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Biology

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Published: July 21st, 2023

DOI:

10.3791/65384

1Department of Cardiovascular Medicine, The University of Tokyo Hospital, 2Department of Therapeutic Strategy for Heart Failure, Graduate School of Medicine, The University of Tokyo, 3Division of Cardiology, Department of Medicine, The Johns Hopkins Medical Institutions

The present protocol describes obtaining the pressure-volume relationship through transesophageal pacing, which serves as a valuable tool in evaluating diastolic function in mouse models of heart failure.

Heart failure with preserved ejection fraction (HFpEF) is a condition characterized by diastolic dysfunction and exercise intolerance. While exercise-stressed hemodynamic tests or MRI can be used to detect diastolic dysfunction and diagnose HFpEF in humans, such modalities are limited in basic research using mouse models. A treadmill exercise test is commonly used for this purpose in mice, but its results can be influenced by body weight, skeletal muscle strength, and mental state. Here, we describe an atrial-pacing protocol to detect heart rate (HR)-dependent changes in diastolic performance and validate its usefulness in a mouse model of HFpEF. The method involves anesthetizing, intubating, and performing pressure-volume (PV) loop analysis concomitant with atrial pacing. In this work, a conductance catheter was inserted via a left ventricular apical approach, and an atrial pacing catheter was placed in the esophagus. Baseline PV loops were collected before the HR was slowed with ivabradine. PV loops were collected and analyzed at HR increments ranging from 400 bpm to 700 bpm via atrial pacing. Using this protocol, we clearly demonstrated HR-dependent diastolic impairment in a metabolically induced HFpEF model. Both the relaxation time constant (Tau) and the end-diastolic pressure-volume relationship (EDPVR) worsened as the HR increased compared to control mice. In conclusion, this atrial pacing-controlled protocol is useful for detecting HR-dependent cardiac dysfunctions. It provides a new way to study the underlying mechanisms of diastolic dysfunction in HFpEF mouse models and may help develop new treatments for this condition.

Heart failure represents a leading cause of hospitalization and death across the globe, and heart failure with preserved ejection fraction (HFpEF) accounts for around 50% of all heart failure diagnoses. HFpEF is characterized by diastolic dysfunction and impaired exercise tolerance, and the associated hemodynamic abnormalities, such as diastolic dysfunction, can be clearly detected through exercise-stressed hemodynamic testing or MRI scans1,2.

In experimental models, however, available modalities for assessing the physiological abnormalities related to HFpEF are limited.css-f1q1l5{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:flex-end;-webkit-box-align:flex-end;-ms-flex-align:flex-end;align-items:flex-end;background-image:linear-gradient(180deg, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0.8) 40%, rgba(255, 255, 255, 1) 100%);width:100%;height:100%;position:absolute;bottom:0px;left:0px;font-size:var(--chakra-fontSizes-lg);color:#676B82;}

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This animal protocol was approved by the Institutional Animal Care and Use Committee and followed the regulations for animal experiments and related activities at the University of Tokyo. For the present study, 8-12 week old male C57/Bl6J mice were used. The animals were obtained from a commercial source (see the Table of Materials). A model of HFpEF was established by administering a high-fat diet for 15 weeks in conjunction with NG-nitro-L-arginine methyl ester, as described previously

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The baseline PV loop data are displayed in Figure 1 and Table 1. At baseline (in the absence of pacing), there were no significant differences in diastolic parameters such as the relaxation time constant (Tau), the minimum rate of pressure change (dP/dt min), and EDPVR between the control and HFpEF mice. However, the HFpEF mice exhibited higher blood pressure and arterial elastance (Ea), as shown in Figure 1, and demonstrated a typical mountain-.......

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We present a methodology to assess pressure-volume relationships with the application of transesophageal pacing. Exercise intolerance is one of the key characteristics of HFpEF, yet there are no techniques available for the evaluation of cardiac function in mice during exercise. Our pacing protocol offers a valuable tool for detecting diastolic dysfunction, which may not be apparent under resting conditions.

To achieve a PV loop of accurate and consistent quality, the following steps must be m.......

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This work was supported by research grants from the Fukuda Foundation for Medical Technology (to E.T. and G. N.) and the JSPS KAKENHI Scientific Research Grant-in-Aid 21K08047 (to E.T.).

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Name Company Catalog Number Comments
2-0 silk suture, sterlie Alfresa Pharma Corporation, Osaka, Japan 62-9965-57 Surgical Supplies
2-Fr tetrapolar electrode catheter Fukuda Denshi, Japan and UNIQUE MEDICAL, Japan custom-made Surgical Supplies
Albumin Bovine Serum Nacalai Tesque, Inc., Kyoto, Japan 01859-47 Miscellaneous
C57/BI6J mouse Jackson Laboratory animals
Conductance catheter Millar Instruments, Houston, TX PVR 1035
Electrical cautery, Electrocautery Knife Kit ellman-Japan,Osaka, Japan 1-1861-21 Surgical Supplies
Etomidate Tokyo Chemical Industory Co., Ltd., Tokyo Japan E0897 Anesthetic
Grass Instrument S44G Square Pulse Stimulator Astro-Med, West Warwick, RI Pacing equipment
Isoflurane Viatris Inc., Tokyo, Japan 8803998 Anesthetic
Ivabradine Tokyo Chemical Industory Co., Ltd., Tokyo Japan I0847 Miscellaneous
LabChart software ADInstruments, Sydney, Australia LabChart 7 Hemodynamic equipment
MPVS Ultra Millar Instruments, Houston, TX PL3516B49 Hemodynamic equipment
Pancronium bromide Sigma Aldrich Co., St. Louis, MO 15500-66-0 Anesthetic
PE10 polyethylene tube Bio Research Center  Co. Ltd., Tokyo, Japan 62101010 Surgical Supplies
PowerLab 8/35 ADInstruments, Sydney, Australia PL3508/P Hemodynamic equipment
PVR 1035 Millar Instruments, Houston, TX 842-0002 Hemodynamic equipment
Urethane (Ethyl Carbamate) Wako Pure Chemical Industries, Ltd., Osaka, Japan 050-05821 Anesthetic
Vascular Flow Probe Transonic, Ithaca, NY MA1PRB Surgical Supplies

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