Heart rate, synchrony and arterial hemodynamics

Heart rate is a conventional index quantifying the pulsatile action of the heart and is a basic parameter used throughout medical history and practice. However, modern science often places relatively little emphasis on heart rate in relation to the oscillatory nature of blood flow in the circulatory system, and the unyielding cyclic stress on the heart and blood vessels. Heart rate is relevant not only as an elemental measure, but also as a statistical entity and a possible confounding factor when considering its interaction with vascular hemodynamics. Pulse pressure amplification from the central aorta to peripheral arteries increases with heart rate. This has significant implications when assessing vascular function based on peripheral (brachial) pressure measurements, as the pressure changes at the central aorta with changes in arterial stiffness (as occurs with age) can be markedly different from changes at the peripheral site at different heart rates. Similarly, heart rate is a significant parameter when assessing cardiac and vascular implications of anti-hypertensive drug treatments. Heart rate, itself an independent parameter of cardiovascular risk, should also be considered in the statistical treatment of cardiovascular risk factors in large epidemiological studies. Disturbance in the regular pulsatile action of the heart due to altered synchrony of the cardiac chambers leads to heart failure, which can be treated with resychronization therapy. Cardiovascular models show that arterial stiffness can significantly affect the modification of parameters associated with cardiac resynchronization therapy. Thus, pulsatile hemodynamic parameters play a significant role when associated with both regular heart rate and with disturbed synchrony of the contracting heart chambers affecting the pump function of the heart.