Changes in left ventricular diastolic function 6 months after nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy

BACKGROUND: Nonsurgical septal reduction therapy (NSRT) decreases left ventricular outflow tract (LVOT) gradient and improves symptoms in patients with hypertrophic obstructive cardiomyopathy (HOCM). NSRT effects on LV/left ventricular diastolic function are currently unknown. METHODS AND RESULTS: HOCM patients (n=29) had Doppler echocardiography at baseline and 6 months after NSRT to evaluate changes in LV volume, pre-A-wave pressure, early diastolic mitral annulus velocity (Ea) by tissue Doppler, and tau. At 6 months, a significant reduction in LVOT gradient (from 53.6+/-15 to 6+/-5 mm Hg; P<0.001) was accompanied by improvement in exercise duration (from 284+/-147 to 408+/-178 seconds; P=0.04) and New York Health Association class (from III to I; P<0.001). Pre-A pressure (18+/-6 to 14+/-5 mm Hg; P<0.01) and tau (62+/-8 to 51+/-8 ms; P<0.01) decreased, whereas Ea (5.8+/-1.8 to 8+/-1.8 cml/s; P<0.01) and LV end-diastolic volume (117+/-16 to 130+/-22 mL; P<0.01) increased. CONCLUSIONS: NSRT improves LV relaxation and compliance, which contributes to the symptomatic relief seen at 6 months.     

Echocardiography-guided ethanol septal reduction for hypertrophic obstructive cardiomyopathy

BACKGROUND: Left ventricular outflow tract (LVOT) obstruction is frequently responsible for symptoms in hypertrophic obstructive cardiomyopathy (HOCM). Medical therapy is often not sufficient to control these symptoms, and surgical myotomy-myomectomy is required. METHODS AND RESULTS: We enrolled 33 symptomatic patients with HOCM and obstruction (>/=40 mm Hg gradient at rest or >/=60 mm Hg dobutamine-provoked). By contrast echocardiography, the bulging septum was localized and infarcted by injection of 2 to 5 mL of absolute ethanol into the septal artery(ies) supplying the hypertrophied area. Baseline echocardiograms with Doppler, myocardial perfusion tomograms, and treadmill exercise or pharmacological testing were compared with those at 6 weeks and 6 months. The mean rise in creatine kinase was 1964+/-796 U. All patients experienced symptomatic relief; NYHA class decreased from 3. 0+/-0.5 to 0.9+/-0.6 (P<0.001). Exercise time increased from 286+/-193 to 421+/-181 seconds (P=0.03). The resting and dobutamine-provoked gradient decreased from 49+/-33 and 96+/-34 mm Hg to 9+/-19 (P<0.001) and 24+/-31 mm Hg (P<0.001), respectively. Echocardiograms repeated at 6 weeks after the procedure showed a 28% reduction in septal thickness and 17% reduction in left ventricular mass. Myocardial perfusion imaging showed a "septal amputation pattern," with scarring in the upper and middle septal areas. Complete heart block developed in 11 patients, who then required permanent pacemaker implantation. CONCLUSIONS: Echocardiography-guided ethanol septal reduction in patients with HOCM is a safe, minimally invasive procedure that provides symptomatic relief with improved hemodynamic and left ventricular parameters.     

Complex segregation analyses: uses and limitations

It is sometimes difficult to visualize the luminal borders of the vessel even by intracoronary ultrasound (ICUS), especially after coronary intervention. In this study, we evaluated the potential for improving visualization at intervention sites using contrast-enhanced ICUS and the suitable contrast agents for this procedure in humans. In 37 patients, ICUS (30 MHz) was performed with intracoronary injection (3 ml) of 7 different contrast preparations and without the contrast agents (control) after coronary intervention. The contrast agents used were as follows: saline solution, standard iomeprol, standard ioxaglate, sonicated iomeprol, sonicated ioxaglate, 50% Albunex, and 100% Albunex. Vessel wall delineation, contrast homogeneity (Grade 0-3), peak contrast intensity and shadowing were examined. Homogeneous and complete opacification of the vessel lumen and false lumen was observed with sonicated ioxaglate, 50% and 100% Albunex. Shadowing was not observed at all with sonicated ioxaglate and was uncommon with 50% Albunex, whereas 100% Albunex caused shadowing in all cases. The coronary delineation rate with the other contrast agents was only 50-70 %, and the homogeneity and peak intensity were relatively low. Thus, sonicated ioxaglate and 50 % Albunex both achieved good visualization, but the former is cheaper, stable and takes shorter to prepare. Large dissection in 5 patients were found by contrast-enhanced ICUS' whereas they were not detected by coronary angiography. All of them needed additional interventional therapy due to the results of contrast-enhanced ICUS. In conclusion, contrast-enhanced ICUS is useful for evaluation of the results by intervention therapy, and of the agents we studied sonicated ioxaglate is best for contrast-enhanced ICUS.     

International collaboration of Japanese rheumatology

Septal hypoperfusion is often observed in patients with complete left bundle branch block (LBBB) in myocardial perfusion imaging. Abnormal wall motion in the septal region may potentially cause artifactual perfusion abnormalities. To assess the effect of abnormal wall thickening on myocardial perfusion images, ECG-gated sestamibi SPECT was performed on 12 patients with LBBB and 10 normal subjects used as controls. METHODS: After administration of 740 MBq 99mTc-sestamibi injection at rest, ECG-gated SPECT was obtained 60 min later with division of the cardiac cycle into eight frames. RESULTS: Septal hypoperfusion was noted in 10 patients on nongated images and 11 patients on end-systolic (ES) images, whereas only two patients showed abnormalities on end-diastolic (ED) images. The septal to lateral wall count ratio in the LBBB group was lower (0.72 +/- 0.09) than in the control group (0.84 +/- 0.09) (p < 0.01) at nongated images, while it was similar at ED images (0.84 +/- 0.11 versus 0.86 +/- 0.12; ns). In addition, the count increase from ED to ES during a cardiac cycle in the septal region was smaller compared with the lateral region in the LBBB patients (25% +/- 19% in the septal region, versus 48% +/- 14% in the lateral region; p < 0.01), indicating less wall thickening in the septal region. CONCLUSION: Smaller count increase due to reduced wall thickening in the septal region may mimic hypoperfusion in patients with LBBB. This artifact can be eliminated with ECG-gated 99mTc-sestamibi SPECT, particularly with ED images.     

Scatter rejection in modular gamma cameras for use in dynamic 3D spect brain imaging system

This study examined the effects of Albunex (sonicated 5% human serum albumin) infusion on left ventricular inflow velocity by Doppler echocardiography. Left ventricular pressure and left ventricular inflow velocity were recorded simultaneously under eight different conditions in dogs: 1) baseline 1 (control), 2) Albunex 0.2 ml/kg, 3) baseline 2, 4) Albunex 0.5 ml/kg, infusion of dextran 100 ml, 5) baseline 3, 6) Albunex 0.2 ml/kg, 7) baseline 4, and 8) Albunex 0.5 ml/kg. In the normal state (no dextran), Albunex (0.2 ml/kg) caused no hemodynamic changes or inflow velocity changes. In contrast, infusion of Albunex (0.5 ml/kg) caused time velocity integrals of early filling to increase from the baseline (5.51 +/- 1.13 vs 7.19 +/- 1.14 cm, p < 0.05). After dextran infusion (100 ml), Albunex (0.2 ml/kg) caused peak early filling velocity to increase (62.4 +/- 6.9 vs 67.3 +/- 9.4 cm/sec, p < 0.05), and infusion of Albunex (0.5 ml/kg) also caused peak early filling velocity to increase from baseline (64.6 +/- 8.5 vs 73.7 +/- 14.5 cm/sec, p < 0.05). Infusion of Albunex (0.5 ml/kg) after dextran infusion caused increases in left ventricular pressure at the mitral valve opening (12.7 +/- 3.1 vs 15.2 +/- 3.3 mmHg, p < 0.05) and in left atrial driving force (13.5 +/- 3.6 vs 16.7 +/- 5.9 mmHg, p < 0.05). Clinicians should be cautious about using Albunex at doses of greater than 0.2 ml/kg when evaluating the pressure gradient of the left ventricle in patients with elevated left ventricular diastolic pressure. In patients with normal hemodynamics, Albunex infusion at doses of less than 0.2 ml/kg apparently did not affect the velocity measurement.     

Accuracy and feasibility of contrast echocardiography for detection of perfusion defects in routine practice: comparison with wall motion and technetium-99m sestamibi single-photon emission computed tomography. The Nycomed NC100100 Investigators

OBJECTIVES: We sought to assess the feasibility and accuracy of myocardial contrast echocardiography (MCE) using standard imaging approaches for the detection of perfusion defects in patients who had a myocardial infarction (MI). BACKGROUND: Myocardial contrast echocardiography may be more versatile than perfusion scintigraphy for identifying the presence and extent of perfusion defects after MI. However, its reliability in routine practice is unclear. METHODS: Fundamental or harmonic MCE was performed with continuous or triggered imaging in 203 patients with a previous MI using bolus doses of a perfluorocarbon-filled contrast agent (NC100100). All patients underwent single-photon emission computed tomography (SPECT) after the injection of technetium-99m (Tc-99m) sestamibi at rest. Quantitative and semiquantitative SPECT, wall motion and digitized echocardiographic data were interpreted independently. The accuracy of MCE was assessed for detection of segments and patients with moderate and severe sestamibi-SPECT defects, as well as for detection of patients with extensive perfusion defects (>12% of left ventricle). RESULTS: In segments with diagnostic MCE, the segmental sensitivity ranged from 14% to 65%, and the specificity varied from 78% to 95%, depending on the dose of contrast agent. Using both segment- and patient-based analysis, the greatest accuracy and proportion of interpretable images were obtained using harmonic imaging in the triggered mode. For the detection of extensive defects, the sensitivity varied from 13% to 48%, with specificity from 63% to 100%. Harmonic imaging remained the most accurate approach. Time since MI and SPECT defect location and intensity were all determinants of the MCE response. The extent of defects on MCE was less than the extent of either abnormal wall motion or SPECT abnormalities. The combination of wall motion and MCE assessment gave the best balance of sensitivity (46% to 55%) and specificity (82% to 83%). CONCLUSIONS: Although MCE is specific, it has limited sensitivity for detection of moderate or severe perfusion defects, and it underestimates the extent of SPECT defects. The best results are obtained by integration with wall motion. More sophisticated methods of acquisition and interpretation are needed to enhance the feasibility of this technique in routine practice.     

99mTc-HL91. Effects of low flow and hypoxia on a new ischemia-avid myocardial imaging agent

OBJECTIVES: The aim of this study was to determine whether three-dimensional (3D) myocardial contrast echocardiography (MCE) could provide an accurate in vivo assessment of risk and infarct volumes. BACKGROUND: MCE has been shown to accurately define risk area and infarct size in single tomographic slices. The ability of this technique to measure risk and infarct volumes by using three-dimensional echocardiography (3DE) has not been determined. METHODS: Fifteen open chest dogs underwent variable durations of coronary artery occlusion followed by reperfusion. At each stage, MCE was performed by using left atrial injection of AIP201, a deposit microbubble with a mean diameter of 10 +/- 4 microm and a mean concentration of 1.5 x 10(7) x ml(-1). Images were obtained over a 180 degree arc with use of an automated rotational device and were stored in computer as a 3D data set. Postmortem risk area and infarct size were measured in six to eight left ventricular short-axis slices of equal thickness using technetium-99m autoradiography and tissue staining, respectively. MCE images corresponding to these planes were reconstructed off-line. RESULTS: A close linear relation was noted between the volume of myocardium not showing contrast enhancement on 3D MCE during coronary occlusion and postmortem risk volume (y = 1.2x - 3.0, r = 0.83, SEE = 5.1, n = 15). The volume of myocardium not showing contrast enhancement on 3D MCE after reperfusion also closely correlated with postmortem infarct volume (y = 1.1x - 3.9, r = 0.88, SEE = 4.8, n = 11). No changes in systemic hemodynamic variables were noted with injections of AIP201. CONCLUSIONS: When combined with AIP201, a deposit microbubble, 3D MCE can be used to accurately determine both risk and infarct volumes in vivo. This method could be used to assess the effects of interventions that attempt to alter the infarct/risk volume ratio.     

Quantitative assessment of the operative results after extended myectomy and surgical reconstruction of the subvalvular mitral apparatus in hypertrophic obstructive cardiomyopathy using dynamic three-dimensional transesophageal echocardiography

OBJECTIVES: The aim of this study was to examine the value of dynamic three-dimensional (3D) transesophageal echocardiography (TEE) for the postoperative evaluation after extended myectomy and surgical reconstruction of the subvalvular mitral valve apparatus in patients with hypertrophic obstructive cardiomyopathy (HOCM). BACKGROUND: Two-dimensional imaging techniques such as echocardiography, computed tomography and magnetic resonance imaging have not been able to precisely quantify the effects of surgical therapy on the morphology of the left ventricular outflow tract (LVOT). METHODS: Multiplane TEE with 3D reconstruction was performed in 11 patients before and after the operation and in 16 normal control subjects for comparison. The preoperative maximal systolic pressure gradient in the LVOT was 69 +/- 59 mm Hg. The following variables were measured within the dynamic 3D data set: depth, width, length and cross-sectional area (CSA) gain caused by the myectomy trough, minimal CSA of the LVOT at each time point and its cyclic changes and maximal mitral leaflet deviation during systole. RESULTS: Functional class improved from 3.0 +/- 0.2 before the operation to 1.5 +/- 0.6 after it. The maximal systolic pressure gradient in the outflow tract decreased to 26 +/- 21 mm Hg postoperatively (p < 0.001). Minimal CSA of the outflow tract increased from 1.1 +/- 1.2 to 3.8 +/- 1.9 cm2 postoperatively (p < 0.001), similar to the value of the control group (4.2 +/- 1.5 cm2, p = NS). The area gain due to the myectomy trough was 1.3 +/- 1.0 cm2, corresponding to 48 +/- 12% of the total operative area difference. Maximal systolic depth of the myectomy was 7 +/- 2 mm, maximal width was 20 +/- 8 mm and length was 28 +/- 7 mm. Maximal deviation of the mitral leaflets fell from 15 +/- 7 to 6 +/- 7 mm postoperatively (p < 0.01). In five patients mass measurements of the intracavitary portion of the papillary muscle (PM) revealed an increase from 7.3 +/- 1.0 to 12.1 +/- 2.5 g due to surgical mobilization of PMs (p < 0.01). CONCLUSIONS: 3D TEE quantifies the differences in outflow tract morphology before and after surgery for HOCM. This technique may have an impact on the planning of operative interventions and allow for the evaluation of its results.     

Sonicated albumin in exercise echocardiography: technique and feasibility to enhance endocardial visualization

Left ventricular cavity opacification can be produced by the intravenous injection of sonicated albumin (Albunex 422). A recent study suggested that sonicated albumin may be useful in dobutamine stress echocardiography, but its use in exercise echocardiography has not been reported. The purposes of the study were to assess the feasibility of using Albunex to enhance endocardial visualization and to evaluate the factors affecting Albunex kinetic in exercise echocardiography. Fifteen healthy volunteers underwent two exercise echocardiograms on the same day, with intravenous injection of Albunex during one of the studies. Two injections up to a maximum of 20 ml of Albunex per injection were given to enhance the four- and two-chamber views, both at rest and immediately after exercise. The degree of left ventricular enhancement and the percentages of endocardial visualization were measured in both resting and exercise images. Variables relating to the kinetics of Albunex, which included volume of contrast injected, transit time, heart rate, and cardiac output at the time of image acquisition, were also assessed. There was no difference in the image acquisition time between the two exercise echocardiograms. Albunex produced good left ventricular opacification both at rest and after exercise. More endocardial border was visualized with contrast injection than without (91.2% +/- 11.5% vs 85.8% +/- 14.2%, p = 0.007). The transit times and volumes of Albunex injected were significantly less after exercise than at rest. The parameters were inversely related to heart rate and cardiac output. In conclusion, intravenous injection of Albunex is a promising means to enhance left ventricular endocardial visualization in exercise echocardiography and can be readily incorporated without causing a significant delay in obtaining images after exercise. Whether its use can improve diagnostic accuracy of exercise echocardiography requires further studies.     

Myocardial contrast echocardiography in acute myocardial infarction. Pathophysiological background and clinical applications

Myocardial contrast echocardiography is a technique used in experimental and clinical settings in order to visualize the pattern of intramyocardial perfusion. In the acute phase of myocardial infarction, regional absence of flow during myocardial contrast echocardiography delineates the area at risk of necrosis, while the definitive non-perfused area expresses infarct size. Reopening the infarct-related artery, which may be achieved spontaneously by thrombolysis or percutaneous transluminal coronary angioplasty, is not a reliable indicator of intramyocardial reperfusion. If myocardial ischaemia due to coronary occlusion has been sufficiently prolonged and severe, not only myocyte viability, but also microvascular integrity is lost. Myocardial contrast echocardiography, using intracoronary injection of sonicated contrast medium, gives information about microvascular integrity and the effective presence of intramyocardial reflow. Anatomical integrity of microvasculature does not necessarily imply preserved function, and thus the microvessel vasodilating reserve may also be impaired. Myocardial contrast echocardiography has the potential to assess alterations in microvascular function, showing, in the myocardial area with reduced coronary reserve, a relatively reduced increase in echocontrast signal intensity when an intravenous vasodilator agent is administered.     

Experimental study of the reaction pp-->pp pi 0 in the energy range 600-900 MeV

To compare regional thallium-201 SPECT redistribution patterns with rubidium-82 PET, we studied 81 patients with both imaging modalities. Sixty patients had significant coronary artery disease. All patients underwent PET imaging after dipyridamole infusion, while SPECT imaging was performed after exercise stress (38 patients) and dipyridamole (43 patients). Sixty-eight percent of patients with prior infarct had fixed defects on SPECT, compared to 39% with PET. Sixty-one percent of patients with prior infarct had PET perfusion defects which exhibited 'reflow' or normal rubidium-82 tracer uptake (p < 0.05 vs. SPECT). Similar results were seen in patients without prior infarct (26% fixed defects on SPECT vs. 12% for PET, p < 0.05). Regional analysis showed that 57% of fixed SPECT defects corresponded to PET defects with reflow or normal rubidium-82 uptake, while 78% of 'fixed' PET defects corresponded to fixed SPECT defects. PET reflow and normal rubidium-82 uptake in sites of fixed thallium-201 SPECT perfusion defects suggest that imaging modalities employing separate tracer injections at rest and after stress, such as rubidium-82 PET, may be more specific in the assessment of myocardial viability, especially in patients with prior myocardial infarction.     

Prospective identification of myocardial stunning using technetium-99m sestamibi-based measurements of infarct size

OBJECTIVES: We sought to prospectively identify patients with stunning and hyperkinesia at hospital discharge on the basis of mismatches between left ventricular (LV) function and infarct size as assessed by technetium-99m (Tc-99m) sestamibi perfusion tomographic imaging. BACKGROUND: Mechanical indexes of LV function may not accurately reflect myocardial damage after acute myocardial infarction (MI) because of myocardial stunning and compensatory hyperkinesia in noninfarct-related territories. Myocardial perfusion techniques are unaffected by these variables. METHODS: Eighty-four patients with acute MI underwent hospital admission and discharge Tc-99m-sestamibi tomographic imaging. Global LV ejection fraction (LVEF) was measured at hospital discharge and 6 weeks later. The perfusion defect size was quantified and expressed as a percentage of the LV. The discharge perfusion defect, which is a measure of infarct size, was used to predict the 6-week LVEF for each patient based on a previously reported regression equation. Patients were classified into one of three groups depending on whether their LVEF at hospital discharge fell within, above or below one standard error (6.8 LVEF points) of the predicted 6-week LVEF. RESULTS: There were 48 patients classified as having a "match" between function and infarct size; these patients demonstrated no significant change in LVEF at 6 weeks. There were 21 patients (25%) classified as "mismatch stunned" who had discharge LVEFs lower than those predicted by infarct size. These patients demonstrated a significant improvement in mean LVEF at 6 weeks (mean [+/-SD] discharge LVEF 0.41 +/- 0.08, 6-week LVEF 0.47 +/- 0.10; p = 0.003). Fifteen patients (18%) were classified as "mismatch-hyperkinetic." The mean LVEF for these patients significantly declined at 6 weeks (discharge LVEF 0.64 +/- 0.06, 6-week LVEF 0.58 +/- 0.09; p = 0.002). There was a marked increase in LVEF within the infarct zone (8 +/- 15 LVEF points; p = 0.03) for patients predicted to have stunning and a marked decline in LVEF outside the infarct zone (9 +/- 15 LVEF points; p = 0.06) in patients predicted to have hyperkinesia. Both discharge LVEF (p < 0.0001) and group classification (p = 0.005) were independent predictors of LVEF 6 weeks later. CONCLUSIONS: Perfusion imaging with Tc-99m-sestamibi can identify post-MI patients at hospital discharge in whom LV function is discordant with the measured infarct size. Patients with stunning have late increases in LVEF; patients with hyperkinesia have late decreases. This methodology, performed at discharge, is predictive of late changes in LV function.     

Atopic dermatitis and related factors observed at infant physical examination at health centers

OBJECTIVE: To evaluate the clinical usefulness of cardiac SPECT in the detection of coronary artery disease, and the relation with the site, number and severity of the angiographic lesions. METHOD: We studied 216 patients; with myocardial perfusion imaging with SPECT (T1-201 and/or Tc-99 Sestamibi) and coronary angiogram. We defined the localization of myocardial perfusion defects (anterior, inferior, septal, lateral or apex), and their correlation with coronary angiogram, based on the location, number and severity of coronary angiographic lesions. We considered significative coronary stenosis obstructions of 60% or more. RESULTS: Of the 216 patients studied, 181 (83.8%) were male and 35 (16.2%) female. Age ranged between 30 and 82 years; 143 males and 23 females had a previous myocardial infarction. The SPECT sensitivity for diagnosing ischemia of one, two and three vessel disease was 94%, 96% and 100%. The sensitivity for diagnosing disease in specific vascular territories was 91.6% for LAD 100% for RCA, 92.8% for CX and 100% for left main. CONCLUSIONS: Myocardial perfusion imaging with SPECT has high sensitivity for diagnosing coronary artery disease. The sensitivity and specificity were more accurate in proximal anterior descending artery disease, left main and three-vessel coronary artery disease. We found correlation in the site, number and severity of the angiographic lesions and in myocardial perfusion defects.     

Assessment of blood flow distal to coronary artery stenoses. Correlations between myocardial positron emission tomography and poststenotic intracoronary Doppler flow reserve

BACKGROUND: Previous studies have correlated quantitative coronary angiographic stenosis severity with positron emission tomography (PET) myocardial perfusion and proximal measurements of intracoronary flow velocities in normal and diseased coronary arteries. The aim of this study was to correlate regional myocardial blood flow (RMBF) derived from [15O]H2O PET with directly measured poststenotic intracoronary Doppler flow velocity data acquired under basal conditions and dipyridamole-induced hyperemia. METHODS AND RESULTS: Eleven consecutive patients 53 +/- 13 years old with ischemic chest pain and isolated proximal left coronary artery stenoses (left anterior descending, 9; left circumflex, 2; mean, 59 +/- 23% diameter stenosis) underwent [15O]H2O myocardial PET and intracoronary Doppler flow velocity studies within 1 week. PET RMBF (mL.g-1.min-1) and myocardial perfusion reserve (MPR) were calculated in poststenotic and normal reference vascular beds. Poststenotic Doppler average peak flow velocities (APV; cm/s) and coronary flow velocity reserve (CFR) were compared with corresponding PET data and quantitative angiographic lesional parameters. PET RMBF and Doppler APV were linearly correlated (r = .60; P < .001), as were poststenotic PET MPR and Doppler CFR (r = .76; P < .0002). Relative coronary flow velocity and MPR ratios between poststenotic and angiographically normal vascular beds were comparably reduced (0.83 +/- 0.25 versus 0.86 +/- 0.21, respectively; P = NS). CONCLUSIONS: Intracoronary Doppler flow velocities acquired distal to isolated left coronary artery stenoses correlated with [15O]H2O PET regional myocardial perfusion and are useful for assessment of the physiological significance of coronary stenoses in humans.     

Correlates of unrecognized acute myocardial infarction detected via perfusion imaging

Research using the electrocardiogram (ECG) indicates that about 1/3 of acute myocardial infarctions (AMIs) are unrecognized. To date, no studies of unrecognized AMIs have employed perfusion imaging, although it is more sensitive than the ECG and provides more information about infarct characteristics, such as size and location. In this study, 82 of 258 consecutive patients (31.8%) undergoing exercise testing with technetium-99m sestamibi perfusion imaging had fixed, nonartifactual perfusion defects, suggesting AMI. These patients were interviewed regarding their recognition of AMI; 27 patients (32.9%) had unrecognized AMI. Unrecognized AMI was significantly associated with (1) smaller infarcts, (2) infarcts not in the apical or septal regions, (3) diabetes mellitus, (4) lack of angina, (5) a negative family history for cardiac disease, and (6) being African-American. Many of these variables were significantly intercorrelated, and in multivariate analysis, unrecognized AMI remained significantly predicted by a smaller infarct and lack of angina. This study suggests that the incidence of unrecognized AMI detected via perfusion imaging on a clinic population is similar to that detected via electrocardiographic studies on community samples. This study also replicates prior findings of the medical history and demographic correlates of unrecognized AMI, and indicates that infarct size and location are also associated with unrecognized AMI.     

Effects of injection rates of contrast material on arterial phase hepatic CT

PURPOSE: The aim of our study was twofold: to determine the frequency and magnitude of perfusion defect in stroke patients who qualify for rtPA therapy within 3 hours of stroke onset and to determine the ability of rtPA to improve perfusion by 24 hours. SUBJECTS AND METHODS: Patients with suspected hemispheric stroke who fulfilled entry criteria into the National Institute of Neurological Disorders and Stroke (NINDS) rt-PA Stroke Study and also had pretreatment injection of (99m)Tc-HMPAO, with single-photon emission computed tomography (SPECT) performed using a triple-head camera at baseline and 24 hours, were included. RESULTS: All 12 patients who qualified for rtPA therapy had perfusion defects on baseline SPECT (SPECT graded scale [SGS] score range, 16 to 79). Mean+/-SD perfusion defect was comparable in rtPA (n=4)versus placebo (n=5) groups (SGS score, 36+/-18 versus 39+/-12; NS) despite earlier injection time in the rtPA group (98+/-24 versus 141+/-21 minutes; P=.02). Total SPECT scanning time was 20 to 25 minutes. At 24 hours, reperfusion was greater in rtPA patients compared with the placebo group (SGS score, 7+/-9 versus 29+/-17; P=.05), with relative improvement in the region-of-interest scores of 87+/-16% after rtPA compared with 28+/-30% with placebo (P=.01). CONCLUSIONS: A substantial perfusion defect exists in stroke patients with larger hemispheric infarcts who meet NINDS criteria for rtPA therapy, and rtPA is better able than placebo to rectify this defect. SPECT is feasible for clinical trials and should be evaluated as a substituted end point in stroke therapeutic trials.     

Accuracy of single-photon emission computed tomography myocardial perfusion imaging in patients with stents in native coronary arteries

Strategies to noninvasively evaluate patients after coronary stenting have not been evaluated. To determine the accuracy of single-photon emission computed tomography (SPECT) myocardial perfusion imaging in patients after coronary stenting, 209 patients who had undergone stenting followed by late stress SPECT myocardial perfusion imaging were evaluated. Quantitative coronary angiography was performed in 33 patients following SPECT imaging. SPECT restenosis was defined as a reversible or fixed defect within the stented vascular territory. Angiographic restenosis was examined using 2 definitions: total area narrowing > or =50% or > or =70% of the stent site or stented artery. The SPECT and angiographic findings were concordant in 22 of 33 stented vascular territories using the 50% definition of restenosis and in 29 of 33 stented territories using the 70% definition. Use of the 70% definition of restenosis resulted in improved accuracy of SPECT to detect a significant stenosis in the stented artery. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of SPECT were 95%, 73%, 88%, 89%, and 88% respectively. In patients with positive SPECT scans, the most significant stenosis in the stented artery was outside the stent site in 50% of cases. SPECT imaging appears to be accurate to predict significant stenosis in the stented artery, although the most severe stenosis is frequently distant from the stent site.     

Benzodiazepine receptors in chronic cerebrovascular disease: comparison with blood flow and metabolism

The brain benzodiazepine (BZD) receptor distribution in patients with chronic cerebrovascular disease was assessed with 123I-iomazenil (IMZ) SPECT, and the findings were compared with the data for the cerebral blood flow (CBF) and cerebral metabolism. METHODS: We examined nine patients with chronic cerebrovascular diseases, six patients with cerebral infarction and three with moyamoya disease. Iodine-123-IMZ SPECT images were obtained for 15 min, 3 hr after the administration of 167 or 222 MBq 123I-IMZ. In seven patients, the CBF and oxygen metabolism were measured by the 50 steady-state method. In two patients, the CBF and glucose metabolism were measured by 99mTc-HMPAO SPECT and 18F-fluoro-2-deoxy-D-glucose-PET, respectively. The brain was initially classified into 18 regions, and abnormalities in the BZD receptor distribution, CBF and cerebral metabolism were visually evaluated. The count ratio of lesion-to-contralateral normal region (L-to-C ratio) was then used for comparison. RESULTS: In the core of the infarct, the 123I-IMZ uptake decreased (L-to-C ratios of the blood flow 0.42 +/- 0.26; metabolism 0.45 +/- 0.24; and 123I-IMZ uptake 0.46 +/- 0.14). In the peri-infarct region, the 123I-IMZ uptake slightly decreased (L-to-C ratios of 0.81, 0.82 and 0.89, respectively). In the region of misery perfusion, the 123I-IMZ uptake was preserved (L-to-C ratios of 0.73, 1.07 and 1.02, respectively). In the remote deafferentiated areas in the ipsilateral cerebrum, the 123I-IMZ uptake was preserved (L-to-C ratios of 0.76 +/- 0.10, 0.75 +/- 0.04 and 0.98 +/- 0.05, respectively). In the remote areas in the contralateral cerebellum, the 123I-IMZ uptake was preserved (L-to-C ratios of 0.84 +/- 0.08, 0.85 +/- 0.04 and 0.94 +/- 0.05, respectively). CONCLUSION: The BZD receptor distribution, as measured by 123I-IMZ SPECT, is not considered to reflect neuronal function, but it may reflect neuronal cell viability. Iodine-123-IMZ SPECT may, therefore, hold promise as a potential probe for neuronal damage.     

Hypertension and retinopathy, arteriolar narrowing, and arteriovenous nicking in a population

OBJECTIVES: The purpose of this study was to determine the relative value of single-photon emission computed tomographic (SPECT) imaging at rest using technetium-99m methoxyisobutyl isonitrile (technetium-99m sestamibi) with positron emission tomography for detection of viable myocardium. BACKGROUND: Recent studies comparing positron emission tomography and thallium-201 reinjection with rest technetium-99m sestamibi imaging have suggested that the latter technique underestimates myocardial viability. METHODS: Twenty patients with a previous myocardial infarction underwent rest technetium-99m sestamibi imaging and positron emission tomography using fluorine (F)-18 deoxyglucose and nitrogen (N)-13 ammonia. In each patient, circumferential profile analysis was used to determine technetium-99m sestamibi, F-18 deoxyglucose and N-13 ammonia activity (expressed as percent of peak activity) in nine cardiac segments and in the perfusion defect defined by the area having technetium-99m sestamibi activity < 60%. Technetium-99m sestamibi defects were graded as moderate (50% to 59% of peak activity) and severe (< 50% of peak activity). Estimates of perfusion defect size were compared between technetium-99m sestamibi and N-13 ammonia. RESULTS: Sixteen (53%) of 30 segments with moderate defects and 16 (47%) of 34 segments with severe defects had > or = 60% F-18 deoxyglucose activity considered indicative of viability. Fluorine-18 deoxyglucose evidence of viability was still present in 50% of segments with technetium-99m sestamibi activity < 40%. There was no significant difference in the mean (+/- SD) technetium-99m sestamibi activity in segments with viable (40 +/- 7%) and nonviable segments (49 +/- 7%, p = 0.84). Of the 18 patients who had adequate F-18 deoxyglucose studies, the area of the technetium-99m sestamibi defect was viable in 5 (28%). In 16 patients (80%), perfusion defect size determined by technetium-99m sestamibi exceeded that measured by N-13 ammonia. The difference in defect size between technetium-99m sestamibi and N-13 ammonia was significantly greater in patients with viable (21 +/- 9%) versus nonviable segments (7 +/- 9%, p = 0.007). CONCLUSIONS: Moderate and severe rest technetium-99m sestamibi defects frequently have metabolic evidence of viability. Technetium-99m sestamibi SPECT yields larger perfusion defects than does N-13 ammonia positron emission tomography when the same threshold values are used.     

Adenosine technetium-99m sestamibi single-photon emission tomography for the assessment of jeopardized myocardium early after acute myocardial infarction. Paradoxical scintigraphic underestimation of jeopardized myocardium in patients with a severe infarct-related stenosis

This study investigated the value of technetium-99m sestamibi scintigraphy in identifying patients at risk for post-infarct ischaemia (=jeopardized myocardium), especially within the reperfused infarct region. In 51 patients with a recent (<1 month) myocardial infarction, adenosine 99mTc-sestamibi single-photon emission tomography (SPET) and dobutamine stress echocardiography (DSE) were performed and correlated with the presence of significant coronary artery stenosis [% diameter stenosis (DS) >50%] on quantitative coronary angiography. Regional perfusion activity was analysed semi-quantitatively (score 0-4) on a 13-segment left ventricular model. DSE was used for the estimation of the infarct size (low-dose DSE) and for concomitant evaluation of ischaemia (high-dose DSE). A reversible perfusion defect within the infarct region was observed in 20 of the 37 patients with a significant infarct-related lesion (sensitivity of 54%) and only in one patient without a significant infarct-related lesion (specificity of 93%). Further analysis revealed that the scintigraphic assessment of jeopardized myocardium was fairly good in patients with a moderate (DS 51%-64%) infarct-related stenosis but was inadequate in patients with a severe (DS>/=65%) infarct-related stenosis (sensitivity of 80% vs 36%, P<0.01), while the echocardiographic detection of ischaemia was not influenced by stenosis severity (sensitivity of 73% in both subgroups). This scintigraphic underestimation of jeopardized myocardium was mainly related to a severely impaired myocardial perfusion under baseline conditions, as was evidenced by a significantly more severe rest perfusion score in the infarct region in patients with a severe stenosis as compared to those with a moderate stenosis (average score: 1.5+/-0.7 vs 2.1+/-0.6, P<0.01), while infarct size on echocardiography was similar for both subgroups. It may be concluded that early after an acute myocardial infarction, adenosine 99mTc-sestamibi SPET may underestimate reperfused but still jeopardized myocardium, particularly in patients with a severe infarct-related stenosis. In these patients the evaluation of the ischaemic burden on rest-stress scintigraphy is hampered by the presence of a severely impaired myocardial perfusion in resting conditions.