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Ann Thorac Surg 2001;71:1448-1453
© 2001 The Society of Thoracic Surgeons

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Original article: cardiovascular

Surgical management of valvular disease in patients requiring left ventricular assist device support

^a Department of Cardiothoracic Surgery, New York Presbyterian Hospital, College of Physicians and Surgeons, Columbia University, New York, New York, USA
^b Mid Atlantic Surgical Association, Morristown, New Jersey, USA

Accepted for publication January 17, 2001.

Address reprint requests to Dr Oz, New York Presbyterian Hospital, NHB 7-435, 177 Fort Washington Ave, New York, NY 10032
e-mail: mco2{at}columbia.edu

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Success with long-term implantable left ventricular assist devices (LVAD) has led to increased use in patients previously thought to be unsuitable for mechanical circulatory assistance. Patients with preexisting or newly diagnosed valvular disease have been traditionally excluded from device placement. The purpose of this study was to review our experience with LVAD support in patients with valvular disease and to develop a management algorithm for these difficult patients.

Methods. We reviewed the clinical records of 199 consecutive patients who received the ThermoCardiosystems, Inc, HeartMate Pneumatic or Vented Electric LVAD. There were 18 patients (9%) who required surgical management of native or prosthetic valvular disease during LVAD implantation.

Results. Suture or patch closure of the aortic valve was performed in 6 patients, aortic valve plication and repair in 1 patient, mitral valve repair in 4 patients, and tricuspid valve annuloplasty in 5 patients. Two patients with mechanical mitral valve prostheses were treated with postoperative warfarin anticoagulation. Fifteen of the 18 patients with valvular pathology survived the immediate postoperative period (17% mortality). Eleven patients have either undergone transplantation or continue to be supported with an LVAD (61%). Operative mortality in LVAD patients without concomitant valve repair was 18% (n = 33) with a late mortality of 7% (n = 13). Seven of these late deaths occurred in patients who received a device as destination therapy. In the remaining 6 patients, the cause of death was sepsis (n = 2), multisystem organ failure (n = 2), driveline rupture (n = 1), and massive gastrointestinal bleed (n = 1).

Conclusions. Preexisting native or prosthetic valve pathology does not increase the immediate perioperative risk of LVAD insertion; however, these patients continue to pose a challenge for postoperative management while awaiting transplantation.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
The continued disparity among available donor organs and patients awaiting heart transplantation has led to the increased use of implantable left ventricular assist devices (LVAD) as a bridge to transplantation [1, 2]. The initial success with long-term LVADs has encouraged their use in patients previously thought to be unsuitable for device insertion [3, 4]. The presence of native aortic valve disease, particularly aortic insufficiency, or a valvular prosthesis has traditionally been considered a contraindication to LVAD placement. The original Novacor (Novacor Division, World Heart Corp, Ottawa, Canada) LVAD investigational protocol listed mechanical aortic valves as an exclusion criteria. However, successful management of aortic and other valvular pathology may allow device insertion in patients who are otherwise excellent candidates for mechanical circulatory assistance [5].

The purpose of this study was to review our experience with native or prosthetic valvular pathology in patients receiving the ThermoCardiosystems, Inc (Woburn, MA) (TCI) HeartMate LVAD and to establish a treatment algorithm for the successful management of this difficult cohort of patients.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
The clinical records were reviewed of 199 consecutive patients who received the TCI HeartMate pneumatic (HeartMate 1000; n = 53) or electrically actuated (HeartMate VE; n = 146) device at our institution between August 1990 and September 2000. Detailed descriptions of pump mechanics and implantation techniques have been published previously [2, 3]. Briefly, the inflow cannula is passed through an opening cored in the apex of the left ventricle which allows the device to completely unload the left ventricle, thereby preventing native aortic valve opening. The outflow graft is sewn to the ascending aorta. Porcine bioprosthetic valves are positioned within the inflow and outflow conduits to ensure unidirectional flow. However, native aortic valve regurgitation can result in circuitous blood flow through the device and limit forward cardiac output.

We identified 18 patients (9%) who presented for LVAD insertion with previously treated (n = 6) or newly diagnosed valvular disease (n = 12). Transesophageal echocardiography (TEE) was routinely used intraoperatively in all patients to assess left and right ventricular wall motion as well as native valve structure and function [6]. A two-dimensional bubble study was performed to rule out the presence of an atrial septal defect, which, if found, was closed at the time of device insertion.

Mitral insufficiency was graded using standard TEE criteria and classified as trace, mild, moderate, or severe [6]. Aortic insufficiency was graded echocardiographically in a similar fashion and quantitated using a 1-minute timed collection of left ventricular apical vent return. Left ventricular vent return of greater than 1.5 L/min suggested the need for aortic valve repair. Tricuspid regurgitation was defined as severe if the right atrial pressure was greater than 20 mmHg in the presence of standard TEE criteria.

Treatment strategies varied according to the valvular lesion. In patients with severe aortic insufficiency, the native valve was repaired by creating a bicuspid orifice (see Fig 1) or closed by oversewing the free margins of all three adjoining cusps. In patients with a mechanical aortic valve, a Dacron (C.R. Bard, Haverhill, MA) patch was fashioned and sewn to the aortic aspect of the valve preventing leaflet motion and limiting thrombus formation to the ventricular aspect of the outflow tract (see Fig 2). In patients with severe mitral insufficiency, a "bow-tie" repair was performed using a modification of the technique described by Maisano and colleagues [7]. In all 4 patients, the repair was performed through the LV apical incision during LVAD implant. In patients with a mechanical mitral prosthesis, treatment consisted of postoperative anticoagulation to achieve an International Normalized Ratio (INR) of 3.0 to 3.5. In 5 patients, tricuspid valve repair was performed using a Carpentier-Edwards annuloplasty ring (Edwards LifeSciences, Irvine, CA).

View larger version (43K): [in this window] [in a new window]   Fig 1. Aortic valve repair with creation of a bicuspid valve.

View larger version (52K): [in this window] [in a new window]   Fig 2. Prevention of thromboembolism by Dacron graft closure of mechanical aortic valve prosthesis.

Statistical analysis
The SAS statistical software program (SAS Institute, Cary, NC) was employed for all statistical analyses. All categorical data are expressed as the absolute and percentage frequency and were analyzed using chi-squared or Fisher’s exact test as appropriate. Continuous data are expressed as the mean ± standard deviation and were analyzed using Student’s t test.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
The TCI HeartMate was implanted as a bridge to transplant in 187 patients and as destination therapy in 12 patients according to the REMATCH (Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart-failure) protocol [8]. Fifteen patients in the bridge to transplant group (8%) and 3 patients in the REMATCH group (25%) were identified with previously treated or newly diagnosed valvular disease. The demographic data of these 18 patients are presented in Table 1.

Operative mortality (death within 30 days of LVAD insertion) in the group who did not undergo concomitant valve repair was 18% (n = 33) compared to 17% (n = 3) in the valve repair group (p = 0.85). In the valve repair group, 2 patients died of sepsis and 1 of a suspected pulmonary embolus. Late deaths due to sepsis occurred in 4 patients, 2 of whom suffered septic emboli resulting in fatal strokes. For patients being bridged to transplantation, survival to transplant was 60% (9 of 15) in the valve repair group compared to 75% (129 of 172) in the control group (p = 0.2). The mean duration of support in the valve repair group was 68 ± 56 days (range 13 to 198 days) compared to 90 ± 98 days (range 0 to 541 days) in the control group (p = 0.8).

In the valve repair group, one death occurred in a patient 606 days after he received an LVAD as destination therapy. Two patients continue to be supported by a device as destination therapy.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
The successful experience with long-term implantable ventricular assist devices has led several centers to revise their selection criteria [3]. Patients previously thought to be unsuitable for mechanical assistance are now being considered for device insertion. The presence of native or prosthetic aortic valve disease has traditionally been considered a contraindication to LVAD placement due to the concerns of thrombus formation or significant aortic insufficiency. Similarly, lesions of the mitral and tricuspid valve can also pose problems for the postoperative management of LVAD recipients. This report summarizes our total experience with surgical management of native or prosthetic valve disease in patients receiving a HeartMate left ventricular assist device.

Patients in the valve repair group were slightly older than the general LVAD population (56 versus 50 years), but they were otherwise demographically very similar. Surprisingly, the underlying myocardial pathology was similar to the general population as was the mean duration of support. Patients in the valve repair group did not suffer from a higher perioperative mortality (17% versus 18%, p = 0.85). However, for bridge patients, survival to transplant was lower than the general population (60% versus 75%), although this difference did not achieve statistical significance (p = 0.2). The late risk of stroke in LVAD patients valve disease (n = 2, 13%) does not appear to be greater than other published series of device recipients without valvular lesions, and always occurred in the setting of device endocarditis [2, 9, 10]. Despite the small number of patients who require management of valvular disease at the time of LVAD insertion, our results suggest that these patients can be successfully supported with mechanical circulatory assistance. Our clinical experience with the management of these patients has enabled us to formulate guidelines for the intraoperative treatment of native or prosthetic valve disease (see Fig 3).

View larger version (16K): [in this window] [in a new window]   Fig 3. Algorithm for the management of valvular disease during left ventricular assist device (LVAD) support. (AI = aortic insufficiency; AV = aortic valve; CO = cardiac output; LV = left ventricle; TEE = transesophageal echocardiography.)

In patients requiring long-term LVAD support as a bridge to transplant, our preferred strategy is to oversew an incompetent aortic valve. In patients who have the potential for myocardial recovery and subsequent LVAD explant, the valve is repaired by resuspending the prolapsing cusp or by suturing it to the adjacent normal cusp, thereby creating a bicuspid valve [11].

Based on early clinical experience, patients with mechanical prosthetic valves had been excluded from LVAD insertion. Blood stasis has been described to cause thrombus formation during device support due to the inactivity of the aortic prosthesis that usually remains in the closed position. However, during venting of a pneumatic device, intentional weaning, intermittent periods of exercise, or device malfunction, the aortic valve may open with subsequent embolization. We have previously reported this complication in a patient who suffered a stroke during LVAD support [9].

Our current strategy for patients with mechanical aortic prostheses is to prevent thromboembolism by using a Dacron graft to occlude the outflow of the valve (Fig 2). Patients being supported with pneumatic devices may become lightheaded during venting, but this is usually well tolerated in the supine position. Device explantation would require thrombectomy or replacement of the valve, but neither of the 2 patients (patient 6, patient 17) with oversewn mechanical valves in this series have undergone device explant. Patient #17 underwent transplantation and at the time of surgery, the ventricular aspect of the mechanical valve was thrombosed. In the unlikely event of pump failure, the native heart (if capable of ejection) can pump through the device itself into the outflow conduit. All surgical interventions on the aortic valve can be easily performed through the aortotomy created for the LVAD outflow graft after aortic cross-clamping and cardioplegic arrest.

For patients with bioprosthetic aortic valves, we have elected not to occlude the valve. However, reports of bioprosthetic valve thrombosis suggest that even tissue valves should be oversewn [12–15]. In fact, the 1 patient (patient 2) in our series who presented with an aortic bioprosthesis was noted to have significant subvalvar thrombus at autopsy.

Isolated aortic stenosis is not critical to the LVAD recipient since systemic blood flow is not dependent upon antegrade flow through the aortic valve. However, in the patient undergoing aortic valve replacement with LVAD backup, consideration should be given to the use of a tissue valve to prevent thromboembolism during device support.

Three patients in this series received devices as destination therapy. One patient was supported for 606 days, nearly four standard deviations longer than the mean support time for the valve repair group. During LVAD support, his previously competent aortic valve developed insufficiency, requiring reoperation for aortic valve closure. During device support, the closed native valve is exposed to systolic pressure rather than diastolic pressure and is therefore at increased risk for the development of regurgitation [16]. The incidence of this unique problem may become more prevalent as the use of mechanical circulatory assistance for destination therapy increases.

Mitral valve
Since native cardiac contraction and LVAD ejection are not synchronous, left ventricular ejection during device systole may result in blood flow against the mitral valve (due to a closed aortic valve). Depending upon the unloading characteristics of the device in situ, a significant volume of blood may be ejected through an incompetent mitral valve and result in pulmonary edema. Similarly, in the event of pump failure or inflow valve regurgitation, mitral competence may significantly affect patient symptomatology. We therefore advocate repair of severe mitral insufficiency at the time of LVAD insertion. We have found that the "bow-tie" repair described by Maisano and colleagues is easily accomplished via the apical left ventriculotomy at the time of device implant [7]. This repair satisfactorily diminishes the severity of mitral regurgitation and may allow for weaning and device explantation in selected patients.

Severe mitral stenosis restricts blood flow to the left ventricle and consequently to the device. A low output syndrome then develops due to impaired LVAD flow and can lead to right heart failure due to increased pulmonary vascular resistance. Although no patient in this series presented with severe mitral stenosis at the time of LVAD insertion, we would advocate repair at the time of operation. Simple mitral commisurotomy can be performed via the apical ventriculotomy and should prevent converting mitral stenosis into severe mitral regurgitation. Again, in patients considered for LVAD backup during surgery for mitral valve disease in the setting or poor ventricular function, a bioprosthesis should be considered to reduce the risk of valve thrombosis. Although normal flows across a mechanical mitral valve can allow for the presence of a mechanical prosthesis, the avoidance of postoperative anticoagulation is desirable. In the 3 patients with prosthetic mitral valves in this series (patients 7, 11, and 18), no adverse embolic events were observed even in the 2 patients with mechanical valves. Although no anticoagulant-related hemorrhage was observed in these 2 patients, we are cautious about the postoperative use of coumadin due to the subclinical fibrinolytic state that we have observed in our LVAD recipients.

Tricuspid valve
Isolated tricuspid stenosis is a rare entity and was not present in any patient in this series. In contrast, tricuspid insufficiency is extremely common due to either right ventricular failure or, more commonly, elevated pulmonary vascular resistance secondary to left ventricular failure. In the immediate postoperative period, LVAD flows will be limited by output across the pulmonary vascular bed. LVAD patients require high volume loading conditions and frequently require blood product transfusion. Both of these factors exacerbate right heart failure and predispose to tricuspid insufficiency. Early in our experience, we treated even moderate tricuspid insufficiency with an annuloplasty ring. However, we found that tricuspid repair did little to improve right ventricular performance and 1 patient (patient 2) suffered from a pulmonary embolus. Catastrophic heart failure has been reported following thrombosis of a tricuspid prosthesis [15]. For these reasons, we no longer advocate prophylactic tricuspid repair unless the insufficiency is severe and ascites is present. We have found that as left ventricular failure resolves with ongoing device support, right-sided failure improves and tricuspid regurgitation abates. The early use of nitric oxide has also led to improved right ventricular hemodynamics [17].

Conclusion
The continued success of left ventricular assist devices as a bridge to transplantation has encouraged their use in a more diverse patient population and has prompted their consideration as destination therapy. The incidence of previously treated or newly diagnosed valvular disease can therefore be expected to increase. Our clinical experience suggests that surgical interventions can be employed to make patients with valvular lesions acceptable candidates for LVAD support. These interventions do not increase the early morbidity or mortality of device insertion and may facilitate the postoperative management of these challenging patients.

	References

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