Angiographic Determination of Right Ventricular Volumes

Abstract

In response to the article by E. Wellnhofer et al. (Int. J. Cardiovasc. Imaging 21,[575][576][577][578][579][580][581][582][583][584][585] In this issue of the International Journal of Cardiovascular Imaging, Wellnhofer et al.[1] report on the validation of angiographic right ventricular volume determination using magnetic resonance imaging as gold standard. Besides, there is another paper in this volume that is based on angiographic volume determination [2]. It describes right ventricular function after repair of tetralogy of Fallot using not only end-diastolic and end-systolic volumes but also the volume curve over a complete cardiac cycle.The angiographic determination of the ventricular volumes belongs to the oldest methods of quantitative image analysis. The basic techniques were developed 30 years ago, before digital imaging and multi-axial gantries were at our disposal in the catheterization laboratory. Other powerful image modalities were developed like echocardiography, cardiac magnetic resonance tomography and fast multi-slice computed tomography. The question arises whether it is still worthwhile to quantify right ventricular volumes from angiography. Are the results sufficient and accurate? And if the answers are yes, which method for angiographic right ventricular volume determination should be used in clinical routine? We will try to answer these questions based on the results of Wellnhofer et al.The assessment of the right ventricular volume and function is important for prognostic prediction and clinical decision making especially in paediatric cardiology. Although echocardiography has replaced angiocardiography for the diagnosis and follow-up of many patients, catheterization and the recording of angiograms are inevitable where local pressures and oxygen saturation should be measured or interventional procedures should be performed. Also the development of cardiac magnetic resonance tomography will not completely remove the more flexible and cost-efficient X-ray angiography. Especially for complex heart diseases and in paediatric cardiology the quantitative evaluation of the right ventricular size and function from angiograms are still of great importance.Using angiocardiography the ventricular volumes can be estimated from the opacified ventricular silhouettes only with the aid of model assumptions. There is no doubt that the variable and complex shape of the right ventricle cannot be approximated accurately from one projection alone. For the normal heart the combined use of the frontal and lateral views are well suited. However, for complex heart diseases other orthogonal projections may also be utilized. There are two approved techniques to calculate the volume from these projections: the area-length method and the multiple slices method. These techniques use the same information in a different order: either multiplication follows integration (of the silhouettes) or integration follows multiplication (of orthogonal diameters). In each case, the result has to be corrected to the true volume of ...