Accuracy of noninvasive ejection fraction measurement in a large community-based clinic

Abstract

Objective: Compare the agreement of two dimensional echocardiography (echocardiography) and electrocardiogram (ECG)-gated single photon emission computed tomography (SPECT), with left ventricular contrast angiography (angiography) for the evaluation of left ventricular ejection fraction (LVEF).

Design: Retrospective cohort study.

Data source: American College of Cardiology National Cardiovascular Data Registry(TM) (ACC-NCDR).

Participants: Patients from a large, community-based clinic in central Wisconsin.

Methods: Consecutive patients (1999-2002) were identified from the ACC-NCDR dataset who underwent angiography and echocardiography or SPECT within 1 month of each other for evaluation of LVEF. Noninvasive LVEF values were compared to those obtained by angiography using the paired t-test. Regression analysis was used to assess the relation between the compared methods. Bland-Altman analyses were performed to assess the agreement between LVEF values obtained by the noninvasive techniques and angiography. Sensitivity and specificity of detecting depressed LVEF were determined for noninvasive techniques. Regression equations were determined for estimating angiographic values from the echocardiographic or SPECT values.

Results: Five hundred thirty-four patients underwent 542 angiographic studies: SPECT in all 534 patients, combined SPECT and echocardiographic studies in 201 patients, and combined angiographic and echocardiographic studies in 202 patients. Correlation of angiographic LVEFs with both echocardiographic and SPECT LVEFs was significant (r = 0.70 and r = 0.69, respectively; p < 0.0001). Echocardiographic LVEFs were lower than those determined by angiography (49% +/- 1.0% versus 54% +/- 1.0%; p < 0.0001). SPECT LVEFs were also lower than angiographic LVEFs (49% +/- 0.6% versus 57% +/- 0.6%; p < 0.0001). For 201 patients who underwent both SPECT and echocardiography, SPECT LVEFs were lower (47% +/- 1.0% for SPECT versus 49% +/- 1.0% for echocardiography; p < 0.05). Bland-Altman analysis revealed widely varying differences between techniques with broad confidence intervals. Nonetheless, sensitivity and specificity for determining LVEFs of <40% for SPECT and echocardiography were 90% and 86%, and 75% and 89%, respectively. LVEF of < or = 35% was correctly assessed by both SPECT and echocardiography. Sensitivity and specificity for SPECT were 82% and 89%, and 81% and 88% for echocardiography.

Conclusion: At our institution, LVEFs obtained noninvasively by echocardiography or SPECT are lower than angiographic LVEFs with widely fluctuating differences. Regression equations can be used to correct the noninvasive readings. Although lower, noninvasive techniques appear to accurately assess depressed LVEFs (<40% and <35%). The accuracy of noninvasive techniques for the evaluation of LVEF should be considered when managing and determining prognoses of patients with cardiac conditions. Individual institutions should determine the validity of the noninvasive techniques they use to assess LVEF.

Figure 1.

Scatter plot of echocardiographic LVEF determinations versus angiographic LVEF values in 202 patients in which the readings were determined within 30 days of one another. The 45 degree line of equality is plotted as a reference.

Figure 2.

Bland-Altman plot of the difference between the echocardiographic and angiographic LVEF values against their mean in 202 patients in which the readings were determined within 30 days of one another. The 95% confidence interval (mean ± 1.96 std. dev.) is also plotted.

Figure 3.

Scatter plot of SPECT LVEF determinations versus angiographic LVEF values in 542 patients in which the readings were determined within 30 days of one another. The 45 degree line of equality is plotted as a reference.

Figure 4.

Bland-Altman plot of the difference between the SPECT and angiographic LVEF values against their mean in 202 patients in which the readings were determined within 30 days of one another. The 95% confidence interval (mean ± 1.96 std. dev.) is also plotted.

Figure 5.

Scatter plot of echocardiographic LVEF determinations versus SPECT LVEF values in 201 patients in which the readings were determined within 30 days of one another. The 45 degree line of equality is plotted as a reference.

Figure 6.

Bland-Altman plot of the difference between the echocardiographic and SPECT LVEF values against their mean in 201 patients in which the readings were determined within 30 days of one another. The 95% confidence interval (mean ± 1.96 std. dev.) is also plotted.