Stress Perfusion Defects Research Articles

Diagnostic accuracy of high-resolution attenuation-corrected Anger-camera SPECT in the detection of coronary artery disease

BackgroundThere is limited data on diagnostic accuracy of recently introduced high-resolution Anger (HRA) SPECT incorporating attenuation correction (AC), noise reduction, and resolution recovery algorithms. We therefore studied 54 consecutive patients (excluding those with prior MI or cardiomyopathy) who had HRA-AC SPECT and coronary angiography (CA) ≤ 30 days and no change in symptoms. MethodsThe HRA-AC studies were acquired in 128 × 128 matrix (3.2 mm pixel) format with simultaneous Gd-153 line-source AC. Measured variables were image quality, interpretive certainty, sensitivity and specificity for any CAD, sensitivity for single- and multivessel CAD, and the influence of gender, body mass index (BMI), and stress modality. ResultsThe mean age of the patients was 66 ± 11 years with a BMI of 32 ± 7 kg·m−2. Mean interpretive certainty score was 2.7 on a 3-point scale and mean image quality score was 3.3 on a 4-point scale. Stress perfusion defects were detected in 34 of 38 patients with obstructive CAD [sensitivity 89%, 95% confidence interval (CI) 76%-95%]. The specificity was 75% (CI 51%-90%) and overall diagnostic accuracy was 85% (CI 73%-92%). Accuracy did not differ for females vs males, for BMI ≤30 vs >30, or for pharmacologic vs exercise SPECT. Sensitivity for single-vessel disease was 88% (CI 69%-96%) and for multivessel disease was 93% (CI 69%-99%). ConclusionNew Anger technology incorporating innovative improvements results in high image quality with excellent interpretive certainty and high diagnostic accuracy.

Assessment of semi-quantitative parameters for visual interpretation of stress-perfusion CMR in obstructive coronary artery disease

Background Adenosine stress CMR with visual interpretation is increasingly used in the evaluation of patients with CAD. The definition of a stress perfusion defect is inconsistent in the literature regarding i) the duration from contrast arrival, ii) persistence relative to a remote segment, iii) transmural extent, and iv) reversibility on rest perfusion. In this study we sought to test several semi-quantitative parameters assessed by rapid visual analysis, and determine their utility to identify stress-perfusion defects from obstructive CAD.

Evaluating the Prognostic Value of Positron‐Emission Tomography Myocardial Perfusion Imaging Using Automated Software to Calculate Perfusion Defect Size

Myocardial perfusion imaging by positron-emission tomography (PET MPI) is regarded as a valid technique for the diagnosis of coronary artery disease (CAD), but the incremental prognostic value of PET MPI among individuals with known or suspected CAD is not firmly established. Myocardial perfusion defect sizes as measured by PET MPI using automated software will provide incremental prognostic value for cardiac and all-cause mortality. This study included 3739 individuals who underwent rest-stress rubidium-82 PET MPI for the evaluation of known or suspected CAD. Rest, stress, and stress-induced myocardial perfusion defect sizes were determined objectively by automated computer software. Study participants were followed for a mean of 5.2 years for cardiac and all-cause mortality. Cox proportional hazards models were developed to evaluate the incremental prognostic value of PET MPI. A strong correlation was observed between perfusion defect sizes assessed visually and by automated software (r = 0.76). After adjusting for cardiac risk factors, known CAD, noncoronary vascular disease, and use of cardioprotective medications, stress perfusion defect size was strongly associated with cardiac death (P < 0.001). Rest perfusion defects demonstrated a stronger association with cardiac death (P < 0.001) than stress-induced perfusion defects (P = 0.01), yet both were highly significant. Similar patterns held for all-cause death. The current study is the largest to date demonstrating PET MPI provides incremental prognostic value among individuals with known or suspected CAD. Automated calculation of perfusion defect sizes may provide valuable supplementary information to visual assessment.

Prognostic value of myocardial perfusion scintigraphy in elderly patients with hypertension: a 10-year follow-up analysis

The aim of the study was to assess the role of myocardial perfusion scintigraphy (MPS) in the prediction of future cardiac events in elderly hypertensive patients and to investigate if its prognostic value is maintained during a 10-year follow-up period. A total of 229 consecutive patients ≥ 65 years old (range 65-88 years) with arterial hypertension, who were referred to our institution for stress/rest (99m)Tc-sestamibi MPS between January 2000 and November 2001, were followed up for 10-12 years. Cardiac death, myocardial infarction and a coronary revascularization procedure were considered as events. Survival curves were computed by the Kaplan-Meier method. A stepwise Cox proportional hazards analysis was used to identify predictors of events. Follow-up was completed in 221 (96.5 %) patients; 26 patients experienced cardiac death, 29 myocardial infarction and 51 coronary revascularization. Annual event rates for cardiac death, cardiac death/myocardial infarction and cardiac death/myocardial infarction/coronary revascularization were, respectively, 0, 0.2 and 0.4 % for patients with a normal scan and 1.5, 3.0 and 5.3 % after an abnormal MPS. Event-free survival was significantly different according to extent and severity of perfusion defects (all p < 0.01). An increase in global chi-square in predicting cardiac events occurred when MPS data were added to pre-scan information (from 47.28 to 88.87; p < 0.001). MPS provides incremental prognostic information for the prediction of cardiac events in elderly patients with hypertension. Subjects with a normal scan have an excellent 10-year outcome, and the risk of experiencing a cardiac event increases with extension and severity of stress perfusion defect.

085 Systolic vs diastolic acquisition in cardiovascular magnetic resonance myocardial perfusion imaging

IntroductionAlthough differences in systolic and diastolic myocardial blood flow (MBF) estimates have been shown in healthy volunteers, the impact of cardiac phase on detecting coronary artery disease (CAD) using cardiovascular...

The prognostic association between resting heart rate and cardiac death—Myocardial perfusion defects as a potential mechanism

ObjectiveElevated resting heart rate (RHR) is a robust risk factor for cardiac events, and recent clinical trial evidence suggests lowering RHR may reduce cardiac risk among individuals with elevated RHR and known coronary artery disease (CAD). This study sought to elucidate the extent to which myocardial perfusion defects explain the association between RHR and cardiac death among individuals with known or suspected CAD undergoing myocardial perfusion imaging (MPI). MethodsThis retrospective cohort study included 3708 individuals with known or suspected CAD who underwent clinically indicated MPI with positron emission tomography (PET MPI). Stress, rest, and stress-induced myocardial perfusion defect sizes were measured objectively by automated computer software as percent of left ventricular myocardium hypoperfused. RHR was measured by electrocardiography prior to rest PET MPI. Cardiac and non-cardiac death information was obtained through the National Death Index. All analyses were stratified by beta blocker (BB) use. ResultsRHR was consistently associated with the presence of significant myocardial perfusion defects, though associations were stronger among BB than non-BB users. Among BB users, RHR was strongly associated with an increased risk of cardiac death in adjusted models before (hazard ratio [HR]=2.6 comparing RHR≥80bpm vs. RHR<60, p<0.05) and after (HR=2.4, p<0.05) including stress myocardial perfusion defect size in the model. Results were similarly strong among non-BB users. ConclusionsResting heart rate was independently associated with cardiac death, however there was little evidence suggesting this association was explained by the presence of myocardial perfusion defects.

Quantitative Comparison of Myocardial Perfusion Defects using Different Reconstruction Algorithms

Objective: To investigate the impact of a reconstruction method incorporating corrections for scatter, attenuation, and distance dependent detector response on cardiac single emission computed tomography (SPECT) perfusion studies compared with filtered back projection (FBP). Materials and methods: A total of 20 patients underwent same-day, rest-stress SPECT/CT myocardial perfusion imaging. Images were reconstructed using iterative 3D ordered-subsets expectation-maximization (OSEM 3D) and FBP algorithms. Stress and rest myocardial perfusion defects were quantified using polar maps and normal database comparisons. The Bland-Altman plots were used to assess their degree of agreement. Results were confirmed by coronary angiography. The contrast, contrast to noise ratio and signal to noise ratio were used for the quantitative evaluation of the reconstruction quality. Results: Perfusion defect extent quantification on OSEM 3D reconstructed images agreed and correlated well with defect extent quantification on FBP reconstructed images (bias ± standard deviation, -15% ± 20; r = 0.63) during stress and at rest (-10% ±15; r=0.70). Agreement and correlation were similar for severity scores during stress (-1.02 ± 1.77 SD’s; r=0.62), and at rest (-1.10 ± 1.49 SD’s; r=0.61). There were no statistically significant differences between the methods regarding perfusion defect extent or severity. The overall agreement rate with coronary angiography was similar. OSEM 3D reconstruction algorithm significantly increases the image contrast by 31% (P<0.05). Conclusions: Compensation for detector response, attenuation and scatter improves image contrast compared with FBP. Applying quantitative analysis, OSEM 3D reconstruction produced increased image contrast compared to FBP, but similar results regarding the size and severity of left ventricular perfusion defects.

P3-13-06: Cardiovascular Magentic Resonance Imaging and Radiation-Induced Heart Disease Following Radiotherapy for Breast Cancer.

Abstract Background: Radiotherapy (RT) forms a vital component of treatment for breast cancer, contributing to the increasing number of survivors worldwide. It is known from historical cohorts that breast RT increased the risk of developing heart disease 10 years or more following treatment. It is less certain whether the lower cardiac radiation doses received during modern RT still increase cardiac risk. Cardiovascular Magnetic Resonance (CMR) imaging has the potential to provide early surrogate markers of radiation-induced heart disease that may help predict which women will be at increased risk in the future. Methods: This is a prospective longitudinal imaging study to evaluate CMR findings in a cohort of women receiving adjuvant RT for early breast cancer at the Oxford Cancer Centre. The patients undergo CMR imaging (with gadolinium enhancement and adenosine stress), Doppler echocardiography, blood testing (including BNP and troponin), ECG and clinical examination prior to RT, within 72 hours of completing RT, and at 3 months, 6 months and 5 years following RT. The results of these investigations will be related to cardiac radiation exposure estimated using 3D-dosimetric data obtained by analysis of CT-based RT planning. Recruitment and Provisional Results: As of May 2011, 30 women have been recruited. The women had a mean age of 57.1 years (range = 42.0 to 63.9). All women had left-sided cancer and none received adjuvant cytotoxic chemotherapy. The mean whole heart dose was 1.47 Gray (range = 0.65 to 4.20), the mean left ventricle dose was 2.03 (range = 0.88 to 6.99) and the mean left coronary artery dose was 7.55 Gray (range = 1.50 to 24.59). Preliminary analysis of the first 10 participants showed that all had a normal left ventricular ejection fraction at baseline (mean 76%, range 60–82%) and immediately following RT (mean reduction 3%, p=0.18). None had myocardial oedema as detected by T2-STIR imaging or fibrosis and scarring as demonstrated by late gadolinium enhancement (LGE). Conclusion and Future Plans: Preliminary results suggest that the relatively low heart doses received by the women undergoing modern CT-planned left breast RT at the Oxford Cancer Centre do not result in any cardiovascular abnormality detectable by CMR imaging. Further and updated results will be available for the San Antonio Breast Cancer Symposium. Recruitment will continue until at least 20 women have completed baseline scans and follow-up scans up to 6 months. At this stage a full analysis will be performed including a wider range of CMR endpoints including: - Overall LV systolic function (EF and volumes) - Regional wall motion analysis - T2-weighted imaging (oedema) - T1 and T2 mapping (quantitative T1 and T2 relaxation times) - Tagged myocardial strain analysis - Stress perfusion defects (endothelial/microcapillary damage) - Late gadolinium (LGE) imaging (fibrosis/scarring) Depending on the results of this analysis, recruitment may be expanded to include women with either lower cardiac risk (e.g. with right-sided breast cancer) or higher cardiac risk (e.g. receiving anthracycline chemotherapy). Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-13-06.

Cardiovascular outcomes are predicted by exercise-stress myocardial perfusion imaging: Impact on death, myocardial infarction, and coronary revascularization procedures

The aim of this study was to determine the impact of myocardial perfusion imaging (MPI) on the outcomes of death, myocardial infarction (MI), and late coronary revascularization procedures. In patients undergoing exercise-stress MPI (January 1, 2003-March 31, 2007), we determined the impact of summed stress score (SSS) and percent left ventricular (LV) ischemia on (a) death or MI and (b) composite of death, MI, or late coronary revascularization occurring more than 90 days post-MPI. During 35,007 person-years of follow-up among 9,605 patients (mean ± SD age 54.4 ± 13.2 years, 60.3% men), there were 290 deaths, 175 MIs, and 525 coronary revascularization procedures. Of those who attained ≥10 metabolic equivalents (METS) workload, major stress perfusion defects (SSS ≥7) were present in 4.2% overall and in 3.7% without ST-segment shifts, whereas large ischemic defects (≥10% LV ischemia) were present in 1% overall and 0.7% without ST-segment shifts. For those with 1% to 4%, 5% to 9%, and ≥10% LV ischemia, adjusted hazard ratios were 1.40 (95% CI 1.13-1.73, P = .002), 2.07 (95% CI 1.56-2.74, P < .001), and 3.03 (95% CI 2.21-4.16, P < .001) for the outcome of late revascularization, MI, or death versus no ischemia. Summed stress scores ≥7 were associated with increased risk of death or MI, with an adjusted hazard ratio of 1.57 (95% CI 1.16-2.13, P = .004) compared with those with no stress perfusion defects. Although workload ≥10 METS conferred lower frequency of major ischemia (≥10%), %LV ischemia predicted the occurrence of cardiovascular events and death (eg, MI, late coronary revascularization, or death). Presence of a large stress perfusion defect (SSS ≥7) predicted increased risk of MI or death.

Prognostic utility and clinical impact of adenosine stress perfusion CMR scan in patients with known coronary disease

Results Mean age was 62 ± 12 years, and 24% were female. 19 patients had a history of previous coronary artery bypass grafting. A stress perfusion defect in viable myocardium was identified in 71 patients (71%). Of these, 52 (73%) subsequently underwent revascularization by either PCI (n = 49) or CABG (n = 3). Revascularisation was either unsuccessful or not performed in 19 patients (27%) due to the absence of significant symptoms, presence of mild perfusion abnormality or poor revascularisation targets. Among the 29 patients in whom no inducible perfusion defects were identified, revascularization was performed in 3 patients (1%) either due to ongoing symptoms (n = 2) or presence of significant luminal area reduction on intravascular ultrasound (IVUS) (n = 1). Follow-up data was available in 93 patients (93%). During a mean follow-up of 10.2 months, no adverse events were observed in patients without inducible perfusion defects on stress perfusion CMR. Among those patients with inducible perfusion defects on CMR who were treated initially with PCI, one patient died during follow-up and four patients were referred for surgical revascularisation due to significant disease progression/restenosis post PCI.

Tolerance, safety and accuracy of stress cardiovascular magnetic resonance in routine clinical practice

Methods We retrospectively examined all stress CMR studies performed at our tertiary referral centre over a 20-month period, since the service was started in 2007. Patients were scanned in a 1.5T magnet (Avanto, Siemens), using a standardised protocol with routine imaging for late gadolinium enhancement (LGE). They were screened for contraindications to adenosine, and routine anti-anginal therapies, including beta-blockers, were not discontinued. Dobutamine stress was given in small number of patients in whom adenosine was contraindicated. Angiograms of patients who also had cardiac catheterization within 6 months of their CMR scan, were reassessed by an interventional cardiologist, blinded to the CMR data. For receiver-operator curve (ROC) analysis, CMR stress perfusion defects were graded into 5 categories (normal, probably normal, possibly abnormal, probably abnormal, abnormal).

Predictors of abnormal heart rate response to dipyridamole in patients undergoing myocardial perfusion SPECT

To identify predictors of abnormal HR response to dipyridamole (DIP) in patients undergoing myocardial perfusion SPECT (MPS). Patients with a reduced heart rate (HR) response to DIP have higher cardiac mortality, but the mechanism is unknown. We studied 432 patients who underwent dual-isotope gated MPS. DIP (0.56 mg/kg) was infused over 4 min, and Tc-99m tetrofosmin was injected 3 min after the end of the infusion. MPS was semiquantitatively interpreted. Left ventricular ejection fraction (LVEF) and volumes were automatically calculated. The population was categorized into quartiles according to HR ratio, and characteristics in each quartile were compared. Logistic regression analysis was performed to identify predictors of abnormal HR response, using the lowest quartile as the independent variable. Patients with abnormal HR response were more frequently without chest pain, with a history of chronic renal failure and taking digoxin. Baseline HR was higher and had fewer symptoms during stress. The stress and rest perfusion defects were greater, but reversibility was not; in addition, LVEF was lower. Multivariable logistic regression analysis demonstrated that the independent predictors of abnormal HR response were baseline HR and low LVEF. LV dysfunction is an independent predictor of abnormal HR response to DIP, and the association between low LVEF and low HR ratio may explain the link between abnormal HR ratio and increased mortality.

Assessment of the relationship between stenosis severity and distribution of coronary artery stenoses on multislice computed tomographic angiography and myocardial ischemia detected by single photon emission computed tomography

BackgroundThe relationship between luminal stenosis measured by coronary CT angiography (CCTA) and severity of stress-induced ischemia seen on single photon emission computed tomographic myocardial perfusion imaging (SPECT-MPI) is not clearly defined. We sought to evaluate the relationship between stenosis severity assessed by CCTA and ischemia on SPECT-MPI. Methods and ResultsECG-gated CCTA (64 slice dual source CT) and SPECT-MPI were performed within 6 months in 292 patients (ages 26-91, 73% male) with no prior history of coronary artery disease. Maximal coronary luminal narrowing, graded as 0, ≥25%, 50%, 70%, or 90% visual diameter reduction, was consensually assessed by two expert readers. Perfusion defect on SPECT-MPI was assessed by computer-assisted visual interpretation by an expert reader using the standard 17 segment, 5 point-scoring model (stress perfusion defect of ≥5% = abnormal). By SPECT-MPI, abnormal perfusion was seen in 46/292 patients. With increasing stenosis severity, positive predictive value (PPV) increased (42%, 51%, and 74%, P = .01) and negative predictive value was relatively unchanged (97%, 95%, and 91%) in detecting perfusion abnormalities on SPECT-MPI. In a receiver operator curve analysis, stenosis of 50% and 70% were equally effective in differentiating between the presence and absence of ischemia. In a multivariate analysis that included stenosis severity, multivessel disease, plaque composition, and presence of serial stenoses in a coronary artery, the strongest predictors of ischemia were stenosis of 50-89%, odds ratio (OR) 7.31, P = .001, stenosis ≥90%, OR 34.05, P = .0001, and serial stenosis ≥50% OR of 3.55, P = .006. ConclusionsThe PPV of CCTA for ischemia by SPECT-MPI rises as stenosis severity increases. Luminal stenosis ≥90% on CCTA strongly predicts ischemia, while <50% stenosis strongly predicts the absence of ischemia. Serial stenosis of ≥50% in a vessel may offer incremental value in addition to stenosis severity in predicting ischemia.

Simultaneous dual-radionuclide myocardial perfusion imaging with a solid-state dedicated cardiac camera

We compared simultaneous dual-radionuclide (DR) stress and rest myocardial perfusion imaging (MPI) with a novel solid-state cardiac camera and a conventional SPECT camera with separate stress and rest acquisitions. Of 27 consecutive patients recruited, 24 (64.5+/-11.8 years of age, 16 men) were injected with 74 MBq of (201)Tl (rest) and 250 MBq (99m)Tc-MIBI (stress). Conventional MPI acquisition times for stress and rest are 21 min and 16 min, respectively. Rest (201)Tl for 6 min and simultaneous DR 15-min list mode gated scans were performed on a D-SPECT cardiac scanner. In 11 patients DR D-SPECT was performed first and in 13 patients conventional stress (99m)Tc-MIBI SPECT imaging was performed followed by DR D-SPECT. The DR D-SPECT data were processed using a spill-over and scatter correction method. DR D-SPECT images were compared with rest (201)Tl D-SPECT and with conventional SPECT images by visual analysis employing the 17-segment model and a five-point scale (0 normal, 4 absent) to calculate the summed stress and rest scores. Image quality was assessed on a four-point scale (1 poor, 4 very good) and gut activity was assessed on a four-point scale (0 none, 3 high). Conventional MPI studies were abnormal at stress in 17 patients and at rest in 9 patients. In the 17 abnormal stress studies DR D-SPECT MPI showed 113 abnormal segments and conventional MPI showed 93 abnormal segments. In the nine abnormal rest studies DR D-SPECT showed 45 abnormal segments and conventional MPI showed 48 abnormal segments. The summed stress and rest scores on conventional SPECT and DR D-SPECT were highly correlated (r=0.9790 and 0.9694, respectively). The summed scores of rest (201)Tl D-SPECT and DR-DSPECT were also highly correlated (r=0.9968, p<0.0001 for all). In six patients stress perfusion defects were significantly larger on stress DR D-SPECT images, and five of these patients were imaged earlier by D-SPECT than by conventional SPECT. Fast and high-quality simultaneous DR MPI is feasible with D-SPECT in a single imaging session with comparable diagnostic performance and image quality to conventional SPECT and to a separate rest (201)Tl D-SPECT acquisition.

Diagnostic and prognostic value of myocardial perfusion gated SPECT in orthotopic heart transplant recipients

BackgroundCardiac allograft vasculopathy (CAV) limits long-term survival after heart transplantation. Diagnostic and prognostic value of gated single photon emission computed tomography (gated SPECT) has not been documented in this setting. Methods and ResultsWe identified 110 consecutive heart transplant recipients (with transplantation >18 months) who underwent stress–rest gated SPECT and coronary angiography within 1 month, and were clinically monitored in a single heart transplantation center. Visual scoring of perfusion and wall motion images used a 16-segment model. Left ventricular function was automatically calculated. Coronary angiography was normal in 64 patients (58%) and abnormal in 46 (any CAV, 42%), of whom 19 had severe stenoses. Sensitivity and negative predictive (NPV) value were .63 and .75 for identification of any CAV, and .84 and .96 for severe CAV. Cox regression analysis showed that independent predictors of cardiac death and retransplantation were the presence of any angiographic CAV lesions (RR = 8.816, P = .043) and a stress perfusion defect >3 segments (RR = 5.607, P = .0053). A stress perfusion defect >3 segments predicted the need for late coronary revascularization >2 months (RR = 6.11, P = .0002). ConclusionsWe conclude that perfusion gated SPECT is a useful noninvasive screening test and may be proposed to help identify heart transplant recipients with a high risk of poor clinical outcome. A normal gated SPECT was associated with a low risk of cardiac hard event and might alleviate the need for coronary angiography.

Changes in platelets and anticoagulant protein activity during adenosine-exercise single-photon emission computed tomography stress test

Activation of haemostasis during physical stress or during myocardial ischemia could be an important mechanism to trigger coronary and stent thrombosis. We examined changes in haemostatic parameters and its association with myocardial ischemia during adenosine-exercise-SPECT (adeno-EX) stress test in coronary patients at least 4 months after coronary stenting. The aim of this study was to examine relationship between changes in haemostatic parameters and stress induced myocardial ischemia quantified by perfusion scintigraphy in stented coronary patients. Thirty-seven patients on dual antiplatelet therapy (26 on clopidogrel plus aspirin and 11 on aspirin only) 4-8 months after successful intracoronary stent implantation were enrolled in the study. We determined the levels of platelet aggregability (PA) on ADP (PA-ADP) and epinephrine (PA-EPI), beta-thromboglobulin, platelet factor-4, protein C (PC) and antithrombin (AT) before and 15 minutes after intravenous injection of 150 micro/kg adenosine for4 minutes concomitant with supine ergo-bicycle exercise test for 50 W. The size of stress perfusion defect was measured 15 minutes after stress and in rest 4 hours later by 99mTc-tetrofosmin single photon emission computed tomography (SPECT) within 17 myocardial segments. There were no differences between haemostatic parameters before and after stress. A significant myocardial ischemia after exercise was registered in 12 patients on combined antiaggregation therapy and in 5 patients on aspirin. In this preliminary report, because of a small number of patients in the aspirin group we did not analyse difference in the levels of haemostatic markers and their correlations with the size of perfusion defect. The only significant difference between measured haemostatic parameters in the patients with stress induced ischemia compared to the patients without it, was a lower level of AT activity after stress (81.0% vs. 87.5%; p = 0.027). Antithrombin activity before stress had significant negative correlation with the size of perfusion defect in rest (R2 = 0.219; p = 0.016) and PC activity before stress had significant linear correlation with stress perfusion defect (R2 = 0.248; p = 0.010). Baseline activities of natural anticoagulant proteins AT and PC are associated with the size of myocardial perfusion defect during adeno-EX-SPECT test. Patients with significant stress-induced ischemia had lower levels of AT activity after stress.

Can metamizol play a role in nuclear medicine practice?

I read with great interest the letter to the editor by Georgoulias et al., published in the January 2009 issue concerning the drug enhancement of myocardial tracer uptake during myocardial perfusion imaging [1]. The authors also focused on our article “Tc sestamibi myocardial perfusion scintigraphy (MPS) with the novel use of metamizol for the detection of perfusion reversibility” published in the August 2008 issue [2]. Metamizol has been in clinical use for more than three quarters of a century, and recent reports have shown that metamizol also has a relaxing activity in vascular smooth muscle as assessed in in vitro tissue bath techniques and in vivo animal models [3–8]. In our above-mentioned study [2], we aimed to investigate whether the vascular smooth muscle relaxing effect of metamizol has the potential to better define myocardial ischaemia during MPS and we found that metamizol rest MPS displayed the defect reversibility better than baseline rest MPS and that metamizol-induced myocardial sestamibi uptake was significantly higher (p<0.001) than stress/baseline rest MPS examinations. Blood pressure remained unaltered after metamizol induction. So, we concluded that metamizol increases the detection of the viable myocardium regions during MPS and helps to make a confident interpretation for defect reversibility. In their letter to the editor, Georgoulias et al. [1] summarized the use of technetium-labelled tracers (sestamibi and tetrofosmin) for the detection of viable myocardium with one or a combination of the approaches such as determining the severity of resting defects according to the percent of the peak myocardial activity, assessing the radiotracer uptake after nitroglycerin administration and assessing the regional myocardial function and thickening by performing gated SPECT. The authors also shared that they had great experience with gated SPECT on this issue and they emphasized the clinical dilemma in the differentiation of viable myocardium from scar in patients without a history of myocardial infarction who had undergone gated SPECT study. In our study [2], we postulated that since metamizol is no longer detectable in the serum soon after its oral administration, its active metabolite 4-MAA may be responsible from the enhancement of perfusion seen on MPS due to its vasorelaxing effect. 4-MAA has a longer elimination half-life (2.7 h) than nitroglycerin (a few minutes). So, Georgoulias et al. indicated that the investigation of metamizol’s influence on cardiac function would be of interest and proposed that studies are needed to increase the information regarding the use of metamizol in combination with MPS. We are of the same opinion as Georgoulias et al. on this issue. Additionally, in our opinion correlative studies comparing the effects of metamizol and nitroglycerin on the myocardial uptake of the radiopharmaceuticals might be undertaken. Metamizol might have an advantage over nitroglycerin since it causes no significant alteration in blood pressure [2], and we did not observe any complaints such as vertigo, dizziness, nausea or vomiting due to metamizol in our patients. In our above-mentioned study [2], baseline rest MPS showed an average perfusion improvement of 7.8% in the regions where stress perfusion defects were seen. On the other hand, metamizol induction displayed an average perfusion improvement of 18.2% in the same myocardial regions when compared to stress MPS. Consequently, the Eur J Nucl Med Mol Imaging (2009) 36:1191–1192 DOI 10.1007/s00259-009-1149-2

Changes in Myocardial Perfusion Correlate With Deterioration of Left Ventricular Systolic Function in Chronic Chagas' Cardiomyopathy

This study aimed at analyzing the association between myocardial perfusion changes and the progression of left ventricular systolic dysfunction in patients with chronic Chagas' cardiomyopathy (CCC). Pathological and experimental studies have suggested that coronary microvascular derangement, and consequent myocardial perfusion disturbance, may cause myocardial damage in CCC. Patients with CCC (n = 36, ages 57 +/- 10 years, 17 males), previously having undergone myocardial perfusion single-positron emission computed tomography and 2-dimensional echocardiography, prospectively underwent a new evaluation after an interval of 5.6 +/- 1.5 years. Stress and rest myocardial perfusion defects were quantified using polar maps and normal database comparison. Between the first and final evaluations, a significant reduction of left ventricular ejection fraction was observed (55 +/- 11% and 50 +/- 13%, respectively; p = 0.0001), as well as an increase in the area of the perfusion defect at rest (18.8 +/- 14.1% and 26.5 +/- 19.1%, respectively; p = 0.0075). The individual increase in the perfusion defect area at rest was significantly correlated with the reduction in left ventricular ejection fraction (R = 0.4211, p = 0.0105). Twenty patients with normal coronary arteries (56%) showed reversible perfusion defects involving 10.2 +/- 9.7% of the left ventricle. A significant topographic correlation was found between reversible defects and the appearance of new rest perfusion defects at the final evaluation. Of the 47 segments presenting reversible perfusion defects in the initial study, 32 (68%) progressed to perfusion defects at rest, and of the 469 segments not showing reversibility in the initial study, only 41 (8.7%) had the same progression (p < 0.0001, Fisher exact test). In CCC patients, the progression of left ventricular systolic dysfunction was associated with both the presence of reversible perfusion defects and the increase in perfusion defects at rest. These results support the notion that myocardial perfusion disturbances participate in the pathogenesis of myocardial injury in CCC.

Abstract 2685: Assessment of Myocardial Perfusion With Stress-Contrast Echocardiography in Diabetics

Background and purpose: The combination of myocardial contrast echocardiography with dobutamine-atropine stress echocardiography has shown promising results in the diagnostic approach of coronary heart disease (CHD). However, its diagnostic value in specific patient populations has not been clearly specified. The aim of the present study was to assess the value of stress contrast echocardiography (SCE) in diagnosing significant coronary heart disease in diabetic versus non-diabetic patients. Methods: 127 individuals (60 males, 62±9.8 years old) with no known history of CHD, among which 59 patients with Type 2 diabetes mellitus, were submitted to stress echocardiography (four-stage dobutamine protocol 10 – 40 mcg/kg/min, with use of atropine as required to reach 90% of age-adjusted target heart rate), combined with intravenous contrast use to perform myocardial contrast echocardiography. New or worsening wall motion abnormalities during stress or reversible perfusion defects in &gt;2 contiguous segments were considered as signs of ischemia. Significant CHD was defined as &gt;50% stenosis in a major epicardial artery on coronary angiography (CAG). Results: Among the 68 non-diabetic subjects and the 59 diabetics, 58 (85.3%) and 45 (76.3%) were found to have significant CHD on CAG, respectively. There were no significant differences as regards to age, sex and other major risk factors between diabetics and non-diabetics. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) in the total of 127 patients were 92%, 63%, 91%, 65% and 87%, respectively. These diagnostic parameters in non-diabetic vs. diabetic subjects were 93% vs. 91% (p= NS ), 90% vs. 43% (p&lt;0.01), 98% vs. 84% (p&lt;0.05) and 69% vs. 60% (p= NS ). Conclusions: Stress contrast echocardiography is an exceptionally reliable technique for CHD diagnosis. However, our findings suggest that in diabetic patients it appears to exhibit inferior specificity and PPV compared to non-diabetics. A possible explanation could be that microcirculation abnormalities, which are common in diabetes, may cause appearance of signs of ischemia (wall-motion abnormalities and/or perfusion defects) on SCE, without presence of angiographically significant CHD.

Holistic polar map for integrated evaluation of cardiac imaging results

Polar map display (PM) is a comprehensive interpretation of the left ventricle. This is a non-rigid registration of the left ventricle originally for the visual and quantitative analysis of tomographic myocardial perfusion scintigrams. In this scheme the maximal-count circumferential profiles of well-defined short- and long-axis planes are plotted to a map showing the distribution of the perfusion tracer onto a two-dimensional polar representation. The usual coronary artery distribution is often indicated on the PMs of SPECT studies by referring to the regions of the three main coronary branches, nevertheless, the individual variations may differ extensively. We set out to develop an Access (Microsoft)-based computer program that permits an integrated evaluation of the imaging results (coronary angiography, echocardiography and SPECT) on patients with coronary artery disease. This semi-quantitative registration of the coronary tree to a PM focused on the relation between the supplying coronary branches and the myocardial regions of the 16-segment left ventricular evaluating model. All the recorded anatomical and functional data were related to these 16 left ventricular segments, which allowed the direct comparison and holistic synthesis of the results. Two projections were taken into consideration for generation of the coronary PM: from the right anterior oblique projections, the left anterior descendent (LAD)/right coronary artery (RCA) border was assessed through the comparison of the left and right coronary angiograms. The terminations of the visually detected end-arteries showed the separation of the myocardial beds supplied by the two branches. The border of the myocardial beds on the polar map was determined on the “vertical axis” of the local coordinate system. The RCA/ left circumflex (LCx) separation can be determined from the left anterior oblique view. In this projection, the left ventricular septal edge was delineated by the LAD, while the LCx indicated the lateral epicardial surface. The individual coronary artery circulation was typified from among 12 variations in the Holistic Coronary Care program. With this determination of the individual coronary circulation, the lesion-associated segments are generated automatically by the software. The lesion-associated regions are defined as the myocardial bed of a diseased artery distal to the lesion. The PMs generated from the coronary angiographic results were compared with those of 99Tc-labelled MIBI single photon emission computed tomography (SPECT) in order to test the accuracy of the localizing method. The overlap between the segments associated with the coronary lesion and the stress perfusion defects (<80% relative MIBI activity during stress tests) was analyzed in 10 patients with (sub)total coronary occlusion after myocardial infarction. The distributions of the segments with stress perfusion defects on MIBI SPECT gave positive and negative predictive values of coronary occlusion of 0.94 and 0.8, respectively. According to the 16-segment wall motion analysis by echocardiography, the positive and negative predictive values of coronary occlusion for wall motion abnormality were 0.82 and 0.76, respectively. While the distal part of the subtended region usually demonstrated a higher degree perfusion abnormality than the proximal part, the high positive predictive value proved that, during the stress condition, the perfusion defect could be detected in practically all the subtended regions. The low negative predictive value of the coronary lesion for the wall motion abnormality was associated with the remodeling of the entire left ventricle.