Ventricular flutter induced during electrophysiologic studies in patients with old myocardial infarction: clinical and electrophysiologic predictors, and prognostic significance

INTRODUCTION

Induction of ventricular flutter during electrophysiologic (EP) studies (similar to that of ventricular fibrillation [VF]) often is viewed as a nonspecific response with limited prognostic significance. However, data supporting this dogma originate from patients without previously documented ventricular tachyarrhythmias. We examined the significance of ventricular flutter in patients with and without spontaneous ventricular arrhythmias.

METHODS AND RESULTS

We conducted a cohort study of all patients with myocardial infarction (MI) undergoing EP studies at our institution. Of 344 consecutive patients, 181 had previously documented spontaneous sustained ventricular arrhythmias, 61 had suspected ventricular arrhythmias, and 102 had neither. Ventricular flutter was induced in 65 (19%) of the patients. Left ventricular ejection fraction was highest among patients with inducible VF (35 +/- 13), lowest for patients with inducible sustained monomorphic ventricular tachycardia (SMVT; 27 +/- 9), and intermediate for patients with inducible ventricular flutter (30 +/- 10). Similarly, the coupling intervals needed to induce the arrhythmia were shortest for VF (200 +/- 28 msec), intermediate for ventricular flutter (209 +/- 27 msec), and longest for SMVT (230 +/- 35 msec). During 5 +/- 8 years of follow-up, the risk for ventricular tachycardia/VF was high for patients with SMVT and ventricular flutter and low for patients with inducible VF and noninducible patients (46%, 34%, 17%, and 14%, P < 0.005).

CONCLUSION

Patients with inducible ventricular flutter appear to be "intermediate" between patients with inducible VF and patients with SMVT in terms of clinical and electrophysiologic correlates. However, the prognostic value of inducible ventricular flutter is comparable to that of SMVT.

Flumazenil is innocuous in a paroxysmal supraventricular tachycardia and radiofrequency ablation: a paediatric case report and review of the literature

The efficacy and safety of flumazenil in reversing midazolam-induced paradoxical reaction in a child suffering from paroxysmal supraventricular tachycardia (PSVT) and undergoing radiofrequency ablation procedure has not been described before. We report a boy who had suffered for years from poorly controlled PSVT because of noncompliance to medications and was being sedated by midazolam and morphine (4 mg each) and prepared for radiofrequency ablation when he began attempting to speak, writhing and flailing his arms, for which physical restraint was required. We also review the current knowledge on the subject. Two doses of flumazenil 0.05 mg i.v. swiftly halted the untoward episode. The child opened his eyes and was calm, coherent and able to answer simple questions. All haemodynamic and respiratory parameters remained stable throughout this event, except for a temporary increase in heart rate (from 68 to 83 b x min-1). The aberrant behaviour did not resume when he was allowed to fall asleep during the ablation of a concealed left lateral accessory pathway. After that procedure, he awoke calm and pain free with no recollection of the aggressive episode. He was kept for 24 h in an intermediate cardiac care unit and was then discharged home. This apparent first report on the efficacious use of flumazenil for the reversal of a paradoxical reaction to midazolam during an electrophysiological study suggests that it neither induces abnormal heart rate nor interferes with the electrophysiological study or the ablation procedure.

Incidence of dual AV node physiology following termination of AV nodal reentrant tachycardia by adenosine-5'-triphosphate: a comparison with drug administration in sinus rhythm

Administration of adenosine triphosphate (ATP) in sinus rhythm identifies dual atrioventricular node physiology (DAVNP) in 75% of patients with inducible slow/fast AV nodal reentrant tachycardia (AVNRT). The incidence of DAVNP following termination of AVNRT with ATP is unknown. Incremental doses of ATP (10-60 mg) were administered, first in sinus rhythm and then during tachycardia induced at electrophysiologic study, to 84 patients with inducible AVNRT and to 18 control patients with inducible AV reentrant tachycardia (AVRT) and no electrophysiologic evidence of DAVNP. Study end-points were the occurrence of DAVNP or > or = 2nd degree AV block following administration of ATP in sinus rhythm and tachycardia termination following administration of ATP during tachycardia. Of the 82 patients with AVNRT who completed the study, 62 (75.6%) exhibited DAVNP following administration of 17.1 +/- 9.4 mg ATP in sinus rhythm, while 30 (36.5%) exhibited DAVNP at the termination of AVNRT following administration of 10.6 +/- 2.4 mg ATP. The occurrence of DAVNP following the administration of 10 mg ATP in sinus rhythm.was a good predictor (62%) of its occurrence after termination of AVNRT with ATP. The dose of ATP had a strong correlation between the presence of DAVNP following AVNRT termination and the ATP doses needed for tachycardia termination. Of the 18 control patients, none had DAVNP at ATP test during sinus rhythm but 1 (5.5%) showed slight (60 msec) PR jump after termination of AVRT with ATP. In conclusion, DAVNP is present in a relatively high proportion (36.5%) of patients following termination of AVNRT with ATP but is much less frequent (5.5%) in control patients. Thus, findings at termination of tachycardia by ATP may be useful in the noninvasive diagnosis of the mechanism of a paroxysmal supraventricular tachycardia.

Genetic analysis of Brugada syndrome in Israel: two novel mutations and possible genetic heterogeneity

Idiopathic ventricular fibrillation in patients with an electrocardiogram (ECG) pattern of right bundle branch block and ST-segment elevation in leads V1 to V3 (now frequently called Brugada syndrome) is associated with a high incidence of syncopal episodes or sudden death. The disease is inherited as an autosomal dominant trait. Mutations in SCN5A, a cardiac sodium channel gene, have been recently associated with Brugada syndrome. We have analyzed 7 patients from Israel affected with Brugada syndrome. The families of these patients are characterized by a small number of symptomatic members. Sequencing analysis of SCN5A revealed two novel mutations, G35S and R104Q, in two Brugada patients, and a possible R34C polymorphism in two unrelated controls. No mutations were detected in 5 other patients, suggesting genetic heterogeneity. Low penetrance is probably the cause for the small number of symptomatic members in the two families positive for the SCN5A mutations.

[Diagnostic use of adenosine triphosphate in cardiac arrhythmias]

Adenosine triphosphate (ATP) has been used for more than 50 years as a major medication in our therapeutic arsenal for the termination of supraventricular tachycardia crises for which the mechanism is re-entry implicating the atrioventricular node. In the present article other applications of ATP as a diagnostic agent for several cardiac arrhythmias are described: differential diagnosis of narrow or wide QRS tachycardia, diagnosis of a latent accessory pathway (intermittent or hidden), diagnosis of intranodal duality, and non-invasive evaluation of the results of the ablation of the slow pathway, and finally non-invasive diagnosis of the tachycardia mechanism in patients with palpitations or tachycardia with an obscure mechanism.

Pause-dependent torsade de pointes following acute myocardial infarction: a variant of the acquired long QT syndrome

OBJECTIVES

We report on a previously unrecognized form of the long QT syndrome (QT interval prolongation and pause-dependent polymorphic ventricular tachycardia [VT]) entirely related to myocardial infarction (MI).

BACKGROUND

Polymorphic VT in the setting of acute MI generally occurs during the hyperacute phase, is related to ischemia, and is not associated with QT prolongation. Although QT prolongation after MI is well described, typical pause-dependent polymorphic VT (torsade de pointes) secondary to uncomplicated MI was previously unknown.

METHODS

Of 434 consecutive admissions for acute MI, 8 patients had progressive QT prolongation that led to typical torsade de pointes. None of these patients had active ischemia or other known causes of QT prolongation. These patients were compared with 100 consecutive patients with uncomplicated MI who served as controls.

RESULTS

The incidence of torsade de pointes following MI was 1.8% (95% confidence interval 0.8% to 3.6%). The QTc intervals of patients and controls were similar on admission. The QTc lengthened by day 2 in both groups, but more so in patients with torsade de pointes (from 470 +/- 46 to 492 +/- 57 ms [p < 0.05] and from 445 +/- 58 to 558 +/- 84 ms, respectively [p < 0.01]). Maximal QT prolongation and torsade de pointes occurred 3 to 11 days after infarction. Therapy included defibrillation, magnesium, lidocaine and beta-blockers. Three patients required rapid cardiac pacing. The long-term course was uneventful.

CONCLUSIONS

Infarct-related torsade de pointes is uncommon but potentially lethal. An acquired long QT syndrome should be considered in patients recovering from MI who experience polymorphic VT as specific therapeutic measures are mandatory.

The adenosine triphosphate test: a bedside diagnostic tool for identifying the mechanism of supraventricular tachycardia in patients with palpitations

OBJECTIVES

This study assesses the value of the "ATP test" (injection of adenosine triphosphate [ATP] during sinus rhythm) for identifying patients with palpitations of unclear etiology who actually have atrioventricular (AV) nodal re-entry tachycardia (AVNRT) or AV re-entry tachycardia (AVRT).

BACKGROUND

Because AVNRT and AVRT can be cured with radiofrequency ablation, documentation of spontaneous AVNRT or AVRT usually prompts referral for electrophysiologic (EP) evaluation. However, these paroxysmal arrhythmias may elude clinical diagnosis. We recently showed that administration of ATP during sinus rhythm often reveals dual AV node physiology or a concealed accessory pathway (AP) in patients with documented AVNRT or AVRT. Thus, we postulated that the ATP test could identify patients with palpitations who actually have AVNRT or AVRT and would therefore benefit from EP evaluation.

METHODS

One hundred forty-six patients (54 with "palpitations without documented arrhythmias" and 92 with "documentation of arrhythmias of unclear mechanism") underwent a noninvasive ATP test. ATP was injected during sinus rhythm using 10 mg increments. The ATP test was considered positive when prospectively defined signs of dual AV node physiology or concealed AP were disclosed in the electrocardiogram. These findings were correlated with the results of EP evaluation.

RESULTS

A positive ATP test predicted induction of AVNRT or AVRT with a positive predictive value of 93% (sensitivity 71%) but a negative predictive value of 37% (specificity 76%).

CONCLUSIONS

A bedside ATP test identifies patients with palpitations who are likely to have AVNRT or AVRT (and who are therefore likely to benefit from EP evaluation) with a high positive predictive value.

Adenosine-5'-triphosphate test for the noninvasive diagnosis of concealed accessory pathway

OBJECTIVES

This study assessed the use of adenosine triphosphate (ATP) in the noninvasive diagnosis of concealed accessory pathway (AP) and dual atrioventricular (AV) node physiology in patients with inducible AV reentrant tachycardia (AVRT).

BACKGROUND

Administration of ATP during sinus rhythm identifies dual AV node physiology in 76% of patients with inducible sustained slow/fast AV nodal reentry tachycardia (AVNRT).

METHODS

Incremental doses of ATP were intravenously administered during sinus rhythm to 34 patients with inducible sustained AVRT involving a concealed AP and to 27 control patients without AP or dual AV node physiology. One study group patient could not complete the study and was excluded from analysis.

RESULTS

The AV reentrant echo beats (AVRE), or AVRT, suggestive of the presence of concealed AP, were observed after ATP administration in 24 (73%) study patients and in none of the control group. Electrocardiographic signs suggestive of dual AV node physiology were observed after ATP administration in 7 (21%) study patients and in none of the control group. Most instances of AVRE/AVRT were preceded by a slight increase (<50 ms) in PR interval. In 8 of 9 patients tested, neither AVRE nor AVRT was no longer observed following ATP administration after successful radiofrequency ablation of the AP. In the remaining patient, a different AVRE due to the presence of an additional AP was observed.

CONCLUSIONS

Administration of ATP during sinus rhythm may be a useful bedside test for identifying patients with concealed AP who are prone to AVRT and those with associated dual AV node pathways.

Prevalence of the Brugada sign in idiopathic ventricular fibrillation and healthy controls

OBJECTIVE

To determine the prevalence of the Brugada sign (right bundle branch block with ST elevation in V1-V3) in idiopathic ventricular fibrillation and in an age matched healthy population.

DESIGN

ECGs from 39 consecutive patients with idiopathic ventricular fibrillation and 592 healthy controls were reviewed. They were classified as definite, questionable, and no Brugada sign (according to predetermined criteria) by four investigators blinded to the subjects' status.

RESULTS

Eight patients (21%) with idiopathic ventricular fibrillation but none of the 592 controls had a definite Brugada sign (p < 0.005). Thus the estimated 95% confidence limits for the prevalence of a definite Brugada sign among healthy controls was less than 0.5%. A questionable Brugada sign was seen in two patients with idiopathic ventricular fibrillation (5%) but also in five controls (1%) (p < 0.05). Normal ECGs were found following resuscitation and during long term follow up in 31 patients with idiopathic ventricular fibrillation (79%). Patients with idiopathic ventricular fibrillation and a normal ECG and those with the Brugada syndrome were of similar age and had similar spontaneous and inducible arrhythmias. However, the two groups differed in terms of sex, family history, and the incidence of sleep related ventricular fibrillation.

CONCLUSIONS

A definite Brugada sign is a specific marker of arrhythmic risk. However, less than obvious ECG abnormalities have little diagnostic value, as a "questionable" Brugada sign was observed in 1% of healthy controls. In this series of consecutive patients with idiopathic ventricular fibrillation, most had normal ECGs.

Arrhythmias in the congenital long QT syndrome: how often is torsade de pointes pause dependent?

OBJECTIVE

To determine the frequency and predictors of pause dependent torsade de pointes among patients with the congenital long QT syndrome and spontaneous ventricular tachyarrhythmias.

DESIGN

The literature on the "congenital long QT" was reviewed. Articles with illustrations demonstrating the onset of spontaneous polymorphic ventricular arrhythmias in the absence of arrhythmogenic drugs were included.

RESULTS

Illustrations of 62 spontaneous episodes of torsade de pointes among patients with congenital long QT syndrome were found in the literature. The majority (74%) of documented arrhythmias were "pause dependent"; 82% of these pauses were longer than the basic cycle length by > 100 ms. Age and sex correlated with the mode of arrhythmia initiation. Arrhythmias in infants (</= 3 years old) were not pause dependent, while female sex correlated with pause dependent torsade. Using multivariate analysis, age was the only independent predictor of the mode of onset of torsade de pointes.

CONCLUSION

Available data suggest that the majority of spontaneous arrhythmias in the congenital long QT syndrome are pause dependent. Torsade de pointes that is not preceded by pauses appears to be limited to patient subgroups with severe forms of the disease, like symptomatic infants. These findings have important implications regarding the use of cardiac pacing for arrhythmia prevention.

Simplified "ATP test" for noninvasive diagnosis of dual AV nodal physiology and assessment of results of slow pathway ablation in patients with AV nodal reentrant tachycardia

INTRODUCTION

We recently reported that administration of adenosine triphosphate (ATP) during sinus rhythm identifies dual AV nodal physiology (DAVNP) in 76% of patients with inducible sustained AV nodal reentrant tachycardia (AVNRT) at electrophysiologic (EP) study. In that report, however, the ATP test was considered positive for DAVNP only when the results were reproducible at a given dose of ATP. The aim of the present study was to assess the value of a simplified ATP test for noninvasive diagnosis of DAVNP and abolition or modification of the slow pathway (SP) after radiofrequency ablation (RFA) in patients with inducible sustained AVNRT.

METHODS AND RESULTS

The value of a single dose of ATP was studied in 105 patients with inducible sustained AVNRT and in 31 control patients before placement of EP catheters in the cardiac chambers. ATP (10 to 60 mg, in 10-mg increments) was injected during sinus rhythm until ECG signs of DAVNP (> or = 50 msec increase or decrease in PR interval in two consecutive beats, or occurrence of > or = 1 AV nodal echo beat) or > or = second-degree AV block was observed. DAVNP was observed in only 1 (3.2%) control patient. The test could be completed in 96 study patients. DAVNP was found by ATP test in 72 (75%) patients, whereas it was diagnosed by EP criteria in 82 (85%) patients. DAVNP by ATP test disappeared in 27 (96%) of 28 patients who underwent SP abolition and in 18 (60%) of 30 patients who underwent SP modification. In the 12 patients with persistent DAVNP determined by ATP test after SP modification, the number of beats conducted over the SP was significantly reduced (from 6.3+/-3.3 to 2.5+/-2.2 beats; P = 0.002).

CONCLUSION

A single administration of ATP during sinus rhythm (at a given dose) enables noninvasive diagnosis of DAVNP in a high percentage of patients with inducible AVNRT and reliably confirms the results of RFA of the SP.

Long-term follow-up of patients with long-QT syndrome treated with beta-blockers and continuous pacing

BACKGROUND

The long-QT syndrome is associated with sudden cardiac death. Combination of beta-blocker and pacing therapy has been proposed for treatment of drug-resistant patients. The purpose of this study was to summarize our long-term experience with combined therapy in patients with long-QT syndrome.

METHODS AND RESULTS

A total of 37 patients with idiopathic long-QT syndrome were treated with combined therapy consisting of continuous cardiac pacing and maximally tolerated beta-blocker therapy and followed up for 6.3+/-4. 6 years (mean+/-SD). The group consisted of 32 female and 5 male patients with a mean age of 31.6 years. The mean paced rate was 82+/-7 bpm (range, 60 to 100 bpm). On follow-up, recurrent symptoms caused by pacemaker malfunction were documented in 3 patients. Four patients died during the follow-up period: 2 adolescents stopped beta-blocker therapy, 1 patient died suddenly while treated with combined therapy, and 1 patient died of unrelated causes. In addition, 3 patients had resuscitated cardiac arrest while on combined therapy, and 1 patient had repeated, appropriate implantable cardioverter-defibrillator discharges on follow-up.

CONCLUSIONS

Because 28 of 37 patients remain without symptoms with beta-blocker therapy and continuous pacing, combined therapy appears to provide reasonable, long-term control for this high-risk group. However, the incidence of sudden death and aborted sudden death (24% in all patients and 17% in compliant patients) strongly suggests the use of a "back-up" defibrillator, particularly in noncompliant adolescent patients. Implantable cardioverter-defibrillator therapy, however, may be associated with recurrent shocks in susceptible patients.