Planar, SPECT, PET: the quest to predict the unpredictable?
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Coronary Circulation↗
Biomedical subjects
F J Wackers
Publications and source records attributed to F J Wackers.
Variables predictive of good functional outcome following thrombolytic therapy in the Thrombolysis in Myocardial Infarction phase II (TIMI II) pilot study.
Before commencing the randomized Thrombolysis in Myocardial Infarction phase II (TIMI II) study, 370 patients were administered intravenous recombinant tissue plasminogen activator (rt-PA) within 4 hours of onset of acute myocardial infarction (AMI) and assigned to 2-hour (immediate) percutaneous transluminal angioplasty (n = 33), 18- to 48-hour (delayed) angioplasty (n = 288) or no angioplasty (n = 49) in a nonrandomized, observational pilot study. Left ventricular ejection fraction at rest and during exercise was assessed by gated equilibrium radionuclide ventriculography at hospital discharge and again at 6 weeks. At hospital discharge, ejection fraction averaged 50% at rest and 56% at peak exercise. At 6-week follow-up, ejection fraction averaged 50% at rest and 53% at peak exercise. At 6-week follow-up, resting ejection fraction average 49% in the 2-hour angioplasty group, 49% in the 18- to 48-hour angioplasty group and 55% in the no-angioplasty group. Variables independently predicting "good functional outcome" at 6-week follow-up (survival with resting ejection fraction greater than equal to 50% and no decrease with exercise) in the 18- to 48-hour angioplasty group were fewer leads with ST-segment elevation greater than or equal to 0.1 mV, younger age, rapid normalization during rt-PA infusion of ST segments or dramatic relief of chest pain, absence of arrhythmias within the first 24 hours of treatment initiation, no prior infarction and not a cigarette smoker at entry. Thus, the TIMI II pilot study demonstrates that most patients with AMI of less than or equal to 4-hour duration treated with rt-PA have good ventricular function after AMI.(ABSTRACT TRUNCATED AT 250 WORDS)
Angiography↗
Transient left ventricular dysfunction during provocative mental stress in patients with coronary artery disease.
We studied the temporal effects of various types of mental stress and physical exercise on the left ventricular ejection fraction (LVEF) in seven normal volunteers and nine patients with coronary artery disease. Three types of psychological stress were administered: mental arithmetic, the Stroop color word test, and a personally relevant speaking task. In the normal volunteers the LVEF response was either flat or increased (p less than 0.05) compared to the baseline value during the mental tasks and increased by a mean of 10 +/- 5% (p less than 0.05) during exercise. In contrast, in patients with coronary disease in whom LVEF did not increase greater than or equal to 5% during exercise, LVEF decreased significantly during the mental tasks (p less than 0.05 for arithmetic and Stroop tasks). Typically LVEF decreased quickly during mental stress with an immediate rebound after intervention. Decreases in LVEF during mental stress occurred without chest pain and were not associated with ECG changes. In patients with coronary disease in whom LVEF increased normally with exercise (LVEF increase greater than or equal to 5%), no significant changes in LVEF occurred during mental stress. The heart rate x systolic blood pressure double product during mental stress was significantly less than that achieved during exercise (p less than 0.05) in each normal subject and patient. Thus psychological stress can provoke acute decreases in LVEF in patients with coronary disease and exercise-inducible dysfunction. The silent nature of the mental stress-induced abnormalities and their occurrence at a lower physiologic workload compared to abnormalities during exercise parallel characteristics of transient ischemia noted during ambulatory monitoring.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Quantitative radionuclide assessment of regional ventricular function after thrombolytic therapy for acute myocardial infarction: results of phase I Thrombolysis in Myocardial Infarction (TIMI) trial.
In Thrombolysis in Myocardial Infarction (TIMI) Phase I,290 patients with acute myocardial infarction were randomized to either intravenous recombinant tissue-type plasminogen activator (rt-PA) or intravenous streptokinase. Two hundred twenty-nine patients had radionuclide ventriculograms at discharge for assessment of global and regional left ventricular ejection fraction. Among these 229 patients 185 had totally occluded infarct-related arteries, and angiographic reperfusion of the infarct-related artery occurred in 69% of patients treated with rt-PA and 28% of patients treated with streptokinase (p less than 0.001). Mean global left ventricular ejection fraction was not different for rt-PA-treated patients compared with streptokinase-treated patients (0.46 versus 0.45). However, the average regional ejection fraction of the regions subtended by the infarct-related artery showed a trend toward better average infarct region ejection fraction in patients treated with rt-PA than in patients treated with streptokinase (0.40 versus 0.36; 0.05 less than p less than 0.06). Analysis of data according to perfusion status of the infarct-related artery showed no difference in mean global left ventricular ejection fraction between patients with sustained versus nonsustained reperfusion (0.47 versus 0.44). However, there was better average regional ejection fraction of the region subtended by the infarct-related artery in patients with sustained reperfusion (0.40 versus 0.36; p less than 0.01). Thus, quantitation of regional left ventricular function by radionuclide techniques provides a noninvasive means for evaluating the effects of thrombolysis. This study suggests a direct relation between improvement of regional left ventricular function and the greater infarct-related artery patency rate achieved by rt-PA compared with streptokinase.
Aged↗
Serial quantitative planar technetium-99m isonitrile imaging in acute myocardial infarction: efficacy for noninvasive assessment of thrombolytic therapy.
Technetium-99m isonitrile is a new myocardial perfusion imaging agent that accumulates according to the distribution of myocardial blood flow. However, unlike thallium-201, it does not redistribute over time. This imaging agent was used with serial quantitative planar imaging to assess the initial risk area of infarction, its change over time and the relation to infarct-related artery patency in 30 patients with a first acute myocardial infarction. Twenty-three of 30 patients were treated with recombinant tissue-type plasminogen activator (rt-PA) within 4 h after the onset of chest pain. Seven patients were treated in the conventional manner without thrombolytic therapy. Technetium-99m isonitrile was injected before or at the initiation of thrombolytic therapy, and imaging was performed several hours later. These initial images demonstrated the area at risk. Repeat imaging was performed 18 to 48 h later and at 6 to 14 days after the onset of myocardial infarction to visualize the ultimate extent of infarction. The initial area at risk varied greatly (range defect integral 2 to 61) both in patients treated with rt-PA and in those who received conventional treatment. For the total group, the initial imaging defect decreased in size in 20 patients and was unchanged or larger in 10 patients. Patients with a patent infarct-related artery had a significantly greater decrease in defect size than did patients with persistent coronary occlusion (-51 +/- 38% versus -1 +/- 26%, p = 0.0001). All patients with a decrease in defect size greater than 30% had a patent infarct-related artery. In 12 patients who also had predischarge quantitative exercise thallium-201 imaging, good agreement existed between the extent and severity of myocardial perfusion defect on the last technetium-99m isonitrile study before discharge and that noted on delayed thallium-201 imaging. It is concluded that serial planar technetium-99m isonitrile myocardial imaging in patients with acute myocardial infarction undergoing thrombolytic therapy offers a new quantitative noninvasive approach for assessment of the initial risk zone as well as the success of reperfusion.
Contrast Media↗
Feasibility of tomographic 99mTc-hexakis-2-methoxy-2-methylpropyl-isonitrile imaging for the assessment of myocardial area at risk and the effect of treatment in acute myocardial infarction.
99mTc-hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-Sestamibi), a new myocardial perfusion radiopharmaceutical, was injected intravenously in 11 patients within 4 hours of the onset of acute myocardial infarction before treatment with intravenous tissue-type plasminogen activator and 6-14 days later. Five patients with acute myocardial infarction who did not receive intravenous thrombolytic therapy underwent a similar injection of radiopharmaceutical. The absence of redistribution of Tc-Sestamibi permitted imaging with single-photon emission computed tomography up to 6 hours after intravenous injection to assess the distribution of myocardial perfusion at the time of administration. The region of hypoperfused myocardium on the initial images varied widely from 9% to 68% of the left ventricle and was significantly greater in anterior than in inferior infarcts (p less than 0.01). The region of hypoperfused myocardium on the final images varied widely from 0% to 63% of the left ventricle and was also greater in anterior infarcts (p less than 0.01). The final hypoperfused region correlated (r = -0.82) with the late resting ejection fraction and with the late regional wall motion score in the infarct segment for both anterior (r = -0.74) and inferior (r = -0.97) infarcts. There was a significant decrease (-13 +/- 11%, p less than 0.003) in the extent of hypoperfused myocardium between the initial and final studies in the patients who received thrombolytic therapy compared with an insignificant increase (4 +/- 6%, p greater than 0.5) in the patients who did not receive thrombolytic therapy. Tomographic imaging with Tc-Sestamibi permits determination of the amount of hypoperfused myocardium "at risk" in acute myocardial infarction. The change in myocardial perfusion determined by Tc-Sestamibi before and after therapy in acute myocardial infarction is a promising tool for assessing treatment.
Aged↗
Technetium-99m hexakis 2-methoxyisobutyl isonitrile: human biodistribution, dosimetry, safety, and preliminary comparison to thallium-201 for myocardial perfusion imaging.
The biodistribution, dosimetry, and safety of a new myocardial imaging agent, 99mTc-hexakis-2-methoxyisobutyl isonitrile (HEXAMIBI), was evaluated in 17 normal volunteers at rest and exercise (Phase I studies). Technetium-99m HEXAMIBI clears rapidly from the blood with good myocardial uptake and favorable myocardial-to-background ratios for myocardial imaging. Dosimetry allows for administration of up to 30 mCi (1, 110 Bq) of [99mTc]HEXAMIBI. The myocardial images were of good quality and appeared less granular with sharper myocardial walls compared to 201T1 images. The clinical efficacy of [99mTc]HEXAMIBI planar stress and rest imaging was evaluated in a multicenter Phase II clinical trial involving 38 patients. Of 36 patients with significant coronary artery disease, 35 patients (97%) had abnormal 201T1 stress images, and 32 (89%) had abnormal [99mTc]HEXAMIBI stress images (P = N.S.). Technetium-99m HEXAMIBI images correlated in 31/35 patients (86%) who had either scar or ischemia on 201T1 images. By segmental myocardial analysis, exact concordance was obtained in 463/570 myocardial segments (81%). This multicenter Phase I and II study indicates that planar [99mTc]HEXAMIBI stress imaging is safe and compares well with 201T1 stress imaging for detection of coronary artery disease.
Adult↗
Clinical assessment of myocardial perfusion with thallium-201.
Assessment of myocardial perfusion and coronary blood flow in man can be performed reliably and successfully using thallium-201 imaging. The extent of exercise myocardial perfusion abnormalities reflects the functional significance of coronary artery stenosis. Accordingly, myocardial perfusion imaging is not only useful for the detection of coronary artery disease, but it also provides unique functional information which should be helpful in the management of patients with known coronary artery disease. The unfavorable physical properties of thallium-201 have limited to a certain extent full utilization of the clinical potential of the methodology. Now technetium-99m-labeled myocardial perfusion imaging agents promise to further enhance the clinical usefulness of myocardial perfusion imaging in patients.
Coronary Disease↗
Electrophysiologic effects of thrombolytic therapy in patients with a transmural anterior myocardial infarction complicated by left ventricular aneurysm formation.
To assess the effects of early thrombolytic therapy on the incidence of clinical and induced ventricular arrhythmias in high risk postmyocardial infarction patients, 32 patients with a transmural anterior myocardial infarction complicated by left ventricular aneurysm formation were prospectively evaluated. Sixteen patients (Group A) received routine care because of contraindication to thrombolytic therapy or other factors and 16 (Group B) received either tissue plasminogen activator or streptokinase within 6 h of the onset of chest pain. The two groups were similar in left ventricular ejection fraction (mean +/- SD, 28 +/- 9% [Group A] versus 30 +/- 8% [Group B]) and occurrence of spontaneous nonsustained ventricular tachycardia, new bundle branch block and congestive heart failure. Group B patients had higher peak creatine kinase MB levels (446 +/- 336 versus 205 +/- 120 IU; p = 0.017) and earlier time to peak creatine kinase values (13.4 +/- 6.6 versus 19.1 +/- 6.1 h; p = 0.006). Twenty patients who had no clinical sustained ventricular arrhythmias underwent electrophysiologic study 13 +/- 6 days after infarction. Ventricular tachycardia was induced during the study in 7 (88%) of 8 Group A patients, but in only 1 (8%) of 12 Group B patients given thrombolytic therapy (p = 0.0008). During a mean follow-up period of 11 +/- 8 months, eight Group A patients (50%) died suddenly or were resuscitated from sustained ventricular tachycardia; all Group B patients are alive and have had no clinical arrhythmic events (p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Peak filling rate normalized to mitral stroke volume: a new Doppler echocardiographic filling index validated by radionuclide angiographic techniques.
The noninvasive measurement of left ventricular filling has relied predominantly on radionuclide-derived peak filling rate normalized to end-diastolic volume. Doppler echocardiography also has the ability to measure peak filling rate, but wide application of this technique has been limited by technical errors involved in quantitative echocardiographic determination of mitral anulus cross-sectional area and ventricular volumes. For Doppler echocardiography, normalization of peak filling rate to mitral stroke volume rather than end-diastolic volume permits the derivation of a diastolic filling index that is relatively free of errors caused by geometric assumptions, diameter measurements and sample volume positioning. This normalization process can be achieved by simply dividing early peak filling velocity by the time velocity integral of mitral inflow. To validate this new Doppler echocardiographic filling index, Doppler echocardiographic and radionuclide-derived peak filling rate, both normalized to mitral stroke volume, were compared in 30 patients; there was an excellent correlation (r = 0.91, SEE = 0.88). This variable was not influenced by the position of the sample volume in relation to the mitral apparatus in contrast to early filling velocity, which increased 37%, and early/late filling (E/A) ratio, which increased 43% as the sample volume was moved from the anulus to the tips of the mitral leaflets. In a cohort of 22 normal patients, the mean peak filling rate normalized to mitral stroke volume (SV) was 5.25 +/- 1.47 SV/s. The mean peak filling rate for a subgroup of eight normal patients aged 57 to 89 years (mean 71 +/- 9) was 3.9 +/- 1 SV/s.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Demonstration of reperfusion after thrombolysis with technetium-99m isonitrile myocardial imaging.
Technetium-99m isonitrile myocardial perfusion imaging was employed in a patient undergoing thrombolytic therapy with recombinant tissue plasminogen activator for acute anteroseptal myocardial infarction. Technetium-99m isonitrile does not demonstrate significant myocardial redistribution after intravenous injection. The imaging agent was administered in the emergency room, prior to the initiation of thrombolytic therapy. The initial area at risk for infarction was visualized on images obtained after the patient had been effectively treated. Imaging performed 5 days later, after repeat injection of [99mTc]isonitrile, showed a smaller myocardial perfusion defect indicating salvage of myocardium. Thus, this technique offers promise as a noninvasive means of assessing the area at risk, the success of reperfusion, and the presence of salvaged myocardium, early in the course of acute myocardial infarction.
Fibrinolytic Agents↗
The role of nuclear cardiology in assessment of acute myocardial infarction.
In summary, nuclear techniques have important roles in both the acute and convalescent phase of MI. Acutely, both myocardial perfusion and ventricular function may be assessed. In patients treated with thrombolytic therapy, perfusion imaging, and metabolic imaging using PET may be able to delineate ischemic myocardium. These techniques are being developed to accurately quantify salvaged myocardium for assessing the efficacy of an acute intervention, and to characterize (functionally) the remaining myocardium for possible further intervention. In the convalescent phase, prognostic information is obtained from both rest and exercise evaluation of ventricular function and reserve, ambulatory monitoring, as well as from the presence of exercise-induced ischemia as documented by quantitative thallium imaging. The results of these studies can be used to determine appropriate management strategies.
Energy Metabolism↗
Usefulness of residual ischemic myocardium within prior infarct zone for identifying patients at high risk late after acute myocardial infarction.
This study examines the prognostic implications of ischemia within the territory of a prior acute myocardial infarction (AMI) vs ischemia at a distance, which develops late after AMI. Sixty-one consecutive patients who underwent both exercise thallium-201 (TI-201) imaging and cardiac catheterization for evaluation of chest pain that developed after discharge from the hospital for AMI form the study group. Mean interval between infarction to the TI-201 study was 10 +/- 17 months. Initial and 2-hour delay TI-201 images were analyzed quantitatively to determine the presence and location (within vs outside the prior infarct zone) of TI-201 redistribution, a marker of ischemic viable myocardium. TI-201 imaging results were separated into 3 groups based on presence and location of TI-201 redistribution: no significant TI-201 redistribution was found in 16 patients; in 29, TI-201 redistribution was confined to the infarct zone; and in 16, TI-201 redistribution was outside the infarct zone. Stepwise multivariate logistic regression analysis was used to examine the comparative ability of TI-201 results and other patient variables to predict cardiac events. For total cardiac events (cardiac death, recurrent nonfatal AMI, unstable angina and coronary revascularization), both the presence of any TI-201 redistribution and multivessel angiographic coronary artery disease were significant predictors. However, when coronary revascularization was excluded as an endpoint, TI-201 redistribution limited to the prior infarct zone was the only significant predictor of cardiac events. All 8 cardiac events occurred in patients with T1-201 redistribution limited to the infart zone.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Right ventricular myocardial infarction with anterior wall left ventricular infarction: an autopsy study.
Right ventricular myocardial infarction has been reported to occur exclusively in association with inferior left ventricular infarction. To determine the frequency of right ventricular myocardial infarction in association with anterior left ventricular myocardial infarction, all hearts with anterior myocardial infarction studied over a 3-year period were examined for evidence of right ventricular necrosis or scar. Of 97 hearts with anterior myocardial infarction, 13 (13%) had anterior right ventricular myocardial infarction. The right ventricular infarcts involved from 10% to 50% (mean 28%) of the circumference of the right ventricular free wall from base to apex. The associated left ventricular infarcts were all anteroseptal and large and involved from 36% to 67% (mean 50%) of the total area of the left ventricular free wall and septum. Nine of the 13 patients underwent equilibrium radionuclide angiography and six had demonstrable right ventricular regional and global dysfunction. Thus, right ventricular myocardial infarction does occur with anterior wall left ventricular infarction, and right ventricular dysfunction may be demonstrable by radionuclide angiography. Further investigation is needed to define the hemodynamic characteristics, clinical importance, and therapeutic implications of anterior right ventricular myocardial infarction.
Adult↗
Thallium-201 stress imaging in hypertensive patients.
To assess the potential effect of hypertension on the results of thallium-201 stress imaging in patients with chest pain, 272 thallium-201 stress tests performed in 133 hypertensive patients and 139 normotensive patients over a 1-year period were reviewed. Normotensive and hypertensive patients were similar in age, gender distribution, prevalence of cardiac risk factors (tobacco smoking, hyperlipidemia, and diabetes mellitus), medications, and clinical symptoms of coronary disease. Electrocardiographic criteria for left ventricular hypertrophy were present in 16 hypertensive patients. Stepwise probability analysis was used to determine the likelihood of coronary artery disease for each patient. In patients with mid to high likelihood of coronary disease (greater than 25% probability), abnormal thallium-201 stress images were present in 54 of 60 (90%) hypertensive patients compared with 51 of 64 (80%) normotensive patients. However, in 73 patients with a low likelihood of coronary disease (less than or equal to 25% probability), abnormal thallium-201 stress images were present in 21 patients (29%) of the hypertensive group compared with only 5 of 75 (7%) of the normotensive patients (p less than 0.001). These findings suggest that in patients with a mid to high likelihood of coronary artery disease, coexistent hypertension does not affect the results of thallium-201 exercise stress testing. However, in patients with a low likelihood of coronary artery disease, abnormal thallium-201 stress images are obtained more frequently in hypertensive patients than in normotensive patients.
Cardiomegaly↗
Radionuclide methods for evaluating the results of thrombolytic therapy.
In summary, a variety of nuclear techniques may be used to investigate the effects of thrombolytic therapy and myocardial reperfusion. Assessments of global and regional ventricular function, myocardial perfusion, and metabolic integrity are available and appear to add substantially to conventional assessment. Timing of studies appears to be critical. Complementary data can be obtained in both the acute and convalescent phase of myocardial infarction.
Diphosphates↗
Fast washout of thallium-201 from area of myocardial infarction: possible artifact of background subtraction.
A recent report described a pattern of "reverse redistribution" on poststreptokinase 201Tl studies which was believed to be due to rapid washout of 201Tl from the infarct area related to reperfusion of the infarct vessel. We have also observed the phenomenon of rapid washout of 201Tl from the area of infarction in the absence of thrombolytic therapy. This study was undertaken to test the hypothesis that rapid washout of 201Tl from an area of infarction is an artifact of background subtraction usually employed in analysis of washout. A total of 61 patients with previous myocardial infarction who underwent cardiac catheterization and exercise 201Tl imaging were examined. Thallium-201 images were analyzed using a validated quantitative method employing interpolative background correction. Abnormally increased 201Tl washout was noted in 11 infarct segments in 10 (18%) patients. Infarct segments with rapid washout had significantly less initial uptake, and more severe associated wall motion abnormalities than infarct segments with normal washout. When quantitative analysis was repeated without background subtraction, no segments with rapid washout were observed. A phantom model was constructed to further test our hypothesis. The frequency of observed rapid washout was directly related to the severity of the initial defect and was entirely dependent upon utilizing background correction during the quantitative analysis. Our study suggests that rapid washout of 201Tl in an area of previous infarction reflects an artifact of background subtraction involved with standard quantitative analysis.
Humans↗
The diagnosis of myocardial infarction in the presence of left bundle branch block.
Our analysis confirms the limited value of the electrocardiogram for the diagnosis of acute myocardial infarction in the presence of complete left bundle branch block. The various electrocardiographic criteria that have been proposed in the past as indicators of myocardial infarction lack sensitivity and predictive accuracy. In addition, they are subject to considerable inter-observer variability. In order of decreasing sensitivity, the following electrocardiographic criteria may be of diagnostic value: (1) serial changes of QRS complex or ST segment (sensitivity, 67 per cent); (2) ST segment elevation (sensitivity, 54 per cent; for anteroseptal infarction, 76 per cent); (3) abnormal Q waves (sensitivity, 31 per cent; for anteroseptal infarction, 53 per cent; highly specific: appearance of RV1, Qv6); and (4) sign of Cabrera (sensitivity, 27 per cent, for anteroseptal infarction, 47 per cent).
Bundle-Branch Block↗