Detection Of Myocardial Perfusion Abnormalities Research Articles

Role of Positron Emission Tomography Cardiac Perfusion Imaging in Clinical Management, Prognosis, and Risk Stratification of Cardiovascular Disease

Coronary artery disease (CAD) is an important cause of morbidity and mortality worldwide. Perfusion abnormalities precede wall motion abnormalities, ECG changes, and angina in the etiology of CAD. myocardial perfusion imaging (MPI) can detect perfusion alterations due to pathology at sites such as the endothelium, microvasculature, and epicardial coronary arteries. Thus, it measures the universal burden of ischemic heart disease (IHD). Nuclear medicine MPI is an important noninvasive imaging modality to evaluate the perfusion of the myocardium. Positron Emission Tomography (PET) and single-photon emission computed tomography (SPECT) with or without computed tomography (CT) are 2 primary modalities. PET is a highly sensitive modality with an inherent ability to quantify absolute myocardial blood flow (MBF) and variations in MBF due to various stress agents. PET has immense potential to change clinical management, prognosticate, and risk stratify patients presenting with clinical or preclinical CAD. Evidence shows that early PET detection of myocardial perfusion abnormalities, followed by aggressive intervention for cardiovascular risk factors, can reinstate myocardial perfusion. This may reduce morbidity and mortality. We shall be reviewing the clinical impact of PET in CAD and preclinical CAD patients.

Diagnostic accuracy of stress-only myocardial perfusion SPECT improved by deep learning.

Deep convolutional neural networks (CNN) for single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has been used to improve the diagnostic accuracy of coronary artery disease (CAD). This study was to design and evaluate a deep learning (DL) approach to automatic diagnosis of myocardial perfusion abnormalities from stress-only MPI. The new DL approach developed for this study was compared to a conventional quantitative perfusion defect size (DS) method. A total of 37,243 patients (51.5% males) undergone stress 99mTc-Tetrofosmin or 99mTc-Sestamibi MPI were selected retrospectively from Yale New Haven Hospital. Patients were dichotomized as studies with normal (75.4%) or abnormal (24.6%) myocardial perfusion based on final diagnoses of clinical nuclear cardiologists. Stress myocardial perfusion defect size was calculated using Yale quantitative analytic software. A deep CNN was trained using the circumferential count profile maps derived from SPECT MPI and was evaluated for the diagnosis of perfusion abnormality with a 5-fold cross-validation approach. In each fold, 27,933, 1862 and 7448 patients were used as training, validation and testing datasets, respectively. The area under the receiver-operating characteristic curve (AUC) was calculated and analyzed for all patients as well as for the eight sub-groups classified based on patient genders, quantitative algorithms, radioactive tracers and SPECT cameras. The AUC value resulted from the DL method was significantly higher than that from the DS method (0.872 ± 0.002 vs. 0.838 ± 0.003, p < 0.01). Across the eight sub-groups, the DL method provided more consistent AUC values in terms of smaller standard deviation and higher diagnostic accuracy and specificity, but slightly lower sensitivity than the DS method (AUC: 0.865 ± 0.010 vs. 0.838 ± 0.019, Accuracy: 82.7% ± 2.5% vs. 78.5% ± 3.6%, Specificity: 84.9% ± 3.7% vs. 77.5% ± 6.5%, Sensitivity: 74.4% ± 4.2% vs. 79.8% ± 5.8%). The incorporation of deep learning for stress-only MPI has a considerable potential to improve the diagnostic accuracy and consistency in the detection of myocardial perfusion abnormalities.

Myocardial Perfusion Imaging: A Brief Review of Nuclear and Nonnuclear Techniques and Comparative Evaluation of Recent Advances.

Coronary artery disease (CAD) is the leading cause of morbidity and mortality worldwide. Invasive coronary angiography (ICA) is the gold standard for the evaluation of epicardial CAD. In the pathogenesis of the CAD, myocardial perfusion abnormalities are the first changes that appear followed by wall motion abnormalities, electrocardiogram changes, and angina. Myocardial perfusion imaging (MPI) demonstrates the cumulative effect of pathology at epicardial coronary arteries, small vessels, and endothelium. Thus, it evaluates the overall burden of ischemic heart disease (IHD). MPI is used noninvasively to diagnose early asymptomatic CAD or to know the functional significance of known CAD. There are evidence that early detection of myocardial perfusion abnormalities followed by aggressive intervention against cardiovascular risk factors may restore myocardial perfusion. This may lead to reduce morbidity and mortality. Various MPI modalities have been used to diagnose and define the severity of CAD. Cardiac myocardial perfusion single-photon emission computed tomography (myocardial perfusion scintigraphy [MPS]) has been in use since decades. Several newer modalities such as positron emission tomography, cardiac magnetic resonance imaging, computed tomography perfusion, and myocardial contrast echocardiography are developing utilizing the similar principle of MPS. We shall be reviewing briefly these modalities, their performance, comparison to each other, and with ICA.

The predictive value of Cardiodynamicsgram in myocardial perfusion abnormalities.

Myocardial perfusion abnormalities are the first sign of the ischemic cascade in the development of coronary artery disease (CAD). Thus, the early detection of myocardial perfusion abnormalities is significant for the prevention of CAD. Recently, a novel noninvasive method named Cardiodynamicsgram (CDG) has been proposed for early detection of CAD. This study aims to evaluate the predictive value of CDG in myocardial perfusion abnormalities for suspected ischemic heart disease. In the study, 86 suspected patients were enrolled. Standard 12-lead ECG and CDG were performed simultaneously before single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Diagnostic accuracy of CDG for myocardial perfusion abnormalities detection is assessed using SPECT MPI as the reference standard. Of these 86 suspected patients, 37 patients were positive in CDG, 49 patients were negative in CDG. Diagnostic accuracy of CDG at presentation for myocardial perfusion abnormalities was 84.9%, sensitivity 84.0%, and specificity 89.4%. Furthermore, of the 10 patients whose SPECT MPI results are reverse redistribution, 9 patients were positive in CDG. Underlying causes of false positive CDG findings included the factors that can change the stability of cardiac electrical conduction and measurement noise. Myocardial remodeling in patients with old myocardial infarction might be the major cause of false negative findings. Results show a good consistency between the CDG and SPECT MPI in evaluating myocardial perfusion abnormalities. It suggests that CDG might be used as a cost-effective tool for assessing the myocardial perfusion abnormalities in the clinic.

Contrast echocardiography for detection of myocardial perfusion abnormalities : Aclinical perspective.

Myocardial contrast echocardiography (MCE) is awell-established imaging technique in the assessment of patients with known or suspected coronary artery disease. The use of ultrasound contrast agents has optimized the evaluation of left ventricular function and, moreover, permits simultaneous assessment of the myocardial perfusion. This technique utilizes microbubbles that remain in the intravascular space and the contrast intensity reflects the concentration of the microbubbles in the myocardium. Ahomogeneous opacification of the myocardium after destruction of the microbubbles during high-power imaging is regarded as normal perfusion and absence of CAD. If the replenishment rate is reduced, this is suggestive of significant CAD. In comparison with other techniques, MCE shows comparable sensitivity, specificity, and diagnostic accuracy while it is an easy-to-perform bedside technique that can be avaluable tool for the clinician.

13N-Ammonia PET/CT Detection of Myocardial Perfusion Abnormalities in Beagle Dogs After Local Heart Irradiation.

Our objective was to determine the potential value of 13N-ammonia PET/CT myocardial perfusion imaging (MPI) for early detection of myocardial perfusion changes induced by radiation damage. Methods: Thirty-six Beagle dogs were randomly divided into a control group (n = 18) or an irradiation group (n = 18). The latter underwent local irradiation to the left ventricular anterior cardiac wall with a single dose of 20 Gy, whereas the former received sham irradiation. All dogs underwent 13N-ammonia PET/CT MPI 1 wk before irradiation and at 3, 6, and 12 mo after sham or local irradiation. One week after undergoing 13N-ammonia PET/CT MPI, the irradiation group underwent coronary angiography. Six randomly selected dogs from each group were sacrificed and used to detect pathologic cardiac injury at 3, 6, and 12 mo after irradiation. Results: Compared with the control group and baseline, the irradiation group showed significantly increased perfusion in the irradiated area of the heart at 3 mo after irradiation, perfusion reduction at 6 mo after irradiation, and a perfusion defect at 12 mo after irradiation. There was no significant difference in the left ventricular ejection fraction between the control and irradiation groups at baseline or at 3 mo after irradiation. The irradiation group showed a reduction of left ventricular ejection fraction compared with the control group at 6 mo (50.0% ± 8.1% vs. 59.3% ± 4.1%, P = 0.016) and 12 mo (47.2% ± 6.7% vs. 57.4% ± 3.3%, P = 0.002) after irradiation. No coronary stenosis was observed in the irradiation group. Regional wall motion abnormalities appeared in the irradiated area at 6 mo after irradiation, and its extent was enlarged at 12 mo after irradiation. Pathologic changes were observed; radiation-induced myocardial tissue damage and microvascular fibrosis in the irradiated area progressively increased over time. Conclusion:13N-ammonia PET/CT MPI can dynamically detect myocardial perfusion changes together with global and regional left ventricular dysfunction induced by irradiation and may be a valuable method for monitoring radiation-induced heart disease.

Value of strain analysis with feature tracking in adenosine stress myocardial perfusion magnetic resonance imaging

Background Adenosine stress magnetic resonance is highly accurate for the detection of myocardial perfusion abnormalities. Visual assessment of inducible wall motion abnormalities (IWMA) during adenosine has low sensitivity but high specificity since only high-grade perfusion defects are associated with detectable IWMAs. The novel technique Feature Tracking (FT) measures myocardial strain and gives detailed information about regional myocardial deformation. The aim of this study was to investigate FT for the detection of myocardial ischemia during adenosine stress.

Rapid Detection of Coronary Artery Stenoses With Real-Time Perfusion Echocardiography During Regadenoson Stress

Real-time myocardial contrast echocardiography permits the detection of myocardial perfusion abnormalities during stress echocardiography, which may improve the accuracy of the test in detecting coronary artery stenoses. We hypothesized that this technique could be used after a bolus injection of the selective A2A receptor agonist regadenoson to rapidly and safely detect coronary artery stenoses. In 100 patients referred for quantitative coronary angiography, real-time myocardial contrast echocardiography was performed during a continuous intravenous infusion of 3% Definity at baseline and at 2-minute intervals for up to 6 minutes after a regadenoson bolus injection (400 μg). Myocardial perfusion was assessed by examination of myocardial contrast replenishment after brief high mechanical index impulses. A perfusion defect was defined as a delay (>2 seconds) in myocardial contrast replenishment in 2 contiguous segments. Wall motion was also analyzed. The overall sensitivity/specificity/accuracy for myocardial perfusion analysis in detecting a >50% diameter stenosis was 80%/74%/78%, whereas for wall motion analysis it was 60%/72%/66% (P<0.001 for differences in sensitivity). Sensitivity for myocardial perfusion analysis was highest on images obtained during the first 2 minutes after regadenoson bolus (P<0.001 compared with wall motion), whereas wall motion sensitivity was highest at the 4-to-6-minute period after the bolus. No significant side effects occurred after regadenoson bolus injection. Regadenoson real-time myocardial contrast echocardiography appears to be a feasible, safe, and rapid noninvasive method for the detection of significant coronary artery stenoses.

Absolute myocardial blood flow determination using real-time myocardial contrast echocardiography during adenosine stress: comparison with single-photon emission computed tomography

Objective:To assess the feasibility and diagnostic accuracy of real-time myocardial contrast echocardiography (MCE)-derived absolute myocardial blood flow for detection of myocardial perfusion abnormalities compared with simultaneous technetium 99 m sestamibi...

Real-time perfusion imaging with low mechanical index pulse inversion Doppler imaging

OBJECTIVESWe sought to determine how successful pulse inversion Doppler (PID) imaging would be in detecting myocardial perfusion defects during dobutamine stress echocardiography.BACKGROUNDBy transmitting multiple pulses of alternating polarity (PID) at a low mechanical index, myocardial contrast enhancement from intravenously injected microbubbles can be detected using real-time frame rates.METHODSPulse inversion Doppler imaging was performed in 117 patients during dobutamine stress echocardiography by using an intravenous bolus of a perfluorocarbon-filled, albumin- (Optison: n = 98) or liposome- (Definity: n = 19) encapsulated microbubble and a mechanical index of <0.3. The visual identification of myocardial contrast defects and wall motion abnormalities was determined by blinded review. Forty of the patients had quantitative angiography (QA) performed to correlate territorial contrast defects with stenosis diameter >50%.RESULTSThere was a virtual absence of signal from the myocardium before contrast injections in all patients. Bright myocardial opacification at peak stress was observed in at least one coronary artery territory at frame rates up to 25 Hz in 114 of the 117 patients during dobutamine stress echocardiography. Regional myocardial contrast defects at peak stress were observed in all 30 patients with >50% stenosis in at least one vessel (13 with single-vessel and 17 with multivessel disease). Contrast defects were observed in 17 territories subtended by >50% diameter stenosis that had normal wall motion at peak stress. Overall agreement between QA and myocardial contrast enhancement on a territorial basis was 83%, as compared with 72% for wall motion.CONCLUSIONSPulse inversion Doppler imaging allows the detection of myocardial perfusion abnormalities in real-time during stress echocardiography and will further add to the quality and sensitivity of this test.

Role of intravenous ultrasound contrast in stress echocardiography.

Intravenous newer generation perfluorocarbon containing microbubbles have been shown to enhance endocardial borders, especially during harmonic imaging. Although this significantly improves the detection of wall-motion abnormalities during stress echocardiography, intermittent imaging consistently results in myocardial contrast following intravenous infusions or injections of perfluorocarbon microbubbles. Detection of myocardial perfusion abnormalities during both exercise and pharmacologic stress echocardiography appears to be feasible clinically with either intravenous injections or continuous infusions of microbubbles using intermittent harmonic imaging. Accelerated intermittent harmonic imaging allows one to rapidly acquire both myocardial perfusion and wall motion during exercise and dobutamine stress echocardiography.

Assessment of myocardial perfusion by intermittent harmonic power Doppler using SonoVue, a new ultrasound contrast agent.

The authors evaluated the potential of SonoVue, a new echo contrast agent, for the detection of myocardial perfusion abnormalities using intermittent harmonic power Doppler (IHPD) imaging and different pulse repetition frequencies (PRFs). Experiments were performed in vitro (in a tissue-mimicking phantom) and in vivo (in minipigs) in harmonic power Doppler using an ATL HDI 3000 with second harmonic software. SonoVue was injected intravenously in an auricular vein in bolus (dose range 0.01-0.05 mL/kg) in closed-chest animals or as an infusion (rate = 0.1 mL/kg/minute) in open-chest minipigs with reversible left anterior descending coronary artery (LAD) occlusion. The animals were imaged using IHPD gated on the electrocardiogram at end-systole (pulsing interval at each cardiac cycle). The efficacy of SonoVue was evaluated at six PRFs from 500 to 6000 Hz either qualitatively using a subjective scoring system or quantitatively using a digital image analyzer. SonoVue at a dose of 0.01 mL/kg produced a strong and homogeneous myocardial opacification in IHPD. Higher doses prolonged the duration of the contrast effect. Varying the PRF allowed the discrimination of flow velocities in vitro and the detection of perfusion differences within the myocardium during transient LAD occlusion and during immediate reperfusion in vivo. Low PRFs were particularly useful to differentiate the ischemic bed from the healthy one during LAD occlusion. The high flows caused by coronary hyperemia during immediate reperfusion were detected clearly in the reperfused area at high PRFs. SonoVue is a promising agent for myocardial opacification studies using IHPD. The latter imaging modality is particularly well suited for blood flow detection in tissues. Varying the PRF provides additional information on flow velocity and improves the detection of perfusion differences in the myocardium.

Effect of Significant Two-Vessel Versus One-Vessel Coronary Artery Stenosis on Myocardial Contrast Defects Observed With Intermittent Harmonic Imaging After Intravenous Contrast Injection During Dobutamine Stress Echocardiography

Objectives. We sought to determine the effect of multivessel as opposed to single-vessel coronary artery stenosis on myocardial contrast defects observed with intermittent harmonic imaging and intravenous perfluorocarbon-exposed sonicated dextrose albumin contrast injection.Background. Intermittent harmonic imaging has permitted the detection of myocardial perfusion abnormalities with an intravenous ultrasound contrast agent. The effect of multivessel disease on inducibility of these perfusion abnormalities is unknown.Methods. In 10 dogs, intravenous injections of contrast agent were given at rest and during dobutamine stress echocardiography when a single coronary artery stenosis was present (≥50% diameter by quantitative angiography) and again when a second stenosis (range 44% to 92% diameter) was present in the vessel supplying the adjacent perfusion bed. The peak myocardial contrast was visually and quantitatively assessed in the mid and lateral regions of the perfusion bed of the first stenosis (original stenosis zone) in the presence of one- and two-vessel stenosis.Results. Peak myocardial contrast defects in both the mid and lateral segments of the original stenosis zone during dobutamine stress echocardiography was significantly lower when two-vessel stenosis was present (p = 0.015), especially in the lateral segment. The spatial extent of the perfusion defect in the original stenosis zone risk area increased significantly when two-vessel stenosis was present, and correlated closely with actual risk area (r = 0.99). Previous total occlusion followed by reperfusion of the vessel supplying the original stenosis zone significantly increased the amount of collateral activity between perfusion beds.Conclusions. Collateral flow limits the spatial extent of inducible ischemia within the risk area of single-vessel stenosis. Restoring blood flow to one perfusion bed reduces the extent of a perfusion abnormality that can be induced in an adjacent stenosed bed.

Detection of myocardial perfusion abnormalities during dobutamine and adenosine stress echocardiography with transient myocardial contrast imaging after minute quantities of intravenous perfluorocarbon-exposed sonicated dextrose albumin

We have recently discovered that if ultrasound transmission is briefly suspended (triggered to just one frame per cardiac cycle) after very small doses of intravenous perfluorocarbon-exposed sonicated dextrose albumin, the myocardial contrast produced is significantly enhanced. The objective of this study was to test whether this technique (termed transient response imaging) could identify myocardial perfusion abnormalities during adenosine and dobutamine stress echocardiography. In 10 open-chest dogs with a significant (>50%) coronary stenosis determined by quantitative angiography, intravenous perfluorocarbon-exposed sonicated dextrose albumin (0.005 to 0.01 ml/kg) was given at rest and during peak dobutamine stress (20 to 30 μg/kg/min). Adenosine stress (100 to 140 μg/kg/min) was also given in seven of these dogs. The peak myocardial videointensity and spatial extent of contrast defect with transient response imaging (TRI) were compared with conventional 30 Hz frame rates, as well as wall thickening and coronary flow responses. In all 10 dogs there was visually evident myocardial contrast with TRI. In comparison, myocardial contrast was visually evident in only one of these dogs with conventional imaging. The peak myocardial videointensity ratio in the stenosed perfusion bed divided by the normally perfused bed when TRI was used decreased in all dogs during dobutamine stress and correlated with minimal coronary lumen diameter ( r = 0.70; p = 0.02). Visually evident myocardial contrast defects were detectable in nine of 10 dogs at peak dobutamine stress but only in one of the dogs with conventional imaging. All seven dogs that received adenosine demonstrated contrast defects with TRI, whereas none demonstrated contrast defects with conventional imaging. We conclude that the myocardial contrast produced with transient response imaging can be used to detect functionally significant coronary stenoses.

Comparison of ultrafast dipyridamole magnetic resonance imaging with dipyridamole sestamibi SPECT for detection of perfusion abnormalities in patients with one‐vessel coronary artery disease: Assessment by quantitative model fitting

The value of ultrafast MRI for detection of myocardial perfusion abnormalities in patients with coronary artery disease (CAD) was assessed in 10 patients with stable angina pectoris and angiographically proven one-vessel CAD using double-level short-axis ultrafast MRI with bolus injection of gadolinium-DTPA and tomographic technetium-99m SestaMIBI imaging (SPECT) during dipyridamole-induced coronary hyperemia. Abnormally perfused regions were assessed with SPECT and MRI in all (100%) patients. Agreement in localization between arteriography and SPECT was 80%; between arteriography and MR, 70%; and between SPECT and MR, 90%. The signal intensity increase after the bolus injection of gadolinium-DTPA using a linear fit, and the slope of gadolinium-DTPA wash-in using double exponential model fitting were significantly different between abnormally and normally perfused regions. These preliminary results demonstrate the potential of dipyridamole ultrafast MR to monitor stress-induced flow maldistribution in patients with single vessel CAD.

Myocardial Perfusion Imaging With 99m Tc Tetrofosmin

Background Our objective was to compare the sensitivity and specificity of tetrofosmin, a new 99m Tc-labeled myocardial perfusion imaging agent for the detection of myocardial perfusion abnormalities, with those of 201 Tl and coronary angiography. Our hypothesis was that same-day stress/rest tetrofosmin imaging could provide data comparable to those of 201 Tl imaging. Myocardial perfusion imaging plays an important role for the evaluation of coronary artery disease. Newer 99m Tc-labeled agents offer several advantages over 201 Tl, the conventional myocardial perfusion imaging agent. Tetrofosmin is a new 99m Tc-labeled agent with promising results in preliminary studies. Methods and Results Two hundred fifty-two patients with suspected coronary artery disease were enrolled in 10 centers in the United States and Europe. All patients underwent exercise and rest myocardial perfusion imaging with 99m Tc-tetrofosmin using two separate injections of the radiotracer 4 hours apart on the same day. Planar images were obtained in three standard views 15 to 60 minutes after radiotracer injection. Patients also underwent standard exercise and redistribution planar 201 Tl imaging within 2 weeks of tetrofosmin imaging. In addition, 58 healthy subjects with low likelihood of coronary artery disease underwent exercise and rest tetrofosmin imaging. Coronary angiograms were available in 181 patients with suspected coronary artery disease. All radionuclide images were processed in the central core laboratory and interpreted blindly by a panel of four experienced readers. 201 Tl images and tetrofosmin images were read separately. Discrepancies were resolved by consensus. The workload, peak heart rate, and double products were comparable during exercise for both imaging agents. Technically acceptable paired 201 Tl and tetrofosmin images were available in 224 of 252 patients. Tetrofosmin images were generally of good quality, with low extracardiac activity, and easy to interpret. Patients were categorized as showing normal, ischemia, infarction, or mixture with each imaging modality. Precise concordance for each of these categories was 59.4% (κ=0.44; 95% CI, 0.35 to 0.53). When patients were categorized as normal or abnormal, the concordance was 80.4% (κ=0.55; 95% CI, 0.43 to 0.67). When each of five anatomic territories (septal, anterior, inferior, lateral, and apical) was categorized as normal versus abnormal, the concordance varied from 81% to 90%. When similar comparison was made for the specific category of abnormality, the concordance was 64% to 84%. When coronary angiography was used as the criterion, the sensitivity and positive and negative predictive accuracy of tetrofosmin and 201 Tl were comparable. The normalcy rate of tetrofosmin images in the healthy subjects with low likelihood of coronary artery disease was 97%. Conclusions 99m Tc tetrofosmin is a new myocardial imaging agent with favorable imaging characteristics with results comparable to those of 201 Tl.

Performance of the rotating slant-hole collimater for the detection of myocardial perfusion abnormalities

Performance of the rotating slant-hole collimater for the detection of myocardial perfusion abnormalities