McKee Jane L, Ferrier Katherine
Registrar, Hutt Valley DHB, Wellington.
Cardiologist, Hutt Valley DHB, Wellington.
N Z Med J. 2017 Oct 27;130(1464):57-63.
To determine whether or not cardiomegaly identified on chest radiograph (CXR) is indicative of true cardiomegaly as determined using echocardiography (echo) as the gold standard tool, and therefore whether or not cardiomegaly on CXR should be investigated further.
CXR and echocardiogram reports were reviewed for the presence of cardiomegaly in a population following non-ST segment elevation myocardial infarction (NSTEMI). Data was evaluated to determine whether cardiomegaly reported on CXR did indeed represent true cardiomegaly. Exploratory analysis was undertaken to determine whether or not Body Surface Area (BSA) was a significant explanatory variable.
Data was collected for 244 patients. Thirty-nine were reported to have cardiomegaly on CXR, 22 of those also had cardiomegaly on echo, giving a true positive rate of 56% and a false positive rate of 44%. Fifty-five were reported to have cardiomegaly on echo, of which 33 (60%) did not have cardiomegaly identified on CXR. Sensitivity of CXR to identify cardiomegaly was 40% and specificity was 91% with a positive predictive value of 56% and negative predictive value of 84%. BSA does not appear to be a significant explanatory variable for the discrepancy between the CXR and echo estimates of cardiomegaly.
In patients following an NSTEMI, the true positive rate of cardiomegaly identified on CXR is not too dissimilar to the false positive rate, thereby suggesting that reporting "cardiomegaly" based on CXR findings is inaccurate and rather reporting should simply focus on the cardiothoracic ratio and defining this as an enlarged cardiac silhouette rather than true cardiomegaly. In clinical practice the data indicates that the number needed to investigate to identify true cardiomegaly on echo is only two, thereby concluding that all patients post-NSTEMI with cardiomegaly on CXR should go on to have an echo, consistent with current national guidelines. As the study population were all post-MI, further study is necessary to evaluate whether this association holds true in a wider population.
确定胸部X线片（CXR）显示的心脏扩大是否指示超声心动图（echo，作为金标准工具）所确定的真正心脏扩大，因此CXR显示的心脏扩大是否应进一步检查。
回顾非ST段抬高型心肌梗死（NSTEMI）患者群体的CXR和超声心动图报告，以确定是否存在心脏扩大。评估数据以确定CXR报告的心脏扩大是否确实代表真正的心脏扩大。进行探索性分析以确定体表面积（BSA）是否为显著的解释变量。
收集了244例患者的数据。39例CXR报告有心脏扩大，其中22例echo检查也有心脏扩大，真阳性率为56%，假阳性率为44%。55例echo检查有心脏扩大，其中33例（60%）CXR未发现心脏扩大。CXR识别心脏扩大的敏感性为40%，特异性为91%，阳性预测值为56%，阴性预测值为84%。BSA似乎不是CXR和echo对心脏扩大估计差异的显著解释变量。
在NSTEMI患者中，CXR识别的心脏扩大真阳性率与假阳性率相差不大，这表明基于CXR结果报告“心脏扩大”是不准确的，而报告应仅关注心胸比率，并将其定义为心脏轮廓增大而非真正的心脏扩大。在临床实践中，数据表明通过echo识别真正心脏扩大所需检查的患者数量仅为2例，因此得出结论，所有NSTEMI后CXR显示心脏扩大的患者都应进行echo检查，这与当前国家指南一致。由于研究人群均为心肌梗死后患者，有必要进一步研究以评估这种关联在更广泛人群中是否成立。
