Restoration Of Pulsatile Flow Research Articles

Gastrointestinal Bleeding Ceases after Heart Transplantation in Patients Bridged on Continuous-Flow LVAD Support

Purpose Continuous flow left ventricular assist device (CF-LVAD) support has been associated with gastrointestinal bleeding (GIB), primarily from arteriovenous malformations or ulcers, and exacerbated by the requirement for anticoagulation. In this report, we explore whether GIB persisted after heart transplant in patients who experienced GIB events while on CF-LVAD support. Methods We performed a retrospective review of 701 patients who underwent implantation of CF-LVADs from August 2002 through August 2017 at our center, and identified patients who underwent CF-LVAD implantation as a Bridge-to-Transplant, experienced at least one GIB event during CF-LVAD support, and were successfully bridged to heart transplantation. We evaluated the incidence of GIB events in these patients after heart transplantation. Results A total of 46 heart transplant recipients fit the inclusion criteria. There were a total of 63 total GIB events while on CF-LVAD support. Locations of GIB events included esophagus (N=3), stomach (N=21), duodenum (N=7), jejunum (N=3), small intestine not-otherwise-specified (N=12), colon (N=14), and rectum (N=3). Etiologies included gastritis (N=10), ulcer (N=11), arteriovenous malformation (N=13), angiodysplasia (N=3), polyp (N=2), diverticulosis (N=8), and Mallory Wiess tear (N=2). Mean LVAD support time was 1.4±1.5 years (65.4 cumulative patient-years). Mean follow-up time after transplantation was 4.0±3.5 years (183.3 cumulative patient-years after transplantation). There was only 1 GIB event after heart transplantation (events per patient-year: 0.005). The etiology was non-specific acute colitis in a patient who had prior GIB from a gastric ulcer while on LVAD therapy. Time from transplant to GIB event was 3.9 years. The patient was taking aspirin 81mg daily at the time of GIB. Conclusion GIB during CF-LVAD therapy did not persist after heart transplantation. This may be due to restoration of pulsatile flow. Introduction of a greater degree of pulsatility into LVAD flow technology may improve the incidence of GIB while on CF-LVAD support.

Restoration of Pulsatile Flow Reduces Sympathetic Nerve Activity Among Individuals With Continuous-Flow Left Ventricular Assist Devices.

Current-generation left ventricular assist devices provide circulatory support that is minimally or entirely nonpulsatile and are associated with marked increases in muscle sympathetic nerve activity (MSNA), likely through a baroreceptor-mediated pathway. We sought to determine whether the restoration of pulsatile flow through modulations in pump speed would reduce MSNA through the arterial baroreceptor reflex. Ten men and 3 women (54 ± 14 years) with Heartmate II continuous-flow left ventricular assist devices underwent hemodynamic and sympathetic neural assessment. Beat-to-beat blood pressure, carotid ultrasonography at the level of the arterial baroreceptors, and MSNA via microneurography were continuously recorded to determine steady-state responses to step changes (200-400 revolutions per minute) in continuous-flow left ventricular assist device pump speed from a maximum of 10,480 ± 315 revolutions per minute to a minimum of 8500 ± 380 revolutions per minute. Reductions in pump speed led to increases in pulse pressure (high versus low speed: 17 ± 7 versus 26 ± 12 mm Hg; P<0.01), distension of the carotid artery, and carotid arterial wall tension (P<0.05 for all measures). In addition, MSNA was reduced (high versus low speed: 41 ± 15 versus 33 ± 16 bursts per minute; P<0.01) despite a reduction in mean arterial pressure and was inversely related to pulse pressure (P=0.037). Among subjects with continuous-flow left ventricular assist devices, the restoration of pulsatile flow through modulations in pump speed leads to increased distortion of the arterial baroreceptors with a subsequent decline in MSNA. Additional study is needed to determine whether reduction of MSNA in this setting leads to improved outcomes.

VH8. Retrograde Angioplasty During a Transtibial Amputation

The importance of the preservation of the knee joint for better rehabilitation of the vascular amputee is recognized but frequently underestimated. In the common practice of vascular surgery, all efforts are done for limb salvage, but this effort is mainly focused on foot preservation. When the foot is not salvageable, the level of amputation is mainly decided on ground of the perfusion status of the lower limb at the time of evaluation for the surgical procedure. The philosophy of revascularization for level preservation is proposed. Open or endovascular procedures should be done if it is understood that a patient considered for a transfemoral amputation may benefit from a transtibial amputation and the revascularization is feasible and the risk reasonable. The technique described is a procedure to enhance the healing capabilities of a transtibial amputation with marginal perfusion restoring absent popliteal pulse by means of a retrograde angioplasty done during the operation. The usual technique of a transtibial amputation is planned, with a long posterior flap that can be modified if necessary by skin necrosis extension or infection. The procedure goes anatomically through all leg compartments. After skin incision and deepening on surgical planes, section of anterior and peroneal muscles and vessels and nerves allow removal of a gap of peroneal bone and dissection of peroneal artery and vein. The tibia is then sectioned in a beveled fashion with a Gigli saw, from a posterior to anterior access, and then the posterior tibial nerve, vein, and artery are dissected. Specimen is removed, after treatment of sural nerve and vein. The posterior tibial artery is then approached, for the particular case described, and a retrograde angioplasty is done, by insertion of guide wires, catheters, and balloons as necessary. Angioplasty is performed and restoration of pulsatile flow at the area of the operative field documented.

Invited commentary

Pulsatile ventricular assist is a recognized treatment for life threatening heart failure [1Rose E.C. Gelijns A.C. Moskowitz A.J. et al.Long-term use of a left ventricular assist device for end-stage heart failure.N Engl J Med. 2001; 345: 1435-1443Crossref PubMed Scopus (3288) Google Scholar]. This type of therapy is a laborious undertaking and the complication rate following device implantation remains high, with an overall survival rate of 65% to transplant. Significant ongoing problems include bleeding, infection, right heart failure, and mechanical failure of the assist device [1Rose E.C. Gelijns A.C. Moskowitz A.J. et al.Long-term use of a left ventricular assist device for end-stage heart failure.N Engl J Med. 2001; 345: 1435-1443Crossref PubMed Scopus (3288) Google Scholar, 2Miller L.W. Patient selection for the use of ventricular assist devices as a bridge to transplantation.Ann Thorac Surg. 2003; 75: S66-71Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar]. Nonpulsatile continuous flow devices have been developed and, very recently, implanted in the hope of reducing procedural complications due to their small size, ease of implantation, and easier maintenance [3Grinda J.M. Latremouille C.H. Chevalier P. et al.Bridge to transplantation with the Debakey VAD axial pump a single center report.Eur J Cardiothorac Surg. 2002; 22: 965-970Crossref PubMed Scopus (24) Google Scholar, 4Vitali E. Lanfranconi M. Ribera E. et al.Successful experience in bridging patients to heart transplantation with the Micro- Med Debakey ventricular assist device.Ann Thorac Surg. 2003; 75: 1200-1204Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar]. Some of the potential drawbacks with these newer assist devices are the negative effects of not completely unloading the failing ventricle and the consequences nonpulsatile flow over the long term. In their paper, Klotz and colleagues attempt to address these concerns. In this small, yet well-studied series of patients, right heart catheterizations as well as echocardiograms were performed before and at an average of 3.4 months after left ventricular device implantation in a relatively similar group of patients with either a pulsatile (21 patients) or nonpulsatile device (10 patients). They found that both devices were equally effective in reducing LV pressure as measured by mean pulmonary pressure and wedge pressure. As anticipated, left ventricular volume unloading was superior in the pulsatile group and, as such, the mean arterial pressure was also higher. Interestingly, the degree of LV volume unloading in the nonpulsatile group was dependent on the length of time the device had been implanted. Device contribution to overall cardiac output was higher soon after implant and then diminished over time in a near linear fashion. Five of the ten patients with the nonpulsatile device had resumption of antegrade flow across the aortic valve and two had a return of pulsatile flow measured noninvasively. Taken together, this is consistent with an improving and remodeling ventricle overtime in the nonpulsatile group. Clinically, both groups of patients were able to exercise to at least 50 W. The overall outcome to transplant was similar in both groups, but the numbers are too small to make meaningful judgments. What this information does mean is that it is not physiologically necessary to have complete volume unloading to support the failing ventricle and the underperfused patient. Rehabilitation of both the patient and the ventricle appears possible with a nonpulsatile device, and a sign of ventricular improvement is the restoration of pulsatile flow. Whether one could further the ventricular recovery using this device to the point of explant is an intriguing concept. That being said, we need more data regarding the overall outcome and complication rate of these newer nonpulsatile devices. In those patients with profound shock where complete unloading and circulatory support is crucial, this device may not work or may require significant inotropic supplementation. Patient selection may again play a significant role in outcome.

Primary stent deployment in occlusive subclavian artery disease.

Primary (without antecedent balloon dilation) Palmaz stent implantation was successfully performed in 27 consecutive patients entering with 31 obstructed subclavian arteries. Stents (n = 50) were successfully deployed, using the brachial (n = 7), femoral (n = 16), or combined (n = 8) approach, to revascularize 31 subclavian vessels [8 occluded (26%); 23 stenotic (74%)], using a 6 or 7.5 French delivery system. The indications for intervention were arm claudication in 8 patients (30%), subclavian steal syndrome in 11 patients (41%), angina pectoris secondary to impaired blood flow to the left internal mammary artery coronary bypass in 6 patients (22%), and recanalization of a left subclavian occlusion to permit central arterial access and performance of a second interventional procedure 2 patients (7%). The percent diameter stenosis improved from 85 +/- 12% to 6 +/- 7% (P < 0.001); and, the peak and mean translesion gradients decreased, respectively, from 56 +/- 35 mm Hg to 3 +/- 4 mm Hg (P < 0.01), and 29 +/- 18 mm Hg to 2 +/- 2 mm Hg (P < 0.01). Procedural complications encountered were one stent dislodgement with migration into and uneventful deployment within the right external iliac artery, and two brachial artery repairs. No acute vessel closures, deaths, myocardial infarctions, cerebrovascular accidents, transient ischemic attacks, or need for transfusions occurred. Therefore, primary subclavian artery stent deployment can be performed using low-profile sheath systems with excellent success (100%), resulting in immediate restoration of pulsatile flow, and few complications. The incidence of lesion recurrence remains for follow-up studies.

Fibronectin coating of an experimental PTFE vascular prosthesis

Because of the known inefficiency of endothelial cell seeding of vascular prostheses, some investigators have pretreated their grafts with fibronectin in an effort to increase endothelial cell adhesion. However, the most efficient method of coating vascular prostheses with fibronectin has not yet been determined and more importantly, the durability of this coating following restoration of pulsatile perfusion has not yet been established. This experiment measured the adsorption of fibronectin which was perfused at three different concentrations through an experimental, highly porous PTFE vascular graft. Most efficient coating of the prosthetic appeared to occur with a 250 mg/ml concentration of fibronectin perfused through the graft for 60 min. Grafts so prepared were subsequently studied in a pulsatile perfusion system which mimicked the canine circulation. Fifteen additional fibronectin-coated grafts were also interposed in the canine carotid artery. Flow was restored, grafts were removed at varying intervals, and fibronectin disappearance was measured. In both the in vitro and in vivo models, three distinct phases of fibronectin dissociation were seen: an initial rapid loss which resulted in an average 30.5% retention of the initial concentration of fibronectin following 30 min of perfusion; a second phase, which occurred from 30 to 120 min, demonstrated an average 2.5% loss of fibronectin per hour; and a final phase, from 2 to 24 hr, during which no significant additional loss of fibronectin was seen. This study describes a new method by which PTFE vascular prostheses can be effectively coated by perfusing them with physiologic concentrations of fibronectin and demonstrates that the resulting bond between fibronectin and prosthetic is stable following restoration of pulsatile flow.

Evaluation of the patient with intermittent claudication.

The most common cause of intermittent claudication is atherosclerotic occlusive arterial disease. Differentiation of the common musculoskeletal and neurologic conditions that may mimic intermittent claudication is often possible with a careful history, but when insufficient detail is provided or multiple conditions exist, the findings on physical examination and noninvasive studies are useful. While physical examination provides a rough estimate of the degree of ischemia, assessment of functional impairment produced by occlusive arterial disease is best made with noninvasive studies before and after standard exercise. Arteriography is reserved for the patient for whom restoration of pulsatile flow is planned.