Long-term multicenter experience with a second-generation implantable pacemaker-defibrillator in patients with malignant ventricular tachyarrhythmias. The Guardian Multicenter Investigators Group.

A second-generation implantable pacemaker-cardioverter-defibrillator was evaluated in 200 patients with sustained ventricular tachycardia, ventricular fibrillation or prior cardiac arrest. The device permits demand ventricular pacing for bradyarrhythmias and for long QT interval or tachycardia suppression, uses programmable (3 to 30 J) energy shocks for conversion of ventricular tachycardia and ventricular fibrillation and is used with conventional pacing and defibrillation leads. Ventricular tachycardia/fibrillation recognition is based on the ventricular electrogram rate and requires reconfirmation before shock delivery. Two hundred patients (mean age 62 years, mean left ventricular ejection fraction 36%) were enrolled and followed up for 0 to 23 months (mean 12). Epicardial lead system implantation was performed with use of an anterolateral thoracotomy (38%), median sternotomy (26%) and subxiphoid (20%) or subcostal (16%) approach. Perioperative mortality rate was 5.5% (all nonarrhythmic deaths). Implant defibrillation threshold ranged from 3 to 30 J (mean 15), with initial programmed shock energy ranging from 3 to 30 J (mean 22). Ventricular tachycardia/fibrillation sensing threshold ranged from 0.7 to 1.8 mV (median 1) and the tachycardia detection interval from 288 to 416 ms (median 320). Reprogramming of implant variables was necessary for reliable electrographic sensing (54 patients), programmed shock therapy (61 patients) and tachycardia detection rate (63 patients). Device activation for potential shock delivery occurred in 111 patients (55.5%) with actual shock delivery after ventricular tachycardia/fibrillation reconfirmation in 66 patients (33%). During follow-up study, there was a 1% arrhythmia mortality rate, 6.5% cardiac mortality rate and 10.5% total mortality rate. This study demonstrates that the programmable implantable pacemaker-cardioverter-defibrillator is effective in preventing arrhythmic death, yet reduces patient exposure to repeated shock therapy. Reprogramming is usually necessary during follow-up for optimal function.

Single-chamber ventricular pacing is not associated with worsening heart failure in sick sinus syndrome.

Ventricular pacing (with loss of normal atrioventricular synchrony) has been considered to have a role in the development or progression of congestive heart failure (CHF) in patients with sick sinus syndrome (SSS). No rigorous study has tested this hypothesis. Five hundred seven consecutive patients with SSS who received an initial pacemaker from January 1980 to December 1989 were studied. Atrial or dual-chamber pacemakers were implanted in 395 patients and ventricular pacemakers in 112. After a mean follow-up of 65 +/- 37 months, 97 patients (19%) developed new CHF or increased their New York Heart Association functional class. By univariate analysis, preimplant predictors for these events were left ventricular dysfunction (p < 0.001), valvular heart disease (p = 0.004), peripheral vascular disease (p = 0.005), diabetes (p = 0.02), coronary artery disease (p = 0.02), high New York Heart Association functional class (p = 0.03) and complex ventricular arrhythmia (p = 0.03). By multivariate analysis (logistic regression), the only predictors for CHF were valvular heart disease (p = 0.002; odds ratio [OR] 2.51), peripheral vascular disease (p = 0.003; OR 1.7) and complex ventricular arrhythmia (p = 0.027; OR 2.74). When the analysis was restricted to patients who had preimplant assessment of left ventricular function, independent predictors for CHF were left ventricular dysfunction (p < 0.001; OR 1.66), and complex ventricular arrhythmia (p < 0.001; OR 1.75). In conclusion, progressive or new-onset CHF is a consequence of the underlying cardiovascular disease. In the present population of patients with SSS, ventricular pacing mode was not associated with an increased incidence of CHF.

Chronic transvenous pacemaker lead removal using a unique, sequential transvenous system.

Transvenous removal of 43 consecutive chronic pacemaker leads was successful in 28 patients. For leads not removed by traction at the pacemaker connection terminal, a unique locking stylet was advanced through the inner coil lumen and engaged at the tip to allow traction without lead elongation. Leads not extracted with the locking stylet alone had traction maintained on the stylet as sheaths were advanced over the lead to dilate and detach any fibrous tissue adherent to the lead. By applying traction at the pacemaker connection terminal, 2 leads were removed. The locking stylet alone extracted 9 leads. Both the locking stylet and sheaths were necessary to explant 32 leads. There were 15 right atrial and 22 right ventricular leads completely removed. Additionally, 6 right ventricular leads were subtotally removed leaving only the tip in the right ventricular apex. Avulsed myocardium was removed with the lead in 1 patient without sequelae. A subacute hemothorax developed in 1 patient 18 days after discharge requiring drainage, and subclavian vein thrombosis developed in another, which was successfully treated with anticoagulation. Hypotension occurred in 1 patient during final positioning of new leads, which responded to conservative treatment. Chronic pacemaker leads can be reliably removed without thoracotomy. Both a unique locking stylet to allow traction without lead elongation and a sheath to dilate and detach adherent fibrous tissue are needed for consistent success. Recognized complications included myocardial avulsion without sequelae, subacute hemothorax, subclavian vein thrombosis and transient hypotension.

Long-term control of congestive heart failure with captopril.

The long-term effects of captopril therapy were assessed by sequential hemodynamic studies over a 6 month period in 19 patients with resistant congestive heart failure. Initial improvement during the first week of therapy was noted only in 11 and was marked by significant (p less than 0.005) increases in cardiac output and stroke volume, slowing of heart rate, and reduction of total peripheral resistance. Of the remaining eight patients, seven improved subsequently with maintained therapy so that by the end of 3 months of treatment only one patient failed to respond significantly. The hemodynamic index that reflected response most consistently was the shortening in pulmonary mean transit time. Simultaneously with clinical improvement there was a reduction in cardiopulmonary volume that reflected a reduction in pulmonary congestion and probably systemic vasodilation. Associated with these hemodynamic changes there was an increase in plasma renin activity and a significant reduction in plasma aldosterone, but these changes did not differ significantly between patients who responded markedly and those who responded moderately to converting enzyme inhibition. These results suggest that the response of congestive heart failure to captopril can occur gradually. Improvement was related to peripheral hemodynamic changes which led to a reduction in both total peripheral resistance and cardiopulmonary volume. The reduction in the plasma aldosterone/renin activity ratio was an effective marker of compliance.

Initial experience with the maze procedure for atrial fibrillation.

From January 1991 until May 1992, a total of 14 patients (mean age 48 years) underwent the maze procedure for refractory atrial fibrillation (mean duration, 7 years; mean number of antiarrhythmic medications, six). Three patients had had embolic events, one patient had had a cardiac arrest from flecainide, one had pulmonary fibrosis from amiodarone, and six of ten who were employed were temporarily disabled. Two patients underwent successful mitral valve repair in which the maze procedure was added as a secondary goal of the operation. Postoperative fluid retention was a problem in five patients (36%). Six patients (43%) were temporarily treated with an antiarrhythmic medication. Two patients (14%) with preoperative sick sinus syndrome required pacemakers. One patient was discharged from the hospital but died suddenly less than 1 month after the operation (7% operative mortality) of hyperkalemia caused by acute renal failure. All patients beyond 3 postoperative months (100% "cure") are receiving no antiarrhythmic medications, have sinus rhythm, or have p-wave tracking with ventricular pacing. Atrial contraction has been documented by cinegraphic magnetic resonance imaging studies and by Doppler echocardiography performed when sinus rhythm had resumed. The maze procedure is an extensive operation but is indicated for selected patients who have the severe sequelae of atrial fibrillation.

Potassium loading as adjunct treatment of repetitive ventricular arrhythmias.

To evaluate potassium supplementation as adjunct therapy for ventricular arrhythmias, consecutive normokalemic patients undergoing in-hospital antiarrhythmic therapy for ventricular tachycardia were randomly assigned to one of four groups: intravenous potassium chloride (Group I, 44 patients) v intravenous saline (Group II, 48 patients); and oral potassium chloride capsules (Group III 50 patients) v no additional treatment (Group IV, 47 patients). All groups underwent serial serum potassium determinations and 24-hour electrocardiographic monitoring. Analysis revealed no significant differences in ventricular ectopic activity among groups, and there was no significant association between serum potassium level and incidence of ventricular arrhythmias. We conclude that normokalemic patients undergoing antiarrhythmic therapy for ventricular tachycardia benefit little from concomitant short-term potassium supplementation.

The Maze procedure: surgical therapy for refractory atrial fibrillation.

Although atrial fibrillation is well tolerated by most patients, in some patients the consequences may be severe. The Maze procedure is a new open-heart operation that creates a carefully designed maze of incisions in the atrial myocardium; this maze then acts as an electrical conduit to channel atrial impulses from the sinoatrial node to the atrioventricular node. The Maze procedure has been shown to restore sinus rhythm and atrial systole (thus reducing the risk of thromboembolism), improve hemodynamics, alleviate palpitations, and eliminate the need for antiarrhythmic and anticoagulant drugs. We describe our first patient to undergo this operation.

Transcatheter electrical AV junction ablation: predictors of success.

The initial and long-term results of transcatheter electrical ablation in 29 patients with drug-refractory supraventricular tachyarrhythmias were analyzed. Ablation was immediately successful (defined as induction of chronic complete heart block) in 25 patients (86.2%). Among the group in whom ablation was unsuccessful, there were more patients with ectopic atrial tachycardia and a higher incidence of narrow QRS escape rhythm following the initial ablation. A His amplitude equal to or greater than 0.3 mV was correlated with success. Complications of ablation included deep venous thrombosis and ventricular arrhythmias. Post-ablation stress testing was superior to ambulatory monitoring in identifying early return of atrioventricular conduction.

Durability of bipolar coaxial endocardial pacemaker leads compared with unipolar leads.

BACKGROUND: The coaxial design allows for thinner bipolar endocardial pacemaker leads, but recent reports have suggested a higher incidence of failure for this sophisticated configuration. OBJECTIVE: To compare the long-term survival of bipolar coaxial and unipolar leads. METHODS: Retrospective follow-up. RESULTS: Between January 1, 1980 and June 30, 1991, 1142 bipolar coaxial leads and 1181 unipolar leads were implanted at the Cleveland Clinic. The mean follow-up was 33 +/- 32 months (range 1 to 138 months). Ten bipolar coaxial leads failed (0.88%), as did 9 unipolar leads (0.76%). At 5 years the cumulative survival was 98.6% for both types of leads; however, at 10 years the survival of bipolar coaxial leads was only 92.4% compared with 98.6% of unipolar leads (P = .03; relative risk 2.7, 95% confidence interval = 1.1 to 6.9). CONCLUSIONS: The sophisticated design of bipolar coaxial leads could be the cause of their increased vulnerability. The benefit-to-risk ratio of this design should be prospectively reevaluated.

Pacemaker and defibrillator combination therapy for recurrent ventricular tachycardia.

The judicious use of antitachycardia pacemakers can enhance the benefits of automatic implantable cardioverter defibrillators in certain patients. Both devices were implanted in 10 highly selected patients with drug-refractory pace-terminable sustained ventricular tachycardia. During the observation period of 8 +/- 4.8 months, the automatic pacemakers detected 1,542 episodes of ventricular tachycardia and appropriately managed 1,373. The automatic implantable defibrillator was activated at least once in every patient; on two documented occasions, the defibrillator discharged because the automatic pacemaker accelerated the tachycardia. Concomitant antiarrhythmic drugs could be reduced but not withdrawn. With meticulous device programming and testing, the two systems in combination can work synergistically to manage malignant ventricular arrhythmias in carefully selected patients.

Atrial pacemaker leads compared.

In order to analyze the impact of different polarity and electrode designs on the acute pacing and sensing characteristics of pacemaker leads, 80 patients with complete heart block or sinus node dysfunction undergoing pacemaker implantation received eight different leads from five manufacturers. Once the leads were positioned, volt and current thresholds, P wave, peak-to-peak, and slew rate were assessed prospectively. There was no statistically significant difference between acute pacing thresholds, sensing characteristics, or unipolar and bipolar pacing thresholds. Active fixation leads allow atrial mapping and lead placement in areas generally inaccessible to tined tip leads. This is an advantage, especially for patients with a history of open heart surgery.

Long-term follow-up of young adults following permanent pacemaker placement for complete heart block.

Young adults with nonsurgically induced complete heart block (CHB) do not necessarily have a benign prognosis and pacemaker (PM) implantation may be necessary. No one has reported long-term PM follow-up in young adults with CHB. We studied 13 patients aged 15 to 37 years (mean 24 years) at PM implantation. There were nine female and four male patients. All were functional class II or III (NYHA) before PM implantation. Syncope, dizziness, fatigue, shortness of breath, and dyspnea on exertion were the most common symptoms. Cardiac catheterization findings (11 of 13 patients) were normal in five, and additional cardiac anomalies were present in six. His bundle studies (9 of 13 patients) showed absent AH intervals in all patients, with HV intervals not identified in two, 20 to 30 msec in one, and 30 to 50 msec in six patients. Holter monitor recordings (8 of 13 patients) demonstrated CHB in all eight with intermittent second- to third-degree block in two of three patients. Two patients had occasional premature ventricular contractions. Stress exercise tests (9 of 13 patients) demonstrated increased ventricular rate response (although subnormal in some patients); symptoms developed in seven. One patient had ventricular ectopy. All 13 patients were contacted 3 months to 7 years (mean 4 years) after PM implantation. Two patients had died, but the deaths were not related to PM dysfunction. All patients who are currently alive had marked improvement in functional symptomatology and all are currently functional class I. CHB is not a benign condition in young adults and may require PM implantation, which improves symptoms and allows the patient to lead a normal life.

Safety and diagnostic yield of noninvasive ventricular stimulation performed via tiered therapy implantable defibrillators.

Extensive electrophysiological testing is critical for the effective utilization of sophisticated tachycardia detection and termination algorithms available in tiered therapy ICDs. To evaluate the safety and diagnostic yield of electrophysiological testing via noninvasive ventricular stimulation, we performed 294 electrophysiological studies in 154 patients (age 65 +/- 10; left ventricular ejection fraction 0.36 +/- 0.15) with tiered therapy ICDs. Stimulation was performed under methohexital anesthesia. A total of 918 sustained ventricular tachyarrhythmias were induced (3.1 +/- 2.5 per procedure): monomorphic VT, 550; ventricular flutter, 74; and VF, 246. The results of invasive and noninvasive programmed stimulation were compared for 79 patients who had both studies under similar treatment. Overall concordance was 83%, and did not differ significantly between patients who had the noninvasive stimulation via epicardial or endocardial pacing leads. VF could be induced in 206 of 257 studies (82%), and it was less likely to be induced in patients on amiodarone (74% vs 85%; P = 0.02), or beta blockers (55% vs 83%; P = 0.017). No patient presented a serious complication. Minor complications occurred during 39 studies: transient laryngospasm in 1, unintended delivery of an ICD shock to a conscious patient in 4; induction of sustained atrial fibrillation in 8; need for external rescue defibrillation shocks in 13; and delivery of inappropriate shocks for supraventricular rhythms in 14 studies. Noninvasive ventricular stimulation performed under methohexital anesthesia is safe. Its diagnostic yield compares favorably with that of conventional electrophysiological studies. VF can be induced in a majority of patients. There is good correlation between invasive and noninvasive programmed stimulation for induction of VT. Noninvasive ventricular stimulation may emerge as standard procedure for the initial programming and follow-up of ICDs.

Noninvasive assessment of ventriculo-atrial conduction and early experience with the tachycardia termination algorithm in pacemaker-mediated tachycardia.

Since the advent of physiologic dual chamber pacing systems, pacemaker-mediated tachycardia (PMT) has occurred and the need for invasive measurement of ventriculo-atrial conduction (VAC) has arisen. The variability in VAC and the potential for PMT often make it necessary to assess for the presence or absence of VAC at different points in time. We noninvasively evaluated 20 pacemaker patients for the presence or absence of VAC. We compared ventriculo-atrial conduction time (VACT) obtained with the atrial sense event maker with that obtained from Holter monitoring and invasive methods. The incidence of spontaneous (S) and induced (I) PMT and the efficacy of the tachycardia termination algorithm (TTA) was assessed. Fourteen of 20 had VAC with invasive or noninvasive methods. Twelve of 19 had PMT (63%); three were sustained (greater than 15 beats). We conclude that VACT assessed with the atrial sense event marker (ASEM) yielded a high correlation when compared to the Holter monitor data obtained utilizing our methodology. PMT is commonly a nonsustained (less than 15 beats) event, and the TTA is effective in sustained PMT. Myopotential sensing, atrial premature contractions and loss of atrial capture are common mechanisms in the initiation of PMT.

The usefulness of head-up tilt testing and hemodynamic investigations in the workup of syncope of unknown origin.

To enhance the clinical evaluation of patients suffering from recurrent syncope of unknown origin, the integrity of mechanisms controlling blood pressure was examined in 151 patients utilizing a screening tilt test. Ninety-eight patients had an abnormal blood pressure and/or heart rate response to tilt testing, including provoked syncopal attacks in 63 patients. Whenever indicated, the screening tilt test was followed by blood volume and hemodynamic determinations, as well as autonomic nervous system testing to identify contributing pathophysiological abnormalities (hypovolemia, venous pooling, autonomic dysfunction). Detailed analysis of this battery of tests allowed us to conclude that: (1) The tilt test is commonly a provocative tool in the workup of patients with recurrent syncope due to vasovagal - vasodepressor reactions and other abnormalities of blood pressure regulation; (2) Its usefulness is augmented by associated hemodynamic and blood volume evaluations; (3) The identification of contributory pathophysiological mechanisms of blood pressure control facilitates specific therapeutic interventions.