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Biomedical subjects

Amos Katz

Publications and source records attributed to Amos Katz.

15 recordsLinked to original sources
PubMed2006

Crosstalk between L-type calcium channels and ZnT-1, a new player in rate-dependent cardiac electrical remodeling.

Crosstalk between two membrane transport systems is an established mechanism underlying regulation. In this study, we investigated the interaction between ZnT-1, a putative plasma membrane zinc transporter, and L-type voltage-dependent calcium channels (LTCC). In the atrium of the myocardium decreased activity of the LTCC is a dominant feature of patients with atrial fibrillation. The trigger for this inhibition has been attributed to the rapid firing rates and consequent calcium overload in the atrial cardiomyocytes. However, the underlying mechanism of LTCC inhibition is still to be elucidated. Here, we showed that the expression of ZnT-1 inhibits the activity of L-type channels during electrical remodeling induced by rapid pacing. (i) Direct manipulations of ZnT-1 expression in cultured cardiomyocytes either by ZnT-1 overexpression or by ZnT-1 silencing with siRNA, decreased or enhanced, respectively, the barium influx through the LTCC. (ii) Co-expression of ZnT-1 with LTCC in Xenopus oocytes decreased whole cell barium current through LTCC. (iii) Rapid pacing of cultured cardiomyocytes (4 h, 100 ms cycle) increased ZnT-1 protein expression and inhibited the voltage-dependent divalent cation influx through the LTCC. Moreover, silencing ZnT-1 with siRNA prevented the rapid pacing induced inhibition of the LTCC (iv) Atrial pacing of anesthetized adult rats (4 h, 50 ms cycle) led to a significant increase in atrial ZnT-1 protein expression in parallel with the typical decrease of the refractory period in the atria. Taken together, these findings demonstrate that crosstalk between ZnT-1 and the L-type calcium channels may underlie atrial response to rapid pacing, suggesting that ZnT-1 is a significant participant in rate-dependent cardiac electrical remodeling.

Animals↗
PubMed2006

Association of statin therapy and the risk of atrial fibrillation in patients with a permanent pacemaker.

BACKGROUND: Recent studies have shown conflicting results regarding a protective effect of statin therapy on atrial fibrillation (AF). HYPOTHESIS: We sought to determine whether statins are effective in reducing the risk of developing arrhythmia in a cohort of 264 patients (49% women, mean age [+/-standard deviation] 71 [+/-12] years) with permanent pacemakers who are at high risk for AF. METHODS: All patients who underwent implantation of a permanent pacemaker over a 3-year period were eligible for inclusion in the study. We excluded patients with AF at implantation, incomplete medication information, or less than a yearly follow-up visit. Atrial fibrillation was diagnosed by ECG documentation, pacemaker interrogation, and Holter monitoring. Statin treatment was verified through a central pharmacy-computerized database (for most patients) or by chart review. Of the 264 patients, 36% had coronary artery disease. RESULTS: Atrial fibrillation developed in 70 patients (26%) at a median of 359 days post pacemaker implantation. The incidence rate for the first occurrence of AF post pacemaker implantation among patients treated and not treated with statins was 10.5 versus 9.8 events per 100 patient-years, respectively (p = 0.81). Even after controlling for baseline differences, the hazard ratio (HR) for developing AF among statin users did not achieve statistical significance (HR = 0.59 [0.31-1.12]). CONCLUSIONS: We could not demonstrate that statin therapy had a protective effect against the risk of AF in patients implanted with a permanent pacemaker. The low prevalence of coronary artery disease in our patients may partly explain our results.

Aged↗
PubMed2006

[Automatic external defibrillator (AED) and public access defibrillation (PAD)].

Sudden death is a major public hazard and is usually caused by ventricular fibrillation (VF). Although in the majority of cases witnesses are to be found, resuscitation efforts are begun only in a minority of victims. The only treatment for VF is electrical shock and the time from collapse to resuscitation and defibrillation determine prognosis. Automated external defibrillator (AED) is a new device capable of effectively identifying and treating VF. It is unique in the sense that it can be operated by a non-medical operator following short training. Recent evidence of the survival benefit of AED utility is emerging. During the coming years, AEDs will be introduced to a growing number of hospitals and public places. This review summarizes the rationale for use, advantages, and disadvantages as well as the current status of AEDs and recommendations for placement of AEDs in Israel.

Arrhythmias, Cardiac↗
PubMed2005

Provocation of sudden heart rate oscillation with adenosine exposes abnormal QT responses in patients with long QT syndrome: a bedside test for diagnosing long QT syndrome.

AIMS: As arrhythmias in the long QT syndrome (LQTS) are triggered by heart rate deceleration or acceleration, we speculated that the sudden bradycardia and subsequent tachycardia that follow adenosine injection would unravel QT changes of diagnostic value in patients with LQTS. METHODS AND RESULTS: Patients (18 LQTS and 20 controls) received intravenous adenosine during sinus rhythm. Adenosine was injected at incremental doses until atrioventricular block or sinus pauses lasting 3 s occurred. The QT duration and morphology were studied at baseline and at the time of maximal bradycardia and subsequent tachycardia. Despite similar degree of adenosine-induced bradycardia (longest R-R 1.7+/-0.7 vs. 2.2+/-1.3 s for LQTS and controls, P=NS), the QT interval of LQT patients increased by 15.8+/-13.1%, whereas the QT of controls increased by only 1.5+/-6.7% (P<0.001). Similarly, despite similar reflex tachycardia (shortest R-R 0.58+/-0.07 vs. 0.55+/-0.07 s for LQT patients and controls, P=NS), LQTS patients developed greater QT prolongation (QTc=569+/-53 vs. 458+/-58 ms for LQT patients and controls, P<0.001). The best discriminator was the QTc during maximal bradycardia. Notched T-waves were observed in 72% of LQT patients but in only 5% of controls during adenosine-induced bradycardia (P<0.001). CONCLUSION: By provoking transient bradycardia followed by sinus tachycardia, this adenosine challenge test triggers QT changes that appear to be useful in distinguishing patients with LQTS from healthy controls.

Adenosine↗
PubMed2004

Do the recently modified pacemaker guidelines for neurocardiogenic syncope also apply to young patients? Analysis based on five-year follow-up of israeli soldiers with syncope and a positive tilt test.

To assess the classification of neurocardiogenic syncope (NCS) as a IIA indication for pacemaker implantation in the recent American College of Cardiology/American Heart Association Task Force on Practice Guidelines/North American Society for Pacing and Electrophysiology guidelines, we performed chart reviews and follow-up interviews in a cohort of 45 consecutive young Israeli soldiers (age 18-24 years) with a history of syncope (mean of 9 prior syncopal episodes) and a positive tilt test treated with drug therapy. Asystole longer than 5 s during tilt testing occurred in 11 patients. Five years later, we found that only 2 patients were still taking medications, only 1 patient (2%) still reported frequent syncopal or near-syncopal episodes and 3 patients (7%) had rare symptoms (no more than one syncopal episode during the past 2 years), while the remaining 40 (89%) were symptom free off medications. Thus, NCS in young patients, even with prolonged asystole during tilt testing, a history of frequent syncopal episodes and other high- risk factors described in the guidelines, is often a self-limiting disorder, perhaps stress related or situational in nature; an overwhelming number of patients become asymptomatic and stop taking medications within 1-2 years. These patients do not require long-term therapy; thus, our data would suggest that the IIA pacing indication for NCS should be restricted to older patients.

Adolescent↗
PubMed2004

Efficacy of substituting innovator propafenone for its generic formulation in patients with atrial fibrillation.

The clinical outcomes of 114 patients with atrial fibrillation who had been treated with the innovator propafenone, and in whom the drug was then replaced with generic propafenone because of cost containment, were compared. The generic formulation was found to be at least as safe and effective as the innovator drug, with regard to atrial fibrillation recurrence, emergency room and hospital admissions, and necessity for concomitant therapy.

Aged↗
PubMed2004

Is idiopathic ventricular fibrillation a short QT syndrome? Comparison of QT intervals of patients with idiopathic ventricular fibrillation and healthy controls.

OBJECTIVE: The purpose of this study was to determine if patients with idiopathic ventricular fibrillation (VF) have shorter QT intervals than comparable healthy controls. BACKGROUND: The upper limit of the normal QT is well defined. Less is known about the lower limit of the normal QT. Patients with the recently described "short QT syndrome" have characteristics resembling those of patients with idiopathic VF. METHODS: The ECGs of 28 consecutive patients with idiopathic VF (17 men and 11 women, age 31 +/- 17 years) were compared to those of 270 age- and gender- matched healthy controls. Based on published literature, we defined "short QT" as QTc < or = 360 ms for males and < or = 370 ms for females. RESULTS: Despite significant overlapping, the QTc of males with idiopathic VF was shorter than the QTc of healthy males (371 +/- 22 ms vs 385 +/- 19 ms, P = .034). Short QT intervals were found more frequently among males with idiopathic VF (35% vs 10%, P = .003). No such differences were apparent among women. Short QTc intervals were more commonly seen during bradycardia. However, the correlation between short QT and a history of VF was independent of heart rate. CONCLUSIONS: "Short" QTc values are commonly seen in male patients with idiopathic VF. However, "short" QTc values are not rare among healthy adults, especially at slow heart rates. Further studies are needed to define when a given QT is really "too short."

Adult↗
PubMed2004

Prevention of infections associated with permanent cardiac antiarrhythmic devices by implementation of a comprehensive infection control program.

OBJECTIVE: To implement a comprehensive infection control (IC) program for prevention of cardiac device-associated infections (CDIs). DESIGN: Prospective before-after trial with 2 years of follow-up. SETTING: A tertiary-care, university-affiliated medical center. PATIENTS: A consecutive sample of all adults undergoing cardiac device implantation between 1997 and 2002. INTERVENTION: An IC program was implemented during late 2001 and included staff education, preoperative modification of patient risk factors, intraoperative control of strict aseptic technique, surgical scrubbing and attire, control of environmental risk factors, optimization of antibiotic prophylaxis, postoperative wound care, and active surveillance. The clinical endpoint was CDI rates. RESULTS: Between 1997 and 2000, there were 7 CDIs among 725 procedures (mean annual CDI incidence, 1%). During the first 9 months of 2001, there were 7 CDIs among 167 procedures (4.2%; P = .007): CDIs increased from 7 among 576 to 3 among 124 following pacemaker implantation (P = .39) and from 0 among 149 to 4 among 43 following cardioverter-defibrillator implantation (P = .002). Of the 14 CDIs, 5 involved superficial wounds, 7 involved deep wounds, and 2 involved endocarditis. Following intervention, there were no cases of CDI among 316 procedures during 24 months of follow-up (4.2% reduction; P = .0005). CONCLUSIONS: We observed a high CDI rate associated with substantial morbidity. IC measures had an impact on CDI. Although the relative weight of each measure in the prevention of CDI remains unknown, our results suggest that implementation of a comprehensive IC program is feasible and efficacious in this setting.

Adult↗
PubMed2004

Dilated cardiomyopathy in a pregnant woman after doxorubicin and radiotherapy for Hodgkin's disease: a case report.

BACKGROUND: Hodgkin's disease occurs frequently in women of reproductive age. Anthracyclines in general and doxorubicin in particular are integral parts of therapy. CASE: A 24-year-old primigravida had dilated cardiomyopathy diagnosed at 34 weeks'gestation. Three years earlier she had been treated with chest radiation and combination chemotherapy, including doxorubicin, for Hodgkin's disease. CONCLUSION: The clinician should be aware of this manifestation. Multidisciplinary supervision throughout pregnancy as well as planned timing and mode of delivery are mandatory.

Adult↗
PubMed2003

Advanced atrioventricular conduction block in acute rheumatic fever.

We carried out a retrospective case control analysis to evaluate the outcome, and the need for treatment, of problems with atrioventricular conduction occurring during an acute attack of rheumatic fever, assessing the occurrence of second and third atrioventricular block versus first degree block. We reviewed and analysed the clinical, electrocardiographic and echocardiographic records of all children diagnosed in a single institute as having acute rheumatic fever during a period of seven consecutive years. During the period from October, 1994, through October, 2001, 65 children meeting the modified Jones criterions for acute rheumatic fever were hospitalized in the Soroka University Medical Center, Israel. First-degree atrioventricular block was identified in 72.3% of the children, and resolved with no specific treatment other than non-steroidal anti-inflammatory medications. Second-degree atrioventricular block of Mobitz type I, was observed in one child (1.5%), which progressed from first-degree block, and subsequently resolved. Complete atrioventricuar block was found in 3 children (4.6%), one progressing from Mobitz type I second-degree block, and two being seen as the first presentation. Of the three children with complete atrioventricular block, one patient was not treated, the second was treated with aspirin, and the final one with combined aspirin and steroids. The disturbances of conduction resolved in all three. We conclude that advanced atrioventricular block is rare during acute rheumatic fever. If occurring, block appears to be temporary, and resolves with conventional anti-inflammatory treatment. Specific treatment, such as insertion of a temporary pacemaker, should be considered only when syncope or clinical symptoms persist.

Acute Disease↗
PubMed2002

Implantable cardioverter defibrillators in Israel: utilization and implantation trends.

BACKGROUND: Since its introduction, the implantable cardioverter defibrillator (ICD) has evolved to its present status as the dominant therapeutic modality for patients with life-threatening arrhythmias. Several randomized studies have shown the benefit of ICD implantation as the first choice of treatment for primary as well as secondary indications for ventricular arrhythmias. Therefore, it is expected that the use of ICDs will increase further. The main objectives of this study were to analyze the Israeli experience with ICD implantation from 1993 to 1999, to examine the diffusion of ICD therapy in Israel and the evolution of implantation patterns and indications. METHODS: We conducted a retrospective review and analysis of an ICD registry for the period of January 1993-December 1999. Data collected included demographic, administrative, clinical and survival data. RESULTS: A total of 732 new implantations were identified and reviewed. The mean length of follow up of all patients was 30.7+/-21.1 months. 86% of patients were males and the mean age at implantation was 62.6+/-12.4 years. 79% of patients had CAD and the mean EF of all patients was 29.2+/-11.2%. 135 patients (18.4%) died during follow-up. One, two and three-year survival rates were calculated and were 92.7%, 87.8% and 82.0% respectively. A steady increase in implantation rate and in implanting centers was observed over the years. CONCLUSIONS: ICD therapy is relatively expensive; therefore a national registry which is continuously monitored may be the most expedient method to follow clinical and economic aspects of the utilization of this therapeutic modality.

Aged↗
PubMed2002

Mexiletine related chronic defibrillation threshold elevation: case report and review of the literature.

Many antiarrhythmic drugs may produce a rise in defibrillation threshold. Mexiletine is a frequently used antiarrhythmic drug in patients with an implantable cardioverter defibrillator, usually thought of as producing no or minimal effects on the defibrillation threshold. The current case report presents a patient with an endocardial implantable cardioverter defibrillator being treated with mexiletine, which precluded the ability to defibrillate the patient.

Adult↗