Malignant ventricular arrhythmia in the Wolff-Parkinson-White syndrome during amiodarone treatment

The ventricular rate during rapid atrial rhythms is related in Wolff-Parkinson-White (WPW) syndrome to antegrade effective refractory period of the accessory pathways. Among the many antiarrhythmic drugs available, amiodarone is most commonly used for its large therapeutic window and very long half-life. We report a case of cardiac pre-excitation syndrome in a young male patient in whom amiodarone therapy (3000 mg/weekly) was instituted to modify the dangerous ventricular response during atrial fibrillation (shortest R-R interval 190 ms, ventricular rate 210 beats/min). Four months later, starting pharmacological treatment, a new electrophysiological study documented a malignant ventricular arrhythmia: during atrial fibrillation the minimum R-R interval was 160 ms and the ventricular rate 280 beats/min. Finally, the possible mechanism of paradoxical effect observed in our patient is hypothesized. Amiodarone could favor conduction over the accessory pathways by slowing or blocking conduction into the atrioventricular node and decreasing concealed retrograde conduction into the accessory bypass tract by normally conducted beats.     

利用单极标测在心房颤动时消融显性房室旁道

对12例预激综合征患者在心房颤动时以单极标测指导消融房室旁道，其中左侧显性旁道9例、右侧显性旁道3例。在消融成功的靶点图上，单极标测的心室激动较体表心电图QRS波群显示预激成分最明显的Delta波平均提前46±7ms。全部病例消融成功。平均随访7．9±5．1个月，除1例右侧旁道4个月后恢复旁道前向传导需再次消融外，其余11例常规和动态心电图既未见Delta波，也无房室折返性心动过速和心房颤动发生。结果提示对于心房颤动合并显性房室旁道的患者，采用单极标测，其图形易于迅速辨认、测量方法亦简单，用以指导消融成功率高。     

Ventricular fibrillation in the Wolff-Parkinson-White syndrome

Ventricular fibrillation (VF) is a well-known but rare complication of the Wolff-Parkinson-White syndrome (WPW). Clinical and electrophysiological data of 23 patients with spontaneous VF were compared with data from 100 consecutive patients with WPW without VF but with symptomatic supraventricular tachycardia. The 23 patients were collected in a multicentre retrospective study in seven European centres. VF occurred in only one patient who was receiving antiarrhythmic drugs, and was the first manifestation of the syndrome in six. No significant differences were found between those with VF and without VF in age, complaints of palpitations, syncope, and presence of structural heart disease. The retrograde effective refractory period of the accessory pathway, the atrial refractory period and the fastest atrial pacing rate with 1:1 anterograde conduction over the accessory pathway were similar in both groups. Significant differences were found for sex, permanent pre-excitation on the electrocardiogram, type of documented supraventricular tachyarrhythmias, shortest RR interval less than or equal to 220 ms during spontaneous atrial fibrillation (AF), inducibility of supraventricular tachycardias, ventricular effective refractory period less than or equal to 190 ms, mean shortest RR interval during induced AF less than or equal to 180 ms and presence of multiple accessory pathways.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Enhanced A-V nodal conduction (Lown-Ganong-Levine syndrome) by congenitally hypoplastic A-V node.

The basic anatomical substrate of enhanced A-V nodal conduction, manifesting or not as Lown-Ganong-Levine syndrome, is still a controversial issue. We describe the case of a 34-year-old man who presented episodes of ventricular fibrillation. Electrophysiological studies showed that the AH interval was 55 ms, and increased by only 20 ms at paced cycle lengths of 300 ms; atrial pacing induced atrial fibrillation, with a shortest RR interval of 240 ms. Despite verapamil therapy, this patient died suddenly at home. Histological study disclosed a severe A-V node hypoplasia that was evidently congenital in nature; the rest of the conduction system was normal, and no accessory A-V pathways were present. We suggest that enhanced A-V nodal conduction in this patient was due to the developmental defect in the A-V node; this abnormality caused a loss of specific impulse-delaying function, and thus allowed rapid, unfiltered atrial impulses to reach the lower A-V junction and ventricles.     

心房颤动患者体表心电图QT间期的变化

探讨心房颤动(简称房颤)患者体表心电图QT间期的变化。入选81例房颤患者和71例对照者,测量Ⅰ导联和V2导联QT间期,根据Bazett公式计算QTc。结果:窦性心律时V2导联QT间期可测量性略高于Ⅰ导联,而房颤时相反。V2导联测得的QTc比Ⅰ导联长。房颤组与对照组比较,窦性心律时Ⅰ导联和V2导联的QTc两组间均无明显差异;房颤发作时Ⅰ导联QTc较对照组延长(429.01±43.08msvs408.50±31.93ms,P<0.05);V2导联QTc较对照组也延长(444.45±33.16msvs414.82±25.57ms,P<0.05)。房颤组房颤发作时与窦性心律时的自身对照比较,V2导联的QTc也延长(448.63±31.59msvs426.22±29.08ms,P<0.05)。结论:房颤患者在房颤发作时QTc延长,而房颤患者窦性心律时QTc与对照组无差异。     

Effects of oral sotalol on the conduction of accessory atrioventricular pathways

The effects of oral Sotalol were assessed by electrophysiological investigations in 6 patients with ventricular preexcitation (Wolff-Parkinson-White syndrome) and a short anterograde refractory period (less than or equal to 280 ms) of the accessory pathway. After 27 to 80 days (mean 41 +/- 19 days) of oral Sotalol (160 mg daily in 5 patients, 320 mg daily in 1 patient). The effective anterograde refractory period of the accessory pathway increased from 268 +/- 13 ms to 318 +/- 33 ms (less than 0.05); the shortest QR interval with appearances of preexcitation increased either during rapid atrial pacing (272 +/- 19 ms to 374 +/- 74 ms: p less than 0.05) or during induced atrial fibrillation (258 +/- 61 to 335 +/- 56 ms: p less than 0.01). The effective refractory period could only be measured in 4 cases during Sotalol therapy and increased by 10 ms, 130 ms and by at least 220 and 300 ms. During the repeat electrophysiological investigation the plasma concentrations of Sotalol ranged from 0.33 to 2.3 g/ml. These results show that oral Sotalol significantly increases the effective refractory periods of accessory pathways even when they are short under basal conditions. This product could therefore be effective in preventing the rapid ventricular response to atrial fibrillation in patients with the WPW syndrome and also in the prevention of reciprocating tachycardias.     

Mode of onset of atrial fibrillation in the Wolff-Parkinson-White syndrome: how important is the accessory pathway?

The mode of onset of 103 episodes of atrial fibrillation lasting greater than or equal to 30 s was studied in 79 patients with the Wolff-Parkinson-White syndrome during electrophysiologic study. No patient had organic heart disease, and 31 had clinical atrial fibrillation before study. These 79 patients were then compared with a control group of 53 patients with Wolff-Parkinson-White syndrome in whom atrial fibrillation could not be induced. Ninety-five of the 103 episodes were technically suitable for analysis. Atrial fibrillation invariably began with rapid atrial tachycardia that became progressively disorganized within 10 to 20 cycles. It was initiated during right atrial stimulation (n = 52), right ventricular stimulation (n = 8), reciprocating tachycardia (n = 33) and spontaneously (n = 2). Most episodes started at a high right atrial site regardless of accessory pathway location, with only 19% of episodes starting at the electrode closest to the accessory pathway. During reciprocating tachycardia (n = 33), either atrial (n = 8) or ventricular (n = 5) extrastimuli initiated atrial fibrillation. Atrial fibrillation started at the accessory pathway site in 6 of 20 episodes occurring spontaneously during reciprocating tachycardia. Patients with atrial fibrillation had a longer PA interval (54 +/- 14 versus 42 +/- 12 ms, p less than 0.0001), shorter atrial functional refractory period (226 +/- 38 versus 240 +/- 30 ms, p = 0.049) and shorter anterograde effective refractory period of the accessory pathway (279 +/- 26 versus 304 +/- 75 ms, p = 0.03). Clinical reciprocating tachycardia was documented with equal frequency in both the atrial fibrillation and control groups (59.5% versus 52.9%, p = 0.58).(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of exercise on the permeability of accessory pathways and supraventricular arrhythmia in Wolff-Parkinson-White syndrome]

The influence of adrenergic stimulation on the effective anterograde refractory period of the accessory pathways and on supraventricular arrhythmias, was studied in 20 patients (average age 38 +/- 16 years) with an untreated permanent Wolff-Parkinson-White syndrome and a resting anterograde refractory period < or = 400ms. Repeated electrophysiological studies with a single endocavity catheter positioned near the atrial pole of the accessory pathway were performed under basal conditions and during a standardised exercise test on a bicycle ergometer. The effective anterograde refractory period of the accessory pathway, the length of the tachycardia cycle during reciprocating orthodromic tachycardia, the average heart rate, the percentage of preexcited QRS complexes during induced atrial fibrillation, were measured in all patients under basal conditions and at the peak of exercise. Exercise significantly reduced the anterograde refractory period of the accessory pathway (287 +/- 49 ms at rest versus 238 +/- 24 ms on exercise: p < 0.001), the cycle of orthodromic tachycardia (302 +/- 32 vs 260 +/- 22 ms p < 0.001), the minimal R-R interval (270 +/- 65 vs 227 +/- 46 ms: p < 0.05) and % of preexcited QRS complexes (75 +/- 33 vs 51 +/- 39: p < 0.05) in atrial fibrillation whilst increasing the average heart rate (165 +/- 42 vs 202 +/- 39 bpm: p < 0.02). Adrenergic stimulation significantly improves anterograde conduction in the accessory pathway. The reduction in the % of preexcited QRS complexes in atrial fibrillation could indicate a preferential action of catecholamines on the nodo-hisian pathway.(ABSTRACT TRUNCATED AT 250 WORDS)     

Value of transesophageal auricular stimulation for evaluating the accessory pathway and effect of treatment in Wolf-Parkinson-White syndrome

In order to assess the value of the various atrial pacing techniques employed to evaluate the anterograde conduction of the accessory pathway and the effect of antiarrhythmic agents in Wolff-Parkinson-White syndrome, transesophageal atrial pacing was performed in 12 patients before and during treatment with oral flecainide acetate in doses of 200 mg per day. Before treatment, the shortest interval conducted with a 1/1 atrioventricular conduction by the accessory pathway ranged from 225 to 600 ms (mean 311 +/- 98 ms), and the effective refractory period of the accessory pathway, measured by the extrastimulus method in 11 patients, varied from 240 to 320 ms (mean 273 +/- 22 ms). These two values were very close in each patient and correlated well with each other (r = 0.90; p less than 0.001). Atrial fibrillation could be induced in 3 patients. Three patients were considered "at risk" since their effective refractory period or minimal R-R interval in atrial fibrillation was 250 ms or less. Tachycardia was induced in 8 patients, and it was possible to induce arrhythmias in the 6 patients for whom we had recordings in spontaneous tachycardia. Under treatment with flecainide acetate, an anterograde conduction block appeared in 3 patients. In the remaining 9 patients the shortest interval conducted with a 1/1 atrioventricular conduction by the accessory pathway was longer in every case: it ranged from 270 to 540 ms (mean 407 +/- 84 ms; p less than 0.001), which corresponded to a 20 to 240 ms prolongation (mean 133 +/- 78 ms).(ABSTRACT TRUNCATED AT 250 WORDS)     

The Utility of Unipolar Electrogram Recording for Catheter Ablation of Accessory Pathways During Atrial Fibrillation

INTRODUCTION: Atrial fibrillation, a commonly occurring rhythm in patients with manifest accessory pathways, may prevent the usual mapping criteria for successful catheter ablation from being obtained. Unipolar electrogram recordings may be of value in this situation. METHODS: Unipolar recordings were obtained during atrial fibrillation in one patient with a manifest left-sided accessory pathway, and another patient with a septal accessory pathway with Mahaim-like properties. The timing of the intrinsic deflection, and the presence of a QS complex, were utilized as criteria to define the successful ablation site. RESULTS: Successful ablation of the accessory pathways was achieved during atrial fibrillation. CONCLUSIONS: The use of unipolar recordings can aid successful catheter ablation of the accessory pathways during atrial fibrillation, giving added information to the bipolar electrograms.     

心房颤动时显性房室旁道的射频消融治疗

对 2 6例预激综合征患者于心房颤动 (简称房颤 )时射频消融显性房室旁道。其中左侧旁道 9例、右侧旁道17例 ,2 2例有阵发性房颤史。房颤发作伴旁道前传时的心室率为 171± 32 ( 132～ 2 37)bpm。采用经主动脉逆行法或穿间隔法消融左侧旁道、经股静脉途径消融右侧旁道 ,以最早心室前向激动点且有小A波处为消融靶点。房颤时成功消融靶点的V波较体表心电图预激波的起点提前 37.2± 8.1( 2 6～ 5 3)ms。放电 6± 3( 1～ 16 )次后 ,2 6例中有2 5例 ( 96 % )旁道前传被阻断 ,1例失败。阻断旁道前传后 30min ,3例自行恢复窦性心律 ,2 2例经直流电复律后恢复窦性心律 ,心室起搏示 2 5例中有 2 3例旁道逆传已被阻断 ,2例仍存在 ,经继续消融获得成功。随访 19.2± 11.7( 1～ 38)个月 ,除 1例复发正向前传型房室折返性心动过速 (O AVRT) ,经再次消融旁道逆传成功外 ,其他患者无O AVRT发作及旁道前传恢复的证据。结论 :心房颤动时射频消融显性房室旁道方法可行、成功率高     

双房室旁道合并Mahaim纤维(附一例分析)

报道１例束室纤维合并双房室旁道的电生理表现。患者有心动过速史１５年，心电图示右侧游离壁显性旁道，分别于三尖瓣环８点半和５点半处消融阻断旁道，原心电图发生了改变，但存在Ｄｅｌｔａ波。上述两条旁道消融前，ＰＲ间期均为０．０６ｓ，心房递增刺激Ｄｅｌｔａ波增大，房室传导无文氏现象。两条房室旁道消融后，ＰＲ间期为０．１０ｓ、ＡＨ间期１００ｍｓ、ＨＶ间期２０ｍｓ。心房递增刺激时ＡＨ间期逐渐延长且出现文氏型房室阻滞，ＨＶ间期不变、预激程度不变，提示为Ｍａｈａｉｍ纤维（束室支）。心室刺激时逆传Ａ波在Ｈｉｓ束电图最早，提示Ｈｉｓ束逆传。三尖瓣环上未能标测到Ａ、Ｖ波融合。心房、心室刺激未能诱发心动过速。     

Acute effect of disopyramide on atrial fibrillation in the Wolff-Parkinson-White syndrome

Disopyramide was administered intravenously to 54 patients during atrial fibrillation and predominantly pre-excited QRS configuration at the time of electrophysiologic study. All patients had Wolff-Parkinson-White syndrome and no patient had coexistent heart disease. The drug was given during sustained atrial fibrillation (n = 45) or during sinus rhythm before induction of atrial fibrillation for patients whose atrial fibrillation was self-terminating in the control state (n = 9). Atrial fibrillation converted to sinus rhythm within 15 min after disopyramide in 37 (82%) of the 45 patients. The shortest RR intervals between two pre-excited cycles increased from 208 +/- 42 to 293 +/- 117 ms (p less than 0.0001). The average RR interval of all cycles prolonged from 332 +/- 60 to 396 +/- 117 ms(n = 45, p less than 0.0001). The 9 patients in whom pre-excitation was abolished after the drug had a significantly longer initial shortest RR interval than that of the 36 patients in whom pre-excitation persisted (246 +/- 47 versus 199 +/- 36 ms, p = 0.0022). No patients developed significant hemodynamic or other adverse effects after disopyramide. These data support the intravenous use of disopyramide in patients with normal ventricular function who have atrial fibrillation and a predominant ventricular response over an accessory atrioventricular pathway.     

Atrial fibrillation in patients with Wolff-Parkinson-White syndrome: incidence after surgical ablation of the accessory pathway

The effect of surgical ablation of ablation of atrioventricular accessory pathways on the incidence of atrial fibrillation in patients with Wolff-Parkinson-White syndrome was examined and the results of preoperative electrophysiologic testing were studied to determine factors predictive of outcome. Among 50 consecutive surgical cases, 19 patients were identified with a past history of at least one episode of spontaneous atrial fibrillation documented by electrocardiogram before surgery. The mean number of episodes of atrial fibrillation was 1.97/patient/year during a mean symptomatic period of 6.9 years before surgery. These patients were compared with 19 consecutive patients undergoing surgery during the same time period who had a history of only reciprocating tachycardia. Patients with atrial fibrillation had a significantly shorter antegrade accessory pathway effective refractory period (270 +/- 39 vs 330 +/- 107 msec; p less than .05) and much faster ventricular rates during induced atrial fibrillation (shortest RR interval 219 +/- 73 vs 294 +/- 60 msec, p less than .005; average RR interval 324 +/- 109 vs 405 +/- 127 msec, p less than .01). Patients with atrial fibrillation also had longer PA intervals (47 +/- 13 vs 37 +/- 7 msec; p less than .02). At preoperative electrophysiologic testing, 18 patients with atrial fibrillation had atrial fibrillation induced and 14 sustained the arrhythmia for longer than 10 min. In contrast, atrial fibrillation, although induced in 14 of 19 patients with reciprocating tachycardia, was not sustained in any. Thus electrophysiologic testing suggested that both accessory pathway properties and atrial vulnerability may predispose to atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The diagnosis and management of supraventricular tachycardia by transesophageal cardiac stimulation and recording

Twenty-two consecutive patients underwent esophageal stimulation and recording for the diagnosis and management of supraventricular tachycardia. In 13 of these patients, the resting electrocardiogram was normal and in nine it showed pre-excitation. Of the 13 patients with a normal resting electrocardiogram, supraventricular tachycardia was initiated in all. Seven patients had a ventricular-to-atrial interval greater than 70 ms during supraventricular tachycardia suggesting the presence of a concealed accessory pathway, and six patients had a ventricular-to-atrial interval less than 70 ms during supraventricular tachycardia suggesting reentry within the atrioventricular node. Supraventricular tachycardia was initiated in four of nine patients with pre-excitation on the resting electrocardiogram and the accessory pathway was confirmed by a ventricular-to-atrial interval of greater than 70 ms during supraventricular tachycardia in these four patients. Atrial fibrillation was initiated in eight of the nine patients with pre-excitation on the resting electrocardiogram and the shortest R-R interval during atrial fibrillation was measured. The response to therapy was assessed in seven of these nine patients by further measurement of the shortest R-R interval during atrial fibrillation following treatment. Esophageal stimulation and recording provides a simple noninvasive procedure which can be utilized as a screening technique to identify patients with intranodal reentry and those with reentry utilizing an accessory pathway. Sequential assessment of the response to therapy, especially in those patients with pre-excitation, is of considerable value in treatment.     

Observations on the antidromic type of circus movement tachycardia in the Wolff-Parkinson-White syndrome

In the differential diagnosis of tachycardias showing a wide QRS complex and having a 1 to 1 relation between ventricular and atrial events, a supraventricular tachycardia with anterograde conduction over an accessory pathway and retrograde conduction by way of the specific conduction system must be considered. Five patients showing this type of circus movement tachycardia were studied by programmed electrical stimulation of the heart. Sudden changes in the tachycardia cycle length were observed in these patients that were based on changes in the VH interval. This finding suggested a change in the reentrant circuit with anterograde conduction over the accessory pathway but retrograde conduction sometimes occurring over the right bundle branch and at other times over one of the two divisions of the left bundle branch system. Characteristically, the tachycardia cycle length changed suddenly depending on the bundle branch used in retrograde direction. In one patient, an important difference was also observed between the anterograde effective refractory period of the accessory bypass (280 ms) and the shortest RR interval between preexcited QRS complexes during atrial fibrillation (measuring 190 ms). It is postulated that the short RR intervals during atrial fibrillation in the Wolff-Parkinson-White syndrome could result from bundle branch reentry after activation of the ventricles over the accessory pathway.     

The QT interval in atrial fibrillation.

The electrocardiogram was recorded for 100 seconds in 50 patients with atrial fibrillation to determine the relations between QT intervals and both the mean and instantaneous ventricular rates. The mean ventricular rate was 94 beats per minute with a mean QT interval of 357 ms. The mean QTc, corrected beat by beat with Bazett's formula, was 444 ms--longer than reported for sinus rhythm. Between subjects, the mean QT interval was linearly related to the mean RR interval, with a slope of +21%. Within all 50 recordings there was a statistically significant correlation between QT intervals and immediately preceding RR intervals, with an average slope of +7%. This within subject QT/RR interval slope was greater at faster mean ventricular rates. In atrial fibrillation, as in sinus rhythm, the QT interval is a function of both the mean ventricular rate and the instantaneous ventricular rate, with the mean ventricular rate predominating; a simple correction of QT intervals for heart rate is therefore inadequate. Comparison of uncorrected QT intervals with those of earlier published series of people in sinus rhythm, however, suggested that atrial fibrillation is associated with prolongation of the mean QT interval.     

Gender differences in arrhythmias

Electrocardiographic and electrophysiologic differences between men and women have long been noted. Women have a higher intrinsic heart rate than men, along with a longer corrected QT interval and a shorter sinus nodal recovery time. The incidence of and risk factors for a variety of arrhythmias differ between men and women. Atrioventricular nodal reentry tachycardia has a 2:1 female-to-male predominance, while accessory pathways are twice as frequent in men. Although atrial fibrillation is more prevalent in men of all age groups, the absolute numbers of men and women with atrial fibrillation are equal, and the associated morbidity and mortality experienced by women with atrial fibrillation appear to be worse. Women have a lower incidence of sudden cardiac death, and female survivors of sudden cardiac death have a lower frequency of spontaneous or inducible ventricular tachycardia. On the other hand, drug-induced torsade de pointes and symptomatic long QT syndrome have a female predominance. Therefore, greater caution should be used when prescribing QT-prolonging drugs in women. The incidence of arrhythmias is increased during pregnancy, and management of pregnant patients poses a significant challenge. The mechanisms of these gender differences are unclear but may be related to hormonal effects and the shorter QT interval in adult males. Pharmacologic and nonpharmacologic therapies are usually equally efficacious, but the risks of pharmacologic therapy are different in men and women. Atrial fibrillation may be more difficult to treat in women.     

Radiofrequency catheter ablation of an accessory pathway during preexcited atrial fibrillation

Radiofrequency catheter ablation of accessory pathways can not routinely be performed during preexcited atrial fibrillation. However, atrial fibrillation occurs frequently in patients with Wolff-Parkinson-White syndrome during an electrophysiologic study, causing difficulty for both the patient and the operator. In this case report we present two cases with Wolff-Parkinson-White syndrome treated by catheter ablation during preexcited atrial fibrillation. The localizations of accessory pathways were left lateral in one case, and right posteroseptal in the other.