Estimating ejection fraction and heart failure severity using cardiac apex angles: a multiphase pilot study

Heart failure (HF) affects 6.7 million American adults. The gold standard for HF assessment is echocardiography (echo) to determine the ejection fraction (EF). Evaluating the cardiac apex angle may be a possible way to estimate EF; however, there is a lack of investigation into this relationship.

This study aimed to evaluate whether a correlation exists between the cardiac apex angle and EF.

A new, standardized method was developed to measure the cardiac apex angle, with the apex as the vertex, the inferior ray extending from the vertex to the right heart border, and a superior ray extending to the intersection of the left atrial appendage and ventricle. Cadaveric hearts were assessed and patient data from the Medical Information Mart for Intensive Care (MIMIC-IV) database were retrospectively analyzed. Chest X-rays (CXR) provided the cardiac apex angles, and echocardiogram reports contained matched EF values.

In 15 cadaveric hearts, the average apex angle was 47.2°, and the average EF was 48.5 %. Linear regression analysis revealed an R² value of 0.6543. In the MIMIC-IV cohort of 583 unique patients with matched echocardiograms and CXRs, the average EF was 52.7 %, and the average apex angle was 47.2°, with linear regression analysis revealing an R² value of 0.7018. This was further broken down by sex and CXR direction.

Access to echo may be limited in resource-constrained settings. Utilizing CXRs to estimate EF offers a practical alternative, potentially enabling early diagnosis and standardized treatment. This approach leverages common imaging modalities to bridge diagnostic gaps and improve HF management.