Intraoperative Grading of Mitral Regurgitation During General Anesthesia: Is Hemodynamic Matching Useful?

Abstract

With great interest, I read the recent publication by Sanfilippo et al concerning the grading of mitral regurgitation (MR) in the outpatient setting compared with under general endotracheal anesthesia (GA).1Sanfilippo F. Johnson C. Bellavia D. et al.Mitral regurgitation grading in the operating room: A systematic review and meta-analysis comparing preoperative and intraoperative assessments during cardiac surgery.J Cardiothorac Vasc Anesth. 2017; (Feb 13 [Epub ahead of print])Abstract Full Text Full Text PDF Scopus (25) Google Scholar The authors reported that MR grading with the patient under GA resulted in a significant underestimation of the severity compared with grading in the outpatient setting. In addition, the meta-analysis further revealed that “hemodynamic matching” (augmenting the afterload with vasopressors) enables an accurate assessment of the MR grade in the operating room, albeit with a small risk for overestimation, and encourages the use of this strategy. I commend the authors for tackling the important issue regarding MR underestimation in patients under GA and positive-pressure ventilation, and believe their findings may improve the care of MR patients. I commend the authors for tackling the important issue regarding MR underestimation in patients under GA and positive pressure ventilation and believe their findings could improve the care of MR patients. MR is a valvular pathology influenced by multiple variables such as preload, afterload, heart rhythm, and left ventricular contractility.1Sanfilippo F. Johnson C. Bellavia D. et al.Mitral regurgitation grading in the operating room: A systematic review and meta-analysis comparing preoperative and intraoperative assessments during cardiac surgery.J Cardiothorac Vasc Anesth. 2017; (Feb 13 [Epub ahead of print])Abstract Full Text Full Text PDF Scopus (25) Google Scholar, 2Essandoh M. Intraoperative echocardiographic assessment of mitral valve area after degenerative mitral valve repair: A call for guidelines or recommendations.J Cardiothorac Vasc Anesth. 2016; 30: 1364-1368Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar In the ambulatory setting, these variables are at baseline, and MR grading in a spontaneously ventilating patient can be assessed with minimal confounding. In the operating room, under GA and positive pressure ventilation, multiple hemodynamic variables are altered. The preload, afterload, and the contractility of the left ventricle are reduced, causing a reduction in the regurgitant volume and underestimation of MR severity with echocardiography. When intraoperative decision-making is based solely on the intraoperative echocardiographic examination, surgical decision-making may be negatively affected. This is where the findings of Sanfilippo et al’s systematic review and meta-analysis are valuable. The reduction in afterload can be counteracted with vasopressor therapy, increasing aortic impedance, reducing forward stroke volume of the left ventricle, and increasing the degree of MR; however, vasopressor therapy does not mitigate the negative inotropic effects of anesthetics. Therefore, patients with systolic dysfunction may not respond positively to hemodynamic matching, and administering an inotrope in the setting of MR assessment with the patient under GA may be useful in this scenario. Inotropes should be administered carefully however because excessive tachycardia may reduce the grade of MR. Intraoperative echocardiographic quantification of MR in cardiac surgery patients under GA affects patient care and should be performed with accuracy. Taking into account the negative effects of GA and positive-pressure ventilation on the cardiovascular system, hemodynamic matching with vasopressors, and in some cases inotropes, to mimic baseline systemic vascular resistance and left ventricular contractility respectively, may be useful and should be considered whenever there is significant discrepancy between preoperative and intraoperative measurements. Although beneficial, hemodynamic matching may cause overestimation of MR severity at times, particularly if the afterload of the patient exceeds the baseline value, and so deserves careful manipulation of hemodynamics to avoid misdiagnosis and unwarranted surgery of the mitral valve. Anatomic assessment of the mitral valve also should be performed to determine the mechanism of MR and guide decision-making.