Pacing for Carotid Sinus Syndrome and Sick Sinus Syndrome

BRIGNOLE, M., ET AL: Pacing for Carotid Sinus Syndrome and Sick Sinus Syndrome. The real incidence of pacemaker implants for carotid sinus syndrome (CSS) and the relation between CSS and sick sinus syndrome (SSS) is not precisely known. Patients who needed pacing therapy because of atrial bradyarrhythmias were investigated by means of carotid sinus massage, dynamic ECG, and invasive electrophysiological sinus node evaluation. Of 298 consecutive patients receiving a pacemaker implant, 36 (12%) had a severe cardioinhibitory carotid sinus reflex with reproducible spontaneous symptoms (CSS), 33 (11%) had sinus bradycardia < 50 beat/min or an abnormal electrophysiological evaluation (SSS) and 24 (8%) had both (CSS + SSS). The annual incidence was 40, 37, and 26, respectively, implants per year/million of inhabitants (total incidence 325). Patients affected by CSS, if compared with those affected by SSS, showed: a higher prevalence of syncope (97% vs 42%); more syncopal, episodes per patient (2.9 ± 2 vs 1.8 ± 0.9); a lower prevalence of associated cardiac diseases (53% vs 100%); cardiac enlargement (36% vs 88%); heart failure (6% vs 36%) and paroxysmal atrial fibrillation (0% vs 42%); and a more frequent indication for VVI pacing (75% vs 3%). In patients with CSS + SSS, intermediate characteristics were present. In conclusion, CSS is as frequent an indication to cardiac pacing as SSS; clinical differences justify a distinction between them, even if they are associated in 26% of cases.     

Spontaneous Occurrence of the Induced Cardioinhibitory Vasovagal Reflex

ECG recording of spontaneous, neurally-mediated syncope is rare. We have observed ten patients who sustained 70 syncopal episodes in whom: (1) ECG monitoring recorded syncope caused by ventricular asystole (AV block, three patients; sinus arrest; seven patients); (2) syncope and the spontaneously observed arrhythmias were reproducible by carotid sinus massage, upright tilt test, or eyeball pressure; and (3) no discernable cause of precipitating factors were detected. Two patients had a history of cardiac disease and four patients had only mild nonclinical ECG or echocardiographic abnormalities. Syncopal episodes recorded during Holter monitoring were of sudden onset in four patients and preceded by prodromal symptoms in six patients. The maximum RR pause was 9.4 +/- 3.7 seconds (range 4.5-15). Electrophysiological evaluation was normal in seven patients. Slight sinus node dysfunction or atrioventricular conduction abnormalities were noted in three others. The clinical characteristics of spontaneous and induced episodes strongly suggest that increased vagal tone played a role in causing the spontaneous events. Vagal stimulation tests are useful for the diagnosis of syncope of unknown origin.     

Malignant Ventricular Tachycardia During Propafenone Treatment in a Child with Junctional Automatic Tachycardia: Effectiveness of Intravenous Molar Sodium Lactate

Propafenone may aggravate the preexisting arrhythmia or induce another one. Usually, such proarrhythmic effects occur in patients with spontaneous ventricular arrhythmias and/or coronary heart disease with poor left ventricular function. We report the case of a 5-year-old girl with Junctional automatic tachycardia and no structural heart disease, in whom malignant ventricular tachycardia occurring during propafenone treatment could be terminated by molar sodium lactate (MSL) infusion. The serum propafenone level obtained before MSL infusion was within the therapeutic range. Two hypothesis could explain the beneficial effects of MSL in our patient: (1) alkalinization facilitates the cell membrane hyperpolarization and thus can decrease the voltage-dependent effect of Class Ic drugs, (2) alkalinization could displace propafenone from its tissue receptor sites by an increase in the nonionized fraction.     

The Effect of Exogenous Adenosine in Patients with Neurally-Mediated Syncope and Sick Sinus Syndrome

The effects of a 20-mg IV, bolus of adenosine 5'triphosphate (ATP) on the heart rhythm was studied in 79 patients affected by neurally-mediated syncope (26 cases) or sick sinus syndrome (22 cases) or both syndromes (31 cases) and in 31 healthy control subjects in order to examine the sensitivity of cardiac purinoceptors in such circumstances. During ATP infusion, the sinus cycle lengthened to > 2 seconds in no control, in 1 (4%) patient with neurally-mediated syncope, in 5 (23%) patients with sick sinus syndrome, and in 13 (42%) patients with both neurally-mediated and sick sinus syndromes (P = 0.01). Atrioventricular block occurred in 14 (45%) of controls, in 10 (38%) patients with neurally-mediated syncope, in 4 (18%) patients with sick sinus syndrome, and in 13 (42%) patients with both neurally-mediated syncope and sick sinus syndrome (n.s.). Thus, exogenous ATP exerts different effects on patients with neurally-mediated syncope and patients with sick sinus syndrome. In fact, intrisic disease of the sinus node is necessary to modulate an abnormal adenosine-mediated sinus arrest, whereas patients affected by neurally-mediated syncope alone show a normal sensitivity to the drug administration. The effect of ATP on atrioventricular conduction is greater than that on sinus node and is of similar magnitude in patients and controls; thus the clinical meaning of ATP induced atrioventricular block remains uncertain.     

Coronary calcification and its association with mortality in haemodialysis patients

Aim:   Coronary artery calcification (CAC) has been associated with higher mortality in chronic renal disease. The purpose of this study was to assess coronary artery calcium score (CaCs) in haemodialysis patients and to correlate calcium scores with clinical parameters and mortality.
Methods:   A cross-sectional study was conducted in 59 haemodialysis patients. CaCs was assessed by multidetector-row computed tomography and stratified as: CaCs of less than 10 Agatston units (U), no calcification; CaCs of 10–400 U, mild-to-moderate; and CaCs of more than 400 U, severe calcification. The effects of age, haemodialysis duration and biochemical and inflammatory markers on CaCs logarithm were evaluated by multiple linear regression analysis. Cox regression analysis was used to measure the impact of CaCs of more than 400 on 2-year mortality.
Results:   Coronary calcifications were detected in 64.5% of patients, and the median of CaCs was 31.7 U (0–589.7) with a range of 0–5790.0 U. Twenty-one (35.5%) patients had mild-to-moderate and 17 (29%) severe CaCs. Patients with severe CaCs were older and showed a higher prevalence of ischaemic heart disease and a higher body mass index ( P  = 0.04). A trend towards higher C-reactive protein levels was found in patients with severe CaCs. Advanced age was the only variable that influenced CaCs logarithm independently. The effect of severe CaCs on 2-year mortality did not persist after adjustment for other covariates.
Conclusion:   Coronary calcification was highly prevalent in these uraemic patients on chronic haemodialysis. A correlation was evidenced between CaCs and advanced age, but severity of the CAC score did not have an impact on 2-year mortality of this cohort.     

Occupational health promotion amongst cattle farmers in Zambia

One of the main activities of the Italian Animal Health Programme(IAHP) in the Republic of Zambia, a bilateral project betweenthe Ministry of Agriculture of the Zambian Government and theGeneral Directorate for Development Cooperation of the ItalianMinistry of Foreign Affairs, is the control of Malignant Theileriosisin Southern Province, through immersion of cattle in dip tankscontaining an acaricide. There are potentially important healthrisks to farm workers and the environment as a result of thisintervention and these are discussed. The control measures undertaken,with special reference to health education programmes, are described.     

Release of platelet-activating factor (PAF-acether) from alveolar macrophages by the calcium ionophore A 23187 and phagocytosis

Platelet-activating factor (PAF-acether) was recovered from rabbit, rat and human alveolar macrophages stimulated with the Ca++ ionophore A23187. PAF-acether release was also obtained from rat and rabbit macrophages in the presence of zymosan, but not from human alveolar preparations in spite of the phagocytic activity exhibited by the latter cells. Observed releases were active, Ca++ dependent, and plateaued at 45 min. No PAF-acether was released from lungs washed out of their macrophages, another argument against the mastocyte origin of this mediator. Given the potent bronchoconstrictive activity of PAF-acether, its release from alveolar macrophages may provide an alternative explanation for non IgE-dependent asthmas and the implication of platelets in pulmonary diseases.     

FLUORESCENCE PROPERTIES OF NEUTRAL PROTEASE FROM BACILLUS SUBTILIS

The fluorescence properties of neutral protease from B. subtilis have been investigated under a variety of conditions and the results compared with those previously reported for the homologous metalloendopeptidase thermolysin (Fontana et al., 1977). In the pH range 5–9 neutral protease displayed a quite unusual fluorescence emission spectrum with a maximum near 320 nm, when excitation was at 295 nm. At this wavelength the protein fluorescence is due to tryptophan residues only, which, considering their blue-shifted emission, appear rather buried in the hydrophobic protein interior. Specific removal of the functional zinc ion from the enzyme with tetraethylenepentamine does not lead to alteration of the microenvironment around tryptophan residues. On the other hand, removal of both zinc and calcium with ethylenediaminetetraacetic acid brings these residues in full contact with the aqueous solvent medium. Fluorescence quenching measurements were also used to determine the exposure of tryptophan residues in the native enzyme as well as in the presence of chelating agents and protein denaturants. Melting profile experiments carried out by monitoring the fluorescence intensity at 320 nm indicated a cooperative transition at 60–70°. Temperature effects were also determined under conditions perturbed with respect to pH, guanidine hydrochloride and chelating agents. The results reveal differences in the fluorescence properties of the tryptophanyl residues of B. subtilis neutral protease relative to those of thermolysin, which are interpretable considering the location of these residues in the sequences of the two homologous proteins.     

BINDING OF TUBOCURARINE, FAZADINIUM, PANCURONIUM AND ORG NC 45 TO SERUM PROTEINS IN NORMAL MAN AND IN PATIENTS WITH CIRRHOSIS

The protein binding of four non-depolarizing neuromuscular blockingdrugs-tubocuranne, fazadinium, pancuronium and Org NC45-wasmeasured, in serum from normal patients and from patients withcirrhosis of the liver, by an ultracentrifugation method. Thefraction bound to serum protein in normal panents was 56% fortubocuranne, 51percnt; for fazadinium, 29% for pancuronium and30percnt; for Org NC 45 In patients with cirrhosis, the proteinbinding of the four drugs was similar to that obtained in thenormal patients.