Accuracy of Highly Limited Echocardiographic Screening Images for Determining a Structurally Normal Heart: The Quick-Six Study

Introduction: Experienced echocardiographers can quickly glean diagnostic information from limited echocardiographic views. The use of limited cardiac ultrasound, particularly as a screening tool, is increasing. During the COVID-19 pandemic, limited cardiac ultrasound has the major advantage of reducing exposure time between sonographer and patient. The sensitivity and negative predictive value of a “screening” echocardiogram with highly limited views is uncertain. Aim/Method: We examined the accuracy of limited echocardiography in 203 consecutive, de novo studies. We used six images: parasternal long axis, with colour Doppler over the mitral valve, and aortic valve, and apical four-chamber with colour Doppler over the mitral valve, and tricuspid valve. We compared the interpretation of 12 subjects with the final echocardiogram report, (gold standard). The subjects comprised four experienced echocardiography-specialised cardiologists, four experienced cardiologists with non-imaging subspecialty interests, and four senior cardiac sonographers. Studies were graded as: (1) normal or (2) needs full study (due to inadequate images or abnormality detected). Sensitivity, specificity, negative predictive value, positive predictive value and accuracy are reported. Results: Forty-one per cent (41%) of studies were normal by the gold standard report. Overall, a screening echocardiogram had a sensitivity of 71.2%, specificity of 57.1% to detect an abnormal echocardiogram, negative predictive value 58.4%, positive predictive value of 70.2%, and accuracy of 65.4%. When inadequate images were excluded, overall accuracy was nearly identical at 64.6%. The overall accuracy between the three groups of interpreters was similar: 66.5% (95% CI 63.1–69.7) for echocardiography-specialised cardiologists, 65.3% (95% CI 61.9–68.5) for non-echocardiography specialised cardiologists, and 64.4% (95% CI 61.0–67.7) for sonographers. These groups are all highly experienced practitioners. There was no difference in sensitivity or specificity comparing echocardiography-specialised cardiologists with cardiologists of other subspecialty experience. Comparing cardiologists to sonographers, cardiologists had lower sensitivity (echocardiography specialists 67.6%, 95% CI 63.2–71.8, non-echocardiography specialists 62.0%, 95% CI 57.4–66.4) compared to sonographers (84.0% [95% CI 80.4–87.2, p<0.05]), but cardiologists had higher specificities (64.9% [95% CI 59.5–70.0] for the echocardiography specialists, and 69.9% [95% CI 64.7–74.8] for non echocardiography specialists), compared to 36.6% (95% CI 31.4–42.0, p<0.05) for the sonographer group. When looking at only the studies considered to be interpretable, cardiologists had higher positive predictive value (echocardiography specialists 73.7%, 95% CI 69.0–78.1, non echocardiography specialists 74.1%, 95% CI 68.8–79.9), as compared to sonographers (64.3%, 95% CI 59.8–68.5%). Conclusions: Limited cardiac ultrasound as a screening tool for a normal heart had a sensitivity of only 71%, when performed and interpreted by experienced personnel, raising questions regarding the safety of this practice. Caution is especially recommended in extrapolating its use to non-specialised settings.