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Biomedical subjects

H Garan

Publications and source records attributed to H Garan.

At least 37 records · Page 2Linked to original sources
PubMed1995

Subclavian crush syndrome complicating transvenous cardioverter defibrillator systems.

UNLABELLED: Subclavian crush syndrome, described with pacemaker leads implanted via subclavian puncture, may occur when conductor fractures and insulation breaches develop by compression of a lead between the first rib and clavicle. We reviewed our experience in 164 patients who underwent intended implantation of transvenous defibrillator systems to determine the clinical relevance of subclavian crush syndrome in defibrillator patients. Venous access was obtained via subclavian puncture in 114 patients (70%) and via cephalic cut-down in 50 patients (30%). Nonthoracotomy lead systems, with or without subcutaneous patch, were successfully implanted in 131 of 164 patients (79.9%). Thoracotomy was required in 32 patients (19.5%) and subxiphoid patch in 1 patient (0.6%). Over a mean of 12.9 months (range 1-62 months), 3 patients (1.8%) required revision of the rate sensing lead/coil or superior vena cava coil after development of lead compression fractures in the region of the clavicle and first rib. In all 3 patients the leads had been implanted via subclavian puncture (2.6% of patients in whom the subclavian technique was utilized). Two patients presented with spurious shocks. One patient was asymptomatic. CONCLUSIONS: When venous access is obtained via subclavian puncture, subclavian crush syndrome may develop in patients with transvenous defibrillator systems. Patients may be asymptomatic and lead fractures may go unrecognized. When implanting transvenous defibrillator systems, strong consideration should be given to obtaining venous access primarily via the cephalic cut-down technique.

Aged↗
PubMed1995

Malfunction of implantable cardioverter defibrillators placed by a nonthoracotomy approach: frequency of malfunction and value of chest radiography in determining cause.

OBJECTIVE: The purpose of this study was to determine the frequency of system malfunction in patients with nonthoracotomy implantable cardioverter defibrillators and to assess the role of chest radiography in detecting and determining the cause of malfunction. MATERIALS AND METHODS: The study population consisted of 300 consecutive patients in whom implantable cardioverter defibrillators were implanted using an initial nonthoracotomy approach between September 1990 and October 1994. Transvenous electrodes were placed via the subclavian or cephalic vein under local anesthetic. Intraoperative testing, pulse generator implantation, and, if necessary, subcutaneous patch or extrapericardial patch placement via thoracotomy were done in the operating room under general anesthetic. Follow-up consisted of routine device interrogation every 2-3 months and annual chest radiography. Chest radiographs were obtained more often if patients were symptomatic or if results of device interrogation were abnormal. RESULTS: Patients were followed up for a mean +/- SD of 19 +/- 14 months following implantation. Implantable cardioverter-defibrillator malfunction occurred in 17 patients (6%) during the follow-up period. Of these, 12 (71%) had component abnormalities on chest radiographs. Patients with radiographically apparent implantable cardioverter-defibrillator abnormalities presented in two discrete time periods after device implantation, early (mean, 35 +/- 14 days) and late (mean, 18 +/- 5 months). CONCLUSION: Malfunction of nonthoracotomy implantable cardioverter-defibrillator systems develops infrequently after device implantation. In most cases, the cause can be identified on chest radiographs.

Adolescent↗
PubMed1994

Three-year outcome of a nonthoracotomy approach to cardioverter-defibrillator implantation in 189 consecutive patients.

To date, no long-term clinical data have been published in patients undergoing a nonthoracotomy approach to cardioverter-defibrillator system implantation. In the present report, 189 consecutive patients prospectively underwent a standardized approach to cardioverter-defibrillator system implantation in which the nonthoracotomy configurations were tested first. If satisfactory defibrillation thresholds were not obtained, thoracotomy was performed during the same intraoperative session. A nonthoracotomy system was successfully implanted in 149 of 189 patients (79%), with a higher success rate (90%) observed in patients who had more recent implantations. The overall rate of complications associated with these systems was low (11%). Over a mean follow-up of 12.5 +/- 9.3 months, 17 patients (9%) died. Three-year total, cardiac, and sudden death-free actuarial survival for all patients was 83 +/- 11%, 88 +/- 7%, and 94 +/- 2%, respectively. Three-year sudden death-free actuarial survival was higher in the nonthoracotomy than in the thoracotomy patients (97 +/- 2% vs 87 +/- 6%, p = 0.047), although total survival was similar (77 +/- 11% vs 83 +/- 7%, p = 0.77). These data suggest that a majority of patients (> 80%) requiring a cardioverter-defibrillator system can undergo implantation using a nonthoracotomy approach. Patients receiving nonthoracotomy systems have 3-year outcomes comparable to those implanted via thoracotomy. If these results are maintained, a nonthoracotomy approach will supplant thoracotomy-implanted systems as the preferred method because of the simpler implant procedure and lower overall cost involved.

Actuarial Analysis↗
PubMed1994

Curative transcatheter radiofrequency current ablation for atrioventricular nodal reentry tachycardia.

BACKGROUND: To evaluate the efficacy of atrioventricular nodal modification by transcatheter ablation using radiofrequency energy in preventing electrically inducible and spontaneous symptomatic atrioventricular nodal reentry tachycardia, a prospective, nonrandomized, "before-after" trial was performed. Fifty consecutive patients with recurrent spontaneous symptomatic atrioventricular nodal reentry tachycardia referred to the Massachusetts General Hospital, Boston, were recruited. METHODS: A diagnostic intracardiac electrophysiologic study was performed to define the mechanism of each patient's supraventricular tachycardia. Thereafter, selective ablation of one or more slow atrioventricular nodal pathways was attempted in 47 patients, and in three patients selective ablation of a retrograde fast atrioventricular nodal pathway was carried out. Repeated programmed cardiac stimulation was performed 30 minutes after catheter ablation therapy and, where possible, before hospital discharge to evaluate the presence of electrically inducible supraventricular tachycardia. RESULTS: Electrically inducible atrioventricular nodal reentry tachycardia was eliminated in all 50 patients. No patient developed early heart block. During a mean (+/- SD) follow-up period of 8.9 +/- 5.3 months, three patients experienced a recurrence of spontaneous atrioventricular nodal reentry tachycardia and underwent a successful second ablation procedure. Two patients required permanent pacemaker implantation, one for symptomatic first-degree atrioventricular block and one for late complete heart block. CONCLUSIONS: Catheter ablation of slow atrioventricular nodal pathways by means of radiofrequency current is a safe and effective technique for eliminating electrically inducible and spontaneous atrioventricular nodal reentry tachycardia.

Adolescent↗
PubMed1994

Electrical alternans and vulnerability to ventricular arrhythmias.

BACKGROUND: Although electrical alternans (alternating amplitude from beat to beat on the electrocardiogram) has been associated with ventricular arrhythmias in many clinical settings, its physiologic importance and prognostic implications remain unknown. METHODS: To test the hypothesis that electrical alternans is a marker of vulnerability to ventricular arrhythmias, we developed a technique to detect subtle alternation in the morphologic features of the electrocardiogram (which would not be detectable by visual inspection of the electrocardiogram). In a group of 83 patients referred for diagnostic electrophysiologic testing, we prospectively examined whether levels of alternans predicted vulnerability to arrhythmias as defined by the outcome of electrophysiologic testing and arrhythmia-free survival. RESULTS: Sustained ventricular arrhythmias were induced during electrophysiologic testing in 32 of the patients (39 percent). In this group, low-level electrical alternans (a beat-to-beat change in amplitude of < 15 microV) was detected over a broad range of physiologic heart rates (from 95 to 150 beats per minute) and primarily involved the ST segment and the T wave (i.e., the phase of repolarization). Alternans during repolarization was a significant and independent predictor of inducible arrhythmias on electrophysiologic testing (sensitivity, 81 percent; specificity, 84 percent; relative risk, 5.2). Of 66 patients followed for up to 20 months, 13 had arrhythmic events. Alternans affecting the T wave and inducibility of ventricular arrhythmias were significant and essentially equivalent predictors of survival without arrhythmia (P < 0.001). Actuarial survival without arrhythmia at 20 months was significantly lower among the patients with T-wave alternans (19 percent) than among the patients without T-wave alternans (94 percent). CONCLUSIONS: Electrical alternans affecting the ST segment and T wave is common among patients at increased risk for ventricular arrhythmias. Subtle electrical alternans on the electrocardiogram may serve as a noninvasive marker of vulnerability to ventricular arrhythmias.

Actuarial Analysis↗
PubMed1994

Intraventricular conduction abnormalities in patients with clinically suspected myocarditis are associated with myocardial necrosis.

Twenty-nine patients with suspected myocarditis, either with or without intraventricular conduction abnormalities, were investigated for degree of myocardial necrosis by antimyosin scintigraphy. Among those 29 patients, 16 had intraventricular conduction abnormalities. Antimyosin scans were analyzed for heart/lung ratios and semiquantitative visual uptake scores (0 to 4+ scale). Of the 16 patients with conduction abnormalities, 15 (94%) demonstrated visual antimyosin uptake versus 7 (54%) of 13 cases without conduction abnormalities (p < 0.03). In addition, the heart/lung ratios and uptake scores were significantly higher in the group with conduction abnormalities than in the group without (1.64 +/- 0.31 vs 1.39 +/- 0.20, p < 0.03; and 2.3 +/- 0.7 vs 1.4 +/- 0.7, p < 0.005; respectively). In conclusion, intraventricular conduction abnormalities in patients with suspected myocarditis were more strongly associated with active and more severe myocardial necrosis as judged by antimyosin imaging than patients with normal electrocardiograms.

Adult↗
PubMed1994

Analysis of the initiation of spontaneous monomorphic ventricular tachycardia by stored intracardiac electrograms.

OBJECTIVES: This study was designed to analyze stored intracardiac electrograms generated during spontaneous monomorphic ventricular tachycardia to examine the possible mechanisms responsible for the initiation of ventricular tachycardia in a group of postinfarction patients. BACKGROUND: Implantable cardioverter-defibrillators capable of storing electrograms during an arrhythmic event provide an intracardiac electrogram analog to Holter ambulatory electrocardiographic monitoring. Such electrograms are of value in arrhythmia diagnosis and in determining the appropriateness of implantable cardioverter-defibrillator therapy and may aid in understanding the initiation of ventricular arrhythmias. METHODS: We studied 73 stored electrograms in 22 postinfarction patients with spontaneous monomorphic ventricular tachycardia. Premature depolarizations before tachycardia were classified by morphology and number. Electrogram morphology was compared with the morphology of the baseline rhythm and ventricular tachycardia. Prematurity was assessed by the coupling interval and a calculated prematurity ratio. RESULTS: During baseline rhythm, ectopic activity was present in 30 (41%) of 73 stored episodes. Ventricular tachycardia was preceded by a short-long-short sequence in 14% of episodes and by a rapid ventricular rhythm in 5.5% of episodes. The onset of ventricular tachycardia was marked by single premature depolarizations in 33 episodes (45%), by pairs in 16 (22%) and by multiple complexes in 24 (33%). Morphology was similar to that of the ensuing tachycardia in 35 episodes (48%). The mean coupling interval was 364 ms, and the mean prematurity ratio was 0.56. In all 10 episodes (14%) where the prematurity ratio was < 0.40, a short-long-short sequence was responsible. When classified by morphology, the mean prematurity ratio of depolarizations dissimilar to ventricular tachycardia (0.53) was significantly less than that of the morphologically similar group (0.60, p = 0.035). CONCLUSIONS: In this select group of postinfarction patients with recurrent sustained monomorphic ventricular tachycardia treated with implantable cardioverter-defibrillators, ventricular tachycardia was most often preceded by late-coupled premature depolarizations. Not infrequently, a short-long-short sequence occurred before tachycardia. Premature depolarizations with a morphology different from that of the tachycardia occurred earlier in the cardiac cycle than did those with a morphology similar to that of the tachycardia. These findings may reflect different mechanisms of ventricular tachycardia initiation.

Adolescent↗
PubMed1994

Treatment of ventricular tachycardia by transcatheter radiofrequency ablation in patients with ischemic heart disease.

BACKGROUND: Recurrent sustained ventricular tachycardia (VT) is not responsive to antiarrhythmic drugs in the majority of patients, who therefore need therapy with nonpharmacological methods. We evaluated prospectively the feasibility, safety, and efficacy of transcatheter radiofrequency (RF) ablation of VT in 21 selected patients with ischemic heart disease and VT. METHODS AND RESULTS: Twenty-one patients with ischemic heart disease and recurrent, drug-refractory VT documented by 12-lead ECG were selected who had sufficient hemodynamic tolerance of VT to undergo transcatheter mapping. Documented clinical VT was reproduced by programmed cardiac stimulation (PCS), and the site of origin was localized by a combination of techniques, including pace mapping, activation-sequence mapping, recordings of middiastolic potentials, and application of resetting and entrainment principles. RF current at 55 V was applied (3.8 +/- 3.1 applications per patient) for as long as 30 seconds at a time to target sites. Twenty-four distinct clinical VTs (mean cycle length, 445 +/- 52 milliseconds) were mapped and ablated in 21 patients. In 17 of 21 patients (81%), the procedure was acutely successful, and the target clinical VT could no longer be induced by PCS after the procedure, whereas in 4 patients, clinical VT remained inducible. By contrast, VTs with shorter cycle length and different QRS morphology than the ablated VT could still be induced by PCS in 12 of 21 patients. One patient died in intractable congestive heart failure 10 days after the procedure, and the remaining 20 are alive at the end of the follow-up period. The majority of the patients continued to be treated with at least one additional mode of antiarrhythmic therapy; 12 patients were still taking antiarrhythmic drugs, and 9 patients received an implantable cardioverter/defibrillator. During a mean follow-up period of 13.2 +/- 5.0 months, 9 of 20 patients (45%) had recurrent VT. In 4 patients, the recurrent VT was different than the previously ablated one. Clinical VT recurred in all 4 patients in whom RF ablation had been acutely unsuccessful. Four patients with recurrent VT underwent repeat RF ablation procedures that were acutely successful and had no further recurrence. CONCLUSION: Transcatheter RF ablation is feasible but has only moderately high efficacy in a small, selected group of patients with ischemic heart disease and drug-refractory, highly frequent, hemodynamically tolerated, sustained VT. In the majority of the patients, this treatment technique is palliative rather than definitive, and many of the patients continue to require other methods of antiarrhythmic therapy.

Aged↗
PubMed1994

Relation between shock-related myocardial injury and defibrillation efficacy of monophasic and biphasic shocks in a canine model.

BACKGROUND: Certain biphasic waveforms with specific time ratios of positive and negative components require less energy for successful defibrillation of the fibrillating ventricles than monophasic waveforms. However, if more efficient waveforms were also to be associated with more injurious effects on myocardial function, they might not provide a true biological advantage. This study investigates the relation between defibrillation efficacy and potential toxicity of monophasic and asymmetric, single capacitor, biphasic waveforms with equal durations of positive and negative components. METHODS AND RESULTS: The myocardial lactate extraction rate (LER) was used to measure the injurious effects on myocardial oxidative metabolism of two synchronized 35-J shocks in sinus rhythm. LER, mean arterial pressure (MAP) and, in a subset of experiments, cardiac output (CO) and coronary blood flow (CBF) were measured at baseline, 30 seconds, 60 seconds, 90 seconds, 150 seconds, 300 seconds, and 600 seconds after the shocks. In 12 dogs, three different waveforms (M 10: monophasic 10 milliseconds; BI 10: biphasic 10 milliseconds; BI 20: biphasic 20 milliseconds) were tested as series of two consecutive shocks (60 seconds apart) resulting in a total of 36 sets of data. At baseline, LER was 25 +/- 11%. After monophasic shocks, LER decreased significantly more than after biphasic shocks (LER at 150 seconds: M 10: -6 +/- 31% versus BI 10: 21 +/- 15% versus BI 20: 21 +/- 16%; M 10 versus BI 10 and M 10 versus BI 20, P < .05) and showed also a slower recovery (LER at 300 seconds: M 10: 1 +/- 24% versus BI 10: 20 +/- 11% versus BI 20: 20 +/- 15%; M 10 versus BI 10 and M 10 versus BI 20, P < .05). The maximal decrease in LER was 41 +/- 27% for M 10 compared with 18 +/- 15% for BI 10 and 15 +/- 11% for BI 20 (both, M 10 versus BI 10 and M 10 versus BI 20, P < .05). There was a similar decrease in CO and MAP, with the lowest MAP after monophasic shocks. The maximal decrease in MAP was significantly greater after M 10 compared with BI 20 (-29 +/- 15 mm Hg versus -13 +/- 11 mm Hg, P < .05). The defibrillation threshold was 18.6 +/- 8 J for M 10 compared with 11.5 +/- 4.0 J for BI 10 (P < .05) and 15.0 +/- 6.1 J for BI 20, respectively (P = NS). CONCLUSIONS: Our results suggest that these specific biphasic waveforms are associated with less injurious effects on myocardial oxidative metabolism and hemodynamic performance. Given their higher defibrillation efficacy as well, biphasic waveforms may provide important long-term benefits in patients receiving frequent shocks from implantable cardioverter-defibrillators.

Animals↗
PubMed1994

Operation for recurrent ventricular tachycardia. Predictors of short- and long-term efficacy.

The success of ventricular operation in ablating drug-refractory ventricular tachycardia secondary to ischemic heart disease varies with surgical technique, the presence of certain identified risk factors, and patient selection biases. Forty-eight patients with drug-refractory ventricular tachycardia secondary to ischemic heart disease underwent directed ventricular operation. All patients had previous myocardial infarction, and 46 of 48 patients had a left-ventricular aneurysm. Mapping was done in 81% of patients. Patients underwent a combination of subendocardial resection, aneurysmectomy, and cryoablation. The operative mortality rate was 8%. Age greater than 65 years was the only risk factor for operative mortality. Forty-one patients underwent postoperative programmed electrical stimulation. In 26 patients (63%) tachycardia was noninducible, whereas it was inducible in 15 patients (37%). Stepwise logistic regression identified septal and inferior focus location as the most significant predictors of outcome. Septal focus location was a significant (p = 0.008) predictor of surgical success whereas inferior focus location was a significant (p = 0.015) predictor of surgical failure. Other identified independent risk factors for surgical failure were (1) use of cardioplegia, (2) lack of a completed intraoperative endocardial map, and (3) decreased ejection fraction. This generated model to predict success or failure had a sensitivity of 93.3% and a specificity of 92.4%. The success of ventricular operation is affected by the presence of certain risk factors. In the management of those patients at high risk for failure, other surgical options such as the placement of implantable cardioverter-defibrillator electrode patches at the time of ventricular operation or the alternative placement of a palliative implantable cardioverter-defibrillator should be considered.

Cardiac Pacing, Artificial↗
PubMed1993

Prospective evaluation of day-to-day reproducibility of upright tilt-table testing in unexplained syncope.

To evaluate the day-to-day reproducibility of upright tilt-table testing, 109 patients with unexplained syncope prospectively underwent testing on 2 consecutive days using a uniform protocol. Results of testing on 2 separate days were concordant in 69 of 109 patients (63%), and discordant in 40 of 109 patients (37%). Thirty-six of 109 patients (33%) had vasodepressor syncope on 1 or both days of testing. Nineteen of 30 patients (63%) with vasodepressor responses on the first day did not reproduce this response during the second day of testing. An additional 6 patients with an initial negative tilt test had a vasodepressor response on the second day. Only 11 of 36 patients (31%) had reproducible vasodepressor responses on both days of testing. Patients with reproducible vasodepressor responses had a significantly higher mean number of preceding clinical syncopal events than patients with 2 normal tests (p < 0.02) or nonreproducible results (p < 0.04). In addition, these patients had a significantly longer duration of clinical symptoms relative to patients with 2 tests that yielded negative results (p < 0.008) and nonreproducible results (p < 0.01). The elapsed time between the most recent clinical event and the performance of tilt-table testing was not significantly different among the 3 groups, and did not appear to influence the outcome of testing. These data show that vasodepressor responses elicited by upright tilt-table testing show day-to-day variability in many patients, a finding that may limit the interpretation of initial and follow-up test results.

Adult↗
PubMed1993

Successful implantation of cardioverter-defibrillator systems in patients with elevated defibrillation thresholds.

OBJECTIVES: . The purpose of this study was to conduct a retrospective analysis of 16 patients with high initial defibrillation thresholds in whom a three-electrode system was used to lower defibrillation thresholds and permit implantation of a cardioverter-defibrillator system. BACKGROUND: Patients with high defibrillation thresholds (> 25 J) are uncommon but may be problematic to physicians implanting cardioverter-defibrillator systems. Most conventional systems use two defibrillating electrodes, most commonly two epicardial patches. When defibrillation thresholds remain elevated despite extensive testing of a two-electrode system, a third electrode can be incorporated and tested. However, few published data exist on the use of a three-electrode system in patients with high defibrillation thresholds. METHODS: After failure to achieve satisfactory defibrillation thresholds < 25 J with a two-patch electrode system, a third electrode was incorporated and tested. In all cases, two electrodes were joined to form a common cathode or anode, while a single electrode was used as the opposite polarity electrode. Various three-electrode configurations were then tested. RESULTS: In all 16 patients, satisfactory defibrillation thresholds were achieved and a cardioverter-defibrillator was implanted (95% confidence interval [CI] = 0% to 21%). The mean final defibrillation threshold using the revised three-electrode system was 19.5 +/- 3.7 J (p < 0.0001). A mean of 6 +/- 3 electrode configurations/patient were tested before the final configuration was selected. A total of nine different electrode configurations were used in the 16 study patients; the most common of these incorporated left and right ventricular patches as combined cathode and a superior vena cava coil (n = 5) or right atrial patch electrode (n = 3) as single anode. CONCLUSION: Patients with high initial defibrillation thresholds can generally undergo successful cardioverter-defibrillator implantation with a three-electrode system if enough electrode configurations are tested after a third electrode is incorporated.

Aged↗
PubMed1993

Determinants of successful nonthoracotomy cardioverter-defibrillator implantation: experience in 101 patients using two different lead systems.

OBJECTIVES: This study was conducted to identify the determinants of successful nonthoracotomy cardioverter-defibrillator implantation. BACKGROUND: Until recently, either median sternotomy or thoracotomy was necessary to implant the electrodes used for internal cardioverter-defibrillator systems. A number of manufacturers have developed nonthoracotomy lead systems comprising two transvenous coil electrodes and a subcutaneous patch electrode. At present, the factors associated with the success or failure of a nonthoracotomy approach are unknown. METHODS: A total of 101 consecutive patients requiring a cardioverter-defibrillator underwent an initial nonthoracotomy approach. Factors associated with successful nonthoracotomy implantation were prospectively determined. RESULTS: A nonthoracotomy system was implanted in 72 (71%) of 101 patients. Twenty-nine patients (29%) required thoracotomy. Univariate predictors of successful nonthoracotomy implantation included smaller cardiac size (p < 0.0001), smaller cardiothoracic ratio (p < 0.0002), QRS duration < 120 ms (p = 0.003), female gender (p = 0.006), ventricular fibrillation as the presenting arrhythmia (p = 0.03) and smaller echocardiographic left ventricular size (p = 0.04). Multivariate predictors included smaller cardiac size (p < 0.002) and female gender (p < 0.007). Total actuarial survival over a mean (+/- SD) follow-up interval of 12 +/- 7 months was 91 +/- 0.03% and was not different in the thoracotomy and nonthoracotomy groups. CONCLUSIONS: A nonthoracotomy cardioverter-defibrillator system can be implanted in a majority of patients. Smaller cardiac size and female gender are associated with a high probability of successful implantation.

Actuarial Analysis↗
PubMed1993

Pseudo-pacemaker syndrome following inadvertent fast pathway ablation for atrioventricular nodal reentrant tachycardia.

Atrioventricular nodal reentrant tachycardia that is refractory to drug treatment has recently been treated with radiofrequency catheter ablation. In this case report we describe a patient with atrioventricular nodal reentrant tachycardia in whom radiofrequency ablation of slow pathway was attempted, with inadvertent damage to the fast pathway. The patient developed marked first-degree atrioventricular block associated with symptoms mimicking pacemaker syndrome.

Cardiac Pacing, Artificial↗
PubMed1993

Efficacy of a tiered therapy defibrillator system used to treat recurrent ventricular arrhythmias refractory to drugs.

OBJECTIVE: To evaluate an implantable tiered therapy defibrillator system that delivered antitachycardia pacing treatment for slower well tolerated ventricular tachycardias and cardioversion or defibrillation for fast tachycardias or ventricular fibrillation. METHODS: A tiered treatment device (Ventritex Cadence V-100) was implanted in 30 patients with ventricular tachycardia that was refractory to drugs. Efficacy was evaluated by the responses of induced or spontaneous arrhythmias to the treatments delivered. RESULTS: Antitachycardia pacing successfully terminated 80% of episodes of ventricular tachycardia induced by non-invasive programmed stimulation, but acceleration was brought about by pacing in six patients in 10% of episodes. During a follow up of two to 17 (mean seven) months, 18 patients (60%) had recurrence of ventricular arrhythmias. Antitachycardia pacing terminated ventricular tachycardia in 17 of 18 patients in 87% of episodes. Twelve patients received shocks for ventricular tachycardia or fibrillation. Failure of pacing, with subsequent cardioversion, occurred in nine patients (50%) in one or more episodes. Acceleration of tachycardia by pacing occurred in 10 patients in 5% of episodes. Only two of these patients had experienced acceleration of previously induced arrhythmia. Five patients had spontaneous fast ventricular tachycardia or fibrillation treated by cardioversion or defibrillation. Spurious treatment was delivered in nine patients (30%), during atrial fibrillation in five, sinus tachycardia in two, and because of fracture of the sensing lead system in two patients. The retrieval of stored intracardiac electrograms was of clinical value in assessing spurious treatment. CONCLUSIONS: Tiered treatment was effective in terminating recurrent ventricular arrhythmias in these selected patients. Most episodes were treated successfully by pacing, and resistant tachycardias, pacing induced acceleration, or haemodynamically compromising arrhythmias were treated by shocks.

Adolescent↗
PubMed1993

Influence of implantable cardioverter-defibrillators on the long-term prognosis of survivors of out-of-hospital cardiac arrest.

BACKGROUND: Survivors of out-of-hospital cardiac arrest not associated with acute myocardial infarction are at high risk for recurrent cardiac arrest and sudden cardiac death. The impact of the implantable cardioverter-defibrillator on long-term prognosis in these patients is uncertain. METHODS AND RESULTS: Three hundred thirty-one survivors of out-of-hospital cardiac arrest (age, 56 +/- 13.7 years) underwent electrophysiologically guided therapy. Implantable defibrillators were placed in 150 patients (45.3%), and 181 patients (54.7%) received pharmacological and/or surgical therapy alone. Left ventricular ejection fraction was 35.2 +/- 16.6% in defibrillator recipients and 45.3 +/- 18.2% in nondefibrillator patients. Median patient follow-up was 24 months in the defibrillator group and 46 months in the nondefibrillator group. In a proportional hazards model, the independent predictors of total cardiac mortality were left ventricular ejection fraction of less than 0.40 (relative risk, 4.55; 95% confidence interval, 2.44 to 8.33; P = .0001), absence of an implantable defibrillator (relative risk, 2.70; confidence interval, 1.41 to 5.00; P = .017), and persistence of inducible sustained ventricular tachycardia (relative risk, 1.84; 95% confidence interval, 0.97 to 3.49; P = .045). The 1- and 5-year probabilities of survival free of cardiac mortality in patients with left ventricular ejection fraction of less than 0.40 were 94.3% and 69.6% with a defibrillator and 82.1% and 45.3% without a defibrillator, respectively. For patients with left ventricular ejection fraction of 0.40 or more, the 1- and 5-year probabilities of survival free of cardiac mortality were 97.7% and 94.6% with a defibrillator and 95.4% and 86.9% without a defibrillator, respectively. CONCLUSIONS: In survivors of out-of-hospital cardiac arrest, the implantable defibrillator is associated with a reduction in cardiac mortality, particularly in patients with impaired left ventricular function.

Anti-Arrhythmia Agents↗
PubMed1993

Experience with an implantable tiered therapy device incorporating antitachycardia pacing and cardioverter/defibrillator therapy.

The implantable cardioverter-defibrillator provides an alternative therapy for medically refractory ventricular tachyarrhythmias in patients who are not candidates for ventricular operations or in whom these operations have failed. Currently, however, available devices have limitations. In this report we describe our experience with a programmable, tiered therapy device with anti-ventricular tachyarrhythmia pacing and VVI pacing capabilities (Cadence V-100, Ventritex Inc., Sunnyvale, Calif.). This device offers certain advantages compared with conventional implantable cardioverter-defibrillators: (1) tiered, anti-ventricular tachyarrhythmia therapy incorporating programmable, rate-adaptive burst pacing in addition to energy-programmable cardioversion/defibrillation, (2) biphasic cardioversion/defibrillation waveforms, resulting in lower defibrillation thresholds, (3) the ability to abort therapy for nonsustained ventricular tachyarrhythmias, (4) electrogram storage of detected events for later retrieval and analysis, (5) noninvasive, device-generated programmed stimulation for system testing, and (6) backup VVI pacing capability. Forty patients (aged 14 to 79 years) with ventricular tachyarrhythmias refractory to medical therapy received this device. The mean left ventricular ejection fraction was 33% +/- 16%. Preoperative electrophysiologic testing revealed inducible monomorphic ventricular tachyarrhythmia responsive to rapid ventricular pacing in 36 patients (90%). An extrapericardial two-patch configuration was used with either epicardial screw-in or bipolar endocardial sensing/pacing wires. No operative mortality and no device-related infection occurred. During a follow-up period of 16 +/- 7 months (range 3 to 30 months), 38 patients remained active with the implanted device; one patient died of congestive heart failure 4 months after implantation, and the system was explanted in one patient who underwent cardiac transplantation. In 33 patients a total of 1815 ventricular tachyarrhythmias were detected that resulted in therapy. Rate-adaptive burst pacing was used as the initial therapy in 1470 episodes and was successful in 1352 instances (92%). Pacing-induced ventricular tachyarrhythmia acceleration occurred in 4% of episodes. The remaining ventricular tachyarrhythmia episodes were treated with cardioversion. In 18 patients (45%) cardioversion therapy was aborted after spontaneous termination of ventricular tachyarrhythmia.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗