Effect of General Endotracheal Anesthesia and Mechanical Ventilation on the Echocardiographic Measurements in Severe Aortic Stenosis

Introduction: We measured the peak pressure gradient (pPG) and mean pressure gradient (mPG) obtained by transesophageal echocardiography (TEE) after induction of anesthesia and compared it with the preoperative pPG and mPG by transthoracic echocardiography (TTE) in adults with aortic stenosis (AS). We also compared the aortic valve area (AVA) measurements as obtained preoperatively by TTE versus those by TEE following induction of general endotracheal anesthesia (GETA) during the inspiratory phase, expiratory phase of the ventilatory cycle and with incremental increases in tidal volume. Materials and Methods: All patients had preoperative TTE within 1 month of surgery and was reviewed 1 day before the surgery. After anesthetic induction, precardiopulmonary bypass (CPB) TEE evaluation was done to measure mPG and pPG across AV, under steady-state conditions. Three different controlled tidal volumes: 8 ml, 10 ml, and 12 ml per kg body weight were utilized during the TEE measurements. Results: A total of 90 adults underwent aortic valve replacement from 2017 to 2018. The preoperative pPG and mPG across the AV by TTE was 96.7 ± 23.27 mmHg and 60.7 ± 18.1 mmHg, respectively. Compared to preoperative TTE, pre-CPB TEE pressure gradient during both phases of ventilation under GETA was significantly lower. The pPG and mPG were higher during inspiration as compared to those in the expiratory cycle during mechanical ventilation under GETA (pPG during inspiration = 66.63 ± 22.15 mmHg; mPG during inspiration = 38.24 ± 13.65 mmHg; pPG during expiration = 52.49 ± 19.10 mmHg; mPG during expiration = 30.76 ± 12.66 mmHg). There were no significant changes in AVA between TTE/TEE and inspiration/expiration. Conclusions: The findings of this study demonstrate that the TEE pre-CPB PGs underestimated the severity of AS; hence, the severity of AS must be interpreted with caution during GETA and mechanical ventilation (MV). In addition, PGs must be done at similar points in the respiratory cycle.