For a normal young person, where the arteries are generally compliant, the slow travelling reflected wave from the peripheral occurs during diastole, thus enhancing perfusion of the coronary arteries.
Pulse Waveform of a 47 year old person
With age, the arteries stiffen. Pulse wave velocity increases and the reflected wave now travels faster and gives rise to a "shouldering" at the primary wave, and occurs during systole. This effect prolongs the systolic cycle increasing the workload and oxygen requirement of the heart muscles. The poor notch also compromises the flow of the coronaries.
Pulse Waveform of a 80 year old person
In the elderly, further arterial stiffening cause the reflected wave to return much faster and gives rise to a "shouldering" at the primary wave; and coincide very close to the systolic peak, resulting in an augmented wave. The heart now needs to contract even harder (to overcome the oncoming reflected wave) and for a longer period. At the same time, coronary artery perfusion is further compromised.