Reverse Mismatch Research Articles

Reverse blood flow-glucose metabolism mismatch indicates preserved oxygen metabolism in patients with revascularised myocardial infarction

Positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) has been reported to be unreliable for identifying viable myocardium in acute myocardial infarction (AMI), especially in areas with discordance in myocardial blood flow (MBF) and glucose metabolism. In myocardium with decreased FDG uptake but preserved MBF, referred to as exhibiting reverse mismatch, myocardial viability remains controversial and little is known about the metabolic state. The aims of this study were to clarify substrate use and to estimate myocardial viability in infarct areas exhibiting reverse mismatch. Eighteen AMI patients with successful revascularisation were included in this study. Two weeks after onset, (11)C-acetate and (18)F-FDG PET were performed to evaluate regional oxygen consumption (k mono), MBF and glucose metabolism. Free fatty acid (FFA) metabolism was evaluated with (123)I-15-(p-iodophenyl)-3-(R, S)-methylpentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT). To assess wall motion, movement in left ventricular endocardial surface was calculated using ECG-gated (99m)Tc-tetrofosmin SPECT. The %k mono values in reverse mismatch segments (52.6 ± 13.6%) were not significantly different from those in non-infarct segments (60.4 ± 12.8%, p = 0.071) and normal match segments (preserved MBF and FDG uptake) (58.6 ± 11.6%, p = 0.396), although regional wall motion was more severely impaired (3.06 ± 2.52 mm vs 6.78 ± 3.17 mm, p < 0.0001, and vs 5.30 ± 2.33 mm, p = 0.042, respectively). Compared to segments with reduced match (reduced MBF and FDG uptake), %k mono and %BMIPP uptake were significantly higher in reverse mismatch segments (52.6 ± 13.6% vs 37.4 ± 8.9%, p = 0.0002, and 58.8 ± 10.6% vs 40.2 ± 10.7%, p < 0.0001). Reverse mismatch in reperfused AMI patients, high oxygen consumption and FFA metabolism were observed despite decreased glucose metabolism. We conclude that reverse mismatch indicated the myocardium with early restoration of MBF and aerobic FFA metabolism.

Abstract TP60: Intravenous Thrombolysis For Patients With Reverse MRA-DWI Mismatch: SAMURAI And NCVC Rt-PA Registries

Background and purpose: Characteristics of reverse MRA-DWI mismatch, defined as large DWI lesion despite absence of the major artery occlusion (MAO), remain unknown, especially in patients treated with IV rt-PA. This study aimed to clarify the frequency, associated factors, and outcomes of patients showing reverse MRA-DWI mismatch prior to IV rt-PA therapy. Methods: From the multicenter (SAMURAI) and additional single-center (NCVC) rt-PA registries, patients with the MCA territorial stroke were included. Early ischemic changes (EIC) were assessed with the Alberta Stroke Program Early CT score (ASPECTS) on pretreatment DWI. MAO was defined as ICA or M1 occlusion on MRA. Patients were divided into 4 groups: the large-EIC match (LM) group (MAO, ASPECTS &lt;7); the reverse mismatch (RMM) group (no MAO, ASPECTS &lt;7); the conventional mismatch (CMM) group (MAO, ASPECTS ≧7); and the small-EIC match (SM) group (no MAO, ASPECTS ≧7). Outcomes included sICH per ECASS II criteria, and mRS 0-2 and death at 90 days. Multivariate backward stepwise logistic regression analysis was performed to identify independent clinical characteristics (demographic factors, risk factors, stroke subtypes by TOAST classification, and blood tests) associated with the reverse MRA-DWI mismatch and to compare the outcomes among the 4 groups. Results: Of the 486 patients (167 women, median age 74 years) enrolled, reverse MRA-DWI mismatch was observed in 24 (5%, RMM group); 108 belonged to LM, 161 to CMM, and 193 to SM groups. Among clinical characteristics, cardioembolism (RMM 92%, LM 76%, CM 69%, SM 49%) was only independently associated with the RMM group (OR 5.49, 95%CI 1.25-24.1). Median initial NIHSS score was 18 in RMM, 18 in LM, 13 in CMM, and 8 in SM (p&lt;0.001). MRS 0-2 (RMM 54%, LM 19%, CMM 46%, SM 69%) was more common in the RMM than the LM group (OR 4.02, 95% CI 1.28-12.7). SICH (RMM 13%, LM 6%, CMM 2%, SM 2%) and death (RMM 8%, LM 12%, CMM 9%, SM 2%) were not different between the RMM and LM groups after multivariate analysis. Conclusion: Reverse MRA-DWI mismatch was observed in 5% of patients eligible for rt-PA. Cardioembolism was independently associated with reverse mismatch. Patients with reverse mismatch may benefit from thrombolysis, compared to those with extensive EIC with MAO.

Visual-Functional Mismatch Between Coronary Angiography and Fractional Flow Reserve

The goal of this study was to identify clinical and lesion-specific local factors affecting visual-functional mismatch. Although lesion severity determined by coronary angiography has not been well correlated with physiological significance, the mechanism of the discordance remains poorly understood. The authors assessed quantitative coronary angiography, intravascular ultrasound (IVUS), and fractional flow reserve (FFR) in a prospective cohort of 1,000 patients with 1,129 coronary lesions. Three-dimensional computational simulation studies were performed. Lesions with angiographic diameter stenosis (DS) ≥50% and FFR >0.80 ("mismatches") were seen in 57% of non-left main lesions and in 35% of the left main lesions, respectively (p = 0.032). Conversely, among the lesions with DS <50% and FFR <0.80 ("reverse mismatches") 16% were found in the non-left main lesions and 40% in the left main lesions (p < 0.001). The independent predictors for mismatch were advanced age, non-left anterior descending artery location, absence of plaque rupture, short lesion length, large minimal lumen area, smaller plaque burden, and greater minimal lumen diameter. Conversely, reverse mismatch was independently associated with younger age, left anterior descending artery location, the presence of plaque rupture, a smaller minimal lumen area, and larger plaque burden. In a computational simulation study, FFR was influenced by DS, lesion length, different lesion shape, plaque eccentricity, surface roughness, and various shapes of plaque rupture. There were high frequencies of visual-functional mismatch between angiography and FFR. The discrepancy was related to the clinical and lesion-specific factors frequently unrecognizable by angiography, thus suggesting that coronary angiography cannot accurately predict FFR. (Natural History of FFR-Guided Deferred Coronary Lesions [IRIS FFR-DEFER]; NCT01366404).

Reduced septal glucose metabolism predicts response to cardiac resynchronization therapy

BackgroundUp to 50% of patients do not respond to Cardiac Resynchronization Therapy (CRT). Recent work has focused on quantifying mechanical dyssynchrony and left ventricular scar. Septal reverse-mismatch (R-MM) (reduced FDG uptake vs perfusion) has been observed in patients with cardiomyopathy and prolonged QRS duration. We hypothesized that a greater quantity of septal R-MM would indicate a greater potential for reversibility of the cardiomyopathy, when the dyssynchrony is improved with CRT. Therefore, this study’s objective was to assess whether greater septal R-MM pattern predicts response to CRT. Methods and ResultsForty-nine patients had pre-implant Rubidium-82 and Fluorine-18-fluorodeoxyglucose PET scanning. Total and regional left ventricular scar size and extent of R-MM were calculated. Response to CRT was defined as ≥10% improvement in left ventricular end-systolic volume or ≥5% absolute ejection fraction improvement. In the non-ischemic cardiomyopathy subset non-responders had significantly less septal R-MM than responders (13.1% compared to 27.1%, P = .012). There were correlations between the extent of septal R-MM and the increase in ejection fraction (r = 0.692, P = .0004) and reduction in left ventricular end-systolic volume (r = −0.579, P = .004). For each 5% absolute increase in extent of septal R-MM the odds ratio of being a responder was 2.17 (95% CI 1.15, 4.11, P = .017). Extent of septal R-MM displayed high sensitivity and specificity (area under curve = 0.855, P = .017) to predict response. ConclusionsIn patients with non-ischemic cardiomyopathy, greater extent of septal glucose metabolic R-MM pattern, predicted response to CRT. This parameter may be useful for identifying patients who benefit from CRT.

Altered myocardial glucose utilization and the reverse mismatch pattern on rubidium-82 perfusion/F-18-FDG PET during the sub-acute phase following reperfusion of acute anterior myocardial infarction

BackgroundReperfused myocardium post-acute myocardial infarction (AMI) may have altered metabolism with implications for therapy response and function recovery. We explored glucose utilization and the “reverse mismatch” (RMM) pattern (decreased F-18-fluorodeoxyglucose (FDG) uptake relative to perfusion) in patients who underwent mechanical reperfusion with percutaneous coronary intervention (PCI) for AMI. Methods and ResultsThirty-one patients with anterior wall AMI treated with acute reperfusion, with left ventricular ejection fraction ≤45%, underwent rest rubidium-82 (Rb-82) and FDG PET 2-10 days post-AMI. Resting echocardiograms were used to assess wall motion abnormalities. Significant RMM occurred in 15 (48%) patients and was associated with a shorter time to PCI of 2.9 hours (2.2, 13.3 hours) compared to patients without significant RMM: 11.4 hours (3.9, 22.4 hours) (P = .03). Within the peri-infarct regions, segments with significant RMM were more likely to have wall motion abnormalities (OR = 2.3 (1.1, 4.7), P = .02) compared to segments without significant RMM. ConclusionsRMM is a common pattern on perfusion/FDG PET during the sub-acute phase following reperfusion of AMI and is associated with shorter times to PCI. Within the peri-infarct region, RMM occurs frequently and is more often associated with wall motion abnormalities than segments without RMM. Whether this represents a myocardial metabolic shift during the sub-acute phase of recovery warrants further study.

Ventilation–Perfusion SPECT with 99mTc-DTPA Versus Technegas: A Head-to-Head Study in Obstructive and Nonobstructive Disease

Lung scintigraphy is primarily used to diagnose pulmonary embolism. Ventilation imaging is often performed using (99m)Tc-DTPA or Technegas, an ultrafine dispersion of (99m)Tc-labeled carbon. Despite the common use of these radioaerosols, they have not been compared in an intraindividual study, and not with ventilation-perfusion (V/P) SPECT. The aim of the present head-to-head study was to systematically investigate differences in ventilation studies performed with (99m)Tc-diethylenetriaminepentaacetate (DTPA) and Technegas. Sixty-three patients, 28 without and 35 with obstructive lung disease, were examined with V/P SPECT using both (99m)Tc-DTPA and Technegas. V/P SPECT images were randomized and assessed independently by 2 masked physicians according to a predefined scoring system. A paired comparison was performed using the Wilcoxon signed-rank test. In both obstructive and nonobstructive disease, the overall unevenness of radiotracer deposition and the degree of central deposition were more pronounced in (99m)Tc-DTPA than Technegas studies. Because of better peripheral penetration, the extent of reverse mismatch was less when Technegas was used. Additionally, in obstructive disease, the degree of focal deposition in distal airways was more pronounced with (99m)Tc-DTPA. Mismatched perfusion defects were more frequently found with Technegas in obstructive disease. This intraindividual comparative study shows that Technegas is the preferred radioaerosol, particularly in obstructive disease.

V / Q-Szintigrafie zur Diagnostik der Lungenembolie – I. Durchführung und Beurteilung

V / Q scintigraphy remains even today exceptionally well-suited for diagnosis of pulmonary embolism. The combination of ventilation and perfusion scintigraphy in this sequence is standard. Suitable tracers for ventilation scintigraphy are Technegas and Krypton-81m, with wet aerosols as second-choice alternatives. Acquisition in SPECT-technique is optimal. Regional perfusion defects with maintained ventilation (V / Q mismatch) correlate to pulmonary embolism without diagnostic limitations. Evaluation by means of PIOPED criteria should be rejected. Increased attention should be paid to partially-occluding embolisms, since they also influence the prognosis. Relevant alternative diagnoses refer to respiratory tract obstruction (V / Q match with intact v. Euler-Liljestrand reflex) and functional right-left shunt (V / Q reverse mismatch with impaired v. Euler-Liljestrand reflex).

Comparing two methods for assessment of perfusion–diffusion mismatch in a rodent model of ischaemic stroke: a pilot study

This stroke experiment was designed to define the mismatch between perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) in MRI by applying early or instantly acquired PWI. Eight rats were induced with stroke through photothrombotic occlusion of the middle cerebral artery and scanned serially between 1 h and day 3 after induction using DWI and PWI with a 1.5 T MR scanner. The relative lesion volumes (rLV) on MRI and triphenyl tetrazolium chloride-stained specimens were defined as the proportion of lesion volume over brain volume. Discrepancies in the rLV between PWI- and DWI-derived apparent diffusion coefficient (ADC) maps were expressed by subtraction of the ADC from PWI, resulting in three possible patterns: (i) (PWI-ADC > 10% of PWI) denoting a mismatch; (ii) (-(10% of PWI) <or= PWI-ADC <or= 10% of PWI) denoting a match; and (iii) (PWI-ADC < -(10% of PWI)) denoting a reverse mismatch. The differences were compared with the minuend being either early PWI (ePWI) or instant PWI (iPWI) and the subtrahend being instant ADC (iADC). The occurrence and evolution of PWI-ADC patterns were analysed. Over time, PWI-ADC discrepancies evolved from mismatch, through to match, to reversed mismatch. The PWI-ADC mismatch still existed 3 days after MCA occlusion in one to three of the eight cases. The rLVs and mismatch incidences between the ePWI-iADC and iPWI-iADC models were linear correlated. A higher mismatch rate occurred in iPWI-iADC within day 1 and in ePWI-iADC at day 3. Both ePWI and iPWI proved useful to define PWI-ADC patterns within day 1. At day 3, iPWI appeared more adequate.

Reverse Perfusion-Metabolism Mismatch Predicts Good Prognosis in Patients Undergoing Cardiac Resynchronization Therapy A Pilot Study

Cardiac resynchronization therapy (CRT) improves glucose metabolism in the septum of patients with heart failure, so in the present study the predictive value of combined fluorodeoxyglucose (FDG)-positron emission tomography (PET) and metoxy-isobutyl isonitrile (MIBI)-single photon emission computed tomography (SPECT) for the prognosis of patients undergoing CRT was investigated. Fourteen patients (70.3+/-8.2 years) who underwent FDG-PET and MIBI-SPECT before implantation of a biventricular pacemaker were enrolled. The total number of matches, mismatches, reverse mismatches, summed difference score (SDS: sum total of FDG - MIBI scores) and SDS per segment (%SDS) in each of 5 areas of myocardium (septum, anterior, lateral, inferior area, apex) was calculated and compared between the survival groups (all survival: survival group; survival without ischemic heart disease (IHD): non-IHD survival group) and non-survival group. Both the number of reverse mismatch segments and the %SDS in the septum in the non-IHD survival group were significantly greater than in the non-survival group (3.2+/-1.6 vs 0.5+/-0.6, p<0.05; 0.62+/-0.61 vs -0.11+/-0.19, p<0.05). The receiver-operating characteristics curves for prognosis showed that the area under the curve for the number of reverse mismatch segments in the septum (0.93; confidence interval 0.61-0.98) was significantly greater. A reverse mismatch pattern in the septum can predict a good prognosis for patients treated with CRT.

Is Affirmative Action Responsible for the Achievement Gap Between Black and White Law Students?

While the Supreme Court upheld some affirmative action programs as constitutional in 2003, the wisdom of affirmative action as a policy decision remains hotly contested. In the law school context, the challenge is to determine how affirmative action policies affect law schools, law students, and the legal profession. This paper takes up one strand of this challenge, estimating how minority students would fare in a world with different affirmative action policies than those currently implemented. I posit a model of law school performance that controls for entering credentials and allows for a mismatch between student and school (where the student is outmatch by his fellow students). The model also allows for differences in the law school experience for students of different races, which may be the result of discrimination or other differences in the way that law school cultures affect students. The results indicate that, if anything, reverse mismatch boosts the performance of students with low credentials. Using monte carlo simulations of graduation and bar passage with bootstrapped standard errors, I find that removing affirmative action policies decreases the number of new black lawyers each year by 13.4% ± 5.2%. This is in direct conflict with a recent study by Richard Sander that estimates an increase in the number of new black lawyers. Sander, however, assumes that there is no discriminatory effect on law student performance, and therefore confounds discriminatory effects with the mismatch effect in his analysis. Finally, recognizing that the data upon which I and others rely is imperfect and unable to provide a definitive answer regarding whether the mismatch theory applies in the law school context, I suggest some experimental additions to the data to correct for these problems.

Etiology of Perfusion-Diffusion Magnetic Resonance Imaging Mismatch Patterns

Diffusion-and perfusion-weighted magnetic resonance imaging (DWI and PWI) are useful tools for the assessment of brain ischemia. Discrepancies between the extent of DWI and PWI abnormalities are thought to depend pre dominantly on time from symptom onset to magnetic resonance imaging (MRI) examination. However, underlying ischemic stroke etiology can also be important. A mismatch may indicate the presence of tissue at risk for infarction, whereas the relevance of other DWI/PWI patterns is uncertain. The authors therefore investigated the etiology of brain ischemia in patients with different DWI/PWI patterns. Retrospective study of 130 patients with acute brain ischemia and detailed stroke workup, including MRI within a week after symptom onset (40 +/- 39 hours). Patients were divided into the following groups: mis-match (PWI > DWI), reverse mismatch (DWI > PWI), and match (<25% difference between PWI and DWI). Mismatch occurred in 49% of patients, whereas 22% had reverse mis-match and 29% matched lesions. Time from symptom onset to MRI examination was similar between the 3 groups. Largeartery atherosclerosis increased by almost 4-fold the odds of mismatch (odds ratio: 3.89, 95% confidence interval: 1.72-8.78; P < .001), whereas patients with reverse mismatch were likely to have cryptogenic stroke. Patients with matched lesions were similarly distributed among different stroke subtypes. Ischemic stroke etiology appears to influence the development of specific DWI/PWI patterns. Prospective studies are needed to confirm these observations.

Etiology of Perfusion‐Diffusion Magnetic Resonance Imaging Mismatch Patterns

ABSTRACT Background and Purpose. Diffusion‐and perfusion‐weighted magnetic resonance imaging (DWI and PWI) are useful tools for the assessment of brain ischemia. Discrepancies between the extent of DWI and PWI abnormalities are thought to depend pre dominantly on time from symptom onset to magnetic resonance imaging (MRI) examination. However, underlying ischemic stroke etiology can also be important. A mismatch may indicate the presence of tissue at risk for infarction, whereas the rele vance of other DWI/PWI patterns is uncertain. The authors therefore investigated the etiology of brain ischemia in patients with different DWI/PWI patterns. Methods. Retrospective study of 130 patients with acute brain ischemia and detailed stroke workup, including MRI within a week after symptom onset (40 ± 39 hours). Patients were divided into the following groups: mis‐match (PWI &gt; DWI), reverse mismatch (DWI &gt; PWI), and match (&lt;25% difference between PWI and DWI). Results. Mismatch occurred in 49% of patients, whereas 22% had reverse mis‐match and 29% matched lesions. Time from symptom onset to MRI examination was similar between the 3 groups. Largeartery atherosclerosis increased by almost 4‐fold the odds of mismatch (odds ratio: 3.89, 95% confidence interval: 1.72–8.78; P &lt; .001), whereas patients with reverse mismatch were likely to have cryptogenic stroke. Patients with matched lesions were similarly distributed among different stroke subtypes. Con clusions. Ischemic stroke etiology appears to influence the development of specific DWI/PWI patterns. Prospective studies are needed to confirm these observations.

414 Reverse perfusion-metabolism mismatch is the predictor of good prognosis of patients treated with cardiac resynchronization therapy

414 Reverse perfusion-metabolism mismatch is the predictor of good prognosis of patients treated with cardiac resynchronization therapy

414 Reverse perfusion-metabolism mismatch is the predictor of good prognosis of patients treated with cardiac resynchronization therapy

414 Reverse perfusion-metabolism mismatch is the predictor of good prognosis of patients treated with cardiac resynchronization therapy

Chlamydia pneumoniae Serology in Donors and Recipients and the Risk of Bronchiolitis Obliterans Syndrome after Lung Transplantation

Bronchiolitis obliterans syndrome (BOS) is a common late complication in lung transplant recipients (LTR). Chlamydia pneumoniae (C. pneumoniae) is a common but difficult to diagnose respiratory pathogen with a propensity to latency. We studied the impact of C. pneumoniae on BOS development using donor-recipient serology obtained before transplantation in a cohort of 76 LTR. BOS was present in 29.9% patients (mean follow-up 866 days). High donor C. pneumoniae immunoglobulin (Ig)G titers were associated with BOS in the recipient (area under the curve [AUC] 0.71, 95% confidence interval [CI] 0.52-0.91, P=0.027), whereas high recipient titers were inversely associated with BOS (AUC 0.27, 95% CI 0.11-0.44, P=0.018). The risk of developing BOS was 75.0% in the case of a primary seromismatch for C. pneumoniae (D+/R-), whereas a reverse mismatch had a risk of 4.6% (likelihood ratio 9.8, P=0.02). In a multivariate model that included human leukocyte antigen matching, acute rejection and cytomegalovirus pneumonitis, C. pneumoniae IgG donor 32 or greater and C. pneumoniae IgG recipient 32 or greater remained positive and negative independent risk factors, respectively, for BOS in LTR. In the freedom from BOS analysis, BOS occurred more frequently and earlier in C. pneumoniae seropositive donors, and the reverse was true in seronegative recipients. C. pneumoniae serology in donor and recipient is associated with the development of BOS in LTR.

The reverse flow-metabolism mismatch pattern seen in cardiac PET viability scans is unrelated to underlying degree of coronary stenosis

Background: Cardiac PET with N-13 ammonia (NH 3) is frequently used to quantify myocardial blood flow (MBF). Myocardial metabolism is often evaluated with F-18 fluorodeoxyglucose (FDG) in patients with ischemic cardiomyopathy. The interplay between MBF and FDG uptake in areas with a reverse flow-metabolism, or reverse mismatch (RMM), pattern [normal NH 3 / decreased FDG] remains unclear, but such regions have been found to be dysfunctional. The aim of this study was to determine if MBF in areas showing RMM is abnormal in patients with documented coronary artery disease undergoing cardiac PET for the assessment of viability. Methods: PET viability studies of 28 patients (age 62±12 yrs; 22 males) were evaluated. Scans were divided into nine standardized segments. The flow-metabolism pattern in each segment was classified by two experienced readers as normal [normal NH 3/ normal FDG], RMM [normal NH 3 / ↓FDG], hibernating [↓NH 3/ ↑FDG], infarcted [↓NH 3/ ↓FDG] or admixture [inhomogeneous NH 3/ inhomogeneous FDG]. The global MBF within each segment was quantified using a 2-compartment kinetic model. Cardiac catheterization data for all 28 patients were reviewed. Results: A total of 242 cardiac segments were analyzed. The global MBF in 38 normal segments did not differ from that in 82 RMM segments (0.79±0.23 vs. 0.75±0.23 ml/g/min; p = NS). MBF was lower in 63 hibernating (0.65±0.21 ml/g/min), 43 infarcted (0.49±0.18 ml/g/min), and 16 admixture (0.61±0.23 ml/g/min) segments compared with normal regions (p<0.05 for all). No relationship was noted between the severity of coronary stenoses in arteries subtending RMM segments; while 44% of RMM segments were supplied by totally occluded vessels, 40% of RMM segments were supplied by arteries without obstructive lesions. Conclusions: MBF in regions of RMM is not different from MBF in normal regions. The RMM pattern is unrelated to the presence of obstructive coronary stenoses in vessels supplying affected regions, but likely reflects a metabolic derangement in glucose uptake in regions that are viable, but dysfunctional and likely jeopardized.

The reverse flow-metabolism mismatch pattern seen in myocardial viability PET scans reflects altered substrate utilization

Background: Cardiac PET utilizing N-13 ammonia (NH 3) to quantify flow and F-18 fluorodeoxyglucose (FDG) to assess metabolism is often used to assess for viable myocardium in patients with ischemic cardiomyopathy. The flow-metabolism patterns characteristic of normal (NL) [normal NH 3/ normal FDG] and hibernating (HIB) [↓ NH 3/ normal or ↑ FDG], and infarcted (INF) [↓ NH 3/ ↓ FDG] myocardium are well established. However, a fourth “reverse mismatch” pattern (RMM) [normal NH3 / ↑ FDG] is often seen, but its etiology is not well understood. We postulated that RMM does not result from improper scaling of PET images, but reflects a true defect in FDG uptake in normally perfused, dysfunctional regions. Methods: The PET scans from 18 patients showing both NL and RMM regions were quantitatively analyzed. Tracer activity (counts/pixel) and MBF (ml/g/min) were measured in identical 1-cm regions of interest (ROI's), selected in myocardial segments identified by experienced readers as NL, RMM, HIB or INF. Values were normalized to the most normal ROI for that patient. Results: A total of 81 ROI's were analyzed. Compared to NL, flow in RMM was somewhat decreased (p = 0.03), but was significantly greater than in HIB and INF (p <0.005). Uptake of FDG in NL and HIB was equal, but was decreased in RMM and INF. Whereas the normalized FDG:NH 3ratio was near unity in NL and INF, it was decreased in RMM and increased in HIB. * NL (n = 23) RMM (n = 27) HIB (n = 10) INF (n = 21) Normalized MBF 0.95 ± 0.12 0.84 ± 0.22 * 0.55 ± 0.20 * # 0.40 ± 0.18 * # Normalized FDG Activity 0.97 ± 0.08 0.66 ± 0.12 * 1.07 ± 0.35 * 0.47 ± 0.16 * # Normalized NH 3 Activity 0.97 ± 0.07 0.94 ± 0.08 0.63 ± 0.18 * # 0.47 ± 0.15 * # Normalized FDG:NH 3 Ratio 0.99 ± 0.08 0.71 ± 0.13 * 1.77 ± 0.53 * # 1.06 ± 0.40 # Data are mean ± SD of ROI values as % of corresponding value measured in the most normal ROI for the same patient: * p < 0.05 vs. NL; p < 0.05 vs. HIB # p < 0.005 vs. RMM Conclusions: The RMM pattern often seen in PET viability studies can be mathematically described by an FDG:NH 3ratio <1.0. It reflects a deficit in FDG uptake that is out of proportion to the slight decrease in perfusion to affected regions, not from improper image scaling. This pattern stands in marked contrast to the HIB pattern and likely reflects diminished glucose uptake in regions with viable, but jeopardized, myocardium.

Effect of biventricular pacing on metabolism and perfusion in patients affected by dilated cardiomyopathy and left bundle branch block: evaluation by positron emission tomography.

Evaluate the possible changes in myocardial metabolism and perfusion induced by biventricular pacing (BIVP) in patients affected by dilated cardiomyopathy (DC) and left bundle branch block (LBBB). Eight male patients (aged 60-79 years, mean 69) affected by DC (NYHA functional class III and ejection fraction <40%) were submitted to cardiac PET in basal condition and 3 weeks after the implantation of a biventricular device. Metabolism was evaluated using F18-fluorodeoxyglucose (FDG), by the glucose load-insulin technique, and perfusion by N13-ammonia (NH3), injected at rest. Visual and a semi quantitative analyses were performed, calculating by ROIs the septum to lateral uptake ratio (SLR). The myocardial blood flow (MBF) was also calculated in ml/min/g using a dynamic acquisition and a modified Patlak method. In all 8 patients a selective defect in FDG uptake in the septum was present in basal condition (mean SLR 0.59+/-0.17) with a 'reverse mismatch' effect with respect to NH3 (mean SLR 1.07+/-0.18). During BIVP the distribution of FDG in the septal area significatively improved (mean SLR 0.86+/-0.15 P=0.011 with respect to basal); on the contrary, no significant changes were found in NH3 uptake (mean SLR 1.02+/-0.23, P=ns). On quantitative analysis the mean MBF in the septum was 1.05+/-0.37 in basal condition and did not significantly change during BIVP (0.95+/-0.34, P=0.06). Our results suggest that, in patients affected by DC and LBBB, BIVP improves the septal glucose metabolism without significant changes in myocardial perfusion.

Prolonged ischemic heart disease and coronary artery bypass - relation to contractile reserve.

A major effect of coronary artery bypass grafting (CABG) in patients with ischemic heart disease and impaired left ventricular (LV) contractile function is believed to be an improvement in LV function due to recovery of dysfunctional, but viable myocardium. However, recent studies have indicated a time limit for such a recovery. We therefore investigated the extent of viable myocardium in patients with impaired LV function due to ischemic heart disease after a prolonged strategy of medical treatment and its relation to changes in clinical variables after CABG. Forty-five consecutive patients with a mean duration of ischemic heart symptoms of 9 years and LV ejection fraction (EF) <45% referred for CABG were included and LV extent of viable myocardium was measured preoperatively by glucose metabolism--blood flow positron emission tomography imaging and dobutamine stress echocardiography. Symptoms, exercise-capacity and LV function were evaluated before and 7 months after surgery in event-free survivors. LV extent of myocardial viability was <30% in most patients. In event-free survivors, LVEF decreased from 31+/-7 to 26+/-8% 7 months after CABG. The decrease in LVEF was correlated to the LV extent of myocardial metabolism--blood flow reverse mismatch. Most of the patients experienced an improvement in their angina pectoris, heart failure symptoms and exercise capacity after CABG; the overall 3-year survival was 77%. Patients with chronic ischemic heart disease and impairment of LV function, in whom an initial long-standing conservative treatment has been practiced, benefit from CABG, despite a lack of LV functional reserve.

Ventilation-perfusion "reverse mismatch" from aspirated medication.

A woman with acute respiratory distress had a chest radiograph that showed volume loss on the left side. A radioxenon lung scan revealed normal ventilation of the right lung and visualization of both trachea and main stem bronchi. Perfusion lung imaging showed some of the left lung to be perfused. This suggested a foreign body or mass obstructing the left main stem bronchus. An aspirated medication pill was found and removed at bronchoscopy. The left lung then became air filled.