Muscular counterpulsation: preliminary results of a non-invasive alternative to intra-aortic balloon pump

Objectives: IABP is the most widely used form of temporary cardiac assist and its benefits are well established. We designed an animal study to evaluate a device based on muscular counterpulsation (MCP) that should reproduce the same hemodynamic effects as IABP in a completely non-invasive way. Methods: Six calves, 60±4 kg, divided into 2 groups, in general anaesthesia, equipped with EKG, Swan-Ganz, pressure probe in the femoral artery and flow probe in the left carotid artery, received either IABP through right femoral artery, or muscle counterpulsation (MCP). MCP consists of electrically induced skeletal muscle contraction during early diastole, triggered by EKG and microprocessor controlled by a portable device. For each animal the following parameters were also considered: mean aortic pressure (mAoP), CO, CI, left ventricular stroke work index (LVSWI), systemic vascular resistance (SVR) and mean femoral artery flow (Faf). We did 3 sets of measurements: baseline (BL), after 20 (M20) and 40 (M40) min of cardiac assistance. These measurements have been repeated after 40 min of rest for 3 times. Results are expressed as mean±SD. Results: Baseline values: mAoP, 76.51±12 mmHg; mCVP, 11.5±3 mmHg; CO, 5±1 l/min per m2; LVSWI, 0.77±0.2KJ/m2; SVR, 1040±15dyns/cm−5; Faf, 75.5±10 ml/min. IABP group: mAoP, 81.1±6 mmHg; mCVP, 1±0.1 mmHg; CO, 4.5±0.7 l/min per m2; LVSWI, 0.69±0.2KJ/m2; SVR, 1424±8dyns/cm−5; Faf, 64.3±3 ml/min. MCP group: mAoP, 60.1±7 mmHg; mCVP, 23.6±2 mmHg; CO, 4.8±0.4 l/min per m2; LVSWI, 0.69±0.2KJ/m2; SVR, 608±25dyns/cm−5; Faf, 92.3±12 ml/min. Conclusions: MCP and IABP had the same effects on CO and LVSWI. Moreover, MCP reduced SVR and increased the peripheral circulation without requiring any vascular access nor anticoagulation therap

Cross-sectional compliance overestimates arterial compliance because it neglects the axial strain.

A high resolution echo-tracking system permits the calculation of cross-sectional compliance considering vessel diameter variations alone, and assumes that longitudinal movement of the vessel wall due to pulse pressure is negligible. However, using piezoelectric crystals sutured on the adventitia of the vessel wall we demonstrated that arterial length changes up to 5% (mean 2.7%) as a function of pulse pressure. Therefore, cross-sectional compliance seems to provide a limited approximation of the real phenomenon because it neglects axial vessel movement. Axial vessel movement is taken into account when the vessel compliance is calculated according to the principle of continuity of the mass: [equation: see text]. To verify this hypothesis we measured the blood flow gradient through 10 cm long segments of 10 pig carotid arteries (Qin - Qout) and divided it for the derivative of blood pressure over a given time (deltaP/deltat). For the same vessels, we calculated the cross-sectional compliance (CC) using the echo-tracking system (NIUS 02). We found a CC of (5.91 +/- 0.4) x 10(-7) micro m(2)/mm Hg and a segmental carotid compliance or dynamic compliance (C(d)) of (6.21 +/- 0.2) x 10(-8) micro m(3)/mm Hg. The impact of axial strain in calculations of compliance results in a dynamic compliance, which is one order of magnitude smaller than traditionally calculated arterial compliance

Late removal of retrievable caval filters.

The advent of retrievable caval filters was a game changer in the sense, that the previously irreversible act of implanting a medical device into the main venous blood stream of the body requiring careful evaluation of the pros and cons prior to execution suddenly became a "reversible" procedure where potential hazards in the late future of the patient lost most of their weight at the time of decision making. This review was designed to assess the rate of success with late retrieval of so called retrievable caval filters in order to get some indication about reasonable implant duration with respect to relatively "easy" implant removal with conventional means, i.e., catheters, hooks and lassos. A PubMed search (www.pubmed.gov) was performed with the search term "cava filter retrieval after 30 days clinical", and 20 reports between 1994 and 2013 dealing with late retrieval of caval filters were identified, covering approximately 7,000 devices with 600 removed filters. The maximal duration of implant reported is 2,599 days and the maximal implant duration of removed filters is also 2,599 days. The maximal duration reported with standard retrieval techniques, i.e., catheter, hook and/or lasso, is 475 days, whereas for the retrievals after this period more sophisticated techniques including lasers, etc. were required. The maximal implant duration for series with 100% retrieval accounts for 84 days, which is equivalent to 12 weeks or almost 3 months. We conclude that retrievable caval filters often become permanent despite the initial decision of temporary use. However, such "forgotten" retrievable devices can still be removed with a great chance of success up to three months after implantation. Conventional percutaneous removal techniques may be sufficient up to sixteen months after implantation whereas more sophisticated catheter techniques have been shown to be successful up to 83 months or more than seven years of implant duration. Tilting, migrating, or misplaced devices should be removed early on, and replaced if indicated with a device which is both, efficient and retrievable

Alloimmunity and nonimmunologic risk factors in cardiac allograft vasculopathy

Graft vasculopathy is an accelerated form of coronary artery disease that occurs in transplanted hearts. Despite major advances in immunosuppression, the prevalence of the disease has remained substantially unchanged during the last two decades. According to the ‘response to injury' paradigm, graft vasculopathy is the result of a continuous inflammatory response to tissue injury initiated by both alloantigen-dependent and independent stress responses. Experimental evidence suggests that these responses may become self-sustaining, as allograft re-transplantation into the donor strain at a later stage fails to prevent disease progression. Histological evidence of endothelitis and arteritis, in association with intima fibrosis and atherosclerosis, reflects the central role of alloimmunity and inflammation in the development of arterial lesions. Experimental results in gene-targeted mouse models indicate that cellular and humoral immune responses are both involved in the pathogenesis of graft vasculopathy. Circulating antibodies against donor endothelium are found in a significant number of patients, but their pathogenic role is still controversial. Alloantigen-independent factors include donor-transmitted coronary artery disease, surgical trauma, ischaemia-reperfusion injury, viral infections, hyperlipidaemia, hypertension, and glucose intolerance. Recent therapeutic advances include the use of novel immunosuppressive agents such as sirolimus (rapamycin), HMG-CoA reductase inhibitors, calcium channel blockers, and angiotensin converting enzyme inhibitors. Optimal treatment of cardiovascular risk factors remains of paramount importanc

Atrial assist device, a new alternative to lifelong anticoagulation?

OBJECTIVE: Atrial fibrillation is a very common heart arrhythmia, associated with a five-fold increase in the risk of embolic strokes. Treatment strategies encompass palliative drugs or surgical procedures all of which can restore sinus rhythm. Unfortunately, atria often fail to recover their mechanical function and patients therefore require lifelong anticoagulation therapy. A motorless volume displacing device (Atripump) based on artificial muscle technology, positioned on the external surface of atrium could avoid the need of oral anticoagulation and its haemorrhagic complications. An animal study was conducted in order to assess the haemodynamic effects that such a pump could provide. METHODS: Atripump is a dome-shape siliconecoated nitinol actuator sewn on the external surface of the atrium. It is driven by a pacemaker-like control unit. Five non-anticoagulated sheep were selected for this experiment. The right atrium was surgically exposed, the device sutured and connected. Haemodynamic parameters and intracardiac ultrasound (ICUS) data were recorded in each animal and under three conditions; baseline; atrial fibrillation (AF); atripump assisted AF (aaAF). RESULTS: In two animals, after 20 min of AF, small thrombi appeared in the right atrial appendix and were washed out once the pump was turned on. Assistance also enhanced atrial ejection fraction. 31% baseline; 5% during AF; 20% under aaAF. Right atrial systolic surfaces (cm2) were; 5.2 +/- 0.3 baseline; 6.2 +/- 0.1 AF; 5.4 +/- 0.3 aaAF. CONCLUSION: This compact and reliable pump seems to restore the atrial "kick" and prevents embolic events. It could avoid long-term anticoagulation therapy and open new hopes in the care of end-stage heart failure

Animal model to compare the effects of suture technique on cross-sectional compliance on end-to-side anastomoses

Objective: An animal model has been developed to compare the effects of suture technique on the luminal dimensions and compliance of end-to-side vascular anastomoses. Methods: Carotid and internal mammalian arteries (IMAs) were exposed in three pigs (90 kg). IMAs were sectioned distally to perform end-to-side anastomoses on carotid arteries. One anastomosis was performed with 7/0 polypropylene running suture. The other was performed with the automated suture delivery device (Perclose/Abbott Labs Inc.) that makes a 7/0 polypropylene interrupted suture. Four piezoelectric crystals were sutured on toe, heel and both lateral sides of each anastomosis to measure anastomotic axes. Anastomotic cross-sectional area (CSAA) was calculated with: CSAA = π × mM/4 where m and M are the minor and major axes of the elliptical anastomosis. Cross-sectional anastomotic compliance (CSAC) was calculated as CSAC = δCSAA/δP where δP is the mean pulse pressure and δCSAA is the mean CSAA during cardiac cycle. Results: We collected a total of 1 200 000 pressure-length data per animal. For running suture we had a mean systolic CSAA of 26.94±0.4 mm2 and a mean CSAA in diastole of 26.30±0.5 mm2 (mean δCSAA was 0.64 mm2). CSAC for running suture was 4.5×10−6m2/kPa. For interrupted suture we had a mean CSAA in systole of 21.98±0.2 mm2 and a mean CSAA in diastole of 17.38±0.3 mm2 (mean δCSAA was 4.6±0.1 mm2). CSAC for interrupted suture was 11×10−6 m2/kPa. Conclusions: This model, even with some limitations, can be a reliable source of information improving the outcome of vascular anastomoses. The study demonstrates that suture technique has a substantial effect on cross-sectional anastomotic compliance of end-to-side anastomoses. Interrupted suture may maximise the anastomotic lumen and provides a considerably higher CSAC than continuous suture, that reduces flow turbulence, shear stress and intimal hyperplasia. The Heartflo™ anastomosis device is a reliable instrument that facilitates performance of interrupted suture anastomose

Transfemoral versus transapical approach for transcatheter aortic valve implantation: hospital outcome and risk factor analysis.

Transcatheter aortic valve implantation is indicated in high-risk patients with aortic stenosis. We compared the clinical outcome of 180 consecutive patients who underwent transapical (TA) and transfemoral (TF) procedures in a single centre. Ninety consecutive TA (TA-group) and 90 consecutive TF (TF-group) were performed from 2009 to 2014. Clinical variables were prospectively collected and retrospectively analysed for hospital outcomes and to identify risk factors for hospital mortality, vascular complications and stroke. Mean age was 80 ± 8.5 and 83 ± 8.4 years, in the TA and TF-group, respectively. TA-group presented higher prevalence of comorbidities: more vascular disease (79% vs 22%, p < 0.001), chronic pulmonary disease (32% vs 10%, p < 0.001), previous vascular surgery (14% vs 4%, p = 0.039), coronary disease (60% vs 40%, p = 0.007), and previous cardiac surgery (28% vs 17%, p = 0.073). Logistic Euroscore was 36 ± 15% in the TA-group and 25 ± 14% in the TF-group (p < 0.001), but hospital mortality was similar (TA:9%, TF:10%, p = 0.799). Access-related vascular complications occurred more often in transfemoral patients (TA:3%, TF:11%, p = 0.081) while major bleeding (TA:3%, TF:4%, p = 1) and stroke (TA:2%, TF:3%, p = 1) were equally distributed. Postoperative renal failure and dialysis were associated with impaired neurological outcome (p = 0.035 and p = 0.020, respectively). Mild to severe paravalvular leak was more prevalent in transfemoral patients (TA:5%, TF:25%, p < 0.001). In our experience, the TA and TF-group presented different risk profiles but mortality rate and adverse neurological outcome had a similar incidence. The transfemoral approach carried more vascular complications and paravalvular leaks but last-generation devices will improve this outcome