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Biomedical subjects

V Kalff

Publications and source records attributed to V Kalff.

67 records · Page 4Linked to original sources
PubMed1982

Radionuclide evaluation of postextrasystolic potentiation of left ventricular function induced by atrial and ventricular stimulation.

Postextrasystolic potentiation of left ventricular function induced by ventricular and atrial stimulation was compared in 10 patients using radionuclide ventriculography. After insertion of pacing wires, a preliminary radionuclide ventriculogram was obtained and then ventricular and atrial trigeminy was induced in random order, each with identical R-R coupling intervals, each for 6 to 10 minutes. During the stimulation studies, radionuclide data were acquired in electrocardiographic gated list mode format. Left ventricular ejection fraction and relative end-diastolic and end-systolic volume changes were measured for each reformatted composite sinus, atrial and ventricular premature beat and potentiated beat. The volume changes were normalized to the count-based values obtained for the sinus beat of the appropriate study. Postextrasystolic potentiation induced by either ventricular or atrial stimulation was characterized by similar significant increases in left ventricular ejection fraction (mean +/- standard deviation 7 +/- 3 percent, p less than 0.01 versus 7 +/- 5 percent, p less than 0.01; difference not significant [NS]) and decreases in relative end-systolic volume (-12 +/- 12 percent, p less than 0.01 versus -12 +/- 8 percent, p less than 0.01; NS) but little change in relative end-diastolic volume (+5 +/- 10 percent, NS versus +4 +/- 7 percent, NS; NS). This was despite a longer compensatory pause (1,120 +/- 220 versus 1,050 +/- 190 ms, p less than 0.01) after the ventricular premature beat. It is concluded that there is no difference in the postextrasystolic potentiation induced by atrial or ventricular premature stimulation.

Adult↗
PubMed1982

Radionuclide angiographic assessment of global and segmental left ventricular function at rest and during exercise after coronary artery bypass graft surgery.

Left ventricular ejection fraction (LVEF) was measured by radionuclide angiography at rest and during supine bicycle exercise before and 3 months after coronary artery bypass graft surgery (CABG) in 20 patients with chronic stable angina. The right anterior oblique gated first-pass technique was used to assess LVEF response to maximal exercise (Wmax), while the left anterior oblique equilibrium-gated technique was used to assess LVEF and relative LV volume changes during graded submaximal exercise. Mean LVEF was unchanged at rest after CABG by both the first-pass (60 +/- 12% vs 60 +/- 12%) and equilibrium-gated (61 +/- 13% vs 62 +/- 13%) measurements. At Wmax, mean first-pass LVEF was significantly higher postoperatively than preoperatively (63 +/- 17% vs 53 +/- 17%; p less than 0.01) with a higher Wmax (750 +/- 182 vs 590 +/- 202 kpm/min; p less than 0.001) and higher rate-pressure product (302 +/- 59 vs 222 +/- 57 units; p less than 0.001). Similarly, equilibrium-gated LVEF levels during graded exercise, using stepwise regression analysis, were significantly higher postoperatively than preoperatively (p less than 0.001); at the highest graded work load, they averaged 63 +/- 19% postoperatively and 53 +/- 17% preoperatively, with higher work loads (500 +/- 190 vs 417 +/- 155; p less than 0.05) and higher rate-pressure products (271 +/- 55 vs 207 +/- 53; p less than 0.001). The increase in exercise LVEF after surgery was due to a marked decrease in the ratio, relative to resting values, of counts-based end-systolic volumes during submaximal exercise (preoperatively 1.91 +/- 1.04; postoperatively 1.14 +/- 0.46; p less than 0.01). The five subjects in whom LVEF decreased significantly during exercise postoperatively all had one or more blocked or stenosed grafts. This study documents, by two independent radionuclide techniques, an improved LVEF during exercise at an increased maximal work capacity and rate-pressure product 3 months after successful CABG.

Adult↗
PubMed1982

The spectrum of pheochromocytoma in hypertensive patients with neurofibromatosis.

We have found an appreciable number of pheochromocytomas in patients with neurofibromatosis and concurrent hypertension (ten of 18 cases). At diagnosis, the patient age range was 15 to 62 years, the clinical appearance of the neurofibromatosis did not predict who would and who would not have pheochromocytomas, but the age at diagnosis was helpful in that our younger patients tended to have causes of hypertension other than pheochromocytoma. However, several causes of hypertension may coexist. The biochemical findings were highly diagnostic. The pheochromocytomas secreted epinephrine as well as norepinephrine and resided in or next to the adrenal gland. Where pheochromocytoma is the cause of hypertension, its resection generally results in a better control of hypertension than that obtained in patients whose BPs were elevated from other unknown causes.

3-Iodobenzylguanidine↗
PubMed1982

Scintigraphic demonstration of ventriculo atrial conduction in the ventricular pacemaker syndrome.

A patient with the sick-sinus syndrome was evaluated because of symptomatic deterioration after insertion of a ventricular demand pacemaker. Clinical features of the ventricular pacemaker syndrome were recognized and confirmed by electrophysiological and hemodynamic studies. Phase analysis--a new technique for detecting patterns of cardiac emptying from gated cardiac blood-pool scintigrams--demonstrated a pattern consistent with 1:1 ventriculo-atrial conduction. Phase analysis of the gated cardiac blood-pool scintigram may be useful in the assessment of patients with ventricular demand pacemakers who complain of fatigue and effort intolerance.

Aged↗
PubMed1980

Isotope angiocardiography of the left ventricle.

Radionuclide imaging of the left ventricle is a recent innovative procedure requiring a gamma-camera interfaced to a computer. It has the advantages of being non-invasive and of allowing studies at rest and exercise. Left ventricular function may be assessed by viewing the images as an endless loop cine-display, or by quantitating the over-all and segmental functions. Validation studies comparing the technique with standard contrast angiograms have confirmed its reliability. Clinical studies have been undertaken in normal volunteers, and in patients. The technique will have increasing application in assessing the aetiology of chest pain, in selection of patients for cardiac surgery, and in determining the effects of interventions, such as drug therapy or coronary artery bypass surgery, on ventricular performance.

Adult↗
PubMed1980

The radionuclide assessment of left ventricular function using graded exercise in normal subjects.

In 20 normal volunteers, two minute equilibrium gated blood pool scanning (GBPS) was used to assess left ventricular function during rest and three stages of graded supine exercise on a bicycle ergometer. The three work loads were individualised for each subject from a previously performed exercise test and corresponded to mild, moderate and severe stress. The short imaging time was validated against standard GBPS. With exercise all subjects increased their left ventricular ejection fraction and in the majority, most of this rise occurred with the lowest work load. This change was predominantly due to a marked fall in end-systolic volume. The end-diastolic volume initially fell, then at peak exercise returned to baseline values. The major change in stroke volume occurred at peak exercise.

Adult↗
PubMedDate not supplied

Variations on calculating left-ventricular volume with the radionuclide count-based method.

Various methods for the calculation of left-ventricular volume by the count-based method utilizing red-blood-cell labeling with 99mTc and a parallel-hole collimator are evaluated. Attenuation correction, linked to an additional left posterior oblique view, is utilized for all 26 patients. We examine (1) two methods of calculating depth, (2) the use of a pair of attenuation coefficients, (3) the optimization of attenuation coefficients, and (4) the employment of an automated program for expansion of the region of interest. The standard error of the estimate (SEE) from the correlation of the radionuclide volumes with the contrast-angiography volumes, and the root-mean-square difference between the two volume sets at the minimum SEE are computed. It is found that optimizing a single linear attenuation coefficient assumed for attenuation correction best reduces the value of the SEE. The average of the optimum value from the end-diastolic data and that from the end-systolic data is 0.11 cm-1. This value agrees with the mean minus one standard deviation value determined independently from computed tomography scans (0.13-0.02 cm-1). It is also found that expansion of the region of interest beyond the second-derivative edge with an automated program, in order to correctly include more counts, does not lower the SEE as hoped. This result is in contrast to the results of others with different data and a manual method. Possible causes for the difference are given.

Aortic Valve Insufficiency↗
PubMedDate not supplied

Central nervous system noradrenergic control of sympathetic outflow in normotensive and hypertensive humans.

We applied transmitter washout methodology, sampling internal jugular venous plasma via a percutaneously placed catheter, to study CNS norepinephrine release in humans and its relation to peripheral sympathetic activity. Norepinephrine overflows into the venous drainage of the brain, as do its precursor, DOPA, and metabolites DHPG and MHPG, indicating that the blood-brain barrier provides an incomplete impediment to their outward flux from the brain. Pharmacological testing with two drugs which altered CNS norepinephrine turnover, the tricyclic antidepressant desipramine and the ganglionic blocker, trimethaphan, demonstrated a direct relation existed between CNS norepinephrine release and sympathetic nerve firing rates. In essential hypertension, the sympathetic activation commonly present was associated with, and possibly caused by increased CNS release of norepinephrine, manifested in elevated overflow of norepinephrine, MHPG and DHPG from the brain. Bilateral jugular sampling, coupled with a cerebral venous sinus scan to delineate the drainage pattern, demonstrated that this increased norepinephrine release was confined to subcortical forebrain regions.

Blood Pressure↗