Integration of critical care echo with other noninvasive cardiac imaging techniques

Abstract

The gradual integration of echocardiography with other noninvasive imaging techniques continues to progress, giving the practicing critical care clinician increasing diagnostic capability. Such capability can be divided into four main areas – coronary artery disease, myocardial pathology, valvular disease, and cardiac function. Coronary artery disease The presence of segmental wall defects on echocardiography alerts the clinician as to a high likelihood of underlying epicardial coronary artery disease (CAD). At the bedside the use of echocardiographic myocardial perfusion techniques can often further differentiate between ischaemic and nonischaemic aetiologies. Coronary computerized Tomographic Angiography (CCTA) over the last decade has moved from being a guide to the presence of CAD, to now offering accurate anatomical assessment, often being used as a first line diagnostic tool.The addition of Fractional Flow Reserve (FFR-CT) now adds a functional assessment of perfusion, reaching an accuracy of that obtained with invasive coronary angiography FFR studies.A noninvasive nuclear medicine alternative is SPECT or Single Photon Emission Computed Tomography which also has high diagnostic capability. Myocardial Pathology When abnormal myocardial appearances are found with echocardiography, it is difficult to be certain of the underlying pathology and historically a myocardial biopsy is considered when seeking to identify presumed inflammatory changes of unknown aetiology. The advent of Cardiac Magnetic Resonance (CMR) assists the physician in the differential diagnosis. The judicious use of T1 mapping, T2 mapping and gadolinium helps differentiate between fibrosis,inflammation and oedema. Valve pathology Although echocardiography remains the major modality is assessing valve function in the critically ill patient, CMR can improve evaluation with prosthetic valves. Myocardial function Echocardiography using Strain have enhance our ability to assess myocardial function. Positron Emission Tomography (PET) using isotopic-labelled substrates offers opportunities to exam metabolic function in the myocardium.It can determine glucose and fatty acid uptake in addition to targeting the mitochondria and angiogenesis. Although challenges arise in the need for a patient to be transferred, information gained may outweigh the risks in some patients. The sophistication of echocardiographic techniques continues to evolve but the wise physician will be cognizant of other noninvasive imaging modalities in an effort to further optimize patient management.