The radionuclide diagnosis of dilated cardiomyopathy: a new approach to assessing myocardial perfusion function by 201Tl scintigraphic data at rest and during the performance of the dipyridamole test]

A method for quantitative determination of the percentage of left ventricular myocardial 201Tl isotope uptake at rest and during dipyridamole test was first used in patients with dilated cardiomyopathy and coronary heart disease complicated by circulatory insufficiency or chronic myocarditis. This method makes it possible to judge the level of myocardial blood flow and perfusion reserve in these diseases. The most common differences were found between patients with coronary heart disease and those with chronic myocarditis. The patients with chronic myocarditis exhibited the greatest sizes of perfusion defects, highest values of 201Tl uptake at rest and a lower myocardial perfusion reserve during dipyridamole test. In response to exercise, most patients with chronic myocarditis had diminished perfusion defects, whereas those with coronary heart disease displayed increased defects. The myocardial perfusion was varied in patients with dilated cardiomyopathy. Some patients had a scintigraphic pattern close to that in patients with chronic myocarditis and others had a pattern identical to that in patients with coronary heart disease.     

Functional significance of myocardial perfusion defects induced by dipyridamole using thallium-201 single-photon emission computed tomography and two-dimensional echocardiography

The mechanisms responsible for inhomogeneous myocardial blood flow after oral administration of a large dose (300 mg) of dipyridamole were assessed in 27 patients with serial thallium-201 single-photon emission computed tomography (SPECT) and simultaneous 2-dimensional echocardiograms. Myocardial tomographic images were obtained 50 minutes and 3 to 4 hours after administration of dipyridamole. Two-dimensional echocardiograms were recorded at baseline and then every 15 minutes for 60 minutes. Dipyridamole caused only a mild reduction in blood pressure (from 129 +/- 18 to 126 +/- 16 mm Hg) and a mild increase in heart rate (from 69 +/- 15 to 73 +/- 4 beats/min). Sixteen patients had perfusion defects after dipyridamole by SPECT, which underwent partial or total filling-in. Fourteen of these patients (87.5%) had either a new abnormality or further deterioration of a preexisting wall motion abnormality by 2-dimensional echocardiography, and thus were considered to have developed transient ischemia during dipyridamole administration. Ten of 11 patients (91%) with normal perfusion or fixed defects by SPECT had no further deterioration in wall motion after oral dipyridamole, and were thus considered to have no evidence of myocardial ischemia. In conclusion, most patients with transient thallium-201 defects after dipyridamole develop transient worsening of resting wall motion by 2-dimensional echocardiography, suggestive of true myocardial ischemia. Because myocardial oxygen demand, as indicated by the heart rate-blood pressure product, did not change significantly, the mechanism of myocardial ischemia in these patients is likely to be diminished regional blood flow related to a "subendocardial steal" induced by dipyridamole.     

Resting echocardiography and quantitative dipyridamole technetium-99m sestamibi tomography in the identification of cardiac allograft vasculopathy and the prediction of long-term prognosis after heart transplantation.

AIMS: To evaluate the accuracy of echocardiography in conjunction with quantitative high-dose dipyridamole technetium-99m sestamibi tomography (SPECT) in detecting coronary allograft vasculopathy. METHODS AND RESULTS: Seventy-eight consecutive heart transplant recipients underwent echocardiography while at rest and high-dose dipyridamole SPECT within 48 h of a yearly angiogram. Resting wall motion abnormalities were considered significant if present in two or more segments. SPECT was considered abnormal in the presence of reversible/fixed defects. The coronary angiogram was normal in 53, showed non-significant coronary allograft vasculopathy in 13 and significant (> or = 50% stenosis) coronary allograft vasculopathy in 12 cases. Resting wall motion abnormalities were observed in nine cases and perfusion defects in 20. Echocardiography and SPECT were concordant in 59 cases (five positive and 54 negative); in these, accuracy was 100% for significant coronary allograft vasculopathy and 83% for any coronary allograft vasculopathy. Over 6.5+/-2 years, 17 patients suffered coronary allograft vasculopathy-related events, including death in six and retransplantation in three. Resting wall motion abnormalities, SPECT perfusion defects and angiographic coronary allograft vasculopathy were significant predictors of cardiac events. CONCLUSION: Normal resting wall motion at echocardiography coupled to normal stress myocardial perfusion, rules out the presence of significant coronary allograft vasculopathy in many heart transplant recipients. Conversely, resting wall motion abnormalities and perfusion defects strongly predict cardiac events. Therefore, a strategy which reserves angiography for patients with resting wall motion abnormalities and/or perfusion defects may be safe and cost-effective.     

Dipyridamole stress thallium perfusion scan for evaluating myocardial involvement in systemic sclerosis

To evaluate the usefulness of a dipyridamole stress thallium-201 (Tl-201) perfusion scan in detecting myocardial involvement in systemic sclerosis we performed Tl-201 scans, electrocardiograms (ECG), and echocardiograms (UCG) on 24 patients with systemic sclerosis (11 diffuse type, 13 limited type) sequentially selected randomly over an 8-month period, and compared the findings. Cardiac catheterization, coronary angiography (CAG), and right ventricular endomyocardial biopsy were performed as necessary. Of the 24 patients, Tl-201 scans revealed fixed defects (FDs; myocardial fibrosis) and/or reversible defects (RDs; myocardial ischemia) in nine patients, whereas ECG and UCG revealed defects in four and three patients, respectively. Biopsy specimens obtained from the three patients with FDs also showed both ECG and UCG abnormalities indicative of myocardial fibrosis despite their normal appearance with CAG. Autopsy findings on the heart of a patient who died of acute heart failure showed myocardial fibrosis predominantly in the left anteroposterior wall. This was consistent with the FDs area detected using the Tl-201 perfusion scan. In a patient with chronic heart failure, left ventriculography showed a decrease in the anterior wall motion of the left ventricle which coincided with the FDs area in the Tl-201 perfusion scan. In conclusion, dipyridamole stress Tl-201 scanning is useful for evaluating myocardial involvement in systemic sclerosis. Received: September 21, 2000 / Accepted: February 26, 2001     

Reversibility by dipyridamole of thallium-201 myocardial scan defects in patients with sarcoidosis

PURPOSE: In order to clarify the significance of anginal pain and myocardial thallium-201 scan defects in cardiac sarcoidosis, the pharmacologic effect of dipyridamole on myocardial perfusion was assessed by planar thallium-201 myocardial scintigraphy in patients with sarcoidosis. PATIENTS and METHODS: Thallium-201 myocardial scintigraphy was performed at rest and after 0.56 mg/kg intravenous dipyridamole during four minutes in 16 patients with sarcoidosis. The myocardial scan (45-degree and 70-degree left anterior oblique, and anterior views) was divided into 15 segments. Results were evaluated by the number of segmental defects and with a global perfusion score (from 0 to 60) by a semi-quantitative index depending on the size and severity of myocardial thallium-201 defects. RESULTS: Thirteen of the 16 patients showed partial or total reversion of their thallium-201 defects on redistribution scanning either at rest or after dipyridamole. The mean (+/- SD) number of myocardial perfusion defects that were present in all the patients decreased from 5.31 +/- 1.78 at rest to 3.25 +/- 2.52 after redistribution (p less than 0.001) and to 2.19 +/- 2.10 after dipyridamole (p less than 0.001). The mean global perfusion score increased from 53.2 +/- 3.0 at rest to 56.2 +/- 2.9 after redistribution (p less than 0.001) and to 57.2 +/- 2.7 after dipyridamole (p less than 0.001). A significant correlation (r = 0.82, p less than 0.001) was found between the increase of global perfusion score on redistribution and after dipyridamole. CONCLUSION: The reversibility of myocardial scan defects is a common finding in sarcoidosis. It makes unlikely the role of scar fibrosis or extensive confluent granulomas as a mechanism for such defects. The effect of dipyridamole suggests the presence of reversible disorders lying at the coronary microvascular level.     

Dipyridamole magnetic resonance imaging: a comparison with thallium-201 emission tomography.

Limitation of space and motion artefact make magnetic resonance imaging during dynamic exercise difficult. Pharmacological stress with dipyridamole can be used as an alternative to exercise for thallium scanning. Forty patients with a history of angina and an abnormal exercise electrocardiogram were studied by dipyridamole thallium myocardial perfusion tomography and dipyridamole magnetic resonance wall motion imaging with a cine gradient refocused sequence. Images for both scans were obtained in the oblique horizontal and vertical long axis and short axis planes before and after pharmacological stress with dipyridamole. The myocardium was divided into nine segments for direct comparison of perfusion with wall motion. Segments were assessed visually into grades--normal, hypokinesis or reduced perfusion, and akinesis or very reduced perfusion. After dipyridamole there were reversible wall motion abnormalities in 24 (62%) of 39 patients with coronary artery disease and 24 (67%) of 36 patients with reversible thallium defects. The site of wall motion deterioration was always the site of a reversible thallium defect. Thallium defects affecting more than two segments were always associated with wall motion deterioration but most single segment thallium defects were undetected by magnetic resonance imaging. There was a significant correlation between detection of wall motion abnormality, the angiographic severity of coronary artery disease, and the induction of chest pain by dipyridamole. There were no significant differences in ventricular volume or ejection fraction changes after dipyridamole between the groups with and without detectable reversible wall motion changes but the normalised magnetic resonance signal intensity of the abnormally moving segments was significantly less than the signal intensity of the normal segments. In nine patients the change was apparent visually and it was maximal in the subendocardial region. Magnetic resonance imaging of reversible wall motion abnormalities in patients with coronary artery disease is feasible during pharmacological stress with dipyridamole and may be associated with a reduced magnetic resonance signal. The failure to show wall motion abnormalities in all cases of reversible thallium defects may be because the defect was small or because dipyridamole caused perfusion defects in the absence of myocardial ischaemia.     

Dipyridamole magnetic resonance imaging: a comparison with thallium-201 emission tomography

Limitation of space and motion artefact make magnetic resonance imaging during dynamic exercise difficult. Pharmacological stress with dipyridamole can be used as an alternative to exercise for thallium scanning. Forty patients with a history of angina and an abnormal exercise electrocardiogram were studied by dipyridamole thallium myocardial perfusion tomography and dipyridamole magnetic resonance wall motion imaging with a cine gradient refocused sequence. Images for both scans were obtained in the oblique horizontal and vertical long axis and short axis planes before and after pharmacological stress with dipyridamole. The myocardium was divided into nine segments for direct comparison of perfusion with wall motion. Segments were assessed visually into grades--normal, hypokinesis or reduced perfusion, and akinesis or very reduced perfusion. After dipyridamole there were reversible wall motion abnormalities in 24 (62%) of 39 patients with coronary artery disease and 24 (67%) of 36 patients with reversible thallium defects. The site of wall motion deterioration was always the site of a reversible thallium defect. Thallium defects affecting more than two segments were always associated with wall motion deterioration but most single segment thallium defects were undetected by magnetic resonance imaging. There was a significant correlation between detection of wall motion abnormality, the angiographic severity of coronary artery disease, and the induction of chest pain by dipyridamole. There were no significant differences in ventricular volume or ejection fraction changes after dipyridamole between the groups with and without detectable reversible wall motion changes but the normalised magnetic resonance signal intensity of the abnormally moving segments was significantly less than the signal intensity of the normal segments. In nine patients the change was apparent visually and it was maximal in the subendocardial region. Magnetic resonance imaging of reversible wall motion abnormalities in patients with coronary artery disease is feasible during pharmacological stress with dipyridamole and may be associated with a reduced magnetic resonance signal. The failure to show wall motion abnormalities in all cases of reversible thallium defects may be because the defect was small or because dipyridamole caused perfusion defects in the absence of myocardial ischaemia.     

Abnormal nondefect zone myocardial thallium washout ratio in patients with reversible thallium defects and normal coronary arteriograms.

Thallium myocardial defects in patients with no angiographic coronary artery stenosis have been attributed to attenuation effects and other artifacts. Of 323 patients having thallium myocardial imaging following dipyridamole infusion, 10 of 159 patients with a segmental perfusion abnormality were found to have no luminal diameter stenosis greater than 20% on coronary angiography and no electrocardiographic (ECG) evidence of myocardial infarction or left bundle branch block. A time-standardized regional thallium washout ratio was calculated as thallium myocardial counts with dipyridamole to counts without dipyridamole. In comparison to 10 age-matched control patients with no evidence of cardiac disease and no myocardial thallium defect, study patients had a lower regional myocardial thallium washout ratio from both the defect and nondefect (1.57 +/- 0.40 versus 2.27 +/- 0.92, p = 0.041) zones. Nine of the 10 study patients had independent evidence of noncoronary heart disease, including echocardiographic or ECG evidence of left ventricular hypertrophy in six patients. In patients with thallium defects and normal coronary arteriograms, a time-standardized regional thallium myocardial washout ratio for the nondefect zone may aid in the differentiation of patients with noncoronary heart disease from those with soft tissue artifacts.     

Noninvasive tests for risk stratification in major vascular surgery

BACKGROUND: The predictive values of noninvasive tests versus perioperative cardiac events in patients undergoing major vascular surgery has not been definitively established. PATIENTS AND METHODS: According to clinical markers and left ventricular function at rest, 188 patients were assigned to the following groups: 40 low, 115 moderate and 33 high risk. They were then randomly submitted to dipyridamole (n = 64), dobutamine (n = 63) stress echocardiography and dipyridamole perfusion scintigraphy (n = 61). RESULTS: No events were observed in low-risk patients, whereas 12 (10.4%) and 8 (24%) events in moderate- and high-risk categories occurred, respectively. Only the high-risk category, as a predictive variable, was significantly related to the onset of cardiac complications (p < 0.05). A positive dipyridamole/dobutamine stress test was related to cardiac events, but multivariate analysis showed that only severity and extent of ischemia were the best predictors of events (p < 0.01 for dipyridamole and p < 0.005 for dobutamine). The presence of reversible, but not fixed, perfusion defects at scintigraphy was significantly related to perioperative events; at multivariate analysis, only > 3 reversible perfusion defects represented a strong predictor of events (p < 0.05). CONCLUSIONS: Among subjects undergoing major vascular surgery, severity and extent of ischemia during dipyridamole/dobutamine stress echocardiography and presence of > 3 reversible perfusion defects are strong predictors of cardiac events, particularly in moderate-risk category of patients.     

Dipyridamole stress thallium perfusion scan for evaluating myocardial involvement in systemic sclerosis

Abstract

To evaluate the usefulness of a dipyridamole stress thallium-201 (Tl-201) perfusion scan in detecting myocardial involvement in systemic sclerosis we performed Tl-201 scans, electrocardiograms (ECG), and echocardiograms (UCG) on 24 patients with systemic sclerosis (11 diffuse type, 13 limited type) sequentially selected randomly over an 8-month period, and compared the findings. Cardiac catheterization, coronary angiography (CAG), and right ventricular endomyocardial biopsy were performed as necessary. Of the 24 patients, Tl-201 scans revealed fixed defects (FDs; myocardial fibrosis) and/or reversible defects (RDs; myocardial ischemia) in nine patients, whereas ECG and UCG revealed defects in four and three patients, respectively. Biopsy specimens obtained from the three patients with FDs also showed both ECG and UCG abnormalities indicative of myocardial fibrosis despite their normal appearance with CAG. Autopsy findings on the heart of a patient who died of acute heart failure showed myocardial fibrosis predominantly in the left anteroposterior wall. This was consistent with the FDs area detected using the Tl-201 perfusion scan. In a patient with chronic heart failure, left ventriculography showed a decrease in the anterior wall motion of the left ventricle which coincided with the FDs area in the Tl-201 perfusion scan. In conclusion, dipyridamole stress Tl-201 scanning is useful for evaluating myocardial involvement in systemic sclerosis.     

Thallium-201 scintigraphy perfusion defect with dipyridamole in a patient with a myocardial bridge

A patient with myocardial bridging and a thallium-201 scintigraphy perfusion defect after the administration of intravenous dipyridamole is presented. The same patient had a normal perfusion study on exercise stress testing. The effects of coronary vasodilators and dipyridamole on coronary artery flow patterns in patients with myocardial bridging are discussed. We suggest that coronary vasodilators may induce perfusion defects in patients with myocardial bridging and should be avoided in such patients.     

Treadmill exercise produces larger perfusion defects than dipyridamole stress N-13 ammonia positron emission tomography.

OBJECTIVES: The aim of this study was to compare treadmill exercise (TEX) and dipyridamole stress on the uptake and retention of N-13 ammonia. BACKGROUND: Size and severity of stress-induced myocardial perfusion defects are clinically important. Because ammonia uptake and retention seems to be related to perfusion, viability, and metabolism, exercise stress might induce larger perfusion defects than dipyridamole stress. METHODS: Twenty-six patients underwent TEX and dipyridamole stress N-13 ammonia positron emission tomography (PET). Images were assessed with a 17-segment model and a five-point score. Summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated. Left ventricular (LV) defect sizes were measured quantitatively with a 70% threshold for abnormal perfusion. RESULTS: Compared with dipyridamole stress, TEX yielded larger SSS (9.1 +/- 5.7 vs. 6.9 +/- 5.9; p < 0.01), SDS (5.8 +/- 4.7 vs. 3.7 +/- 4.6; p < 0.02), and percentage of LV stress defect (19.3 +/- 11.5% vs. 13.8 +/- 13.6%; p < 0.02). CONCLUSIONS: In patients achieving adequate exercise, TEX N-13 ammonia PET myocardial perfusion imaging (MPI) yields larger stress perfusion defects than dipyridamole stress and might reflect the true myocardial ischemic burden. Treadmill exercise might be the preferred method of stress for routine N-13 ammonia PET MPI.     

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.     

Effect of maintenance oral theophylline on dipyridamole-thallium-201 myocardial imaging using SPECT and dipyridamole-induced hemodynamic changes

To evaluate the effect of maintenance oral theophylline therapy on the diagnostic efficacy of dipyridamole-thallium-201 single photon emission computed tomography (SPECT) imaging for coronary artery disease, dipyridamole-thallium-201 SPECT imaging was performed in eight men with documented coronary artery disease before initiation of theophylline treatment and repeated while these patients were receiving therapeutic doses of oral theophylline. Before theophylline treatment, intravenous dipyridamole caused a significant increase in heart rate, decrease in blood pressure, angina in seven of eight patients, and ST segment depression in four of eight patients. While they were being treated with theophylline, none of the patients had angina or ST segment depression, and there were no hemodynamic changes with intravenous dipyridamole. Before theophylline treatment, dipyridamole-thallium-201 SPECT imaging showed reversible perfusion defects in myocardial segments supplied by stenotic coronary arteries. With theophylline treatment, dipyridamole-thallium-201 SPECT showed total absence of reversible perfusion defects. Treatment with theophylline markedly reduced the diagnostic accuracy of dipyridamole-thallium-201 imaging for coronary artery disease.     

Thallium-201 perfusion imaging with atrial pacing or dipyridamole stress testing for evaluation of cardiac risk prior to nonvascular surgery

Preoperative assessment of cardiac risk using thallium-201 scintigraphy and atrial pacing (n=42) or dipyridamole stress testing (n=35) was performed in 77 patients (mean age 65±7 years), who subsequently underwent elective nonvascular surgery. All patients were at low cardiac risk by clinical criteria; none could perform exercise stress testing due to physical limitations. ST depression consistent with ischemia occurred in 11 patients during atrial pacing and in 1 patient during dipyridamole stress testing (p<0.01). Nine patients had reversible perfusion defects with atrial pacing, and 10 patients with dipyridamole stress testing; fixed defects were present in 15 and 8 patients, respectively. Only one patient (fixed perfusion defect with atrial pacing, left main disease on coronary angiography) underwent preoperative coronary revascularization. Two patients subsequently had postoperative cardiac events. One patient (reversible perfusion defect with dipyridamole stress testing) experienced sudden death after a nonvascular procedure, while a second patient (normal thallium images with dipyridamole testing) had a nonfatal myocardial infarction. In patients having atrial pacing or dipyridamole stress testing, thallium-201 scans that are normal or show only a fixed perfusion defect confirm a low risk of cardiac complications following nonvascular surgery. The presence of a reversible perfusion defect does not preclude a postoperative course free of cardiac complications in patients at low cardiac risk by clinical criteria.     

Larger perfusion defects with exercise compared with dipyridamole SPECT (exercise-dipyridamole mismatch) may reflect differences in epicardial and microvascular coronary dysfunction: when the stressor matters.

BACKGROUND: Previous studies have reported larger myocardial perfusion defects with exercise as compared with dipyridamole. The aim of this study was to assess the hypothesis that this mismatch may reflect differences in epicardial and microvascular coronary vasomotor function. METHODS AND RESULTS: The response to intracoronary acetylcholine, nitroglycerin, and adenosine was studied in 36 patients with suspected angina and normal or near-normal coronary angiography findings who underwent both exercise and dipyridamole perfusion imaging. Of the patients, 27 (75%) had reversible defects with exercise (group I) and 9 had normal scans or nonreversible defects (group II). Repeated imaging with dipyridamole showed significant improvement or disappearance of perfusion defects in group I patients. The mean summed difference score (SDS) decreased from 5.52 +/- 3.19 with exercise to 1.11 +/- 1.60 with dipyridamole (P = .0001) in group I and did not change in group II. An abnormal epicardial response to acetylcholine, reflecting endothelial dysfunction, occurred in 93% of group I patients compared with only 33% of group II patients (chi(2) = 9.46, P = .002) and was significantly related to exercise SDS (r = 0.49, P = .002) but not to dipyridamole SDS. By contrast, most patients showed normal epicardial and microvascular responses to the mainly non-endothelium-dependent vasodilators nitroglycerin and adenosine with no differences in coronary flow reserve between groups (2.91 +/- 0.72 vs 2.98 +/- 0.52, P = .79). CONCLUSIONS: Exercise-dipyridamole perfusion mismatch may reflect differences in epicardial endothelial and microvascular dysfunction.     

Relationship of thallium-201 defect and left ventricular function after dipyridamole infusion

Tl-201 imaging and first-pass radionuclide ventriculography (RNV) by 4 min infusion of 0.56 mg/kg dipyridamole were performed on 22 patients with coronary artery disease in order to know the relationship of myocardial perfusion and left ventricular function after dipyridamole-infusion, and thereby to define whether Tl-201 defect with dipyridamole could imply myocardial ischemia. Initial and delayed Tl-201 images were divided into anterior, apical, and infero-posterior segments, and segmental perfusion defects were categorized as reversible, fixed and no defect. RNV on the 30-degree right anterior oblique view was also divided into anterior, apical, and infero-posterior wall to be evaluated for regional wall motion by a 5 point score before and after dipyridamole. Changes in left ventricular ejection fraction (LVEF) with dipyridamole were also calculated. Normal responses of regional wall motion and LVEF to dipyridamole were established from the data of 14 normal subjects. Reversible defects were closely associated (69%) with an abnormal response of regional wall motion (score decrease of 1 or more after dipyridamole). Both fixed defects and no defects showed little association with abnormal response of regional wall motion. Moreover, 77% of the patients having reversible-defect segment showed an abnormal response of LVEF (reduction of 3% or more following dipyridamole). However, patients without reversible defect did not show an abnormal response to dipyridamole. These results suggest that dipyridamole-induced Tl-201 defects represent a myocardial ischemia which causes a reduction of ventricular function.     

Myocardial perfusion in patients with permanent ventricular pacing and normal coronary arteries

OBJECTIVES: The purposes of this study were to test the specificity of dipyridamole myocardial perfusion scintigraphy in patients with permanent ventricular pacing (PVP) and to evaluate coronary blood flow and reserve in these patients. BACKGROUND: Permanent ventricular pacing is associated with exercise perfusion defects on myocardial scintigraphy in the absence of coronary artery disease (CAD). On the basis of studies in patients with left bundle brunch block, coronary vasodilation with dipyridamole has been proposed as an alternative to exercise testing for detecting CAD in paced patients, but this approach has never been tested. METHODS: Fourteen patients with a PVP and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In these patients and in eight control subjects, coronary flow velocities were measured in the left anterior descending coronary artery (LAD) and in the dominant coronary artery before and after adenosine administration. RESULTS: In the paced patients, coronary flow velocities in the LAD and in the dominant coronary artery were significantly lower than those in the control subjects. In addition, seven patients showed perfusion defects on dipyridamole thallium-201 single-photon emission computed tomography, with a specificity of 50% for this test. The defect-related artery in these patients had lower coronary flow reserve (2.6 +/- 0.5) as compared with those without perfusion defects (3.9 +/- 1.0, p < 0.05) or the control group (3.5 +/- 0.5, p < 0.05). CONCLUSIONS: Permanent ventricular pacing is associated with alterations in regional myocardial perfusion. Furthermore, abnormalities of microvascular flow, as indicated by reduced coronary flow reserve in the defect-related artery, are at least partially responsible for the uncertain specificity of dipyridamole myocardial perfusion scintigraphy.     

Association of ventricular ectopy with nuclear scintigraphic perfusion defects during dipyridamole stress testing

Background and hypothesis: No information is available regarding the significance of ventricular ectopic activity induced during dipyridamole nuclear scintigraphic stress testing. This study tested the hypothesis that dipyridamole-induced ventricular ectopy predicts a thallium-201 or technetium-99m sestamibi perfusion defect. Methods: A group of 186 consecutive patients with premature ventricular contractions and/or couplets occurring during dipyridamole stress testing (ventricular tachycardia did not occur) was compared with a control group of 194 patients without ventricular ectopy during dipyridamole stress testing. Results: The results indicated that ventricular ectopy induced during dipyridamole infusion occurred more frequently in patients demonstrating either a fixed or reversible perfusion defect on scintigraphic imaging (p <0.01). The higher frequency of perfusion defects in this group of patients was attributable to a higher frequency of “fixed” compared with “reversible” defects (p<0.05). This finding is consistent with the additional observation that ventricular ectopy induced by dipyridamole was associated with the presence of Q waves on the resting ECG (p<0.05). The positive and negative predictive values of the presence of ventricular ectopy in predicting a fixed myocardial perfusion defect were 59 and 54%, respectively. Conclusions: Ventricular ectopy induced during dipyridamole infusion suggests the presence of a fixed myocardial perfusion defect.     

Pharmacodynamic effect of dipyridamole on thallium-201 myocardial perfusion in progressive systemic sclerosis with diffuse scleroderma.

We evaluated the effect of dipyridamole on thallium-201 myocardial perfusion in 23 patients with progressive systemic sclerosis (PSS) with diffuse scleroderma. Thallium-201 single photon emission computed tomography (SPECT) was performed at rest and after coronary artery vasodilatation with intravenous dipyridamole (0.14 mg/kg/min for four minutes). The left myocardium was divided into nine segments; each segment was graded as 2.0, 1.5, 1.0, 0.5, 0 (zero represents no activity). Dipyridamole significantly improved resting thallium-201 myocardial perfusion: the mean (SD) number of segments with thallium defects decreased from 6.0 (2.1) at rest to 4.1 (2.5) after dipyridamole (p less than 0.0001); the mean (SD) score in segments with resting defects increased from 0.92 (0.24) at rest to 1.13 (0.38) after dipyridamole (p less than 0.0001); the mean (SD) global score per patient increased from 10.2 (1.8) at rest to 11.4 (2.1) after dipyridamole (p less than 0.02); the global score increased by at least 2.0 in 12 patients and worsened by at least 2.0 in three patients only (p = 0.05). The results of this acute study suggest that some drugs with potent vasodilator activity on small coronary arteries may be beneficial in the treatment of PSS patients with thallium-201 myocardial perfusion abnormalities.