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

Magnetic Resonance Assessment of Ejection Fraction Versus Echocardiography for Cardioverter-Defibrillator Implantation Eligibility

Simple Summary

Nonischemic cardiomyopathies with low left ventricular ejection fractions (LVEF) are eligible for an implantable cardioverter defibrillator. However, the guidelines do not specify which method should be used to assess LVEF. In our study we investigated the potential impact of performing two-dimensional echocardiography (2DE) compared to cardiovascular magnetic resonance (CMR) for LVEF regarding ICD eligibility. We found that 2DE both overestimated and especially underestimated the need for implantation, which can have serious implications in the quality of life and the prevention of death events.

Abstract

Background: The aim of this study was to investigate the potential impact of performing two-dimensional echocardiography (2DE) compared to cardiovascular magnetic resonance (CMR) for left ventricular ejection fraction (LVEF) on implantable cardioverter defibrillator (ICD) eligibility. Methods: A prospective cohort of 166 consecutive patients with nonischemic cardiomyopathy (NICM) was designed to compare transthoracic 2DE and CMR imaging. Results: Echocardiography measurements have important differences and large limits of agreement compared to CMR, especially when assessing ventricle volumes, and smaller but relevant differences when assessing LVEF. The agreement between CMR and 2DE regarding the identification of subjects with EF <= 35, respectively <= 30, and thus eligible for an ICD measured by Cohen’s Kappa was 0.78 (95% CI: 0.68–0.88), p < 0.001, respectively 0.65 (95% CI: 0.52–0.78), p < 0.001. The disagreement represented 7.9%/11.3% of the subjects who had EF < 35%/< 30% as observed by CMR, who would have been classified as eligible for an ICD, resulting in an additional need to use an ICD. Moreover, 2.6%/3.3% would have been deemed eligible by echocardiography for an ICD. Conclusions: These measurement problems result in incorrect assignments of eligibility that may have serious implications on the quality of life and the prevention of death events for patients assessed for eligibility of an ICD.

MEDICAL DEVICE PRICES IN ECONOMIC EVALUATIONS

Objectives: Economic evaluations, although not formally used in purchasing decisions for medical devices in Canada, are still being conducted and published. The aim of this study was to examine the way that prices have been included in Canadian economic evaluations of medical devices.

Methods: We conducted a review of the economic concepts and implications of methods used for economic evaluations of the eleven most implanted medical devices from the Canadian perspective.

Results: We found Canadian economic studies for five of the eleven medical devices and identified nineteen Canadian studies. Overall, the device costs were important components of total procedure cost, with an average ratio of 44.1 %. Observational estimates of the device costs were obtained from buyers or sellers in 13 of the 19 studies. Although most of the devices last more than 1 year, standard costing methods for capital equipment was never used. In addition, only eight studies included a sensitivity analysis for the device cost. None of the sensitivity analyses were based on actual price distributions.

Conclusions: Economic evaluations are potentially important for policy making, but although they are being conducted, there is no standardized approach for incorporating medical device prices in economic analyses. Our review provides suggestions for improvements in how the prices are incorporated for economic evaluations of medical devices.

Cardiac autonomic imaging with SPECT tracers

Radionuclide cardiac imaging has potential to assess underlying molecular, electrophysiologic, and pathophysiologic processes of cardiac disease. An area of current interest is cardiac autonomic innervation imaging with a radiotracer such as (123)I-meta-iodobenzylguanidine ((123)I-mIBG), a norepinephrine analogue. Cardiac (123)I-mIBG uptake can be assessed by planar and SPECT techniques, involving determination of global uptake by a heart-to-mediastinal ratio, tracer washout between early and delayed images, and focal defects on tomographic images. Cardiac (123)I-mIBG findings have consistently been shown to correlate strongly with heart failure severity, pre-disposition to cardiac arrhythmias, and poor prognosis independent of conventional clinical, laboratory, and image parameters. (123)I-mIBG imaging promises to help monitor a patient's clinical course and response to therapy, showing potential to help select patients for an ICD and other advanced therapies better than current methods. Autonomic imaging also appears to help diagnose ischemic heart disease and identify higher risk, as well as risk-stratify patients with diabetes. Although more investigations in larger populations are needed to strengthen prior findings and influence modifications of clinical guidelines, cardiac (123)I-mIBG imaging shows promise as an emerging technique for recognizing and following potentially life-threatening conditions, as well as improving our understanding of the pathophysiology of various diseases.

Potential clinical impact of cardiovascular magnetic resonance assessment of ejection fraction on eligibility for cardioverter defibrillator implantation

BACKGROUND

For the primary prevention of sudden cardiac death, guidelines provide left ventricular ejection fraction (EF) criteria for implantable cardioverter defibrillator (ICD) placement without specifying the technique by which it should be measured. We sought to investigate the potential impact of performing cardiovascular magnetic resonance (CMR) for EF on ICD eligibility.

METHODS

The study population consisted of patients being considered for ICD implantation who were referred for EF assessment by CMR. Patients who underwent CMR within 30 days of echocardiography were included. Echocardiographic EF was determined by Simpson's biplane method and CMR EF was measured by Simpson's summation of discs method.

RESULTS

Fifty-two patients (age 62±15 years, 81% male) had a mean EF of 38 ± 14% by echocardiography and 35 ± 14% by CMR. CMR had greater reproducibility than echocardiography for both intra-observer (ICC, 0.98 vs 0.94) and inter-observer comparisons (ICC 0.99 vs 0.93). The limits of agreement comparing CMR and echocardiographic EF were - 16 to +10 percentage points. CMR resulted in 11 of 52 (21%) and 5 of 52 (10%) of patients being reclassified regarding ICD eligibility at the EF thresholds of 35 and 30% respectively. Among patients with an echocardiographic EF of between 25 and 40%, 9 of 22 (41%) were reclassified by CMR at either the 35 or 30% threshold. Echocardiography identified only 1 of the 6 patients with left ventricular thrombus noted incidentally on CMR.

CONCLUSIONS

CMR resulted in 21% of patients being reclassified regarding ICD eligibility when strict EF criteria were used. In addition, CMR detected unexpected left ventricular thrombus in almost 10% of patients. Our findings suggest that the use of CMR for EF assessment may have a substantial impact on management in patients being considered for ICD implantation.

Limitations in the current screening practice of assessing left ventricular ejection fraction for a primary prophylactic implantable defibrillator in southern Ontario

BACKGROUND

Screening echocardiography (ECHO) is commonly performed to determine whether the patient's left ventricular ejection fraction (LVEF) is appropriate for primary prophylactic implantable cardiac defibrillator (ICD) referral. However, radionuclide ventriculography (RNA) is used by many implantation centres for decision making.

OBJECTIVE

To determine whether current screening ECHO techniques are effective in identifying patients suitable for primary prophylactic ICD referral.

METHODS

Correlation, sensitivity, specificity and likelihood ratios (LRs) of semiquantitative and numerical quantitative ECHO LVEFs were calculated for predicting RNA LVEFs that met implantation criteria (LVEF less than 30% and less than 35%).

RESULTS AND DISCUSSION

Among 193 patients, the LRs for a semiquantitative ECHO predicting an RNA LVEF of less than 30% (negative LR was 0.21 to 0.69 and positive LR was 1.22 to 2.83) or RNA LVEF of less than 35% (negative LR was 0.24 to 0.73 and positive LR was 1.33 to 3.46) demonstrated that current screening ECHO techniques are ineffective. However, the positive predictive value of grade 4 ECHO was 93.0%, suggesting that these patients may not require further LVEF investigation before implantation. Among 102 patients, current quantitative ECHO techniques did not improve the screening characteristics.

CONCLUSIONS

Current screening ECHO techniques may not be adequate for screening patients for consideration of a primary prophylactic ICD, but a grade 4 ECHO finding has a high positive predictive value in meeting implantation LVEF criteria. Improved screening standards should increase the number of patients referred with appropriate LVEF for primary prophylactic ICD implantation.