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.     

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.     

Late Retesting of System Performance in ICD Patients Without Spontaneous Shocks

One hundred five implantable cardioverter defibrillator (ICD) patients (71 ± 9 years of age, 83% men) without spontaneous ICD discharges for ≥ 12 months were tested to assess high voltage (HV) circuit integrity and the system's ability to recognize and terminate ventricular fibrillation (VF). Indications for ICD implantation were sustained ventricular tachycardia (VT) (35%), cardiac arrest (27%), and inducible VT (38%). Eighty-two percent of the patients had coronary artery disease (CAD), and the mean left ventricular ejection fraction (LVEF) was 36%± 13%. Results: One hundred patients had inducible VF and five did not. Testing led to ICD reprogramming in 50 (49%) patients. Two (1.9%) patients required ICD replacement: (1) a 45-year-old patient with a Ventritex 110 ICD implanted for 13 months interfaced with a CPI 0062 lead implanted for 46 months could not be defibrillated internally (impedance nonmeasurable); (2) an 82-year-old patient with a 23-month-old Medtronic 7219 ICD interfaced with 6936 and 6933 leads whose defibrillation threshold (DFT) had doubled since implantation (24 J from 12 J). Lead fractures were found in both cases (proximal coil of the 0062, and subcutaneously in the 6933). Based on DFT determinations, the first shock output was programmed lower in 37 patients and higher in 10 patients. Shock pulse width was changed in one patient and the ventricular refractory period in another. No programming changes were made in 54 (51%) patients. Conclusions: (1) Late testing of HV circuit integrity in ICD patients without an ICD shock in ≥ 12 months identifies previously unsuspected HV lead fractures; (2) chronic DFT testing resulted in HV output reprogramming in one-half of the patients.     

A Prospective, Randomized Evaluation of a Nonthoracotomy Implantable Cardioverter Defibrillator Lead System

Nonthoracotomy lead systems for ICDs have been developed that obviate the need for a thoracotomy and reduce the morbidity and mortality associated with implantation. However, an adequate DFT cannot be achieved in some patients using transvenous electrodes alone. Thus, a new subcutaneous "array" electrode was designed and tested in a prospective, randomized trial that compared the DFT obtained using monophasic shock waveforms with a single transvenous lead alone that has two defibrillating electrodes, the transvenous lead linked to a subcutaneous/submuscular patch electrode, and the transvenous lead linked to the investigational array electrode. There were 267 patients randomized to one of the three nonthoracotomy ICD lead systems. All had DFTs that met the implantation criterion of ≤ 25 J. The resultant study population was 82% male and 18% female, mean age of 63 ± 11 years. The indication for ICD implantation was monomorphic VT in 70%, VF in 19%, monomorphic VT/VF in 6%, and polymorphic VT in 4% of the patients, respectively. The mean LVEF was 0.33 ± 0.13. The mean DFT obtained with the transvenous lead alone was 17.5 ± 4.9 J as compared to 16.9 ± 5.5 J with the lead linked to a patch electrode (P = NS), and 14.9 ± 5.6 with the lead linked to the array electrode (array versus lead alone, P = 0.0001; array versus lead/patch, P = 0.007). The results of this investigation suggest that the subcutaneous array may be superior to the standard patch as a subcutaneous electrode to lower the DFT and increase the margin of safety for successful nonthoracotomy defibrillation.     

Late Gadolinium Enhancement in Patients with Nonischemic Dilated Cardiomyopathy

One‐third of all patients with heart failure have nonischemic dilated cardiomyopathy (NIDM). Five‐year mortality from NIDM is as high as 20% with sudden cardiac death (SCD) as the cause in 30% of the deaths. Currently, the left ventricular ejection fraction (LVEF) is used as the main criteria to risk stratify patients requiring an implantable cardioverter defibrillator (ICD) to prevent SCD. However, LVEF does not necessarily reflect myocardial propensity for electrical instability leading to ventricular tachycardia (VT) or ventricular fibrillation (VF). Due to the differential risk in various subgroups of patients for arrhythmic death, it is important to identify appropriate patients for ICD implantation so that we can optimize healthcare resources and avoid the complications of ICDs in individuals who are unlikely to benefit. We performed a systematic search and review of clinical trials of NIDM and the use of ICDs and cardiac magnetic resonance imaging with late gadolinium enhancement (LGE) for risk stratification. LGE identifies patients with NIDM who are at high risk for SCD and enables optimized patient selection for ICD placement, while the absence of LGE may reduce the need for ICD implantation in patients with NIDM who are at low risk for future VF/VT or SCD.     

Survival and Appropriate Device Interventions in Recipients of Cardioverter Defibrillators Implanted for the Primary Versus Secondary Prevention of Sudden Cardiac Death

Background: Implantable cardioverter-defibrillators (ICD) implanted after an episode of ventricular tachyarrhythmia (VTA) or in patients at high risk of VTA lower the long-term mortality. Comparisons of the clinical outcomes of the two indications are scarce.
Methods: The study enrolled 360 consecutive ICD recipients. The device was implanted for secondary prevention in 150 patients, whose mean age was 60 ± 14 years, and mean left ventricular ejection fraction (LVEF) was 40 ± 16%, and for primary prevention in 210 patients, whose mean age was 61 ± 11 years, and mean LVEF was 31 ± 13%. All-cause mortality and time to first appropriate ICD therapy were measured.
Results: The two study groups were similar with respect to age and prevalence of coronary artery disease. Mean LVEF was higher in the secondary prevention group (P = 0.001). Cox regression analysis revealed a significantly shorter time to first appropriate ICD therapy in the secondary prevention group (HR = 0.51, 95% CI = 0.30 – 0.87, P = 0.01). Over a mean follow-up of 37 ± 19 months, the all-cause mortality in the overall population was 12.7%, and was similar in both subgroups (HR = 0.99, 95% CI = 0.55–1.77, P = 0.97).
Conclusions: The long-term mortality in this unselected population of ICD recipients was low. Patients treated for secondary prevention received earlier appropriate ICD therapy than patients treated for primary prevention. Long-term mortality was similar in both groups. The higher VT incidence of VTA was effectively treated by the ICD and was not associated with a higher mortality.     

Prevention of Inappropriate Shocks in ICD Recipients: A Review of 10,000 Tachycardia Episodes

Background: The efficacy of dual-chamber ICD arrhythmia classification algorithms is crucial to prevent inappropriate shocks. We report our experience from a meta-analysis of five prospective clinical studies with inclusion phases ranging between 1997 and 2003.
Methods: Dual-chamber ICD using standard dual-chamber arrhythmia classification algorithms were implanted in 802 patients (mean age = 64 ± 11 years, 88% men) in 74 medical centers. The ICD indication was secondary prevention in 95% of patients. Supraventricular tachyarrhythmias (SVT) were previously documented in 26% of patients. All spontaneous tachyarrhythmic events documented by the device memories were analyzed by a adjudicating committee. The episodes lasting >12 seconds and/or treated by the ICD were analyzed.
Results: Over a mean follow-up of 302 ± 113 days, 9,690 events were reported. Mean heart rate at the time of events was 131 ± 45 bpm (100–430). Events were classified as oversensing in 1.4%, sinus tachycardia (ST) in 66%, SVT in 13%, slow (<150 bpm) ventricular tachycardia (VT) in 8.7%, and VT or ventricular fibrillation (VF) in 10.3%. The sensitivity of slow VT detection was 94%, and of VT/VF detection 99.3%. The specificity of sinus rhythm/ST/SVT recognition was 94%, positive predictive value 79.3%, and negative predictive value 99.2%. A total of 1,918 episodes were treated in 330 patients: 1,472 appropriately in 213, and 446 inappropriately in 117 (15% of the overall population) patients. Only 62 episodes were inappropriately treated by shocks in 40 patients, representing 5% of the overall population.
Conclusions: In this conventional ICD population, the overall specificity of standard dual-chamber arrhythmia detection settings reached 94%. This feature allows efficient detection of fast as well as slow VT events with a very low rate of inappropriate shocks.     

The Role of Implantable Cardioverter Defibrillators in Non VT/VF Sudden Deaths

Implantable cardioverter defibrillator (ICD) therapy has been an impressive success in preventing sudden cardiac death (SCD). Electrocardiographic documentation of SCD in ICD patients has been rare, but usually arrhythmias other than ventricular tachycardia/ventricular fibrillation (VT/VF; asystole and electromechanical dissociation [EMD]) have been implicated. This raises the question whether backup bradycardia pacing can prevent deaths due to asystole and EMD in such patients. We studied the outcome of 88 patients with permanent bradycardia pacemakers and compared them to 500 consecutive nonpacemaker patient controls, sustaining out-of-hospital cardiac arrest and undergoing resuscitation by paramedics. Mean age of the pacemaker patients was 73.5 ± 10.3 years and 64% males, compared to mean age of 68.2 ± 6.7 years and 67% males in the control group. Overall success of resuscitation and survival rates were similar. When the documented rhythm was VT/VF or asystole there were no differences in resuscitation or survival rates for the pacemaker or nonpacemaker patients. However, resuscitation rate was significantly higher in pacemaker patients than nonpacemaker patients with EMD: 47% versus 20% ( P < 0.03). For EMD, survival rate for the pacemaker patients was 13% compared to 5% in the nonpacemaker patients, but this difference was not statistically significant. Backup bradycardia pacing in future generation devices may improve the outcome of non VT/VF sudden cardiac death in at least some of the ICD recipients.     

Left Ventricular Ejection Fraction as Criterion for Implantation of an Implantable Cardioverter-Defibrillator in Heart Failure Patients Undergoing Surgical Left Ventricular Reconstruction

Background: Besides implantation of an implantable cardioverter-defibrillator (ICD), a proportion of patients with left ventricular (LV) dysfunction due to ischemic cardiomyopathy are potential candidates for surgical LV reconstruction (Dor procedure), which changes LV ejection fraction (LVEF) considerably. In these patients, LVEF as selection criterium for ICD implantation may be difficult. This study aimed to determine the value of LVEF as criterium for ICD implantation in heart failure patients undergoing surgical LV reconstruction.
Methods: Consecutive patients with end-stage heart failure who underwent ICD implantation and LV reconstruction were evaluated. During admission, two-dimensional (2D) echocardiography (LV volumes and LVEF) was performed before surgery and was repeated at 3 months after surgery. Over a median follow-up of 18 months, the incidence of ICD therapy was evaluated.
Results: The study population consisted of 37 patients (59 ± 11 years). At baseline, mean LVEF was 23 ± 5%. Mean left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV) were 175 ± 73 mL and 225 ± 88 mL, respectively. At 3-month follow-up, mean LVEF was 41 ± 9% (P < 0.0001 vs. baseline), and mean LVESV and LVEDV were 108 ± 65 mL and 176 ± 73 mL, respectively (P < 0.0001 vs. baseline). During 18-month follow-up, 12 (32%) patients had ventricular arrhythmias, resulting in appropriate ICD therapy. No significant relations existed between baseline LVEF (P = 0.77), LVEF at 3-month follow-up (P = 0.34), change in LVEF from baseline to 3-month follow-up (P = 0.28), and the occurrence of ICD therapy during 18-month follow-up.
Conclusion: LVEF before and after surgical LV reconstruction is of limited use as criterium for ICD implantation in patients with end-stage heart failure.     

A Comparison of Ventricular Arrhythmias Induced with Programmed Stimulation Versus Alternating Current

In patients undergoing implantation and testing of the implantable cardio-verter defibrillator (ICD), alternating current (AC) may be used to induce ventricular tachyarrhythmias in a prompt, safe, and efficient manner. These arrhythmias have been previously reported to be similar to those induced during programmed electrical stimulation (PES). We compared the ventricular tachyarrhythmias induced by both methods in 14 patients: 8 male, 6 female; mean age 61 years; coronary disease in 10, cardiomyopathy in 4; mean ejection fraction 31%. The presenting arrhythmia was nonsustained ventricuiar tachycardia (VT) in four, sustained monomorphic ventricular tachycardia (SMVT) in five, ventricular fibrillation (VF) in four, and unknown in one patient with syncope. PES (single, double, triple extrastimuli; burst pacing) and AC (1–2 sec application) stimulation via right ventricular endocardial electrode catheter was performed off antiarrhythmic drugs in the nonsedated state. PES induced SMVT in nine, polymorphic VT in two, and VF in three. AC induced VF in all patients. Although AC can reliably induce ventricular tachyarrhythmias during de/ibrillation threshold and ICD testing, there is poor correlation to PES induced tachyarrhythmias.     

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.     

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.     

Value of Heart Rate Variability to Predict Ventricular Arrhythmias in Recipients of Prophylactic Defibrillators with Idiopathic Dilated Cardiomyopathy

GRIMM, W., et al. : Value of Heart Rate Variability to Predict Ventricular Arrhythmias in Recipients of Prophylactic Defibrillators with Idiopathic Dilated Cardiomyopathy. This study investigated the relation between heart rate variability (HRV) measured as standard deviation of normal to normal RR intervals (SDNN) on baseline 24-hour ambulatory electrocardiogram (ECG) and subsequent appropriate implantable cardioverter defibrillator (ICD) interventions in 70 patients with idiopathic dilated cardiomyopathy (IDC) in whom ICDs were implanted prophylactically in the presence of a low left ventricular ejection fraction (LVEF). During   43 ± 26   months of follow-up, 26 of 70 (37%) study patients with IDC received one or more appropriate ICD interventions for sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) documented by electrograms stored in the ICD. Mean SDNN at ICD implant was   94 ± 33 ms   . No difference was found between patients with   (90 ± 25 ms)   versus without   (96 ± 37 ms)   appropriate ICD interventions for VT or VF during follow-up. Multivariate Cox regression analysis of baseline clinical characteristics including age, gender, LVEF, NYHA functional class, nonsustained VT on Holter, history of syncope, left bundle branch block, baseline medication and HRV revealed LVEF as the only significant predictor of arrhythmia. These findings do not support the use of HRV measured as SDNN on 24-hour ambulatory ECG to select patients with IDC for prophylactic ICD therapy. (PACE 2003; 26[Pt. II]:411–415)     

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.     

Results of Delivered Therapy for VT or VF in Patients with Third-Generation Implantable Cardioverter Defibrillators

Third-generation implantable cardioverter defibrillators (ICDs) offer tiered therapy and can provide significant advantage in the management of patients with life-threatening arrhythmias. Three different types of ICDs were implanted in 21 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia presentation was VT(76%), VF(10%), or both (14%). The mean left ventricular ejection fraction for the group was 32.4 ± 7%. No surgical mortality occurred. Prior to discharge individual EPS determined the final programmed settings of the ICDs. During a mean follow-up of 13 ± 1.4 months (range 2–20) the overall patient survival was 85.7%. No sudden arrhythmic or cardiac death occurred. Twenty of 21 patients (95%) received therapy by their device. In 14 patients (67%) antitachycardia pacing (A TP) was programmed "on," 13 of which was self-adaptative autodecremental mode. There were 247 VT episodes, 231 of which were subjected to ATP with 97% success and 3% acceleration or failure. Low energy shocks reverted all other VT episodes. VF episodes were successfully reverted by a single shock (93%), two shocks (6%), or three shocks (1 %). We conclude that ATP therapy of VT is successful in the large majority of episodes with rare failures, and that VF episodes are generally terminated by a single ICD shock.     

End Tidal CO2 Is a Quantitative Measure of Cardiac Arrest

SEHRA, R., et al.: End Tidal CO₂ Is a Quantitative Measure of Cardiac Arrest. Purpose of the study: Predictors of severity of cardiac arrest or efficacy of cardiopulmonary resuscitation are few. Respiratory end tidal CO₂ (ETCO) is a marker of pulmonary blood flow and, possibly, cardiac arrest. The purpose of this study was to evaluate ETCO as a quantitative marker of cardiac arrest in a human model of ventricular fibrillation (VF). Methods: Thirty-one cardiac arrest/VF episodes (mean BP < 40 mmHg) in 8 men and 3 women mean age = 42 ± 24 years, mean left ventricular ejection fraction = 39%) undergoing defibrillator (ICD) implant for ventricular tachycardia or previous cardiac arrest were evaluated with continuous ETCO monitoring during defibrillation threshold testing. All patients but one were intubated. Results: Significant differences   (P < 0.001)   were noted between ETCO values prior (mean 37.2 ± 6.8 mmHg) versus during VF (mean 27.1 ± 5.9 mmHg), and during VF versus return of spontaneous circulation (mean 36.6 ± 6.6 mmHg). ETCO decreased by 23%± 8% from pre-VF to during VF. It increased by 37%± 16% during VF to return of spontaneous circulation. These changes were significantly different   (P < 0.001)   . Conclusion: Significant changes in ETCO were measured during VF arrest. ETCO can predict acute cardiac arrest in a quantitative manner. (PACE 2003; 26[Pt. II]:515–517)     

Initial Clinical Experience with a New Small Sized Third-Generation Implantable Cardioverter Defibrillator: Results of a Multicenter Study

This study reports the acute clinical experience with the new CPI VENTAK MINI: a small sized (68 cc), implantable cardioverter defibrillator (ICD) with 33 J stored energy. Implantation of the device was attempted in 113 patients (90 men, mean age 57 ± 16 years, 64 with coronary artery disease, mean left ventricular ejection fraction 41%) with ventricular tachycardia or ventricular fibrillation (VF). All 113 patients (100%) were ultimately implanted, 12% of them for ICD replacement. Transvenous lead implantation was accomplished in all 104 patients (100%) receiving new leads, 95% of them with a single lead configuration. The safety criteria for implantation (2 consecutive VF conversions at 15 J or 3 at 20 J. in both cases without failures to convert) were demonstrated in all but 7 patients (6%). In 6 of these, safety criteria were not fully assessed while in the last patient defibriliation efficacy was not determined. Of the 104 patients with new leads, 90% underwent pectoral implantation. Of the 9 patients (9%) abdominally implanted, only 4 (4%) (3 children) were judged small sized for pectoral implant. At predischarge testing, reliable VF detection and conversion were noted in 96 of 97 patients tested. There was no perioperative mortality. At a 3.6 ± 1.3 months follow-up, 34% of the patients had a spontaneous arrhythmic event, and 24% of the patients received shocks. Clinically inappropriate therapies occurred in 8% of the episodes in which any kind of therapy was delivered. This study demonstrates the short-term clinical efficacy and safety of the new device, and that pectoral implantation can be performed in the large majority of patients.     

Effect of Antiarrhythmic Drug Therapy on the Incidence of Shocks in Patients who Receive an Implantable Cardioverter Defibrillator after a Single Episode of Sustained Ventricular Tachycardia/Fibrillation

Seventy-four patients (16 women, 58 men, age 58 ± 21 years, mean ± standard deviation) who received an implantable Cardioverter de/ibrillator (ICD) after experiencing a single episode of ventricular tachycardia or ventricular fibrillation were followed to determine if antiarrhythmic drug therapy affects the incidence of ICD discharges. Thirty-three patients (group A) were treated with an antiarrhythmic drug that was either untested or previously demonstrated during electropharmacological testing to be ineffective in suppressing the induction of ventricular tachycardia. Forty-one patients (group B) were not treated with an antiarrhythmic drug. There were no significant differences between the two groups in regards to age, sex, incidence of coronary artery disease, left ventricular function or the type of ICD pulse generator used. During a mean follow-up of 14 months for the entire cohort, 15 patients (46%) in group A and 18 patients (44%) in group B experienced at least one ICD shock. The time to the first appropriate shock (5 ± 5 months in both groups) and the frequency of ICD shocks (0.3 ± 0.2/month in group A vs 0.4 ± 0.5/month in group B) were similar in both groups. The incidence of syncope at the time of ICD discharge was higher in group A than group B patients (31% vs 5%, P < 0.05). In conclusion, antiarrhythmic drugs that are untested or have failed electropharmacological testing do not appear to reduce the probability of ICD discharge over a short-term (mean 14 months) follow-up in patients who have had only one clinical episode of VT/VF and may increase the risk of syncope during ICD discharge. Studies with a larger sample size and longer follow-up period will be needed to confirm these findings.     

T-Wave Variability as a Risk Stratifier in Patients with Dilated Cardiomyopathy

Background: T-wave alternans is an important identifier of patients at risk of sudden cardiac death (SCD), but the procedure usually requires stress testing. In this study, the variability of T-wave amplitude (TVAR) was evaluated at rest, as a risk stratifier for SCD.
Methods: This study included 57 patients in sinus rhythm and with a left ventricular ejection fraction ≤40%, of whom 34 (60%) received an implantable cardioverter-defibrillator (ICD) after surviving SCD, and 23 (40%) presented with ischemic or nonischemic cardiomyopathy and no history of SCD. A 20-minute high-resolution electrocardiographic recording for TVAR assessment was performed during supine rest. The vector magnitude was used as a primary lead for TVAR analysis.
Results: The mean, median, and maximum (max) values of TVAR were measured. The patients with ICD had a lower max TVAR than the patients without ICD (67 vs 95 μV; P = 0.045), though the mean and median TVAR values were similar. By multivariate logistic analysis, max TVAR remained a predictor of SCD, after adjustments for potentially confounding factors (P = 0.044).
Conclusion: Max TVAR was a predictor of arrhythmic events in patients with dilated cardiomyopathy at rest.     

Experience with Two Different Nonthoracotomy Systems for Implantable Defibrillator in 170 Patients

Implantation of a nonthoracotomy system (Medtronic PCD or CPI Endotak) was attempted in 170 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) not requiring concomitant cardiac surgery. A nonthoracotomy system could be successfully implanted in 95 of the 115 patients with the PCD system and 49 of 55 patients receiving the Endotak lead system. In 26 patients with failed nontboracotomy system because of defibrillation threshold (DFT) > 25 joules (J), an epicardial system was implanted at the same setting. Patients receiving the two lead systems were comparable with regard to age, sex, and ejection fraction. However, since tbe PCD system offers tiered therapy multiprogrammable options, all attempts were made to implant tbis lead system in patients with VT that could be pace terminated. Mean DFT(15 ± 4.7 vs 17 ± 4.6 J;P = 0.03) and implant time (2.5 ± 0.6 vs 3.3 ± 0.7 hours; P = 0.02) were less with the Endotak lead system. There was no perioperative mortality. During a mean follow-up of 20 ± 4 months, there were eight instances of lead dislodgment in patients receiving the PCD system. Tbere were four nonsudden cardiac deaths and one sudden death in the Endotak group and three nonsudden deaths in the PCD group. Sudden cardiac death and total survival using the intention-to-treat analysis during this follow-up period were 99% and 95%, respectively. In conclusion, successful implantation, perioperative mortality, and survival rate are comparable with both lead systems; however, incorporating two defibrillating electrodes in one lead minimizes lead dislodgment and reduces implant time.