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Biomedical subjects

J Tobis

Publications and source records attributed to J Tobis.

34 records · Page 2Linked to original sources
PubMed1985

Digital coronary roadmapping as an aid for performing coronary angioplasty.

In an attempt to improve visualization of the position of the guidewire and dilatation balloon during coronary angioplasty, a method was developed called digital coronary roadmapping. With this method a digitally acquired coronary angiogram is interlaced with the live fluoroscopic image of the guidewire and balloon catheter. The digital coronary angiogram is superimposed at the same magnification and radiologic projection as the live fluoroscopic image onto the video monitor above the catheterization table. The digital roadmap image thus provides immediate feedback to the angiographer to assist in directing the guidewire into the appropriate coronary artery branch and to help in placement of the balloon so that it straddles the site of stenosis.

Adult↗
PubMed1984

Detection and quantitation of coronary artery stenoses from digital subtraction angiograms compared with 35-millimeter film cineangiograms.

To assess the ability to detect coronary artery narrowings from computer-acquired angiograms, a panel of 4 observers independently identified and measured focal coronary narrowings from digital subtraction angiograms and compared the results to those obtained from standard 35-mm cine film angiograms. Both cine and digital angiograms were obtained sequentially using selective intracoronary artery injection of standard amounts of iodinated contrast media. Digital images were obtained at 8 frames/s with a 512 X 512 X 8-bit pixel matrix. Modifications in the imaging chain for computer acquisition included a slower pulsed radiographic mode, a progressive scan camera, and initial storage of the images on an 80-megabyte digital hard disk. Postprocessing computer algorithms were used to enhance the unsubtracted digital images; these included single-frame, mask-mode subtraction, vessel boundary edge enhancement, and 4-fold pixel magnification. In 19 patient studies, 32 arteries were reduced more than 25% in diameter according to at least 1 of 4 observers on either the digital or cine film angiograms. There was no significant difference in the mean percent diameter narrowing for all the narrowings between the digital angiograms (53 +/- 31%) and the cineangiograms (52 +/- 31%). In addition, a 2-way analysis of variance yielded no significant difference between the amount of variability in the measurements between the cine film and the digital technique. This similar variability persisted when subsets of patients based on the degrees of stenosis were considered (e.g., only narrowings from 50 to 90% diameter reduction).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Measurement of left ventricular ejection fraction by videodensitometric analysis of digital subtraction angiograms.

Left ventricular ejection fraction (LVEF) was calculated from 25 first-pass digital subtraction angiograms using a densitometric analysis. Digital subtraction angiograms are obtained in a computerized format; therefore, they can be readily analyzed with computer software to measure the density of the iodine signal within the image. The video signals from the image intensifier were logarithmically amplified so that there was a linear correlation between the video signal intensity and the depth of the iodine contrast material represented by that video signal. LVEF was also calculated by the area-length method from the same digital subtraction angiograms. There was close correlation between these two techniques (r = 0.94, standard error of the estimate = 5.04%). The videodensitometric EF technique is simple to perform, it correlates well with the standard area-length method, and is not dependent on geometric assumptions of LV geometry.

Absorptiometry, Photon↗
PubMed1983

Digital angiography in assessment of ventricular function and wall motion during pacing in patients with coronary artery disease.

Using digital subtraction angiography, left ventriculograms were obtained with 10 ml of iodinated contrast material in 21 patients both at rest and during atrial pacing. In 15 patients with significant coronary artery lesions (CAD) (greater than 50% diameter narrowing in at least 1 major artery), ejection fraction decreased during atrial pacing from a mean of 62 +/- 14% to 51 +/- 15% (p less than 0.001). In 14 (93%) of 15 patients, ejection fraction decreased or was unchanged during pacing. In 6 patients with chest pain but normal coronary arteries, ejection fraction increased from a mean of 66 +/- 9% at rest to 72 +/- 6% during atrial pacing (p less than 0.01). Ejection fraction increased by greater than or equal to 5% during pacing in 5 of 6 patients with normal coronary arteries. Patients with CAD also had an abnormal response in end-systolic volume during atrial pacing (50 +/- 31 ml at rest versus 47 +/- 24 ml during pacing) compared with patients with normal coronary arteries (46 +/- 16 ml at rest versus 26 +/- 9 ml during pacing; p less than 0.01). The digital ventriculograms demonstrated new or increased wall motion abnormalities during atrial pacing in 4 of 5 patients with CAD who had wall motion abnormalities at rest and in 8 of 10 patients with CAD who had normal wall motion at rest. Moreover, these wall motion abnormalities occurred in myocardial wall segments that were supplied by coronary arteries with significant lesions. Thus, because digital subtraction angiography allows multiple left ventriculograms to be obtained during routine cardiac catheterization, intervention studies such as atrial pacing can be used to obtain a functional assessment of the severity of coronary arterial lesions.

Adult↗
PubMed1983

Evaluation of dilated cardiomyopathy by pulsed Doppler echocardiography.

The ability of pulsed Doppler echocardiography to identify patients with left ventricular systolic dysfunction was evaluated in 12 patients with dilated (congestive) cardiomyopathy. A range-gated, spectrum analyzer-based Doppler velocimeter was used to record blood flow velocity in the ascending aorta and main pulmonary artery. The following blood flow velocity parameters were measured or derived: peak flow velocity, acceleration time, average acceleration, deceleration time, average deceleration, ejection time, and aortic flow velocity integral. Doppler blood flow velocity data in the cardiomyopathy patients were compared to data from 20 normal subjects. Measurements from the ascending aorta revealed that peak aortic flow velocity discriminated between cardiomyopathy patients (mean 47 cm/sec, range 35 to 62) and normal subjects (mean 92 cm/sec, range 72 to 120) with no overlap in data (p less than 0.001). Aortic flow velocity integral was also able to separate the patients with dilated cardiomyopathy (mean 6.7 cm, range 3.5 to 9.1) from normal subjects (mean 15.7 cm, range 12.6 to 22.5) with no overlap in data (p less than 0.001). Although mean values for average aortic acceleration and aortic ejection time were also significantly different (both p less than 0.005), there was some overlap between the two groups. Pulmonary artery blood flow studies demonstrated significantly increased average acceleration, as well as decreased ejection time (both p less than 0.05), but no difference in average deceleration or peak flow velocity in cardiomyopathy patients compared to normals. Compared to pulmonary flow measurements, aortic Doppler flow velocity measurements allowed better separation of cardiomyopathy and normal groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Magnesium therapy for intractable ventricular tachyarrhythmias in normomagnesemic patients.

Intractable ventricular tachyarrhythmia associated with hypomagnesemia responds well to magnesium given intravenously. Two patients with recurrent ventricular tachycardia and ventricular fibrillation associated with normal serum magnesium levels and resistant to treatment with potassium chloride, lidocaine and bretylium tosylate responded dramatically to the administration of magnesium sulfate. A third patient in whom the serum magnesium level was unknown also showed dramatic response to magnesium therapy. Magnesium depletion probably interferes with sodium-potassium adenosine triphosphatase enzyme activity and causes ionic imbalance and electrical instability of purkinje's fibers. Without obvious magnesium depletion this element in high concentration may still prolong transient inward current, prolong the effective refractory period, increase the membrane potential and control ventricular tachyarrhythmia. When ventricular fibrillation or malignant ventricular tachycardia cannot be controlled with lidocaine and other conventional drugs, we recommend infusing magnesium sulfate, 2 to 3 grams in one minute, followed by 10 grams over five hours.

Aged↗
PubMed1981

Right ventricular performance in essential hypertension after beta-blockade.

Recent studies indicate that right ventricular performance is impaired even in uncomplicated systemic hypertension. Because of widespread use of beta-blockade in essentially hypertension, it is possible that such treatment often further depresses right ventricular contractility. To test this premise, and to evaluate the changes induced by different beta-adrenoceptor blocking agents on the contractility of right ventricular myocardium, 20 patients with essential hypertension were divided into two groups on a double-blind randomised basis, and maintained on oral oxprenolol or propranolol for five weeks. Cardiac catheterisation and right ventricular cineangiography were performed at the beginning and again at the end of the five week period. Right ventricular end-diastolic volume index did not change significantly in either group. In contrast, right ventricular end-systolic volume index increased, and right ventricular ejection fraction significantly decreased after chronic beta-blockade. Cardiac index decreased in both groups, but these changes were not statistically significant. When the intergroup differences were compared for all measured indices none of the changes between the two groups was statistically significant. Despite its intrinsic sympathomimetic activity, oxprenolol therefore impairs right ventricular performance to an extent nearly equal to that of propranolol. Moreover, right ventricular contractility is clearly diminished after the institution of beta-blockade in hypertensive patients--an effect that has until now been thought to be limited to the left side of the heart. Great caution must therefore be exercised when beta-blockade is initiated in patients with severely abnormal right ventricular function, because frank right ventricular decompensation may result.

Clinical Trials as Topic↗
PubMed1981

A case of Munchausen syndrome masquerading as unstable angina.

The authors report the case of a man who presented with unstable angina and who, at different hospitals over a period of several months, underwent two heart catheterizations, intra-aortic ballon counterpulsation, and eventual bypass surgery despite essentially normal coronary arteries.

Angina Pectoris↗
PubMed1980

Antihypertensive and hemodynamic effects of oxprenolol versus propranolol.

Oxprenolol is an experimental beta adrenergic blocker with intrinsic sympathomimetic activity. To compare the effects of long-term administration of oxprenolol on hypertension and hemodynamics with the effects of propranolol, 20 patients with essential hypertension were divided in a double-blind random manner into two 10-patient groups and given placebo for 2 wk, followed by equipotent doses of oxprenolol or propranolol for 5 wk and by placebo for another 2 wk. Right heart cardiac catheterization was performed at the beginning and at the end of the 5-wk beta blockade. Heart rates and blood pressures fell markedly with both agents, although standing heart rate was lowered more by propranolol than by oxprenolol. Plasma renin activity was much lower after beta blockade with either drug. There was no correlation between decreases in blood pressure and renin activity. Although during the stress of repeat cardiac catheterization heart rates remained significantly lower than control, the intra-arterial pressures were not altered significantly by oxprenolol or propranolol, nor was there significant change in pulmonary pressure, vascular resistance, or cardiac output. Thus oxprenolol closely parallels the effects of propranolol in essential hypertension. The negative chronotropic action of both drugs is more marked than their antihypertensive activity.

Adult↗
PubMed1977

Comparison of trimazosin and methyldopa in hypertension.

Eighteen patients with hypertension participated in a double-blind, randomized study to evaluate the effect of trimazosin, methyldopa, and placebo on supine and standing blood pressure and heart rate. Of 6 patients on methyldopa, one developed drug fever (and was dropped from the study) and one developed impotence. None of 6 patients on trimazosin and none of 6 patients on placebo developed any adverse effects. The mean supine blood pressure on 900 mg trimazosin daily was 17.0/12.8 mm Hg lower than that on the first placebo trial (p less than 0.01) and 17.0/12.1 mm Hg lower than that on the second placebo trial (p less than 0.01). The mean supine blood pressure on 2,250 mg methyldopa daily was 17.8/12.4 mm Hg lower than that on the first placebo trial (p less than 0.01) and 16.8/13.0 mm Hg lower than that on the second placebo trial (p less than 0.01). The mean supine blood pressure was not significantly affected by placebo. Trimazosin, 900 mg daily, and methyldopa, 2,250 mg daily, were equally effective in lowering supine and standing systolic and diastolic blood pressure and did not affect supine or standing heart rate.

Blood Pressure↗
PubMedDate not supplied

Matched comparison of slotted tubular and coil stents: differences in acute gain, loss index, and clinical outcome.

Different stent designs may produce differences in immediate and long-term outcome. The objective of this study was to compare the immediate results and long-term outcomes of patients with lesions undergoing implantation of a single slotted tubular stent (Palmaz-Schatz) or a single coil stent (Gianturco-Roubin I). For this purpose, the authors studied patients matched for lesion length and vessel size. The consisted of 135 patients (141 lesions), and the Gianturco-Roubin group was composed of 50 patients (56 lesions). The coil stent was more often used for bailout indications. Larger immediate lumen gain was achieved with the slotted tubular stent. At follow-up examination, there was no difference in stent thrombosis; however, there was a trend toward lower angiographic restenosis and target-lesion revascularization in the Palmaz-Schatz group. Randomized trials using larger numbers of patients are needed to determine differences in outcome among different stent designs.

Aged↗