Role of cardiac CTA in estimating left ventricular volumes and ejection fraction

Abstract

Left ventricular ejection fraction (LVEF) is an important predictor of cardiac outcome and helps in making important diagnostic and therapeutic decisions such as the treatment of different types of congestive heart failure or implantation of devices like cardiac resynchronization therapy-defibrillator. LVEF can be measured by various techniques such as transthoracic echocardiography, contrast ventriculography, radionuclide techniques, cardiac magnetic resonance imaging and cardiac computed tomographic angiography (CTA). The development of cardiac CTA using multi-detector row CT (MDCT) has seen a very rapid improvement in the technology for identifying coronary artery stenosis and coronary artery disease in the last decade. During the acquisition, processing and analysis of data to study coronary anatomy, MDCT provides a unique opportunity to measure left ventricular volumes and LVEF simultaneously with the same data set without the need for additional contrast or radiation exposure. The development of semi-automated and automated software to measure LVEF has now added uniformity, efficiency and reproducibility of practical value in clinical practice rather than just being a research tool. This article will address the feasibility, the accuracy and the limitations of MDCT in measuring LVEF.

Keywords: Computerized tomography; Stroke volume; Ventricular ejection fraction; X ray.

Figure 1

Multi-planar reconstruction of left ventricular cavity in 4 chamber and 2 chamber views and semi-automated calculation of left ventricular volume in both end-systole and end-diastole in biplane and 4 and 2 chamber views by the area length method. Patient with cardiomyopathy and a very low left ventricular ejection fraction of 0.20.

Figure 2

Automatic recognition of left ventricular cavity by automated software to calculate left ventricular volumes in end-diastole (A) and end-systole (B) to calculate left ventricular ejection fraction.

Figure 3

Time-volume curve display of left ventricular volume over different phases of the cardiac cycle (R-R interval) and calculation of left ventricular ejection fraction is displayed automatically. Please note the smooth normal curve without registration artifact.

Figure 4

Shows some compromise in the time volume data as shown by the lack of smooth transition of the volume curve, and this likely represents some registration artifact towards the later part of diastole due to arrhythmias such as atrial fibrillation or frequent PVCs. This can lead to errors in the calculation of Left ventricular ejection fraction (LVEF). A quick look at the analysis of this time volume curve data is helpful to assess the quality of the data obtained for LVEF assessment and its limitations.