Effects of Coronary Artery Bypass Grafting on Ventricular Arrhythmias: Results with Electrophysiological Testing and Long-Term Follow-Up

Myocardial revascularization was performed in 56 patients with coronary artery disease who presented with ventricular tachycardia (VT) (n = 39) or ventricular fibrillation (n = 17). There were 46 men and 10 women, aged 65 ± 10 years. Three vessel (n = 42) or left main disease (n = 4) was present in 82%. Left ventricular ejection fraction averaged 36%± 11%. Electrophysioiogical studies were performed preoperatively in all patients; 50 (89%) had inducible ventricular arrhythmias. Sustained monomorphic VT was induced in 40 patients (cycle length 284 ± 61 msec). Reproducible symptomatic nonsustained VT was induced in four patients and ventricular fibrillation in six patients, while six patients had no inducible arrhythmia. Preoperatively the patients with inducible VT failed 3.3 ± 1.2 drug trials during electrophysiological studies. In addition to coronary bypass, 22 patients also received an automatic implantable cardioverter defibrillator (ICD), 26 patients received prophylactic ICD patches, and 1 patient had resection of a false aneurysm. There were no perioperative deaths. Postoperative electrophysiological studies were performed in all 56 surgical survivors. Ventricular tachyarrhythmia could not be induced in the six patients who had no inducible VT preoperatively and in 13 of 40 (33%) with preoperatively inducible sustained VT or in 19 of 50 (38%) patients with any previously inducible ventricular arrhythmia, thus a totaJ of 25 patients (45%) had no inducible VT postoperatively. Of the remaining, 11 patients were treated with antiarrhythmic drugs alone, 11 had already received an ICD (combined with drugs in 7), and another 9 received the ICD postoperatively (combined with drugs in 4). At a mean foJJow-up of 28 ± 21 months there were 11 deaths (20%): 2 sudden, 5 nonsudden cardiac, and 4 noncardiac deaths. There were 16 nonfatal VT recurrences (29%): 14 among patients with persistently inducible arrhythmias, and onJy 2 among those with no inducible arrhythmia postoperatively (P = 0.004); 13 occurred in patients with an ICD (P = 0.01). Thus among these patients with malignant ventricular arrhythmias who underwent revascuJarization, 45% had no inducible arrhythmia postoperatively with 33% of those with preoperatively inducible sustained VT apparently rendered noninducible by revascularization, while the majority (70%) remained free of major arrhythmic events during long-term follow-up. We conclude that myocardial revascularization alone can result in no ventricular arrhythmia induction in selected patients with VT inducible prior to surgery. Long-term follow-up of such patients indicates a low sudden death and arrhythmia recurrence rate. Furthermore, in patients with persistently inducible ventricular tachyarrhythmias after coronary revascuJarization, the sudden death rate is low despite a high frequency of nonfatal arrhythmia recurrence when antiarrhythmic medications are guided by programmed stimulation or an ICD is used.     

Electrocardiographically Documented Unnecessary, Spontaneous Shocks in 241 Patients With Implantable Cardioverter Defibrillators

The incidence and cause of electrocardiographically documented spontaneous implantuble Cardioverter defibrillator (ICD) discharges for a rhythm other than ventricular tachycardia (VT) or fibrillation (VF) (unnecessary shocks) were determined in 241 patients who underwent ICD implantation between March 1983 and November 1991. During follow-up of 24 ± 20 months, 54 of 241 patients (22%) received a total of 132 unnecessary ICD shocks confirmed by Holler or telemetry monitoring or stored electrograms (Egs) from the ICD. The rhythm preceding these unnecessary ICD shocks was atrial fibrillation in 30 patients, sinus or supraventricular tachycardia (SVT) in 11 patients, antitachycardia pacing triggered by atrial fibrillation or SVT resulting in VT in 5 patients, nonsustained VT in 3 patients, and normal sinus or pacemaker rhythm in 10 patients. Unnecessary ICD discharges occurred most frequently during the first week after implantation or generator replacement (18 of 54 patients [33%]). Unnecessary ICD discharges could be documented more often by stored Egs in patients with devices with Eg storage capability (Ventritex Cadence(tm), 19 of 54 patients [35%]) than by Holter or telemetry monitoring in patients with devices without Eg storage capabilities (34 of 193 patients [18%], P < 0.01), despite a shorter mean follow-up duration of 14 ± 9 months versus 26 ± 21 months, respectively. Only six of 54 patients (11%) in whom unnecessary ICD discharges occurred had recurrent unnecessary shocks during 22 ± 20 months of follow-up after treatment directed at the cause of the first episode or device reprogramming to preclude non-VT rhythm detection. In conclusion, unnecessary ICD shocks are a frequent complication of ICD therapy occurring in at least 22% of patients. The cause of these shocks is most frequently atrial fibrillation with a rapid ventricular response. The availability of Eg storage capabilities facilitates the diagnosis of the electrical event precipitating inappropriate ICD shocks. Diagnosis of the cause of unnecessary shocks allows for the institution of therapy that may reduce the risk for subsequent events.     

Complications of Third-Generation Implantable Cardioverter Defibrillator Therapy

To determine the incidence of complications of third-generation implantable cardioverter defibrillator (ICD) therapy, 144 patients were prospectively studied who underwent first implant of third-generation devices (i.e., ICD systems with biphasic shocks, ECC storage capability, and nonthoracotomy lead systems). During 21 ± 15 months of follow-up, 41 (28%) patients had one or more complications. No patient died perioperatively (30 days) and no ICD infection was observed during follow-up. Complications included bleeding or pocket hematoma (hemoglobin drop > 2 g/dL) in 5 (3%) patients, prolonged reversible ischemic neurological deficit in 1 (1%) patient, postoperative deep venous thrombosis of leg in 1 (1%) patient, pneumothorax in 2 (1%) patients, difficulty to defibrillate ventricular fibrillation intraoperatively in 2 (1%) patients, generator malfunction in 1 (1%) patient, arthritis of the shoulder in 3 (2%) patients, and allergic reaction to prophylactic antibiotics in 2 (1%) patients. A total of seven lead related complications were observed in six (4%) patients including endocardial lead migration in four (3%) patients. Twenty-three (16%) patients received inappropriate shocks for supraventricular tachyarrhythmias (n = 13), non-sustained ventricular tachycardia (VT) (n = 7), or myopotential oversensing (n = 3). We conclude that serious complications such as perioperative death or ICD infection are rare in patients with third-generation ICDs. Lead-related problems and inappropriate shocks during follow-up are the most frequent complications of third-generation ICD therapy. Recognition of these complications should promote advances in ICD technology and management strategies to avoid their recurrence.     

Antitachycardia pacing for spontaneous rapid ventricular tachycardia in patients with prophylactic cardioverter-defibrillator therapy

AIMS: Antitachycardia pacing (ATP) has not routinely been used in patients who received implantable cardioverter defibrillators (ICDs) for primary prevention of sudden death. This study investigated the efficacy of empirical ATP to terminate rapid ventricular tachycardia (VT) in heart failure patients with prophylactic ICD therapy. METHODS AND RESULTS: Ninety-three patients with a mean left ventricular ejection fraction of 22 +/- 7% (range: 9-35%) due to nonischemic or ischemic cardiomyopathy received prophylactic ICDs with empiric ATP. At least 2 ATP sequences with 6-pulse burst pacing trains at 81% of VT cycle length (CL) were programmed in one or two VT zones for CL below 335 +/- 23 ms and above 253 +/- 18 ms. Ventricular flutter and fibrillation (VF) with CL below 253 +/- 18 ms were treated in a separate VF zone with ICD shocks without preceding ATP attempts. During 38 +/- 27 months follow-up, 339 spontaneous ventricular tachyarrhythmias occurred in 36 of 93 study patients (39%). A total of 232 VT episodes, mean CL 293 +/- 22 ms, triggered ATP in 25 of 36 patients with ICD interventions (69%). ATP terminated 199 of 232 VT episodes (86%) with a mean CL of 294 +/- 23 ms in 23 of 25 patients (88%) who received ATP therapy. ATP failed to terminate or accelerated 33 of 232 VT episodes (14%) with a mean CL of 287 +/- 19 ms in 12 of 25 patients (48%) who received ATP therapy. CONCLUSIONS: Painfree termination of rapid VT with empirical ATP is common in heart failure patients with prophylactic ICD therapy. The occasional inability of empiric ATP to terminate rapid VT in almost 50% of patients who receive ATP for rapid VT warrants restrictive ICD programming with regard to the number of ATP attempts in order to avoid syncope before VT termination occurs.     

Characteristics and relevance of clustering ventricular arrhythmias in defibrillator recipients

INTRODUCTION: Studies of recurrent ventricular tachycardia and ventricular fibrillation (VT/VF) have been limited to "electrical storms," where recurrent arrhythmias necessitate repeated external cardioversions or defibrillations. Patients with an implantable cardioverter-defibrillator (ICD) may also suffer frequently recurrent arrhythmias. The aim of this study was to analyze the temporal pattern and the clinical relevance of clustering ventricular arrhythmias in ICD recipients. METHODS: The incidence and the type of arrhythmias were determined by reviewing stored electrograms. VT/VF clusters were defined as the occurrence of three or more adequate and successful ICD interventions within 2 weeks. Two hundred and fourteen consecutive ICD recipients were followed during an average of 3.3 +/- 2.2 years (698 patient-years). RESULTS: Fifty-one patients (24%) suffered 98 VT/VF clusters 21 +/- 22 months after ICD implantation, 93% of these clusters consisting of recurrent regular VT. Monomorphic VT as index event leading to ICD implantation was the only factor predicting VT/VF clusters. Kaplan-Meier estimates of the combined end-point of death or heart transplantation showed a 5-year event-free survival of 67% versus 87% in patients with and without clusters, respectively (P = 0.026). Adjusted hazard ratios for death or heart transplantation in the group with arrhythmia clusters was 3.5 (95% confidence interval 1.5-7.9 P = 0.003). CONCLUSIONS: VT/VF clusters are frequent late after ICD implantation particularly in patients who had VT as index-event. As arrhythmias and recurrent ICD interventions are responsible for an important morbidity, there is a possible role for a prophylactic intervention. Furthermore, VT/VF clusters are an independent marker of increased risk of death or need for heart transplantation.     

The Value of Electrophysiology Study and Prophylactic Implantation of Cardioverter Defibrillator in Patients with Hypertrophic Cardiomyopathy

Fifty-three consecutive patients with hypertrophic cardiomyopathy (HCM) and no history of sudden death underwent electrophysiology (EP) study. Sustained polymorphic ventricular tachycardia (VT) or ventricular fibrillation (VF) was induced in 19 patients (35%). Patients with prior syncope or near syncope had a higher incidence of VT/VF inducibility. An implantable cardioverter defibrillator (ICD) was placed in 14 of the 19 patients. Of the remaining 5 patients with inducible VT/VF, three refused ICD implantation, while two underwent septal myectomy and VT/VF was no longer inducible afier the operation. None of the patients received antiarrhythmic drugs. During a mean follow-up period of 47 ± 31 (2–117) months, no events occurred in the 34 patients with negative EP study. Three events occurred among the 19 patients with inducible VT/VF. One patient died suddenly, one developed wide complex tachycardia which required resuscitation, and one patient received an appropriate ICD shock. In conclusion, sustained polymorphic VT/VF was inducible in about one-third of patients with HCM. Noninducibility of VT/VF appeared to predict a favorable prognosis. Although the overall event rate was low in patients with inducible VT/VF, prophylactic ICD implantation in patients with multiple risk factors may be appropriate.     

Sustained polymorphic arrhythmias induced by programmed ventricular stimulation have prognostic value in patients receiving defibrillators

BACKGROUND: Patients with ischemic cardiomyopathy (ICM) who have monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation (PVS) are at increased risk of sudden cardiac death (SCD). Among a primary prevention population, the prognostic significance of induced polymorphic ventricular arrhythmias is unknown. METHODS: A total of 105 consecutive patients who received an implantable cardioverter-defibrillator (ICD) for primary prevention of SCD in the setting of ICM and non-sustained VT were retrospectively evaluated. Seventy-five patients (group I) had induction of monomorphic VT and 30 patients (group II) had a sustained ventricular arrhythmia other than monomorphic VT (ventricular flutter, ventricular fibrillation, and polymorphic VT) induced during PVS. RESULTS: Baseline characteristics were similar between group I and group II except for ejection fraction (25% vs. 31%, P = 0.0001) and QRS duration (123 milliseconds vs. 109 milliseconds, P = 0.04). Sixteen of 75 (21.3%) patients in group I and 6 of 30 (20%) patients in group II received appropriate ICD therapy (P = 0.88). Survival free from ICD therapy was similar between groups (P = 0.54). There was a trend toward increased all-cause mortality among patients in group I by Kaplan-Meier analysis (P = 0.08). However, when adjusted for age, EF, and QRS duration mortality was similar (P = 0.45). CONCLUSIONS: There is no difference in rates of appropriate ICD discharge or mortality between patients dichotomized by type of rhythm induced during PVS. These results suggest that patients in this population who have inducible VF or sustained polymorphic VT have similar rates of subsequent clinical ventricular tachyarrhythmias as those with inducible monomorphic VT.     

Ventricular Arrhythmia Inducibility Predicts Subsequent ICD Activation in Nonischemic Cardiomyopathy Patients: A DEFINITE Substudy

Objectives: We evaluated whether electrophysiologic (EP) inducibility predicts the subsequent occurrence of spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in the Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial.
Background: Inducibility of ventricular arrhythmias has been widely used as a risk marker to select implantable cardioverter defibrillator (ICD) candidates, but is believed not to be predictive in nonischemic cardiomyopathy patients.
Methods: In DEFINITE, patients randomized to the ICD arm, but not the conventional arm, underwent noninvasive EP testing via the ICD shortly after ICD implantation using up to three extrastimuli at three cycle lengths plus burst pacing. Inducibility was defined as monomorphic or polymorphic VT or VF lasting 15 seconds. Patients were followed for a median of 29 ± 14 months (interquartile range = 2–41). An independent committee, blinded to inducibility status, characterized the rhythm triggering ICD shocks.
Results: Inducibility, found in 29 of 204 patients (VT in 13, VF in 16), was associated with diabetes (41.4% vs 20.6%, P = 0.014) and a slightly higher ejection fraction (23.2 ± 5.9 vs 20.5 ± 5.7, P = 0.021). In follow-up, 34.5% of the inducible group (10 of 29) experienced ICD therapy for VT or VF or arrhythmic death versus 12.0% (21 of 175) noninducible patients (hazard ratio = 2.60, P = 0.014).
Conclusions: In DEFINITE patients, inducibility of either VT or VF was associated with an increased likelihood of subsequent ICD therapy for VT or VF, and should be one factor considered in risk stratifying nonischemic cardiomyopathy patients.     

Ventricular tachyarrhythmias in patients receiving an implantable cardioverter-defibrillator for primary versus secondary prophylaxis indications

Introduction: Data on the mechanisms of sudden cardiac death are limited and may be biased by delays in rhythm recording and selection bias in survivors. As a result, the relative contributions of monomorphic ventricular tachycardia (VT) (cycle length [CL] > 260 ms), monomorphic fast VT (FVT) (CL ≤ 260 ms), and polymorphic VT (PMVT)/ventricular fibrillation (VF) have not been well characterized nor compared in patients with and without prior arrhythmic events. Methods: A retrospective cohort study of implantable cardioverter‐defibrillator (ICD) recipients with primary or secondary implant indications was used to evaluate intracardiac electrograms (EGMs) for the first spontaneous VT/VF resulting in appropriate ICD therapy. EGMs were categorized into VT, FVT, and PMVT/VF based on CL and morphologic criteria. Results: Of 616 implants, 145 patients (58 [40%] primary indications) received appropriate ICD therapy for VT/VF over mean follow‐up of 3.8 ± 3.2 years. Primary implants had more diabetes (28% vs 12%; P = 0.02) and less antiarrhythmic use (15% vs 33%; P = 0.02). In those patients with spontaneous arrhythmia, PMVT/VF occurred in 20.7% of primary versus 21.8% of secondary implants, FVT in 19.0% versus 21.8%, and VT in 60.3% versus 56.4%, respectively (P = 0.88). Spontaneous VT CL was similar regardless of implant indication (284 ± 56 [primary] vs 286 ± 67 ms [secondary]; P = 0.92). Conclusions: Monomorphic VT is the most common cause of appropriate ICD therapy regardless of implant indication. These results provide insight into the mechanisms of sudden cardiac death and have implications for the use of interventions designed to limit ICD shocks. (PACE 2011; 34:571–576)     

Optimizing ICD programming for shock reduction

With the increasing numbers of patients with implantable cardioverter/defibrillators for primary prevention (PP), the topic of inappropriate therapy becomes more and more important. If a shock intervention, e.g. for rapidly conducted atrial fibrillation or fast VT (FVT), represents the first reminder of the implantable cardioverter/defibrillator (ICD), the adherence to the therapy will decrease. Moreover, anxiety to receive the next inappropriate ICD Rx is able to initiate a bad quality of life or depression. Starting with the PainFREE Rx II Trial results, the programming of antitachycardia pacing was able to terminate even fast ventricular arrhythmia, i.e. ≥188 bpm, in three of four episodes. Thereafter, several studies evaluated whether a prolongation in ventricular tachyarrhythmia (VT) detection is able to reduce unnecessary ICD Rx owing to nonsustained VT. The PREPARE trial evaluated this concept in a cohort of PP patients. This nonrandomized study compared a historical control group to patients with a prolonged detection interval. The results underline the idea that an extension in detection time leads to a significant decrease in ICD Rx for supra‐ as well as VT. The RELEVANT study investigated in a randomized fashion the outcome of an increase in detection time in nonischemic patients under CRT including an ICD. The findings clearly demonstrated a reduction in ICD Rx as well as hospital admissions, significantly. Currently, the ADVANCE III trial investigates a 30/40 interval detection compared to 18/24 for FVT in prospective randomized fashion in patients for primary or secondary prevention including all ICD devices.     

Experience of ICD management at a UK center: cardiovascularly stable VT presentation predicts higher risk for appropriate ICD therapy

BACKGROUND: It would be useful to identify patients at high risk of implantable cardioverter defibrillator (ICD) therapy via additional antiarrhythmic measures to minimize the morbidity of ICD therapies. OBJECTIVE: We assessed baseline characteristics for predictors of device therapy in a general ICD population. We also compared the likelihood of therapy delivery by replacement ICDs implanted for battery depletion with the original implants. METHODS: Clinical and ICD interrogation data from patients followed up at a UK center were analyzed looking for predictors of appropriate ICD therapy. Univariate and multivariate analysis was performed using Cox regression. We compared time to first appropriate therapy between first and second ICDs in patients who had undergone ICD replacement for battery depletion by log-rank testing. RESULTS: One hundred and sixty-one patients were studied (129 men, age 65.7 +/- 12.9 years, follow-up 908 +/- 676 days). Appropriate therapy was delivered in 68 patients (42%). Univariate risk factors for appropriate ICD therapy were presentation with stable ventricular tachycardia (VT) (P = 0.0002), ischemic etiology (P = 0.03), tiered therapy programmed ICDs (P = 0.01), and beta-blocker use (P = 0.001). Stable VT and beta blocker use were independent predictors of ICD therapy on multivariate analysis. Thirty-three patients (20%) had at least one ICD replacement. Time to first appropriate therapy was no different between first and second ICD implants (P = 0.8). CONCLUSION: Patients who present with cardiovascularly stable VT have a higher probability of receiving appropriate ICD therapy than those who do not. Following battery depletion of an original ICD, the replacement device is no less likely to administer therapy than the first.     

Time to First Shock in Implantable Cardioverter Defibrillator (ICD) Patients with Chagas Cardiomyopathy

The time to first ICD shock has been extensively studied in patients with coronary artery disease (CAD). However, there are no published data on ICD shocks in patients with Chagas cardiomyopathy (ChC). The occurrence of the first appropriate ICD shock during the first 6 months of follow-up in 20 patients with ChC (group 1) and 35 CAD patients (group 2) was analyzed retrospectively. All patients had received a third-generation pectoral ICD for ventricular tachycardia or fibrillation (VT/VF). Indications for ICD implantation were refractoriness to drug therapy or noninducibility of VT/VF at EPS in cardiac arrest survivors. Results: The mean age, left ventricular ejection fraction (LVEF), and sex in groups I and II were 57.4 ± 7 years versus 64 ± 9 (P < 0.01), 30.9%± 10% versus 32.9%± 10% (P = NS), and 10 men versus 31 women (P < 0.005), respectively. Six months after ICD implantation, 85% (17/20) group I patients received appropriate ICD shocks versus 51 % (18/35) in group 2, a statistically significant difference (P < 0.02, RR: 1.65, OR: 5.35). Conclusions: The incidence of appropriate ICD shocks within the first 6 months postimplantation was significantly higher in ChC patients than in CAD patients. ChC patients were younger and more often women than CAD patients.     

Significance of Supraventricular Tachyarrhythmias in Patients with Implanted Pacing Cardioverter Defibrillators

Eighty-six patients were treated with an implantable cardioverter defibrillator (ICD) because of sustained ventricalar tachycardia (VT) or ventricular fibrillation (VF). In 27 patients an epicardial system was used, in 59 patients a transvenous system with a subcutaneous patch electrode was implanted. During a mean follow-up time of 17 ± 9 months, inappropriate activations of the ICD due to supraventricular tachycardia were documented by Holter monitoring in 14 patients (16%). In 8 patients paroxysmal atrial fibrillation (AF), in 2 patients chronic AF, in 1 patient atrial flutter, and in 3 patients sinus tachycardia triggered antitachycardia pacing functions (12 patients) or internal defibrillation (2 patients). In 3 patients (5%) VT was induced by inappropriate antitachycardia pacing. In an additional 18 patients (21%) inappropriate activation of antitachycardia functions due to atrial tachyarrhythmias were suspected based on telemetry readouts or the patient's history. Inappropriate activation of ICD therapy triggered by intermittent supraventricular tachyarrhythmias is common. Further improvements of detection algorithms for supraventricular tachycardia are required in future device generations.     

Results of Electrophysiological Testing and Long-Term Follow-Up in Patients Sustaining Cardiac Arrest Only While Receiving Type IA Antiarrhythmic Agents

Therapeutic management of patients sustaining a cardiac arrest while receiving antiarrhythmic agents can be difficult since the role of the drug in possibly facilitating the arrhythmia is often difficult to define. To determine if the response to programmed stimulation could give insight into which patients may have experienced a drug-induced cardiac arrest, we studied 29 patients (61 +/- 9 years) with no prior history of sustained ventricular tachyarrhythmias (VT) who suffered a cardiac arrest only while receiving type Ia antiarrhythmic agents. Patients with documented myocardial infarction, acute ischemia, electrolyte abnormalities, or torsade de pointes were excluded from the study. Twenty-four patients had coronary artery disease with prior myocardial infarction (ejection fraction 28% +/- 9%) and five patients had idiopathic dilated cardiomyopathy (ejection fraction 31% +/- 6%). During baseline electrophysiological testing, 19 patients (66%) had inducible sustained ventricular arrhythmias: uniform VT, n = 14 (group I), polymorphic VT or ventricular fibrillation, n = 5 (group II). Ten patients (group III) had no inducible sustained ventricular arrhythmias. To determine if rechallenge with a type Ia agent could facilitate induction of a sustained ventricular arrhythmia in group III, eight patients underwent ten electrophysiological studies during therapy with either procainamide or quinidine. Only two patients developed sustained VT in response to programmed stimulation. Patients in groups I and II received therapy guided by electrophysiological testing, including antiarrhythmic agents alone (n = 8), subendocardial resection (n = 4), or an implantable cardioverter defibrillator (n = 7). Patients in group III received antiarrhythmic agents empirically (n = 3), or for treatment of atrial tachyarrhythmias (n = 2) or nonsustained VT (n = 1). In addition, four patients in group III received an implantable cardioverter defibrillator. During a mean follow-up of 28 +/- 27 months (range: 1 day-84 months) 13 patients died suddenly or received a defibrillator shock preceded by syncope or presyncope: group I: n = 5; group II: n = 2; group III: n = 6. In conclusion: (1) most patients sustaining a cardiac arrest only in the presence of type Ia antiarrhythmic agents have inducible sustained VT in the absence of antiarrhythmic agents, and (2) the risk of recurrent VT persists in patients without inducible sustained arrhythmias in the drug-free state, regardless of whether they manifest inducible arrhythmias after rechallenge with a type Ia agent.     

New ICD-Technologies: First Clinical Experience with Dual-Chamber Sensing for Differentiation of Supraventricular Tachyarrhythmias

Inappropriate ICD therapy for supraventricular arrhythmias remains an unsolved problem and may lead to serious clinical situations. Current algorithms for differentiation of supraventricular and ventricular arrhythmias are based on ventricular sensing solely and, therefore, lack semitivity and specificity. This preliminary analysis from a multicenter trial comprises data from the first 26 patients who received a Res-Q? Micron active-can ICD (Stdzer Intermedics) with a ventricular defibrillation lead and an additional bipolar lead for atrial sensing. Digitized atrial and ventricular waveform storage as well as interval charts from 102 induced and 30 spontaneous arrhythmia episodes were prospectively collected and analyzed with regard to appropriateness of ICD therapy. From all 132 arrhythmia episodes, high-quality stored dual-chamber intracardiac electrograms (JFXJM) could be retrieved for further analysis: in 40 (30%) episodes, atrial fibrillation (AF with rapid ventricular response 22, AF with VT9, AF with VF 9) was identified as the underlying intrinsic rhythm, and inappropriate ICD therapy was delivered in 4/22 (18%) episodes of AF with rapid ventricular response. In the remaining 92 (70%) episodes, sinus rhythm was the underlying atrial rhythm (SR with VT 13, SR with VF 79), and no inappropriate therapy was observed. Three of 22 (15%) high-energy shocks delivered for ventricular arrhythmias (VT 9, VF 9, rapid AF 4) terminated AF at the same time. In total, there were 3 complications (2 atrial lead dislodgments, I revision for bleeding). Both atrial lead dislodgments occurred in the 2 patients with passive-fixation leads compared to none in the 24 patients with active-fixation leads (p - 0.003). In conclusion, dual-chamber sensing and waveform storage of the new Res-Q? Micron offer very helpful diagnostic tools for the detection of inappropriate ICD-therapy. Placement of an additional atrial lead is safe and does not interfere with proper ICD function. However, for avoidance of atrial lead dislodgment, active fixation leads are recommended With the tested active-can lead configuration, the efficacy of successful atrial cardioversion by high-energy shocks delivered for ventricular arrhythmias seems to be low.     

Are Electrophysiological Studies Needed Prior to Defibrillator Implantation?

At present, patients with documented sustained VT or resuscitated cardiac arrest (CA) are treated with ICDs. The aim of this study was to retrospectively evaluate if a routine electrophysiological study should be recommended prior to ICD implantation. In 462 patients referred for ICD implantation because of supposedly documented VT (n = 223) or CA (n = 239), electrophysiological study was routinely performed. In 48% of the patients with CA, sustained VT or VF was inducible. Electrophysiological study suggested conduction abnormalities (n = 11) or supraventricular tachyarrhythmias (n = 3) in conjunction with severely impaired left ventricular function to have been the most likely cause of CA in 14 (5.9%) of 239 patients. Likewise, sustained VT was only inducible in 48% of patients with supposedly documented VT. Of these inducible VTs, nine were diagnosed as right ventricular outflow tract tachycardia or as bundle branch reentry tachycardia. Supraventricular tachyarrhythmias judged to represent the clinical event were the only inducible arrhythmia in 35 (16%) patients (AV nodal reentrant tachycardia [n = 7], AV reentry tachycardia [n = 4], atrial flutter [n = 19], and atrial tachycardia [n = 5]). Based on findings from the electrophysiological study, ICD implantation was withheld in 14 (5.9%) of 239 patients with CA and in 44 (19.7%) of 223 patients with supposedly documented VT. During electrophysiological study, VT or VF was only reproducible in about 50% of patients with supposedly documented VT or CA. Electrophysiological study revealed other, potentially curable causes for CA or supposedly documented VT in 12.6% (58/462) of all patients, indicating that ICD implantation can potentially be avoided or at least postponed in some of these patients. Based on these retrospective data, routine electrophysiological study prior to ICD implantation seems to be advisable.     

Implanted cardioverters-defibrillators in the treatment of arrhythmias and prevention of sudden death

AIM: To present 15-year experience in use of implantable cardioverters-defibrillators (ICD) in patients with life threatening arrhythmias and a high risk of sudden cardiac death (SCD). MATERIAL AND METHODS: A total of 151 patients (116 males and 35 females aged 12-75 years) with life threatening arrhythmias and ICD were studied. RESULTS: There were neither complications nor lethality. Electrocardiotherapy was performed in 89 (58.9%) patients 4.5 +/- 9.4 months, on the average, after ICD implantation. Attacks of ventricular tachycardia (VT) were arrested by antitachycardia stimulation (974 episodes, 37.5 +/- 92.5 per patient, on the average). Effective cardioversion in VT was observed in 63 (41.7%) cases. Episodes of rapid ventricular tachycardia and ventricular fibrillation were stopped by defibrillation shocks in 28 (18.5%) patients. Additional surgical interventions were made in 3 patients because of electrodes dislocation, in 1--because of electrode brakage and in 1--suppuration of the bed. Fifteen patients (9%) died during follow-up because of cardiac failure (n = 13), cancer (n = 1), unknown cause (n = 1). CONCLUSION: Clinical application of ICD is not only treatment of arrhythmia and prevention of SCD but it is also a method of diagnosis, collection and accumulation of information about the disease course.     

Hybrid Therapies for Ventricular Arrhythmias

In recent years several trials demonstrated the efficacy of implantable cardioverter-defibrillation (ICD) therapy in reducing cardiac and total mortality in patients affected by rapid ventricular tachycardia (VT) and/or ventricular fibrillation. Nevertheless, ICD do not prevent arrhythmia recurrences, thus being a palliative and not a curative treatment modality. The tolerance to ICD therapy varies greatly, and within individuals, this leading to a nonuniform acceptance of this form of therapy. The very frequent occurrence of VT, defined as an arrhythmic storm, may be a life threatening condition. The majority of ICD patients is under antiarrhythmic drug therapy, to reduce episodes of VT or to make antitachycardia pacing more effective by slowing the tachycardia rate. Drug therapy, however, may cause additional problems, and does not represent the optimal solution. The prevention of VT and/or ventricular fibrillation episodes and excessive ICD therapy, remains a worthwhile goal. Radiofrequency catheter ablation (RFCA) is a curative approach, and can be expected to reduce the frequency of recurrent VT episodes in the majority of patients. The combination of these treatment modalities (ICD and RFCA) is often described as hybrid therapy, implying that the two treatments act providing some form of synergism. In experienced centers, RFCA is now performed, regardless of whether the VT rate is rapid and/or is hemodynamically unstable. Newer mapping and ablation techniques are now available, enhancing the acute success rate of the procedure. In this review the most recent application of VT catheter ablation and the use of advanced mapping and ablation techniques will be discussed.     

Pectoral cardioverter defibrillators: comparison of prepectoral and submuscular implantation techniques

The purpose of this study was to compare the two techniques of pectoral ICD implantation, prepectoral and submuscular, performed by an electrophysiologist in the catheterization laboratory with use of general or local anesthesia in 45 consecutive patients. Over a period of 30 months, we implanted pectoral transvenous ICDs in 43 men and 2 women, aged 59 +/- 12 years, with use of general (n = 20) or local (n = 25) anesthesia in the catheterization laboratory. Patients had coronary (n = 30) or valvular (n = 4) disease, cardiomyopathy (n = 10) or no organic disease (n = 1), a mean left ventricular ejection fraction of 31%, and presented with ventricular tachycardia (n = 40) or fibrillation (n = 5). One-lead ICD systems (18 Endotak, 10 Transvene/8 Sprint, 2 EnGuard) were used in 38 patients, 2-lead (5 Transvene, 1 EnGuard) systems in 6 patients, and 1 atrioventricular lead ICD system in 1 patient. The prepectoral technique was employed in 29 patients with adequate subcutaneous tissue, while the submuscular technique was used in 16 patients who had a thin layer of subcutaneous tissue. The defibrillation threshold averaged 9-10 J in both groups and there were no differences in pace/sense thresholds. All implants were entirely transvenous with no subcutaneous patch. Biphasic ICD devices were employed in all patients. Active or hot can devices were used in 39 patients. There were no complications, operative deaths, or infections. Patients were discharged at a mean of 3 days. All devices functioned well at predis-charge testing. Over 14 +/- 8 months, 20 patients received appropriate device therapy (antitachycardia pacing or shocks). No late complications occurred. One patient died at 3 months of pump failure; there were no sudden deaths. In conclusion, for exclusive pectoral implantation of transvenous ICDs, electrophysiologists should master both prepectoral and submuscular techniques. One can thus avoid potential skin erosion or need for abdominal implantation in patients with a thin layer of subcutaneous tissue. Finally, there are no differences in pacing or defibrillation thresholds between the two techniques.     

Catheter Ablation of Electrical Storm Due to Monomorphic Ventricular Tachycardia in Patients with Nonischemic Cardiomyopathy: Acute Results and Its Effect on Long‐Term Survival

Background: Electrical storm due to recurrent ventricular tachycardia (VT) in patients with implantable cardioverter defibrillator (ICD) can adversely affect their long‐term survival. This study evaluates the efficiency of the radiofrequency catheter ablation of electrical storm due to monomorphic VT in patients with idiopathic dilated cardiomyopathy (DCM) and assesses its long‐term effects on survival. Methods and Results: Between April 2004 and October 2008, 13 consecutive patients (nine men, mean age 56.8 ± 17.8 years) with DCM and electrical storm due to monomorphic VT who had ICD underwent 17 catheter ablation procedures, including four epicardial, at our center. Acute complete success was defined as the lack of inducibility of any VT at the end of procedure during programmed right ventricular stimulation and was achieved in eight patients (61.5%). During a median follow‐up of 23 months (range 3–63 months) nine patients (69%) were alive and eight patients (61.5%) were free from VT recurrence. Among those with acute complete (n = 8) and partial (n = 5) success, seven patients (87.5%) and one patient (20%) were free from any VT recurrence and ICD therapy, respectively (P = 0.025). Among those with acute complete and partial success, seven patients (87.5%) and two patients (40%) were alive, respectively (Mantel‐Cox test P = 0.082). Among those who had an initially failed endocardial ablation (n = 8), four underwent further epicardial ablation that was completely successful in three patients (75%). Conclusion: Catheter ablation in patients with DCM and electrical storm due to monomorphic VT who had an ICD prevents further VT recurrence in 61.5% of the patients. Complete successful catheter ablation may play a protective role and was associated with reduced mortality during the follow‐up period. More aggressive ablation strategies in patients with initially failed endocardial ablation might improve the long‐term survival of these patients; however, further studies are needed to clarify this issue. (PACE 2010; 33:1504–1509)