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Biomedical subjects

W N van Asten

Publications and source records attributed to W N van Asten.

At least 37 records · Page 2Linked to original sources
PubMed1994

Importance of the coronary collateral circulation for the distribution of anterograde and retrograde delivered cardioplegic solution in aortocoronary bypass surgery: a haemodynamic study.

The importance of coronary collateral circulation for homogeneous distribution of anterograde and retrograde delivery of cardioplegia was evaluated in 36 patients undergoing myocardial revascularization. All patients had three-vessel coronary artery disease, with a stenosis of the right coronary artery of at least 80%. The patients were randomized into two groups: group A (n = 19) received anterograde delivered cardioplegic solution and group B (n = 17) received retrograde. Both groups were further subdivided depending on the pathology of the right coronary artery, as evaluated on preoperative coronary angiography. In group A1 (n = 8) and group B1 (n = 7) there was no visualization of collateral circulation from the left to the right coronary artery system, whereas in group A2 (n = 11) and group B2 (n = 10) there was retrograde filling of the right coronary artery by collateral circulation. Right atrial pressure increased significantly (P < 0.05) in group A1 and was elevated in group A2, but not significantly (P = 0.07). By contrast, right arterial pressure decreased in groups B1 and B2. Analysis of the individual differences in the right atrial filling pressure showed a statistical significance between the two subgroups (group B1-1.0(0.5) versus group B2-1.8(1.1), P < 0.05), although the individual decrease of the right ventricular stroke work index was not significant. It is concluded that collateral circulation is important for an adequate distribution of anterogradely delivered cardioplegia and is also beneficial in cases of retrograde delivery.

Adult↗
PubMed1993

High incidence of arteriovenous fistula after biopsy of kidney allografts.

Arteriovenous fistula (AVF) is a well known but rarely diagnosed complication of percutaneous biopsy of kidney allografts. In the past diagnosis was usually made when clinical signs of an AVF occurred but Doppler ultrasonography has now enabled non-invasive diagnosis. Doppler examination of kidney allografts was performed after 100 biopsies. A total of ten AVFs were diagnosed within 2 weeks of biopsy. On repeated examination 2 months later, no additional fistula was detected. All fistulas were detected by abnormal colour shading of the artery and vein of the fistula caused by high blood velocity. Quantification in the artery supplying the fistula showed a higher systolic velocity compared with that in a normal artery of comparable size and location in the graft (mean (range) 64 (25-150) versus 36 (20-65) cm/s, P < 0.05). Diastolic velocity was also higher in the artery supplying the fistula than in a normal artery (mean (range) 34 (9-72) versus 7 (0-13) cm/s, P < 0.05). In the group with an AVF the proportion with a prolonged bleeding time (> 3 min) was higher (80 versus 47 per cent, P < 0.05), as was the prevalence of a platelet count < 200 x 10(9)/l (60 versus 22 per cent, P < 0.05). After detection of the fistula, four of the grafts were lost because of rejection and two patients died from sepsis during antirejection treatment. During follow-up of the remaining four AVFs, three disappeared spontaneously and one persisted. None of the fistulas has had an impact on renal function requiring intervention. In conclusion, AVF is a complication observed frequently after kidney allograft biopsy that can be detected and monitored by Doppler ultrasonography.

Arteriovenous Fistula↗
PubMed1993

Noninvasive hemodynamic assessment of the internal mammary artery in myocardial revascularization.

Using transthoracic B-mode imaging and Doppler spectrum analysis it was found that the luminal diameter of the internal mammary artery and its hemodynamics were not significantly different among 15 preoperative patients (64 +/- 10 years) who underwent myocardial revascularization using the left internal mammary artery and young and older control groups (25 +/- 3 years and 61 +/- 9 years, respectively). These data indicate that older age does not significantly adversely influence the degree of intimal thickening and compliance in the internal mammary artery. Doppler spectrum analysis of the internal mammary artery in the patients who were operated on revealed conversion from a triphasic systolic waveform preoperatively to a unidirectional combined systolic/diastolic waveform at 1 week and 2 and 6 months postoperatively, characterized by a significant increase in the diastolic blood flow velocity and a significant decrease in the systolic blood flow velocity and the pulsatility and resistance indices. This study indicates that transthoracic B-mode imaging and Doppler spectrum analysis are promising noninvasive techniques in the preoperative assessment of internal mammary artery morphology and physiology. In addition, Doppler spectrum analysis can also be used in the long-term serial assessment of the internal mammary artery conduit after myocardial revascularization.

Adult↗
PubMed1993

Computer simulations in comparison with in vivo measurements of nifedipine-induced changes in renal allograft hemodynamics.

Analysis of Doppler spectrum waveforms is increasingly used in the differential diagnosis of human renal allograft dysfunction. The physiologic interpretation of changes in Doppler spectra obtained from renal allografts, however, remains a major problem. Computer simulation models of the renal circulation may provide insight into the physiologic mechanisms responsible for changes in Doppler spectrum characteristics. The results of measurements of renal allograft hemodynamics with both determinations of PAH clearance and Doppler spectrum analysis in 11 kidney allograft recipients were explained physiologically using a computer simulation model of kidney allograft hemodynamics. Using PAH clearance and blood pressure measurements a significant decrease in RVR was found (from 0.32 +/- 0.17 to 0.20 +/- 0.07 mm Hg x min/ml, P < 0.05) after administration of the vasodilatory drug nifedipine. The Doppler spectrum waveform obtained from interlobar renal arteries showed a decrease in the RI (from 0.60 +/- 0.04 to 0.56 +/- 0.06; P < 0.05) and Tmax (from 133 +/- 32 to 98 +/- 32 ms; P < 0.05). The user-designed simulation model of renal hemodynamics showed comparable changes of the waveform when, in the model, the analogs of blood pressure, impedance of the artery, and the impedance of the peripheral vascular bed were altered proportionally.

Administration, Oral↗
PubMed1993

Haemodynamic evaluation of retrograde versus anterograde delivery of cardioplegic solution in aortic valve replacement.

A total of 44 patients undergoing isolated aortic valve replacement received either anterograde (20 patients) or retrograde (24 patients), cold St Thomas's Hospital cardioplegia. The patients were similar with respect to age, sex, left ventricular ejection fraction, left ventricular-aortic pressure gradient, cross-clamping time and mean dose of cardioplegia. After surgery, there were no differences in enzyme release, low cardiac output syndrome, rhythm disturbances or clinical outcome between the two groups. Analysis of the postoperative haemodynamic data, however, suggests better preservation of left ventricular contractility with retrograde delivery of cardioplegic solution.

Adult↗
PubMed1993

Sternal closure: comparison of two techniques.

A clinical trial was performed to evaluate sternal closure with the controlled tension osteosynthesis system and closure with twisted stainless steel wires. Some 451 consecutive patients who underwent isolated coronary bypass surgery between January 1991 and December 1991 were subdivided into three groups. Patients in group A (94 patients) and group B (98 patients) were all operated on by one surgeon, to reduce variability before, at the time of and after surgery, which might influence sternal wound healing. To exclude a possible preference of the surgeon in the study, group C was formed, consisting of 259 patients operated on by other hospital surgeons. In groups A and C, sternal closure was performed with the controlled tension osteosynthesis system. In group B, sternal closure was performed with (six) twisted stainless steel wires. Among groups A, B and C, no statistical significant difference could be found between the rate and the type of sternal wound complications. Despite this finding, there were significantly more reoperations, a longer cross-clamp time and more extensive use of the internal mammary artery as a graft in group B. Despite the non-randomization of the study, and the small patient numbers being a limitation, the use of the controlled tension osteosynthesis system in adults did not result in a decrease of early sternal wound complications.

Adult↗
PubMed1993

Retrograde versus antegrade delivery of cardioplegic solution in myocardial revascularization. A clinical trial in patients with three-vessel coronary artery disease who underwent myocardial revascularization with extensive use of the internal mammary artery.

The effects of retrograde and antegrade delivery of cardioplegic solution on myocardial function were evaluated and compared in 60 patients who underwent myocardial revascularization. All patients had three-vessel coronary artery disease, and the revascularization was done with extensive use of the internal mammary artery. Seventy-five percent of the distal anastomoses were performed with the internal mammary artery. Myocardial protection consisted of St. Thomas' Hospital cardioplegic solution, topical slushed ice, and systemic hypothermia (28 degrees C). The patients were randomly separated into two groups: group A (n = 30), who received antegrade cardioplegia, and group B (n = 30), who received retrograde cardioplegia. With the exception of the total dose of cardioplegic solution (p = 0.02), there was no significant difference between the two groups that concerned septal myocardial temperature at the moment of asystole and after infusion of the total dose of cardioplegic solution. Cardiac function was assessed before and after the patient was weaned from cardiopulmonary bypass. In the immediate postoperative period there was a significant increase in right atrial pressure of the patients who underwent antegrade cardioplegia. For the other registered parameters there was no significant difference either in the immediate postoperative period or 6 hours later. Release of creatine kinase MB isoenzyme was the same in the two groups. Clinical outcome in terms of mortality, prevalence of perioperative infarction, prevalence of low cardiac output, and rhythm and conduction disturbances was similar in both groups. Technical problems related to cannulation and decannulation of the coronary sinus were not encountered. Multivariate analysis showed that occlusion of the left anterior descending coronary artery (p = 0.012) is an essential contraindication of antegrade delivery of cardioplegic solution. Analysis of the patients with an occlusion of the left anterior descending coronary artery who underwent antegrade (n = 9) and retrograde (n = 10) cardioplegia showed a significant difference in the total dose of cardioplegic solution (p = 0.02) and septal myocardial temperature at the moment of asystole (p = 0.008) and after infusion of the total dose of cardioplegic solution (p = 0.015). The mean arterial systolic blood pressure in the antegrade group was significantly lower than in the retrograde group (p = 0.003). Preservation of the left ventricular stroke work index was significantly better in the retrograde group (namely, 85% of its initial value versus 71% in the antegrade group, p = 0.0116).(ABSTRACT TRUNCATED AT 400 WORDS)

Bicarbonates↗
PubMed1992

Early results with bilateral internal mammary artery grafting in coronary reoperations.

In recent years, use of the internal mammary artery (IMA) as first graft of choice has been expanded with bilateral and sequential grafts in primary myocardial revascularization. The use of bilateral IMA grafts in reoperation has seldom been reported. The experience and early results with bilateral IMA grafting in 47 patients undergoing coronary reoperation are described. Hospital mortality was 6.3%. Four patients had postoperative signs of low cardiac output, and 4 had a perioperative myocardial infarction. At follow-up (18 +/- 18 months), 2 cardiac-related, late deaths were noted. Thirteen patients (29%) improved 1 New York Heart Association class, and 28 (63%) improved > 1 class. In 1 of 44 surviving patients, operation did not result in a decrease in angina. On the basis of the early results, the bilateral use of the IMA in coronary reoperation appears justified.

Adult↗
PubMed1992

Haemodynamic changes in human kidney allografts following administration of nifedipine: assessment with Doppler spectrum analysis.

Cyclosporin (CyA) has been demonstrated to increase the vascular resistance of renal allografts (RVR), whereas calcium channel blocking agents like nifedipine may counteract this effect. In this study RVR was calculated from renal blood flow (RBF), measured by the clearance of para-aminohippurate (PAH), and mean arterial pressure (MAP). Analysis of Doppler spectra obtained under ultrasonographic guidance was used as a non-invasive method of assessing renal haemodynamics. A comparison was made between these two methods to detect changes in renal haemodynamics which were caused by the administration of 10 mg nifedipine orally to 11 renal transplant recipients treated with CyA. RBF increased significantly (444 +/- 176 vs 559 +/- 192 ml/min per 1.73 m2; P < 0.05) despite a decrease in MAP (116 +/- 10 vs 101 +/- 11 mmHg; P < 0.05) after administration of nifedipine. Calculated RVR decreased from 0.31 +/- 0.17 to 0.20 +/- 0.07 mmHg x min/ml (P < 0.05). Results of Doppler spectrum analysis were in concordance with these observations. Resistance index (RI) in interlobar arteries decreased from 0.60 +/- 0.04 to 0.56 +/- 0.06 (P < 0.05) and acceleration time (Tmax) of the Doppler spectrum decreased from 133 +/- 32 to 98 +/- 32 ms (P < 0.05). Theoretically, a lower RI and decreased Tmax indicate a reduced vascular resistance and changes in vascular wall compliance, respectively. Analysis of Doppler spectra may thus become a useful device for non-invasive assessment of acute changes in RVR.

Adult↗
PubMed1992

Diagnostic value of automatically interpreted oculopneumoplethysmography.

The diagnostic value of the Gee-oculopneumoplethysmography test for the detection of hemodynamically significant carotid artery obstructions has frequently been questioned due to the rather low agreement with arteriography. The kappa-corrected diagnostic accuracy of this test has been reported to be in the range between 0.54 and 0.68. These values indicate a "fair to good" agreement with arteriography. One of the causes for this rather low agreement is the variability in the interpretation of oculopneumoplethysmography recordings. Automatic analysis of oculopneumoplethysmography recordings might minimize the risks of misinterpretation and might improve the clinical significance of the Gee-oculopneumoplethysmography test. By assessing the signals of a conventional Gee-oculopneumoplethysmography apparatus in a personal computer, this automatic analysis has been realized. In a clinical study (population of 85 patients) the diagnostic value of automatic analysis of oculopneumoplethysmography recordings has been evaluated. The automatically interpreted Gee-oculopneumoplethysmography test had a kappa-corrected diagnostic accuracy of 0.71 on a "per side" base and of 0.76 on a "per patient" base.

Adult↗
PubMed1992

Reactive hyperemia in the nonused internal mammary artery after median sternotomy.

Doppler spectrum analysis was performed in the nonused internal mammary artery in a group of patients who underwent myocardial revascularization using the contralateral internal mammary artery and in both internal mammary arteries in a group of patients who underwent median sternotomy for cardiac surgical procedures in which the internal mammary artery was not used. In all nonused internal mammary arteries the preoperatively triphasic systolic flow pattern had postoperatively converted into a unidirectional systolic flow pattern with a large diastolic flow component, characterized by a significant increase in the diastolic flow parameters and a significant decrease in the resistance and pulsatility indices. This effect had almost subsided at 6 months postoperatively. This study indicates that the reactive hyperemia observed in the nonused internal mammary artery in the early postoperative period is mainly caused by the temporarily increased metabolic demand of the anterior thoracic wall and mediastinum, rather than by the metabolic demand of the anterior diaphragm and the contralateral rectus abdominis muscle after deprivation of their main nutritional vessel.

Adolescent↗
PubMed1992

Penile pharmacological duplex ultrasonography: a dose-effect study comparing papaverine, papaverine/phentolamine and prostaglandin E1.

Alternations of penile blood flow are believed to be the most frequent organic cause of erectile dysfunction. Penile duplex ultrasonography following intracavernous injection of a vasoactive agent is an accepted method for diagnosis of penile vascular dysfunction. To determine the diagnostic efficacy of commonly used vasoactive drugs we studied the hemodynamic effects of different dosages of papaverine, the combination of papaverine and phentolamine, and prostaglandin E1 in men with erectile dysfunction and men with normal erectile potency using color duplex ultrasonography. We concluded that 12.5 mg. papaverine and 10 micrograms. prostaglandin E1 are the drugs of choice to be used in conjunction with penile duplex ultrasonography because of optimal effects on cavernous arterial dilatation and low risk of prolonged erection. However, low dose papaverine or prostaglandin E1 has a limited value in evaluating veno-occlusive function.

Aged↗
PubMed1992

Assessment of penile blood flow by duplex ultrasonography in 44 men with normal erectile potency in different phases of erection.

Duplex ultrasonography is important in the diagnosis of vasculogenic erectile dysfunction. We measured the ultrasonographic parameters of cavernous blood flow in different phases of penile erection. We examined 44 volunteers with normal erectile potency. Doppler spectra of the cavernous artery were obtained in a time-dependent manner after intracavernous administration of papaverine. Following intracavernous pharmacological stimulation, the Doppler spectrum alters according to a specific pattern indicating the different hemodynamic phases of erection. Peak flow velocity and acceleration time, measured in the early post-injection phase, may be used to grade arterial inflow. The difference between resistance index in the pre-injection and late post-injection phases may be used to estimate veno-occlusive function. References values are defined.

Blood Flow Velocity↗
PubMed1992

Retrograde coronary sinus cardioplegia in myocardial revascularization: hemodynamic evaluation of the influence on the right-ventricular function.

The problem of the efficacy of right-ventricular protection with retrograde coronary sinus cardioplegia is studied. Sixty patients undergoing myocardial revascularization were prospectively assigned to receive cold St. Thomas' Hospital cardioplegia into the aortic root (30 patients) or retrogradely in the coronary sinus (30 patients). The two groups were similar concerning preoperative and operative data. The hemodynamic recovery postoperatively was good in both groups, the increase of the heart rate, the decrease of the mean aortic pressure and the right-ventricular stroke-work index were not significantly different in the two groups. However, right atrial pressure increased significantly (p less than 0.001) in patients who received cardioplegia anterogradely and decreased, but not significantly, in the retrograde group. The data suggest that the decrease of the right-ventricular stroke-work index in the anterograde group is related to a depressed contractility and in the group with retrograde delivery of cardioplegia to a decreased preload. There were no differences between the groups with respect to clinical outcome. We conclude that retrograde delivery of cardioplegia results in an excellent protection of the right-ventricular function in elective myocardial revascularization.

Adult↗
PubMed1992

Use of internal mammary artery in myocardial revascularization after mediastinal irradiation.

Ten patients with radiation-associated proximal coronary artery disease underwent myocardial revascularization. In seven patients (group A) the internal mammary artery was used and in the other three (group B) only venous conduits were used. Except for mild adhesions between the pericardium and the epicardium, no unusual technical problems were encountered. In all patients in group A the internal mammary artery exhibited excellent flow, and histologic examination in two patients revealed a normal intima and media with only slight fibrosis of the adventitia. In two patients in group B, fibrosis of the internal mammary artery precluded its use, whereas the third patient had contraindications prohibiting use of the internal mammary artery. Long-term follow-up (range 6 to 72 months) revealed that one patient in group A died late of metastatic disease, and of the remainder (nine patients), seven were in New York Heart Association class I and two were in class II. Preoperative assessment of the internal mammary artery by angiography or, alternatively, B-mode imaging with Doppler spectrum analysis is recommended in patients with radiation-induced coronary artery disease who are scheduled to undergo myocardial revascularization with intended use of the internal mammary artery. In our experience, despite previous exposure to irradiation, the internal mammary artery should still be considered as a viable conduit for myocardial revascularization when preoperative assessment shows patency.

Adult↗
PubMed1991

Assessment of hemodynamic changes in human kidney grafts induced by cyclosporin infusion.

Cyclosporin A (CyA) nephrotoxicity is at least partly caused by the vasoconstrictive action of the drug. In this study we set out to assess this hemodynamic effect of CyA on Doppler spectra obtained in arteries of human renal allografts. Doppler spectra of renal arteries were obtained shortly before and after the start of CyA infusion in renal transplant recipients. Doppler spectrum analysis revealed a significant change in several spectrum-derived parameters. Tmax (acceleration time of the systolic frequency peak), in particular, showed a decrease after 4 h of CyA administration (106 +/- 58 ms vs 76 +/- 36 ms in segmental arteries; P less than 0.05). On day 2 the Tmax returned to its original value (117 +/- 57 ms). Thus, Doppler spectrum analysis enables one to detect temporary hemodynamic changes in the transplanted kidney following CyA administration. These observations may be useful in differentiating causes of renal dysfunction by Doppler spectrum analysis in clinical transplantation.

Cyclosporine↗
PubMed1991

Intraoperative Doppler spectrum analysis of blood flow in the internal mammary artery used for myocardial revascularization.

Intraoperative Doppler-derived measurements of blood flow velocity were used to characterize the hemodynamics in 6 internal mammary artery grafts before and after anastomosis to the left anterior descending artery. Pulsed Doppler spectrum analysis demonstrated a change from a systolic to a predominantly diastolic flow pattern. The presented technique is a valuable aid to differentiate intraoperatively between normal and low flow states in the internal mammary artery. In addition, this study serve as a pilot study to investigate the clinical applicability of Doppler spectrum analysis in the functional assessment of the internal mammary artery in the pre- and postoperative stages of myocardial revascularization.

Aged↗