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

Effects of PDE-5 Inhibition on the Cardiopulmonary System After 2 or 4 Weeks of Chronic Hypoxia.

In pulmonary hypertension (PH), hypoxia represents both an outcome and a cause of exacerbation. We addressed the question whether hypoxia adaptation might affect the mechanisms underlying PH alleviation through phosphodiesterase-5 (PDE5) inhibition. Eight-week-old male Sprague-Dawley rats were divided into two groups depending on treatment (placebo or sildenafil, a drug inhibiting PDE5) and were exposed to hypoxia (10% O <sub>2</sub> ) for 0 (t0, n = 9/10), 2 (t2, n = 5/5) or 4 (t4, n = 5/5) weeks. The rats were treated (0.3 mL i.p.) with either saline or sildenafil (1.4 mg/Kg per day). Two-week hypoxia changed the body weight (- 31% vs. - 27%, respectively, P = NS), blood hemoglobin (+ 25% vs. + 27%, P = NS) and nitrates+nitrites (+ 175% vs. + 261%, P = 0.007), right ventricle fibrosis (+ 814% vs. + 317%, P < 0.0001), right ventricle hypertrophy (+ 84% vs. + 49%, P = 0.007) and systolic pressure (+ 108% vs. + 41%, P = 0.001), pulmonary vessel density (+ 61% vs. + 46%, P = NS), and the frequency of small (< 50 µm wall thickness) vessels (+ 35% vs. + 13%, P = 0.0001). Most of these changes were maintained for 4-week hypoxia, except blood hemoglobin and right ventricle hypertrophy that continued increasing (+ 52% vs. + 42%, P = NS; and + 104% vs. + 83%, P = 0.04). To further assess these observations, small vessel frequency was found to be linearly related with the right ventricle-developed pressure independent of hypoxia duration. Thus, although hypoxia adaptation is not yet accomplished after 4 weeks, PH alleviation by PDE5 inhibition might nevertheless provide an efficient strategy for the management of this disease

Transposition of great arteries and single coronary artery: a new surgical technique for the arterial switch operation.

A single coronary artery can complicate the surgical technique of arterial switch operations, impairing early and late outcomes. We propose a new surgical approach, successfully applied in a 2.1 kg neonate, aimed at reducing the risk of early and late compression and/or distortion of the newly constructed coronary artery system

Remote control of pulmonary blood flow: a dream comes true.

The indication for pulmonary artery banding is currently limited by several factors. Previous attempts have failed to produce adjustable pulmonary artery banding with reliable external regulation. An implantable, telemetrically controlled, battery-free device (FloWatch) developed by EndoArt SA, a medical company established in Lausanne, Switzerland, for externally adjustable pulmonary artery banding was evaluated on minipigs and proved to be effective for up to 6 months. The first human implant was performed on a girl with complete atrioventricular septal defect with unbalanced ventricles, large patent ductus arteriosus and pulmonary hypertension. At one month of age she underwent closure of the patent ductus arteriosus and FloWatch implantation around the pulmonary artery through conventional left thoracotomy. The surgical procedure was rapid and uneventful. During the entire postoperative period bedside adjustments (narrowing or release of pulmonary artery banding with echocardiographic assessment) were repeatedly required to maintain an adequate pressure gradient. The early clinical results demonstrated the clinical benefits of unlimited external telemetric adjustments. The next step will be a multi-centre clinical trial to confirm the early results and adapt therapeutic strategies to this promising technology

Ebstein's anomaly: one and a half ventricular repair.

Patients with Ebstein's anomaly can present after childhood or adolescence with cyanosis, arrhythmias, severe right ventricular dysfunction and frequently with left ventricular dysfunction secondary to the prolonged cyanosis and to the right ventricular interference. At this point conventional repair is accompanied by elevated mortality and morbidity and poor functional results. We report our experience with three patients (8, 16 and 35 years of age) with Ebstein's anomaly, very dilated right atrium, severe tricuspid valve regurgitation (4/4), bi-directional shunt through an atrial septal defect and reduced left ventricular function (mean ejection fraction = 58%, mean shortening fraction = 25%). All underwent one and a half ventricular repair consisting of closure of the atrial septal defect, tricuspid repair with reduction of the atrialised portion of the right ventricle and end-to-side anastomosis of the superior vena cava to the right pulmonary artery. All patients survived, with a mean follow-up of 33 months. In all there was complete regression of the cyanosis and of the signs of heart failure. Postoperative echocardiography showed reduced degree of tricuspid regurgitation (2/4) and improvement of the left ventricular function (mean ejection fraction = 77%, mean shortening fraction = 40%). In patients with Ebstein's anomaly referred late for surgery with severely compromised right ventricular function or even with reduced biventricular function, the presence of a relatively hypoplastic and/or malfunctioning right ventricular chamber inadequate to sustain the entire systemic venous return but capable of managing part of the systemic venous return, permits a one and a half ventricular repair with good functional results

Treatment of congenital aortic valve stenosis: impact of the Ross operation.

GOAL: To evaluate the impact of the Ross operation, recently (1997) introduced in our unit, for the treatment of patients with congenital aortic valve stenosis. METHODS: The period from January 1997 to December 2000 was compared with the previous 5 years (1992-96). Thirty-seven children (< 16 yrs) and 49 young adults (16-50 yrs) with congenital aortic valve stenosis underwent one of these treatments: percutaneous balloon dilatation (PBD), aortic valve commissurotomy, aortic valve replacement and the Ross operation. The Ross operation was performed in 16 patients, mean age 24.5 yrs (range 9-46 yrs) with a bicuspid stenotic aortic valve, 7/10 adults with calcifications, 2/10 adults with previous aortic valve commissurotomy, 4/6 children with aortic regurgitation following PBD, and 1/6 children who had had a previous aortic valve replacement with a prosthetic valve and aortic root enlargement. RESULTS: PBD was followed by death in two neonates (fibroelastosis); all other children survived PBD. Although there were no deaths, PBD in adults was recently abandoned, owing to unfavourable results. Aortic valve commissurotomy showed good results in children (no deaths). Aortic valve replacement, although associated with good results (no deaths), has been recently abandoned in children in favour of the Ross operation. Over a mean follow-up of 16 months (2-40 months) all patients are asymptomatic following Ross operation, with no echocardiographic evidence of aortic valve regurgitation in 10/16 patients and with trivial regurgitation in 6/16 patients. CONCLUSIONS: The approach now for children and young adults with congenital aortic valve stenosis should be as follows: (1) PBD is the first choice in neonates and infants; (2) Aortic valve commissurotomy is the first choice for children, neonates and infants after failed PBD; (3) The Ross operation is increasingly used in children after failed PBD and in young adults, even with a calcified aortic valve