Evaluation of Cardiac Hemodynamic Modifications During Temporary Left Atrial Appendage Occlusion

Brugmann University Hospital20 enrolled

Overview

The left atrium appendage (LAA) is a remnant of the original embryonic left atrium formed during the third week of gestation. LAA is believed to function as a decompression chamber during left ventricular systole and other periods when left atrial pressure is elevated. The LAA is also a major endocrine organ and is the main producer of ANP (atrial natriuretic peptide) in the human heart. The ANP concentration is 40 times higher in the LAA walls than in the rest of the atrial wall. A study of patients having undergone the maze procedure and associated LAA removal found a significantly lower ANP secretion and an increase in salt and water retention. Whether this could eventually lead to hypertension or heart failure symptoms is not known. Removal of the LAA is routinely performed during antiarrhythmic surgical techniques ("MAZE surgery") to reduce the risk of subsequent LAA thrombus. Furthermore, new percutaneous ablation techniques target LAA to reduce further risks of atrial fibrilation recurrences. However, in addition to effects on diastolic atrial function and atrial natriuretic peptide (ANP) secretion, this could potentially reduce stroke volume and cardiac output and may thus promote heart failure. Its removal could be particularly detrimental in patients with existing heart failure and high intraatrial pressure, as it would further promote pulmonary congestion and also reduce their cardiac output. The study will be conducted at the CHU Brugmann Hospital, with collaboration between cardiac surgery and cardiology wards. Subjects referred for non valvular cardiac surgery will be prospectively included during the first 6 months following the onset of the protocol. Echocardiographic and invasive data will be collected simultaneously. The goals of the study are: * To evaluate the immediate impact of temporary closure of the LAA using a vascular clamp in the beating heart of human subjects during cardiac surgery. Impact of LAA occlusion will be measured using transesophageal echocardiography and hemodynamic measurement of the cardiac output. * To correlate echocardiographic parameters with in situ hemodynamic data. A significant role of the LAA in the cardiac hemodynamic including the left ventricle outflow might have different clinical implications and will raise questions about: * Appropriateness of LAA resection in antiarrhythmic surgery * Importance of restoring sinus rhythm in atrial fibrilation patients * Importance to spare LAA from ablation during atrial fibrilation ablation to avoid significant consequences on cardiac function. * Appropriateness of the LAA occluding device in atrial fibrillation patients.

Study Type

INTERVENTIONAL

Interventions

Transesophageal echocardiogramDEVICE

All patients will undergo a standard surgical procedure by the surgical team of CHU Brugmann. A transesophageal echocardiogram (TEE) will be performed and the TEE probe will stay continuously during the entire procedure, to allow all necessary measurements.

Thermistor-tipped catheterDEVICE

All patients will undergo a standard surgical procedure by the surgical team of CHU Brugmann.During the procedure, a thermistor-tipped catheter (model 93A-131-7F, Edwards, Santa Ana, CA) will be inserted into the pulmonary artery to measure right atrial pressure (Pra), pulmonary arterial pressure (Ppa), Ppao and thermodilution cardiac output. Ringer's lactate will be infused to maintain an occluded pulmonary arterial pressure (Ppao) of 8-10 mmHg.

Pressure/volume catheterDEVICE

All patients will undergo a standard surgical procedure by the surgical team of CHU Brugmann.During the procedure, a pressure/volume catheter (CD Leicom, Zoetermeer, Netherland) will be placed in the left ventricle through a left superior pulmonary vein purse string, in order to measure alternatively LV pressure/volume loops and LA pressure.

Transthoracic echocardiographyDEVICE

A complete transthoracic echocardiography will be performed the day before the surgical procedure. It will establish the presence of the inclusion and exclusion criteria, as stipulated above. This will be done using a Philips IE33 echocardiograph (Koninklijke Philips Electronics N.V., Netherlands). During the surgical procedure, a transesophageal echocardiogram will be performed, using an Acuson Sequoia system (Siemens AG, Germany).

Outcomes

Primary Outcomes

Left atrium (LA) dP/dt max

Fluid-filled catheter-derived pressures will be zero-referenced at mid-chest level and processed using disposable transducers (Baxter-Bentley, Uden, the Netherlands) and a Sirecust 404 monitoring system (Siemens, Erlangen, Germany). Micromanometer-derived pressures and conductance catheter data will be processed using a Leicom INCA intracardiac monitor (CD Leycom, Zoetermeer, Netherlands). All pressures and volume signals will be digitalized at 200 Hz and stored in a PC for off-line analysis.