Accuracy of 4 different algorithms for the analysis of tomographic radionuclide ventriculography using a physical, dynamic 4-chamber cardiac phantom

Various automatic algorithms are now being developed to calculate left ventricular (LV) and right ventricular (RV) ejection fraction from tomographic radionuclide ventriculography. We tested the performance of 4 of these algorithms in estimating LV and RV volume and ejection fraction using a dynamic 4-chamber cardiac phantom.

METHODS

We developed a realistic physical, dynamic 4-chamber cardiac phantom and acquired 25 tomographic radionuclide ventriculography images within a wide range of end-diastolic volumes, end-systolic volumes, and stroke volumes. We assessed the ability of 4 algorithms (QBS, QUBE, 4D-MSPECT, and BP-SPECT) to calculate LV and RV volume and ejection fraction.

RESULTS

For the left ventricle, the correlations between reference and estimated volumes (0.93, 0.93, 0.96, and 0.93 for QBS, QUBE, 4D-MSPECT, and BP-SPECT, respectively; all with P < 0.001) and ejection fractions (0.90, 0.93, 0.88, and 0.92, respectively; all with P < 0.001) were good, although all algorithms underestimated the volumes (mean difference [+/-2 SDs] from Bland-Altman analysis: -39.83 +/- 43.12 mL, -33.39 +/- 38.12 mL, -33.29 +/- 40.70 mL, and -16.61 +/- 39.64 mL, respectively). The underestimation by QBS, QUBE, and 4D-MSPECT was greater for higher volumes. QBS, QUBE, and BP-SPECT could also be tested for the right ventricle. Correlations were good for the volumes (0.93, 0.95, and 0.97 for QBS, QUBE, and BP-SPECT, respectively; all with P < 0.001). In terms of absolute volume estimation, the mean differences (+/-2 SDs) from Bland-Altman analysis were -41.28 +/- 43.66 mL, 11.13 +/- 49.26 mL, and -13.11 +/- 28.20 mL, respectively. Calculation of RV ejection fraction correlated well with true values (0.84, 0.92, and 0.94, respectively; all with P < 0.001), although an overestimation was seen for higher ejection fractions.

CONCLUSION

Calculation of LV and RV ejection fraction based on tomographic radionuclide ventriculography was accurate for all tested algorithms. All algorithms underestimated LV volume; estimation of RV volume seemed more difficult, with different results for each algorithm. The more irregular shape and inclusion of a relatively hypokinetic RV outflow tract in the right ventricle seemed to cause the greater difficulty with delineation of the right ventricle, compared with the left ventricle.

Validation of planar and tomographic radionuclide ventriculography by a dynamic ventricular phantom

Although there is increasing interest in the automatic processing of tomographic radionuclide ventriculography (TRV) studies, validation is mainly limited to a comparison of TRV results with data from planar radionuclide ventriculography (PRV) or gated perfusion single photon emission computed tomography (SPECT). The aim of this study was to use a dynamic physical cardiac phantom to validate the ejection fraction (EF) and volumes from PRV and TRV studies. A new dynamic left ventricular phantom was constructed and used to obtain 21 acquisitions in the planar and tomographic mode. The directly measured volumes and EFs of the phantom during the acquisitions were considered as the gold standard for comparison with TRV and PRV. EFs were calculated from PRV by background-corrected end-diastolic and end-systolic frames. Volumes and EFs were calculated from TRV by region growing with different lower thresholds to search for the optimal threshold. EF from PRV correlated significantly with the real EF (r=0.94, P=0.00). The optimal threshold value for volume calculation from TRV in 336 cases was 50% (r=0.98, P=0.00) yielding the best slope after linear regression. When considering these calculated end-diastolic and end-systolic volumes, EF correlated well (r=0.99, P=0.00) with the real EF, and this correlation was significantly (P=0.04) higher than that of the EF from PRV. Our experiments prove that EF measured by TRV yields more accurate results compared with PRV in dynamic cardiac phantom studies.

Single crystal biplane equilibrium radionuclide ventriculography: an improved planar imaging technique

Radionuclide ventriculography in the best septal view is an established method to assess both global and regional ventricular function. Additional projections may be used to delineate the wall motion of inferior myocardial segments. Radionuclide ventriculography was performed in 65 patients using both a single plane (in the best septal view) and a biplane technique. The biplane collimator allowed simultaneous assessment in two planes 40 degrees apart, allowing simultaneous visualization of all four myocardial walls. Seventeen patients with regional wall motion abnormalities were detected with the single plane best septal view and a further 18 patients with impaired wall motion were identified with the biplane collimator (51% of the abnormal ventricles). The additional abnormal segments were seen in only the steep lateral projection. Left ventricular ejection fraction estimation with the biplane technique remains highly reproducible and correlates well with that derived from the best septal view. Biplane radionuclide ventriculography improves the detection of inferior wall motion abnormalities at no expense of time, and offers the possibility of performing two-view stress ventriculography with inotropic agents.

Continuous ambulatory radionuclide monitoring of left ventricular function: effect of body position during ergometer exercise

We assessed the reliability of a continuous ambulatory radionuclide monitoring system (the VEST system, Capintec, Inc., Ramsey, NJ) for measurement of left ventricular performance during exercise in the upright and supine positions.

METHODS

Sixteen healthy male volunteers (aged 32-46 yr; mean age 37 +/- 4 yr) were studied. All volunteers underwent ergometer exercise testing in both the upright and supine positions, and left ventricular performance was determined with the VEST system.

RESULTS

The resting heart rate, systolic blood pressure, pressure rate product, relative end-diastolic volume, relative end-systolic volume and left ventricular ejection fraction (LVEF) all showed no differences between the upright and supine positions. At peak exercise, the heart rate, systolic blood pressure and pressure rate product showed no differences between the upright and supine positions. In the upright position at peak exercise the relative end-diastolic volume was increased (83% +/- 9% to 91% +/- 11%, p < 0.001); the relative end-systolic volume remained unchanged (34% +/- 3% to 33% +/- 15%), and LVEF was significantly increased from 58% +/- 6% to 66% +/- 11% (p < 0.01). In the supine position at peak exercise, the relative end-diastolic volume remained unchanged (85% +/- 5 to 83% +/- 7%), the relative end-systolic volume was increased (35% +/- 5% to 43% +/- 13%, p < 0.01), and LVEF was decreased from 58% +/- 5% to 48% +/- 17% (p < 0.01). These results indicated inferior data collection by the VEST system in the supine position.

CONCLUSION

Since the detector of the VEST system may be too small, the data collection is impaired during exercise in the supine position by shifting the heart with deep respiration. The VEST system is very useful for determining left ventricular performance when applied in the sitting or upright position. However, in the supine position during exercise, the use of the VEST system should be avoided because it might indicate an artifactual deterioration of left ventricular performance.

Monitoring of left ventricular ejection fraction with a miniature, nonimaging nuclear detector: accuracy and reliability over time with special reference to blood labeling

BACKGROUND

The purpose of this study was to determine the accuracy of determinations of left ventricular ejection fraction (LVEF) by a nonimaging miniature nuclear detector system (Cardioscint) and to evaluate the feasibility of long-term LVEF monitoring in patients admitted to the coronary care unit, with special reference to the blood-labeling technique.

METHODS AND RESULTS

Cardioscint LVEF values were compared with measurements of LVEF by conventional gamma camera radionuclide ventriculography in 33 patients with a wide range of LVEF values. In 21 of the 33 patients, long-term monitoring was carried out for 1 to 4 hours (mean 186 minutes), with three different kits: one for in vivo and two for in vitro red blood cell labeling. The stability of the labeling was assessed by determination of the activity of blood samples taken during the first 24 hours after blood labeling. The agreement between Cardioscint LVEF and gamma camera LVEF was good with automatic background correction (r = 0.82; regression equation y = 1.04x + 3.88) but poor with manual background correction (r = 0.50; y = 0.88x - 0.55). The agreement was highest in patients without wall motion abnormalities. The long-term monitoring showed no difference between morning and afternoon Cardioscint LVEF values. Short-lasting fluctuations in LVEFs greater than 10 EF units were observed in the majority of the patients. After 24 hours, the mean reduction in the physical decay-corrected count rate of the blood samples was most pronounced for the two in vitro blood-labeling kits (57% +/- 9% and 41% +/- 3%) and less for the in vivo blood-labeling kit (32% +/- 26%). This "biologic decay" had a marked influence on the Cardioscint monitoring results, demanding frequent background correction.

CONCLUSION

A fairly accurate estimate of LVEF can be obtained with the nonimaging Cardioscint system, and continuous bedside LVEF monitoring can proceed for hours with little inconvenience to the patients. Instability of the red blood cell labeling during long-term monitoring necessitates frequent background correction.

Effects of short-term aminophylline administration on cardiac functional reserve in patients with syndrome X

OBJECTIVES

This study sought to evaluate the effect of adenosine receptor blockade by aminophylline on cardiac functional reserve in patients with syndrome X.

BACKGROUND

Aminophylline may have a potentially antiischemic effect through the inhibition of adenosine and, thus, the coronary steal phenomenon in patients with syndrome X.

METHODS

A single-blind, placebo-controlled study of an intravenous infusion of aminophylline (6 mg/kg body weight over 15 min) or placebo (20 ml of saline solution over 15 min) was performed during continuous radionuclide monitoring of left ventricular ejection fraction in 12 patients performing supine bicycle ergometric exercise.

RESULTS

Aminophylline increased exercise time (aminophylline 400 s vs. placebo 355 s, p < 0.01), decreased degree of ST segment depression (aminophylline 1.6 mm vs. placebo 2.4 mm, p < 0.01) and either abolished (seven patients) or diminished (five patients) chest pain during exercise. Aminophylline also increased left ventricular ejection fraction at rest (aminophylline 66.5% vs. placebo 62.3%, p < 0.05) but did not improve its deterioration at peak exercise (aminophylline 60.1% vs. placebo 56.6%, p = NS) or shorten the abnormally prolonged interval between the end of exercise and the overshoot (aminophylline 115 s vs. placebo 130 s, p = NS).

CONCLUSIONS

Aminophylline infusion increases ischemic threshold and prolongs exercise duration in patients with syndrome X. It is hypothesized that aminophylline acts by inhibiting the coronary steal phenomenon through adenosine receptor blockade. It does not improve the deterioration in left ventricular function at peak exercise or the delayed response in ejection fraction in the recovery period, presumably because the beneficial effects of aminophylline that result from the redistribution of coronary blood flow are limited.

Ambulatory monitoring of left ventricular function during cardiopulmonary exercise tests in normal sedentary subjects

Ambulatory monitoring (VEST) of left ventricular (LV) function is a useful and accurate method to measure cardiac function during exercise and rest. The aim of this study was to evaluate LV response to exercise in normal sedentary subjects.

METHODS

Ten normal sedentary subjects underwent continuous ambulatory monitoring of LV function by VEST during upright bicycle exercise associated with combined analysis of pulmonary gas exchange. All parameters of LV function were measured in control conditions at rest, at the anaerobic threshold (point of nonlinear increase in ventilation relative to oxygen uptake) and at peak oxygen uptake (peak VO2).

RESULTS

Heart rate and cardiac output significantly increased from control conditions to anaerobic threshold (p < 0.001) and from anaerobic threshold to peak VO2 (p < 0.001). Ejection fraction, end diastolic volume and stroke volume significantly increased from control conditions to anaerobic threshold (p < 0.001), showing no significant change from anaerobic threshold to peak VO2. Finally, end-systolic volume significantly decreased from control conditions to anaerobic threshold (p < 0.001), showing no significant change from anaerobic threshold to peak VO2.

CONCLUSION

VEST is particularly useful in the evaluation of cardiac response to exercise in normal sedentary subjects, providing a better understanding of the spectrum of the normal LVEF response to exercise. Our data demonstrate that ejection fraction response to exercise is variable after anaerobic threshold, and a uniform increase is not necessarily expected in normal sedentary subjects.

Ambulatory monitoring of left ventricular function in patients with Parkinson's disease and postural hypotension

Left ventricular (LV) function was continuously monitored using a radionuclide detector (VEST) after intravenous injection of 25 mCi technetium-99m labelled red blood cells in nine patients with Parkinson's disease and postural hypotension (group 1) and ten patients with Parkinson's disease but without postural hypotension (group 2). LV function and blood pressure were monitored in the supine position for 15 min (period A), upon changing posture from the supine to the upright position for 10 min (period B), and upon returning to the supine position for 10 min (period C). In group 1, the passage from period A to period B induced a significant decrease in end-diastolic volume, end-systolic volume and ejection fraction (all P < 0.01). In group 2, ejection fraction increased (P < 0.05) upon changing posture from the supine to the upright position. Ejection fraction (F = 33, P < 0.01), end-diastolic volume (F = 9, P < 0.05) and end-systolic volume (F = 10, P < 0.05) were significantly different between the two groups. In group 1, stroke volume, cardiac output and vascular peripheral resistance decreased from period A to period B (all P < 0.001). In group 2, no changes in stroke volume, cardiac output and vascular peripheral resistance were observed from period A to period B. All parameters were similar in the two groups during the periods A and C. Upon changing posture from the supine to the upright position, patients with Parkinson's disease and postural hypotension showed marked changes in parameters of LV function induced by vascular abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

The application of a non-imaging nuclear probe system to the critically ill: laboratory validation and a clinical trial

Non-imaging nuclear probe systems have been available for bedside monitoring of left ventricular function since the early 1970s. The purpose of this study was to evaluate a recently developed system, the Cardioscint (Oakfield Instruments, Oxford, UK), both in the laboratory and clinically prior to its application in the critically ill on the intensive care unit. The probe system was stable at body temperature for prolonged periods and its count rate capability was adequate for those encountered clinically. An adequate period of data acquisition was shown to be important because random isotope decay produces a significant noise at these count rates. Left ventricular ejection fraction in patients with symmetrical ventricular contraction agree closely with the results obtained with radionuclide ventriculography (mean difference = 0.98%, S.D. = 2.8%, n = 30). However, in patients with asymmetrical ventricular contraction the agreement is poor (mean difference = -3.0%, S.D. = 6.2%, n = 10).

Clinical validation of a radionuclide detector to measure ejection fraction in critically ill patients

The use of a new non-imaging nuclear probe (Cardioscint) capable of continuous online monitoring of left ventricular function is described in critically ill patients undergoing mechanical ventilation. Ejection fraction, measured by the Cardioscint, was compared with that measured by echocardiography. The mean difference was -1.1% (95% confidence interval -2.9 to +0.6%). Mean difference +/- 2 SD was +10.6 to -12.8% (95% confidence intervals +7.5 to 13.6% and -15.8 to -9.0%, respectively). Examples of fluid loading and inotropic support showed comparable changes in stroke counts measured by the Cardioscint and stroke index measured by thermodilution. The Cardioscint is a practical bedside method for continuous or repeated measurement of ejection fraction and for assessing the response to therapeutic interventions in critically ill patients.

Myocardial alterations during hemodialysis: insights from new noninvasive technology

Eighteen patients with chronic renal failure had their cardiac status monitored during hemodialysis (HD). Ten studies were carried out using an ambulatory nuclear vest to assess ejection fraction (EF), heart rate (HR), relative end-systolic (ESV) and end-diastolic (EDV) volumes every 60 s. A total of 36 episodes of EF falls occurred in 9 patients, all asymptomatic. These EF falls were associated with a rise in ESV, while HR, BP, and EDV remained unchanged. The EF falls correlated best with the volume of ultrafiltrate removed. Ten patients had on-line ST-segment monitoring with sestamibi injection either at the time of ST depression (STD) or at the end of dialysis, if no STD occurred, in order to detect the presence of transient ischemia. Seven of ten patients had perfusion defects after dialysis, with STD occurring in 3 of 10 patients. Predialysis imaging was available in only 8 of 10 patients, and 6 of these patients had perfusion defects. Changes in perfusion defects were not significantly different in the 3 patients with STD compared with those without STD. EF falls and perfusion defects are common in HD patients even in the absence of known coronary artery disease; however, ST segment monitoring is not a sensitive tool for its detection. These changes in function and perfusion may represent myocardial ischemia and contribute to the high incidence of cardiovascular morbidity and mortality in this patient population.

Left ventricular systolic and diastolic function measurements using an ambulatory radionuclide monitor: effects of different time averaging on accuracy

The accuracy of an ambulatory radionuclide detector (VEST) for left ventricular systolic (ejection fraction, EF) and diastolic (peak filling rate, PFR) measurements was assessed at different time averaging of the nuclear and electrocardiographic data. Fifty-one patients, in a total of 67 studies, underwent equilibrium radionuclide angiography (RNA) immediately before a VEST study. VEST data were analyzed using single-beat analysis and different time averaging of 5, 10, 15, 30 and 60 sec. Agreement between VEST and RNA in estimating EF and PFR was evaluated by computing limits of agreement (LA). These were computed as 1.96 times the s.d. of the mean differences between the two methods, expressed in the same unit as EF and PFR. Differences between the two methods were plotted against their mean, allowing investigation of any possible relationship between measurement error and the true value (whose best estimate is the mean between the two methods). The entire statistical analysis was repeated at each different time averaging. LAs for EF measurement by VEST were -10.4:8.8 (single-beat analysis), -11.2:9.9 (5-sec averaging), -5.4:4.8 (10-sec averaging), -4.9:4.5 (15-sec averaging), -6.2:5.6 (30-sec averaging), -6.9:4.5 (60-sec averaging). Results indicate good agreement between VEST and RNA in measuring EF, at least for time averaging > or = 10 sec. LAs for PFR ranged from -0.6:0.6 (single beat) to -1.0:0.6 (60-sec averaging), which was considered a clinically acceptable agreement between VEST and RNA. No relationship between measurement error and true value was found either for EF and PFR.

Accuracy and repeatability of left ventricular systolic and diastolic function measurements using an ambulatory radionuclide monitor

The accuracy and repeatability of a new ambulatory radionuclide detector (VEST) for left ventricular systolic (ejection fraction) and diastolic (peak filling rate) measurements were assessed. Seventeen patients underwent equilibrium radionuclide angiography immediately before and immediately after a VEST study. The accuracy was evaluated at the beginning and at the end of the VEST studies. Limits of agreement for the ejection fraction were -1%:2% at the beginning of the VEST study and -4%:4% at the end. Limits of agreement for the peak filling rate were -0.6:0.6 at the beginning of the VEST study and -0.7:0.5 at the end. For both measurements the limits of agreement were well within the clinical range. Repeatability was evaluated in a second group of 11 patients who underwent VEST studies in 2 separate days. The coefficient of repeatability (twice the standard deviation of the differences between the 2 studies) was 13 for the ejection fraction and 0.4 for the peak filling rate. Thus, the VEST is an accurate and repeatable method to measure both the ejection fraction and peak filling rate.

Left ventricular perfusion and performance from a single radiopharmaceutical and one camera

To test the hypothesis that a small field of view portable multicrystal scintillation camera can perform stress/rest combined LV function by first-pass and perfusion studies using 99mTc-teboroxime, 26 patients with positive stress thallium studies within 2 wk and 8 healthy volunteers were studied. A 241Am point source marker over the sternum was used for motion correction. Dynamic dual-isotope (99mTc/241Am) acquisition was performed following injection of 15.6 +/- 2.3 mCi of 99mTc-teboroxime at peak treadmill exercise. Two minutes later (blood-pool clearance), while still standing on the flat treadmill, 3-4 40-sec planar images were acquired. One hour later patients were reinjected with 22.7 +/- 3.4 mCi of 99mTc-teboroxime while standing in front of the camera and the same dynamic/static acquisition protocol repeated. The planar images were interpolated from a 20 x 20 matrix to a 160 x 160 matrix, a sharpening filter and an interpolative background subtraction algorithm applied. The scans were divided into segments, each scored as normal, reversible and fixed. The agreement with thallium imaging for identifying an abnormal scan was 24/26 (92%) and for identifying abnormal vascular territories was 43/52, (83%). Fourteen patients had exercise LVEF less than 50% and all had either prior myocardial infarction, myocardial infarction plus ischemia or LAD ischemia. Diagnostic planar perfusion images and exercise LVEF can be acquired in less than 4 min using 99mTc-teboroxime and a portable multicrystal scintillation camera.

Exercise response assessed by continuous monitoring of ventricular function in patients with coronary bypass operations

The response of left ventricular function during exercise and recovery after exercise was assessed in 35 patients with coronary artery bypass grafting before and after the operation by means of a continuous ventricular function monitor, which records serial beat-to-beat radionuclide data and calculates left ventricular ejection fractions every 20 seconds. The mean ejection fraction decreased with graded bicycle exercise from 48% +/- 9% to 41% +/- 11% (p less than 0.001) before operation but increased with exercise from 50% +/- 9% to 55% +/- 11% (p less than 0.001) after operation. Cardiac response was divided into four types with respect to the profiles of the ejection fractions during exercise. Type A continued to increase; type B initially increased but then decreased in late exercise stages; type C did not change significantly; type D continued to decrease. Most patients had type C or D responses before operation but type A after operation. Seven patients with occluded grafts or ungrafted coronary arteries had type B or D responses. Three patients with complete revascularization, including an internal thoracic artery and saphenous vein grafts, had type B responses. Three patients with extensive infarction and poor left ventricular function showed type C. In the early recovery period after exercise, most patients had an "overshoot" elevation of ejection fraction. The mean value increased from 59% +/- 10% before operation to 64% +/- 11% after operation (p less than 0.01). The recovery time after exercise was reduced from 2.8 minutes before operation to 1.8 minutes after operation (p less than 0.001). The continuous ventricular function monitor elucidated changes in left ventricular function both during exercise and recovery after exercise, as well as unmasking abnormalities in left ventricular function after coronary bypass operation.

Assessment of ventricular function with an ambulatory left ventricular function monitor

Changes in ventricular function caused by activities of daily living, including standing, walking, stair climbing, and mental stress, were evaluated using a radionuclide device that recorded left ventricular function on a beat-by-beat basis. The ambulatory monitor was positioned over the patient's left ventricle after a gated blood pool scan. Monitoring revealed a 10% increase of left ventricular ejection fraction from baseline to brisk walking, an 18% increase during stair climbing, and a 6% increase with mental stress. In some subjects, however, the increase in ejection fraction during mental stress exceeded that during exercise.

Ventricular responses to mental stress testing in patients with coronary artery disease. Pathophysiological implications

Recent research examining the effects of mental stress on left ventricular wall motion and/or ejection fraction has used four techniques to measure contractile function: radionuclide ventriculography, a stationary nuclear probe, two-dimensional echocardiography, and an ambulatory radionuclide left ventricular function monitor. This research has consistently revealed that mental stress-induced myocardial ischemia occurs frequently during laboratory stress testing, particularly among patients with exercise-induced ischemia. This ischemia is usually silent, occurs at low heart rate elevations but with significant blood pressure increases compared with exercise-induced ischemia, and is frequently not detected when electrocardiographic markers are used alone. Exploration of factors underlying differences between mental stress- and exercise-induced ischemia has provided a means for studying the complex pathophysiology of myocardial ischemia.

[Results of computerized cardio-tomography and radionuclide ventriculography in patients with aortocoronary bypass]

Cardiocomputer tomography and radionuclide assessment of left ventricular function complete each other in postoperative control of patients with coronary artery bypass grafts. 70 patients with 163 coronary artery bypass grafts had 85% or total bypass graft early postoperative period, 77% after one year and 69% after two years. Sensitivity of cardiocomputer tomography was 75% and accuracy was 84%. The left ventricular functions was unchanged postoperatively.

Comparison of physiologic ejection fraction responses to activities of daily living: implications for clinical testing

The recent development of the VEST, an ambulatory radionuclide detector, to measure left ventricular ejection fraction may enhance the detection of ischemia during daily activities in patients with coronary artery disease. The normal range and determinants of ejection fraction responses to stimuli other than physical exercise, however, are not adequately characterized. Therefore, ejection fraction responses to various activities were measured in 18 normal subjects utilizing the VEST. Uniform increases (greater than 5%) in ejection fraction were seen during physical exercise, uniform decreases were seen during cold pressor testing and modest changes (including decreases greater than 5%) were seen in ejection fraction during mental stress, micturition and hyperventilation. Different forms of stress produced significantly different changes in ejection fraction, even when values were controlled for changes in heart rate. Ventricular loading conditions in the form of enhanced blood pressure responses during mental stress may have contributed to the relatively smaller changes in ejection fraction compared with those during exercise. Subjects demonstrating a decrease in ejection fraction during mental stress did not differ from other subjects in hemodynamic reactivity during mental testing but did have evidence of increased parasympathetic tone during cold pressor and bicycle exercise testing. The results reveal that normal ejection fraction response differs among varying physiologic stimuli. These changes are in part related to changes in heart rate and blood pressure; however, other factors, such as neurohumoral regulation, may also play a role. These findings indicate that the patient's activity and the setting in which it occurs must be considered when interpreting ambulatory ejection fraction responses.

[Correction of time resolution of an ambulatory cardiac monitor (VEST)--using a pulsate cardiac phantom]

Using ambulatory cardiac monitor (VEST) at exercise study, its time resolution is very important factor. We evaluated the time resolution of VEST using pulsate cardiac balloon phantom. Four analyses were carried out; no smoothing (NS) method, 3 points smoothing (3S) method, short sampling interval (SS) method, and digital filter (DF) method. By comparison of [delta EF[ ([EF: HR120-EF: HR60[) among 4 analysis methods, [delta EF[ by DF method was significant small. (NS: 3.58 +/- 3.01, 3S: 4.46 +/- 0.95, SS: 3.35 +/- 3.26, DF: 1.11 +/- 1.28%). We conclude that correction of time resolution by digital filter is necessary when we use VEST during exercise.

Evaluation of left ventricular diastolic function using an ambulatory radionuclide monitor: relationship to left ventricular systolic performance

Abnormalities of left ventricular (LV) filling may occur prior to systolic dysfunction in patients with both coronary and noncoronary heart disease. To determine the incidence of diastolic dysfunction and to assess the relationship of such dysfunction to systolic performance, we measured systolic and diastolic function at rest in a series of healthy volunteers (n = 10) and in patients with cardiovascular disease (n = 42). Twenty patients had coronary artery disease (CAD) with prior myocardial infarction, six patients had CAD without myocardial infarction, and the remaining 16 patients had a variety of noncoronary heart diseases, including valvular heart disease, dilated cardiomyopathy, and hypertensive disease. The 42 patients manifested a wide variation in LV systolic function (ejection fractions ranged from 6% to 65%). Patients with reduced LV ejection fraction (EF) manifested a reduction in cardiac output and peak ejection rate proportionate to the reduction in EF. Diastolic function showed a fall in LV peak (PFR) and average (AFR) filling rates; these were reduced in proportion to the fall in EF. Heart rate was an insensitive index of the magnitude of impairment of LV systolic function. These data suggest that measurements of diastolic function do not provide additional information in patients with impaired systolic function.

Validation of left ventricular function parameters acquired with the non-imaging nuclear probe: comparison with tantalum marker cine-fluoroscopy

We evaluated the accuracy of the non-imaging nuclear probe for measuring various parameters of left ventricular function by comparing these with simultaneous measurements acquired via tantalum marker cine-fluoroscopy. Eight patients with surgically implanted mid-myocardial tantalum markers were studied during cardiac catheterization. High temporal resolution tantalum marker-derived volume/time curves were generated and calibrated to absolute endocardial volumes by comparison with contrast left ventricular angiography. Left ventricular function parameters were acquired at baseline and during atrial pacing, nitroprusside infusion and volume loading. Simultaneous measurements obtained with the nuclear probe and via tantalum marker cine-fluoroscopy were compared. The following correlation coefficients were obtained: ejection fraction, r = 0.49, P less than 0.001; peak ejection rate, r = 0.41, P less than 0.01; mean ejection rate, r = 0.62, P less than 0.001; time to peak ejection, r = 0.73, P less than 0.001; peak filling rate, r = 0.73, P less than 0.001; time to peak filling, r = 0.58, P less than 0.001. Relative changes in end-diastolic volume were accurately tracked by the nuclear probe in six of seven patients (r values 0.77-0.93). These results suggest that measurements of certain left ventricular volume parameters with the nuclear probe may not accurately reflect true volume changes as measured by tantalum marker cine-fluoroscopy. Although, the probe may be useful in tracking relative changes in end-diastolic volume, we would advise caution in using this instrument for studies requiring accurate measurements of ejection and filling parameters.