Stress Echocardiography

Concise Review: Cardiac Disease Modeling Using Induced Pluripotent Stem Cells

Genetic cardiac diseases are major causes of morbidity and mortality. Although animal models have been created to provide some useful insights into the pathogenesis of genetic cardiac diseases, the significant species differences and the lack of genetic information for complex genetic diseases markedly attenuate the application values of such data. Generation of induced pluripotent stem cells (iPSCs) from patient-specific specimens and subsequent derivation of cardiomyocytes offer novel avenues to study the mechanisms underlying cardiac diseases, to identify new causative genes, and to provide insights into the disease aetiology. In recent years, the list of human iPSC-based models for genetic cardiac diseases has been expanding rapidly, although there are still remaining concerns on the level of functionality of iPSC-derived cardiomyocytes and their ability to be used for modeling complex cardiac diseases in adults. This review focuses on the development of cardiomyocyte induction from pluripotent stem cells, the recent progress in heart disease modeling using iPSC-derived cardiomyocytes, and the challenges associated with understanding complex genetic diseases. To address these issues, we examine the similarity between iPSC-derived cardiomyocytes and their ex vivo counterparts and how this relates to the method used to differentiate the pluripotent stem cells into a cardiomyocyte phenotype. We progress to examine categories of congenital cardiac abnormalities that are suitable for iPSC-based disease modeling.

Stress echo applications beyond coronary artery disease

Stress echocardiography is an established method for the diagnosis and prognostic stratification of coronary artery disease. In the last few years, the tremendous technological and conceptual versatility of this technique has been increasingly applied in challenging diagnostic fields. Today, in the echocardiography laboratory we can detect not only ischaemia from coronary artery stenosis, but can also recognize abnormalities of the coronary microvessels, myocardium, heart valves, pulmonary circulation, alveolar-capillary barrier, and right ventricle. Therefore, we evaluate coronary arteries as well as coronary microvascular disease (associated with diabetes and hypertension), suspected or overt dilated cardiomyopathy, systolic and diastolic heart failure, hypertrophic cardiomyopathy, athletes' hearts, valvular heart disease, congenital heart disease, incipient or overt pulmonary hypertension, and heart transplant patients for early detection of chronic or acute rejection as well as potential donors for better selection of suitable donor hearts. From a stress echo era with a one-fits-all approach (wall motion by 2D-echo in the patient with known or suspected coronary artery disease) now we have moved on to an omnivorous, next-generation laboratory employing a variety of technologies (from M-Mode to 2D and pulsed, continuous and colour Doppler, to lung ultrasound and real-time 3D echo, 2D speckle tracking and myocardial contrast echo) on patients covering the entire spectrum of severity (from elite athletes to patients with end-stage heart failure) and ages (from children with congenital heart disease to the elderly with low-flow, low-gradient aortic stenosis). For each patient, we can tailor a dedicated stress protocol with a specific method to address a particular diagnostic question. Provided that the acoustic window is acceptable and the necessary expertise available, stress echocardiography is useful and convenient in many situations, from valvular to congenital heart disease, and whenever there is a mismatch between symptoms during stress and findings at rest. Increasing societal concern regarding cost, environment and radiation risks of medical imaging will lead to a preferential application of ultrasound over competing techniques, due to its unsurpassed versatility, portability, absence of radiation, and low cost.