Left ventricular ejection fraction in patients with normal and distorted left ventricular shape by three-dimensional echocardiographic methods: a comparison with radionuclide angiography

Effect of variable left ventricular ejection fraction assessed by equilibrium radionuclide angiocardiography using different software packages on the diagnosis of cardiotoxicity in patients with cancer

BACKGROUND

The equilibrium radionuclide angiocardiography (ERNA) scan is an established imaging modality for assessing left ventricular ejection fraction (LVEF) in oncology patients. This study aimed to explore the interchangeability of two commercially available software packages (MIM and JS) for LVEF measurement for a cancer-therapy-related cardiac dysfunction (CTRCD) diagnosis.

METHODS

This is a single-center retrospective study among 322 patients who underwent ERNA scans. A total of 582 scans were re-processed using MIM and JS for cross-sectional and longitudinal LVEF measurements.

RESULTS

The median LVEF for MIM and JS were 56% and 66%, respectively (P < 0.001). LVEF processed by JS was 9.91% higher than by MIM. In 87 patients with longitudinal ERNA scans, serial studies processed by MIM were classified as having CTRCD in a higher proportion than serial studies processed by JS (26.4% vs 11.4%, P = 0.020). There were no significant differences in intra- or inter-observer LVEF measurement variability (R = 0.99, P < 0.001).

CONCLUSIONS

Software packages for processing ERNA studies are not interchangeable; thus, reports of ERNA studies should include details on the post-processing software. Serial ERNA studies should be processed on the same software when feasible to avoid discrepancies in the diagnosis and management of CTRCD.

LVEF by Multigated Acquisition Scan Compared to Other Imaging Modalities in Cardio-Oncology: a Systematic Review

Purpose of Review

The prevalence of cancer therapy-related cardiac dysfunction (CTRCD) is increasing due to improved cancer survival. Serial monitoring of cardiac function is essential to detect CTRCD, guiding timely intervention strategies. Multigated radionuclide angiography (MUGA) has been the main screening tool using left ventricular ejection fraction (LVEF) to monitor cardiac dysfunction. However, transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR) may be more suitable for serial assessment. We aimed to assess the concordance between different non-radiating imaging modalities with MUGA to determine whether they can be used interchangeably.

Recent Findings

In order to identify relevant studies, a PubMed search was performed. We included cross-sectional studies comparing MUGA LVEF to that of 2D TTE, 3D TTE, and CMR. From 470 articles, 22 were selected, comprising 1017 patients in total. Among others, this included three 3D TTE, seven 2D harmonic TTE + contrast (2DHC), and seven CMR comparisons. The correlations and Bland-Altman limits of agreement varied for CMR but were stronger for 3D TTE and 2DHC.

Summary

Our findings suggest that MUGA and CMR should not be used interchangeably whereas 3D TTE and 2DHC are appropriate alternatives following an initial MUGA scan. We propose a multimodality diagnostic imaging strategy for LVEF monitoring in patients undergoing cancer treatment.

Value of peak exercise oxygen consumption combined with B-type natriuretic peptide levels for optimal timing of cardiac transplantation

BACKGROUND

Peak exercise oxygen consumption (VO(2)) is widely used to select candidates for heart transplantation (HTx). However, the prognosis of patients with advanced heart failure and peak VO(2) of 10 to 14 mL/min per kg in the era of modern medical therapy for heart failure is not fully elucidated. B-type natriuretic peptide (BNP) is a useful prognostic marker in patients with heart failure.

METHODS AND RESULTS

A total of 424 patients undergoing HTx evaluation were classified according to peak VO(2) during cardiopulmonary exercise testing (>14, 10-14, and <10 mL/min per kg). Survival after cardiopulmonary exercise testing without HTx or ventricular assist device (VAD) support was compared with survival of 743 de novo HTx recipients. Multivariable analysis revealed that high BNP and low peak VO(2) were independently associated with death, HTx, or VAD requirements (hazard ratio, 3.5 and 0.6; 95% CI, 1.24-9.23 and 0.03-0.71; P=0.02 and <0.0001, respectively). VAD-free or HTx-free survival of patients with peak VO(2) 10 to 14 mL/min per kg was identical to post-HTx survival. When patients with peak VO(2) 10 to 14 mL/min per kg were dichotomized by a cutoff value of BNP of 506 pg/mL, those with BNP<506 pg/mL was equivalent to post-HTx survival (1 year: 90.8% versus 87.2%; P=0.61), whereas those with BNP≥506 showed worse VAD-free or HTx-free survival (1 year: 79.7%; P<0.001 versus post-HTx). Patients with peak VO(2) <10 mL/min per kg showed worse survival compared with post-HTx survival, and there was a survival difference between those with BNP≥506 and <506 pg/mL (1 year: 77.2% versus 56.1%; P=0.01).

CONCLUSIONS

Patients with peak VO(2) 10 to 14 mL/min per kg and low BNP levels have a VAD-free or HTx-free survival similar to post-HTx survival in heart recipients, whereas high BNP levels indicate worse outcome in this group of patients.

Real-time Three-dimensional Color Doppler Echocardiography Overcomes the Inaccuracies of Spectral Doppler for Stroke Volume Calculation

Real-time 3-dimensional echocardiography is increasingly used in clinical cardiology. Studies have been shown that this technique can be accurately used to assess both cardiac mass and chamber volumes. We review the work showing that real-time 3-dimensional Doppler echocardiography can be used to accurately calculate intracardiac flow volumes that can potentially be used to assess cardiac function, intracardiac shunt, and valve regurgitation.

Live 3D Echocardiography: A Replacement for Traditional 2D Echocardiography?

OBJECTIVE

We describe the development of real-time 3D imaging and review the previously used versions of 3D echocardiography so that the reader will appreciate why current developments truly do represent a quantum leap in the technology.

CONCLUSION

Three-dimensional echocardiography has now been shown to have several advantages over 2D echocardiography, particularly for volume measurements, visualization of septal defects, and whole-valve evaluation. Given these data, it is clear that 3D echocardiography is here to stay and soon will become part of routine echocardiographic examinations.

Three-Dimensional Echocardiography: Rational Mode of Component Images for Left Ventricular Volume Quantitation

Three-dimensional echocardiography (3DE) improves the accuracy of left ventricle (LV) volumetry compared with the two-dimensional echocardiography (2DE) approach because geometric assumptions in the algorithms may be eliminated. The relationship between accuracy of mode (short- versus long-axis planimetry) and the number of component images versus time required for analysis remains to be determined. Sixteen latex models simulating heterogeneously distorted (aneurysmatic) human LVs (56-303 ml; mean 182+/-82 ml) were scanned from an 'apical' position (simultaneous 2DE and 3DE). For 3DE volumetry, the slice thickness was varied for the short (C-scan) and long axes (B-scan) in 5-mm steps between 1 and 25 mm. The mean differences (true-echocardiographic volumes) were 16.5+/-44.3 ml in the 2DE approach (95% confidence intervals -27.8 to +60.8) and 0.6+/-4.0 ml (short axis; 95% confidence intervals -3.4 to +4.6) as well as 2.1+/-9.9 ml (long axis; 95% confidence intervals -7.8 to +12.0) in the 3DE approach (in both cases, the slice thickness was 1 mm). Above a slice thickness of 15 mm, the 95% confidence intervals increased steeply; in the short versus long axes, these were -6.5 to +8.5 versus -7.0 to +10.6 at 15 mm and -10.1 to +15.7 versus -11.3 to +10.9 at 20 mm. The intra-observer variance differed significantly (p<0.001) only above 15 mm (short axis). Time required for analysis derived by measuring short-axis slice thicknesses of 1, 15, and 25 mm was 58+/-16, 7+/-2 and 3+/-1 min, respectively. The most rational component image analysis for 3DE volumetry in the in vitro model uses short-axis slices with a thickness of 15 mm.

Volume measurements in nuclear medicine gated SPECT and 4D echocardiography: validation using a dynamic cardiac phantom

PURPOSE

A dynamic cardiac phantom was used as a reference to compare volumes measured with gated SPECT and 4D echocardiography.

MATERIAL AND METHODS

Gated SPECT data were acquired with a standard single-head gamma camera, and the volume reconstructions were carried out using the Mirage software by Segami. 4D echocardiography used a new prototype of rotating scan head to acquire ultrasound images during a cardiac cycle, used to reconstruct the volume deformations as a function of time. End-diastolic volume, end-systolic volume, and ejection fraction were measured using both gated SPECT and 4D echocardiography.

RESULTS

The results obtained showed a good correlation between volumes measured with the two modalities, but a slight overestimation of volumes with gated SPECT. The influence of filtering and pixel size parameters on the measured volumes was quantified for gated SPECT, in order to correct the overestimation.

CONCLUSION

The agreement between gated SPECT (after correction) and 4D echocardiography confirmed the relevance of the comparisons. This study was an initial step before conducting clinical trials to compare exhaustively left ventricular volumes obtained with the two modalities.

Determination of Asymmetric Cavity Volumes Using Real-Time Three-Dimensional Echocardiography: An In Vitro Balloon Model Study

OBJECTIVES

We designed a new in vitro model to test the accuracy and reproducibility of real-time three-dimensional (RT3D) ultrasound imaging for determining a variety of asymmetric cavity volumes with aneurysm.

METHODS

Fifteen individual balloon models mimicking ventricular aneurysm were filled with water (170-322.5 ml) without air bubbles and kept in a compressor pump. Compression of the models produced only a change in shape of the balloon and no change in volume. The models were scanned with RT3D echocardiography (RT3DE) and the images recorded on an optical disk. Volumes were measured off line in two phases; maximal compression, where there was maximal change in shape and nil compression, where there was minimal or no change in shape. Volumes were measured by manual tracing technique of the inner border of B-scan images and compared with the drained volume of water from the balloon.

RESULTS

There was a high correlation between the drained volume and measured volume at maximal compression (equivalent to end-systole, r = 0.99, y = 0.99x + 3.69, SEE = 6.5 ml), between the drained volume and measured volume at nil compression (equivalent to end-diastole, r = 0.99, y = 0.94x + 12.07, SEE = 5.9 ml), and between volumes measured at maximal and nil compressions (r = 0.99, y = 0.94x + 10.55, SEE = 4.6 ml).

CONCLUSION

The results of this experiment show that RT3DE can accurately measure the volumes of a variety of asymmetric ventricular cavities.

Validation of a volumic reconstruction in 4-d echocardiography and gated SPECT using a dynamic cardiac phantom

A dynamic cardiac phantom was used as a reference to compare the volumes reconstructed with 4-D echocardiography and gated single-photon emission computed tomography (SPECT). 4-D echocardiography used a new prototype of rotating scan head to acquire ultrasound (US) images during a cardiac cycle, associated with a new protocol (left ventricular 4-D or LV 4-D) to reconstruct the volume deformations of the heart as a function of time. Gated SPECT data were acquired with a standard single-head gamma camera, and the reconstructions were carried out using the Mirage software released by Segami. The influences of different LV 4-D parameters were tested and analyzed. End-diastolic volume, end-systolic volume, and ejection fraction were measured using both LV 4-D and gated SPECT. Results obtained showed a straight correlation between the two examinations. The agreement confirmed the relevance of the comparisons. This study is an initial step before conducting clinical trials to exhaustively compare the two modalities.

Quantification of left ventricular volumes and ejection fraction using freehand transthoracic three-dimensional echocardiography: comparison with magnetic resonance imaging

OBJECTIVES

Our aim was to validate 3-dimensional echocardiography (3DE) for assessment of left ventricular (LV) end-diastolic volume, end-systolic volume (ESV), stroke volume, and ejection fraction (EF) using the freehand-acquisition method. Furthermore, LV volumes by breath hold-versus free breathing-3DE acquisition were assessed and compared with magnetic resonance imaging (MRI).

METHODS

From the apical position, a fan-like 3DE image was acquired during free breathing and another, thereafter, during breath hold. In 27 patients, 28 breath hold- and 24 free breathing-3DE images were acquired. A total of 17 patients underwent both MRI and 3DE. MRI contours were traced along the outer endocardial contour, including trabeculae, and along the inner endocardial contour, excluding trabeculae, from the LV volume.

RESULTS

All 28 (100%) breath hold- and 86% of free breathing-3DE acquisitions could be analyzed. Intraobserver variation (percentual bias +/- 2 SD) of end-diastolic volume, ESV, stroke volume, and EF for breath-hold 3DE was, respectively, 0.3 +/- 10.2%, 0.3 +/- 14.6%, 0.1 +/- 18.4%, and -0.1 +/- 5.8%. For free-breathing 3DE, findings were similar. A significantly better interobserver variability, however, was observed for breath-hold 3DE for ESV and EF. Comparison of breath-hold 3DE with MRI inner contour showed for end-diastolic volume, ESV, stroke volume, and EF, a percentual bias (+/- 2 SD) of, respectively, -13.5 +/- 26.9%, -17.7 +/- 47.8%, -10.6 +/- 43.6%, and -1.8 +/- 11.6%. Compared with the MRI outer contour, a significantly greater difference was observed, except for EF.

CONCLUSIONS

3DE using the freehand method is fast and highly reproducible for (serial) LV volume and EF measurement, and, hence, ideally suited for clinical decision making and trials. Breath-hold 3DE is superior to free-breathing 3DE regarding image quality and reproducibility. Compared with MRI, 3DE underestimates LV volumes, but not EF, which is mainly explained by differences in endocardial contour tracing by MRI (outer contour) and 3DE (inner contour) of the trabecularized endocardium. Underestimation is reduced when breath-hold 3DE is compared with inner contour analysis of the MRI dataset.

Three-dimensional echocardiographic determination of cardiac output at rest and under dobutamine stress: comparison with thermodilution measurements in the ischemic pig model

Determination of cardiac output is a potentially important clinical application of three-dimensional (3-D) echocardiography since it could replace invasive measurements with the Swan-Ganz-catheter. To date, there are no studies available to determine whether cardiac output measured by thermodilution can be predicted reliably under changing hemodynamic conditions. Fifteen pigs with ischemic myocardium were examined under four hemodynamic conditions at rest and under pharmacological stress with 5, 10, and 20 microg/kg/min dobutamine. The 3-D datasets were recorded by means of transesophageal echocardiography. The endocardial definition was enhanced by administering the contrast agent FS069 (Optison). Cardiac output was calculated as the product of stroke volume (end-diastolic - end-systolic volume) and heart rate. The invasive measurements were performed with a continuous thermodilution system. In general, there was moderate correlation between 3-D echocardiography and thermodilution(r = 0.72, P < 0.001). At rest, the 3-D echocardiographic measurements were slightly but significantly lower than the invasive measurements (mean difference 0.6 +/- 0.5L/min,P < 0.001). Under stress with 5, 10, and 20 microg/kg/min dobutamine, there was a marked increase in the deviation (1.3 +/- 0.5L/min,P < 0.001; 1.6 +/- 0.7 L/min,P < 0.001; and 2.1 +/- 1.1L/min,P < 0.001, respectively). The deviation was based on two factors: (1). Under stress, the decreasing number of frames per cardiac cycle acquired with 3-D echocardiography led to imprecise recording of end-diastolic and end-systolic volumes, and thus to an underestimation of cardiac output. At least 30 frames per cardiac cycle are needed to eliminate this effect. (2). There is a systematic difference between 3-D echocardiographic and invasive measurements, which is independent of the imaging rate. This is based on an overestimation of the true values by thermodilution. In conclusion, cardiac output can be determined correctly by 3-D echocardiography for normal heart rates at rest. At elevated heart rates, the temporal resolution of 3-D systems currently available is not adequate for reliable determination. In performing and evaluating future clinical comparative studies, the systematic difference between 3-D echocardiography and thermodilution, based on overestimation by thermodilution, must be taken into account.

Four-dimensional reconstruction of the left ventricle using a fast rotating classical phased array scan head: preliminary results

The evaluation of left ventricular function by noninvasive methods is still a major problem in cardiology. Two-dimensional echocardiography requires mental reconstruction of the heart by the physician and is always based on approximation of heart shapes and volumes. Three-dimensional echocardiography is promising but has rhythmic and function constraints because of the acquisition during many cardiac cycles. This article reports a study carried out to validate a new 4-dimensional echocardiography method. With the use of a classical phased-array sensor with a fast rotating motorized motion and a standard ultrasound system, many slices at different angulations are obtained in a single cardiac cycle. After manual endocardial delineation and computation, a representation of the left ventricle (beating heart) and a volume quantification are obtained at each instant of the cardiac cycle. This method has been tested on 11 healthy volunteers and the results are in agreement with those obtained with standard 2-dimensional echocardiography. Because of its simplicity of operation and short time acquisition, this new imaging modality is highly valuable in left ventricle evaluation, even if further studies on pathologic hearts need to be performed.

Importance of transducer displacement and tilting on three-dimensional echocardiographic volume assessment using apical or off-axis rotational acquisition: an in vitro study

OBJECTIVE

The goal of this study was to assess effects of translation (horizontal displacement) and angulation (transducer tilting) on 3-dimensional (3D) echocardiographic volumes of both balloons and human left ventricles after autopsy.

METHODS

Six water-filled (non-) aneurysmatic balloons of 150, 250, and 350 mL and 3 hearts of different sizes and shapes were suspended upright in a water bath. Angulation and/or translation was performed respectively by tilting the transducer with a mechanical arm in a vertical plane relative to the balloon tip or true apex of the hearts and by shifting the water bath in the same vertical plane. For balloon and left ventricular (LV) volume assessment, a 3D conical data set was obtained by TomTec rotational acquisition in combination with a HP Sonos 5500 ultrasound machine.

RESULTS

For the 6 balloons, translation from 1 to 4 cm yielded volumes of up to 74% of the optimal volume (100%); angulation of 10 degrees or 20 degrees, volumes of up to 80% and 34%. Translation with 10-degree angulation yielded volumes up to 64%; for 20-degree angulation and translation, there was no volume loss. Results were similar for the left ventricles.

CONCLUSIONS

Even minor angulation or translation of the transducer yields substantial underestimation of the true volume. Off-axis para-apical views, however, defined as angulation of 20 degrees and greater than 0.5 cm translation in this in vitro model, obviate volume underestimation. Such views in patients, if obtainable, may be an attractive alternative for conventional apical 3D acquisition, especially in dilated and aneurysmatic hearts.

Quantification of aortic regurgitation by real-time 3-dimensional echocardiography in a chronic animal model: computation of aortic regurgitant volume as the difference between left and right ventricular stroke volumes

BACKGROUND

The accuracy of conventional 2-dimensional echocardiographic and Doppler techniques for the quantification of valvular regurgitation remains controversial. In this study, we examined the ability of real-time 3-dimensional (RT3D) echocardiography to quantify aortic regurgitation by computing aortic regurgitant volume as the difference between 3D echocardiographic-determined left and right ventricular stroke volumes in a chronic animal model.

METHODS

Three to 6 months before the study, 6 sheep underwent surgical incision of one aortic valve cusp to create aortic regurgitation. During the subsequent open chest study session, a total of 25 different steady-state hemodynamic conditions were examined. Electromagnetic (EM) flow probes were placed around the main pulmonary artery and ascending aorta and balanced against each other to provide reference right and left ventricular stroke volume (RVSV and LVSV) data. RT3D imaging was performed by epicardial placement of a matrix array transducer on the volumetric ultrasound system, originally developed at the Duke University Center for Emerging Cardiovascular Technology. During each hemodynamic steady state, the left and right ventricles were scanned in rapid succession and digitized image loops stored for subsequent measurement of end-diastolic and end-systolic volumes. Left and right ventricular stroke volumes and aortic regurgitant volumes were then calculated and compared with reference EM-derived values.

RESULTS

There was good correlation between RT3D left and right ventricular stroke volumes and reference data (r = 0.83, y = 0.94x + 2.6, SEE = 9.86 mL and r = 0.63, y = 0.8x - 1.0, SEE = 5.37 mL, respectively). The resulting correlation between 3D- and EM-derived aortic regurgitant volumes was at an intermediate level between that for LVSV and that for RVSV (r = 0.80, y = 0.88x + 7.9, SEE = 10.48 mL). RT3D tended to underestimate RVSV (mean difference -4.7 +/- 5.4 mL per beat, compared with -0.03 +/- 9.7 mL per beat for the left ventricle). There was therefore a small overestimation of aortic regurgitant volume (4.7 +/- 10.4 mL per beat).

CONCLUSION

Quantification of aortic regurgitation through the computation of ventricular stroke volumes by RT3D is feasible and shows good correlation with reference flow data. This method should also be applicable to the quantification of other valvular lesions or single site intracardiac shunts where a difference between right and left ventricular cavity stroke volumes is produced.

The validation of volumetric real-time 3-dimensional echocardiography for the determination of left ventricular function

The objective of this study was to validate a real-time 3-dimensional echocardiography (3DE) technique for the determination of left ventricular (LV) volume and ejection fraction (EF). In 10 mongrel dogs, an electromagnetic flow (EMF) probe was placed on the aorta, and the thorax was closed. Transthoracic imaging was performed during multiple hemodynamic conditions (n = 58) with simultaneous measurement of stroke volume (SV) with the use of EMF. From the volumetric data set, LV volumes were manually traced off-line by 2 independent observers with an apical rotation method (6 planes) and a conventional method (biplane) in a subset of conditions. This tracing technique was also evaluated in 18 human subjects in whom the calculated EF values were compared with values derived by multigated radionuclide angiography (MUGA). Excellent correlation and close limits of agreement were noted between SV measured by 3DE and EMF (r = 0.93) in dogs. In comparison with EMF-derived SV, 3DE provided better correlation than the biplane method (r = 0.93 versus r = 0.61). Interobserver and intraobserver variabilities were comparable (r = 0.94 and r = 0.94, respectively). In a comparison of MUGA-derived EF values and those obtained by 3DE in human subjects, 3DE provided better correlation than the biplane method (r = 0.94 versus r = 0.85). Real-time 3DE accurately measures left ventricular volumes transthoracically over a wide range of hemodynamic conditions in dogs and accurately determines EF in humans.

Assessment of left ventricular function by real-time 3-dimensional echocardiography compared with conventional noninvasive methods

Quantitative assessment of left ventricular ejection fraction is an essential component of cardiac evaluation. We performed real-time 3-dimensional echocardiography in 56 consecutive patients who underwent multigated radionuclide angiography. Thirteen patients were excluded for the following reasons: 5 for large size of left ventricle required for image acquisition, 5 for suboptimal image quality in real-time 3-dimensional echocardiography, and 3 for atrial fibrillation. Finally, we compared left ventricular ejection fraction assessed by real-time 3-dimensional echocardiography and conventional 2-dimensional echocardiography with that obtained by multigated radionuclide angiography in 43 patients. Left ventricular ejection fraction was determined by real-time 3-dimensional echocardiography with the use of parallel plane-disks and sector plane-disks summation methods. A good correlation was obtained between both real-time 3-dimensional echocardiography methods and multigated radionuclide angiography (r = 0.87 and 0.90, standard error of estimate = 3.7% and 4.2%), whereas the relation between the 2-dimensional echocardiography method and radionuclide angiography demonstrated a significant departure from the line of identity (P <.001). In addition, interobserver variability was significantly lower (P <.05) for the real-time 3-dimensional echocardiography methods than that by the 2-dimensional echocardiography method. Real-time 3-dimensional echocardiography may be used for quantification of left ventricular function as an alternative to conventional methods in patients with adequate image quality.