This project aims to provoke severe right-sided cardiac remodeling to evaluate whether the induced myocardial inflammatory profile is associated with susceptibility to cardiac arrhythmias. The pulmonary artery tract bending successfully leads to right heart failure and physiological changes responsible for the development of cardiac rhythm disorders, including atrial fibrillation, or AF.Most available in vivo models of induced inflammation involve genetic or drug-induced systemic inflammatory status. Unlike the well-known model of the left-side heart disease by myocardial infarction or aortic constriction, proof of concept was lacking to study arrhythmias and inflammation specifically localized in the right side of the heart.
Recent clinical in fundamental studies converged to designate inflammation as an important common denominator of most AF risk factors. In addition, the pathophysiology of AF in right heart failure is poorly understood. Our approach helps to characterize the role of inflammation in the development of AF in right heart failure Compared to experimentally drug-induced right heart failure, including the monocrotaline approach, which leads to pulmonary inflammation, our methods helped to focus on right heart failure associated inflammation to study atrial and ventricular arrhythmias.
Our findings will help to better understand and describe the mechanisms orchestrating the association between right heart failure and the activation of inflammation, leading to atrial fibrillation. To begin, blunt the tip and bend the 19-gauge needle to a 90-to-110-degree angle using forceps. After anesthetizing the rat, intubate it with an endotracheal tube.
To initiate a left-side thoracotomy, using sharp forceps, pierce a small hole in the midclavicular line of the muscle located between the third and fourth ribs, and complete the hole using forceps with blunted tips. Introduce the curved forceps into the opening and slide it along the left interior wall of the muscle between the two ribs to slightly lift the left chest wall and avoid touching the lungs while cutting the muscle. Use the introduced forceps as a guide to make an incision longitudinally along the ribs, approximately one centimeter, with iris scissors.
Expand the intercostal incision to one to two centimeters to the left of the rat using round-tip scissors. Reposition their retractors under the ribs to keep the wound open. Observe the inferior part of the thymus and a portion of the left lobe of the lung.
Separate the thymus lobes using blunt dissection with forceps. Dissect the thin layer of the pericardium and attached adipose tissue without touching the pleural membrane. Hold the lung on the left side using wet gauze.
Then expose the upper portion of the heart, the left atrium, the pulmonary trunk and the aortic arch. Now, insert the curved forceps in a closed position into the space between the left atrial appendage and the pulmonary trunk to reach the other side of the vessel. Visualize the tip of the forceps through the conjunctive membrane cranially to the pulmonary trunk.
Using a second forcep, dissect over the tip and carefully pierce the membrane to create a small opening. Slightly open, the curved forceps positioned under the pulmonary trunk to grab a 5 0 silk thread. Retract the forceps to bring the thread from one side to the other of the pulmonary trunk.
Next, perform the constriction of the pulmonary trunk by first practicing a loose double knot of the 5 0 silk close to the artery. Insert the 19-gauge needle along the vessel and under the thread. Then tighten the first knot and fix it with a second simple knot before removing the 19-gauge needle.
Perform a final simple knot and cut the remaining 5 0 silk thread around 0.5 to one centimeter from the knot. To close the rib cage, perform a cross-stitch pattern using a synthetic absorbable 5 0 suture thread. Apply a few drops of 0.9%saline over the wound area.
Then compress each side of the chest wall to remove air bubbles and reestablish the thoracic negative pressure. Reposition the pectoral muscles and wipe off the remaining saline with a sterile gauze. Using a syringe, apply a splash block of lidocaine on the surface and surrounding area of the wound.
Close the skin using a synthetic absorbable 5 0 suture thread with a needle in a continuous subcuticular pattern. After removing isoflurane inhalation, maintain the rat under mechanical ventilation with oxygen flow. Turn the rat on its right side or ventral position to facilitate breathing.
Once the rat starts to move on its own, transfer it from the heating pad to a new sterile cage for recovery. During the postoperative period, place the cage over a heating pad to maintain body temperature and monitor the rat. After the PAB surgery and the postoperative recovery period, place the anesthetized rat on an image acquisition system for transthoracic echocardiography.
Use color mapping in a two-dimensional parasternal short axis view by positioning the 12S probe at the level of the aortic valve. Click on the color doppler button on the echo machine to visualize the blood flow pattern crossing the PAB area in the pulmonary trunk. Perform continuous wave doppler in the two-dimensional parasternal short axis view to record the properties of the blood flow crossing the PAB area, including the peak velocity and the mean pressure gradient.
Apply a two-dimensional apical four-chamber view by positioning the 12S probe at the level of the apex of the heart. Demonstrate the enlargement of the right atrium, or RA, and right ventricle, or RV, following the surgery, and determine the RA horizontal dimension at the end of cardiac systole. Apply color mapping in a two-dimensional apical four-chamber view to reveal tricuspid regurgitation due to PAB by acquiring cine loops on the echo machine.
To study the tricuspid annulus plane systolic excursion, perform M-mode echocardiography in the apical four-chamber view by crossing the conjunction of the tricuspid annulus and RV lateral wall. Use tissue doppler imaging in the apical four-chamber view at the level of the conjunction of the tricuspid annulus and RV lateral wall for the measurement of the RV lateral wall systolic contractility to evaluate RV systolic performance. Record diastolic transtricuspid flow using pulsed wave doppler in the apical four-chamber view to study peak velocity in the early filling wave, atrial filling wave, and the ratio of the early filling wave by atrial filling wave.
Perform M-mode echocardiography in the parasternal long axis view at the level of the aortic valve. Measure the RV outflow tract at the end of cardiac diastole and the left atrium dimension at the end of cardiac systole. Using the following sets of simulation thresholds, apply a voltage burst equivalent to four times the threshold voltage to evaluate the atrial fibrillation vulnerability.
Identify and quantify the occurrence of cardiac tachyrhythmias, including atrial fibrillation, or atrial flutter, after each burst. Compared to the sham group, PAB rats exhibited significantly higher pulmonary artery peak velocity and mean gradient, confirming increased pulmonary artery pressure. Increased RV thickness and RA dilation were confirmed through echocardiography and histological analysis post-PAB.
RV systolic pressure was significantly increased, and RV contractility rate was decreased in PAB rats compared to sham. PAB induced a significant increase in right atrial diameter, while left atrial diameter remained unchanged. Tricuspid valve malfunction leading to regurgitation was observed in PAB rats, characterized by blood leakage into the RA during systole.
The RR interval and P-wave duration were significantly increased in PAB rats compared to sham, indicating altered heart rate and atrial conduction. The QT interval was significantly prolonged in PAB rats, suggesting impaired ventricular contractility. PAB rats exhibited a significantly higher inducibility and duration of atrial fibrillation compared to sham rats.
