T. Haberl

Viennese approach to minimize the invasiveness of ventricular assist device implantation

OBJECTIVE Avoiding full sternotomy and cardiopulmonary bypass (CPB) could significantly reduce the invasiveness of left ventricular assist device (LVAD) implantation. Therefore, we developed minimally invasive implant strategies for the Heartware® VAD (HVAD) and the Thoratec® HeartMate II (HMII) covering isolated LVAD implantation as well as concomitant valve procedures (aortic/tricuspid). We present the surgical techniques and the initial clinical experience. METHODS From February 2012 to March 2013, 27 patients (mean age 58 ± 8 years; male 85%; Ischemic Cardiomyopathy 63%; redo surgery 22%; Interagency Registry for Mechanically Assisted Circulatory Support Level I: 29%, II: 22%, III: 33%, IV-VII: 16%) underwent minimally invasive LVAD implantation at our department. Apical cannulation was performed via a left lateral minithoracotomy in HVAD patients (n = 20) or a left subcostal incision in HMII patients (n = 7). The outflow graft anastomosis was performed to the ascending aorta via a right minithoracotomy in the second intercostal space (n = 22) or the right subclavian artery (n = 2). If additional valve procedures (aortic/tricuspid) were necessary (n = 3), a hemisternotomy was performed to access the valve and perform the outflow graft anastomosis. Circulatory support for LVAD implantation was CPB (33%), extracorporeal membrane oxygenation (48%) or off-pump (19%). RESULTS The minimally invasive approach was feasible in all patients with no need for conversions. Thirty-day and in-hospital mortality were 7.4 and 14.8%, respectively. In-hospital stay was 30.0 ± 22.5 days. One patient (4%) died during follow-up from pump thrombus formation. Three patients (11%) underwent surgical revision for bleeding. CONCLUSIONS Minimally invasive LVAD implantation is feasible and safe. The very encouraging results obtained in this initial series justify a broad application of this technique.

Preoperative patient optimization using extracorporeal life support improves outcomes of INTERMACS Level I patients receiving a permanent ventricular assist device.

OBJECTIVES Interagency Registry for Mechanical Assisted Circulatory Support (INTERMACS) Level I patients have the highest early mortality after ventricular assist device (VAD) implantation. This is determined by the exposure of patients in shock with acutely damaged end-organs and high catecholamine support to a significant surgical trauma. We report our experience with a bridge-to-bridge concept consisting of initial veno-arterial extracorporeal life support (ECLS) and deferral of VAD implantation to recovery of end-organ function in INTERMACS Level I patients. METHODS We reviewed the concept of initial ECLS implantation and deferral of VAD implantation to end-organ recovery in 22 consecutive patients (mean age 54 ± 14 years; 72.2% males; 50% ischemic cardiomyopathy; 100% INTERMACS Level I; 18.2% Heartmate II, 68.2% Heartware HVAD, 4.5% Heartware BiVAD, 9.1% DeBakey LVAD) receiving a VAD for refractory cardiogenic shock between June 2004 and February 2013. Study endpoints were end-organ recovery during ECLS and survival. RESULTS ECLS significantly improved renal (creatinine 1.86 ± 0.91 vs 1.32 ± 0.52 mg/dl, P = 0.02), hepatic (aspartate aminotransferase 1426 ± 2176 vs 277 ± 259 U/l, P = 0.04; alanine aminotransferase 982 ± 1466 vs 357 ± 447 U/l, P = 0.04) and pulmonary functions (fraction of inspired oxygen 52 ± 18 vs 26 ± 23%, P < 0.01; positive end-expiratory pressure 7 ± 3 vs 5 ± 4 mbar, P = 0.02) over a period of 8 ± 7 days. Catecholamines could be reduced during ECLS (levosimendan 0.056 ± 0.085 vs 0.010 ± 0.032 μg/kg/min, P = 0.06; dobutamine 4.362 ± 5.268 vs 0.056 ± 0.097 μg/kg/min, P = 0.06; noradrenaline 0.408 ± 0.355 vs 0.056 ± 0.097 μg/kg/min, P < 0.01). Thirty-day and in-hospital mortality after VAD implantation were 4.5 and 9.1%, respectively, and 1-year survival was 86.4%. CONCLUSIONS Preoperative patient optimization using ECLS improves outcomes of INTERMACS Level I patients receiving a permanent VAD.

Low-molecular-weight heparin for anti-coagulation after left ventricular assist device implantation

BACKGROUND Anti-coagulation is required in patients with left ventricular assist devices (LVADs). We evaluated the feasibility of low-molecular-weight heparin (LMWH) for initiation of anti-coagulation and transitioning to oral anti-coagulation after LVAD implantation. METHODS This single-center study included 78 consecutive patients who underwent either Thoratec HeartMate II LVAD (n = 27) or HeartWare ventricular assist device (HVAD, n = 51) implantation. The LMWHs enoxaparin (n = 50) and dalteparin (n = 28) were used. LMWH was started within 24 hours post-operatively in 79.5% of patients. No anti-coagulation was given before starting LMWH therapy. LMWH activity was monitored by determination of anti-factor Xa levels in plasma. RESULTS The majority of patients (80.7%) had peak anti-Xa activity within the defined range of efficacy of 0.2 to 0.4 IU/ml by the second day of treatment. Mean effective peak anti-Xa activity was 0.28 ± 0.06 IU/ml. Mean duration of anti-coagulation with LMWH was 25.8 ± 18 days. Ischemic strokes were observed in 3 patients (3.8%), with a total of 4 events. Three events occurred while on LMWH, and 1 event occurred during follow-up on oral anti-coagulation. There was 1 fatal stroke. No pump thrombus was observed. Major bleeding was observed in 5 patients (6.4%), with a total of 6 events. Gastrointestinal bleeding was the most common complication (n = 3). There were no fatal bleeding events. CONCLUSIONS LMWH in the setting of LVAD shows rapid and constant biologic efficacy. Anti-coagulation with LMWH appears feasible after LVAD implantation. These findings support further evaluation of LMWH as an alternative to unfractionated heparin in this patient cohort.

Off-Pump HeartWare Ventricular Assist Device Implantation With Outflow Graft Anastomosis to the Left Subclavian Artery

A novel, off-pump implantation technique for the HeartWare ventricular assist device with outflow graft anastomosis to the left subclavican artery is described. Cannulation of the left ventricular apex is performed through an incision in the left fourth or fifth intercostal space. The outflow graft is anastomosed to the left subclavian artery after tunneling through the left thoracic cavity and the first intercostal space. This technique is especially appealing in redo cases as well as in patients with significant calcifications of the ascending aorta or in destination-therapy patients.

Repair of Left Ventricular Assist Device Driveline Damage Directly at the Transcutaneous Exit Site

With increasing support duration of cardiac assist devices, transcutaneous drivelines remain a weak point of the therapy. First, they can be an entry point for infections, and second, cable lesions and even electrical failures due to material fatigue and eventual carelessness can occur. We report a case of a damaged outer sheath of a ventricular assist device driveline cable directly at the exit site, where the standard repair procedure with self-fusing tape may lead to biocompatibility problems and irritation of the entrance through the skin. Therefore, a new procedure was developed using a special sleeve expander tool and a highly expandable latex tubing to stabilize the defect in a flexible and biocompatible manner. A patient experienced a fracture of the outer sheath of a HeartWare HVAD driveline directly at the skin entrance (approximately 15 mm long, 5 mm distal from the skin). The metal strands and the electrical functionality were yet not affected, therefore, a pump exchange was not indicated. After considering several conventional solutions for repair as not applicable, a new approach was developed: a sleeve expander tool was applied, which allowed radial stretching of the latex tubing. After preparations of the tool and the cable site, the pump was briefly disconnected, the tubing was moved over the connector and was released at the site of fracture. The problem could be solved by keeping the cables flexibility and without additional risks to the skin. Within a still ongoing (5-month) follow-up, the skin entrance returned to perfect condition and no further intervention was necessary. In conclusion, this method allows a quick stabilization and repair of damaged driveline isolations even near the exit site, resulting in a biocompatible surface and consistent flexibility of the cable.

Increased Thromboembolic Events With Dabigatran Compared With Vitamin K Antagonism in Left Ventricular Assist Device PatientsCLINICAL PERSPECTIVE

Background— Left ventricular assist device–supported patients are usually anticoagulated with a combination of aspirin and vitamin K antagonists. Long-term vitamin K antagonist therapy can be complicated by unstable international normalized ratio values and patient-related compliance problems. Therefore, direct thrombin inhibitors may represent an alternative to vitamin K antagonists. Methods and Results— Thirty HeartWare ventricular assist device patients with stable renal function were planned for this prospective, randomized, open-label, single-center study. Patients were randomized to receive either phenprocoumon or dabigatran in addition to aspirin for long-term anticoagulation. Treatment duration was scheduled for 1 year and stopped after observation of a primary end point. Dabigatran dose was 110 and 75 mg BID in patients with normal or impaired renal function (glomerular filtration rate >80 mL/min or between 80 and 30 mL/min, respectively). The study was stopped prematurely for safety reasons after 16 patients (61±8 years, 1 female) were randomized. Thromboembolic events occurred in 4 subjects receiving dabigatran (50%) and in 1 receiving phenprocoumon (13%; P=0.28). No major bleeding was recorded, and no patient died during the study. Median time to treatment termination was significantly shorter in dabigatran patients (8.5 versus 12.0 months; P=0.015). Conclusions— Thromboembolic events on dabigatran led to early termination of a randomized controlled trial of dabigatran versus phenprocoumon in left ventricular assist device patients. Clinical Trial Registration— https://www.clinicaltrials.gov. Unique identifier: NCT02872649.

Duration of extracorporeal membrane oxygenation support and survival in cardiovascular surgery patients

Objective: The overall therapeutic goal of venoarterial extracorporeal membrane oxygenation (ECMO) in patients with postcardiotomy shock is bridging to myocardial recovery. However, in patients with irreversible myocardial damage prolonged ECMO treatment would cause a delay or even withholding of further permanent potentially life‐saving therapeutic options. We therefore assessed the prognostic effect of duration of ECMO support on survival in adult patients after cardiovascular surgery. Methods: We enrolled into our single‐center registry a total of 354 patients who underwent venoarterial ECMO support after cardiovascular surgery at a university‐affiliated tertiary care center. Results: Through a median follow‐up period of 45 months (interquartile range, 20–81 months), 245 patients (69%) died. We observed an increase in mortality with increasing duration of ECMO support. The association between increased duration of ECMO support and mortality persisted in patients who survived ECMO support with a crude hazard ratio of 1.96 (95% confidence interval, 1.40–2.74; P < .001) for 2‐year mortality compared with the third tertile and the second tertile of ECMO duration. This effect was even more pronounced after multivariate adjustment using a bootstrap‐selected confounder model with an adjusted hazard ratio of 2.30 (95% confidence interval, 1.52–3.48; P < .001) for 2‐year long‐term mortality. Conclusions: Prolonged venoarterial ECMO support is associated with poor outcome in adult patients after cardiovascular surgery. Our data suggest reevaluation of therapeutic strategies after 7 days of ECMO support because mortality disproportionally increases afterward.

High-Intensity Transient Signals in the Outflow Graft and Thrombosis of a HeartWare Left Ventricular Assist Device

We report the echocardiographic detection of microbubbles in the outflow prosthesis of a HeartWare HVAD left ventricular assist device using transthoracic echocardiography. In this case it was a specific sign associated with device thrombosis that resolved after successful treatment with systemic thrombolysis.

Interaction of a Transapical Miniaturized Ventricular Assist Device With the Left Ventricle: Hemodynamic Evaluation and Visualization in an Isolated Heart Setup.

New left ventricular assist devices (LVADs) offer both important advantages and potential hazards. VAD development requires better and expeditious ways to identify these advantages and hazards. We validated in an isolated working heart the hemodynamic performance of an intraventricular LVAD and investigated how its outflow cannula interacted with the aortic valve. Hearts from six pigs were explanted and connected to an isolated working heart setup. A miniaturized LVAD was implanted within the left ventricle (tMVAD, HeartWare Inc., Miami Lakes, FL, USA). In four experiments blood was used to investigate hemodynamics under various loading conditions. In two experiments crystalloid perfusate was used, allowing visualization of the outflow cannula within the aortic valve. In all hearts the transapical miniaturized ventricular assist device (tMVAD) implantation was successful. In the blood experiments hemodynamics similar to those observed clinically were achieved. Pump speeds ranged from 9 to 22 krpm with a maximum of 7.6 L/min against a pressure difference between ventricle and aorta of ∼50 mm Hg. With crystalloid perfusate, central positioning of the outflow cannula in the aortic root was observed during full and partial support. With decreasing aortic pressures the cannula tended to drift toward the aortic root wall. The tMVAD could unload the ventricle similarly to LVADs under conventional cannulation. Aortic pressure influenced central positioning of the outflow cannula in the aortic root. The isolated heart is a simple, accessible evaluation platform unaffected by complex reactions within a whole, living animal. This platform allowed detection and visualization of potential hazards.

Surgical minimally invasive techniques for mitral valve repair—cannulation techniques and the Vienna approach

Minimally invasive approaches for mitral valve repair are increasingly applied in current clinical practice. Patients admitted to our clinic with suitable diagnoses are routinely screened for a right minithoracotomy and if suitable planned primarily for this approach. Herein we provide details regarding our minimally invasive mitral valve replacement or repair techniques with special emphasis on the cannulation strategy.