Internal Cardioverter Defibrillator Implantation Research Articles

Catecholaminergic polymorphic ventricular tachycardia complicated by dilated cardiomyopathy: a case report.

Background Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a severe genetic arrhythmogenic disorder characterized by adrenergically induced ventricular tachycardia manifesting as stress-induced syncope and sudden cardiac death. While CPVT is not associated with dilated cardiomyopathy (DCM) in most cases, the combination of both disease entities poses a major diagnostic and therapeutic challenge.Case summary We present the case of a young woman with CPVT. The clinical course since childhood was characterized by repetitive episodes of exercise-induced ventricular arrhythmias and a brady-tachy syndrome due to rapid paroxysmal atrial fibrillation and sinus bradycardia. Medical treatment included propranolol and flecainide until echocardiography showed a dilated left ventricle with severely depressed ejection fraction when the patient was 32 years old. Cardiac magnetic resonance imaging revealed non-specific late gadolinium enhancement. Myocardial inflammation, however, was excluded by subsequent endomyocardial biopsy. Genetic analysis confirmed a mutation in the cardiac ryanodine receptor but no pathogenetic variant associated with DCM. Guideline-directed medical therapy for HFrEF was limited due to symptomatic hypotension. Over the next months, the patient developed progressive heart failure symptoms that were finally managed by heart transplantation.Discussion Management in patients with CPVT and DCM is challenging, as Class I antiarrhythmic drugs are not recommended in structural heart disease and prophylactic internal cardioverter-defibrillator implantation without adjuvant antiarrhythmic therapy can be detrimental. Regular echocardiographic screening for DCM is recommendable in patients with CPVT. A multidisciplinary team of heart failure specialists, electrophysiologists, geneticists, and imaging specialists is needed to collaborate in the delivery of clinical care.

P1724 Bidimensional echocardiographical radial strain abnormalities mandate differential diagnosis between athlete heart syndrome and incipient genetic cardiomyopathy

Abstract Background Left ventricular dilation and mild systolic dysfunction at rest in young endurance athletes may mandate differential diagnosis between adaptive physiology and various forms of incipient non-ischemic dilated cardiomyopathies, especially if family history is positive. Multimodal imaging (i.e. bidimensional echocardiography (TTE), speckle tracking echography (STE) and cardiac magnetic resonance (CMR)) can accurately diagnose "true" underlying heart disease. Purpose We sought to outline the efficacy of multimodality imaging in dilated left ventricular phenotypes with mild systolic dysfunction of athletes. Methods We present the case of a 45 year old Caucasian male, rock climbing athlete (14 hours of training per week), with no prior personal medical history, who was admitted for fast palpitations leading to syncope immediately after a training session. Family history revealed maternal non-ischemic cardiomyopathy with complete atrioventricular (AV block requiring permanent pacing at a similar age. Stable, clinically asymptomatic, nodal complete AV block ∼ 40 bpm was diagnosed by ECG. TTE revealed a dilated LV (61 mm left ventricular end-diastolic diameter (LVIDd)) with no hypertrophy, with decreased diffuse contractility (LVEF ∼ 43%). Exercise echocardiography showed no improvement in LVEF, despite transition from complete AV block to first AV grade block. Moreover, moderate mitral regurgitation by posterior mitral leaflet (PML) prolapse was discovered. STE demonstrated normal global longitudinal strain (GLS), but decreased interventricular septum (IVS) radial strain (RS) (figure A). Late gadolinium enhancement was evident along the interventricular septum and the right ventricular insertion points in CMR (figure B), with no edema. Results The association of LV dilation (with multiple apparent causes – endurance training, genetic substrate, PML prolapse) with mild systolic dysfunction that persisted during echocardiographic exercise testing and a reduced IVS RS (with physiological GLS) was observed. Subsequently, mid-myocardial septal scarring in CMR was consistent with a diagnosis of "true" dilated cardiomyopathy. A cardiac resynchronization defibrillator device was implanted and genetic testing is in progress (lamin disease suspicion). Conclusions Athlete’s heart syndrome phenotypes may overlap with forms of genetic dilated cardiomyopathy. 1. The diagnostic suspicion of structural heart disease derived from echocardiography (radial strain & exercise echocardiography abnormalities), with subsequent confirmation by late gadolinium enhancement myocardial fibrosis. 2. The prospective sudden cardiac death risk requires careful assessment. The presence of clinical arrhythmic syncope, septal CMR fibrosis and specific genetic mutation lead to the decision of ICD (internal cardioverter defibrillator) implantation. Abstract P1724 Figure. A - 2D Radial strain B - LGE CMR

P887Atrial fibrillation is associated with sudden cardiac death risk factors in patients with hypertrophic cardiomyopathy

Abstract Background Atrial Fibrillation (AF) is prevalent in a fourth of patients with Hypertrophic Cardiomyopathy (HCM), but its clinical impact in these patients remains ill-defined. Aim To compare clinical characteristics in HCM patients with vs without AF and assess indirectly potential sudden cardiac death (SCD) risk. Methods Retrospective study in a single tertiary referral HCM center. Patients with HCM and AF were compared with matched controlled HCM patients without AF. NYHA class was assessed by a single physician. Propensity score matching was performed with a ratio of 2:1 by nearest neighbor with adjustment for age, sex, and left ventricular tract obstruction (LVOTO). Ordinal regression was used with NYHA as outcome. Results Among 298 patients with HCM, 68 patients (22.8%) had AF. After propensity matching, 66 patients with AF and 112 without AF had similar distribution of age (67.1 vs. 65.1 years), gender (57.6% vs. 61% males) and Basal Surface Area (1.88 vs. 1.87 m2) respectively. The prevalence of LVOTO (57.6% vs. 58.5%) and apical hypertrophy (19.7% vs 19.5%) was similar in the two groups. Cardiac risk factors including Hypertension (60.6% vs. 60.2%) and Diabetes Mellitus (15.2 vs. 20.3%) were similar in both groups. AF patients were diagnosed with HCM at a younger age than patients without HCM (48.5 vs. 55 years; p=0.01). HCM patients with AF had significantly lower LVOT gradients compared with patients without AF (28.1 mmHg vs 47.4 mmHg, p=0.005), had a higher prevalence of non-sustained ventricular tachycardia (39.4% vs. 9.4%; p<0.01), and ventricular tachycardia (9.1% vs 1.7%; p<0.04) and were more likely to have undergone implantation of an internal cardioverter defibrillator (ICD) (23.1% vs. 8.5%; p=0.001), respectively. Dyspnea was the most prevalent symptom in both groups (51.1% and 46.6% in AF and non-AF respectively). NYHA Class was similar in both groups: 1.88±0.69 in patients with AF vs. 1.73±0.74 in patients without AF (p=0.17). NYHA class did not differ in 26 patients with chronic persistent AF vs. 42 patients with paroxysmal AF (being in sinus rhythm at evaluation). Conclusion AF does not seem to impact functional level class in patients with HCM, but carries a higher burden of sudden cardiac death prognostic factors, incurring a higher rate of ICD implantation. Acknowledgement/Funding None

Impact of Income and Place of Residence on Internal Cardioverter-Defibrillator Implantation in Victorian Patients With Non-Ischaemic Cardiomyopathy

Impact of Income and Place of Residence on Internal Cardioverter-Defibrillator Implantation in Victorian Patients With Non-Ischaemic Cardiomyopathy

Internal Cardioverter Defibrillator Indications and Therapies after Atrial Baffle Procedure for d-Transposition of the Great Arteries: A Multicenter Analysis.

Sudden cardiac death (SCD) is the most important cause of late mortality after atrial baffle procedure for d-transposition of the great arteries (d-TGA). Experience with internal cardioverter defibrillator (ICD) therapy in this population is limited. We conducted a multicenter cohort study to determine the current state of ICD therapy in individuals after atrial baffle procedure. Demographic and clinical data as well as data on device implantation, programming, ICD discharges, and complications after atrial baffle procedure for d-TGA from four German centers were analyzed retrospectively. ICD implantation was undertaken in 33 subjects. ICD implantation was undertaken as primary prevention in 29 (88%) and secondary prevention in four (12%) individuals. There were 21 (64%) subjects with atrial reentrant tachycardia (IART). During a median follow-up of 4.8 years, seven appropriate ICD therapies were delivered in three (10%) individuals with primary prevention indication. No appropriate shocks were documented in subjects with secondary prevention indication. A total of 12 inappropriate ICD discharges occurred in eight (24%) individuals due to IART (n = 6) or lead failure (n = 2). ICD-related complications were noted in seven individuals (21%): lead dislodgement/failure in five (15%) and ICD infection in two subjects (6%). The majority of individuals received an ICD for primary prevention of SCD, thus representing a liberal attitude of physicians for ICD implantation. During a median follow-up of 4.8 years, the rate of appropriate ICD therapies was low and clearly exceeded by inappropriate ICD discharges. Lead failure and IART were present in >20% of the individuals and were frequent reasons for inappropriate ICD discharges. Facing these results, rigorous treatment of IART and careful ICD programming seems mandatory.

Propofol sedation administered by cardiologists for patients undergoing catheter ablation for ventricular tachycardia

Propofol sedation has been shown to be safe for atrial fibrillation ablation and internal cardioverter-defibrillator implantation but its use for catheter ablation (CA) of ventricular tachycardia (VT) has yet to be evaluated. Here, we tested the hypothesis that VT ablation can be performed using propofol sedation administered by trained nurses under a cardiologist's supervision. Data of 205 procedures (157 patients, 1.3 procedures/patient) undergoing CA for sustained VT under propofol sedation were analysed. The primary endpoint was change of sedation and/or discontinuation of propofol sedation due to side effects and/or haemodynamic instability. Propofol cessation was necessary in 24 of 205 procedures. These procedures (Group A; n = 24, 11.7%) were compared with those with continued propofol sedation (Group B; n = 181, 88.3%). Propofol sedation was discontinued due to hypotension (n = 22; 10.7%), insufficient oxygenation (n = 1, 0.5%), or hypersalivation (n = 1, 0.5%). Procedures in Group A were significantly longer (210 [180-260] vs. 180 [125-220] min, P = 0.005), had a lower per hour propofol rate (3.0 ± 1.2 vs. 3.8 ± 1.2 mg/kg of body weight/h, P = 0.004), and higher cumulative dose of fentanyl administered (0.15 [0.13-0.25] vs. 0.1 [0.05-0.13] mg, P < 0.001), compared with patients in Group B. Five (2.4%) adverse events occurred. Sedation using propofol can be safely performed for VT ablation under the supervision of cardiologists. Close haemodynamic monitoring is required, especially in elderly patients and during lengthy procedures, which carrying a higher risk for systolic blood pressure decline.

ICD therapy for primary prevention of sudden cardiac death after Mustard repair for d-transposition of the great arteries.

Years and decades after the Mustard atrial switch repair for d-Transposition of the great arteries, there is a subset of patients at increased risk for sudden cardiac death due to ventricular tachyarrhythmias. To date, little is known about indications, efficacy and benefit of internal cardioverter defibrillator (ICD) therapy indication in these patients. To characterize the Mustard patients already treated with an ICD, we conducted a single center case control study (n=41). The charts of all patients after Mustard procedure at our institution were systematically reviewed for history, echocardiographic findings, arrhythmias, hemodynamics and medication as well as ICD discharges and complications. Significant differences between ICD (n=12) and non-ICD patients (n=29) were found regarding the stage of heart failure, need for heart failure medication, QRS duration and left ventricular diameter and performance. Inappropriate ICD discharges due to rapidly conducted atrial reentrant tachycardia and sensing failure were frequently observed. In 17% of our Mustard patients with an ICD, infection of the implantation site required surgical revision. All ICD patients were of male gender. Patients after ICD implantation represent a subgroup among our Mustard patients with a more advanced state of cardiac disease. Not only systemic right ventricular diameter and performance but also subpulmonary left ventricular performance was an important factor predicting the long-term course of these patients. Prevention of inappropriate discharges requires decent device programming, close monitoring of lead integrity and treatment of atrial tachycardias.

Cardiac resynchronisation therapy: pacemaker versus internal cardioverter-defibrillator in patients with impaired left ventricular function

ObjectiveStudies have shown beneficial effects of cardiac resynchronisation therapy (CRT) on mortality among patients with heart failure. However the incremental benefits in survival from CRT with a defibrillator (CRT-D) are...

How reliable are left ventricular ejection fraction cut offs assessed by echocardiography for clinical decision making in patients with heart failure?

We aimed to study the potential influence of the variability in the assessment of echocardiographically measured left ventricular ejection fraction (LVEF) on indications for the implantation of internal cardioverter defibrillator and/or cardiac resynchronization devices in heart failure patients. TIME-CHF was a multicenter trial comparing NT-BNP versus symptom-guided therapy in patients aged ≥60 years. Patients had their LVEF assessed at the recruiting centre using visual assessment, the area-length or biplane Simpson's method. Echocardiographic data were transferred to the study core-lab for re-assessment. Re-assessment in the core-lab was done with biplane Simpson's method, and included an appraisal of image quality. 413 patients had the LVEF analyzed at the recruiting centre and at the core lab. Image quality was optimal in 191 and suboptimal in 222. Overall, the correlation between LVEF at the recruiting centres and at the core-lab was good, independent of image quality (R² = 0.62). However, when a LVEF ≤30 % or ≥30 % was used as a cut-off, about 20 % of all patients would have been re-assigned to having either a LVEF above or below the cut-off, this proportion was not significantly influenced by image quality. We conclude that correlation between LVEF assessed by different centres based on the same ultrasound data is good, regardless of image quality. However, one fifth of patients would have been re-assigned to a different category when using the clinically important cut-off of 30 %.

Clinical Profile of Patients with Electrical Ventricular Tachycardia/Fibrillation Storm

Electrical storm refers to multiple occurrences of ventricular tachycardia or fibrillation occurring three or more times in a 24 hour period. We reviewed the clinical profile, risk factors and outcome of patients admitted for electrical storm at the University of Santo Tomas Hospital from June 2008 to February 2011. Ten patients, aged 30 to 72 years old were included. There were 3 cases of acquired long QT syndrome, 2 cases of congenital long QT syndrome, 1 case of ischemic and 2 cases of dilated cardiomyopathy s/p ICD implantation and 2 cases of NSTEMI. Seven of the nine patients presented with hypokalemia. Most of the patients were managed medically with antiarrhythmics, a combination of intravenous amiodarone and lidocaine. Four patients underwent temporary pacemaker insertion for overdrive pacing. One patient with NSTEMI developed the electrical storm after emergency CABG. Among the 2 patients with congenital long QT syndrome, one underwent implantation of an internal cardioverter-defibrillator (ICD) while the other one is being managed medically. Two patients with cardiomyopathy and heart failure underwent ICD implantation while the other patient with already a previous implant developed storm with multiple ICD shocks. Eight patients were discharged from the hospital improved. Two patients with electrical storm had multiple organ failure and died. In our 2 year review of electrical storm patients, the major etiologies include long QT syndrome, and ischemic cardiomyopathy with heart failure.

Hypertrophic cardiomyopathy in childhood and adolescence – strategies to prevent sudden death

Clinically overt hypertrophic cardiomyopathy is the most common cause of sudden unexpected death in childhood and has significantly higher sudden death mortality in the 8- to 16-year age range than in the 17- to 30-year age range. A combination of electrocardiographic risk factors (a limb-lead ECG voltage sum >10 mV) and/or a septal wall thickness >190% of upper limit of normal for age (z-score > 3.72) defines a paediatric high-risk patient with great sensitivity. Syncope, blunted blood pressure response to exercise, non-sustained ventricular tachycardia and a malignant family history are additional risk factors. Of the medical treatments used, only beta-blocker therapy with lipophilic beta-blockers (i.e. propranolol, metoprolol or bisoprolol) have been shown to significantly reduce risk of sudden death, with doses ≥ 6 mg/kg BW in propranolol equivalents giving around a tenfold reduction in risk. Disopyramide therapy is a very useful adjunct to beta-blockers to improve prognosis in those patients that have dynamic outflow obstruction in spite of large doses of beta-blocker, and its use in patients with hypertrophic cardiomyopathy is not associated with significant pro-arrhythmia mortality. Calcium-channel blockers increase the risk of heart failure-associated death in hypertrophic cardiomyopathy (HCM) patients with severe generalized hypertrophy and should be avoided in such patients. Amiodarone does not protect against sudden death, and long-term use in children usually has to be terminated because of side effects. Therapy with internal cardioverter defibrillator implantation has high paediatric morbidity, 27% incidence of inappropriate shocks, and does not absolutely protect against mortality but is indicated as secondary prevention or in very high-risk patients.

Proof Positive

The administration of prophylactic antibiotics before pacemaker or internal cardioverter-defibrillator implantation has been implemented widely and routinely. The acceptance of this practice has occurred despite the absence of rigorous examination or definitive evidence. The existing data for the use of prophylactic antibiotic therapy in device implantation consist of 7 randomized, controlled trials, with all but 1 having an open design.1 Early trials yielded contradictory results, citing small study numbers, a low incidence of infection, and inconsistent definitions of infection as possible explanations.2–4 Four of the 7 trials found antibiotic prophylaxis effective in preventing infection; the lone double-blind, randomized, controlled study consisted of 106 patients and failed to demonstrate a difference in infection rate with antibiotic prophylaxis because there were no documented infections at 7 to 35 months of follow-up.3 In addition to their inconsistent results, widely varying antibiotic regimens were implemented in these trials, further confounding the ability of operators to interpret the available data and to implement evidence-based medicine into practice. Despite the equivocal findings of these individual studies, a meta-analysis of antibiotic prophylaxis for permanent pacemaker implantation by Da Costa et al1 in 1998 demonstrated a significant reduction …

Relation between the outcome of electophysiological study and internal cardioverter-defibrillator implantation in Japanese patients with Brugada syndrome

Relation between the outcome of electophysiological study and internal cardioverter-defibrillator implantation in Japanese patients with Brugada syndrome

ICD Implantation in Infants and Small Children: The Extracardiac Technique

There is no clear methodology for implantation of an internal cardioverter-defibrillator (ICD) in infants and small children. The aim of this study was to assess efficacy and safety of an extracardiac ICD implantation technique in pediatric patients. An extracardiac ICD system was implanted in eight patients (age: 0.3-8 years; body weight: 4-29 kg). Under fluoroscopic guidance a defibrillator lead was tunneled subcutaneously starting from the anterior axillar line along the course of the 6th rib until almost reaching the vertebral column. After a partial inferior sternotomy, bipolar steroid-eluting sensing and pacing leads were sutured to the atrial wall (n = 2) and to the anterior wall of the right ventricle (n = 8). The ICD device was implanted as "active can" in the upper abdomen. Sensing, pacing, and defibrillation thresholds (DFTs) as well as impedances were verified intraoperatively and 3 months later, respectively. In seven of eight patients, intraoperative DFT between subcutaneous lead and device was <15 J. In the eighth patient ICD implantation was technically not feasible due to a DFT >20 J. During follow-up (mean 14.5 months) appropriate and effective ICD discharges were noted in two patients. DFT remained stable after 3 months in four of six patients retested. A revision was required in one patient due to lead migration and in another patient due to a lead break. In infants and small children, extracardiac ICD implantation was technically feasible. Experience and follow-up are still limited. The course of the DFT is unknown, facing further growth of the patients.

Neuronal Injury After Repeated Brief Cardiac Arrests During Internal Cardioverter Defibrillator Implantation Is Associated With Deterioration of Cognitive Function

To determine the degree of neurocognitive dysfunction after placement of internal cardioverter defibrillators (ICD) and its relationship to the extent of neuronal injury, we studied 42 patients undergoing ICD (n = 21) or pacemaker (PM) insertion (control patients, n = 21). The Mini Mental State Examination, the Trailmaking A test and the forward and backward Digit Span tests were used and P300 latencies were determined preoperatively and postoperatively. Serum neuron-specific enolase (NSE) was determined before and at the end of, as well as 2, 6, and 24 h after surgery. Preoperatively, PM patients scored worse in the Digit Span backward and the Trailmaking tests and showed prolonged P300 latencies. Postoperatively, the Digit Span backward scores declined and NSE levels increased only in the ICD group (P < or = 0.05). The difference between preoperative and postoperative Digit Span backward scores correlated with the increase in serum NSE levels (r2 = 0.3, P < or = 0.05). Moreover, P300 latencies increased in 13 of 17 ICD patients, but decreased in 7 of 10 PM patients (P < or = 0.05). PM patients even improved in the Trailmaking test (P < or = 0.05). Neuronal injury from even brief periods of global brain ischemia seems to be associated with deteriorating neurocognitive function.

Indications for internal cardioverter defibrillator implantation predict time to first shock and the modulating effect of β-blockers

Patients receive implantable cardioverter defibrillator (ICD) for varying indications. Whether these indications influence the time to first ICD shock is suspected but not confirmed. The modulating effect of beta-blockers on shock-free survival is not fully elucidated. A retrospective analysis of 230 consecutive patients (age 63 +/- 14 years, 79% men, 75% ischemic, 70% beta-blockers) implanted with an ICD was performed. Patients were divided into 4 groups depending on the ICD indication: groups A (secondary prevention of sudden death), B (left ventricular ejection fraction < or = 35% and positive electrophysiology study [EPS]), C (left ventricular ejection fraction < or = 35% and negative EPS or no EPS performed), and D (patients who did not meet inclusion criteria for groups A, B, or C). Time to shock was analyzed by the Kaplan-Meier method. During a mean follow-up of 489 +/- 280 days, 57 (24.7%) patients received 82 shocks (49% appropriate). The 1-year shock-free survival for patients in groups A, B, C, and D were 57%, 77%, 79%, and 91%, respectively (P = .03), for total shocks and 75%, 92%, 92%, and 100%, respectively (P = .007), for appropriate shocks. For patients in group A, the use of beta-blockers increased the 1-year shock-free survival from 48% to 61% for total shocks and from 65% to 79% for appropriate shocks. Time to first shock is determined by the indication for ICD implantation and is not predicted by the results of EPS. Patients with secondary indications for ICD implantation are at highest risk of shocks and may deserve consideration for prophylactic antiarrhythmic drugs. beta-Blockers increase the time to first ICD shock in patients implanted for secondary prevention of sudden death.

Indications for Internal Cardioverter Defibrillator Implantation Predict Time to First Shock and the Modulating Effect of b-Blockers

Indications for Internal Cardioverter Defibrillator Implantation Predict Time to First Shock and the Modulating Effect of b-Blockers

Defibrillator for Primary Prevention in Congenital Heart Disease

A 21-year-old patient with repaired double-outlet right ventricle and normal ventricular function underwent internal cardioverter defibrillator implantation for primary prevention of sudden death. First occurrence of spontaneous ventricular tachycardia resulted in hemodynamic collapse and syncope but the internal cardioverter defibrillator rescued the patient. ICD implantation for primary prevention may be an appropriate goal in adults with repaired congenital heart disease, even in the setting or normal ventricular function.

Domains of concern of intimate partners of sudden cardiac arrest survivors after ICD implantation.

There is limited research that describes the experiences of intimate partners of sudden cardiac arrest (SCA) survivors. The purposes of this article are to (1) describe the domains of concern of intimate partners of SCA survivors during the first year after internal cardioverter defibrillator (ICD) implantation and (2) outline strategies used by partners of SCA survivors in dealing with the concerns and demands of recovery in the first year after ICD implantation. This is a secondary analysis of interview data collected for the primary study "Family Experiences Following Sudden Cardiac Arrest." A grounded theory method was used to identify experiences of SCA survivors and their family members from hospitalization through the first year after ICD implantation. Data were collected from the SCA survivor and one intimate partner at 5 times: hospital discharge, and at 1, 3, 6, and 12 months postdischarge. Eight Domains of Concern were identified for intimate partners following SCA and ICD implantation during the first year. These included (1) Care of the survivor, (2) My (partner) self-care, (3) Relationship, (4) ICD, (5) Money, (6) Uncertain future, (7) Health care providers, and (8) Family. Five categories of strategies to deal with the Domains of Concerns were identified (1) Care of the survivor, (2) My (partner) self-care, (3) Relationship, (4) Uncertain future, and (5) Controlling the environment. Nursing intervention programs should include the intimate partner of SCA survivors and contain education and support in the following areas: (1) information on the function of the ICD, (2) normal progression of physical and emotional recovery experiences, (3) safety and maintenance of the ICD, (4) activities of daily living after an ICD, (5) strategies to assist with the survivors care, and (6) strategies to assist with partner self care.

Endocardial wave front organization during ventricular fibrillation in humans

ObjectivesThis study was designed to characterize the organization of ventricular fibrillation (VF) on the endocardium of humans. BackgroundMost proposed mechanisms for the maintenance of VF postulate the propagation of a number of activation wave fronts that reenter to maintain the arrhythmia. We tested the hypothesis that, in patients undergoing internal cardioverter-defibrillator implantation, VF consists primarily of a few large wave fronts on the endocardium. MethodsElectrograms were recorded from a 36-electrode catheter in the left ventricle of 16 patients during VF. Activation times were chosen for a 2-s epoch for each fibrillation episode, and a two-dimensional Kolmogorov-Smirnov test was performed to determine if activation occurred randomly along the catheter over that time interval. The maximum cross-correlation was found for all possible pairs of electrodes on the catheter, and these values were plotted relative to the distance between the two electrodes. An exponential curve was then fit to the data, and a length constant was determined. Activation times were grouped into wave fronts along the catheter, and the lengths of the wave fronts were estimated. ResultsThe Kolmogorov-Smirnov test showed that activation was not random along the catheter in any of the patients studied. The correlation length determined was 9 ± 2 cm. The number of wave fronts recorded by the catheter was 9.2 ± 2.9 wave fronts/s. The length of the pathway of each wave front along the catheter was 6.5 ± 4.5 cm. ConclusionsVentricular fibrillation is well organized on the endocardial surface of humans, consisting primarily of a few large wave fronts on the order of 6 to 9 cm.