Physical principles of hemodynamic and bioreology The Heart

Physical principles of hemodynamic and bioreology

The Heart and the Cardiovascular System (2) Cardiac Mechanics. (1) Cardiac electrophysiology.

The Heart: two pumps in series: (1) Pulmonary circulation: propels blood through lungs for exchange of O 2 and CO 2. (2) Systemic circulation: propels blood to all other tissues or organs of body.

Anatomy of the Heart

Longitudinal cross section

Basic Hemodynamics

Types of flow Flow of fluid in a cylindrical tube may be laminar of turbulent. Laminar flow: flow in lamina, fluid particles do not move in radial or circumferential direction. In Laminar flow the pressure drop (DP) is proportional to flow.

Poiseuille’s law Effect of stenosis degree on resistance

Types of flow Turbulent flow: irregular flow of fluid elements. Rapid radial and circumferential mixing. In turbulent flow the pressure drop is approximately proportional to square of flow.

Pressure and Volume in the Circulation Pressure is pulsatile in the arteries but steady in the capillaries and veins. Pressure falls along the circuit with the greatest fall across arterioles. Volume is greatest in the venous system. At any time most of the blood is in veins

The Cardiac Cycle Atrial Systole Pressure (mm Hg) 120 100 Ventricular Ejection Phase Isovolumetric Contraction Ventricular Filling Isovolumetric Relaxation Semi-Lunar Valve Closes Semi-Lunar Valve Opens Arterial Pressure 80 60 40 AV Valve Closes 10 AV Valve Opens Ventricular Pressure 0 R S Q Atrial Systole Approx. Time 0 Electrocardiogram T P 0. 1 Ventricular Systole 0. 2 0. 3 0. 4 Diastole 0. 5 Arterial Pressure Curve 0. 6 0. 7 0. 8

The cardiac cycle

Relationship of myocardial resting sarcomer length (end-diastolic volume) to developed force (peak systolic ventricular pressure) during ventricular contraction in the intact dog heart

Pressure-volume loop

Pressure-volume loop C D B A ESV

Pressure-volume loop for changing preload

Compliance: Definition: C= DV DP In regards to aortic mechanics DV or Dva is stroke volume (SV) and DP or DPa is pulse pressure (PP, or Ps-Pd). For aorta DPa = DVa Ca

Aortic Pressure Waveform 120 Systolic mm Hg Dicrotic Notch 100 Mean Pressure 80 Pulse Pressure Diastolic Systole Diastole