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.     

The Six-Minute Walk—An Adequate Exercise Test for Pacemaker Patients?

LANGENFELD, H., ET AL.: The Six-Minute Walk—An Adequate Exercise Test for Pacemaker Patients? In many pacemaker patients bicycle and treadmill ergometry are not practicable. As an alternative, we performed a 6-minute walk on a 20-m corridor in 97 pacemaker patients, who were asked to walk as far as possible determining their speed by themselves. Results were compared with those of bicycle ergometry in 42 of these patients and with treadmill exercise of a group of 92 other pacemaker patients. In the 6-minute walk, performance and maximal heart rate were slightly lower (49 ± 18 W; 96 ± 23 beats/min) than in bicycle (57 ± 16 W; 110 ± 26 beats/min) and treadmill ergometry (50 ± 37 W; 102 ± 35 beats/min). A good correlation was found between walking and bicycling (r = 0.74) and in subgroups of patients with different pacemaker indications. All patients preferred the walk to bicycle ergometry considering it to be more related to daily physical activity. In conclusion, a 6-minute walk is a simple and physiological exercise test for nearly all pacemaker patients with good correlation to other types of exercise. It seems to be preferable to other tests because of its better acceptance and practicability.     

Dissimilar Action of Two Cyclic Adenosine-Monophosphate Analogues on the Sodium Current in Intact Rat Papillary Muscle

In intact papillary muscles from rat we have found with the loose-patch-clamp technique an increase of the fast cardiac sodium current (I_Na⁺) by isoproterenol (ISO). In this study we have tested two membrane permeable analogues of the intracellular second messenger cyclic adenosine-monophosphate (cAMP) to investigate the intracellular pathway: 8-Br-cAMP (50 μM) and the newer developed S_p5,6-Dichloro-1-β-D-ribofuranosylbenzimidazole-3′, 5′-cyclic-monophosphor-othioate (5,6-DCl-cBiMPS, 20 μM). The availability of I_Na⁺ was determined with test pulses to ± 0 mV every 3.5 seconds after 2.5-second conditioning between -130 mV and-50 mV and a holding potential at the resting potential of the cell under examination, and after wash-in of either compound. The peak currents were fit to a Boltzmann equation, and expressed by the maximal attainable current INa⁺_Na,max the mid-point potential V½, and a steepness parameter a. Values are given by mean ± SEM. 8-Br-cAMP showed a significant shift of the availability curve in the hyperpolarized direction (V½= -82 ± 2 mV vs - 66 ± 2 mV, n = 5, P < 0.05) with only minor changes of I⁺_No,max and a. In contrast, 5,6-DCI-cBiMPS had no significant effect on V½ but increased I⁺_Na,max by 8%± 2% versus control (n = 5. P < 0.05). In an intact muscle preparation we have found that 5,6-DCI-cBiMPS has a similar effect as that observed with the β-adrenergic agonist ISO (100 nM), whereas 8-Br-cAMP exhibited a dissimilar action. This indicates, that ihe effects of ISO are transmitted by the cAMP system. On the other hand, 8-Br-cAMP, which is not as permeable and specific an activator of the cAMP dependent proteinkinase, may have other effects on the sodium channel, perhaps mediated through purinergic receptors.     

Symptoms, Cardiovascular Risk Profile and Spontaneous ECG in Paced Patients: A Five-Year Follow-Up Study

GRIMM, W., ET AL.: Symptoms, Cardiovascular Risk Profile and Spontaneous ECG in Paced Patients: A Five-Year Follow-Up Study. Only few data are available about the course of symptoms, cardiac diseases, and spontaneous rhythm in pacemaker patients. Therefore, we followed the course of 308 paced patients (age 72 ± 11 years) with a mean implantation time of 63 ± 45 months. Results: The symptom triad of syncope, dizziness, and dyspnea improved remarkably in 93% of patients. Thirty-nine percent suffered from coronary heart disease. The risk factors of hypertension (47%), nicotine (37%), and diabetes mellitus (25%) were found significantly more often than in a normal population with the same age and sex profile. In VVI paced patients with sick sinus syndrome (SSS, n = 67) atrial fibrillation (AF) occurred significantly more often (42%) than in patients with AV block (n = 80, 23%, p < 0.05). Only one out of 41 DDD paced patients showed AF at follow-up. VVI stimulation seems to favor AF due to retrograde conduction in SSS. Only 3% of patients with SSS developed second- or third-degree AV block. Therefore, atrial pacing is preferable in most patients with SSS.     

Course of Symptoms and Spontaneous ECG in Pacemaker Patients: A 5-Year Follow-up Study

We investigated the course of symptoms and the spontaneous ECG retrospectively in 308 patients who had received a pacemaker because of atrioventricular (AV) block (n = 115), sick sinus syndrome (SSS, n = 107), bradyarrhythmic atrial fibrillation (bradyarrhythmia, n = 51), carotid sinus syndrome (CSS, n = 16), complete bifascicular block associated with 1st degree AV block (n = 13) and with other indications (n = 6). The mean implantation time was 63 months. The clinical state of 93% of all patients improved after pacemaker implantation; their symptoms decreased markedly. Persisting syncopy in some patients with SSS, however, supports a restricted implantation policy. We rarely saw improved AV conduction in patients with AV block (11%). Furthermore, in patients with SSS, atrial fibrillation occurred significantly more often (35%) than in those with AV block (17%; P less than 0.01). Only 3% of patients with SSS developed 2nd and 3rd degree AV block within the observation period. In all patients with initial bifascicular block and additional 1st degree AV block, pacing prevented further syncopal attacks; four of them showed 3rd degree AV block at control, indicating that pacemaker implantation is mandatory in symptomatic patients with bifascicular disease and 1st degree AV block.     

Evaluating an indicator of preventive health behaviour derived from a national study

This article considers a composite indicator of preventive healthbehaviour in the Swiss population using data collected withinthe framework of the first representative Swiss health survey(SOMIPOPS) and tries to categorize preventive health behaviourby defining a score of preventive action. The analysis of thedata reveals that sex, health status, age and education arerelated to preventive health behaviour in the Swiss population.These results are similar to those found in other studies andsupport the conclusion that preventive action may be a validindicator of preventive health orientation and behaviour.     

Synthesis of partial sequences of ribosomal proteins and their derivatization with acryloyl residues

Peptide sequences B-X-B (B = Arg and/or Lys; X = Glu or Asp) are of considerable interest because of their possible interactions with ribosomal RNA. The syntheses of various protected peptides with the sequence Ala-B-X-B-Ala (X = Glu or Ala) and [Arg]_n-Pro (n = 1–3) are described. They are carried out in solution according to the conventional peptide synthesis method. The carbobenzoxy group is used for Nα-protection and the methyl group for the protection of the terminal carboxyl group. The side chains of Lys and Glu are respectively blocked with the tert.-butyloxycarbonyl and the tertiary butyl group and the guanidinic function of arginine with the NO₂-group. The intermediate peptides are purified either by extraction or by size exclusion chromatography. A specially adapted strategy of peptide synthesis allows removal of the amino terminal Cbo-group at the end of the synthesis and introduction of an acryloyl group. By radical copolymerization with cross-linking agents these acryloyl derivatives can be transferred into insoluble peptide gels suitable for affinity chromatography and for investigating peptide-oligonucleotide interactions. The isolation of the unprotected peptides Arg-Arg-Arg-Pro, Ala-Arg-Glu-Arg-Ala, Ala-Arg-Glu-Lys-Ala, Ala-Arg-Ala-Lys-Ala, Ala-Lys-Glu-Lys-Ala and their characterization using amino acid analysis, electrophoresis, and FAB-mass spectrometry is also reported.