Biomedical subjects

H O Vallin

Publications and source records attributed to H O Vallin.

8 recordsLinked to original sources

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↗

PubMed1986

Diurnal variation of the QT interval--influence of the autonomic nervous system.

To assess the influence of diurnal changes in the autonomic nervous system on the QT interval, 24 hour dynamic electrocardiographic monitoring was performed in six pacemaker dependent patients with normally innervated hearts, in six cardiac transplant patients with anatomically denervated hearts (but which respond to circulating catecholamines), and in nine diabetic patients with confirmed autonomic neuropathy. QT and RR intervals from hourly intervals were measured and Bazett's formula was used to correct QT intervals during sinus rhythm. All QT intervals were normalised by dividing by the mean QT for the 24 hours in each patient and were expressed as a percentage. There was pronounced diurnal variation of normalised QT in the patients with normally innervated hearts. QT intervals were longer during sleep than during waking hours (06.00 vs 18.00 h, 102.5% vs 97.8%). Diurnal variation was blunted in the transplant patients (101.3% vs 98.1%) and absent in the diabetic patients (100.0% vs 100.3%). In the normally innervated patients changes were most pronounced at the time of waking (06.00 vs 09.00 h, 102.5% vs 95.4%). There was no change in normalised QT in the transplant and diabetic patients at this time. There was no significant difference between normalised QT for the three groups during sleep, but this variable was shorter in innervated patients during waking hours (for example at 10.00 h, innervated 96.5%, transplant 100.7%, diabetic 100.7%). Diurnal changes of the QT interval may be pronounced in the innervated heart and are dependent on both variations in autonomic tone and concentrations of circulating catecholamines. These changes in repolarisation may be related to the reported diurnal pattern of ventricular arrhythmias.

Adult↗

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↗

PubMed1980

Autonomous influence on sinus node and AV node function in the elderly without significant heart disease: assessment with electrophysiological and autonomic tests.

Eighteen volunteers with a mean age of 63.3 years, who were asymptomatic and without significant heart disease, were investigated with standard electrophysiological tests, performed before and after inhibition of autonomous neural tone with propranolol (0.1 mg . kg-1) and atropine (0.02 mg . kg-1). In addition heart rate responses to maximal exercise, carotid sinus pressure and bolus injection of isoprenaline (0.01 microgram . kg-1) were studied to evaluate the relation between different functional qualities of the cardiac conduction system. Autonomous tone inhibition (ATI) caused significant reductions in the mean PP-interval, sinus code recovery time (SNRT) and corrected sinus node recovery time (CSNRT). Furthermore, the precision of CSNRT determinations increased after ATI. In contrast, the AV-node effective refractory period and conduction time (AH-interval) did not change after ATI. A significant correlation existed between CSNRT and heart rate after ATI, both variables reflecting sinus node automaticity, while no covariation was found between CSNRT and the response to isoprenaline stimulation. AV-node refractoriness and conduction time showed covariation after, but not before, autonomous inhibition. As elderly asymptomatic non-patients were examined the use of the presented group characteristics as reference values for diagnostic investigations is suggested. For example pre-drug CSNRT above 545 ms (mean + 2 SD) or above 505 ms after ATI, indicates impaired sinus node automaticity.

Aged↗

PubMed1976

Left main stem coronary artery disease. Retrospective review of 26 patients treated surgically or medically.

The clinical, angiographic, exercise testing, operative, and follow-up data of 26 patients found at angiography to have left main stem coronary artery stenosis, defined as a reduction in the lumen diameter of 50% or more, are reviewed. There was a high incidence of significant proximal stenosis in the branches of the left main stem. No clinical features were found to distinguish patients with left main stem stenosis. All patients were considered for saphenous vein bypass grafting, selection being based upon the severity of symptoms, left ventricular function, and suitability of the coronary vessels for grafting. Two patients died within 24 hours of coronary angiography. Nine patients were operated on with no mortality. There has been one late cardiac death during a mean follow-up time of 13 months. All patients were symptomatically improved with a significant (P less than 0-01) increase in exercise ability postoperatively. Fifteen patients were not operated on. Six of these patients were regarded as operable but surgery was deferred; five have died at a mean time of 7-2 months. Five of the nine patients regarded as inoperable have died at a mean follow-up time of 14-8 months. The five non-surgical survivors remain symptomatic with no significant change in exercise ability. Recently reported surgical and medical series of patients with left main stem stenosis are reviewed.

Angiography↗