Measurement Of Tissue Blood Flow Research Articles

Modeling ultrasound contrast measurement of blood flow and perfusion in biological tissue

The aim of this paper was to obtain a parametric description of ultrasound (US) contrast dilution curves obtained in piglet brain after a bolus injection of contrast agent (Sonovue™). Several models for so-called dye-dilution curves were considered, and a choice for the gamma probability density function (pdf) was made. This function was chosen primarily because of the elegant mathematical opportunities to achieve a practical one-parameter curve fitting and to extend this model for incorporating recirculation. The model was fitted to US contrast data obtained in piglet brain. The software enables interactive insertion of curve landmarks and a single parameter ( i.e., order of gamma pdf) iterative least squares fit was then made to the first bolus passage part of the curve. Sequential recirculation curve fits were calculated from this fit. A preliminary result for 24 experimental curves is a median value of 3 (range 3 to 5) for the order of the gamma function (κ) and a median of 0.6/s (range 0.3 to 0.9) for the event rate (λ). The theoretical background for obtaining the relative plasma flow and volume in tissue ( i.e., “blood flow index”, BFI, and “blood volume index”, BVI, respectively) from the reconstructed first passage curve is given as well. The potential of assessment of the relative fraction of left-to-right shunting of the cardiac output in case of persistent ductus arteriosis is outlined. The requirements for an absolute measurement of tissue blood flow and tissue perfusion are discussed. The conclusion is that the gamma model can well be fitted to the experimental contrast curves; thus, yielding the parameters κ and λ. Assessment of BFI and BVI is feasible. (E-mail: J.Thijssen@CUKZ.UMCN.NL)

Evaluation of a novel method for measuring tissue blood flow and gases

In clinical practice a method for assessment of tissue vitality is a sought-after tool. We have developed a new sensor principle, which is able to register changes in tissue concentration of O2 and tissue flow. The technique is based on diffusion of inert gases and mass spectrometer detection of gaseous metabolites. It was hypothesized that the new sensor could register changes in vital parameters after induction and release of an ischaemic insult to muscular tissue. The sensor performance was evaluated in ten anaesthetized pigs subjected to local muscular ischaemia. Preliminary data from this study indicate the validity of registered hypoxia and reduction in tissue flow as a consequence of compromised blood supply. It was concluded that although precise calibration of the technique is not yet established, it holds promise as a technique that can be used to monitor changes in tissue vitality.

Epinephrine Prevents Muscle Blood Flow Increases after Perineural Injection of Tetrodotoxin

The local anesthetic properties of tetrodotoxin, a potent naturally occurring sodium channel blocker, have been recently reexamined. It was found that sciatic nerve block duration could be greatly increased and systemic toxicity greatly decreased if epinephrine was injected with tetrodotoxin. The mechanism that underlies epinephrine-mediated prolongation of tetrodotoxin nerve blocks is not known, but indirect evidence suggests that epinephrine may slow the clearance of tetrodotoxin from the site of injection. The authors hypothesized that tetrodotoxin causes vasodilatation at its injection site, which accelerates its systemic uptake, and that this vasodilatation is attenuated by coinjected epinephrine. The radiolabeled microsphere technique was used to measure tissue blood flow in anesthetized rats before and after perisciatic injection of tetrodotoxin alone and in combination with epinephrine. Tetrodotoxin, in a dose of 0.1 ml of a 60 microM solution, significantly increased blood flow in perisciatic muscle at the injected side compared with simultaneous contralateral control and ipsilateral preinjection baseline. Tetrodotoxin did not increase blood flow in the sciatic nerve. Coinjection of epinephrine with tetrodotoxin prevented tetrodotoxin-induced increases in perisciatic muscle blood flow over time and did not alter sciatic nerve blood flow. Arterial blood pressure was maintained with this dose of tetrodotoxin, although brain blood flow decreased. Coinjection of epinephrine with tetrodotoxin prevented decreases in brain blood flow. Higher doses of tetrodotoxin produced hypotension. Vasoconstriction in the perisciatic muscles by epinephrine may contribute to the prolongation of tetrodotoxin-induced sciatic nerve blocks and the reduction of systemic toxicity of tetrodotoxin.

Xenon-inhalation computed tomography for noninvasive quantitative measurement of tissue blood flow in hepatocellular carcinoma.

The purpose of this study was to separately measure the arterial and portal venous tissue blood flow (TBF) of hepatocellular carcinoma (HCC) with a noninvasive method using xenon inhalation CT (xenon-CT) and to differentiate between well-differentiated HCCs and moderately and poorly differentiated HCCs. Total, arterial and portal venous TBFs of 38 surgically proven HCC nodules from 38 patients were measured by means of xenon-CT. Serial abdominal CT scans were obtained before and after inhalation of nonradioactive xenon gas. TBF was computed using the Fick principle, after which the correlation between TBF and pathologic features of the tumors was determined. Total, arterial, and portal venous TBFs of HCC were 125.7 +/- 59.9 mL/min/100g, 102.5 +/- 37.3, and 22.2 +/- 11.4, respectively, and the corresponding findings for hepatic parenchyma were 67.3 +/- 13.1, 25.2 +/-9.6, and 42.4 +/- 11.0. Total and arterial TBFs of HCC were significantly higher than those of the hepatic parenchyma (P < 0.01), whereas portal venous TBF of HCC was significantly lower than that of hepatic parenchyma (P < 0.01). Arterial TBF of moderately or poorly differentiated HCC (120.4 +/- 38.2) was significantly higher than that of well-differentiated HCC (60.4 +/- 43.5) (P < 0.01). Arterial and portal venous TBFs of HCC could be measured separately, noninvasively, and safely with xenon-CT. Correlation between TBF and pathologic features of tumors indicate that xenon-CT can be used to differentiate between well-differentiated HCCs and moderately and poorly differentiated HCCs.

Effect of lumbar sympathectomy on muscle blood flow: distribution of perfusion measured by hydrogen clearance in skeletal muscle.

Measurements of local tissue blood flow using a technique of hydrogen clearance were used to examine the effect of lumbar sympathectomy on skeletal muscle blood flow. Polarographic recordings on 25 hydrogen desaturations were obtained with platinized platinum electrodes. Lumbar sympathectomies were done on five canines leaving the contralateral limb as a control. The hydrogen clearance data were modeled with biexponential curves: the initial rapid component and the second slow component yielded a weighted average perfusion through tissue. Average volumetric blood flow in the control limb was 6.08 +/- 0.45 ml/min/100 g tissue while the sympathectomized limb averaged 9.54 +/- 0.61 ml/min/100 g tissue (p less than 0.005). Average blood flow increases ranged from 33 to 83 percent in the sympathectomized limb over the control limb. This significant increase in muscle blood flow following lumbar sympathectomy, if of prolonged duration, may be cause for re-evaluation of the role of sympathectomy in the management of arteriosclerotic occlusive disease.

Noninvasive quantitative measurement of tissue blood flow in hepatocellular carcinoma using xenon-enhanced computed tomography.

The aim of this study was to quantitatively measure tissue blood flow (TBF) in hepatocellular carcinoma (HCC) by a noninvasive method using xenon (Xe) inhalation/CT scans and to correlate the measured TBF with histological features. TBF was measured in HCC with xenon-enhanced CT (xenon/CT) in 20 patients. In 15 patients with HCC diagnosed as hypervascular tumors by conventional CT, TBF of the tumors was significantly higher than that of noncancerous liver tissue (151.1 +/- 20 vs 42.6 +/- 20 ml/min/100 g). Histologically, these tumors were diagnosed as moderately-to-poorly differentiated HCC. In contrast, in five patients with hypovascular HCC, TBF of HCC was almost comparable to that of the noncancerous regions (45.3 +/- 6 vs 48.3 +/- 6 ml/min/100 g). All these tumors were well-differentiated HCC. In conclusions, the measured values of TBF correlate with the clinicopathologic features of liver tumors and nontumorous liver tissue in patients with HCC.

Modification of the radioactive microsphere technique for assessment of regional blood flow to the craniofacial skeleton in the New Zealand rabbit

Background The radioactive microsphere technique has been used extensively for the accurate measurement of tissue blood flow in experimental animals. However, the need for carotid artery cannulation for injection of microspheres may significantly impair blood flow to the head and neck region. Objective This study assessed an alternative technique of injecting microspheres directly into the left ventricle to ensure a symmetric distribution of microspheres to the head. Methods Twenty-five New Zealand rabbits (seven to nine weeks of age) underwent blood flow measurement to the orbitozygomatic complex (OZC) regions bilaterally. Under general anesthesia, a sternotomy was performed and a cannula was inserted into the left ventricle. Radioactive microspheres were injected after a stabilization period of 15 min. Blood pressure and cardiac output were measured during the procedure and the animals were sacrificed at the end of the experiment. Tissue samples were harvested bilaterally from the OZC, hemimandibles, masseter muscles and overlying skin for measurement of blood flow. Results There was no significant difference in blood flow between the right and left side specimens. Animals were hemodynamically stable during the procedure. Conclusion Assessment of blood flow to the craniofacial region in experimental animals using radioactive microspheres may be facilitated by sternotomy and direct intracardiac injection.

Measurement of endometrial tissue blood flow: a novel way to assess uterine receptivity for implantation

Objective: To assess endometrial receptivity in terms of endometrial tissue blood flow (ETBF) measured hysterofiberscopically by laser blood-flowmetry, and to examine the technique’s effectiveness in an in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) program. Design: A prospective clinical study. Setting(s): IVF program in a university hospital. Patient(s): A total of 75 infertile women with normal menstrual cycles undergoing IVF/ICSI. Intervention(s): ETBF, conventional ultrasonographic, endocrinologic, and histologic parameters for receptivity and immunoreactivity for vascular endothelial growth factor (VEGF) in endometrium were assessed between days 4 and 6 of the luteal phase in a spontaneous menstrual cycle. Then all patients underwent IVF/ICSI. Main Outcome Measure(s): Achievement of clinical pregnancy by IVF/ICSI. Result(s): ETBF, VEGF expression, and the number of embryos were significantly higher in the women who became pregnant than in those who did not. By stepwise multiple logistic regression, significant predictors of pregnancy were the number of embryos and ETBF but not conventional receptivity markers. The rate of pregnancy was significantly higher in women with ETBF values of at least 29 mL/min per 100 grams of tissue than in women with lower values (42 vs. 15% in 36 and 39 women, respectively). ETBF was significantly greater in morphologically normal than abnormal uteri. In normal uteri, ETBF was greatest in the fundus. Correspondingly, in normal uteri 85% of gestational sacs were implanted in the fundus. Conclusion(s): ETBF is superior to conventional parameters for determining endometrial receptivity for implantation.

The roles of platelet-activating factor and endothelin-1 in renal damage after total hepatic ischemia and reperfusion.

This study was designed to verify the involvement of platelet-activating factor (PAF) in renal damage associated with hepatic ischemia and reperfusion (HIR) injury through the release of endothelin (ET)-1 and to determine the modulating effect of a specific PAF receptor antagonist on these insults in rats. Male rats pretreated with either normal saline as a vehicle (NS group) or intravenous TCV-309, a PAF receptor antagonist (TCV group), were subjected to 120 min of total hepatic ischemia under an extracorporeal portosystemic shunt. Plasma aspartate transaminase, creatinine, blood urea nitrogen, and ET-1 levels and the relative renal wet weight were determined under nonischemic conditions and at 1, 3, and 6 hr of reperfusion after hepatic ischemia. Changes in mean arterial blood pressure and renal tissue blood flow measurements in the kidney were determined throughout the experiment. Increased plasma aspartate transaminase, creatinine, blood urea nitrogen, and ET-1 levels and the relative renal wet weight after HIR in the NS group were significantly suppressed by TCV-309 pretreatment. Mean arterial blood pressure and renal tissue blood flow after HIR in the TCV group were significantly improved when compared with those in the NS group. These effects resulted in attenuation of structural hepatic and renal damage with the improvement of 7-day survival (62%). The present study demonstrates that renal damage as well as critical liver injury is produced after reperfusion following 120 min of total hepatic ischemia. A PAF receptor antagonist may be therapeutically useful to protect against these types of damage via indirect modulation of plasma ET-1 levels.

Simplified model of laser Doppler signals during reactive hyperaemia.

Laser Doppler flowmetry (LDF) is a non-invasive method to measure tissue blood flow. During reactive hyperaemia, the LDF signal increases to a peak and then returns to a resting value. A simplified model is developed to explain these variations. The emphasis is on simulating the effects occurring rather than on trying to mimic the anatomical structure of the microcirculation. A single blood vessel is therefore analysed. The increasing value of blood velocity is studied, and vasodilatation as well as vasoconstriction are taken into account. The model parameters are calculated using wavelets. For a 2-min occlusion on a healthy subject, the radius of the vessel is initially 15 microns, increasing to 24.6 microns at the peak, reached 14 s after the release of the occlusion. The model shows that the high value of the LDF signal during the initial phase of reactive hyperaemia is produced by an increasing number of erythrocytes in a cross-section, due to vasodilatation rather than an increase in moving blood cell velocities. Moreover, the rapidity of the vasodilatation and vasoconstriction effects determine the rapidity of the signal variations. The paper aims to give a basic solution to develop a numerical model.

Tissue blood flow assessment of pulsed Doppler ultrasound using autoregressive modeling.

Tissue blood flow measurement using 20 MHz pulsed Doppler ultrasound is presented. Autoregressive modeling is applied to Doppler signals obtained from tissue blood flow. The measurement system is tested on the reference flow model and then applied to man right hand tissue. It is seen that the reasonable results are obtained.

Experiences of the 14C-ethanol technique for blood flow measurements in human subcutaneous adipose tissue

We compared the 14C-ethanol technique and 133Xe-clearance for adipose tissue blood flow measurements in young healthy subjects before and after exercise on an ergometer bicycle. The results showed a decrease in outflow/inflow ratio of 14C-ethanol during the basal situation before the exercise, indicating an increased blood flow. However, there was a great range of values, and no correlation between the 14C-ethanol technique and 133Xe-clearance was found. Our data indicate that the 14C-ethanol technique can not be recommended in its current form.

Development of noninvasive measurement of peripheral circulation and its medical application

Surveys were carried out on tissue blood flow measurement based on the thermal diffusion method and on the assessment of peripheral circulatory function using photosensors.Regarding the thermal diffusion method, first noninvasive measurement using a Peltier stack was carried out. Then, measurements using a thermal clearance curve at various temperatures were performed.For noninvasive measurement of the mechanical properties of peripheral arteries using photosensors, the author determined the vascular volume ratio and/or the relative vascular volume.For clinical application in field studies, it is necessary to develop an apparatus with which absolute evaluation of the intravascular volume can be carried out using the blood volume around the unit volume as an indicator. Therefore, an apparatus that removes a signal constituent from tissue other than the blood using two-wavelength photosensors is required.If a noninvasive method to accurately measure the intravascular volume is established, changes in the mechanical properties of the peripheral arteries that correspond to functional and organic changes in the normal response can be observed more directly. Moreover, quantitative assessment of peripheral circulatory function will become possible, and diagnosis of the severity of peripheral circulatory disorders will be facilitated.

A transient spherical source method to determine thermal conductivity of liquids and gels

A method developed for the measurement of tissue blood flow is modified to measure the thermal conductivity of liquids and silica gels. The method controls a thermistor temperature at a set point above the baseline and determines conductivity from the power as a function of time. Natural convection in the liquids is suppressed by reducing the measurement time to 10 s and by reducing the temperature step, thus decreasing the magnitude of buoyancy. Conductivities were measured in six aqueous liquids and in gels constituted from these liquids with various amounts of silica. The technique determined the conductivity with a 95% confidence interval to less than 1% in nearly all cases. It was found that conductivity varied 0.3% per 1% silica for gels made from a CuSO 4 solution and 1% per 1% silica for gels made from a Cu(BF 4) 2 solution.

Imaging brain injury using time-resolved near infrared light scanning.

Conventional brain imaging modalities are limited in that they image only secondary physical manifestations of brain injury, which may occur well after the actual insult to the brain and represent irreversible structural changes. A real-time continuous bedside monitor that images functional changes in cerebral blood flow or oxygenation might allow for recognition of brain tissue ischemia or hypoxia before the development of irreversible injury. Visible and near infrared light pass through human bone and tissue in small amounts, and the emerging light can be used to form images of the interior structure of the tissue and measure tissue blood flow and oxygen utilization based on light absorbance and scattering. We developed a portable time-of-flight and absorbance system which emits pulses of near infrared light into tissue and measures the transit time of photons through the tissue. Images can then be reconstructed mathematically using either absorbance or scattering information. Pathologic brain specimens from adult sheep and human newborns were studied with this device using rotational optical tomography. Images generated from these optical scans show that neonatal brain injuries such as subependymal and intraventricular hemorrhages can be successfully identified and localized. Resolution of this system appears to be better than 1 cm at a tissue depth of 5 cm, which should be sufficient for imaging some brain lesions as well as for detection of regional changes in cerebral blood flow and oxygenation. We conclude that light-based imaging of cerebral structure and function is feasible and may permit identification of patients with impending brain injury as well as monitoring of the efficacy of intervention. Construction of real-time images of brain structure and function is now underway using a fiber optic headband and nonmechanical rotational scanner allowing comfortable, unintrusive monitoring over extended periods of time.

Gut mucosal ischemia during normothermic cardiopulmonary bypass results from blood flow redistribution and increased oxygen demand

Impaired gut mucosal perfusion has been reported during cardiopulmonary bypass. To better define the adequacy of gut blood flow and oxygenation during cardiopulmonary bypass, we measured overall gut blood flow and ileal mucosal flow and their relationship to mucosal pH, mesenteric oxygen delivery and oxygen consumption in immature pigs ( n = 8). Normothermic, noncrossclamped, right atrium–to–aorta cardiopulmonary bypass was maintained at 100 ml/kg per minute for 120 minutes. Animals were instrumented with an ultrasonic Doppler flow probe on the superior mesenteric artery, a mucosal laser Doppler flow probe in the ileum, and pH tonometers in the stomach, ileum, and rectum. Radioactive microspheres were injected before and at 5, 60, and 120 minutes of cardiopulmonary bypass for tissue blood flow measurements. Overall gut blood flow significantly increased during cardiopulmonary bypass as evidenced by increases in superior mesenteric arterial flow to 134.1% ± 8.0%, 137.1% ± 7.5%, 130.3% ± 11.2%, and 130.2% ± 12.7% of baseline values at 30, 60, 90, and 120 minutes of bypass, respectively. Conversely, ileal mucosal blood flow significantly decreased to 53.6% ± 6.4%, 49.5% ± 6.8%, 58.9% ± 11.6%, and 47.8% ± 10.0% of baseline values, respectively. Blood flow measured with microspheres was significantly increased to proximal portions of the gut, duodenum and jejunum, during cardiopulmonary bypass, whereas blood flow to distal portions, ileum and colon, was unchanged. Gut mucosal pH decreased progressively during cardiopulmonary bypass and paralleled the decrease in ileal mucosal blood flow. Mesenteric oxygen delivery decreased significantly from 67.0 ± 10.0 ml/min per square meter at baseline to 42.4 ± 4.6, 44.9 ± 3.5, 46.0 ± 3.6, and 42.9 ± 3.9 ml/min per square meter at 30, 60, 90, and 120 minutes of bypass. Despite the decrease in mesenteric oxygen delivery, mesenteric oxygen consumption increased progressively from 10.8 ± 1.4 ml/min per square meter at baseline to 13.4 ± 1.2, 15.9 ± 1.2, 16.7 ± 1.4, and 16.6 ± 1.54 ml/min per square meter, respectively. We conclude that gut mucosal ischemia during normothermic cardiopulmonary bypass results from a combination of redistribution of blood flow away from mucosa and an increased oxygen demand. (J T HORAC C ARDIOVASC S URG 1995;110:819-28)

Polystyrene microspheres decrease bronchial artery resistance in anesthetized sheep.

The use of microspheres to measure tissue blood flow requires that the microspheres themselves do not alter regional arterial tone. To determine whether microspheres affected bronchial artery resistance, we cannulated and perfused the bronchial artery in anesthetized sheep. In seven sheep, the change in bronchial artery pressure at constant flow was recorded during infusion of 5 doses (1 x 10(5), 2 x 10(5), 5 x 10(5), 1 x 10(6), and 1.5 x 10(6)) of 15-microns microspheres. Microspheres produced a dose-dependent, self-limited decrease in bronchial artery pressure (1.5 x 10(6) microspheres decreased bronchial artery pressure by 36% for 31 min). This was a decrease in bronchial artery resistance, as evidenced by a shift in the slope, but not the intercept, of a pressure-flow curve (n = 4 sheep). Left atrial injection of 1 x 10(7) microspheres decreased bronchial artery resistance by 17% in six sheep with intact bronchial arteries in which flow was measured by ultrasound probe. The adenosine-receptor antagonist 8-phenyltheophylline attenuated the fall in resistance by 79% (n = 4 sheep). Cyclooxygenase inhibition by indomethacin attenuated the response by 37% (n = 4 sheep). These results suggest that microspheres caused the release of adenosine and a vasodilator prostaglandin. Repetitive measurements of bronchial blood flow by microspheres could overestimate true bronchial blood flow if the interval between measurements is < 30 min.

Measurement of hepatic blood flow using 111In colloid.

The reduced hepatic blood flow calculated from hepatic scintigram with 198Au colloid was elucidated as the primary responsible factor for postoperative hepatic insufficiency. However 198Au colloid is no longer in use because of the high levels of radiation. Although 99mTc-phytate behaves similarly to 198Au on imaging, there were discrepancies between the hepatic blood flow index (KL) value and the severity of cirrhosis determined by laboratory data or by histology. In the measurement of hepatic blood flow using a radioactive colloid, factors like organ distribution, stability and uniformity of the colloid particles influence the values. In the present study, a 111In colloid was prepared and administered to rats to investigate the usefulness: as much as 95.4 (0.8) [Mean (+/- SD)]% of the colloid accumulated in the liver at pH 6.8. The distribution of particle diameter was within a relatively narrow range with the peak at 0.2 to 0.4 microns. Moreover, the KL values were not affected by condition of the reticuloendothelial system. The values showed a significant correlation with the measurements of the hepatic tissue blood flow obtained by the hydrogen gas clearance method (gamma = 0.83, P < 0.001). Thus, the 111In colloid can be clinically used as a substitute for 198Au colloid in the preoperative examination for estimation of the limit of resection.

Measurements of tissue blood flow by the hydrogen clearance technique (HCT): A comparative study including laser Doppler flowmetry (LDF) and the erlangen micro‐lightguide spectrophotometer (EMPHO)

The purpose of this study was to compare the hydrogen clearance technique (HCT) with two different, well-established techniques, i.e., the laser Doppler flowmetry (LDF) and the Erlangen micro-lightguide spectrophotometer (EMPHO), for tissue blood flow measurements in an experimental setting. For the animal experiments, we chose a rat model for arterial and venous flap thrombosis, using the epigastric groin flap. Forty male dark Aguty rats were included in the study. The animals were divided into eight groups, each with a different vascular thrombotic model. HCT was used to collect 1,467 measurements, and 2,934 graphs were recorded; 27 measurements (54 graphs) had to be discarded due to faulty electrode placements and electronic noise. In 19 of the 27 discarded measurements the cause of failure was moving of the awaking animal with disruption of the decay signal. The LDF and EMPHO measurements were performed continuously during each measuring phase. Simple and multiple linear regression and paired t-tests were used to compare the three techniques. The reproducibility of registered blood flow values in phases 1, 3, 6 and 7 varied between 7.8% and 13.6% which is in about the same range as LDF and EMPHO. We could not find a significant difference between the three techniques in this regard. The correlation coefficient for HCT and LDF was r = 0.89. For HCT and EMPHO we found r = 0.67. Sensitivity and specificity values for HCT were both 1.0 in detecting arterial and venous flap thrombosis; for LDF we found values of 0.89 and 0.92, respectively. Sensitivity and specificity values for EMPHO were 0.92 and 0.95, respectively. After careful evaluation of three different techniques (HCT, LDF, and EMPHO) for measurements of local tissue blood flow we came to the conclusion that HCT must be favoured as a reliable tool for quantitative measurement of local tissue blood flow and early diagnosis of arterial and venous flap thrombosis.

Blockade of adenosine receptors during ischaemia increases systolic dysfunction but does not affect diastolic creep in stunned myocardium.

The impact of adenosine receptor blockade on left ventricular systolic function and diastolic creep in stunned myocardium was studied in 20 sodium pentobarbital anaesthetized cats. A control group (n = 10) was compared with a group (n = 10) where adenosine receptors were blocked by 8-phenyltheophylline (7.5 mg.kg-1 i.v.) prior to a 10 min occlusion of the left anterior descending coronary artery. Regional function was assessed by sonomicrometry of the left ventricular anterior wall. Tissue blood flow and haemodynamic measurements were obtained at pre-occlusion, during occlusion, and after 30 and 60 min of reperfusion. Tissue blood flow in the LAD region was low and homogeneous during coronary occlusion in both groups. Systolic function assessed by regional shortening and inotropic parameters was significantly more reduced in the 8-PT treated group (P < 0.05). Diastolic creep and compliance assessed by the end-diastolic pressure-length relationship did not differ between groups. Thus, endogenous adenosine protects against systolic dysfunction, but appears to have no impact on diastolic creep in stunned myocardium. Furthermore, our results show that the protective effect of endogenous adenosine is not caused by increased collateral blood flow into the ischaemic area during coronary artery occlusion or by increased blood flow in the reperfusion period.