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Biomedical subjects

R Zelis

Publications and source records attributed to R Zelis.

At least 145 records · Page 8Linked to original sources
PubMed1976

Distribution of coronary artery disease. Prediction by echocardiography.

To assess the sensitivity of standard echocardiography in detecting ventricular motion abnormalities in patients with coronary artery disease (CAD) without prior myocardial infarction, 56 consecutive patients with a history of angina pectoris were studied during an angina-free period. In the 48 patients with adequate echocardiograms, the amplitude of septal and posterior wall motion in the high, mid, and low left ventricle was determined and used to predict prospectively in a blinded fashion the sites of angiographically-determined CAD. Twenty-eight of 35 patients (80%) with disease of the left anterior descending artery (LAD) had diminished interventricular septal motion (P less than 0.001) and 14 of 27 patients (52%) with disease of posterior vessels had diminished posterior wall motion on echocardiogram. When abnormalties of echocardiographic wall motion were compared with left ventriculography, the results were similar. Echocardiography may aid in predicting the presence and distribution of CAD, especially LAD disease.

Adult↗
PubMed1976

Functional reductions in left ventricular volume. Minimum chamber size consonant with effective hemodynamic performance.

A heart model in dogs was developed to evaluate quantitatively the extent to which left ventricular chamber size could be reduced and yet retain residual mechanical function to perform adequately as a pump. In 9 animals placed on right heart bypass perfusion to control systemic flows; left ventricular performance was estimated from high-fidelity left ventricular pressure and aortic flowmeter recordings and from lateral plane left ventricular angiograms. Studies were made during unrestricted left ventricular filling at varying cardiac outputs and with inflation of a balloon in the left ventricular cavity at a physiological cardiac output. As compared with control data (cardiac output 1.4 L. per minute), balloon inflation to 18.7 ml. caused an increase in total left ventricular end-diastolic volume (from 35.4 to 44.3 ml., p less than 0.001) and left atrial pressure (from 7.8 to 21.2 mm. Hg; p less than 0.001); it also caused a reduction in left ventricular stroke work (from 12.5 to 8.1 Gm.-M., P LESS THAN 0.005) ANd max. dp/dt (from 2,487 to 1,320 mm. Hg per second, p less than 0.05). Importantly, left ventricular stroke volume was unchanged. When compared with preload augmentation (with the balloon deflated), the magnitude of depression of cardiac performance caused by balloon inflation was more fully appreciated (left ventricular stroke work, max. dp/dt, and ejection fraction reduced 69, 61, and 45 per cent, respectively). Even so, with appropriate compensations, principally by the Frank-Starling mechanism, up to 42 per cent of the left ventricular cavity volume could be functionally eliminated with retention of adequate mechanical performance. Such data may have implications regarding the extent of resections possible in patients undergoing surgery for left ventricular aneurysm.

Angiography↗
PubMed1976

Persistence of biologic activity after disappearance of propranolol from the serum.

In order to evaluate the duration of the biologic effects of propranolol after the drug was discontinued, we evaluated a variety of noninvasively determined hemodynamic parameters. Significant depression was found in the heart rate (18 per cent), cardiac output (13 per cent) (determined echocardiographically), and the triple product of blood pressure, heart rate, and systolic ejection time (16 per per cent) during administration or propranolol (200 mg. per day) to 9 normal volunteers. Significant depression of these parameters was present 12 hours after discontinuing the drug. By 12 hours, serum propranolol levels had returned 90 per cent toward their base line; however, at the same time, the heart rate and cardiac output had returned only 19.4 and 14.3 per cent toward their base-line values, and the triple product had returned 41 per cent toward its baseline. By 36 hours no biologic effect was seen. Thus if propranolol were discontinued 2 days prior to cardiac surgery, no significant biologic effect would remain to complicate the patient's postoperative course.

Adult↗
PubMed1975

Isosorbide dinitrate. Effect on the vasodilator response to nitroglycerin.

To evaluate whether there is cross-tolerance to the circulatory effects of isosorbide dinitrate and nitroglycerin, six subjects were given 120 mg/day of sustained-action isosorbide dinitrate in three divided doses for six to eight weeks. Prior to and during the last week of long-term isosorbide dinitrate administration, the effects of sublingually given nitroglycerin (0.9 mg) on plethysmographically measured calf blood flow and venous volume at 30 mm Hg (VV[30]) were measured on three occasions and averaged. Although the arteriolar dilation produced by nitroglycerin was unaltered by isosorbide dinitrate, the venodilation was significantly attenuated. The VV[30] increased from 3.00 to 3.28 ml/100 ml (P less than .02) with nitroglycerin prior to isosorbide dinitrate administration, but failed to increase with nitroglycerin during the long-term administration of isosorbide dinitrate (2.95 to 2.95 ml/100 ml, P greater than .5).

Administration, Oral↗
PubMed1975

Improvement of reduced left ventricular diastolic compliance in ischemic heart disease after successful coronary artery bypass surgery.

To determine the effects of myocardial revascularization on decreased left ventricular diastolic compliance consequent to chronic stable coronary artery disease, 15 patients with patent coronary artery bypass grafts (Group I) were compared with 8 patients with occluded grafts (Group II) studied before and after operation. In addition, eight normal patients served as controls. Left ventricular diastolic compliance was assessed by: (1) total observed diastolic compliance: stroke volume (V) related to left ventricular diastolic pressure (P) change (deltaV/deltaP) normalized for end-systolic volume; (2) left ventricular stiffness index of passive elastic modulus (a equals slope of deltaP/deltaV related to mean left ventricular diastolic pressure); and (3) fractional pattern of left ventricular filling. All patients had normal sinus rhythm and none had preoperative or postoperative mitral regurgitation. The two groups with coronary disease were well matched preoperatively for ventricular function, volumes, mass, segmental contraction and compliance. Ejection fraction increased in Group I (0.56 preoperatively to 0.65 postoperatively, P less than 0.05) but was unchanged in Group II (0.63 To 0.61, P greater 0.05). Postoperative indexes of left ventricular compliance improved in Group I: (1) 0.110 to 0.150 (P less 0.05); (2) 0.030 TO 0.019 (P less 0.05); and (3) 37 to 30 percent filling during last one third of diastole (P less 0.05). These indexes were unchanged postoperatively in Group II: (1) 0.109 to 0.102 (P greater 0.05); (2) 0.033 to 0.039 (P greater than 0.05); and (3) 36 to 41 percent (P greater 0.05). Compliance indexes were not altered (P greater 0.05) in a subset of seven patients in Group I with preoperative or intercurrent myocardial infarction. Thus, this investigation demonstrates the relatively reversible nature of abnormal left ventricular compliance after successful coronary artery bypass surgery in certain patients with ischemic heart disease.

Angiocardiography↗
PubMed1975

Plasma lipid changes in young adult couples consuming polyunsaturated meats and dairy products.

Twenty-five young couples consumed either a saturated or polyunsaturated fat diet for a 20-week period. The polyunsaturated beef, lamb and dairy products, high in linoleic acid, were produced by feeding ruminant animals "protected lipid" feeds which prevent hydrogenation of fats in the rumen. The experimental design provided for four dietary groups: A) saturated diet for 20 weeks; B) polyunsaturated diet for 20 weeks; C) saturated diet for 10 weeks then polyunsaturated diet for 10 weeks; and D) polyunsaturated for 10 weeks then saturated diet for 10 weeks. Polyunsaturated-to-saturated ratios (linoleic: total saturated fatty acids) for the diets were: prestudy, 0.43-0.56; saturated 0.11-0.14; polyunsaturated, 0.56-0.62. Factors other than diet that appeared to affect cholesterol responses were carefully considered. During the initial 3 weeks (regimentation period) plasma cholesterol concentration decreased in all groups irrespective of diet. This was followed by two experimental periods in which the effects of the prescribed diets were readily apparent (response periods I and II). The final 4 weeks of the study were characterized by diminishing compliance with the dietary discipline (abatement period). Subjects in each group (A,B,C,D) were subdivided into high and low on a basis of each group's initial median cholesterol level. Those in the high subgroups were very responsive to dietary changes whereas those in the low subgroups were not. Combined responses of high subjects were: polyunsaturated diet, -10.7 mg/dl (P less than 0.025), saturated diet, d8 mg/dl (P less than 0.05). Combined difference between saturated and polyunsaturated diets was 18.5 mg/dl or approximately a 10% cholesterol difference between the experimental polyunsaturated and saturated diets.

Adult↗
PubMed1975

Clinical use of sodium nitroprusside in chronic ischemic heart disease. Effects on peripheral vascular resistance and venous tone and on ventricular volume, pump and mechanical performance.

Although hemodynamic benefit has been shown with sodium nitroprusside (NP) in acute coronary pump failure, complete understanding of the mechanisms of action of the agent on the cardiocirculation and its value in chronic ventricular dysfunction are lacking. This investigation evaluates the effects of NP on the systemic and regional arterial and venous beds and on cardiac dynamics, ventricular volumes, contractile state and myocardial energetics in long-standing congestive heart failure. Twelve patients with chronic coronary pump dysfunction received NP infusion to lower systolic pressure to 95-105 mm Hg. Left ventricular (LV) function was assessed directly by angiographic volumes and high fidelity pressure, and peripheral circulatory dynamics were determined simultaneously by forearm arterial and venous plethysmography. NP reduced mean arterial pressure (MAP) from 88.2 to 73.4 mm Hg (P less than 0.05) and significantly (P less than 0.05) enhanced the variables of LV performance: LV end-diastolic pressure (EDP) diminished from 18.5 to 9.9 mm Hg; ejection fraction rose from 0.47 to 0.55; percent of LV segmental shortening increased; and isovolumic and ejection indices of contractility improved. Concomitantly, NP reduced the indices of myocardial oxygen demands of ventricular tension time index and LVED volume index. These salutary effects on LV performance and energetics occurred secondary to peripheral arterial and venous dilation (P less than 0.05) produced by NP: total systemic vascular resistance was lowered from 1590 to 1310 dynes sec cm--5; forearm vascular resistance diminished from 46 to 37 mm Hg/ml/100 gm/min; and forearm venous tone fell from 14.2 to 10.1 mm Hg/cc. Depressed stroke index (SI) and cardiac index (CI) increased (P less than 0.05) with NP: despite the fall in LVEDP, when ventricular filling pressures with the agent were at levels slightly above normal. Dextran infusion given with NP to restore LVEDP to moderately elevated values increased SI and CI (P less than 0.05) when NP alone produced no change in stroke output. Thus, the peripheral vasodilator properties of nitroprusside improve LV function by reducing impedance to ventricular ejection, while MVO2 is diminished by decreasing LV preload and afterload through relaxing actions

Adult↗
PubMed1975

Evaluation of skeletal muscle capillary basement membrane thickness in congestive heart failure.

Although it has been demonstrated that during isotonic grip exercise patients with chronic congestive heart failure have an abnormally reduced forearm oxygen consumption resulting from a depressed forearm flood flow, there may be additional etiologies of this abnormality. To explore this possibility biopsies of the pronator teres muscle were taken in eight control subjects with normal cardiac hemodynamics and in seven severely decompensated chronic congestive heart failure subjects. Each sample was fixed, stained, and photomicrographs of the sections were obtained and the capillary basement membrane thickness determined. The control capillary basement membrane thickness was 3028 plus or minus 187 A (mean plus or minus SEM) compared to the congestive heart failure thickness of 4924 plus or minus 538 A (pless than .01). It is possible that the increased basement membrane thickness in congestive heart failure may result from or actually cause the depressed oxygen consumption by altering diffusion.

Adult↗
PubMed1975

Effects of hemodynamic overload on canine myocardial myosin.

After mild banding of pulmonary artery in dogs there was a rapid elevation in protein and RNA synthesis, followed by an elevation in myosin content and myosin ATPase activity. There was an increase in myosin ATPase activity when K+ or Ca++ was used as activator effector but not with the cations, Mn++ or NH4+. Concomitant with an increase in myosin ATPase activity there was a decrease in one of the C1 light chain components, previously named C1d.

Adenosine Triphosphatases↗
PubMed1975

Modulation of myosin in right ventricular hypertrophy.

Mild pulmonic stenosis was performed in dogs to evaluate the effect of systolic pressures overloading on the activity and subunits of myosin in the early hypertrophied right ventricle. Three weeks following pulmonary constriction, six hypertrophied dogs were sacrificed and compared to six sham-operated dogs which served as controls. In the right ventricular free wall of hypertrophied right ventricles (HRV), the heart/body weight was 46% greater than that of normal right ventricles (NRV) (p less than 0.01). Myosin ATPase activity (Vmax values) in mumoles phosphate/mg/min, was elevated significantly in the stressed ventricle for both K+ and Ca++ activity in hypertrophied right ventricles. Associated with the increase in myosin activity, there was an increase in proportion of heavy to light chains in myosin from HRV. There were approximately 2 moles of myosin light chains per mole of myosin heavy chains in NRV and approximately 1 mole of myosin light chains per mole of myosin heavy chains in HRV. The proportion of light chain C1 to C2, did not change in myosin from NRV and HRV. Of the C1 light chains, according to two-dimensional gel electrophoresis, there was less C1d as compared to C1c in HRV as compared to NRV. Thus K+- and Ca++- activated myosin is elevated in early canine HRV by pressure overload. It is suggested taht the augmented myosin activity is due to a reduction of light chain inhibition of myosin ATPase activity, which appears to result from the slower turnover rate of myosin light chains relative to heavy chains. Furthermore, when myosin light chains are added to hypertrophied right ventricular myosin, the ATPase activity is lowered.

Adenosine Triphosphatases↗
PubMed1975

Effect of variations in pH on kinetics of myosin.

The pH optimum was the same in canine tissue for cardiac and skeletal muscle myosin; when myosin was activated by monovalent cations, the pH optimum was 7.5 while activation of myosin by divalent cations gave a pH optimum of 5.5. Protons were needed for divalent cation activation of myosin. With changes in pH there were concomitant changes in the apparent affinity of enzyme for substrate (S 0.5), such that with a decrease in pH there was an elevation in K+- or NH4+ -activated myosin's apparent affinity for adenosine triphosphate (ATP), and at the same time a decrease in Vmax values of myosin. The converse was true with the divalent cations, Ca++ and Mn++; here with a decrease in pH there was a concomitant decrease in apparent affinity of myosin for ATP, and at the same time an increase in the enzymatic Vmax values. It appeared that hydrogen ions affected the apparent affinity of myosin for substrate and this in turn affected the rate-limiting step in ATPase reaction. Addition of monovalent cations to the divalent cation activating system lowered the activity of myosin, and the converse was true: divalent cations lowered the activity of myosin when activated by monovalent ones in a monovalent cation activating system.

Adenosine Triphosphatases↗