Developing a comprehensive mechanical support program.

As cardiac surgery centers appreciate that ventricular assist devices (VAD) can dramatically impact patient survival as a bridge to transplant or recovery, and possibly permanent therapy, increasing numbers will desire to establish mechanical support programs. A number of vital elements must be put in place in order to operate a successful mechanical support program. Of utmost importance is the assembly of a dedicated team focused on comprehensive care of critically ill patients in need of circulatory support. An ongoing commitment from anesthesiologists, cardiologists, nephrologists, and other support staff is essential. Selection of complementary assist devices should be made to cover the spectrum of required support scenarios, both short- and long-term. Outpatient therapy has become increasingly important in mechanical cardiac assistance and establishment of an office where "LVAD coordinators" see outpatients facilitates this aspect of the program. Critically ill patients in need of cardiac assistance may benefit from specialized medical therapies such as: (1) intravenous arginine vasopressin for vasodilatory hypotension; (2) inhaled nitric oxide for right heart failure; (3) aprotinin to reduce hemorrhage; and (4) early enteral feeding in an effort to reduce infectious complications and improve rehabilitation following VAD implantation. A regional network with spoke hospitals centered around a hub hospital with long-term VAD and heart transplant programs can improve survival of patients with postcardiotomy cardiogenic shock via early transfer to the hub hospital. In this article, we describe the components of our mechanical support program that have allowed us to successfully support patients with heart failure in need of circulatory support.

Recurrent remodeling after ventricular assistance: is long-term myocardial recovery attainable?

BACKGROUND: Long-term left ventricular assist devices (LVAD) have been used both as a bridge to heart transplantation and to recovery of native myocardial function. Despite much evidence for reversal of some of the structural and functional changes present in the failing heart during LVAD support, clinical evidence for sustained myocardial recovery is scant. We describe 2 patients in whom myocardial recovery during LVAD support led to device explanation only to have heart failure recur. This necessitated a second LVAD implantation, a process that we have termed recurrent remodeling. METHODS: The medical records of 2 patients with cardiomyopathy supported with HeartMate LVADs (Thermo Cardiosystems, Inc, Woburn, MA) were retrospectively reviewed. RESULTS: One patient was supported with an LVAD for 2 months, at which time the LVAD was explanted. Progressive deterioration of cardiac function followed, requiring a second LVAD 19 months after LVAD explanation. After 2 months of further LVAD support, a second episode of apparent myocardial recovery was observed during a period of device malfunction. The other patient was supported with an LVAD for 12 months, at which time the LVAD was explanted. The patient experienced progressive hemodynamic deterioration and required a second LVAD 6 months after LVAD explantation. Heart transplantations of both patients were successful. CONCLUSIONS: Our understanding of myocardial recovery in the setting of hemodynamic unloading with LVAD support has not yet progressed to the point where we are able to accurately predict successful long-term LVAD explantation. The evolution of reliable predictors of sustainable myocardial recovery will help to avoid further cases of recurrent remodeling requiring repeat LVAD implantation.

A randomized trial of antithrombin concentrate for treatment of heparin resistance.

BACKGROUND: Heparin resistance is an important clinical problem traditionally treated with additional heparin or fresh frozen plasma. We undertook a randomized clinical trial to determine if treatment with antithrombin (AT) concentrate is effective for treating this condition. METHODS: Patients requiring cardiopulmonary bypass who were considered to be heparin resistant (activated clotting time < 480 seconds after > 450 IU/kg heparin) were randomized to receive either 1000 U AT or additional heparin. RESULTS: AT concentrate was effective in 42 of 44 patients (96%) for immediately obtaining a therapeutic activated clotting time. This compared favorably to 28 of 41 patients (68%) treated with additional heparin (p = 0.001). All patients who failed heparin therapy were successfully treated with AT. The patients receiving AT required less time to obtain an adequate ACT but there was no difference in clinical outcomes among the groups. Study patients had deficient AT activity at baseline (56%+/-25%), which improved in those given AT concentrate (75%+/-31% versus 50%+/-23%, p < 0.0005). CONCLUSIONS: Heparin resistance is frequently associated with AT deficiency. Treating this deficiency with AT concentrate is more effective and faster for obtaining adequate anticoagulation than using additional heparin.

History of mechanical circulatory support.

End-stage heart failure exerts a tremendous impact on individuals and society in terms of personal and economic suffering. The development of mechanical circulatory support devices has been driven by the shortage of donor organs for heart transplantation. Collaborative efforts in the fields of surgery, medicine, and biomedical engineering, sponsored by both government and industry, have led to devices capable of providing reliable circulatory support. Future mechanical cardiac assist devices will likely play an important role in the treatment of an ever-growing population of patients with end-stage heart failure.

Implantable left ventricular assist devices can successfully bridge adolescent patients to transplant.

BACKGROUND: Left ventricular assist devices (LVAD) have been used successfully as a life-sustaining bridge to transplantation in adults with end-stage heart failure. Long-term implantable cardiac assist devices for smaller adolescent patients are not yet available in the United States. METHODS: This study reviews the experience with patients less than 21 years old that received HeartMate LVADs (TCI) at our institution. Twelve patients were implanted with 13 LVADs. The patients ranged in age from 11 to 20 years (mean 16 years). Body surface area ranged from 1.4 to 2.2 m2 (mean 1.8 m2). Patients were selected for LVAD placement based on eligibility for heart transplant and evidence of end-organ dysfunction. Device placement in small patients was facilitated with prosthetic graft abdominal wall closure. No patient received systemic anticoagulation. RESULTS: The duration of LVAD support ranged from 0 to 397 days (mean 123 days). Seven of the 8 patients eligible for discharge from the hospital with a vented-electric LVAD were supported at home while awaiting transplantation. Outcomes of LVAD support were: LVAD explantation in 2 cases (15%), expiration with LVAD in place in 3 cases (23%), and successful transplantation in 8 cases (62%). Complications included 4 patients with systemic infection, 3 re-operations for hemorrhage, 1 embolic event, and 1 intraoperative air embolus that proved fatal. One explanted patient required a subsequent LVAD and the other expired 4 months after explantation. Six of the 8 transplanted patients are alive and well with follow-up ranging from 8 to 43 months. CONCLUSIONS: Adolescent patients with heart failure can be successfully supported on a long-term basis to heart transplantation with the HeartMate LVAD. The wearable device allows for discharge home while awaiting transplantation. Device explantation without subsequent transplantation can be unpredictable. The incidence of thromboembolism remains low despite the absence of systemic anticoagulation. The technique of prosthetic graft closure of the abdominal wall facilitates the use of this device in smaller patients.

Arginine vasopressin in the treatment of 50 patients with postcardiotomy vasodilatory shock.

BACKGROUND: The barroreflex-mediated secretion of arginine vasopressin has been found to be defective in a variety of vasodilatory shock states, such as postcardiotomy shock, and administration of the hormone markedly improves vasomotor tone and blood pressure. The high incidence of vasodilatory shock in patients undergoing left ventricular assist device (LVAD) implantation makes this population an ideal model in which to assess the risks and benefits of vasopressin. METHODS: The medical records of the 102 patients receiving LVADs at Columbia-Presbyterian Medical Center from January 1995 to August 1998 were reviewed. Fifty patients were eligible for study based on a history of arginine vasopressin administration in the operating room or intensive care unit within 24 hours of implantation. RESULTS: Despite LVAD implantation and the administration of vasopressors, patients were hypotensive with a mean arterial pressure less than 60 mm Hg. The administration of vasopressin (0.09+/-0.05 U/min) increased mean arterial pressure (58+/-13 to 75+/-14 mm Hg; p<0.001) while reducing norepinephrine administration (11.7+/-13 to 7.9+/-6.0 mcg/min; p = 0.023). There was no significant change in LVAD flow. The incidence of compromised regional perfusion was not different between LVAD patients who received vasopressin as compared to hemodynamically stable LVAD patients who did not receive vasopressin. CONCLUSIONS: We have demonstrated vasopressin at low doses to be a safe and an effective vasopressor in 50 patients with postcardiotomy vasodilatory shock.

Six-year experience of caring for forty-four patients with a left ventricular assist device at home: safe, economical, necessary.

OBJECTIVE: With increasing numbers of implantations, left ventricular assist device programs can put a financial strain on a hospital unless an efficient and safe outpatient program is developed. However, the left ventricular assist device is not widely recognized in the medical community as being reliable enough to support a patient at home. We reviewed our experience with these patients at home to assess the safety and the benefits of such a program. METHODS: Our institutional 6-year experience with 90 consecutive recipients of a wearable left ventricular assist device was analyzed. RESULTS: Forty-four (49%) of the 90 patients who received TCI vented-electric left ventricular assist devices (Thermo Cardiosystems, Inc, Woburn, Mass) were discharged, spending a total of 4546 days (12.5 years) at home with an average of 103 +/- 16 days of outpatient support (range 9-436 days). Of these 44 patients, all were successfully bridged to transplantation (42 patients, 96%) or planned explantation (2 patients, 4%). None of the outpatients died. The cumulative events per outpatient month were 0.020 for bleeding, 0.053 for device infection, 0.0068 for thromboembolus, and 0.020 for major malfunctions. Our estimated average cost to bridge a patient to transplantation or explantation once discharged is $13,200 and as an inpatient over the same length of time, including only room and board, is $165,200. Thirty percent of outpatients were able to return to work or school, 33% to sexual activity, and 44% to driving. All outpatients performed activities of daily living. CONCLUSION: Current left ventricular assist device technology provides effective and economical outpatient support and is associated with limited morbidity and a satisfactory quality of life.

Gender differences in patients undergoing coronary artery bypass surgery, from a mandatory statewide database.

OBJECTIVE: To determine why women have a higher mortality rate than men when undergoing coronary artery bypass grafting. DESIGN: Retrospective analysis of patients entered in a mandatory state database. PARTICIPANTS: 19,224 patients who underwent coronary artery bypass grafting in New York State in 1995. METHOD: The authors evaluated data pertaining to 27 variables. They conducted univariate analysis using the Student t test for continuous variables and the chi-square test or the Fisher exact test for discrete data. They conducted multivariate analysis using a logistic regression model. RESULTS: Analysis of body surface area revealed that smaller size was a risk factor for both women and men. Analysis of age demonstrated increased risk for mortality in women in both older and younger subpopulations. Other significant variables included a lesser degree of revascularization and less frequent use of the internal mammary artery in women. CONCLUSION: Smaller size and advanced age alone do not explain why female gender is an independent risk factor for mortality from coronary artery bypass grafting. Increased mortality is probably due to the fact that women have more comorbid conditions than men at the time of referral, perhaps because they are not being evaluated aggressively enough.

Left ventricular assist device bridge-to-transplant network improves survival after failed cardiotomy.

BACKGROUND: Postcardiotomy cardiogenic shock has been reported to occur following 2% to 6% of cardiac surgical procedures. Both the mandatory New York state cardiac surgery database and a voluntary ventricular assist device registry have reported hospital discharge rates of only 25% in postcardiotomy patients supported with ventricular assist devices. Although many centers have access to short-term mechanical cardiac assist devices, most lack a dedicated team which can resuscitate these critically ill patients. Equally important, these centers do not have easy access to effective cardiac replacement options, including implantable left ventricular assist devices (LVADs) and heart transplantation. METHODS: A referral network based upon the use of implantable LVADs as a bridge to transplantation in patients with postcardiotomy heart failure was established in the New York City region. Cardiac surgery centers were encouraged to contact our center early following any failed cardiotomy. RESULTS: Forty-four patients entered our postcardiotomy network: 12 recovered without an implantable LVAD, 23 received implantable LVADs, and six expired without long-term LVAD support. Of the 44 referrals, 29 (66%) survived to hospital discharge. Of the 23 patients receiving implantable LVADs, two recovered myocardial function and underwent LVAD explant, 14 were bridged to heart transplant, one underwent an emergent heart transplant, and six expired. Of the 23 implantable LVAD patients, 17 (74%) survived to hospital discharge. CONCLUSIONS: Regional networks centered around bridge-to-transplant facilities that have an aggressive approach to implantable LVAD placement may substantially improve the survival rate of patients with postcardiotomy heart failure.

Development of an off bypass mitral valve repair.

BACKGROUND: The Bow Tie Repair (BTR), a single edge-to-edge suture opposing the anterior and posterior leaflets of the mitral valve (MV), has led to satisfactory reduction of mitral regurgitation (MR) with few re-operations and excellent hemodynamic results. The simplicity of the repair lends itself to minimally invasive approaches. A MV grasper has been developed that will coapt both leaflets and fasten the structures with a graduated spiral screw. METHODS: Eleven explanted adult human MVs were mounted in a mock circulatory loop created for simulating a variety of hemodynamic conditions. The MV grasper was used to place a screw in each valve, which was then continuously run for 300,000 to 1,000,000 cycles with a fixed transvalvular pressure gradient. At the completion of these studies, the valves were stressed to a maximal transvalvular gradient for ten minutes. In seven cases, MR was induced and subsequently repaired using the MV screw. In vivo, the MV screw was tested in nine male canines. Through a subcostal incision, the MV grasper entered the left ventricle, approximated the mitral leaflets and deployed the MV screw under direct visualization via an atriotomy. Follow-up transthoracic echocardiograms were done at postoperative week 1, 6, and 12 to identify screw migration, MV regurgitation/stenosis or clot formation. Dogs were sacrificed up to postoperative week 12 to allow gross and histologic assessment. RESULTS: In vitro, no MV screw detached from the valve leaflets or migrated during the durability testing period of 6.8 million cycles, including periods of stress load testing up to 350 mm Hg. The percent regurgitant flow used to assess MR statistically decreased with the placement of the screw from 72 +/- 7% to 34 +/- 17%; p = 0.0025. In vivo, seven dogs whose valves were examined within the first 48 hours revealed leaflet coaptation with an intact MV screw and no evidence of MR. Two dogs, followed for a prolonged period, had serial postoperative echocardiograms demonstrating consistent coaptation, no screw migration, no clot, and no regurgitation or stenosis. In the animal sacrificed at 12 weeks, the MV screw was integrated into the tissue of both leaflets. CONCLUSIONS: The MV screw has provided durable leaflet coaptation and has reduced regurgitation in human MVs. Initial data on the MV screw's biocompatibility and interactions with living valve tissue is promising. Our early success supports further efforts towards the maturation of this prototype into off bypass mitral valve repair technology.