Final answer:
The condition where cardiac valve leaflets do not close properly allowing backward blood flow is referred to as valvular regurgitation, which can be indicated by a heart murmur and lead to heart failure.
Step-by-step explanation:
The condition described, where the cardiac valve leaflets or cusps are floppy and do not shut completely allowing blood to flow in the reverse direction when the valve should be closed, is referred to as valvular regurgitation. This situation can indeed lead to progressive heart failure if left untreated because the heart must work harder to maintain the blood circulation. When the valves' structure is perturbed due to conditions such as damaged or broken chordae tendineae, the valve may prolapse, which can lead to regurgitation. Disruption of one-way blood flow produces a characteristic heart murmur detectable by stethoscope, indicating the presence of regurgitation. While conditions like infective endocarditis and valvular stenosis also affect heart valves, they have different pathophysiological mechanisms compared to regurgitation.