Biomedical subjects

K O Edhag

Publications and source records attributed to K O Edhag.

8 recordsLinked to original sources

PubMed1988

Responses to carotid sinus stimulation before and after propranolol.

The response to carotid sinus stimulation was studied in nine elderly men (mean age 67) with no history of cardiac disease, dizziness, or syncope. The response to manual carotid sinus pressure (during one of two studies) was positive (an RR interval of greater than 3s) in three men. But seven men showed positive responses after intravenous propranolol (0.1 mg/kg). Similarly, the RR interval was lengthened by greater than 10 ms/mm Hg in two men during neck suction. Neck suction produced a positive result in four men after intravenous propranolol. The detection of hypersensitivity of the carotid sinus in a high proportion of apparently healthy men, especially during beta blockade, suggests that an abnormal response to carotid sinus massage may not be a reliable indicator for pacemaker treatment.

Aged↗

PubMed1987

Analysis of sinus cycle variation: a new method for evaluation of suspected sinus node dysfunction.

Momentary sinus cycle variations in 30 patients with unequivocal sinus node disease (SND) were compared with those found in 18 healthy control subjects to assess their potential diagnostic value. The range of variation of sinus cycle length (SCL; standardized by dividing by mean SCL) and the maximal change in SCL between any two consecutive cycles (max delta SCL) were measured in short (about 1 minute) continuous ECG recordings from invasive electrophysiologic investigations. Age-stratified reference values from 1 minute surface ECG recordings obtained at rest during quiet breathing in about 70 healthy persons were applied. For diagnosing SND, an increased standardized variation range had a sensitivity of 63%, a specificity of 94%, and a predictive value of a positive test of 95%. The corresponding figures for an increased max delta SCL were 77%, 78%, and 85%, respectively. A combination of increased range of variation and increased max delta SCL was observed in 63% of the patients but not in any healthy subject, which gives a specificity and a predictive value of a positive test of 100% for this combination.

Adult↗

PubMed1985

Electrophysiologic evaluation of the cardiac conduction system and its autonomic regulation in familial amyloid polyneuropathy.

A high incidence of cardiac conduction disturbances is a salient feature in familial amyloid polyneuropathy (FAP) and amyloid infiltration of the conduction system has been found. In patients with FAP autonomic nervous dysfunction involving gastrointestinal, urogenital and cardiovascular systems has been described. However, the present study is the first to evaluate the results of autonomic tests and pharmacologic intervention in the autonomic nervous regulation of the cardiac conduction system during an invasive electrophysiologic study. Seven patients with FAP and severe disturbances of the conduction system, evaluated concerning indications for pacemaker treatment, were studied; in 3 of them the parasympathetic regulation was found to be abolished. In 1 patient the observations indicated either vagal overactivity or denervation oversensitivity of the receptors. The function of the beta adrenoceptors was intact in all patients, but a disturbance of sympathetic innervation could not be excluded. Dysfunction of autonomic nervous regulation of the cardiac conduction system was thus found in 4 of 7 patients. However, most conduction abnormalities were irreversible, indicating amyloid infiltration of the conduction system as the predominant pathophysiologic mechanism, in accordance with the findings of pathoanatomic studies.

Amyloidosis↗

PubMed1984

Pacemaker dependence in transient high-grade atrioventricular block.

In a prospective study 16 patients who had been given a pacemaker because of symptomatic high-grade atrioventricular block and whose conduction had been recovered were checked for their dependence on the pacemaker. During a follow-up time ranging from 32 to 158 months (median 62 months) six patients proved to be dependent on the device owing to the development of recurrent stable high-grade atrioventricular block. The subsequent return of atrioventricular block was evidently not associated with etiology, age, sex, ECG-pattern or length of follow-up period. Five additional patients equipped with a bradycardia-indicating pacemaker all proved to be pacemaker-dependent after a follow-up time ranging from 1-20 months (median 7 months), even though atrioventricular conduction had recovered and its presence had been confirmed at regular outpatient checks. It is thus evident that the conventional clinical methods are of limited value for examining the course of conduction defect and assessing the prognosis for patients whose spontaneous cardiac activity has returned after periods of symptomatic high-grade atrioventricular block. When a bradycardia-indicating pacemaker was furnished, pacemaker dependence was demonstrated in most of the patients whose atrioventricular conduction had recovered. This confirms that pacing introduced because of symptomatic high-grade atrioventricular block should not be discontinued even if a conducted heart rhythm has been established and maintained for long periods.

Aged↗

PubMed1984

Rate hysteresis pacing: how valuable is it? A comparison of the stimulation rates of 70 and 50 beats per minute and rate hysteresis in patients with sinus node disease.

The main disadvantages of VVI pacing are absence of acceleration of the heart rate and loss of atrial synchronization. The alternatives to AAI and DDD pacing are stimulation at a low rate or hysteresis in order to decrease pacing time and thus reduce AV asynchrony. Nine patients who suffered from sinus node disease and who had been given a multiprogrammable pacemaker were monitored at each of three stimulation rates: 70, 50, and 70 bpm with an inhibition rate of 50 bpm (hysteresis). The total pacing time was shortest (p less than 0.05) for the stimulation rate of 50 bpm as compared to 70 bpm and hysteresis. It was also shorter for the hysteresis mode than for the 70 bpm mode (p less than 0.05). Only for hysteresis pacing was there a significant reduction in the number of changes from conducted cardiac rhythm to pacemaker-induced rhythm. Most patients found the 50 bpm mode preferable. None favored the hysteresis mode. In patients with sinus node disease and intermittent bradycardia being permanently paced, the periods of AV-conducted rhythm may be lengthened by reducing the stimulation rate from 70 bpm, with or without hysteresis pacing, to 50 bpm. In paced patients with sinus node disease and symptoms due to AV asynchrony, it might be worth trying a decrease in the stimulation rate before resorting to other pacemaker systems.

Aged↗

PubMed1983

An implantable pulse generator indicating asystole or extreme bradycardia.

The design of a pacemaker which indicates the occurrence of significant bradyarrhythmia is described. Significant bradyarrhythmia is defined as either asystole for 6 seconds, bradycardia with three successive RR-intervals greater than 2 seconds each, or five or more RR-intervals of 2 seconds or more over a period of 25 seconds, but without three such intervals in succession. During bradyarrhythmia the generator initially stimulates at an interval of 2 seconds (30 per minute) and when the described criteria have been fullfilled the pacemaker automatically converts to a conventional ventricular inhibited pulse generator stimulating at a rate of 70 per minute.

Arrhythmias, Cardiac↗

PubMed1983

Clinical experience with a bradycardia indicating pacemaker.

The beneficial effect of permanent pacing is controversial in certain patient groups. Once pacing has been instituted it is seldom terminated and an evaluation of pacemaker dependence is therefore not possible. An implantable pulse generator, detecting bradycardia below 30 bpm has been developed in order to broaden our knowledge about the natural history of bradyarrhythmias treated by permanent pacing. This pacemaker has been implanted in 38 patients who did not have clear-cut indications for permanent pacing. They have been followed for a mean of 13 months. Bradycardia was detected in 33 patients 1 to 21 months (4.6 mean) after implantation. Twenty-one patients did not have a detected bradycardia for long periods (months-years). Minor symptoms of lightheadedness attributable to bradycardia were reported by 15 patients during periods when the pacemaker had been activated. Holter monitoring for at least 24 hours was carried out in all patients and electronic analysis of explanted generators was performed in eleven cases. No technical failure related to the bradycardia-detecting facility was observed. The combination of diagnostic and therapeutic properties in the bradycardia-indicating pacemaker provides means for safe evaluation of pacemaker dependency over long time periods in patient groups with controversial indications for permanent pacing.

Aged↗

PubMed1980

Heat rate responses in patients with sinus node disease compared to controls: physiological implications and diagnostic possibilities.

The autonomic regulation of heart rate was examined in 30 patients with symptoms of sinus node disease (SND) and 18 control subjects. Heart rate, expressed as sinus cycle length, was determined after injection of isoprenaline (0.1 microgram/kg), propranolol (0.1 mg/kg), and atropine (0.02 mg/kg); heart rate was also determined at maximal exercise and during carotid sinus stimulation. In addition, heart rate responses, expressed as the absolute change in sinus cycle length, were calculated. Mean heart rates after the applied maneuvers were all significantly different in the patient group, but so was the mean spontaneous heart rate. None of the induced changes differed significantly between the groups. Thus, although all these patients had impaired sinus node automaticity no uniform decrease in responsiveness to adrenergic or cholinergic stimulation or to inhibition of autonomic influences could be detected. The response patterns were heterogeneous, indicating diversity of the underlying mechanisms. No single heart rate reaction provided a satisfying diagnostic capacity for SND. However, the combined sensitivity of the three tests--isoprenaline stimulation, carotid sinus pressure, and autonomic inhibition--was 97% with a specificity of 50%. Clinically, normal findings in all these three tests, i.e., with resulting heart rates greater than 100, 55, and 70 beats/min, respectively, strongly suggest absence of SND.

Aged↗