[Detection by contrast ultrasonography of patent foramen ovale before neurosurgery]

Air embolism may occur during neurosurgery if performed in the seated position. Paradoxical systemic air embolism represents a potentially severe complication in case of patent foramen ovale. Contrast echocardiography detected such a malformation in 10/100 patients, which contra-indicated the sitting position in these 10 patients. No episode of paradoxical air embolism was observed in the 90 remaining patients, although 16 cases of pulmonary air embolism were detected during surgery.

[Detection of cardiac graft rejection using proton nuclear magnetic resonance]

Rejection of cardiac transplants can be detected by NMR imaging if it is associated with a change in myocardial T1 and/or T2 proton relaxation time. T1 and T2 were studied in 14 Lewis rats that underwent heterotopic cardiac transplantation. T1 and T2 were measured in vitro immediately after sacrifice 3, 4, 7 or 11 days after the graft using a Minispec BRUKER PC20. The myocardial water content was measured by dehydration in a vacuum for 24 hours. Histological analysis of sections classified the rejection process in 4 stages according to the degree of lymphocyte infiltration and percentage of myolysis. There was a significant difference between the ortho and heterotopic hearts: (Formula: see text). In particular, there was highly significant relationship between T2 and the stage of rejection (r = 0.90, p less than 0.005), and between T2 and % myolysis (r = 0.84, p less than 0.005). In addition, there was a close relationship between the T2 of the ortho and heterotopic hearts and their water content (r = 0.95, p less than 0.001). If these results are confirmed in man, is should be possible to detect rejection by NMR imaging using sequences of activation concentrating on changes of T2.

Verapamil depresses the synthesis of lipoxygenase products by hypoxic cardiac rat fibroblasts in culture

Lipoxygenase metabolites of arachidonic acid are potent chemotactic and vasoconstrictive agents and their local production in the myocardium induces the migration of polymorphonuclear cells into ischemic myocardium. These cells have been shown to play a role in the development of ischemic myocardial lesions. In the present study, the synthesis of arachidonic acid lipoxygenase metabolites by rat cardiac cells in culture and the effect of verapamil were investigated under normal and hypoxic conditions. Myocytes and fibroblasts metabolized exogenous arachidonic acid into 12-HETE and an unidentified metabolite (X). Fibroblasts synthesized significantly greater amounts of 12-HETE than myocytes (P less than 0.01). Hypoxia (glucose-free medium and low PO2) and verapamil (10(-7) M) under normal conditions, did not change metabolite synthesis by either type of cells. Under hypoxia, verapamil decreased significantly 12-HETE and X production by fibroblasts (P less than 0.01 and P less than 0.05), whereas the synthesis in myocytes was not changed. It is concluded that the decrease in lipoxygenase product synthesis under hypoxia by verapamil may contribute to its therapeutic effects on the ischemic heart.

[Angiographically tight coronary stenoses without transstenotic pressure gradient]

The availability of coronary angioplasty catheters has made it possible to measure transstenotic pressure gradients. This parameter provides direct information on coronary haemodynamics. In 2 patients with proximal concentric stenosis of the left anterior descending artery the gradient was zero in spite of a more than 50% reduction in vascular diameter. The reason for this emerged from a study of the characteristics of these stenoses: they were short, and the vascular area at their level clearly was superior to 1 mm2. None of the 2 patients suffered from angina. One had negative exercise ECG, the other had an inconclusive exercise test without pain but with ST segment depression on anterior leads. This patient had a history of posterior infarction with postero-inferior dyskinesia at angiography, and exercise scintigraphy with thallium showed no decreased uptake in the antero-septal territory. The presence of coronary transstenotic pressure gradient implies a fall in coronary blood pressure downstream of the stenosis, a pressure which constitutes the perfusion pressure in the territory fed by the narrowed artery. on the value of this perfusion pressure depends the possibility of coronary blood flow autoregulation in the territory threatened by ischaemia.

[Regression of post-infarction parietal dyskinesia after percutaneous coronary angioplasty]

Normalisation of abnormal segmental wall motion is rarely observed after myocardial revascularisation by aorto-coronary bypass when the territory revascularised is the site of post-transmural infarction dyskinesia. In particular, normalisation of segmental wall motion is extremely rare when dynamic tests designed to detect potential for improvement (trinitrin test and post-extrasystolic potentiation) are negative. We present the case of a 41 year old man who had anterior and septal wall dyskinesia 2.5 months after antero-septal infarction which was not improved by trinitrin. Dilatation of the left anterior descending artery by percutaneous coronary angioplasty was undertaken because of recurrent effort angina. Control angiography at 6 months showed almost complete normalisation of left ventricular contraction. This myocardial recovery is paradoxical because the trinitrin test did not show potential for improvement. The case illustrates the possibility of normalisation of segmental abnormalities of left ventricular contraction after revascularisation of the dyskinetic zone by percutaneous coronary angioplasty.

The effect of 4'-deoxypyridoxine on rat heart cell cultures under oxygen deficiency

The purpose of this work was to study the consequences of an intracellular depletion of pyridoxal-phosphate (PLP) in rat heart cells in culture submitted to oxygen deficiency. Glucose (GLc) and 4'-deoxypyridoxine (DOP) effects were separately evaluated after 150 mn of partial oxygen deprivation (N2) with regard to enzyme leakage, beating rates, intracellular concentrations of PLP and the ratio glycogen phosphorylase activity (-5'-AMP/+5'-AMP). PLP concentrations were higher in the air-GLc group than in the air group. alpha-Hydroxybutyrate dehydrogenase (alpha-HBDH) and creatine kinase (CK) leakages were observed in the N2 group, whereas 1.17 +/- 0.17 mM GLc prevented leakage. Beatings stopped in the N2 group, slightly decreased in the N2-GLc group; the ratio (-5'-AMP/+5'--AMP) increased only in the N2 group. With a 1 mM DOP pretreatment a significant decline of PLP was observed either with or without GLc in the culture medium. The ratio (-5'-AMP/+5'-AMP) was lower in the air-DOP group than in the air group, whereas beatings, alph-HBDH and CK activities were identical to the control group. ImM DOP in the N2-DOP group partially prevented alpha-HBDH and CK leakages into the medium but did not prevent the decrease in contractile activity. Surprisingly, PLP concentration increased in the N2-DOP group/air-DOP group and the increase in ratio (-5'-AMP/+5'-AMP) was higher in the N2-DOP group than in the N2 group when compared to the respective control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipotency of anti-curare activity of 4-aminopyridine and 3,4-diaminopyridine in anesthetized rats

In the curarized preparation, 3,4-diaminopyridine (3,4-DAP) and 4-aminopyridine (4-AP) were equiactive in their ability to antagonize d-tubocurarine caused complete depression of the indirectly elicited twitches of the sciatic nerve-tibialis anterior muscle preparation in anesthetized rats. In the non-curarized preparation, 3,4-DAP showed 2.3 to 4.0 times stronger augmentation of the indirectly elicited twitches than 4-AP, but both the drugs increased equivalently and slightly the maximally elicited twitches of the chronically denervated muscle. The results suggest that the difference of their prejunctional effects is masked by the postjunctional effects of d-tubocurarine in the indirectly elicited twitches.

[Effects of injectable nitroglycerin on atheromatous coronary stenoses]

The beneficial effects of glyceryl trinitrate (GTN) are the result of several mechanisms which reduce venous return, cardiac work and intraparietal tension, and redistribute blood flow to the subendocardial layer and ischaemic zones. A direct action on atheromatous coronary stenosis is disputed. The coronary angiogram of 45 patients with organic stenosis and no clinical or electrocardiographic signs of coronary spasm were studied under basal conditions and after intravenous injection of 1.5 mg of GTN. Eighty stenotic segments and the corresponding 80 prestenotic segments were traced for comparison after enlargement on a Vanguard retroprojector and calibrated with reference to the coronary angiographic catheter. Aortic pressure fell 2 minutes after the injection in all patients to return to initial values at the end of the investigation. The diameter of the stenosed segment increased in 17 cases, remained unchanged in 54 cases and decreased in 9 cases. When expressed as a percentage of stenosis, the narrowing increased in 25 cases, decreased in 16 cases and remained the same in 39 cases. In the cases aggravated by GTN the diameter of the stenosis decreased or remained the same, whilst the diameter of the prestenotic decreased; in the cases improved by GTN, the diameters of both stenotic and prestenotic segments increased and prestenotic segments showed only slight variations. There was no difference in the diameter of the prestenotic segments between the 3 groups, but the diameter of the stenotic segments was larger in the group aggravated by GTN in comparison with the other two groups. Different haemodynamic factors and neurotumoral and local metabolic autoregulatory mechanisms may be activated by GTN.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium butyrate-induced changes in cultured rabbit articular chondrocyte transmembrane electrical potentials. Relationship between these changes and the proliferative response

Sodium butyrate at 5mM reversibly induced a significant increase of transmembrane potentials (Em) in normal chondrocytes (24 hours after seeding) and arrested their proliferation. This increase in Em levels, which could be temporarily abolished by Tetra-ethyl Ammonium (TEA 5mM), was related to an increase in membrane permeability to K+. This hyperpolarization was correlated with the reversible inhibition of growth in G1 induced by the sodium butyrate.

[Hemodynamic effects of ARL 115 in left ventricular insufficiency]

ARL 115 has vasodilator and positive inotropic properties which justify its use in heart failure. The effects of this drug were studied in 8 patients with advanced myocardial failure (7 cases of primary cardiomyopathy and 1 case of ischaemic cardiomyopathy) undergoing diagnostic cardiac catheterization, 15 minutes after angiocardiography. The cardiac output pressures were measured and the M mode electrocardiogram was recorded under basal conditions and following an infusion of 1 mg/kg of ARL 115 over 10 minutes. An improvement was observed in 7 cases, with an increase in the cardiac output and a decrease in the left ventricular diastolic pressure (p less than 0.05). There was no significant modification in the heart rate and there were no side effects. In one case, an abrupt fall in the diastolic pressure led to a decrease in the cardiac output. The arterial and venous vasodilator properties were demonstrated in every case, but a positive inotropic action (increase in the dp/dtmax and modification of the end-diastolic pressure: dimension ratio) was demonstrated in only two cases. The absence of positive inotropic action in the 6 other cases could be due to the advanced myocardial deterioration in these patients or to a delay in the positive inotropic effect in relation to the vasodilator effect.

[Endocavitary electric shock. Problems related to equipment]

Endocavitary catheter ablation is a new method of treating cardiac arrhythmias. It may be used indirectly, interrupting conduction through the His bundle in supraventricular arrhythmias, or directly by altering the arrhythmogenic substrate to prevent ventricular tachycardia or fibrillation. We have observed, together with other workers, that changes in the electrical properties of the catheters used to deliver the endocavitary electrical discharge. This was unexpected as the shock was delivered through a unipolar electrode with the indifferent electrode placed on the patient's back. An analysis of the morphology of the discharge impulse in intensity and voltage at increasing energy values showed that the unconnected electrodes of the multi-electrode catheter were raised to approximately the same voltage as the indifferent electrode. The change in electrical properties of some catheters was therefore the result of an insulation defect between the conducting wires leading to the electrodes. A study of the rupturing voltage of 32 USCI endocavitary catheters showed that 5 were able to sustain repeated shocks of 2 Kv and that 3 were able to sustain 3.5 Kv. The insulation of Cordis catheters was good but problems were encountered due to the resistance of the wires leading to the electrodes which dissipated an abnormally high amount of energy, so reducing the energy actually reaching the myocardium. These observations may explain the inconsistency of results obtained by different groups performing endocavitary catheter ablation with material not designed specifically for this purpose.

Unipolar electrode system for an implantable defibrillator: new experimental approaches

Defibrillation thresholds are studied in normal dog hearts after induction of ventricular fibrillation by alternating current. Shocks of progressively increasing energies are tried after a period of 10 seconds of sustained ventricular fibrillation. The endocardial electrode system may be either unipolar or bipolar, the distal electrode being situated at the right ventricular apex. The results suggest that for an optimal capacitor in the range of 9-20 uF, unipolar shocks are more effective than bipolar shocks (3-10 versus 10-30 Joules). In addition, several cardiac arrhythmias, including rapid ventricular tachycardia, accelerated idioventricular rhythm, and transient AV block are frequently observed. We conclude that (1) an implantable unipolar endocardial defibrillator seems feasible; and (2) the design should include the appropriate circuits to treat the arrhythmias observed after the shocks.

Effects of sodium butyrate on growth and cell-cycle kinetics of cultured rabbit articular chondrocytes

The sodium salt of n-butyric acid was found to inhibit the growth of asynchronous cultures of rabbit articular chondrocytes. This inhibitory effect was dose-dependent between 1 mM and 5 mM, reversible, and accompanied by volume enhancement and modification of cellular morphology. Flow-cytometric analysis showed that drug exposure led to a slowing-down of the cell-cycle progression; after 1 day's exposure, cells accumulated in G1, and after 2 or 3 days' treatment, in G2, without a blockage in M; the increase of cells in G2 was in fact due to an enhancement of binculeated cells. The treated cells had an increased RNA content. Articular chondrocytes seem to be target cells for sodium butyrate and therefore it represents a valuable biological tool for studying the mechanisms of their growth regulation.

[Electrocardiographic effects and antiarrhythmic action of 1200 mg of oral amiodarone per day]

The authors administered 1 200 mg of amiodarone orally to 30 patients with paroxysmal supraventricular and ventricular arrhythmias for a period of 6 days. They evaluated the electrocardiographic modifications induced on the surface ECG as well as the anti-arrhythmic action which was assessed by continuous Holter ECG monitoring and endocavitary electrophysiological investigations. They found that the sinus rhythm was slowed by 22%, that the PR interval was prolonged by 22%, that the QTc interval was increased by 13.5% and that there were alterations in ventricular repolarisation in 48% of cases. These ECG modifications were maximal between the 5th and 7th days. The amiodarone controlled the arrhythmia in 57% of cases. Independent of the nature of the arrhythmia, the anti-arrhythmic effect appeared after a mean of 3.9 +/- 1.8 days. There was no significant relationship between the electrocardiographic modifications and the anti-arrhythmic effect. In three cases (10%), major side effects were observed, related to depression of sinus automatism. They only appeared after the 6th day. Thus, a loading dose of 1 200 mg/day of amiodarone p.o. can be administered without fear of major side effects for 4 to 5 days. Such treatment will control about 60% of cases of severe paroxysmal arrhythmias after 4 days.

Evaluation of 4-aminopyridine and 3,4-diaminopyridine penetrability into cerebrospinal fluid in anesthetized rats

4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP) when injected intracisternally to anesthetized rats induced qualitatively similar central nervous system stimulant and convulsant effects at equimolar concentrations. Overall penetrability into cerebrospinal fluid of 4-AP is significantly higher than that of 3,4-DAP after single i.v. administration as evaluated by a high-performance liquid chromatographic determination. The present results can account for the lower central nervous system toxicity of 3,4-DAP when compared to 4-AP previously described after systemic administration.