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Biomedical subjects

L Guize

Publications and source records attributed to L Guize.

At least 55 records · Page 3Linked to original sources
PubMed1986

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.

Animals↗
PubMed1986

Inhomogeneity of cellular refractoriness in human atrium: factor of arrhythmia?

Spatial inhomogeneity of refractory periods, as measured during clinical electrophysiological studies, is a known predisposing factor of arrhythmia. We studied effective refractory periods (ERP) and action potential duration (ADP90) on isolated human atrium. Twelve samples of right atrium obtained during cardiac surgery from patients with (n = 6) and without (n = 6) atrial fibrillation (AF) were studied by microelectrode technique. For each preparation, ERP were measured at basic cycle lengths (BCL) of 1,600, 1,200, 800, and 400 msec in five different cells located around (0.8 mm) the stimulating electrode. Dispersion of ERP was significantly greater in the AF group (96.7 +/- 9 versus 70.9 +/- 9 msec, p = 0.01). In the non-AF group, we observed a positive linear correlation between ERP and BCL (r = 0.86) ADP90 and BCL (r = 0.93). On the contrary, in the AF group this correlation was absent between ERP and BCL (r = 0.28), poor between ADP90 and BCL (r = 0.62). These results suggest that nonhomogeneous recovery of excitability (dispersion and poor adaptation) may be an important factor of arrhythmia. This inhomogeneity is present at the cellular level as well as in the entire heart.

Action Potentials↗
PubMed1986

Effects of physical parameters of fulguration on electrophysiological and anatomical properties of canine myocardium.

In order to determine the respective roles of catheter (Ct) physical properties and of energy levels in myocardial effects of fulguration, we delivered an electrical shock between the tip electrode of a Ct placed at the apex of the right ventricle and a large cutaneous cathodal electrode in 12 dogs. Two energy levels were used: Group A = 25 J (n = 6) and group B = 100 J (n = 6), and three Cts were studied. These Cts had different resistances (R) and active surface electrodes (S): Ct 1 (R = 0.3 omega, S = 12 mm2), Ct 2 (R = 0.3 omega, S = 2 mm2), Ct 3 (R = 2 omega, S = 13 mm2). Complex ventricular arrhythmias were observed in 5/6 cases at 100 J but only in 1/6 cases at 25 J and were independent of the Ct type. Following the shock, the effective ventricular refractory period (S1 S1 = 300 msec) increased significantly only at 100 J (11%, p = 0.03). Anatomical lesions were wider (10.6 vs. 5.2 mm, p less than 0.05) and deeper (100 vs. 55%, p less than 0.05) in the 100 J group. In contrast, there was no significant difference in the electrophysiological and anatomical changes between the three Cts. In conclusion, arrhythmogenic adverse effects of ventricular Ct fulguration are related to the delivered energy; on the contrary, they seem only slightly dependent on Ct physical properties at these energy levels; a 2 J/kg shock is not only effective but also seems to be safe.

Animals↗
PubMed1986

[Experimental induction of sino-auricular blocks on isolated atria. Microelectrode study of the effects of bepridil].

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.

Action Potentials↗
PubMed1985

Is the relationship between blood pressure and cardiovascular risk dependent on body mass index?

The relationship between blood pressure and cardiovascular mortality according to body mass index has been analyzed in two French prospective studies: the Paris Prospective Study, composed of 7,704 men aged 40-53 years examined in 1967-1972, and the Investigations Pré-Cliniques Study, made up of 19,618 men aged 40-69 years who underwent a checkup in 1970-1980. In the Paris Prospective Study, during a mean follow-up of 11.2 years, 241 cardiovascular deaths occurred, while in the Investigations Pré-Cliniques Study, with a mean follow-up of 7.6 years, 262 cardiovascular deaths occurred. A Cox survival analysis was performed on the data of each study to test the interaction of blood pressure and body mass index in the prediction of cardiovascular risk. Both analyses demonstrate a significant negative interaction, suggesting that a decreasing trend of the relative risk of cardiovascular death with increasing body mass index is better supported by the data than a constant relative risk. These results might have some bearing on the problem of the management of hypertension in overweight subjects.

Adult↗
PubMed1985

[Clinical and electrophysiological aspects of median intra-His bundle block with normal electrocardiogram at rest].

The clinical and electrophysiological features and the natural history of median intra-His block with a normal resting electrocardiogram were studied: 11 patients had a fixed split H1-H2 potential with a spontaneous or induced block between H1 and H2. The patients (5 men and 6 women) were aged 17 to 70 years (average 53 years). Associated pathology included 2 cases of aortic stenosis (1 severe), 1 case of ischaemic heart disease (effort angina), 1 case of mitral valve prolapse and 2 cases of hypertension. The presenting symptoms were syncope (4 cases), dizziness (2 cases), effort angina (1 case) and tiredness (3 cases); 1 patient was asymptomatic. Holter monitoring (24 hours) was performed in 8 patients and s-owed paroxysmal conduction defects in 6 cases; 4 Mobitz II 2nd degree AV block, 1 3rd degree AV block with narrow QRS complexes and 1 case of blocked atrial extrasystoles at coupling intervals longer than 480 ms and sinus cycle lengths of over 800 ms. Exercise testing by bicycle ergometry (4 patients) was normal in 1 case and revealed Mobitz II 2nd degree AV block in 3 cases. Baseline electrophysiological studies showed an A-H1 interval ranging from 60 to 100 ms (average 78 ms), a H1-H2 interval of 20 to 40 ms (average 31 ms) and a H2-V interval of 30 to 50 ms (average 32 ms). Block between H1 and H2 was observed: "spontaneously" during electrophysiological investigation in 6 cases, after IV atropine in 1 case, during overdrive atrial pacing at rates slower than 150/min in 7 cases, after atrial extrastimulus with a functional intra-His refractory period of over 420 ms in 7 cases, after ajmaline in 3 of the 4 cases in which this test was performed. A cardiac pacemaker was implanted in 10 patients in whom the initial symptoms have all regressed; the remaining patient considered to be "epileptic" had another syncopal attack under therapy and was finally paced. This series demonstrates that the diagnosis of median intra-His block depends on precise electrophysiological criteria and should be looked for even when the presenting symptoms are atypical; some of our patients complained only of tiredness. The value of Holter monitoring and careful endocavitary investigation is emphasised. Median intra-His block should be distinguished from longitudinal and functional His bundle dissociation.

Adolescent↗
PubMed1985

[Prevalence and course of Wolf-Parkinson-White syndrome in a population of 138,048 subjects].

The prevalence of the Wolff-Parkinson-White (WPW) syndrome, frequency of arrhythmias and their evolution were studied in a group of volunteers consisting in 79,978 men and 59,070 women, aged from 20 to over 70. The higher prevalence of WPW in men than in women (p less than 0.001) decreased significantly with age, much more in men (p less than 0.001) than in women (p less than 0.05). Ventricular pre-excitation was intermittent in 6.7 p. 100 of men and in 16 p. 100 of women. The probable site of pre-excitation, determined on the orientation of the delta wave was more often left than right (104 vs 66, p less than 0.02). The frequency of paroxysmal tachycardia increased with age: 10 p. 100 of the cases from 20 to 39 years of age, 29 p. 100 from 40 to 59, 36 p. 100 at 60 and over (p = 0.05). It was 1.7 times more frequent in cases of left pre-excitation. A hundred and fifty-one patients were followed-up from 1 to 11 years (4.6): 5 patients died, 3 of non-cardiac and 2 of undetermined causes, with one sudden death in a 29 year old man. Fifty-three patients were reviewed 4.5 years after the initial examination: 9 pre-excitations (7 right, 2 left) had disappeared. In conclusion, the higher prevalence of WPW in men decreases with age. This decrease appears to be essentially due to the disappearance of the ventricular pre-excitation and not to an increased mortality. Arrhythmias are more frequent in older patients with left-sided pre-excitation.

Adult↗
PubMed1984

[Biological profile in acute coronary insufficiency: study of blood myoglobin, enzymes and inflammatory proteins].

17 patients admitted to an intensive coronary care unit for premonitory syndrome or acute myocardial infarction were divided into four groups (premonitory syndrome, non-transmural infarction, transmural infarction with and without inflammation) on the basis of electrocardiographic findings and total CK activity. Serum levels of CK and CK2, myoglobin, ASAT and ALAT, LDH, haptoglobin, CRP and alpha-1 acid glycoprotein were determined daily for ten days. Patients with premonitory syndrome had no significant increase in markers of cytolysis or myoglobin. In acute myocardial infarction, regardless of clinical type, time course of peak values for biologic factors assayed was as follows: D0: myoglobin; D1: CK and CK2; D0 to D2: ASAT; D2 to D5: LDH and CRP; D5 to D6: ALAT; D4 to D7: haptoglobin and alpha-1 acid glycoprotein. These parameters may increase with size of myocardial necrosis and association with an inflammatory syndrome (CK, LDH, CRP and alpha-1 acid glycoprotein). They may be predictive of poor prognosis (LDH at peak CK concentrations). Some determinations, both more difficult to perform and less specific, have a particular value: prompt diagnosis of myocardial necrosis and detection of early repeat infarction by myoglobin assay, retrospective diagnosis by inflammatory protein assays when total CK has returned to normal.

Angina, Unstable↗
PubMed1984

[Measured and estimated sinoatrial conduction during variations in rhythm. Microelectrode study of the isolated rabbit atrium].

Strips of isolated atrium were obtained from 10 rabbits to study the validity of indirect methods of estimating sinoatrial conduction time during variations of the sinus rhythm. Direct recordings of the trans-membrane action potential of the sinus node were made. Mapping of the sinus region was undertaken to determine the site of the dominant pacemaker. A quadripolar surface electrode was positioned on the lower part of the crista terminalis for stimulation and recording of the atrial potential. This enabled a comparison to be made between the indirect estimated and the directly measured conduction times. An intrasinusal shift of the dominant pacemaker was obtained by cooling from 38 degrees C to 35 degrees C. This shift occurs progressively in the cranino-candal direction. The estimated and measured conduction times were compared under basal conditions and after cooling. The sinus cycle was significantly longer (p less than 0.001) at 35 degrees C (318 +/- 68 ms) than at 38 degrees C (255 +/- 48 ms). The mean measured anterograde conduction time also decreased from 36 to 31 ms (p less than 0.01) and the mean measured retrograde conduction time also decreased from 39 to 33 ms (p less than 0.02); the total conduction time decreased from 75 to 64 ms (p less than 0.001). The results of the total estimated conduction times were discordant. The associated effects of stimulation and cooling can cause conduction defects and an overestimation of the conduction time.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1984

[Magnesium deficiencies in cardiovascular diseases].

Plasma (pl), red blood cell (ery) and urinary magnesium (Mg) concentrations were measured by spectrophotometry in over 300 patients at the Cardiology Department of Broussais Hospital. Other biological parameters, including pl and ery potassium, calcium and phosphate concentrations were measured simultaneously. In a control group (54 subjects) the mean pl Mg was 0,851 mmol/l in men and 0,819 mmol/l in women; mean ery Mg was 2,12 mmol/l and 2,09 mmol/l respectively. Magnesium depletion was observed in several pathological cardiovascular conditions: -- mitral valve prolapse: the Mg levels were significantly lower in women (19 cases) (pl Mg 0,740 mmol/l; ery Mg 1,83 mmol/l: p less than 0,001); the deficit was less pronounced in men: pl Mg 0,829 mmol/l, p less than 0,01, and ery Mg 2,01 mmol/l (NS); -- recurrent junctional tachycardia (21 cases): the Mg levels were significantly lower than normal: pl Mg = 0,796 mmol/l in men and 0,763 mmol/l in women; ery Mg = 1,93 and 1,88 mmol/l, respectively; -- coronary insufficiency (86 cases): pl Mg = 0,821 mmol/l in men and 0,768 mmol/l in women (p less than 0,001). In a subgroup with coronary spasm (22 cases), the mean ery Mg was decreased (2,01 mmol/l, p less than 0,05); -- unstable or labile hypertension (24 cases): the decrease was significant, especially in women (pl Mg = 0,796 mmol/l, ery Mg = 1,88 mmol/l). These magnesium deficits were sometimes associated with a low pl Ca, and often associated with a low ery K although pl K was usually raised. In some privileged cases of cardiac arrhythmia and coronary spasm, intravenous Mg repletion was beneficial but did not affect plasma concentrations. The role of magnesium depletion in cardiovascular disease remains obscure and requires further study.

Adolescent↗
PubMed1984

[A large aneurysm of the inferior mesenteric artery. Apropos of a case. Review of the literature].

The prevalence of inferior mesenteric aneurysms is difficult to evaluate in the literature, only four cases having been published up to the present. The case described here was a large aneurysm of the inferior mesenteric artery measuring 10 cm by 8 cm of atheromatous origin, discovered echotomographic investigation of an abdominal mass and confirmed by aortography. Operation consisted in endoaneurysmorrhaphy with reimplantation of the main branch supplying the sigmoid arteries into the aorta combined with reimplantation of the right common iliac eroded by the aneurysm into the right side of the aorta. This type of lesion raises two problems: diagnostic: echotomography and digitalised angiography will certainly facilitate the detection of such lesions, the risk of rupture of which is considerable; therapeutic: distal reimplantation of the inferior mesenteric artery which is decided on the basis of its anatomical state and above all the superior mesenteric and coeliac collateral circulation in order to avoid any risk of ischaemia of the descending colon.

Aneurysm↗
PubMed1983

[Comparison of various indirect methods for evaluation of sinus function].

Sinus node function was evaluated by Mandel, Strauss and Narula's methods in 60 consecutive patients: 20 females, 40 males; average age 59 +/- 17 years. Three had second degree sinoatrial block, 2 had bradycardia-tachycardia syndromes and 10 had sinus bradycardia. The corrected sinus node recovery time was 414 +/- 417 ms. It exceeded 520 ms in 8 cases, 5 where the two other methods confirmed sinus node dysfunction, 1 where the two other methods showed no abnormality. In the last two patients pathological results with Narula's method coincided with normal values with Strauss' method but the basal sinus cycle and the post return cycle differed from one method to the other. The atriosinoatrial conduction time estimated by Narula's method was 274 +/- 117 ms. In the thirteen cases where it exceeded 300 ms abnormal results were also recorded with Strauss' (11 cases) and/or Mandel's method (7 cases). The atriosinoatrial conduction time assessed by Strauss' method was 239 +/- 106 ms. It exceeded 300 ms in 18 patients. In these patients the results of Narula and Mandel's methods were normal in 7 cases. This discordance cannot be explained either by variations in the catheter position, or by the duration of the basal sinus or the post return cycles. This raises the question of penetration of the sinus node by the last stimulus when Narula's technique is used. A significant linear correlation was observed between the atriosinoatrial conduction time assessed by Narula's method and the atriosinoatrial time assessed by Strauss' method (N = 60; r = 0,59) and with the corrected sinus node recovery time (N = 60; r = 0,43) and a double linear correlation was found with these two parameters (N = 60; r = 0,62). There was no significant linear correlation between the atriosinoatrial conduction time assessed by Strauss' method and the corrected sinus node recovery time (N = 60; r = 0,27). The atriosinoatrial conduction time evaluated by Narula's method seems to be intermediary between the two other parameters which seem to be independent of each other.

Adolescent↗
PubMed1983

[Conduction disorders and aneurysms of the sinus of Valsalva].

A series of 15 sinus of Valsalva aneurysms (SVA) admitted between 1961 and 1981 was reviewed to analyse associated conduction defects. It comprised 11 men and 4 women; the mean age was 31 years (range 16 to 53). The diagnosis of SVA was made at the time of rupture (4 cases), during investigation of associated cardiac disease (8 cases), at surgery (1 case) and during advanced conduction disorders (2 cases). All patients underwent catheterisation and angiography. Endocavitary electrophysiological studies were performed in 3 patients. Eight out of 15 patients had conduction defects which comprised: incomplete right bundle branch block (2 cases), atrioventricular block (AVB) (6 cases). Endocavitary investigation of 3 of the 6 AVB showed conduction defects at several levels: sino atrial, suprahisien, intrahisian and infrahisian blocks (1 case); transient complete AVB with 1 degree and 2 degree intrahisian block (1 case); complete AVB, six years after correction of SVA, due to infrahisian block (1 case). Thirteen of the 15 patients underwent surgery; none of the 9 cases of SVA without conduction defects before surgery developed conduction defects. Four of the 6 cases of AVB required permanent pacing; there was 1 postoperative death. One patient was not operated. These conduction defects were caused by the close relationship of the SVA to the intracardiac conduction pathways. The right anterior was the most commonly affected sinus. The investigation of AV conduction should be systematic in cases of SVA, and, conversely, the finding of AVB in young patients should alert the physician to the possibility of a SVA.

Adolescent↗