Ventricular Pressure-Volume

Left ventricular pressure-volume loops are widely used in the hemodynamic assessment of baseline & occlusion studies, heart hypertrophy and failure models, effects of specific gene manipulation, and pharmacology/toxicology studies. Left ventricular pressure and volume are recorded from a single catheter inserted directly into the left ventricle. Pressure volume loops are then used to derive cardiac output, ejection fraction, stroke work, stroke volume, end-systolic pressure-volume relationship (ESPVR), and end-diastolic pressure-volume relationship (ESDPVR) along with many other parameters in determining hemodynamic function. An example of a left ventricular pressure-volume loop is shown below:

Ventricular Pressure-Volume
ADInstruments and Millar Instruments provide researchers with the world's first system for simultaneous pressure-volume recordings in small to large animals using a single catheter. The systems are specifically designed for beat-to-beat monitoring of cardiac performance in animals ranging in size from mice to sheep. A single catheter with a high-fidelity pressure sensor and conductance electrodes is used to simultaneously measure left ventricular pressure and volume. PV catheters connect to PowerLab data acquisition systems via the MPVS Ultra Pressure-Volume Unit.

Surgical Techniques
Pressure-volume catheters may be inserted into the left ventricle by either a closed chest carotid artery catheter insertion or an open chest apical stab catheter insertion.

Impedence/Conductance Technique
The impedance/conductance technique is based on Ohm’s Law (V=IR) where V is equal to the voltage potential between the sensing electrodes, I is equal to a low excitation constant current, and R is the resistance of the left ventricular blood pool. Since conductance is equal to the inverse of resistance, we can derive the following relationship between volume and conductance:

 
The volume of the left ventricular blood pool is high during diastole. Therefore, resistance of the blood pool is low and conductance of the blood pool is high. The voltage drop across the sensing electrodes is low during diastole. During systole the volume of the left ventricular blood pool is low. Therefore, resistance is high and conductance of the blood pool is low. The voltage drop across the sensing electrodes is high during systole. Pressure Calibration
The MLA1052 Pressure Gauge is used to calibrate both conventional fluid-filled pressure transducers and Millar Mikro-Tip pressure catheters. For information on Pressure Transducer Calibration, please consult Pressure Transducer Calibration (64 KB) technique note.

Recording Settings
For information on recommended pressure-volume sampling rates and filtering options, please consult Signal Filtering (199 KB) technique note.

Related Areas of Interest:

• Atrial & Venticular Pressure application page
• Langendorff Heart and Working Heart application pages
• Radnoti Isolated Perfused Heart (255 KB) technique note
• Intraventricular Pressure Measurement in a Langendorff Preparation (92 KB) technique note

 

LabChart
LabChart software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with LabChart Extensions and LabChart Modules. LabChart Modules are available as part of LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.

LabChart software can be used to simultaneously record pressure and volume, in addition to other physiological parameters such as ECG, blood flow, heart rate and intravascular blood pressure. Labchart’s XY View plots PV loops in real time.

Data is easily imported into PVAN Software (supplied with every Pressure-Volume system) using the LabChart PVAN Extension (Win only). PVAN allows for the calculation of up to 30 hemodynamic parameters. Parameters calculated by PVAN Software include

• Heart Rate
• Max and min volume
• End-systolic volume
• End-diastolic volume
• Max and min pressure
• End-systolic pressure
• End-diastolic pressure
• End-systolic Elastance
• Arterial Elastance
• Cardiac Output
• Stroke Work (SW)
• Stroke Volume
• Ejection Fraction
• Preload Recruitable SW
• Max and min dP/dt
• Max and min dV/dt
• Pressure at dP/dt max and dV/dt max
• Volume at dP/dt min and dV/dt min
• Tau-Weiss method
• Tau-Glantz method
• Tau-Logistic method
• ESPVR
• EDPVR

 Blood Pressure Module (Windows)
The MLS370/6 Blood Pressure Module for Windows automatically detects, analyzes and reports cardiovascular parameters from arterial or ventricular pressure signals.


The settings dialog allows the user to select ventricular pressure for analysis and the Classifier View allows for easy selection of pressure waveforms for further analyses. Pressure cycles that are contaminated by artifact, have abnormal cycle heights or cycle durations (frequency) can be excluded from analysis using the classifier.

The Analysis View displays pressure cycles as beat-by-beat or as the average of a specified number of cycles. Ventricular parameters such as EDP, Max dP/dt, Min dP/dt, Min and Max Pressure are labeled. These measurements along with other calculated parameters are logged in the Table View for easy exporting.

Features and benefits include:

• Suitable for analysis of pressure signals from humans as well as large and small animals
• Pressure signals can be analyzed in real time during acquisition
• The BP Classifier makes detection and exclusion of atypical waveforms easy
• Parameters can be displayed as continuous data on separate channels
• Values are logged to the Table View
• Averages any number of pressure waveforms

Calculated arterial parameters include:

• Systolic, Diastolic and Mean Pressure
• Pulse Pressure
• Dichrotic Notch Pressure
• Ejection and Non-ejection duration
• Cycle Duration
• Heart Rate

Calculated ventricular parameters include:

• Maximum Pressure
• Maximum dP/dt
• Isovolumic Relaxation
• Minimum Pressure
• Minimum dP/dt
• Mean Pressure
• End Diastolic Pressure (EDP)
• Maximum-Minimum Pressure
• Contractility Index

GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.

Mikro-Tip Pressure Volume Systems

• ML880B46 MPVS-Ultra Foundation System - It is configured for measurement of left ventricular pressure (LVP) and volume in small (rat or mouse) through to large animal (sheep, pig) hearts, using the appropriate pressure-volume (PV) catheter. A variety of PV catheters are available for particular species.

Mikro-Tip Pressure-Volume Catheters (large animal)
ADInstruments offers the full line of Millar Mikro-Tip Pressure Volume Catheters ranging from 1F (for small animals) through to 7F (for large animals). These catheters are for use ONLY in animal research. Due to their small size the sensors can be directly placed into the left ventricle of the heart for simultaneous measurement of pressure and volume with minimal disruption to heart function. In vivo, the catheters can be used in either closed or open-chest preparations as well as being used in the isolated working heart preparation.

The pressure sensors used in the pressure-volume catheters are identical to those used in the Mikro-Tip Blood Pressure Catheters. As the sensor is positioned at tip of the catheter there is no signal attenuation (reduction) or movement artifact that is commonly found when using fluid-filled pressure-sensing systems.

Multi-segment PV catheters range in size from 3 to 7 French in single field or dual field configurations. These catheters include up to 12 conductance electrodes with varying electrode spacing to accommodate animals ranging in size from rabbits to sheep. Multi-segment PV catheters are available with straight tips or closed-end pigtails and a second pressure transducer (e.g. aortic pressure).

• Mikro-Tip Multi-Segment P-V Catheters – Dog/Pig/Sheep: Mikro-Tip pressure-volume catheters, cables and accessories for use in dogs, sheep or pigs with the MPVS Ultra unit.
• Mikro-Tip Multi Segment P-V Catheters – Rabbits/Cats: Mikro-Tip pressure-volume catheters, cables and accessories for use in rabbits or cats with the MPVS Ultra unit.

Mikro-Tip Pressure-Volume Catheters (mice and rats)
The pressure sensors used in the pressure-volume catheters are identical to those used in the Mikro-Tip Pressure Catheters. As the sensor is positioned at tip of the catheter there is no signal attenuation (reduction) or movement artifact that is commonly found when using fluid-filled pressure-sensing systems. The Millar pressure-volume system measures ventricular volume using an impedance/ conductance technique. The catheter has two miniature electrodes positioned on both sides of the pressure sensor (total of 4 electrodes). The distance between the 1st (proximal) and 4th (distal) electrodes should span the entire length of the ventricle (apex –> aortic valve). A low amplitude constant current is generated between the two outer excitation electrodes to create an electrical field within the ventricular blood pool. The two inner sensing electrodes function as sensors that measure the change in voltage potential during ventricular contraction/relaxation (ie. emptying and filling).

• Mikro-Tip P-V Catheters – Mice/Rats: Mikro-Tip pressure-volume catheters, cables and accessories for use in rats or mice using the MPVS-300.

Pressure-Volume Units

• 880-0168 MPVS-Ultra Pressure-Volume Unit (large and small animals): The MPVS-Ultra Pressure-Volume Unit provides analog outputs for two pressure, a composite volume and a maximum of seven volume segments. The combined pressure and volume signals can be plotted in real time using LabChart to generate pressure-volume loops, which are used to determine cardiac function. The  880-0169 MPVS Ultra Cable Pack (10ft) is required for connecting PV catheters to the MPVS-Ultra Pressure-Volume Unit.

Accessories

• 910-1049 Volume Calibration Cuvette (1.5 to 4.0 mm)
• 910-1048 Volume Calibration Cuvette (2 to 15 mm)
• SP0127 Touhy Borst Replacement Kit
• MLA1052 Pressure Gauge

Haemodynamic profile and responsiveness to anandamide of TRPV1 receptor knock-out mice

P Pacher, S Batkai and G Kunos, Journal of Physiology, 647-657, 2004

Male TRPV1–/– and TRPV1+/+ mice weighing 25–30 g were used for the study. Mice were anaesthetized with pentobarbital sodium (80 mg/kg I.P.) and tracheotomized to facilitate breathing. Animals were placed on controlled heating pads, and core temperature measured via a rectal probe was maintained at 37°C. A microtip pressure–volume catheter (SPR-839; Millar Instruments, Houston, TX, USA) was inserted into the right carotid artery and advanced into the left ventricle (LV). Polyethylene cannulae (P10) were inserted into the right femoral artery and vein for measurement of mean arterial pressure (MAP) and administration of drugs, respectively. After stabilization for 20 min, the signals were continuously recorded at a sampling rate of 1000/s using an ARIA pressure–volume conductance system (Millar Instruments) coupled to a Powerlab/4SP A/D converter (AD Instruments, Mountain View, CA, USA), and then stored and displayed on a computer. All pressure–volume loop data were analysed with a cardiac pressure–volume analysis program (PVAN3.2; Millar Instruments), and the heart rate (HR), maximal left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), MAP, maximal slope of systolic pressure increment (+dP/dt) and diastolic decrement (–dP/dt), ejection fraction (EF), stroke volume (SV), arterial elastance (Ea; end-systolic pressure/stroke volume), cardiac output (CO) and stroke work (SW) were computed. The relaxation time constant, an index of diastolic function, was also calculated by two different methods (Weiss method: regression of log[pressure]versus time; Glantz method: regression of dP/dt versus pressure) using PVAN3.2. Total peripheral resistance (TPR) was calculated by the equation: TPR = MAP/CO.

Left ventricular pressure-volume relationship in a rat model of advanced aging-associated heart failure

P Pacher, J G Mabley, L Liaudet, O V Evgenov, A Marton, G Hasko, M Kollai and C Szabo, American Journal of Physiology: Heart and Circulatory Physiology, H2132-H2137, 2004

Rats were anesthetized with thiopental sodium (60–80 mg/kg ip): aging animals with heart failure required ~15–20% less anesthetic than young rats. The animals were tracheotomized to facilitate breathing and placed on controlled heating pads. The core body temperature measured via a rectal probe was maintained at 37°C. A microtip P-V catheter (SPR-838, Millar Instruments; Houston, TX) was inserted into the right carotid artery and advanced into the LV under pressure control as described previously. Polyethylene (PE) catheters (PE-50) were inserted into the right femoral artery for measurement of mean arterial pressure (MAP) and the right femoral vein for fluid administration. After stabilization for 20 min, the signals were continuously recorded at sampling rate of 1,000/s using an ARIA P-V conductance system (Millar Instruments) coupled to a PowerLab/4SP A/D converter (AD Instruments; Mountain View, CA) and a personal computer. HR, maximal LV systolic pressure (LVSP),

Deficiency of TIMP-1 exacerbates LV remodeling after myocardial infarcation in mice

E E J M Creemers, J N Davis, A M Parkhurst, P Leenders, K B Dowdy, E Hapke, A M Hauet, M J A P Daemen, M R Zile and F G Spinale, American Journal of Physiology: Heart and Circulatory Physiology, H364-H371, 2003

A 1.1-mm steel endotracheal tube was placed, and the anesthesized mice were mechanically ventilated (MiniVent 845; Hugo Sachs/Harvard Apparatus, March-Hugstetten, Germany). The mice were positioned on a feedback temperature-controlled operating table (Vestavia Scientific, Birmingham, AL)..…….. the right carotid artery was exposed. A precalibrated four-electrode pressure sensor catheter (1.4-Fr, SPR-839; Millar Instruments, Houston, TX) was positioned in the LV. The catheter was interfaced to a pressure conductance unit (ARIA, MPCU-200; Millar Instruments), in which electrical excitation was performed under digital control (DAQ, PV Analysis Software; Millar Instruments). The continuous digital pressure and conductance signals were integrated with an ECG signal (PowerLab; AD Instruments) and displayed in real time with a dual-display heads-up flat screen (Sony Electronics).