generated by contraction. We first obtained a reference VO2-PVA relation in a baseline contractile state. Then, the end-diastolic and stroke volumes were fixed constant and a global index of ventricular contractility, Emax, was enhanced by infusing epinephrine. The VO2-PVA data point was shifted linearly right-upward with the increases in Emax. From the slopes of both the reference VO2-PVA relation line and the regression line of VO2 on PVA during the gradually increased Emax, we calculated the oxygen cost for contractility, i.e., the ratio of the elevation of the VO2-PVA relation to enhanced Emax in each heart. The ratio was 0.00095 +/- 0.00013 ml O2.ml.mmHg-1.beat-1.100 g LV-2. The result indicates that the oxygen cost for contractility can be reliably and efficiently determined by this new method.

Animals↗
PubMed1990

Comparison between Bretschneider's total myocardial energy demand (Et) and our total mechanical energy (PVA) as a predictor of cardiac oxygen consumption in dogs.

We compared the predictive capability of two indexes of ventricular oxygen consumption (VO2) in excised cross-circulated dog hearts. One of the indexes was Bretschneider's Et, formulated as the sum of energies for 5 different mechanical and nonmechanical activities of myocardium. The other one was the left ventricular systolic pressure-volume area (PVA), originally proposed by Suga. PVA is a measure of total mechanical energy and has been combined with Emax (ventricular contractility index) to predict VO2 in different inotropic states. When all data sampled from different hearts under various loading and inotropic conditions were pooled, both VO2 (Bret) predicted from Bretschneider's index and VO2 (Suga) predicted from Suga's index correlated well with the measured VO2 (VO2 (Measured)). However, VO2 (Bret) was more affected by the contraction mode as compared with VO2 (Suga), because the former includes ejection period as a parameter. Among the 5 terms of VO2 (Bret), the major correlate of VO2 (Measured) was found to be tension development energy term E3 which includes dP/dtmax as a parameter. VO2(Suga), as a predictive index of VO2 (Measured), was more reliable in each heart than in pooled data from all the hearts because of the interindividual variations of the coefficients. We conclude that both indexes have usefulness and limitations, and should be chosen depending on the application.

Animals↗
PubMed1990

Assessment of left ventricular regional work under ischemia.

The wall tension-regional area (T-A) loop method, a new approach assessing regional contractile function of the left ventricle, has been developed in experiments performed on the isolated dog heart. Regional work is quantitatively determined by the area within a T-A loop with physically correct dimensions of energy (Joule) and regional contractility can be reliably assessed by the end-systolic T-A relation (ESTAR). During global ischemia, both the T-A loop area and the slope of the linear ESTAR decreased in proportion to the decreases in left ventricular stroke work and contractility. During regional ischemia, the T-A loop area in an ischemic region decreased to near zero, and the ESTAR markedly shifted to the right with a decreased slope and an increased regional area intercept. In contrast, the T-A loop in a non-ischematic region showed an increase in systolic area shrinkage and a decrease in regional work, demonstrating hyperkinesis due to regional afterload reduction. In addition, the ESTAR in a non-ischemic region remained almost unchanged. Thus, using the T-A loop method we can reliably assess regional work and contractility of a left ventricular region under ischemia.

Animals↗
PubMed1990

[Cross circulation (CC) as an assist method for canine orthotopic cardiac transplantation--estimation of usefulness judging from intra- and postoperative hematological and biochemical examinations].

We employed cross circulation (CC) as an assist method for canine orthotopic cardiac transplantation in 8 dogs to obtain long term survivals. Hematological and biochemical examinations were performed intra- and postoperatively, to estimate usefulness of CC. The support dog weighted about 3 times as much as the recipient dog. Using different anesthesia, the systolic pressure of the support dog and the pressure gradient between the support and recipient were kept above 150 mmHg and 50 mmHg, respectively. Cyclosporin and prednisolone were administered for immunosuppressive therapy. All could be extubated on the 1st to 3rd postoperative day, and 6 survived more than 2 weeks. During the operation under CC, changes of LDH and lactic acid were much less, no free hemoglobin was detected, and total protein and hematocrit remained well compared with operation under heart-lung machines. CRK, CPKMB, GOT and GPT increased shortly after operation, but returned to the preoperative values within 2 weeks. In CC, owing to avoidance from mechanical destruction of red blood cells, coagulation disorders and hemodilution, hemolysis and hemorrhage could be decreased, and oncotic pressure remained well, and no severe damage occurred in the recipient organs. Thus, CC is useful as an assist method for canine orthotopic cardiac transplantation.

Animals↗
PubMed1989

Effect of ouabain on the relation between left ventricular oxygen consumption and systolic pressure-volume area (PVA) in dog heart.

We studied the effect of ouabain (digitalis) on the relation between left ventricular (LV) O2 consumption (VO2) and pressure-volume (P-V) area (PVA) in 7 excised cross-circulated canine heart preparations. PVA is a measure of the total mechanical energy generated by LV contraction and was obtained as the specific area in the P-V diagram circumscribed by the end-systolic P-V line, end-diastolic P-V curve, and the systolic P-V trajectory. Ouabain (0.11 mg, intracoronary-arterially) increased Emax (LV contractility index) by 58 +/- 44% (mean +/- SD) from 7.8 +/- 3.4 to 12.0 +/- 4.8 mmHg/(ml/100 g LV). PVA correlated linearly with LV VO2 per beat in either the control (r greater than 0.97) or the ouabain run (r greater than 0.96) in individual hearts. Ouabain increased the VO2-axis intercept of the regression line of VO2 on PVA from 0.029 +/- 0.004 in the control run to 0.036 +/- 0.009 ml O2/beat/100 g LV without significantly changing the slope [(1.53 +/- 0.24).10(-5) ml O2/(mmHg/ml)] of the regression line. This slope is equivalent to the contractile efficiency value of 44 +/- 6% from the excess VO2 above unloaded VO2 to PVA. The parallel elevation of the VO2-PVA relation with ouabain was similar to the results produced by epinephrine and Ca2+ in our previous studies. Ouabain, like epinephrine and Ca2+, did not change the contractile efficiency from the PVA-dependent fraction of VO2 to PVA.

Animals↗
PubMed1989

Arteriovenous oximeter for O2 content difference, O2 saturations, and hemoglobin content.

We combined two spectrophotometric oximeters to measure continuously and simultaneously arteriovenous O2 content difference (AVOD) as well as arterial and venous oxyhemoglobin saturations (SaO2, SvO2) and total hemoglobin concentration (Hb). AVOD of the flowing arterial and venous whole blood was determined by the method of Guyton et al. (J. Appl. Physiol. 10: 158-163, 1957) and Shepherd and Burgar [Am. J. Physiol. 232 (Heart Circ. Physiol. 1): H437-H440, 1977]. The new arteriovenous oximeter was tested in dog experiments in which SaO2, SvO2, Hb, and AVOD were variously changed by temporary suffocation, electric muscle stimulation, hemorrhage and transfusion, and hemodilution with saline. AVOD, SaO2, SvO2, and Hb were compared with the data of the arterial and venous blood sampled near the oximeter cuvettes and measured with an IL282 CO oximeter. In one dog experiment and one in vitro blood experiment, AVOD data of the same arterial and venous blood were compared by connecting the present oximeter in series with an A-VOX Systems oximeter developed by Shepherd and Burgar. The results showed that the new arteriovenous oximeter can continuously measure AVOD, SaO2, SvO2, and Hb over wide ranges with reasonable accuracy.

Animals↗
PubMed1989

[A case report of successful treatment using ECMO in severe status asthmaticus during open heart surgery].

A 6-year-old boy who had a history of asthma attack since 3 years old, but whose symptom was well controlled with medication received a radical operation for ASD. During the operation, he suffered from severe asthma attack. In blood gas analysis, PCO2 was increased to 302 mmHg with a decrease of pH to 6.740. Every conventional treatment for asthma attack was not effective, and then extracorporeal membrane oxygenation (ECMO was performed within 2 hours after operation. Blood gas data normalized and his hemodynamic condition was well maintained by ECMO. After 4 hours 20 minutes, he was weaned off from ECMO. Post operative course was uneventful except for pneumothorax.

Asthma↗
PubMed1989

[Postoperative thromboembolism of acquired mitral valve disease--comparison between valve replacement and commissurotomy].

Thromboembolism after mitral commissurotomy (MC) was compared with that after mitral valve replacement (MVR). In 216 surgical cases of acquired mitral valve diseases, including combined operative cases of other valves, thromboembolic complications after MC were observed in 9/137 cases (13 times, 0.94%/patient-year), and those after MVR in 8/70 cases (11 times, 2.55%/patient-year). No thromboembolism occurred in 9 cases of annuloplasty. Thromboembolism-free period after MVR (49 +/- 44 months) was significantly shorter than that after MC (102 +/- 43 months, p less than 0.05). Postoperative CTR of thromboembolic cases (69.5 +/- 8.2%) was significantly larger than that of non-thromboembolic cases (61.4 +/- 9.9%) in MVR group (p less than 0.005), but no significant difference existed between thromboembolic and non-thromboembolic cases in MC group. Thromboembolism after MVR occurred in severe cases, but that after MC often occurred in mild cases. Postoperative echocardiogram of MC group showed significantly lower DDR in thromboembolic cases (1.9 +/- 0.7 cm/sec) than in non-thromboembolic cases (3.2 +/- 1.2 cm/sec, p less than 0.025). Mitral valve area (MVA) of all re-stenotic cases in thromboembolic cases after MC was under 1.5 cm2, comparing that in non-thromboembolic cases there were only two cases that had MVA under 1.5 cm2. After MC, careful management including anticoagulant therapy and reoperation is necessary especially in patients with atrial fibrillation, DDR under 2 cm/sec, and MVA under 1.5 cm2, even though they don't have cardiomegaly.

Adult↗
PubMed1988

Paired pulse pacing increases cardiac O2 consumption for activation without changing efficiency of contractile machinery in canine left ventricle.

The relation between cardiac O2 consumption (VO2) and the total mechanical energy (TME) generated by contraction was studied under paired-pulse (PP) pacing and compared with that under single-pulse pacing at the same basic rate as PP pacing and at the double-pacing rate in ten excised cross-circulated canine left ventricles (LV). TME was assessed by the systolic pressure-volume (P-V) area (PVA) defined as the area bounded by the end-systolic and end-diastolic P-V curves and the systolic P-V trajectory. The VO2-PVA relation was linear under PP pacing as well as at control and double heart rates. PP pacing increased LV contractility index Emax from 6.3 +/- 3.3 (SD) to 18.0 +/- 8.6 mmHg/(ml/100 g) and elevated markedly the VO2-PVA relation by increasing the VO2-axis intercept (or PVA-independent VO2) from 0.62 +/- 0.11 to 1.13 +/- 0.35 J.beat-1.100 g-1. However, PP pacing did not change the slope of the VO2-PVA relation at 2.24 +/- 0.53 (dimensionless). The efficiency from PVA-dependent VO2 (total VO2-PVA-independent VO2) to PVA (=TME), calculated as the reciprocal of the slope of the VO2-PVA relation, was also constant at 47 +/- 11% regardless of PP pacing. These results are similar to previous results obtained by positive inotropic interventions with catecholamines and Ca2+. We conclude that PP pacing augments the PVA-independent VO2 for activation without affecting the efficiency of the contractile machinery to generate TME from the PVA-dependent VO2.

Animals↗
PubMed1985

[A case of surgical correction of the inferior vena cava obstruction with Budd-Chiari syndrome].

A 37-year-old man is presented with Budd-Chiari syndrome associated with a membranous obstruction of the inferior vena cava. Clinical symptoms were ascites, leg edema and dilatation of the superficial abdominal veins. Aggressive surgery was carried out for this case. Midsternal incision and right subcostal oblique incision were made, and hepatic segment of the inferior vena cava was reconstructed using pericardial patch after endovenectomy and partial cardiopulmonary bypass was used without temporary interruption of liver circulation. Blood flow from the right hepatic vein was restored. Postoperative course was not eventful and this patient remains free of any evidence of ascites and liver dysfunction after operation. This procedure may be useful particularly for protecting the liver function which is damaged by hemostasis.

Adult↗
PubMedDate not supplied

Effects of nilvadipine on the cardiovascular responses to tracheal intubation.

STUDY OBJECTIVE: To evaluate the efficacy of nilvadipine given orally in attenuating the hypertensive response to laryngoscopy and intubation. DESIGN: Controlled, randomized, double-blind study. SETTING: Induction of anesthesia for elective surgery at a university hospital. PATIENTS: Thirty normotensive patients (ASA physical status I) undergoing elective surgery were divided into three groups of ten patients each. INTERVENTIONS: Either 2 mg of nilvadipine, 4 mg of nilvadipine, or a placebo (control) was administered orally 90 minutes before induction of anesthesia. Anesthesia was induced with thiopental sodium 5 mg/kg intravenously, and tracheal intubation was facilitated with vecuronium 0.2 mg/kg. During anesthesia, ventilation was assisted or controlled with 1% enflurane and 50% nitrous oxide (N2O) in oxygen. Laryngoscopy lasting 30 seconds was attempted 2 minutes after administration of thiopental sodium and vecuronium. MEASUREMENTS AND MAIN RESULTS: Patients receiving the placebo showed a significant increase in mean arterial pressure (MAP) and heart rate associated with tracheal intubation. The increase in MAP following tracheal intubation was significantly lower in nilvadipine-treated patients than in the control group (p less than 0.05). However, neither dose of nilvadipine attenuated the tachycardic response to intubation. CONCLUSIONS: Oral administration of nilvadipine before induction of anesthesia is a simple and practical method for attenuating pressor response to laryngoscopy and tracheal intubation after standard elective induction under additional 1% enflurane-N2O anesthesia.

Administration, Oral↗