Accuracy of low load exercise-induced T wave normalization in predicting the presence of contractile reserve after an anterior myocardial infarction.

BACKGROUND AND METHODS. Exercise-induced T wave normalization occurring at a low (less-than-or-equal50 watt) workload in infarct-related electrocardiographic leads was studied in 30 consecutive patients with a recent transmural anterior acute myocardial infarction. Patients underwent both ergometric stress testing (within 30 days after the infarction) and low dose dobutamine echocardiography. The T wave normalization was considered significant when it occurred in at least two infarct-related leads. A significant contractile reserve was considered present in an infarcted region when 50% or more of the dyskinetic segments functionally improved on exercise during dobutamine infusion. RESULTS. Eighteen patients showed exercise-induced T wave normalization (group 1), and 12 patients did not (group 2). Myocardial contractile reserve in the infarct area was detected in 16 patients of group 1 (88%) and in 3 patients (25%) of group 2 (p=0.004). The overall sensitivity, specificity, and diagnostic accuracy of T wave normalization, as it reflects contractile reserve in the infarct area, were 84%, 82%, and 83%, respectively. CONCLUSION. Low load exercise-induced T wave normalization in infarct-related leads appears to be an accurate marker of residual contractile reserve in the infarct area in patients with recent transmural acute anterior myocardial infarction. (c) 2000 by CHF, Inc.

Intermittent sinus bigeminy as an expression of sinus parasystole: a case report.

A case of sinus parasystole is reported. The diagnosis of sinus parasystole is relatively difficult because there is no difference between the basic sinus P wave and the parasystolic wave. Sinus parasystole is diagnosed according to the following electrocardiographic criteria: (1) premature P waves having contour identical to P waves of basic beats; (2) intervals between premature P waves mathematically related. In the case reported, the coupling intervals during long phases of intermittent sinus bigeminy were nearly fixed, because there was little variability in the returning cycles, making the diagnosis of sinus parasystole difficult.

Irregular sinus parasystole due to intermittency and modulation of parasystolic activity.

A case of intermittent sinus parasystole in which the parasystolic focus is protected from the dominant sinus rhythm only during the second half of its intrinsic cycle is reported. In addition, a modulating (i.e., electronic) effect is often clearly exerted from the dominant rhythm upon the focus during the protected period. Coexistence of both modulation and intermittency in sinus parasystole, as well as a modulating effect limited to the second part of the parasystolic cycle, have not been previously reported.

[A comparison between propafenone and hydroquinidine perorally in the treatment of recent-onset atrial fibrillation]. / Confronto tra propafenone e idrochinidina per via orale nel trattamento della fibrillazione atriale di recente insorgenza.

The aim of this study was to assess the effectiveness of propafenone and quinidine to restore sinus rhythm in patients with paroxysmal atrial fibrillation. Eighty consecutive patients with recent onset atrial fibrillation were randomized to one of the following oral treatments: a) propafenone 450 mg as single dose followed by 300 mg t.i.d.; b) hydroquinidine 900 mg/24 hours + digoxin if necessary. Drugs were given for a maximum of three days and withdrawn at the restoration of sinus rhythm. If atrial fibrillation was persistent, the other drug was administered after two days wash out. The two groups did not differ from each other with respect to left atrial size, age and presence of organic heart disease, and kind of cardiopathies between the two groups. Sinus rhythm was restored in 39 patients of group 1 (93%) and 36 of group 2 (95%). In conclusion, oral propafenone is as effective as quinidine in the treatment of paroxysmal atrial fibrillation.

[The allorhythmic distribution of ectopic ventricular beats. Observations on the electrogenesis and dynamics of concealed ventricular extrasystole]. / Distribuzione alloritmica dei battiti ectopici ventricolari. Osservazioni sull'elettrogenesi e sulla dinamicità dell'extrasistolia ventricolare occulta.

BACKGROUND: A regular distribution of ventricular ectopic beats is thought to be a relatively uncommon phenomenon, known as "concealed extrasystole". Several experimental studies suggest that the phenomenon originates from a "protected" ventricular focus. The aim of the present study was to evaluate the 24-hour ECG monitoring incidence of ventricular concealed extrasystole in patients with highly frequent ventricular ectopic beats, looking for signs useful in postulating the electrogenesis of the arrhythmia. METHODS: The 24-hour ECGs of 10 patients (pts) with highly frequent ventricular extrasystoles were analysed, searching for significant sequences in the distribution of ectopic beats (i.e., ectopic beats separated by a number of interectopic sinus beats fulfilling one of the formulas of concealed extrasystole). RESULTS: Five cases (50%) showed an allorhythmic distribution resulting in a prevalent pattern of concealed bigeminy (2n-1) in 3 cases, and concealed trigeminy (3n-1) in 2 cases. The phenomenon, however, showed a dynamic behaviour, alternating the distributions from patterns of concealed bigeminy to concealed trigeminy or less common patterns, and vice versa. The evidence of the pure ectopic cycle and mathematically related interectopic intervals in 2 cases, the variability of coupling intervals, and the presence of fusion beats in the remaining 3 cases, strongly suggests a parasystolic origin of the phenomenon. CONCLUSIONS: The results suggest the following: Concealed extrasystole is a relatively common phenomenon, at least in patients with highly frequent ventricular extrasystoles; the phenomenon, however, is somewhat underestimated due to prevalent quantitative, instead of qualitative, Holter monitoring analyses. Among patients with allorhythmically distributed ventricular extrasystoles, none showed only one pattern of distribution. In fact, each single patient showed two or more patterns throughout the 24-hour recordings. Changes from one pattern to another is governed by several factors, such as sinus heart rate and/or the influence of electrotonic "modulation" upon the ectopic focus. Ventricular extrasystoles with regular allorhythmic distribution show a significantly higher variability of coupling intervals than the others (p = 0.005).

[Arrhythmia in thalassemia major: evaluation of iron chelating therapy by dynamic ECG]. / Aritmie nella talassemia major: valutazione della terapia ferrochelante mediante ECG dinamico.

Arrhythmias and sudden death represent striking features in the natural history of thalassemia major. Antiarrhythmic treatment, however, does not appear to change the clinical course. During recent years the disease's therapeutics approach has undergone a substantial evolution, being more adequate the transfusional regimens as well as more effective the iron chelation therapy through subcutaneous infusion of deferoxamine. The aim of the present study was to determine possible influences exerted by the current treatment upon disease's arrhythmic disorders. Thirty patients of both sexes were enrolled in the study. The age ranged from 9 to 24 years. No congenital or acquired heart diseases were present. Each patient underwent concentrated red cell transfusions (in order to obtain pretransfusional hemoglobin levels of 10-11 g%), and iron-binding therapy through continuous subcutaneous microinjection of deferoxamine 40-50 mg/kg/day (6-8 hours/day, 6 days/week). Patients were divided in 2 groups: the first group (group A) comprising the 16 patients with good therapeutic compliance and regular pharmacological regimen; the second group (Group B) including the remaining poorly compliant 14 patients. The following parameters were analyzed: age, average hemoglobin levels during the last year, total amount of red cell transfusions, ferritin levels, starting age of iron-binding therapy. Moreover, each patient underwent 24-hour ECG Holter monitoring. Age (Group A: 18 +/- 4.6; Group B: 14 +/- 2.7; p < 0.02), total amount of transfusions (Group A: 272 +/- 73; Group B: 211 +/- 44; p < 0.03), and ferritin levels (Group A: 1697 +/- 860; Group B: 2908 +/- 730; p < 0.002) proved to be significantly different in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

[The many faces of parasystolic rhythm]. / Le molte facce del ritmo parasistolico.

BACKGROUND: Parasystole is the expression of a pacemaker that is protected from, and thus independent of, the dominant rhythm. The arrhythmia is not always associated with the 3 classic signs: variable coupling, mathematically related interectopic intervals, and fusion beats. A large amount of experimental and clinical data have pointed out several atypical phenomena that make the recognition of parasystole difficult. This especially occurs in the presence of influence exerted from sinus impulses upon the parasystolic rhythm. METHODS: A pattern of ventricular parasystole was evident throughout a 24-hour Holter recording obtained from a 55-year-old female. The following data were analyzed: a) distribution of ectopic complexes; b) parasystolic cycle duration; c) regularity of parasystole, as assessed by means of the variation index. In some sections of the tracing in which an electrotonic influence (modulation) exerted by the sinus rhythm on the parasystolic rhythm appeared as very likely, phase-response curves were constructed in order to express the time-dependent modulation effected by sinus impulses. RESULTS: Parasystole occurred in two separate periods, lasting 4 hours and 90 minutes, respectively. On both occasions, the arrhythmia was apparently precipitated by a brief episode of atrial tachycardia. Phases of regular parasystole, as well as periods of irregular modulated parasystole, were observed. The distribution of ectopic complexes was at times typical for concealed bigeminy (intervening beats always in odd numbers), but on other occasions reflected the even variant of concealed bigeminy where the intervening beats conform to the formula 1 + n (n being zero or an odd number). Some couplets of identical ectopic complexes were also observed. CONCLUSIONS: The study shows that several different expressions of parasystolic rhythm may be present within the same tracing. A minimal or absent modulation results in the classical picture of parasystole; when a mild modulating influence is present, the typical pattern of modulated parasystole ensues, whereas a strong modulation leads to disappearance of the typical features of parasystole and manifestation of concealed bigeminy. Finally, supernormal modulation is responsible for the occurrence of couplets.

Triple ventricular parasystole.

This presentation reflects the analysis of an electrocardiographic recording obtained from a patient with hypertensive heart disease. In the initial section of the tracing, fixed coupled monomorphic ectopic ventricular beats occurred in regular trigeminal rhythm. The pattern changed following an atrial extrasystole and several ventricular ectopic beats of various configuration occurred, often in sequence. Analysis demonstrated the presence of three independent parasystolic rhythms, two of which manifested with the character of intermittency, namely they were occasionally reset by extraneous impulses. The interplay of the sinus pacemaker with three parasystolic foci resulted in a very complex arrhythmic pattern. In some periods, however, two out of three ectopic rhythms were inapparent, and the third one manifested with fixed coupled complexes, so that a regular extrasystolic trigeminy ensued, and parasystole was not recognizable.

Irregular ventricular tachycardia: a possible manifestation of longitudinal dissociation within the reentry pathway.

Sustained monomorphic ventricular tachycardia is usually regular; that is, it is associated with constant R-R intervals. In several cases, however, the cycles of ventricular tachycardia are more or less variable. Fifty-four cases of sustained monomorphic ventricular tachycardia were evaluated in order to assess whether tachycardia was regular. Nine cases were defined as irregular (i.e., the R-R cycles varied by more than 40 msec throughout a 1-minute recording). In five cases tachycardia was "regularly irregular," since the R-R cycles could be divided into two separate groups: the group of long cycles and that of short cycles. In these cases the variability manifested according to a defined and constant pattern: bigeminal pattern (alternation of short and long cycles), trigeminal pattern (two short cycles followed by a long cycle), and so on. The regular variability of tachycardia cycle length suggests one of the following possibilities. (1) There are two alternative circuits (a short circuit and a long circuit) that share the same exit pathway. Whenever the reciprocating impulse runs through the short circuit, the R-R cycle is short; but if a block in the short circuit occurs, the impulse runs through the long circuit, resulting in a long R-R cycle. (2) There is a longitudinal dissociation within the reentry circuit; two separate pathways with different inherent conduction velocities are present. When the impulse runs through the fast pathway, the R-R cycle is short; whereas when a block in the fast pathway occurs, the impulse traverses the slow pathway, resulting in a long R-R cycle.

Failure of parasystolic impulses to appear on schedule. Exit block due to concealed conduction of sinus impulses.

A 45-year-old patient free of any heart disease was admitted to the hospital with an electrocardiographic pattern of ventricular parasystole. The parasystolic rhythm was relatively fast, such that several consecutive ectopic complexes manifested. A later tracing reflected only isolated parasystolic complexes with long and fixed coupling intervals. The interectopic intervals, however, were once more in multiple of the parasystolic cycle as directly measured during the phases of undisturbed parasystolic rhythm. In the latter tracing, several scheduled parasystolic impulses did not yield a response, despite calculation suggesting that these impulses occurred outside the refractory period. In other words, an exit block was present. Analysis of the tracing suggests that the exit block was caused by concealed penetration of the sinus impulses into the ectopic-ventricular junction. That is, any sinus impulse penetrates into the junction and renders it refractory, in such a way that only parasystolic impulses that are relatively late within the sinus cycle may be conducted to the surrounding myocardium and result in a parasystolic complex.

Supernormal conduction in the left bundle branch unmasked by the linking phenomenon.

This presentation reflects a case of phase-3 left bundle branch block (LBBB). Analysis reveals that relatively early QRS complexes are wide, whereas beats occurring later than a critical time are narrow. There are, however, two unexpected phenomena: (1) an overlap occurs between the range of R-R intervals resulting in normal intraventricular conduction and the range of R-R intervals resulting in LBBB pattern. Complexes that follow a wide beat are often wide although they are associated with relatively long R-R intervals, whereas complexes that follow a normal beat tend to be normal even after relatively short R-R cycles. This is due to concealed retrograde penetration of the bundle branch that is blocked in anterograde direction (the so-called linking phenomenon). (2) Some early supraventricular impulses, paradoxically, resulted in normal intraventricular conduction. The phenomenon is a manifestation of supernormal LBB conduction, and only occurs following a wide QRS complex associated with retrograde activation of the LBB. The linking phenomenon reveals or unmasks the supernormal phase of LBB conduction. Following a retrograde and delayed activation of the LBB, the refractory period of the bundle branch is postponed, in such a way that a supraventricular impulse is allowed to occur during the early phase of supernormal conduction.

Atrial parasystole and tachycardia. Modulation and automodulation of a parasystolic focus.

This report deals with a patient reflecting atrial parasystole and episodes of atrial tachycardia. The P' waves during tachycardia were identical to the parasystolic P' waves. Atrial parasystole was at times regular, as revealed by a precise mathematical relationship between the interectopic intervals, and on other occasions irregular. Irregularity was due to modulation, namely electrotonic influence exerted by the sinus impulses upon the parasystolic focus. Atrial tachycardia occurred only during the periods when atrial parasystole was modulated. Atrial tachycardia has been interpreted as due to automodulation, a situation where the propagated parasystolic impulse exerts an electrotonic influence on the ectopic focus itself, leading to a marked unexpected acceleration of the ensuing parasystolic discharge.

Electrocardiographic changes associated with haematocrit variations.

The electrical resistivity of intracardiac blood is less than the resistivity of the surrounding tissues. This affects the transmission of cardiac forces to the body surface: the radial forces are enhanced, whereas the transmission of tangential forces is diminished (the Brody effect). Blood resistivity is directly related to haematocrit, hence, haematocrit changes are expected to affect the transmission of cardiac forces, resulting in changes in QRS complex voltage. To assess this hypothesis, a 12-lead electrocardiogram was recorded in 40 patients affected by thalassaemia before and after a transfusion of concentrated red cells. The voltage of each QRS component was carefully measured in every lead, and the sum of all R wave amplitudes (sigma R) was calculated. The post-transfusional electrocardiogram reflected a significant decrease in the R wave amplitude in every lead. sigma R also decreased, whereas S wave amplitude in lead V6 increased. A negative correlation between the ratio of haematocrit pre/post transfusion and that of the corresponding sigma R values was also observed (r = -0.434; P less than 0.01). An increase in haematocrit is therefore associated with a decrease in R wave amplitude. These findings explain why several patients with high haematocrit manifest relatively low voltage QRS complexes.

[Electrocardiographic diagnosis of ventricular tachycardia in patients with previous myocardial infarct: frequency and significance of diverse diagnostic criteria]. / Diagnosi elettrocardiografica di tachicardia ventricolare in pazienti con pregresso infarto miocardico: frequenza e significato dei diversi criteri diagnostici.

Electrocardiographic tracings of ventricular tachycardia were recorded from 34 patients with old myocardial infarction. The diagnostic criteria of ventricular tachycardia were carefully assessed in each tracing. The most commonly observed signs were: 1) QRS duration greater than 140 msec; 2) a prevalent negative deflection in Lead V6; 3) an interval from the beginning of the QRS complex to the S wave nadir greater than 100 msec in at least one precordial lead. The cases were subdivided into two groups on the basis of a predominant positive or negative deflection in Lead V1 (Group 1 and 2, respectively). The most common signs in Group 1 were a monophasic R wave configuration of the QRS complex in Lead V1, and a QS configuration in Lead V6. On the other hand, the most frequent criteria in Group 2 were an interval between the beginning of the QRS complex and the S wave nadir greater than 60 msec in Lead V1, and a QS configuration in Lead V6. Furthermore, none of the cases reflected a normal frontal plane QRS axis, but an axis deviation was evident in all 29 cases where axis could be calculated.

[A-V conduction in atrial fibrillation and flutter]. / La conduzione A-V nella fibrillazione e nel flutter atriale.

The assessment of A-V conduction in the presence of atrial fibrillation is based upon analysis of the R-R intervals. This is because in atrial fibrillation it is impossible both to identify the impulse that has been conducted to the ventricles, and to measure the A-V conduction time. The first step is, therefore, to evaluate whether the QRS complexes are the expression of conducted atrial impulses, or they are A-V junctional or ventricular in origin. In other words, it is necessary to distinguish between A-V conduction and A-V dissociation. Conduction in atrial fibrillation commonly results in irregular R-R cycles, whereas in the presence of dissociation the R-R cycles are mainly regular. This differentiation can be difficult in the presence of: aberrant conduction; A-V conduction disturbances; or A-V junctional tachycardia with anterograde 2nd degree exit block. The problem occurs both with tachycardia-dependent (or phase 3), and with bradycardia-dependent (or phase 4) aberrant conduction. Distinction between aberration and ectopy is helped by: the sequence long cycle-short cycle; the pause that follows the wide QRS complex; the configuration of the wide QRS complex. Since aberrant conduction may be sustained, due to the linking phenomenon, the pattern may mimick ventricular tachycardia. In atrial flutter the atrial electrical activity is far less chaotic than in atrial fibrillation, so that assessment of A-V conduction is less difficult. Nevertheless, it is impossible to determine exactly which out of the atrial impulses has been conducted, due to the extremely fast atrial rate: the conducted impulse, indeed, is not always the one that immediately precedes the QRS complex. Furthermore, it is also difficult to measure the A-V conduction time, because the F waves follow to each other without any interruption, so that it is impossible to define exactly the beginning of atrial activation. In atrial flutter, thus, as well as in atrial fibrillation, A-V conduction may be assessed by analysis of the R-R intervals, apart from measurement of F-R intervals. In the absence of drugs, atrial flutter is usually associated with 2:1 (or, less frequently, 4:1) conduction ratio, being the odd ratios (3:1, 5:1) far more rare. Due to concealed penetration of non-conducted impulses, A-V conduction intervals are often variable, so that the R-R cycles are irregular even in the presence of a constant A-V conduction ratio. The most common mechanisms leading to irregularity are the alternation of A-V conduction times, and the alternating Wenckebach phenomenon.(ABSTRACT TRUNCATED AT 400 WORDS)

Sinus parasystole.

Sinus parasystole is the expression of a protected nondominant sinus pacemaker, which is totally independent of the dominant rhythm. Two forms of sinus parasystole are described: (1) an active form, where both the dominant and the parasystolic pacemakers are located within the sinus node and (2) a passive form, where the basic rhythm is ectopic and the sinus pacemaker is protected as a result of complete retrograde SA block. Three cases of sinus parasystole are analyzed. In the active form of the arrhythmia the parasystolic sinus P waves are identical to those of the basic sinus rhythm. The diagnosis is suggested by variably coupled premature sinus P waves occurring with mathematically related intervals. This relationship between the parasystolic intervals can not be precise whenever complicating factors such as modulation occur. The recognition of active sinus parasystole is difficult, since the parasystolic P waves do not differ from basic P waves, so that the pattern resembles that of sinus arrhythmia or sinus extrasystoles. The passive form of sinus parasystole is more easily recognized due to the clear-cut difference between the dominant ectopic atrial waves and the "parasystolic" sinus P waves, which manifest with variable coupling intervals and reflect mathematically related intervals in between.

Longitudinal dissociation within the reentry pathway of ventricular tachycardia.

Two cases of nonsustained, repetitive ventricular tachycardia are analyzed. In both, the episodes of tachycardia do not contain random numbers of beats, but the complexes in each phase of tachycardia are either always in even numbers (case 1) or always in odd numbers (case 2). This indicates longitudinal dissociation within the reentry circuit: i.e., there are two functionally separate pathways in some part of the reentry circuit, and the reciprocating impulse runs alternatively through the two pathways. Tachycardia ends due to block of the impulse always in the same pathway, thus, the number of beats in each episode of tachycardia is always either in odd or even numbers.

[A-V conduction in atrial flutter. Electrocardiographic study]. / La conduzione A-V nel flutter atriale. Studio elettrocardiografico.

One hundred and twenty-nine cases of atrial flutter were analyzed to assess the A-V conduction. The R-R intervals, the A-V conduction ratio, and the F-R intervals were measured in each case. Conduction in atrial flutter was defined either as constant or as variable depending on whether the A-V conduction ratio was fixed or variable. Furthermore, atrial flutter was defined as regular whenever the R-R intervals were mathematically related to each other, any interval being a multiple of the F-F cycle. On the other hand, atrial flutter was defined as irregular when the R-R cycles did not reflect a precise mathematical relationship. The R-R intervals in irregular atrial flutter were not exactly multiples of the F-F cycle. This was because the F-R intervals were variable. Sixty-five cases of atrial flutter had constant A-V conduction, whereas 64 cases were associated with variable A-V conduction. Eighty-eight per cent of cases with constant conduction were regular. On the contrary, 91% of cases with variable A-V conduction were irregular. These data reflect a relationship between the constancy of the A-V conduction ratio and the regularity of the R-R intervals. Several mechanisms were identified as being responsible for atrial flutter irregularity. Alternation of the F-R intervals was the most frequent mechanism leading to irregularity of atrial flutter with constant A-V conduction. Alternating Wenckebach periodicity was the most common cause of irregularity in atrial flutter with variable conduction ratio. Concealed conduction of blocked impulses was also frequently involved in determining atrial flutter irregularity.