PubMed Health⌕ Search

Biomedical subjects

L Guize

Publications and source records attributed to L Guize.

At least 37 records · Page 2Linked to original sources
PubMed1988

Cardiac prognosis in hypertensive patients. Incidence of sudden death and ventricular arrhythmias.

The cardiac prognosis of hypertensive patients has been able to be precisely determined over the last 20 years as a result of large-scale epidemiologic surveys. The incidence of ischemic heart disease and the importance of left ventricular hypertrophy have been clearly defined in the literature. In contrast, the incidence of sudden death and ventricular arrhythmias has been poorly taken into account, although hypertension increases the risk of sudden death to the same degree as coronary artery disease. The relative risk increases progressively as a function of the quintiles of distribution of blood pressure, reaching a value of 3.2 for the highest quintile. There is also a significant correlation between hypertension and ventricular arrhythmias. Hypertensive subjects with other cardiovascular risk factors such as hypercholesterolemia or smoking and with ventricular extrasystoles, reflecting the presence of silent ischemia, can be considered to be at high risk of cardiac death.

Adult↗
PubMed1988

Change in human cardiac rhythm induced by a 2-T static magnetic field.

The influence of a 2-T static magnetic field on the cardiac rhythm was studied with 24-hour electrocardiographic monitoring in 12 healthy volunteers for 1 hour before exposure, 1 hour during exposure, and 22 hours after exposure. Four other subjects were exposed to 1 T, and nine control subjects were exposed to 0 T. In the 2-T group, the mean cardiac cycle length (CCL) was 912 msec +/- 83 before exposure. A significant 17% increase in CCL was observed after 10 minutes of exposure. No further significant variation was observed during exposure, and the CCL was back to preexposure values 10 minutes after exposure. No other arrhythmogenic effect was noted during the 24-hour monitoring. No statistically significant change was observed at either 0 or 1 T. The magnetically induced blood-flow potentials superimposed on the T wave were observed. The CCL increase during exposure could reflect a direct or indirect effect of magnetic fields on the sinus node, which is probably harmless in healthy subjects. However, its safety in dysrhythmic patients remains to be determined.

Adult↗
PubMed1988

[Recurrent myocardial abscess during Streptococcus B endocarditis].

The authors report a case of serious streptococcus B endocarditis with a myocardial abscess that recurred after surgery. Streptococcus B endocarditis is a rare disease which is characterized by a pronounced tropism of the organism for cardiac tissues, with severe cardiac valve mutilation and abscess formation in 40% of the cases. A myocardial abscess makes the prognosis worse and must be treated surgically during the acute phase of endocarditis. Modern imaging methods, notably trans-oesophageal two-dimensional echocardiography and computerized tomography should now be used to detect such abscesses.

Abscess↗
PubMed1988

[Effect of the sinusal rate on experimental vagal atrial arrhythmia].

Factors that facilitate the occurrence of cholinergic atrial arrhythmias were studied on 16 rabbit biatrial preparations in spontaneous rhythm. Sinus cycle length and characteristics of the atrial action potential were measured by the microelectrode technique in the basal state, then in the presence of acetylcholine at a concentration of 1.4 x 10(-5) M. Induction of arrhythmia was attempted by programmed stimulation, using an increasing number of extrastimuli. In the presence of acetylcholine the sinus cycle length increased by 106 +/- 63 p. 100 (p less than 0.0001) and the action potential duration, measured at 90 p. 100 repolarization (APD90) decreased from 60 +/- 15 ms to 40 +/- 11 ms (p less than 0.001). Reentrant activities, which had not been found in the basal state, were induced in 5 preparations. Under acetylcholine the sinus cycle of inducible preparations was shorter than that of non inducible preparations (663 +/- 272 ms vs 1218 +/- 531 ms, p less than 0.05). The percentage of sinus cycle lengthening was significantly smaller in inducible preparations (54 +/- 31 p. 100 vs 129 +/- 60 p. 100, p less than 0.05). Although sinus cycle lengthening was different in the two types of preparations, the APD90 was shortened in the same proportions. The vulnerability of the preparations seemed to depend mainly on a frequency effect. Vagal atrial arrhythmias occurred with a relatively small reduction in sinus rhythm. It is probable that an overpotent vagal effect is less arrhythmogenic because of its more homogeneous action on tissues.

Acetylcholine↗
PubMed1987

[Study of sinus function and nodal conduction using transesophageal recordings].

Transoesophageal pacing is mainly used for treatment of supraventricular tachycardias and assessment of refractory periods of accessory pathways. It has been proposed for the study of sinus node function and A-V nodal conduction. The aim of this study was to know if transoesophageal pacing could modify the vago-sympathetic tone, therefore the results of the tests, knowing it can be discomfortable and that endodigestive procedures can induce vagal responses. Furthermore, the stimulation is elicited near the left atrium, and not in the right atrium as during endocavitary tests. We have compared in 20 patients (age 68 +/- 12) the results obtained by both endocavitary and transoesophageal pacing (tension 21.2 +/- 4.5 V, duration 16 msec, interelectrode spacing 30 mm). We measured sino-atrial conduction time (SACT), sinus node recovery time (SNRT), Wenckebach's point and nodal refractory periods. After introduction of the oesophageal lead we observed a significant (p less than 0.01) but slight and transitory tachycardia. The results of A-V nodal conduction parameters were not significantly different and were significantly correlated (r = 0.94 for Wenckebach's point and effective refractory period). For the sinus node function, there was no significant difference between the parameters if the oesophago-atrial delay (mean 104.4 +/- 25.9 msec) is taken into account. The correlation is poor for sino-atrial conduction time (corrected SACT, r = 0.55), tighter for sinus node recovery time (maximal corrected SNRT, r = 0.92).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

[Electrophysiological, hemodynamic and histological effects of fulguration on the ventricular myocardium in the dog].

The myocardial repercussions of endocavitary fulguration depend upon the interaction of different physical phenomena. We studied the influence of energy level on the one hand and of the physical properties of the catheter (Ct) on the other hand on the cardiac effects of right endoventricular fulguration in the dog. A monopolar anodal shock was delivered in 12 dogs. Two levels of energy were applied: 25 J (group A, n = 6) and 100 J (group B, n = 6), and three Ct were used which differed in resistance (R) and active surface (S): Ct 1 (R = 0.3 omega, S = 12 mm2), Ct 2 (R = 0.3 omega, S = 2 mm2) and Ct 3 R = 2 omega, S = 13 mm2). Immediately after fulguration a significant rise of the right ventricular effective refractory periods was observed in group B only (193 +/- 28 vs 174 +/- 19 ms; p less than 0.03). Compared to baseline values, the systolic and diastolic pressures fell by 12% (p less than 0.01) and 18% (p less than 0.01) respectively in group A and by 33% (p less than 0.05) and 34% (p less than 0.002) respectively in group B. In contrast, there was no significant difference between variations of these parameters with the three types of Ct. The incidence of complex ventricular arrhythmia was higher in group B (5/6) than in group A (1/6).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

[Treatment of unstable angina. A randomized double-blind study of propranolol, diltiazem and molsidomine].

A randomized, multicentric, double blind study attempted to compare in 41 patients hospitalized for unstable angina, the efficacy of diltiazem (D) 240 mg/day, propranolol (P) 160 mg/day and molsidomine (M) 8 mg/day. The patients included in the study presented one or several spontaneous angina episodes accompanied by a transient and significant lowering of ST and/or an inverted T wave without necrosis. The evaluation criteria were the occurrence of new angina pain and electrical alterations on a continuous Holter for 5 days. 11 patients received diltiazem, 13 patients received propranolol and 15 patients received molsidomine (including an early death). Clinically, the number of painful episodes per day and per patient goes, in an average, from 1.2 to 0.23 diltiazem, from 2.2 to 0.44 for propranolol and from 2.2 to 0.45 for molsidomine. Pain disappeared on the 5th day in 54.5 per cent of patients under diltiazem, 58.8 per cent of patients under propranolol and 53.5 per cent of patients under molsidomine. Electrically, the number of ischemic accidents per day and per patient was 0.45 under diltiazem, 2.12 under propranolol (0.53 in excluding one patient with latent angina) and 0.81 under molsidomine. The number of patients without any ischemic accident was 63.6 per cent under diltiazem, 53.8 per cent under propranolol and 40 per cent under molsidomine. In conclusion, diltiazem, propranolol, and molsidomine have a comparable efficacy in unstable angina. The association of these medications could have a synergistic effect.

Angina Pectoris↗
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↗