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PubMed1987

Detection of coronary artery disease by thallium imaging using a combined intravenous dipyridamole and isometric handgrip test in patients with aortic valve stenosis.

Detection of coronary artery disease (CAD) in patients with aortic valve stenosis (AS) is clinically difficult. Thallium-201 images were generated in 27 patients with AS during combined intravenous dipyridamole and handgrip test, which induces a marked acute increase in coronary blood flow. Isolated AS was noted in 21 patients and combined AS and aortic regurgitation in 6. Thirteen patients had more than 50% diameter stenosis in 1 or more coronary arteries on angiography. Eleven of them had reversible perfusion defects on post-stress thallium scans (sensitivity 85%). Two patients had thallium defects without angiographic evidence of significant CAD (specificity 86%). In the other 12 patients with normal coronary angiographic findings, the thallium scans were normal. Two patients had dizziness and hypotension after dipyridamole infusion, which disappeared during the handgrip test; 2 others had chest pain during handgrip. One of them was treated with aminophylline and the other with aminophylline and nitroglycerin. No other adverse effects were reported by the patients and no major complications occurred during stress testing. Thus, thallium imaging during combined intravenous dipyridamole and handgrip test appears to be a promising noninvasive method of revealing CAD in patients with AS.

Aged↗
PubMed1987

Comparison of the high-dose dipyridamole-echocardiography test and exercise two-dimensional echocardiography for diagnosis of coronary artery disease.

Fifty-five patients with effort angina pectoris and technically satisfactory baseline echocardiograms performed a supine exercise-echocardiography test (EET) and a high-dose dipyridamole-echocardiography test (DET, up to 0.84 mg/kg of intravenous dipyridamole in 10 minutes). All underwent coronary arteriography, which showed that at least 1 major artery had more than 70% stenosis in 34 patients. For each patient, the same physician performed both tests, with the same echocardiographic equipment. Detection of new onset or worsening regional asynergy was the only criterion of positivity for both tests. DET yielded interpretable studies in all 55 patients (100%); EET yielded only 40 such studies (73%) (p less than 0.01). In the 40 patients in whom both tests were interpretable, DET showed, compared with EET, a similar sensitivity (72% vs 76%) and specificity (100% vs 87%) (difference not significant for both) for detecting angiographically assessed coronary artery disease. In the 16 patients in whom both DET and EET yielded positive responses for ischemia, the same myocardial region showed reversible asynergy. Thus, independent of all factors that can affect the performance of each test (operator, patient and instrumentation), DET was significantly more feasible than EET, with comparable sensitivity and specificity. Dipyridamole provokes asynergy in the same regions that show ischemia during exercise.

Adult↗
PubMed1989

Usefulness of the severity and extent of reversible perfusion defects during thallium-dipyridamole imaging for cardiac risk assessment before noncardiac surgery.

Thallium-dipyridamole imaging is a very sensitive test for predicting cardiac events after noncardiac surgery, but it lacks specificity. To improve specificity, a semiquantitative scoring system was developed that combined dipyridamole-induced reversible left ventricular dilatation with scintigraphic indexes for severity and extent of reversible perfusion defects. Using this scoring system, patients were classified into low, intermediate and high risk subgroups. Thallium-dipyridamole imaging was performed in 66 patients before major general and vascular surgery. Thirty-nine patients classified as low risk (30 with normal scans and 9 with fixed defects) underwent surgery uneventfully. Surgery was cancelled in 6 patients with extensive thallium redistribution and coronary angiography was performed because of severe coronary artery disease in 5 and idiopathic dilated cardiomyopathy in 1. In the remaining 21 patients with thallium redistribution, a positive statistical correlation (p = 0.001) between scintigraphic indexes of severity and extent, and cardiac events was noted. Using cutoff values for the scintigraphic indexes, patients with reversible defects could be classified into intermediate and high risk subgroups. Only 1 of 11 patients at intermediate risk developed a complication, whereas 8 of 10 patients at high risk had a postoperative event (7 deaths and 1 myocardial infarction). Thus, using scintigraphic indexes for severity and extent, patients with reversible defects can be stratified into an intermediate risk subgroup that can safely undergo surgery and a high risk subgroup that requires coronary angiography.

Angiography↗
PubMed1989

Comparison of myocardial washout rate of thallium-201 between rest, dipyridamole with and without aminophylline, and exercise states in normal subjects.

The myocardial washout rate of thallium-201 was studied in 85 subjects with a less than 5% likelihood of coronary artery disease undergoing rest (group I, n = 12), dipyridamole (group II, n = 24) and exercise (group III, n = 49) stress thallium-201 scintigraphy. Subjects receiving dipyridamole were subdivided into group IIA (n = 11), who received an aminophylline injection 10 minutes after dipyridamole infusion, and group IIB (n = 13), who did not. The mean and highest washout rate values in each of 3 segments in the anterior, 45 degrees and 85 degrees left anterior oblique views were calculated. In group II the mean washout rate of thallium-201 was similar in all segments of each view and the overall mean washout rate did not differ between the 3 views studied. There was a good correlation between the mean and highest washout rate values in individual subjects (r = 0.98, p less than 0.001). The mean +/- standard deviation myocardial 4-hour washout rate of thallium-201 (anterior view) was 10 +/- 6% in group I compared with 40 +/- 14% in group IIA (p less than 0.05 vs group I), 31 +/- 13% in group IIB (p less than 0.05 vs group I) and 54 +/- 11% in group III (p less than 0.05 each vs group IIA and group IIB, respectively). There was a wide variation in mean washout rate values in group II (range 12 to 58%), and this variation was not altered by aminophylline administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Technetium-99m sestamibi myocardial imaging: same-day rest-stress studies and dipyridamole.

Unlike thallium-201, technetium-99m (Tc-99m) sestamibi does not redistribute in the myocardium after injection. Thus, 2 separate injections, 1 at rest and the other at stress (or after dipyridamole), are required to differentiate ischemia from scar. From a physical viewpoint, a 24-hour interval between the 2 injections is preferable for detection of coronary artery disease (CAD) with Tc-99m sestamibi imaging. However, same-day studies are more convenient in clinical practice. Results of studies using different Tc-99m sestamibi injection protocols are presented with emphasis on the advantages of a rest-stress injection sequence with a low dose at rest (7 mCi) followed 2 hours later by a higher dose at stress (25 mCi). A prospective study was conducted in a patient population with proven CAD using same-day studies to compare a rest-stress (7 and 25 mCi, respectively) to a stress-rest (7 and 25 mCi) Tc-99m sestamibi injection sequence. There was an agreement in 87.3% of the analyzed segments between the 2 protocols. However, the largest discordance for type of defect applied to 7.4% of the segments judged ischemic in the rest-stress protocol, which were called scars on stress-rest. This study showed that a rest-stress sequence is preferable when using a same-day protocol with a short time interval (less than 2 hours) between the 2 Tc-99m sestamibi injections because the rest image performed initially represents a "true" rest study, which is not necessarily the case with the stress-rest sequence. Preliminary studies were performed to evaluate dipyridamole with Tc-99m sestamibi imaging in normal subjects and in patients with CAD. These studies showed that treadmill and dipyridamole Tc-99m sestamibi imaging are comparable and the results are similar to those obtained with thallium-201.

Coronary Disease↗
PubMed1990

Effect of pretreatment with aspirin versus aspirin plus dipyridamole on frequency and type of acute complications of percutaneous transluminal coronary angioplasty.

It is unknown whether the addition of dipyridamole to aspirin as pretreatment for patients undergoing percutaneous transluminal coronary angioplasty (PTCA) decreases acute complications. In this study 232 patients were prospectively randomized to receive either aspirin 325 mg orally 3 times daily (group 1, n = 115) or aspirin 325 mg orally 3 times daily plus dipyridamole 75 mg orally 3 times daily (group 2, n = 117) before elective PTCA. All clinical, angiographic and PTCA-related variables were similar between groups. Angiographic success rate was 93% in both groups. Clinical success was achieved in 107 patients (92%) in group 1 and in 101 patients (88%) in group 2 (difference not significant). Q-wave myocardial infarction occurred in 2 patients (1.7%) in group 1 and 5 patients (4.3%) in group 2 (difference not significant). Emergency coronary artery bypass grafting was required in 3 patients (2.6%) in group 1 and 7 patients (6.1%) in group 2 (difference not significant). There was 1 in-hospital death (in group 2). In this study, the addition of dipyridamole to aspirin as pretreatment of patients undergoing PTCA did not significantly reduce acute complications compared to aspirin alone.

Angioplasty, Balloon, Coronary↗
PubMed1991

Usefulness of technetium-99m-MIBI and thallium-201 in tomographic imaging combined with high-dose dipyridamole and handgrip exercise for detecting coronary artery disease.

Forty-two patients with known stable coronary artery disease, referred for coronary angiography, were examined with technetium-99m-hexakis-2-methoxy-2-methylpropyl-isonitrile (MIBI) tomography combined with a high-dose dipyridamole infusion (0.7 mg/kg) and handgrip stress. MIBI tomography was unable to show coronary artery disease only in 2 patients, thus yielding a sensitivity figure of 95%. MIBI tomography correctly identified 27 (82%) of 33 stenotic lesions (greater than or equal to 50% diameter stenosis) of the left anterior descending artery, 17 (61%) of 28 of those of the left circumflex artery, and 28 (90%) of 31 of those of the right coronary artery. The overall vessel sensitivity was 78%. The computed lumen diameter stenoses were more advanced in cases detected than in those not detected with MIBI tomography: 87 +/- 14 vs 76 +/- 14% (p less than 0.01). The 50 to 69% stenoses did not show any tendency to produce less positive findings than those with greater than or equal to 70% stenoses. In the subgroup of 21 patients who also presented for thallium scintigraphy, the overall diseased vessel identification rate was 76% for thallium tomography and 83% for MIBI tomography (p = not significant). Minor noncardiac side effects related to the dipyridamole-handgrip test occurred only in 5% of 63 study sessions. A high-dose dipyridamole combined with isometric exercise is a safe stress method, and when used during scintigraphy, MIBI tomography is at least as efficient a tool as thallium tomography in detecting diseased vessel territories in patients in coronary artery disease.

Aged↗
PubMed1992

Preoperative coronary artery disease risk stratification based on dipyridamole imaging and a simple three-step, three-segment model for patients undergoing noncardiac vascular surgery or major general surgery.

A 3-step, 3-segment scintigraphic model was developed to improve the accuracy of dipyridamole-thallium imaging for preoperative cardiac risk assessment and to simplify the prognostic interpretation of the images. The model was developed in a pilot study of 60 patients and validated in a group of 355 patients referred for vascular and major general surgery. Study end points included myocardial infarction and cardiac death. Step 1: The postoperative cardiac event rate was 1.3% in 225 patients with normal anterior, inferio- and posterolateral segment perfusion and without transient left ventricular dipyridamole-induced cavitary dilation. Step 2: The physiologic rationale for step 2 consists of identifying patients who are most likely to have left main, 3-vessel or high-risk 2-vessel coronary artery disease or a significant amount of jeopardized myocardium in the territory of a critical coronary stenosis. Of 29 patients with either reversible defects of all 3 segments, transient cavitary dilation, or at least 1 severe grade 3/3 reversible defect, 52% (15 of 29) sustained a postoperative cardiac event. Step 3: The remaining 101 patients were stratified according to age greater than 70 years (p = 0.01), presence of diabetes (p = 0.0004) and the number of segments displaying reversible defects (1 or 2) with cardiac event rates ranging from 5 to 36%. The 3-step, 3-segment model is a useful alternative to the conventional interpretation of dipyridamole myocardial perfusion images for the purpose of quick and efficient preoperative risk stratification based on the rationale of correlating surgical risk with the amount of potentially ischemic myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Prediction of late cardiac events by dipyridamole thallium imaging in patients undergoing elective vascular surgery.

Dipyridamole thallium scintigraphy has previously been shown to have prognostic value in the preoperative assessment of patients scheduled to undergo vascular surgery, but its effect on the long-term outcome is less well-defined. In the largest series to date, dipyridamole thallium scanning was performed in 360 patients before elective vascular surgery and survivors were followed for a mean of 31 months. In the 327 patients who underwent vascular surgery, operative death and nonfatal myocardial infarction occurred in 4.9 and 6.7%, respectively. A cardiac event (nonfatal myocardial infarction or cardiac death) occurred in 14.4% of patients with a transient thallium defect, as opposed to 1% with a normal scan (p < 0.001). Logistic regression analysis revealed that the best predictor of a perioperative event was the presence of a reversible thallium defect, elevating the risk by 4.3-fold. Late cardiac events occurred in 53 (15.2%) surgical survivors or nonsurgically treated patients. Patients with a fixed perfusion abnormality had a 24% late event rate, compared with 4.9% in those with a normal dipyridamole thallium study (p < 0.01). Cox analysis demonstrated that a fixed thallium defect was the strongest factor for predicting a late event and increased the relative risk by almost fivefold. A history of congestive heart failure was the only significant variable that contributed additional value to that of a fixed defect alone. Life-table analysis confirmed the strong relation of a fixed defect to cardiac event free survival (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Preoperative diagnosis of coronary artery disease in patients with valvular heart disease using technetium-99m isonitrile tomographic imaging together with high-dose dipyridamole and handgrip exercise.

Forty-seven consecutive patients (mean age 61 +/- 8 years) referred for cardiac catheterization due to moderate to severe aortic (n = 30) or mitral (n = 17) valvular heart disease were examined by technetium-99m isonitrile tomography together with a high-dose dipyridamole infusion (0.7 mg/kg) and handgrip stress. Tomography did not identify coronary artery disease (CAD) in 3 of the 21 patients with angiographically proven disease (sensitivity 86%) and suggested false positive results in 5 of the 26 without the disease (specificity 81% and negative predictive accuracy 88%). No patient without angina pectoris and with negative scintigraphy (n = 14) had angiographically significant (greater than or equal to 50% diameter stenosis) CAD. Overall vessel sensitivity was 63%, and specificity was 92%. The frequency of side effects during the dipyridamole-handgrip test was only 7%. No serious complications occurred during stress tests. Thus, technetium-99m isonitrile tomographic imaging, together with high-dose dipyridamole and handgrip exercise, is a useful noninvasive method in excluding significant CAD in patients with valvular heart disease.

Coronary Angiography↗
PubMed1994

Frequency of prosthetic valve-related complications with very low level warfarin anticoagulation combined with dipyridamole after valve replacement using St. Jude Medical prostheses.

The safety of a very low level of anticoagulation combined with dipyridamole in a rheumatic population (mean age 31 +/- 13 years) with the St. Jude Medical (SJM) prosthesis has not yet been tested. Furthermore, no data are available on the safety of relatively infrequent monitoring of anticoagulation levels and of the necessity for different therapeutic targets according to valve position, number of risk factors, and other baseline risk factors for thromboembolism. In this study, the performance of the SJM prosthesis was tested using a target international normalized ratio (INR) of 2.0 to 2.5 combined with dipyridamole 300 mg/day applied uniformly to all patients. Clinical, biochemical, and echocardiographic data were acquired prospectively in 200 consecutive patients at 3-month intervals. Follow-up (mean 27 +/- 13 months) was complete in 95% of patients. Thirteen patients died (2.9%/patient year). Severe left ventricular dysfunction was the cause of death in 10 of 13 patients. Probability of survival (Kaplan-Meier) was 0.92 at 36 months and of event-free survival 0.84 at 36 months. The median INR was 2.0 +/- 0.9. Valve obstruction did not occur, and there were 3 thromboembolic events (0.6%/patient year). Incidence of bleeding was 1.6%/patient year (n = 7) and was major (hemorrhagic stroke) in 1 (0.2%/patient year). Thus, the SJM prosthesis performs very well despite the use of very low level warfarin anticoagulation combined with dipyridamole. A 3-month assessment of the anticoagulation level is safe. Left ventricular dysfunction rather than valve-related complications is the leading cause of mortality in this population.

Adult↗
PubMed1994

Prognostic value of dipyridamole technetium-99m sestamibi myocardial tomography in patients with stable chest pain who are unable to exercise.

Unlike dipyridamole testing with thallium-201, the ability of technetium-99m sestamibi (MIBI) myocardial imaging to evaluate risk of later cardiac events has not been established. In this study, the prognostic value of dipyridamole MIBI myocardial tomography (same-day, rest-stress protocol) was assessed in 534 patients with stable chest pain consistent with angina pectoris. During follow-up (mean 13 +/- 5 months), 58 patients (11%) had a major cardiac event--nonfatal myocardial infarction (n = 14) or cardiac death (n = 44). A history of congestive heart failure, prior myocardial infarction or diabetes mellitus, and either a reversible or fixed myocardial perfusion defect on MIBI scans were univariate and multivariate predictors of increased cardiac risk. Cardiac events occurred in 2% of patients with normal MIBI scans, compared with 15% with abnormal scans, 17% with reversible perfusion defects and 16% with fixed defects (all p < 0.01). Relative risks (univariate Cox analysis) associated with an abnormal MIBI scan, a reversible perfusion defect and a fixed defect were 8.4 (95% confidence interval [CI] 2.6 to 26.8), 1.9 (95% CI 1.1 to 3.2) and 2.4 (95% CI 1.4 to 4.3), respectively. Patients with any kind of perfusion abnormality (reversible or fixed) had a significantly lower cardiac event-free survival than those with normal scans (all p < 0.0001). It is concluded that, as with thallium-201 myocardial scintigraphy, a normal MIBI scan is associated with low cardiac risk, whereas dipyridamole-induced myocardial perfusion defects identify patients with significantly increased risk.

Aged↗
PubMed1995

Hemostatic efficacy of dipyridamole, tranexamic acid, and aprotinin in coronary bypass grafting.

Sixty patients (four groups of 15 patients) were entered in a randomized, controlled study to compare the efficacy of prophylactic treatment with dipyridamole, tranexamic acid, and aprotinin to reduce bleeding after elective coronary artery bypass grafting. Only patients with a preoperative platelet count of less than 246 x 10(9)/L were selected because a previous study showed that these individuals are at risk for increased postoperative bleeding. Compared to control subjects, postoperative blood loss 6 hours after operation was significantly reduced by tranexamic acid (674 +/- 411 versus 352 +/- 150 mL; p < 0.05) and by aprotinin (270 +/- 174 mL; p < 0.01). Dipyridamole did not reduce postoperative blood loss and was associated with complications in 3 patients. We conclude that hemostasis after cardiac operations can be improved with tranexamic acid and aprotinin. Dipyridamole appeared to be ineffective.

Aprotinin↗
PubMed1993

Tomographic thallium-201 myocardial perfusion imaging after intravenous dipyridamole in asymptomatic subjects with quadriplegia.

Cardiovascular disease is the leading cause of mortality in those with a spinal cord injury (SCI). As a consequence of changes in body composition and level of activity, individuals with a SCI tend to have a high prevalence of multiple risk factors for coronary artery disease (CAD). In this report, we have demonstrated the usefulness of tomographic thallium-201 myocardial perfusion imaging after intravenous dipyridamole in six clinically asymptomatic subjects with quadriplegia. The average age of the subjects was 47 +/- 2 years, and they had a duration of injury of 15 +/- 2 years. On average, the individuals had five risk factors for CAD. After intravenous administration of dipyridamole and mild upper extremity exercise, the subjects reported no adverse symptoms and had no electrocardiographic evidence suggestive of ischemia. By contrast, three of the six subjects had reversible defects noted on thallium scintigraphy, and one additional subject had a fixed defect that was suggestive of infarction. The remaining two subjects had abnormal scans with fixed defects of the inferioposterior region, which may be ascribed to diaphragmatic attenuation, perhaps a result of partial diaphragmatic paralysis. Thus, dipyridamole thallium myocardial imaging is a safe and effective noninvasive method for the detection of myocardial ischemia or infarction in individuals with quadriplegia who are at increased risk for CAD.

Adult↗
PubMed1993

Effects of dipyridamole in spontaneously hypertensive rabbits with diffuse chronic cerebral ischemia.

The effect of intravenous dipyridamole (0.7 mg/kg) on cerebral blood flow (CBF), mean arterial blood pressure (MABP), heart rate, respiration rate, cerebral electrical activity, arterial blood gases, pH, and glucose was investigated in 14 normotensive and 14 stroke-prone spontaneously hypertensive anesthetized rabbits. CBF was measured by hydrogen and heat clearance. In both groups, MABP decreased (normotensive: -24 mm Hg, hypertensive: -47 mm Hg; ANOVA: P < 0.0001) and CBF increased (normotensive: +59 ml/100 g/min, hypertensive: +72 ml/100 g/min; ANOVA: P < 0.0002). CBF returned to the initial level 21 min later in hypertensive than in normotensive rabbits. Changes in other parameters were insignificant. In additional experiments, 30 mg/kg theophylline entirely prevented the cerebral vasodilator and systemic hypotensive effects of dipyridamole in both normotensive and hypertensive rabbits. We conclude that, in stroke-prone spontaneously hypertensive rabbits, the longer-lasting and larger CBF increase in response to dipyridamole may be attributed to reversible functional changes in the cerebral vasculature resulting from hypertension.

Analysis of Variance↗
PubMed1994

High expression of nitrobenzylthioinosine-insensitive dipyridamole binding sites in postmortem human ependymal tissue.

The presence of both nitrobenzylthioinosine-sensitive and nitrobenzylthioinosine-insensitive dipyridamole binding sites in postmortem human ependymal tissue is reported. Displacement studies using 15 nM [3H]dipyridamole revealed 50-60% of the sites were sensitive to nitrobenzylthioinosine. Non-linear analysis of binding isotherms to estimate the density of nitrobenzylthioinosine-sensitive and -insensitive sites revealed a maximum number of nitrobenzylthioinosine-sensitive binding sites (Bmax) of 395 +/- 19 fmol/mg protein and a nitrobenzylthioinosine-insensitive Bmax of 3910 +/- 700 fmol/mg protein (corresponding Kd values of 0.1 nM and 114 nM respectively). Thus there are approximately 10 times as many nitrobenzylthioinosine-insensitive sites as nitrobenzylthioinosine-sensitive [3H]dipyridamole binding sites in human ependymal membranes.

Adult↗
PubMed1996

Zaprinast, but not dipyridamole, reverses hemodynamic tolerance to nitroglycerin in vivo.

Hemodynamic tolerance to nitroglycerin was developed in spontaneously hypertensive rats following 2-3 days of pretreatment with 100 mg/kg of nitroglycerin administered s.c. 3 times/day. Tolerance was evaluated both in vivo, by administering ascending bolus doses of nitroglycerin of 1-300 micrograms/kg i.v., and ex vivo in isolated, denuded aortic vascular rings by exposure to ascending concentrations of nitroglycerin of 0.0003-100 microM. Tolerance was observed as a significant blunting of the hypotensive and vasorelaxant effect of nitroglycerin. Co-incubation of tolerant aortic rings and pretreatment of tolerant SHR with 10 microM and 0.1-10 mg/kg zaprinast, respectively, resulted in full restoration of the vasorelaxant and hypotensive effect of nitroglycerin. Zaprinast partially reversed hemodynamic tolerance at 0.01 mg/kg. Conversely, dipyridamole (10 microM) reversed tolerance ex vivo, but was ineffective in reversing tolerance in vivo at pretreatment doses of 30 and 60 mg/kg. Following a 100-micrograms/kg i.v. challenge dose of nitroglycerin, aortic cyclic guanosine monophosphate (cGMP) levels were lower in nitroglycerin tolerant SHR when compared to non-tolerant SHR. Pretreatment of tolerant SHR with 10 mg/kg zaprinast restored the increase in cGMP levels to nitroglycerin to that seen in non-tolerant SHR. Conversely, dipyridamole (30 mg/kg) pretreatment was not effective in restoring cGMP levels. These data therefore suggest that reversal of hemodynamic tolerance in vivo is related to restoration of changes in vascular cGMP levels. Zaprinast, a selective cGMP phosphodiesterase inhibitor, effectively reverses tolerance and dipyridamole, a rather non-selective inhibitor, does not.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1986

Effects of dipyridamole on myocardial glucose uptake in the newborn lamb.

Carbohydrates are an important source of energy for the immature myocardium. Since dipyridamole (DPY) has been reported to facilitate glucose uptake in the adult heart, the present study was designed to determine whether DPY could enhance glucose uptake in the nonischemic newborn. In anesthetized, open chest lambs (n = 8), circumflex coronary blood flow (CBF), myocardial adenine nucleotide content, and aortic and coronary sinus concentrations of glucose, lactate, and pyruvate were determined before and after a single dose of DPY (0.2 mg/kg, intravenously). Adenine nucleotides were measured by HPLC. The consumption of substrates was calculated as the product of CBF and the aortic-coronary sinus difference in substrate concentration. Coronary blood flow averaged 114 +/- 6 ml/min/100 g in the untreated animals, and increased by 44% following treatment with dipyridamole (P less than 0.01). This was associated with a 32% decrease in coronary vascular resistance (P less than 0.01). Glucose uptake increased from 9 to 46 mumoles/min/100 g (P less than 0.01) following dipyridamole treatment; lactate uptake decreased by 97% (P less than 0.01). There was a net release of pyruvate from the neonatal hearts; this increased from 18 to 25 mumole/min/100 g (P less than 0.05). Myocardial ATP content averaged 4.08 mumole/g wet wt in the untreated animals, and increased 11% to 4.52 following DPY (P less than 0.01). The agent had no effect on the myocardial tissue levels of AMP or ADP. These data indicate that DPY is a coronary vasodilator in the newborn lamb and augments both glucose uptake and myocardial ATP content. These metabolic effects provide a rationale for further studies during periods of hypoxia and ischemia.

Adenine Nucleotides↗