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PubMed1989

Significance of ST segment depression in exercise-induced supraventricular extrasystoles.

The significance of exercise-induced ST segment depression in supraventricular extrasystoles (STx), in the preceding sinus beats (STs), as well as the significance of the difference between the two of them (STx-s), was studied in 96 patients with angiographically documented coronary artery disease (CAD) (group A)--34 with myocardial infarction (group A1) and 62 without (group A2)--compared to 37 subjects with normal coronary arteries (group B). All patients had supraventricular extrasystoles during exercise testing, the results of which were positive in 72 (75%) patients in group A and six (16.2%) patients in group B (sensitivity 75%, specificity 84%). Among patients in group A STx was greater than STs (1.7 +/- 1.0 vs 1.2 +/- 0.8 mm; p less than 0.001), and STx-s was positive in 70 (sensitivity 73%), whereas in group A2 there were 44 patients with these values (sensitivity 71%). Among patients in group B no statistically significant difference was found between STx and STx (0.4 +/- 0.6 vs 0.6 +/- 0.7 mm; p = NS), whereas STx-s was positive in three (specificity 92%). Among the 24 patients in group A with false negative results of exercise tests, 15 (62.5%) had a positive STx-s, whereas of the 17 patients in group A2 with false negative results, 10 (58.8%) had a positive STx-s. Among the six patients in group B with false positive exercise test results, the STx-s was positive in two.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Complexes, Premature↗
PubMed1982

Role of early cycle ventricular extrasystoles in initiation of ventricular tachycardia and fibrillation: evaluation of the R on T phenomenon during acute ischemia in a canine model.

Eighteen open chest dogs anesthetized with pentobarbital sodium were studied to determine the role of early cycle premature ventricular beats in the initiation of ventricular tachycardia and fibrillation during the initial 30 minutes of acute myocardial ischemia. The coupling interval and prematurity index (R-R'/R-R) of every premature beta after a sinus beat were determined during both the "immediate" (2 to 12 minutes) and "delayed" (13 to 30 minutes) phases of ventricular arrhythmias that follow acute coronary ligation. During the immediate phase, characterized by marked fractionation of local electrograms and delayed intramyocardial conduction, early cycle beats were infrequent (8 percent of extrasystoles) and initiated only 3 (4 percent) of 75 episodes of ventricular tachycardia and fibrillation. However, during the delayed phase, characterized by less fractionation and more uniform conduction, early cycle beats were both more frequent (24 percent of extrasystoles, p less than 0.001) and more successful (20 [34 percent] of 59 episodes, p less than 0.001) in initiating ventricular tachycardia and fibrillation. Thus, the underlying electrophysiologic derangements appeared to be of primary importance in determining both the frequency and relative malignancy of early cycle beats during acute myocardial ischemia.

Acute Disease↗
PubMed1990

Intermittent ventricular parasystolic bigeminy accompanied by reentrant ventricular extrasystoles.

An extremely rare case of intermittent ventricular parasystolic bigeminy is presented, in which coexisting reentrant ventricular extrasystoles of sinus origin, showing mainly trigeminy, and those of ventricular parasystolic origin, showing a close coupling to the ventricular parasystolic beat, are demonstrated. Such a unique case has never been reported. Timely parasystolic exit block occurring just prior to the anterograde ventricular activation of the sinus impulse was considered to be of critical importance in developing the reentrant extrasystolic trigeminy.

Aged↗
PubMed1994

Differentiation between parasystole and extrasystoles. Influence of vagal stimulation on parasystolic impulse formation.

Recently, it has been shown that when a sinus impulse falls late in the parasystolic cycle, it usually hastens the next ectopic discharge. Thus, in many cases, the classic criteria for the diagnosis of parasystole (ie, varying coupling intervals and constant shortest interectopic intervals) cannot be used. To differentiate between parasystole and extrasystoles in such cases, the influence of vagal stimulation on parasystolic impulse formation was investigated in seven cases of "true" parasystole in which one or more "pure" ectopic cycles without any intervening nonectopic QRS complexes were found spontaneously. In all cases pure ectopic cycles were found during sinus arrest caused by vagal stimulation; namely, none of the cases showed extreme prolongation of the parasystolic cycle. These results strongly suggest that instead of the classic criteria, vagal stimulation causing temporary sinus arrest is the optimal method for differentiation between parasystole and extrasystoles in cases without spontaneous pure ectopic cycles.

Adult↗
PubMed1976

Mobitz II atrioventricular block due to infra-Hisian block and bundle branch extrasystoles.

An asymptomatic elderly male presented with complete right bundle branch block, left anterior fascicular block and Mobitz Type II second degree atrioventricular block. In addition, he was noted to have ventricular premature systoles. Electrophysiologic studies demonstrated two apparently different mechanisms for the second degree A-V block--infra-Hisian block and A-V block due to bundle branch extrasystoles arising in the affected right bundle branch. Concealed conduction of the bundle branch extrasystoles as the proximate cause of infra-Hisian block could not be excluded. However, both forms of A-V block were evidently dependent upon significant distal conduction system disease; this consideration was felt to warrant permanent pacemaker implantation.

Aged↗
PubMed1980

Type A alternating Wenckebach periodicity in the re-entrant path of ventricular extrasystoles.

A patient with ventricular extrasystoles is reported in whom Type A alternating Wenckebach periodicity in the re-entrant path of the extrasystoles is suggested for the first time. Namely, it appears that 2:1 exit block occurs at a proximal level in the re-entrant path and block of the Wenckebach form occurs at a distal level in the path. The presence of three-level block in the re-entrant path is also suggested in this patient.

Aged↗
PubMed1980

Unifocal origin of multiform extrasystoles in concealed bigeminy.

A case of concealed bigeminy is presented in which two forms of extrasystolic complexes were evident on the ECG. One form (type B) appeared after a single conducted sinus beat, in a pattern of manifest bigeminy. The other form (type A) occurred after a sequence of more than one conducted sinus beat. The two configurations have previously been explained on the basis of different foci and mechanisms. Certain features of the ECG from our patient suggested that the two forms originated from a common site. An experimental model was developed in which the right ventricle of a dog was stimulated at sub- or suprathreshold voltages on alternate sinus beats to simulate concealed bigeminy. The ECG obtained during stimulation of a single site was remarkably similar to that recorded from the patient. We have proposed that the extrasystoles that occur after a compensatory pause may spread in a manner different from those that follow a basic cardiac cycle length. The different pattern of propagation is probably ascribable to the lengthening of the refractory period of the cardiac tissues by the compensatory pause.

Animals↗
PubMed1999

Left ventricular end-diastolic extrasystole with pseudonormalization of a left bundle branch block unmasking inferior ischemia.

An electrocardiogram tracing of a patient in conducted sinus rhythm with left bundle branch block is shown, in which occasional pseudonormalization of intraventricular conduction is seen. This event is attributed to ventricular fusions with end-diastolic extrasystoles of the left His-Purkinje system distal to the block site. This type of extrasystole is discussed. In this case, normalization of ventricular activation allowed for diagnosis of inferior subepicardial ischemia.

Bundle-Branch Block↗
PubMed2001

Termination of pacemaker endless loop tachycardia by an atrial extrasystole.

This article documents the termination of a pacemaker endless loop tachycardia by a critically timed atrial extrasystole. Although predictable electrophysiologically, this mode of termination has not been previously reported. The observation is conceptually important because it provides the final link in establishing the similarity of endless loop tachycardia and spontaneous reentrant AV nodal or junctional tachycardias in terms of initiation and termination by single atrial or ventricular extrasystoles.

Atrial Premature Complexes↗
PubMed1982

[Propafenon and propranolol in the management of cardiac extrasystoles (author's transl)].

The anti-arrhythmic effectiveness of propafenon (3 x 150 mg daily) combined with propranolol (3 x 20 mg daily) was compared with that of each drug alone in 15 patients with stable ventricular and (or) supraventricular extrasystoles. The frequency of extrasystoles decreased on propafenon alone by 70% (P less than 0.05), without further decrease on additional propranolol administration. Propranolol alone on average caused no significant decrease infrequency (35%). The most important ECG changes with the combined treatment consisted of a definite increase in P-Q interval by an average of 25% (P less than 0.01) while with propafenon alone it was 13%, with propranolol alone 19% . Propafenon plus propranolol decreased heart rate by a mean of 17% (P less than 0.01). The additive effect of both substances can lead to an inhibition of atrioventricular conduction and of sinus node function.

Adult↗
PubMed1980

[Antiarrhythmic drugs in chronic ventricular extrasystole (author's transl)].

Several class I antiarrhythmic drugs were used in an intraindividual comparative study in 15 patients with chronic stable ventricular extrasystole of various origins. In a randomised sequence lidocaine, ajmalin and, in a cross-over double blind study with placebo, the new antiarrhythmic Org 6001 were tested. Propafenon was given as a final preparation. Each substance was administered parentally in therapeutic doses. A significant placebo effect could be excluded, baseline control values before administration of individual substances correlated well. Comparing mean values obtained over one hour before and after administration of the substance it was shown that the effectiveness of drugs decreased as follows: ajmalin, propafenon, lidocaine, Org 6001. Whereas suppression of extrasystole was most marked after ajmalin, propafenon showed the longest period of activity. After Org 6001 divergent activity of arrhythmia could be observed; in some patients good antiarrhythmic effects could be demonstrated. For evaluation of effectiveness and validity of new antiarrhythmic substances intraindividual comparison with placebo and well established standard antiarrhythmic drugs is advisable.

17-Ketosteroids↗
PubMed1990

Characterisation of decay of frequency induced potentiation and post-extrasystolic potentiation.

STUDY OBJECTIVE: The aim was to elucidate the processes underlying the beat by beat decay of frequency induced and post-extrasystolic potentiation. DESIGN: The ventricular pacing protocol consisted of a "priming period" followed by a "decay" period of pacing at 1 s intervals, characterised by a decaying potentiation of left ventricular (LV) dP/dtmax; these were identified as test beats 1,2,3,4,5. The magnitude of potentiation of test beat 1 (P1) was increased both by increased priming frequency (frequency potentiation) and by alternately shorter priming intervals (paired pulse stimulation) at a given average frequency (post-extrasystolic potentiation). The exponential decay constant (P2) and the asymptotic value (P3) were determined and compared with the measured values and with the slope of the linear relationship between the contractility of one beat and that of the preceding beat. The lowest values after decay were related to the magnitude of preceding potentiation. EXPERIMENTAL MATERIAL: Six anaesthetised dogs with induced heart block and beta adrenergic blockade were used. Beat to beat interval was controlled by ventricular pacing from a programmable stimulator. MEASUREMENTS AND MAIN RESULTS: Contractility of each beat was assessed from maximum rate of rise of LV pressure (LVdP/dtmax) obtained from an intraventricular micromanometer. The asymptotic value of the exponential fit to the decay of potentiation (P3) was found to be below the measured nadir value, which was followed by an increase in LVdP/dtmax to the final steady state value P4. The decay constant (P2) was found to be equivalent to the natural logarithm of the slope of the linear relationship between the contractility of one beat and that of the preceding beat; it was unaffected by priming frequency or interval at a given average priming frequency. The asymptote P3 was inversely related to P1. CONCLUSIONS: P1 was interpreted as the expression of accumulation of activator in an internal release store; P3 was interpreted as a manifestation of negative feedback control of activator entry by the released activator itself, and the slow recovery to P4 as due to the slow lengthening of action potential duration and/or recovery from accumulation of an intracellular metabolite or ion.

Action Potentials↗
PubMed1989

Cod liver oil does not reduce ventricular extrasystoles after myocardial infarction.

Previous work has shown that in experimental animal models a lower incidence of arrhythmias and sudden death was observed if the animals were fed cod liver oil or fish oil. After a 48-h control period starting, on average, 8 days after the onset of symptoms, 18 men who were recovering from acute myocardial infarction were given 20 ml d-1 cod liver oil for 6 weeks, either immediately after the control period, weeks 0-6 (n = 10), or during weeks 6-12 (n = 8). Forty-eight-hour Holter monitoring was carried out before cod liver oil administration and at the end of weeks 6 and 12. The eicosapentaenoic acid content of plasma phospholipids was increased by 230% during cod liver oil administration. However, no significant change was observed in the 24-h prevalence of ventricular extrasystoles or other arrhythmias during the study period. The mean ln number of ventricular extrasystoles was 2.95 +/- 0.51 (+/- SEM) during cod liver oil ingestion and 2.63 +/- 0.30 when not taking cod liver oil.

Adult↗
PubMed1976

Association of ventricular extrasystoles and ventricular tachycardia with idioventricular rhythm.

Patients with acute myocardial infarction were monitored for ventricular arrhythmias in the first 48 hours. Idioventricular rhythm (rate less than 100/minute) occurred in 35 out of 224 patients (15.6%) during the first day and in 13 out of 192 patients not receiving treatment on the second day (6.8%). This arrhythmia was frequently preceded by late ventricular extrasystoles, which often showed variation of their coupling intervals to the preceding QRS. Double ventricular extrasystoles separated by larger than or equal to 600 ms were also precursors of idioventricular rhythm. Idioventricular rhythm at times could be described as an escape rhythm, but on other occasions it was undoubtedly an accelerated rhythm. Spontaneous changes in the idioventricular cycle length were frequent on single one-minute electrocardiographic recordings. The rate of the dominant rhythm in patients with episodes of idioventricular rhythm was significantly slower than the heart rate of patients without this arrhythmia. Idioventricular rhythm was more frequent in patients with inferior infarction. Idioventricular rhythm sometimes preceded ventricular tachycardia but there was only a significant association between ventricular tachycardia and idioventricular rhythms with rates of over 75/minute. Irregular idioventricular rhythm frequently accelerated to ventricular tachycardia. It is suggested that the term benign idioventricular rhythm be reserved for those rhythms below 75/minute, and that the term rapid idioventricular rhythm should be used for rhythms between 75 and 120/minute. The rate of idioventricular rhythm is related to the probability of development of life-threatening ventricular arrhythmias during the first 48 hours after myocardial infarction.

Cardiac Complexes, Premature↗
PubMed1982

Permanent right bundle-branch block heralded by intermittent block and ventricular extrasystoles. A 13-year observation.

A patient is described in whom the occurrence of frequent ventricular extrasystoles of right ventricular origin and intermittent right bundle-branch block caused by interpolation of these extrasystoles heralded the slow development of permanent right bundle-branch block over a period of observation of 13 years. Such a clinical course suggested gradual progression of an organic lesion in the intraventricular conducting system. The differential diagnosis of intermittent bundle-branch block and aberrant intraventricular conduction, and possible mechanisms of ectopic impulse formation in the presence of bundle-branch block are discussed.

Aged↗
PubMed1984

Determination of left ventricular residual function by analysis of post-extrasystolic beat in mitral stenosis.

Residual function of the left ventricle was assessed in 25 patients with mitral stenosis and a normal left ventriculogram. The post-extrasystolic beat (R2) in sinus rhythm (nine patients) and the first beat after an early beat (R2) in atrial fibrillation (16 patients) were analysed angiocardiographically. Five subjects with a normal heart (controls) were also studied. The results are expressed as percentage changes in left ventricular contractility from the beat preceding the extra beat (R1) to the beat R2. In the control group the mean changes from R1 to R2 were: end diastolic volume +68.3% (increase), end systolic volume -21.7% (decrease), ejection fraction +36.2%, mean systolic ejection rate +22.1%, and mean velocity of circumferential fibre shortening +31%. A significant increase in proportional systolic shortening of all left ventricular axes was found in R2 compared with R1. In five patients with sinus rhythm and nine with atrial fibrillation the results fell within the normal range. In the remaining patients the beat R2 indicated signs of poor left ventricular function. The mean changes from R1 to R2 in the patients with sinus rhythm and those with atrial fibrillation were respectively: end diastolic volume +47.8% and +36.6%, end systolic volume +20% and +27%, ejection fraction +12.5% and +6.2%, mean systolic ejection rate -23.3% and -30.2%, and mean velocity of circumferential fibre shortening -25.5% and -39.2%. The increase in the left ventricular axial systolic shortening was not significant. Thus analysing a post-extrasystolic beat in sinus rhythm of the beat following an early beat with a long diastole in atrial fibrillation is a valuable method of determining the residual function in patients with mitral stenosis who have a normal left ventriculogram in basic rhythm.

Adolescent↗
PubMed1977

A new, noninvasive technique for inducing post-extrasystolic potentiation during echocardiography.

Left ventricular function was evaluated in 34 patients with the echocardiogram, and an external mechanical cardiac stimulator was used to induce a ventricular premature contraction (VPC) noninvasively. Extent of post-extrasystolic potentiation (PESP) was determined by comparing systolic dimensional shortening and ejection fraction of the sinus beat preceding the VPC to that of the potentiated beat which followed it. Using this technique, a VPC could be introduced into the cardiac cycle of 30 of the 34 patients, six of whom were free of obvious cardiac disease and 24 of whom had valvular, coronary or myopathic heart disease. The only complication observed was mild breast ecchymosis in a female patient. Systolic dimensional shortening and ejection fraction increased from control values by an average of 21% and 17% respectively, with a range of 0-100%. The degree of PESP was very reproducible in repeat studies and when the same patients were subsequently evaluated during a spontaneously occurring or catheter-induced VPC. The technique can safely and reliably induce post-extrasystolic potentiation during echocardiography and is a potentially important adjunct to the noninvasive evaluation of left ventricular function.

Adult↗
PubMed1993

Pinacidil-induced electrical heterogeneity and extrasystolic activity in canine ventricular tissues. Does activation of ATP-regulated potassium current promote phase 2 reentry?

BACKGROUND: Pinacidil is known to augment a time-independent outward current in cardiac tissues by activating the ATP-regulated potassium channels. Activation of this current, IK-ATP, is thought to be responsible for increased potassium permeability in ischemia. The contribution of IK-ATP activation to arrhythmogenesis and the role of activation of this current in suppression of arrhythmias are areas of great interest and debate. Because electrical depression attending myocardial ischemia is more accentuated in ventricular epicardium than in endocardium, we endeavored to contrast the effects of pinacidil-induced IK-ATP activation on the electrophysiology of canine ventricular epicardium and endocardium. METHODS AND RESULTS: Standard microelectrode techniques were used. Pinacidil (1 to 5 mumol/L) produced a marked dispersion of repolarization and refractoriness in isolated canine ventricular epicardium as well as between epicardium and endocardium. In endocardium, pinacidil abbreviated action potential duration (APD90) and refractoriness by 8.0 +/- 2.3%. In epicardium, the effects of pinacidil were nonhomogeneous. At some sites, pinacidil induced an all-or-none repolarization at the end of phase 1 of the action potential, resulting in 55.5 +/- 8.7% abbreviation of APD90 and refractoriness. Adjacent to these were sites at which the dome was maintained with only minor changes in APD and refractoriness. Extrasystolic activity displaying features of reentry was observed in isolated sheets of epicardium (63.2%) after exposure to pinacidil (1 to 5 mumol/L) but never in its absence. Dispersion of repolarization and ectopic activity was most readily induced in epicardium by a slowing of the stimulation rate in the presence of pinacidil. Electrical homogeneity was restored and arrhythmias abolished after washout of pinacidil or addition of either a transient outward current blocker, 4-aminopyridine, or a blocker of the ATP-regulated potassium channels, glybenclamide. CONCLUSIONS: Our data suggest that the activation of IK-ATP can produce a marked dispersion of repolarization and refractoriness in epicardium as well as between epicardium and endocardium, leading to the development of extrasystolic activity via a mechanism that we have called phase 2 reentry. The available data also suggest that blockade of the transient outward current and/or the ATP-regulated potassium channels may be useful antiarrhythmic interventions under ischemic or "ATP depleted" conditions.

Action Potentials↗