Beating-heart mitral valve replacement assisted by rapid ventricular pacing after Bentall procedure: a case report

Abstract

Background

Beating-heart open mitral valve replacement (MVR) precludes aorta clamping, cardioplegic arrest, and reperfusion injury in cardiac surgery. However, beating-heart MVR still poses the risk of air embolism. The main cause of air embolisms is effective ventricular contraction and stroke. Rapid ventricular pacing (RVP) is commonly used in transcatheter valve implantation to temporarily halt cardiac output. However, its application in open beating-heart surgery has not explored in depth. Recently, we successfully employed RVP to perform MVR on an on-pump beating heart, without cross-clamping, in a patient with mitral valve prolapse developed 5 years after Bentall procedure.

Case presentation

A 63-year-old female, who underwent simultaneous Bentall and Sun’s procedures five years back, was admitted for dyspnea, orthopnea, and palpitations since 20 days. Echocardiography revealed severe mitral valve regurgitation and prolapse. She had a European System for Cardiac Operative Risk Evaluation II of 6.8%. After multidisciplinary consultations, open-heart MVR on beating heart was scheduled. Following induction of anesthesia, a balloon-tipped flotation pacemaker catheter was introduced into the right ventricle. RVP was activated at 180 beats/min during valve resection and de-airing. The mitral valve was replaced by a pericardial bioprosthesis under cardiopulmonary bypass (CPB). Transesophageal echocardiography confirmed the absence of intracardiac air bubbles. The patient was then successfully weaned off CPB and recovered without complications, regaining consciousness 45 min following the operation. She was discharged on the 8th postoperative day, with a New York Heart Association class I. At the 6-month postoperative follow-up visit, the patient showed satisfactory recovery with no complications.

Conclusions

This case demonstrates that beating-heart MVR with RVP, without aortic cross-clamping, can be used as a viable and feasible option in selected patients who are at a high risk of complications secondary to routine CPB and cardioplegia.

Background

Open-heart mitral valve replacement (MVR) is routinely performed via the conventional sternal approach or minimally invasive intercostal approach under cardiopulmonary bypass (CPB) and cardioplegic relaxation. However, cardiac relaxation induced by the cardioplegic solution causes ischemic and reperfusion injury, which is one of the main contributors to postoperative cardiac dysfunction. In patients who require reoperation, adhesions that occurred following the prior operation may make aortic dissection and clamping challenging, significantly increasing the difficulty of surgical manipulation and leading to a high mortality and morbidity risk [1]. In 1989, Praeger et al. introduced the beating-heart surgery as an alternative approach for MVR [2]. Beyond eliminating the need for aortic dissection and clamping, beating-heart surgery offers several advantages, including continuous myocardial perfusion and oxygenation, reduced cardiac workload to minimize ischemia injury and facilitate myocardial recovery, ability to perform atrial fibrillation ablation on a beating heart, and assessment of mitral valve function under near-physiological conditions [3, 4]. However, in addition to technical challenges arising from myocardial contractility during valve exposure and manipulation, beating-heart MVR carries a critical risk of air embolism, which has impeded the widespread acceptance of this approach in left heart-open surgery [5].

Rapid ventricular pacing (RVP) was recently introduced as a feasible method to induce transit cardiac standstill and achieve rapid hemodynamic reversal during balloon valvuloplasty and valve deployment [6, 7]. By inhibiting ventricular diastole and abolishing effective stroke, RVP may prevent air embolism during the opening and closure of the left atrium. To date, published data on experience with RVP in beating-heart open surgery remain scarce. We recently performed a successful RVP-assisted MVR on a beating heart without aortic clamping in a patient with mitral valve prolapse occurring 5 years after Bentall procedure. In this paper, we share our experience on the successful handling of this case and describe our approach, which we believe may mitigate the risks associated with conventional CPB and cardioplegia in complex MVR cases.

Case presentation

This case report was reviewed by the ethical committee board of our hospital, and informed consent was obtained from the patient for publication.

A 63-year-old woman (height 165 cm; weight 55 kg) was admitted to our hospital with progressive dyspnea, orthopnea, and palpitations for 20 days. Five years ago, the patient underwent an operation that included implantation of an ascending aortic conduit with a prosthetic valve and coronary reimplantation (Bentall procedure), total aortic arch replacement with descending thoracic aortic stent elephant trunk surgery (Sun’s operation), and tricuspid valvuloplasty for type I aortic dissection. Following the placement of the mechanical aortic prosthesis, she was under long-standing warfarin treatment.

Preoperative transthoracic echocardiography (TTE) revealed prolapse of the mitral valve, severe regurgitation, and left ventricle dilatation (diastolic diameter of 61 mm). The performance of the aortic prosthesis was satisfactory, with left ventricle ejection fraction (LVEF) of 65% (Fig. 1A). Computed tomography angiography revealed occlusion of the proximal part of the left subclavian artery in addition to dissecting aneurysms of the thoracic aorta and the upper abdominal aorta. Electrocardiography (ECG) revealed sinus rhythm with frequent premature, short paroxysms of atrial tachycardia. Laboratory test results included hemoglobin 89 g/L, serum albumin 41.7 g/L, serum alanine transaminase 6 U/L, and serum troponin I level 0.005 ng/mL. The patient had a European System for Cardiac Operative Risk Evaluation II of 6.8%. After comprehensive considerations and consultations, open-heart MVR on beating heart was scheduled.

Fig. 1.

Images revealing the echocardiography findings and rapid ventricular pacing. (A) Preoperative transthoracic echocardiography showing the severe regurgitation and prolapse in the mitral valve (arrow). (B) Transesophageal echocardiography confirmed the position of the pacing catheter (arrow). (C) Image showing rapid ventricular pacing. (D) Transesophageal echocardiography reveals well-performed mitral valve function (arrow)

Under continuous monitoring of ECG, pulse oxygen saturation, and arterial blood pressure, anesthesia was induced with etomidate (0.3 mg/kg) and sufentanil (1.5 µg/kg). Rocuronium (0.6 mg/kg) was used to facilitate tracheal intubation. Anesthesia was maintained with propofol (200 mg/h), sufentanil (25 µg/h), and cis-atracurium (5 mg/h), titrated using bispectral index monitoring. Mechanical ventilation was initiated with a 70% oxygen/air mixture (tidal volume 500 mL, 12 breaths/min) and an end-tidal carbon dioxide (CO₂) target of 35–40 mmHg.

An 8.5-F Fast-Cath introducer (Abbott Medical, USA) was catheterized into the right internal jugular vein. Subsequently, a balloon-tipped bipolar flotation pacing catheter (BP2502-10, Biosensors International, Singapore) was advanced into the right ventricle. Proper positioning and functioning of the device were ensured by transthoracic echocardiography (TEE) and ECG monitoring (Fig. 1B).

CPB was instituted by cannulating the right axillary artery and right femoral vein. An incision was made in the right fifth intercostal space, which was followed by continuous insufflation of CO₂ into the thoracic cavity at a flow rate of 5 L/min, through a CO₂ delivery catheter attached to the side port of the trocar. Once CPB was initiated and stabilized with mild hypothermia (rectal temperature 34–36 °C), esmolol was infused to reduce the heart rate to 50–60 bpm. Mean arterial pressure was maintained at 60 to 80 mmHg for a CPB flow of 2.5 L/min/m².

Before opening the left atrium, RVP was initiated at 180 beats/min in ventricular-inhibited mode (output 10 mA, sensitivity 5 mV; Fig. 1C) to minimize cardiac output, as confirmed by TEE. Then, the interatrial groove was opened. Two minutes later, after the native valve was removed, RVP was stopped. Sinus rhythm resumed immediately, with empty beating at a heart rate of 50–60 bpm under esmolol infusion.

A 31-mm St. Jude Biocor perimount pericardial bioprosthesis was selected. During the implantation, the left atrial tube extended into the left ventricle through the new valve orifice, maintaining the patency of the valve orifice. After the completion of the valve implantation and before the closure of the heart, RVP was restarted. In addition to placing the patient in the Trendelenburg position, the heart and lungs were passively filled with blood from the CPB circuit. Assisted by repeated manual pulmonary inflation, the left heart was de-aired through the left apical vent and a left atrial incision vent. After the absence of any obvious intracardiac air was confirmed by TEE, RVP was stopped and sinus rhythm resumed spontaneously. Low-dose adrenaline (0.1 µg/kg/min) was administered to stabilize blood pressure at 120/60 mmHg. Repeat TEE revealed satisfactory prosthetic valve function with LVEF of 45% (Fig. 1D). Then, CPB was smoothly weaned. Blood analysis revealed a pH of 7.451, PCO₂ of 38.5 mmHg, PO₂ of 398 mmHg, lactate level of 1.1 mmol/L, and hematocrit of 27.6%. After the operation, the patient was transferred to the intensive care unit, with adrenaline infusion at 0.03 µg/kg/min.

The duration of surgery was 211 min, including 66 min on CPB, with the amount of blood loss estimated to be 300 mL. The patient regained consciousness 45 min postoperatively and was weaned off inotropic support 16 h later. Her peak troponin I level was 2.28 ng/mL.The tracheal tube was removed 21 h after the operation. Forty-five hours postoperatively, she was downgraded into the general medical ward.

TTE performed prior to discharge revealed normal functioning of the prosthetic valve, normal left ventricular diastolic diameter (54 mm), and a LVEF of 60%. At the 6-month postoperative follow-up visit, the patient stated that she had improved exercise tolerance, with no dyspnea recurrence, indicating a New York Heart Association class I. Additionally, repeat TTE revealed stable functioning of the bioprosthesis, absence of mitral valve regurgitation, and preservation of left ventricular function.

Discussion and conclusions

Open-heart MVR performed under CPB and cardioplegia carries the risk of ischemia-reperfusion injury due to aortic cross-clamping and cardioplegia and complicates reoperation in the event of postoperative aortic calcification or dense adhesions around the ascending aorta. To minimize these risks, beating-heart surgery under CPB has emerged as an alternative technique [5, 8].

Our patient, with a history of the Bentall and Sun’s procedures performed 5 years earlier, presented significant challenges, including a difficult re-entry, risks associated with extensive aortic manipulation, and potential dense mediastinal adhesions and altered anatomy from prior sternotomy. All of these factors could complicate aortic dissection and clamping [9, 10]. Therefore, the surgical team opted for beating-heart MVR to avoid aortic exposure and cross-clamping. This approach yielded a satisfactory outcome in this patient, with an uneventful intraoperative course and a smooth postoperative recovery.

Since its introduction by Dr. Praeger et al. 30 years ago, beating-heart MVR has undergone continuous refinement in terms of both surgical techniques and perioperative management to reduce associated risks. However, beyond the technical complexity, air embolism remains a critical challenge hindering its widespread adoption [5, 11]. Air embolism during left heart-open surgery is mainly caused by effective ventricular contraction in the stroke phase when the valve is functional. To prevent this, Durukan et al. suggested aortic root de-airing combined with Trendelenburg positioning [12], while others advocated for induced ventricular fibrillation (VF) [8, 13]. However, both methods have significant limitations. Aortic de-airing requires exposure of the aortic root, resulting in incomplete air evacuation, while induced VF leads to a disorganized myocardial contraction, resulting in injury and energy depletion and contributing to poor postoperative cardiac performance [14].

RVP has recently emerged as an auxiliary tool in transcatheter valve implantation. The onset and duration of RVP can be precisely controlled, offering an easily manageable setting to transiently reduce cardiac output [6, 7]. By decreasing ejection force and stroke volume, RVP may prevent air from being pumped into the aorta when the valves are in situ. In this case, we employed a balloon-tipped flotation catheter to induce RVP, temporarily interrupting the cardiac output to minimize the risk of air embolism. After the RVP was discontinued, sinus rhythm was resumed immediately. The total RVP duration was approximately 4 min, with each episode lasting less than 2 min per application. The patient was then weaned from CPB without the need for defibrillation or significant inotropic support, indicating effective prevention of myocardial ischemia and re-perfusion injury.

The clinical safety of the catheterization of the pacing catheter has been demonstrated previously [15]. At our hospital, we have extensive experience with bedside placement of pacing catheter without significant adverse events [7]. RVP offered several potential advantages over the VF approach: (1) although RVP required an additional puncture, it avoided deep hypothermia or potassium boluses to induce VF; (2) the use of a pacing catheter to suppress cardiac output was more controllable on hemodynamics; and (3) the indwelling transvenous pacing catheter provided an immediate safeguard and subsequent therapeutic option if there was postoperative malignant arrhythmias. However, its generalizability requires further studies in a large number of patients.

Nevertheless, air embolism still remains a potential hazard when performing beating-heart MVR under RVP assistance. For example, trade-offs of RVP may result in ejection. Therefore, in addition to CO₂ insufflation, the patient was placed in the Trendelenburg position during de-airing [16]. If inadvertent air entry into the aorta occurs, bilateral common carotid artery compression can be performed to prevent the air embolus from entering the brain.

Safe implementation of this protocol, however, still requires careful patient selection. We believe that candidates most suitable for this RVP-assisted beating-heart MVR are those in whom aortic cross-clamping is contraindicated due to a history of previous extensive aorta surgery, severe calcified aortas, or sever mediastinal adhesions. While this approach was well tolerated by our patient, it should be employed with caution in patients with pre-existing cardiac conduction disorders, pacemaker dependence, or serious electrolyte imbalances.

The expertise of the surgical team in pacing catheter placement and the synchronization of CPB flow adjustment during RVP are additional critical determinants of procedural success. In this case, intraoperative TEE proved invaluable not only in guiding the pacing catheter placement but also for monitoring de-airing and ensuring the precise positioning of the prosthesis. Multidisciplinary cooperation between the surgical, anesthesia, and perfusion teams is essential. Centers new to this approach should anticipate a brief learning curve. Postoperatively, constant monitoring is warranted to identify any early signs of low cardiac output or arrhythmia, especially during the immediate hours after weaning from CPB. Our patient showed only mild transient ejection fraction decrease and did not require high-dose ionotropic support.

Follow-up assessments at 6 months demonstrated long-term sustainability and clinical efficacy of our approach. The patient reported improved exercise tolerance with New York Heart Association class I, satisfactory left ventricular remodeling, and a functioning mitral prosthesis on TTE. These outcomes indicated that RVP-based beating-heart MVR could be an alternative approach in selected patients at high surgical risk owing to prior aortic interventions or contraindications to aortic clamping. However, the possibility of increased myocardial oxygen demand and reduced diastolic coronary perfusion at a high pacing rate following RVP needs to be taken into consideration. Further studies are warranted to validate the safety and efficacy of this approach in a larger patient population.

Abbreviations

MVR

Mitral valve replacement

CPB

Cardiopulmonary bypass

RVP

Rapid ventricular pacing

TTE

Transthoracic echocardiography

LVEF

Left ventricle ejection fraction

ECG

Electrocardiography

TEE

Transesophageal echocardiography

VF

Ventricular fibrillation

Author contributions

All authors were involved in patient management. YLT and YMJ collected the patient’s initial data, YLT and FH drafted the manuscript, TTT prepared the figure, YLT, YMJ and YYX completed the anesthesia management, and NYM and YYX revised the manuscript. All the authors have read and approved the final version of the manuscript.

Funding

This study was funded by a clinical research fund from the First Affiliated Hospital, Zhejiang University School of Medicine (BL202234). The funder played no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The case was reviewed by the ethics committee of our hospital.

Consent for publication

Written informed consent was obtained from the patient for publication of this case report. A copy of the written consent is available for review by the editor of this journal.

Competing interests

The authors declare no competing interests.