Follow-up technetium-99m stannous pyrophosphate myocardial scintigrams after acute myocardial infarction

Current Status of Radionuclide Imaging of Transthyretin Cardiac Amyloidosis

Cardiac single photon emission computed tomography using 99mTc-bone avid tracers allows for an accurate noninvasive diagnosis of transthyretin (ATTR) cardiac amyloidosis, a historically underdiagnosed disease. This imaging is recommended in select populations who demonstrate clinical and imaging features of infiltrative cardiomyopathy. It is imperative to concomitantly assess for light chain (AL) cardiac amyloidosis independent of radionuclide scintigraphy for timely management of AL amyloidosis, a deadly disease requiring urgent therapy. Clinical judgement is also key and in some select scenarios an endomyocardial biopsy may be needed even after a noninvasive evaluation.

99mTc Bone-Avid Tracer Cardiac Scintigraphy: Role in Noninvasive Diagnosis of Transthyretin Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR-CA) is an overlooked cause of heart failure, with substantial morbidity and mortality. The emergence of several novel therapies has fueled the interest in early and accurate diagnosis of ATTR-CA so that potentially life-saving pharmacologic therapy can be administered in a timely manner. The most promising imaging modality and biomarker is SPECT imaging with technetium 99m (99mTc)-radiolabeled bone-seeking tracers, which have high specificity in the diagnosis of ATTR-CA, potentially obviating biopsy. In this article, the authors provide a focused review on the use of 99mTc pyrophosphate (PYP), 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD), and hydroxymethylene diphosphonate (HMDP) for diagnosis of ATTR-CA, present a systematic approach to interpretation of the scans, and highlight several common pitfalls to illustrate important diagnostic principles for accurate interpretation of these images. The authors indicate when to use endomyocardial biopsy for the diagnosis of cardiac amyloidosis and conclude with a section on quantitation of 99mTc-PYP/DPD/HMDP imaging.

Standardization of 99mTechnetium pyrophosphate imaging methodology to diagnose TTR cardiac amyloidosis

BACKGROUND

Technetium pyrophosphate (99mTc-PYP) imaging to diagnose transthyretin cardiac amyloidosis (ATTR-CA) has been increasingly utilized. The objective of this study is to provide a standardized 99mTc-PYP imaging protocol to diagnose ATTR-CA.

METHODS

104 scans from 45 subjects with biopsy-proven ATTR-CA or light-chain cardiac amyloidosis (AL) were assessed. Multiple scans were obtained using different counts (750 vs 2000 K), times to acquisition (1 vs 2 to 4 hours), processing matrix (256 vs 128), and 99mTc-PYP dose. Image quality and extracardiac activity was assessed. Quantitative methods using heart-to-contralateral ratios (H/CL) and a visual semiquantitative scale were used to diagnose ATTR-CA.19 The correlation between H/CL ratios and reproducibility of semiquantitative visual scores, acquired using various imaging parameters, were evaluated.

RESULTS

All imaging parameters had good to excellent image quality. 750 vs 2000 K counts, 1 hour acquisition and 256 matrix, had lower extracardiac activity (P = .00018). 10 mCi of 99mTc-PYP v. higher doses showed excellent image quality and less extracardiac activity (P = .0015). Correlation of H/CL ratios was strong (r ≥ 0.92) and reproducibility of semiquantitative visual scores was high (Kappa = 95%).

CONCLUSION

An imaging protocol using 750 K counts, 10 mCi of 99mTc-PYP, and a 256 matrix was chosen as the standardized imaging protocol since it provided the shortest overall study time (1 vs 2 to 4 hours) and lowest radiation exposure (3 vs 8 to 10 mSv).

Imaging of isoproterenol-induced myocardial injury with 18F labeled fluoroglucaric acid in a rat model

Positron emission tomography (PET) of myocardial infarction (MI) by infarct avid imaging has the potential to reduce the time to diagnosis and improve diagnostic accuracy. The objective of this work was to synthesize ¹⁸F-labeled glucaric acid (FGA) for PET imaging of isoproterenol-induced cardiomyopathy in a rat model.

METHODS

We synthesized ¹⁸F-FGA by controlled oxidation of ¹⁸F-fluorodeoxy glucose (FDG), mediated by 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in presence of NaBr and NaOCl in highly-buffered reaction conditions. After ascertaining preferential uptake of ¹⁸F-FGA in necrotic as compared to normal H9c2 myoblasts, the biodistribution and circulation kinetics of ¹⁸F-FGA was assessed in mice. Moreover, the potential of ¹⁸F-FGA to image myocardial damage was investigated in a rat model of isoproterenol-induced cardiomyopathy. Isoproterenol-induced myocardial injury was verified at necropsy by tissue staining and plasma cardiac troponin levels.

RESULTS

Synthesis of radiochemically pure ¹⁸F-FGA was accomplished by a 5 min, one step oxidation of ¹⁸F-FDG. Reaction yield was quantitative and no side-products were detected. Biodistribution studies showed rapid elimination from the body (k_e = 0.83 h^-1); the major organ of ¹⁸F-FGA accumulation was kidney. In the rat model, isoproterenol-treatment resulted in significant increase in cardiac troponin. PET images showed that the hearts of isoproterenol-treated rats accumulated significant amounts of ¹⁸F-FGA, whereas healthy hearts showed negligible uptake of ¹⁸F-FGA. Target-to-nontarget contrast for ¹⁸F-FGA accumulation became significantly more pronounced in 4 h images as compared to images acquired 1 h post-injection.

CONCLUSION

¹⁸F-FGA can be easily and quantitatively synthesized from ubiquitously available ¹⁸F-FDG as a precursor. The resultant ¹⁸F-FGA has a potential to serve as an infarct-avid agent for PET imaging of MI. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: ¹⁸F-FGA/PET will complement existing perfusion imaging protocols in therapeutic decision making, determination of revascularization candidacy and success, differentiation of ischemia from necrosis in MI, discrimination of myocarditis from infarction, and surveillance of heart transplant rejection.

The current role of infarct avid imaging

Tc-99m pyrophosphate is the grandfather of infarct avid agents. Its value is its clinical availability and ease of use. However, its shortcomings are the delay of 2 to 3 days for reliable interpretation in nonreperfused myocardial infarction (MI) and the overarching bone activity. Antimyosin provides exquisite specificity for the detection of myocardial necrosis irrespective of the cause of the injury. Therefore, diagnosis of equivocal MI or confirmation of diffuse myocardial necrosis would benefit from the availability of In-111 labeled antimyosin Fab. The drawback of antimyosin, like that of Tc-99m pyrophosphate, is the delay, in this case because of the protracted blood clearance of the antibody protein macromolecules. Tc-99m glucaric acid, on the other hand, may fulfill the original role envisioned for antimyosin, which was to enable early, rapid diagnosis of acute MI. However, the window for the use of Tc-99m glucaric acid appears to be limited to within the first day of the acute event. Therefore, there is a potential use of both Tc-99m glucaric acid and In-111 antimyosin in tandem with Tc-99m glucaric acid, which would not only facilitate early detection and diagnosis of acute MI and diagnosis of equivocal MI, but also may permit stratification of the infarct age.

Technetium 99m glucarate: what will be its clinical role?

With publication of the studies by Khaw et al. and Beanlands et al. in this issue of the Journal, there is mounting evidence that 99mTc glucarate is taken up by infarcted but not by ischemic myocardium. The early myocardial distribution and rapid blood-pool clearance of 99mTc glucarate suggest important diagnostic potential in the very early detection of acute myocardial infarction and for the identification of successful acute revascularization therapy. To understand the full diagnostic implications of 99mTc glucarate accumulation in the myocardium, larger human trials are now needed. It will be critically important to document the capabilities of 99mTc glucarate to identify, early on, acute myocardial infarction in the presence of a persistently occluded infarct-related coronary artery in human beings.

Relation of technetium-99m pyrophosphate accumulation to time interval after onset of acute myocardial infarction as assessed by a tomographic acquisition technique

Technetium-99m pyrophosphate (Tc-99m PYP) myocardial scintigraphy was performed in 110 clinically stable patients with acute or healed acute myocardial infarction (AMI). Tomography was performed 12 hours to 7 days (group A), 7 to 30 days (Group B), 1 to 6 months (Group C) and after greater than 6 months (group D) after AMI. All 40 patients in group A, 9 of 31 in group B, 1 of 22 in group C, and no patient (0 of 17) in group D had a pathologic Tc-99m PYP tomogram. Relative Tc-99m PYP accumulation within the area of infarction was measured as infarct zone to blood pool ratio, which decreased significantly (p less than 0.001) from group A (1.54 +/- 0.39) to group B (0.89 +/- 0.24), group C (0.8 +/- 0.19) and group D (0.76 +/- 0.13). These data were confirmed by sequential scintigraphy in 17 patients. It is concluded that a persisting Tc-99m PYP uptake is rarely found greater than 1 month after AMI using tomographic imaging techniques in clinically stable patients with coronary artery disease. Positive results on Tc-99m PYP tomography are a reliable indicator of AMI. Thus, Tc-99m PYP tomography is not only a sensitive but also a specific imaging technique for AMI, which might be especially useful for diagnosis of reinfarction.

Scintigraphic quantification of myocardial necrosis in patients after intravenous injection of myosin-specific antibody

The Fab fragments of antimyosin antibodies, labeled with 99mTc, were used in the scintigraphic examination of 30 patients with myocardial infarction. The ability to detect necrosis and determine its extent from the antimyosin scan were compared with the results of quantitative regional wall motion analysis by contrast ventriculography at 10 to 14 days and 99mTc-pyrophosphate imaging. Antimyosin images recorded by planar and single photon-emission computed tomography (SPECT) delineated areas of myocardial necrosis in 27 of 30 patients (90%) compared with a 91% sensitivity of pyrophosphate in 21 of 23 patients. Infarct size was determined by both antimyosin and pyrophosphate SPECT images. Results by both techniques showed a significant correlation with computer-derived hypokinetic segment length (r = .79 for both, p = .002) and peak creatine kinase (r = .9 for both, p less than .01). Although sensitivity for and correlations with markers of necrosis were similar with both techniques, infarct size by pyrophosphate SPECT was 1.7 times larger than infarct size by antimyosin SPECT (p less than .01). Certain zones in the infarct area were differentially labeled; the nature and irreversibility of injury within these zones remains to be clarified.

Prognostic implications of complicated ventricular arrhythmias early after hospital discharge in acute myocardial infarction: a serial ambulatory electrocardiography study

To assess the prevalence and prognostic implications of complicated ventricular ectopic depolarizations (VEDs) after hospital discharge in patients with acute myocardial infarction (AMI), we obtained serial 24-hour Holter recordings in 85 patients during the first 6 weeks after AMI. Recordings were obtained during two coronary care unit time intervals, two hospital ward time intervals, and during four weekly time intervals after discharge. Complicated VEDs were defined as unifocal VEDs greater than or equal to 10/1000 beats for 24 hours, multiform VEDs, pairs, or ventricular tachycardia. At 1 year follow-up, there were nine cardiac deaths (six sudden deaths and three deaths from recurrent AMI). The mean left ventricular ejection fraction at discharge in the cardiac death patients was 29 +/- 12% (sudden death patients 24 +/- 11% and AMI death patients 40 +/- 6%) compared to 49 +/- 13% in the survivors (p less than 0.001). Patients with complicated VEDs at discharge (2 weeks after AMI) or during the first 4 weeks after discharge (3 to 6 weeks after AMI) were significantly more likely to have sudden death at follow-up compared to patients without complicated VEDs. Of the six sudden death patients, four (66%) had complicated VEDs at discharge compared to 18 of 68 survivors (26%) (p less than 0.05). One of three patients who died of recurrent AMI had complicated VEDs. No Holter data were obtained at hospital discharge in eight of the survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of left ventricular function and infarct size in patients with and without persistently positive technetium-99m pyrophosphate myocardial scintigrams after myocardial infarction: analysis of 357 patients

One hundred nine patients with persistently positive technetium-99m pyrophosphate (Tc-99m-PPi) myocardial scintigrams 6 months after acute myocardial infarction (MI) (Group A) and 185 patients without such persistently positive scintigrams (Group B) were compared with regard to enzymatically determined infarct size, early and late measurements of left ventricular (LV) function determined by radionuclide ventriculography, and preceding clinical course during the 6 months after MI. The CK-MB-determined infarct size index in Group A (17.4 +/- 10.6 g-Eq/m2) did not differ significantly from that in Group B (16.0 +/- 14.6 g-Eq/m2). Similarly, myocardial infarct areas in the 2 groups, determined by planimetry of acute Tc-99m-PPi scintigrams in those patients with well-localized 3+ or 4+ anterior pyrophosphate uptake, were not significantly different (35.7 +/- 13.4 vs 34.4 +/- 13.1 cm2, respectively). However, patients in Group A had significantly lower LV ejection fractions than those in Group B, both within 18 hours of the onset of MI (0.42 +/- 0.14 vs 0.49 +/- 0.14, p less than 0.01) and at 3 months after MI, both at rest (0.42 +/- 0.14 vs 0.51 +/- 0.14, p less than 0.01) and at maximal symptom-limited supine bicycle exercise (0.44 +/- 0.17 vs 0.51 +/- 0.17, p less than 0.01). Peak exercise levels achieved in the 2 groups were not significantly different. Furthermore, patients in Group A demonstrated a greater incidence of congestive heart failure during the initial hospital admission (41 vs 24%; p less than 0.01) and a greater requirement for digoxin (p less than 0.05) and furosemide (p less than 0.01) after discharge.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of cardiovascular nuclear medicine in evaluating trauma and the postoperative patient

In the patient with cardiac trauma, radionuclide imaging may provide important information about cardiac mechanical function, vascular anatomy and integrity, myocardial perfusion, and myocardial metabolism. Studies require only minimal patient cooperation, can be performed relatively rapidly and often at the bedside, and may be repeated at frequent intervals for serial evaluations. These studies provide valuable adjunctive knowledge when selected and interpreted with knowledge of the mechanism of injury, timing of the examination relative to the time of injury, and most likely differential diagnoses.

Increased incidence and clinical correlation of persistently abnormal technetium pyrophosphate myocardial scintigrams following acute myocardial infarction in patients with diabetes mellitus

"Persistently abnormal" technetium-99m stannous pyrophosphate myocardial scintigrams (PPi+) appear to be associated with a relatively poor prognosis after acute myocardial infarction (AMI). To assess the incidence and implications of PPi+, we performed a retrospective analysis in 29 patients with and 25 patients without diabetes mellitus who had abnormal myocardial scintigrams within 4 days of AMI and who had follow-up scintigrams at least 3 months after hospital discharge. There were no significant differences between patients with and without diabetes as regards age, incidence of transmural or nontransmural AMI, or degree of left ventricular dysfunction after AMI. Persistently abnormal PPi+ occurred more commonly in patients with diabetes than in nondiabetic patients (18 of 29, 62%, compared to 3 of 25, 12%; p less than 0.001). Patients with chronic PPi+ had more frequent cardiac complications following hospital discharge (p less than 0.005) including death, recurrent AMI, unstable angina, and intractable congestive heart failure. Postmortem analysis in two patients with diabetes and chronic PPi+ revealed marked myocytolysis. Thus, patients with diabetes mellitus have an increased incidence of post-AMI "persistently abnormal" technetium (PPi+) scintigrams and relatively poor prognosis following myocardial infarction.

The high-risk angina patient. Identification by clinical features, hospital course, electrocardiography and technetium-99m stannous pyrophosphate scintigraphy

We evaluated 193 consecutive unstable angina patients by clinical features, hospital course and electrocardiography. All patients were managed medically. Of the 193 patients, 150 (78%) had a technetium-99m pyrophosphate (Tc-PYP) myocardial scintigram after hospitalization. Of these, 49 (33%) had positive scintigrams. At a follow-up of 24.9 +/- 10.8 months after hospitalization, 16 of 49 patients (33%) with positive scintigrams died from cardiac causes, compared with six of 101 patients (6%) with negative scintigrams (p less than 0.001). Of 49 patients with positive scintigrams, 11 (22%) had had nonfatal myocardial infarction at follow-up, compared with seven of 101 patients (7%) with negative scintigrams (p less than 0.01). Age, duration of clinical coronary artery disease, continuing angina during hospitalization, ischemic ECG, cardiomegaly and a history of heart failure also correlated with cardiac death at follow-up. Ischemic ECG and a history of angina with a crescendo pattern also correlated with nonfatal infarction at follow-up. Patients with continuing angina, an ischemic ECG and a positive scintigram constituted a high-risk unstable angina subgroup with a survival rate of 58% at 6 months, 47% at 12 months and 42% at 24 and 36 months. We conclude that the assessment of clinical features, hospital course, ECG and Tc-PYP scintigraphy may be useful in identifying high-risk unstable angina patients.

Thallium-201 versus technetium-99m pyrophosphate myocardial imaging in detection and evaluation of patients with acute myocardial infarction

Thallium-201 myocardial imaging is of value in the early detection and evaluation of patients with suspected acute infarction. The extent of a thallium defect in an initial myocardial image may have important prognostic value. Tomographic imaging techniques hold promise for increased diagnostic sensitivity and more accurate quantitation of both infarcted and residual viable myocardium. Thallium imaging may have a special value in characterizing patients with cardiogenic shock and in detecting patients at risk for subsequent infarction or death or death or both, before hospital discharge. Approximately 95 percent of patients with transmural or nontransmural myocardial infarction can be detected with technetium-99m pyrophosphate myocardial imaging if the imaging is performed 24 to 72 hours after the onset of symptoms. Pyrophosphate imaging has been useful in localizing the site and determining the extent of acute myocardial infarction. The "doughnut" pattern is associated with a relatively large incidence of subsequent congestive heart failure and death. However, the clinical utility of this information is limited because it is usually not available when it is most needed, on admission to the coronary care unit. Pyrophosphate imaging may have an important role in the evaluation of patients during the early follow-up period after hospital discharge from an episode of acute infarction. The finding of a persistently positive pyrophosphate image suggests a poor prognosis and is associated with a relatively large incidence of subsequent myocardial infarction and death.

Diagnostic criteria for acute myocardial infarction in patients undergoing coronary artery bypass surgery

Current techniques for diagnosing perioperative myocardial infarction were studied in 58 patients who underwent coronary bypass surgery. All patients had preoperative and postoperative ECGs and technetium-99m stannous pyrophosphate myocardial scintigrams; serum CK-MB was measured immediately after surgery and daily for 3 days. Postoperative bypass graft visualization and left ventriculography were performed before hospital discharge in every patient. Nine patients (16%) had new Q waves postoperatively. Five of these nine patients had positive pyrophosphate scintigrams, postive CK-MB and new wall motion abnormalities, and the remaining four had negative CK-MB, negative phyrophosphate scintigrams and no new wall motion abnormalities. Seven patients (12%) had newly positive postoperative pyrophosphate scintigrams, positive CK-MB and new wall motion abnormalities on postoperative ventriculography, but only four had new Q waves postoperatively. Eight patients (14%) had new wall motion abnormalities; seven had positive pyrophosphate scintigrams and all had positive CK-MB, but only five had new Q waves. Sixteen patients (28%) had positive CK-MB, including all patients with either positive pyrophosphate scintigrams or new wall motion abnormalities, Eight patients had positive CK-MB without other evidence of perioperative infarction. A newly positive postoperative pyrophosphate scintigram is more senstive and specific than the development of new postoperative Q waves for the diagnosis of hemodynamically significatn perioperative myocardial in farction. CK-MB is highly sensitive, but too nonspecific to be useful for the diagnosis of perioperative infarction.

Technetium-99m stannous pyrophosphate myocardial scintigrams in pericardial disease

Technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigrams were obtained in 35 acute pericarditis and in three chronic constrictive pericarditis patients. Thirteen of 35 acute pericarditis patients (37%) and one of three chronic constrictive pericarditis patients (33%) had abnormal scintigrams (a diffuse pattern in eight patients and a regional pattern in six patients). Of the 17 acute pericarditis patients with classic ST-segment changes of acute pericarditis, 10 (56%) had abnormal scintigrams compared to three of 17 patients (18%) without these ECG changes (P less than 0.02). These data indicate that pericardial disease may cause an abnormal scintigram. Therefore, one must rule out pericardial disease before concluding that a positive scintigram is due to acute myocardial infarction.

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.

Acute myocardial infarct scintigraphy with infarct-avid radiotracers

The selective uptake of radiopharmaceuticals by acutely infarcted myocardium has emerged as an independent, noninvasive technique to aid in the detection, localization, and quantification of myocardial necrosis.

Value and limitations of technetium-99m stannous pyrophosphate in the detection of acute myocardial infarction

Technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial imaging was performed in 436 consecutive patients for the evaluation of chest pain and suspected acute myocardial infarction (AMI). Scintigrams were assessed independently by three observers with a 90% interobserver agreement. In 134 patients with documented AMI (97 TRANSMURAL, 37 NONTRANSMURAL), THE SENSITIVITY OF 99MTc-PYP imaging was significantly lower in patients with nontransmural AMI (41%) than in patients with transmural AMI (78%), 99mTc-PYP imaging correctly localized the site of transmural infarction in 53 patients (70%). A diffuse 99mTc-PYP uptake was found in nine (10%) of 91 patients with positive scintigrams: six of these had a transmural AMI and three nontransmural AMI. In 226 patients without AMI, the specificity of infarct imaging was 95%. A false-positive scintigram was found in 0%, 8%, 9%, and 2% of patients with unstable angina, progressive angina, stable angina, and noncardiac chest pain, respectively. A diffuse uptake was found in six (54%) of 11 patients with false-positive scintigrams. No patient with the clinical diagnosis of noncardiac chest pain showed discrete uptake. In 76 patients with uncertain diagnosis for AMI, 99Tc-PYP imaging was considered of value in 11 patients with ventricular conduction defects (two patients with WPW syndrome, nine patients with LBBB). These data suggest that: 1. 99mTc-PYP imaging is moderately sensitive in detecting and localizing transmural AMI and is insensitive in detecting nontransmural AMI; 2. A discrete 99mTc-PYP uptake is highly specific for AMI; 3. a diffuse uptake is neither sensitive to, nor specific for AMI. Myocardial imaging with 99m-Tc-PYP is of clinical value when the standard electrocardiographic and enzymatic techniques are inadequate for an accurate diagnosis of AMI.

Abnormal technetium-99m pyrophosphate images in unstable angina: ischemia versus infarction?

There is controversy concerning the specificity of myocardial infarct imaging with technetium-99m pyrophosphate due to the high frequency of false positive images, especially in patients with unstable angina. In this study technetium-99m pyrophosphate images were compared with frequent determinations of plasma creatine kinase, MB isoenzyme (MB CK) activity in 116 patients admitted with the diagnosis of unstable angina. It was hypothesized that frequent measurement of MB CK activity, a sensitive and specific marker for myocardial necrosis, using sensitive assay techniques would detect small amounts of myocardial necrosis which might have been unrecognized by conventional clinical methods. The scintigraphic results and isoenzyme determinations agreed in 88 percent of patients; both tests were normal in 69 percent and both were abnormal, indicating acute myocardial infarcation, in 19 percent of patients. In the remaining 14 patients (12 percent), the scans were abnormal, but MB CK activity was normal. In five of these patients (4 percent), abnormal scintigrams presumably reflected persistent scan positivity after previous myocardial infarction. Only the remaining nine patients (8 percent) could be classified as having unexplained false positive scans, a frequency substantially less than that reported by other investigators who based the diagnosis of myocardial infarction on conventional clinical criteria. These results suggest that abnormal technetium-99m pyrophosphate images in patients with unstable angina generally indicate myocardial necrosis.

Doughnut pattern of technetium-99m pyrophosphate myocardial uptake in patients with acute myocardial infarction: a sign of poor long-term prognosis

Thirty survivors of acute myocardial infarction with 3+ or 4+ positive technetium-99m pyrophosphate myocardial scintigrams were followed up for 28 +/- 3.1 months (mean +/- standard deviation). Three patient groups were identified from the pattern of radioactive uptake in the scintigram: Group I, 16 patients with focal uptake (anterior in 7, lateral in 2, posterior in 3 and inferior in 4); Group II, 6 patients with anterior myocardial infarction and a doughnut pattern of uptake; Group III, 8 patients with nontransmural myocardial infarction and a diffuse pattern of uptake. Late complications developed in all patients with the doughnut pattern of uptake compared with 43 percent of patients with the focal pattern and 12 percent of patients with the diffuse pattern. After discharge from the hospital, five of six patients with a doughnut pattern of uptake died (mean survival time 9.8 months after the initial myocardial infarction). This mortality rate (83 percent) was significantly greater than that of patients with a focal (mortality rate 6 percent) or diffuse (no mortality) pattern of uptake. The doughnut pattern of technetium-99m pyrophosphate myocardial uptake in patients with acute myocardial infarction appears to identify a subgroup of patients with a very poor long-term prognosis.

Prognostic value of a persistently positive technetium-99m stannous pyrophosphate myocardial scintigram after myocardial infarction

Technetium-99m stannous pyrophosphate myocardial scintigrams were obtained in 138 clinically stable patients 32.7 +/- 47.3 weeks (range 6 to 260) after acute myocardial infarction. Of the 138 patients, 74 (54 percent) had a persistently positive scintigram. Patients with such a scintigram were more likely to have severe angina pectoris, compensated congestive heart failure, anterior location of acute myocardial infarction, Q waves and S-T segment elevation in the electrocardiograms, cardiomegaly, left ventricular dyssynergy (dyskinesia or global dyssynergy), and an ejection fraction of less than 50 percent. During a follow-up period of 11.6 +/- 6.9 months after scintigraphy, 42 percent of the patients with a persistently positive scintigram had either a cardiac death, a nonfatal myocardial infarction, unstable angina pectoris or decompensated congestive heart failure compared with 13 percent of the patients with a negative scintigram (P less than 0.001). Of the 14 patients with cardiac death, 13 (93 percent) had a persistently positive scintigram. A persistently positive scintigram not only was the best single predictor of cardiac death and combined end points, but also added significantly to the predictive ability of the other clinical variables, including age, location of acute myocardial infarct, clinical status, electrocardiographic findings, and chest X-ray findings. It is concluded that technetium-99m stannous pyrophosphate myocardial scintigraphy has prognostic value in patients after acute myocardial infarction.

Clinicopathologic findings in 52 patients studied by technetium-99m stannous pyrophosphate myocardial scintigraphy

Scintigraphic, clinical and pathological findings were correlated in 52 patients studied by technetium-99m stannous pyrophosphate (99mTc-PYP) myocardial scintigraphy before death or surgical resection of myocardium. Fifty-nine clinical events were studied with scintigraphy in the 52 patients; 41 of the 59 were associated with one or more abnormal 99mTc-PYP studies and 18 with normal 99mTc-PYP scintigrams. Myocardial scintigrams were positive in 29 of 31 cases with clinicopathological evidence of a corresponding discrete, grossly obvious acute myocardial infarct, including 16 of 16 transmural myocardial infarcts and 13 of 15 subendocardial infarcts. In 16 of 18 cases, negative myocardial scintigrams correlated with the absence of acute myocardial infarction determined by clinicopathological evidence. In two cases small subendocardial infarcts (less than 3 g) were not detected by 99mTc-PYP myocardial scintigraphy. Of the 12 additional instances of positive 99mTc-PYP myocardial scintigrams, five were associated with clinical unstable angina pectoris and seven were in the category of persistently positive scintigrams, since the scans were obtained 2.5 months or longer after proven or suspected acute myocardial infarcts. In all 12 instances, the positive 99mTc-PYP scintigrams were associated with evidence of multifocal irreversible myocardial damage consisting of myocytolysis, coagulation necrosis and/or fibrosis, and the histological age of the lesions was compatible with acute injury corresponding to the time of scintigraphy. The findings indicate that a positive 99mTc-PYP myocardial scintigram is a sensitive indicator of significant myocardial injury which may occur as confluent coagulation necrosis corresponding to clinical acute myocardial infarction, or as multifocal coagulation necrosis or myocytolysis associated with unstable angina pectoris or recurrent ischemic heart disease, especially after previous infarctions.

Inexpensive radiation protective glasses

Using the services of a local optical supply house, fabrication and testing of eyeglasses of a high lead content that could be used to protect the eye from the hazards of radiation were evaluated. Two separate types of eyeglasses were manufactured (a prototype followed by a second pair), and these were tested against a commercially available pair of radiation protective glasses. The protection offered by the locally manufactured pair of glasses exceeded the commercial pair and the cost savings are significant.

Cardiovascular nuclear medicine and intensive care

The clinical application of cardiovascular nuclear imaging techniques to intensive care medicine holds great promise for improved non-invasive assessment of the patient. With the development of new radiopharmaceutical agents and better instrument resolution, it is now possible to provide quantitative information concerning myocardial perfusion, acute myocardial ischaemia, left ventricular function, thromboembolic pulmonary disease and analysis of the patient's respiratory function. The patient can be studied during various phases of his disease, with these techniques furnishing objective guidelines of the therapy and prognosis.

Technetium-99m stannous pyrophosphate imaging of experimental infective endocarditis

Technetium-99m stannous pyrophosphate (99mTc-PYP) cardiac scintigraphy was performed in 15 rabbits with experimental Streptococcus sanguis aortic valve infective endocarditis. The animals were imaged five to seven days after the administration of bacteria, and in each case abnormal accumulation of the tracer was visualized in the region of the aortic valve. Three types of cardiac scintigraphic patterns were demonstrated: focal, multifocal and extensive, each correlating well with the anatomical extent of the lesion as defined by gross pathology. Tissue distribution studies demonstrated a 30 +/- 5.3 (mean +/- SEM) fold excess of radionuclide uptake in the infective endocarditis lesion compared with that of normal myocardium. Imaging of excised hearts from four animals showed an excellent correlation with in vivo imaging as well as gross pathology. Five animals with nonbacterial thrombotic aortic valve endocarditis demonstrated similar scintigraphic and tissue distribution results. In contrast, four normal animals failed to demonstrate abnormal 99mTc-PYP cardiac scintigrams or tissue uptake. This study demonstrates that 99mTc-PYP cardiac scintigraphy is a sensitive technique to detect experimental aortic valve endocarditis.

The prognostic implications of acute myocardial infarct scintigraphy with 99mTc-pyrophosphate

The predictive value of the myocardial scintigraphy with 99mTc-pyrophosphate was studied in 100 patients admitted to the coronary care unit with suspected acute myocardial infarction. None of the 21 patients with normal scintigrams had acute myocardial infraction by other criteria. Fifty-five percent of patients with diffuse uptake (pattern B), 73% of patients with focal uptake (pattern C) and all patients with intense focal uptake (pattern D) and massive uptake (pattern E) had acute infarction. The complication rate in the hospital and after discharge (mean followup: 6.1 months) for patients with pattern E was 88% compared to 42% for D, 30% for C, 36% for B and 10% for patients with normal scintigrams (A). For patients with acute infarction with patterns C, D and E, the complication rate rose with increasing size of the myocardial uptake of 99mTc-pyrophosphate. In addition to its diagnostic potential, scintigraphy provides prognostic information which is useful for patient triage and for therapeutic decisions early in the evolution of the infarct.