[Development and short-term effects of a standardized patient education program for in-patient cardiologic rehabilitation]. / Entwicklung und kurzfristige Effektivität eines standardisierten Schulungsprogramms für die Rehabilitation bei koronarer Herzkrankheit.

BACKGROUND: Patient education is an essential part in the treatment of coronary heart disease in medical rehabilitation. In the German-speaking area, no standardized and evaluated patient education program for coronary heart disease is available so far. In this paper, we demonstrate the development of a quality assured patient education program based on a health-education program of the German statutory pension insurance scheme. METHODS: In a multi-level approach, an existing program was modified concerning treatment evidence, practical guidelines, theories of health and illness behavior and quality criteria for patient education as well as clinical experience and thereafter manualized. In a formative evaluation, feasibility and patient acceptance of this modified program were assessed using evaluation questionnaires of patients and trainers. Afterwards, effects of the patient education program as compared to a traditional education program were assessed on a short-term (at discharge), medium-term (6-month follow-up) and long-term (12-month follow-up) basis in a multicenter quasi-experimental control group study of patients with coronary heart disease (n=434). RESULTS: Results of the formative evaluation demonstrate an overall good acceptance and a good feasibility of the manualized program. Short-term results show a significant small treatment effect in the primary outcome variable patients' knowledge (p=0.001, η2 =0.028). Furthermore, small effects were also observed among some secondary outcomes, such as attitude towards medication, planning of physical activity, psychological quality of life and satisfaction with the education program. CONCLUSION: A standardized education program for patients with coronary heart disease has been developed in a systematic process based on established quality standards. Depending on the outstanding medium and long-term effects, the program may be recommended for general use in medical rehabilitation. The manual provides the prerequisites allowing for a successful transfer into clinical practice.

[Telemedicine during cardiac rehabilitation after acute myocardial infarction]. / Telemedizin in der Rehabilitation nach Herzinfarkt.

After acute myocardial infarction, cardiac rehabilitation should be an essential part of any therapy aimed at long-term success. Telemedical studies have mostly investigated ECG-monitored exercise training at home and internet-based counseling for lifestyle modification in selected patients. This approach cannot replace the holistic and multidisciplinary approach of cardiac rehabilitation. Telemedicine should be further evaluated, however, as it offers significant opportunities to facilitate access to rehabilitation for those patients who would otherwise not be able to attend for geographical, logistic or psychosocial reasons.

[Cardiovascular rehabilitation]. / Kardiovaskuläre Rehabilitation.

Cardiovascular rehabilitation encompasses the optimization of secondary prevention to reduce morbidity and mortality, the improvement of physical fitness and quality of life as well as the reintegration into social life and employment. This requires a multifactorial intervention on the physical, psychological, educative and social level by a multidisciplinary team. In Germany, cardiac rehabilitation started early after an index event, could demonstrate a significant reduction of total mortality, myocardial infarction and hospitalization during a follow-up of 1-2 years in 4 cohort studies including 10,758 patients with myocardial infarction and bypass surgery. This reduction of clinical events was obtained in addition to rapid revascularization therapy during the acute coronary event and on top of an evidence based secondary preventive medication. By national and international medical societies, cardiac rehabilitation is recommended as well in patients with congestive heart failure, after valve replacement or valve repair, after heart transplantation and cardioverter/defibrillator implantation. In the future, cardiac rehabilitation in Germany should be evaluated by a randomized controlled trial and multifactorial interventions should be tailored individually to specific patient subgroups and medical conditions.

Exercise-based cardiac rehabilitation in patients with reduced left ventricular ejection fraction: The Cardiac Rehabilitation Outcome Study in Heart Failure (CROS-HF): A systematic review and meta-analysis.

BACKGROUND: In heart failure with reduced left ventricular ejection fraction (HFrEF) patients the effects of exercise-based cardiac rehabilitation on top of state-of-the-art pharmacological and device therapy on mortality, hospitalization, exercise capacity and quality-of-life are not well established. DESIGN: The design of this study involved a structured review and meta-analysis. METHODS: Evaluation of randomised controlled trials of exercise-based cardiac rehabilitation in HFrEF-patients with left ventricular ejection fraction ≤40% of any aetiology with a follow-up of ≥6 months published in 1999 or later. RESULTS: Out of 12,229 abstracts, 25 randomised controlled trials including 4481 HFrEF-patients were included in the final evaluation. Heterogeneity in study population, study design and exercise-based cardiac rehabilitation-intervention was evident. No significant difference in the effect of exercise-based cardiac rehabilitation on mortality compared to control-group was found (hazard ratio 0.75, 95% confidence interval 0.39-1.41, four studies; 12-months follow-up: relative risk 1.29, 95% confidence interval 0.66-2.49, eight studies; six-months follow-up: relative risk 0.91, 95% confidence interval 0.26-3.16, seven studies). In addition there was no significant difference between the groups with respect to 'hospitalization-for-any-reason' (12-months follow-up: relative risk 0.79, 95% confidence interval 0.41-1.53, four studies), or 'hospitalization-due-to-heart-failure' (12-months follow-up: relative risk 0.59, 95% confidence interval 0.12-2.91, four studies; six-months follow-up: relative risk 0.84, 95% confidence interval 0.07-9.71, three studies). All studies show improvement of exercise capacity. Participation in exercise-based cardiac rehabilitation significantly improved quality-of-life as evaluated with the Kansas City Cardiomyopathy Questionnaire: (six-months follow-up: mean difference 1.94, 95% confidence interval 0.35-3.56, two studies), but no significant results emerged for quality-of-life measured by the Minnesota Living with Heart Failure Questionnaire (nine-months or more follow-up: mean difference -4.19, 95% confidence interval -10.51-2.12, seven studies; six-months follow-up: mean difference -5.97, 95% confidence interval -16.17-4.23, four studies). CONCLUSION: No association between exercise-based cardiac rehabilitation and mortality or hospitalisation could be observed in HFrEF patients but exercise-based cardiac rehabilitation is likely to improve exercise capacity and quality of life.

Influence of right ventricular stimulation site on left ventricular function in atrial synchronous ventricular pacing.

OBJECTIVES: The study investigates the correlation between left ventricular function and QRS duration obtained by alternate right ventricular pacing sites. BACKGROUND: 1. Right ventricular apical pacing is associated with alterations of left ventricular contraction sequence. 2. A stimulation producing narrow QRS complexes is supposed to provide for better left ventricular contraction patterns. METHODS: Fourteen patients with third degree AV block received one ventricular pacing lead in apical position. The alternate lead was attached to that site on the septum that produced the smallest QRS complex as measured from the earliest to the last deflection in any of the orthogonal Frank leads (xyz). During atrial synchronous ventricular pacing, the AV delay was optimized individually and for each stimulation site using mitral valve doppler or impedance cardiography. By radionuclide ventriculography, the phase distribution histogram of left ventricular contraction was evaluated as area under the curve (AuC); systolic function was determined as ejection fraction (EF) and as absolute ejected counts (EC) in random order. The difference (delta) in QRS duration between apical and septal stimulation (deltaxyz) was correlated with the difference in phase distribution (deltaAuC) and ejection parameters (deltaEF, deltaEC). RESULTS: QRS duration was shorter with septal than with apical pacing in 9 out of 14 patients (64%); it was longer in 4 (29%), and no difference was seen in 1 patient. There was a significant positive correlation between the change in QRS duration (deltaxvz) and phase distribution (deltaAuC: r = 0.66393, p = 0.010) and a significant negative correlation to systolic function (deltaEF: r = 0.70931, p = 0.004; deltaEC: r = 0.74368, p = 0.002). CONCLUSIONS: In atrial synchronous right ventricular pacing, if the AV delay is adapted individually, decreased QRS duration obtained by alternate pacing sites is significantly correlated with homogenization of left ventricular contraction and with increased systolic function in acute tests.

Cardio-metabolic characterisation of patients with coronary heart disease: specific consideration of the 1-h postprandial plasma glucose.

Cardiovascular events and type 2 diabetes are closely correlated. The clinical impact of this knowledge still appears improvable, since patients frequently develop macrovascular diseases directly after, or even before reaching the routine criteria for diabetes. Consideration of the 1-h plasma glucose in the oral glucose tolerance test (OGTT) might allow detecting a high cardiovascular and/or diabetes risk earlier. We performed OGTTs in patients with unknown diabetes after acute coronary syndromes and compared data of patients reaching either a 1-h plasma glucose<140 mg/dl (n=151) or≥200 mg/dl (n=125). Patients with a low or high 1-h plasma glucose differed in BMI 26.2±3.7 vs. 28.1±3.6 kg/m², waist circumference 95.3±10.7 vs. 101.5±11.7 cm, hypertension 59.6 vs. 73.6%, HDL-cholesterol 46.2±13.5 vs. 43.2±13.9 mg/dl, triglycerides 118.6±57.9 vs. 135.9±59.3 mg/dl, cardiac septum/posterior wall thickness 12±2 vs. 13±2 mm, respectively, left atrium diameter 42±6 vs. 45±7 mm, diabetes 1.3 vs. 36.0%, impaired glucose tolerance 6.6 vs. 35.2%; p<0.05, respectively. In summary, a 1-h OGTT plasma glucose≥200 mg/dl suggests a high cardiovascular risk and might help to identify such patients independently of reaching the definition criteria for manifest diabetes.

Comparable short-term prognosis in diabetic and non-diabetic patients with acute coronary syndrome after cardiac rehabilitation.

BACKGROUND: Patients with pathological glucometabolism are at increased risk of recurrent cardiovascular events after acute coronary syndrome (ACS). The goal of this study was to investigate the association of glucometabolism and the one-year outcome of cardiac rehabilitation patients. DESIGN: Prospective multicentre registry from four German rehabilitation clinics. METHODS: During 2005-2006, 1614 consecutive patients (85.9% male, mean age 55 ± 10.3 years) were included after the first ACS (mean 18.9 days) and classified into group 1 (apparent diabetes mellitus, n = 268), group 2 (no diabetes, impaired oral glucose tolerance [OGT], n = 185), and group 3 (normal fasting glucose and normal OGT, n = 1161). The mean follow-up was 13.4 months and the follow-up events were analysed by multivariate logistic regression models with backward elimination. RESULTS: The overall mortality was 1.3% (group 1: 1.2%; group 2: 1.8%; group 3: 1.5%; p(Trend) = NS). The target blood pressure values at discharge (<140/90 mmHg) were achieved by 88.7%, 89.1% and 90.8% of patients in groups 1, 2 and 3, respectively (p(Trend) = NS). The target value for LDL cholesterol (<100 mg/dl) was attained by 87.0%, 80.8% and 81.5% of the patients in groups 1, 2 and 3, respectively (p(Trend) = NS). There was a trend of a lower proportion of patients reaching the target values for HDL-C of 46.1%, 51.4% and 60.8% (p(Trend) < 0.001) and triglycerides of 65.1%, 79.9% and 74.6% (p(Trend) = 0.004) for groups 1, 2 and 3, respectively. The strongest multivariate predictors for overall mortality were patients experiencing a previous stroke (OR, 6.29 [95% CI: 1.06-37.19]; p = 0.042) and, with a trend, peripheral arterial disease (OR, 3.60 [95% CI: 0.95-13.68]; p = 0.061). In the multivariate analysis, the diabetic state had no association with poor outcomes (i.e. death or rehospitalization). CONCLUSION: The short-term prognosis for both diabetic and non-diabetic patients was good and was determined by end organ damage rather than by glucometabolic status. Diabetic patients received comparable (and not more aggressive) pharmacotherapy and therefore achieved target values for cardiovascular risk factors to a lesser extent than the non-diabetic and pre-diabetic patients.

[Telemedicine in cardiac rehabilitation--a literature review and critical appraisement]. / Telemedizin in der kardiologischen Rehabilitation--Eine Literaturübersicht mit kritischer Wertung.

The propagation of telemedicine has influenced the development of cardiac rehabilitation as well. Especially on an outpatient basis, there is an increasing number of publications about exercise training at home controlled by telemedical ECG. These trials, however, are predominantly feasibility studies including only few patients. In addition, most of the patients were male, classified as uncomplicated low-risk patients, and the vast majority was not included until weeks and months after the acute event. So far, there is no randomized controlled trial about telemedicine in cardiac rehabilitation in a large representative population. Furthermore, in most of the studies, only telemedically conducted exercise training was evaluated, and education classes as well as psychosocial interaction with the multidisciplinary team were not considered. The argument most often cited for the further spread of telemedicine, i.e. that its use will reduce the costs of medical care, has been proven so far neither. In conclusion, telemedical supervision of exercise training at home is technically feasible. As controlled data are lacking, risks and benefits of telemedical interventions in cardiac rehabilitation are not well evaluated yet. By no means may the sole telemedically supervised exercise training at home replace the multidisciplinary cardiac rehabilitation on an in- or outpatient basis. However, as there is the great opportunity to facilitate access to cardiac rehabilitation programmes for patients living in rural areas as well, the application of telemedical techniques should be further evaluated scientifically in this setting giving special attention to cost-effectiveness in times of limited financial resources.

The influence of right atrial septal pacing on the interatrial contraction sequence.

UNLABELLED: Right atrial septal pacing yields shorter interatrial conduction delays than conventional right atrial pacing at the free wall or the right atrial appendage. However, the hemodynamic effects of right atrial septal pacing are less well known. This study measured the delay between right and left atrial contractions during right atrial septal pacing (n = 21), conventional right atrial pacing (n = 32) and atrial multisite pacing (n = 6) by pulse Doppler echocardiography of transtricuspidal and transmitral blood flow. The effects of right atrial septal pacing (n = 14) versus conventional right atrial pacing (n = 22) on the optimal AV delay during dual chamber pacing was examined in patients with high degree atrioventricular (AV) block. Compared to sinus rhythm, conventional right atrial pacing increased P wave duration from 119 +/- 21 ms to 137 +/- 24 ms (P < 0.001), whereas both right atrial septal pacing (119 +/- 10 ms before, 106 +/- 13 ms during pacing, P = 0.002) and atrial multisite pacing (123 +/- 20 ms before, 112 +/- 11 ms during pacing, P = 0.5) shortened P wave duration. Atrial pacing caused a significant (P < 0.002) prolongation of atrial contraction [corrected] delays from 24 +/- 21 ms to 41 +/- 26 ms during conventional right atrial pacing, and reversed the right-to-left into a left-to-right contraction sequence in 20 of 21 patients during right atrial septal pacing (atrial conduction delay during sinus rhythm: 34 +/- 23 ms vs -37 [corrected] +/- 26 ms during atrial pacing, P < 0.0001). Atrial multisite pacing caused a nonsignificant shortening of the usual right-to-left contraction delay from 22 +/- 34 ms to 11 +/- 18 ms. The optimal left heart AV delay during AV sequential pacing was significantly (P = 0.002) shorter during right atrial septal pacing (108 +/- 38 ms) than during conventional right atrial pacing (152 +/- 33 ms). During conventional right atrial pacing the optimal right heart AV delay was significantly (P = 0.029) shorter than the optimal left heart AV delay. The opposite relation was observed for right atrial septal pacing (P = 0.033). CONCLUSIONS: Interatrial septal pacing does not synchronize right and left atrial contractions. It reverses the atrial mechanical timing from a right-to-left to a left-to-right contraction sequence, and requires the setting of shorter AV delays during dual chamber pacing if based on the optimization of left heart timing. Interatrial septal pacing is a technique which allows pacing of the left atrium from a right atrial site, rather than a single site approach to biatrial pacing.

Longevity of dual chamber pacemakers: device and patient related determinants.

In 382 patients with three different dual chamber pulse generators, the median time interval to battery depletion was 98.3 months. Cox regression analysis revealed the following variables as significant predictors of battery longevity: programmed pacing rate, energy of the stimulation output, mode of stimulation (i.e., proportion of paced cycles in one or two chambers), battery capacity, and internal sensing current of the pacemaker. Although 27% of all patients died before the service life of the pacemaker was over and despite a rate of premature reoperations of 8.6%, the majority of pacemaker patients (55%) fully used the expected battery life span of the pulse generator. Patients who died before the pacemaker had reached its end of service were significantly older at implantation than patients who survived until pacemaker replacement. The vast majority (92%) of patients received another dual chamber pulse generator when replacement was required. These data underline the need for long-lasting dual chamber devices.

Evolution of an active fixation atrial pacing lead.

UNLABELLED: Three bipolar atrial pacing leads from one manufacturer differing in a single electrode design characteristic were compared. Each lead had nonretractable screw and a microporous electrode tip made of activated carbon. Model S84F had a tip surface area of 8 mm2. In model S44F, the tip surface area was reduced to 4 mm2 by insulation of the screw, and in model BS45D, steroid elution was added to the 4 mm2 tip. Ten patients in each group received identical pulse generators. During implantation, atrial potentials (5.4 +/- 2.0, 4.2 +/- 2.0, 4.6 +/- 2.1 mV), pacing thresholds at 0.5 ms (0.47 +/- 0.14, 0.41 +/- 0.15, 0.55 +/- 0.33 V) and lead impedance at 2.5 V/0.5 ms (515 +/- 80, 575 +/- 152, 546 +/- 131 omega) were comparable among groups. The early postoperative threshold peak was significantly lower with the BS45D than with the S84F and S44F lead models. One year after implantation, charge threshold was significantly lower with the BS45D lead than with the S84F and the S44F model (0.34 +/- 0.11 vs. 0.68 +/- 0.20 and 0.56 +/- 0.21 microC; P < 0.05). Lead impedance at 2.5 V/0.5 ms (557 +/- 90, 549 +/- 36, 524 +/- 72 omega) and atrial sensing (4.3 +/- 2.1, 4.7 +/- 1.9, 4.7 +/- 0.9 mV) were not significantly different. One year postimplant, current drain of the pacing system was measured by pacemaker telemetry at chronic output settings in AAI mode/70 beats/min. Battery current measured among the three atrial lead models did not differ significantly (S84F: 11.9 +/- 0.90, S44F: 12.2 +/- 1.8, BS45D: 11.5 +/- 0.26 microA). IN CONCLUSION: reduction of the tip surface area by insulation of the screw did not improve pacing performance. Addition of steroid elution to the 4 mm2 tip significantly lowered the early threshold peak and the long-term pacing threshold. Lowering of the pacing threshold, however, did not lower the current drain of the pacing system.

[Feasibility and reliability of a transtelephonic 12 leads ECG]. / Zur Praktikabilität und Reliabilität des selbst abgeleiteten und telefonisch übertragenen 12-Kanal-EKG.

Feasibility and reliability of a 12 lead electrocardiogram (ECG), recorded by the patient himself and transmitted via telephone are mandatory for prehospital diagnosis of myocardial ischemia in patients with coronary heart disease. In this study, a 12-lead ECG recorded by patients and transmitted to the cardiology call center via telephone (Tele-ECG; model CG-7100; Card Guard) was compared with the conventional 12-lead ECG from the same patient recorded at the same time in 128 cases. The Tele-ECGs received by the call center were compared with conventional ECG by two cardiologists and one internist independently and blindly. In relation to the conventional ECG, reproducibility of PQ, QRS and QT-durations [ms] as measured in the Tele-ECG was 85%. Concordance between Tele-ECG and conventional ECG in the detection of negative T-waves was very high (Kappa value (kappa) 0.94, 0.96 and 0.97), respectively, depending on the physician. ST-segment changes were diagnosed correctly in most of the cases in Tele-ECG (kappa=0.98-0.99), as compared with the conventional ECG by all physicians. Concordance between Tele- and conventional ECG concerning the pattern of old myocardial infarction was very high (kappa=0.99) for all infarct localization. The limitations of Tele-ECG were of technical nature. In 14 cases, the peripheral electrodes were displaced; in 12 cases, there were baseline artifacts. These technical errors could be corrected in 126/128 patients (98.4%) by transtelephonic verbal communication. In conclusion, the reliability and feasibility of the 12-lead Tele-ECG-recorder used in this pilot study could be demonstrated. In an ongoing randomized controlled multicenter study, it is being investigated whether the strategy of prehospital diagnosis of acute coronary syndromes by Tele-ECG in combination with verbal communication is able to reduce pre- and in-hospital time delay, to avoid unnecessary hospital admissions and to reduce the economic burden of coronary heart disease.

[Effect of programmed safety margin on function time of modern dual chamber pacemakers]. / Einfluss der programmierten Sicherheitsmarge auf die Funktionszeit moderner Zweikammer-Schrittmacher.

In 55 consecutive patients with the same dual chamber pacemaker (Relay, Intermedics) and different pacing leads, the influence of different safety margins for pacing on battery current was investigated. 2.8 +/- 0.9 years after implantation, atrial and ventricular pulse-width thresholds (tRS) (ms) were determined at 0.5, 1.0, and 2.0 V, and the charge delivered at threshold was telemetered. If tRS was < 1.50 ms at 0.5 V, an amplitude of 1.0 V was programmed in the atrium and the ventricule; if tRS was < 1.50 ms at 1.0 V, then an amplitude of 2.0 V was chosen. Two times the charge threshold (2 x QRS), two times the voltage threshold (2 x URS), and three times the pulse-width threshold (3 x tRS) were programmed as the safety margins for pacing. With every safety margin, battery current (IBat) (microA) was averaged from 5 telemetric readings in D00 mode with 70 bpm. IBat was significantly lower with 2 x QRS as compared with 2 x URS (13.43 +/- 1.0 vs. 14.20 +/- 1.2 microA, p < 0.01) and as compared with 3 x tRS (13.99 +/- 1.2 microA, p < 0.05). Pacemaker longevity derived from these current data was significantly longer with 2 x QRS (112 +/- 8 months) as compared with 2 x URS (106 +/- 9, p < 0.01) and as compared with 3 x tRS (108 +/- 8, p < 0.05). If current consumption is compared intraindividually in dependance on the programmed amplitude, battery current is significantly lower at 1.0 V as compared with 2.0 V resulting in a mean reduction of 0.63 microA (-4.9%, p < 0.05) and an average gain in longevity of 5 months. This applies to every safety margin tested. Differences in battery current caused by the safety margins will translate into a greater gain in longevity in future pacemaker models with reduced internal current consumption.

Telemetry guided pacemaker programming: impact of output amplitude and the use of low threshold leads on projected pacemaker longevity.

In a prospective study, a low threshold screw-in electrode (Medtronic 5078, group I, n = 9) was compared to a conventional active fixation lead (Biotronik Y60BP, group II, n = 9) to investigate whether lower pacing thresholds really translate into longer projected service life of the pacemaker. The leads were implanted in the atrium and were connected to a dual chamber pacing system which included the same ventricular lead (Medtronic 5024) and the same pulse generator model (Intermedics 294-03) in both groups. Eighteen months after implantation, atrial and ventricular pacing thresholds were measured as the charge delivered per pulse [microC] at 0.5, 1.0, 1.5, 2.0, and 3.5 V, respectively. For chronic output programming in both channels, patients capturing at 0.5 V were set to 1.0 V, those capturing at 1.5 V were permanently programmed to 2.0 V with the double of the charge threshold as the safety margin for pacing ("safety charge"). A combination of atrial and ventricular output settings was optimal, if it resulted in minimum battery current drain (microA] as measured by pacemaker telemetry. In both groups, current consumption [microA] decreased significantly as output amplitude was decreased, exhibiting its lowest value at 1.0 V in either channel. All ventricular leads could be programmed to the optimum output amplitude of 1.0 V in groups 1 and 2. As the 2:1 "safety charge" values were almost identical, the ventricular channel essential contributes the same amount to the battery drain of the pacing system in both groups. In the atrium, all patients of group 1 could be programmed to the optimum output amplitude of 1.0 V with an average pulse duration of 0.42 +/- 0.15 ms. In group 2, however, all patients had to be programmed to 2.0 V with a mean pulse width of 0.52 +/- 0.15 ms. With the atrial and ventricular output being optimized, the average battery drain of the whole pacing system was 12.19 +/- 0.63 microA in group 1 versus 14.42 +/- 0.32 microA in group 2 (P < 0.001). As patients were chronically programmed to these output settings, this difference translates into a clinically relevant gain in projected pacemaker longevity of 17 months or 18.3% (121 +/- 4 vs. 104 +/- 2 months; P < 0.001). Thus, programming a 2:1 safety margin in terms of charge and optimizing the output parameters by real-time telemetry of the battery current is a useful approach to reduce battery current drain. Making the most of modern lead technology with a different performance in only one channel of an otherwise identical DDD pacing system translates into a significant prolongation of projected pacemaker service life which is of great importance with the increasing awareness of health care expenditures. The gain in projected longevity is mainly due to the option of reducing the output amplitude which is still significantly beneficial well below the nominal voltage of the power source.

Chronic ventricular pacing using an output amplitude of 1.0 volt.

Thirty-seven patients (21 male, 16 female, mean age 71 years) received identical DDD pacemakers. They also received the same bipolar ventricular passive fixation electrode, which has a microporous tip of platinum-iridium, a surface area of 5.8 mm2, and steroid elution. Eighteen months after implantation the ventricular charge threshold [microC] was measured telemetrically at 0.5, 1.0, and 2.0 V, respectively. For the 1.0 and 2.0 V amplitudes the pulse duration was increased until the charge per pulse [microC] was twice the threshold value, thus giving a 100% safety margin in terms of charge ("safety charge"). Patients who had ventricular capture at 0.5 V were permanently programmed to 1.0 V (30/37 patients), while those who did not capture at 0.5 V were set to 2.0 V (7/37 patients). In both cases, the pulse duration was programmed according to the rationale of "safety charge." During a routine follow-up period of 6 months, no complications were observed and none of the patients suffered from symptoms indicating loss of ventricular capture. Twenty-four-hour Holter recordings, obtained from all patients at the end of the follow-up with the output parameters unchanged, revealed constant ventricular capture. In patients with chronic stable pacing thresholds and steroid-eluting low threshold leads who have capture at 0.5 V, chronic ventricular pacing at an output amplitude of 1.0 V is feasible, and it seems to be safe if the pacing threshold is measured as charge delivered per pulse and a 100% safety margin in terms of charge is programmed. Reducing the output amplitude to well below the battery voltage may increase pacemaker longevity.

Rate adaptive atrial pacing in the bradycardia tachycardia syndrome.

In 42 patients (26 men, 16 women; mean age 69 +/- 10 years), who were paced and medicated with antiarrhythmic drugs for the bradycardia tachycardia syndrome, chronotropic response and AV conduction with rapid atrial pacing during exercise were studied. Patients were included if they had no second- or third-degree AV block, no complete bundle branch or bifascicular block, and a PQ interval < or = 240 ms during sinus rhythm at rest. The interval between the atrial spike and the following Q wave (SQ) was measured in the supine position at rest with an AAI pacing rate of 5 beats/min above the sinus rate (SQ-R + 5), and at the end of exercise with 110 beats/min (SQ-E110). Bicycle ergometry was performed using the Chronotropic Assessment Exercise Protocol with the pacemakers being programmed to AAI with a fixed rate of 60 beats/min. Chronotropic incompetence was defined as peak exercise heart rate: (1) < 100 beats/min; (2) < 75% of the maximum predicted heart rate; or (3) the heart rate at half the maximum workload < 60 + 2 beats/min per mL O2/kg per minute (calculated O2 consumption). During exercise, one patient developed atrial fibrillation. Chronotropic incompetence was present in 71% (29/41) of the patients according to definition 2, and in 76% (31/41) according to definition 1 or 3. Ten out of 41 patients (24%) exhibited a second-degree AV block with atrial pacing at 110 beats/min at the end of exercise. Only 9 out of the remaining 31 patients (29%) showed a physiological adaptation of the SQ-E110, and 21 patients (68%) exhibited a paradoxical increase of the SQ interval with rapid atrial pacing at the end of exercise as compared to the SQ-R + 5. These observations indicate that the pacing system to be used in most patients paced and medicated for the bradycardia tachycardia syndrome should be dual chamber, and the option of rate adaptation should be considered.