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PubMed1997

Implantable cardioverter defibrillator utilization among device recipients presenting exclusively with syncope or near-syncope.

INTRODUCTION: Implantable cardioverter defibrillators (ICDs) are occasionally used in presumed high-risk patients with electrocardiographically undocumented syncope, although the incidence of ventricular tachyarrhythmias in this population is not well defined. METHODS AND RESULTS: We studied 33 consecutive patients receiving an ICD (67% nonthoracotomy and 70% tiered therapy) after electrophysiologic testing for unmonitored "syncope" (n = 29) or "near-syncope" (n = 4). Atherosclerotic heart disease was present in 24 (73%); mean left ventricular ejection fraction (LVEF) was 0.39 +/- 0.15; and sustained monomorphic ventricular tachycardia (SMVT) was inducible in 18 (55%). Over a median follow-up of 17 months (range 4 to 61), 12 patients (36%) received > or = 1 appropriate ICD discharge triggered by SMVT (cycle length 230 to 375 msec) in 10 and ventricular flutter or fibrillation in 2--without concomitant antiarrhythmic medication in 8 of 12 cases. Inducible SMVT and LVEF < or = 0.35 were statistically significant, independent predictors of an appropriate ICD discharge (P < 0.02 and P < 0.03, respectively). Estimated 1-year cumulative survival free of appropriate discharge was 34% versus 87%, respectively, in patients with versus without inducible SMVT (P < 0.02), and 18% versus 56%, respectively, in patients with LVEF < or = 0.35 versus LVEF > 0.35 (P < 0.03). CONCLUSION: In this highly select, multicenter population of ICD recipients with electrocardiographically undocumented syncope, a substantial incidence of appropriate device discharges was observed, particularly in patients with inducible SMVT and LVEF < or = 0.35. These findings support the notion that, in patients with LV dysfunction and inducible SMVT, ventricular tachyarrhythmias are likely to account for episodes of syncope or near-syncope.

Adult↗
PubMed1989

[Combination use of an automatic anti-tachycardia pacemaker and an automatic implantable cardioverter-defibrillator in sustained recurrent ventricular tachycardia resistant to drugs].

We used the combination of an antitachycardia automatic ventricular pacemaker with the automatic implantable cardioverter-defibrillator in two patients with sustained, recurrent, drug-resistant ventricular tachycardias in whom a surgical ablation was not indicated. The indications for the combined use of the two systems were the possibility to control: a) the ventricular tachycardias with ventricular programmed stimulation; b) the arrhythmias which might eventually degenerate into ventricular flutter or fibrillation (as a result of anti-tachycardia pacing) with the defibrillator. To avoid any possible interference between the two systems we used the following protocol: a) endocardial bipolar pacing; b) the sensing electrodes of the defibrillator were placed as far as possible from the endocardial one; c) a suitable programming of the pacemaker output; d) a careful selection of the anti-tachycardia pacing programme (burst rate inferior to the cut-off rate of the cardioverter-defibrillator and/or a duration of the burst pacing inferior to the arrhythmia sensing time of the defibrillator); e) use of cardioverter-defibrillators with a high cut-off rate. We never observed, during the follow-up (11 and 4 months, respectively), interference between the two systems. Both patients had ventricular tachycardia recurrences (51 and 3 episodes, respectively). The arrhythmias were correctly detected and interrupted by the pacemaker without the intervention of the defibrillator. These data confirm the feasibility of the combined use of the two systems in patients with ventricular tachycardias and, in selected cases, this approach is preferable. The anti-tachycardia pacemaker counteracts some limitations of the defibrillators available at present. It offers a protection against bradyarrhythmias and allows a more precise storage of arrhythmic events. The anti-tachycardia pacemaker often controls ventricular tachycardias without the intervention of the defibrillator, thus giving the same a longer life-span and allowing patients to avoid the shock.

Aged↗
PubMed1994

Safety and diagnostic yield of noninvasive ventricular stimulation performed via tiered therapy implantable defibrillators.

Extensive electrophysiological testing is critical for the effective utilization of sophisticated tachycardia detection and termination algorithms available in tiered therapy ICDs. To evaluate the safety and diagnostic yield of electrophysiological testing via noninvasive ventricular stimulation, we performed 294 electrophysiological studies in 154 patients (age 65 +/- 10; left ventricular ejection fraction 0.36 +/- 0.15) with tiered therapy ICDs. Stimulation was performed under methohexital anesthesia. A total of 918 sustained ventricular tachyarrhythmias were induced (3.1 +/- 2.5 per procedure): monomorphic VT, 550; ventricular flutter, 74; and VF, 246. The results of invasive and noninvasive programmed stimulation were compared for 79 patients who had both studies under similar treatment. Overall concordance was 83%, and did not differ significantly between patients who had the noninvasive stimulation via epicardial or endocardial pacing leads. VF could be induced in 206 of 257 studies (82%), and it was less likely to be induced in patients on amiodarone (74% vs 85%; P = 0.02), or beta blockers (55% vs 83%; P = 0.017). No patient presented a serious complication. Minor complications occurred during 39 studies: transient laryngospasm in 1, unintended delivery of an ICD shock to a conscious patient in 4; induction of sustained atrial fibrillation in 8; need for external rescue defibrillation shocks in 13; and delivery of inappropriate shocks for supraventricular rhythms in 14 studies. Noninvasive ventricular stimulation performed under methohexital anesthesia is safe. Its diagnostic yield compares favorably with that of conventional electrophysiological studies. VF can be induced in a majority of patients. There is good correlation between invasive and noninvasive programmed stimulation for induction of VT. Noninvasive ventricular stimulation may emerge as standard procedure for the initial programming and follow-up of ICDs.

Aged↗
PubMed1995

[Influence of the duration of myocardial infarction on QRS duration measured by signal averaged electrocardiography].

The aim of this study was to determine the influence of the chronicity of myocardial infarction on QRS duration. The signal-averaged electrocardiogram (SA ECG) was recorded with a 40 Hz filter in 239 patients with a history of myocardial infarction. The infarction was recent (up to 6 weeks) in 105 patients (group A) and chronic (> 1 year) in the other 134 cases (group B). In group A, 35 patients had inductible sustained ventricular tachycardia (VT) at less than 270/mn; 40 had negative electrophysiological investigations and 30 had inducible ventricular flutter or fibrillation (VF). In group B, 58 had inducible VT, 54 had negative investigations and 22 had inducible VF. The three SA ECG parameters (QRS duration, amplitude of RMS 40 and duration of LAS) differed significantly in subjects with VT with respect to those with negative investigations and inducible VF, irrespective of the chronicity of infarction. On the other hand, only QRS duration differentiated patients with recent infarction from those with chronic infarction, irrespective of the results of programmed pacing, QRS duration being longer in group B. The best diagnostic value of QRS duration for identifying subjects with VT < 270/mn and negative investigations was 110 ms in group A and 120 ms in group B (sensitivity 46% and 77.5% respectively). In chronic infarction, the increase in QRS duration was significantly correlated to the decrease in left ventricular ejection fraction. The authors conclude that the criteria of abnormality of QRS duration are dependent on the chronicity of myocardial infarction. Although a duration of 110 ms is abnormal in the early post-infarction period, after a period of one year, a value of 120 ms should be considered to be pathological, especially when the sequellae of infarction are important.

Adult↗
PubMed1994

Is digoxin an independent risk factor for long-term mortality after acute myocardial infarction?

The safety of treatment with digoxin in patients with acute myocardial infarction (MI) was investigated in 584 hospital survivors of MI. All patients were examined by radionuclide ventriculography, with determination of left ventricular ejection fraction (LVEF), close to the time of discharge. Clinical data were collected on admission. All patients were followed up with regard to death (median 6.2 years, range 3.9-7.8 years). Patients treated with digoxin (N = 172 (29%) were older (median 66 vs 59 years; (P < 0.001), had a higher incidence of diabetes (13% vs 7%; P = 0.025), and a lower LVEF (0.33 vs 0.49; P < 0.001). As expected, clinical heart failure was more frequent among them (84% vs 14%; P < 0.001), than in patients not receiving digoxin. The 1- and 5-year mortality of patients treated with digoxin was 38% and 74% compared to 8% and 26% in patients not receiving digoxin (P < 0.001). The increased risk associated with digoxin therapy remained statistically significant when patients were stratified according to the presence or absence of heart failure or atrial fibrillation/flutter during hospitalization, or to LVEF above or below 0.45 at discharge. In a proportional hazard model including age, LVEF, diabetes mellitus, heart failure, atrial fibrillation or flutter, ventricular fibrillation, gender, dose of furosemide at discharge and calcium antagonists and digoxin treatment as covariates, digoxin was independently associated with an increased risk of death (relative risk 1.8 (95% confidence limit 1.2-2.5)). We conclude that administration of digoxin may be harmful in hospital survivors of MI.

Aged↗
PubMed1995

Comparison of monophasic and biphasic defibrillating pulse waveforms for transthoracic cardioversion. Biphasic Waveform Defibrillation Investigators.

All transthoracic defibrillators on the US market use nominally monophasic shock waveforms. However, biphasic waveforms have a lower defibrillation threshold than monophasic waveforms for transthoracic defibrillation of animals and for defibrillation of humans by implantable cardioverter defibrillators. The relative efficacies of Edmark monophasic and Gurvich biphasic transthoracic cardioversion waveforms (200 J into 50 omega) were compared for transthoracic cardioversion in 171 patients undergoing electrophysiologic study for evaluation of ventricular arrhythmias. Patients were randomized in a blinded fashion to receive either a monophasic or a biphasic waveform for the initial shock for conversion of induced ventricular arrhythmias (ventricular fibrillation [VF] = 53, monomorphic ventricular tachycardia [VT] = 80, polymorphic VT = 30, ventricular flutter = 8). Delivered energies for the Edmark and Gurvich waveforms were 215 +/- 11 and 171 +/- 11 J, respectively. There were no significant differences in patient characteristics, use of antiarrhythmic agents, arrhythmia cycle length, or duration of arrhythmia prior to shock for monophasic and biphasic waveform groups. The first shock for all arrhythmias was successful in 75 of 88 patients (85.2%) for the monophasic waveform compared with 81 of 83 patients (97.6%) for the biphasic waveform, p = 0.0054. The first shock for VF was successful in 22 of 28 patients (78.6%) for the monophasic waveform compared with 25 of 25 (100%) for the biphasic waveform, p = 0.0241. The Gurvich biphasic waveforms delivering a mean of 171 J were superior to Edmark monophasic waveforms delivering a mean of 215 J for transthoracic cardioversion of arrhythmias of short duration. This finding may have important implications for the development of future transthoracic defibrillators.

Adult↗
PubMed1993

Low-energy endocardial defibrillation using an axillary or a pectoral thoracic electrode location.

BACKGROUND: A significant proportion of patients receiving endocardial defibrillation lead systems must accept either high defibrillation thresholds (DFTs) with lower safety margins or lead implantation by thoracotomy. We examined the feasibility of achieving universal application of endocardial leads and lower defibrillation energy requirements by optimizing the lead system location in conjunction with biphasic shocks. METHODS AND RESULTS: Two defibrillation catheter electrodes were positioned in the right ventricle and superior vena cava. Thoracic patch electrodes were placed at three sites (apical, pectoral, and axillary). Fifteen-joule, 10-J, and 5-J bidirectional simultaneous biphasic shocks were delivered across three different triple electrode configurations (right ventricle, superior vena cava, and patch) after inducing ventricular fibrillation (VF), and DFT was determined. All patients in whom VF was reproducibly inducible (14 patients) could be reproducibly defibrillated at 15 J at one or more patch electrode locations. Fifteen-joule shocks were effective at three thoracic electrode locations in 12 patients and at two electrode locations in 6 patients. The lowest mean single-shock DFT was 8.1 +/- 3.8 J. In 4 patients, ventricular flutter was reproducibly induced and reverted at 15 J in all patients. Mean DFT for the axillary location was 8.3 +/- 3.5 J and was significantly lower than apical (12.8 +/- 5.6 J, P = .008) and pectoral (11.6 +/- 4.1 J, P < .04) patch locations. The probability of success was significantly higher at 10 J with axillary location (78% of patients, P < .03 compared with both other sites) and at 15 J (P < .05 compared with the apical location). Low-energy endocardial defibrillation (< or = 10 J) was feasible in 10 of 14 tested patients at more than 1 thoracic electrode location at 10 J, whereas only 1 of 7 successful patients could be reverted at more than 1 electrode location at 5 J (P < .02). CONCLUSIONS: The use of axillary or pectoral patch lead location can allow endocardial defibrillation with biphasic shocks at energies < or = 15 J in this lead configuration. Virtually universal application of endocardial defibrillation lead systems can be predicted from these data. Reduction in maximum pulse generator output to < or = 25 J using these two thoracic electrode locations with bidirectional shocks can be feasible and maintain an adequate safety margin and permit thoracic pulse generator implantation. Lowering endocardial defibrillation energy < 10 J requires increasing specificity of thoracic electrode location.

Aged↗
PubMed1975

[Lethal intoxication with leaves of the yew tree (Taxus baccata) (author's transl)].

A case of a rare lethal intoxication with yew leaves (taxus baccata) is reported. The clinical signs were dizziness (onset 1 hr after yew leaves were ingested), nausea, diffuse abdominal pain, unconsciousness, weak breathing, tachycardia, brief ventricular flutter afterwards a slow pulse, and finally death by respiratory arrest and diastolic cardiac standstill. Particular attention was given to the ECG. It showed an atypical bundle branch block with a maximal QRS-duration of 0.24 sec. A striking resemblence to the ECG in the case of hyperkalemia is seen in that P-waves were absent. Therefore, the possibility is noted that an acute hyperkalemia could be partly responsible for the cardiotoxic effect of the leaf.

Adult↗
PubMed1995

Myocardial protection by ischemic preconditioning: the influence of the composition of myocardial phospholipids.

It was the aim of this study to investigate (1) whether preconditioning modifies the fatty acid (FA) composition of myocardial phospholipids (PL), (2) whether a previous modification of membrane PL composition by the administration of coconut oil or fish oil influences the preconditioning, and (3) to compare the protective effects of preconditioning to those of dietary fish oil. To this end, three groups of rats were given during 10 weeks either a standard diet, or a standard diet + 10% coconut oil, or a standard diet + 10% fish oil. The preconditioning was performed in situ in the anesthetized open-chest rats by 2 cycles of 3 min left anterior descending coronary artery occlusion and 10 min reperfusion. It was followed by a 40 min ischemia and a 60 min reperfusion. ECG was recorded and used for the continuous count of the salves of extrasystoles, ventricular flutter and fibrillation. These rhythm disturbances were subsequently added and evaluated as total arrhythmias. The FA of tissue PL were analyzed in a sample of the ischemic zone the size of which was determined by means of malachite green. Coconut oil diet (rich in saturated FA) modified slightly the myocardial PL by increasing oleic acid and decreasing linoleic acid and resulted in the highest incidence of arrhythmias. Fish oil diet had the opposite effect in modifying drastically the PLFA (replacement of the n-6 FA by the n-3 FA) and minimizing significantly the arrhythmias in comparison with the standard diet group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Study of cardiac arrhythmia using the Kalman filter.

It has been known for some time that the variability of the R-R intervals in the electrocardiogram signal yields valuable information concerning the various types of arrhythmia that might be present. It has recently been suggested that the identification of cardiac arrhythmia might be possible by applying spectral analysis techniques to the data. An investigation is made into the possible application of the Kalman filter identifier in the calculation of time varying spectra of the data, with a view to studying the onset of arrhythmia and also short bursts of arrhythmia. To this end, data from the MIT-BIH database are analysed; in particular, cases of bigenimy, trigenimy, second degree block and ventricular flutter have been looked at. It is found that this technique can, in many cases, detect the onset of arrhythmia and sometimes actually identify the arrhythmia that is present. It is suggested that the Kalman filter identifier could have a general application in studying both the normal and arrhythmic segments of data to yield valuable medical information concerning the subject under study.

Arrhythmias, Cardiac↗
PubMed1982

Malignant hyperpyrexia and Duchenne muscular dystrophy: A case report.

We report a patient with Duchenne muscular dystrophy who developed malignant hyperpyrexia during general anaesthesia. During anaesthesia bradycardia was followed by ventricular fibrillation, on which ventricular flutter supervened and a body temperature rise of 0.6 degrees C for 15 minutes, myoglobinuria and elevation of CPK level were observed. The caffeine sensitivity test of biopsied muscle fibers revealed an increase in sensitivity, although there was no sign of muscle rigidity during or after anaesthesia. Diagnosis of Duchenne muscular dystrophy was first established after the development of malignant hyperpyrexia in the present case as well as in previously reported cases. Determination of serum CPK is very important before general anaesthesia.

Adenosine Triphosphatases↗
PubMed1985

Autoregressive modeling and power spectral estimate of R-R interval time series in arrhythmic patients.

The signal constituted by the successive R-R intervals in the ECG tracing carries important information about the control mechanisms of heart rate. The present paper describes advanced methods of parameter extraction from the R-R duration time series which use autoregressive (AR) modeling and power spectral estimates applied to patients in the MIT-BIH arrhythmia data base. The described methodologies enhance information which characterize the most common rhythm disturbances (A-V block, bigeminy/trigeminy, atrial and ventricular flutter, atrial fibrillation, etc.). Important applications of such methods are in the area of the pathophysiological comprehension of cardiac rhythm control mechanisms in the research side and the classification of abnormal rhythms as well in the clinical side. A few examples from the data base are illustrated which show interesting properties of signal processing and classification in respect to the more traditional methods.

Arrhythmias, Cardiac↗
PubMed1987

The effect of the specific PAF antagonist BN 52021 and the calcium blocker diltiazem on PAF induced arrhythmogenicity.

Platelet-activating factor (PAF) in a concentration of 10(-11) mole per animal decreased the threshold doses for onsets of arrhythmia, ventricular flutters and fibrillation in ouabain induced arrhythmia in guinea-pigs in a statistically significant manner. The specific PAF antagonist BN 52021 (20 mg/kg, orally) completely inhibited the PAF effect for all types of arrhythmia, while the Ca2+ antagonistic drug diltiazem (0.1 mg/kg, i.v.) failed to counteract the PAF action. BN 52021 (20 mg/kg, per os) alone did not exert any effect on ouabain induced arrhythmia, but as expected, diltiazem (0.1 mg/kg, i.v.) showed antiarrhythmic effects. These results confirm the specific PAF antagonistic activity of BN 52021, its usefulness for PAF related cardiac rhythm disturbances and indicate that the method used could be a further useful tool to screen PAF antagonistic substances.

Administration, Oral↗
PubMed1987

The effect of PAF (platelet-activating factor) on experimental cardiac arrhythmias and its inhibition by substances influencing arachidonic acid metabolites.

Platelet-activating factor (PAF), 10(-11) mol decreased the threshold of ouabain induced arrhythmia in guinea-pigs. The thresholds inducing premature ventricular beats and ventricular flutter were statistically significantly decreased by 27.4% and 15.6%, respectively. BM 13.177 (30 mg/kg), a thromboxane receptor antagonizing substance, and esculetin (1.2 mg/kg), a lipoxygenase inhibitor, abolished this arrhythmogenic effect of PAF. Acetylsalicylic acid (10 mg/kg) showed only a tendency to inhibit the PAF effect. These results suggest that PAF could play a role in cardiac arrhythmias under special conditions and it supports the hypothesis that PAF action is mediated by the release of leukotrienes and thromboxane.

Animals↗
PubMed1993

Sudden death of calves by experimental infection with Strongyloides papillosus. IV. Electrocardiographic and pneumographic observations at critical moments of the disease.

Electrocardiographic and pneumographic observations at critical moments were carried out on five calves that died suddenly following experimental infections with Strongyloides papillosus. Time which elapsed during these critical moments was calculated from the time of observation of ventricular flutter (VF) to the appearance of accelerated respiration and cessation of respiration. The beginning of accelerated respiration ranged from -19 to 41 s after VF. Time (minutes:seconds) of cessation of respiration ranged from 2:10 to 3:50 after VF. The results of the experiment suggested sudden cardiac death as the cause of death in calves following infection with Strongyloides papillosus.

Animals↗
PubMed1987

Electrocardiographic alterations induced by AGEPC in Wistar rats in relation to its hypotensive and hematologic effects.

AGEPC administration into Wistar rats caused no remarkable thrombocytopenia, slight decrease of the percent count of PMNs in whole blood accompanied by anequal leukocytopenia and a transient increase in hematocrit, due to fluid extraversion. Apart from the dramatic fall in blood pressure caused by AGEPC, relatively sinus bradycardia was recorded at doses over 6 micrograms/kg b.w. S-T segment elevation, mainly evident in II, III and AVF leads, was also recorded within the first minutes after AGEPC administration, at doses over 1 microgram/kg b.w. At lethal doses, various degrees of A-V block resulting in complete A-V block with idioventricular rhythm, or injury pattern resulting in ventricular fibrillation or ventricular flutter, were recorded. At sublethal doses no arrhythic manifestations were recorded, while S-T segment elevation upward inversion became gradually normal.

Animals↗
PubMed2003

Outcomes of cardiac surgery in nonagenarians: a 10-year experience.

BACKGROUND: With an increasing awareness of health issues and greater emphasis on preventive medicine, the general population is living longer and healthier lives than ever before. Physicians are taking care of older patients, many of whom may require cardiac surgical procedures. Improving cardiopulmonary bypass technology allows for safer procedures with reduced morbidity and mortality even in older patients. METHODS: We have performed a retrospective analysis of 42 consecutive nonagenarian patients who underwent open-heart procedures over a 10-year period (1993 to 2002) at our institution. Their demographic profiles, operative data, perioperative results, and long-term outcomes were recorded and analyzed. RESULTS: Twenty-two women and 20 men with an age range of 90 to 97 years (mean, 91.4 years) had open-heart surgery over the study period. The complication rate was 67% overall, consisting of 7% respiratory (pneumonia, respiratory failure, reintubation), 7% hemorrhagic or embolic (postoperative bleeding, cerebral vascular accident), 12% infectious (wound infection, sepsis), and 31% new arrhythmia (atrial fibrillation, atrial flutter, ventricular tachycardia, ventricular fibrillation). Despite these complication rates, average hospital stay was 17.5 days (median, 11 days), with an intensive care unit stay of 12.0 days (median, 5 days). Thirty-day survival was 95% and survival to discharge was 93% (three deaths total; one cardiac arrest at hospital day 134 and two perioperative deaths; one ventricular arrhythmia, one cerebral vascular accident). The only statistically significant risk factor of mortality was emergency surgery. Currently, 81% are still alive an average of 2.53 years since surgery (range, 0.16 to 7.1 years). CONCLUSIONS: With improving techniques and greater attention to detail, the select nonagenarian can safely undergo cardiac surgery.

Age Factors↗
PubMed2000

Fetal arrhythmias.

Fetal arrhythmias may be benign or life-threatening. Benign disturbances in fetal cardiac rhythm are relatively common, and their clinical manifestations are reviewed. Life-threatening fetal arrhythmias include supraventricular tachycardias, atrial flutter, ventricular or junctional tachycardia, chaotic atrial tachycardia, and bradyarrhythmias such as second or third degree AV block. The incidence, diagnostic characteristics and treatment of each of these are reviewed. In addition, the pathophysiology of hydrops fetalis, embryology of the conduction system and transplacental drug transfer characteristics are reviewed.

Journal Article↗