Separate Valves Research Articles

In Vivo and in Vitro Experience with the PUCA-II, a Single-Valved Pulsatile Catheter-Pump

The Pulsatile Catheter (PUCA) pump is a trans-arterial pulsatile ventricular assist device that can be used for short-term left ventricular support. The separate inflow and outflow valves in the first version of the device (PUCA-I) were replaced by a single inflow/outflow valve in the latest PUCA pump version (PUCA-II). The new combined valve was tested during in vitro (mock circulation) and in vivo experiments for valve leakage, flow resistance, and thrombus formation. During the in vitro experiments a maximum valve leakage of 6% during ejection and 21% during aspiration was found. The maximum flow resistance coefficient (K) was 4. The animal experiments demonstrated that the PUCA-II could be positioned within a few minutes into the left ventricle without X-ray guidance and without using a vascular graft. Thrombi were not found in the combined valve after total pump time of 3 hours, which proved the good washout of the valve. Initial experiments to position the pump in the right ventricle through the pulmonary artery were successful and contributed to the development of a new application for the device.

A metal aerosol holding chamber devised for young children with asthma

The low tidal volume and flow in preschool children may reduce the efficiency of aerosol delivery from a pressurized metered-dose inhaler (pMDI) through a traditional holding chamber. A prototype small-volume steel holding chamber with two one-way valves was devised to prolong aerosol availability in the chamber and to ensure unidirectional airflow. Dead space between the valves was minimized to less than 2 ml. The dose-delivery and rate of passive disappearance of a budesonide pMDI aerosol were compared between this prototype and the large-volume, single-valved plastic Nebuhaler, in 164 asthmatic children less than 8 yrs of age. In vitro, the half life of aerosol disappearance in the steel prototype and the plastic Nebuhaler was > 30 s and 9 s, respectively. In vivo, the prototype delivered an age-independent mean dose of 38% of the nominal dose, and the Nebuhaler delivered an age-dependent mean dose, ranging from 42% of the nominal dose in children > or = 4 yrs to 19% of the nominal dose in infants. We conclude that the use of plastic for holding chambers may influence dose-delivery, and single-valve control may cause age-dependent dose-delivery. Reproducible age-independent drug-delivery may be achieved by pMDI aerosol inhaled through a small-volume metal holding chamber with separate inlet and outlet valves and minimized dead space. This holding chamber would improve the possibilities of aerosol therapy for young children.

Replacement of the left atrioventricular valve after repair of atrioventricular septal defect

SummaryA retrospective analysis of 55 patients who underwent replacement of the left atrioventricular valve following surgery for atrioventricular septal defect with separate right and left atrioventricular valves or with a common valvar orifice has revealed a marked decrease in the need for valvar replacement over time. Between 1983 and 1987, the incidence of replacement following repair has been 3% in infants. Overall early mortality for the entire series, extending from 1970 to 1987, was 22%. Mortality in the first year of life was 58%, which was significantly greater than mortality beyond one year of age (14%, p<0.01). Obstruction of the left ventricular outflow tract was a frequent incremental risk factor for death during infancy. The incidence of complete heart block (25%) is disappointingly high, and may reflect distortion of the left atrioventricular junction in an attempt to place as large a prosthesis as possible. The incidence of complete heart block has not decreased with time. These results confirm the desirability of secondary valvoplasty procedures to enable a child to be larger before ultimate replacement of the valve is required.

Function of the gizzard in Bryozoa

The gizzard, a modified region of the stomach cardia incorporating chitinized teeth or plates surrounded by circular muscle, has been reported in 16 bryozoan genera (one Cheilostomata, 12 Ctenostomata, three Cyclostomata) and has independently evolved at least six times. Its occurrence is reviewed in the light of revised taxonomy of stolonate ctenostomes. The ability to crush diatom frustules and to separate valves intact has been investigated in bryozoans with ( Bowerbankia spp., Amathia pruvoti Calvet) and without [ Electra pilosa (L.) and Flustrellidra hispida (Fabricius)] a gizzard. The gizzard-bearers have significantly greater ability to break the frustules, except for Amathia pruvoti in comparison with Flustrellidra hispida. F. hispida and Electra pilosa have good ability to open frustules of some diatoms, even to the extent of equalling the percentage broken by the gizzard of Bowerbankia. These findings have been related to the size of the lophophore and mouth in bryozoans, and to the size of the diatoms. Notwithstanding the recently recognized profusion of nanoplanktonic diatoms, a majority of the common species are large, often too large to be ingested by the characteristically small bryozoans that possess a gizzard. This paradox is discussed in the context of gut function, habitat, and possible specialization by the bryozoans to exploit different food resources.

Angiography of atrioventricular canal defects

The axial angiograms of 20 patients with an atrioventricular (A-V) canal defect were carefully examined and compared with anatomic observations made at operation. A common A-V valve was present in 15 patients and two separate valves in 5. The atrial septal defect, the anatomy of the ventricular septum and the morphology and functional status of the A-V valves were well demonstrated. There was consistent angiographic deformation of the normally straight contour extending from the noncoronary aortic cusp to the crux cordis observed in the four chamber and elongated right anterior oblique projections of the left ventricular angiogram of each patient. This deformity is caused by the deficiency or absence of the A-V septum and is the best angiographic sign of the malformation. The differentiation of two separate valves from a common A-V valve was uniformly made. When a common A-V valve was present, three of the five leaflets were usually identified but distinction of the free floating from the tethered anterior leaflet was not always possible. It is concluded that axial techniques provide more complete angiographic definition of the anatomic abnormalities of A-V canal defects than are demonstrated from frontal and lateral views.

Univentricular heart of right ventricular type with double or common inlet.

Seventeen cases are described in which both atria connect directly to a chamber with right ventricular characteristics. The atria connected through separate atrioventricular valves in six hearts and a common valve in 11. All hearts had a posterior rudimentary chamber. The septum which separated it from the main chamber was directed to the crux of the heart. Ten hearts were from patients with atrial situs solitus and seven from patients with atrial situs ambigous. Arterial connections were concordant in three cases, had a double outlet from the main ventricular chamber in nine and single outlet of the heart in five. The patent artery always arose from the main chamber, with pulmonary atresia in three and aortic atresia in two. This and other studies indicate that double inlet atrioventricular connection does not predict the morphology of the main chamber. Although usually associated with a main chamber of left ventricular type, it may also be associated with a main chamber having right ventricular characteristics. Both types should be considered as univentricular hearts; the posterior chamber in hearts of right ventricular type are analogous to the anterior chamber in univentricular hearts of left ventricular type and are a rudimentary chamber rather than a hypoplastic ventricle. In the right ventricular form of univentricular heart, the trabecular zone of the rudimentary chamber is of left ventricular type.

Contrast echocardiography in single or common ventricle.

Common ventricle is a rare congenital anomaly in which the ventricular chamber receives blood from two separate atrioventricular valves or from a common atrioventricular valve. We used contrast echocardiography during cardiac catheterization to confirm ventricular anatomy and to characterize blood flow dynamics in 35 patients with common ventricle. After injections of dye, a cloud of echoes anterior to the mitral valve echo during the rapid inflow phase of ventricular diastole is indirect evidence of common ventricle with two atrioventricular valves. Common ventricle with an outflow chamber is characterized by a smaller ventricular chamber visualized anterior to both atrioventricular valves which opacifies with subsequent ventricular systole. The arrival of all dye posterior to the only recorded atrioventricular valve further established the presence of a single atrioventricular valve. These contrast flow patterns gave greater specificity to the standard M-mode echocardiographic assessment of patients suspected of having common ventricle.

Single ventricle: a new angiographic classification.

The authors recommend that the "single ventricle" be differentiated into two types. There are single ventricles of the left ventricular type, and others of the primitive type; in other words, the chamber is typically left ventricular or cannot be differentiated into left or right. In the latter case we are dealing with a primitive chamber. In addition there may be variations of the large vessels. Of 40 patients with a single ventricle of the left ventricular type, ten showed normal topography of the major vessels, 13 had a d-transposition and 17 an 1-transposition. In the d-transposition, the outflow track of the ventricle was anterior and to the right and the aorta arises in front of the pulmonary artery; in the 1-transposition and sub-aortic portion is anterior and to the left, the aorta is ventral and to the left of the pulmonary artery. In the discussion it is pointed out that the "single ventricle" must be included in the differential diagnosis of cyanotic, congenital heart disease. Angiographic confirmation of the "single ventricle" depends on the demonstration of an absent ventricular septum and of two separate atrio-ventricular valves.

A TWO LAYER FLOW THROUGH A CONTRACTION

This paper describes the withdrawal from a reservoir of two layers through separate valves which are downstream of a contraction. The fluid is considered as inviscid and the flow gradually varied. The variations of flow profiles obtained are shown and the limitation the contraction places on the total discharge and on the ratio of the discharge from each layer is discussed.

Ultrasound cardiography in single ventricle and hypoplastic left and right heart syndromes.

Seven cases of single ventricle, six cases of hypoplasia of the right heart (tricuspid atresia), and one case of hypoplasia of the left heart were investigated with reflected ultrasound. In hypoplasia of the right heart there was abnormal anterior movement of the mitral valve; in hypoplasia of the left heart, abnormal anterior movement of the tricuspid valve, and in single ventricle, similiar movement of the anterior component of a single valve. In one case of single ventricle, two separate valves were identified at different depths. In none of the cases could a ventricular septum separating two ventricular cavities be identified. Ultrasound cardiography may be particularly useful as a non-invasive preliminary investigation of infants with congenital heart disease. Failure to demonstrate a ventricular septum combined with the presence of a single atrioventricular valve moving abnormally far anteriorly may be an expression of marked hypoplasia of the left or right ventricles or an anatomically single ventricle with one valve.