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PubMed1999

Magnetic resonance first-pass myocardial perfusion imaging: clinical validation and future applications.

Clinical studies suggest that magnetic resonance first-pass (MRFP) perfusion imaging is comparable to current diagnostic tests that are used clinically for the assessment of myocardial perfusion. In addition, magnetic resonance imaging (MRI) perfusion imaging is a noninvasive method for determining myocardial blood flow. The spatial resolution (in-plane spatial resolution < 3 mm) is sufficient to differentiate between subendocardial perfusion and subepicardial perfusion. The measurement can be repeated regularly without any adverse effects for the patient. MRI perfusion measurements can be combined with the evaluation of global function and regional wall thickening. Currently, there is no other imaging technique that offers similar advantages. The MRI perfusion measurements can be carried out during baseline conditions and during maximal hyperemia induced with either adenosine or dipyridamole. The ratio of the measured myocardial blood flows provides an estimate of the absolute and relative myocardial perfusion reserve. The perfusion reserve determined with MRFP imaging is a quantitative measure for the assessment of the collateral-dependent myocardial flow. Based on the available data using MRFP perfusion imaging, the current clinical first-line perfusion imaging tests are going to be challenged in the near future. J. Magn. Reson. Imaging 1999;10:676-685.

Coronary Circulation↗
PubMedDate not supplied

MR perfusion imaging of the kidney pre- and post-dipyridamole stress.

Animal studies have demonstrated that renal MR contrast enhancement depends on the timing of image acquisition. Limited human studies have demonstrated effects of dipyridamole (DP) on total renal perfusion. This study assessed the effect of DP on total and regional renal perfusion using gated perfusion MRI for patients undergoing DP stress. Five subjects with no evidence of renal ischemia were examined at rest and after DP stress. Rest MRI images in the left kidney were acquired using electrocardiogram (ECG)-gated MR: turbo fast low-angle shot (FLASH); echo time (TE) = 12, repetition time (TR) = 6, flip angle = 12, inversion time (TI) = 100) 10 to 45 seconds after injection of gadopentetate dimeglumine. Stress was induced in the MRI scanner (DP, .56 mg/kg over 4 minutes) followed by stress MRI after a second bolus of gadopentetate dimeglumine in the same position and identical time intervals. MR signal in the whole left kidney and renal medulla and cortex pre- and post-DP demonstrated a 70% depression of total renal perfusion with relative preservation of cortical perfusion at the expense of medullary perfusion. Post-DP MR images demonstrated a decrease in cortical perfusion with an additional 29% depression of medullary perfusion (P < .001) with respect to cortical perfusion. Turbo FLASH MRI can provide adequate time and spatial resolution to demonstrate changes in renal perfusion. Depression of renal medullary perfusion after DP appears to be caused by the intrarenal effect of DP and may have clinical impact.

Aged↗
PubMed2006

Characterization of human liver dendritic cells in liver grafts and perfusates.

It is generally accepted that donor myeloid dendritic cells (MDC) are the main instigators of acute rejection after organ transplantation. The aim of the present study was to characterize MDC in human donor livers using liver grafts and perfusates as a source. Perfusates were collected during ex vivo vascular perfusion of liver grafts pretransplantation. MDC, visualized in wedge biopsies by immunohistochemistry with anti-BDCA-1 monoclonal antibody (mAb), were predominantly observed in the portal fields. Liver MDC, isolated from liver wedge biopsies, had an immature phenotype with a low expression of CD80 and CD83. Perfusates were collected from 20 grafts; perfusate mononuclear cells (MNC) contained 1.5% (range, 0.3-6.6%) MDC with a viability of 97 +/- 2%. Perfusates were a rich source of hepatic MDC since 0.9 x 10(6) (range, 0.11-4.5 x 10(6)) MDC detached from donor livers during vascular perfusion pretransplantation. Perfusate MDC were used to further characterize hepatic MDC. Perfusate MDC expressed less DC-LAMP (P = 0.000), CD80 (P = 0.000), CD86 (P = 0.003), and CCR7 (P = 0.014) than mature hepatic lymph node (LN) MDC, and similar CD86 (P = 0.140) and CCR7 (P = 0.262) as and more DC-LAMP (P = 0.007) and CD80 (P = 0.002) than immature blood MDC. Perfusate MDC differed from blood MDC in producing significantly higher amounts of interleukin (IL)-10 in response to lipopolysaccharide (LPS), and in being able to stimulate allogeneic T-cell proliferation. In conclusion, human donor livers contain exclusively immature MDC that detach in high numbers from the liver graft during pretransplantation perfusion. These viable MDC have the capacity to stimulate allogeneic T-cells, and thus may represent a major player in the induction of acute rejection.

Antigens, CD↗
PubMed1996

Dichotomy in the post-ischemic metabolic and functional recovery profiles of isolated blood-versus buffer-perfused heart.

There is evidence that buffer- and blood-perfused hearts differ in their postischemic functional recoveries. The present study was designed to: (i) compare ischemia-induced contracture and post-ischemic functional recovery, and (ii) investigate whether the recovery profiles were related to either the release of purines and norepinephrine or high-energy phosphate content. Rat hearts (n = 8/group) were perfused at 37 degrees C with buffer (60 mmHg) or blood (60 mmHg from a support rat), made globally ischemic (15 min) and reperfused (15 min). The onset and severity of ischemic contracture were identical in both models [left ventricular end-diastolic pressure (LVEDP) at the end of 15 min ischemia was 30 +/- 5 and 27 +/- 4 mmHg respectively; P = N.S.]. However, the rate and extent of post-ischemic left ventricular developed pressure (LVDP) differed considerably. Blood-perfused hearts exhibited an initial rapid and complete recovery of LVDP followed by a steady decline to approximately 60% of pre-ischemic values. Buffer-perfused hearts recovered to only 80% after 5 min reperfusion and remained at this level for the duration of reperfusion LVEDP was higher in buffer-perfused than in blood-perfused hearts during the first 5 min of reperfusion; thereafter, LVEDP fell in buffer-perfused hearts to a level than was not significantly different from the observed in blood-perfused hearts. In buffer-perfused hearts, coronary flow recovered to 90% within 5 min and then remained constant; in blood-perfused hearts flow recovered to 100% by 1 min and continued to rise to a maximum by 7 min (201 +/- 15%). This increase appeared to mirror the secondary decline in LVDP. During the first 4 min of reperfusion, in both preparations, venous norepinephrine increased to six- to nine-fold of pre-ischemic values and then fell rapidly to near control levels by 6-9 min. Total purine release was high in early reperfusion in both groups. At the end of 15 min reperfusion, the tissue adenylate pool was similar in both groups. This study demonstrates that the nature of the perfusate used for an isolated rat heart preparation: (i) does not appear to influence the severity of ischemic injury as assessed by ischemic contracture, but (ii) does influence the qualitative and quantitative characteristics of the temporal profile that describes the recovery of systolic and diastolic function during the first 15 min of reperfusion: and (iii) it has no effect upon the changes seen in a number of metabolic indices that are often used for the assessment of injury and protection.

Animals↗
PubMed2002

Effect of deep hypothermia on cerebral hemodynamics during selective cerebral perfusion with systemic circulatory arrest.

OBJECTIVE: We studied the effect of deep hypothermia on cerebral hemodynamics during selective cerebral perfusion with systemic circulatory arrest. METHODS: Ten anesthesized pigs were placed on cardiopulmonary bypass and cooled to a rectal temperature of 22 degrees C (n = 5) or 15 degrees C (n = 5). During selective cerebral perfusion, the descending aorta was clamped and perfusion of the lower body was discontinued. As the pump flow was changed, we monitored the perfusion pressure, local cerebral blood flow, and local cerebral oxygenation using laser Doppler flowmetry and near-infrared spectroscopy. We also measured the free flow of the left internal thoracic artery during selective cerebral perfusion. RESULTS: Perfusion pressure and local cerebral blood flow decreased as the pump flow decreased. Oxygenated and deoxygenated hemoglobin in cerebral tissue remained unchanged at a perfusion flow of 10 ml/kg/min, whereas oxygenated hemoglobin decreased and deoxygenated hemoglobin increased progressively and reciprocally as the pump flow decreased. The pump flow for maintaining perfusion pressure above 35 mmHg with stabilized local cerebral oxygenation was significantly higher at 15 degrees C than at 22 degrees C. The internal thoracic artery free flow was higher at 15 degrees C than at 22 degrees C. CONCLUSIONS: Selective hypothermic cerebral perfusion with systemic circulatory arrest produces an extracranial shunt through the internal thoracic artery, especially under deep hypothermia. Our data suggests that selective cerebral perfusion during deep hypothermia is best managed by perfusion pressure control rather than by flow control.

Animals↗
PubMed2003

Assessment of ischemic heart disease using magnetic resonance first-pass perfusion imaging.

METHODS: Cardiovascular magnetic resonance (MR) perfusion imaging has matured to a point where it can be routinely applied to assess patients with coronary artery disease and ischemic cardiomyopathy. The method has been compared to invasive, catheter-based as well as other noninvasive imaging modalities (echocardiography, single-photon emission computed tomography [SPECT], and positron emission tomography [PET]) for the evaluation of patients with coronary artery disease. Besides qualitative evaluation of MR perfusion images, an absolute quantification of global, regional and transmural myocardial perfusion is possible. A relative or absolute myocardial perfusion reserve has been determined noninvasively with MR perfusion imaging, and can provide good agreement with the invasive assessment. Based on the perfusion reserve, the severity of an epicardial coronary stenosis can be evaluated in patients with known or suspected coronary artery disease. Besides the absence of radiation exposure, MR perfusion imaging offers good temporal and excellent spatial resolution. In particular, the spatial resolution increases the sensitivity and specificity for the detection of coronary artery disease. New parameters such as the "endo-/epimyocardial resting perfusion ratio", may under some circumstances sufficiently enhance the sensitivity for detecting an abnormal perfusion, and thus avoid potentially harmful and expensive stress testing in patients with suspected ischemic heart disease. New revascularization modalities such as therapeutic angiogenesis need to be matched by sensitive imaging tools to prove their benefits. Thus, the optimization of therapeutic angiogenesis may profit from the diagnostic advantages provided by MR perfusion imaging. Furthermore, MR might yield new insights into the pathophysiology of cardiac diseases such as "syndrome X", or might help in the repetitive assessment of heart transplant recipients, possibly obviating the need for further invasive testing. CONCLUSION: The breadth of cardiac MRI allows the combined noninvasive assessment of myocardial perfusion, function, as well as myocardial viability. The combination gives MRI a unique and strong position in the field of noninvasive diagnostic cardiology.

Coronary Disease↗
PubMed2006

Contrast-enhanced 3D MRI of lung perfusion in children with cystic fibrosis--initial results.

This paper is a feasibility study of magnetic resonance imaging (MRI) of lung perfusion in children with cystic fibrosis (CF) using contrast-enhanced 3D MRI. Correlation assessment of perfusion changes with structural abnormalities. Eleven CF patients (9 f, 2 m; median age 16 years) were examined at 1.5 T. Morphology: HASTE coronal, transversal (TR/TE/alpha/ST: 600 ms/28 ms/180 degrees /6 mm), breath-hold 18 s. Perfusion: Time-resolved 3D GRE pulse sequence (FLASH, TE/TR/alpha: 0.8/1.9 ms/40 degrees ), parallel imaging (GRAPPA, PAT 2). Twenty-five data sets were acquired after intravenous injection of 0.1 mmol/kg body weight of gadodiamide, 3-5 ml/s. A total of 198 lung segments were analyzed by two radiologists in consensus and scored for morphological and perfusion changes. Statistical analysis was performed by Mantel-Haenszel chi-square test. Results showed that perfusion defects were observed in all patients and present in 80% of upper, and 39% of lower lobes. Normal lung parenchyma showed homogeneous perfusion (86%, P<0.0001). Severe morphological changes led to perfusion defects (97%, P<0.0001). Segments with moderate morphological changes showed normal (53%) or impaired perfusion (47%). In conclusion, pulmonary perfusion is easy to judge in segments with normal parenchyma or severe changes. In moderately damaged segments, MRI of lung perfusion may help to better assess actual functional impairment. Contrast-enhanced 3D MRI of lung perfusion has the potential for early vascular functional assessment and therapy control in CF patients.

Adolescent↗
PubMed1984

Calcium-dependent effects of cadmium on energy metabolism and function of perfused rat heart.

Postequilibrated isolated rat hearts were perfused for 60 min with a standard supporting electrolyte buffer containing one of the following calcium concentrations: 0.9, 1.8, 3.5, or 5.0 mM, either with or without added cadmium. Doses of cadmium which proved to be minimally (0.03 microM Cd)--and maximally (3.0 microM Cd)--effective at 0.9 mM Ca were studied at all other calcium concentrations. A dose-dependent positive inotropy that persisted throughout the 60-min perfusion period was induced by the graded increases in the perfusate calcium concentration throughout the range from 0.9 to 5.0 mM. Atrioventricular node conductivity was prolonged significantly in hearts perfused with 0.9 mM Ca as compared to hearts perfused with higher calcium concentrations. Increasing the perfusate calcium concentration caused a dose-dependent increase in heart glycerol 3-phosphorylcholine (GPC) content. The other measured phosphatic metabolites of the heart were not altered significantly by varying the perfusate calcium level. In contrast, cadmium (3.0 microM Cd) induced extensive functional and metabolic aberrations which varied in magnitude as an inverse function of the perfusate calcium concentration. Contractile tension, rate of tension development (dT/dt), heart rate, coronary flow rate, and atrioventricular node conductivity were decreased significantly in response to cadmium perfusion. Moreover, these hearts characteristically had significantly elevated low energy phosphate (inosine monophosphate and inorganic phosphate) and decreased high energy phosphate (ATP, PCr) levels relative to their respective calcium controls. Furthermore, various phosphorylated intermediates of glycolysis (glucose 6-phosphate, fructose 6-phosphate, glucose 1-phosphate), as well as glycerol 3-phosphate, and uridine diphosphoglucose accumulated significantly in hearts perfused with cadmium at certain calcium concentrations below 5.0 mM. The calcium-activated increase in heart GPC was inhibited completely by 3 microM cadmium. At the minimally effective dose of cadmium (0.03 microM), demonstrable changes were apparent only at the lowest perfusate calcium concentration examined (0.9 mM). These findings are consistent with the hypothesis that cadmium interferes with calcium-activated and calcium-mediated physiologic and biochemical processes of the mammalian heart. The primary mechanistic basis for the action of cadmium appears to be linked to a competition with calcium for membrane and possibly intracellular binding and activation sites.

Animals↗
PubMed1991

Influence of nicardipine on post-hypoxic injury in the isolated perfused rat liver.

We investigated microcirculatory changes and hepatocellular injury due to hypoxia/reoxygenation and the effects of nicardipine, a calcium channel blocker, using the isolated perfused rat liver technique. Liver perfusion was carried out in three consecutive phases: 30-min pre-hypoxia perfusion, 120-min hypoxia perfusion and 30-min reoxygenation perfusion in two groups, a control (n = 5) group and a nicardipine group (n = 5). In the nicardipine group, nicardipine (2 x 10(-6) M) was added to the perfusate prior to the hypoxia perfusion. Intrahepatic volumes, sinusoidal volume and extravascular volume accessible to albumin, were assessed by the multiple indicator dilution technique. Though 120-min hypoxia per se caused only a slight increase in the lactate dehydrogenase (LDH) release and no significant alterations in perfusion pressure and intrahepatic volumes, reoxygenation elicited hepatocellular injury assessed by the LDH level in the perfusate along with a substantial increase in perfusion pressure and an increase in extravascular volume. Nicardipine pretreatment attenuated the increase in LDH level, perfusion pressure and intrahepatic volumes after reoxygenation, but there were no difference in liver microcirculation during 120-min hypoxia. The data of the current study emphasized the crucial role of Ca2+ influx in hypoxic/reoxygenation hepatocellular injury and suggested that a direct vasodilating effect of nicardipine on the intrahepatic vasculature during hypoxia is unlikely as the mechanism for its cytoprotective effects.

Animals↗
PubMed1994

Assessment of cerebral perfusion using quantitative EEG cordance.

Brain electrical activity is related to cerebral perfusion. The nature of this relationship is unclear, however, and surface-recorded activity has not been a reliable indicator of brain perfusion. We studied 27 subjects, all of whom were examined with single photon emission tomography (SPECT) and quantitative electroencephalography (QEEG), to assess associations between QEEG cordance and relative brain perfusion. Cordance has two indicator states: concordance, which may indicate high perfusion; and discordance, which may indicate low perfusion. We used multiple linear regression to assess the association between cordance and SPECT values, and found that cordance values were strongly associated with tissue perfusion. Concordance in the alpha band was associated both with mean tissue perfusion and the volume of normally perfused tissue, and it had a stronger association with perfusion than any other QEEG variable. Discordance in the beta 1 band was associated with mean perfusion, and it had a stronger association than did relative but not absolute power. These data suggest that cordance may be useful for the noninvasive assessment of brain perfusion.

Adult↗
PubMed2006

Assessment of collateralized myocardium with Cardiac Magnetic Resonance (CMR): transmural extent of infarction but not angiographic collateral vessel filling determines regional function and perfusion in collateral-dependent myocardium.

BACKGROUND: Angiographic collateral vessel filling is limited to evaluate collateral-dependent myocardium. We hypothesize, that quantitative assessment of regional myocardial function, perfusion and viability with Cardiac Magnetic Resonance (CMR) adds complementary information to angiography of collateralized myocardium. METHODS: CMR was performed in 30 patients with one chronic occluded coronary artery and no further flow limiting stenosis to assess transmural extend of infarction (TEI), resting perfusion and perfusion during adenosine-induced hyperemia and regional wall thickening (RWT) in collateral-dependent and antegradely-perfused myocardium. Collateral vessels were evaluated by angiography and the Rentrop grade (0-3). RESULTS: In 15 patients with < 50% TEI in collateral-dependent myocardium resting perfusion (1.08+/-0.22 ml/min/g), hyperemia (2.21+/-0.73 ml/min/g) and RWT (4.0+/-2.6 mm) were similar to antegradely-perfused myocardium (rest 1.14+/-0.20 and hyperemia 2.46+/-0.82 ml/min/g, RWT 4.3+/-1.7 mm). In 15 patients with > or = 50% TEI in collateral-dependent myocardium resting perfusion and hyperemia as well as RWT were significantly lower (rest 0.84+/-0.19, p<0.001 and hyperemia 1.34+/-0.43 ml/min/g, p<0.001; RWT 1.0+/-1.0 mm, p<0.0001) compared to antegradely-perfused myocardium. There was an inverse correlation between TEI and resting or hyperemic perfusion or RWT. In contrary, resting perfusion and hyperemia as well as RWT in collateral-dependent myocardium were not different between patients with good (2-3) compared to patients with poor Rentrop grade (0-1). There was no correlation between TEI and Rentrop grade. CONCLUSION: Function and perfusion in collateral-dependent myocardium are preserved, if transmural extent of infarction is limited (< 50%). This is independent of their angiographic collateral vessel filling. Thus, CMR adds complementary information to angiographic standard assessment of collateral vessels.

Aged↗
PubMedDate not supplied

Measurement of human hepatic and splenic perfusion using dynamic computed tomography: a preliminary report.

The purpose of the study was evaluate hepatic (portal and arterial) and splenic perfusion at parenchymal level using dynamic computed tomography (CT) in patients with diffuse liver disease and controls. Nineteen patients and 30 normal controls underwent dynamic CT of the liver. Single-location dynamic sequences were carried out after intravenous administration of a 40 ml bolus of contrast medium (Ioversol: 5 cc/s). Hepatic arterial perfusion, hepatic portal perfusion and splenic perfusion were calculated from time-attenuation curves. Hepatic portal perfusion was significantly lower in patients (0.63 +/- 0.33 ml/min/ml (mean +/- SD); P = 0.003) compared with that in controls (1.03 +/- 0.43), although hepatic arterial perfusion did not differ (0.090 +/- 0.044 versus 0.102 +/- 0.114). Splenic arterial perfusion was significantly lower in patients (0.92 +/- 0.31; P = 0.0009) than in controls (1.35 +/- 0.44). The decreased hepatic portal perfusion in patients with diffuse liver disease was not supplemented by an increase in hepatic arterial perfusion. The decreased splenic perfusion in patients may be due to increased portal pressure. Dynamic CT enables quantification of hepatic and splenic perfusion.

Evaluation Studies as Topic↗
PubMed1996

Tumor perfusion studies using fast magnetic resonance imaging technique in advanced cervical cancer: a new noninvasive predictive assay.

PURPOSE: This study investigated sequential changes in tumor blood supply using magnetic resonance (MR) perfusion imaging and assessed their significance in the prediction of outcome of patients with advanced cervical cancer. The purpose of this project was to devise a simple, noninvasive method to predict early signs of treatment failure in advanced cervical cancer treated with conventional radiation therapy. METHODS AND MATERIALS: Sixty-eight MR perfusion studies were performed prospectively in 17 patients with squamous carcinomas (14) and adenocarcinomas (3) of the cervix, Stages bulky IB (1), IIB (5), IIIA (1), IIIB (8), and IVA (1), and recurrent (1). Four sequential studies were obtained in each patient: immediately before radiation therapy (pretherapy), after a dose of 20-22 Gy/ approximately 2 weeks (early therapy), after a dose of 40-45 Gy/ approximately 4-5 weeks (midtherapy), and 4-6 weeks after completion of therapy (follow-up). Perfusion imaging of the tumor was obtained at 3-s intervals in the sagittal plane. A bolus of 0.1 mmol/kg of MR contrast material (gadoteridol) was injected intravenously 30 s after beginning image acquisition at a rate of 9 ml/s using a power injector. Time/signal-intensity curves to reflect the onset, slope, and relative signal intensity (rSI) of contrast enhancement in the tumor region were generated. Median follow-up was 8 months (range 3-18 months). RESULTS: Tumors with a higher tissue perfusion (rSI > or = 2.8) in the pretherapy and early therapy (20-22 Gy) studies had a lower incidence of local recurrence than those with a rSI of < 2.8, but this was not statistically significant (13% vs. 67%; p = 0.05). An increase in tumor perfusion early during therapy (20-22 Gy), particularly to an rSI of > or = 2.8, was the strongest predictor of local recurrence (0% vs. 78%; p = 0.002). However, pelvic examination during early therapy (20-22 Gy) commonly showed no appreciable tumor regression. The slope of the time/signal-intensity curve obtained before and during radiation therapy also correlated with local recurrence. Follow-up perfusion studies did not provide information to predict recurrence. CONCLUSION: These preliminary results suggest that two simple MR perfusion studies before and early in therapy can offer important information on treatment outcome within the first 2 weeks of radiation therapy before response is evident by clinical examination. High tumor perfusion before therapy and increasing or persistent high perfusion early during the course of therapy appear to be favorable signs. High perfusion suggests a high blood and oxygen supply to the tumor. The increase in tumor perfusion seen in some patients early during radiation therapy suggests improved oxygenation of previously hypoxic cells following early cell kill. Radiation therapy is more effective in eradicating these tumors, resulting in improved local control. Our technique may be helpful in identifying early-while more aggressive therapy can still be implemented-those patients who respond poorly to conventional radiation therapy.

Adenocarcinoma↗
PubMed2002

Cerebral perfusion defects in combined cocaine and alcohol dependence.

BACKGROUND: Cocaine abuse has been associated with widely distributed areas of significant cerebral blood flow (CBF) reductions or hypo-perfusion as well as CBF hyper-perfusion, but these perfusion abnormalities have not been examined using newer technologies such as statistical parametric mapping (SPM). These areas of abnormal CBF may be more likely among those who abuse cocaine and alcohol together. METHODS: Using SPECT with HMPAO for CBF we compared proportional scaling (PS) to histogram normalization (HEQ) in SPM among 20 controls and 32 recently abstinent cocaine abusers. We then separated the cocaine abusers into two groups (12 cocaine plus alcohol abusers and 20 cocaine alone abusers) and compared both groups to the 20 controls for brain areas of hypo- and hyper-perfusion. RESULTS: Sensitivity to hypo-perfusion was greater with HEQ than PS. Hypo-perfused areas were more likely in the 12 alcohol plus cocaine abusers than in the 20 cocaine alone abusers or 20 controls, and hyper-perfused areas were significantly more likely among the cocaine abusers than controls. The type of CBF abnormality varied by brain location with hypo-perfusion significantly more likely in occipital and temporal cortex or cerebellum and hyper-perfusion more likely in frontal and parietal cortex. CONCLUSIONS: These abnormalities in brain perfusion are consistent with previous non-SPM approaches that showed more hypo-perfusion in cocaine abusers than controls and appear to reflect vasospasm and potential compensations in cerebral blood flow.

Adult↗
PubMed1991

Relation between anterograde blood flow through a coronary artery and the size of the perfusion bed it supplies: experimental and clinical implications.

The relation between anterograde blood flow through a coronary artery and the size of the perfusion bed it supplies is not known. Accordingly, the left circumflex coronary artery was cannulated and perfused with arterial blood in 12 open chest mongrel dogs. In Group I dogs (n = 7), the goal was to correlate the size of the perfusion bed with the magnitude of anterogradely derived myocardial blood flow. The size of the perfusion bed was measured with use of two-dimensional myocardial contrast echocardiography, whereas anterograde myocardial blood flow was determined by injecting radiolabeled microspheres directly into the artery. In Group II dogs (n = 5), the goal was to study the effects of altering coronary blood flow on both anterogradely and collateral vessel-derived myocardial flow within the perfusion bed. In these dogs, microspheres were injected directly into both the coronary artery and the left atrium at each flow rate. In Group I dogs, the left circumflex perfusion bed size, as defined by myocardial contrast echocardiography, decreased at lower anterograde myocardial blood flow rates. The change in perfusion bed size occurred at the lateral zones. There was a linear relation between the normalized perfusion bed size and the normalized anterograde myocardial blood flow: y = 0.45x + 54.2 (p less than 0.001, r2 = 0.77). These results were substantiated in Group II dogs, in which the size of the perfusion bed was approximated with use of radiolabeled microspheres. The size of the perfusion bed was most affected when anterograde myocardial blood flow decreased to less than approximately 33% of normal. At the lowest flow rates, there was a linear relation between anterograde blood flow versus the fraction of the left circumflex flow derived anterogradely: y = 2.41x + 0.22 (p less than 0.001, r2 = 0.90). The lower the level of anterograde flow, the greater was the blood flow derived from remote vessels. It is concluded that the size of the area perfused by a coronary artery is significantly influenced by the magnitude of anterograde blood flow through that artery. These findings may have important implications in experimental and clinical models of myocardial ischemia.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Intraoperative assessment of colonic perfusion using scanning laser Doppler flowmetry during colonic resection.

BACKGROUND: Ischemia occurring on mobilization and mesenteric division is thought to be a major factor in the etiology of anastomotic dehiscence after colorectal resection. This study assessed the ability of the new technique of scanning laser Doppler flowmetry to measure changes in human colonic perfusion during mobilization at and adjacent to the anastomotic site. STUDY DESIGN: Colonic perfusion was measured in 10 patients undergoing large-bowel resection by making laser Doppler scans of the proximal bowel before mobilization, after mobilization and mesenteric division, and after resection of the specimen. Mean perfusion was calculated within 1-cm2 regions of interest, each of which contained 1,750 individual measurements of perfusion. These regions represented the anastomosis site and adjacent areas 1 cm and 2 cm proximal and distal to this. The results were expressed as mean perfusion units (PUs). RESULTS: After mobilization, there were significant decreases in perfusion in all the subjects between each time point and in all areas of the colon scanned. Median perfusion at the anastomosis site was 491 PUs before mobilization, and this fell to 212 PUs after mobilization, representing a decrease of 57%; the median within-person decrease was also 57% (p < 0.01). There was a gradient of reduced perfusion between the area 2 cm proximal to the mesenteric division (median within-person fall 25%; p < 0.05) and the area 2 cm distal to the mesenteric division (median within-person fall 84%; p < 0.01). After resection of the specimen, perfusion increased slightly at the anastomosis site to a median of 240 PUs (median within-person fall 41%; p < 0.01), but 2 cm proximal to this, median perfusion remained depressed at 330 PUs. CONCLUSIONS: This new technique can be used intraoperatively and appears to overcome the limitations of single-point laser Doppler flowmetry. In this small preliminary study, it measured large decreases in colonic perfusion during mobilization, and it may have widespread clinical applications.

Aged↗
PubMed2003

Perfusion distribution between and within muscles during intermittent static exercise in endurance-trained and untrained men.

We have recently shown that muscle perfusion varies between different quadriceps femoris muscles during submaximal exercise in humans. In animals, endurance training changes perfusion distribution between muscles during exercise. Whether the same is observed in humans is currently unknown. Therefore, we compared perfusion levels between different parts of the quadriceps femoris muscle group during one-legged intermittent static exercise in seven endurance-trained and seven untrained men. Muscle perfusion was measured using positron emission tomography with [ 15O]-H 2 O. In addition, relative dispersion of perfusion (standard deviation within a region/mean within a region x 100 %) within each muscle region was calculated as an index of perfusion heterogeneity within the muscles. Muscle perfusion tended to be lower in endurance-trained men (p = 0.16) and it was also different between the regions (p < 0.001). However, perfusion distributed similarly between the groups (p = 0.51). Relative dispersion of perfusion within the muscles was lower in endurance-trained men (p = 0.01) and it was also different between muscles (p < 0.001). These results suggest that endurance training does not alter perfusion distribution between muscles, but it decreases perfusion heterogeneity within the muscles.

Adult↗
PubMed2005

[Evaluation of perfusion in skin flaps by laser-induced indocyanine green fluorescence].

Prediction of necrosis in critically perfused skin flaps is difficult and rarely precise. An early detection of insufficiently perfused skin is highly desirable since it may lead to surgical decisions such as operative flap revision or early resection. The application of laser-induced indocyanine green (ICG) fluoroscopy allows an objective quantification of skin perfusion and a high topographical resolution. Aim of the present study is to determine a threshold value for flap perfusion under well-defined experimental conditions and test the validity of the results in the clinical application. Twenty overdimensioned random pattern flaps with a length to width ratio of 4 : 1 (8 x 2 cm) were dissected at the anterior abdominal wall of 20 male Sprague-Dawley rats weighing 365 g on average. ICG fluorescence was performed at the end of the operation by intravenous injection of 1 g ICG/kg bodyweight into a tail vein and digital recording. On the seventh postoperative day, both the necrotic and surviving areas of the flaps were measured and the ICG-fluorescence was analysed in the areas that had undergone necrosis. 41 flaps with areas of critical perfusion (18 skin flaps, 13 muscle flaps, 8 replantations) were analysed in 39 patients. The surviving part of the flap had a mean perfusion index of 62 % compared to reference skin. The distal parts of the flap that necrotized during the experiment showed an average perfusion index of 19 % postoperatively. Differences were statistically significant (p < 0.001). In clinical application, a number of 13 flaps were found to have a perfusion index less than 25 % in a region of critical perfusion. Eleven of these developed a partial necrosis in that region, one flap underwent total necrosis. Indocyanine green fluoroscopy allows a detailed topographical analysis of flap perfusion and the prediction of necrosis. Experimental findings presented a threshold value for the perfusion index of 25 % which could be confirmed in clinical application.

Animals↗