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Biomedical subjects

R B Krol

Publications and source records attributed to R B Krol.

At least 37 records · Page 2Linked to original sources
PubMed1997

Internal atrial defibrillation: effect on sinus and atrioventricular nodal function and implanted cardiac pacemakers.

Internal atrial defibrillation (IAD) has been extensively evaluated for clinical efficacy but the need for concomitant demand pacing and the effect of IAD shocks on pacemaker function is not well studied. We prospectively evaluated: (1) the incidence of bradycardia as a result of IAD shocks; and (2) effect of these shocks on functioning of implanted cardiac pacemakers. Consecutive consenting patients with atrial fibrillation (AF) requiring cardioversion or undergoing electrophysiological study were selected for IAD. IAD shocks were delivered using the right ventricle to right atrium (RV-RA), right ventricle to superior vena cava (RV-SVC), right atrium to axillary patch (RA-AX), and right atrium to left pulmonary artery or coronary sinus (RA-LPA/CS) lead configurations. Mean RR interval before and after the shocks and the time interval from shock delivery to first QRS complex were analyzed for unsuccessful and successful shocks. Pacing and sensing function was analyzed in patients with previously implanted pacemakers. Twenty-five patients, 18 men, mean age 67.9 +/- 10 years were included in the study. A total of 305 shocks (264 unsuccessful, 41 successful) were analyzed. For unsuccessful shocks the mean post-IAD shock RR interval (795 +/- 205 ms) and the time to first post-IAD shock QRS complex (970 +/- 438 ms) were both significantly greater than the pre-IAD shock RR interval (685 +/- 131 ms, P < 0.001). The increase in post-IAD shock RR interval and time to first post-IAD shock QRS complex was seen with all four lead configurations used. With successful shocks the mean post-IAD shock sinus cycle length (1,105 +/- 450 ms) and time to first post-IAD shock QRS complex (1,126 +/- 443 ms) were both also significantly greater than the pre-IAD shock RR interval (766 +/- 172 ms). Nine patients (36%) had episodes of significant bradycardia after shock delivery. Shocks of up to 20 J using the RA-LPA/CS lead configuration did not affect pacemaker function. IAD can result in transient bradycardia related to sinus and atrioventricular nodal effects requiring backup ventricular pacing. Shocks can be safely delivered using RA-LPA or RA-CS lead configurations in patients with implanted bipolar cardiac pacemakers.

Aged↗
PubMed1997

The role of pacemaker therapy in the prevention of atrial fibrillation.

Atrial fibrillation (AF) has been recognized, with increasing concern, as a potentially disabling illness, occurring either as a symptom of many cardiac diseases or as an isolated disorder. It can independently contribute to mortality and morbidity and may have serious prognostic importance in acute or chronic cardiac disease. In patients with symptomatic drug refractory atrial fibrillation, ventricular rate control by atrioventricular nodal ablation or modification commonly results in pacemaker implantation. The concept of AF prevention by pacemaker therapy has been introduced in patients with bradycardia-tachycardia syndrome or vagally mediated bradycardia-dependent AF. In patients with sick sinus syndrome, atrial pacing has proved to be more effective than VVI pacing in maintaining the electrical stability of the atrium in long-term follow up. Recently, the development of new techniques of atrial pacing employing pacing at two atrial sites may improve the effectiveness of the AF prevention by pacemaker therapy. Dual-site right atrial pacing using overdrive stimulation activates simultaneously the high right atrium and the left atrium via the ostium of the coronary sinus. Two main mechanisms have been proposed to explain the favourable effect of this technique. One is the suppression of atrial premature beats initiating AF by the overdrive pacing. The second is the alteration of atrial activation pattern by preexcitation of the area of the coronary sinus ostium which permits earlier recovery of excitability in sites of atrial conduction delay. The combination of drug therapy and pacing is essential for effective AF control. We have hitherto studied 30 patients with single- and dual-site pacing. Single-site pacing was performed at the high right atrium or coronary sinus ostium. The dual-site pacing mode increased the arrhythmia-free intervals, decreased patients' arrhythmia-related symptoms and anti-arrhythmic drug use as compared to the period preceding institution of pacing and incrementally over conventional high right atrial pacing alone. A multicentre randomized trial, Dual-site Atrial Pacing for Prevention of Atrial Fibrillation (DAPPAF), evaluating three pacing modes (dual-site, single-site and support pacing), is now in progress.

Atrial Fibrillation↗
PubMed1996

Prevention of recurrent atrial fibrillation with chronic dual-site right atrial pacing.

OBJECTIVES: We investigated 1) the feasibility, safety and efficacy of multisite right atrial pacing for prevention of atrial fibrillation (AF); and 2) the ability of atrial pacing in single- and dual-site modes to increase arrhythmia-free intervals in patients with drug-refractory AF. BACKGROUND: We recently developed and applied a novel technique of dual-site right atrial pacing in an unselected group of consecutive patients with AF requiring demand pacing. A prospective crossover study design was used to evaluate single- and dual-site right atrial pacing modes. METHODS: The frequency of AF during the 3 months before pacemaker implantation was analyzed. Consecutive consenting patients underwent insertion of two atrial leads and one ventricular lead with a DDDR pulse generator. Patients were placed in a dual-site pacing mode for the first 3 months and subsequently mode switched to single site pacing for 3 months. Mode switching was repeated at 6-month intervals thereafter. RESULTS: Atrial pacing resulted in a marked decline in AF recurrences (p < 0.001). During dual-site pacing with an optimal drug regimen, there was no AF recurrence in any patient compared with five recurrences in 12 patients during single-site pacing (p = 0.03). The mean (+/-SD) arrhythmia-free interval before pacing (14 +/- 14 days) was prolonged with dual- (89 +/- 7 days, p < 0.0001) and single-site pacing (76 +/- 27 days, p < 0.0001). Symptomatic AF episodes showed a declining trend during dual- and single-site pacing compared with those during the preimplantation period (p = 0.10). Mean antiarrhythmic drug use for all classes declined from 4 +/- 1.9 drugs before implantation to 1.5 +/- 0.5 (p < 0.01) drugs after implantation. Twelve (80%) of 15 patients remained in atrial paced rhythm at 13 +/- 3 months. CONCLUSIONS: We conclude that multisite right atrial pacing is feasible, effective and safe for long-term application. Atrial pacing significantly prolongs arrhythmia-free intervals in patients with drug-refractory paroxysmal AF. Dual-site right atrial pacing may offer additional benefits and should be considered either as the primary mode or in patients unresponsive to single-site pacing.

Adult↗
PubMed1996

New generations of implantable pacemaker defibrillators for ventricular and atrial tachyarrhythmias.

Implantable defibrillation devices have now been extensively applied to patients requiring cardioversion and defibrillation of sustained ventricular tachyarrhythmias. The focus of new developments is in improving technology, achieving physiologic operation in the atrium and ventricle, seeking new indications and identifying patient populations amenable to this therapy. Ventricular application technology is focusing on simplifying and improving robustness of lead systems yet seeking lower defibrillation thresholds. Dual chamber pacing, sensing and defibrillation are being developed. New populations for ventricular application include non-sustained ventricular tachycardia patients with coronary artery disease, dilated cardiomyopathy at risk for sudden death, long QT syndrome, pediatric patients with risk of sudden death and high risk postoperative coronary bypass patients. New applications include atrial defibrillation combined with atrial pacing in future devices. These devices are planned to have capabilities of ventricular defibrillation as a backup to address proarrhythmia concerns. It can be anticipated that implantable cardioverter defibrillator devices will be used for arrhythmia reversion in an expanding group of patients in the future.

Arrhythmias, Cardiac↗
PubMed1995

Clinical efficacy and safety of atrial defibrillation using biphasic shocks and current nonthoracotomy endocardial lead configurations.

We undertook a prospective randomized clinical trial evaluating efficacy and safety of internal atrial defibrillation in patients with drug-refractory atrial fibrillation (AF). Consecutive patients with paroxysmal or chronic AF were randomly tested with 3 internal atrial defibrillation lead configurations and biphasic shocks. Patients with implanted cardiac pacemakers were tested with the right atrium (RA) and left pulmonary artery or coronary sinus (CS) configuration. Shocks were initially delivered without anesthesia to assess patient tolerance. The need for backup ventricular defibrillation and pacing support was evaluated. Eighteen patients with (n = 15) or without (n = 3) structural heart disease, mean left ventricular ejection fraction 36 +/- 14%, and mean left atrial diameter 4.5 +/- 0.6 cm were studied. The mean defibrillation threshold in the best randomized lead configuration was 9.9 +/- 7.7 J. Mean defibrillation threshold for the right ventricle (RV) and superior vena cava configuration was 13.3 +/- 5 J, which was significantly lower than the RA and axilla configuration (20.1 +/- 7.4 J, p < 0.04) but not the RV to RA configuration (16.5 +/- 11 J, p > 0.2). The mean defibrillation threshold using the RA-left pulmonary artery/CS configuration was 8.9 +/- 9 J (p > 0.2 vs RV-superior vena cava). There was a bimodal distribution of defibrillation thresholds. Low atrial defibrillation thresholds correlated with absence of heart disease, higher ejection fraction, and smaller left ventricular end-diastolic diameter. Shocks were hemodynamically well tolerated, but 2 of 18 patients (11%) had nonsustained ventricular tachycardia after shock delivery. Six of 18 patients (33%) had postshock bradyarrhythmias. Fourteen of 16 patients perceived shocks > or = 3 J as intolerable.(ABSTRACT TRUNCATED AT 250 WORDS) [corrected]

Adult↗
PubMed1995

Efficacy and safety of radiofrequency catheter ablation of left-sided accessory pathways through the coronary sinus.

Radiofrequency catheter ablation of left-sided accessory pathways (APs) with the use of an endocardial technique carries all potential risks of left heart catheterization. We analyzed the determinants of success, efficacy, and safety of radiofrequency catheter ablation from the coronary sinus (CS), as a potential alternative to the endocardial technique in these patients. Thirteen patients (mean age 40 +/- 20 years) with 15 left-sided APs and a history of symptomatic supraventricular tachycardia were included in the study. Nine APs were localized in the left posteroseptal region, and the remaining 6 in the left free wall. Ablation from CS was attempted in 12 patients with 14 APs. In 1 patient ablation within the CS was not deemed safe because of a small venous lumen. All 14 APs were successfully ablated using either CS ablation alone or combined with the endocardial technique. Efficacy of the CS ablation as a primary technique was 56% (5 of 9 APs). In 5 additional APs, ablation in the CS eliminated pathway conduction after failed endocardial attempts. CS ablation either as a primary or a secondary technique eliminated conduction in 10 of 14 APs (71.4%) (group 1). In the remaining 4 APs (group 2), the primary CS attempt was unsuccessful and APs were ablated with a subsequent endocardial approach. Determinants of success for the CS method were local AP to atrial and/or ventricular electrogram amplitude ratios > or = 1 (p < 0.05). The success rate of CS ablation was 83% in the left posteroseptal APs adjoining the branching point of the middle cardiac vein or a CS anomaly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Innovations in pulse generators and lead systems: balancing complexity with clinical benefit and long-term results.

Technologic development of implantable cardioverter defibrillators (ICDs) is now in an exponential growth phase, and many new concepts are being examined. Major innovations have occurred in pulse generators and in lead systems. This may increase ICD use for primary and secondary prevention of sudden cardiac death. Pulse generators now include hybrid pacemaker-defibrillators. Clinical data suggest a need for demand pacing in primary and secondary prevention applications, with antitachycardia pacing being most valuable in the latter group. Atrial leads will allow dual chamber sensing, pacing, and defibrillation. Low energy cardioversion with biphasic shocks can enhance shock efficacy in rapid monomorphic ventricular tachycardia and flutter. Modifications of lead design, biphasic shock waveforms, and optimal thoracic electrode location in axillary or pectoral regions will permit lower energy defibrillation and smaller pulse generators with lower maximum energy outputs of < or = 25 joules. Dual chamber sensing will improve detection of atrial flutter or fibrillation. Minimum data storage requirements for tachycardia events in ICDs still need to be defined. Intracardiac electrogram analysis is still in evolution, and better analytic methods are awaited. Lead system development is likely to support generic pacing and defibrillation catheter electrodes for atrial and ventricular application. Advances in thoracic electrode design are in progress, and a variety of intercostal electrodes are being tested. Improvements in lead design with further impact on defibrillation energy requirements have the potential to permit generator miniaturization. Significant technologic improvements in ICD devices are imminent and should improve clinical results, patient safety, and quality of life.

Algorithms↗
PubMed1994

Third- and fourth-generation implantable cardioverter defibrillators: current status and future development.

Implantable cardioverter defibrillator (ICD) therapy has become the mainstay of therapy for patients with a history of sudden cardiac death or life-threatening ventricular arrhythmias. The current generation of ICDs used for secondary prevention combines features for tachycardia reversion with demand ventricular pacing, antitachycardia pacing, programmable shock therapy, and tachycardia events memory. Although demand pacing and defibrillation is indicated for primary prevention usage of ICDs, the application of antitachycardia pacing modes is more controversial. High energy cardioversion and defibrillation shocks remaining the mainstay of sudden death prevention will be redefined as more effective defibrillation shock modes and lead systems are developed. Fourth-generation ICD systems accomplished a significant reduction of device size and almost universal success using an endocardial lead configuration and pectoral implant. A variety of new directions of ICD therapy in clinical practice such as primary prevention applications and the adjunctive role of antiarrhythmic drug therapy are currently being examined in clinical trials. The concepts underlying initiation of tachyarrhythmias are being studied to develop new approaches to tachycardia prevention. These include rate support, subthreshold stimulation, and multiple site pacing. The current developments of ICD therapy promise continued growth of this technology.

Anti-Arrhythmia Agents↗
PubMed1993

Endocardial pacing, cardioversion and defibrillation using a braided endocardial lead system.

The clinical efficacy and safety of a second-generation braided endocardial pacing, cardioversion and defibrillation lead system was evaluated in 25 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). The lead system consisted of two 8Fr active fixation endocardial leads each with pacing and defibrillation electrodes and a thoracic patch electrode. Monophasic and biphasic shocks were delivered using a triple-electrode configuration with a right ventricular common cathode and right atrial and thoracic patch anodes. VT and VF were electrically induced. Rapid VT (rate > or = 180 beats/min) and VF were initially terminated by 20 J (550 V) shocks and slow VT (rate < 180 beats/min) by 10 J (400 V) shocks. One hundred fourteen episodes (rapid VT/VF 73, slow VT 41) were treated with 128 shocks (monophasic 80, biphasic 48). Mean ventricular pacing threshold was 0.7 +/- 0.5 ms before and 0.9 +/- 0.5 ms after endocardial shock delivery (p > 0.2). Mean ventricular electrogram amplitude in sinus rhythm was 11.9 +/- 5.7 mV before and 11.4 +/- 5.1 mV after shock delivery (p > 0.2). Simultaneous monophasic endocardial shocks terminated 53% of VF episodes at < or = 20 J. Simultaneous biphasic shocks terminated 94% of all VF episodes at < or = 20 J (p < 0.03). Efficacy of > or = 10 J shocks for rapid VT/VF was greater for biphasic (92%) versus monophasic (74%) shocks (p < 0.05) at lower average shock energy (15 +/- 7 J vs 19 +/- 7 J, respectively, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Device use patterns and clinical outcome of implantable cardioverter defibrillator patients with moderate and severe impairment of left ventricular function.

The beneficial effects of implanted cardioverter defibrillator (ICD) therapy in patients with malignant ventricular tachyarrhythmias and variable degrees of left ventricular (LV) dysfunction are debated. ICD use and patient survival were examined in 128 patients with malignant ventricular arrhythmias and moderate or severe LV dysfunction. Group I included 64 patients with moderate LV dysfunction (LV ejection fraction of > 30%) and group II, 64 patients with severe LV dysfunction (LV ejection fraction of < or = 30%). Follow-up period ranged from 1 to 78 months. The two groups were similar in age, incidence of coronary artery disease and presenting arrhythmia. The mean LV ejection fraction in group I was 44% +/- 8% and group II was 22% +/- 5% (P < 0.0001). At 4 years of follow-up, 66% of patients from group I and 62% from group II (P = NS) had ICD activation for presumed ventricular tachyarrhythmia. Survival was calculated using actuarial analysis. Arrhythmic or sudden death mortality at 4 years of follow-up was 4% in group I and 7% in group II (P = NS). Cardiac mortality was for group I, 7% (P < 0.05), 12% (P < 0.01), 15% (P < 0.01), and 15% (P < 0.01) for follow-up years 1, 2, 3, and 4, respectively. For group II, cardiac mortality was 27%, 36%, 41%, and 41% for follow-up years for 1, 2, 3, and 4, respectively. The majority of cardiac deaths in both groups was observed in the first 2 years of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1993

Low-energy endocardial defibrillation using an axillary or a pectoral thoracic electrode location.

BACKGROUND: A significant proportion of patients receiving endocardial defibrillation lead systems must accept either high defibrillation thresholds (DFTs) with lower safety margins or lead implantation by thoracotomy. We examined the feasibility of achieving universal application of endocardial leads and lower defibrillation energy requirements by optimizing the lead system location in conjunction with biphasic shocks. METHODS AND RESULTS: Two defibrillation catheter electrodes were positioned in the right ventricle and superior vena cava. Thoracic patch electrodes were placed at three sites (apical, pectoral, and axillary). Fifteen-joule, 10-J, and 5-J bidirectional simultaneous biphasic shocks were delivered across three different triple electrode configurations (right ventricle, superior vena cava, and patch) after inducing ventricular fibrillation (VF), and DFT was determined. All patients in whom VF was reproducibly inducible (14 patients) could be reproducibly defibrillated at 15 J at one or more patch electrode locations. Fifteen-joule shocks were effective at three thoracic electrode locations in 12 patients and at two electrode locations in 6 patients. The lowest mean single-shock DFT was 8.1 +/- 3.8 J. In 4 patients, ventricular flutter was reproducibly induced and reverted at 15 J in all patients. Mean DFT for the axillary location was 8.3 +/- 3.5 J and was significantly lower than apical (12.8 +/- 5.6 J, P = .008) and pectoral (11.6 +/- 4.1 J, P < .04) patch locations. The probability of success was significantly higher at 10 J with axillary location (78% of patients, P < .03 compared with both other sites) and at 15 J (P < .05 compared with the apical location). Low-energy endocardial defibrillation (< or = 10 J) was feasible in 10 of 14 tested patients at more than 1 thoracic electrode location at 10 J, whereas only 1 of 7 successful patients could be reverted at more than 1 electrode location at 5 J (P < .02). CONCLUSIONS: The use of axillary or pectoral patch lead location can allow endocardial defibrillation with biphasic shocks at energies < or = 15 J in this lead configuration. Virtually universal application of endocardial defibrillation lead systems can be predicted from these data. Reduction in maximum pulse generator output to < or = 25 J using these two thoracic electrode locations with bidirectional shocks can be feasible and maintain an adequate safety margin and permit thoracic pulse generator implantation. Lowering endocardial defibrillation energy < 10 J requires increasing specificity of thoracic electrode location.

Aged↗
PubMed1992

Prospective comparison of biphasic and monophasic shocks for implantable cardioverter-defibrillators using endocardial leads.

Bidirectional shocks using 2 current pathways have been used in endocardial lead systems for implantable cardioverter-defibrillators, but the optimal shock waveform for endocardial defibrillation is unknown. The clinical efficacy and electrical characteristics of bidirectional monophasic and biphasic shocks for endocardial cardioversion-defibrillation of fast monomorphic or polymorphic ventricular tachycardia (VT), or ventricular fibrillation (VF) were evaluated. Thirty-three patients (mean age 60 +/- 12 years, and mean left ventricular ejection fraction 34 +/- 13%) were studied. Defibrillation catheter electrodes were located in the right ventricular apex and superior vena cava/right atrial junction. A triple-electrode configuration including the 2 catheter electrodes and a left thoracic patch was used to deliver bidirectional shocks from the right ventricular cathode to an atrial anode (pathway 1) and the thoracic patch (pathway 2). The shock waveforms examined were sequential and simultaneous monophasic, and simultaneous biphasic. The efficacy of 580 V (20 J) shocks for fast monomorphic VT were comparable for the 3 waveforms (73% for sequential monophasic, 73% for simultaneous monophasic, and 100% for simultaneous biphasic). However, for polymorphic VT and VF, 580 V sequential monophasic shocks had a significantly lower efficacy (25%) than did simultaneous monophasic (75%; p = 0.01) or biphasic (89%; p less than 0.001) shocks. Single-shock defibrillation thresholds with simultaneous biphasic shocks were significantly lower (9 +/- 5 J) than were those with simultaneous monophasic shocks (15 +/- 4 J; p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Electric Countershock↗
PubMed1992

Survival of implantable cardioverter-defibrillator recipients: role of left ventricular function and its relationship to device use.

The quantitative benefit of ICD therapy in patients with malignant ventricular tachyarrhythmia with different degrees of left ventricular dysfunction is unclear. We evaluated patterns of ICD use and survival in 112 patients with moderate to severe left ventricular dysfunction. Group 1 included 57 patients with moderate left ventricular dysfunction (defined as left ventricular ejection fraction greater than 30%) and group 2 comprised 55 patients with severe left ventricular dysfunction (defined as ejection fraction equal to or less than 30%). The follow-up period ranged from 1 to 78 months. Age, incidence of coronary artery disease, and presenting arrhythmia in the two groups were similar. The mean left ventricular ejection fraction in group 1 was 44.6 +/- 8.2% and in group 2 was 21.6 +/- 6% (p < 0.0001). At 3 years of follow-up 65% of the patients in group 1 and 71% in group 2 (p = NS) had ICD activation for presumed ventricular tachycardia. Survival was calculated by means of actuarial analysis. Arrhythmia or sudden death mortality at 4 years of follow-up was 5% in group 1 and 9% in group 2 (NS). Cardiac mortality was higher in patients with severe left ventricular dysfunction reaching levels of statistical significance at 2 years of follow-up. At 2 years of follow-up it was 12% in group 1 and 40% in group 2 (p = 0.05), and at 4 years of follow-up it was 15% in group 1 and 43% in group 2 (p < 0.01). In both groups there was no difference in cardiac mortality in patients who did and did not have appropriate ICD shocks.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Comparison of clinical benefits and outcome in patients with programmable and nonprogrammable implantable cardioverter defibrillators.

Technological advances in implantable cardioverter defibrillators (ICDs) have provided a variety of programmable parameters and antitachycardia therapies whose utility and impact on clinical outcome is presently unknown. ICDs have capabilities for cardioversion defibrillation alone (first generation ICDs), or in conjunction with demand ventricular pacing (second generation ICDs), or with demand pacing and antitachycardia pacing (third generation ICDs). We examined the pattern of antitachycardia therapy use and long-term survival in 110 patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Group I included 62 patients with nonprogrammable first generation ICDs that delivered committed shock therapy after ventricular tachyarrhythmia detection based on electrogram rate and/or morphology was satisfied. Group II included 48 patients with multiprogrammable ICDs (including second and third generation ICDs) that had programmable tachyarrhythmia detection based on rate and tachycardia confirmation prior to delivery of electrical treatment with either programmable shocks and/or, as in the third generation ICDs, antitachycardia pacing. Incidence and patterns of antitachycardia therapy use and long-term survival were compared in the two groups. The incidence of appropriate shocks in patients who completed 1 year of follow-up was significantly greater in group I (30 of 43 patients = 70% vs 11 of 26 patients = 42%; P less than 0.05). In the total follow-up period, a significantly larger proportion of group I patients as compared to group II patients used the shock therapies (46 of 62 patients = 74% vs 25 of 48 patients = 52%; P less than 0.01), with the majority doing so within the first year of implantation (96% and 92%, respectively). Although the frequency of antitachycardia therapy activation was similar, the number of shocks delivered per patient was lower in group II, particularly in the initial 3 months of follow-up (P = 0.06). No clinical variable aided in identifying users from nonusers of antitachycardia therapy. Arrhythmic mortality was virtually eliminated in both groups. Two-year actuarial cardiac survival in the two groups was similar (group I = 78% vs group II = 84%; P greater than 0.2). Survival from cardiac mortality in users and nonusers of antitachycardia therapies was also similar in both groups (P greater than 0.2) and in the total patient group (P greater than 0.2). We conclude that programmable ICDs continue to confer advantages in prevention of sudden death that were observed with nonprogrammable ICDs and can be expected to improve patient tolerance and physician acceptance of device therapy for VT/VF.

Adult↗
PubMed1991

Experience with a third-generation implantable cardioverter-defibrillator.

A Medtronic 7216A pacemaker cardioverter-defibrillator was implanted in 16 patients (mean age 56 years) with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and organic heart disease with a mean left ventricular ejection fraction of 33%. Endocardial and epicardial defibrillation shock efficacy was evaluated before or at implant using 1 to 3 shock patterns, i.e., monophasic single, sequential or simultaneous shocks with dual and triple electrode configurations. Endocardial leads used a common right ventricular cathode and dual anodes, whereas epicardial leads used 2 or 3 helical coil patches. VT termination was evaluated using pacing or shock therapy, or both, whereas only shocks were used in VF. Programmable bradycardia pacing, individual zones for VT and VF detection and individualized pacing and shock therapy for VT and VF were used. Monophasic shocks had epicardial defibrillation thresholds ranging from 3 to 18 (mean 10) J and were comparable for sequential and simultaneous shocks (p greater than 0.2). VT detection rates ranged from 340 to 470 ms and VF detection rates from 270 to 330 ms. VT or VF induction, or both, was performed noninvasively in 13 patients after implant and was reproducibly terminated by rapid pacing alone (5 patients), low-energy shocks (2 patients), high-energy shocks (3 patients) and combined therapy (3 patients). Intermediate or high-energy shocks terminated all induced VF episodes. During follow-up (2 to 12 months), there have been 2 noncardiac deaths. Electrical therapy was delivered in 7 patients, for VT (3 patients), VT and VF (3 patients) and indeterminate tachyarrhythmia (1 patient). All VT/VF episodes were successfully terminated, with 78 of 96 (81%) spontaneous VT episodes terminated by pacing. Follow-up reprogramming was required in 5 patients. It is concluded that successful application of individualized electrical therapy prescriptions in patients with VT/VF is feasible. Pacing therapies, which are effective for induced VT, can be reliably used for effective long-term spontaneous VT termination in conjunction with shock therapy and can permit reduced patient exposure to shock therapy. Thus, a programmable hybrid pacemaker cardioverter-defibrillator system provides nonthoracotomy implantation, effective VT/VF termination, demand ventricular pacing and noninvasive modes for arrhythmia induction, event monitoring and clinical trouble-shooting.

Adult↗