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PubMed1994

[Thallium-dipyridamole in acute myocardial infarction treated by thrombolysis: diagnostic and prognostic value].

BACKGROUND: The management of patients who received thrombolytic therapy for acute myocardial infarction is still controversial. It is not clear if the strategies usually followed after myocardial infarction for risk stratification have the same value when applied to patients treated with thrombolysis. METHODS: To assess the diagnostic and prognostic value of dipyridamole thallium-201 scintigraphy in the "thrombolytic era", we studied 110 consecutive patients younger than 75 recovering from first uncomplicated acute myocardial infarction treated with thrombolytic agents. Patients with early angina, recurrent acute myocardial infarction, heart failure, life-threatening arrhythmias, non Q wave myocardial infarction were excluded. Ninety patients were treated with streptokinase, 14 with rtPA, 6 with APSAC: All patients underwent dipyridamole thallium scintigraphy with standard dose and coronary angiography before discharge (10-20 days). Ninety-nine patients underwent exercise test. All patients were followed-up for 22 +/- 9 months (range 8-42). Perfusion abnormalities were classified as reversible (totally or partially) defects or persistent defects and within or outside the infarct zone. RESULTS: Fifty-eight patients developed anterior and 52 inferior acute myocardial infarction. Coronary angiography showed single vessel coronary artery disease in 66 patients, multivessel disease in 34, and normal coronary arteries or sub-critical stenosis in 10. No major complications (death, myocardial infarction, threatening arrhythmias, prolonged severe hypotension) occurred after dipyridamole infusion. Sixty-two patients had reversible perfusion defects at thallium scanning (34 within the infarct zone, 21 within and outside the infarct zone, 7 outside); 38 patients had persistent defects; 10 patients had a normal scintigraphic pattern. The diagnostic value of homozonal perfusion reversible defects for identifying a patent infarct-related vessel was poor (sensitivity 69.7%, specificity 64.7%). The diagnostic values of the same scintigraphic pattern improved in detecting patent infarct-related artery with residual critical stenosis (sensibility 75.4%, specificity 77.3%); in all the false positive cases (reversible defects within the infarct zone and occluded infarct-related artery) a good collateral flow was present. The sensitivity of reversible defects outside the infarct zone in detecting multivessel disease was 64.7% vs 56.3% of exercise test; the specificity was 92% vs 64%; the positive predictive value 78.6% vs 44%; the negative predictive value 85.3% vs 74.5%; the diagnostic accuracy 83.6% vs 61.4%. During the follow-up 2 deaths, 7 recurrent myocardial infarction, 1 sustained ventricular tachycardia, 1 heart failure, 13 recurrence of unstable angina and 9 revascularization procedures occurred among patients with reversible defects (either within or outside the infarct zone) at thallium scanning. One recurrent myocardial infarction, 4 recurrence of unstable angina and 2 revascularization procedures were the events among patients with persistent defects or normal scintigraphic pattern (p < 0.001). Ischemic events occurred with similar frequency in patients with reversible perfusion defects within the outside the infarct zone (55% vs 50%, NS). CONCLUSIONS: Dipyridamole thallium-201 scintigraphy performed after uncomplicated myocardial infarction treated with thrombolytic agents is a valuable diagnostic tool in identifying viable jeopardized myocardium within the infarct zone perfused by a patent but critically narrowed vessel; it shows better diagnostic accuracy in detecting multivessel disease than does the exercise test and is able to identify a subset of patients at risk for future ischemic events after thrombolytic therapy.

Adult↗
PubMed1993

Thallium scintigraphy in the evaluation of mass abnormalities of the breast.

Palpable mass abnormalities of the breast are often difficult to evaluate mammographically, especially in patients with fibrocystic change and dense breasts. The current study evaluates 201TI scintigraphy as a potential test in detecting malignancy and in differentiating malignant from benign masses. Eighty-one female patients underwent thallium scintigraphy of the breast because of palpable breast masses. An additional 30 females with no palpable breast abnormalities were also studied using 201TI. Of 44 patients with palpable breast carcinomas, 42 carcinomas (96%) were detected using 201TI scintigraphy. Three of three patients had other primary breast malignancies that were also detected. In contrast, 19 patients with palpable breast abnormalities shown on biopsy to be benign fibrocystic disease processes were not detectable on thallium studies. Of two patients with fat necrosis, none were detectable. Three of 13 patients had adenomas of the breast (23%) that were detected. The three detectable adenomas were all highly cellular. The smallest detectable carcinoma was an adenocarcinoma measuring 1.3 x 1.1 x 0.9 cm. Thallium-201 scintigraphy of palpable breast lesions is an effective test for evaluation of palpable masses. Sensitivity for detection of malignant masses greater than 1.5 cm is high. Highly cellular adenomas, however, may demonstrate significant 201TI uptake. Benign fibrocystic disease is not detectable with thallium scintigraphy. Thallium scintigraphy of breast lesions is an effective means of differentiating benign from malignant lesions.

Adenocarcinoma↗
PubMed1993

[Assessment of myocardial perfusion abnormality and hibernating myocardium by gated blood pool and exercise-stress thallium tomographies after successful coronary angioplasty].

Cardiac function and myocardial perfusion were assessed by exercise-stress thallium SPECT and resting gated blood pool SPECT techniques before and after 47 successful coronary angioplasties. Thallium perfusion was analyzed visually and quantitatively in stress and resting studies. Left ventricular ejection fraction (LVEF) and peak filling rate (PFR) were calculated and regional wall motion was scored by amplitude and phase images in radionuclide planar and tomographic imagings. The thallium redistribution in delayed or resting SPECTs was more sensitive (87%) for detecting myocardial ischemia compared to symptoms (36%) and ECG changes (60%). An exercise capacity, LVEF, PFR, and the scores of perfusion and regional wall motion were improved significantly after coronary angioplasty. Stress thallium and gated blood pool SPECTs showed the improvements of myocardial perfusion in 159 (79%) of 201 segments and regional wall motion in 47 (51%) of 92 segments, respectively. These results suggest that the combined use of stress thallium SPECT, gated blood pool planar and SPECT techniques can contribute not only to the assessment of the efficacy of coronary angioplasty but also to detecting the mismatching of myocardial perfusion and contraction ("myocardial hibernation") in infarct-related myocardial lesions.

Angina Pectoris↗
PubMed1996

[The 3-year prognosis of patients with suspected coronary disease and a normal myocardial scintigraphy with thallium-dipyridamole].

OBJECTIVES: To assess the 3-year prognosis of patients with suspected coronary artery disease and a normal dipyridamole-thallium scintigram. POPULATION: 43 patients, 16 male and 27 female, mean age 55.8 +/- 9.2 years with suspected coronary artery disease. Forty-two patients had anginal complaints. There was a previous positive treadmill exercise test in 14 patients. All the patients had a normal dipyridamole-thallium SPECT. METHODS: Dipyridamole was infused at a rate of 0.56 mg/kg in 4 minutes followed by 3 minutes of low-level cycloergometer exercise. Two mCi of thallium-201 were injected 3 minutes after the end of dipyridamole infusion. Stress and redistribution SPECT acquisitions were performed respectively 5-10 minutes and 4 hours after thallium-201 injection. The cardiac events during a 3-year follow-up were analysed. RESULTS: No patient had unstable angina, PTCA, CABG or death. One patient suffered an inferior myocardial infarction 28 months after the scintigraphy. The event rate was 0.78% per patient per year. CONCLUSION: Three-year prognosis in patients with suspected coronary artery disease after a normal dipyridamole thallium SPECT is excellent approaching that of the general population.

Adult↗
PubMed1997

Incremental prognostic value of thallium reinjection after stress-redistribution imaging in patients with previous myocardial infarction and left ventricular dysfunction.

UNLABELLED: This study evaluated the incremental prognostic value of 201TI reinjection imaging over clinical, exercise and thallium stress-redistribution data in patients with previous myocardial infarction and left ventricular dysfunction. METHODS: Thallium-201 reinjection after stress-redistribution SPECT was performed in 104 consecutive patients with a first Q-wave myocardial infarction (> 8 wk) and left ventricular ejection fraction < or = 40%. Follow-up data (mean 22 mo) were available for 98 patients; 16 patients underwent early revascularization procedures within 3 mo after exercise testing and were not considered for the analysis. RESULTS: During follow-up there were 13 hard events (cardiac death and myocardial infarction) and 11 soft events (coronary revascularization procedures > 3 mo after thallium imaging). With multivariate Cox regression analysis, the sum of defects at stress-redistribution imaging that were reversible or moderate irreversible after reinjection was a powerful predictor of subsequent events. The addition of thallium reinjection imaging data significantly improved the prognostic power of clinical, exercise and stress-redistribution data for the occurrence of hard events (p < 0.01). CONCLUSION: In patients with previous myocardial infarction and left ventricular dysfunction, thallium reinjection imaging provides incremental prognostic information over those obtained from conventional stress-redistribution imaging.

Analysis of Variance↗
PubMed1997

Potassium and thallium uptake in dog myocardium.

UNLABELLED: We sought to ascertain the rates and mechanisms of uptake of markers for regional myocardial blood flows. METHODS: The rates of exchange of potassium and thallium across capillary walls and cell membranes in isolated blood-perfused dog hearts were estimated from multiple indicator dilution curves recorded for 131I-albumin, 42K and 201Tl from the coronary sinus outflow following injection into arterial inflow. Analysis involved fitting the observed dilution curves with a model composed of a capillary-interstitial fluid-cell exchange region and nonexchanging larger vessels. RESULTS: Capillary permeability surface products (PSc) for potassium and thallium were similar, 0.82 +/- 0.33 (mean +/- s.d., n = 19) and 0.87 +/- 0.32 ml min-1 g-1 (n = 24) with a ratio for simultaneous pairs of 1.02 +/- 0.27 (n = 19). For the myocardial cells, PSpc averaged 3.7 +/- 3.1 ml min-1 g-1 (n = 19) for K+ and 9.5 +/- 3.9 (n = 24) for Tl+; the ratio of potassium to thallium averaged 0.40 +/- 0.19 (n = 18), thereby omitting a single high value for potassium. This high cellular influx for thallium is interpreted as due to its passage through ionic channels for both Na+ and K+. CONCLUSION: The high permeabilities and large volumes of distribution make thallium and potassium among the best ionic deposition markers for regional flow. Their utility for this purpose is compromised by significant capillary barrier limitation retarding uptake; so regional flow is underestimated modestly in high-flow regions particularly.

Animals↗
PubMed1996

[Methods of diagnosis of thallium intoxication and its antidote therapy].

Absence of early signs specific for thallium intoxication requires objective diagnostic methods. The studies covered 4 techniques: electroretinography (ERG), assessment of urine levels of thallium and delta-aminolevulinic acid, capillaroscopy. The authors supported their previous foundation concerning diagnostic value of ERG for early diagnosis of thallium effects (higher amplitude of b-wave in one and that of a-wave in 8 out of 10 examinees). Further experimental and clinical basis for grading the intoxication through amounts of urinary thallium were found promising. Capillaroscopy method appeared informative: 8 out of 12 examinees demonstrated spastic and atonic state of hand capillaries--that provided objective verification of vascular disorders in workers exposed to thallium and its derivatives.

Aminolevulinic Acid↗
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↗
PubMed1988

The effect of thallium on the growth of Lemna minor and plant tissue concentrations in relation to both exposure and toxicity.

The effect of thallium on frond production and the rates of increase in surface area and fresh weight in Lemna minor were examined in terms of concentrations of the element in the growth medium and in the plant. The toxicity indices, EC(50) and threshold concentration, indicate that curtailment of frond expansion occurs at a lower thallium exposure than inhibition of frond multiplication. Production of smaller fronds, rather than chlorosis, was the most notable initial response to thallium stress and, below the threshold of toxicity, enhanced multiplication rates were recorded. Subsequent recovery in thallium-free medium was significant in the region of EC(50) exposures and below, but very little recovery occurred at higher exposures. Lemna minor has a remarkable capacity to accumulate thallium, and accumulation factors of 88 x 10(3) at low exposures, and 6 x 10(3) at high exposures, were recorded, which would suggest some form of active uptake.

Journal Article↗
PubMed1996

A Six-Coordinate Tris(3,5-dimethyl-1-pyrazolyl)methane-Thallium(I) Complex with a Stereochemically Inactive Lone Pair: Syntheses and Solid State Structures of {[HC(3,5-Me(2)pz)(3)](2)Tl}PF(6) and {[HC(3,5-Me(2)pz)(3)]Tl}PF(6) (pz = Pyrazolyl).

The addition of the tris(pyrazolyl)methane ligand HC(3,5-Me(2)pz)(3) (pz = pyrazolyl ring) to a THF solution of TlPF(6) results in the immediate precipitation of {[HC(3,5-Me(2)pz)(3)](2)Tl}PF(6). The structure has been determined crystallographically. The arrangement of the nitrogen donor atoms about the thallium is best described as a trigonally distorted octahedron. The thallium atom sits on a crystallographic center of inversion; thus the planes formed by the three nitrogen donor atoms of each ligand are parallel. The Tl-N bond distances range from 2.891(5) to 2.929(5) Å (average = 2.92) Å. The lone pair on thallium is clearly stereochemically inactive and does not appear to influence the structure. The pyrazolyl rings are planar, but are tilted with respect to the thallium atom so as to open up the N.N intraligand bite distances. The thallium(I) complex with a ligand to metal ratio of 1/1, {[HC(3,5-Me(2)pz)(3)]Tl}PF(6), is prepared in acetone by the reaction of equimolar amounts of HC(3,5-Me(2)pz)(3) and TlPF(6). The structure of the cation is a trigonal pyramid, with Tl-N bond distances that range from 2.64(1) to 2.70(1) Å (average = 2.67) Å. Pyrazolyl ring tilting is also observed in this complex, but the degree of tilting is smaller. Crystal data for {[HC(3,5-Me(2)pz)(3)](2)Tl}PF(6): monoclinic, P2(1)/c, a = 9.210(6) Å, b = 13.36(1) Å, c = 16.067(8) Å, beta = 92.48(5) degrees, V = 1975(2) Å(3), Z = 2, R = 0.029. For {[HC(3,5-Me(2)pz)(3)]Tl}PF(6): monoclinic, P2(1)/n, a = 10.685(2) Å, b = 16.200(5) Å, c = 13.028(3) Å, beta = 94.02(2) degrees, V = 2249.6(8) Å(3), Z = 4, R = 0.042.

Journal Article↗
PubMed2003

Complexity of coordinative bonding in thallium(I) anthranilates and salicylates.

An inventory of the structural chemistry of thallium(I) shows many unexpected, almost random coordination numbers and coordination geometries that appear erratic and inconsistent. This nonstandard behavior is often ascribed to the specific lone-pair characteristics originating from relativistic effects. To provide data on a set of closely related compounds from which simple general rules of coordinative bonding at Tl(+) can be established, three thallium(I) anthranilates and three thallium(I) salicylates have been prepared from Tl(2)CO(3) and the corresponding 2-amino- and 2-hydroxy-benzoic acids and crystallized from aqueous solutions. All six compounds, the simple anthranilate (1) and salicylate (4) and the 3- and 4-methyl-substituted homologues (2, 3 and 5, 6) show different structures with large variations in the coordination motif. The coordination by oxygen in a geometry which covers less than a coordination hemisphere is the only common feature, complemented (only in 1) by a nitrogen coordination and by eta(6)-coordination of one (in 1, 2, 3, 6) or two phenyl rings (in 4). Tl-Tl contacts for which "thallophilic" bonding between closed shell metal atoms could be invoked, are generally very long (close to 4.0 A) or even well beyond the limit of standard van der Waals contacts. Hydrogen bonding is only obvious for the internal contacts of the amino- or hydroxy-benzoate ligands and does not contribute significantly to the assembly of the supramolecular structure which is dominated by oxygen bridges between thallium atoms. With the exception of 5, the formula units Tl[O(2)C(2-R)(3-R')(4-R'')C(6)H(2)] are generally aggregated into dimers of various configurations depending on the relative orientation of the edge-sharing four-membered rings, and these dimers are further linked into strings or columns establishing N-Tl or Tl-O contacts and arene coordination. The drastic changes induced in the structures upon only small variations such as methyl substitution in 3- or 4-position of the ligand suggest that thallium(I) coordination is generally restricted to one hemisphere of nearest neighbors, but is extremely flexible in this realm. The open hemisphere may be partially capped by arene coordination (which is weak at a distance of ca. 3.1 A to the centroid of the ring) or feature very weak thallophilic contacts.

Journal Article↗
PubMed1994

Thallium and indium antimyosin dual-isotope single-photon emission tomography in acute myocardial infarction to identify patients at further ischaemic risk.

Dual-isotope single-photon emission tomography (SPET) with indium-111 antimyosin and thallium-201 chloride was performed in 54 patients with acute myocardial infarction (AMI) to detect the location and extent of myocardial necrosis (antimyosin) and viable myocardium (201Tl). All patients underwent intravenous thrombolytic therapy with either streptokinase (1.5 million units/90 min) or tissue plasminogen activator (80 mg/90 min). Sensitivity in detecting MI was 91% (49/54 patients). With regard to dual-isotope SPET patterns, patients were divided into three groups: match, i.e. antimyosin uptake in segments with thallium defect (n = 8); mismatch, i.e. no uptake of either of the nuclides in corresponding segments (presence of perfusion abnormalities in the absence of antimyosin uptake) (n = 5); and overlap, i.e. thallium uptake in segments with uptake of antimyosin (n = 41). Coronary angiography and thallium exercise tests were performed in 40 and 45 patients, respectively, 5-14 days after MI. Exercise-induced ischaemia occurred in 66% of patients with overlap, 14% with match and 0% with mismatch (P < 0.05 for overlap vs other groups). If, however, major in-hospital complications (sudden cardiac death, severe arrhythmias; five overlap, three overlap in addition to match/mismatch, two match, two mismatch) were included in the statistical analysis, there was no significant difference between the three groups (P = NS). Thus, although the dual-isotope pattern "overlap" identifies a subgroup of patients with a substantial amount of residual viable tissue after MI and a high probability of exercise-induced ischaemia, this criterion is of limited value in assessing short-term prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Prognostic value of thallium-201 perfusion defects in idiopathic dilated cardiomyopathy.

To assess the prognostic significance of thallium-201 perfusion defects in patients with idiopathic dilated cardiomyopathy (IDC), 43 patients underwent thallium scintigraphy in addition to clinical, echocardiographic, angiographic and hemodynamic evaluation. Eleven patients had no significant thallium perfusion abnormality, 19 had multiple small defects and 13 had a large defect. During 3.2 +/- 2.2 years, 14 patients had disease-related mortality. The patients who died had a higher incidence of ventricular tachycardia (71 vs 31%; p less than 0.02), increased cardiothoracic ratio (60 +/- 6 vs 54 +/- 6; p = 0.005), decreased fractional shortening (11 +/- 6 vs 15 +/- 5; p less than 0.05), increased pulmonary wedge pressure (15 +/- 7 vs 10 +/- 6 mm Hg; p = 0.05), increased left ventricular end-diastolic pressure (21 +/- 8 vs 14 +/- 6 mm Hg; p = 0.02) and abnormal thallium perfusion defects (13 of 14 vs 16 of 26; p less than 0.05) compared with survivors. Age, gender, left ventricular end-systolic and end-diastolic dimensions, cardiac index and ejection fraction were not statistically different in the survivors versus the patients who died. Kaplan-Meier survival estimates at 1, 3 and 5 years were 100% in patients without significant perfusion abnormality; 89, 77 and 64%, respectively, in patients with multiple small defects; and 84, 76 and 30%, respectively, in patients with a large defect (p less than 0.025 by log rank test).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1991

Dipyridamole thallium scanning in the evaluation of coronary artery disease in elective abdominal aortic surgery.

Dipyridamole thallium scanning was routinely performed on 68 consecutive patients who presented for elective aortic surgery. All 68 patients were judged by clinical assessment to be at low risk for perioperative cardiac complications. In addition, 42 of 68 patients had a history of myocardial infarction, stable angina, or abnormal echocardiographic findings (group 1). Twenty-six of 68 patients did not have a history of myocardial infarction, angina, or abnormal echocardiographic findings (group 2). In group 1, 34 of 4 patients had positive results on dipyridamole thallium scanning, and 15 of these patients were found to have critical coronary artery disease on subsequent cardiac catheterization; nine underwent immediate coronary artery bypass grafting, and six had their coronary artery disease treated medically and their vascular operations cancelled. The remaining 27 patients in group 1 underwent elective operations, with six (22%) of 27 sustaining postoperative cardiac complications. None of the group 2 patients was found to have critical coronary artery disease. All patients in group 2 underwent aortic operation without cardiac complication. Routine dipyridamole thallium scanning detected a 22% (15 of 68) incidence of critical coronary artery disease overall. There was a 36% (15 of 42) incidence of critical coronary artery disease in group 1 patients vs 0% in group 2 patients (95% confidence interval, 21% to 50%). We conclude that the use of dipyridamole thallium scanning in low-risk patients for cardiac screening prior to elective aortic operations is beneficial in selected patients who have a history of myocardial infarction, angina, or abnormal echocardiographic findings, but is not necessary in patients with no history of coronary artery disease.

Aged↗
PubMed1993

Dipyridamole thallium imaging in patients being considered for vascular procedures.

We routinely performed intravenous dipyridamole thallium imaging and resting radionuclide ventriculography on 190 patients being considered for elective vascular procedures. Patients with thallium redistribution underwent coronary arteriography. Patients in group 1 (n = 78) had clinical evidence of coronary artery disease, and patients in group 2 (n = 112) had no history or electrocardiographic evidence of coronary artery disease. The frequency of thallium redistribution was not significantly different in the two groups (45% in group 1 and 46% in group 2). Coronary arteriography identified severe three-vessel or left main disease in eight patients (10%) in group 1 and 16 patients (14%) in group 2. Selection of patients for dipyridamole thallium imaging prior to vascular reconstruction should be based on whether or not documentation of the extent of coronary artery disease would influence therapy rather than on clinical indicators of coronary disease.

Aged↗
PubMed1985

Mechanism underlying the absence of ischemic changes on the exercise electrocardiogram in patients with abnormal exercise thallium-201 imaging and coronary artery disease.

Patients with coronary artery disease may have reversible abnormalities on a thallium myocardial perfusion study without simultaneous ischemic changes on the exercise electrocardiogram, but the mechanisms responsible for this disparity have not been fully elucidated. A group of 37 patients with angiographically demonstrated coronary artery disease and abnormal thallium perfusion imaging were divided into two groups on the basis of their exercise electrocardiographic ST segment response. Thirteen patients (Group A) had no significant electrocardiographic changes with exercise, while 24 patients (Group B) had ST changes consistent with ischemia during the test. There were no significant differences in clinical or angiographic characteristics between the two groups. Stress test results showed a similar mean duration of exercise in the two groups (6.2 +/- 1.8 versus 6.7 +/- 2.5 min, p = NS), but the patients in Group A achieved a significantly lower mean maximal heart rate (117 +/- 26 versus 132 +/- 21 beats/min, p less than 0.05) and mean maximal double product (19,650 +/- 5116 versus 22,650 +/- 4871, p less than 0.05). There was no consistent pattern of thallium perfusion abnormality noted in Group A to suggest that a particular region of electrically silent myocardium was responsible for ischemia in the absence of electrocardiographic changes. These results suggest that exercise thallium-electrocardiogram discordance is mediated by the level of myocardial workload achieved. An abnormal perfusion scan accompanying an exercise electrocardiogram which does not demonstrate any ischemic ST change may occur when there is sufficient increase in myocardial oxygen demand to result in differential augmentation of myocardial blood flow, but insufficient imbalance of supply and demand to result in signs of ischemia on the surface electrocardiogram.

Cardiac Catheterization↗
PubMed1986

Effect of nifedipine on dipyridamole thallium-201 myocardial scintigraphy.

The effect of a calcium antagonist drug, nifedipine, on dipyridamole thallium-201 images was assessed in 10 angina patients with positive dipyridamole test. Two dipyridamole thallium-201 tests were performed, the first in basal conditions, the second after administration of 20 mg nifedipine. After dipyridamole, heart rate and double product increased respectively from 68.0 +/- 8.2 to 94.7 +/- 11.5 beats/min (p less than 0.01) and from 9459.5 +/- 1800.2 to 12,770.0 +/- 1864.7 mmHg X beats/min (p less than 0.01). Dipyridamole when infused after nifedipine induced an increase in heart rate from 74.2 +/- 7.16 to 88.8 +/- 5.6 beats/min (p less than 0.01) and in double product from 9650.5 +/- 1348.0 to 11,399.0 +/- 1146 mmHg X beats/min (p less than 0.05). Systolic and diastolic blood pressures were unmodified during the two studies. Segment scores were comparable before and after nifedipine. Thus, nifedipine does not worsen thallium-201 myocardial images obtained during dipyridamole infusion, therefore, this test could provide an alternative to exercise thallium-201 in patients receiving calcium antagonist drugs.

Coronary Circulation↗
PubMed1986

Two-dimensional echocardiographic evaluation of ventricular asynergy induced by dipyridamole: correlation with thallium scanning.

Myocardial asynergies detected by two-dimensional echocardiography during intravenous administration of Dipyridamole (0.75 mg/kg) were evaluated in 54 patients referred for angiographic evaluation of chest pain. Technically adequate two-dimensional echocardiograms suitable for analysis were recorded in 42 of 54 (77.7%) patients studied. Thallium-201 myocardial perfusion scintigraphy, during dipyridamole test was performed in the same patients. Thirty of the 42 patients studied showed significant coronary narrowing at cardiac catheterization. Dipyridamole-induced wall motion abnormalities and myocardial perfusion defects were detected, respectively, in 19 (63.3%) and 21 (70%) of 30 patients with significant coronary artery disease. Wall by wall comparison of the distribution of dipyridamole-induced echocardiographic asynergy with reversible thallium-201 (201Tl) perfusion defects demonstrated complete correlation in 42 segments examined. Three segments with perfusion defects at thallium scanning did not show asynergy during the test while two segments showing wall motion abnormalities during dipyridamole infusion did not manifest perfusion defects. Our study demonstrates that two-dimensional echocardiography during dipyridamole testing is useful in detecting patients with coronary artery disease. Furthermore, ventricular asynergies detected during the test show a high correspondence with site of myocardial perfusion defects at thallium scanning.

Cardiac Catheterization↗