Intracellular and extracellular recordings of sinus node activity: comparison with estimated sinoatrial conduction times during pacemaker shifts in rabbit heart.

Sinoatrial conduction times, estimated by premature atrial stimulation, were compared with direct measurement of the sinoatrial conduction time in 15 isolated rabbit sinus node preparations before and after intrasinusal pacemaker shifts induced by cooling. Transmembrane potentials and surface electrograms were recorded from the sinus node and crista terminalis. Extracellular sinus node activity was recorded in five preparations. Mapping was performed at 38 degrees C and 35 degrees C to determine the site of the dominant pacemaker. The sinus cycle was significantly longer at 35 degrees C (319.4 ms vs 258.1 ms). Intracellular measured conduction time was significantly shorter (63.8 ms vs 70.4 ms) because of caudal shift of the dominant pacemaker. Estimated sinoatrial conduction time was significantly longer (110.3 ms vs 85.4 ms) owing to the depression of automaticity by the extrastimulus. Extracellular measured conduction time did not differ significantly from intracellular measured conduction time. These results suggest that intrasinusal pacemaker shift may explain inaccuracies in indirect estimations of sinoatrial conduction time by atrial pacing techniques. Extracellular recordings appear to be a better method of evaluating sinoatrial conduction times.

Hemodynamic criteria for diagnosis of right ventricular ischemia associated with inferior wall left ventricular acute myocardial infarction.

To test the diagnostic value of different hemodynamic indexes for the diagnosis of acute right ventricular (RV) ischemic dysfunction, we studied 2 groups of consecutive patients admitted for an acute left ventricular inferior wall myocardial infarction: 51 patients with (group 1) and 32 patients without (group 2) RV ischemia as determined by coronary angiography. In both groups, we analyzed by right-sided cardiac catheterization right-sided heart pressures, pulmonary capillary wedge pressure, and cardiac index. We also calculated pressure ratios (mean right atrial pressure or RV end-diastolic over pulmonary capillary wedge pressures), pulmonary vascular resistance, and RV stroke work index. We found significant differences (p < 0.01) between the 2 groups when comparing mean right atrial pressure, RV end-diastolic pressure, ratio of these 2 pressures over pulmonary capillary wedge pressure, RV stroke work index, and right atrial and RV pressure waveforms. The best combined sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were found for the right atrial M or W waveform pattern, isolated or combined with a disproportionate elevation of RV end-diastolic over pulmonary capillary wedge pressures (respectively, 92%, 94%, 90%, 87%, and 89%). Volume loading was performed in 27 patients (18 with and 9 without RV ischemia). Right heart pressures and RV stroke work index increased significantly and similarly in both groups. Cardiac index increased significantly only in patients without RV ischemia (p = 0.02). However, volume loading did not significantly modify the diagnostic value of the different hemodynamic criteria studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Relations between Doppler tracings of pulmonary regurgitation and invasive hemodynamics in acute right ventricular infarction complicating inferior wall left ventricular infarction.

To test the hypothesis that flow characteristics from pulmonary regurgitation (PR) can predict right ventricular (RV) involvement in patients with inferior wall acute myocardial infarction, we prospectively recorded continuous-wave Doppler tracings and right-sided cardiac hemodynamics in 48 consecutive patients with inferior wall acute myocardial infarction and PR. Right heart hemodynamics enabled the identification of 29 patients with (group 1) and 19 without (group 2) RV involvement. In patients with RV involvement, the pulmonary regurgitant flow pattern was characterized by a rapid rise in flow velocity to a peak level followed by an abrupt deceleration in mid-diastole, whereas in patients without RV involvement, the deceleration in mid-diastole was gradual. The pressure half-time of PR (PHTPR) and the lowest mid-diastolic to peak early diastolic velocity ratio were significantly lower in group 1 than in group 2 (91 +/- 31 vs 214 +/- 57 ms [p < 0.001], 0.35 +/- 0.08 vs 0.59 +/- 0.13 [p < 0.001], respectively). The best diagnostic accuracy (95%) was obtained with cut-off values of PHTPR < or = 150 ms and the lowest mid-diastolic to peak early diastolic velocity ratio < or = 0.5: sensitivity 100%, specificity 89%, positive predictive value 94%, and negative predictive value 100%. Using multiple logistic regression analysis, we found that PHTPR was the strongest predictor of RV involvement. Thus, these parameters, derived from pulmonary regurgitant tracings, are useful in the noninvasive bedside diagnosis of RV infarction.

Usefulness of pulmonary regurgitation Doppler tracings in predicting in-hospital and long-term outcome in patients with inferior wall acute myocardial infarction.

Right ventricular (RV) involvement is frequent during inferior wall acute myocardial infarction (AMI) and has been reported as a risk factor for in-hospital morbidity and mortality. The objectives of the present study were: (1) to evaluate in-hospital events in patients with and without RV involvement as diagnosed by abnormal flow characteristics derived from pulmonary regurgitation (PR) analysis (pressure half-time of PR, PHT(PR) < or = 150 ms and the lowest mid-diastolic to peak early diastolic velocity ratio, Vmin/Vmax < or = 0.5); and (2) to determine the influence of RV involvement in complications at long-term follow-up. Among 126 consecutively admitted patients with inferior wall AMI (mean age, 58 +/- 13 years), 101 had PR. We determined the prognostic significance of in-hospital and long-term events for the following variables: age > or = 65 years, ST-segment elevation > or = 1 mm in lead V4R, RV dilation, PHT of PR < or = 150 ms and Vmin/Vmax < or = 0.5, thrombolytic therapy, 3-vessel disease, and diabetes mellitus. We found that the PR derived Doppler index (PHT of PR < or = 150 ms and Vmin/Vmax < or = 0.5) was the only predictor of overall in-hospital clinical events (hazards ratio, 2.7, 95% confidence interval, 1.2 to 6.1, p = 0.016). At long-term follow-up (mean: 20 +/- 12 months, range 12 to 69), event-free survival analysis showed that age > or = 65 years was the only predictor of any event (relative risk, 3.7, 95% confidence interval, 2.1 to 6.3, p < 0.0001). Thus, RV involvement diagnosed with the use of PR flow-derived variables is an accurate and independent predictor of in-hospital complications. However, RV involvement does not influence long-term prognosis.

Aortic dissection and cardiovascular syphilis: report of an observation with transesophageal echocardiography and anatomopathologic findings.

We report the case of a man who had thoracic pain and stroke. Transesophageal echocardiography enabled us to diagnose an intramural hematoma and a saccular aneurysm of the thoracic aorta before he died. Autopsy showed lesions compatible with syphilitic aortitis in the aortic wall. Transesophageal echocardiography and anatomopathologic findings are correlated, and the role of syphilis as a causal factor is discussed.

Is dobutamine stress echocardiography useful for noninvasive differentiation of ischemic from idiopathic dilated cardiomyopathy?

Dobutamine stress echocardiography was performed in 56 consecutive patients, mean age: sixty-two +/- twelve years. Twenty-two patients had an idiopathic dilated cardiomyopathy (group 1) and 34 had angiographically proven ischemic dilated cardiomyopathy (group 2). Wall motion score index and left ventricular ejection fraction were determined at baseline, 5 micrograms/kg/min, peak, and ten minutes after stepwise dobutamine infusion. Worsening or no change in global wall motion score was observed in 9 group 2 patients (26%) and 1 group 1 patient (5%, P = .07). No significant difference was observed with regard to wall motion score index decrease between baseline and peak dose. Left ventricular ejection fraction increase during dobutamine infusion was comparable in both groups. Thus, an ischemic response was observed more often in the coronary artery disease group, yielding a good specificity and positive predictive value although sensitivity was low. However, left ventricular function improvement did not help to discriminate patients with or without significant CAD.

[Re-operations on patients with ball valve prostheses]. / Réintervention sur prothèses valvulaires à bille. 66 observations.

Out of 989 cases with a ball-valve prosthesis, 66 have been reoperated (6.7%). 2.9% of the cases reviewed annually have thus been reoperated. The main indications for reoperation were displacement (75.5%), malfunction (10.5%) which was related to a failure of the material of the prosthesis or to the deposition of fibrinous plaques, and associated lesions (14%) which were valvular, coronary or myocardial. There were multiple complications in 36 patients. The operative mortality was 31.8% (21.7% over the last two years). On statistical analysis, the significant risk factors were a previous history of bacterial endocarditis, grouping in Class IV of the NYHA classification, enlargement of the QRS complex (0.12 s), urgency of reoperation, and prolonged extracorporeal circulation (2 hours). The rapid fall in survival time was due in part to late deaths (16 patients). By way of contrast, the clinical result was satisfactory in 71% of the survivors. Analysis of the causes of failures has lead to a search for ways of preventing the necessity for reoperation.

[Long-term anticoagulant therapy in subjects over 75 years of age. 100 cases]. / Traitment anticoagulant au long cours chez les sujets âgés de plus de 75 ans. 100 observations.

100 patients (median age 79 years) were given anticoagulant therapy (ACT) for a period of time averaging 5 years 3 months (522 follow-up years).--Out of 3 522 Quick tests, converted into prothrombin times and all carried out in the same laboratory, the prothrombin time was at or less than 32% in 60.5%, and 34% in 69.6% of the tests.--The mean therapeutic doses were less than 27% of those for adults, and were decreased by 3 mg of phenindione per year over the age of 75, only the actively treated cases being retained.--The risks are the same as those for the middle-aged adult. They depend more on the quality of the investigations than upon age. In the group which has been studied, slight or frank haemorrhagic complications (0.05/year/patient) were the result of a demonstrable overdosage in only one case in four. They were not responsable for any deaths in this series.--because of the referral patterns, the patients studied consisted of 79 with ischaemic heart disease, 27 with peripheral vascular disease, 9 cerebrovascular accidents, and 6 with thrombo-emoblic problems, not counting the 23 complications during the course of the study. In those patients with ischaemic heart disease, well-regulated anticoagulant treatment was associated with a favourable clinical course, and the correlation was significant.--there is not argument against the administering of a full and prolonged course of ACT to a patient of more than 75 years of age.

[Does ambulatory determination of blood pressure allow the measurement of white coat effect?]. / L'enregistrement ambulatoire de la pression artérielle permet-il de mesurer l'effet blouse blanche?

UNLABELLED: The aim was to find an objective indicator in order to evaluate white coat effect (WE). The first hour average values after placing an ambulatory blood pressure recorder (15 mn intervals) were compared to those of the 4 following hours of diurnal activity. A first hour systolic arterial blood pressure (SBP 1H) increase of 10 mmHg or more was considered as an ambulatory WE positive (AWE+) and was compared to clinical WE (CWE). CWE+ was observed in 78 pts and AWE+ in 72 among a group of 172 unselected pts referred for hypertension. RESULTS: the correlation between AWE and CWE is weak (r = 0.49) but significant (p < 0.001). There was no difference between the two groups in age, sex, clinical blood pressure, heart rate or ambulatory BP after the first hour (table). There was a significant difference in SBP between the 2 groups (p < 0.001) during the first hour only. [table: see text] CONCLUSION: Ambulatory blood pressure recording is able to recognize and evaluate the white coat effect. We suggest to consider independently the first hour of each recording and to compare it with the mean pressure measured during the period of diurnal activity.

[Arterial pressure changes during exertion in the normal subject]. / Variations de la pression artérielle à l'effort chez le sujet normal.

The exercice electrocardiogram, carried out in 160 normal subjects, has allowed us to witness the physiological mechanisms of adaptation to exercise as a function of age and sex. The relationship between systolic arterial pressure (SAP) and cardiac rate (CR) is very narrow (R = 0.97), and is a linear function. Its slope increases with age in both sexes, and differs significantly in the male and female (P less than 0.001). Systolic pressure is related to the relative cardiac rate (CR%) by the formula SAP = 1.55.CR% + 70.

[Valve replacement by ball prosthesis. Study of risk factors]. / Remplacement valvulaire par prothèse à bille. Etude des facteurs de risque

245 patients had consecutive operations for replacement of a valve by a ball-valve prosthesis in the aortic position (114) in the mitral position (91), or in more than one position (40) between 1970 and March 1973. The operative mortality was 14.3% (9.5% if emergency operations are excluded). A statistical study of the risk factors has shown the relatively minor influence of the patients' preoperative status (age, NYHA functional classification, cardiomegaly, mean pulmonary arterial pressure, mean capillary pressure) and of the conditions during surgery (duration of extacorporeal circulation, size of the prosthesis). The majority of the early deaths (19 deaths out of 35) occur as part of a syndrome of low cardiac output (9) and/or of a severe disorder of ventricular rhythm (11). 9 of the 14 post-mortem examinations on such patients showed a haemorrhagic subendocardial lesion and/or, in 4, an intracardiac thrombosis on the prosthesis. The coronary arteries were normal (14), or slightly atheromatous (1). The histological picture is one of a haemorrhagic interstitial infiltration mainly in the subendocardial layers. The late failures (secondary deaths and poor results) are essentially related with poor preoperative status (age, functional classification, cardiothoracic ratio) or with complications which would be treatable given proper and regular follow-up supervision of the patients (porsthesis which pulls away or fails to function, thromboembolic accident, coronary complication).

[Evaluation by Doppler echocardiography of systolic and diastolic functions of the left ventricle of the athlete's heart]. / Evaluation par échocardiographie Doppler des fonctions systolique et diastolique du ventricule gauche due coeur d'athléte.

A doppler-echocardiographuc study of left ventricular hypertrophy and systolic functions was performed in 99 professional cyclists and 26 age, body surface and blood pressure-matched controls. The following T-mode echocardiographic parameters were determined: wall thickness and cavitary diameter, left ventricular mass (LVM), fibre shortening fraction (FSF) and ejection fraction (EF). The following doppler parameters were measured at the annulus (a) and tip (p) of the mitral valve leaflets: protodiastolic velocity peak (E), velocity peak during atrial systole (A) and A/E ratio. Compared with controls, the cyclists showed a significant increase of LVM (305 +/- 53 vs 174 +/- 41 g, p less than 0.0001) and of the h/R ratio of mean wall thickness (h) to cavitary radius (R) (0.40 +/- 0.04 vs 0.35 +/- 0.06, p less than 0.001). There was no significant difference between the two groups as regards FSF, EF and protodiastolic filling peak (E). In contrast, subjects in the cyclist group showed a significant increase of Ap (0.39 +/- 0.07 vs 0.47 +/- 0.09, p less than 0.001), Aa (0.36 +/- 0.07 vs 0.41 +/- 0.08, p less than 0.01) and A/Ep (0.54 +/- 0.12 vs 0.62 vs 0.62 +/- 0.11, p less than 0.0001). It is concluded that professional cyclists have an increase in size of their left ventricle and that repercussions of this enlargement on ventricular filling only appear during the atrial systole and are related to a slower heart rate.

[Nyctohemeral changes in arterial pressure in hospitalized subjects]. / Etude des variations nycthémérales de la pression artérielle chez les sujets hospitalisés.

Systolic and diastolic arterial blood pressures (SBP, DBP) were measured in 181 consecutive patients (pts) by non-invasive method (oscillometric recorder SpaceLabs 90202). Hospitalised pts (N = 54) and ambulatory pts (N = 127) did not differ significantly in 24 hrs mean SBP, diurnal SBP, DBP nor heart rate (HR): respectively 132.9 vs 136.1 137.6 vs 138.2 86.2 vs 84.4 mmHg 79.6 vs 77.1 bpm. The circadian variation of HR was identical in the 2 groups. During night (0-6 hr AM) pressures decreased significantly less in hospitalised pts than in outpatients: respectively SBP - 6.4 vs - 17.9 p. cent DBP - 5.7 vs - 17 p. cent SBP day/SBP night ratio 1.06 vs 1.17 (p less than 0.001). This "equalization" was observed since the first day of hospitalisation, even if pts were not restricted to bed (pts in intensive care unit were excluded). It did not depend on age, sex, mean SBP nor antihypertensive treatments. Heart work, as evaluated by HR.SBP product, did not differ significantly during the day in the 2 groups. In hospitalised pts it decreased twice less and remains at a significantly higher level than in outpatients: respectively - 166 vs - 300 906 vs 792 cmHg/min (p less than 0.001). The standard deviation of SBP was significantly correlated with the SBP day/SBP night ratio (r = 0.64 p less than 0.001). The chronology of the circadian variations of HR and SBP are identical, but their amplitude differed in hospitalised pts suggesting that the regulatory mechanisms of HR and SBP are different.

[Incidental finding of an isolated thrombus in the left atrium in a young woman with sinus rhythm 5 years after cerebral ischemic accident]. / Découverte fortuite d'un thrombus isolé de l'auricule gauche chez une femme jeune en rythme sinusal 5 ans après un accident ischémique cérébral.

The authors report the case of a 40 year old woman who had an ischemic stroke. The initial investigation including a complete blood clotting analysis, failed to demonstrate the cause. Five years later, the investigations were completed systematically by transesophageal echocardiography which demonstrated an isolated thrombus localised in the left atrial appendage though the localisation heart was in sinus rhythm and morphologically normal. This case illustrates in the diagnostic yield of transesophageal echocardiography in the investigation of systemic embolism in young patients who have had a cerebral ischemic event of unknown cause, even in the absence of predisposing cardiac cause.

[Mitral commissurotomy under direct vision. 37 cases]. / Commissurotomie mitrale sous contrôle de la vue. 37 observations.

1 188 mitral commissurotomies were carried out between 1962 and 1976, 37 of them (3.1%) being under direct vision. The two operative deaths (5.4%) occurred early in the series. Longer term follow-up showed that 3 cases died secondarily, and 3 had revision surgery. The main complication was mitral incompetence (51% of operated cases had a systolic murmur). The varying indications and results are presented; these justify a prospective study, but not a recommendation for the systematic adoption of mitral commissurotomy by an open heart technique.

[Valve replacement and aorto-coronary bypass]. / Remplacement valvulaire avec pontage aorto-coronaire.

Combined surgery on the valves and on the coronary arteries by bypass grafts has been carried out on 27 consecutive patients (1970 to 1976) and involved 18 aortic valve replacements, 8 mitral valve replacements, and one double mitro-aortic replacement; the mean duration of extra-corporeal circulation (145 mn) was significantly higher than that for valve replacements alone carried out during the same period (p less than 0.01). The five deaths occurring in hospital (18.5%) all occurred in the aortic valve group, and were amongst the first 15 cases operated on (1970 to 1974). The 4 post-mortem studies carried out showed similar findings, namely myocardial infarction and significant coronary lesions which had not been bypassed. Two secondary deaths due to infective complications occurred in the first six months. The 17 patients who were followed up after surgery and had a mean follow-up period of 24 months, were all substantially improved by comparison with their pre-operative state, despite certain complications affecting either the valves (1 requiring re-operation) or the coronary arteries (3 infarcts). The indications for coronary arteriography, which are related to the indications for surgery, are being enlarged so that they will include the majority of patients operated on excluding those of more than 65 to 70 years of age and also those aged less than 40 years who have no risk factors for atherosclerosis and no clinical or electrocardiographic signs suggesting a coronary lesion. A study of the operative risk factors has shown the importance of unsuspected coronary lesions, and would appear to indicate correction of all valvular and coronary lesions seen at the time of operation.

[Experimental induction of sino-auricular blocks on isolated atria. Microelectrode study of the effects of bepridil]. / Induction expérimentale de blocs sino-auriculaires sur oreillette isolée. Etude par microélectrodes des effets du bépridil.

The effects of bepridil on sinoatrial conduction were studied by perfusing 15 isolate rabbit right atrial preparations. In a preliminary series an increase in cycle length was observed with a dose-dependent effect with concentrations of between 5 X 10(-7) M and 1 X 10(-5) M. At the latter dose, sinoatrial block was observed. Bepridil was therefore used in a series of 10 preparations to induce sinoatrial block (SAB). After 10 minutes perfusion the cycle length increased significantly (14.3%, p less than 0.02). In 4 preparations SAB occurred 18.7 +/- 2.5 minutes after the onset of the perfusion. Sinoatrial block did not occur in 6 cases and in 4 cases an intrasinus shift of the dominant pacemaker was observed. The types of SAB observed were varied and their mechanisms were complex. Different types of SAB occurred in the same preparation. The different types of block recorded were: Blumberger type I SAB, anterograde 2/1 SAB, intrasinus 2/1 block, retrograde 2/1 and advanced block, complete atrio-sinusal dissociation.

[Left ventricular function in dilated cardiomyopathy. Noninvasive determination of end-systolic stress-diameter and shortening fraction-stress relations]. / Etude de la fonction ventriculaire gauche des cardiomyopathies dilatées. Détermination non invasive des relations contrainte-diamètre et fraction de raccourcissement-contrainte en télésystole.

The ejection fraction and fractional shortening are parameters of left ventricular function dependent on the conditions of load. They are not perfect indices of myocardial contractility. The study of the relationships between stress and diameter and fractional shortening and stress in end-systole provides a better means of assessing the contractile state of the myocardium. The relationships between end-systolic stress-diameter and end-systolic stress-fractional shortening were studied non-invasively in 10 normal subjects (Group I) and 7 patients with severe dilated cardiomyopathy (Group II). End-systolic longitudinal stress of the left ventricle was calculated from Grossman's formula by coupling automatic measurement of blood pressure (cuff method) with simultaneous M mode recordings guided by 2D echocardiography. The line of regression of end-systolic stress-end-systolic diameter was determined in all cases from a series of 14 points obtained after sublingual administration of 10 mg of isosorbide dinitrate. The line of regression of fractional shortening-end-systolic stress was established in both groups by using the values observed under basal conditions and at the peak of action of the isosorbide dinitrate. The following results obtained: Under basal conditions, patients in Group II had greater end-diastolic diameters (69 +/- 8 vs 49 +/- 4 cm, p less than 0.01), greater end-systolic diameters (61 +/- 8 vs 33 +/- 4 mm, p less than 0.001) and higher end-systolic stress (140 +/- 54 vs 67 +/- 13 10(3) dyn/cm2, p less than 0.001). Fractional shortening was lower in Group II than in Group I (12 +/- 5 vs 33 +/- 5%, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Arrhythmia and syndrome of obstructive sleep apnea in adults]. / Arythmies et syndrome d'apnées obstructives du sommeil de l'adulte.

Many nocturnal cardiac arrhythmias and conduction defects have been reported in the adult sleep apnoea syndrome. The most original is the great variability of the heart rate which is cyclical and related to the apnoeic episodes, and easily differentiated from simple respiratory sinus arrhythmia. It is characterised by an initial bradycardia followed by rebound tachycardia. The bradycardia is vagally dependent (inhibited by atropine) probably secondary to carotid chemoreceptor stimulation by the hypoxaemia. The tachycardia is mainly attributed to the cessation of vagal hypertonicity although catecholamine stimulation has been suggested. The origin of these changes is purely functional, regressing with treatment of apnoea (waking, tracheotomy), the maintenance of arterial oxygen concentrations with oxygen therapy and parasympathetic blockade (atropine). The intensity of the phenomenon is related to the degree of arterial desaturation, which is itself related to basal arterial saturation (SaO2) and the duration of the apnoeas. Prolonged systole due to paroxysmal sino-atrial or atrioventricular block may be observed at night in these patients. The influence of vagal overactivity is confirmed (suppression of vagotomy) with no organic pathology (diurnal absence, tracheotomy, normal electrophysiological testing) in favour of a relationship with apnoea. Though less common than conduction abnormalities, atrial arrhythmias (extrasystoles, flutter, fibrillation) are also possible complications of sleep apnoea. The absence of an organic substrate is indicated by their regression post-tracheotomy and the efficacy of atropine (again in favour of a vagally-induced mechanism). Finally, nocturnal ventricular hyper-excitabilty is sometimes observed, the probable mechanism being the association of severe hypoxaemias (SaO2 < 60%) and the increased sympathetic tone at the end of the apnoea.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ventricular tachycardia during theophylline overdose. Apropos of a case of reduction by magnesium chloride]. / Tachycardie ventriculaire au cours d'un surdosage en théophylline. A propos d'un cas de réduction par le chlorure de magnésium.

The authors report a case of ventricular tachycardia (VT) induced by theophylline toxicity in a patient with ischaemic heart disease complicated by left ventricular failure and chronic asthma. Two episodes of VT were reduced by intravenous injection of magnesium chloride. The aggravating role of a moderate magnesium deficiency is suggested by the synergy of hypomagnesemia and theophylline on intracellular calcium fluxes contributing to an accumulation of intracytoplasmic calcium, a situation which has been shown experimentally to generate delayed after depolarisations. The respective roles of the correction of the metabolic deficiency and of the specific antiarrhythmic action related to the calcium blocking effect of magnesium salts at cellular level are discussed.