Peak Endocardial Acceleration-Based Clinical Testing of the "BEST" DDDR Pacemaker

The peak endocardial acceleration (PEA, unit g) shows a near correlation with myocardial contractility during the isometric systolic contraction of the heart (dP/dtmax), with sympathetic activity and, thus, with physiological heart rate modulation. The (Biomechanical Endocardial Sorin Transducer (BEST) sensor is incorporated in the tip of a pacing lead and measures PEA directly near the myocardium. In an international study, the lead was implanted with the dual chamber pacemaker Living-1 (Sorin) in 105 patients. The behavior of the PEA signal was tested under conditions of physical and mental stress and during daily life activities by 24-hour recordings of PEA (PEA Holter) at 1 to 2 months and approximately 1 year after implantation. Implantation of the BEST lead was performed without complications in all patients. The sensor functioned properly in the short- and long-term in 98% of patients. Although PEA values differed from patient to patient, the values closely reflected the variations in sympathetic activity due to physical and mental stress in each patient. During exercise and during daily life activities a close correlation between PEA and heart rate was observed among patients with normal sinus rhythm. Peak endocardial acceleration allows a nearly physiological control of the pacing rate.     

Management of Patients After Catheter Ablation of Ventricular Tachycardia

The management of patients after catheter ablation of ventricular tachycardia is not well defined. In this article we summarize recently published results and report our own experience. Factors influencing the clinical outcome of these patients and methods to identify patients with an increased risk of recurrence of ventricular tachycardia are discussed. Furthermore, a review is given on current concomitant therapeutic tools including antiarrhythmic drugs and the implantation of an automatic cardioverter defibrillator.     

Electrophysiological Characteristics of Bipolar Membrane Carbon Leads With and Without Steroid Elution Compared With a Conventional Carbon and a Steroid-Fluting Platinum Lead

In a controlled study, the following four bipolar leads with passive fixation were implanted in 46 patients with the Siemens-MuItilog-VVI or Sensolog-VVIR-pacemakers: membrane covered activated porous carbon with steroid elution (Siemens 1402 T, 11 patients) and without (Siemens 1403 T, 15 patients); activated carbon (Siemens 1010T, 10 patients); and platinum with steroid elution (Medtronic CapSure 5026, 10 patients). Stimulation threshold (STH) (assessed by a vario-test), impedance (IMP), and the intracardial R wave potential (IRW) (both gauged by a telemetric method) were measured 1, 5, and 10 days as well as 3 and 6 months after implantation during unipolar and bipolar stimulation, chronaxie rheobase product (CBP) and energy consumption (EC) were systematically determined. Differing insignificantly at the first day after implantation, STH is significantly lower for the 1402 T and CapSure 5026 leads at the tenth day. However, the 1402 T lead shows a significant increase of STH in the follow-up, in contrast to the other leads. The lowest chronic STH was found in the CapSure 5026 lead (CRP is significantly lower in all other leads, too). IMP is significantly lower in the CapSure 5026 lead compared to 1010 T lead. EC does not differ significantly during chronic stimulation in spite of the best possible programming of pulse amplitude and duration. No significant changes of IRW were observed. Unipolar versus bipolar stimulation shows significantly lower STH, CRP, and IMP, differences of EC and IRW were insignificant. In conclusion, the addition of steroid in membrane covered carbon leads protracts the increase of STH, but does not prevent it. The CapSure 5026 lead shows advantageous stimulation characteristics, but energy consumption is not significantly reduced because of low impedance and impossibility of programming an appropriate low output in Multilog pacemakers.     

Catheter Ablation of Chronic Atrial Fibrillation with Noncontact Mapping:

SEIDL, K., et al .: Catheter Ablation of Chronic Atrial Fibrillation with Noncontact Mapping: Are Continuous Linear Lesions Associated with Ablation Success? Catheter-based, right and left atrial compartmentalization procedure was evaluated using a noncontact mapping (NCM) system. Its usefulness to identify and close discontinuities in linear lesions in both atria was evaluated. The impact of linear lesion continuity on ablation success of chronic AF was also investigated. Nineteen patients with symptomatic, drug refractory chronic AF were studied. Right atrial ablation with three predefined lines was attempted in all patients. In 18 patients, left atrial ablation was performed with four linear lesions. During a follow-up of 12 ± 3 months , 6 of 19 patients remained in sinus rhythm (SR) without antiarrhythmic agents (AAs). In addition, four patients were maintained in SR with AA. Thirteen of 14 patients with gaps identified during off-line analysis had recurrence of AF. Only one patient with a gap was free of recurrence without AAs. In the remaining five patients without recurrence of AF, no gap was observed during off-line analysis. In all four patients who were free of AF with additional treatment of AAs, two gaps had been identified. In the remaining nine patients with chronic AF recurrence, a mean of 4.9 gaps were identified. Excluding the initial learning period (first five patients) the success rate increased to 43% (6/14 patients) without and to 71% (10/14 patients) with AA. NCM identifies discontinuities in lines of ablation. Successful ablation of chronic AF is associated with continuity of linear lesions and good clinical technique demands a vigilant search for and closure of every gap. (PACE 2003; 26[Pt. I]:534–543)     

Assessment of the Chronotropic Response at the Anaerobic Threshold: An Objective Measure of Chronotropic Function

MEINE, M., et al. : Assessment of the Chronotropic Response at the Anaerobic Threshold: An Objective Measure of Chronotropic Function. The evaluation of the heart rate response to exercise is important for the diagnosis of chronotropic incompetence and the assessment of a rate responsive algorithm of sensorcontrolled pacemakers. The aim of the present study was to examine a classification of the chronotropic response at an individually moderate exercise level. Sixteen pacemaker patients (patient group, age 62.9 ± 7.6 years ) with sick sinus syndrome and 15 age‐matched healthy subjects (control group, age 57.6 ± 9.4 years ) underwent a maximum cardiopulmonary exercise test on a treadmill after a protocol with individually selected incremental steps. To analyze the patients' intrinsic heart rate response, the rate responsive mode of the pacemaker was switched off. Chronotropic incompetence was diagnosed in eight patients whose maximal heart rate was < 80% of the age‐predicted heart rate. The heart rate at the anaerobic threshold was significantly lower in the chronotropically incompetent subgroup than in the chronotropically competent patients and the healthy subjects (85.9 ± 6.6 beats/min vs 100.3 ± 9.9 beats/min and 112.9 ± 11.7 beats/min , respectively). The chronotropic slope of the heart rate reserve as a function of the metabolic reserve was significantly higher in the control group than in the patient groups with either mild or severe chronotropic incompetence (0.94 ± 0.17 vs 0.64 ± 0.08 and 0.43 ± 0.14 , respectively). Furthermore, the chronotropically incompetent response could be divided into a linear type with and without a threshold, an exponential, and a logarithmic type. The anaerobic threshold was an objectively detectable breakpoint at an individually moderate exercise level that could be used for characterization of chronotropic function. At the anaerobic threshold, a physiological heart rate response was about 220 ‐ age – 50 beats/min. A deviation of more than 10 beats/min below this physiological value characterized chronotropic incompetence.     

Influence of Using Different Sources of Carotenoid Data in Epidemiologic Studies

Objective This study compared distributions of carotenoid intake and diet-serum correlations using two sources of carotenoid data: the US Department of Agriculture-National Cancer Institute (USDA-NCI) carotenoid food composition database and values accompanying the Block-NCI Health Habits and History Questionnaire (HHHQ).

Design and subjects A 100-item food frequency questionnaire was used to collect dietary data from 2,152 adults, aged 43 to 85 years, who were participating in the Nutritional Factors in Eye Disease Study, a population-based study designed to evaluate nutritional factors associated with age-related eye disease. Blood samples were collected from a random sample of 400 nonfasting participants in the study.

Results Median carotenoid intakes using HHHQ vs USDA-NCI data were alpha carotene (229 vs 223 μg/day), beta carotene (1,321 vs 1,325 μg/day), beta cryptoxanthin (72 vs 21 μg/day), lutein + zeaxanthin (653 vs 811 μg/day), and lycopene (593 vs 1,615 μg/day). All paired differences in carotenoid intake were significantly different from zero (Wilcoxon signed-rank, P<.0001). Despite these differences, the two databases similarly ranked individuals according to carotenoid intake: Spearman correlations ranged from .71 (lycopene) to .93 (alpha carotene). Differences between diet-serum correlations (adjusted for energy, body mass index, high density lipoprotein, and total cholesterol) using HHHQ vs USDA-NCI data were minor and not significant (P>.05): alpha carotene (r=.33 vs .32), beta carotene (r=.27 vs .32), beta cryptoxanthin (r=48 vs .53), lutein + zeaxanthin (r=.28 vs .24), and lycopene (r=.29 vs .25).

Conclusions Although estimates of carotenoid intake differed significantly, only minor differences in carotenoid rankings and diet-serum correlations were observed using either data source in this population. J Am Diet Assoc. 1996; 96:1271-1275.