Clinical significance of right ventricular activity on treadmill thallium-201 myocardial single-photon emission computerized tomography using cadmium-zinc-telluride cameras.

OBJECTIVE: Identification of right ventricular (RV) abnormalities is important in patients with suspected coronary artery disease (CAD). RV activity can be better visualized on myocardial single-photon emission computerized tomography (SPECT) using a higher sensitivity cadmium-zinc-telluride (CZT) detector. The aim of this study was to investigate the clinical significance of RV/left ventricular (LV) uptake ratios during exercise thallium-201 SPECT using CZT detectors. PATIENTS AND METHODS: A total of 102 patients underwent treadmill ECG-gated SPECT, coronary angiography, and echocardiography. SPECT myocardial perfusion was interpreted using a 17-segment model and a 0-4-point scale. RV/LV uptake ratios were calculated on the basis of maximum counts per pixel within the entire RV and LV walls. The relationships between RV/LV uptake ratio and gated SPECT, presence of CAD (≥50% stenosis in the left main or ≥70% in the main branches), demographics, and echocardiographic parameters were analyzed. RESULTS: Stress RV/LV ratios correlated positively with the presence of left main or multivessel disease, and tricuspid regurgitation maximum pressure gradient. After multivariate regression, stress/rest RV/LV ratios correlated positively with mitral flow deceleration time, age, female sex, and use of ß-blockers. CONCLUSION: RV/LV uptake ratios on the basis of exercise myocardial perfusion SPECT imaging using CZT cameras are useful for the detection of severe CAD and could serve as an indicator of pulmonary hypertension and LV diastolic dysfunction.

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.

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.

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

UNLABELLED: 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.

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.

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.

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

UNLABELLED: 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.

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

UNLABELLED: 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.

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.

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.

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).

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.

[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.

Dedicated radial ventriculography pigtail catheter.

A new dedicated cardiac ventriculography catheter was specifically designed for radial and upper arm arterial access approach. Two catheter configurations have been developed to facilitate retrograde crossing of the aortic valve and to conform to various subclavian, ascending aortic and left ventricular anatomies. The "short" dedicated radial ventriculography catheter is suited for horizontal ascending aortas, obese body habitus, short stature and small ventricular cavities. The "long" dedicated radial ventriculography catheter is suited for vertical ascending aortas, thin body habitus, tall stature and larger ventricular cavities. This new design allows for improved performance, faster and simpler insertion in the left ventricle which can reduce procedure time, radiation exposure and propensity for radial artery spasm due to excessive catheter manipulation. Two different catheter configurations allow for optimal catheter selection in a broad range of patient anatomies. The catheter is exceptionally stable during contrast power injection and provides equivalent cavity opacification to traditional femoral ventriculography catheter designs.

Pigtail catheter fracture and embolization into the abdominal aorta: an extremely rare angiographic complication.

Coronary angiography is a widely used diagnostic method for coronary artery disease. In clinical practice, although complications of the procedure often involve the vascular access point, there is no previous report of the fracture and embolization of the distal tip of a pigtail catheter. Herein, we present the case of a 51-year-old woman whose left ventriculography was interrupted by fracture of the curved tip of a pigtail catheter, which remained at the renal artery level in the abdominal aorta.