What is Hemodynamics.

 Hemodynamics

The study of the dynamic behaviour of blood is termed hemodynamics.) Pressures are generated in the various parts of heart (cardiovascular pressures) when blood flows from one chamber to another, when valves open and close, and when the myocardium contracts and relaxes. Catheters are used to measure and monitor these pressures by placing their tips in the atria, pulmonary artery, or systemic arteries; these are called the hemodynamic lines.

 Hemodynamic lines have multiple uses:

 1) They allow the sampling of venous and arterial blood without having to stick a patient frequently. 

2) They help in monitoring different waveforms, thus providing evidences to patient's status.

3) The cardiac output can be calculated with the combination of pulmonary, arterial, and systemic arterial lines.

 4) They allow direct monitoring of varjous cardiac pressures, and analysis of these pressures helps in planning and assessing therapy in shock, cardiac failure, fluid overload or deficit, and other conditions.

electrophysiology of heart 

The cardiac cell is a polarised membrane. It has a resting membrane potential of S0 to -90mV, and a high Na ion concentration outside the membrane and K* ion concentration the membrane. Upon excitation, depolarisation occurs as the cell membrane permeability to Na' ions increases, the negativity of resting Electrophysiology of Heart a characteristics of action potential contractile cell, or pacemaker, or potential pacemaker cell. There are five phases of the action potential of cardiac cells 

Phase type of the cell-myocardial

1) phase  0: In this phase, rapid depolarisation of the cell membrane is observed as The sodium ions rapidly enter the cell through sodium channels. This phase is followed by re-polarisation. 

 2) Phase 1: In this (short and initial) phase, rapid re-polarisation observed as the potassium ions move out of the cell. out 

3) Phase 2: This prolonged plateau phase is observed as calcium Tons enter the cell slowly through the calcium channels. This, phase of action potential is present only in the cardiac cells. 

4) Phase 3: This phase is the. second perind of rapid re-polarisation as the potassium ions move out of the cell. 

5) Phase 4: This is the resting phase as resting membrane potential is re- established when the potassium ions return into the cell and sodium and calcium ions move out of it.  

The cells do not depolarise in response to another impulse during the phases 1 and 2; and this is called the absolute refractory period. The cells depolarise in response to a powerful impulse during the phases 3 and 4; and this is called relative refractory period.

The heart rate and' stroke volume are used for determining the cardiac output. The stroke volume depends on the preload (which itself depends on venous return), af:erload, and contractility. The load on the heart due to the blood volume reaching the left ventricle is called preload; white the Resistance w the teft ventricular ejection, i.e., the total peripheral resistance is called afterload.

FAQ

Q.1 What is normal hemodynamics?