Biomedical subjects

David Bar-Lev

Publications and source records attributed to David Bar-Lev.

6 recordsLinked to original sources

PubMed2006

Mechanism of diastolic mitral regurgitation in candidates for cardiac resynchronization therapy.

It was hypothesized that restricted diastolic leaflet motion is implicated not only in the mechanism of systolic mitral regurgitation (MR) but also in the mechanism of diastolic MR observed in patients with severe heart failure. Cardiac resynchronization therapy (CRT) can oppose increased mitral leaflet tethering by increasing transmitral pressure, thereby providing an opportunity to explore this hypothesis. A total of 26 consecutive candidates for CRT with diastolic MR were compared with 26 candidates without diastolic MR. Maximal diastolic mitral leaflet opening and inflow direction and measures of mitral valve apparatus (i.e., mitral annular diameters, calculated mitral annular area, and tethering distance) were assessed from the apical 4-chamber view before and during CRT. There were no significant differences in New York Heart Association functional class, ejection fraction, QRS duration, PR interval, systolic MR grade, or 2-dimensional geometry of the mitral valve apparatus between the groups. Patients with diastolic MR had more restricted maximal diastolic leaflet openings (54 degrees +/- 17 degrees vs 71 degrees +/- 11 degrees , p = 0.003) and substantially smaller inflow angles (66 degrees +/- 7 degrees vs 79 degrees +/- 9 degrees , p = 0.0003) compared with patients without diastolic MR. After the institution of CRT, diastolic MR was eliminated in all patients, although there were no significant changes in any of the parameters of mitral valve apparatus. In conclusion, abnormal mitral valve tethering is a constitutive element of the mechanism of diastolic MR in patients with left ventricular dysfunction. Its acute resolution after CRT does not seem to be caused by changes in mitral valve geometry but rather by an increase in transmitral closing forces.

Cardiac Pacing, Artificial↗

PubMed2006

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. BACKGROUND: The role of CRT in patients with wide QRS and HF due to RVAP is less well established than in other CRT candidates. METHODS: Ninety-eight consecutive patients with CRT were studied (mean age 70, mean ejection fraction 0.23). Group A: patients having RVAP prior to CRT implantation (n = 25), group B: patients without prior RVAP (n = 73). Clinical and echocardiographic parameters were recorded prior to, and 3 months after, CRT implantation. RESULTS: Group A patients had a wider QRS at baseline compared to group B (203 +/- 32 ms vs 163 +/- 30 ms respectively, P < 0.001), and a shorter 6-minute walking distance (222 +/- 118 m vs 362 +/- 119 m, respectively, P < 0.005). Otherwise, clinical and echocardiographic parameters were not different. At follow up, group A patients had an average 0.7 +/- 0.5 decrease in their NYHA functional class, compared to 0.3 +/- 0.7 in group B patients (P < 0.05). Six-minute walking distance increased by 93 +/- 113 m in group A, versus 36 +/- 120 m in group B (P = 0.22). There was no difference in echocardiographic response to CRT between the groups. CONCLUSIONS: HF patients with prior RVAP demonstrate clinical improvement after upgrading to CRT that is comparable, and in some aspects, even better than that observed in HF patients with native conduction delay who undergo de novo CRT implantation.

Aged↗

PubMed2005

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. SUBJECTS AND METHODS: A total of 208 consecutive patients were randomized for implantation with a Medtronic 4568 JL model (n = 103) versus a Medtronic 4068 SL model (n = 105), and all lead-related measurements and complications were recorded. RESULTS: Lead-related complications occurred in JL and SL with similar frequency (6% and 9%, respectively, P = 0.45). Lead dislodgment occurred in 8 (7.8%) cases in SL versus none in JL (P = 0.004). Lead malfunction and excessive pacing thresholds without macrodislodgment occurred more frequently in JL (11; 10.7%) than in SL (4; 3.8%), P = 0.055. Lead material failure (insulation break) occurred only once in SL at the 5-year checkup. Most complications occurred during the first year after implantation. Other events occurred in both leads with similar frequency and included: death in 39 and 35, loss of follow-up in 8 and 6, and development of atrial fibrillation in 9 and 15 patients, respectively. Of those who completed follow-up, lead impedance and pacing threshold increased significantly in both groups. P wave decreased in SL but not in JL. CONCLUSION: More dislocations occurred in SL, but were counterbalanced by more lead malfunctions and excessive pacing thresholds in the JL group. Both leads demonstrated minor deterioration in electrical measurements during follow-up, with only 1 case of lead material failure in SL. Overall, both groups demonstrated favorable lead performance throughout follow-up.

Aged↗

PubMed2005

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. METHODS: CRT systems capable of multiple LVP configurations (Guidant models H155 and H145) were implanted in 43 patients (study group). An additional 49 patients (control group) received CRT systems (Guidant, Medtronic, Biotronik, St. Jude Medical, various models) lacking this feature. RESULTS: Overall, acute high (> or =2.5 V/0.5 ms) LVP thresholds were encountered in 13 (30%) of the study group, and 25 (50%) of control group patients (P = 0.03). PNS was encountered in 5 (12%) of the study group and 12 (24%) of control group patients (P = 0.13). All cases of high LVP thresholds and PNS in the study group were managed by switching to a different LVP configuration, while high thresholds remained in control group patients, and PNS was managed by replacing the lead. The CS lead was successfully placed in a lateral branch in 95% of study group, compared to only 77% of control group patients (P = 0.004). CONCLUSIONS: Multiple LVP configurations were clinically useful in a significant number of patients undergoing CRT system implantation by helping to overcome high LVP thresholds and PNS, and by providing more flexibility in placing the LV lead.

Aged↗

PubMed2004

Pericarditis following permanent pacemaker insertion.

BACKGROUND: The appearance of pericarditis following insertion of a permanent pacemaker is not widely acknowledged in the literature. OBJECTIVES: To describe our experience with pericarditis following 395 permanent pacemaker implantations over 2 years. METHODS: We retrospectively reviewed the medical records of 395 consecutive patients in whom new pacing systems or pacemaker leads had been implanted over a 2 year period. We searched the records for pericarditis that developed within 1 month after pacemaker implantation according to the ICD-9 code. The incidence, clinical picture, response to treatment, and relationship to lead design and location were studied. RESULTS: Eight cases (2%) of pericarditis following implantation were detected. Clinical manifestations in all patients were similar to those of post-pericardiotomy syndrome and included chest pain (n = 7), friction rub (n = 1), fever (n = 2), fatigue (n = 2), pleural effusion (n = 2), new atrial fibrillation (n = 2), elevated erythrocyte sedimentation rate (n = 4), and echcardiographic evidence of pericardial effusion (n = 8). All affected patients had undergone active fixation (screw-in) lead implantation in the atrial position. The incidence of pericarditis with screw-in atrial leads was 3% compared to 0% in other cases (P < 0.05). CONCLUSIONS: Pericarditis is not uncommon following pacemaker implantation with active fixation atrial leads. Special attention should be paid to identifying pericardial complications following pacemaker implantation, especially when anticoagulant therapy is resumed or initiated. The use of passive fixation leads is likely to reduce the incidence of pericarditis but this issue should be further investigated.

Adrenal Cortex Hormones↗

PubMed2003

Managing pacemaker safety alerts: experience with three successive models of a single manufacturer.

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.

Adolescent↗