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Biomedical subjects

T van der Werf

Publications and source records attributed to T van der Werf.

At least 19 recordsLinked to original sources
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

Evaluation of myocardial protection by combination of lidoflazine pretreatment and St. Thomas' Hospital cardioplegia in aorto-coronary bypass grafting.

The concept of pretreatment of the myocardium with a pharmacological agent protecting the cell against ischemic and reperfusion injury is very attractive. Lidoflazine, a calcium overload blocker, predominantly membrane stabilizing, is able to prevent cell damage during ischemic arrest and reperfusion. The purpose of this study was to determine whether the combination of lidoflazine pretreatment and St. Thomas' Hospital cardioplegia can provide, in clinical practice, better myocardial protection in aorto-coronary bypass grafting than St. Thomas' Hospital cardioplegia alone. As indices for myocardial protection, recovery of cardiac function, enzyme release, and clinical outcome were registered. Ninety-three patients undergoing aorto-coronary bypass surgery were studied. These patients were randomized into two groups in a double blind fashion. Patients in group A (n = 48) received lidoflazine 1 mg/kg intravenously over a period of 20 min before initiation of cardiopulmonary bypass. Group B (n = 45) receiving placebo, acted as a control group. Myocardial protection consisted of intermittent infusion of cold 4 degrees C St. Thomas' Hospital cardioplegia, topical slush ice, and systemic hypothermia (28 degrees C rectal). No significant differences between the two groups were noted in terms of recovery of cardiac function, enzyme release, incidence of myocardial infarction, low cardiac output, rhythm, and conduction disturbances. In conclusion, our data suggest that the combination of intravenous pretreatment with lidoflazine and St. Thomas' Hospital cardioplegia did not provide significant additional myocardial protection in the clinical situation.

Aged↗
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↗
PubMed1991

Concept of maximal flow ratio for immediate evaluation of percutaneous transluminal coronary angioplasty result by videodensitometry.

BACKGROUND: In the setting of percutaneous transluminal coronary angioplasty (PTCA), immediate information about the result of the intervention is important, whereas morphological parameters are often less reliable than in diagnostic coronary arteriography. Recently, a new videodensitometric method was introduced and validated in animal experiments, which allows accurate comparison of maximal myocardial perfusion between situations with different degrees of stenosis. This method uses mean transit time (Tmn) of the contrast agent at maximal hyperemia as a parameter for maximal flow and is strictly in accordance with indicated dilation theory. METHODS AND RESULTS: In 40 patients with angina pectoris, single-vessel disease, and a positive exercise test at the time of acceptance for PTCA, this approach was applied for evaluation of the improvement of maximal flow achieved by the PTCA. Maximal vasodilation was induced immediately before and 15 minutes after PTCA by intracoronary administration of papaverine, and digital angiographic studies were performed. By special breath-holding instruction, almost motionless, triggered image acquisition was possible during 15-20 heartbeats. Excellent subtraction images could be obtained, and reliable determination of Tmn at maximal hyperemia was possible in 33 patients both before and after PTCA. The ratio between maximal flow after and before PTCA, called maximal flow ratio (MFR), was represented by the ratio between Tmn before and after the intervention and compared with the results of exercise testing 24-48 hours before and 7-10 days after the procedure. After correction for pressure changes, MFR was 2.2 +/- 1.5 for the 33 dilated vessels and 1.0 +/- 0.2 for 25 normal vessels serving as a control. In 94% of all patients, an MFR value of more than 1.6 or less than 1.6 discriminated between presence or absence of reversal of exercise test result from positive to negative. If on-line judgment of success was based upon angiographic parameters or measurement of trans-stenotic pressure gradient, the relation with noninvasive functional improvement was present only in 66% and 74% of all patients, respectively. A definite range of what can be called normal Tmn at maximal hyperemia could be distinguished, and post-PTCA values for successfully dilated arteries returned completely to this normal range. CONCLUSIONS: Accurate comparison of maximal myocardial perfusion before and after PTCA is possible in man, improvement of maximal flow is highly related to functional improvement as indicated by exercise test results, and, therefore, this method provides a straightforward way for on-line evaluation of the result of the intervention.

Absorptiometry, Photon↗
PubMed1991

Effects of steady hypothermia and normothermia on the electrocardiogram in human poikilothermia.

The electrocardiographic changes observed in (short-term) induced and accidental hypothermia are well known. We studied the electrocardiographic effects of steady mild hypothermia in 4 female patients with poikilothermia. 24h Holter recording revealed during mild hypothermia significantly decreased heart rate and prolongation of the QT interval in comparison with normothermia. During hypothermia the short-term heart rate variability and the circadian rhythm of heart rate variability were significantly higher than during normothermia. We conclude that in our patients even mild steady hypothermia induces electrocardiographic alterations. In patients with disorders of thermoregulation one should be on the alert for cardiovascular complications, especially in cold climates.

Adult↗
PubMed1990

Mean transit time for videodensitometric assessment of myocardial perfusion and the concept of maximal flow ratio: a validation study in the intact dog and a pilot study in man.

Over the last decade it has become more and more obvious that besides anatomical information about the severity of coronary artery stenoses, information about coronary and myocardial blood flow is necessary to understand the functional significance of these obstructions and to evaluate the result of an intervention. Several methods have been proposed for this purpose, each of these having their particular limitations. In this study a new method is shortly described which allows the accurate calculation of relative maximal myocardial perfusion by ECG-triggered digital radiography (videodensitometry), using mean transit time (Tmn) as time parameter; this technique is based on the original physiologic principles of indicator dilution theory. This method was validated in 8 instrumented dogs in which an excellent linear relation was present between 1/Tmn and flow (r = 0.96 +/- 0.03). Although this method does not allow assessment of resting flow and therefore coronary flow reserve (CFR), it provides a means for the reliable comparison of maximal myocardial flow in different situations and it is independent of most factors affecting coronary flow reserve. The ratio between maximal flow after and before an intervention is called maximal flow ratio (MFR) and this concept was applied in a pilot study in man to evaluate PTCA results in 10 patients undergoing elective angioplasty. MFR was compared with the result of exercise testing 24 hours before and 10 days after the angioplasty. MFR greater than or equal to 1.5 was always accompanied by reversal of exercise test result from positive to negative. We conclude that the accurate calculation of relative maximal perfusion of the myocardium is possible by videodensitometry and suggest that comparison of maximal flow after and before an intervention can be valuable in man for functional evaluation of the result of the intervention.

Adult↗
PubMed1990

Cardiopulmonary resuscitation on the general ward: no category of patients should be excluded in advance.

In this study 91 consecutive CPR cases in 90 patients on general wards were evaluated during 18 months. Fifteen patients (16.5%) could be discharged, which is relatively favourable in comparison to the literature. Children proved to have a better chance to leave the hospital alive than adults (6/18 vs. 9/72; P less than 0.05). No factors with negative predictive value before the cardiopulmonary arrest could be isolated. Even oncological patients, often described as a prognostically poor category, with a success rate of 27% (6/22) did not differ from other categories. Patients with isolated respiratory arrest, ventricular tachycardia or ventricular fibrillation at the arrival of the CPR-team had a better chance to be discharged from the hospital. A rapid decrease in survival was noted if a CPR attempt lasted longer than 10 min (P less than 0.001). When there is no return of vital signs within 30 min the CPR attempt can be stopped. During follow-up period (mean 6 month) 2 of the 15 survivors (13.3%) died from a non-cardiopulmonary cause. It is concluded that no category of patients can be excluded from CPR in advance. Although ultimate success rate for CPR in the general wards will rarely exceed 15%, CPR has to be initiated in most cases of cardiopulmonary arrest.

Adolescent↗
PubMed1990

Post-extrasystolic potentiation without a compensatory pause in normal and diseased hearts.

Variables derived from left ventricular volume were used to study post-extrasystolic potentiation. Left ventriculograms were obtained from 11 healthy individuals and 49 patients with coronary heart disease (30 with a previous myocardial infarction and 19 without any signs of myocardial damage). Post-extrasystolic potentiation was induced by a regularly driven right atrial rhythm that was interrupted by one atrial extrasystole in such a way that the post-extrasystolic RR interval was kept equal to the basic RR interval. The left ventricular end diastolic volumes of the pre-extrasystolic and post-extrasystolic beats were equal. In all groups there was evidence of post-extrasystolic potentiation in one or more of the indices of left ventricular function (ejection fraction, mean normalised systolic ejection rate, and systolic volume, and stroke volume). Potentiation was especially evident in patients with left ventricular damage; this suggests that a compensating mechanism is an intrinsic property of the myocardium. The Frank-Starling mechanism does not contribute to the increased performance of the post-extrasystolic beat in normal individuals or in patients with coronary artery disease.

Action Potentials↗
PubMed1990

Mean transit time for the assessment of myocardial perfusion by videodensitometry.

The intrinsic limitations of coronary arteriography to predict the physiological effects of coronary obstructions are well known. Therefore, more direct assessments of the functional significance of coronary stenoses are becoming increasingly important. Study of contrast passage by electrocardiogram-triggered digital radiography has been proposed as a way of assessing changes in myocardial perfusion. The main problems in this approach are the limited time for motionless image acquisition, the potential alteration of vascular volume between different states, and the changing flow pattern induced by contrast agents. This has led to empiric substitution of mean transit time (Tmn) by other time parameters and to representation of vascular volume by maximal contrast intensity (Dmax). To avoid these problems, intact dogs were studied during almost motionless image acquisition of 20-25 consecutive paced heart beats obtained with synchronous radiographic pulses. In this way, unequivocal and reproducible determination of Tmn was possible. Constant and maximal vascular volume was created by continuous infusion of dipyridamole, and it was proved that coronary flow in this model was not influenced by contrast injections. Flow in the circumflex artery was measured by a ring mounted and calibrated Doppler probe. In each dog, flow in the circumflex artery was varied by a balloon occluder in 12 small steps (range, 0-174 +/- 42 ml/min). Inverse appearance time (1/Tapp), Dmax, Dmax/Tapp, inverse time of maximal intensity (1/Tmax), and 1/Tmn were calculated and the relations of these parameters to measured flow were investigated. Tmn proved to be the most reliable parameter for this purpose (r = 0.97 +/- 0.02; mean +/- SD), followed by Tmax (r = 0.93 +/- 0.04). Dmax failed to represent vascular volume but, in fact, showed a moderate correlation with flow (r = 0.78 +/- 0.22), as did Tapp (r = 0.64 +/- 0.18, 0.75 +/- 0.27, and 0.59 +/- 0.26 for the three definitions of Tapp used in this study). Dmax/Tapp correlated better with flow than either component separately. Our results indicate that the mean transit time calculated by videodensitometry can be used to accurately assess changes in myocardial perfusion strictly according to the original principles of indicator dilution theory.

Animals↗
PubMed1989

The influence of heart rate and age on diastolic blood flow velocity in the left ventricular inflow tract.

To investigate the relationship between age-related blood flow velocity and heart rate in the left ventricular inflow tract, we studied 118 healthy volunteers (age greater than 15 years). The maximal velocity (Vmax) of the transmitral diastolic flow during early ventricular filling (E) and during filling due to atrial contraction (A) was measured at 3 sites in the left ventricle with pulsed Doppler echocardiography. At all these sites a significant positive correlation was found between the VmaxA and the EA ratio and the interaction of heart rate and age. VmaxA increases if age and heart rate increase. The influence of the interaction of age and heart rate on VmaxA is most pronounced near the mitral annulus. VmaxA is only related to age and decreases with advancing age. Our observations contribute to the explanation of the more important role of the atrial contraction in the elderly.

Adolescent↗
PubMed1989

Kissing balloon angioplasty of a circumflex artery bifurcation lesion. A new approach utilizing two balloon-on-wire probes and a single guiding catheter.

A new approach to angioplasty of a coronary artery bifurcation lesion is described. Via a single guiding catheter, two ultra low-profile balloon-on-wire probes were advanced into the AV sulcus branch and a large obtuse marginal branch of the circumflex artery. The balloons were inflated simultaneously. The technique was easy to perform and remarkably effective.

Angioplasty, Balloon↗
PubMed1988

Reference values for pulsed Doppler signals from the blood flow velocity on both sides of the pulmonary valve.

Pulsed Doppler signals were recorded from the pulmonary artery and the right ventricular outflow tract in 215 healthy subjects (120 males, 95 females; 1-65 years). Amplitude spectra from these Doppler signals were stored in digital form together with adjustment data for the instrument and the simultaneously recorded ECG. From these Doppler spectra the median of the maximal velocity (Vmax), the maximal acceleration (Amax) and the dispersion of the velocity distribution around Vmax (width) were calculated. These three median values were used to characterize the Doppler spectra and to define normal values for bloodflow velocities. Thus, calculations were made without observer interacting using a well-defined computer program. The effect of age, gender, body surface area and heart rate were studied. Reference ranges were calculated. There is a slight decrease of the median value of Vmax and Amax in the pulmonary artery during lifetime from 80 to 70 cm s-1 and from 1,200 to 800 cm s-2, respectively. On the other hand, there is no correlation between age and Vmax and Amax in the right ventricular outflow tract. The width of the spectra increases with age at both sites. No significant changes with age were seen with the other variables.

Adolescent↗
PubMed1988

Prinzmetal's angina associated with alcohol withdrawal.

A 39-year-old woman developed critical anginal attacks 2-7 days after abruptly stopping long-lasting excessive alcohol drinking. The coronary angiogram demonstrated spasms in the left anterior descending and the right coronary artery without signs of preexistent stenosis. In previous reports alcohol-related coronary spasm always followed ingestion of alcohol several hours before. Because of the time delay in this case, we suggest that not the intake but the withdrawal of alcohol was the factor provoking coronary spasm in our patient.

Adult↗