A continuous murmur, heard throughout systole and diastole, is most characteristically caused by a patent ductus arteriosus (PDA). PDA represents persistent communication between the aorta and pulmonary artery, allowing continuous blood flow during both phases of the cardiac cycle.
Ventricular septal defect usually produces a holosystolic murmur. Concomitant aortic stenosis and mitral regurgitation cause separate murmurs but not continuous. Ebstein anomaly with atrial septal defect typically produces murmurs related to tricuspid regurgitation or ASD but not a continuous murmur.
This clinical correlation is detailed in the "Textbook of Clinical Echocardiography, 6e", Chapter on Congenital Heart Disease and Murmur Etiologies#20:420-425Textbook of Clinical Echocardiography#.

Comprehensive and Detailed Explanation From Exact Extract:
Contrast echocardiography is recommended to enhance the visualization of left ventricular endocardial borders when the image quality is suboptimal. Specifically, contrast agents should be used when at least three contiguous left ventricular segments are poorly visualized on standard two-dimensional imaging. This approach improves the accuracy and reliability of assessing regional wall motion and global systolic function.
The use of contrast is particularly important during stress echocardiography to ensure detection of ischemic segments, which might otherwise be missed due to inadequate image quality. Studies suggest that contrast enhancement is required in approximately 30% to 50% of stress echocardiographic studies depending on patient factors and laboratory practices.
These recommendations are detailed in the echocardiography guidelines and in the "Textbook of Clinical Echocardiography, 6e" (Chapter 8: Coronary Artery Disease and Stress Echocardiography) which emphasize the utility of contrast agents for better endocardial border definition when at least three segments are not clearly seen .

Assessment of left ventricular diastolic function by echocardiography involves evaluating mitral inflow velocities with pulsed wave Doppler (E and A waves), pulmonary venous flow patterns (systolic and diastolic waves), and tissue Doppler imaging of the mitral annulus to measure early diastolic (e') velocities.
This combination allows differentiation of normal versus abnormal relaxation, elevated filling pressures, and grading of diastolic dysfunction. The myocardial performance index evaluates global ventricular function but does not specifically require these Doppler measures. Systolic function is assessed mainly by ejection fraction and wall motion. Mitral regurgitation severity uses color Doppler and vena contracta measurements.
This multiparameter diastolic function evaluation is outlined in the "Textbook of Clinical Echocardiography,
6e", Chapter on Diastolic Function Assessment#20:210-220Textbook of Clinical Echocardiography#.

The Valsalva maneuver transiently reduces preload, which can unmask or exaggerate diastolic dysfunction during mitral inflow Doppler assessment. During Valsalva, changes in mitral E and A wave velocities can differentiate between normal and pseudonormal filling patterns by observing alterations in filling pressures.
Hand grip, leg air cycling, and squatting affect afterload and preload differently but are less specific for assessing diastolic dysfunction via mitral Doppler.
This technique is outlined in the "Textbook of Clinical Echocardiography, 6e", Chapter on Diastolic Function Assessment and Maneuvers#20:210-215Textbook of Clinical Echocardiography#.

The video shows thickened, retracted, and possibly regurgitant valve leaflets with a characteristic appearance seen in drug-induced valvulopathy. Drugs such as ergot derivatives (e.g., methysergide) and appetite suppressants (e.g., fen-phen) can cause fibrotic thickening of valve leaflets mimicking carcinoid heart disease or rheumatic valve disease.
Infective endocarditis presents with vegetations and potentially valve destruction but typically not the diffuse thickening seen here. Rheumatic fever causes leaflet thickening but has a different chronic clinical course.
Systemic lupus may cause valve thickening but often involves Libman-Sacks vegetations rather than diffuse fibrosis.
This is discussed in the "Textbook of Clinical Echocardiography, 6e", Chapter on Valvular Heart Disease - Drug Induced and Secondary Causes#20:400-405Textbook of Clinical Echocardiography#.