Sinus node recovery after 25 years of atrial flutter.

This case report demonstrates that the sinus node can recover relatively quickly even after being suppressed by atrial flutter for 25 years, and that a permanent pacemaker may not always be necessary in all patients with sinus arrest after a successful atrial flutter ablation.

Case report: is this SVT or VT? An exception to the rule.

This case illustrates the difficulties sometimes encountered by clinicians when using algorithms in diagnosing a wide-complex tachycardia based on a 12-lead EKG.

Histopathological correlation of ablation lesions guided by noncontact mapping in a patient with peripartum cardiomyopathy and ventricular tachycardia.

A patient with peripartum cardiomyopathy developed a nearly incessant nonsustained VT. Guided by a noncontact mapping system, the tachycardia was mapped to the mid-septum of the right ventricle and ablated. Despite transient success, the tachycardia recurred and the patient subsequently died of multiorgan failure. Histopathological correlation of the ablation site revealed a nontransmural lesion that may have contributed to the failure of the ablation.

Internal transcardiac pericardiocentesis for acute tamponade.

If the catheter is still in the pericardium when tamponade is recognized during catheterization or electrophysiologic procedures, it can be used for definitive aspiration and relief of tamponade. This is physiologically beneficial to the patient, and psychologically beneficial to both patient and medical staff.

Cardiac memory after radiofrequency ablation of accessory pathways: the post-ablation T wave does not forget the pre-excited QRS.

INTRODUCTION: Normalization of the pre-excited QRS following ablation is accompanied by repolarization changes but their directional relationship to changes in ventricular activation has not been well characterized. METHODS: Accordingly, we measured QRS and T wave vectors and QRS-T angles from 12 lead ECG recordings immediately before and after accessory pathway (AP) radiofrequency ablation in 100 consecutive patients. Patients with bundle branch block, intraventricular conduction defect or intermittent pre-excitation were excluded, leaving a study group of 45 patients: 35 with pre-excitation and 10 with concealed APs. RESULTS: With AP ablation, changes occurred in the QRS and T wave vectors and QRS-T angles that were essentially equal and opposite, so that the newly normalized QRS complex and QRS vector were accompanied by a T wave whose vector approximated that of the pre-ablation QRS vector. This tended to maintain a large QRS-T angle: 72 degrees +/- 50 degrees before, and 54 degrees +/- 34 degrees after QRS normalization (p = NS). A QRS-T angle >40 degrees was found before and after ablation in 22/35 patients (63%) with baseline pre-excitation; but never in patients with a concealed AP (p = 0.001). The angle between the pre-excited QRS and the post-ablation T wave was 35 degrees +/- 37 degrees, and

Lead failure due to the subclavian crush syndrome in a patient implanted with both standard and thin bipolar spiral wound leads.

Subclavian crush syndrome is a well-described cause of pacemaker lead failure resulting from an entrapment of a lead or leads between the clavicle and the first rib. A new thinner lead (ThinLine) was designed to minimize this complication. Our patient developed atrial and ventricular lead subclavian crush syndrome with both conventional and thin leads.

Current perspectives on pacing therapy in cardiomyopathies.

Hypertrophic cardiomyopathy (HCM) is a complex disease that is sometimes difficult to control with medical therapy. Surgical treatment is highly effective but can be associated with significant morbidity and mortality. It has been suggested in uncontrolled studies that patients with obstructive HCM may improve symptomatically when treated with dual-chamber pacing. Several hypotheses have been suggested to explain this phenomenon, but the mechanism still remains unclear. Many recent randomized trials showed much less uniform effects on symptoms than previously reported. These results indicate the need for further comprehensive inquiry into the effects of pacing on HCM before it can be recommended for widespread use. The data on the benefit of pacing therapy in dilated cardiomyopathy are much more recent and limited. Initial optimistic reports have been only partially confirmed.

Insulation lead failure: is it a matter of insulation coating, venous approach, or both?

Lead insulation material and implant route have a major impact on lead reliability and durability. We compare the incidence of lead insulation failure resulting from both the venous approach and insulation type. Two hundred ninety consecutive leads were followed for a mean period of 57 +/- 30 months; leads with < 1 year follow-up were excluded. There were 116 Silicone Rubber insulated leads and 174 with polyurethane (151 Pellethane 80A and 23 Pellethane 55D) insulation; 279 leads were bipolar and 11 unipolar; 274 leads were implanted in the ventricle and 66 in the atrium. The venous route was the subclavian vein for 170 leads (58%) and the cephalic vein for 120 leads (42%). Insulation failure was diagnosed when a single sign of oversensing, undersensing, failure to capture, early pulse battery depletion, and lead impedance < 250 omega was present. Measurement of lead impedance was performed intraoperatively at implantation and during lead revision or pulse generator replacement. Lead failure caused by conductor coil fracture was not considered. There were 13 lead insulation failures, all among leads with polyurethane insulation (12 Pellethane 80A and 1 Pellethane 55D). Eleven failures (10%) occurred when the subclavian vein and 2 (3%) when the cephalic vein approach was used. The cumulative survival rate of polyurethane and silicone rubber insulated leads was 88.7% and 100%, respectively (P = 0.02); the cumulative survival rate of polyurethane insulated leads was 83.2% when the subclavian vein and 95.1% when the cephalic vein were used (P = 0.03). The mean time to polyurethane lead failure when the subclavian vein approach was used was 54 +/- 17 months and when the cephalic route was 73 +/- 4 months (P < 0.02). By multivariate analysis, the route of entry was found to be a significant variable related to polyurethane insulated lead failure (P < 0.05). At lead revision failure to capture was present in 7, oversensing in 4, and undersensing in 2 instances; impedance was < 250 omega in all cases. Pellethane 80A insulated leads are prone to insulation failure, but more when the subclavian vein is used, rather than the cephalic vein.

Transtelephone monitoring for pacemaker follow-up 1981-1994.

Transtelephone monitoring (TTM) is capable of detecting pacemaker pulse generator malfunction, battery depletion, and lead failure. The accuracy of TTM was analyzed by a review of Montefiore Medical Center records between October 1981 and March 1994. Each group of transmissions from a single patient, starting with implant and ending with a pacemaker operation, was defined as a closed cycle (CLOSE), if undergoing continuing follow-up at the time of analysis, as a continuing cycle (CONT), and if a cycle had ended with death or loss to follow-up, an open cycle (OPEN). TTM records of 2,632 patients were analyzed, providing 3,291 cycles. There were 731 CONT, 433 CLOSE, and 2,127 OPEN cycles; 331 procedures were indicated by TTM, of which 279 were impending depletion, 30 sudden depletion, and 22 lead malfunctions. Of the 102 procedures not indicated by TTM, 85 were for nonurgent reasons (recall: 41; DDD upgrade: 16; patient/MD request: 28) and 17 for urgent reasons. In patients followed by TTM who had a lead problem, 22 were detected by TTM before clinical manifestations and 16 were not. There were no cases in which TTM follow-up did not detect battery depletion. The total number of TTM contacts, available for 3,094 cycles, was 88,654 (range, 1-163, median 19), of which 0.4% yielded a procedure. During the same period, 75% of all secondary interventions during the first 2 years occurred during the first 2 months after implant because of lead malfunction, with a subsequent SI rate of 0.005 per month for the third through the twenty-fourth months.

Effect of varying atrial sensitivity, AV interval, and detection algorithm on automatic mode switching.

UNLABELLED: Automatic mode switching (AMS) is absolutely dependent on atrial tachyarrhythmia detection. The effects of programming several features that could influence tachyarrhythmia detection were assessed in 18 patients (six women; mean age 64 years) with pacemakers having AMS capability. The atrial electrogram amplitude in sinus rhythm at implant (SR-EGM), last measured atrial sensing threshold prior to tachycardia (A-SENS), and atrial sensing threshold for effective AMS during atrial tachyarrhythmia (AMS-SENS) were obtained. Additionally, ten patients had AV intervals increased from 60 to 200 ms, while seven patients had detection algorithms made more stringent from 5 beats at 150 beats/min to 11 beats at 200 beats/min to assess their effects on AMS efficacy. RESULTS: Sensitivities:Mean SR-EGM = 3.55 mV; mean A-SENS = 2.06 mV; and mean AMS-SENS = 1.46 mV. Fourteen patients developed atrial fibrillation and four atrial flutter. Thirteen of 14 patients who developed atrial fibrillation sensed adequately at > or = 1.0 mV in normal sinus rhythm (NSR), but only six patients had effective AMS at these settings in atrial fibrillation. Three of four patients who developed atrial flutter had effective AMS at > or = 2.0 mV. AV Interval:AMS was effective in eight of ten patients at AV intervals up to 200 ms. One patient lost AMS at an AV interval of 120 ms. Algorithm: In two of seven patients, AMS was not effective if the detection algorithm was more stringent than five beats at 150 beats/min. CONCLUSIONS: (1) In atrial fibrillation, effective AMS requires more sensitive atrial settings than in NSR; (2) AV intervals as short as 120 ms can interfere with AMS function; and (3) More stringent detection algorithms may be inappropriate for effective AMS function.

Lead fracture in cephalic versus subclavian approach with transvenous implantable cardioverter defibrillator systems.

Lead fracture, occurring in approximately 1%-4% of patients, is an infrequent, but potentially catastrophic complication of permanent pacing systems. Its incidence in transvenous defibrillator systems has not been established. We analyzed data from 757 patients undergoing implantation of transvenous cardioverter defibrillator systems using the Medtronic Transvene Lead system between October 20, 1989 and June 25, 1992 to determine if site of venous approach influenced incidence of lead fracture. All patients received a 3-lead system in 1 of 3 configurations: (1) right ventricle/superior vena cava/subcutaneous patch; (2) right ventricle/coronary sinus/subcutaneous patch; or (3) right ventricle/superior vena cava/coronary sinus. Of 767 right ventricular leads placed, 523 were placed via the subclavian vein, 221 via cephalic vein, and 18 via the internal jugular (5 leads were implanted using another vein). The total number of leads is greater than the total number of patients, as five patients received a second defibrillator system if the initial system was explanted and reimplanted for any reason. Seven patients (0.9%) had right ventricular lead fracture, presenting with inappropriate defibrillator shocks (1), loss of pacing ability (3), both loss of pacing ability and inappropriate shocks (1), or increased pacing threshold (2). All patients required reoperation. All had leads placed by the subclavian venous approach, with chest X ray confirming fracture at the clavicle-first rib junction in 6 of 7 cases. Using Fisher's Exact test, the difference in lead fracture between subclavian and cephalic vein implant approached statistical significance (P = 0.08). The trend toward increased lead fracture incidence with leads placed via subclavian vein suggests that cephalic vein approach may be preferable to avoid this complication.

Suppression of ventricular output by noise in the atrial channel in a dual chamber pacemaker.

In a pacemaker dependent, 60-year-old man with complete heart block, programming high (5.0 V and 1.0 ms) atrial output and 5.0 volt and 0.5 ms ventricular output while in the DDD mode of a pulse generator, resulted in loss of ventricular channel output with resulting asystole, while the simultaneous, pulse generator produced ECG interpretation channel falsely indicated continuing ventricular channel output. Ventricular pacing was promptly restored by programming to the emergency VVI mode. At later operation the atrial lead was determined to be defective, with a low impedance, while the ventricular lead was intact (lead impedance telemetry was not available). The manufacturer has acknowledged a pulse generator design anomaly that may occur in the setting of a low atrial impedance and issued a Health Safety Alert.

Long-term follow-up of pacemaker lead systems: establishment of standards of quality.

The functional details of all 5,405 pacemaker leads implanted on Montefiore Medical Center were contemporaneously recorded between 1960 and May 31, 1993. Some models have been observed for as long as 24 years. Ventricular leads with more than 50 and atrial leads with more than 30 implanted units have been continually and repeatedly subjected to actuarial cumulative survival rate (CSR) analysis during which clinical decisions, such as continued lead implantation, cessation of use, or early withdrawal from service, were made. CSR evaluation for many lead models by the Mantel-Haenszel method allowed comparison of the performance of contemporaneous lead models with older and new technologies. No effect on lead longevity, durability, on mode of end of lead service, lead removal independent of function (e.g., for infection), materials, or physiological failure was found due to an operator or anatomical route of venous access. Multifilar silicone rubber insulated leads have longevity (CSR) superior to monofilar silicone rubber leads. The cumulative survival of silicone rubber insulated monofilar models 6901, 6907, continuous lead (CL), 4 mm, and 2 mm was 79%-91%, 20 years after implantation. Multifilar silicone rubber insulated models 6961 and 4116 had a cumulative survival of 99%-100%, 15 years after implantation. Among multifilar polyurethane insulated leads, distinct longevity differences exist between formulations and contemporaneous models that are normally similar, yielding a bimodal longevity distinction; model 6971 (ventricular) has 95% CSR and 6991U (atrial) has 94% CSR, 10 years after implantation. Both performed less well than other contemporaneous models, which approximate 100% CSR. The 10-year CSR for leads implanted between 1960-1975 (Era 1) is 98.7%, and the 10-year CSR of leads implanted between 1981-1985 (Era 3) is 99.4%. Comparison of individual lead models, and all leads of specific eras, allows development of survival expectations and standards of quality for comparison between contemporaneous lead models and different eras of manufacture. As the highest available lead CSR sets the standard, statistical deviation of a model from the best performance of a specific era should be considered as an indication of reduced quality.

Direct and telemetered lead impedance.

OBJECTIVES: We undertook this study to determine whether telemetered lead impedance measurements (LIM) can be correlated with direct LIM and to determine the stability of LIM over time when measured directly and via telemetry. METHODS: Direct LIM and telemetered LIM were measured in 91 patients; 101 leads during initial implantation and 40 leads during pulse generator replacement. Differences in direct LIM measured during initial implant and pulse generator replacement (direct-direct) were compared in 41 patients (28 atrial leads and 37 ventricular leads). The stability of telemetered LIM obtained immediately postoperatively, at 1 month and 1 year, postimplantation was assessed in 50 patients (23 atrial and 49 ventricular leads). RESULTS: In atrial leads acute direct LIM was 633.9 +/- 18.4 omega versus 575.8 +/- 18.5 omega for telemetered LIM (r = 0.58), and chronic direct LIM was 670.9 +/- 49.3 omega versus 607.0 +/- 36.3 omega for telemetered LIM (r = 0.87). In ventricular leads acute direct LIM was 747.3 +/- 16.9 omega and 684.7 +/- 16.4 omega for telemetered LIM (r = 0.69), and chronic direct LIM was 674.8 +/- 29.9 omega and 625.2 +/- 28.5 omega for telemetered LIM (r = 0.68). The mean direct-direct LIM rose 124 omega (P < 0.001) in atrial leads and 10 omega (P = NS) in ventricular leads. Telemetered LIM for atrial leads was 581.0 +/- 27.6 omega immediately postimplantation compared to 625.7 +/- 34.8 omega at 1 month and 754.1 +/- 43.0 omega at 1 year. Telemetered LIM for ventricular leads was 661.3 +/- 17.5 omega at implant, 684.6 +/- 20.7 omega at 1 month and 724.7 +/- 22.7 omega at 1 year. CONCLUSIONS: There is a good but limited correlation between direct and telemetered LIM. Mean direct LIM obtained at initial implantation is similar to that measured at pulse generator replacement. The telemetered LIM is stable over the first month postimplantation but tends to rise during the first year of follow-up and substantial changes in impedance are not uncommon in individuals with normal function. There is a tendency for LIM to rise with lead maturation. If telemetered LIM is to be followed over time, a baseline telemetered value should be obtained immediately postoperatively.

Surgical removal of infected transvenous pacemaker leads.

Infection, though uncommon, can be the most lethal of all potential complications following transvenous pacemaker implantation. Eradication of infection associated with pacemakers requires complete removal of all hardware, including inactive leads. Since 1972, 5,089 patients have had 8,508 pacemaker generators implanted at Montefiore Medical Center. There were 91 infections (1.06%); four of our patients required surgical removal. Nine additional patients were referred for surgical removal of infected transvenous pacemaker leads from other institutions. Surgical methods for removal included use of cardiopulmonary bypass or inflow occlusion. Surgery may be safely used in unstable or elderly patients and should not be reserved as a last resort. This article reviews our surgical experience removing infected pacemaker leads at Montefiore Medical Center.

Transcutaneous cardiac pacing during thoracic surgery. Feasibility and hemodynamic evaluation by transesophageal echocardiography.

BACKGROUND: Occasionally, emergency perioperative pacing is necessary. Transcutaneous cardiac pacing is noninvasive, safe, and readily available. Its feasibility and hemodynamic effects during thoracic surgery and one-lung ventilation have not been established. METHODS: Twenty anesthetized patients (aged 25-70 yr) without cardiac disease undergoing elective pulmonary resection (right n = 10, left n = 10) were studied in normal sinus rhythm and during transcutaneous cardiac pacing. Patients were paced in supine and lateral decubitus positions (with closed and opened chest) at the minimal current necessary to produce ventricular capture. Invasive arterial monitoring permitted calculation of mean arterial pressure, and transesophageal echocardiography was used to assess atrial and ventricular wall motion and the evaluation of transmitral flow. Twelve patients underwent Doppler analysis of pulmonary venous flow. RESULTS: Pacing was achieved in all patients, with a mean threshold of 86.9 +/- 20.6 mA for the right thoracotomy group, and 106.7 +/- 16.2 mA for the left thoracotomy group. The mean paced heart rates for the right and left thoracotomy groups were 101.6 +/- 18.2 and 105.4 +/- 11.5 beats/min, respectively. During pacing, all patients sustained reversible transient decrements in mean arterial pressure (9-19%) from baseline, the loss of AV synchrony, and the development of paradoxical ventricular septal wall motion. No patient had significant mitral regurgitation during sinus or paced rhythms. Decreased systolic pulmonary venous flow velocity and abnormal systolic flow reversal were seen during pacing in 11 of the 12 patients studied. CONCLUSIONS: Transcutaneous cardiac pacing is effective in patients undergoing thoracotomy and one-lung ventilation. Its use in patients in normal sinus rhythm induces reversible decrements in mean arterial pressure because of the effects of altered atrioventricular association, ventricular wall motion, and pulmonary venous return.

Variability of cardiac output as determined by impedance cardiography in pacemaker patients.

Hemodynamic assessment of pacemaker patients is necessary for gauging responses to changes in programming or other conditions affecting circulation. Impedance cardiography permits noninvasive determinations of cardiac output at short intervals but data regarding variability of this method in patients with pacemakers is unavailable. Thirty-eight patients with pacemakers (24 with DDD and 14 with VVI devices) and 6 normal subjects were studied. Each patient was studied in the supine position and repeated impedance measurements were obtained. Fourteen patients were studied during sinus rhythm, 24 were studied during DDD pacing, and 32 patients were studied during VVI pacing. Variability was assessed by methods that analyzed both serial measurements and variability between 2 consecutive and nonconsecutive measurements. The mean indexes and coefficients of variation of 2 and serial measurements in sinus rhythm and DDD were 4%; in VVI it was 6%. The precision of impedance cardiography in all pacing modes, as demonstrated by analysis of variability, indicates that detected changes of stroke volume and cardiac output > 7% on serial (2 and more) measurements, performed by the same operator and during the same session, represent true hemodynamic alterations with 95% confidence. The precision of impedance cardiography demonstrated may be comparable or superior to other frequently used techniques, and the data obtained are valuable both investigationally and clinically.