Tali Sharir

High-Speed Myocardial Perfusion Imaging : Initial Clinical Comparison With Conventional Dual Detector Anger Camera Imaging

OBJECTIVESnThe purpose of this study was to compare myocardial perfusion imaging (MPI) with high-speed single-photon emission computed tomography (SPECT) with conventional SPECT imaging for the evaluation of myocardial perfusion in patients with known or suspected coronary artery disease.nnnBACKGROUNDnA novel technology has been developed for high-speed SPECT MPI by employing a bank of independently controlled detector columns with large-hole tungsten collimators and multiple cadmium zinc telluride crystal arrays.nnnMETHODSnA total of 44 patients (39 men) underwent same-day Tc-99m sestamibi stress/rest MPI. High-speed SPECT images were performed within 30 min after conventional SPECT. Stress and rest acquisition times were 16 and 12 min for conventional imaging and 4 and 2 min for high-speed SPECT, respectively. Myocardial counts/min (cpm) were calculated for both conventional SPECT and high-speed SPECT. Images were visually analyzed, and the summed stress score (SSS) and summed rest score (SRS) were calculated. Image quality and diagnostic confidence were qualitatively assessed.nnnRESULTSnHigh-speed SPECT SSS and SRS correlated linearly with conventional SPECT respective scores (r = 0.93, p < 0.0001 for SSS, and r = 0.93, p < 0.0001 for SRS). Image quality was rated good and higher in 17 (94%) cases for high-speed SPECT and 16 (89%) cases for conventional SPECT. Of the 44 patients studied, 36 (81.8%) and 35 (79.5%) were diagnosed definitely normal or abnormal by conventional and high-speed SPECT, respectively (p = NS). Myocardial count rate was significantly higher in high-speed versus conventional SPECT (384 x 10(-3) +/- 134 x 10(-3) cpm/min vs. 47 x 10(-3) +/- 14 x 10(-3) cpm/min, respectively, p < 0.0001) for stress and (962 x 10(-3) +/- 426 x 10(-3) cpm/min vs. 136 x 10(-3) +/- 37 x 10(-3) cpm/min, respectively, p < 0.001) for rest.nnnCONCLUSIONSnHigh-speed SPECT provides fast MPI with high image quality and up to 8 times increased system sensitivity. The amount of perfusion abnormality visualized by high-speed SPECT is highly correlated to conventional SPECT, with an equivalent level of diagnostic confidence.

Ventricular systolic assessment in patients with dilated cardiomyopathy by preload-adjusted maximal power. Validation and noninvasive application.

BACKGROUNDnNoninvasive cardiac-specific analysis of contractile function in patients with dilated heart failure remains problematic. This study tests whether maximal power divided by the square of end-diastolic volume (PWRmx/EDV2, or preload-adjusted PWRmx) can provide such assessment.nnnMETHODS AND RESULTSnTo validate the load insensitivity of the PWRmx index and determine its response to contractile change, 24 subjects with chronic dilated cardiomyopathy underwent invasive pressure-volume catheterization study using the conductance catheter technique. Preload was transiently reduced by 30% using balloon occlusion of the inferior vena cava, and afterload impedance was lowered by 50%, induced by a bolus injection of nitroglycerin. Contractile state was varied by intravenous dobutamine, verapamil, or esmolol. PWRmx was calculated from the simultaneous product of ventricular pressure and rate of volume change (dV/dt), the latter derived from the volume catheter signal. PWRmx varied directly with preload but was minimally influenced by afterload. However, PWRmx/EDV2 was not significantly altered by either loading change. PWRmx/EDV2 did vary with contractility, correlating closely with changes in the end-systolic pressure-volume relation (r = .91, P < .001). To test the noninvasive application of this index, 12 additional patients were studied, with PWRmx/EDV2 derived from nuclear ventriculography combined with a novel method to measure central arterial pressures. Subjects received intravenous nitroprusside or dobutamine in random order. Ejection fraction increased similarly with both agents (+42.9 +/- 8.9% for dobutamine and +29.4 +/- 5.3% for nitroprusside, both P < .01). In contrast, PWRmx/EDV2 did not significantly change with nitroprusside but increased by 126 +/- 16.1% with dobutamine (P < .01).nnnCONCLUSIONSnPreload-adjusted PWRmx is a steady-state index of ventricular systolic function that is sensitive to inotropic state and minimally influenced by physiological changes in afterload impedance or volume load. It appears useful for noninvasive cardiac-specific analysis of acute drug effects.

Validation of a method for noninvasive measurement of central arterial pressure

The goal of this study was to validate a newly improved noninvasive method for calibrated measurement of the ascending portion of the central arterial pressure wave in humans. Noninvasive pressure waveforms were generated by measuring the time delay between the R wave of the electrocardiogram and onset of brachial artery flow (by Doppler) during computer-controlled upper arm cuff deflation. This delay shortens with falling cuff pressure (becoming near constant at and below diastolic pressure), so that a plot of pressure versus time delay yields the ascending portion of the arterial waveform. These waveforms were compared with simultaneous invasive ascending aortic pressures in 57 adult patients (31 by fluid manometer [group A] and 26 by catheter-tipped micromanometer [group B]) during routine cardiac catheterization. Patient age ranged from 26 to 77 years. Eighty percent of group A patients and 40% of group B had coronary artery disease. Noninvasive systolic and diastolic pressures were very similar to invasive values in both groups (Pni = 0.98 x Pi, r = 0.99, p < 0.0001). Instantaneous pressure differences between waveforms were also similar in both groups, averaging between 4.5 and 5.5 mm Hg. Micromanometer and noninvasive pressure data were also obtained before and after intravenous nitroglycerin (n = 5) and isometric handgrip (n = 8) and demonstrated good agreement. A potential application of these pressures is for estimating maximal ventricular power to assess systolic function. This was tested using invasive pressure-volume data from four patients under a variety of conditions (exercise, pacing, etc.).(ABSTRACT TRUNCATED AT 250 WORDS)

Incremental Prognostic Value of Rest-Redistribution 201Tl Single-Photon Emission Computed Tomography

Background —The incremental prognostic value of rest-redistribution 201Tl compared with stress and rest perfusion abnormalities has not been defined.nnMethods and Results —We identified 458 patients who underwent rest 201Tl /stress (exercise or adenosine) 99mTc sestamibi single-photon emission computed tomography (SPECT) and had late (18 to 24 hours) 201Tl imaging, were not revascularized within 60 days of SPECT, and were followed up at >1 year. SPECT images were visually analyzed with the use of a 20-segment model on a scale of 0 to 4. Thirty-seven cardiac deaths (CDs) and 17 nonfatal myocardial infarctions occurred. Univariate Cox proportional hazards analysis showed that the presence of a large amount of rest 201Tl reversibility (rest-late summed difference score [SDS] of >8) was a significant predictor of CD (χ2=5.77, P =0.02) and CD or myocardial infarction (χ2=5.3, P =0.02). The CD rate was 9.3% y−1 in patients with rest-late SDS of >8 compared with 3.6% y−1 in patients with a mild/moderate amount of rest reversibility (rest-late SDS 3 to 8) and 3.4% y−1 in patients with no rest reversibility (rest-late SDS 8 ( P =0.01). Multivariate Cox proportional hazards analysis demonstrated that the presence of a large amount of resting reversibility was an independent and incremental predictor of CD after adjustment for stress and rest perfusion information. Multivariate logistic regression analysis demonstrated that resting reversibility was not an independent predictor of referral to coronary angiography and revascularization.nnConclusions —The identification of a large amount of resting 201Tl reversibility is an independent predictor of CD over stress and rest perfusion abnormalities.

Comparison of the diagnostic accuracies of very low stress-dose with standard-dose myocardial perfusion imaging: Automated quantification of one-day, stress-first SPECT using a CZT camera

BackgroundPrevious studies have demonstrated accurate diagnosis of reduced dose myocardial perfusion imaging (MPI) using Cadmium-Zinc-Telluride (CZT) technology. We compared the diagnostic performances of very low stress-dose (<2xa0mSv) with standard-dose stress-first, quantitative MPI using a CZT camera.MethodsPatients without known coronary artery– disease who underwent a stress-first Tc-99xa0m sestamibi CZT-MPI and invasive coronary angiography (ICA), and low-risk patients without ICA were included. A stress-rest standard-dose (10/30xa0mCi) MPI and a low-dose (5/15xa0mCi) MPI were compared. Normal limits for quantification were developed from 40 (20 males) low-risk patients, and total perfusion deficit (TPD) was derived.Results208 patients who underwent MPI and ICA, and 76 low-risk patients were included. Of these, 128 had a standard-dose MPI and 156 had a low-dose MPI. Stress-doses in low-dose and standard-dose groups were 5.9xa0±xa01.2 vs 10.2xa0±xa00.5xa0mCi (1.7xa0±xa00.3 vs 3.0xa0±xa00.1xa0mSv), respectively, Pxa0<xa00.001, and stress-rest effective radiation was 6.9xa0±xa01.1 vs 11.7xa0±xa00.4xa0mSv, respectively, Pxa0<xa00.001. Sensitivity, specificity, and accuracy values in the low-dose and standard-dose groups were 86.1%, 76.6%, and 81.4%; and 90.6%, 78.1%, and 84.4%, respectively, Pxa0=xa0ns. Using TPD prone, specificity values were 84.9% and 80.3%, respectively, Pxa0=xa0ns.ConclusionOne-day stress-first MPI with 50% radiation reduction and a very low stress-dose (<2xa0mSv) using CZT technology and quantitative supine and prone analysis provided a high diagnostic value, similar to standard-dose MPI.

Initial multicentre experience of high-speed myocardial perfusion imaging: comparison between high-speed and conventional single-photon emission computed tomography with angiographic validation

PurposeHigh-speed (HS) single-photon emission computed tomography (SPECT) with a recently developed solid-state camera shows comparable myocardial perfusion abnormalities to those seen in conventional SPECT. We aimed to compare HS and conventional SPECT images from multiple centres with coronary angiographic findings.MethodsThe study included 50 patients who had sequential conventional SPECT and HS SPECT myocardial perfusion studies and coronary angiography within 3xa0months. Stress and rest perfusion images were visually analysed and scored semiquantitatively using a 17-segment model by two experienced blinded readers. Global and coronary territorial summed stress scores (SSS) and summed rest scores (SRS) were calculated. Global SSS ≥3 or coronary territorial SSS ≥2 was considered abnormal. In addition the total perfusion deficit (TPD) was automatically derived. TPD >5xa0% and coronary territorial TPD ≥3xa0% were defined as abnormal. Coronary angiograms were analysed for site and severity of coronary stenosis; ≥50xa0% was considered significant.ResultsOf the 50 patients, 13 (26xa0%) had no stenosis, 22 (44xa0%) had single-vessel disease, 6 (12xa0%) had double-vessel disease and 9 (18xa0%) had triple-vessel disease. There was a good linear correlation between the visual global SSS and SRS (Spearman’s ρ 0.897 and 0.866, respectively; pu2009<u20090.001). In relation to coronary angiography, the sensitivities, specificities and accuracies of HS SPECT and conventional SPECT by visual assessment were 92xa0% (35/38), 83xa0% (10/12) and 90xa0% (45/50) vs. 84xa0% (32/38), 50xa0% (6/12) and 76xa0% (38/50), respectively (pu2009<u20090.001). The sensitivities, specificities and accuracies of HS SPECT and conventional SPECT in relation to automated TPD assessment were 89xa0% (31/35), 57xa0% (8/14) and 80xa0% (39/49) vs. 86xa0% (31/36), 77xa0% (10/13) and 84xa0% (41/49), respectively.ConclusionHS SPECT allows fast acquisition of myocardial perfusion images that correlate well with angiographic findings with overall accuracy by visual assessment better than conventional SPECT. Further assessment in a larger patient population may be needed to confirm this observation.

Prognostic Value of Combined Clinical and Myocardial Perfusion Imaging Data Using Machine Learning

OBJECTIVESnThis study evaluated the added predictive value of combining clinical information and myocardial perfusion single-photon emission computed tomography (SPECT) imaging (MPI) data using machine learning (ML) to predict major adverse cardiac events (MACE).nnnBACKGROUNDnTraditionally, prognostication by MPI has relied on visual or quantitative analysis of images withoutxa0objective consideration of the clinical data. ML permits a large number of variables to be considered in combination and at a level of complexity beyond the human clinical reader.nnnMETHODSnA total of 2,619 consecutive patients (48% men; 62 ± 13 years of age) who underwent exercise (38%) or pharmacological stress (62%) with high-speed SPECT MPI were monitored for MACE. Twenty-eight clinical variables, 17xa0stress test variables, and 25 imaging variables (including total perfusion deficit [TPD]) were recorded. Areas under thexa0receiver-operating characteristic curve (AUC) for MACE prediction were compared among: 1) ML with all available data (ML-combined); 2) ML with only imaging data (ML-imaging); 3) 5-point scale visual diagnosis (physician [MD] diagnosis); and 4) automated quantitative imaging analysis (stress TPD and ischemic TPD). ML involved automated variable selection by information gain ranking, model building with a boosted ensemble algorithm, and 10-fold stratified cross validation.nnnRESULTSnDuring follow-up (3.2 ± 0.6 years), 239 patients (9.1%) had MACE. MACE prediction was significantly higher for ML-combined than ML-imaging (AUC: 0.81 vs. 0.78; pxa0< 0.01). ML-combined also had higher predictive accuracy compared with MD diagnosis, automated stress TPD, and automated ischemic TPD (AUC: 0.81 vs. 0.65 vs. 0.73 vs. 0.71, respectively; p < 0.01 forxa0all). Risk reclassification for ML-combined compared with visual MD diagnosis was 26% (pxa0< 0.001).nnnCONCLUSIONSnML combined with both clinical and imaging data variables was found to have high predictive accuracyxa0for 3-year risk of MACE and was superior to existing visual or automated perfusion assessments. ML could allowxa0integration of clinical and imaging data for personalized MACE risk computations in patients undergoing SPECT MPI.

Deep Learning Analysis of Upright-Supine High-Efficiency SPECT Myocardial Perfusion Imaging for Prediction of Obstructive Coronary Artery Disease: A Multicenter Study

Combined analysis of SPECT myocardial perfusion imaging (MPI) performed with a solid-state camera on patients in 2 positions (semiupright, supine) is routinely used to mitigate attenuation artifacts. We evaluated the prediction of obstructive disease from combined analysis of semiupright and supine stress MPI by deep learning (DL) as compared with standard combined total perfusion deficit (TPD). Methods: 1,160 patients without known coronary artery disease (64% male) were studied. Patients underwent stress 99mTc-sestamibi MPI with new-generation solid-state SPECT scanners in 4 different centers. All patients had on-site clinical reads and invasive coronary angiography correlations within 6 mo of MPI. Obstructive disease was defined as at least 70% narrowing of the 3 major coronary arteries and at least 50% for the left main coronary artery. Images were quantified at Cedars-Sinai. The left ventricular myocardium was segmented using standard clinical nuclear cardiology software. The contour placement was verified by an experienced technologist. Combined stress TPD was computed using sex- and camera-specific normal limits. DL was trained using polar distributions of normalized radiotracer counts, hypoperfusion defects, and hypoperfusion severities and was evaluated for prediction of obstructive disease in a novel leave-one-center-out cross-validation procedure equivalent to external validation. During the validation procedure, 4 DL models were trained using data from 3 centers and then evaluated on the 1 center left aside. Predictions for each center were merged to have an overall estimation of the multicenter performance. Results: 718 (62%) patients and 1,272 of 3,480 (37%) arteries had obstructive disease. The area under the receiver operating characteristics curve for prediction of disease on a per-patient and per-vessel basis by DL was higher than for combined TPD (per-patient, 0.81 vs. 0.78; per-vessel, 0.77 vs. 0.73; P < 0.001). With the DL cutoff set to exhibit the same specificity as the standard cutoff for combined TPD, per-patient sensitivity improved from 61.8% (TPD) to 65.6% (DL) (P < 0.05), and per-vessel sensitivity improved from 54.6% (TPD) to 59.1% (DL) (P < 0.01). With the threshold matched to the specificity of a normal clinical read (56.3%), DL had a sensitivity of 84.8%, versus 82.6% for an on-site clinical read (P = 0.3). Conclusion: DL improves automatic interpretation of MPI as compared with current quantitative methods.