Biomedical subjects

N Edvardsson

Publications and source records attributed to N Edvardsson.

At least 19 recordsLinked to original sources

PubMed2004

Sinus rhythm maintenance following DC cardioversion of atrial fibrillation is not improved by temporary precardioversion treatment with oral verapamil.

OBJECTIVE: To evaluate prospectively the effects of pretreatment with verapamil on the maintenance of sinus rhythm after direct current (DC) cardioversion. DESIGN: Randomised, active control, open label, parallel group comparison of verapamil versus digoxin. SETTINGS: Multicentre study in three teaching and three non-teaching hospitals in Sweden. PATIENTS: 100 consecutive patients with atrial fibrillation (AF) of at least four weeks' duration and indications for cardioversion were assigned randomly to two groups, one treated with verapamil (verapamil group) and the other with digoxin (digoxin group) before cardioversion. Fifty patients were assigned randomly to each treatment arm. After dropout of four patients from the digoxin group and seven patients from the verapamil group, data obtained from 89 patients were analysed. INTERVENTIONS: After randomly assigned pretreatment with either verapamil or digoxin for four weeks, DC cardioversion was performed. If sinus rhythm was restored then verapamil treatment was discontinued. MAIN OUTCOME MEASURES: The rate of AF recurrence was assessed one, four, eight, and 12 weeks after cardioversion. RESULTS: 6 patients in the verapamil treated group and none in the digoxin treated group reverted to sinus rhythm spontaneously (p < 0.05). DC cardioversion restored sinus rhythm in 24 of 37 (65%) patients in the verapamil group and 41 of 46 patients (89%) in the digoxin group (p < 0.05). After 12 weeks' follow up 28% (13 of 46) of digoxin pretreated patients versus 9% (four of 43) of verapamil pretreated patients remained in sinus rhythm (p < 0.05). CONCLUSION: Pretreatment with verapamil alone does not improve maintenance of sinus rhythm after DC cardioversion in patients with AF. The rate of spontaneous cardioversion may be improved by verapamil.

Administration, Oral↗

PubMed2003

Effects of low-dose warfarin and aspirin versus no treatment on stroke in a medium-risk patient population with atrial fibrillation.

OBJECTIVES: To assess the optimal stroke prevention treatment for patients with atrial fibrillation (AF) and a low-medium risk (< or =4%) of stroke. DESIGN: A total of 668 patients with persistent or permanent AF, without an indication for full dose and with adequate rate control on sotalol, were randomized to warfarin 1.25 mg + aspirin 75 mg daily (W/A, 334 patients) or no anticoagulation (C, 334 patients). The mean follow-up period was 33 months. The protocol intended to verify a 37% relative risk reduction provided a 4% stroke incidence in the C group. RESULTS: The stroke incidence was less in the W/A group, although the reduction was not statistically significant (W/A 9.6% versus C 12.3%). Four haemorrhagic strokes were identified, two in each group. Secondary end-points were transient ischaemic attacks (TIA) (W/A 3.3% versus C 4.5%), all cause mortality (W/A 9.3% versus C 10.8%), cardiovascular morbidity (W/A 17.7% versus C 22.2%) and the combination of stroke + TIA (W/A 11.7% versus C 16.5%). Bleedings were documented in 19 versus four patients (W/A 5.7% versus C 1.2%) (P = 0.003), although none fatal. Sinus rhythm (SR) was recorded occasionally in 68 patients (W/A 9.6% versus C 10.8%). The stroke incidence tended to be higher in those with SR than without, 16.2% versus 10.4%. CONCLUSIONS: Our results were inconclusive, but consistent with a small beneficial effect of W/A for reduction of stroke and major vascular events in AF patients at moderate risk. The low-dose regiment produced, however, a significantly increased risk of bleedings. Documented SR occasionally recorded may represent a subpopulation that warrants full dose warfarin.

Aged↗

PubMed2003

Heart failure in an elite soccer player.

The following case illustrates several important features: firstly, the occurrence of tachycardia-induced cardiomyopathy during sustained atrial tachycardia at a relatively modest heart rate of 130 beats per minute, in an elite athlete. Secondly, tachycardia may induce severe and occasionally life-threatening impairment of the systolic ventricular function without a history of palpitations. Finally, our patient is an excellent example of the complete recovery that may follow successful radiofrequency catheter ablation, performed promptly once the correct diagnosis has been confirmed.

Adolescent↗

PubMed2002

Episodes of atrial fibrillation and atrial vulnerability after successful radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome.

UNLABELLED: Episodes of atrial fibrillation occur in patients with WPW syndrome but frequently disappear after successful radiofrequency ablation. AIMS: To analyze the incidence of atrial fibrillation before and after successful ablation and the presence of increased atrial vulnerability. METHODS AND RESULTS: Fifty-four of 183 WPW patients had at least one documented episode of atrial fibrillation before ablation. During a follow-up of 24 +/- 12 months 13/54 patients (24%) experienced atrial fibrillation. At baseline, the patients with atrial fibrillation were more often men (74%) vs 53%, P=0.007), were older (45 +/- 15 vs 34 +/- 16 years, P=0.0001), more often had pre-excitation during sinus rhythm (87% vs, 73%, P=0.04) and had increased atrial vulnerability (41%, vs 18%, P<0.001). Only patients with atrial fibrillation before, developed atrial fibrillation after ablation. The 13 (of 54) patients who relapsed were also older (53 +/- 13 vs 42 +/- 15 years, P= 0.03), had increased atrial vulnerability at baseline (77% vs 29%, P=0.002), and were more symptomatic, (13 +/- 21 vs 1 +/- 3 arrhythmia attacks/month, P=0001). No patient without atrial fibrillation before ablation developed atrial fibrillation after treatment. CONCLUSIONS: The accessory pathway was important for the development of atrial fibrillation. Frequent tachycardias seem to promote an electrical remodelling and an increased atrial vulnerability to atrial fibrillation, whereas after successful ablation the majority of patients remain free of atrial fibrillation.

Adolescent↗

PubMed2001

Life situation of patients with an implantable cardioverter defibrillator: a descriptive longitudinal study.

The aim of this study was to describe changes in the life situation of patients with an implantable cardioverter defibrillator over a period of 1 year. A sample of 56 consecutive patients took part in the study. Life situation was measured through uncertainty in illness, satisfaction, and fear of the life situation. Descriptive statistics were used to present results, and analytical statistics were used to map out changes over time. Overall uncertainty showed a decrease over time. A statistically significant difference was found within the domain uncertainty related to information (P < 0.001). Satisfaction increased within the domains health-functioning, socio-economic, psychological-spiritual, and family. The ability to act within the domain health-functioning showed a statistical significance (P < 0.05). The domain life changes within fear in the life situation decreased and showed a statistical significance (P < 0.05). The overall life situation showed increased satisfaction as well as lower uncertainty and fear in the life situation. The research indicates that patients need more information about changes in the life situation after the implantable cardioverter defibrillator-implantation. The study encourages more humanistic, holistic research about patients' life situations as well as more education in teaching skills for health care personnel.

Activities of Daily Living↗

PubMed2001

Bidirectional defibrillation using implantable defibrillators: a prospective randomized comparison between pectoral and abdominal active generators.

The objective of this study was to compare the effects of active abdominal and pectoral generator positions on DFTs in a bidirectional tripolar ICD system. Twenty-five consecutive patients had ICD systems implanted under general anesthesia. A transvenous single lead bipolar defibrillation system and an active 57-cc test emulator in the abdominal and pectoral positions were used in the same patient. A randomized, alternating step-down protocol was used starting at 15 J with 3-J decrements until failure. The mean implantation time was 114 +/- 23 minutes, the mean arrhythmia duration was 14.5 +/- 1.5 seconds, and the mean recovery time was 5.4 +/- 1.1 minutes. The mean DFTs in the abdominal and pectoral positions were 10.9 +/- 5.1 and 9.7 +/- 5.2 J, respectively (NS), the mean intraindividual DFT difference (abdominal minus pectoral) was -0.89 +/- 4.15 J (range -9.5 to 8 J). The 95% confidence interval showed a -2.60 to +0.82 J mean difference (NS). The DFT was < 15 J in 72% and 88% of the patients and the defibrillation impedance was 41 +/- 3 and 44 +/- 3 omega, abdominal versus pectoral positions. There was no difference in DFT between active abdominal and pectoral generator bidirectional tripolar defibrillation. The pectoral position may be considered the primary option, but in cases of high DFTs the abdominal site should be considered an alternative to adding a subcutaneous patch. In some patients, the anatomy may favor an abdominal position. Possible differences in the long-term functionality on the leads are not yet well known and need to be further evaluated.

Aged↗

PubMed2001

Perception and documentation of arrhythmias after successful radiofrequency catheter ablation of accessory pathways.

BACKGROUND: Some patients continue to have palpitations in spite of successful ablation of Wolff-Parkinson-White (WPW) syndrome. Recurrence of accessory pathways as well as unrelated arrhythmias may explain the symptoms. METHODS: We followed 194 consecutive patients after successful radiofrequency catheter ablation of overt (147) or concealed (47) WPW syndrome. The mean duration of symptoms was 16 +/- 13 years. Atrial fibrillation was documented in 54 patients (24%) prior to ablation. 185 patients responded to a questionnaire 24 +/- 12 months after ablation. RESULTS: The physical well-being was improved in 94%, unchanged in 5%, and deteriorated in 1%. However, 76 patients (39%) reported arrhythmia symptoms, in 40 patients causing pharmacological treatment (14 patients) and/or continued contact with their doctor. The underlying arrhythmias were orthodromic tachycardia (10), atrial fibrillation (12), premature beats (12), atrial flutter (1), and ventricular tachycardia (1), while in four patients no explanation was found. Minor symptoms in the other 36 patients were explained by premature beats in 29, while unexplained in 7. All patients with atrial fibrillation after ablation had atrial fibrillation before ablation. Ten relapses of WPW syndrome occurred: eight were known before the time of the questionnaire, two were confirmed at transesophageal atrial stimulation. CONCLUSION: 94% patients with a long history of tachyarrhythmias due to the WPW syndrome reported improved physical well-being after ablation, but palpitations were common during a 2-year follow-up period; 8% continued to use pharmacological antiarrhythmic treatment. Five percent had symptomatic relapses and in 6% atrial fibrillation episodes reoccurred, i.e., in half of those who had atrial fibrillation before ablation.

Adolescent↗

PubMed2000

The short-term and long-term reproducibility of spectral turbulence and late potential variables of the signal-averaged ECG in a population sample of healthy subjects and the impact of gender, age, and noise.

Previous methods for frequency domain analysis of the signal-averaged ECG (SAECG) have had low reproducibility. The reproducibility of time domain late potential analysis and spectral turbulence analysis was evaluated with 2 immediately consecutive SAECG recordings in 121 randomly selected subjects without heart disease (short-term) and also in 47 subjects after 1 month (long-term). A test was late potential positive if 2 or more of 3 variables were outside the reference limits and spectral turbulence positive if the score was 3 or 4. The short-term reproducibility was high for the filtered QRS duration (FQRSD), root mean square amplitude of the last 40 ms (RMS40) and high frequency low amplitude signals less than 40 microV (HFLAS40) of the time domain and total QRS duration (TQRSD), power spectral density of the last 40 ms and the late potential duration of time domain analogous analyses. The Spearman rank order correlation coefficients were 0.89, 0.88, and 0.84 and 0.97, 0.91 and 0.97, respectively. The reproducibility of the spectral score variables varied, and the correlation for the low slice correlation ratio was 0.71, spectral entropy 0.61, interslice correlation mean 0.58, and interslice correlation SD 0.28. A diagnostic inconsistency between 2 tests occurred in 0 (0%) subjects in late potential analysis if FQRSD was required for positivity, and in 7 (6%) otherwise, and in 9 (7%) of spectral turbulence analysis. If the spectral variable mean peaks per slice, with a correlation of 0.89, replaced interslice correlation SD in the spectral score, diagnostic inconsistency occurred in 0 (0%) subjects. The reproducibility seemed higher in women and in younger people but significantly only for interslice correlation subjects mean and HFLAS40. The long-term reproducibility did not differ significantly from short-term for any variable. In conclusion, the reproducibility was high in all time domain and time domain analogous variables. It varied among the spectral turbulence score variables and was very low for interslice correlation SD. The reproducibility of the spectral score improved substantially if this variable was replaced by mean peaks per slice.

Adult↗

PubMed2000

Comparison of QT dispersion during atrial fibrillation and sinus rhythm in the same patients, at normal and prolonged ventricular repolarization.

AIMS: Drug-induced increase in QT dispersion has been associated with increased risk of ventricular proarrhythmia. The aim of the present study was to compare QT dispersion during atrial fibrillation and sinus rhythm in the same patients at normal and prolonged ventricular repolarization. METHODS AND RESULTS: Sixty-one patients who had had chronic atrial fibrillation for 8 +/- 14 months received a 6 h infusion of the Ikr-blocker almokalant, the first 90 min of which are used for this analysis. The following day, after conversion to sinus rhythm, by almokalant (n = 19) or direct current cardioversion (n=42), an identical 90 min infusion was administered. Prior to infusion, there was no difference in precordial QT dispersion between atrial fibrillation and sinus rhythm (29 +/- 12 vs 36 +/- 17 ms, P=ns). During infusion, at prolonged repolarization, the increase in QT dispersion was greater during sinus rhythm than during atrial fibrillation (58 +/- 49 vs 30 +/- 15 ms, P=0.0011, after 30 min infusion). No correlation was found between QT dispersion and the QT or RR interval. CONCLUSION: QT dispersion during atrial fibrillation does not differ from QT dispersion during sinus rhythm during normal repolarization. while measurement of QT dispersion during prolonged repolarization, induced by an Ikr-blocker, yielded larger values during sinus rhythm than during atrial fibrillation.

Action Potentials↗

PubMed2000

Spectral turbulence and late potentials in the signal-averaged electrocardiograms of patients with monomorphic ventricular tachycardia versus resuscitated ventricular fibrillation.

Signal-averaged electrocardiograms (SAECG) were analyzed for late potentials and spectral turbulence in 208 patients with ischemic heart disease with a history of sustained monomorphic ventricular tachycardia (MVT) (n = 62), resuscitation from ventricular fibrillation (VF) (n = 64) or no ventricular tachyarrhythmia (n = 82). Receiver operating characteristic curves were utilized to optimize cut-off values for prediction of MVT and VF. Patients with MVT had a lower ejection fraction (mean = 0.37) than patients with VF (0.44; p = 0.01) and controls (0.48; p < 0.0001). The mean FQRSD in MVT patients (126 ms) was longer than in VF and controls (113 ms; p = 0.005 and 102 ms; p < 0.0001, respectively). The RMS40 was lower in MVT (19 microV) than in VF and controls (29 microV; p = 0.0003 and 28 microV; p < 0.0001, respectively); 81% of the MVT patients were spectral turbulence-positive vs 47% of VF patients and 31% of control patients (p < 0.0001 for both differences). With optimized reference values, FQRSD, TQRSD and ISCSD contributed significantly to the identification of MVT patients and FQRSD to VF patients. The sensitivity of combined time-domain and spectral turbulence analysis was 90% for MVT and 58% for VF, with 63% specificity. MVT patients had a lower ejection fraction and were more often late potential and spectral turbulence positive than VF and control patients. These findings indicate that a large electroanatomic substrate is required in MVT. A long FQRSD was a risk marker for both MVT and VF. Spectral turbulence analysis added independent information, and the combination of time-domain and spectral turbulence analysis was superior to either method alone in identifying the MVT patients. Neither method of analysis, singly nor in combination, performed satisfactorily in identification of VF risk.

Aged↗

PubMed2000

Sensing of atrial fibrillation by a dual chamber pacemaker: how should atrial sensing be programmed to ensure adequate mode shifting?

Patients with atrial fibrillation and a DDDR pacemaker were studied to assess mode switching at different atrial sensitivity settings. Thirty-one patients were investigated 7 +/- 9 months after pacemaker implantation and 20 of those patients were reinvestigated 23 +/- 9 months after implant. Adequate mode switching was evaluated by stepwise programming the atrial sensitivity setting from maximal to minimal in the bipolar mode. Adequate mode switching was observed in all 31 patients during the first evaluation. The lowermost sensitivity average allowing for mode switching was 1.1 +/- 0.7 mV (range 0.3-4.0 mV). A total of 22 (71%) patients demonstrated intermittent mode shifting at sensitivity settings above the atrial sensing threshold. In six (19%) patients, the adequate sensitivity threshold ranged from 0.3 to 0.5 mV, which did not allow for a two-fold sensitivity safety margin. During the second evaluation, adequate mode switching was achieved in all 20 patients, the lowermost sensitivity average allowing for mode switching being 1.1 +/- 0.7 mV (range 0.3-2.0 mV). A total of 16 (80%) patients showed intermittent mode shifting at a sensitivity setting above the atrial sensing threshold. In five (25%) patients, the sensitivity threshold ranged from 0.3 to 0.5 mV, which did not allow for a two-fold sensitivity safety margin. Adequate mode switching was achieved in 31 of 31 patients in response to atrial fibrillation on one occasion and in all 20 patients on two occasions. It was necessary to program the atrial sensitivity to the highest possible level (0.3 mV) to ensured adequate mode switching in all cases.

Aged↗

PubMed1999

Atrial fibrillation detection and R-wave synchronization by Metrix implantable atrial defibrillator: implications for long-term efficacy and safety. The Metrix Investigators.

BACKGROUND: The long-term efficacy of atrial fibrillation (AF) detection and R-wave synchronization are critical safety requirements for the development of an implantable atrial defibrillator (IAD) for treatment of AF. METHODS AND RESULTS: The long-term efficacy of the Metrix IAD for AF detection and R-wave synchronization was tested in 51 patients. The mean duration of follow-up was 259+/-138 days (72 to 613 days). AF detection tests were performed 2240 times during observed operation with 100% specificity and 92.3% sensitivity for differentiation between sinus rhythm and AF; 2219 episodes and their electrograms stored in the device during AF detection were analyzed. The positive predictive value of the AF detection algorithm was 97.4% (lower 95% confidence limit [CL], 94.5%) in the out-of-hospital setting. A total of 242 435 R waves were analyzed for R-wave synchronization. Of these, 49% were marked for synchronized shock delivery, 82% of sinus rhythm and 36% of AF R waves, respectively. All shock markers were properly synchronized and within the R wave (overall synchronization accuracy, 100%; lower 95% CL, 99.999%). Overall, 3719 shocks have been delivered via the IAD with no instance of unsynchronized shock delivery or any episode of proarrhythmia. The observed proarrhythmic risk was 0%, with an estimated maximum proarrhythmic risk of 0.084% per shock (95% upper CL). CONCLUSIONS: The Metrix IAD can appropriately detect AF with a high specificity and sensitivity and reliably synchronize within a suitable R wave for shock delivery to minimize the risk of ventricular proarrhythmia.

Aged↗

PubMed1999

Effects of digoxin on electrocardiogram in patients with acute atrial fibrillation--a randomized, placebo-controlled study. Digitalis in Acute Atrial Fibrillation (DAAF) Trial Group.

BACKGROUND: Studies of healthy volunteers or patients in sinus rhythm have indicated that treatment with digoxin produces characteristic changes in the electrocardiogram (ECG). No randomized, placebo-controlled studies are available and no study has investigated the effect on ECG in patients with atrial fibrillation. HYPOTHESIS: In a substudy to a trial comparing the therapeutic effect of intravenously administered digoxin with placebo in patients with acute atrial fibrillation, we investigated these effects as well as the relation between ECG changes and serum concentration of digoxin. METHODS: In all, 167 patients were included. Standard ECGs recorded at baseline, and at 2, 6, 12, and 16 h after randomization were digitized, and changes in RR-intervals, QRS width, ST-segment amplitude at 60 ms after the J point, T-wave amplitude, and QTc interval were calculated. Furthermore, the correlation between the serum concentration of digoxin at 16 h after inclusion and changes on the ECG was analyzed. RESULTS: Compared with placebo, digoxin resulted in an increase in RR-interval (p < 0.0001), a decrease in ST-segment and T-wave amplitude (p = 0.009 and p = 0.002, respectively), and in the QTc interval (p = 0.01). These changes were present 2 h after the first dose, but were more pronounced after 16 h. There was no significant correlation between serum concentration of digoxin and ECG changes at 16 h. CONCLUSION: Compared with placebo, digoxin produces significant changes on ECG in patients with acute atrial fibrillation. The changes are in accordance with previous findings in individuals in sinus rhythm. There was no correlation between serum concentration of digoxin and ECG changes.

Acute Disease↗

PubMed1999

Effects of the Ikr-blocker almokalant and predictors of conversion of chronic atrial tachyarrhythmias to sinus rhythm. A prospective study.

PURPOSE: To assess the efficacy of the Ikr-blocker almokalant attempting to convert chronic atrial tachyarrhythmias, and to find predictors of conversion, to sinus rhythm. METHODS: The electrophysiological effects of a 6-hour infusion of almokalant, to a total dose of 25 +/- 4 mg, were assessed by ECG and transesophageal atrial electrograms (TAE) in 100 consecutive patients with atrial fibrillation/flutter (n = 95/5) of 8 +/- 12 months' duration (range 1 to 99 months). RESULTS: The conversion rate was 32%. The time to conversion was 3.5 +/- 2.2 hours. During infusion increases in QTtop (292 +/- 35 to 335 +/- 44 ms, p < 0.001, after 30 minutes), QT (387 +/- 40 to 446 +/- 60 ms, p < 0.001), corrected QT (425 +/- 30 to 487 +/- 44 ms, p < 0.001), and QT dispersion (21 +/- 12 to 29 +/- 31 ms, p = 0.02), were paralleled by decreases in T wave amplitude (0.31 +/- 0.19 to 0.23 +/- 0.16 mV, p < 0.001), and atrial rate (425 +/- 78 to 284 +/- 44 beats per minute (bpm) on ECG, and 396 +/- 72 to 309 +/- 44 bpm on TAE), with no differences between converters to sinus rhythm and non-converters. Patients with aberrantly conducted beats, and T wave variation, also increased. Calcium antagonists were more common among converters. A decreasing T wave amplitude predicted conversion. Four patients developed torsades de pointes. CONCLUSIONS: This study demonstrates class III action of almokalant, with a conversion rate of 32% of long-standing, chronic atrial tachyarrhytmias. An early decrease in T wave amplitude was associated with conversion to sinus rhythm.

Aged↗

PubMed1999

Acute ischemic chest pain is not associated with increased calcitonin gene-related peptide (CGRP) levels in peripheral plasma nor in the coronary circulation.

Calcitonin gene-related peptide (CGRP) and substance P co-exist in capsaicin-sensitive primary sensory neurons and are released from the myocardium after activation of sensory nerve fibres as well as by ischemia in animals. This study was undertaken to try to clarify the potential involvement of immunoreactive (ir) CGRP in anginal pain and myocardial ischemia in humans. One clinical group (n = 87) and one experimental group (n = 14) were studied. The clinical group was admitted to a coronary care unit with suspected or definite acute myocardial infarction (AMI). The experimental group consisted of patients with severe angina pectoris (NYHA III-IV). This group was subjected to atrial pacing up to the appearance of angina pectoris. Mean irCGRP levels at admission for the clinical group with and without AMI showed no significant difference. Neither were any significant differences found in irCGRP concentrations between patients with pain as compared to those without pain or in the group who had had chest pain >30 min before hospital admission as compared to those with chest pain <30 min. Extraction ratios for lactate and irCGRP was calculated in the experimental group. No statistically significant covariance was found between irCGRP extraction ratio and lactate extraction ratio (r(xy) = -0.006) at the time of appearance of angina during atrial pacing. Despite the facts that CGRP may be liberated by a variety of physiological stimuli and may act as a potent vasodilator in the human vasculature, no evidence has been found in this study that CGRP release is increased as a consequence of ischemia or ischemic pain.

Aged↗

PubMed1998

Electrocardiographic and clinical predictors of torsades de pointes induced by almokalant infusion in patients with chronic atrial fibrillation or flutter: a prospective study.

The aim of this study was to identify predictors of torsades de pointes (TdP) in patients with atrial fibrillation (AF) or flutter exposed to the Class III antiarrhythmic drug almokalant. TdP can be caused by drugs that prolong myocardial repolarization. One hundred patients received almokalant infusion during AF (infusion 1) and 62 of the patients during sinus rhythm (SR) on the following day (infusion 2). Thirty-two patients converted to SR. Six patients developed TdP. During AF, T wave alternans was more common prior to infusion (baseline) in patients developing TdP (50% vs 4%, P < 0.01). After 30 minutes of infusion 1, the TdP patients exhibited a longer QT interval (493 +/- 114 vs 443 +/- 54 ms [mean +/- SD], P < 0.01), a larger precordial QT dispersion (50 +/- 74 vs 27 +/- 26 ms, P < 0.05), and a lower T wave amplitude (0.12 +/- 0.21 vs 0.24 +/- 0.16 mV, P < 0.01). After 30 minutes of infusion 2, they exhibited a longer QT interval (672 +/- 26 vs 489 +/- 74 ms, P < 0.001), a larger QT dispersion in precordial (82 +/- 7 vs 54 +/- 52 ms, P < 0.01) and extremity leads (163 +/- 0 vs 40 +/- 34 ms, P < 0.001), and T wave alternans was more common (100% vs 0%, P < 0.001). Risk factors for development of TdP were at baseline: female gender, ventricular extrasystoles, and treatment with diuretics; and, after 30 minutes of infusion: sequential bilateral bundle branch block, ventricular extrasystoles in bigeminy, and a biphasic T wave. Patients developing TdP exhibited early during almokalant infusion a pronounced QT prolongation, increased QT dispersion, and marked morphological T wave changes.

Aged↗

PubMed1998

Full ventricular capture indicated by the QT interval function.

UNLABELLED: The atrioventricular (AV) interval is critical in dual chamber (DDD) pacing in patients with hypertrophic obstructive cardiomyopathy (HOCM) to obtain full ventricular capture (FVC) with maximal reduction of the left ventricular (LV) outflow gradient and optimal LV diastolic filling. We studied the relationship of FVC, fusion, spontaneous AV conduction, and the QT interval. METHODS: 11 patients with various cardiac diseases and stable AV conduction received a QT sensing Diamond, Vitatron, DDD pacemaker. Software was downloaded into the pacemaker. In the DDD pacing mode, with the QT interval measured from the ventricular pacing stimulus to the end of the T wave, the AV interval was shortened from 400 ms, in 20-ms steps, to 90 ms. At 90 ms the stimulation rate was increased by 30 beats/min and the AV interval was increased stepwise. FVC and fusion was examined on the surface ECG. RESULTS: At 400 ms interval, spontaneous AV conduction inhibited the pacemaker. Shortening the AV interval resulted in pacing with a short QT interval. Further reduction of the AV interval resulted in a longer QT interval up to a point where the QT interval became stable. This point, the bending point in the plot of measured QT interval versus shortened AV intervals, coincided with the point of FVC. The relation of the QT-AV interval plot and the point of fusion was comparable when lengthening the AV interval at a 30 beats/min faster stimulation rate. CONCLUSION: The bending point in the QT interval versus AV interval plots showed a good correlation with the FVC and fusion points observed on ECG. The results suggest that automatic discrimination between fusion and full capture using QT interval measurements may be feasible.

Aged↗

PubMed1997

Incidence of sudden death after radiofrequency ablation of the atrioventricular junction for atrial fibrillation.

This study assesses the incidence of sudden death and classifies the causes of death following radiofrequency ablation of the atrioventricular (AV) junction. We studied 220 patients with paroxysmal (n = 105) or chronic (n = 115) atrial fibrillation (AF) and a mean age of 64 +/- 12 years. These patients were followed 31 +/- 15 months after radiofrequency ablation of the AV junction and pacemaker implantation. In 86 patients, structural heart disease was identified before the procedure. All patients were traced via the Swedish National Civic Registry and Cause of Death Registry. The cause-of-death was classified according to data from death certificates, autopsy protocols, and medical records. Thirty-one patients (mean age 69 +/- 11 years, 16 men) died 15 +/- 15 months (range 0.2 to 60) after the procedure. There were 6 sudden unexplained deaths, 14 cardiovascular deaths, and 11 deaths from noncardiovascular causes. Eleven patients, all with structural heart disease, died suddenly out of hospital 16 +/- 16 months (range 0.2 to 42) after the procedure. In 6 of these there was no obvious cause of death. Three of these 6 patients underwent autopsy, which showed extensive coronary artery disease (n = 1), severe heart failure (n = 1) and cardiac hypertrophy and dilation (n = 1). The remaining 3 all had depressed left ventricular systolic function and a history of congestive heart failure. Five of the patients who died suddenly from cardiovascular causes had autopsies that revealed acute myocardial infarction (n = 4) and massive pulmonary embolism (n = 1).

Aged↗