Contrast harmonic color Doppler left ventriculography: machine-interpreted left ventricular ejection fraction compared with equilibrium-gated radionuclide ventriculography

Cardiac MRI and radionuclide ventriculography for measurement of left ventricular ejection fraction in ICD candidates

OBJECTIVE

Current guidelines provide left ventricular ejection fraction (LVEF) criterion for use of implantable cardioverter defibrillators (ICD) but do not specify which modality to use for measurement. We compared LVEF measurements by radionuclide ventriculography (RNV) vs cardiac MRI (CMR) in ICD candidates to assess impact on clinical decision making.

METHODS

This single-centre study included 124 consecutive patients referred for assessment of ICD implantation who underwent RNV and CMR within 30 days for LVEF measurement. RNV and CMR were interpreted independently by experienced readers.

RESULTS

Among 124 patients (age 64 ± 11 years, 77% male), median interval between CMR and RNV was 1 day; mean LVEF was 32 ± 12% by CMR and 33 ± 11% by RNV (p = 0.60). LVEF by CMR and RNV showed good correlation, but Bland-Altman analysis showed relatively wide limits of agreement (-12.1 to 11.4). CMR LVEF reclassified 26 (21%) patients compared to RNV LVEF (kappa = 0.58). LVEF by both modalities showed good interobserver reproducibility (ICC 0.96 and 0.94, respectively) (limits of agreement -7.27 to 5.75 and -8.63 to 6.34, respectively).

CONCLUSION

Although LVEF measurements by CMR and RNV show moderate agreement, there is frequent reclassification of patients for ICD placement based on LVEF between these modalities. Future studies should determine if a particular imaging modality for LVEF measurement may enhance ICD decision making and treatment benefit.

Cost of preimplantation cardiac imaging in patients referred for a primary-prevention implantable cardioverter-defibrillator

Recent guidelines have focused on ejection fraction cut-off values to determine eligibility for primary-prevention implantable cardioverter-defibrillators (ICDs). Clinical trials that led to the guidelines used varying techniques for ejection fraction assessment, including echocardiography and multigated acquisition (MUGA) scan. A prospective cohort study to determine the economic attractiveness of repeated echocardiography and MUGA scanning during the evaluation process of patients referred for consideration of a primary-prevention ICD was undertaken. From January 2005 to December 2006, data were collected for patients aged >18 years with ejection fraction <30% referred for a primary-prevention ICD based on referral assessment of heart function in any form. Costs based on the 2006 Ontario Health Insurance Plan fee schedule were determined for clinical assessment, echocardiography, MUGA scanning, and ICD implantation in patients who remained eligible based on MUGA ejection fraction. The 100 patients (age 61.1 +/- 10.2 years; 78 men) assessed for primary-prevention ICD implantation had an ejection fraction of 28.9 +/- 12.3% using MUGA scan. Thirty-one of 100 patients (31%) had an ejection fraction >30% and were no longer eligible for an ICD. Although imaging increased preimplantation cost from dollars 130 to dollars 536 per patient, averted inappropriate ICDs decreased the overall per-patient cost from dollars 20,914 to dollars 14,877. Despite an additional testing cost of dollars 40,599, the overall cost savings was dollars 603,722 in the 100 patients, with a cost savings of dollars 6,037 per patient. In conclusion, verification of ejection fraction identified a significant proportion of patients who were not eligible for an ICD.

Improved assessment of left ventricular volumes and ejection fraction by contrast enhanced harmonic color Doppler echocardiography

AIMS

Test the accuracy of contrast enhanced harmonic color Doppler technique (CHCD) to determine left ventricular volumes and ejection fraction (LVEF) compared to equilibrium radionuclide ventriculography (MUGA).

METHODS AND RESULTS

A total of 35 patients were enrolled (male 74.3%) with the mean age of 64.5 +/- 10 years and 6.8 +/- 4.9 days between echo and MUGA scans. The correlation of LVEF by CHCD with MUGA was better (R2 = 0.89) than that of harmonic 2D (H2D) and of contrast enhanced harmonic 2D (CH2D) (R2 = 0.74, R2 = 0.82, respectively). The RMS residual of CHCD (0.056) was smaller than that of H2D and CH2D (0.079, 0.067, respectively). The LVED and LVES volumes by H2D, CH2D and CHCD correlate well with MUGA but there was a significant over estimation of LVED and LVES volumes by H2D and CH2D as compared to MUGA. Also, the RMS residuals were the lowest for the CHCD method. The CHCD had the highest mean inter-observer agreement (90.9%) for LVEF compared with H2D and CH2D (78.9% and 88.1%, respectively).

CONCLUSIONS

CHCD has been feasible in all patients in the present study and it has shown a good concordance with ejection fraction and volumes provided by MUGA.

Left ventricular myocardial mass determination by contrast enhanced colour Doppler compared with magnetic resonance imaging

OBJECTIVE

To assess the feasibility of using contrast enhanced colour Doppler echocardiography to determine left ventricular (LV) mass and to compare its accuracy with LV mass obtained by magnetic resonance imaging (MRI).

METHODS

Images were acquired in the short axis plane of the heart, derived from coronal and sagittal scout views and double oblique angulation. The LV mass was calculated by two methods: Simpson's rule and the area-length method. Levovist (Schering AG, Berlin, Germany) 2.5 g was given by slow intravenous bolus or infusion over about 45 seconds for contrast imaging. LV images were captured in the apical two chamber, four chamber, and three chamber views. Each contrast harmonic colour Doppler image was converted to a cavity-only image by simple image mathematics.

RESULTS

27 (77.1%) of the patients (mean (SD) age 66.2 (8.9) years) were men. There was a mean (SD) interval of 6.6 (8.6) days (range 0-27 days) between echocardiography and MRI. The mean (SD) LV mass determined by MRI Simpson's rule method was 171.0 (52.4) g (range 105.1-318.7 g). The mean LV mass (SD) determined by the echocardiographic Simpson's rule method was 178.2 (47.0) g (range 112.6-307.6 g). The mean (SD) MRI area-length LV mass was 187.3 (64.5) g (range 109.0-393.6 g). The linear regression correlation between LV mass determined by MRI Simpson's and echocardiographic Simpson's methods was excellent (y = 1.022x, R2 = 0.986) with a mean (SD) difference of 7.20 (20.9) g. The linear regression correlation between the MRI area-length LV mass and MRI Simpson's LV mass was excellent (y = 1.101x, R2 = 0.989) with a mean (SD) difference of 16.3 (22.3) g.

CONCLUSIONS

LV mass may be obtained reliably by contrast enhanced colour Doppler and two dimensional echocardiography. The contrast Doppler method accurately determines LV mass with excellent agreement with the MRI technique.

Reliability of reporting left ventricular systolic function by echocardiography: a systematic review of 3 methods

BACKGROUND

An accurate assessment of left ventricular (LV) systolic function is of central importance to the diagnosis and management of heart failure. Echocardiography is currently the technique most widely used for this purpose.

METHODS

A systematic review was performed of the evidence for the accuracy of 3 echocardiographic methods--Simpson's rule, wall motion index (WMI), and subjective visual assessment--compared with radionuclide or contrast ventriculography for the assessment of LV ejection fraction (LVEF).

RESULTS

Twenty-five studies were identified in which data on agreement between echocardiography and reference methods were obtainable. A further 18 studies provided correlation data alone. For Simpson's rule, Bland-Altman limits of agreement (95% CI) ranged from LVEF +/-7% to +/-25% (median +/-18%); for WMI +/-13% to +/-20% (median +/-16%); and for subjective visual assessment +/-16% to +/-24% (median +/-19%). Subject echogenicity, the nature of underlying disease, and the use of additional imaging technology, including secondary harmonic imaging and contrast agents, is likely to influence the accuracy of different methods. No method appears to systematically under- or overestimate LVEF to any major extent.

CONCLUSION

These findings have important implications for the investigation of heart failure and for the practice and reporting of echocardiography.

Automated quantitative analysis of the shift of frequency spectra generated by attenuated signals from contrast microbubbles

The ultrasound-induced harmonic microbubble response spectrum is known to shift to lower frequencies with increasing tissue attenuation. We hypothesized that this shift could be reproducibly detected in received broadband radiofrequency spectra. We used an automatic Gaussian curve-fitting technique to measure the mean harmonic response generated by three different contrast agents at six incremental levels of attenuation. Analytical curve fitting identified a consistent, reproducible, and statistically significant shift in mean harmonic frequency with increasing attenuation. The presented method could be a step toward attenuation estimation by contrast harmonic imaging; optimization of harmonic signal reception by ultrasound systems; and, ultimately, automatic detection of contrast agents in tissue.