Emission Computed Tomography Myocardial Perfusion Imaging Research Articles

Deep Learning for Prediction of Obstructive Disease From Fast Myocardial Perfusion SPECT: A Multicenter Study

ObjectivesThe study evaluated the automatic prediction of obstructive disease from myocardial perfusion imaging (MPI) by deep learning as compared with total perfusion deficit (TPD). BackgroundDeep convolutional neural networks trained with a large multicenter population may provide improved prediction of per-patient and per-vessel coronary artery disease from single-photon emission computed tomography MPI. MethodsA total of 1,638 patients (67% men) without known coronary artery disease, undergoing stress 99mTc-sestamibi or tetrofosmin MPI with new generation solid-state scanners in 9 different sites, with invasive coronary angiography performed within 6 months of MPI, were studied. Obstructive disease was defined as ≥70% narrowing of coronary arteries (≥50% for left main artery). Left ventricular myocardium was segmented using clinical nuclear cardiology software and verified by an expert reader. Stress TPD was computed using sex- and camera-specific normal limits. Deep learning was trained using raw and quantitative polar maps and evaluated for prediction of obstructive stenosis in a stratified 10-fold cross-validation procedure. ResultsA total of 1,018 (62%) patients and 1,797 of 4,914 (37%) arteries had obstructive disease. Area under the receiver-operating characteristic curve for disease prediction by deep learning was higher than for TPD (per patient: 0.80 vs. 0.78; per vessel: 0.76 vs. 0.73: p < 0.01). With deep learning threshold set to the same specificity as TPD, per-patient sensitivity improved from 79.8% (TPD) to 82.3% (deep learning) (p < 0.05), and per-vessel sensitivity improved from 64.4% (TPD) to 69.8% (deep learning) (p < 0.01). ConclusionsDeep learning has the potential to improve automatic interpretation of MPI as compared with current clinical methods.

Visual estimation of coronary calcium on computed tomography for attenuation correction

BackgroundThe coronary calcium score (CCS) provides independent diagnostic and prognostic information on top of myocardial perfusion imaging (MPI) in patients suspected for coronary artery disease, but requires an additional computed tomography (CT) scan. ObjectiveWe investigated the accuracy and inter-reader reproducibility of visual estimation of the CCS on the CT used for attenuation correction. Methods250 patients undergoing single photon emission computed tomography MPI and Agatston CCS were included. The CCS was also visually estimated on the CT for attenuation correction by two separate readers blinded to the Agatston CCS, and was categorized into a six-point scale (0, 1–10, 11–100, 101–400, 401–1000 and > 1000). ResultsThe median Agatston CCS was 82 [25th–75th percentile: 0-562], with a range from 0 to 7287. Of the visually estimated CCS, 60% (reader 1) and 65% (reader 2) were classified correctly into the 6 categories. 93% (reader 1) and 88% (reader 2) of the visually estimated CCS did not vary by more than one category from the Agatston CCS. The intraclass correlation coefficient for agreement between the Agatston CCS and the visually estimated CCS was 0.95 for reader 1 and 0.94 for reader 2. The intraclass correlation coefficient for inter-reader reproducibility of the visually estimated CCS was 0.96. ConclusionThe CCS can be accurately estimated on the CT for attenuation correction, as high agreement is demonstrated with the Agatston CCS and inter-reader reproducibility is excellent. If no traditional Agatston CCS is performed, the degree of atherosclerosis should be assessed by means of estimating CCS on the CT for attenuation correction.

Prognostic implications of stress modality on mortality risk and cause of death in patients undergoing office-based SPECT myocardial perfusion imaging

BackgroundPatients requiring vasodilator single-photon emission computed-tomography myocardial perfusion imaging (SPECT-MPI) have a higher mortality risk than those selected for exercise or vasodilator with low-level exercise SPECT-MPI. However, it is unknown whether the increased mortality is driven by cardiac deaths alone or cardiac and non-cardiac deaths. MethodsIn a prospective cohort of 1,511 consecutive patients referred for SPECT-MPI, patients were classified according to stress test modality: exercise, adenosine with low-level exercise (AdenoEx), and adenosine. Subjects were followed for events of all-cause mortality and cause of death. Survival analyses using multivariate Cox regression and propensity score matching methods were performed. ResultsDuring a follow-up of 4.9 ± 0.9 years, a total of 68 (4.5%) deaths occurred: 50 non-cardiac and 18 cardiac. The adenosine group had the highest annual mortality (all-cause 3.65%, non-cardiac 2.36%, cardiac 1.29%), while exercise stress had the lowest mortality (all-cause 0.42%, non-cardiac 0.37%, cardiac 0.05%) and AdenoEx had an intermediate mortality (all-cause 1.3%, non-cardiac 0.91%, cardiac 0.39%); all P values <0.001. The majority of non-cardiac deaths were attributed to cancer. Using exercise stress as a reference standard, multivariable Cox regression analyses demonstrated that adenosine stress was independently predictive of all-cause mortality [HR 3.23 (CI 1.77-5.88); P < 0.001], non-cardiac death [HR 2.67 (CI 1.34-5.31); P = 0.005], and cardiac death [HR 6.30 (CI 1.55-25.56); P = 0.010] after adjusting for univariate predictors of mortality. These findings were consistent in the subgroups of patients with normal and abnormal MPI. AdenoEx was predictive of all-cause, non-cardiac, and cardiac deaths in univariate analysis, but it was not predictive by multivariate analysis. Propensity score matched cohort analysis showed that the adenosine stress group had the highest all-cause (P < 0.001), non-cardiac (P = 0.013), and cardiac deaths (P < 0.001), while the exercise stress group had the lowest mortality of any cause. ConclusionsThe inability to perform any level of exercise during a SPECT-MPI stress is associated with high mortality risk, which is derived from both cardiac and non-cardiac deaths.

Usefulness of the Chang attenuation correction method with use of a CT-based μ map by FBP reconstruction in 201Tl SPECT-MPI

Attenuation correction (AC) on nuclear images of non-uniform domains is generally performed by a change of the computed tomography (CT) values to μ values, which are then inserted as components into the detection probability of iterative reconstruction techniques (OS-EM Iterative AC). We established an AC technique which uses a CT μ map based on the Chang AC. Our purpose in this study was to confirm the appropriateness of the Chang AC with the OS-EM and the FBP method (OS-EM Chang AC and FBP Chang AC) by evaluating the results obtained in a phantom and clinical study for (201)Tl single-photon emission-computed tomography-myocardial perfusion imaging (SPECT-MPI). Myocardial phantom study and retrospective clinical study were performed. Evaluations for image quality (uniformity and contrast) and image quantitative values [accurate left ventricular (LV) volume and radioactivity] were performed for both studies. FBP Chang AC showed good image uniformity and proper contrast in phantom and clinical study. Accurate LV volume and radioactivity in the myocardium were also obtained by the phantom study. On the other hand, the number of iterations influenced the image quality both in OS-EM Iterative AC and OS-EM Chang AC in the phantom study. Different numbers of iterations were necessary for obtaining good contrast ratio in each of the anterior and inferior wall, and accurate LV volume. The number of iterations influences the image quality and quantitative values on OS-EM Iterative Chang AC and OS-EM Chang AC images. In addition, it is difficult to set an appropriate number of iterations for the iterative reconstruction of these images in phantom and clinical studies. Therefore, FBP Chang AC is considered to be clinically useful.

Cardiovascular risk stratification in diabetic patients following stress single-photon emission-computed tomography myocardial perfusion imaging: The impact of achieved exercise level

BackgroundPrevious studies have demonstrated that diabetic patients undergoing exercise stress single-photon emission-computed tomography (SPECT) myocardial perfusion imaging (MPI) have significantly lower cardiac events when compared to the diabetic patients undergoing pharmacologic stress SPECT MPI across all perfusion categories. However, there are limited data on the level of exercise achieved during exercise SPECT MPI among diabetic patients and its impact on cardiovascular outcomes. MethodsWe retrospectively analyzed 14,849 consecutive patients (3,654 diabetics and 11,195 non-diabetics) undergoing exercise stress, combined exercise and pharmacologic stress, and pharmacologic stress SPECT MPI from 1996 to 2005 at a single tertiary care center. Diabetic and non-diabetic patients were categorized into 3 groups based on the metabolic equivalents (METs) achieved: ≥5 METs, <5 METs, and pharmacologic stress groups. All studies were interpreted using the 17-segment ASNC model. The presence, extent, severity of perfusion defects were calculated using the summed stress score (SSS), and patients were classified into normal (SSS < 4), mildly abnormal (SSS 4-8), and moderate-severely abnormal (SSS > 8) categories. Annualized event rates (AER) for the composite end point of non-fatal myocardial infarction and cardiac death were calculated over a mean follow-up period of 2.4 ± 1.4 years with a maximum of 6 years. ResultsIn moderate-severe perfusion abnormality (SSS > 8) category, diabetic patients who were able to achieve ≥5 METs had significantly lower AER compared to diabetic patients who were unable to achieve ≥5 METs (3% vs 5.5%, P = .04), and non-diabetic patients unable to achieve ≥5 METs (3% vs 4.8%, P < .001). Diabetic patients who achieved a high workload of ≥10 METs had a very low AER of 0.9%. Diabetic patients, who attempted exercise but were unable to achieve ≥5 METs, still had significantly lower AER than diabetics undergoing pharmacologic stress MPI across all perfusion categories [1.5% vs 3.2%, P = .006 (SSS < 4); 2.5% vs 4.9%, P = .032 (SSS 4-8); 5.5% vs 10.3%, P = .003 (SSS > 8)]. After adjustment for cardiovascular risk factors, the percentage decrease in cardiac event rate for every 1-MET increment in exercise capacity was 10% in the overall cohort, 12% in diabetic group, and 8% in non-diabetic group. ConclusionsDespite significant perfusion defects, diabetic patients who achieve ≥5 METs during stress SPECT MPI have significantly reduced risk for future cardiac events. Diabetic patients who achieve ≥10 METs have a very low annualized event rate. These findings support that exercise capacity obtained during SPECT MPI is a surrogate for outcomes among diabetic patients undergoing nuclear stress testing.

Left ventricular remodeling after late revascularization correlates with baseline viability.

The ideal management of stable patients who present late after acute ST-elevation myocardial infarction (STEMI) is still a matter of conjecture. We hypothesized that the extent of improvement in left ventricular function after successful revascularization in this subset was related to the magnitude of viability in the infarct-related artery territory. However, few studies correlate the improvement of left ventricular function with the magnitude of residual viability in patients who undergo percutaneous coronary intervention in this setting. In 68 patients who presented later than 24 hours after a confirmed first STEMI, we performed resting, nitroglycerin-enhanced, technetium-99m sestamibi single-photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) before percutaneous coronary intervention, and again 6 months afterwards. Patients whose baseline viable myocardium in the infarct-related artery territory was more than 50%, 20% to 50%, and less than 20% were divided into Groups 1, 2, and 3 (mildly, moderately, and severely reduced viability, respectively). At follow-up, there was significant improvement in end-diastolic volume, end-systolic volume, and left ventricular ejection fraction in Groups 1 and 2, but not in Group 3. We conclude that even late revascularization of the infarct-related artery yields significant improvement in left ventricular remodeling. In patients with more than 20% viable myocardium in the infarct-related artery territory, the extent of improvement in left ventricular function depends upon the amount of viable myocardium present. The SPECT-MPI can be used as a guide for choosing patients for revascularization.

Effect of caffeine on SPECT myocardial perfusion imaging during regadenoson pharmacologic stress: a prospective, randomized, multicenter study.

A multicenter, double-blind, randomized study was conducted to assess the effect of caffeine on regadenoson stress myocardial perfusion imaging (MPI). Subjects with a high likelihood of coronary artery disease underwent a rest single-photon emission computed tomography MPI on day 1 (MPI-1) and a stress MPI with regadenoson on day 3 (MPI-2). Individuals with ≥1 segment with a reversible defect received double-blind caffeine tablets (200 or 400 mg) or placebo 90 min before a repeat regadenoson stress MPI (MPI-3) on day 5. Overall, 207 subjects completed the study (caffeine 200 mg, n = 70; caffeine 400 mg, n = 71; placebo, n = 66). The mean number of segments with reversible defects decreased from MPI-2 to MPI-3 in the caffeine 200 and 400 mg groups versus no significant change in the placebo group [mean ± standard deviation: −0.61 ± 1.097, −0.62 ± 1.367, and 0.12 ± 0.981, respectively (overall treatment effect, P < 0.001)]. The majority of subjects who received caffeine shifted to a lower ischemia size category from MPI-2 to MPI-3, with no clear pattern observed in subjects who received placebo. For caffeine exposed patients with ≥3 segments with reversible defects at MPI-2, 21/23 had fewer detected at MPI-3. Both the 200 and 400 mg doses of caffeine significantly reduced the number of segments with reversible defects detected by regadenoson stress MPI.

Appropriate-Use Criteria for Myocardial Perfusion Imaging and Prognosis

Professional societies have published criteria for use of single-photon emission computed tomography–myocardial perfusion imaging (SPECT-MPI),

Prevalence and Predictors of Ischemia and Outcomes in Outpatients With Diabetes Mellitus Referred for Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging

Background- The prevalence of ischemia and its prediction of events are unclear in outpatients with diabetes mellitus in the modern era of intensive medical management. We sought to identify the prevalence of ischemia, subsequent cardiac events, and impact of sex, stress type, and symptom status on these findings in a cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging (MPI). Methods and Results- The study cohort included 575 consecutive outpatients with diabetes mellitus who underwent quantitative, gated single-photon emission computed tomography MPI. Clinical information, stress MPI variables, and cardiac events were prospectively collected and analyzed. The study population was at intermediate risk of coronary artery disease or had known coronary artery disease (40.3%); 29% of patients were asymptomatic at the time of stress testing. Scintigraphic ischemia and significant (≥10%) left ventricular ischemia were present in 126 patients (21.9%) and 29 patients (5.0%), respectively, and <1% of patients had early revascularization. The risk of ischemia was increased >2-fold by male sex (P<0.001), but was not impacted by pharmacological stress (P=0.15) or presence of symptoms (P=0.89). During a median 4.4 years follow-up, the rate of cardiac death/nonfatal myocardial infarction was moderate at 2.6%/y (cardiac death 0.8%/y) in the total cohort, but was 5.7%/y in those with ischemia (P<0.001). Pharmacological stress predicted a higher cardiac event rate (P<0.001) but symptoms did not (P=0.55). Conclusions- This cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography had low rates of significant ischemia and early revascularization; an initially low cardiac event rate increased after 2 years. Independent predictors of cardiac death/nonfatal myocardial infarction were known coronary artery disease, pharmacological stress, and MPI ischemia. Nearly one third of those with events had a normal MPI, indicating a need for improved risk stratification.

Aligning Coronary Anatomy and Myocardial Perfusion Territories

Background— Appropriate clinical decisions concerning diagnosis and treatment of coronary artery disease rely on correct integration of data on coronary anatomy and myocardial perfusion. The purpose of this article is to introduce a new left ventricular segmentation model for improved alignment of coronary arterial segments and myocardial perfusion territories, designed for the CORE320 study. Methods and Results— CORE320 is a prospective, multicenter study with a primary objective to evaluate the diagnostic accuracy of 320-row detector computed tomography (CT) to detect coronary artery luminal stenosis and corresponding myocardial perfusion deficits in patients with suspected coronary artery disease compared with the gold standard of conventional coronary angiography and single-photon emission CT myocardial perfusion imaging. We describe a 19-coronary segment and 13-myocardial territory alignment model, its application in both standard and CT image data sets, and the adjudication process of the initial cohort of patients recruited for the CORE320 study. Adjudication committees reviewed the images of the first 101 gold standard and 107 CT data sets. On the basis of the presented model and rules, all cases for adjudication were correctly identified. During image review, 6 (5.9%) gold standard and 9 (8.4%) CT data sets needed further realignment not triggered by the algorithm. Conclusions— We present a vascular territory distribution model developed for the CORE320 multicenter study, which accounts for variability in coronary anatomy and potential myocardial perfusion territory overlap. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00934037.

Safety of regadenoson in patients with end-stage liver disease

BackgroundRegadenoson is a selective A2A receptor agonist that is used for vasodilator stress myocardial perfusion imaging (MPI). Since the drug is partially metabolized by the liver, its safety in patients with end-stage liver disease (ESLD) needs to be determined. Methods and ResultsWe studied 168 consecutive patients with ESLD who had regadenoson stress gated single photon emission computed tomography MPI between January 2008 and March 2010 before planned orthotopic liver transplantation and compared the hemodynamic responses and safety profile to 168 control patients. There were 72 women (43%) in ESLD versus 87 (52%) in the control group (P= .1). The patients with ESLD were younger (58 ± 7 vs 62 ± 12 years, P= .0002), but more likely to be Caucasians (P= .002). The MPI images were normal in 161 patients (96%) in each group. The left ventricular ejection fraction was 72 ± 10% in ESLD and 66 ± 11% in the control patients (P= .0001). The heart rate increase in response to regadenoson was lower in patients with ESLD than in the control group (16 ± 11 vs 23 ± 16 bpm, P= .0001), but the changes in systolic and diastolic blood pressures were similar (−9 ± 12 vs −11 ± 14 mmHg and −6 ± 8 vs −7 ± 10 mmHg, respectively, P= NS). There were no deaths or medication-related adverse events that required hospitalization in either group within 30 days of the study. ConclusionThis is the first study to document the tolerability and safety profile of regadenoson in patients with ESLD.

A Study of the Effects of Ranolazine Using Automated Quantitative Analysis of Serial Myocardial Perfusion Images

This study examined the hypothesis that the improvement in myocardial blood flow (MBF) with ranolazine therapy could be detected by serial automated quantitative myocardial perfusion imaging (MPI) in patients with coronary artery disease (CAD) and myocardial ischemia. Myocardial ischemia enhances late sodium current, which then causes cellular calcium overload leading to mechanical left ventricular dysfunction and arrhythmias. Ranolazine inhibits late sodium current and improves diastolic tension and MBF in the animal model. In this open-label, nonrandomized pilot study, we recruited 20 patients with known or a high probability of CAD and who had reversible perfusion defects on exercise treadmill gated single-photon emission computed tomography MPI while receiving conventional antianginal therapy. Ranolazine (up to 1,000 mg twice daily) was added to baseline therapy and a repeat treadmill MPI was obtained after 4 weeks. The extent and severity of total and reversible left ventricular perfusion abnormality (based on polar maps and a 17-segment model) were determined quantitatively using automated methods. We screened 100 patients for 27 potential candidates; 5 declined and 2 did not complete the follow-up study. The mean age of the remaining 20 patients was 64 +/- 9 years; 30% were women and 50% had diabetes mellitus. The exercise time increased (425 +/- 105 s vs. 393 +/- 116 s, p = 0.017), and angina improved in 15 (75%) patients after ranolazine treatment. In the entire cohort, summed stress scores (10 +/- 7 vs. 13 +/- 8, p = 0.04) and summed difference scores (4.7 +/- 4 vs. 7.4 +/- 5, p = 0.0037) decreased at follow-up. An improvement in perfusion pattern and severity was noted in 14 (70%) patients. In these patients, the polar maps showed a decrease in total abnormality from 26 +/- 17% to 19 +/- 15% and a decrease in the reversible abnormality from 16 +/- 10% to 8 +/- 6% (all p values <0.05). In this preliminary hypothesis-driven study, short-term ranolazine therapy was shown to improve myocardial perfusion and decrease the ischemic burden in patients with CAD.

Randomized, single-blind, factorial design study of the interaction of food and time on intestinal activity in 99mTc-tetrofosmin stress myocardial perfusion scintigraphy

Intestinal activity at the inferior myocardial wall represents an issue for assessment of myocardial perfusion imaging (MPI) with 99mTc-labelled tracers. The aim of this study was to investigate the effect of time and food on upper abdominal activity in 99mTc-tetrofosmin MPI. The study population consisted of 152 consecutive patients referred for routine MPI. All patients underwent 2-day stress-rest 99mTc-tetrofosmin single-photon emission computed tomography MPI. Before stress testing, patients were randomized in a factorial design to four different regimens. Group A: early scan (image acquisition initiated within 15 min after injection of the tracer) and no food; group B: early scan and food (two pieces of white bread with butter and a minimum of 450 ml of water); group C: late scan (image acquisition 30-60 min after injection of the tracer) and no food; and group D: late and scan with food. Patients underwent standard bicycle exercise or pharmacological stress test. The degree of upper abdominal activity was evaluated by trained observers blinded to the randomization code. The primary endpoint was the proportion of accepted scans in the intention-to-treat population in stress MPI. The results showed statistical significant impact on both time and food on upper abdominal activity. The primary endpoint showed that the acceptance rate improved from 55% in group A to 100% success rate in group D. An early scan reduced the acceptance rate by 30% versus a late scan [hazard ratio 0.70, 95% confidence interval 0.58-0.84; P<0.0001], whereas the addition of food improved the success rate versus no food by 27% (hazard ratio 1.27, 95% confidence interval 1.07-1.51; P=0.006). No significant interaction between food and time was observed. An analysis of accepted scans according to the actual scan time and food consumption confirmed the findings of the intention-to-treat analysis. In addition, similar findings were seen in 116 of 152 patients with a rest MPI (success rate of 53% in group A vs. 96% in group D). A combination of solid food and water administered after injection of the tracer and delayed image acquisition led to significant and clinically relevant decrease of interfering upper abdominal activity in 99mTc-tetrofosmin MPI.

What is the Prognostic Value of Myocardial Perfusion Imaging Using Rubidium-82 Positron Emission Tomography?

The objective was to determine the prognostic value of rubidium-82 (82Rb) positron emission tomography (PET) myocardial perfusion imaging (MPI). 82Rb PET MPI accurately diagnoses coronary artery disease (CAD). However, there are limited data evaluating its prognostic value. Follow-up (3.1 +/- 0.9 years) was obtained in 367 patients who underwent dipyridamole 82Rb PET MPI. Patients were divided into groups based on their summed stress score (SSS): group I, normal (<4); group II, mild (4 to 7); and group III, moderate (8 to 11) to severe (> or =12). There were significant differences among patients in the 3 SSS groups for hard events (cardiac death and myocardial infarction [MI]) (p < 0.001) and total cardiac events (hard events, revascularization and hospitalization) (p < 0.001). The annual hard events rates were 0.4%, 2.3%, and 7.0% in the normal, mild, and moderate-severe groups, respectively. In adjusted survival models, 82Rb PET SSS was the strongest predictor of total cardiac events and a significant predictor of hard events. Among patients referred for PET after 99mTc single-photon emission computed tomography, the annual total event rate was higher with abnormal versus normal SSS on PET (15.2% vs. 1.3%, p < 0.001). In patients with obesity, the annual total event rate was 11.1% with an abnormal scan and 1.5% with a normal scan (p < 0.001). This study shows that 82Rb PET MPI has significant prognostic value for predicting cardiac events, including death and MI. It also seems to have prognostic value in patients whose diagnosis remains uncertain after single-photon emission computed tomography MPI and in obese patients. The prognostic value of PET MPI may improve the management of cardiac patients.

Predictive Value of Silent Myocardial Ischemia for Cardiac Events in Diabetic Patients

Silent myocardial ischemia (SMI) in asymptomatic subjects with no history of myocardial infarction or angina is a frequent condition in diabetic patients. The aim of the study was to examine the predictive value of SMI for cardiac events in a multicenter cohort and to determine whether this value is higher in patients with a particular clinical profile. A total of 370 asymptomatic diabetic patients with at least two additional cardiovascular risk factors was recruited in four departments of diabetology. SMI was assessed by either exercise or dipyridamole single-photon emission-computed tomography myocardial perfusion imaging with thallium-201. If dipyridamole stress was used, an electrocardiogram stress test was performed separately on another day. Follow-up duration was 3-89 months (38 +/- 23 months). There was evidence of SMI in 131 patients (35.4%) on at least one positive noninvasive test. The patients with SMI were significantly older and had significantly higher serum triglycerides and lower HDL cholesterol levels. Cardiac events occurred in 53 patients (14.3%). Major cardiac events (death or myocardial infarction) occurred in 38 patients (10%) and other events (unstable angina, heart failure, or coronary revascularization) occurred in 15 patients. The patients who had cardiac events were older and had higher serum triglyceride levels at baseline. There was a significant association between SMI and cardiac events (hazard ratio 2.79 [95% CI 1.54-5.04]) and in particular major cardiac events (3 [1.53-5.87]). In the patients >60 years of age, the prevalence of SMI was higher (43.4 vs. 30.2% in those <60 years). SMI was associated with a significant risk of cardiac events (2.89 [1.31-6.39]) and in particular major cardiac events (3.66 [1.36-9.87]) for the patients >60 years old but not for those <60 years old. In asymptomatic diabetic patients with additional cardiovascular risk factors, SMI is a potent predictor of cardiac events and should be assessed preferably in the patients >60 years of age.

‘Hot spot’–‘cool cath’: Myocardial perfusion scintigraphic findings in coronaro-cameral micro-communications

A 50-year-old gentleman with end-stage alcoholic cirrhosis was referred for cardiac risk stratification prior to orthotropic liver transplantation. He had no significant prior cardiac history. A dobutamine stress test with single photon emission computed tomography–myocardial perfusion imaging (SPECT-MPI) using Technitium 99 was performed. Resting and stress EKG did not show any signs of ischemia. SPECT-MPI revealed a small, nonreversible, mild defect in the inferoseptal and inferior wall, which was thought to be due to sub-diaphragmatic attenuation artifact. However, there was a focal area of significantly increased (‘hot spot’) tracer uptake localized to the mid-ventricular anterolateral segments, mainly on rest images (Fig. 1, arrowheads). The stress images showed essentially normal tracer uptake in the corresponding region. The left ventricular cavity size and wall motion, lung–heart ratio and ejection fraction were normal.