Biomedical subjects

R D Okada

Publications and source records attributed to R D Okada.

At least 37 records · Page 2Linked to original sources

PubMed1989

Kinetics of Tc-99m hexakis t-butyl isonitrile in normal and ischemic canine myocardium.

Hexakis 99mTc-tertiary butyl isonitrile (99mTc-TBI) was studied as a cardiac perfusion imaging agent in nine dogs with partial occlusion of the LAD. Thirty min after applying the stenosis, 99mTc-TBI was injected into the right atrium (RA) in five dogs and left atrium (LA) in four dogs. Normal and ischemic zone regional myocardial 99mTc-TBI activities were monitored continuously for 4 h. Dogs with LA injections had minimal and equivalent 4 h fractional clearance from the normal and ischemic zones. Dogs with RA injections had minimal, but significantly lower 4 h fractional 99mTc clearances in the ischemic zone (0.08 +/- 0.08) compared to the normal zone (0.16 +/- 0.07, P less than 0.05). The delayed ischemic zone clearance is probably due to the high initial lung uptake observed after RA injection. Despite the differences in clearance, this minimal amount of redistribution could not be detected on gamma camera images. The minimal myocardial washout and redistribution, and the 140 keV gamma make 99mTc-TBI a promising cardiac perfusion imaging agent.

Animals↗

PubMed1989

The effect of dipyridamole on transmural blood flow gradients.

The effect of dipyridamole (DP) on subendocardial (ENDO) and subepicardial (EPI) blood flow in stenosed and normal regions was determined with radioactive microspheres before and after intravenous infusion of 0.08 mg/kg.min-1 of DP in two groups of dog hearts in situ. Group 1 (n = 6) had coronary stenoses that did not reduce distal perfusion at rest, but did attenuate hyperemic response, and group 2 (n = 6) had stenoses which reduced resting blood flow. In nonstenosed zones, a doubling in perfusion during DP infusion induced proportionate changes in ENDO and EPI flows (unchanged ENDO/EPI ratio) in group 1 hearts, but increased EPI more than ENDO flows in group 2 hearts (decreased ENDO/EPI ratio). In mildly stenosed regions, a 47 percent increase in perfusion during DP was associated with an increase in only EPI flow, which thereby reduced the ENDO/EPI ratio. In severely stenosed zones, the ENDO/EPI ratio was already significantly reduced at rest and a further reduction in ENDO flow during DP caused a significant decline in the ENDO/EPI ratio. Therefore, during pharmacologic vasodilation, a redistribution of coronary transmural flow occurs (relative ENDO to EPI steal) in non- and mildly stenosed regions while an absolute decrease or steal in ENDO flow was noted only in regions distal to more severe stenoses. These studies suggest that an interaction between the stenosis severity and vasodilation is a determining factor in ENDO/EPI ratios with dipyridamole.

Angina Pectoris↗

PubMed1988

Serial changes in nuclear magnetic resonance relaxation times after myocardial infarction in the rabbit: relationship to water content, severity of ischemia, and histopathology over a six-month period.

To determine the serial changes in T1 and T2 relaxation times of myocardial infarction, and their relationship to observed changes in water content, regional myocardial blood flow, and histopathology, rabbits were studied at 14 time intervals ranging from 30 min to 6 months after coronary artery ligation. All values were compared to a control group. Hearts were subdivided into infarct and normal segments for measurement of blood flow, water content, and relaxation times (20-MHz spectrometer); other hearts were excised intact for histopathologic studies. T1 relaxation time of infarcted myocardium did not change significantly compared to control over the 6-month study period. T2 relaxation time increased (P less than 0.0001) at 3 days and returned to baseline by 2 months. Consonant with the increase in T2 of infarct, nuclear magnetic resonance (NMR) images at 3 days demonstrated an increase in signal intensity of infarct compared to surrounding normal myocardium. At 6 months, marked myocardial thinning was observed without changes in signal intensity. Changes in T2 of infarcted myocardium were not related to changes in water content or severity of ischemia, but correlated best with infarct healing and scar formation as detected on histopathology. In conclusion, the findings of this study indicate that T2 relaxation time of the infarcted myocardium increases markedly at 3 days and remains elevated for 2 months. These changes correlate best with the onset and progression of infarct healing. These data demonstrate the potential of T2-weighted NMR imaging for assessing healing patterns following ischemic myocardial injury.

Animals↗

PubMed1988

Cardiac imaging and myocardial kinetics of technetium-tertiary butyl-isonitrile during dipyridamole-induced hyperemia.

UNLABELLED: To determine the myocardial kinetics of technetium-tertiary-butyl-isonitrile (Tc-TBI) during dipyridamole-induced hyperemia, the circumflex coronary arteries (LCX) of 15 dogs were partially occluded. Dipyridamole was then infused intravenously over 4 minutes, creating hyperemic flows in the anterior descending (LAD) coronary system. Tc-TBI was administered, then LAD and LCX regional myocardial Tc-TBI activities were continuously monitored with miniature detectors and gamma camera imaging over 3 hours. Microsphere-determined regional myocardial blood flows demonstrated an LCX/LAD flow ratio of 0.81 +/- 0.21 at rest and 0.45 +/- 0.24 (SD) during dipyridamole infusion. Three-hour fractional Tc-TBI clearance rates were minimal and were equal in the LAD (0.14 +/- 0.11) and LCX (0.13 +/- 0.12) zones (p = ns). Excellent gamma camera images, demonstrating the LCX defect, were obtained in all dogs. The correlation coefficient was 0.98 for regional myocardial blood flow vs initial Tc-TBI distribution. IN CONCLUSION: (1) Dipyridamole vasodilation unmasked coronary stenoses despite no flow disparities at rest. (2) The initial distribution of Tc-TBI is proportional to regional myocardial blood flow. (3) There is minimal washout and no redistribution into the initial defect over time, and thus image quality is stable over time. (4) Tc-TBI myocardial kinetics may be applicable to closely related agents currently being developed.

Animals↗

PubMed1988

Superiority of quantitative exercise thallium-201 variables in determining long-term prognosis in ambulatory patients with chest pain: a comparison with cardiac catheterization.

The purpose of this study was to determine the prognostic utility of quantitative exercise thallium-201 imaging and compare it with that of cardiac catheterization in ambulatory patients. Accordingly, long-term (4 to 9 years) follow-up was obtained in 293 patients who underwent both tests for the evaluation of chest pain: 89 had undergone coronary artery bypass graft surgery within 3 months of testing and were excluded from analysis, 119 experienced no cardiac events and 91 had an event (death in 20, nonfatal myocardial infarction in 21 and coronary artery bypass operations performed greater than 3 months after cardiac catheterization in 50). When all variables were analyzed using Cox regression analysis, the quantitatively assessed lung/heart ratio of thallium-201 activity was the most important predictor of a future cardiac event (chi 2 = 40.21). Other significant predictors were the number of diseased vessels (chi 2 = 17.11), patient gender (chi 2 = 9.43) and change in heart rate from rest to exercise (chi 2 = 4.19). Whereas the number of diseased vessels was an important independent predictor of cardiac events, it did not add significantly to the overall ability of the exercise thallium-201 test to predict events. Furthermore, information obtained from thallium-201 imaging alone was marginally superior to that obtained from cardiac catheterization alone (p = 0.04) and significantly superior to that obtained from exercise testing alone (p = 0.02) in determining the occurrence of events. In addition, unlike the exercise thallium-201 test, which could predict the occurrence of all categories of events, catheterization data were not able to predict the occurrence of nonfatal myocardial infarction. The exclusion of bypass surgery and previous myocardial infarction did not alter the results. In conclusion, data from this study demonstrate that exercise thallium-201 imaging may be superior to data from both exercise testing alone and cardiac catheterization data alone for predicting future events in ambulatory patients who have undergone both exercise thallium-201 imaging and catheterization for the evaluation of chest pain.

Adult↗

PubMed1988

Myocardial kinetics of technetium-99m-hexakis-2-methoxy-2-methylpropyl-isonitrile.

To study the potential usefulness of technetium-99m hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-MIBI) as a cardiac perfusion imaging agent, the left circumflex coronary arteries of 12 dogs were partially occluded. Eight additional control dogs had no coronary artery stenosis. Myocardial Tc-MIBI activities in the left circumflex and left anterior descending zones were continuously monitored by miniature implantable radiation detectors for 4 hr after administration of the isotope. The dogs were then killed. Serial gamma camera images were also acquired during the study. Heart rate, arterial blood pressure, pressure distal to the stenosis, and cardiac output did not change significantly during the experiment. Microsphere-determined regional myocardial blood flow was significantly reduced in the left circumflex distribution in the 12 dogs with coronary artery stenoses. In the 12 dogs with left circumflex coronary artery stenoses, the 4 hr fractional Tc-MIBI clearances from the normal and ischemic zones were minimal and equivalent (0.15 +/- 0.05 vs 0.15 +/- 0.07). In the eight control dogs, 4 hr fractional Tc-MIBI clearances from the left anterior descending and left circumflex artery zones were minimal and equivalent (0.11 +/- 0.06 vs 0.10 +/- 0.07). Four hour fractional Tc-MIBI clearance from the blood was 0.98 +/- 0.03 for the dogs with stenosis and 0.97 +/- 0.02 for the dogs without stenosis. One additional dog had complete occlusion of the left circumflex coronary artery followed by administration of Tc-MIBI and scandium-46-labeled microspheres. This heart was immediately sectioned and counted to determine the relationship of regional blood flow to Tc-MIBI distribution (r = .92).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Increased exercise thallium-201 lung uptake: a noninvasive prognostic index in two-vessel coronary artery disease.

To determine the physiologic impact of two-vessel coronary artery disease and its effect on prognosis, a series of clinical, angiographic, exercise and quantitative thallium-201 (Tl-201) imaging parameters were analyzed in 85 consecutive two-vessel coronary artery disease patients followed for 52 +/- 27 months after coronary angiography and Tl-201 scintigraphy. End points were cardiac death (n = 3), myocardial infarction (n = 6) and coronary bypass graft surgery more than three months after testing (n = 16). Using Cox Hazards survival analysis, early cardiac events were not predicted by: myocardial infarction or anginal history; resting left ventricular function; exercise blood pressure response; angina or severity of ECG ST segment depression (mm); Tl-201 defect size; redistribution or clearance; angiographic patterns; or the presence of proximal left anterior descending disease. Significant predictors of adverse cardiac events were: increased exercise lung to heart Tl-201 ratio (0.59 +/- 0.12 versus 0.46 +/- 0.1; P less than 0.0001); ECG lead extent of ST segment depression (P less than 0.03); and exercise heart rate response (P less than 0.047). Event-free survival for patients with normal and abnormally increased lung to heart Tl-201 ratios at 48 months was 76% versus 63% (P less than 0.003). It was concluded that two-vessel coronary artery disease survival correlates with exercise Tl-201 uptake which reflects exercise induced left ventricular dysfunction.

Actuarial Analysis↗

PubMed1987

Left ventricular ejection fraction response during exercise in asymptomatic systemic hypertension.

To study the effect of mild-to-moderate elevations in diastolic blood pressure (BP) on systolic left ventricular (LV) function, 28 hypertensive patients and 20 normal subjects underwent upright exercise first-pass radionuclide angiography. All were asymptomatic, had normal rest and exercise electrocardiographic findings and no evidence of LV hypertrophy or coronary artery disease. LV function at rest was similar in the 2 groups, but with exercise hypertensive patients had a greater end-systolic volume (69 +/- 19 vs 51 +/- 19 ml, p less than 0.002) and lower ejection fraction (EF) (0.59 +/- 0.09 vs 0.72 +/- 0.07, p less than 0.0001), stroke volume (101 +/- 28 vs 130 +/- 36 ml, p less than 0.005) and peak oxygen uptake (23 +/- 7 vs 33 +/- 9 ml/kl/min, p less than 0.05). Hypertensive patients were separated into 3 groups: group 1-12 patients with an increase in EF with exercise greater than or equal to 0.05; group 2-7 patients with a change in EF with exercise less than 0.05; and group 3-9 patients with a decrease in EF with exercise greater than or equal to 0.05. Group 3 hypertensive patients were older, had a higher heart rate at rest and lower peak oxygen uptake. Rest LV function was similar in the 3 hypertensive subgroups, but exercise end-systolic volumes were higher in groups 2 and 3. Exercise thallium-201 images was normal in all but 1 of 14 hypertensive group 2 or 3 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Measurement of both left ventricular function and regional myocardial perfusion with 133Xe in dogs.

A technique to measure left ventricular (LV) function and myocardial perfusion was validated in 12 dogs. 133Xe in saline was injected into the left atrium (LA) or LV and two data sets were obtained using gamma camera imaging: 1) A first pass gated scan for LV function; followed by 2) Sequential images for regional myocardial perfusion. LV ejection fraction and wall motion measurements from the 133Xe blood pool images were compared to ejection fraction (r = 0.88, P less than 0.01) and wall motion (r = 0.83, P less than 0.01) data from 99mTc labeled blood pool scans. The perfusion measurements obtained with the 133Xe method were compared to microsphere data (r = 0.79, P less than 0.01). Measurements after LV 133Xe injection were similar to data following LA injection. Thus, quantitative assessment of global LV function, regional wall motion and myocardial perfusion is possible with LA or LV 133Xe injection and gamma camera imaging.

Animals↗

PubMed1987

Computer versus visual analysis of exercise thallium-201 images: a critical appraisal in 325 patients with chest pain.

Although computer-aided analysis of planar thallium images has been previously reported to be superior to visual analysis, a segment-by-segment comparison of all thallium variables (presence of initial defect, presence of redistribution, and presence of abnormal lung:heart thallium ratio) has not been performed with the use of both methods. In the present study, such a comparison was performed to determine which thallium variable(s) are superior, when the computer method is used. In addition, both methods were compared to determine their correlations with the angiographic extent of coronary artery disease (no disease, or one-vessel disease vs multivessel, or left main disease) and the occurrence of future events (cardiac-related death or nonfatal myocardial infarction). Computer-aided analysis was superior to visual analysis (an average of three independent blinded observers) for detection of coronary disease because: (1) it was more specific for detecting initial defects despite having the same sensitivity (89.6% vs 91.0%, p = NS) and (2) it was more sensitive for detecting redistribution in the territory of a stenosed vessel (68% vs 46%, p less than 0.001). However, absolute myocardial clearance of thallium had very poor specificity compared to visually assessed redistribution. Only when segmental clearance was considered abnormal on a relative basis (if it was slower by 98% or more than the fastest clearing segment in the heart) did abnormal clearance achieve the same specificity (99%) and a better sensitivity (60% vs 48%, p less than 0.01) than visual analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗

PubMed1987

Differentiation of viable and nonviable myocardium after acute reperfusion using serial thallium-201 imaging.

This study was performed to determine if differences in regional myocardial thallium clearance rates could differentiate salvaged from nonsalvaged myocardium after reperfusion. Twenty-one dogs underwent 2 hours of left anterior descending coronary artery ligation followed by reperfusion. Thallium was administered 5 minutes later and serial images were acquired over 3 hours. Of the 21 dogs, 15 had infarctions of which nine had initially reduced anterior wall thallium activity (group 1) and six had normal or increased activity (group 2). Six dogs did not have an infarction (group 3). All group 1 dogs demonstrated reduced clearance rates in the anterior wall (T1/2 = 15.0 +/- 4.7 hours, SD) compared to the posterior wall (T1/2 = 9.0 +/- 4.4 hours; p less than 0.001). Group 2 dogs demonstrated increased clearance rates in the anterior wall (T1/2 = 5.7 +/- 2.0 hours) compared to the posterior wall (T1/2 = 10.5 +/- 4.6 hours; p less than 0.001). Group 3 dogs demonstrated no difference in clearance rates. In conclusion, although thallium uptake is frequently reduced in nonsalvaged myocardium, tracer uptake can be normal or increased if perfusion has been completely restored. However, an increased clearance rate from the reperfused zone compared to the normal zone is a reliable indicator of nonsalvaged myocardium, despite normal initial thallium uptake.

Animals↗

PubMed1987

Comparison of intravenous dipyridamole thallium cardiac imaging with exercise radionuclide angiography.

Sixty-eight patients underwent dipyridamole thallium imaging and exercise blood pool imaging in order to determine the functional significance of various dipyridamole thallium imaging redistribution patterns. Serial thallium images and blood pool regional wall motion were interpreted by three independent observers. Rest and exercise left ventricular ejection fractions were calculated by two observers and were averaged. Transient thallium defects were associated with normal rest and exercise left ventricular ejection fraction and regional wall motion. Mild persistent thallium defects were associated with normal ejection fraction and regional wall motion at rest, with a deterioration in both with exercise. Severe persistent thallium defects were associated with reduced ejection fraction and regional wall motion at rest, but no further deterioration with exercise. These data support the following postulates: Transient dipyridamole thallium defects are due to mild coronary artery stenoses that cause no detectable functional consequence during levels of exercise achieved in this study. Mild persistent defects are due to more severe stenoses that do cause a functional reduction in wall motion during exercise. Although appearing qualitatively persistent, these defects probably represent very slow thallium redistribution and ischemia rather than scar. Finally, severe persistent defects probably represent myocardial scar.

Adult↗

PubMed1987

Quantitative aspects of myocardial perfusion imaging.

Computer quantitation of myocardial perfusion images has enhanced the detection of thallium perfusion abnormalities compared to visual analysis. Computer analysis is more specific than visual analysis for detection of initial defects and more sensitive for detection of redistribution. Computer analysis is equally good for detecting thallium abnormalities in the distribution of the three major coronary arteries. Measurement of absolute clearance of thallium results in an unacceptable high false-positive rate. However, when clearance in a myocardial segment is compared to the fastest clearing segment in the heart, the specificity of clearance improves significantly. Quantitation of lung:heart ratio is very useful. Increased lung:heart ratio reflects exercise induced left ventricular dysfunction and is a strong marker of prognosis. Single photon emission computerized tomography (SPECT) offers the potential of more precisely sizing the risk area. The question of whether this technique offers a significant advantage over planar thallium imaging has to be answered.

Algorithms↗

PubMed1987

Prognostic value of computer-quantitated exercise thallium imaging early after percutaneous transluminal coronary angioplasty.

To develop an approach to predicting adverse events after percutaneous transluminal coronary angioplasty (PTCA), 50 patients had thallium-201 exercise testing within 1 month after successful single vessel coronary angioplasty and were followed up for a mean of 18 months. Adverse events were: 1) clinical events consisting of recurrent angina (17 patients) and myocardial infarction (1 patient); 2) treatment events consisting of repeat coronary angioplasty (10 patients) and coronary bypass surgery (1 patient); and 3) restenosis, defined as a greater than 30% increase in luminal stenosis (15 of 38 recatheterized patients). There were no deaths. Of the clinical, exercise, angiographic and thallium scan variables analyzed by stepwise logistic regression, postangioplasty gradient greater than 20 mm Hg predicted clinical events and treatment events, and the number of segments with slower thallium clearance predicted clinical events, treatment events and restenosis. Using Cox Hazards model regression of survival without events, the number of transient qualitative thallium defects also predicted clinical events and restenosis. At 1 year after angioplasty, 24% of patients with these variables had restenosis compared with only 6% of those without these variables and 36% of patients with these variables had a clinical or treatment event compared with 8% of patients without these variables. Three measures of the adequacy of myocardial perfusion (post-angioplasty gradient, reduced thallium clearance and transient thallium defects) were additive predictors of adverse events after coronary angioplasty with the relative risk being approximately four times greater in patients with these variables than in those without. Such adverse events, therefore, are usually a consequence of inadequate revascularization.

Adult↗

PubMed1987

In vivo detection of reperfused myocardium by nuclear magnetic resonance imaging.

To assess the potential of in vivo nuclear magnetic resonance imaging for the detection of reperfused myocardium, in vivo T2-weighted spin echo images were obtained of dogs at 0.15 tesla. Imaging was done during 3 hours of coronary occlusion (group I), and during 3 hours of coronary occlusion followed by 1 hour of reperfusion (group II). On sacrifice, the hearts were drained of blood and imaged in situ to determine the effect of in vivo imaging on myocardial signal intensity. The hearts were then excised and imaged at 1.4 tesla to compare the effect of high resolution imaging on image quality. Of the six hearts in group I and the eight hearts in group II with a myocardial infarction and suitable image quality, four of the former hearts and six of the latter demonstrated a small but visible increase in infarct signal intensity at 3 hours of occlusion on the time to echo [TE] = 60 ms, single echo images. The T2 (transverse) relaxation time of the infarct (measured in vitro by spectrometer) increased by 13% when compared with normal tissue. In contrast, the reperfused infarct was more easily visualized, with signal intensity increasing by 31 +/- 17% and infarct T2 increasing by 20%. Imaged at 1.4 tesla, the excised hearts showed the infarct to be subendocardial during occlusion and extending transmurally with reperfusion. It is concluded that, although visualized, the increase in infarct signal intensity at 3 hours of coronary occlusion is small and this is consistent with the small increase in infarct signal intensity and T2 relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Quantitative analysis of dipyridamole-thallium images for the detection of coronary artery disease.

To determine if the detection of coronary artery disease by dipyridamole-thallium imaging is improved by quantitative versus qualitative analysis, and combining quantitative variables, 80 patients with chest pain (53 with and 27 without coronary artery disease) who underwent cardiac catheterization were studied. Segmental thallium initial uptake, linear clearance, monoexponential clearance and redistribution were measured from early, intermediate and delayed images acquired in three projections. Normal values were determined from 13 other clinically normal subjects. When five segments per view were used for quantitative analysis, sensitivity and specificity were 87 and 63%, respectively, for uptake, 77 and 67% for linear clearance, 60 and 60% for monoexponential clearance and 62 and 56% for redistribution. Of the four variables, uptake and linear clearance were the most sensitive (p less than 0.01) and specificity did not differ significantly. Using three segments per view, the specificity of uptake increased (p less than 0.05) to 78% without a significant change in sensitivity (85%). With this approach, sensitivity and specificity did not differ from those of qualitative analysis (85 and 78%, respectively). Stepwise logistic regression analysis demonstrated that the best quantitative thallium correlate of the presence of coronary artery disease was a combination variable of "either abnormal uptake or abnormal linear clearance, or both." Using five segments per view, the model's specificity (85%) was greater than that of uptake alone (p less than 0.02), with similar sensitivity (92%). Using three segments per view, the model's specificity (93%) was greater than that of uptake alone (p less than 0.05) and of qualitative analysis (p less than 0.05), with similar sensitivity (85%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Myocardial uptake and clearance of thallium-201 in normal subjects: comparison of dipyridamole-induced hyperemia with exercise stress.

Thallium-201 uptake and clearance after dipyridamole infusion may differ from that after exercise stress because the hemodynamic effects of these two interventions are different. In this study of normal volunteers, thallium kinetics after dipyridamole (n = 13) were determined from three serial image sets (early, intermediate and delayed) and from serial blood samples and compared with thallium kinetics after exercise (n = 15). Absolute myocardial thallium uptake was greater after dipyridamole compared with exercise (p less than 0.0001), although the relative myocardial distribution was similar. The myocardial clearance (%/h) of thallium was slower after dipyridamole than it was after exercise. Comparing dipyridamole and exercise, the differences in clearance were large from the early to the intermediate image (anterior, -11 +/- 17 versus 24 +/- 5, p = 0.0005; 50 degrees left anterior oblique, -7 +/- 11 versus 15 +/- 8, p = 0.004; 70 degrees left anterior oblique, 3 +/- 9 versus 21 +/- 6, p = 0.001). In contrast, the differences in clearance were small from the intermediate to the delayed image (anterior, 15 +/- 4 versus 20 +/- 2, p = 0.025; 50 degrees left anterior oblique, 15 +/- 4 versus 19 +/- 3, p = 0.13; 70 degrees left anterior oblique, 15 +/- 3 versus 18 +/- 2, p = 0.047). Thallium uptake and clearance in the liver, splanchnic region and spleen were greater after dipyridamole (p less than 0.001). Blood thallium levels were greater after dipyridamole (p less than 0.05) and cleared more slowly (p = 0.07). Thus, myocardial thallium-201 uptake and clearance after dipyridamole infusion differ from thallium kinetics after exercise. This difference is, in part, related to associated differences in extracardiac and blood kinetics. Diagnostic criteria for the detection of abnormal thallium-201 clearance must be specific for the type of intervention.

Adult↗

PubMed1987

Relationship between left ventricular systolic function and plasma clearance of 169Yb-DTPA in normal and ischemic dogs.

UNLABELLED: Plasma clearance of 169Yb-DTPA, a heavy chelate metal excreted only by glomerular filtration, was measured serially in a canine model to determine whether the clearance of this substance correlates with left ventricular systolic function. Fourteen anesthetized open-chest dogs were studied. Six dogs (group I) were used to estimate the clearance of 169Yb-DTPA in the setting of normal left ventricular function. Eight dogs (group II) were used to estimate clearance of 169Yb-DTPA in the presence of ischemic left ventricular dysfunction. Cardiac output, mean arterial pressure, and plasma levels of 169Yb-DTPA were measured serially. In group II dogs, area at risk for necrosis was defined using myocardial contrast echocardiography. The change in clearance of 169Yb-DTPA in group II dogs correlated well with change in cardiac output and area at risk (r = 0.80 and -0.93, respectively) and was significantly different from group I dogs (p less than 0.01). However, changes in clearance of 169Yb-DTPA in the group II dogs did not correlate well with change in mean arterial pressure (r = 0.26). IN CONCLUSION: (1) clearance of 169Yb-DTPA is constant over time in the absence of ischemic left ventricular dysfunction and derangement of other hemodynamic parameters; (2) changes in clearance of 169Yb-DTPA correlate well with changes in systolic pump function and left ventricular area at risk in the setting of ischemic left ventricular dysfunction, and (3) clearance of 169Yb-DTPA is not related to mean arterial pressure.

Animals↗