[Paradoxal lowering of parasympathetic indices in myasthenic patients]. / Diminution paradoxale des paramètres parasympathiques chez les patients myasthéniques.

Myasthenia gravis is an autoimmune disease presenting antibodies developed against the nicotinic receptors of acetylcholine. The aim of this study was to evaluate heart rate variability in these patients. Heart rate variability was studied with 24 hour Holter recordings. Eighteen myasthenic patients, 7 men and 11 women, under pyridostigmine treatment, with an average age of 40 years (25 to 63 years) were aged and gender matched to a control group of 18 healthy subjects. All patients exhibited normal cardiac status and Doppler echocardiography. The following parameters were collected over 24 hours and the data further differentiated between night and day: for the temporal domain: heart rate, SDNN, pNN50, rMSSD; and for the spectral domain: total power, high frequency (HF) and low frequency (LF) power. The mean heart rate was slightly higher in the myasthenic group (non significant), due to a less marked nocturnal bradycardia. There was a decrease in the observed absolute values of SDNN as well as temporal and spectral parasympathetic indices (pNN50, rMSSD, HF) (p < 0.01) over the 24 hour period. The results were more significant during the night. Cardiac parasympathetic modulation is significantly modified in myasthenic patients. Considering that lack of bradycardia argues against an over active vagal tone, three hypothesis are discussed that favor of a low vagal tone: antibodies effects on the nicotinic receptors of the autonomic nervous system, respiratory impairment and a desensitization of the acetylcholine receptors.

Optimizing the hemodynamic performance of the DDD pacemaker: impact of the atrioventricular delay on the pulmonary venous flow pattern.

UNLABELLED: This study evaluated the impact of the atrioventricular delay (AVD) on the pulmonary venous flow pattern (PVFP). METHODS: Transthoracic Doppler PVFP were obtained during atrial and ventricular pacing at a fixed rate of 70 beats/min in 20 patients equipped with a DDD pacemaker, diastolic dysfunction linked to an impaired relaxation, a mean ejection fraction of 49%, and AV block. Two subgroups were analyzed equally: group I: seven patients with a normal ejection fraction and group II: 13 patients with decreased ejection fraction. Three different AVDs were studied: short (50 ms), intermediate (150 ms), and long (250 ms). RESULTS: As the AVD increased, the diastolic filling time and the peak atrial reverse flow wave decreased (P < 0.001). There was a decreasing D wave and no significant change in the peak velocity of the S wave. The S wave became biphasic in all patients at the longest AVD of 250 ms. The systolic (S) velocity time integral (VTI) of the pulmonary wave and the systolic/total PVF-VTI ratio increased significantly (P < 0.001). A similar response was seen in both group of patients. CONCLUSIONS: These data correlated the AVD with PVFP, supplying critical systolic information completing the diastolic data obtained from mitral Doppler patterns. These systolic measurements were especially useful for patients with heart failure and a DDD pacemaker, in order to obtain the longest diastolic filling time at the lowest atrial pressure.

[Variability of heart rate after heart surgery under extracorporeal circulation: aortocoronary bypass or aortic valve replacement]. / Evolution de la variabilité de la fréquence cardiaque après chirurgie cardiaque sous circulation extra-corporelle: pontages aorto-coronariens ou remplacements valvulaires aortiques.

The study of heart rate variability allows analysis of modulations of heart rate by the sympathetic vagal system. The authors studied the course of sinus variability by 24-hour Holter monitoring preoperatively, and on the 6th and 42nd postoperative day, in 25 patients undergoing coronary bypass graft (group I) and 10 patients undergoing aortic valve replacement (group II). Surgery was performed under cardiopulmonary bypass with selective antegrade cold crystalloid cardioplegia. The preoperative ejection fraction of these patients was 62% with a mean age of 59.5 years in group I and 61.5 years in group II. All temporal or spectral parameters were significantly decreased in the two groups on the sixth day (p < 0.05). Parameters which remain altered on D42 compared to baseline values were temporal parameters: pNN50 and rMSSD for group I and ASDNN for group II, with a tendency to return to baseline values, but with a higher mean heart rate in group II on D6 and D42 (p < 0.05). In the spectral domain, TP (total power of the spectrum) and LF (Low frequencies) remained decreased in both groups. A reversible alteration of sinus variability parameters was therefore observed in the two groups of patients. Other studies are necessary to define the mechanisms of these alterations, which are most probably related to catecholaminergic flooding related to CPB or partial vagal denervation by ischaemic or surgical damage to nerve structures.

[Doppler echocardiography of left ventricular filling in chronic renal insufficiency: before and after dialysis]. / Etude écho-Doppler du remplissage ventriculaire gauche chez l'insuffisant rénal chronique: avant et après dialyse.

Hemodialysis can achieve loss of body water, variable in the different water compartments, and that depends on the dry weight and the composition of the dialysate. We have studied echocardio-Doppler findings in 26 end stage renal disease patients (from 26 to 84 years), in whom 25 have hypertension, in sinusal rythm and ejection fraction above 55%. When they achieved a 3.52% decrease in body weight, without modification of heart rate and decrease in median arterial pression, these patients exhibited decrease in auricular (p = 0.001) and ventricular diameter both in systole and diastole (p = 0.001), in maximum velocity of E wave (p = 0.001) and E/A ratio. There was no significant reduction of maximum velocity of A wave, but 4 differents patterns of E/A ratio were demonstrated. The main determinant factor of these patterns was found to be the age of the patient.