Incidence of nonsustained and sustained ventricular tachyarrhythmias in patients with an implantable cardioverter defibrillator

INTRODUCTION: Nonsustained ventricular tachycardia (NSVT) is a frequent phenomenon in some patients with heart disease, but its association with sustained ventricular tachycardias (ventricular tachycardia [VT]/ventricular fibrillation [VF]) is still not clear. The aim of this study was to determine whether NSVT incidence was associated with sustained VT/VF in patients with an implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: Retrospective data analysis was conducted in 923 ICD patients with a mean follow-up of 4 months. NSVT and sustained VT/VF were defined as device-detected tachycardias. The incidence rates of NSVT and sustained VT/VF as well as ICD therapies were determined as episodes per patient. The NSVT index was defined as the product of NSVT episodes/day times the mean number of beats per episode, i.e., total beats/day. The NSVT index peak was defined as the highest value on or prior to the day with sustained VT/VF episodes. Patients (n = 393) with NSVT experienced a higher incidence of sustained VT/VF (17.2 +/- 63.0 episodes/patient) and ICD therapies (15.2 +/- 61.4 episodes/patient) than patients (n = 530) without NSVT (sustained VT/VF: 0.5 +/- 6.6 and therapies: 0.5 +/- 5.6; P < 0.0001). Approximately 74% of NSVT index peaks occurred on the same day or <3 days prior to sustained VT/VF episodes. The index was higher for peaks < or =3 days prior to the day with sustained VT/VF (94.3 +/- 140.1 total beats/day) than for peaks >3 days prior to the day with sustained VT/VF (32.7 +/- 55.9 total beats/day; P < 0.0001). CONCLUSION: ICD patients with NSVT represent a population more likely to experience sustained VT/VF episodes with a temporal association between an NSVT surge and sustained VT/VF occurrence.     

Limited predictive value of inducible sustained ventricular tachycardia for future occurrence of spontaneous ventricular tachycardia in patients with coronary artery disease and relatively preserved cardiac function

To evaluate the significance of inducible sustained ventricular tachycardia (VT) in patients with coronary artery disease and relatively preserved cardiac function, 33 patients who met the following criteria were studied; documented nonsustained VT but no history of life-threatening arrhythmia, inducible sustained VT at electrophysiologic study, and implantation of a cardioverter-defibrillator. Eighteen patients developed clinical sustained VT within 2 years. By univariate analysis, left ventricular ejection fraction (EF) and the cycle length of induced VT were associated with clinical VT occurrence. By multivariate analysis, however, EF was the only independent predictor. Among 23 patients with EF 40% (P <.01). In coronary artery disease patients with relatively preserved EF, the incidence of clinical VT is considerably low even though sustained VT is inducible. Inducible VT is therefore not appropriate for risk stratification in this patient population.     

Electrophysiologic manifestations of ventricular tachyarrhythmias provoking appropriate defibrillator interventions in high-risk patients with hypertrophic cardiomyopathy

Introduction: Our objective was to determine features of ventricular tachyarrhythmias triggering appropriate implantable cardioverter-defibrillator (ICD) interventions in hypertrophic cardiomyopathy (HCM).
Methods and Results: The study cohort was 68 high-risk HCM patients who received ICDs for primary sudden cardiac death prevention from 1995 to 2003. All episodes of sustained ventricular tachyarrhythmias identified by stored intracardiac electrograms were analyzed. Nine patients had 51 episodes of sustained ventricular tachyarrhythmic events that required device therapy (mean follow-up, 3.4 ± 2.2 years; cumulative event rate, 3.2% per year): five had 47 episodes of monomorphic ventricular tachycardia (VT); four each had one episode of ventricular fibrillation (VF). Sinus tachycardia or atrial fibrillation was the initiating rhythm in five of nine patients and in 43 of 51 episodes of events. Of the 17 episodes of monomorphic VT detected in the VT zone, 16 (94%) were terminated by antitachycardia pacing. Thirty episodes of monomorphic VT were detected in the VF zone and were terminated by defibrillation.
Conclusion: Sustained monomorphic VT is common in a high-risk cohort with HCM. Sinus tachycardia is often the initiating rhythm, suggesting that high sympathetic drive may be proarrhythmic when a susceptible substrate is present. Antitachycardia pacing is highly effective in terminating VT in this patient population.     

The clinical implications of cumulative right ventricular pacing in the multicenter automatic defibrillator trial II

INTRODUCTION: This study was designed to assess whether right ventricular pacing in the implantable cardioverter defibrillator (ICD) arm of the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II was associated with an unfavorable outcome. METHODS AND RESULTS: Data on the number of ventricular paced beats were available in 567 (76%) of 742 MADIT II patients with ICDs. The number of ventricular paced beats over the total number of beats showed a bimodal distribution with patients being predominantly paced or nonpaced. Therefore, patients were dichotomized at 0-50% and 51-100% of cumulative pacing with median pacing rate 0.2% and 95.6%, respectively. Endpoints included new or worsening heart failure, appropriate ICD therapy for VT/VF, and the combined endpoint of heart failure or death. Clinical features associated with frequent ventricular pacing included age >or=65 years, advanced NYHA heart failure class, LVEF < 0.25, first degree AV and bundle branch block, and amiodarone use. During follow-up, 119 patients (21%) had new or worsened heart failure, 130 (23%) had new or worsened heart failure or death, and 142 (25%) had appropriate therapy for VT/VF. In comparison to patients with infrequent pacing, those with frequent pacing had significantly higher risk of new or worsened heart failure (hazard ratio = 1.93; P = 0.002) and VT/VF requiring ICD therapy (HR = 1.50; P = 0.02). CONCLUSIONS: Patients in MADIT II who were predominantly paced had a higher rate of new or worsened heart failure and were more likely to receive therapy for VT/VF. These results suggest the deleterious consequences of RV pacing, particularly in the setting of severe LV dysfunction.     

Analysis of the pattern of initiation of sustained ventricular arrhythmias in patients with implantable defibrillators

INTRODUCTION: The purpose of this study was to analyze the pattern of initiation of sustained ventricular arrhythmias in patients with varying types of underlying structural heart disease. METHODS AND RESULTS: The study group consisted of 90 patients with an implantable cardioverter defibrillator. Cardiovascular diagnoses included coronary artery disease in 64 patients (71%). The patients were divided into four groups based on the type and severity of structural heart disease. Two hundred sixty episodes of sustained ventricular arrhythmias were analyzed. The mean coupling interval of the initiating beat of all ventricular arrhythmias was 523 +/- 171 msec. The coupling interval of the initiating beat was longer in patients with impaired ventricular function, particularly those with nonischemic dilated cardiomyopathy. The prematurity index was similar regardless of the type of underlying structural heart disease. However, the prematurity index was shorter in patients with polymorphic ventricular tachycardia (VT) compared to those with monomorphic VT. A pause was observed more commonly before the onset of polymorphic VT/ventricular fibrillation than sustained monomorphic VT. Two hundred twenty-two (85%) of the arrhythmia episodes were initiated by a late-coupled premature beat, 33 (13%) were initiated by an early-coupled premature beat, and 5 episodes (2%) were initiated with a short-long-short sequence. The pattern of initiation of the ventricular arrhythmias was similar in all patient groups and for both monomorphic and polymorphic tachycardias. CONCLUSION: These findings demonstrate that sustained ventricular arrhythmias typically are initiated by late-coupled ventricular premature depolarizations, regardless of the type or severity of underlying structural heart disease or resultant arrhythmia.     

Efficacy of flecainide in pacing-induced sustained ventricular tachyarrhythmias: correlation to clinical parameters and tachycardia-characteristics

Seventy-two patients with sustained ventricular tachycardiaor syncope of unknown origin underwent electrophysiologic evaluationbefore and after therapy with flecainide (200–300 mg day^–1).In all patients, sustained ventricular tachycardia or ventricularfibrillation was inducible during control electrophysiologicstudy. During flecainide therapy, sustained ventricular tachycardia(VT) was no longer inducible in 18 patients (25%) whereas in54 patients, VT was still inducible. In five of the latter patients,VT became more difficult to induce (overall efficacy 32%). Therate of VT decreased from 214±49 beats min^–1 duringthe control electrophysiologic study to 178±48 beatsmin^–1 during flecainide (P<0.01). The ERP of the rightventricle increased from 251±27 ms during the controlstudy to 267±34 ms on flecainide (P<0.01). Mean ejectionfraction and mean LVEDP did not differ between responders andnon-responders, yet the presence of a left ventricular aneurysmcorrelated with a lack of antiarrhythmic response to flecainide.VT rate as well as VT morphology during the control study discriminatedbetween responders and non-responders; 11% of patients withVT-rate 230 beats min^–1 responded to oral flecainidecompared with 31% with a VT rate > 230 beats min^–1at control. 26% with induced monomorphic VT responded, comparedwith 100% with induced VF during the control study. 18 of 23responders were discharged on flecainide. During a mean follow-upof 26±18 months, two patients experienced a recurrenceof VT and in one patient, flecainide had to be discontinueddue to side-effects. Thus, the acute efficacy of flecainide, evaluated by serialdrug testing, correlates with haemodynamic parameters and thecharacteristics of tachycardia.     

Inflammatory biomarkers are not predictive of intermediate-term risk of ventricular tachyarrhythmias in stable CHF patients

BACKGROUND: Elevated levels of inflammatory biomarkers and brain natriuretic peptide (BNP) are associated with increased mortality in patients with heart failure (HF). HYPOTHESIS:: The aim of the current study was to assess the correlation between circulating biomarkers and ventricular tachyarrhythmias among patients with HF. METHODS: Blood samples from 50 stable ambulatory HF patients with moderate to severe systolic left ventricular (LV) dysfunction and an implantable cardioverter defibrillator (ICD) were analyzed for interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), high-sensitivity C-reactive protein (hsCRP) and BNP. Thereafter, the patients were followed for a mean period of 152 +/- 44 days, during which ventricular tachyarrhythmias were recorded by the ICDs. RESULTS: Follow-up data were obtained from 47 patients. Of them, 45 (96%) had ischemic cardiomyopathy, 38 (81%) had New York Heart Association class I-II, 43 (91%) were males, and the mean age was 68.6 +/- 11.1 years. During follow-up, 5 patients (11%) had nonsustained ventricular tachycardia (NSVT), 6 patients (13%) had sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and 36 patients (76%) had no events. The circulating biomarkers' levels upon enrollment were not significantly different between patients who subsequently had NSVT or VT/VF and patients who were free of events. CONCLUSIONS: No correlation was found between plasma levels of IL-6, TNF-alpha, hsCRP and BNP and ventricular arrhythmic events among stable HF patients during an intermediate term follow-up of 5.1 months. Further studies are still required to assess the association between these biomarkers and long-term risk of ventricular tachyarrhythmia.     

Implantable defibrillator event rates in patients with unexplained syncope and inducible sustained ventricular tachyarrhythmias: a comparison with patients known to have sustained ventricular tachycardia

OBJECTIVES

To assess the clinical significance of inducible ventricular tachyarrhythmias among patients with unexplained syncope.

BACKGROUND

Induction of sustained ventricular arrhythmias at electrophysiology study in patients with unexplained syncope and structural heart disease is usually assigned diagnostic significance. However, the true frequency of subsequent spontaneous ventricular tachyarrhythmias in the absence of antiarrhythmic medications is unknown.

METHODS

In a retrospective case-control study, the incidence of implantable cardiac defibrillator (ICD) therapies for sustained ventricular arrhythmias among patients with unexplained syncope or near syncope (syncope group, n = 22) was compared with that of a control group of patients (n = 32) with clinically documented sustained ventricular tachycardia (VT). Sustained ventricular arrhythmias were inducible in both groups and neither group received antiarrhythmic medications. All ICDs had stored electrograms or RR intervals. Clinical variables were similar between groups except that congestive cardiac failure was more common in the syncope group.

RESULTS

Kaplan-Meier analysis of the time to first appropriate ICD therapy for syncope and control groups produced overlapping curves (p = 0.9), with 57 ± 11% and 50 ± 9%, respectively, receiving ICD therapy by one year. In both groups, the induced arrhythmia was significantly faster than spontaneous arrhythmias, but the cycle lengths of induced and spontaneous arrhythmias were positively correlated (R = 0.6, p < 0.0001). During follow-up, three cardiac transplantations and seven deaths occurred in the syncope group, and two transplantations and five deaths occurred in the control group (36-month survival without transplant 52 ± 11% and 83 ± 7%, respectively, p = 0.03).

CONCLUSIONS

In patients with unexplained syncope, structural heart disease and inducible sustained ventricular arrhythmias, spontaneous sustained ventricular arrhythmias occur commonly and at a similar rate to patients with documented sustained VT. Thus, electrophysiologic testing in unexplained syncope can identify those at risk of potentially life-threatening tachyarrhythmias, and aggressive treatment of these patients is warranted.     

Devices for the management of ventricular arrhythmias in cardiac failure

Heart failure is a common clinical syndrome with a high morbidity and mortality. Despite advances in medical treatment, death from dangerous ventricular arrhythmias is frequently implicated. Emerging evidence supports the use of the implantable cardioverter defibrillator for selected patients. This includes secondary prevention indications for patients who have survived life-threatening ventricular arrhythmias. In addition, patients who have not suffered spontaneous sustained ventricular arrhythmias, but who are at high risk for sudden arrhythmic death are starting to be recognized as candidates for ICD therapy. At present the only primary prevention indication with a good evidence base is the presence of inducible ventricular arrhythmias at electrophysiologic testing in patients with prior myocardial infarction, impaired left ventricular systolic function and non-sustained ventricular tachycardia on Holter monitoring. Studies planned or in progress are likely to expand further the role of device therapy in the treatment of patients with cardiac failure.     

Implantable defibrillator-detected heart failure status predicts ventricular tachyarrhythmias

Introduction

The prediction of ventricular tachyarrhythmias among patients with implantable cardioverter defibrillators is difficult with available clinical tools. We sought to assess whether in patients with heart failure (HF) and reduced ejection fraction with defibrillators, physiological sensor-based HF status, as summarized by the HeartLogic index, could predict appropriate device therapies.

Methods

Five hundred and sixty-eight consecutive HF patients with defibrillators (n = 158, 28%) or cardiac resynchronization therapy-defibrillators (n = 410, 72%) were included in this prospective observational multicenter analysis. The association of both HeartLogic index and its physiological components with defibrillator shocks and overall appropriate therapies was assessed in regression and time-dependent Cox models.

Results

Over a follow-up of 25 (15–35) months, 122 (21%) patients received an appropriate device therapy (shock, n = 74, 13%), while the HeartLogic index crossed the threshold value (alert, HeartLogic ≥ 16) 1200 times (0.71 alerts/patient-year) in 370 (65%) subjects. The occurrence of ≥1 HeartLogic alert was significantly associated with both appropriate shocks (Hazard ratios [HR]: 2.44, 95% confidence interval [CI]: 1.49–3.97, p = .003), and any appropriate defibrillator therapies. In multivariable time-dependent Cox models, weekly IN-alert state was the strongest predictor of appropriate defibrillator shocks (HR: 2.94, 95% CI: 1.73–5.01, p < .001) and overall therapies. Compared with stable patients, patients with appropriate shocks had significantly higher values of HeartLogic index, third heart sound amplitude, and resting heart rate 30–60 days before device therapy.

Conclusion

The HeartLogic index is an independent dynamic predictor of appropriate defibrillator therapies. The combined index and its individual physiological components change before the arrhythmic event occurs.     

T Wave Pacing Inducing Electrical Storm and Multiple Shocks in an ICD-Recipient: A Novel Complication of the Automatic Gain Control Function

Implantable cardioverter-defibrillator (ICD) is highly effective in treating life-threatening ventricular arrhythmias, but it can also have proarrhythmic effect in some cases. We report the case of a 72 years old patient with an ischemic cardiomyopathy in whom an ICD was implanted for a poorly tolerated ventricular tachycardia (Profiles MD—Ventritex). Forty-eight hours after implantation, the patient suddenly received 15 successive shocks. ECG tracings and intracardiac EGM showed the presence of several VT episodes, all induced by the antibradycardia pacing of the ICD: the automatic gain control function of the device failed to detect ventricular premature beats in this patient, leading to a bradycardia pacing falling on the T wave and inducing multiple VTs and shocks.     

Incomplete bundle-branch block and st-segment elevation: Syndrome associated with sustained monomorphic ventricular tachycardia in patients with apparently normal heart

This paper reports on three cases of patients with an apparently normal heart admitted for sustained monomorphic ventricular tachycardia. The only abnormal finding showed in the electrocardiogram (ECG) in sinus rhythm that exhibited an entity associated with incomplete right bundle-branch block and persistent ST-segment elevation. The ECG entity was variable and disappeared transiently. Spontaneous ventricular tachycardia in one patient was inducible by programmed stimulation. There was no underlying heart disease. The origin of the ventricular tachycardia in one patient was located by pace mapping in the left ventricle at the left ventricular basal septum. The follow-up (from 6 months up to 6 years) demonstrated a good prognosis. This particular ECG entity associated with monomorphic ventricular tachycardia could have been missed because of the variations in the ECG in sinus rhythm and was associated with a favorable prognosis.