Measurement of left heart ejection fraction and end-diastolic volume by a computerized,scintigraphic technique using a wedged pulmonary arterial catheter

A technique is described for visualizing the left heart chambers with a bolus injection of radionuclide tracer using a wedged pulmonary arterial catheter. Technetium-99m as pertechnetate is injected and the heart imaged with an Anger scintillation camera interfaced to a digital computer. Time-activity curves are extracted from areas of interest coincident with the cardiac chambers and corrected for background. These curves are analyzed in two ways: high-frequency data (beat by beat ejection fraction) and low frequency data (exponential fitting to the chamber washout curve). Left ventricular ejection fraction and end-diastolic volume determined by this technique correlated with these measurements obtained from left cineventriculography. Correlation was good between the two methods of data analysis, ejection fraction and exponential curve fitting. This technique is an accurate method for measuring left heart function without performing left heart catheterization.     

Mitral regurgitation determined by radionuclide cardiography: dependence on posture and exercise.

OBJECTIVES--To evaluate dependence of posture and exercise on the degree of mitral regurgitation using combined first pass and equilibrium radionuclide cardiography. DESIGN--24 patients with clinically stable chronic mitral regurgitation and sinus rhythm were studied by first pass list mode and simultaneous multigated frame mode equilibrium radionuclide cardiography using red cells labelled with technetium-99m. RESULTS--When patients changed posture from supine to sitting upright, left ventricular volumes decreased considerably. Regurgitation tended to increase in patients with valve prolapse but decreased in patients with ischaemic heart disease and dilated cardiomyopathy. During submaximal bicycle exercise cardiac output increased without dilatation of the left ventricle. The increase in left ventricular forward stroke volume was more pronounced than that in the total stroke volume, leading to a considerable decrease in the regurgitant flow through the mitral valve. The repeatability and observer variability of radionuclide determination of regurgitation was acceptable, with limits of agreement within about 10%. CONCLUSIONS--Change in posture induces a normal haemodynamic response in most patients with chronic mitral regurgitation; the effect of posture on regurgitation depends on the underlying disease. Mild to moderate exercise causes no deterioration in the severity of regurgitation.     

The reproducibility of nongeometric analysis of cardiac output and left ventricular volume by radionuclide angiography

This study examines the reproducibility of individual radionuclide attenuation factors used in the calculation of cardiac output and left ventricular volume by the nongeometric radionuclide method. Twenty male patients were studied at rest with thermodilution measurements of cardiac output on two separate days. Simultaneous equilibrium radionuclide angiograms were performed and left ventricular stroke volume and cardiac output were determined by the nongeometric method. Individual patient attenuation factors were calculated as the ratio of thermodilution and radionuclide cardiac output measurements at each study. There was a close linear relationship between radionuclide and thermodilution measurements of cardiac output in each study (r = 0.88 study 1, r = 0.97 study 2). A similar relationship was found for measurements of left ventricular stroke volume (r = 0.86, study 1, r = 0.97 study 2). Individual radionuclide attenuation factors ranged from 2.49 to 3.46 in study 1 and from 2.77 to 3.29 in study 2. The individual attenuation factors were reproducible to within 10% in 13 patients and to within 15% in 19 patients. When cardiac output was calculated from the radionuclide data of study 2, by means of individual attenuation factors previously determined in study 1, there was a good correlation with the simultaneous thermodilution measurements of cardiac output (r = 0.92, SEE = 0.38 L/min). Individual radionuclide attenuation factors show little variation in serial studies. Thus the nongeometric radionuclide technique can be used to make accurate serial measurements of cardiac output and left ventricular volume.     

Quantitative radionuclide angiocardiography for determination of chamber to chamber cardiac transit times

A radionuclide method is described for determination of chamber to chamber cardiac transit times using only an intravenous injection. Using the Digital Autofluoroscope, counts of radioactivity from each square centimeter over the precordium were recorded onto computer tape at 0.23 second intervals after intravenous injection of 10 millicuries of ^99mtechnetium pertechnetate. Computer analysis of counts grouped detector units with similar time responses into areas corresponding to discrete cardiac regions. From the resulting indicatordilution curves, appearance, peak and mean transit times were calculated for each cardiac region. Studies were obtained in 10 normal subjects, 14 patients with cardiac septal defects and left to right shunting and 20 patients with valvular stenosis or insufficiency. Among the latter patients, 8 had mitral stenosis and 8 had aortic insufficiency.

Patients with a left to right shunt greater than 15 percent consistently demonstrated rapid pulmonary transit of tracer. In addition, specific abnormalities of curve configuration occurred in patients with a shunt greater than 30 percent. Transit times from the right atrium to left ventricle averaged 9.2 ± 1.2 seconds in normal subjects, 13.3 ± 2.2 seconds in patients with mitral stenosis and 14.6 ± 2.8 seconds in patients with aortic insufficiency. Pulmonary mean transit time was 6.6 ± 1.1 seconds in normal patients, 9.2 ± 1.7 seconds in those with mitral stenosis and 11.7 ± 3.1 seconds in those with aortic insufficiency. Pulmonary blood volume was 362 cc/m² in patients with mitral stenosis and 508 cc/m² in those with aortic insufficiency. These data suggest that pulmonary mean transit time was prolonged primarily by decreased cardiac output in mitral stenosis and by increased pulmonary blood volume in aortic insufficiency. The simple technique described consistently provided hemodynamic data that appear to be useful for diagnosis and management of cardiac diseases.     

Limitations of scintigraphically determined left-ventricular/right-ventricular stroke volume in the evaluation of the severity of aortic valve insufficiency

Noninvasive evaluation of aortic regurgitation can be performed by the radionuclide determination of the left/right ventricular stroke volume ratio. This ratio proved to have a relatively low sensitivity. Therefore, we conducted a study comprising 25 patients with angiographically verified aortic regurgitation in order to look for characteristics of patients with false-negative results. In 5 patients with aortic regurgitation the scintigraphically determined left/right ventricular stroke volume ratio was within normal range. In 3 other patients with severe regurgitation the radionuclide ratio was distinctly lower when compared with the angiographic stroke volume ratio (calculated from the left ventricular stroke volume and effective stroke volume). Left heart failure was observed in all these 8 patients, 7 of 8 patients showed additional right heart failure. Only 2 of the other 17 patients had signs of left heart failure. In the 8 patients with discrepant results, the roentgenographically determined heart volume was increased (1617 vs 1057 ml; 2p less than 0.001), left ventricular ejection fraction decreased (31 vs 60%; 2p less than 0.001), and mean pulmonary artery and right atrial pressure were elevated (38 vs 18 mm Hg; 2p less than 0.001; 11 vs 6 mm Hg; 2p less than 0.001). We conclude that in patients with aortic regurgitation, congestive heart failure associated with functional pulmonic and tricuspid regurgitation and geometric reasons can lead to a reduced sensitivity of the radionuclide left/right ventricular stroke volume ratio.     

A scintiphotographic method for measuring left ventricular ejection fraction in man without cardiac catheterization

A radioactive tracer method for the measurement of left ventricular ejection fraction in man without cardiac catheterization is described. The tracer (^99mtechnetium-labeled albumin) is injected intravenously. Images of the heart at end-systole and end-diastole are obtained using a scintillation camera and an electronic gate triggered by the patient's electrocardiogram. Each image is composed of 300,000 counts, representing a summation of 200 to 400 heartbeats at end-systole and end-diastole. An outline of the left ventricular free wall is drawn from each gated image. The position of the aortic and mitral valve planes is determined using a radionuclide angiogram obtained at the time of tracer injection. Left ventricular ejection fraction is calculated from the area and length of the long axis of the ventricular outline at end-systole and end-diastole. Determinations of ejection fraction in 20 patients using this tracer method were correlated with measurements obtained by contrast cineangiography with the following results: ejection fraction r = +0.92, P < 0.001; end-diastolic volume r = −0.76, P < 0.001; and end-systolic volume r = −0.75, P < 0.001.     

Assessment of left ventricular performance and myocardial viability using quantitative radioisotope techniques.

The diagnostic value of a combined radionuclide technique was compared with conventional angiocardiographic techniques in 60 patients with coronary artery disease. Quantitative 201Tl myocardial imaging combined with radionuclide angiocardiography using 99mTc-HSA provided a safe and accurate method for the assessment of left ventricular performance. The defects on the 201Tl images correlated with the severity of asynergy seen on the contrast ventriculogram. Static imaging alone distinguished hypokinetic from akinetic or dyskinetic areas. However, using both tracer techniques, akinesis could bedistinguished from dyskinesis. In patients with disturbed left ventricular function, cardiac transit times correlated with haemodynamic changes, and left ventricular ejection fraction was the most sensitive index. Thus, this combined radionuclide approach provides data for the evaluation of overall and regional wall function. A major advantage of this non-invasive auantitative technique is its applicability to the critically ill patient at the bedside.     

Evaluation of 99mTc-albumin dilution curve with simultaneous injection of 99mTc- and 131I-albumins.

A critical comparison of radiocardiograms with 99mTc- and 131I-albumins was made to determine whether or not 99mTc-albumin can be used as a tracer for measuring blood volume (BV) and cardiac output (CO). Simultaneous injection of both isotopes was given to twenty-two patients to obtain radiocardiograms for each by means of a single scintillation counter with two pulse height analyzers. Such method allows for the determination of the energy levels for both 99mTc and 131I. The radiocardiographic pattern was somewhat different between 99mTc- and 131I-radiocardiograms: The ratio of left to right peak height was 16% on the average lower in the 99mTc-radiocardiogram in the 131I-one. The reason for the lower ratio is explained by greater absorption of 99mTc-radioactivity within the soft tissue interposing between the scintillation probe and heart. The values for 99mtc-derived blood volume were 7.4% on the average larger than those for 131I-derived blood volume (p less than 0.01), although the correlation was excellent (r = 0.98, p less than 0.01). There was no systemic difference between cardiac output determined by 99mTc- and 131I-albumins since the overstimation of blood volume can compensate for the understimation of CO/BV by 99mTc-study. In view of its rapid extravasation, 99mTc-albumin is not so appropriate tracer for accurate measurements of BV and CO/BV, although it may be used for measurement of cardiac output.     

Assessment of left ventricular performance and myocardial viability using quantitative radioisotope techniques.

The diagnostic value of a combined radionuclide technique was compared with conventional angiocardiographic techniques in 60 patients with coronary artery disease. Quantitative 201Tl myocardial imaging combined with radionuclide angiocardiography using 99mTc-HSA provided a safe and accurate method for the assessment of left ventricular performance. The defects on the 201Tl images correlated with the severity of asynergy seen on the contrast ventriculogram. Static imaging alone distinguished hypokinetic from akinetic or dyskinetic areas. However, using both tracer techniques, akinesis could bedistinguished from dyskinesis. In patients with disturbed left ventricular function, cardiac transit times correlated with haemodynamic changes, and left ventricular ejection fraction was the most sensitive index. Thus, this combined radionuclide approach provides data for the evaluation of overall and regional wall function. A major advantage of this non-invasive auantitative technique is its applicability to the critically ill patient at the bedside.     

Volumetric evaluation of aortic regurgitation by combined first-pass/equilibrium radionuclide ventriculography

In 16 men with normal valvular function (group 1) and 23 men and one woman with isolated aortic regurgitation (group 2) effective stroke was determined by first-pass radionuclide ventriculography. Total left ventricular stroke volume was derived from equilibrium radionuclide ventriculography using a geometric approach for the end-diastolic volume multiplied by the ejection fraction. The difference between the two stroke volumes as a fraction of total left ventricular stroke volume was taken as radionuclide regurgitant fraction. Radionuclide lv/rv stroke count ratio was calculated as the ratio of end-diastolic-end-systolic count-rate differences from the left and right ventricles. All patients underwent left heart catheterization. Angiographic regurgitant fraction was evaluated by the method of Sandler and Dodge in 16 patients of group 2. In the others, aortic regurgitation was quantified in 5 grades of severity. Group l was classified correctly by both radionuclide regurgitant fraction and lv/rv stroke count ratio (specificity 100%). In group 2 the radionuclide regurgitant fraction was elevated in all (from + 20% to +88%, sensitivity 100%), radionuclide lv/rv stroke count ratio in 19 of 24 cases (from 0.6 to 5.6, sensitivity 79%). The angiographic regurgitant fraction correlated well with the radionuclide regurgitant fraction (r = 0.78), whereas no significant correlation was found between the angiographic stroke volume ratio (i.e. left ventricular stroke volume/cardiac output per beat) and radionuclide stroke count ratio (r = 0.10) due to the high rate of false-negative results of the latter method.(ABSTRACT TRUNCATED AT 250 WORDS)     

Simultaneous measurement of myocardial perfusion and ventricular function during exercise from a single injection of technetium-99m sestamibi in coronary artery disease

New radiopharmaceuticals permit simultaneous assessment of myocardial perfusion and left ventricular function using a single tracer injection. The purpose of this study was to quantitate the relation between myocardial perfusion and function at rest and during exercise in patients with documented coronary artery disease (CAD). A rest first-pass radionuclide angiocardiogram (RNA) was recorded in 51 patients with CAD during injection of 10 mCi of technetium-99m (Tc-99m) sestamibi, and tomographic perfusion images were obtained 60 minutes later. A treadmill test was then performed, and on attainment of an exercise end point a second first-pass RNA was recorded with 30 mCi of Tc-99m sestamibi. Tomographic images reflecting myocardial perfusion during exercise were obtained 1 hour later. Tomographic perfusion defect size, quantified using modifications of the Cedars-Sinai program, correlated directly with end-systolic volume and inversely with ejection fraction at rest and during exercise. However, perfusion defect size often varied widely in patients with similar left ventricular function. This independence between measurements of perfusion and function suggests that simultaneous assessment of the 2 physiologic variables could improve the diagnostic and prognostic information of radionuclide tests.     

Gated radionuclide angiographic evaluation of valve regurgitation

Gated radionuclide angiography is a new noninvasive technique that can be used to calculate the ratio of left and right ventricular stroke volumes. This stroke volume ratio, which must be unity in normal subjects, increases in patients with aortic or mitral regurgitation in direct proportion to the degree of left ventricular volume overload, provided no shunts or regurgitant right heart lesions are present. In 22 patients with aortic or mitral regurgitation there was excellent correlation between the stroke volume ratio determined with gated radionuclide angiography and with standard quantitative catheterization methods (r = 0.79). Measurement of valve regurgitation with this radionuclide method also correlated well with data obtained from semiquantitative aortic root or left ventricular cineangiography (r = 0.72). Twenty-one of the 22 patients with valve regurgitation had an abnormally elevated stroke volume ratio, thereby suggesting that gated radionuclide angiography may be useful in detecting or excluding hemodynamically significant valve regurgitation.     

New somatostatin analogue 99mTc-HYNIC-TOC in the scintigraphic diagnosis of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) origins from parafollicular cells and secretes calcitonin. It accounts for 5-10% of malignant thyroid tumors. In MTC, radionuclide imaging is employed as complementary method in addition to the routine radiological procedures. Especially, scintigraphy using labelled peptides that specifically bind to the somatostatin receptors is used. Recently a somatostatin analogue labelled with 99mTc (99mTc-HYNIC-TOC) was synthetized. As shown in previous studies, it has favourable pharmacokinetic and clinical characteristics. Aim of this study was to evaluate the utility of 99mTc-HYNIC-TOC in the radionuclide imaging in patients in different stages of MTC. 32 patients in following stages of the disease were studied: evaluation before thyroidectomy (6 patients), remission after surgical treatment (5 patients), stagnation or recurrence after surgical therapy (21 patients). The classification was based on the calcitonin concentrations. The study group included 19 women and 13 men aged 14 to 83 years. Whole body scintigraphy was performed twice: 2 and 4 hours after injection of 20 mCi 99mTc-HYNIC-TOC using dual-head Varicam gamma camera (Elscint). The obtained results were compared to the clinical data and other employed imaging modalities. The scintigraphy using 99mTc-HYNIC-TOC showed 20 true positive, 4 true negative, 1 false positive and 7 false negative results. The sensitivity of this method was 74,1% and specificity - 80,0%. These results are better than those obtained by other authors using other imaging methods. The current study showed high utility of the new peptide tracer in the diagnosis of MTC. Its diagnostic accuracy allows us to recommend it for diagnosis and treatment planning (including radionuclide therapy) in patients with MTC on the routine basis.     

Assessment of function of contractile segments in patients with left ventricular aneurysms by quantitative first pass radionuclide ventriculography. Haemodynamic correlation at rest and exercise.

Thirteen patients with left ventricular aneurysms complicating myocardial infarction were studied by contrast angiography and by first pass radionuclide ventriculography. The ejection fraction of the contractile segment (EFCS) was measured from both studies using a double hemishperoid model, and the values correlated closely. There was a monotonic relation between EFCS and stroke volume index measured from thermodilution cardiac outputs carried out simultaneously with the radionuclide study. When radionuclide ventriculography was performed at submaximal supine exercise, changes in EFCS paralleled changes in the total left ventricular ejection fraction in 10 of the 13 cases. In nine patients, changes in EFCS paralleled changes in stroke volume index and the relation between EFCS and stroke volume index was maintained at exercise. After administration of the vasodilator isosorbide dinitrate to 12 patients, repeat exercise radionuclide ventriculography showed an improvement in left ventricular ejection fraction and in eight patients EFCS improved. First pass radionuclide ventriculography can accurately estimate EFCS, which may be an important factor in predicting the likely response to aneurysmectomy. Changes in EFCS on exercise are reflected in changes in total left ventricular ejection fraction and stroke volume index. Isosorbide dinitrate may improve contractile segment function on exercise.     

Nongeometric determination of right ventricular volumes from equilibrium blood pool scans

It has previously been shown that left ventricular volumes can be measured accurately from radionuclide gated blood pool scintigrams by quantttating the background-corrected and volume-normalized ventricular activity at end-diastole and end-systole. To determine if this same technique can be applied to the calculation of right ventricular volumes, simultaneous measurements of right ventricular stroke volume were performed using gated scintigraphy and the thermodilution technique in 60 patients without clinical or hemodynamic evidence of right-sided regurgitation. Three techniques for the acquisition of the radionuclide studies were evaluated. The best correlation between scintigraphic and thermodilution determinations of stroke volume was obtained for studies acquired with a 25 ° rotating slant hole collimator positioned in a 10 to 15 ° left anterior oblique projection with the collimator slant directed toward the cardiac apex along the axis of the interventricular septum: Thermodilution stroke volume = 4.2 (scintigraphic stroke volume) + 10.3 ml (correlation coefficient [r] = 0.88; standard error of the estimate = 9.3 ml; probability [p] < 0.0001). This scintigraphic acquisition technique was superior to (1) a straight bore collimator positioned in a septal projection (30 to 50 ° left anterior oblique with 15 ° caudal tilt), and (2) a 25 ° slant hole collimator positioned in a similar septal projection with the collimator slant directed caudally. This method was evaluated prospectively in an additional 14 patients, and there was excellent agreement between stroke volumes obtained with thermodilution and scintigraphic methods (r = 0.96, p < 0.001). In addition, measurements of right ventricular ejection fraction by the equilibrium method agreed closely with those obtained with a gated first pass technique (r = 0.94, p < 0.001, n = 14). With use of the scintigraphic right ventricular ejection fraction and the relation between scintigraphic and thermodilution measurements of right ventricular stroke volume, right ventricular end-diastolic and end-systolic volumes can be estimated. Thus, nongeometric radionuclide techniques may be used for the quantitation of right ventricular volumes.     

Measurement of aortic and mitral regurgitation by gated cardiac blood pool scans.

A simple, noninvasive radionuclide technique which measures the severity of valvular regurgitation has been developed. The technique compares right and left ventricular stroke volume indices (change in counts between diastole and systole over the left and right ventricles) from 45 degrees LAO gated cardiac blood pool scans. In 14 control subjects, the left-to-right ventricular stroke index ratio was near unity (1.15 +/- 0.15 [SD]). In 26 patients with mitral and/or aortic regurgitation it was larger (range 1.36--5.30, mean 2.44). Comparison between the stroke index ratio and qualitative angiographic estimates of regurgitation revealed good agreement (F = 45.5, p less than 0.001). Gated cardiac blood pool scans permit noninvasive assessment of the severity of valvular regurgitation.     

Evaluation of myocardial viability in asymptomatic patients early after infarction with perfusion/metabolism single-photon-emission computed tomographic imaging and dobutamine echocardiography

OBJECTIVE: To study the impact of detection of viability of myocardium in asymptomatic patients early (3-10 days) after Q-wave myocardial infarction on segmental recovery of left ventricular function after elective revascularization. METHODS: Patients were studied with low-dose dobutamine echocardiography (LDDE) and single photon-emission computed tomography with 99mTc sestamibi and [18F]-fluorodeoxyglucose (FDG) imaging. Viability of myocardium was defined as detection of improvement in segmental thickening of left ventricle by LDDE (versus baseline echocardiographic data), uptake of 99mTc sestamibi > 50% of maximum counts, uptake of [18F]-FDG > 50% of maximum normal, combined uptake of 99mTc sestamibi or [18F]-FDG > 50% of normal maximum, uptake of [18F]-FDG > 50% or mismatched pattern (uptake of [18F]-FDG greater than that of 99mTc sestamibi). Functional recovery was defined as improvement of segmental thickening of left ventricle detected at follow-up 8 weeks after infarction (versus baseline resting echocardiographic data). Interpretation of the tests was blinded with respect to the angiographic data and the results of the alternative method. RESULTS: In total 18 patients with 133 left-ventricle segments with abnormal contractile function at baseline were analysed; 29% were hypocontractile and 71% were noncontractile. Examination with LDDE showed that 18% of the segments had normal contractility and 26% were hypocontractile; the respective percentages were 29 and 28% according to follow-up resting echocardiography. Radionuclide tests for viability of myocardium gave positive results in 57% (uptake of [18F]-FDG > 50%) and 62% (uptake of 99mTc sestamibi > 50%) of cases. With respect to segmental analysis, there was a 25-27% positive concordance, a 24-27% negative concordance, and a 48-50% discordance between the LDDE and the radionuclide definitions of viability of myocardium. Additionally, there was no significant difference among sensitivities and specificities for the definitions of viability. The sensitivity was 69% for the uptake of 99mTc sestamibi > 50% criterion, and the highest specificity was 66% for the LDDE. Incorporation of imaging with [18F]-FDG into the analysis yielded a marginally higher sensitivity of 71% for the criterion of uptake of [18F]-FDG or 99mTc sestamibi > 50%, versus imaging with the 99mTc sestamibi alone. CONCLUSION: LDDE was more specific and radionuclide imaging more sensitive for detection of viability of myocardium in asymptomatic patients early after infarction. Possibly defective myocardial metabolization of glucose in the period early after infarction and the specific LDDE protocol applied account for the limited benefit of these studies in terms of facilitating prediction of segmental functional recovery after revascularization in this clinical setting.     

Low Sensitivity of Bone Scintigraphy in Detecting Phe64Leu Mutation-Related Transthyretin Cardiac Amyloidosis

ObjectivesThe aim of this study was to assess the diagnostic accuracy of bone scintigraphy in a large multicenter cohort of patients with cardiac amyloidotic involvement and Phe64Leu transthyretin (TTR) mutation.BackgroundDiagnostic accuracy of bone scintigraphy for transthyretin-related cardiac amyloidosis (TTR-CA) is considered extremely high, enabling this technique to be the noninvasive diagnostic standard for TTR-CA. Nevertheless, this approach has not been systematically validated across the entire spectrum of TTR mutations.MethodsA total of 55 patients with Phe64Leu TTR mutation were retrospectively analyzed and evaluated between 1993 and 2018 at 7 specialized Italian tertiary centers. Cardiac involvement was defined as presence of an end-diastolic interventricular septum thickness ≥12 mm, without other possible causes of left ventricular hypertrophy (i.e., arterial hypertension or valvulopathies). A technetium-99m (99mTc)–diphosphonate (DPD) or 99mTc–hydroxyl-methylene-diphosphonate (HMDP) bone scintigraphy was reviewed, and visual scoring was evaluated according to Perugini’s method.ResultsAmong 26 patients with definite cardiac involvement, 19 underwent 99mTc-DPD or 99mTc-HMDP bone scintigraphy. Of them, 17 (89.5%) patients had low or absent myocardial bone tracer uptake, whereas only 2 (10.5%) showed high-grade myocardial uptake. The sensitivity and the accuracy of bone scintigraphy in detecting TTR-CA were 10.5% and 37%, respectively. Patients with cardiac involvement and low or absent bone tracer uptake were similar to those with high-grade myocardial uptake in terms of age, sex, and electrocardiographic and echocardiographic findings.ConclusionsThe sensitivity of bone scintigraphy (DPD and HMDP) in detecting TTR-CA is extremely low in patients with Phe64Leu TTR mutation, suggesting the need to assess diagnostic accuracy of bone scintigraphy to identify cardiac involvement across a wider spectrum of TTR mutations.     

Measurement of microvascular permeability to small solutes in man: limitations of the technique

STUDY OBJECTIVE--The aim was to evaluate the limitation on the measurement of the clearance rate of a small solute, 99mTc DTPA, from intravascular to extravascular spaces imposed by diffusion of the solute back into blood during the period of measurement. DESIGN--The technique for measuring clearance also generates the regional plasma volume from which the solute is cleared. Back diffusion would result in an overestimation of this plasma volume. By applying the same technique to 99mTc labelled human serum albumin, which is not cleared over the period of measurement, a separate estimate of plasma volume can be made. SUBJECTS--The subjects were eight patients undergoing routine 99mTc DTPA renography for suspected outflow obstruction. MEASUREMENTS AND RESULTS--The ratio of plasma volumes based respectively on 99mTc DTPA and human serum albumin in a region of interest below the kidney was 1.04 (SD 0.09). The technique requires a region of interest over the cardiac blood pool from which the blood level of 99mTc DTPA is continuously monitored. When a correction was made for extravascular 99mTc DTPA in this cardiac region of interest, the ratio was unchanged: 0.97 (0.12). CONCLUSION--The technique is capable of measuring the clearance of 99mTc DTPA although, because of its small molecular size, the transfer rate is blood flow dependent, ie, its PS product is greater than its clearance.     

Combined first-pass and equilibrium radionuclide ventriculography and comparison with left ventricular/right ventricular stroke count ratio in mitral and aortic regurgitation

Effective and total left ventricular (LV) stroke volume were assessed in 31 patients with verified aortic or mitral regurgitation, or both, and in 22 patients with normal valvular function using combined first-pass and equilibrium radionuclide ventriculography. The difference between these 2 volumes as a fraction of LV stroke volume was taken as the radionuclide regurgitant fraction. The results were compared with the LV/right ventricular (RV) stroke count ratio and with the angiographic regurgitant fraction according to the method of Sandler and Dodge. Radionuclide regurgitant fraction derived from 2 determinations with a time interval of 1 week showed good reproducibility (n = 15, r = 0.96, SEE = 9.1). Sensitivity was 100% for radionuclide regurgitant fraction and 87% for LV/RV stroke count ratio at equal specificity (100%). Radionuclide regurgitant fraction was more sensitive, especially in severely ill patients, in whom additional RV volume overload led to false-low or false-negative ratios. Angiographic and radionuclide regurgitant fraction showed linear correlation (r = 0.79, p less than 0.001). In contrast, because 5 patients had RV volume overload, only a weak correlation could be noticed between angiography and LV/RV stroke count ratio (r = 0.47, p less than 0.05). Excluding these patients, correlation substantially improved (r = 0.74, p less than 0.001). The combination of first-pass and equilibrium radionuclide ventriculography is a sensitive, specific and well reproducible method for the evaluation of mitral and aortic regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)