Clinical implications of the technetium-99m stannous pyrophosphate myocardial scintigraphic "doughnut" pattern in patients with acute myocardial infarcts

Imaging of Myocardial Ischemia-Reperfusion Injury Using Sodium [18F]Fluoride Positron Emission Tomography/Computed Tomography in Rats and Humans

Positron emission tomography (PET)/computed tomography (CT) using sodium [¹⁸F]fluoride (Na[¹⁸F]F) has been proven to be a promising hot-spot imaging modality for myocardial infarction (MI). We investigated Na[¹⁸F]F uptake in ischemia–reperfusion injury (IRI) of rats and humans. Sodium [¹⁸F]fluoride PET/CT was performed in Sprague-Dawley rats that had IRI surgery, and it readily demonstrated prominent Na[¹⁸F]F uptake in the infarct area post-IRI. Sodium [¹⁸F]fluoride uptake was matched with negative 2,3,5-triphenyl-2H-tetrazolium chloride staining results, accompanied by myocardial apoptosis and associated with positive calcium staining results. Furthermore, area at risk was negative for Na[¹⁸F]F uptake. Cyclosporine A (CysA) treatment reduced standardized uptake value of ¹⁸F over the infarct area, and a significant decrease in infarct size was also observed by the CysA treatment. In humans, Na[¹⁸F]F PET/CT readily demonstrated increased Na[¹⁸F]F uptake in the 2 patients with MI post-percutaneous coronary intervention. In conclusion, this study sheds light on the potential utility of Na[¹⁸F]F PET/CT as a hot-spot imaging modality for myocardial IRI.

Sodium [¹⁸F]fluoride PET/CT in myocardial infarction

PURPOSE

Sodium [(18)F]fluoride (Na[(18)F]F) positron emission tomography with integrated computed tomography (PET/CT) has not been used for imaging myocardial infarction (MI). Here, we aimed to investigate the Na[(18)F]F PET/CT features of MI in a rat model.

PROCEDURES

MI was induced by coronary artery ligation in 8-week-old male Spraque-Dawley rats (300 ± 10 g) and confirmed by triphenyl tetrazolium chloride (TTC) staining. Na[(18)F]F PET/CT images were obtained using an animal-dedicated PET/CT scanner (NanoPET/CT, Mediso) in vivo and ex vivo. Uptake of Na[(18)F]F was quantitated using the standardized uptake value (SUV). Myocardial apoptosis was evaluated using histone-1 targeted peptide (ApoPep-1) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, while calcium accumulation was investigated using von Kossa's staining. Na[(18)F]F PET/CT was compared with (99m)Tc-methoxyisobutylisonitrile (MIBI) or (99m)Tc-hydroxymethylenediphosphonate (HMDP) single photon emission computed tomography/computed tomography (SPECT/CT) in rats with day 1 MI.

RESULTS

The rats showed strong Na[(18)F]F uptake both in vivo and ex vivo; the maximal uptake occurred 1 day after MI (SUV ratio of infarct to lung = 4.56 ± 0.74, n = 7, P = 0.0183 vs the control). The Na[(18)F]F uptake area perfectly matched the apoptotic area, determined by ApoPep-1 uptake and TUNEL assay. However, calcification, assessed by von Kossa's staining, was absent in the infarct. Na[(18)F]F PET/CT showed an increased uptake at the perfusion deficit area in [(99m)Tc]MIBI SPECT/CT and an equivalent signal to [(99m)Tc]HMDP SPECT/CT in rats with day 1 MI.

CONCLUSIONS

Na[(18)F]F PET/CT is a promising hot-spot imaging modality for MI.

Coronary artery occlusion and myocardial infarction: a seldom encountered complication of blunt chest trauma

Myocardial infarction is a rare complication that can occur after blunt chest trauma. The authors describe a 30-year-old man who experienced a fatal anterolateral myocardial infarction after chest trauma in a motorcycle accident. The electrocardiogram and creatine phosphokinase-MB isoenzymes levels suggested myocardial necrosis. Tc-99m phosphate myocardial scintigraphy identified an extensive doughnut-shaped uptake over the cardiac area. An echocardiogram revealed severe left ventricular impairment. Coronary angiography confirmed complete occlusion of the proximal left anterior descending coronary artery.

Resuscitation from out-of-hospital cardiac arrest: implications for cardiac enzyme estimation

BACKGROUND

diagnosis of precipitating myocardial infarction is essential for management of victims of out-of-hospital cardiac arrest, since investigations and treatment are determined by the underlying cause. Skeletal muscle and myocardial damage from external cardiac massage and defibrillation may complicate biochemical diagnosis of myocardial infarction.

OBJECTIVES

(a) to examine the relationship between cumulative defibrillation energy and serum levels of cardiac troponin T and MB creatine kinase (MB-CK) mass in out-of-hospital cardiac arrest survivors without electrocardiographic evidence of myocardial infarction; (b) to reassess diagnostic thresholds for myocardial infarction using MB-CK mass and troponin T in this setting.

METHODS

77 victims of out-of-hospital cardiac arrest were studied. Serum was obtained for MB-CK mass, CK and troponin T estimation on the first 4 days of admission. Patients were divided into three groups using electrocardiographic criteria: group 1, myocardial infarction; group 2, no evidence of infarction; and group 3, equivocal electrocardiograms. Correlation coefficients were calculated for highest recorded levels of the biochemical markers versus defibrillation energy. Receiver-operating characteristic plots were used to determine optimum biochemical diagnostic thresholds for subjects in groups 1 and 2.

RESULTS

using predefined criteria, 27 patients had myocardial infarction, 34 did not have myocardial infarction and 16 had equivocal electrocardiograms. Significant correlations were found for defibrillation energy versus log troponin T (r = 0.42, P < 0.05), log MB-CK mass (r = 0.51, P < 0.01) and total CK (r = 0.68, P < 0.001) in group 2. Within groups 1 and 2, MB-CK mass and troponin T provided additional diagnostic value over MB-CK fraction (P < 0.001). Diagnostic accuracy was not improved by adjusting for shock energy. The optimum threshold value was 4 ng/ml for troponin T (sensitivity 88%, specificity 95%), 60 ng/ml for MB-CK mass (sensitivity 88%, specificity 88%) and 8% of total CK for MB-CK fraction (sensitivity 74%, specificity 82%). These values should be interpreted with caution, since this study is limited by the exclusion of patients with uncertain electrocardiographic diagnoses into group 3.

CONCLUSIONS

skeletal muscle and myocardial damage occurs in survivors of out-of-hospital cardiac arrest and is related to the duration of resuscitation. This complicates biochemical diagnosis of underlying myocardial infarction. Specific high diagnostic threshold values for MB-CK and troponin T are needed to optimise diagnostic accuracy. The use of MB-CK fraction leads to greater diagnostic error because of the variability of muscle CK release after resuscitation.

Comparison in acute myocardial infarction of anisoylated plasminogen streptokinase activator complex versus heparin evaluated by simultaneous thallium-201/technetium-99m pyrophosphate tomography

In a subgroup of 45 patients with acute myocardial infarction (AMI) from the German multicenter trial of anisoylated plasminogen streptokinase activator complex (APSAC) (n = 20) versus heparin (n = 25), simultaneous thallium (TI)-201 technetium (Tc)-99m pyrophosphate (PYP) tomography was initiated to elucidate a possible benefit of APSAC over heparin. Findings in the 2 treatment groups were similar with respect to TI-201 defect score, relative scintigraphic infarct size, and in keeping with the main group coronary artery patency, global ejection fraction and maximal creatine kinase level. However, 2 different TI-201/Tc-99m PYP accumulation patterns within the area of infarction (homogeneous, group A; inhomogeneous, group B) were identified. Both treatment groups were similar with regard to the frequency of the homogeneous and inhomogeneous pattern. In comparing the 2 accumulation patterns, creatine kinase peaked earlier in group A than in group B, and global left ventricular ejection fraction was significantly higher in group A than in group B. In Group A, 30 of 31 patients and in group B 7 of 11 patients had a patent infarct-related vessel (p < 0.025). TI-201 defect score was lower in group A than in group B. Likewise, relative size of the infarction as determined from Tc-99m PYP images was significantly lower in group A than in group B. Fifteen patients experienced cardiogenic shock or severe heart failure. Patients in group B had a higher incidence of these in-hospital complications than patients in group A (92 vs 12%, p < 0.0005). Scintigraphic infarct size and TI-201 defect score were greater in patients with the aforementioned clinical events.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative estimation of infarct size by simultaneous dual radionuclide single photon emission computed tomography: comparison with peak serum creatine kinase activity

To test the hypothesis that simultaneous dual energy single photon emission computed tomography (SPECT) with technetium-99m (99mTc) pyrophosphate and thallium-201 (201TI) can provide an accurate estimate of the size of myocardial infarction and to assess the correlation between infarct size and peak serum creatine kinase activity, 165 patients with acute myocardial infarction underwent SPECT 3.2 +/- 1.3 (SD) days after the onset of acute myocardial infarction. In the present study, the difference in the intensity of 99mTc-pyrophosphate accumulation was assumed to be attributable to difference in the volume of infarcted myocardium, and the infarct volume was corrected by the ratio of the myocardial activity to the osseous activity to quantify the intensity of 99mTc-pyrophosphate accumulation. The correlation of measured infarct volume with peak serum creatine kinase activity was significant (r = 0.60, p less than 0.01). There was also a significant linear correlation between the corrected infarct volume and peak serum creatine kinase activity (r = 0.71, p less than 0.01). Subgroup analysis showed a high correlation between corrected volume and peak creatine kinase activity in patients with anterior infarctions (r = 0.75, p less than 0.01) but a poor correlation in patients with inferior or posterior infarctions (r = 0.50, p less than 0.01). In both the early reperfusion and the no reperfusion groups, a good correlation was found between corrected infarct volume and peak serum creatine kinase activity (r = 0.76 and r = 0.76, respectively; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac nuclear medicine

In this paper, the principal applications of nuclear medicine to studies of the heart are described. First, gated cardiac blood pool imaging is discussed, then thallium-201 myocardial imaging, myocardial infarct scintigraphy with 99mTc pyrophosphate, and evaluation of intracardiac shunts. In gated cardiac blood pool imaging, the patient's red blood cells are labeled with 99mTc. Images of the cardiac blood pool are then obtained in multiple projections and displayed in an endless-loop cine display. Quantitative indices of cardiac function are readily obtained, and a variety of functional images can be generated. Blood pool imaging may also be performed with use of a first-pass technique that yields similar information. Applications of blood pool imaging are discussed. The theory and techniques of planar and tomographic thallium-201 myocardial imaging are described, together with their application in the diagnosis of coronary artery disease. The prognostic value of thallium imaging is also examined. Myocardial infarct imaging with 99mTc pyrophosphate is described, and clinical indications are reviewed. Left-to-right cardiac shunts can be evaluated by following the first transit of a bolus of radiopharmaceutical through the lungs. Right-to-left shunts may be evaluated by injection of 99mTc macroaggregated albumin.

Measurement of myocardial infarction fraction using single photon emission computed tomography

Although infarct size correlates generally with prognosis after acute myocardial infarction, an absolute measure of infarct size may have differing prognostic significance depending on absolute left ventricular mass. To test the hypothesis that single photon emission computed tomography can accurately measure myocardial infarct size as a percent of total left ventricular mass ("infarction fraction"), thallium-201 and technetium-99m pyrophosphate tomograms were acquired in 21 dogs 24 to 48 hours after fixed occlusion of the left anterior descending or circumflex coronary artery. Pathologic infarct weight was measured as the myocardial mass that showed no staining with triphenyltetrazolium chloride. Scintigraphic infarct mass by technetium-99m pyrophosphate was calculated from the total number of left ventricular volume elements (voxels) demonstrating technetium-99m pyrophosphate uptake X voxel dimension [( 0.476 cm]3) X specific gravity of myocardium (1.05 g/cm3). Scintigraphic left ventricular mass was calculated in a similar fashion using an overlay of the thallium-201 and technetium-99m pyrophosphate scans. The "infarction fraction" was calculated as: infarction fraction = infarct mass/left ventricular mass. There was good correlation between single photon emission computed tomography and pathologic measurements of infarct mass (technetium-99m pyrophosphate mass = 1.01 X pathologic infarct mass + 0.96; r = 0.98), left ventricular mass (single photon emission computed tomographic left ventricular mass = 0.60 X pathologic left ventricular mass + 37.4; r = 0.86) and "infarction fraction" (single photon emission computed tomographic infarction fraction = 1.09 X pathologic infarction fraction - 1.7; r = 0.94).(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of infarct size in acute canine myocardial infarction by single-photon emission computed tomography with technetium-99m pyrophosphate

The location and extent of myocardial infarction (MI) are important predictors of patient course. The current study tests the hypothesis that MI size could be measured accurately using rotating gamma camera single-photon emission computed tomography ( SPECT ) and technetium-99m pyrophosphate (PPi) and that the accuracy of these measurements was independent of MI location and transmural or nontransmural distribution. SPECT was performed in 38 dogs 48 hours after ligation of the left anterior descending coronary artery (14 dogs) or left circumflex coronary artery (LC) (24 dogs) at the mid-level or below. Projection images were corrected for center-of-rotation and field nonuniformity and processed with a 1-dimensional low-pass filter to diminish rib activity. Sixteen 0.5-cm-thick transverse sections, including the entire left ventricle, were reconstructed by filtered backprojection , low-pass filtered, contrast enhanced and processed with a 3-dimensional boundary enhancement operator. The boundary of PPi uptake in each slice was marked automatically using an algorithm that combined a directional derivative and a threshold, and required continuity of the boundary in 3 dimensions. The total number of volume elements that showed abnormal tracer uptake were summed, corrected to absolute volume, and multiplied by the specific weight of cardiac muscle. Scintigraphic MI weight was compared with pathologic MI weight. There was an excellent correlation between scintigraphic and pathologic MI weight. The poorer correlation for nontransmural compared with transmural MIs is most likely a function of size alone, since MIs that weighed less than 10 g (n = 12, range 1.3 to 9.5 g), both transmural and nontransmural, showed a similar correlation: S = 1.07 X P + 0.56 (r = 0.81, standard error of the slope = 0.245).(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of acute right ventricular infarction by right precordial electrocardiography

The value of 0.1 mV or greater of S-T segment elevation in at least one right precordial lead (V4R to V6R) in defining right ventricular myocardial infarction was assessed prospectively in 43 subjects (33 consecutive patients with enzymatically confirmed infarction of varying type and location, 4 patients with unstable angina and 6 healthy volunteers). Patients with acute myocardial infarction were studied with radionuclide ventriculography and technetium-99m stannous pyrophosphate myocardial scintigraphy 18.2 +/- 14.3 (mean +/- standard deviation) and 85.1 +/- 18.0 hours after the onset of symptoms, respectively. Eleven patients (Group A: 9 patients with transmural inferior infarction, 1 with transmural inferolateral infarction and 1 with transmural anteroseptal infarction) demonstrated right precordial S-T segment elevation and 22 patients (Group B: 6 patients with transmural inferior infarction, 2 with transmural posterior infarction, 3 with transmural inferolateral infarction, 3 with transmural anteroseptal infarction, 3 with transmural extensive anterior infarction, 4 with subendocardial anterior infarction and 1 with unclassified infarction) did not. Right ventricular ejection fraction was significantly lower in Group A (0.47 +/- 0.11) than in Group B (0.60 +/- 0.12) (p less than 0.01). Right ventricular total wall motion score was 63.8 +/- 15.6 percent of normal in Group A versus 94.3 +/- 8.5 percent in Group B (p less than 0.001). Technetium-99m pyrophosphate uptake (2+ or greater) over the right ventricle occurred in nine patients (81.8 percent) in Group A and in one patient (4.5 percent) in Group B (p less than 0.001). No patient with unstable angina and no healthy volunteer had S-T segment elevation in a right precordial lead. S-T segment elevation of 0.1 mV or greater in one or more of leads V4R to V6R is both highly sensitive (90 percent) and specific (91 percent) in identifying acute right ventricular infarction.

Recent advances in nuclear cardiology. 2. Dynamic myocardial scintigraphy

Nuclear cardiology, a developing subspeciality of cardiology and nuclear medicine, has experienced rapid growth during the past five years. Important advances in "hot-spot" and "cold-spot" myocardial scintigraphy for measurement of myocardial perfusion and detection of myocardial infarction are discussed in part 1 of this article, beginning on page 55. Part 2 concludes the discussion with an update on dynamic myocardial imaging.

Pathophysiologic considerations and clinicopathological correlates of technetium-99m stannous pyrophosphate myocardial scintigraphy

99mTc-PYP myocardial scintigrams represent a means to detect and localize acute myocardial necrosis. These scintigrams are expected to be abnormal with acute myocardial infarcts of at least 3 grams in weight if serial imaging is utilized and proper attention to technique is provided. Any etiology of myocardial necrosis may produce abnormal 99mTc-PYP scintigrams if the damage is relatively localized and includes at least 3 grams of tissue. It is possible to accurately size acute anterior and anterolateral transmural myocardial infarcts using area or 2 dimensional measurements. Further development in imaging cameras and computer techniques allowing three dimensional reconstruction of myocardial infarcts with this and similar imaging techniques may allow relatively precise quantitation of other types of myocardial infarcts. The "doughnut" and "persistently abnormal" 99mTc-PYP scintigrams appear to have anatomic and prognostic significance at least in subsets of patients studied, but larger numbers of individuals need to be evaluated before final conclusions regarding their ultimate prognostic significance can be reached.