Name: Cardiac Catheterization in Mice to Measure the Pressure Volume Relationship: Investigating the Bowditch Effect (Video) | JoVE Journal
Uploaded: 2015-06-14T15:00:00.000+00:00
Duration: 7 min 38 s
Description: Learn cardiac catheterization in mice to measure pressure-volume relationships and investigate the Bowditch effect. This method enables precise in vivo assessment of left ventricular function at varying heart rates.

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5 minutes

This study was supported by NIH grants HL091986 (JPD) and HL094692 (MTZ).

NOTE: This animal protocol was approved by the Institutional Animal Care and Use Committee (IACUC) at The Ohio State University. This procedure can be used on any mouse in which the inner diameter of the carotid artery is large enough to insert the catheter. Use mice that are above 16 g (older than ~2 months).
1. Preparing Mouse for Catheterization
<ol>
	<li>Seal all surgical instruments and supplies in a sterilization pouch. Sterilize the pouch in an autoclave machine. Maintain a sterile field throughout the procedure and wear sterile gloves.</li>
	<li>Anesthetize mice with ketamine (55 mg/kg) plus xylazine (15 mg/kg) by intraperitoneal injection. 
	NOTE: The whole procedure measuring both pressure/volume at various heart rates and ESPRV takes less than 20 min. If additional time is required (i.e., more than 30 min), give an additional &#188; dose of anesthesia every 30 min.</li>
	<li>Remove the hair in the anterior region of neck and chest area using hair removing lotion (e.g., Nair) and tape the limbs of the mouse onto the foam platform. Confirm a state of deep anesthesia by a toe pinch.</li>
	<li>Insert a rectal probe to monitor the body temperature (37 &#177; 1 &#176;C), and maintain using a thermo-regulated heating pad (located between the surgical drape and platform).</li>
	<li>Prepare a length of 4-0 suture (~10 cm). Loop suture around the upper incisors and tape to platform. This will keep the neck straight.</li>
	<li>Sterilize the surgical area by swabbing the area with Betadine and 75% alcohol three times.</li>
</ol>
2. Catheterization
<ol>
	<li>Prepare the catheter by presoaking the tip in saline or distilled water (37 &#176;C) for at least 30 min prior to use (according to manufacturer&#8217;s instructions) to acclimate the pressure sensor diaphragm for the wet biological environment and to prevent pressure signal drift and negative pressure recordings.</li>
	<li>Make a longitudinal 0.8 cm incision between the lower jaw and sternum in the anterior region of the neck. With the fine scissors, separate the skin-muscular connective tissue to expose the trachea located under the stemohyoideus muscle.</li>
	<li>Separate the fat and muscular tissue at the right side of the trachea with curved forceps to expose the right carotid artery. 
	NOTE: The carotid artery is the biggest artery in the anterior region of the neck, contains bright red blood, and is pulsatile. Do not confuse with the jugular vein that runs parallel to the carotid artery. The jugular vein is dark red and non-pulsatile. In addition, during the isolation of the carotid artery, the user should be aware of not damaging the pneumogastric nerve.</li>
	<li>Remove the fat from the right carotid artery with the curved forceps. If there exists branching of the vessel which will impede this operational technique, cut them with a Bovie cautery to dissociate the carotid artery. Separate as much of the tissue as possible under the carotid artery using curved forceps.</li>
	<li>Cut two 5 cm 6-0 silk threads. Pass each silk thread under the right carotid artery.</li>
	<li>Position one thread near the proximal part and the other near the distal part of the artery. Make a tight knot on the thread at the distal part, and make a loose knot on the thread at the proximal part.</li>
	<li>Block blood flow by clamping the proximal part of the artery using a small hemostat vascular clamp (place the clamp below the proximal thread). The sealed region of the artery will be filled with blood making it easy to perform step 2.8.</li>
	<li>Puncture a small hole in the right carotid artery between the two threads (but closer to the distal thread) with a 26 G needle. Insert the catheter into the carotid artery. Slightly tighten the loose knot at the proximal part of the carotid artery onto the catheter to keep in place. 
	NOTE: Using the needle puncture is preferred compared to scissors incision. By making a tight knot in the distal part of the artery first, and then clamping the proximal part, the artery will be fully filled with blood. This makes it very easy to poke through the blood vessel. Furthermore, the size of the needle (26 G) punctures the artery with a hole that nicely fits the size of the catheter. When using the scissors incision method, it was more difficult to control the size of the incision. However, the method chosen should be dependent upon on which one the surgeon feels more comfortable with.</li>
	<li>Start recording pressure signals as in step 3.</li>
	<li>Loosen the hemostat clamp and continue inserting the catheter forward into the left ventricle. If some resistance is experienced when advancing the catheter, gently pull it back and try advancing again. For a mouse weighing ~18-25 g, the estimated length of the catheter that is inserted is 18 mm. 
	NOTE: The arterial pressure signal will fluctuate from 70 to 120 mm Hg. Once the catheter is in the left ventricle the shape of the pressure signal changes and the pressure will fluctuate from 0 to 120 mm Hg (shown in Figure 1). Heart function will stabilize within 2-3 min after insertion of the catheter.</li>
	<li>Continuously monitor body temperature, anesthesia level, and breathing rate.</li>
</ol>
3. Data Acquisition
<ol>
	<li>Use LabChartPro 7 software (or similar software). Use the WorkFlow option of the PV Loop LabChart Module. Using this module, select the Pressure and Volume Loops default setting.</li>
	<li>Set-up three channels: one channel for pressure, one channel for volume, and one channel for heart rate. Set scale ranges of above parameters as 0-150 mm Hg, 0-100 &#181;l and 0-800 beat/min, respectively.</li>
	<li>Press start key to record.</li>
</ol>
4. Bowditch Effect
<ol>
	<li>Make a 1 cm incision in the precordium area parallel to the manubrium. Cut the layer of muscle and expose the intercostal space using scissors.</li>
	<li>Using a square pulse stimulator, set the following parameters: Voltage of 2 V, duration of 2 msec, and enable repeat mode.</li>
	<li>Hold the negative electrode with forceps and insert it through the fourth intercostal space to the apical region of the heart. Hold the positive electrode with forceps and insert it through the second intercostal space to the right atrium region of the heart.</li>
	<li>Turn on the stimulator and change the frequency to pace the heart from 4 Hz (240 beats/min) up to 10 Hz (600 beats/min). At each new heart rate, stimulate the heart for 1 min before data collection.</li>
</ol>
5. Generating the ESPVR and PRSW
<ol>
	<li>Cut the skin and muscle tissue perpendicular to the manubrium in the abdominal area with scissors. Open the enterocoelia and expose the liver.</li>
	<li>Drag the arcus costarum towards the head using metallic traction.</li>
	<li>Gently push the liver downwards with a cotton swab. Be careful not to push too much to affect the chest cavity. This will change heart function.</li>
	<li>Cut the falciform ligament of the liver with scissors to expose the suprahepatic inferior vena cava (IVC).</li>
	<li>Use curved forceps to rapidly squeeze the IVC for 5 sec to block the return of blood to the right atrium. The left ventricular pressure and volume will fall due to the reduced inflow to the heart. In generating these values, do not use loops below 60 mm Hg. The 60 mm Hg is in reference to systolic pressure. 
	NOTE: This value is set at 60 mm Hg because this will cause a significant drop in perfusion pressure to considerably decrease coronary perfusion and affect contractility.</li>
</ol>
6. Volume Calibration
<ol>
	<li>Heparinize the mouse with 0.1 ml of 1:5,000 heparin solution (diluted with normal saline) by intraperitoneal injection.</li>
	<li>Remove the catheter from the carotid artery. When the catheter is pulled out from the carotid artery, heparinized blood will seep from the hole where the catheter was inserted.</li>
	<li>Collect this blood for volume calibration using a 1 ml syringe. Fill each well in calibration cuvette.</li>
	<li>Remove heart to euthanize the mouse via exsanguination.</li>
	<li>Position the catheter in each well and get a steady relative volume unit (RVU) value. Generate a standard curve using the various standard volumes and RVU values from each well.</li>
	<li>Convert the recorded RVU to &#181;l.</li>
</ol>
7. Data Processing
<ol>
	<li>To examine the Bowditch effect, select steady-state pressure/volume traces from each heart rate. Click the baseline analysis to obtain data.</li>
	<li>For ESPVR and PRSW data, select the first ~15 pressure/volume traces, click occlusion analysis in the software to generate the ESPVR (slope of the pressure developed by the LV at end-diastolic volume) and PRSW (the linear regression of stroke work with the end-diastolic volume ) slopes.</li>
	<li>Give attention to the shape of the loops. Make sure the loop is closed with no angular points or twists. This is a sign of improper catheter placement or excess noise. Periodically check loops during the experiment to ensure proper pressure and volume data are being generated.</li>
</ol>

<ol><li>Janssen, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Myocardial+contraction-relaxation+coupling%5BTitle%5D)+AND+%22Am+J+Physiol+Heart+Circ+Physiol%22%5BJournal%5D)">Myocardial contraction-relaxation coupling.</a> Am J Physiol Heart Circ Physiol. 299, H1741-H1749 (2010).</li>
<li>Roman, M. J., Devereux, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Comparison+of+noninvasive+measures+of+contractility+in+dilated+cardiomyopathy%5BTitle%5D)+AND+%22Echocardiography%22%5BJournal%5D)">Comparison of noninvasive measures of contractility in dilated cardiomyopathy.</a> Echocardiography. 8, 139-150 (1991).</li>
<li>Hamlin, R. L., del Rio, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((dP%2Fdt%28max%29--a+measure+of+%27baroinometry%5BTitle%5D)+AND+%22J+Pharmacol+Toxicol+Methods%22%5BJournal%5D)">dP/dt(max)--a measure of 'baroinometry.</a> J Pharmacol Toxicol Methods. 66, 63-65 (2012).</li>
<li>Feneley, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Comparison+of+preload+recruitable+stroke+work%2C+end-systolic+pressure-volume+and+dP%2Fdtmax-end-diastolic+volume+relations+as+indexes+of+left+ventricular+contractile+performance+in+patients+undergoing+routine+cardiac+catheterization%5BTitle%5D)+AND+%22J+Am+Coll+Cardiol%22%5BJournal%5D)">Comparison of preload recruitable stroke work, end-systolic pressure-volume and dP/dtmax-end-diastolic volume relations as indexes of left ventricular contractile performance in patients undergoing routine cardiac catheterization.</a> J Am Coll Cardiol. 19, 1522-1530 (1992).</li>
<li>Kass, D. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Comparative+influence+of+load+versus+inotropic+states+on+indexes+of+ventricular+contractility%3A+experimental+and+theoretical+analysis+based+on+pressure-volume+relationships%5BTitle%5D)+AND+%22Circulation%22%5BJournal%5D)">Comparative influence of load versus inotropic states on indexes of ventricular contractility: experimental and theoretical analysis based on pressure-volume relationships.</a> Circulation. 76, 1422-1436 (1987).</li>
<li>Nemoto, S., DeFreitas, G., Mann, D. L., Carabello, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+changes+in+left+ventricular+contractility+on+indexes+of+contractility+in+mice%5BTitle%5D)+AND+%22Am+J+Physiol+Heart+Circ+Physiol%22%5BJournal%5D)">Effects of changes in left ventricular contractility on indexes of contractility in mice.</a> Am J Physiol Heart Circ Physiol. 283, H2504-H2510 (2002).</li>
<li>Ziolo, M. T., Kohr, M. J., Wang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nitric+oxide+signaling+and+the+regulation+of+myocardial+function%5BTitle%5D)+AND+%22J+Mol+Cell+Cardiol%22%5BJournal%5D)">Nitric oxide signaling and the regulation of myocardial function.</a> J Mol Cell Cardiol. 45, 625-632 (2008).</li>
<li>Barouch, L. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nitric+oxide+regulates+the+heart+by+spatial+confinement+of+nitric+oxide+synthase+isoforms%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Nitric oxide regulates the heart by spatial confinement of nitric oxide synthase isoforms.</a> Nature. 416, 337-339 (2002).</li>
<li>Wang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neuronal+nitric+oxide+synthase+signaling+within+cardiac+myocytes+targets+phospholamban%5BTitle%5D)+AND+%22Am+J+Physiol+Cell+Physiol%22%5BJournal%5D)">Neuronal nitric oxide synthase signaling within cardiac myocytes targets phospholamban.</a> Am J Physiol Cell Physiol. 294, C1566-C1575 (2008).</li>
<li>Georgakopoulos, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vivo+murine+left+ventricular+pressure-volume+relations+by+miniaturized+conductance+micromanometry%5BTitle%5D)+AND+%22Am+J+Physiol%22%5BJournal%5D)">In vivo murine left ventricular pressure-volume relations by miniaturized conductance micromanometry.</a> Am J Physiol. 274, H1416-H1422 (1998).</li>
</ol>

There are no competing financial interests.

A critical step for this technique to obtain a reliable measure of contractility is proper catheter placement into the LV. If the catheter is not placed correctly, when the LV contracts the walls may contact the catheter resulting in very high, and not physiological, pressure values causing irregular shaped PV loops. If needed, the catheter can be rotated to achieve the correct placement. Another key step for this technique is to make sure the mouse received proper anesthesia. If the mouse is over anesthetized, this will...

The purpose of the heart is to pump blood throughout the body to meet the metabolic demands of the organism. Since these demands are constantly fluctuating (e.g., during exercise), the heart must adapt (i.e., increase cardiac output). The heart has devised numerous pathways to accomplish this feat. The prime manner the heart achieves this is via an increase in heart rate (i.e., Bowditch effect)1. That is, as one&#8217;s heart rate increases, this results in an increase in contractility and an increase in cardiac output. Thus, heart function is exceedingly dependent upon heart rate. Unfortunately, heart disease (e.g., myocardial infarction, hypertrophy, etc.) results in poor heart function in which the heart consequently will not be able to meet the metabolic demands of the body. Heart disease is the main cause of morbidity and mortality in Western society. Animal models that recapitulate many human cardiomyopathies are used to investigate molecular mechanisms and to test potential therapies. To discern these mechanisms and determine if a therapy may be viable, investigators must assess heart function in vivo.
There are several ways to assess heart function in vivo (e.g., echocardiography, MRI, etc.), which routinely measure ejection fraction, fractional shortening, cardiac output, etc. However, these parameters are highly dependent upon afterload, preload, and heart rate in addition to contractility2. Measuring contractility is indispensable to comprehend the intrinsic properties of the heart in its native environment. The maximum (dP/dtmax) rate of pressure development brings us a step closer to understanding contractility. Unfortunately, dP/dt is also dependent upon heart rate and loading conditions3. Therefore techniques have been developed to measure load (and heart rate, see below) independent indices of myocardial contractility (i.e., end systolic pressure volume relationship (ESPVR) and preload recruitable stroke work (PRSW))4-6. ESPVR describes the maximal pressure that can be developed by the ventricle at any given LV volume. The slope of ESPVR represents the end-systolic elastance (Ees). PRSW is the linear regression of stroke work (area enclosed by the PV loop) with the end-diastolic volume. These procedures are a more accurate and precise measurement of contractility compared to hemodynamic parameters such as ejection fraction, cardiac output, and stroke volume. ESPVR and PRSW can be obtained via the temporary blocking of the inferior vena cava (IVC). Blocking the IVC can be performed with a closed chest to avoid the effect of changing intrapleural pressure on heart function.
Increasing heart rate also enhances contraction and relaxation1. Thus, when comparing heart function between experimental groups (e.g., &#177; dP/dt), heart rates need to be similar. However, similar heart rates usually do not occur in each animal due to various conditions (disease, research intervention, etc.). It should be noted that anesthesia (injectable and inhaled) lowers heart rate. As heart rate is a major determinant of contractility, anesthesia will considerably affect contractility. For this reason, we are describing our procedure. Additionally, a hallmark of many cardiomyopathies is a decreased contractile reserve (i.e., a decreased Bowditch effect). Therefore, heart function should be measured over a range of heart rates. Here we describe how to use a stimulator (with a closed chest) to achieve these effects.
In addition to heart rate, nitric oxide (NO) is also an important modulator of contractility7. NO is produced via enzymes termed NO synthase (NOS). We and others have shown that mice with knockout of neuronal NOS (NOS1-/-) have blunted myocyte contraction and in vivo cardiac hemodynamics8,9. This mouse will be used to demonstrate the measurement of left ventricular contractility via the LV pressure/volume analysis procedure performed at various heart rates.

<table><tbody><tr><td>Xlyzine 100&amp;nbsp;mg/ml</td><td>Ana Sed</td><td>4821</td><td></td></tr><tr><td>Katamin 50&amp;nbsp;mg/ml</td><td>Ketalar</td><td>310006</td><td></td></tr><tr><td>Heparin</td><td>APP Pharmaceuticals</td><td>6003922</td><td></td></tr><tr><td>4-0 silk thread</td><td>Surgical specialties</td><td>SP102</td><td></td></tr><tr><td>6-0 silk thread</td><td>Surgical specialties</td><td>MBKF270</td><td></td></tr><tr><td>Forceps</td><td>Fine Science Tools</td><td>11251-10</td><td></td></tr><tr><td>Curve forceps</td><td>Fine Science Tools</td><td>11274-20</td><td></td></tr><tr><td>Scissors</td><td>Fine Science Tools</td><td>14090-09</td><td></td></tr><tr><td>Vascular clamp</td><td>Fine Science Tools</td><td>18555-03</td><td></td></tr><tr><td>Microscope</td><td>World precision instruments</td><td>PZM-3</td><td></td></tr><tr><td>Pressure catheter</td><td>Millar instruments</td><td>SPR-839</td><td></td></tr><tr><td>Pressure and volume system</td><td>Millar instruments</td><td>MPVS-300</td><td></td></tr><tr><td>PowerLab4/35</td><td>AD instruments</td><td>N12128</td><td></td></tr><tr><td>LabchartPro 7</td><td>AD instruments</td><td></td><td></td></tr><tr><td>Temperature controller</td><td>CWE</td><td>TC-1000</td><td></td></tr><tr><td>Stimulator</td><td>Grass</td><td>SD-5</td><td></td></tr><tr><td>Sterile glove</td><td>Micro-Touch</td><td>1305018821</td><td></td></tr><tr><td>Hair remover lotion</td><td>Nair</td><td></td><td></td></tr><tr><td>Betadine surgical scrub</td><td>Veterinary</td><td>NDC 6761815401</td><td></td></tr><tr><td>Alcohol</td><td>Decon Laboratories</td><td>2801</td><td></td></tr><tr><td>Bovie cautery</td><td>Bovie</td><td>AA29</td><td></td></tr><tr><td>1&amp;nbsp;ml Syringe (26&amp;nbsp;G needle)</td><td>BD</td><td>8017299</td><td></td></tr></tbody></table>

cardiac catheterization in mice to measure the pressure volume relationship: investigating the bowditch effect

Cardiac Catheterization in Mice to Measure the Pressure Volume Relationship: Investigating the Bowditch Effect

Animal models that mimic human cardiac disorders have been created to test potential therapeutic strategies. A key component to evaluating these strategies is to examine their effects on heart function. There are several techniques to measure in vivo cardiac mechanics (e.g., echocardiography, pressure/volume relations, etc.). Compared to echocardiography, real-time left ventricular (LV) pressure/volume analysis via catheterization is more precise and insightful in assessing LV function. Additionally, LV pressure/volume analysis provides the ability to instantaneously record changes during manipulations of contractility (e.g., &#946;-adrenergic stimulation) and pathological insults (e.g., ischemia/reperfusion injury). In addition to the maximum (+dP/dt) and minimum (-dP/dt) rate of pressure change in the LV, an accurate assessment of LV function via several load-independent indexes (e.g., end systolic pressure volume relationship and preload recruitable stroke work) can be attained. Heart rate has a significant effect on LV contractility such that an increase in the heart rate is the primary mechanism to increase cardiac output (i.e., Bowditch effect). Thus, when comparing hemodynamics between experimental groups, it is necessary to have similar heart rates. Furthermore, a hallmark of many cardiomyopathy models is a decrease in contractile reserve (i.e., decreased Bowditch effect). Consequently, vital information can be obtained by determining the effects of increasing heart rate on contractility. Our and others data has demonstrated that the neuronal nitric oxide synthase (NOS1) knockout mouse has decreased contractility. Here we describe the procedure of measuring LV pressure/volume with increasing heart rates using the NOS1 knockout mouse model.

The proper insertion of the catheter into the left ventricle is an important step to attain appropriate pressure and volume values. Shown in Figure 1, using LabChart Pro 7, is the changing of the pressure waveform (shape and values) as the catheter goes from the artery into the ventricle.
After proper insertion of the catheter into the left ventricle, the pressure (P) and volume (V) values obtained will then be used to generate the PV loops (shown in Figure 2)...

This article describes the measurement of murine left ventricular function via pressure/volume analysis at different heart rates.

Animal models that mimic human cardiac disorders have been created to test potential therapeutic strategies. A key component to evaluating these ...

The overall goal of this procedure is to measure in vivo cardiac contractility at different heart rates. This is accomplished by first prepping the mouse for catheterization. Next, a catheter is inserted into the left ventricle through the carotid artery.Then a stimulator is hooked up to the mouse heart and it is paced at different heart rates and data is recorded. Finally, blood is collected from the catheter insertion site and the volume is calibrated. Ultimately, pressure volume loop analysis is used to investigate the BO effect.The main advantage of this technique over existing methods like echocardio, that pressure and volume, a LI size is more process and accurate measurement of contracting and such a more insightful technique to measure cardiac function. After preparing the mouse for catheterization, according to the text protocol in the anterior region of the neck, make a longitudinal 0.8 centimeter incision between the lower jaw and the sternum with fine scissors. Separate the skin muscular connective tissue to expose the trachea located under the sterno ous muscle.Then use curved forceps along the right side of the trachea to separate the fat and muscular tissue to expose the right carotid artery. Next, remove the fat from the carotid artery. Then if branches are present on the vessel, use a Bovie cautery to cut them and dissociate the carotid artery.Use the curved forceps to separate as much of the tissue as possible under the carotid artery. Now cut two five centimeters, six zero silk threads, and pass each one under the carotid artery position. One thread near the proximal part and the other near the distal part of the artery.Make a tight knot on the thread at the distal part and make a loose knot on the thread at the proximal part. Using a small hemostat vascular clamp block, blood flow by clamping the proximal part of the artery. The sealed region of the artery will fill with blood.Then with a 26 gauge needle, puncture a small hole in the right carotid artery between the two threads and insert the catheter into the carotid artery. Lightly tighten the loose knot at the proximal part of the carotid artery onto the catheter to keep it in place. Following the guidelines in the text protocol, start recording pressure signals.Then loosen the hemostat clamp and continue inserting the catheter forward into the left ventricle. If resistance is felt gently pull the catheter back and try advancing it again. The catheter will be inserted approximately 18 millimeters in an 18 to 25 gram mouse.Continuously monitor body temperature, anesthesia level, and breathing rate. To measure the boic effect, make a one centimeter incision in the precordium area parallel to the manubrium using scissors. Cut the layer of muscle and expose the intercostal space.Using a square pulse simulator, set the following parameters, voltage of two volts, duration of two milliseconds, and enable repeat mode with forceps. Hold the negative electrode and insert it through the fourth intercostal space to the apical region of the heart. Using forceps to hold the positive electrode, insert it through the second intercostal space to the right atrium, region of the heart.Turn on the stimulator and change the frequency to pace the heart from four hertz up to 10 hertz. At each new heart rate, stimulate the heart before data collection using scissors, cut the skin and muscle tissue perpendicular to the manubrium in the abdominal area. Open the entero CLIA and expose the liver with metallic traction.Drag the acus caster towards the head. Now using a cotton swab, gently push the liver downwards, taking care not to affect the chest cavity, which would alter heart function. Use scissors to cut the falciform ligament of the liver to expose the supra hepatic inferior vena cava or IVC with curved forceps.Rapidly squeeze the IVC for five seconds to block the return of blood to the right atrium, the left ventricular pressure and volume will fall due to the reduced inflow to the heart art. To calibrate the volume by intraperitoneal injection, heparinized the mouse with 0.1 milliliters of a one to 5, 000 heparin solution. Remove the catheter from the carotid artery.Heparinized blood will begin to seep from the hole where the catheter was inserted. Using a one milliliter syringe, collect this blood for volume calibration. Fill each well in a calibration vete.After euthanizing the mouse according to the text protocol, position the catheter and get a steady relative volume unit or RVU value. Use the various standard volumes and RVU values from each well to generate a standard curve. As shown in this figure, the pressure wave form changes in shape and value as the inserted catheter travels from the artery into the ventricle.After proper insertion the catheter into the left ventricle, the pressures p and volumes V obtained are used to generate the PV loops as seen here using the pressure values mechanisms that alter contractility can be investigated. In this example, increasing the heart rate from 300 to 600 beats per minute increased the LV pressure from 80 to 100 millimeters of mercury while the diastolic and systolic LV volumes decreased. Illustrated in this figure is the heart rate dependence of the maximum and minimum rates of pressure development DPDT in WT and OS one knockout mice OS one mice have decreased maximum and minimum rates of pressure development compared to wild type mice.Hence knockout of NOS one results in a decreased boat effect. Finally, as seen here, load independent contractility is analyzed using calculated values for N systolic ELASTINS and PRSW in WT and OS one knockout mice. These data suggest that NOS one knockout mice have decreased contractility compared to WT mice ice.After watching this video, you should now have a good understanding of how to make accurate measurements of in vivo cardiac contractility, and thus heart function at different heart rates.

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Learn cardiac catheterization in mice to measure pressure-volume relationships and investigate the Bowditch effect. This method enables precise in vivo assessment of left ventricular function at varying heart rates.

Cardiac Catheterization in Mice to Measure the Pressure Volume Relationship: Investigating the Bowditch Effect

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