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Biomedical subjects

P L Kerkhof

Publications and source records attributed to P L Kerkhof.

13 recordsLinked to original sources
PubMed1998

Age variance of left ventricular diameters in dogs with cardiac disease.

Ventricular size increases during growth, but often due to cardiac disease. This study aims to describe left ventricular dimension interrelations using a representation that is applicable to patients with cardiac disease, and subsequently to statistically study possible age and gender influences in a large population. In retrospect we analyzed echocardiographically obtained diameters of the left ventricle in 442 dogs of various breeds with congenital or acquired heart disease. Also, we compared our findings with published data on humans and other animals. Multivariate regression analysis was applied to assess possible influences of age and gender. A high correlation was found for end-systolic diameter (ESD) versus end-diastolic diameter (EDD): ESD (cm) = -1.01 cm + 0.93 x EDD (cm) with r = 0.94, p < .00001. Next, these patients were categorized into three age groups (divisions at 3 and 7 years). We detected a slight age dependent effect: the regression coefficients for the younger group differed from the two older groups. No significant gender-related influence was detected. The observation of a high correlation for the ESD versus EDD relationship could be confirmed by reanalysis of published data on normal individuals and human patients. The newly described relationship between ESD and EDD applies in particular to cardiac patients. This is a relevant finding, because clinically important indices of ventricular performance generally depend on ESD, EDD or both. Thus, ESD versus EDD offers a convenient framework for studies on cardiac volume regulation and performance in the cardiopathological spectrum, while permitting incorporation of modulating effects related to age.

Age Factors↗
PubMed1998

A unifying representation of ventricular volumetric indexes.

We studied volumetric characteristics of the ventricle in various hearts covering a wide (patho)physiological range, using the individual operating point at basal conditions. The aim of this analysis is to formulate a unifying relationship between volumetric parameters which will be applicable to cardiac ventricles regardless of underlying pathology. Analyzing our own measurements as well as additional data published elsewhere indicates that end-systolic volume (ESV) versus end-diastolic volume (EDV) yields a high linear population based correlation coefficient. This analytical expression can subsequently be used for the evaluation of clinically relevant derived indexes. For example, the new approach permits estimation of important physiological quantities such as stroke work and myocardial oxygen consumption, while isopleths and regions with equal ejection fraction can all be inscribed as linear relationships within a single graph. Based on statistical considerations, we demonstrate that in terms of correlation this new graphical representation is superior to the curve relating output (stroke volume) to input (preload) of the ventricle. We conclude that the ESV versus EDV representation facilitates insight into cardiac volumetric behavior and permits prediction of clinically relevant cardiodynamic effects, as produced by ventricular dimensional changes, for example induced by surgical or pharmacological intervention, or by the progression of cardiac disease.

Cardiac Volume↗
PubMed1990

[Evaluation of clinical-pathological conferences using a program for computer-assisted diagnosis; analysis of 100 case reports].

Case studies as weekly published in the New England Journal of Medicine are analysed using the computer programme Medwise. The programme covers more than 3,500 disease profiles. After entering clinical data on all patients described in 1986 and 1987, the diagnostic outcome was compared with the results of the clinicians and with the eventual patho-anatomical findings. Medwise gave the correct diagnosis in 93% of the 104 cases considered. In 15 cases the clinicians failed to formulate the patho-anatomical diagnosis; Medwise correctly detected nine of these (60%). Medwise missed the diagnosis in seven cases, but the clinicians' answers were also faulty in six of them. These results indicate the usefulness of computer-assisted interpretation of clinical findings for establishing the diagnosis, provided that the course and laboratory data concerning the patient are accurately documented.

Autopsy↗
PubMed1988

Relation between infarct size and left ventricular performance assessed in patients with first acute myocardial infarction randomized to intracoronary thrombolytic therapy or to conventional treatment.

Reperfusion of ischemic myocardium has been reported to increase the cumulative creatine kinase activity in plasma per gram of infarcted myocardium as assessed with the method of Shell et al. In an attempt to find out whether infarct size assessment using the method of Witteveen et al was affected by reperfusion, the relation between enzymatic infarct size was analyzed using Witteveen's method and left ventricular (LV) function parameters in 266 patients with first acute myocardial infarction randomized to intracoronary thrombolysis (n = 134) or conventional therapy (n = 132). Compared with patients allocated to conventional therapy, patients allocated to intracoronary thrombolysis had smaller enzymatic infarct size by 29% (p less than 0.001), smaller LV end-diastolic and end-systolic volume indexes by 10% (p less than 0.05) and 20% (p less than 0.005), respectively, and higher LV ejection fraction (55 +/- 1% vs 49 +/- 1%; p less than 0.001). The beneficial effects of thrombolytic therapy on LV performance were closely associated with thrombolysis-induced limitation of infarct size. The dependence from infarct size of LV end-diastolic volume, LV end-systolic volume, and ejection fraction was not different in the 2 therapy groups. It was concluded that Witteveen's method of infarct size assessment is not influenced by the presence of reperfusion. Therefore, this method was recommended for trials on recanalization in patients with acute myocardial infarction.

Angiography↗
PubMed1981

Continuous stroke volume and cardiac output from intra-ventricular dimensions obtained with impedance catheter.

To improve assessment of ventricular function during cardiac catheterisation there should be available a continuous registration of stroke volume and cardiac output in addition to ventricular pressure. To obtain the desired volumetric quantities a catheter has been developed which measures changes in intraventricular dimensions by electrical impedance. For this purpose, the catheter is equipped with eight electrodes spaced over a distance equal to the long axis of the left ventricle into which it is introduced. A constant current is imposed between the outermost electrodes while the inner six are used to measure resistance of volume segments of the blood contained within the ventricular cavity. The difference in resistance at the beginning and end of ejection is proportional to the contribution of each segment to stroke volume, which follows from addition to the segmental terms. Calibration is obtained by measuring electrical conductivity of a blood sample. The catheter was tested over a tenfold range of cardiac output, both in vitro, using an artificial heart model, while performance in vivo was evaluated in 12 dogs. In the animals study, stroke volume and cardiac output from the catheter were compared with flows obtained with an electromagnetic flowmeter. In both studies, linear regression analysis showed excellent correlation of cardiac output (r = 0.99, n = 10 in vitro, r = 0.95, n = 126 in vivo) while the regression equations were close to those of identity. Very good correlation (r = 0.98, n = 28) was also obtained for stroke volumes on a beat to beat basis during arrhythmia. It is concluded that the catheter, which has great potential for application in man, fulfills its primary aim of continuously recording stroke volume and cardiac output.

Animals↗
PubMed1981

Relations between ejection fraction and ventricular volume, and their alteration by chronic beta-blockade.

This study describes the newly discovered relation between ejection fraction and end-systolic volume index (ESVI) of the left ventricle as obtained by angiography at the time of cardiac catheterisation. Linear regression analysis shows that ejection fraction (%)=82.0-0.62 ESVI (ml/m2) but the correlation for patients receiving beta-adrenergic blocking drugs is significantly lower compared with the untreated group. Non-linear analysis, applied to cover also the asymptotic range for ejection fraction less than 20%, shows similar results. The good relation between the two indices indicates that the index ejection fraction may derive its clinical importance directly from the more fundamental index end-systolic volume index by virtue of the operation of the beta-adrenergic system on the heart.

Adrenergic beta-Antagonists↗