Diastolic dysfunction (DD) is often associated with impaired relaxation, loss of restorative forces, reduced compliance during diastole, and elevated filling pressures within the left ventricular cavity. Various conditions have been linked to the development of DD, and evaluation for DD is most common during an evaluation of heart failure with preserved ejection fraction. Although the gold standard for assessing diastolic function is an invasive hemodynamic study, that is often inaccessible or unpragmatic in clinical settings. Therefore, sonography, specifically echocardiography, is the first-line modality for DD assessment. This review article details the what (i.e., what is diastolic function and dysfunction), when (i.e., when should diastolic function be measured, and when is caution advised) and how (i.e., how should diastolic function be measured) of DD assessment via sonography. For the sake of pragmatism and familiarity, the American Society of Echocardiography/ European Association of Cardiovascular Imaging 2016 algorithms will be discussed in this article. However, clinicians should familiarize themselves with the limitations of those algorithms. Through advances in the field of diastology, including the use of strain imaging, assessment of diastolic function will continue to become more inclusive and comprehensive.

Danon disease is a rare genetic cardio-skeletal myopathy. We present a case of an 18-year-old patient experiencing intermittent chest pain, dyspnea, and palpitations. Initial investigations unveiled elevated NT-pro brain natriuretic peptide, creatinine kinase, and cardiac enzyme levels.Electrocardiogram findings displayed left ventricular hypertrophy with a strain pattern and left bundle branch block. Transthoracic echocardiography and cardiac magnetic resonance imaging confirmed severe concentric left ventricular hypertrophy, accompanied by late gadolinium enhancement in specific myocardial regions. Genetic testing identified prevalent frameshift mutations in the lysosomal-associated membrane protein-2 (LAMP2) gene, indicative of Danon disease. This condition manifests as a severe, early-onset cardiomyopathy with associated complications such as heart failure, arrhythmias, and conduction disturbances, particularly in males. Diagnosis relies on genetic evidence, emphasizing the significance of testing in conjunction with clinical and imaging tools.