Dipyridamole cardiac imaging

Regadenoson versus dipyridamole: Evaluation of stress myocardial blood flow response on a CZT-SPECT camera

BACKGROUND

Regadenoson is a selective adenosine receptor agonist. It is currently unclear if the level of hyperemia differs between stress agents. We compared Myocardial Blood Flow (MBF) and Myocardial Flow Reserve (MFR) response on CZT-SPECT Myocardial Perfusion Imaging (MPI) to evaluate if dipyridamole and regadenoson could induce the same level of hyperemia.

METHODS

228 patients with dynamic CZT-SPECT MPI were retrospectively analyzed (66 patients stressed with regadenoson and 162 with dipyridamole) in terms of MBF and MFR. To rule out confounding factors, two groups of 41 patients were matched for clinical characteristics in a sub-analysis, excluding high cardiovascular risk patients.

RESULTS

Overall stress MBF was higher in regadenoson patients (1.71 ± 0.73 vs. 1.44 ± 0.55 mL·min-1·g-1 for regadenoson and dipyridamole, respectively, p < .05). However, when confounding factors were ruled out, stress MBF (1.57 ± 0.56 vs. 1.61 ± 0.62 mL·min-1·g-1 for dipyridamole and regadenoson, respectively, p = .88) and MFR (2.62 ± 0.77 vs. 2.46 ± 0.76 for dipyridamole and regadenoson, respectively, p = .40) were not different between regadenoson and dipyridamole.

CONCLUSIONS

Our results suggest that dipyridamole and regadenoson induce equivalent hyperemia in dynamic SPECT with similar stress MBF and MFR in comparable patients.

Metal–organic framework derived metal oxide/reduced graphene oxide nanocomposite, a new tool for the determination of dipyridamole

NICo₂O₄/NIO@MOF-5 rGO can detect dipyridamole at trace levels with high selectivity and sensitivity.

Role of Pretransplant Arteriography in Diabetic End-Stage Renal Disease

Diabetic renal transplant candidates have a high prevalence of obstructive coronary artery disease that is a major cause of morbidity and mortality. This study sought to stratify the risk for renal transplantation by correlating noninvasive tests with arteriographic findings. Fifty-two diabetics (46 males, 6 females) with end-stage renal disease were evaluated noninvasively and by coronary arteriography. The mean age was 46 ± 6 years. Twenty-five patients (48%) had noninvasive evidence of coronary artery disease (angina in 10, old myocardial infarction on electrocardiogram in 6, ST-T changes in 8, regional wall motion abnormality on echocardiography in 8, positive dobutamine echocardiogram in 4, and positive dipyridamole thallium tests in 13). Obstructive coronary artery disease was demonstrated by arteriography in 27 (51.9%). Concordance between noninvasive findings and arteriography was 65.3%. Obstructive coronary disease was present in 66.7% of those with 2 noninvasive indications, in all with more than 2 indications, and in all cases of regional wall motion abnormality. Thus, more than 2 positive noninvasive parameters or wall motion abnormality on an echocardiogram were highly predictive of coronary disease.

The early identification of psychosis: can lessons be learnt from cardiac stress testing?

Psychotic disorders including schizophrenia are amongst the most debilitating psychiatric disorders. There is an urgent need to develop methods to identify individuals at risk with greater precision and as early as possible. At present, a prerequisite for a diagnosis of schizophrenia is the occurrence of a psychotic episode. Therefore, attempting to detect schizophrenia on the basis of psychosis is analogous to diagnosing coronary artery disease (CAD) after the occurrence of a myocardial infarction (MI). The introduction of cardiac stress testing (CST) has revolutionized the detection of CAD and the prevention and management of angina and MI. In this paper, we attempt to apply lessons learnt from CST to the early detection of psychosis by proposing the development of an analogous psychosis stress test. We discuss in detail the various parameters of a proposed psychosis stress test including the choice of a suitable psychological or psychopharmacological "stressor," target population, outcome measures, safety of the approach, and the necessary evolution of test to become clinically informative. The history of evolution of CST may guide the development of a similar approach for the detection and management of psychotic disorders. The initial development of a test to unmask latent risk for schizophrenia will require the selection of a suitable and safe stimulus and the development of outcome measures as a prelude to testing in populations with a range of risk to determine predictive value. The use of CST in CAD offers the intriguing possibility that a similar approach may be applied to the detection and management of schizophrenia.

Experience of low-dose aminophylline use to relieve minor adverse effects of dipyridamole in patients undergoing stress myocardial perfusion imaging

BACKGROUND

Intravenous administration of aminophylline is widely adopted to reverse dipyridamole-related adverse effects (AEs) during stress myocardial perfusion imaging (MPI). The study aimed to investigate the efficacy of lower-dose aminophylline to relieve minor AEs.

METHODS

2,250 consecutive patients undergoing dipyridamole-stressed MPI were enrolled. Information concerning AE occurrence and dosages of aminophylline was collected to evaluate the efficacy of lower-dose aminophylline. A logistic regression was used to determine independent predictors of dipyridamole-related AE occurrence.

RESULTS

No severe AE was noted. Overall mild AE incidence was 37.0% (833/2,250 patients). Initial low-dose (25 mg) aminophylline relieved symptoms in 98.8% of patients with mild AEs (823/833 patients). An extra 25 mg aminophylline sufficed to reverse all such AEs. Mean body mass index (BMI) differed significantly between patients with and without any AE [25.6 vs 25.1 (P = .009)]. There was no significant difference between two subgroups in mean age, male gender prevalence, body height and weight, dipyridamole dose/BMI, or prevalence of significant perfusion defect(s) on MPI. Multivariable logistic regression demonstrated BMI remained the independent predictor of dipyridamole-related AE occurrence (odds ratio 1.028, 95% confidence interval 1.007-1.049, P = .01).

CONCLUSION

Low-dose (≦50 mg, and usually 25 mg) aminophylline seems sufficient to relieve mild dipyridamole-related AEs during stress MPI.

Incidence of caffeine in serum of patients undergoing dipyridamole myocardial perfusion stress test by an intensive versus routine caffeine history screening

The coronary vasodilatory effect of dipyridamole is competitively blocked by caffeine. The purposes of this study were to (1) assess the incidence of having detectable serum caffeine and (2) evaluate whether an intensive caffeine history screening strategy was superior to routine history screening before dipyridamole myocardial perfusion imaging. One hundred ninety-four patients who were randomized to an intensive or a routine screening history strategy were prospectively evaluated. Serum caffeine levels were determined in all patients. Outcomes data, including death, nonfatal myocardial infarction, and history of revascularization, were obtained at 24 months. Nearly 1 in 5 patients (19%) who screened negative by history had detectable serum caffeine. In patients who screened negative by history, there was no statistically significant difference in the percentage of caffeine seropositivity between the intensive and routine arms (16% vs 22%, respectively, p = 0.31). The incidence of combined end points of death, myocardial infarction, or revascularization was 22.9% and 7.3% in patients with and without detectable serum caffeine, respectively (p = 0.01). In conclusion, despite initial negative results on screening by history, a considerably high percentage of patients had positive serum caffeine levels. These results do not support the use of an intensive screening strategy. Detectable serum caffeine was associated with a higher incidence of adverse outcomes.

Reproducibility in echocardiographic assessment of the left ventricular global and regional function, the HUNT study

AIMS

The study aimed to compare the inter-observer reproducibility of new and traditional measurements of the left ventricular (LV) global and regional function.

METHODS AND RESULTS

Two experienced echocardiographers performed 20 complete echo/Doppler examinations and 50 analyses on ten healthy subjects. All recordings were analysed for systolic and diastolic conventional and deformation measurements by both echocardiographers. Inter-observer mean error (absolute difference divided by the mean) was 4% and lowest (P = 0.001) for systolic M-mode annulus excursion. Mean error for the regional deformation indices was significantly higher than for all the global measurements (all P < 0.001). Mean error for analyses of the same recording was 34% (P = 0.002) lower for global systolic indices and 44% (P < 0.001) lower for global diastolic indices than inter-observer mean error for analyses made in separate recordings.

CONCLUSION

Systolic M-mode annulus excursion showed better inter-observer reproducibility than other traditional and newer measurements of LV systolic and diastolic function. Repeated analyses of the same recordings underestimate the more clinically relevant inter-observer reproducibility by approximately 40% for most measurements of LV function.

Reduced heart rate response to dipyridamole as a marker of left ventricular dysfunction in diabetic patients undergoing myocardial perfusion scintigraphy

PURPOSE OF THE REPORT

This study sought to find among clinical, hemodynamic and left ventricular perfusion and function data obtained from myocardial perfusion scintigraphy (MPS), those associated with a reduced heart rate (HR) response to dipyridamole in diabetic patients. This phenomenon, although previously described as a marker of autonomic dysfunction in patients with diabetes, has not been fully elucidated.

MATERIALS AND METHODS

One hundred two consecutive diabetic patients undergoing dual-isotope (rest Tl-201/dipyridamole stress Tc-99m tetrofosmin) MPS were prospectively enrolled. A reduced HR response to dipyridamole was considered present if the ratio between maximal HR after dipyridamole infusion and rest HR was <or=1.20. MPS images were interpreted semiquantitatively, and perfusion scores were calculated. Left ventricular ejection fraction (LVEF) was automatically obtained. A logistic regression analysis was used to find variables independently associated with a reduced HR response to dipyridamole.

RESULTS

A reduced HR response to dipyridamole was found in 46.1% of the patients and was associated with the presence of chronic renal failure (chi2 = 6.4), with high baseline HR (chi2 = 4.7) and low poststress LVEF (chi2 = 10.6).

CONCLUSIONS

Attenuation of the HR response to dipyridamole was frequent and was strongly associated with reduced LVEF. Autonomic dysfunction may be reflected in the higher baseline HR but should not be considered the sole mechanism accounting for the reduction in HR response to dipyridamole in patients with diabetes.

Influence of chronic renal failure on the heart rate response to dipyridamole in patients undergoing myocardial perfusion SPECT

BACKGROUND

Dipyridamole promotes a reduction in blood pressure and an increase in heart rate (HR), considered the normal hemodynamic response to the drug. Data suggest that patients with chronic renal failure (CRF) have an attenuation of this hemodynamic response. This study sought to evaluate the HR response to dipyridamole and its determinants in patients with or without CRF undergoing gated myocardial perfusion single photon emission computed tomography.

METHODS AND RESULTS

Consecutive patients (n = 355, 9.6% with CRF) undergoing rest/dipyridamole myocardial perfusion single photon emission computed tomography were evaluated. The HR response to dipyridamole was considered to be reduced if the HR ratio (maximal HR/rest HR) was 1.20 or less. A logistic regression analysis determined independent predictors of a blunted HR response. A reduced HR response was found in 84.4% of patients with CRF and 40.6% of those without CRF (P < .0001). In patients without CRF the independent predictors of abnormal HR response were hypertension, rest and differential perfusion scores, and left ventricular ejection fraction. In contrast, in CRF patients there was no significant association of any of the studied variables with abnormal HR response.

CONCLUSIONS

An abnormal HR response to dipyridamole is frequently found in patients with CRF. Different mechanisms may account for abnormal HR response in patients with or without CRF.

Prognostic value of I-123 15-(p-iodophenyl)-3-(R,S) methylpentadecanoic acid myocardial imaging in patients with known or suspected coronary artery disease

BACKGROUND

Although iodine 123 15-(p-iodophenyl)-3-(R , S) methylpentadecanoic acid (BMIPP) can assess abnormal utilization of fatty acid in the diseased myocardium, the prognostic value of BMIPP imaging at rest in patients with known or suspected coronary artery disease (CAD) remains unclear.

METHODS AND RESULTS

A total of 270 patients were included by a retrospective search of the existing databases of 4 institutions. In addition to hard events, consisting of cardiac death and nonfatal myocardial infarction, any significant events including death, nonfatal myocardial infarction, coronary revascularization, heart failure, and unstable angina were assessed. During a median follow-up of 3.9 years, 33 patients had significant events, among whom 10 had hard events. Kaplan-Meier survival estimates revealed a hard event-free survival rate of 98% at 3 years in patients with a BMIPP defect score lower than 5 but 93% in those with a defect score of 5 or greater ( P = .03). With regard to significant events, the analysis showed an event-free survival rate of 92% at 3 years in patients with a BMIPP defect score lower than 5 but 80% in those with a defect score of 5 or greater ( P = .0003).

CONCLUSIONS

These results indicate that resting BMIPP imaging has prognostic value and may have a role in the risk stratification of patients with known or suspected CAD.

Medium- to long-term prognostic impact of dipyridamole thallum-201 myocardial single-photon emission computed tomography in elderly patients

Dipyridamole thallium-201 single-photon emission computed tomography (SPECT) has not been extensively evaluated for risk stratification and the medium- to long-term prognostic value in elderly cardiac patients who are unable to exercise. The present study group comprised 210 consecutive patients aged at least 70 years with known or suspected coronary artery disease (CAD). The SPECT findings were classified as a reversible, fixed, or combined (reversible and fixed) defect. Of the 210 patients, 201 (77+/-5 years, 85 male) were successfully followed for 49+/-26 months. Thirteen (7%) patients had cardiac events: cardiac death (n=10), non-fatal myocardial infarction (n=1), or coronary artery bypass grafting (n=2). Cardiac events occurred in 3 of 112 patients with normal SPECT and in 10 of 89 patients with an abnormal scan (0.7% /year vs 2.8% /year, p=0.01). Stepwise Cox regression analysis revealed that the significant predictors of cardiac events were combined defects (relative risk 7.3) and the number of defect areas (relative risk 4.4). The predictive value of dipyridamole thallium-201 SPECT is maintained over 4 years in mixed populations of elderly CAD patients who are unable to exercise.

QT dispersion correlates with systolic rather than diastolic parameters in patients receiving anthracycline treatment

OBJECTIVE

The aim of this study was to investigate the relation of QT dispersion to left ventricular (LV) systolic and diastolic function in patients undergoing anthracycline therapy.

METHODS

We used echocardiography to evaluate LV systolic and diastolic function and electrocardiography to evaluate QT dispersion and corrected QT dispersion (QTcD) in patients with hematological diseases, who received anthracycline therapy.

PATIENTS

Seventy-two patients with hematological diseases who were receiving anthracycline treatment were enrolled in the present study.

RESULTS

LV end-diastolic diameter or LV end-systolic diameter had a significant positive correlation to QTcD (r = 0.35, p < 0.01, r = 0.43, p < 0.01). Also left ventricular ejection fraction of (LVEF) or fractional shortening had a significant negative correlation to QTcD (r = -0.46, p < 0.001, r = -0.27, p = 0.02). The highest QTcD group had a significantly larger LV end-diastolic diameter or LV end-systolic diameter than the lowest QTcD [48.5 +/- 5.7 vs. 44.4 +/- 4.5 (mm), p < 0.001, 34.1 +/- 6.4 vs. 28.8 +/- 4.3 (mm), p < 0.001] and the highest QTcD group had a significantly lower LVEF than the lowest QTcD [57.5 +/- 8.0 vs. 65.5 +/- 6.4 (%), p < 0.001]. On the other hand, none of the diastolic function markers were significantly correlated with QTcD.

CONCLUSION

We concluded that increased QTcD is correlated with LV dilation and systolic dysfunction induced by anthracycline therapy, and does not reflect a dispersion of ventricular repolarization or asynchronous motion.

Accuracy of three-dimensional ultrasound for thyroid volume measurement in children and adolescents

The aim of this study was to estimate accuracy, intraobserver variability, and repeatability of thyroid volume measurement by ultrasound using conventional two-dimensional ellipsoid model (2D US) and manual planimetry of three-dimensional images (3D US). The sonographic images of 47 children with thyroid nodular pathology who were referred for thyroid surgery in Belarus were evaluated prospectively. Two-dimensional images were acquired using the ultrasound scanner with 7.5-MHz linear probe. Three-dimensional data sets were created using three-dimensional system, FreeScan. For each patient thyroid volume was measured three times using both two- and three-dimensional methods. Results of volume estimation were then compared to the volume of thyroid gland determined after surgery. Standardized difference between thyroid volume estimated by ultrasound and surgery (mean +/- standard deviation (SD), %) for 3D and 2D US methods was 1.8 +/- 5.2% and 3.2 +/- 15.3%, respectively. The 3D US has lower intraobserver variability (3.4%) and higher repeatability (96.5%) than 2D US with 14.4% variability and 84.8% repeatability (p < 0.001). In conclusion, three-dimensional sonography allows accurate measurement of thyroid volume with low intraobserver variability and high repeatability.

The impact of adjunctive adenosine infusion during exercise myocardial perfusion imaging: Results of the Both Exercise and Adenosine Stress Test (BEAST) trial

BACKGROUND

Failure to achieve an adequate heart rate limits the sensitivity of exercise myocardial perfusion imaging (MPI) for the detection of coronary artery disease. In addition, it is often not possible to discontinue medications that may blunt the heart rate response to exercise, because of conditions such as hypertension or angina. However, if pharmacologic stress testing is performed, the ability to assess functional capacity is lost. Accordingly, we developed a protocol that incorporates adenosine stress with symptom-limited exercise.

METHODS AND RESULTS

As part of a multicenter study, 35 patients were enrolled prospectively and underwent both exercise MPI and exercise MPI with a 4-minute adenosine infusion on a separate day. Technetium 99m sestamibi was injected at or near peak exercise (exercise only) and at 2 minutes into the adenosine infusion (combined exercise and adenosine). The perfusion images were interpreted in a blinded fashion. The combined adenosine and exercise protocol was well tolerated. The summed stress scores and summed difference scores were greater in the exercise-plus-adenosine group than in the exercise-only group (10.0 vs 8.5, P =.02, and 4.9 vs 3.3, P =.002, respectively). Exercise time was slightly but significantly less with the exercise-plus-adenosine protocol (8 minutes 46 seconds vs 8 minutes 11 seconds, P =.027).

CONCLUSION

A protocol combining 4 minutes of adenosine infusion with symptom-limited exercise was safe and well tolerated. Furthermore, this protocol resulted in a greater amount of myocardial ischemia detected on MPI while allowing for the assessment of functional capacity. A combined exercise and adenosine protocol may be a useful test for patients undergoing MPI who are unlikely to achieve an adequate chronotropic response.

Provocative testing for chest pain

Since the first Chest Pain Center (CPC) was set up in 1981 to speed up the evaluation and treatment of patients with acute myocardial infarction, the original concept has been expanded to include rapid evaluation of chest pain patients with the appropriate streamlining of care and incorporation of the latest in technology. It has also been established that among patients presenting with acute chest pain, a very low-risk group with less than 5% probability of a coronary event can be identified. The recognition of this group could prevent unnecessary admissions, affording more appropriate patient care and improved cost-effectiveness. The efficient management of these chest pain patients requires that there be reductions in: (1) delays in therapy, (2) "soft" admissions, (3) inappropriate dispositions, and (4) cost. With time, provocative testing (PT) for chest pain patients has been brought forward to the frontline. PT methods are now being studied in hundreds of emergency department (ED) patients, followed up over several months to ascertain the predictive value of both positive and negative test results. More and more CPCs are now using PT as part of their management protocol, in terms of decision-making pertaining to prognostification, treatment and disposition. This could be in the form of the ECG graded exercise test (GXT), stress echocardiography (SE) and stress single-photon emission computed tomography (SPECT) radionuclide perfusion imaging. The GXT is fairly widely used currently, SE is gaining popularity and stress radionuclide perfusion imaging will perhaps gain more acceptance as the experience with its use as well as the number of randomized controlled studies increase. As we move into the new millennium, the emergency physicians must familiarize themselves with the latest in the state-of-the-art concepts and technology to render improved, up-to-date and more cost-effective patient care.

High incidence of silent myocardial ischemia in elderly patients with non insulin-dependent diabetes mellitus

The present study was designed to reveal the incidence of silent myocardial ischemia in asymptomatic elderly non-insulin-dependent diabetic (NIDDM) patients (aged over 60 years). As a first step screening, maximal treadmill exercise test was performed. Of 140 patients studied, 54 (38.6%) were unable or not expected to achieve diagnostic levels of exercise during treadmill testing. A positive exercise test was noted in 39 of 86 (45.3%) subjects. As a second step examination, dipyridamole thallium scintigraphy was performed for 93 subjects who exhibited a positive exercise test and could not perform a maximal exercise test. Abnormal perfusion pattern was found in 39 of 93 (41.9%), who were finally considered to have a silent myocardial ischemia. Coronary angiography was performed in 18 subjects with diagnosis of silent myocardial ischemia, who gave their consent. Significant coronary artery stenosis was in fact found in 17 of 18 (94.4%) subjects studied, confirming a very high positive predictive value of this diagnostic procedure. In conclusion, elderly NIDDM patients (aged over 60 years) had an extremely high prevalence (estimated 26.3%) of silent myocardial ischemia. This evidence suggests that early and intensive detection may be needed as a part of routine care for this group.

Functional recovery after coronary artery bypass grafting in patients with severe left ventricular dysfunction and preserved myocardial viability in the left anterior descending arterial territory as assessed by thallium-201 myocardial perfusion imaging

To evaluate the functional recovery after coronary bypass surgery in patients with severe left ventricular (LV) dysfunction (ejection fraction (EF) < or = 35%), 100 consecutive patients with viable myocardium in the territory supplied by the left anterior descending artery (LAD) underwent coronary bypass grafting. In addition, cardiac catheterization and single-photon emission computed tomography (SPECT) perfusion imaging with thallium-201 were repeated 1-year postoperatively. Although 12 patients with severe LV dysfunction were preoperatively in a worse New York Heart Association functional class (3.1+/-0.7 vs 2.4+/-0.8; p<0.01), had a higher incidence of heart failure (10/12 vs 14/88; p<0.001) and had a worse LVEF (29+/-5 vs 61+/-14%; p<0.001) compared with 88 patients without severe LV dysfunction, the operative mortality was similar in the 2 groups (1/12 vs 2/88; p=NS). The postoperative NYHA functional class in the patients with severe LV dysfunction was similar to that in the patients without such dysfunction (1.6+/-0.7 vs 1.3+/-0.6; p=NS). In addition, the 1-year postoperative study revealed a significant improvement in the thallium defect score in both the LAD territory (1.7+/-1.2 to 0.7+/-1.0, p=0.01) and all the territories (5.2+/-2.2 to 3.2+/-1.9, p=0.002) in patients with severe LV dysfunction, whereas no improvement in defect score was found in either of these territories in those without severe LV dysfunction (LAD: 0.6+/-1.4 to 0.4+/-1.2, p=NS; All: 1.9+/-2.2 to 1.8+/-2.0, p=NS). Furthermore, a marked 1-year postoperative improvement (15-24%; 95% confidence interval) in LVEF (29+/-5 to 48+/-10%, p<0.001) was demonstrated in patients with severe LV dysfunction, but not in those without such dysfunction (60+/-13 to 61+/-11%, p=NS). These results indicate that myocardial viability in the LAD territory, as demonstrated by thallium-201 SPECT perfusion imaging, predicts a significant improvement in functional class and LVEF of at least 10% or more after coronary artery bypass grafting in patients with severe LV dysfunction.

Dipyridamole TI-201 SPECT imaging in patients with myocardial bridging

PURPOSE: Exercise-induced myocardial perfusion abnormalities have been reported in patients with myocardial bridging, possibly by tachycardia-induced shortening of diastole. Dipyridamole TI-201 SPECT findings were evaluated in patients with myocardial bridging to assess perfusion abnormalities during dipyridamole stress. MATERIALS AND METHODS: Dipyridamole TI-201 SPECT images of 12 patients with myocardial bridging (> or = 50% systolic narrowing) were evaluated. The peak heart rate during dipyridamole stress was less than 110 beats/min in all patients. The control group was 118 patients with fixed left anterior descending artery (LAD) disease. RESULTS: Fourteen sites of systolic arterial narrowing were present in LAD: two in mid-LAD, seven in distal LAD, and five in septal branches. Dipyridamole TI-201 SPECT showed reversible perfusion defects in three of six sites with 50% to 70% systolic narrowing and seven of eight sites with more than 80% systolic narrowing. Overall, 71% (10 of 14) had a reversible perfusion defect. Five patients with septal branch compression had a perfusion defect in the midanteroseptal wall without an apical abnormality. In the control group, no patient had an isolated perfusion defect in the midanteroseptal wall or septal branch disease (5 of 12 compared with 0 of 118; P < 0.001). CONCLUSIONS: Perfusion abnormalities on dipyridamole TI-201 SPECT are observed in LAD or its branches in patients with high-grade myocardial bridging. Myocardial bridging may decrease coronary flow reserve but not necessarily via tachycardia. Isolated perfusion defects in the midanteroseptal wall may be a characteristic finding of septal branch compression, because a fixed lesion involving a septal branch only is rare.

Intravenous dipyridamole thallium imaging V combined arm-leg cycle stress testing of patients unable to exercise on the treadmill

Rehabilitation patients who will undergo noncardiac surgery or strenuous rehabilitation programs often cannot exercise to greater than 85% of predicted maximal heart rate as required for valid treadmill testing. Because many patients have known or suspected coronary artery disease, greatly increasing their risk for a cardiac event, dipyridamole thallium scans are usually performed, despite a cost of approximately $1400, patient radiation exposure, and the need for a gamma camera. Instead, arm-leg cycle stress testing can be continued to an appropriately high heart rate, is done in the physician's office with an electrocardiograph machine and a blood pressure cuff, and costs $250. This study describes nine patients who had both dipyridamole thallium scans and arm-leg cycle ergometry. Four awaited peripheral vascular surgery, one needed bilateral knee replacements, one was an amputee, and three had claudication. Six had documented and three had suspected coronary disease.

RESULTS

In eight of nine patients, the electrocardiograms during both dipyridamole thallium imaging and ergometry were in agreement as to the presence or absence of ischemia (kappa statistic, 0.7273; P = 0.0117). In seven of nine patients, thallium images and ergometry agreed (78% concurrence). To achieve 90% agreement between dipyridamole thallium scans and cycle results, however, 68 patients would have to be studied.

CONCLUSION

In this preliminary study, arm-leg ergometry was feasible in all patients and seemed cost-effective and useful for detecting myocardial ischemia. Clinically, if the ergometry were inconclusive, dipyridamole thallium scans could be performed subsequently to obtain the needed information.

Estimation of Right Atrial Volume and Function by an Online Echocardiographic Edge Detection System

To define the accuracy of real-time two-dimensional echocardiographic imaging with automatic border detection (ABD) for the assessment of right atrial volume and function, we studied with ABD echocardiography 29 healthy subjects and 43 patients with sinus rhythm and various forms of heart disease. Twenty-three patients had right ventricular (RV) dysfunction (fractional area change < 45%), and 20 had RV hypertrophy from pressure overload. Doppler color flow imaging disclosed moderate-to-severe tricuspid regurgitation (TR) in 20 patients and trivial or no TR in 23. The ABD-derived end-diastolic (EDV) and end-systolic (ESV) volumes by the method of discs were used to compute fractional indexes of right atrial (RA) volume changes. Right atrial emptying fraction (RAEF) percent [(ESV - EDV)/ESV x 100] was calculated. The ABD-derived EDV and ESV correlated well with conventional offline measurements of two-dimensional echocardiographic images in the 43 patients (r = 0.94 for the end-diastolic values; r = 0.93 for the end-systolic values). Intraobserver and interobserver variability showed a high correlation between different measurements (r = 0.97 and 0.90, respectively). RA volumes were significantly higher in the patient population than in the control subjects (148.9 +/- 66.7 ml vs 43.1 +/- 9.2 ml, P < 0.0001). The right atrial emptying fraction (RAEF) was higher in patients with RV pressure overload than in normal subjects (61% +/- 11% vs 46% +/- 9%, P < 0.05) and lower in those with RV dysfunction than in the control subjects (29% +/- 7% vs 46% +/- 9%, P < 0.01). In both groups (RV pressure overload and RV dysfunction), RAEF was higher in patients without or with trivial TR compared with those with significant TR (29% +/- 7% vs 23% +/- 6%; 61% +/- 11% vs 42% +/- 7%; P < 0.05). Thus, changes in right atrial volume and function can be measured noninvasively by the ABD method. This imaging technique may prove to be useful for assessing right atrial size and function under different physiological and pathological conditions and for identifying factors that influence atrial function in right ventricular diseases.

Cardiovascular disease in patients with dysvascular amputation

Cardiovascular diseases are the most common causes of morbidity and mortality in individuals with peripheral vascular disease (PVD). Among patients who have undergone lower extremity amputation as a result of PVD, the prevalence of concomitant cardiovascular disease may be as high as 75%. Comorbid heart disease may complicate the postamputation course of recovery, delay initiation of rehabilitation training, and inhibit the achievement of maximal functional independence. A variety of methods have been used to assess cardiac status and risk in amputation patients undergoing physical training; these have included clinical evaluation, resting electrocardiography, and continuous dynamic electrocardiography during either standard physical therapy exercise or adapted ergometry. Several conditioning training programs have been developed to improve the cardiovascular fitness of patients with dysvascular amputation, the results of which have been favorable. These assessment and intervention strategies have extensive applicability in the clinical management of patients with dysvascular amputation.

Correlation between hemodynamic changes and tomographic sestamibi imaging during dipyridamole-induced coronary hyperemia

OBJECTIVES

The purposes of this study were to examine the effects of dipyridamole infusion on hemodynamic variables and to compare these changes with myocardial perfusion.

BACKGROUND

Dipyridamole stress testing with myocardial perfusion imaging is widely used in the assessment of patients with known or suspected coronary artery disease (CAD). Few studies, however, have correlated the hemodynamic effects of dipyridamole using invasive monitoring with perfusion patterns in patients with chest pain syndromes.

METHODS

Hemodynamic measurements were made in the cardiac catheterization laboratory with a Swan-Ganz thermodilution catheter before, during and after infusion of dipyridamole (142 microg/kg body weight per min for 4 min). Technetium-99m sestamibi was injected 3 min after the completion of the infusion.

RESULTS

There were 20 patients with and 6 without CAD, as demonstrated by angiography. Compared with baseline values, dipyridamole resulted in an increase in pulmonary capillary wedge pressure (54 +/- 78% vs. 32 +/- 26%, p = NS), cardiac index (36 +/- 21% vs. 40 +/- 18%, p = NS) and stroke volume index (16 +/- 18% vs. 40 +/- 18%, p = NS) and a decrease in systemic vascular resistance (22 +/- 13% vs. 24 +/- 11%, p = NS), aortic pressure (2 +/- 9% vs. 0 +/- 6%, p = NS) and pulmonary vascular resistance (19 +/- 25% vs. 11 +/- 32%, p = NS) in patients with and without CAD. The peak effect of dipyridamole on heart rate, systemic vascular resistance and pulmonary capillary wedge pressure was evident at 3 min after infusion in 70% of patients. Aminophylline, given to 20 patients, improved hemodynamic variables within 2 min. The single-photon emission computed tomographic sestamibi images were normal in the 6 patients without and abnormal in the 18 patients with CAD.

CONCLUSIONS

Dipyridamole-induced coronary hyperemia produces mild hemodynamic changes in patients with and without CAD; these changes are at or near peak effect at 3 min after infusion and are rapidly reversed by aminophylline.

Cost-minimization analysis of intravenous adenosine and dipyridamole in thallous chloride TI 201 SPECT myocardial perfusion imaging

OBJECTIVE

To conduct a cost-minimization analysis of intravenous adenosine and intravenous dipyridamole in thallous chloride TI 201 single-photon emission computed tomography (SPECT) myocardial perfusion imaging.

DESIGN

A retrospective, open-label, cost-minimization analysis.

SETTING

University hospital, outpatient nuclear medicine department.

PATIENTS

Eighty-three patients undergoing dipyridamole TI 201 SPECT and 166 patients undergoing adenosine TI 201 SPECT.

MAIN OUTCOME MEASURES

A cost-minimization analysis was conducted using a direct cost accounting approach estimating institutional costs. For the purpose of this study, sensitivity and specificity between adenosine SPECT and dipyridamole SPECT were assumed to be identical. Key costs evaluated included acquisition, administration, monitoring, treatment of adverse effects, follow-up care, and repeat tests.

RESULTS

Adenosine increased heart rate and lowered blood pressure to a significantly greater extent than dipyridamole. The frequency of adverse reactions was not significantly different (p = 0.103) between adenosine (1.64 +/- 1.32 per patient) and dipyridamole (1.36 +/- 1.23 per patient). The frequency of prolonged and late-onset adverse effects was significantly greater for dipyridamole than for adenosine (p < 0.001). The frequency of adverse events requiring medical intervention was statistically greater for dipyridamole (24%) compared with adenosine (5%) (p < 0.00001). Total cost was significantly less for adenosine ($378.50 +/- $128.20 per patient) compared with dipyridamole ($485.60 +/- $230.40). Although adenosine had a significantly greater acquisition cost than dipyridamole (p < 0.0001), administration, monitoring, and adverse reaction costs were significantly less for adenosine than for dipyridamole.

CONCLUSIONS

The cost of using dipyridamole is significantly greater than the cost of using adenosine despite adenosine's high acquisition cost. Adenosine is less expensive to use because of lower administration costs, monitoring costs, and adverse effect costs. Adenosine should be the agent of choice for pharmacologic vasodilation in the setting of myocardial perfusion imaging.

Outcomes and costs of positron emission tomography: comparison of intravenous adenosine and intravenous dipyridamole

The objective of this study was to compare the cost of intravenous adenosine and intravenous dipyridamole in positron emission tomography (PET) in patients with coronary artery disease. A retrospective, open-label, case-control, cost-effectiveness analysis was performed in the out-patient nuclear medicine department of a university hospital. Thirty-six patients underwent dipyridamole PET, and 72 matched patients underwent adenosine PET. A cost-effectiveness analysis was conducted using a direct cost accounting approach to estimate institutional costs. Key costs evaluated included acquisition cost, administration cost, monitoring cost, cost of management of side effects, and cost of follow-up care. The total cost of adenosine PET and dipyridamole PET was divided by their respective predictive accuracies to provide a total cost adjusted for efficacy. Adenosine increased heart rate and lowered systolic blood pressure to a significantly greater extent than dipyridamole. The number of patients experiencing adverse drug reactions was significantly greater for adenosine (82%) than for dipyridamole (67%), but the frequency of prolonged (> 5 minutes) and late-onset side effects was significantly greater for dipyridamole than for adenosine. The frequency of side effects requiring medical intervention was also significantly greater for dipyridamole (53%) than for adenosine (6%). Although adenosine had a significantly greater acquisition cost than dipyridamole, costs of monitoring, management of side effects, and follow-up care were significantly less for adenosine than for dipyridamole. As a result, the total cost of using dipyridamole is significantly greater ($928.00 per patient) than the total cost of using adenosine ($672.00 per patient). Based on these results, adenosine may be the drug of choice for pharmacologic vasodilation for PET.

ECG-manifest and ECG-silent dipyridamole technetium-99m sestamibi SPET perfusion defects in patients with ischaemic heart disease

At dipyridamole myocardial scintigraphy, perfusion defects are seldom backed up by significant ECG changes. This would suggest myocardial blood flow heterogeneity, rather than true ischaemia, as the cause of the scintigraphic abnormalities. Electrocardiographic surface mapping has been documented to be more accurate than standard 12-lead ECG in the detection of provoked ischaemia. Thus, to investigate the relationship between ECG changes and perfusion abnormalities, body surface maps were recorded during dipyridamole infusion in 55 subjects (11 normals and 44 patients with ischaemic heart disease) undergoing dipyridamole technetium-99m sestamibi single-photon emission tomography (SPET). All had a normal resting ECG. The extent and severity of the sestamibi defect were quantified. New negative areas in the isointegral maps and rest-dipyridamole map differences >2 SD from normal limits were considered abnormal. After dipyridamole in normals, neither perfusion defects nor >/=1 mm ST segment depression on 12-lead ECG nor new negative areas in isointegral maps occurred. In patients, dipyridamole induced new perfusion defects in 35 (80%) but ST segment depression in only 18 (41%, P<0.001). Of the 35 patients with perfusion defects, 17 (49%, group 1) showed ST segment depression, while the other 18 (51%, group 2) did not. Abnormal body surface maps were found in 100% of group 1 and 88% of group 2 patients (NS). In group 1, the provoked hypoperfusion was of greater extent (P=0.007) and severity (P=0.01) and the onset of map abnormalities was significantly earlier (P<0. 001) than in group 2; time to map abnormalities was also significantly shorter than time to ST segment depression (P=0.01). In the 35 patients with complete scintigraphic, body map and angiographic data, the severity of reversible perfusion defect proved to be the strongest correlate of ST segment depression upon logistic regression analysis. Thus, sestamibi SPET abnormalities after dipyridamole are almost always associated with electrical changes on body surface maps, suggesting myocardial ischaemia as their cause. The much less common 12-lead ECG changes are slower to appear and reflect a more severe hypoperfusion.

Diagnostic significance of an exercise-induced prominent U wave in acute myocardial infarction

A prominent U wave induced by exercise testing in patients with anterior wall myocardial infarction is a highly specific but insensitive marker for the narrowing of the left circumflex or right coronary artery, although a U-wave increase alone with or without ST-segment depression may help better identify these coronary artery narrowings. In patients with inferior and/or posterior myocardial infarction, a prominent U wave is regarded as a simple electrocardiographic marker for inferior and/or posterior residual ischemia.

Dipyridamole technetium-99m Sestamibi imaging in the diagnosis of syndrome X

In a middle-aged woman with anginal chest pain and a normal-appearing angiogram, dypiridamole technetium-99m Sestamibi scintigraphy, a noninvasive method, provided the diagnosis of syndrome X and was used in follow-up to monitor the course of disease.

Prediction of in-hospital cardiac events using dipyridamole-thallium scintigraphy performed very early after acute myocardial infarction

BACKGROUND AND HYPOTHESIS

Ischemic complications occur frequently during hospitalization after acute myocardial infarction. Dipyridamole-thallium scintigraphy performed early after admission can detect residual ischemia, may have additional prognostic value and be useful in the management of these patients.

METHODS

Dipyridamole infusion and 201thallium imaging were performed on the third day of infarction in 114 consecutive patients. Coronary angiography was performed before hospital discharge in 90% of patients and exercise testing was performed at the time of discharge in patients without contraindications.

RESULTS

Side effects occurred in 28 patients, but they were mild and transient or rapidly reversed with intravenous aminophylline. During hospitalization, three patients died and four had a nonfatal reinfarction. Patients with these major cardiac events had previously shown a higher prevalence of reversible perfusion defects during testing (71 vs. 31%, p < 0.05). In addition, 19 patients had early recurrent ischemia requiring early in-hospital revascularization. Overall, cardiac events defined as death, reinfarction, or early myocardial revascularization occurred in 22 patients. Of the patients with these events, 68% had thallium redistribution on initial myocardial scanning compared with 25% of patients without events (p = 0.0001). Patients with cardiac events also showed a higher number of myocardial segments with reversible perfusion defects (1.8 +/- 2.2 vs. 0.6 +/- 1.3, p = 0.001). Logistic regression analysis revealed that among all the other clinical, scintigraphic, and angiographic variables, the presence of thallium redistribution on the dipyridamole-thallium scan was the only independent predictor of cardiac events, increasing the risk by sixfold. Furthermore, during a 1-year follow-up, 14 other patients had ischemic events. Of these, 64% had previously shown thallium redistribution during early dipyridamole testing compared with 19% of patients without cardiac events (p < 0.001).

CONCLUSIONS

Intravenous dipyridamole-thallium-scintigraphy performed very early after myocardial infarction is safe and useful to predict in-hospital ischemic events.

Does dyspnoea during dipyridamole cardiac stress testing indicate bronchospasm and is the pretest clinical history predictive of this side-effect?

This study investigates the acute effects of intravenous dipyridamole (0.7mg/kg) on pulmonary airflow in relation to clinical parameters suggestive of chronic obstructive pulmonary disease (COPD) in order to assess predictive and causative factors of dyspnoea during cardiac stress testing. Mild pulmonary airflow obstruction was noted in all patients, but reached statistical significance only in small airways (FEF75-85%: -7%; P=0.034). The changes in pulmonary function parameters were independent of the clinical history. Dyspnoea under dipyridamole stress testing occurred in parallel with angina, yet was not associated with ischaemic or non-ischaemic left ventricular dysfunction. These data do not support the use of dipyridamole stress testing in asthmatics, but show that (1) the acute effects of a diagnostic dose of dipyridamole on pulmonary airflow are mild even in patients with a history suggestive of COPD and (2) dyspnoea during dipyridamole testing is not necessarily indicative of bronchospasm.

Dipyridamole thallium-201 single-photon emission tomography in aortic stenosis: gender differences

Dipyridamole single-photon emission tomography (SPET) is used for the detection of coronary artery disease (CAD) and the method has also been applied in patients with aortic stenosis. This study was undertaken to establish the gender-specific normal limits of thallium-201 distribution in patients with aortic stenosis and to apply these normal limits in a larger group of patients with aortic stenosis to obtain the sensitivity and specificity for coexisting CAD. A low-dose dipyridamole protocol was used (0.56 mg/kg during 4 min). Thallium was injected 2 min later and tomographic imaging was performed. Following image reconstruction a basal, a midventricular and an apical short-axis slice were selected. The highest activity in each 6 degree segment was normalised to the maximal activity of each slice. The normal uptake for patients with aortic stenosis was obtained from ten men and ten women with aortic stenosis and a normal coronary angiography. Eighty-nine patients were prospectively evaluated. An area reduction of at least 75% in a coronary artery was considered to be a significant coronary lesion and was found in 57 (64%) patients. With gender-specific curves (-2.5 SD) sensitivity for detecting CAD was 100% and specificity was 75% in men, while sensitivity was 61% and specificity 64% in women. It is concluded that the gender-specific normal distribution of 201Tl uptake in patients with aortic stenosis, using dipyridamole SPET, yields a high sensitivity and specificity for coronary artery lesions in men but a lower sensitivity and specificity in women with aortic stenosis.

Detection of coronary artery disease in diabetic patients

Coronary artery disease may be difficult to detect in diabetic patients. This study was designed to determine the specificity and sensitivity of three noninvasive tests. Accordingly, the results of 48-h ambulatory electrocardiogram (ECG) monitoring, maximal ECG exercise test, and intravenous dipyridamole myocardial thallium scintigraphy were compared in 59 middle-aged diabetic patients who were consecutively selected for suspected coronary artery disease. All patients also underwent coronary angiography, which was performed regardless of the results of the non-invasive tests. Twenty patients (34%) had significant coronary lesions, i.e. stenosis equal to or greater than 70%, and 16 of these 20 patients (80%) had double or triple vessel disease. Sensitivity and specificity were, respectively, 25% and 88% for ambulatory ECG monitoring, 75% and 77% for the exercise test and 80% and 87% for thallium myocardial scintigraphy. This observation strongly supports the use of non-invasive tests for the detection of coronary artery disease in those diabetic patients at high risk of such disease. As the exercise test is cheaper and more widely available than thallium myocardial scintigraphy it should be used as a first line examination. Dipyridamole myocardial scintigraphy may provide an alternative solution for those patients who cannot perform maximal exercise, or with atypical clinical presentation.

High-grade atrioventricular block during dipyridamole stress testing

Dipyridamole stress testing may be used in the diagnosis of coronary artery disease and risk assessment of patients who are unable to exercise. Although dipyridamole perfusion imaging has a good safety record, serious side-effects may rarely occur. We present a case in which dipyridamole induced high-grade atrioventricular (AV) block that responded promptly to intravenous aminophylline but not to atropine.

A consideration of current clinical options for stress imaging in the diagnosis and evaluation of coronary artery disease

The evolution of technology and our health care system, tinctured by advocacy groups for specific imaging modalities, has produced controversy, relating to the optimal stress imaging method for coronary disease evaluation. Stress perfusion scintigraphy and stress echocardiography advocates seem to make claims that each nullify the other. This extensive, in-depth review of the subject presents facts as well as opinion and experience in an effort to assess the full portrait of the issue for consideration by advocates as well as those many yet undecided. The issue is an evolving one, affected strongly by the reader's own experience. The presentation is not meant to be the final word. Rather, it seeks to present a basis for understanding and progress in both fields.

Adenosine-induced heterogeneous perfusion accompanies myocardial ischemia in the presence of advanced coronary artery disease

The aim of the present study was to elucidate the characteristics of patients in whom transient myocardial ischemia was evoked during adenosine infusion. Thallium-201 (Tl-201) myocardial imaging and two-dimensional echocardiography during adenosine infusion were performed simultaneously in 61 consecutive patients enrolled for the diagnosis of coronary artery disease. Transient reduction of systolic wall motion after adenosine infusion was considered evidence of myocardial ischemia. Tl-201 redistribution was noted in 38 patients, and 23 of them showed a wall motion abnormality during adenosine infusion. Stepwise discriminant analysis was applied to eight variables that showed significant differences by the univariate analysis between patients with the presence and the absence of adenosine-induced wall motion abnormality: myocardial infarction, anginal pain, ST depression, collateral vessels, Tl-201 redistribution, number of diseased vessels of > or = 75% or 90% stenosis and number of segments with Tl-201 redistribution. The number of diseased vessels with > or = 75% stenosis (F = 43.5, p < 0.0001), ST depression (F = 16.0, p < 0.0002), collateral vessels (F = 11.7, p < 0.001) and Tl-201 redistribution (F = 5.6, p < 0.02) were the statistically significant discriminators relating to adenosine-induced wall motion abnormality. Adenosine-induced myocardial ischemia was related to the number of coronary stenoses, reflecting the presence of severe coronary artery disease, and well-developed collaterals that might be integral factors in a coronary steal phenomenon.

Pretreatment with theophylline does not affect adenosine-induced thallium-201 myocardial imaging

This study was designed to evaluate the effects of intravenous theophylline given before intravenous adenosine for thallium-201 imaging. Sixteen patients with known reversible thallium-201 defects were randomized to a double-blind crossover study of a 45-minute infusion of placebo or theophylline (given as the ethylenediamine salt, aminophylline, mean concentration 16.1 mg/L) before adenosine thallium-201 imaging. Adenosine was infused for 6 minutes at a rate of 140 micrograms/kg/min. Thallium-201 (2.5 to 3.0 mCi) was administered after 3 minutes of infusion. Blood pressure, heart rate, symptoms, and the electrocardiogram were monitored continuously. Planar thallium-201 imaging was obtained in three standard views and was interpreted using blinded segmental analysis and computerized quantitation. Systolic and diastolic blood pressure at baseline and during adenosine administration were similar following treatment with theophylline and placebo. The increase in heart rate observed during adenosine infusion was significantly reduced by theophylline pretreatment. Adenosine-induced symptoms (both cardiac and noncardiac) as well as ischemic electrocardiographic changes were significantly reduced after theophylline infusion (p < 0.05). In one patient, Mobitz type II heart block seen during adenosine infusion following placebo was absent with theophylline pretreatment. The size of adenosine-induced thallium-201 defects was unchanged by theophylline infusion using either segmental analysis (8 +/- 4 vs 9 +/- 5) or a computerized score (47 +/- 27 vs 45 +/- 21). Despite reduction in both symptoms and ischemic electrocardiographic changes, theophylline does not alter thallium-201 imaging following intravenous adenosine infusion.

Assessment of left ventricular wall motion in angina pectoris by two-dimensional echocardiography and myocardial perfusion by technetium-99m sestamibi tomography during adenosine-induced coronary vasodilation and comparison with coronary angiography

Myocardial perfusion and regional wall motion during adenosine-induced coronary vasodilation were assessed in 40 patients with angina pectoris by technetium-99m sestamibi single-photon emission computed tomography (SPECT) and simultaneous 2-dimensional echocardiography. Adenosine was infused intravenously at a dose of 140 micrograms/kg body weight per minute for 6 minutes, and technetium-99m sestamibi was injected at 3 minutes. Adenosine caused a significant decrease in systolic and diastolic blood pressure and a significant increase in heart rate and the heart rate-blood pressure product. Adverse effects were mild and transient and no patient required aminophylline. Completely or partially reversible defects on SPECT were present in 28 patients, a fixed defect was seen in 4 patients, and no defect was seen in 8 patients. Two-dimensional echocardiography revealed a new or worsening wall motion abnormality in 21 patients, a fixed abnormality in 4 patients and no abnormality in 15. Transient perfusion defects were associated with transient wall motion abnormalities in 71% of cases. The overall sensitivity, specificity and predictive accuracy of adenosine echocardiography in detecting significant coronary artery disease (> 50% diameter stenosis) were 74, 100 and 78%, respectively, whereas those of adenosine SPECT were 94, 100 and 95%, respectively (p < 0.05, NS, and < 0.05, respectively). Thus adenosine technetium-99m sestamibi SPECT has a higher sensitivity and predictive accuracy than adenosine echocardiography, suggesting that adenosine-induced perfusion defects are not always associated with wall motion abnormality.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intravenous theophylline on exercise-induced myocardial ischemia: II. A concentration-dependent phenomenon

OBJECTIVES

The effects of varying concentrations of theophylline on exercise-induced myocardial ischemia were evaluated in patients with stable coronary artery disease.

BACKGROUND

Theophylline is a competitive antagonist of adenosine and may have potential as an anti-ischemic medication. It is not known whether these effects on myocardial ischemia are concentration dependent.

METHODS

In a double-blind, randomized, crossover manner, 11 patients received, at 1-week intervals, placebo and each of three theophylline doses by intravenous infusion for 45 min. Graded exercise testing was performed before randomization and immediately after each infusion. Concurrent anti-ischemic medications were withheld for 24 h before each exercise test. Serum theophylline concentrations achieved were 3.9 +/- 1.0 mg/liter (low), 8.2 +/- 1.8 mg/liter (medium) and 13.2 +/- 2.3 mg/liter (high).

RESULTS

Compared with placebo, none of the three theophylline infusions produced a significant alteration in rest heart rate, blood pressure, mean frequency or severity of ventricular ectopic activity or noncardiac symptoms. The time to onset of ischemia was progressively increased, with medium and high concentrations achieving statistical significance. Similar patterns were observed for oxygen uptake and the heart rate-systolic blood pressure product at the onset of ischemia. Total exercise duration was significantly prolonged with the medium and high concentrations.

CONCLUSIONS

It is concluded that administration of varying doses of theophylline before exercise produces a clinically significant and concentration-dependent improvement in the indicators of myocardial ischemia in patients with chronic stable coronary artery disease.