Decline in inducibility of sustained ventricular tachycardia from two to twenty weeks after acute myocardial infarction

To determine temporal evolution of sustained ventricular arrhythmias inducible after acute myocardial infarction (AMI), serial programmed ventricular stimulation (PVS) was performed in 27 patients 15 +/- 4 and 150 +/- 28 days after AMI. These patients did not have worsening of congestive heart failure or angina, coronary artery bypass surgery or spontaneous sustained ventricular tachycardia (VT) in the period between 2 PVS studies. During initial PVS, sustained VT or ventricular fibrillation (VF) was inducible in 17 patients (group I) and was not inducible in 10 (group II). Late PVS in group I induced sustained VT or VF in 8 patients (47%) and nonsustained VT or no VT in 9 (53%). A decrease in late inducibility of sustained VT/VF was greater for arrhythmias induced during initial PVS by triple extrastimuli and burst pacing than for those induced by double extrastimuli (88% vs 25%, p less than 0.04), but appeared to be unrelated to the morphologic characteristics or cycle length of the initially induced sustained VT or VF and to other clinical, hemodynamic or angiographic variables. During late PVS in 10 group II patients, sustained VT or VF remained noninducible in 9 (90% concordance); in 1 patient sustained VT was induced. During a mean follow-up of 14 +/- 5 months since late PVS, none of 27 patients had spontaneous sustained VT and 2 patients in group I died suddenly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spontaneous sustained ventricular tachyarrhythmias during treatment with type IA antiarrhythmic agents

Twenty-six patients who developed their first clinical episode of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) while taking type IA antiarrhythmic agents for more benign rhythm disturbances were rechallenged with the identical drug during electrophysiologic testing. Patients with these new drug-associated spontaneous ventricular arrhythmias often manifested a preexisting substrate for such arrhythmias: sustained VT or VF was induced in 65% of patients at baseline, and in 58% of patients when tested with their previously taken antiarrhythmic drug. Among those without inducible sustained ventricular arrhythmias in the drug-free state, 78% remained free of inducible sustained arrhythmias when tested with the same drug they had been taking at the time of the clinical arrhythmia. Even patients without a definable electrophysiologic substrate for sustained VT or VF remained at risk for arrhythmia recurrence if treated with alternative antiarrhythmic medications: 40% of such patients who continued to receive an antiarrhythmic agent different from that being administered when their clinical VT or VF occurred had recurrent spontaneous ventricular tachyarrhythmias during follow-up. Thus, patients with drug-associated clinical sustained ventricular tachycardias form a heterogenous group that should be evaluated individually and not empirically managed for a "proarrhythmic effect" simply by antiarrhythmic drug withdrawal or drug substitution.     

Electrophysiologic studies in nonsustained ventricular tachycardia: Relation to underlying heart disease

Electrophysiologic studies were performed in 83 patients with spontaneous episodes of nonsustained ventricular tachycardia (VT). The clinical arrhythmia was reproduced in 63% (in 42 patients by programmed stimulation and in 10 by isoproterenol infusion). In 15 patients sustained VT could be reproducibly induced by programmed stimulation. Inducibility was related to the associated heart diseases: programmed stimulation induced VT in 25 of 33 patients (75%) with coronary disease, 6 of 18 patients (33%) with cardiomyopathy (dilated in 16, hypertrophic nonobstructive in 2), in 4 of 8 patients (50%) with mitral valve prolapse and in 7 of 24 patients (29%) without structural heart disease. Isoproterenol infusion induced VT in no other patient with coronary artery disease, 1 other patient with mitral valve prolapse, 3 patients with cardiomyopathy, and in 6 of 24 patients without structural heart disease. Sustained VT was induced only in patients with structural heart disease, and correlated with the presence of left ventricular aneurysms: Sustained VT was induced in 9 of 13 patients with left ventricular aneurysms. The study demonstrates that electrophysiologic techniques can reproduce episodes of nonsustained VT in most patients with spontaneous arrhythmias. Some patients who demonstrate only nonsustained VT spontaneously have inducible, sustained VT, most often in the setting of coronary artery disease and left ventricular aneurysms.     

Programmed ventricular stimulation in mitral valve prolapse: analysis of 36 patients

Programmed ventricular stimulation with 3 extrastimuli was performed in 36 patients with mitral valve prolapse (MVP). Among 11 patients without transient cerebral symptoms, none had inducible ventricular tachycardia (VT) or ventricular fibrillation (VF), whether or not nonsustained VT or ventricular premature complexes (VPC) were present during ambulatory electrocardiographic recordings. These patients remained well without antiarrhythmic drug therapy for 6 to 57 months (mean 23) of follow-up. Two patients with recurrent unexplained syncope and no documented ventricular arrhythmia during electrocardiographic monitoring also had no inducible VT or VF. Among 20 patients with syncope or presyncope and documented nonsustained VT or VPCs during electrocardiographic monitoring, polymorphic nonsustained VT was induced in 8, sustained unimorphic VT in 2, and VF in 3. In 1 patient who had inducible polymorphic nonsustained VT, electrocardiographic monitoring during syncope showed sinus rhythm. Among 3 patients with a history of sustained VT or VF, unimorphic VT was induced in each. Patients with MVP who have asymptomatic ventricular ectopic activity and no inducible VT may have a benign prognosis without treatment. In patients who have transient cerebral symptoms and documented nonsustained VT or VPCs, VT or VF is inducible in 65%, most often polymorphic VT. It is unclear in which patients this finding is clinically significant and in which it is a nonspecific response to programmed stimulation.     

The yield of programmed ventricular stimulation in mitral valve prolapse patients with ventricular arrhythmias

A high-risk subset of patients with mitral valve prolapse (MVP) and a predisposition to sudden cardiac death (SCD) has been proposed. We analyzed the results of programmed ventricular stimulation (PVS) in 20 patients with MVP and ventricular arrhythmias (ventricular premature depolarization in 6, ventricular couplets in 2, nonsustained ventricular tachycardia [VT] in 7, ventricular fibrillation [VF] in 5) and in 12 "normal" control subjects. With the use of an identical stimulation protocol from the right ventricular apex (twice diastolic threshold, three extrastimuli), 9 of 20 MVP patients and 1 of 12 normal subjects had inducible ventricular arrhythmias (p less than 0.05). When more aggressive attempts at ventricular stimulation were used, an additional five MVP patients had positive responses to PVS while no normal subjects did. In the MVP group, the following arrhythmias were induced: nonsustained polymorphic VT in 10, VF in three, and ventricular flutter in one. In all but two patients, triple ventricular extrastimuli were required to elicit this response. Two of the 10 MVP patients undergoing electropharmacologic testing had a successful antiarrhythmic regimen identified, while 13 patients were discharged on empiric antiarrhythmic therapy. At a follow-up of 19.8 +/- 13.1 months, all 19 MVP patients who could be contacted were alive. Five patients had symptomatic recurrences at follow-up including two SCD survivors (VT in one and VF in one). In conclusion, it was found that the majority of MVP patients with ventricular arrhythmias have inducible ventricular tachyarrhythmias during PVS and are more susceptible to this than patients without structural heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostic usefulness of programmed ventricular stimulation in idiopathic dilated cardiomyopathy without symptomatic ventricular arrhythmias

Twenty-four patients, mean age 42 years, with idiopathic dilated cardiomyopathy (DC) and no history of symptomatic ventricular arrhythmias underwent right ventricular programmed stimulation with up to 3 extrastimuli. Ventricular tachycardia (VT) was induced in 8 patients and ventricular fibrillation (VF) in 2. The VT was unimorphic in 2 and polymorphic in 6. No significant differences were noted between patients in whom arrhythmias were inducible and and those in whom they were not with regard to age, symptomatic class, arrhythmia severity or hemodynamic indexes. Over a mean follow-up of 12 months, 4 patients died, 3 suddenly and 1 with progressive heart failure. Only 1 of the 3 who died suddenly had inducible VT. One other patient with induced sustained unimorphic VT later presented with spontaneous sustained VT similar in rate and configuration to induced VT. In conclusion, VT or VF may be induced in approximately 40% of patients with DC and no history of symptomatic VT or VF. Inducibility of polymorphic VT or VF does not correlate with clinical or hemodynamic variables or with the risk of sudden death. However, induction of unimorphic VT may predict later occurrence of spontaneous unimorphic VT.     

Programmed electrical stimulation in healed myocardial infarction using a standardized ventricular stimulation protocol

The diagnostic accuracy of programmed electrical stimulation was prospectively assessed in 111 patients with myocardial infarction (MI) with or without a history of spontaneous ventricular arrhythmias. In 29 patients neither ventricular tachycardia (VT) nor episodes of 10 premature ventricular depolarizations per hour was documented. Fifty patients had documented nonsustained VT and 32 had sustained monomorphic VT. One and 2 extrastimuli (twice diastolic threshold, 2 ms in duration) were given during sinus rhythm and ventricular pacing at 100, 120 and 140 beats/min in the right ventricular apex (part I). When this protocol failed to induce a sustained monomorphic VT, a third extrastimulus was introduced (part II). Repetitive ventricular responses were induced in all patients, and in 15 (14%) polymorphic ventricular arrhythmias requiring DC shock were induced. Incidence of initiation of sustained monomorphic VT and polymorphic ventricular arrhythmias requiring DC shock was related to the clinical arrhythmia and the stimulation protocol. In patients with documented sustained monomorphic VT, a third extrastimulus only increased the incidence of sustained monomorphic VT (68% to 94%), whereas in patients with documented nonsustained VT and without VT the incidence of both polymorphic and monomorphic arrhythmias increased by 7 to 12%. Sustained monomorphic VTs induced in patients without such a history were faster (p less than 0.01), depended on site of MI (p less than 0.05) and were more often preceded by nonsustained polymorphic VT (p less than 0.01) than in patients with documented sustained monomorphic VT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Signal-averaged electrocardiographic late potentials in patients with ventricular fibrillation or ventricular tachycardia: correlation with clinical arrhythmia and electrophysiologic study

High-frequency potentials measured in the terminal 40 ms of the signal-averaged QRS complex during sinus rhythm are of abnormally low amplitude in most patients with ventricular tachycardia (VT). However, less is known about high-frequency late potentials in patients with ventricular fibrillation (VF), and the relation between late potentials and arrhythmia inducibility during electrophysiologic study has not been established. Signal-averaged electrocardiography was used to measure high-frequency (more than 25 Hz) late potentials in 24 patients with spontaneous VF, 27 patients with spontaneous sustained VT, and 19 normal subjects, none of whom were receiving antiarrhythmic drugs. Late-potential amplitude in patients with VT was significantly lower than that in patients with VF (p less than 0.02). Late-potential amplitude in patients with VF was not significantly different from that in normal subjects. Ventricular arrhythmia induction was attempted during electrophysiologic study in 46 of the patients with VF or VT. Late-potential amplitude was significantly lower in 26 patients with reproducibly inducible sustained ventricular arrhythmias than in 20 without (p less than 0.001). The correlation between late-potential amplitude and arrhythmia inducibility was independent of that between late-potential amplitude and clinical arrhythmia (VT vs VF).     

Results of signal-averaged electrocardiography and electrophysiologic study in patients with nonsustained ventricular tachycardia after healing of acute myocardial infarction

Programmed stimulation and signal-averaged electrocardiography were performed in 43 consecutive patients with nonsustained ventricular tachycardia (VT) after healing of inferior (29 patients) or anterior wall (14 patients) acute myocardial infarction. Twenty-two patients had inducible sustained VT. Patients with inferior infarction and inducible sustained VT had significantly longer filtered QRS durations (125 +/- 19 vs 112 +/- 15 ms, p less than 0.01) and significantly lower voltage in the last 40 ms of the filtered QRS complex (19 +/- 5 vs 30 +/- 14 microV, p less than 0.05) than those without inducible sustained VT. In contrast, the signal-averaged electrocardiographic measurements in patients with anterior infarction and inducible sustained VT did not differ significantly from those without inducible sustained VT. The results of these studies were compared with those of 2 control groups: 45 patients without ventricular arrhythmias after myocardial infarction and 95 patients with spontaneous and inducible sustained VT after myocardial infarction. The signal-averaged electrocardiographic measurements in patients with spontaneous nonsustained VT after inferior infarction were intermediate between the control group without arrhythmias and the control group with sustained VT. The signal-averaged electrocardiograms in patients with nonsustained VT after anterior infarction were not significantly different from those in patients without ventricular arrhythmias. The study shows that the site of infarction influences the signal-averaged electrocardiogram in patients with VT after myocardial infarction. The signal-averaged electrocardiogram may be useful in identifying patients with nonsustained VT after a remote inferior myocardial infarction who have inducible sustained VT.     

Induction of clinical ventricular tachycardia using programmed stimulation: value of third and fourth extrastimuli

Initiation of ventricular tachycardia (VT) by right ventricular extrastimulation was analyzed in 142 consecutive patients, 53 with electrocardiographically documented episodes of spontaneous VT or ventricular fibrillation (VF) and 68 with no spontaneous VT or VF; 21 patients with a history of sudden death but no documented arrhythmia were excluded from further analysis. All patients received 1 to 4 extrastimuli (S2, S3, S4 and S5) during pacing at fixed cycle lengths of 600 or 500 msec at 1 or 2 right ventricular sites. Clinical VT was reproduced by extrastimulation in 28 of 43 patients (65%) with sustained VT and in 0 of 10 patients with nonsustained VT. Clinical VT was induced by S2 or S3 in 16 patients and by S4 or S5 in 12 patients. Ventricular burst pacing reproduced clinical VT in 3 other patients. Nonclinical VT, which was most often polymorphic and nonsustained, was induced in 24 of 121 patients (20%), in 11 by S2 or S3 and in 13 by S4 or S5. Ventricular burst pacing induced nonclinical VT in 4 other patients. In patients with spontaneous sustained VT, the use of S4 and S5 in the right ventricle increases the yield of inducible clinical VT compared with use of S2 and S3 alone, but at a cost of increased induction of nonclinical VT. Frequent induction of nonclinical VT limits the interpretation of the results of such stimulation in patients without previously documented VT.     

Value of electrophysiologic testing in patients with nonsustained ventricular tachycardia

This study was undertaken to determine the value of electrophysiologic testing in 61 patients with nonsustained ventricular tachycardia (VT) (3 or more beats) on ambulatory monitoring and no history of sustained ventricular arrhythmia. The study group consisted of 38 patients with coronary artery disease (CAD), 9 with idiopathic dilated cardiomyopathy and 14 with a normal heart. Nonsustained VT (at least 3 but not more than 15 beats) was induced in 46%, sustained VT (more than 15 beats) in 15% and no VT in 39%. Sustained VT was induced more frequently in the presence of left ventricular dysfunction (p = 0.005) but was not related to the presence of CAD. Over a mean follow-up of 26 months, 10 patients died from cardiac causes (4 suddenly), including 1 patient with inducible sustained VT, 2 with nonsustained VT and 7 with no inducible VT. Inducibility was not related to survival, either as a single variable or when combined with CAD, left ventricular dysfunction or recent myocardial infarction. Left ventricular function alone was a good predictor of outcome. Of 46 patients with an ejection fraction of 35% more or in New York Heart Association functional class I or II, 3 (7%) died from cardiac causes, compared with 7 of 13 patients (54%) with an ejection fraction of less than 35% or in functional class III or IV (p = 0.0001). Thus, in patients with nonsustained VT, the incidence of sustained VT during electrophysiologic testing is low and is related to the degree of left ventricular dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Management of refractory sustained ventricular tachycardia with amiodarone: a reappraisal

We examined the value of clinical variables, chronic 24-hour ambulatory ECG monitoring, and chronic electrophysiologic (EP) testing in 49 patients with recurrent and refractory sustained ventricular tachycardia (VT) and ventricular fibrillation (VF) treated with chronic oral amiodarone in order to develop a prospective approach to the management of these patients. All patients underwent control EP studies followed by continuous telemetric cardiac monitoring during oral amiodarone administration (mean duration 29 +/- 6 days, mean dose 739 +/- 230 mg). Follow-up 24-hour ambulatory ECG monitoring and EP studies were performed. Thirty VT recurrences occurred in the first 4 weeks of amiodarone therapy (total incidence, 61%), with the majority (55%) in the first 3 weeks of treatment. During long-term follow-up (1 to 42, mean 15 +/- 12 months), there were 12 symptomatic VT/VF recurrences (incidence 24%). There was a higher incidence of VT recurrences if patients had inducible sustained or nonsustained VT at chronic EP study (p less than 0.01), or complex ventricular arrhythmias on ambulatory ECG monitoring (p less than 0.05). The sensitivity, specificity, and predictive accuracy of chronic EP testing and 24-hour ambulatory ECG monitoring were 100%, 35%, and 51%, and 58%, 84%, and 78%, respectively. Chronic EP testing correctly identified all patients who had their arrhythmia suppressed by amiodarone on long-term follow-up, while 42% of all VT recurrences occurred in patients without complex ventricular arrhythmias on 24-hour ambulatory ECG monitor.(ABSTRACT TRUNCATED AT 250 WORDS)     

Implantable defibrillator event rates in patients with idiopathic dilated cardiomyopathy, nonsustained ventricular tachycardia on Holter and a left ventricular ejection fraction below 30%

OBJECTIVES: This study investigated the incidence of appropriate implantable cardioverter defibrillator (ICD) interventions for ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients with idiopathic dilated cardiomyopathy (IDC) and nonsustained VT in the presence of a left ventricular ejection fraction below 30%, versus in patients with syncope and patients with a history of VT or VF. BACKGROUND: To date, only limited information is available about the prophylactic use of ICDs in patients with IDC. METHODS: From January 1993 to July 2000, 101 patients with IDC underwent implantation of ICDs with electrogram storage capability at our institution. Patients were placed into one of three groups according to their clinical presentation: asymptomatic or mildly symptomatic nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% (49 patients, prophylactic group), unexplained syncope or near syncope (26 patients, syncope group) and a history of sustained VT or VF (26 patients, VT/VF group). RESULTS: During 36 +/- 22 months follow-up, 18 of 49 patients (37%) in the prophylactic group received appropriate shocks for VT or VF, compared with 8 of 26 patients (31%) in the syncope group and with 9 of 26 patients (35%) of the VT/VF group. Multivariate Cox analysis of baseline clinical variables identified left ventricular ejection fraction, atrial fibrillation and a history of sustained VT or VF as predictors for appropriate ICD interventions during follow-up. CONCLUSIONS: Patients with IDC and prophylactic ICD implantation for nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% had an incidence of appropriate ICD interventions similar to that of patients with a history of syncope or sustained VT or VF. These findings indicate that ICDs may have a role in not only secondary but also primary prevention of sudden death in IDC.     

Clinical and electrophysiologic predictors of ventricular tachyarrhythmia recurrence in patients with implantable cardioverter defibrillators

INTRODUCTION: Not all patients experience recurrent sustained ventricular tachyarrhythmias after placement of an implantable cardioverter defibrillator (ICD). We evaluated the clinical and electrophysiologic predictors of ventricular tachycardia (VT) and ventricular fibrillation (VF) recurrence following ICD implantation. METHODS AND RESULTS: Consecutive patients (n = 133) underwent 4 +/- 3 serial electrophysiologic studies (EPS) over 50 +/- 26 months following ICD implantation. Sustained VT/VF could always be induced during follow-up EPS in 49 patients; sustained VT/VF was sometimes induced during follow-up EPS in 47 patients; and sustained VT/VF could never be induced during follow-up EPS in 37 patients. Spontaneous VT/VF requiring ICD therapy occurred in 107 patients during follow-up. Patients with sustained VT/VF that was always inducible or sometimes inducible during follow-up experienced more frequent episodes of VT/VF following ICD implant (20.5, 95% CI 12.7-33.0; and 17.8, 95% CI 11.3-28.1 episodes/patient respectively; vs 3.0, 95% CI 2.0-4.6 episodes/patient for patients with VT/VF never induced, P < 0.001). Inducibility of sustained VT/VF post-ICD implant (P < 0.001) and sustained VT as the presenting arrhythmia (P = 0.02) were independent predictors of spontaneous VT/VF recurrence. CONCLUSION: Reproducibly inducible VT/VF following ICD implantation predicts a high probability of VT/VF recurrence and identifies a cohort of patients who experience frequent episodes of VT/VF over time. Persistent noninducibility of sustained VT/VF identifies a group of patients who experience no or very few episodes of VT/VF recurrence.     

Determinants of induced sustained arrhythmias in survivors of out-of-hospital ventricular fibrillation

We prospectively studied 196 consecutive survivors of out-of-hospital ventricular fibrillation (VF) not associated with acute myocardial infarction and 46 consecutive, control patients without prior ventricular arrhythmias. Programmed stimulation included two extrastimuli (S3 protocol) in all patients and three extrastimuli (S4 protocol) in the last 140 study patients and in all control patients. Sustained ventricular tachycardia (VT) or VF was not induced in any control patient. In study patients, logistic regression identified two independent predictors of induced, sustained VT for both S3 and S4 protocols: prior spontaneous, sustained VT (37 patients; p less than or equal to .001) and prior myocardial infarction (113 patients; p = .005). With the S3 protocol, sustained VT was induced in 54% of patients with both prior myocardial infarction and prior sustained VT vs 4% without either; with the S4 protocol, sustained VT was induced in 91% vs 13%, respectively. Eighty-three percent of induced VT episodes had a cycle length less than 300 msec, and all required termination by cardioversion or pacing. VF was induced only in survivors of out-of-hospital VF without prior, spontaneous, sustained VT (S3 protocol, 9%; S4 protocol, 24%) but not in study patients with prior sustained VT (S3, p = .10; S4, p = .05) or control patients (S3, p = .06; S4, p = .01). The mean coupling intervals of extrastimuli that induced VF were not significantly different from the intervals that induced sustained VT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Does syncope change the results of programmed ventricular stimulation in patients with previous myocardial infarction?

The induction of a ventricular tachycardia (VT) after myocardial infarction (MI) is associated with a high risk of VT and sudden death (SD) in asymptomatic patients; the purpose of the study was to know if syncope modifies the results of programmed ventricular stimulation (PVS) and the clinical consequences. METHODS: PVS using two and three extra stimuli delivered in two sites of right ventricle was performed in 1057 patients without spontaneous VT or resuscitated SD at least 1 month after an acute MI; 836 patients (group I) were asymptomatic and were studied for a low ejection fraction or nonsustained VT on Holter monitoring or late potentials; 228 patients (group II) were studied for unexplained syncope. The patients were followed up to 5 years of heart transplantation. RESULTS: Sustained monomorphic VT (< 280 b/min) was induced in 238 group I patients (28%) and 62 group II patients (29%); ventricular flutter (VT > 270 b/min) or ventricular fibrillation (VF) was induced in 245 group I patients (29%) and 42 group II patients (18%) (P < 0.05); PVS was negative in 353 group I patients (42%) and 124 (55%) group II patients (NS). The patients differ by their prognosis; cardiac mortality was 13% in group I patients and 34% in group II patients with inducible VT < 280 b/min (P < 0.01), 4% in group I patients and 13% in group II patients with inducible VF (P < 0.05), 5% in group I patients and 7% in group II patients with negative study (NS). In conclusion, syncope did not change the results of programmed ventricular stimulation after myocardial infarction. However, syncope increased significantly cardiac mortality of patients with inducible ventricular tachycardia, flutter or fibrillation.     

Programmed ventricular stimulation at a second right ventricular site: An analysis of 100 patients, with special reference to sensitivity, specificity and characteristics of patients with induced ventricular tachycardia

One hundred patients without ventricular tachycardia (VT) initiated from the right ventricular (RV) apex were subjected to stimulation at the RV outflow tract. Sixty-two patients had no clinical arrhythmias, and 38 had sustained VT, ventricular fibrillation (VF) or cardiac arrest. Of the 38 patients with clinical arrhythmias, 22 (58%) had VT or VF induced from the RV outflow tract. Among the 62 patients without arrhythmias, 5 (13%) had polymorphic nonsustained VT or VF induced, which occurred with triple extrastimull in all 5 patients. The 22 patients with VT initiated at the RV outflow tract were a heterogeneous group; 10 (45%) patients had cardiac diagnoses other than coronary artery disease (CAD). In contrast were patients whose VT was initiated at the RV apex (n = 84); in this group, 20 patients (22%) had diagnoses other than CAD (p <0.05). These 22 patients also were younger (mean age 46 years) than patients whose VT was initiated at the RV apex (mean age 58; p <0.01). Of the 16 patients with clinical VT and no induced arrhythmia from either RV site, 7 had CAD (4 with cardiac arrest), 5 had the long QT syndrome, 3 had dilated cardiomyopathy and 1 had valvular heart disease. In conclusion, stimuiation at a second RV site increases the sensitivity of RV stimulation in patients with known VT and seldom initiates VT in patients without cllnical VT.     

Nonsustained ventricular tachycardia in patients with coronary artery disease: role of electrophysiologic study

Sixty-two consecutive patients with chronic coronary artery disease referred for evaluation of nonsustained ventricular tachycardia (VT) underwent electrophysiologic studies. Sustained VT was induced by one to three ventricular extrastimuli in 28 patients (45%). Therapy was guided by the results of electrophysiologic testing in 44 patients: 19 patients without inducible sustained VT received no antiarrhythmic therapy, and 25 patients with inducible sustained or symptomatic nonsustained VT received therapy guided by the results of electrophysiologic studies. The results of electrophysiologic studies were ignored by physicians for a second group of 18 patients: four had inducible sustained VT but received no antiarrhythmic therapy, and 14 had inducible sustained or nonsustained VT and received antiarrhythmic therapy not guided by results of electrophysiologic testing. After a mean follow-up period of 28 months, 11 patients had died suddenly. Seven of the 11 patients who died suddenly had inducible sustained VT. Three of 44 patients in the group receiving therapy guided by electrophysiologic studies died suddenly versus eight of 18 in the group receiving therapy not guided by electrophysiologic studies (p = .001). Only one of 19 patients without inducible sustained VT who were not treated experienced sudden death. Two of four patients with inducible sustained VT who did not receive antiarrhythmic therapy died suddenly. Multivariate analysis of the relationship of induced arrhythmias, left ventricular ejection fraction, site of myocardial infarction, history of syncope, or type of antiarrhythmic therapy to outcome revealed a greater than twofold increased risk for sudden cardiac death in patients whose therapy was not guided by results of electrophysiologic study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrophysiological testing and nonsustained ventricular tachycardia. Use and limitations in patients with coronary artery disease and impaired ventricular function

Electrophysiological testing was performed in 100 consecutive patients with spontaneous asymptomatic nonsustained ventricular tachycardia, chronic coronary artery disease, and ejection fraction of less than 40%. Fifty-seven patients without inducible sustained ventricular arrhythmias were discharged on no antiarrhythmic therapy. Sustained monomorphic ventricular tachycardia was induced in 37 patients, and polymorphic ventricular tachycardia or ventricular fibrillation was induced in six patients. Of the 43 patients with inducible sustained ventricular arrhythmias, three had spontaneous cardiac arrest during serial drug testing and were excluded from further analysis. Twenty patients were discharged on drug therapy, resulting in suppression of inducible sustained ventricular arrhythmias. The remaining 20 patients with persistently inducible sustained arrhythmias were discharged on drug therapy, resulting in maximal rate slowing of the induced tachycardia. During a mean follow-up of 16.7 months, there were 10 recurrent cardiac arrests or sudden deaths. The 1- and 2-year actuarial incidence of these events was 2% and 6%, respectively, in patients without inducible sustained ventricular arrhythmias; 0% and 11%, respectively, in patients in whom inducible arrhythmias were suppressed; and 34% and 50%, respectively, in patients with persistently inducible sustained ventricular arrhythmias. Multivariate Cox analysis identified only the persistence of inducible sustained ventricular arrhythmias as a significant independent predictor of sudden death or recurrent sustained arrhythmias (p less than 0.001; relative risk, 3.5; 95% confidence intervals, 2.1-4.9). In this population, therapeutic intervention to prevent sudden death is unnecessary in patients without inducible sustained ventricular arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of programmed stimulation methods in the evaluation of ventricular arrhythmias in patients 20 years old and younger

The purpose of this study was to systematically evaluate programmed ventricular stimulation in patients less than 21 years of age undergoing electrophysiologic testing. A standardized protocol was applied in 55 consecutive patients (mean age 14 years) with the following clinical presentations: sustained ventricular tachycardia (VT) (n = 17); ventricular fibrillation (VF) (n = 7); syncope with heart disease (n = 10); nonsustained VT (n = 6); and syncope with an ostensibly normal heart (n = 15). The stimulation protocol consisted of 1 and 2 ventricular extrastimuli during sinus rhythm, followed by 1 to 4 (S2, S3, S4, S5) extrastimuli during pacing at 2 ventricular sites. Of the 17 patients with sustained VT, 12 had induction of the arrhythmia (sensitivity = 71%). Overall, 18 of 55 patients had inducible sustained VT, with this response significantly enhanced by use of S4 or S5 protocols (p = 0.02). Although no syncope patients with an ostensibly normal heart had inducible sustained VT, 7 had polymorphic nonsustained VT in response to ventricular stimulation. The mean number of extra-stimuli preceding the induction of nonsustained or sustained VT or VF did not differ. The induction of VF in 5 cases during this study was preceded in each case by extrastimuli intervals less than or equal to 190 ms. Thus, data indicate that aggressive stimulation protocols appear to be required for induction of sustained VT in most young patients, nonsustained polymorphic VT as a response to aggressive programmed stimulation is of uncertain significance, and that coupling intervals less than or equal to 190 ms may correlate with the induction of VF.