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Biomedical subjects

H Ector

Publications and source records attributed to H Ector.

At least 37 records · Page 2Linked to original sources
PubMed1998

Tilt training: a new treatment for recurrent neurocardiogenic syncope and severe orthostatic intolerance.

Medical treatment of neurocardiogenic syncope is insufficient in many cases. We have observed a therapeutic effect of repeated head-up tilt testing. Therefore, we have started a program of tilt training for heavily symptomatic patients. After hospital admission, they were tilted daily (60 degrees inclination) until syncope, or until a duration of 45-90 minutes (90 sessions in 13 patients). The mean tilt tolerance, at the first diagnostic head-up tilt table test, was 22.3 minutes (st. dev. 10.9). Before hospital discharge, 12/13 patients could sustain the full duration of tilt table testing without any symptom. In one patient syncope persisted. The patients were instructed to continue a program of daily tilt training at home, by standing against a wall for 30 minutes, one or two times per day. This resulted in a complete disappearance of syncope in all 13 patients. Orthostatic intolerance and the excessive autonomic reflex activity of neurocardiogenic syncope can be remedied by a program of continued tilt training, without the administration of drugs.

Adult↗
PubMed1998

Prospective evaluation of the length of the lower common pathway in the differential diagnosis of various forms of AV nodal reentrant tachycardia.

The conduction time over the lower common pathway (LCP) in AVNRT can be assessed by subtracting the H A-interval during tachycardia (HAt) from that during ventricular pacing at exactly the same cycle length (HAp) (delta HA = HAp-HAt). It has been suggested that H-A measurements may help in the differentiation of Slow/Fast from Slow/Slow AVNRT. This study evaluated prospectively in 61 consecutive patients with AVNRT (43 +/- 15 y; 46 women, all with antegrade conduction during AVNRT over the slow pathway) how often a reliable measurement of the length of the LCP could be made, and in how far the results were concordant with mapping criteria for the differentiation of Slow/Fast from Slow/Slow AVNRT. A new para-Hisian pacing technique (using only the His bundle catheter) was applied in all patients. Comparison of HAt and HAp was possible in 44 of the 61 patients (72%). In these 44 patients, HAp was longer than HAt in 12 patients, indicating the presence of a LCP. All patients with delta HA > or = 15 ms had earliest retrograde atrial activation in the posterior septum (Slow/Slow AVNRT; n = 6) or simultaneously in the anterior and posterior septum (n = 1). On the other hand, 31 of the 32 patients without evidence of a substantial LCP (delta HA < or = 0) had typical Slow/Fast AVNRT. Moreover, although it appears logical for Slow/Fast AVNRT to have a shorter HAt than Slow/Slow AVNRT, an HAp of > or = 70 ms was a better discriminator between the two forms of AVNRT than any HAt value. Therefore, delta HA > or = 15 ms (sens. > or = 86%; spec. > or = 97%) or HAp > or = 70 ms (sens. = 100%; spec. > or = 89%) were highly indicative for the Slow/Slow variant of AVNRT. Using a para-Hisian pacing technique, H-A measurements can be performed in 72% of AVNRT patients. They can be used as an important tool in the differentiation of Slow/Fast and Slow/Slow AVNRT.

Adult↗
PubMed1998

A case of extensive pulmonary embolism presenting as an acute myocardial infarction--notes on its possible pathophysiology.

Pulmonary embolism is frequently overlooked but may be fatal. Hence, appropriate diagnosis heavily relies on clinical suspicion. Although most ECG features of pulmonary embolism lack specificity and sensitivity, especially when prior cardiopulmonary disease is present, certain ECG findings may heighten the initial clinical suspicion. This is illustrated in the following report on a case of proven pulmonary embolism complicated with cardiac arrest and prolonged shock. The electrocardiographic presentation was suggestive of an extensive acute myocardial infarction, a pattern which to our knowledge never has been reported on. However, many elements of it pointed to the diagnosis of pulmonary embolism. The multifactorial origin of the ECG findings is discussed.

Acute Disease↗
PubMed1997

Use of only a regular diagnostic His-bundle catheter for both fast and reproducible "para-Hisian pacing" and stable right ventricular pacing.

INTRODUCTION: Para-Hisian pacing, i.e., pacing the anteroseptal right ventricle (RV) with or without direct capture of the His bundle (HB), allows the differentiation of VA conduction over the AV node from conduction over an accessory pathway. Classically, it is performed by maneuvering a separate pacing catheter around the HB catheter, which may be difficult and time-consuming. METHODS AND RESULTS: This study prospectively evaluated the use of a single standard octapolar HB catheter with 2-mm interelectrode spacing for simultaneous (para-Hisian) pacing from the distal bipole and recording from the three proximal bipoles in 148 consecutive patients. Para-Hisian pacing was successful in 146 of 148 patients, performed within a median of only 10 seconds, and easily repeated several times during the course of an electrophysiologic study. Retrograde HB activation could be recorded in 132 of 146 patients; a clearly different surface ECG configuration confirmed the presence or absence of HB capture in all other patients. Interestingly, stable RV pacing could be performed from the HB catheter for the rest of the electrophysiologic study in 138 of 142 patients in whom this was tried. RV pacing from this site also led to better interpretation of retrograde conduction, due to clear visualization of retrograde HB activation. CONCLUSION: Pacing from the distal bipole of a regular diagnostic HB catheter provides a fast and reliable way to perform para-Hisian pacing. Therefore, it may be advocated as a routine diagnostic protocol during electrophysiologic procedures. Moreover, pacing from this site obviates the need for a separate RV pacing catheter in most patients.

Adolescent↗
PubMed1996

Survival analysis and clinical medicine. An observational comparison of the implantable cardioverter defibrillator, amiodarone treatment, and heart transplantation.

In clinical practice, observational studies remain necessary for evaluating accepted and new treatments. The comparison of results remains difficult and often controversial, because of a wide variation in clinical characteristics. Survival analysis and calculation of the standardized mortality ratio offer the possibility to compare outcomes in different study groups. We have applied these techniques to an observational comparison of outcomes in three groups of patients, followed in two university centres: (i) patients treated with an implantable cardioverter defibrillator; (ii) patients under amiodarone treatment; and (iii) recipients of a heart transplant. There was no statistically significant difference in the cumulative survival from total mortality. The standardized mortality ratio revealed the different natural history of patients undergoing heart transplantation.

Age Distribution↗
PubMed1996

Heart rate variability after cardiac transplantation in humans.

The reappearance of cardiac innervation after cardiac transplantation remains a matter of debate. We evaluated the ability of heart rate variability (HRV) analysis to detect the extent and time course of functional cardiac allograft reinnervation. Time- and frequency-domain analysis of heart rate was performed on Holter recordings of 120 heart transplant and four heart-lung transplant recipients. A high frequency (HF) component was clearly distinguished on visual inspection of power spectral density in 42 patients. In eight patients an HF component of normal magnitude was detected. The other 34 patients in this group, including all four heart-lung transplants, presented with a very small HF component. The other 82 patients showed a flat spectrum. The group with an HF component of normal amplitude was significantly different, compared to the other groups, for all HRV parameters. Serial plotting of HRV parameters of the patients with an HF component of normal amplitude against time posttransplant, revealed, from 12 months onwards, a progressive increase of parameters denoting HF variability. In five heart transplant patients with acute allograft rejection, the use of HRV analysis for rejection monitoring was unsuccessful. These results suggest that, inasmuch as the HF component of HRV is caused by parasympathetic cardiac innervation, the HF component of normal amplitude, observed in only a minority of cardiac transplant recipients (6%), is a marker for parasympathetic reinnervation. The evolution over time of this HF component is compatible with a biological phenomenon as gradual parasympathetic reinnervation of the sinus node.

Autonomic Nervous System↗
PubMed1995

Review of the reviewer.

Reviewers can disagree substantially when evaluating the same materials. For papers submitted to an editorial board, the Editor-in-Chief can suggest compromises. However, this is not the case in the normal abstract grading procedures for large meetings. If important discrepancies arise between reviewers, a review committee may propose corrective measures. However, this is only feasible for smaller meetings with a limited number of abstract submissions. In this study, when reviewing the same abstracts, a statistically significant correlation between reviewers was present in 15 instances and absent in 13 others. It would appear that some review of the reviewer is highly desirable and may prevent publication bias.

Abstracting and Indexing↗
PubMed1994

Automatic detection of ventricular tachycardia and fibrillation using ECG processing and intramyocardial pressure measurement.

Ventricular electrograms and intramyocardial pressure signals were recorded in 11 dogs during sinus rhythm, during paced ventricular tachycardia, and at the onset of and during ventricular fibrillation. The autocorrelation function and the probability density function of short episodes of the electrograms were analyzed off-line on a digital computer. Peak-to-peak values of the intramyocardial pressure were calculated during sinus rhythm and during ventricular tachycardia and fibrillation. An algorithm was developed to recognize tachycardia and fibrillation using the autocorrelation function, the probability density function, and the intramyocardial pressure as input signals. Results show that in case of sinus rhythm all detection methods are reliable (recognition rate of 100%). In case of ventricular tachycardia with hemodynamic impairment the autocorrelation function is slightly better (66.6%) than the probability density function (44.4%). The onset of ventricular fibrillation is sensed in 81.8% of all episodes with the autocorrelation function and in 63.6% with the probability density function. During ventricular fibrillation this improves, respectively, to 92.3 and 69.2%. In all previous cases the intramyocardial pressure signal was 100% reliable. It is concluded that in this arrhythmia model, the sensitivity of an automatic ventricular tachycardia/fibrillation detection system was increased by combining ECG processing with analysis of an hemodynamic parameter.

Algorithms↗
PubMed1994

Signal-averaged ECG parameters in cardiac normals using Frank lead system and Fourier transform filter and gender specific differences: a multicenter study.

There is only limited data on normal reference values for signal-averaged electrocardiograms (SAECGs) using Frank leads and fast Fourier transform filter (FFT). Furthermore, the influence of gender on reference values and their relation to body characteristics was only the subject of a few studies on small series of normals. One hundred eighty-five cardiac normals (85 women and 100 men) were examined in this multicenter study. The obtained SAECG values (mean +/- standard deviation) are as follows: filtered QRS duration (FQRSD) = 108.6 +/- 7.5 msec; low amplitude signal duration < 40 microV (LASD) = 30.4 +/- 8.4 msec; and root mean square voltage in the terminal 40 msec (RMSV) = 43.5 +/- 20.6 microV. Between men and women, significant differences were found in FQRSD (111.7 +/- 6.5 vs 105.0 +/- 7.0 msec, P < 0.001) and in RMSV (38.6 +/- 17.4 vs 49.4 +/- 22.7 microV, P < 0.001). No difference was observed for LASD. After normalizing the three SAECG parameters for body characteristics, FQRSD normalized for height was the only variable where gender differences were eliminated. For FQRSD and LASD the 90th percentile and for RMSV the 10th percentile are proposed as cut-off values. Only for the 90th percentile of FQRSD a clear difference between men and women was observed. The following gender specific normal values for SAECG, at 40-Hz high pass filtering, using Frank leads and an FFT filter are proposed: for males, FQRSD < 122 msec; for females, FQRSD < 115 msec; for both genders, LASD < 41 msec and RMSV > 20 microV.

Action Potentials↗
PubMed1994

Significance of arrhythmias during the first 24 hours of acute myocardial infarction treated with alteplase and effect of early administration of a beta-blocker or a bradycardiac agent on their incidence.

BACKGROUND: Although early intravenous beta-blocker therapy during acute myocardial infarction (AMI) reduces the incidence of fatal arrhythmias in patients not treated with thrombolytic agents, its antiarrhythmic effect in thrombolysed patients remains controversial. We investigated prospectively the arrhythmia incidence in 244 patients with AMI receiving alteplase and a double-blind randomized adjunctive therapy with intravenous atenolol, alinidine, or placebo. Moreover, the characteristics and prognostic significance of early arrhythmias and their relation with infarct size and coronary patency were evaluated. METHODS AND RESULTS: All patients underwent 24-hour Holter monitoring on day 1 and were clinically followed in the hospital for 10 to 14 days. Coronary angiography was performed on day 10 to 14. Atenolol and alinidine significantly decreased the basic heart rate without causing more sinus arrest or higher-degree atrioventricular block. The prevalence of atrial fibrillation in alinidine patients was lower than in the atenolol patients (P = .007) but not lower than in placebo patients (P = .11). There was no effect of either agent on the incidence and frequency distribution of ventricular or supraventricular premature beats or on the incidence and characteristics of nonsustained ventricular tachycardia, accelerated idioventricular rhythm, sustained ventricular tachycardia (VT), or ventricular fibrillation (VF). On day 1, seven VF episodes were recorded in six patients (2.5%) and five VT episodes in five patients (2%). VF always started at < 2.5 hours after start of thrombolytic treatment and VT always at > 2.5 hours (average of 6 hours). Five of the seven VF and three of the five VT episodes started with an R-on-T. However, for all VT, the morphology of the first beat was the same as that of the following beats, suggesting that the sustained arrhythmia was not induced by an extrasystole. After day 1 and before hospital discharge, VF and VT developed in one and six patients, respectively. Three of the seven patients who developed VF during the first 2 weeks underwent coronary angiography; all three had an occluded infarct-related artery. In contrast, only one of nine patients with early or late VT had an occluded vessel. Patients with VT and VF on day 1 had a significantly larger enzymatic infarct size than those without the arrhythmia (P = .02), and a similar trend was noted for VT or VF after day 1 (P = .19). However, none of the patients with VT or VF on day 1 developed a life-threatening arrhythmia later during the hospital stay. Also, none of the seven patients with VT or VF after day 1 had experienced a major rhythm disturbance during the first 24 hours. CONCLUSIONS: (1) Our data do not support the hypothesis that beta-blockers or bradycardiac agents might reduce the incidence of major arrhythmias when used in conjunction with thrombolytic therapy. (2) The pathogeneses of VT and VF early during AMI are clearly distinct. (3) VT or VF during the first 2 weeks is a marker for a larger infarct. (4) We could not detect a relation between malignant arrhythmias on day 1 and recurrences within the following 2 weeks.

Anti-Arrhythmia Agents↗
PubMed1993

Classification of death in patients under antiarrhythmic treatment.

In the evaluation of antiarrhythmic treatment, total mortality and total cardiac mortality are the only endpoints difficult to misclassify. End-stage cardiac failure competes with "suddenness" in many instances of sudden arrhythmic death. This observational study reports on 23 deaths in a group of 129 patients under antiarrhythmic treatment. In the 21 cases of cardiac death, with respect to the notion "sudden arrhythmic death," classification was problematic in 6 patients. According to different interpretations, the number of deaths listed as "sudden" could vary between one and six. A concise description of cause and circumstances of death, is presented.

Aged↗
PubMed1993

Clinical aspects during long-term follow-up after DC shock ablation of the atrioventricular junction. A Belgian experience.

Ninety-three patients, who underwent DC shock ablation were reviewed over a mean follow-up period of 54 months (range 3 to 84 months). These patients (46 male and 47 female, mean age: 58 years) had failed an average of 3 drugs, and the duration of symptoms was more than 2 years. Paroxysmal atrial fibrillation or flutter was treated in 75 patients (80.6%); the remainder had supraventricular tachycardia or reciprocating tachycardia using an accessory pathway. One shock of 200 J was effective in producing third degree AV block in 40 patients (43%), while 2 or more shocks were used in another 53 patients (57%). Chronic complete heart block (CHB) was obtained in 85 patients (91%), modification of conduction was seen in 2 patients (2.1%), and failure to achieve an improvement in 6 patients (6.4). All the patients of the last group had received more than 4 shocks (200 to 400 J). However no significant difference between the amplitude of atrial and His electrograms could be shown between the CHB patients and those in whom conduction persisted. Over a mean follow-up of 54 months, 66 patients (72%) with successful ablation during the first 48 hours after the procedure remained in CHB. In 18 patients AV conduction resumed but they were all asymptomatic: 10 patients (10.8%) without antiarrhythmic therapy and 8 patients (8.6%) with medication. In conclusion, ablation of the AV junction is effective in more than 82% of patients. Most of the time long-term success can be predicted within 48 hours. However, due to the invasive character of DC shocks, this technique has been supplanted by the less aggressive radiofrequency method.

Adult↗