Hemodynamic recovery after restoration of sinus rhythm after complete atrioventricular block during off-pump coronary artery bypass surgery: a case report

BACKGROUND: Off-pump coronary artery bypass (OPCAB) surgery is frequently chosen for high-risk patients to mitigate cardiopulmonary bypass-related complications. However, OPCAB is associated with significant intraoperative hemodynamic challenges, particularly in patients with impaired ventricular function and pre-existing conduction abnormalities. High-grade atrioventricular (AV) conduction disturbances during off-pump coronary artery bypass surgery are rare but can result in life-threatening hemodynamic collapse. CASE PRESENTATION: We report the case of a 75-year-old man with severe ischemic cardiomyopathy (LVEF 36%) and baseline left bundle branch block who underwent off-pump coronary artery bypass surgery for multivessel coronary artery disease with collateral-dependent coronary circulation. During right internal mammary artery harvesting, the patient developed progressive PR prolongation followed by transient complete atrioventricular block. Although the initial conduction disturbance was hemodynamically tolerated with vasoactive support, subsequent minimal cardiac displacement for left anterior descending artery exposure precipitated profound hemodynamic instability. The instability was refractory to ventricular pacing and maximal pharmacologic support but resolved immediately after spontaneous restoration of sinus rhythm, allowing completion of the procedure without conversion to cardiopulmonary bypass. CONCLUSIONS: This case highlights the critical importance of atrioventricular synchrony in maintaining hemodynamic stability during off-pump coronary artery bypass surgery, particularly in patients with low ejection fraction, baseline conduction abnormalities, and collateral-dependent coronary circulation. Even surgical maneuvers considered relatively safe, such as right internal mammary artery harvesting or minimal cardiac displacement, may precipitate life-threatening hemodynamic collapse when AV synchrony is lost. Awareness of this interaction is essential for timely recognition and appropriate intraoperative decision-making in high-risk patients undergoing OPCAB.