Studying PV Loops in Larger Animals

** Download full PDF brochure here!

Many useful and necessary parameters are used to describe the function of a beating heart, including minimum dP/dt, maximum dP/dt, developed pressure and cardiac output. However, only the pressure-volume (PV) loop properly describes the performance of the heart as a pump.

Over the past 30 years, the PV loop has steadily become the “gold standard” as a means to study myocardial contractility, compliance, muscle energetics and other important quantitative measures of function in vivo (and in certain instances, in vitro).

The challenge for medical technology companies has been to provide an accurate, reliable and minimally invasive tool to study the PV loop in larger animals. Scisense offers a full line of catheterbased sensors to satisfy this need in the scientific community. Our 3F (rabbit), 5F (dog/sheep/pig) and 7F (dog/sheep/pig) pressure-volume catheters provide cardiac research scientists the unique ability to measure almost every imaginable hemodynamic and contractile index of ventricular function with a single instrument. All catheters can be inserted through either the carotid or fimoral arteries for a truly minimally invasive operation.

These catheters have been extensively tested, validated and endorsed by some of the most knowledgeable and well-respected authorities in the world on solid-state pressure and conductance volume measurements.

PRINCIPAL OF OPERATION:
A catheter with multiple ring-electrodes, and at least one pressure sensor, is introduced into the heart such that the rings span the entire ventricular long-axis. The distal and proximal electrodes (apical/basal electrodes) generate a low-current electrical field within the blood. Pairs of intervening recording electrodes delineate discrete segments within the ventricle and measure the electrical conductivity of blood within these segments.

As luminal volume in the heart changes during the cardiac cycle, the conductivity value measured between each pair of recording electrodes will change proportionally. This conductivity value is then applied to an accepted volume formula (Baan’s equation) to generate a real-time segmental volume signal. Total ventricular volume is the sum of all individual segments. Our state-of-the-art hardware outputs an analog voltage, for each segment, that is proportional to this volume change. A variety of software packages are available to perform basic hemodynamic analysis and more complex PV loop analyses on these signals.

Baan’s Equation: V= 1–α (ρL2)(G-Gp)

Click here to see the Functional Parameters from Scisense PV System.

APPLICATIONS:

• Heart Failure
• Cardiac Hypertrophy
• Cardiovascular Remodeling
• Ischemia/Reperfusion injury
• Myocardial Stunning
• Stem Cell Research
• Pharmacology and Toxicology
• Cardiac Resynchronization Therapy
• Surgical Interventions

Scisense Catheter Design , Features and Benefits:

High-fidelity Pressure Sensor:

• High frequency response maintains signal integrity and prevents damping or attenuation of signal
• No motion artifact or overshoot as with conventional fluid-filled catheters
• 10μV/V/mmHg sensitivity provides higher measurement resolution than any other sensor on the market
• Pressure membrane recessed for protection
• Vented to atmosphere to correct for barometric pressure
• Pressure and volume at the source from a single instrument

Conductance Electrodes:

• 5 segmental volumes (3 for rabbit)
• Standard electrode spacing or customized electrode spacing

Catheter:

• Provides ideal balance of flexibility and rigidity, ensuring easy insertion and maneuverability
• Available with or without pigtail
• Second pressure sensor can be added on catheter to simultaneously measure LV pressure and aortic pressure

SCISENSE PRESSURE -VOLUME CATHETERS ARE COMPATIBLE WITH ALL OTHER COMMERCIALLY AVAILABLE PRESSURE -VOLUME SYSTEMS!

The Scisense Advantage

Deriving LV Volumes from the conductance of blood is a well published technique that has been used extensively by researchers over the last 30 years. Scisense has developed patent pending technology to “tune” the electrical field used to derive these volume measurements with adjustable gain and offset controls for each segment. This “tunable segment” technology represents a significant advance over other approaches used in the past, such as single and dual field systems.

Briefly, the electric field generated by any conductance catheter has a nonuniform distribution. Therefore, the sensing electrodes along the length of the catheter measure different field strength levels depending on how far they are from the source of the field.

If this error in the electrical field shape is left uncorrected each segment of a traditional five-segment conductance catheter will report a different voltage for a total cylindrical volume even when each segment is exposed to the same volume. Similarly, other systems do not account for possible micro-variations between catheters in electrode spacing, nor do they account for the effect of insufficient cleaning of catheters between uses.

The Scisense GX5 system also features our standard calibration and offset controls for pressure signals and can be equipped to operate single segment PV catheters for rodent models.