Long-term total cardiac support in a Fontan-type circulation with HeartMate II left ventricular assist device

Abstract

Interest in utilizing long-term mechanical circulatory support for Fontan-type circulation has been high. Unfortunately, so far such attempts have not been successful. Herein, we are presenting the first case of an individual with biventricular heart failure and Fontan-type circulation on long-term mechanical circulatory support with a continuous-flow left ventricular assist device.

CASE REPORT

In 2009, a 36-year old female of small stature (height: 147 cm; weight: 50 kg; body surface area: 1.43 m²) was referred to our colleagues for aortic valve surgery for severe aortic stenosis. Her echocardiogram showed a trileaflet aortic valve with calcified, fused raphe and some thickening of the mitral valve with mild stenosis. This raised rheumatic fever as a possible aetiology; however, no such history could be elicited.

The patient initially underwent an aortic valve replacement with 19-mm bovine pericardial valve prosthesis; however, this was felt to be significantly deformed due to the small aortic root size. The patient then underwent aortic root replacement with 21-mm St Jude mechanical valved conduit with coronary reimplantation. At the end of the procedure, she failed to wean off cardiopulmonary bypass and developed biventricular dysfunction for no clear reason. Revascularization of left anterior descending and right coronary arteries was performed to eliminate the possibility of ischaemia from the coronary reimplantation; however, the patient could not be successfully weaned from cardiopulmonary bypass. Eventually, after prolonged time on cardiopulmonary bypass, the Heart Failure Service was involved and the patient was placed on biventricular assist with centrally cannulated CentriMag extracorporeal continuous-flow centrifugal pumps, and her sternum was left open. Due to the extensive prior surgery and the possibility of recovery, initial attempts were made to allow washing of the mechanical aortic valve utilizing transoesophageal echocardiogram (TOE) and arterial wave forms to achieve 1:1 opening of the prosthesis. The original strategy was to allow for potential myocardial recovery, given that the only other viable option would have required patch closure of the aortic root/mechanical valve and commitment to pump dependence to decrease the risk of thromboembolism at the index surgery.

On postoperative day 1, the patient lost all pulsatility. TOE revealed an extensive thrombus present below the aortic valve. The patient was urgently taken to the operating room where entire aortic root and both coronary artery orifices were found to be thrombosed. No backbleeding was observed from coronary orifices with retrograde cardioplegia. Both bypass grafts were noted to be thrombosed and without demonstrable flow. Attempted embolectomy of the native coronary arteries was unsuccessful. The aortic root required extensive thrombectomy. Subsequently, the patient's mechanical aortic valve was oversewn with GoreTex patch, and HeartMate II left ventricular assist device (LVAD) was implanted. During the LVAD implant, an extensive thrombus was found in the left ventricle extending into the LVOT that was evacuated. The outflow cannula from CentriMag right ventricular assist device (RVAD) was repositioned for future remote decannulation without need to open the chest, as described by us previously [1]. Briefly, after placing two pursestring sutures on the main pulmonary artery (MPA), the outflow cannula was tunnelled through the fifth intercostal space. An 8-mm Dacron graft was placed around the outflow cannula, which was then advanced ∼2 cm into the MPA. The pursestring sutures were tied, the graft was sewn to the adventitia of the MPA and the cannula was tightly secured within the graft with heavy silk ties.

On postoperative day 3, the patient underwent delayed sternal closure. Two days later, she was successfully extubated. The patient slowly recovered and attained normal functional status. During her stay in the intensive care unit (ICU), it was noted that while on positive pressure ventilation her RVAD could not be weaned due to low flow and red heart alarms on the LVAD. Once the patient was successfully extubated and became ambulatory in the ICU, the RVAD could be successfully weaned with the maintenance of normal LVAD index. Eventually, the CentriMag RVAD was explanted through a thoracic incision, without reopening the sternum, 33 days from her original surgery. The patient has not required any further surgical interventions.

Subsequent echocardiograms demonstrated Fontan-type circulation with minimal right ventricular contractility, severe tricuspid regurgitation and continuously open tricuspid, mitral and pulmonary valves, with respiratory augmentation of flow across the pulmonic valve. Seven years later, despite her functionally inert right ventricle (tricuspid annular plane systolic excursion 0.4 cm), the patient lives quite comfortably with mild heart failure symptoms (NYHA II). She is maintained on oral diuretics and sildenafil and is listed as UNOS status 7 for heart transplant. Her most recent echocardiogram images are shown (Figs 1 and 2).

Figure 1:

(A) Tricuspid valve non-coaptation, width of systolic tricuspid regurgitation equalling full width of tricuspid annulus (arrows). (B) M-mode shows triscuspid valve non-coaptation with systolic tricuspid regurgitation (single arrow: diastolic RV filling; double arrows: systolic tricuspid regurgitation).

Figure 2:

(A) Pulse Doppler shows antegrade systolic (double arrows) and diastolic (single arrow) flow through the pulmonary valve. (B) M-mode shows no inspiratory collapse of inferior vena cava with sniff.

With a non-functional right ventricle, the patient's right heart serves as an inert conduit, whereas her low pulmonary vascular resistance is allowing successful univentricular support. Though not technically a true Fontan circulation, the patient demonstrates a functionally Fontan physiology. As such, it could be argued that the patient would be better served as a true Fontan as over time her right ventricle has continued to dilate and may ultimately impact left ventricular filling.

Interest in the potential usefulness of LVAD in this scenario has been high; however, reportedly, these attempts had been unsuccessful and invariably led to the death of the patient [2]. Literature search shows only one case of short-term total cardiac support with LVAD for 45 days as a bridge to heart transplant. [3] To the best of our knowledge, this is the only known case of an individual with biventricular heart failure with Fontan-type circulation who is alive on long-term mechanical circulatory support with an LVAD.

The strategy of sternal closure with the possibility of remote decannulation of RVAD was critical in ultimately transitioning to the LVAD alone. In Glenn and Fontan patients, extensive documentation supports the negative effects of positive pressure ventilation and the positive effects of negative pressure ventilation on pulmonary blood flow and cardiac output [4, 5]. The early sternal closure and the ability to extubate the patient after pulmonary optimization allowed ascertaining the pulmonary blood flow and LVAD flow in a negative pressure state. The ability to forego reoperative sternotomy to remove the RVAD avoids the return to prolonged positive pressure ventilation with its deleterious effects on pulmonary blood flow and LVAD flow which is more critical in this Fontan-type physiology.

Conflict of interest: H.T. Massey is a consultant and proctor for Thoratec Corporation.