Evaluation Of Regional Myocardial Perfusion Research Articles

Evaluation of regional myocardial perfusion in methamphetamine abusers using real-time myocardial contrast echocardiography.

To evaluate the feasibility of assessing regional myocardial perfusion using real-time myocardial contrast echocardiography(MCE) at rest for detecting coronary microcirculation abnormalities in methamphetamine abusers.Materialand methods: Twenty-two male methamphetamine abusers (11 without chest pain, 11 with chest pain), free of ascertainedcoronary artery disease, were enrolled in this study. A control group of 22 age-matched male healthy participants was studiedfor comparison. Standard 2D, flow and tissue Doppler echo with measurements of cardiac morphologic and functional indicators,MCE with measurements of regional myocardial perfusion were performed, respectively. Compared to healthyparticipants, methamphetamine abusers had higher blood pressure, greater left ventricular mass index and more impaireddiastolic function, with preserved cardiac sizes and systolic function. Methamphetamine abusers with chest pain had a fasterheart rate than those without chest pain and healthy participants. MCE in methamphetamine abusers, especially with chestpain, had significant longer contrast agent arrival times, less functional capillary blood volumes, slower microvascular flowvelocities and less myocardial perfusion than healthy participants (p<0.05). Moreover, along with the increases of dosage andduration of use (from group A to group C, group A: 1-2 g/day, <2 years; group B: 2-3 g/day, 2-5 years; group C: >3 g/day, >5years) the reductions in the myocardial perfusion indices were more significant (p<0.01). The cutoff value with 5.1 dB2/s ofthe myocardial perfusion at the left ventricular apex had a sensitivity of 87.5%, specificity of 75.2% and accuracy of 81.9% fordifferentiating methamphetamine abusers from normal subjects. Real-time MCE can effectively detect coronarymicrocirculation abnormalities in methamphetamine abusers at rest and myocardial perfusion is significantly reduced in methamphetamineabusers. This finding may be involved in the occurrence and development of cardiac damage.

Quantitative Coronary Flow Capacity for Risk Stratification and Clinical Decision Making: Is It Ready for Prime Time?

> See the associated article on page [410][1]. Semiquantitative evaluation of regional myocardial perfusion has been standard practice in nuclear cardiology for more than 3 decades. This approach has proven to be accurate and reproducible. Most importantly, semiquantitative measures of total

Inter-study reproducibility of cardiac MRI in free breathing patients at rest for the evaluation of regional myocardial perfusion

Background In the early stages of some cardiovascular diseases (CVDs), myocardial ischemia only occurs in a limited area. Thus, accurate detection of regional myocardial perfusion abnormalities is important for diagnosis. Recently, myocardial perfusion using MRI has become a promising non-invasive method to evaluate myocardial ischemia in CVDs. However, the reproducibility of MRI for assessment of regional perfusion has not been studied. This knowledge gap could affect the use of Cardiac MR in clinical practice. To address this clinical need, we evaluate the reproducibility of MRI perfusion in 12 healthy volunteers.

PET and MRI for the evaluation of regional myocardial perfusion and wall thickening after myocardial infarction

BackgroundDeterioration of left ventricular (LV) function after myocardial infarction (MI) is a major cause of heart failure. Myocardial perfusion performance may play an important role in deterioration or improvement in LV function after MI. The aim of this study was to evaluate the myocardial perfusion reserve (MPR) and stress perfusion in deteriorating and non-deteriorating LV segments in patients after MI by PET and MRI, respectively.MethodsRegional wall thickening of 352 segments in 22 patients was assessed at 4 and 24 months after MI by cardiac MRI. PET was performed to evaluate MPR and adenosine stress 13N-ammonia perfusion 24 months after MI. Segments were divided into four groups according to deterioration or improvement in wall thickening.ResultsNormal functional segments at 4 months after MI that remained stable had a significantly higher mean MPR and mean stress perfusion PET value than deteriorated segments (p < 0.001). Furthermore, dysfunctional segments that improved had a significantly higher mean stress perfusion PET value than dysfunctional segments that remained dysfunctional (p < 0.001).ConclusionThis study demonstrated the additional value of myocardial perfusion assessment in relation to the functional integrity of the injured myocardium. Segmental functional LV improvement after MI was associated with better regional myocardial perfusion characteristics. Furthermore, the amount of wall thickening reduction was associated with regional myocardial perfusion abnormalities in patients after MI.

Regional myocardial ischemia in hypertrophic cardiomyopathy: Impact of myectomy

Objective Chest pain is a common finding in patients with hypertrophic cardiomyopathy and can be observed in 40% to 50% of all patients. However, the pathogenesis of these ischemia-like symptoms is still unclear. Methods Twenty-two patients with hypertrophic cardiomyopathy and 15 controls underwent positron emission tomography for evaluation of regional myocardial perfusion and coronary flow reserve (hyperemic/baseline myocardial blood flow). Myocardial perfusion (mL/min/g) was measured using [ 13N]ammonia at rest and during hyperemia with dipyridamole (0.56 mg/kg intravenously). Regional coronary flow reserve was assessed in 3 planes (apical, midventricular, basal) in 4 regions (septal, anterior, lateral, inferior). Patients were divided into 2 groups: group 1 consisted of 11 patients treated with surgical myectomy (age 56 ± 10 years) and group 2 consisted of 11 patients treated medically (age 53 ± 13 years). Results Mean global coronary flow reserve was 3.87 ± 0.92 in controls but 2.31 ± 0.40 in operated ( P < .001 vs controls) and 1.76 ± 0.58 in medically treated patients ( P < .001 vs controls, P < .05 vs operated). Similarly, septal coronary flow reserve was 4.19 ± 1.22 in controls but significantly reduced in operated patients (2.26 ± 0.48, P < .001 vs controls) and in medically treated patients (1.76 ± 0.58; P < .001 vs controls). However, septal flow reserve was significantly higher in operated patients than in patients with medically treated hypertrophic cardiomyopathy (+37%, P < .05), mainly due to a reduced resting myocardial perfusion. Conclusions Global and regional myocardial perfusion is reduced in patients with hypertrophic cardiomyopathy. However, myectomy may have a beneficial effect on septal perfusion and flow reserve. Thus, ischemia seems to play an important role in the symptomatology and pathophysiology of hypertrophic cardiomyopathy.

178 Quantitative evaluation of regional myocardial perfusion during dipyridamole stress by real-time myocardial contrast echocardiography in patients with and without coronary artery disease

178 Quantitative evaluation of regional myocardial perfusion during dipyridamole stress by real-time myocardial contrast echocardiography in patients with and without coronary artery disease

P606 Quantitative evaluation of regional myocardial perfusion during dipyridamole stress by real-time myocardial contrast echocardiography in patients with and without coronary artery disease

P606 Quantitative evaluation of regional myocardial perfusion during dipyridamole stress by real-time myocardial contrast echocardiography in patients with and without coronary artery disease

Isolated ventricular noncompaction is associated with coronary microcirculatory dysfunction

ObjectivesWe sought to analyze whether a microcirculatory dysfunction might be associated with isolated ventricular noncompaction (IVNC). BackgroundIn IVNC, which is a cardiomyopathy thus far “unclassified” by the World Health Organization, heart failure and sudden cardiac death are common findings, but the pathophysiologic mechanisms are unknown. MethodsIn 12 patients with IVNC and 14 control subjects, quantitative evaluation of regional myocardial perfusion (myocardial blood flow [MBF]) and coronary flow reserve (CFR, hyperemic/baseline MBF) was performed using positron emission tomography and 13N-ammonia. The left ventricular myocardium was divided into nine segments, and the two-dimensional echocardiogram in each patient with IVNC was compared with CFR in each segment. Noncompaction was defined as a two-layered structure with excessive trabeculation. ResultsThe CFR in control subjects averaged 4.2 ± 0.9, providing a cut-off value ≥2.5, but it was 2.1 ± 0.8 in patients with IVNC. A perfusion scan defect was found in 14 of 24 segments with noncompaction, although no defect was found in 76 of 84 normal segments (overall agreement 83%, p < 0.0001 by the chi-square test). In 16 of 21 segments with noncompaction, a decreased CFR was found; but a decreased CFR was also found in 36 of 60 segments without noncompaction (p = NS). In 45 of the 57 segments with wall motion abnormalities, CFR was decreased, but it was preserved in 17 of the 24 segments with normal wall motion (agreement 77%, p < 0.0001). ConclusionsIn patients with IVNC, a decreased CFR is not confined to noncompacted segments, but extends to most segments with wall motion abnormalities. Thus, coronary microcirculatory dysfunction is associated with IVNC.

Myocardial perfusion imaging in breast cancer patients treated with or without post-mastectomy radiotherapy

Purpose: To assess the occurrence and location of myocardial perfusion defects in left-sided mastectomized breast cancer patients, treated with or without postoperative radiotherapy according to the guidelines from the Danish Breast Cancer Cooperative Group (DBCG).Patients and methods: Seventeen left-sided breast cancer patients, with a median age of 59 years (range, 47–75 years), randomized to post-mastectomy irradiation plus systemic treatment, or systemic treatment alone, were examined after a median follow-up of 7.9 years (range, 6.0–12.2 years). The chest wall and the ipsilateral internal mammary nodes had been treated through two anterior-shaped electron fields, and the electron energy was chosen according to chest wall thickness, measured individually by ultrasound. The median absorbed dose was 50 Gy in 25 fractions, with 5 fractions/week. Information on clinical history was obtained and symptoms of ischemic heart disease (IHD), as well as major risk factors, were recorded. All patients had a physical examination, blood chemistry, electrocardiogram (ECG), chest X-ray and myocardial perfusion imaging by sestamibi-single photon emission computerized tomography (SPECT). SPECT-scanning was performed as a rest/dipyridamole 2-day protocol. The evaluation of regional myocardial perfusion was based on scintigrams using a 20-segment model.Results: There was no significant difference between the scintigraphic findings in the two groups. Four of ten irradiated patients and four of seven non-irradiated patients showed scintigraphic defects. An anterior defect was found in one non-irradiated patient.Conclusions: This study does not indicate that the described radiotherapy technique induces detectable coronary artery disease. However, the small number of patients does not allow strong conclusions to be drawn.

Contrast echocardiographic evaluation of regional myocardial perfusion in a porcine model of hibernating myocardium

Contrast echocardiographic evaluation of regional myocardial perfusion in a porcine model of hibernating myocardium

Evaluation of regional myocardial perfusion in patients with severe left ventricular dysfunction: Comparison of 13N-ammonia PET and 99mTc sestamibi SPECT

Positron emission tomography (PET) scanning with 13N-ammonia and 18FDG is well established for the detection of myocardial viability. Due to the limited availability of PET facilities, recent studies have combined technetium 99m sestamibi single photon emission computed tomography (SPECT) with 18FDG PET or 18FDG SPECT. This approach enables simultaneous assessment of regional myocardial blood flow and metabolism and substantially increases the capacity for viability detection. To validate whether 99mTc-Sestamibi SPECT can replace 13N-ammonia PET, we compared these two modalities in patients with severe left ventricular dysfunction due to coronary artery disease. Thirty-one patients (mean age 57+/-8 years; mean ejection fraction 27%+/-8%) with angiographically verified coronary artery disease were included. In random order, ammonia-PET and sestamibi-SPECT scans were performed. In a 20-segment model of the left ventricle, two blinded observers scored a total of 610 segments on a five-point scale. In a subset of 20 patients, 400 segments were scored twice to evaluate the observer variations of the two techniques. Segmental score differences were used to compare the imaging modalities. The impact on viability detection was assessed by combining the two flow tracers with FDG PET. Segmental comparison of the PET and SPECT studies yielded similar (difference < or = 1) results in 74% of segments, reflecting regional concordance values in the lateral, apical, anterior, septal, and inferior myocardial walls of 86%, 82%, 71%, 66%, and 63%, respectively. The differences in the septal and inferior walls were primarily due to overestimation of perfusion defects by sestamibi SPECT, which yielded a higher proportion of mismatch patterns in those regions. The overall observer variations of the PET and SPECT studies were 7.5% and 5.8%. Myocardial perfusion imaging with 13N-ammonia PET and 99mTc-sestamibi SPECT yielded similar results in patients with severe left ventricular dysfunction, except for the septal and inferior regions. In these regions, SPECT tended to overestimate perfusion defects. Hence, attenuation correction should be considered when combining FDG PET and sestamibi SPECT for diagnosing myocardial viability to avoid overestimation of mismatch patterns in those regions.

MRI for the evaluation of regional myocardial perfusion in an experimental animal model.

Myocardial perfusion was assessed in nine pigs using ultrafast gradient-echo MRI (.5 T, 15-mT/m gradients) at different levels of myocardial blood flow (range, .005-1.84 ml/min/g), generated either by adenosine infusion or by a mechanical occluder, and measured independently using radiolabeled microspheres. Sixty-four consecutive, ECG-triggered, diastolic, short axis images of the left ventricle were obtained during intravenous bolus injections (n = 30) of .05 mmol/kg of gadopentetate dimeglumine. Relative changes in peak intensity, time to peak intensity, washin slope, correlation coefficient, and cross-correlation coefficient were computed from the time-intensity curves obtained from four regions of interest, namely septal, anterior, lateral, and inferior walls. The values from the inferior wall acted as reference for evaluating relative changes in the other three regions. The cross-correlation coefficient (P < .001, rho = .60) and the peak intensity (P < .001, r = .72) showed the best correlation with myocardial blood flow. The washin slope showed a weak positive trend (P < .05), but the low value of r (r = .28) indicated that the use of this parameter to predict flow was invalid; the correlation coefficient and time to peak intensity were not correlated (P = ns). In conclusion, this study shows that it is possible to evaluate relative myocardial perfusion after the first pass of a an intravenously injected bolus of gadopentetate dimeglumine, using dynamic MRI on a conventional medium field MRI system. The cross-correlation coefficient and the peak intensity resulted in more efficient parameters to evaluate relative inhomogeneity of regional myocardial perfusion.

Doppler energy: A new acquisition technique for the transthoracic detection of myocardial perfusion defects with the use of a venous contrast agent

This animal experiment was designed to study whether the new technique of Doppler energy imaging could display myocardial perfusion abnormalities with the use of a combination of transthoracic imaging and right atrial injection of a myocardial contrast agent. A series of 11 pigs were studied during (1) normal perfusion, (2) dipyridamole-induced coronary dilatation, and (3) during and after temporary occlusion of the left anterior descending or circumflex artery after a right atrial injection of 8 ml Levovist, 400 mg/ml. Short-axis views were obtained with the four following imaging modes: gray scale imaging (two-dimensional and M-mode), Doppler energy imaging (two-dimensional and M-mode). Visual inspection and off-line video densitometry (results expressed in arbitrary videointensity units 0 to 255) with digital background subtraction were performed. Doppler energy was significantly more sensitive in detecting the presence of contrast than gray scale imaging (background subtracted peak videointensity 32 +/- 17 versus 17 +/- 12, p < 0.001). Mean background-subtracted videointensity increased during dipyridamole-induced coronary hyperemia (40 +/- 14 versus 31 +/- 9, p < 0.003) using Doppler energy technique. Doppler energy imaging consistently detected absent perfusion (background subtracted videointensity -6 +/- 6) and immediate reperfusion (background subtracted peak videointensity 29 +/- 15, p < 0.001). With the use of a galactose-based contrast agent, Doppler energy data acquisition was superior to standard gray scale imaging in transthoracic evaluation of regional myocardial perfusion, absence of perfusion, and reperfusion.

Quantitative evaluation of regional myocardial perfusion using fast X-ray computed tomography.

Clinical quantitation of regional myocardial perfusion using a minimally invasive and easily applied technique could allow for ready quantitation of the functional significance of coronary disease, allow for further understanding of flow reserve in various cardiomyopathic and hemodynamic overload (pressure versus volume) conditions, and possibly provide basic information needed regarding the development and clinical significance of coronary collateral vessels and diseases of the myocardial microcirculation. Electron beam CT (EBCT) is a unique cardiac imaging modality that allows for rapid acquisition tomographic slices of the heart with excellent spatial resolution. It has been demonstrated to provide accurate measurements of cardiac anatomy, biventricular function, myocardial mass, and estimates of mural atherosclerotic plaque burden via quantification of coronary calcium. The application of classical indicator techniques for use by fast x-ray computed tomography techniques such as electron beam CT has been shown to allow quantitative analysis of regional myocardial perfusion throughout the myocardium. Initial studies using central intravenous contrast injection in experimental animals showed a close correlation of regional myocardial perfusion as quantitated by electron beam CT with measurements using radiolabeled microspheres at resting and moderately increased flow states. At high flow states, however, electron beam CT significantly underestimated absolute myocardial perfusion and thus myocardial flow reserve. Using another fast CT device, the Dynamic Spatial Reconstructor (DSR), concepts of intramyocardial vascular blood volume and its relation to myocardial flow have been established. By adapting these concepts to electron beam CT scanning and accounting for the increase in intramyocardial vascular blood volume at vasodilatation, the ability to correctly quantitate perfusion states up to approximately 400 mL.min-1. 100 g-1 using central intravenous contrast administration was demonstrated. This implies that studies can be done with intravenous injection methods for characterization of regional myocardial perfusion up to the normal flow reserve of approximately 4:1. Important physiologic and clinical abnormalities in flow reserve generally result in a ratio < 3:1. Electron beam CT offers the capability to quantitate regional myocardial perfusion in both the clinical and research setting. Of particular interest is the ability to provide quantitative regional myocardial perfusion which can be coupled to the evaluation of cardiac anatomy and function as well as mural coronary atherosclerotic calcium burden during the same scanning session. Thus, electron beam CT has the potential to become a valuable, minimally invasive clinical tool for comprehensive analysis of cardiac function and coronary status.

Evaluation of regional myocardial perfusion in areas of old myocardial infarction after revascularization by means of intraoperative myocardial contrast echocardiography

Because myocardial revascularization to areas of old myocardial infarction brings about functional recovery to some extent to myocytes in those areas, the assessment of regional myocardial perfusion on those areas after myocardial revascularization may allow myocardial viability to be estimated. Using intraoperative myocardial contrast echocardiography by direct injection of 2 ml sonicated 5% human albumin into saphenous vein grafts, we assessed regional myocardial perfusion in 16 revascularized areas of old myocardial infarction. We estimated the myocardial viability of areas with respect to myocardial perfusion, and we compared these results to both the improvement of regional wall motion after myocardial revascularization (increase in segmental wall thickening during systole) and relative thallium 201 activity obtained by quantitative analysis of preoperative exercise myocardial thallium 201 distribution on delayed images. The background-subtracted peak peak intensity of myocardial enhancement and the ratio of endocardial to epicardial intensity were determined in each revascularized area. An inverse correlation existed between peak intensity (18 +/- 7) and the endocardial/epicardial ratio (0.88 +/- 0.17) (r = -0.63, p < 0.01). A good correlation was found between peak intensity and both the percent increase in segmental wall thickening (r = 0.73, p < 0.005) and the relative thallium 201 activity (r = 0.81, p < 0.005). These results suggested that regional myocardial perfusion after myocardial revascularization in areas of old myocardial infarction distributed better to the epicardial halves than to the endocardial halves, and that the peak intensity could be related to myocardial viability.

Single-day combined evaluation of regional myocardial perfusion and function at rest and peak exercise with99mTc-MIBI in patients with coronary artery disease

Single-day combined evaluation of regional myocardial perfusion and function at rest and peak exercise with99mTc-MIBI in patients with coronary artery disease

Effect of spinal cord stimulation on regional myocardial perfusion assessed by positron emission tomography

Spinal cord stimulation (SCS) can relieve symptoms in patients with severe angina pectoris refractory to conventional medical or surgical therapy. This symptomatic improvement may result from decreased myocardial ischemia. To test this hypothesis, positron emission tomography (PET) and potassium-38 as a flow tracer were used in 8 patients for the quantitative evaluation of regional myocardial perfusion at rest and after exercise, before and during SCS. Potassium uptake was evaluated as myocardial clearance (flow times net extraction) in ml/min/100 g. Tomographic segments were categorized as nonaffected and affected on the basis of the absence or presence of arterial stenosis on coronary angiography and on the basis of thallium scintigraphic data. In nonaffected segments, before SCS, regional myocardial clearance significantly increased from rest (28 ± 4) to exercise (47 ± 13 clearance units; p < 0.004). A similar increase occurred after SCS. In affected segments, before SCS, regional myocardial clearance barely increased (p = 0.065) from rest (26 ± 6) to exercise (33 ≤ 12). In comparison, after SCS, the resting regional myocardial clearance was slightly elevated (29 ± 8) reflecting an increased double product, but did not increase (p = 0.192) with exercise (34 ± 12). However, the magnitude and duration of ST-segment depression decreased during treatment with SCS. Anginal pain occurred in all patients during control exercise, but was attenuated in all but one with SCS. These results indicate that SCS improves exercise-induced angina and electrocardiographic signs of ischemia but this influence does not appear to be mediated by changes in regional myocardial perfusion.

Assessment of myocardial perfusion by positron emission tomography

Positron emission tomography (PET) represents an advanced imaging technology for the noninvasive evaluation of regional myocardial blood flow. Several blood flow tracers are available, including cyclotron-produced radiopharmaceuticals such as [15O]H2O and [13N]NH3 and generator-produced rubidium-82 ([82Rb]-) and copper-62 ([62Cu]-) pyruvaldehyde-bis-(N-4-methylthiosemicarbazone) (PTSM). 82Rb and [13N]NH3 are the most commonly employed tracers for the qualitative evaluation of regional myocardial perfusion. Their use allows the accurate detection of coronary artery disease in combination with pharmacologic stress. Initial comparative studies with thallium-201 (201Tl) single-photon emission computed tomography (SPECT) have shown that PET has a higher diagnostic accuracy. Beyond improved diagnostic performance, the quantitative flow measurements provided by PET represent an important advance in nuclear cardiology. The radiopharmaceuticals [15O]H2O and [13N]NH3 have been applied for the noninvasive determination of regional coronary reserve. Quantification of blood flow based on tracer kinetic modeling yields blood flow values in close agreement with determinations provided by invasive procedures. The noninvasive quantification of blood flow provides a useful research and clinical tool for the objective assessment of therapeutic interventions as well as pathophysiologic alterations of regional myocardial blood flow in various cardiac diseases.

Whole heart distribution of myocardial perfusion, metabolism and myocardial viability by positron emission tomography

The three dimensional evaluation of regional myocardial perfusion and metabolism of the whole left ventricular wall is now possible using the new generation of Positron Emission Tomography scanners (PET). We have used whole heart PET to study the metabolic consequences of transient myocardial ischaemia distal to critical coronary obstructions and to assess the viability of non contractile myocardium. At present whole heart PET should be considered a sophisticated technique for clinical research but its remarkable potential and further possible technical advances suggest its diagnostic application could be considered in the future, if justified on a cost benefit basis.

Digital subtraction contrast echocardiography: a new method for the evaluation of regional myocardial perfusion.

The potential of contrast enhanced digital subtraction echocardiography to demonstrate and quantitate myocardial perfusion was evaluated in 36 patients undergoing routine coronary arteriography or angioplasty. In 24 technically successful studies, multiple cross sectional echocardiographic images, obtained before and after intracoronary (sonicated contrast) injection, were stored by high speed, real time data transfer to an on line minicomputer. Subsequent digital subtraction processing of the stored image data provided composite images in which the distribution of myocardial perfusion was easily seen. Quantitative analysis of peak enhanced myocardial grey level and washout half time successfully differentiated between myocardial segments in which angiography had suggested normal, reduced, and grossly impaired or absent perfusion. The results suggest that this new method of digital image capture and quantitative processing has substantial advantages over previous off line qualitative techniques. It is likely to be of considerable value for routine coronary arteriography, angioplasty, and coronary thrombolysis.