New formula for cardiothoracic ratio for the diagnosis of cardiomegaly on post-mortem CT

Cardiothoracic ratio values and trajectories are associated with risk of requiring dialysis and mortality in chronic kidney disease

BACKGROUND

The prognostic role of the cardiothoracic ratio (CTR) in chronic kidney disease (CKD) remains undetermined.

METHODS

We conducted a retrospective cohort study of 3117 patients with CKD aged 18-89 years who participated in an Advanced CKD Care Program in Taiwan between 2003 and 2017 with a median follow up of 1.3(0.7-2.5) and 3.3(1.8-5.3) (IQR) years for outcome of end-stage renal disease (ESRD) and overall death, respectively. We developed a machine learning (ML)-based algorithm to calculate the baseline and serial CTRs, which were then used to classify patients into trajectory groups based on latent class mixed modelling. Association and discrimination were evaluated using multivariable Cox proportional hazards regression analyses and C-statistics, respectively.

RESULTS

The median (interquartile range) age of 3117 patients is 69.5 (59.2-77.4) years. We create 3 CTR trajectory groups (low [30.1%], medium [48.1%], and high [21.8%]) for the 2474 patients with at least 2 CTR measurements. The adjusted hazard ratios for ESRD, cardiovascular mortality, and all-cause mortality in patients with baseline CTRs ≥0.57 (vs CTRs <0.47) are 1.35 (95% confidence interval, 1.06-1.72), 2.89 (1.78-4.71), and 1.50 (1.22-1.83), respectively. Similarly, greater effect sizes, particularly for cardiovascular mortality, are observed for high (vs low) CTR trajectories. Compared with a reference model, one with CTR as a continuous variable yields significantly higher C-statistics of 0.719 (vs 0.698, P = 0.04) for cardiovascular mortality and 0.697 (vs 0.693, P < 0.001) for all-cause mortality.

CONCLUSIONS

Our findings support the real-world prognostic value of the CTR, as calculated by a ML annotation tool, in CKD. Our research presents a methodological foundation for using machine learning to improve cardioprotection among patients with CKD.

Application of postmortem imaging modalities in cases of sudden death due to cardiovascular diseases-current achievements and limitations from a pathology perspective : Endorsed by the Association for European Cardiovascular Pathology and by the International Society of Forensic Radiology and Imaging

Postmortem imaging (PMI) is increasingly used in postmortem practice and is considered a potential alternative to a conventional autopsy, particularly in case of sudden cardiac deaths (SCD). In 2017, the Association for European Cardiovascular Pathology (AECVP) published guidelines on how to perform an autopsy in such cases, which is still considered the gold standard, but the diagnostic value of PMI herein was not analyzed in detail. At present, significant progress has been made in the PMI diagnosis of acute ischemic heart disease, the most important cause of SCD, while the introduction of postmortem CT angiography (PMCTA) has improved the visualization of several parameters of coronary artery pathology that can support a diagnosis of SCD. Postmortem magnetic resonance (PMMR) allows the detection of acute myocardial injury-related edema. However, PMI has limitations when compared to clinical imaging, which severely impacts the postmortem diagnosis of myocardial injuries (ischemic versus non-ischemic), the age-dating of coronary occlusion (acute versus old), other potentially SCD-related cardiac lesions (e.g., the distinctive morphologies of cardiomyopathies), aortic diseases underlying dissection or rupture, or pulmonary embolism. In these instances, PMI cannot replace a histopathological examination for a final diagnosis. Emerging minimally invasive techniques at PMI such as image-guided biopsies of the myocardium or the aorta, provide promising results that warrant further investigations. The rapid developments in the field of postmortem imaging imply that the diagnosis of sudden death due to cardiovascular diseases will soon require detailed knowledge of both postmortem radiology and of pathology.

Radiological Cardiothoracic Ratio in Evidence-Based Medicine

The cardiothoracic ratio (CTR), expressing the relationship between the size of the heart and the transverse dimension of the chest measured on a chest PA radiograph, is a commonly used parameter in the assessment of cardiomegaly with a cut-off value of 0.5. A value of >0.5 should be interpreted as enlargement of the heart. The following review describes the current state of available knowledge in terms of contentious issues, limitations and useful aspects regarding the CTR. The review was carried out on the basis of an analysis of scientific articles available in the PubMed database, searched for using the following keywords: “CTR”, “cardiothoracic ratio”, “cardiopulmonary ratio”, “cardiopulmonary index”, and “heart-lung ratio”. According to the accumulated knowledge, the CTR can still be used as an important parameter that can be easily determined in establishing enlargement of the heart. However, an increased CTR does not directly relate to heart function. In the era following the development of diagnostic methods such as computed tomography, magnetic resonance imaging, and ultrasonography, CTR modifications based on these methods are used with varying clinical usefulness. It is important to consider the definition of the CTR and remember to base measurements on PA radiographs, as attempts to mark it in other projections face many limitations.

Evaluation of the mediastinal-thoracic volume ratio on postmortem computed tomography

Objectives

The aim of this study was to measure the mediastinal-thoracic volume ratio (CTR_VOL) on PMCT as a more accurate version of traditional CTR, in order to assess the terminal positional relationship between the heart and lungs in the different causes of death with regard to age, gender, BMI, cardiomegaly, and lung expansion.

Materials

Two hundred fifty consecutive postmortem cases with pre-autopsy PMCT and full forensic autopsy were retrospectively evaluated. The lungs and the mediastinum were manually segmented on the PMCT data and the correspondent volumes were estimated in situ. CTR_VOL was calculated as the ratio of the mediastinal to the thoracic volume. The volume measurements were repeated by the same rater for the evaluation of the intrarater reliability. Age, gender, body weight and height, heart weight at autopsy, and cause of death were retrieved from the autopsy reports. Presence of lung expansion was radiologically evaluated in situ.

Results

CTR_VOL was positively associated with age and BMI but not with gender and was higher for cardiomegaly compared to normal hearts, lower for asphyxiation-related deaths compared to cardiac deaths and intoxications, and lower for cases with lung expansion. The intrarater reliability was excellent for the calculated volumes of both lungs and mediastinum.

Conclusion

The results of the present study support CTR_VOL as a tool to assess the relationship between the heart and lungs in situ, which differs significantly between the studied cause of death categories.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00414-021-02593-0.

Cardiac hypertrophy at autopsy

Since cardiac hypertrophy may be considered a cause of death at autopsy, its assessment requires a uniform approach. Common terminology and methodology to measure the heart weight, size, and thickness as well as a systematic use of cut off values for normality by age, gender, and body weight and height are needed. For these reasons, recommendations have been written on behalf of the Association for European Cardiovascular Pathology. The diagnostic work up implies the search for pressure and volume overload conditions, compensatory hypertrophy, storage and infiltrative disorders, and cardiomyopathies. Although some gross morphologic features can point to a specific diagnosis, systematic histologic analysis, followed by possible immunostaining and transmission electron microscopy, is essential for a final diagnosis. If the autopsy is carried out in a general or forensic pathology service without expertise in cardiovascular pathology, the entire heart (or pictures) together with mapped histologic slides should be sent for a second opinion to a pathologist with such an expertise. Indication for postmortem genetic testing should be integrated into the multidisciplinary management of sudden cardiac death.

Postmortem imaging as a complementary tool for the investigation of cardiac death

In the past 2 decades, modern radiological methods, such as multiple detector computed tomography (MDCT), MDCT-angiography, and cardiac magnetic resonance imaging (MRI) were introduced into postmortem practice for investigation of sudden death (SD), including cases of sudden cardiac death (SCD). In forensic cases, the underlying cause of SD is most frequently cardiovascular with coronary atherosclerotic disease as the leading cause. There are many controversies about the role of postmortem imaging in establishing the cause of death and especially the value of minimally invasive autopsy techniques. This paper discusses the state of the art for postmortem radiological evaluation of the heart compared to classical postmortem examination, especially in cases of SCD. In SCD cases, postmortem CT is helpful to estimate the heart size and to visualize haemopericardium and calcified plaques and valves, as well as to identify and locate cardiovascular devices. Angiographic methods are useful to provide a detailed view of the coronary arteries and to analyse them, especially regarding the extent and location of stenosis and obstruction. In postsurgical cases, it allows verification and documentation of the patency of stents and bypass grafts before opening the body. Postmortem MRI is used to investigate soft tissues such as the myocardium, but images are susceptible to postmortem changes and further work is necessary to increase the understanding of these radiological aspects, especially of the ischemic myocardium. In postsurgery cases, the value of postmortem imaging of the heart is reportedly for the diagnostic and documentation purposes. The implementation of new imaging methods into routine postmortem practice is challenging, as it requires not only an investment in equipment but, more importantly, investment in the expertise of interpreting the images. Once those requirements are implemented, however, they bring great advantages in investigating cases of SCD, as they allow documentation of the body, orientation of sampling for further analyses and gathering of other information that cannot be obtained by conventional autopsy such as a complete visualization of the vascular system using postmortem angiography.Key pointsThere are no established guidelines for the interpretation of postmortem imaging examination of the heartAt present, postmortem imaging methods are considered as less accurate than the autopsy for cardiac deathsPostmortem imaging is useful as a complementary tool for cardiac deathsThere is still a need to validate postmortem imaging in cardiac deaths by comparing with autopsy findings.