Prediction of Mortality in Pulmonary Embolism Based on Left Atrial Volume Measurements: Do Indexed Values Matter?

Abstract

We read the paper by Aviram et al1Aviram G. Soikher E. Bendet A. et al.Prediction of mortality in pulmonary embolism based on left atrial volume measured on CT pulmonary angiography.Chest. 2016; 149: 667-675Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar published in CHEST (March 2016) with great interest and congratulate the authors on their excellent work. Using CT pulmonary angiography (CTPA), the study demonstrated an association of decreased left atrial (LA) volumes and mortality in patients with acute pulmonary embolism (PE), in which it is theorized that a decrease in right ventricular stroke volume leads to underfilling of the left atrium. These findings are corroborated by previous studies using echocardiography and advocate the need for further studies using CTPA to risk stratify high-risk patients with PE. The current analysis suggests that patients with a smaller LA volume, by nongated CTPA, have a higher risk of mortality after PE. Given the known heterogeneity of LA volumes according to body surface area (BSA), it would be helpful to index LA volumes to BSA. Studies have demonstrated that LA size was larger with increasing body size and male sex, potentially explaining up to 29% of LA size variability.2Pritchett A.M. Jacobsen S.J. Mahoney D.W. Rodeheffer R.J. Bailey K.R. Redfield M.M. Left atrial volume as an index of left atrial size: a population-based study.J Am Coll Cardiol. 2003; 41: 1036-1043Abstract Full Text Full Text PDF PubMed Scopus (483) Google Scholar Additionally, race should be taken into account because of the significantly greater dimensions among whites,3Dewland T.A. Bibbins-Domingo K. Lin F. et al.Racial differences in left atrial size: results from the Coronary Artery Risk Development in Young Adults (CARDIA) study.PLoS One. 2016; 11: e0151559Crossref Scopus (11) Google Scholar as well as evident racial disparities with PE mortality.4Horlander K.T. Mannino D.M. Leeper K.V. Pulmonary embolism mortality in the United States, 1979-1998: an analysis using multiple-cause mortality data.Arch Intern Med. 2003; 163: 1711-1717Crossref PubMed Scopus (488) Google Scholar To partially account for patient BSA, right atrial to LA ratio was used by Chow et al5Chow V. Ng A.C. Chung T. Thomas L. Kritharides L. Right atrial to left atrial area ratio on early echocardiography predicts long-term survival after acute pulmonary embolism.Cardiovasc Ultrasound. 2013; 11: 17Crossref PubMed Scopus (35) Google Scholar to predict long-term mortality; however, this association was not as definitive. The CTPA images are nongated and represent data from a range of cardiac phases, with reduced filling time at higher heart rates. This may partly account for why the right atrial to LA volume ratio association is not as strong by CTPA. The increasing availability of advanced CT scanner systems will enable excellent-quality gated PE examinations, making metrics derived from chamber volumes more reliable. Despite the population-associated risk of low LA volume with increased mortality, the interquartile ranges overlap significantly, making LA volume difficult to apply to a particular patient with acute PE. Finally, to evaluate the discriminatory capacity of new tests in the setting of their widespread application, a comparison with biomarker elevation is necessary to show incremental discriminatory power. The assessment of risk in acute PE is challenging. The findings presented by Aviram et al1Aviram G. Soikher E. Bendet A. et al.Prediction of mortality in pulmonary embolism based on left atrial volume measured on CT pulmonary angiography.Chest. 2016; 149: 667-675Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar provide a framework for further risk stratification at the time of diagnosis by noninvasive methods, providing clinicians additional objective data. Further studies using gated imaging and patient-specific LA metrics in comparison with currently used risk tools will help validate this novel metric for risk assessment in patients with PE. Prediction of Mortality in Pulmonary Embolism Based on Left Atrial Volume Measured on CT Pulmonary AngiographyCHESTVol. 149Issue 3PreviewPreliminary reports suggest that a small left atrium (LA) is associated with severe acute pulmonary embolism (PE). This study used data derived from volumetric analyses of computed tomographic pulmonary angiography (CTPA) to investigate whether a reduced LA volume can predict adverse outcome in a large series of patients with acute PE. Full-Text PDF ResponseCHESTVol. 150Issue 1PreviewWe thank Dr Yadlapati and colleagues1 for their interest in our article in which we described a new tool for risk assessment among 636 patients diagnosed as having pulmonary embolism (PE). The approach is based on a fully automatic volumetric analysis of all four cardiac chambers obtained from diagnostic nongated CT pulmonary angiography (CTPA), which revealed that a decreased left atrial (LA) volume is associated with higher ≤ 30-day mortality.2 Full-Text PDF