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Biomedical subjects

H Tomoike

Publications and source records attributed to H Tomoike.

At least 217 records · Page 12Linked to original sources
PubMed1982

Analysis of in situ heart mechanics.

Analysis of the in situ heart performance has been guided by the concepts of pump and muscle mechanics derived from studies on isolated heart and papillary muscle, respectively. It is occasionally beneficial to evaluate the cardiac performance separately on heart as a pump or as a muscle. Cardiac output is determined by the interaction among preload, afterload and contractility. Thus, it is sometimes difficult to estimate the contractile state of the diseased heart simply from hemodynamic measurements. Therefore, it is necessary to compare hemodynamics between rest and stress states or to apply concepts of "afterload mismatch and preload reserve" as well as end-systolic pressure volume relations in quantitative evaluation of the cardiac performance. Regional wall motion measurements are also useful to detect regional myocardial ischemia.

Blood Pressure↗
PubMed1981

Continuous measurement of coronary artery diameter in situ.

The diameter of the coronary artery was measured in dogs in situ by an ultrasonic dimension gauge using 10-MHz piezoelectric crystals. Underestimation in measurements due to crystal rotation was limited to < 1% by adding a convex lens to the crystal. A pair of small 10- and 5-MHz crystals were sutured to the adventitia of the left circumflex coronary artery (LCX) and the descending aorta (Ao), respectively. Using cuff occluders for vessel constriction of the inferior vena cava (IVC) or the Ao, curvilinear relationships between pressure and diameters were obtained. Phasic changes of the aortic as well as coronary diameter were grossly similar to changes in the pressure wave. After intravenous administration of dipyridamole, aortic pressure (AP) decreased by 17% along with 3% decline of the Ao and LCX diameter, however, after nitroglycerin given by the same route, LCX diameter increased by 5% (P < 0.05) despite 16% and 2.3% reductions in AP and Ao diameter, respectively. This ultrasonic technique, which allows continuous measurement of the diameter of small vessels, should provide a new tool for the study of coronary circulation.

Animals↗
PubMed1981

Functional evaluation of coronary collateral development in conscious dogs.

Gradual coronary constriction was elicited in conscious dogs by means of an implanted ameroid coronary constrictor. The functional state of the coronary collateral circulation was serially evaluated by means of regional contractile responses, using brief occlusions of the left circumflex coronary artery and strenuous running in the field. Although resting regional myocardial function was unchanged throughout the study, regional myocardial shortening during coronary occlusion decreased to 9% of control at 3-4 days after the operation; it then recovered progressively to 24% at 7-9 days, 45% at 15-18 days, and 94% at 20-24 days. Concomitantly, reactive hyperemia measured with a flowmeter declined from 300% at 3-4 days to 228, 88, and 0% at 7-9, 15-18, and 20-24 days, respectively. A bout of running held 21 days after the ameroid implant when resting regional function was well maintained induced severe regional and global dysfunction. These findings indicate the usefulness of regional myocardial contractile responses in assessing coronary collateral reserve.

Animals↗
PubMed1981

Effects of 2-nicotinamidethyl nitrate (SG-75) and/or nitroglycerin on systemic hemodynamics and coronary blood flow in conscious dogs.

The effect of 2-nicotinamidethyl nitrate (SG-75), a newly synthesized nitroester, on hemodynamics and coronary circulation was studied in conscious dogs, comparing it with nitroglycerin (NG). Dogs were previously instrumented with catheters in the aorta and left atrium and a Doppler flow probe on the left circumflex coronary artery. Percent increases in coronary flow rate were 11 (10 micrograms/kg), 20 (50 micrograms/kg), 71 (100 micrograms/kg) and 169% (200 micrograms/kg) in SG-75 and 3 (1 microgram/kg), 28 (5 microgram/kg), 65 (10 micrograms kg) and 99% (20 micrograms/kg) in NG, thus the dose ratio for an equivalent increase in mean coronary flow is about 10:1 between SG-75 and NG. The duration of coronary flow increase was also dose dependent and 2.1 min in 200 micrograms/kg SG-75 and 1.3 min in 20 micrograms/kg NG. Comparable changes in heart rate increase and pressure reduction were noted both in SG-75 and NG. The peculiar difference between two drugs was their time course of coronary flow increase: SG-75 showed monophasic increase while NG showed bipeaked increase in flow. The results suggest that the reflex increase in heart rate elicited by pressure drop after SG-75 did not influence the envelope of coronary flow increase such as observed upon NG administration.

Animals↗
PubMed1981

Difference in site and time course of coronary dilating effects of trapidil, nitroglycerin and dipyridamole in anesthetized dogs.

Effects of trapidil, a non-nitrate type coronary vasodilator, nitroglycerin and dipyridamole on epicardial coronary diameter and total coronary resistance were studied in anesthetized open-chest dogs. The epicardial coronary diameter of the left circumflex coronary artery was measured by sonomicrometry and total coronary resistance was calculated by aortic pressure and coronary blood flow. Intravenous administration of Trapidil, as well as nitroglycerin, produced transient decreases in total coronary resistance followed by sustained dilation of the large coronary artery. Dipyridamole increased coronary blood flow by 2.7-fold, whereas diameter of the large coronary artery decreased along with the reduction of aortic pressure. The first peak of the biphasic increases in coronary blood flow and subsequent dilation of the large coronary artery appeared after an i.v. bolus administration of trapidil or nitroglycerin and remained even after beta adrenergic blockade. Intracoronary administration of either drug produced monophasic increases in coronary blood flow along with subsequent dilation of the large coronary artery. Thus, trapidil, like nitroglycerin, directly dilates the large and small coronary arteries.

Animals↗
PubMed1981

Effects of dilazep on regional myocardial blood flow during selective coronary hypotension.

Effects of 1,4-bis-[3-(3,4,5-trimethoxybenzoyloxy)-propyl]-perhydro-1,4-diazepine (dilazep), a powerful coronary dilator via adenosine potentiation, on regional blood flow during acute selective coronary hypotension were studied in the canine heart under anesthesia and thoracotomy. The proximal left circumflex coronary artery (LCX) was partially obstructed and mean LCX pressure distal to obstruction was reduced to 40-45 mmHg and two different doses of dilazep were given i.v. The left ventricular free wall and interventricular septum were divided into normally perfused, borderline ischemic, moderately ischemic and severely ischemic area according to the level of regional myocardial blood flow measured by tracer microspheres. 50 microgram dilazep/kg b.w. increased myocardial flow in the normally perfused and borderline ischemic areas without a significant alteration of blood flow to the moderately and severely ischemic areas. The fall of aortic pressure was more striking in dogs receiving 100 microgram dilazep/kg b.w. than in animals with 50 microgram dilazep. 100 microgram dilazep increased flow in the normally perfused area, but increased the number of segments in the moderately and severely ischemic area. These results indicate that an appropriate dose of dilazep causing a slight reduction of aortic pressure increased flow to the borderline ischemic as well as normally perfused myocardium in selective coronary hypotension.

Animals↗
PubMed1978

Myocardial infarction in the baboon: regional function and the collateral circulation.

Occlusion of the anterior descending coronary artery was produced in sedated baboons 7-15 days after implantation of a micromanometer and ultrasonic crystals for measurement of regional left ventricular dimensions in ischemic, marginal, and control segments. One minute after coronary occlusion (CO), ischemic segments exhibited a marked systolic bulge with wall thinning, and percent systolic shortening of marginal segments decreased. Over the ensuing weeks, there was a progressive increase of end-diastolic lengths in marginal and ischemic segments, whereas systolic shortening in these segments did not improve significantly. Control segments did not change. In control baboons, the coronary collateral index was 55 +/-25 (SE) compared to 560 +/- 74 in normal dogs. One month after CO, the collateral index was 543 +/- 144 in baboons compared to 6,685 +/- 716 in dogs, regions of normal tissue were seen in the infarct (14.2 +/- 2% of left ventricular mass). Minimal coronary collateral development in the baboon provides a likely explanation for differences from the dog in regional functional responses and in the character of the infarct.

Animals↗
PubMed1978

Role of autonomic and non-autonomic circulatory components in borderline hypertension in young men.

The role of autonomic nervous system and non-autonomic components in hemodynamic abnormalities of young patients with borderline hypertension was examined by comparing the effects of sequential pharmacological autonomic blockade on hemodynamics between 8 patients with borderline hypertension (mean age 20.0 +/- 0.2) and 10 normotensive subjects (mean age 19.3 +/- 0.2). Propranolol (0.2 mg/Kg), atropine (0.04 mg/Kg), and phenotolamine (10 or 15 mg) were given intravenously in that order to produce "total" autonomic blockade. Increased cardiac index, heart rate, and mean arterial blood pressure with normal peripheral vascular resistance were noted at rest in patients with borderline hypertension. Cardiac index and heart rate in patients with borderline hypertension were normalized by propranolol, but after "total" autonomic blockade mean arterial blood pressure and peripheral vascular resistance were higher in patients with borderline hypertension as compared to those in normotensive subjects. These results suggest that, although autonomic nervous system control of circulation is abnormal, non-autonomic components play an important role in maintaining increased peripheral vascular resistance in borderline hypertension in young men.

Adult↗
PubMed1978

[Nitroglycerin in experimental myocardial infarction in the baboon. The effect of reducing the pre-charge and post-charge on regional myocardial function].

A left anterior descending coronary artery occlusion was produced in the sedated state in baboons previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring segmental myocardial lengths of control, marginal and ischemic regions. 3-8 days after the onset of the ischemia, nitroglycerin (0.4 mg IV) was injected. Following the injection (NG), heart rate increased significantly compared to the control ischemic state (CIS); end diastolic pressure and systolic pressure decreased significantly. In control segments, VCF increased from 0.99 +/- 0.11 circ/s to 1.26 +- 0.11 circ/s (p less than 0.01); in marginal segments VCF increased (CIS: 0.32 +/- 0.07 circ/s; NG: 0.42 +/- 0.09/s; p less than 0.01); in ischemic segments, the bulge observed before the injection persisted after nitroglycerin. Increased performances of control and marginal regions were attributed mainly to afterload reduction although preload reduction tended to decrease this response. The contribution of improved marginal function was small indicating that improvement of active hemodynamic function was largely due to changes in control segments function.

Animals↗
PubMed1977

In situ measurement of papillary muscle dynamics in the dog left ventricle.

In five open-chest dogs, pairs of ultrasonic dimension gauges were implanted in the anterior papillary muscle and in a circumferential subendocardial segment of the anterior left ventricular free wall, and simultaneous recordings were made with intracardiac pressure. The average shortening of the anterior segment in isovolumetric systole was 6% of end-diastolic length (EDL), with a total shortening of 19%. In the papillary muscles, isovolumetric shortening averaged 2%, total shortening was 10%, and shortening velocity was only 0.60 length/s. With acute pressure and volume overload, or inotropic interventions, changes in EDL were relatively less in papillary muscles than in the free wall. During acute occlusion of the anterior descending coronary artery, shortening of anterior segments and papillary muscles was replaced by holosystolic lengthening, and occlussion of the circumflex artery produced augmentation of shortening in both these regions, with lengthening of the posterior papillary muscle. The present study documents shortening of the anterior left ventricular papillary muscle throughout systole that is substantially less than that of the circumferential free wall, and demonstrates severe papillary muscle dysfunction with systolic elongation during regional ischemia.

Animals↗
PubMed1977

Loss of regional ventricular postextrasystolic potentiation after coronary occlusion in dogs.

Postextrasystolic potentiation following coronary artery occlusion was studied serially using pairs of ultrasonic crystals to measure regional myocardial function in control, marginally ischemic, and ischemic segments of the left ventricle in dogs. Prior to coronary occlusion (CO), percent shortening in control (normal) segments increased by an average of 51.4 +/- 4.6% in the beat after a premature ventricular contraction (post-PVC beat), and this response changed little after coronary occlusion. During the 1st min after CO, in ischemic segments, systolic expansion developed but was replaced by active shortening in post-PVC beats; however, after 3 min of CO (average) and thereafter, there was no net positive shortening in post-PVC beats. In marginally ischemic segments early after CO, hypokinesia developed, but there was marked augmentation of percent shortening (208.6 +/- 32.6%) which persisted in post-PVC beats even after 2 h. It is concluded that loss of postextrasystolic potentiation occurs rapidly in ischemic regions after CO and is not indicative of irreversible damage; partially ischemic regions retain this mechanism for prolonged periods.

Animals↗