7 research outputs found
In vitro evaluation of the influence of pulsatile intraventricular pumping on ventricular pressure patterns
The Pulsatile catheter (PUCA) pump consists of a single port membrane pump connected to an indwelling valved catheter. This so-called transarterial blood pump was originally designed to be introduced through a superficial artery into the left ventricular cavity to pump blood from the left ventricle into the ascending aorta. By introducing the catheter directly into the thoracic aorta or the pulmonary artery, the possibility is created of applying large-diameter catheter PUCA pumps as left, right, or biventricular assist devices (LVAD, RVAD, or BIVAD) without damaging any of the structures of the heart. The pump performance of an 8 mm PUCA pump prototype (internal diameter catheter, 8 mm; catheter length, 40 cm; stroke volume, 80 ml) was studied in a mock circulation to investigate the influence of pulsatile intraventricular pumping on ventricular pressure patterns. The pumping mode of the PUCA pump was changed from approximately 1:1 ([n + 1]:n) to 1:2 ([1/2n + 1]:n) and 1:3 ([1/3n + 1]:n) in relation to the frequency of a ventricle-simulating membrane pump. Apart from the pumping mode, timing of the PUCA pump driving system (ejection phase) seems to be crucial in obtaining optimal unloading of the ventricle.</p
Suitability of CGP-12177 and CGP-26505 for quantitative imaging of β-adrenoceptors
[H-3]GP-12177, a non-selective beta-adrenoceptor antagonist, and [H-3]CGP-26505, a beta-1-selective beta-adrenoceptor antagonist, were intravenously administered to rats. 94-97% of the injected radioactivity disappeared from plasma with t1/2 0.2 and 0.5 min. Total/non-specific binding ratios of 5.4 and 6.9 (CGP-12177) or 2.0 and 2.8 (CGP-26505) were maintained in heart and lung from 10 to 40 min post-injection. Labelled plasma metabolites appeared after > 20 min (CGP-12177) or within 2 min (CGP-26505). No metabolites were found in the heart. CGP-12177 binds to blood cells, but CGP-26505 does not. CGP-12177 can be used for PET imaging of total (beta-1 and beta-2) adrenoceptors in the heart and lung of experimental animals, but CGP-26505 is less suitable for in vivo analysis of the beta-1-subpopulation
Time course of hemodynamic changes and improvement of exercise tolerance after cardioversion of chronic atrial fibrillation unassociated with cardiac valve disease
This study prospectively assessed the time
course, magnitude and mechanism of the hemodynamic changes after restoration of sinus rhythm in patients with chronic atrial fibrillation (AF) unassociated with valvular disease. Severe cardiac dysfunction may occur after chronic supraventricular
tachycardia in patients with and without
underlying cardiac disease. Improvement may follow abolishment of the arrhythmia or adequate slowing of the ventricular rate. Eight patients were studied with a mean previous duration of AF of 10 ± 9 months. Ejection fraction, exercise capacity
and the atrial contribution to the left ventricular filling (only during sinus rhythm) were studied before cardioversion, after cardioversion and 1 week, 1 month and 6 months thereafter. A significant improvement in ejection fraction from
36 ± 13 to 53 ± 8% (p <0.05) occurred at 1 month after cardioversion. Concomitantly, peak oxygen consumption had increased at 1 month, from 20.1 ± 7 to 25.2 ± 6 ml/min/kg (p <0.05). Thereafter, no further improvement in hemodynamic parameters
occurred. The atrial systole improved already
at 1 week (from 3 ± 5 to 16 ± 11%, p <0.05) and remalned unchanged thereafter. Thus, restoration of sinus rhythm was associated with a delayed improvement in ejection fraction and maximal exercise capacity, preceded by an early restoration of
atrial contractility and an acute slowing of the heart rate. The discrepancy in time course of restoration of atrial and ventricular function parameters suggests that an intrinsic left ventricular cardiomyopathy is present in patients with AF
Treatment effect of syndrome X patients with doxazosine as assessed by positron emission tomography
Left ventricular beat-to-beat performance in atrial fibrillation: Contribution of Frank-Starling mechanism after short rather than long intervals
This study sought to evaluate control mechanisms of the varying left ventricular performance in atrial fibrillation.
Atrial fibrillation is characterized by a randomly irregular ventricular response, resulting in continuous variation in left ventricular beat-to-beat mechanical behavior and hemodynamic variables.
Fourteen patients with chronic nonvalvular atrial fibrillation were studied, using a nonimaging computerized nuclear probe
linked to a personal computer. Left ventricular ejection fraction, end-diastolic and end-systolic volume counts, stroke volume counts and filling time were calculated on a beat-to-beat basis during 500 consecutive RR intervals. Multiple
regression analysis was used to assess how ejection fraction was predicted by these variables. The preceding RR interval and end-diastolic volume showed a positive relation, and prepreceding interval and endsystolic 0.0001). Sensitivity analysis suggested that the preceding interval and the end-diastolic volume were equally important in predicting
ejection fraction. There was a relatively strong interaction between the preceding interval and end-diastolic volume, indicating
that the influence of the end-diastolic volume on ejection fraction was diminished after long intervals. A second interaction showed that the effect of end-diastolic volume on ejection fraction was attenuated after short prepreceding cycles.
Cycle length-dependent contractile mechanisms, including postextrasystolic potentiation and mechanical restitution, determine the varying left ventricular systolic performance during atrial fibrillation over the entire range of intervals. Beat-to-beat changes in preload, consistent with the Frank-Starling mechanism, also play a role, but their influence is diminished