hemodynamic studies in rodents

Hemodynamics is the study of forces that must be developed to circulate blood through the cardiovascular system so that tissues receive an adequate supply of oxygen.

These forces are constantly adapting to the body's requirements and ever changing internal and external conditions. The hemodynamic state is defined by pressure and flow.

The miniaturization of sensors has made it feasible to study hemodynamics in anesthetized rats and mice. All hardware and software applications for running such experiments are available from emka TECHNOLOGIES.

Most setups measure blood pressure and flow, as well as ecg (typically 1-lead ecg, lead LII).

The BP_T transducer is inserted into the femoral artery where it measures systemic blood pressure. It is connected to a strain-gauge amplifier board.

Alternatively or in addition, you can measure left ventricular pressure by using a pressure catheter (model SPR-407 Ultra-Miniature Mikro-Tip catheter by Millar Inc., available from emka TECHNOLOGIES) inserted into the left ventricle. This catheter is connected to a control unit (model TC-510) then to a strain-gauge amplifier board.

For the ecg measurement, the three electrodes are connected to 1-lead ecg amplifier board via a 3-wire cable. Banana and clip connectors for connecting electrodes are supplied.

Both the strain-gauge amplifier and 1-lead ecg amplifier boards can be housed in the same amplifier mainframe.

A flow probe (model MA2PSB flow probe by Transonic Systems Inc. available from emka TECHNOLOGIES) is placed around the aorta and connected to a control unit (model T402 from Transonic Systems). Notably this probe measures aortic flow directly, enabling measurement in real time.

The outputs from the amplifier mainframe and the T402 control unit go directly to the interface box, from which a cable attaches to the acquisition card of the PC.

Data acquisition is performed by iox , with simultaneous analysis made feasible with a variety of add-on analyzer moduless. For the current application, any combination of bp (blood pressure), lvp (left ventricular pressure), bf (blood flow) and ecg-r (ecg rhythm) analyzers may be used.

parameters

bp analyzer (blood pressure):
Systolic and diastolic pressures, amplitude, mean pressure, heart rate

bf analyzer (blood flow):
Systolic & diastolic flows, mean flow, stroke volume, cardiac output, heart rate, mean blood pressure, total peripheral resistance

lvp analyzer (left ventricular pressure):
Peak systolic pressure,start- and end-diastolic pressures, developed pressure, mean systolic and diastolic pressures, systolic ejection period, diastolic filling period, contraction time,relaxation time, maximum & minimum derivatives, contractility index, maximum velocity at P0, heart rate, relaxation constant Tau (3 methods)

ecg-r analyzer (ecg rhythm):
R amplitude, RRinterval, QRS interval, isoelectric line, S average, S area, heart rate

Advanced ecg analysis is possible with ecgAUTO. Parameters:

• PR, QRS, QT, JT, ST, RR durations
  
• P, T wave duration
  
• QTc, JTc corrected values (QTc and JTc values are available with a choice of 6 calculation modes)
  
• ST-segment elevation
  
• P, Q, R, S, Tneg. & Tpos. amplitudes
  
• P, QRS, T wave areas
  
• QT in user-adjustable HR ranges
  
• custom-defined parameters
  

notes

PC must be running Windows XP (development for Vista compatibility is ongoing)

Acquisition card available for laptop computer.

Setup for studying mice hemodynamics differs slightly (transducers and control units).

In mice, the ecgTUNNEL provides another simple method to obtain ecg measurements (avoiding the need for invasive ecg electrode needles).