David Bar-Lev

Programmable multiple pacing configurations help to overcome high left ventricular pacing thresholds and avoid phrenic nerve stimulation.

Background: High left ventricular pacing (LVP) thresholds and phrenic nerve stimulation (PNS) are common problems with cardiac resynchronization (CRT). Newer systems capable of multiple LVP configurations may help overcome these problems without the need for reoperation.

Improvement of Congestive Heart Failure by Upgrading of Conventional to Resynchronization Pacemakers

Aims: To compare the clinical response of patients with right ventricular apical pacing (RVAP) upgraded to cardiac resynchronization therapy (CRT) to that of previously nonpaced heart failure (HF) patients who had de novo CRT implantation.

Tilt training: does it have a role in preventing vasovagal syncope?

Background: Vasovagal syncope is one of the most common medical conditions in young adults. Previous trials have shown effectiveness of tilt training in treating this condition. We conducted a prospective, randomized study in order to evaluate the role of tilt‐training in young adults with vasovagal syncope.

LQT5 masquerading as LQT2: a dominant negative effect of KCNE1-D85N rare polymorphism on KCNH2 current.

AIMS KCNE1 encodes an auxiliary subunit of cardiac potassium channels. Loss-of-function variations in this gene have been associated with the LQT5 form of the long QT syndrome (LQTS), secondary to reduction of I(Ks) current. We present a case in which a D85N rare polymorphism in KCNE1 is associated with an LQT2 phenotype. METHODS AND RESULTS An 11-year old competitive athlete presented with mild bradycardia and a QTc interval of 470 ms. An LQT2 phenotype, consisting of low-voltage bifid T waves, was evident in the right precordial electrocardiogram leads. During the tachycardia phase following adenosine, QTc increased to 620 ms. Genetic analysis revealed a rare heterozygous polymorphism in KCNE1 predicting the substitution of asparagine for aspartic acid at position 85 of minK (D85N). Patch clamp experiments showed that KCNE1-D85N, when co-expressed with KCNH2 in TSA201 cells, significantly reduced I(Kr). Homozygous co-expression of the mutant with KCNH2 reduced I(Kr) tail current by 85%, whereas heterozygous co-expression reduced the current by 52%, demonstrating for the first time a dominant-negative effect of D85N to reduce I(Kr). Co-expression of the mutant with KCNQ1, either homozygously or heterozygously, produced no change in I(Ks). CONCLUSIONS Our results suggest that a rare polymorphism KCNE1-D85N underlies the development of an LQT2 phenotype in this young athlete by interacting with KCNH2 to cause a dominant-negative effect to reduce I(Kr). Our data provide further evidence in support of the promiscuity of potassium channel β subunits in modulating the function of multiple potassium channels leading to a diversity of clinical phenotypes.

Randomized Comparison of J-Shaped and Straight Atrial Screw-in Pacing Leads

OBJECTIVE To study the importance of a J shape in atrial pacing leads. PATIENTS AND METHODS We compared in a randomized controlled study acute and chronic results with 2 steroid-eluting, polyurethane, screw-in atrial lead models that differ only in shape. A total of 208 patients were randomized to have implantation of either a straight atrial lead (n = 105) or a J-shaped atrial lead (n = 103). Patients were followed up for 1 year. RESULTS On implantation, there were no significant differences between leads in rates of failure to implant, implant measurements, number of attempts to achieve an acceptable position, and fluoroscopy times. Before discharge and at 3-month and 1-year follow-up, electrical measurements showed no statistical differences between leads. During the first year after implantation, there were 2.9% early dislodgments (< 1 week after implantation) and 2.9% late dislodgments in the straight lead group (5.9% rate of all dislodgments) vs no dislodgments in the J-shaped lead group (P = .01). There was a trend toward higher rates of exit block and lead malfunction in the J-shaped lead group. Rates of pericardial complications, subclavian/axillary thrombosis, and chronic atrial fibrillation were the same in both groups. CONCLUSIONS Both leads appear to have an equally favorable performance profile for 1 year of follow-up. The J-shaped lead seems to be more stable and have fewer dislodgments, although it may have a somewhat higher malfunction rate.

Long-Term Performance of Screw-In Atrial Pacing Leads: A Randomized Comparison of J-Shaped and Straight Leads

Objective: In this prospective, randomized, control study we compared performance of J‐shaped (JL) and straight atrial leads (SL) with active (screw‐in) fixation mechanism, over a 5‐year follow‐up period.

Managing Pacemaker Safety Alerts

This report describes the experience of a large pacemaker center during three successive replacement operations due to safety alerts involving three models from the same manufacturer. Between March 1993 and May 1999, 210 patients were implanted with three DDD pacemaker models (Sorin Biomedica, Saluggia, Italy) that were subsequently subject to safety alerts. Pacemaker records were reviewed for complications related to device malfunction, and those secondary to the replacement procedure. Pacemaker malfunction was observed in 16.4% of units despite much lower estimates from the company (range 1–4%). With the exception of one, all units were replaced. Malfunctions were discovered in 7 of 20 pacemakers following an urgent call for follow‐up issued as a result of the alert. Twenty units implanted as substitutes for those replaced following the first alert turned out to be subject to the third alert. Significant clinical consequences of malfunction occurred in 5.3% of patients including a near fatal event in one case, while complications related to the replacement procedure occurred in 8.3% of patients, including one fatality. On the issuance of a safety alert, failure rates in a particular center may be higher than published by the manufacturer, and should prompt action by the center to weigh local incidence of device failure against complications of replacement procedures. When device failure mechanism is not entirely clear, particularly in cases of successive model failures, replacement devices from a different manufacturer should be considered. (PACE 2003; 26:2283–2288)

Multiple pulse generator malfunctions with a dual chamber pacemaker.

LIPCHENCA, I., et al.: Multiple Pulse Generator Malfunctions with a Dual Chamber Pacemaker. The aim of this study was to evaluate the dual chamber uni/bipolar pacemaker Minidual 50, manufactured by Sorin Biomedica. Between 1995 and 1998, 66 Minidual 50 models were implanted at the Heart Institute. During the follow‐up period of 33 ± 12.8 months (range 0–50 months), total function loss in seven (10.6%) units and false threshold measurement of sensing and pacing in three (4.5 %) patients were observed. Average time from implantation to malfunction was 37 months (range 28–42). Malfunction was unrelated to battery status and could not be predicted by any measures obtained during the pacemaker follow‐up period. Kaplan Meyer survival curve predicted a 70% 4‐year malfunction‐free survival of that pacemaker model. Given this high rate of total malfunction and the unpredictable nature of its occurrence, the authors recommend the replacement of all remaining Minidual 50 units at risk, at least in dependent patients.

Multiple Adverse Events with a Dual Chamber Pacemaker

The aim of the study was to evaluate our experience with Physiocor 400T, a dual chamber unipolar pacemaker manufactured by Sorin Biomedica. Between March 1993 and December 1994, 63 units of that model were implanted at our center. Patients were followed for 46 ± 16 months. By the end of follow‐up, 15 patients had died, 1 patient was lost to follow‐up, and two units had been replaced for unrelated reasons. During follow‐up the following phenomena had been observed: (1) Spontaneous backup reversion (VOO, 80 ppm) in 6 (9.5%) of 63 patients. In three patients this phenomenon was accompanied by concomitant ineffective pacing artifacts at 130 beats/min with very low pulse widths. (2) Unexpected battery depletion (EOL) occurred in 3 (5%) of 63 patients; two of the three occurred within weeks of routine evaluation that confirmed normal battery status. (3) Early elective replacement time (ERT) unpreceded by a gradual drop in magnet rate in 2 (3.2%) of 63 patients. (4) Total loss of telemetry without change in pacing mode in 1 (1.6%) of 63 patients. The estimated event‐free 5‐year survival of this model was 46%. In conclusion, 12 (19%) of 63 patients had adverse events with Physiocor 400T pacemakers. The potential risk of asynchronous pacing for prolonged periods and the risk of unexpected EOL warrants consideration of elective replacement of all remaining units.