Evaluation of Cardiac Hemodynamic Modifications During Temporary Left Atrial Appendage Occlusion

Evaluation of Cardiac Hemodynamic Modifications During Temporary Left Atrial Appendage Occlusion

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.

Inclusion Criteria:

• Aortic valve stenosis suitable to surgery
• Left Atrium<50 mm in the parasternal long axis view
• Sinus rhythm at the time of patient's inclusion and during the procedure

Exclusion Criteria:

• Hypertrophic cardiomyopathy (diastolic septal thickness > 15mm).
• Heart failure with Left Ventricule Ejection Fraction < 45%.
• Significant mitral regurgitation/stenosis
• Significant aortic regurgitation
• History of atrial fibrillation
• Presence of prosthetic valves
• Complex congenital heart disease