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Biomedical subjects

D Tzivoni

Publications and source records attributed to D Tzivoni.

180 records · Page 10Linked to original sources
PubMedDate not supplied

Direct positive inotropic effect of mannitol on the intact canine heart.

Infusion of 25% mannitol into either the circumflex or left anterior descending coronary artery caused a significant increase in myocardial force development, measured by means of strain gauge in 10 anesthetized dogs. The changes were confined to the area perfused. The increase in developed force was dose-dependent, 20% at an infusion rate of 0.55 ml/min, 28% at 1.4 ml/min, 32% at 2.8 ml/min and 57% at 5.5 ml/min. There was a similar increase in dF/dt. The increase in developed force in the first minute was also dose-dependent, being 9% at 0.55 ml/min and 40% at 5.5 ml/min. No change in developed force occurred in the control (non-perfused) area or during saline infusion of the same artery at similar rates. A decrease in developed force of 10.5% was observed after the initial rise when mannitol was infused at 5.5 ml/min. This effect did not completely abolish the initial increase. No change in blood pressure, heart rate, LV systolic and diastolic pressure of LV dp/dt occurred during the experiment. It is concluded that doses of mannitol which are in clinical use have a direct positive inotropic effect on the intact canine heart.

Animals↗
PubMedDate not supplied

X-ray microanalysis of isolated perfused rat hearts.

X-ray microanalysis was carried out on sections from isolated hearts perfused with a modified Krebs-Henseleit solution with or without isoproterenol. Changes in P, Ca and Zn concentrations could be detected after isoproterenol and some correlation with hemodynamic and morphological parameters was observed. Ratios between P/Ca in myonuclei and the ratios of interstitial cell to myofiber nucleus calcium were related directly to the state of the heart.

Animals↗
PubMedDate not supplied

Comparison of exercise hemodynamics among nonstented aortic bioprostheses, mechanical valves, and normal native aortic valves.

BACKGROUND: While aortic valve prostheses are known to perform well at rest, few studies have examined them under stress. We compared stress hemodynamics of mechanical valves and nonstented porcine valves in the aortic position to that of normal native aortic valves. METHODS: Dobutamine echocardiography was used to assess mean and peak gradients and effective orifice area index (EOAI) at rest and exercise in patients with the Toronto Stentless Porcine Valve (SPV) (n = 13, mean implant size 25.7 mm), Sorin Bicarbon mechanical valve (SOR) (n = 11, mean implant size 24.5 mm), and patients with normal native aortic valves (NOR) (n = 10). Dobutamine infusion was started at 5 micron/kg per minute, and increased by increments of 5 micron/kg per minute until the target heart rate was achieved or until a maximal dose of 40 micron/kg per minute. RESULTS: At rest and exercise, respectively, cardiac output (L/min) was 5.2 and 10.4 for Toronto SPV; 7.4 and 13.5 for SOR; and 4.6 and 11.2 for NOR. Measured EOAI (cm2) was 1.1+/-0.2 and 1.15+/-0.2 for TORONTO SPV; 1.60+/-0.3 and 1.58+/-0.3 for SOR; and 1.45+/-0.2 and 1.46+/-0.2 for NOR. Mean gradients (mmHg) were 5.48+/-1.1 and 5.83+/-0.9 for TORONTO SPV; 5.26+/-0.8 and 11.3+/-1.8 for SOR; and 1.54+/-0.4 and 2.18+/-0.7 for NOR. Peak gradients (mmHg) were 11.9+/-2.0 and 21.0+/-3.7 for TORONTO SPV; 10.79+/-1.7 and 25.9+/-3.4 for SOR; and 2.38+/-0.9 and 6.1+/-2.3 for NOR. CONCLUSIONS: Although the mechanical group (SOR) had larger measured EOAI, the greater increase in gradients with exercise in this group suggests that the TORONTO SPV is less obstructive to flow.

Aortic Valve↗
PubMedDate not supplied

The effect of chronic propranolol therapy on regional cerebral blood flow in hypertensive patients.

In 31 hypertensive patients the effect of chronic oral administration of the beta blocking agent propranolol on regional cerebral blood flow (rCBF) was studied, using the non-invasive 133Xenon inhalation technique. The results of the measurements were compared to the rCBF obtained in an age-matched normal control group. Our study shows that during long-term therapy with low doses of propranolol (less than 120 mg/daily) the rCBF is unaffected, but it is increased significantly if higher doses (greater than 120 mg/daily) are used. In all six patients who served as their own control, as they had basic rCBF measurements before or during low-dose propranolol, the rCBF on high-dose propranolol became significantly increased. The possible mechanisms which may cause the increased rCBF on high-dose propranolol are discussed.

Administration, Oral↗
PubMedDate not supplied

Holter monitoring in the evaluation and rehabilitation of post-cerebrovascular accident patients.

Coronary artery disease, overt or silent, is frequently present in patients who have suffered a cerebrovascular accident (CVA). Rehabilitation therapy of CVA patients is based mostly on physical activity, which may be limited by fear of overloading the cardiovascular system. Therefore, assessment of the severity of coronary heart disease in CVA patients is of utmost importance. In this study we assessed the usefulness of 24-hour electrocardiographic Holter monitoring in the evaluation of post-CVA patients during daily activities and rehabilitation. Of the 43 post-CVA patients, 24 (55.8%) revealed pathological changes on Holter monitoring and 17 (71%) had a history of coronary artery disease prior to CVA. Holter monitoring revealed mainly ventricular and atrial arrhythmias and in three patients detected transient ischaemic episodes. Only six patients (14%) showed aggravation of arrhythmia during rehabilitation therapy, without aggravation of ST-T changes. The mean maximum heart rate during regular daily activities was 104 +/- 20 beats/min, which was significantly higher than the mean maximum heart rate during physical therapy (100 +/- 18 beats/min; p less than 0.01) and during occupational therapy (87 +/- 18 beats/min; p less than 0.001). These findings indicate that more vigorous physical and occupational therapy can be prescribed to these patients. The performance of Holter monitoring in post-CVA patients is a valuable substitute to exercise testing, and is useful for cardiovascular evaluation during daily activities and rehabilitation therapy.

Activities of Daily Living↗
PubMedDate not supplied

Long-term results of valve replacement in children suffering from rheumatic heart disease.

Severe pathological changes in the cardiac valves are often observed at an early age in children in the developing countries. Mitral stenosis is best managed by closed commissurotomy. However, mitral insufficiency, aortic insufficiency and tricuspid lesions may lead to life-threatening hemodynamic effects which necessitate valve replacement. This differs from experience in the developed countries where surgery for rheumatic valvular disease is limited to the adult. Our experience includes 33 children aged 5 to 16 years. Twenty-four children underwent single valve replacement, eight had two valves replaced and one had triple valve replacement. All were classified Grade IV or late Grade III (New York Heart Association). Four children had to be operated on despite known rheumatic activity. Two children in shock and pulmonary edema underwent emergency operation. There were two hospital deaths and eight late deaths. Patients have been followed for up to eight years. Twenty children are now classified as Grade I and lead completely normal lives and the remaining three are classified as Grade II. Postoperative catheterization studies have documented improvement from severe preoperative hemodynamic changes to near normal values at rest after operation. The cardiothoracic ratio has decreased impressively. We conclude that the natural history of rheumatic heart disease in children with severely damaged heart valves is favorably modified by valve replacement.

Adolescent↗