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Biomedical subjects

H Calkins

Publications and source records attributed to H Calkins.

At least 73 records · Page 4Linked to original sources
PubMed1996

Relationship of amiodarone to postoperative complications of transthoracic implantation of automatic implantable cardioverter defibrillators.

The purpose of this study is to report the results and complications associated with transthoracic placement of an implantable defibrillator and their relationship to amiodarone, and to identify clinical predictors of complications. There were 159 men and 41 women. The mean patients age was 61 +/- 11 years, and the mean ejection fraction was 0.33 +/- 0.14. Fifty one percent of patients developed complications including death in 14 patients (7%). Variables which differed in patients who died and those that did not were age, ejection fraction and New York heart failure classifications. Postoperative mortality was unrelated to amiodarone therapy. Twenty patients (10%) developed pneumonia and 15 patients (7.5%) developed respiratory failure. Clinical variables associated with the development of respiratory failure were age, amiodarone therapy and a prior history of pulmonary disease. Patients receiving amiodarone had a higher incidence of an elevated defibrillation threshold (> or = 25 joules) as compared with those not being treated with amiodarone. Clinical factors associated with an elevated defibrillation threshold were a history of a myocardial infarction, prior bypass surgery, and amiodarone. The results of this study demonstrate that placement of an implantable defibrillator using a transthoracic approach is associated with a high incidence of complications. Amiodarone therapy is associated with an increased incidence of pneumonia, respiratory failure, and elevated defibrillation thresholds.

Adolescent↗
PubMed1995

The relationship between neurally mediated hypotension and the chronic fatigue syndrome.

OBJECTIVE: To compare the clinical symptoms and response evoked by upright tilt-table testing in healthy individuals and in a sample of those satisfying strict criteria for chronic fatigue syndrome. DESIGN: Case-comparison study with mean (SD) follow-up of 24 (5) weeks. SETTING: Tertiary care hospital. PATIENTS AND OTHER PARTICIPANTS: A sample of 23 patients with chronic fatigue syndrome (five men and 18 women; mean age, 34 years), each of whom fulfilled the strict diagnostic criteria of the Centers for Disease Control and Prevention, was recruited from regional chronic fatigue support groups and from the investigators' clinical practices. There were 14 healthy controls (four men and 10 women; mean age, 36 years). INTERVENTIONS: Each subject completed a symptom questionnaire and underwent a three-stage upright tilt-table test (stage 1, 45 minutes at 70 degrees tilt; stage 2, 15 minutes at 70 degrees tilt with 1 to 2 micrograms/min of isoproterenol; and stage 3, 10 minutes at 70 degrees with 3 to 4 micrograms/min of isoproterenol). Patients were offered therapy with fludrocortisone, beta-adrenergic blocking agents, and disopyramide, alone or in combination, directed at neurally mediated hypotension. MAIN OUTCOME MEASURES: Response to upright tilt and scores on symptom questionnaires prior to and during follow-up. RESULTS: An abnormal response to upright tilt was observed in 22 of 23 patients with chronic fatigue syndrome vs four of 14 controls (P < .001). Seventy percent of chronic fatigue syndrome patients, but no controls, had an abnormal response during stage 1 (P < .001). Nine patients reported complete or nearly complete resolution of chronic fatigue syndrome symptoms after therapy directed at neurally mediated hypotension. CONCLUSIONS: We conclude that chronic fatigue syndrome is associated with neurally mediated hypotension and that its symptoms may be improved in a subset of patients by therapy directed at this abnormal cardiovascular reflex.

Adolescent↗
PubMed1995

Is neurally mediated hypotension an unrecognised cause of chronic fatigue?

Neurally mediated hypotension is now recognised as a common cause of otherwise unexplained recurrent syncope, but has not been reported in association with chronic fatigue. We describe seven consecutive non-syncopal adolescents with chronic post-exertional fatigue, four of whom satisfied strict criteria for chronic fatigue syndrome. Upright tilt-table testing induced significant hypotension in all seven (median systolic blood pressure 65 mm Hg, range 37-75), consistent with the physiology of neurally mediated hypotension. Four had prompt improvement in their chronic fatigue when treated with atenolol or disopyramide. These observations suggest an overlap in the symptoms of chronic fatigue syndrome and neurally mediated hypotension.

Adolescent↗
PubMed1995

Clinical presentation and long-term follow-up of athletes with exercise-induced vasodepressor syncope.

The purpose of this study is to report on a series of patients who were referred for evaluation of syncope that occurred during or immediately after exercise and in whom a diagnosis of vasodepressor syncope was established (9 women and 8 men; mean age of 28 +/- 17 years). The approach to management was individualized in each patient. All patients were monitored to determine the frequency and type of recurrent symptoms. The mean age at onset of symptoms was 23 +/- 16 years. In 10 patients syncope occurred only in association with exercise. Pharmacologic therapy was successful in normalizing the patients' response to upright tilt in each of the 10 patients in whom it was attempted. During a mean follow-up period of 35 +/- 9 months, none of the patients placed on pharmacologic therapy has had recurrent syncope. Seventeen (88%) of 19 patients have resumed participation in athletics. The results of this study demonstrate that vasodepressor syncope is a cause of syncope in athletes and that patients with exercise-related vasodepressor syncope can safely continue to participate in athletics.

Adolescent↗
PubMed1995

The value of the clinical history in the differentiation of syncope due to ventricular tachycardia, atrioventricular block, and neurocardiogenic syncope.

BACKGROUND: The present study was undertaken to identify and quantitate the symptoms associated with neurocardiogenic syncope, syncope due to ventricular tachycardia, and syncope resulting from atrioventricular block. PATIENTS AND METHODS: Eighty patients referred for evaluation of syncope in whom a diagnosis of neurocardiogenic syncope, atrioventricular block, or ventricular tachycardia was established were studied. Each patient was interviewed using a standard questionnaire. The clinical histories were then compared to identify which variables best differentiated the cause of syncope. RESULTS: The clinical histories of patients with syncope due to ventricular tachycardia and atrioventricular block were similar. Only age, the duration of prodromal symptoms, diaphoresis prior to syncope, and fatigue following syncope differed. In contrast, the clinical history in patients with neurocardiogenic syncope differed greatly from that obtained in patients with syncope due to atrioventricular block or ventricular tachycardia. Features of the clinical history that were predictive of syncope due to atrioventricular block or ventricular tachycardia were male sex, age > 54 years, < or = 2 episodes of syncope, and a duration of warning of < or = 5 seconds. Features of the clinical history predictive of syncope not due to ventricular tachycardia or atrioventricular block were palpitations, blurred vision, nausea, warmth, diaphoresis, or lightheadedness prior to syncope, and nausea, warmth, diaphoresis, or fatigue following syncope. CONCLUSIONS: The results of this study identify and compare the features of the clinical history obtained in patients with syncope due to ventricular tachycardia, atrioventricular block, and neurocardiogenic syncope and demonstrate that the clinical history is of value in distinguishing patients with these three causes of syncope.

Adult↗
PubMed1994

Catheter ablation of atrial flutter using radiofrequency energy.

Sixteen patients with type I atrial flutter underwent an attempt at radiofrequency catheter ablation (8 women, 8 men, mean age 53 +/- 11 years). The primary criterion used to identify sites for radiofrequency energy delivery was the identification of a fractionated electrogram. Radiofrequency energy was delivered for 20 to 30 seconds. Radiofrequency catheter ablation was acutely successful in 13 patients and unsuccessful in 3. During a mean follow-up of 10 +/- 4 months, 9 of 13 patients with a successful acute result (69%) remained free of recurrent atrial flutter or atrial fibrillation. The ability to induce nonclinical types of atrial flutter was associated with an unsuccessful outcome. A greater proportion of electrograms recorded at successful sites demonstrated electrogram stability compared with unsuccessful ablation sites. None of the electrograms recorded at successful ablation sites were fractionated or had a double potential. This study demonstrates that radiofrequency catheter ablation of type I atrial flutter can be achieved safely.

Adult↗
PubMed1994

Implantable cardioverter-defibrillator therapy in 300 patients with coronary artery disease presenting exclusively with ventricular fibrillation.

To determine outcomes of implantable cardioverter-defibrillator (ICD) therapy in a uniform population of survivors of sudden cardiac death, we used epicardial defibrillation lead systems to study 300 patients with coronary artery disease (CAD) presenting exclusively with ventricular fibrillation (VF) unassociated with acute myocardial infarction. Operative (30-day) mortality, 2.7% overall, was lower (0.6%) in patients with ejection fractions (EF) > or = 0.30. Over a median follow-up of 1.9 years, cumulative actuarial shock incidence was similar in patients who underwent concomitant coronary artery bypass graft (CABG) surgery (38%) and in those who did not. The 2-year cumulative actuarial incidences of any or appropriate shocks were 65% and 38%, respectively. Sudden death survival at 2 years was 92.5% and 99.3% for patients with EFs < or = 0.30 and > 0.30, respectively. The total mortality rate was similar in shocked and in unshocked patients. Multivariate analysis identified EF and female gender as significant predictors of any and appropriate shock occurrence (all p values < or = 0.05) and EF as a significant predictor of sudden, cardiac, and total mortality (all p values < 0.03). We conclude that in CAD patients presenting exclusively with VF unassociated with acute myocardial infarction and treated with thoracotomy-requiring ICD therapy: (1) operative (30-day) mortality is minimal for patients with an EF > or = 0.30; (2) device use is high and sudden death rates low regardless of concomitant CABG; (3) low EF is a significant predictor of cumulative shock occurrence and mortality (sudden, cardiac, and total); (4) female gender may be a predictor of shock occurrence; and (5) similar mortalities and low sudden-death rates in shocked and nonshocked ICD patients imply that ICD therapy improves survival in shocked patients to a level observed in comparable patients in whom ventricular tachyarrhythmia does not recur.

Actuarial Analysis↗
PubMed1994

Site of accessory pathway block after radiofrequency catheter ablation in patients with the Wolff-Parkinson-White syndrome.

INTRODUCTION: Recent studies have demonstrated that the most common site of accessory pathway conduction block following the introduction of a premature atrial stimulus during atrial pacing is between the accessory pathway potential and the ventricular electrogram, consistent with block at the ventricular insertion of the accessory pathway. However, no prior study has evaluated the site of conduction block during radiofrequency catheter ablation procedures. Therefore, the objective of this study was to determine the site of conduction block after catheter ablation of accessory pathways by analyzing and comparing the local electrograms recorded before and after radiofrequency energy delivery at successful ablation sites. METHODS AND RESULTS: The electrograms evaluated in this study were obtained from 85 consecutive patients who underwent successful radiofrequency catheter ablation of a manifest accessory pathway. The 50 left free-wall accessory pathways were ablated using a ventricular approach and the 35 right free-wall or posteroseptal accessory pathways were ablated using an atrial approach. The characteristics of local electrograms recorded immediately before and immediately after successful ablation of the accessory pathway were determined in each patient. The site of accessory pathway block was determined by comparing the amplitude, timing, and morphology of the local electrograms at successful sites of radiofrequency catheter ablation before and after delivery of radiofrequency energy. A putative accessory pathway potential was present at the successful target site in 74 of the 85 patients (87%). Conduction block occurred between the atrial electrogram and the accessory pathway potential in 66 patients (78%) and between the accessory pathway potential and the ventricular electrogram in eight patients (9%). The site of block could not be determined in 11 patients (13%) in whom an accessory pathway potential was absent. Conduction block occurred most frequently between the atrial electrogram and the accessory pathway potential regardless of accessory pathway location. No electrogram parameter or accessory pathway characteristic was predictive of the site of conduction block. CONCLUSION: The results of this study demonstrate that conduction block occurs most frequently between the local atrial electrogram and the accessory pathway potential during radiofrequency catheter ablation of accessory pathways. This is true regardless of whether the accessory pathway is ablated from the atrial or ventricular aspect of the mitral or tricuspid annulus.

Adolescent↗
PubMed1994

Temperature monitoring during radiofrequency catheter ablation procedures using closed loop control. Atakr Multicenter Investigators Group.

BACKGROUND: The purpose of this study was to evaluate electrode temperatures obtained using a radiofrequency ablation system that incorporates closed loop feedback control to achieve preset target electrode temperatures and to determine if closed loop temperature control results in a lower incidence of developing a coagulum. METHODS AND RESULTS: Two hundred seventy patients underwent catheter ablation of atrioventricular nodal reentrant tachycardia, an accessory pathway, and/or the atrioventricular junction using an ablation system incorporating closed loop feedback control. Forty-five patients underwent catheter ablation in the power control mode in which power output was fixed, and 225 patients underwent catheter ablation in the temperature control mode. A coagulum occurred during 0.8% of radiofrequency applications in the temperature control mode versus 2.2% in the power control mode (P < .01). Electrode temperatures were within 10 degrees C of the targeted temperature during 35% of applications in the temperature control mode. Ability to achieve the targeted electrode temperature was related to the target, with radiofrequency energy applications at the atrioventricular junction resulting in the highest temperatures (70 +/- 12 degrees C) and those for ablation of the atrioventricular node the lowest (59 +/- 11 degrees C, P < .001), using a maximum of 50 W of power for both. Electrode temperatures were higher during ablation of left free wall and posteroseptal pathways than during ablation of right free wall and septal pathways. The mean and minimum temperatures associated with success were 64 +/- 12 degrees C and 44 degrees C, respectively. Overall, the electrode temperatures at successful and unsuccessful ablation sites did not differ (P > .05). CONCLUSIONS: Temperature monitoring with closed loop control of power output facilitates radiofrequency catheter ablation procedures by minimizing the probability of developing a coagulum while ensuring maximum lesion formation.

Adolescent↗
PubMed1993

A randomized comparison of the right- and left-sided approaches to ablation of the atrioventricular junction.

Radiofrequency ablation of the atrioventricular (AV) junction may be performed using either a right- or left-sided approach. This study prospectively compared the left-sided approach with persistent attempts from the right side in patients in whom initial radiofrequency applications on the right side were unsuccessful. Twenty-one of 54 patients did not have complete AV block induced after 3 right-sided radiofrequency applications. These 21 patients were randomly assigned to undergo either the left-sided approach (n = 10) or to undergo additional attempts from the right side (n = 11). The right-sided approach was performed by positioning the ablation catheter to record the largest possible atrial and His bundle electrograms. The left-sided approach was performed by positioning the ablation catheter along the left ventricular septum, where a His bundle potential was recorded. If either approach was not successful after an additional 17 radiofrequency applications, the alternative approach was then used. The AV junction was successfully ablated in all 10 patients randomized to the left-sided approach, but in only 6 of 11 patients randomized to persistent right-sided attempts (p < 0.05). The 5 patients in whom the AV junction was not successfully ablated using the right-sided approach underwent the left-sided approach and had a successful outcome after a mean of 1.2 +/- 0.4 radiofrequency applications. The left-sided approach required significantly fewer radiofrequency applications after randomization than the right-sided approach (3 +/- 3.4 vs 11 +/- 7.6, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Prospective, randomized comparison of conventional and high dose loading regimens of amiodarone in the treatment of ventricular tachycardia.

OBJECTIVES: The purpose of this prospective randomized study was to compare the electrophysiologic effects of conventional and high dose loading regimens of amiodarone in patients with sustained ventricular tachycardia. BACKGROUND: Uncontrolled studies in which patients have been treated with an oral loading dose of 2 to 4 g/day of amiodarone have suggested that, compared with a conventional loading dose, this dosing regimen results in more rapid control of spontaneous ventricular tachycardia and ventricular tachycardia induced by programmed stimulation. METHODS: Patients in whom sustained monomorphic ventricular tachycardia was inducible by programmed stimulation and who were refractory to class I antiarrhythmic medications were randomly assigned to receive either a conventional (n = 15) or a high (n = 17) loading dose of amiodarone. The conventional dose consisted of 600 mg twice a day for 10 days. The high dose regimen consisted of 50 mg/kg body weight per day on days 1 to 3, 30 mg/kg per day on days 4 and 5 and 600 mg twice a day on days 6 to 10. An electrophysiologic test was performed in the baseline state and after 3 and 10 days of therapy. An adequate response to amiodarone was defined as the inability to induce ventricular tachycardia or the ability to induce only relatively slow (cycle length > or = 350 ms) hemodynamically stable ventricular tachycardia. RESULTS: After 3 days of therapy, 2 of 14 patients who received the conventional loading dose and 6 of 15 patients who received the high dose loading regimen had an adequate response to amiodarone (p = 0.08). After 10 days of therapy, four patients in each group had an adequate response to amiodarone (p = NS). Three patients who received the high dose and one patient who received the conventional dose of amiodarone had an adequate response after 3 days of therapy but not after 10 days of therapy. There were significant increases in the sinus cycle length, atrioventricular block cycle length, ventricular effective refractory period and ventricular tachycardia cycle length after 3 and 10 days of therapy compared with baseline values regardless of the dosing regimen. The extent of the effects of amiodarone on these variables after 3 and 10 days of therapy was similar with both dosing regimens. CONCLUSIONS: The therapeutic and electrophysiologic effects of conventional and high dose loading regimens of amiodarone do not differ significantly after 3 or 10 days of therapy. High oral loading doses of amiodarone do not offer any significant clinical advantage over a conventional loading dose of amiodarone for controlling ventricular tachycardia induced by programmed stimulation.

Aged↗
PubMed1993

Outcome with implantable cardioverter-defibrillator therapy for survivors of ventricular fibrillation secondary to idiopathic dilated cardiomyopathy or coronary artery disease without myocardial infarction.

Patients with idiopathic dilated cardiomyopathy (IDC) constitute a minority among implantable cardioverter-defibrillator (ICD) recipients; how these patients fare versus those with coronary artery disease (CAD) is not well defined, nor is the mechanism of cardiac arrest recurrence, which may involve a more significant role of bradyarrhythmias. A retrospective multicenter study regarding outcome of ICD therapy was conducted in 224 patients with either IDC (n = 69; 31%) or CAD (n = 155; 69%) presenting exclusively with ventricular fibrillation (VF) unassociated with acute myocardial infarction. Patients with IDC were significantly younger (mean age 57 vs 61 years in patients with CAD, p < 0.04) and less male predominant (64 vs 79% in patients with CAD, p < 0.02). There was no significant difference in mean left ventricular ejection fraction (0.27 in IDC patients vs 0.29 in CAD patients), but sustained ventricular tachycardia was induced less often in patients with IDC (21 vs 58% in CAD patients, p < 0.001). Bradycardia pacing, either by an ICD with bradycardia pacing ability or a separate bradycardia pacemaker, was available in only 15% of ICD implantees. During a median follow-up duration of 1.7 years for patients with IDC and 1.9 years for patients with CAD, estimated cumulative event rates were similar for any type shock (2-year incidence of 74% in IDC patients, 69% in CAD patients) as well as for appropriate shock (2-year incidence of 46% in IDC patients, 40% in CAD patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy, Dilated↗
PubMed1993

Relation between efficacy of radiofrequency catheter ablation and site of origin of idiopathic ventricular tachycardia.

The results of radiofrequency catheter ablation of ventricular tachycardia (VT) in patients without structural heart disease are reported. Particular attention was focused on the relation between efficacy and the site of origin of the VT. Eighteen consecutive patients (5 women and 13 men; mean age 41 +/- 13 years) with idiopathic VT underwent catheter ablation using radiofrequency energy. Sites for radiofrequency energy delivery were selected on the basis of pace mapping. A follow-up electrophysiologic test was performed 1 to 3 months after the ablation procedure. Twenty VTs were induced. Radiofrequency catheter ablation was successful in eliminating all 10 VTs originating from the right ventricular outflow tract, and 5 of 10 from other sites in the left or right ventricle. There were no complications. The duration of ablation sessions was shorter, the frequency of identifying a site resulting in an identical pace map was higher, and the efficacy of catheter ablation was greater for VTs originating from the right ventricular outflow tract than for those from other locations. The results of this study demonstrate that radiofrequency catheter ablation of idiopathic VT is safe and effective. The efficacy of the procedure is dependent on the site of origin of the VT, with the efficacy being greater for VTs originating from the outflow tract of the right ventricle than for those from other locations.

Adult↗
PubMed1993

Safety, feasibility and cost of outpatient radiofrequency catheter ablation of accessory atrioventricular connections.

OBJECTIVES: The purpose of this study was to evaluate prospectively the safety, feasibility and cost of performing radiofrequency catheter ablation of accessory atrioventricular (AV) connections on an outpatient basis in 137 cases. BACKGROUND: The efficacy and low complication rate of radiofrequency ablation as performed in the hospital suggested that it might be feasible to perform it on an outpatient basis. METHODS: In 100 cases (73%) performed between September 1, 1991 and April 20, 1992, patients met criteria for treatment as outpatients. Reasons for exclusion were age < 13 or > 70 years (4), anteroseptal location of the accessory AV connection (5 patients), obesity (> 30% of ideal body weight) (4 patients) or clinical indication for hospitalization (24 patients). Patients with only venous punctures had a recovery period of 3 h and those with arterial punctures had a recovery period of 6 h. There were 63 men and 32 women (5 patients underwent two ablation procedures > 1 month apart), with a mean age +/- SD of 36 +/- 13 years. The pathway was left-sided in 67 cases and right-sided or posteroseptal in 33. RESULTS: The procedure was successful in 97 of 100 cases, with a mean procedure duration of 99 +/- 42 min. In 70 cases the patient was discharged the day of ablation, and in 30 cases the patient required a short (< or = 18-h) overnight stay because the procedure was completed too late in the day for recovery in the outpatient facility. The mean duration of observation was 4.8 +/- 1.5 h for outpatients and 15 +/- 1.4 h for patients who underwent overnight hospitalization. At follow-up study, two patients had a clinically significant complication; both had a femoral artery pseudoaneurysm detected > or = 1 week after the procedure and both required surgical repair. Thirty consecutive patients (22 outpatients and 8 hospitalized overnight) undergoing catheter ablation after January 1, 1992 were chosen for a cost analysis. The mean cost of the procedure was $10,183 +/- $1,082. CONCLUSIONS: The majority of patients undergoing radiofrequency catheter ablation of an accessory AV connection can be treated safely on an outpatient basis.

Adult↗
PubMed1993

The economic burden of unrecognized vasodepressor syncope.

BACKGROUND: The objective of this study was to describe the cost of prior diagnostic evaluation in patients referred for evaluation of syncope whose history was typical of vasodepressor syncope. METHODS AND RESULTS: Thirty consecutive patients who were referred for evaluation of syncope of undetermined origin and whose history was highly suggestive of vasodepressor syncope participated in this study. These 30 patients represented 19% of 158 patients referred for evaluation of syncope during the period of enrollment. All patients had positive results of an upright-tilt test, confirming the diagnosis of vasodepressor syncope. At the time of evaluation, the type and results of all diagnostic tests that had been performed prior to referral were recorded for each patient. The cost of diagnostic testing was then determined based on the 1991 cost of these tests at the University of Michigan Medical Center. A mean of 4 +/- 2 major diagnostic tests were performed before referral to the University of Michigan Medical Center. The mean and median costs of diagnostic testing per patient prior to referral were $3,763 +/- 3,820 and $2,678 (range: 0 to $16,606) respectively. Six patients underwent no major diagnostic tests prior to referral and, therefore, the cost of major diagnostic testing was zero in these patients. In the remaining patients, the mean and median costs of diagnostic testing per patient were $4,704 +/- 3,713 and $3,777 (range: $1,025 to $16,606) respectively. CONCLUSIONS: The results of this study demonstrate that a diagnosis of vasodepressor syncope can be established clinically in approximately 20% of patients referred to a university hospital for evaluation of syncope of undetermined origin. Failure to recognize the clinical features of vasodepressor syncope in these patients resulted in up to $16,000 of unnecessary diagnostic testing. A greater awareness of the clinical features of vasodepressor syncope may, therefore, result in significant economic savings.

Adolescent↗
PubMed1993

Ventricular fibrillation in patients without significant structural heart disease: a multicenter experience with implantable cardioverter-defibrillator therapy.

OBJECTIVES: This study was undertaken to characterize the outcome of survivors of ventricular fibrillation with no or minimal structural heart disease who received an implantable cardioverter-defibrillator. BACKGROUND: The prognosis among survivors of ventricular fibrillation with minimal or no structural cardiac abnormalities remains unclear. Since the advent of implantable cardioverter-defibrillators, this question takes on added importance. METHODS: This 10-center retrospective study provided information on 28 survivors of ventricular fibrillation (mean age 42 years) with minimal or no structural abnormalities who were treated with an implantable cardioverter-defibrillator. RESULTS: Ventricular tachyarrhythmias (polymorphic in all but one patient) were induced during baseline programmed stimulation in 39% of patients. During a median 30.6-month follow-up period after implantable cardioverter-defibrillator implantation, there were no cardiac deaths and two noncardiac deaths. Sixteen patients experienced 36 shock episodes (total 88 shocks). The majority of shocks were classified as "indeterminate"; one patient received 47 "spurious" shocks during one shock episode and each of four patients received one "appropriate" shock. Ventricular arrhythmias were not inducible in any of these latter four patients. CONCLUSIONS: Survivors of ventricular fibrillation with minimal or no structural cardiac abnormalities receiving an implantable cardioverter-defibrillator have an excellent 3-year survival rate. The occurrence, albeit infrequent, of appropriate implantable cardioverter-defibrillator shocks in this group suggests that these patients have a potential risk of recurrent cardiac arrest whose fatal outcome may be avoided by implantable cardioverter-defibrillator therapy.

Actuarial Analysis↗