Search PubMed⌕ Search

Biomedical subjects

F M Baer

Publications and source records attributed to F M Baer.

At least 55 records · Page 3Linked to original sources
PubMed1995

Comparison of low-dose dobutamine-gradient-echo magnetic resonance imaging and positron emission tomography with [18F]fluorodeoxyglucose in patients with chronic coronary artery disease. A functional and morphological approach to the detection of residual myocardial viability.

BACKGROUND: There have been conflicting reports of whether substantial myocardial thinning alone as an indirect sign of myocardial scarring is sufficient evidence to exclude the presence of viable myocardium in patients with previous myocardial infarction and persisting regional left ventricular akinesia. Demonstration of a dobutamine-induced contraction reserve in postischemic viable but akinetic myocardium may serve as a direct indicator of myocardial viability. In the present study, end-diastolic wall thickness at rest and dobutamine-induced systolic wall thickening assessed by magnetic resonance imaging (MRI) were compared with corresponding [18F]fluorodeoxyglucose uptake as assessed by positron emission tomography (FDG-PET). METHODS AND RESULTS: Thirty-five patients with myocardial infarction (infarct age, > 4 months) and regional akinesia or dyskinesia assessed by left ventriculography underwent rest and dobutamine MRI studies (10 micrograms dobutamine.min-1.kg-1) and FDG-PET followed by segmental analyses of end-diastolic wall thickness, systolic wall thickening, and FDG uptake in corresponding short-axis tomograms. Two definitions of viability, as assessed by MRI, of a segment akinetic at baseline were used: (1) end-diastolic wall thickness of > or = 5.5 mm (the mean minus 2.5 SD of a healthy control group [n = 21]) and (2) evidence of dobutamine-induced systolic wall thickening > or = 1 mm. Segments were graded as viable by FDG-PET if FDG uptake was > or = 50% of the maximum uptake in a region with normal wall motion as assessed by left ventriculography. Preserved end-diastolic wall thickness in akinetic regions was found in 17 of 35 (48%) patients at rest, and functional recovery within the infarct region was found in 19 of 35 (54%) patients during dobutamine infusion. Viability of the infarct region was indicated by FDG-PET in 23 of 35 patients (66%), yielding a diagnostic agreement between FDG uptake and myocardial morphology in 29 of 35 (83%) and between dobutamine-induced contraction reserve and FDG-PET in 31 of 35 (89%). Of 2200 segments, 482 (22%) were akinetic at rest. Of these akinetic segments, 234 (48%) had preserved end-diastolic wall thickness, 251 (52%) had a dobutamine-induced contraction reserve, and 299 (62%) were graded as viable by FDG-PET. Correlations of FDG uptake with end-diastolic wall thickness at rest (r = .48) and with dobutamine-induced wall thickening (r = .42) were similar. Comparison of segmental MRI and FDG-PET gradings indicated that dobutamine-induced wall thickening was a better predictor of residual metabolic activity (sensitivity, 81%; specificity, 95%; positive predictive accuracy, 96% than was end-diastolic wall thickness (sensitivity, 72%; specificity, 89%; positive predictive accuracy, 91%). However, grading a segment as viable if at least one of both MRI parameters fulfilled viability criteria improved the sensitivity (88%) of MRI for FDG-PET-assessed metabolic activity without a major decrease in specificity (87%) or positive predictive accuracy (92%). CONCLUSIONS: Viable myocardium is characterized by preserved end-diastolic wall thickness and a dobutamine-inducible contraction reserve. Both parameters should be taken into account to maximize the sensitivity of MRI in the detection of regions with signs of viability on FDG-PET images.

Coronary Angiography↗
PubMed1994

Morphologic correlate of pathologic Q waves as assessed by gradient-echo magnetic resonance imaging.

To assess the morphologic correlate of the presence and absence of pathologic Q waves in the electrocardiogram, 30 patients with and 17 patients without pathologic Q waves and chronic myocardial infarction (infarct age > 4 months) and 15 patients without previous myocardial infarction but significant coronary artery disease (> 70% diameter stenoses) were studied by gradient-echo magnetic resonance imaging (MRI). Short-axis MRI tomograms were evaluated on a segmental basis by calculating end-diastolic wall thickness and systolic wall thickening. All segments were graded transmural scar (end-diastolic wall thickness < end-diastolic wall thickness of a healthy control group [n = 21]-2.5 SD and lack of systolic wall thickening), hypokinetic (end-diastolic wall thickness > or = end-diastolic wall thickness of the control group-2.5 SD and systolic wall thickening < or = 2 mm), or normal (end-diastolic wall thickness > or = end-diastolic wall thickness of the control group-2.5 SD and systolic wall thickening > 2 mm) by MRI criteria. Myocardial infarcts were defined as transmural if at least 1 segment fulfilled the MRI criteria for transmural scar. Of 30 patients with Q-wave infarction, 26 (87%) had a transmural defect, and 6 of 17 patients (35%) with non-Q-wave infarction had a transmural infarct. Segmental evaluation yielded 129 of 480 scar segments (27%) for patients with Q-wave infarction, 20 of 272 scar segments (7%) for patients with non-Q-wave infarction, and no scar segments for patients without previous myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Dobutamine 99mTc-MIBI single-photon emission tomography: non-exercise-dependent detection of haemodynamically significant coronary artery stenoses.

Dobutamine pharmacological stress testing in conjunction with technetium-99m methoxyisobutylisonitrile single-photon emission tomography (MIBI SPET) may be a useful alternative to convential exercise stress MIBI SPET for the detection and localisation of coronary artery stenoses. Therefore, 35 patients with stenoses (> or = 50% diameter reduction) of one or more coronary arteries were selected for dobutamine MIBI SPET. Each patient underwent MIBI injection at rest and during dobutamine infusion with incremental doses (5, 10, 15 and 20 micrograms kg-1 min-1). A conventional exercise stress test (EST) was performed in all patients. Peak double product during steady-state dobutamine infusion (18,200 +/- 4200 mmHg min-1) was lower (P = 0.0001) than during EST (21,700 +/- 4900 mmHg min-1). Image quality was good in all but one patient, who had to be excluded from data analysis due to excessive hepatobiliary MIBI activity. Dobutamine-induced perfusion abnormalities were observed in 30/34 MIBI SPET studies, resulting in an overall detection rate for coronary artery disease of 88%. A pathological EST was observed in 23/34 patients (68%). The detection rate of individual coronary artery stenoses was 85% (28/33) for stenosess with a severe diameter reduction (> 70%) and 50% (12/24) for stenoses with a moderate diameter reduction (> or = 50-70%). In particular, sensitivity and specificity for the detection of moderate and severe stenoses (> or = 50%) were 75%/100% for left anterior descending, 67%/95% for left circumflex and 67%/69% for right coronary artery stenoses. Dobutamine MIBI SPET is a well-tolerated, non-exercise-dependent test for detection and localisation of haemodynamically significant coronary artery stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Constriction, Pathologic↗
PubMed1994

Assessment of viable myocardium by dobutamine transesophageal echocardiography and comparison with fluorine-18 fluorodeoxyglucose positron emission tomography.

OBJECTIVES: The aim of this study was to assess whether dobutamine transesophageal echocardiography can identify viable myocardium in patients with chronic myocardial infarction. BACKGROUND: Experimental and clinical studies have shown that dobutamine can recruit a contraction reserve in postischemic viable but akinetic segments, indicating that dobutamine-induced functional recovery is a potential ultrasound marker of myocardial viability. METHODS: Forty patients underwent rest and dobutamine transesophageal echocardiography (dobutamine 5, 10 and 20 micrograms/kg body weight per min) and fluorine-18 (F-18) fluorodeoxyglucose positron emission tomography at rest. Three representative short-axis tomograms and a transverse four-chamber-view were used for wall motion and F-18 fluorodeoxyglucose-uptake analysis in corresponding myocardial regions. A basally asynergic segment was considered viable by transesophageal echocardiography if dobutamine-induced systolic wall motion could be observed. Viability by positron emission tomography was defined as F-18 fluorodeoxyglucose uptake > or = 50% of the maximal uptake in a region with normal wall motion by left ventriculography. RESULTS: Functional recovery within the infarct region was found in 21 (53%) of 40 patients during dobutamine infusion. Infarct region-related viability by F-18 fluorodeoxyglucose uptake was diagnosed in 25 (63%) of 40 patients, yielding a diagnostic agreement between both techniques in 90% of patients. In 210 (89%) of 235 akinetic segments at rest, data on myocardial viability were concordant by the two techniques. The positive and negative predictive accuracy of dobutamine transesophageal echocardiography for viability defined by F-18 fluorodeoxyglucose uptake was 81% and 97%, respectively. Such uptake was significantly different (p < 0.001) between segments remaining akinetic (mean +/- SD 45 +/- 9%) during dobutamine infusion and segments with a dobutamine-induced contraction reserve (68 +/- 11%). CONCLUSIONS: Dobutamine transesophageal echocardiography provides a promising low cost and widely available approach to unmask myocardial viability in patients with chronic myocardial infarction, and results compare favorably with those of F-18 fluorodeoxyglucose positron emission tomography.

Adult↗
PubMed1994

Regional 99mTc-methoxyisobutyl-isonitrile-uptake at rest in patients with myocardial infarcts: comparison with morphological and functional parameters obtained from gradient-echo magnetic resonance imaging.

It is not yet clear whether 99mTc-methoxyisobutyl-isonitrile (MIBI)-uptake is a reliable indicator of myocardial viability, and a threshold value, differentiating viable from scarred myocardium, in comparison to a morphological and functional standard of reference has not been defined. MIBI-uptake was quantified in 800 segments from 55 patients with angiographically proven coronary artery disease with and without a history of myocardial infarction. Viable myocardium was defined from gradient-echo magnetic resonance images (MRI) as regions with systolic wall thickening or an end-diastolic wall thickness above the mean value -2.5 SD of a healthy control group (n = 21). Scar was defined as end-diastolic wall thickness > 2.5 SD below the normal mean value and absent systolic wall thickening or wall thinning. Mean MIBI-uptake of viable (n = 676; 79 +/- 14%) and scar segments by MRI (n = 124; 31 +/- 16%) was significantly different (P < 0.001). Segmental MIBI-uptake vs end-diastolic wall thickness (r = 0.7) and systolic wall thickening (r = 0.71) yielded a fair correlation. The highest values as regards sensitivity and specificity of MIBI-uptake in predicting the presence of scar were 89% and 96% respectively for MIBI-uptake < or = 50%. However, of the 136 segments with MIBI-uptake < or = 50%, 26 (19%) were viable by MRI, resulting in a positive predictive accuracy for scar tissue of 81%. Of the 26 segments diagnosed as scarred by MIBI-SPECT but viable by MRI, 25 (96%) were located in the inferoseptal region. MIBI-SPECT seems useful in the detection of viable myocardium after anterior myocardial infarcts, but over-estimates scar in the inferoseptal regions. Perfusion defects in these regions could be confirmed or denied by additional evaluation of myocardial morphology and function by MRI or tissue metabolism by positron emission tomography (PET).

Adult↗
PubMed1994

Gradient-echo magnetic resonance imaging during incremental dobutamine infusion for the localization of coronary artery stenoses.

Dobutamine pharmacological stress testing in conjunction with gradient-echo magnetic resonance imaging (MRI) may be a useful tool for the assessment of haemodynamically significant coronary artery stenoses. Therefore, 28 patients without previous myocardial infarction but significant proximal stenoses (> or = 70% diameter stenosis) of one or more coronary arteries were selected for dobutamine-MRI. Each patient underwent MRI at rest and during incremental dobutamine infusion (5, 10, 15 and 20 micrograms.kg-1.min-1). Additionally, all patients were submitted to exercise stress electrocardiography (EST). A total of 72 segments per patient obtained from identical short axis and transverse tomograms at rest and during dobutamine infusion were evaluated by two observers. Each segment was graded as normal, hypokinetic, akinetic or dyskinetic. Dobutamine-MRI was considered pathological if segmental wall motion deteriorated by at least one grade after dobutamine infusion. For comparison with coronary angiography, segmental wall motion gradings were related to the respective coronary artery territories. Peak rate-pressure product during steady-state dobutamine infusion (18.493 +/- 4.315 mmHg.min-1) was significantly lower (P < 0.01) than during EST (21.316 +/- 4.937 mmHg.min-1). Dobutamine-induced wall motion abnormalities were observed in 22/26 (85%) MR studies and 20/26 (77%) patients had a pathological EST. Regional asynergy induced by dobutamine-MRI occurred in 11/15 (73%) patients with single and 11/11 (100%) with multi-vessel disease. Sensitivity and specificity for the detection of a stenosed coronary artery were 87% and 100% for the left anterior descending, 62% and 93% for the left circumflex and 78% and 88% for the right coronary artery respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Coronary artery disease: findings with GRE MR imaging and Tc-99m-methoxyisobutyl-isonitrile SPECT during simultaneous dobutamine stress.

PURPOSE: This study compared gradient-recalled echo (GRE) magnetic resonance (MR) imaging with technetium-99m-methoxyisobutyl isonitrile (MIBI) single photon emission computed tomography (SPECT) during the same dobutamine stress for the localization of coronary artery stenoses. MATERIALS AND METHODS: In 35 consecutive patients (28 men and seven women, aged 41-79 years) with angiographically documented coronary artery disease, corresponding GRE MR images and SPECT tomograms were acquired at rest and during dobutamine infusion and were evaluated for regional wall motion or perfusion abnormalities. RESULTS: Images in both examinations could be analyzed in 32 of 35 (91%) patients. Wall motion or perfusion abnormalities were observed in 27 of 32 (84%) GRE MR imaging and in 28 of 32 (87%) SPECT examinations. Sensitivity and specificity of dobutamine GRE MR imaging and dobutamine SPECT for the localization of left anterior descending coronary artery stenoses were 74% and 100% versus 70% and 100% for the combined left circumflex and right coronary artery perfusion territories. CONCLUSION: GRE MR imaging and SPECT have a high concordance with respect to the detection of a dobutamine-induced ischemic response.

Constriction, Pathologic↗
PubMed1994

[Magnetic resonance tomography imaging techniques for diagnosing myocardial vitality].

In contrast to the established nuclear imaging techniques magnetic resonance imaging (MRI) is only in the early phase of its application to detect viable myocardium after myocardial infarction. Although MRI techniques have only recently been employed to assess residual myocardial viability three approaches have been described to achieve this purpose: First, the use of signal intensity changes on spin-echo images with and without the application of contrast media to define irreversible injury to the myocardium in acute and subacute infarcts; second, measurement of metabolite concentrations within the infarct area using magnetic resonance spectroscopy, and third quantitation of myocardial thickness and systolic wall thickening in chronic infarcts with and without positive inotropic stimulation. When applying magnetic resonance techniques to detect viable myocardium by imaging techniques, it is useful to distinguish between acute infarcts and chronic infarcts that are more than 16 weeks old. After the time, practically all infarcts have healed and the necrotic myocardium has been transformed into scar tissue. MRI seems ideally suited to detect and characterize chronic myocardial scar and distinguish it from viable but hibernating myocardium because it clearly depicts the regional wall thinning which is a typical feature of transmural infarcts (Figure 1). In contrast, more recent infarcts, even if they are transmural and fail to show any contraction during systole, may not yet exhibit myocardial thinning. Therefore, simply depicting the acutely injured myocardium by MRI is not sufficient to differentiate between necrotic and stunned, but viable myocardium. On the other hand, an increase in signal intensity of acutely infarcted myocardium, which appears on T2 weighted spin-echo MR images only a few hours after occlusion of a coronary artery, can be used to determine the extent of irreversible myocardial damage (Figure 2). It is not clear, however, whether this area of increased myocardial signal intensity that is seen within the first week after the event only represents necrotic myocardium or incorporates some edematous viable myocardium in the infarct border zone. After three weeks, true infarct size may be more closely approximated by the area of increased signal intensity because the edema surrounding the infarct has presumably regressed and signal abnormalities are restricted to the pathologically determined infarct area. More recently, new pulse sequences and high field magnets permit separate observation of the endocardial and epicardial portion of the left ventricular wall. This may further improve the detection of residual viable cells which are preferentially located near the epicardium.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1994

[Assessing myocardial viability in chronic myocardial infarct with 18F-fluoro-D-glucose positron emission tomography and 99mTc-MIBI SPECT].

The determination of residual viability in regions of myocardial infarcts is of considerable clinical interest. In order to assess residual viability in regions with chronic myocardial infarction, 18 patients with anterior myocardial infarcts and 14 patients with inferior myocardial infarcts as confirmed by ECG and cine ventriculography underwent 99mTc-methoxyisobutyl-isonitrile single photon emission computed tomography (MIBI-SPECT) and 18F-fluoro-D-glucose positron emission tomography (FDG-PET). Tracer uptake was quantified in 13 segments for each patient (a total of 416 segments). MIBI uptake was normalized to the maximal uptake in the heart, FDG uptake was normalized to the maximal uptake of left ventricular segments with normal contraction by cine ventriculography and without significant stenosis of the coronary artery supplying this region. MIBI-SPECT scar and FDG-PET scar were defined as tracer uptake of less than 2.5 SD below mean values of a healthy control group. Both methods scored 258 segments concordantly viable and 74 segments concordantly scar; 61 segments were scored scar by MIBI-SPECT and viable by FDG-PET, 23 segments were scored viable by MIBI-SPECT and scar by FDG-PET (p < 0.0001). In patients with anterior myocardial infarction, 136 segments were scored viable and 53 segments were scored scar by both methods, 29 segments were scored scar by MIBI-SPECT and viable by FDG-PET, 16 were scored discordantly viable by MIBI-SPECT and scar by FDG-PET (p < 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Identification of hemodynamically significant coronary artery stenoses by dipyridamole-magnetic resonance imaging and 99mTc-methoxyisobutyl-isonitrile-SPECT.

Magnetic resonance imaging (MRI) has been used in conjunction with dipyridamole induced wall motion abnormalities for the noninvasive detection of coronary artery disease (CAD). To assess the clinical usefulness of dipyridamole-MRI for the localization of CAD and to evaluate the relation between dipyridamole induced wall motion abnormalities and myocardial perfusion 33 patients with severe CAD (> 70% diameter reduction) underwent MRI at rest and after dipyridamole infusion (0.75 mg dipyridamole/kg over a period of 10 minutes). All patients performed exercise stress testing and 20 patients of the study group additionally had rest and exercise stress 99mTc-methoxyisobutyl-isonitrile-SPECT (MIBI-SPECT). Two patients (6%) could not be evaluated due to severe motion artifacts during dipyridamole MRI. Segmental wall motion and perfusion of corresponding short axis planes were related to the major coronary arteries using a standardized segmental coronary artery perfusion pattern. Detection of wall motion abnormalities or perfusion defects by 2 blinded observers in consensus was the criterion for grading a segment normal or pathologic. For localization of CAD, segmental gradings were related to the presumed coronary artery territories. Stress-ECG was pathologic in 19/31 patients yielding a sensitivity of 61% and dipyridamole induced angina was present in 68% (21/31) of patients. Dipyridamole-MRI detected coronary artery disease with a sensitivity of 84% (26/31 patients) and all patients with new wall motion abnormalities also had dipyridamole induced angina. For the subgroup of 20 patients with MIBI-SPECT images, CAD was detected by both MIBI-SPECT and Dipyridamole-MRI in 90% (18/20) of patients. Dipyridamole-MRI and MIBI-SPECT gradings agreed in 55/60 (92%) coronary artery perfusion territories. There were no significant differences with respect to the sensitivities of Dipyridamole-MRI/MIBI-SPECT for the localization of individual coronary artery stenoses yielding 81%/78% for left anterior descending, 80%/80% for left circumflex and 92%/89% for right coronary artery stenoses. However, specificity of Dipyridamole-MRI (89%) for the detection of RCA stenoses was slightly better than for MIBI-SPECT (80%).

Coronary Angiography↗
PubMed1993

[Dobutamine versus dipyridamole magnetic resonance tomography: safety and sensitivity in the detection of coronary stenoses].

Safety and sensitivity of gradient-echo magnetic resonance imaging (MRI) for the identification of significant coronary artery stenoses using pharmacologic stress testing was assessed in 61 patients with > or = 70% stenosis of a major coronary artery and a normal left ventricle. After MRI at rest 28 patients underwent dobutamine-MRI during steady-state dobutamine infusion (5, 10, 15 and 20 micrograms/kg/min) and 33 patients had dipyridamole-MRI after high-dose dipyridamole infusion (0.75 mg/kg over 10 min). All patients additionally performed standard ECG exercise stress testing (EST). Segmental wall motion analysis was performed in basal and midventricular short axis tomograms by two observers. A segment was graded pathologic if transient dobutamine or dipyridamole induced wall motion abnormalities could be detected. For comparison to coronary angiography findings, each segment was assigned to one of the coronary artery perfusion territories. There were no serious side-effects during dobutamine and dipyridamole infusion leading to termination of the study protocol. Peak double product during dobutamine infusion was significantly higher (p < 0.001) than after dipyridamole infusion (18.493 +/- 4.311 versus 12.799 +/- 2.694 mm Hg/min). Overall sensitivity of dobutamine and dipyridamole-MRI for coronary artery disease (CAD) was 85% and 84%. Regional asynergy by dobutamine and dipyridamole-MRI was observed in 73% versus 79% patients with single- and 100% versus 92% with multi-vessel disease. Individual coronary artery stenoses were correctly identified by segmental wall motion abnormalities in 87% versus 81% for left anterior descending, 62% versus 86% for left circumflex and 78% versus 92% for right coronary artery stenoses. In conclusion, dobutamine and dipyridamole-MRI are well tolerated and safe non-exercise dependent tests for detection and localization of hemodynamically significant coronary artery stenoses with a similar diagnostic accuracy but with a better control of stress intensity and duration provided by dobutamine.

Adult↗
PubMed1992

Feasibility of high-dose dipyridamole-magnetic resonance imaging for detection of coronary artery disease and comparison with coronary angiography.

To assess the feasibility, safety and usefulness of gradient-echo magnetic resonance imaging (MRI) combined with pharmacologic stress testing for the detection of coronary artery disease, 23 patients without previous myocardial infarction but with significant stenosis (greater than 70% diameter stenosis) of greater than or equal to 1 major coronary artery were selected for dipyridamole-MRI stress testing. Each patient underwent MRI at rest, and high-dose dipyridamole-MRI (0.75 mg/kg over 10 minutes) of corresponding basal and midventricular short-axis tomograms. Additionally, these patients performed symptom-limited exercise stress tests. All short-axis tomograms were evaluated on a standardized segmental basis by grading each segment as normal, hypokinetic, akinetic or dyskinetic. Dipyridamole-MRI was considered pathologic if segmental wall motion deteriorated by greater than or equal to 1 grade after dipyridamole. For comparison with coronary angiography, segmental wall motion gradings were related to the respective coronary artery territories in the short-axis plane. Pathologic dipyridamole-MRI was obtained in 18 of 23 (78%) patients. For 1- and 2-vessel diseases, sensitivity was 69 and 90%, respectively. Exercise stress tests were pathologic in 14 of 23 (66%) patients. For 1- and 2-vessel diseases, sensitivity of exercise stress test was 58% (7 of 12 patients) and 77% (7 of 9), respectively. Sensitivity/specificity of dipyridamole-MRI for the localization of the stenosed coronary artery was 78/100% for left anterior descending, 73/100% for left circumflex, and 88/87% for right coronary artery stenoses. It is concluded that dipyridamole-MRI is a feasible nonexercise-dependent test for detection and localization of functionally significant coronary artery disease.

Aged↗
PubMed1992

Chronic myocardial infarction: assessment of morphology, function, and perfusion by gradient echo magnetic resonance imaging and 99mTc-methoxyisobutyl-isonitrile SPECT.

To assess the ability of magnetic resonance imaging (MRI) to identify the anatomic and functional abnormalities associated with completely scarred myocardium, 20 patients with chronic transmural myocardial infarction confirmed by electrocardiography and cineventriculography were examined by gradient echo MRI. Myocardial perfusion at rest was assessed in corresponding transverse sections using 99mTc-methoxyisobutyl-isonitrile single-photon emission computed tomography (MIBI-SPECT). MRI scar was defined as diastolic wall thickness (DWT) 2.5 SD below corresponding normal values or systolic wall thickening (delta WT) less than or equal to 1 mm. For MIBI-SPECT images, scar was defined as a MIBI uptake less than 2.5 SD below normal values. By MIBI-SPECT, 152 segments contained normal tissue and 88 contained scarred myocardium. In 226 of 240 (94%) segments, MRI gradings by DWT and MIBI-SPECT gradings were identical. DWT by MRI was higher in normal than in scarred MIBI-SPECT segments (10 +/- 1 versus 4 +/- 2 mm, p less than 0.001). In 230 of 240 (96%) segments, MRI gradings by delta WT and MIBI-SPECT gradings were identical. Segments graded normal by MIBI-SPECT showed higher delta WT by MRI than scar segments (5 +/- 1 versus 0.3 +/- 1 mm, p less than 0.001). MIBI-SPECT perfusion defect size and regions with reduced DWT on MRI tomograms correlated well (r = 0.85). This study indicates that myocardial regions fulfilling electrocardiographic and ventriculographic criteria for transmural myocardial scar are clearly depicted by regional diastolic wall thinning and delta WT less than or equal to 1 mm on gradient echo MR images.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Magnetic resonance tomography image of transmural myocardial infarct in comparison with 99mTc-methoxyisobutylisonitrile SPECT].

To assess the ability of magnetic resonance imaging (MRI) to identify morphologic and functional abnormalities associated with transmural anterior and inferior myocardial infarction, 18 patients with anterior myocardial infarcts and 11 patients with inferior myocardial infarcts confirmed by ECG and cine-ventriculography underwent gradient-echo MRI of transverse and short-axis imaging planes. Myocardial perfusion of corresponding imaging planes was measured by 99mTc-methoxyisobutyl-isonitrile single-photon emission computed tomography (MIBI-SPECT). Transmural scar by MRI was defined as diastolic wall thickness 2.5 SD below corresponding normal values of a healthy control group (n = 21). MIBI-SPECT scar was defined as a MIBI uptake less than 2.5 SD below mean values of a healthy control group (n = 11). By MIBI-SPECT, 231 segments contained normal tissue and 161 contained scarred myocardium. In 352/392 (90%) segments gradings based on diastolic wall thickness and MIBI-SPECT gradings were identical. Diastolic wall thickness was significantly higher in normal than in scarred MIBI-SPECT segments (10.3 +/- 1.5 vs 5.2 +/- 2 mm, p less than 0.0001). Additionally, normal segments by MIBI-SPECT showed significantly higher systolic wall thickening than scar segments (5.5 +/- 1.5 vs 0.6 +/- 1.6 mm, p less than 0.0001). The correlation between MRI and MIBI-SPECT assessed infarct size was r = 0.91 for anterior and r = 0.77 for inferior myocardial infarcts. The agreement between MIBI-SPECT perfusion defect size and regions with reduced diastolic wall thickness on MRI tomograms was significantly better for anterior myocardial infarcts than for inferior myocardial infarcts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Effort-induced myocardial wall motion abnormalities in the magnetic resonance tomogram: a comparison with effort MIBI SPECT].

In 20 patients with an angiographically documented coronary artery stenosis of > or = 70% and normal LV function at rest MRI was performed before and after dipyridamole infusion (0.75 mg/kg BW). In all patients MIBI-SPECT was obtained at rest and after dynamic symptom-limited exercise. In 18 patients MIBI-SPECT showed ischemia and in 18 patients dipyridamole MRI showed a wall motion impairment. In the segments representing the 29 stenosed vessels ischemia in MIBI-SPECT was diagnosed correctly in 24 instances (sensitivity 83%, specificity 90%) and a wall motion abnormality was present in MRI in 23 instances (sensitivity 79%, specificity 90%). Dipyridamole GE-MRI is not superior to MIBI-SPECT in the diagnosis of ischemia.

Aged↗
PubMed1992

[Magnetic resonance tomography in coronary heart disease].

Although magnetic resonance imaging is currently only employed to solve diagnostic problems in a few selected patients, the special features of the technique such as its inherent three-dimensional capabilities and the prospect of angiographic noninvasive imaging suggest that this technique will become more important with future technical improvements. This overview summarizes the present status of magnetic resonance imaging in the depiction of coronary arteries and bypass grafts, the diagnosis of myocardial ischemia, the depiction of chronic myocardial infarcts including the detection of residual viable myocardium, and the diagnosis of complications associated with myocardial infarction.

Coronary Disease↗
PubMed1988

The Valsalva maneuver as an indirect, non-invasive indicator of central blood volume shift.

Our objective was to determine whether the Valsalva maneuver may be used as an indicator of fluid shift during spaceflights. The subjects, 21 healthy young men, conducted the maneuver against expiratory pressures of 20, 30, and 40 mm Hg, each lasting 30 s, at body positions of vertical, horizontal, and 6 degrees head down tilt (HDT). Heart rate was continuously recorded on a beat by beat basis together with the expiratory pressure. The increase in heart rate at equal intrathoracic pressures was maximal in the vertical position, significantly lower (p less than 0.001) in the horizontal position and lowest (p less than 0.05) in the 6 degrees HDT position. Obviously, the blood volume shift in the horizontal and 6 degrees HDT position partly compensated the impaired venous return during the Valsalva maneuver. This simple and non-invasive technique might be used to indicate the time course of blood volume shift during the initial stage of an orbital flight.

Adult↗