Biomedical subjects

M Mianulli

Publications and source records attributed to M Mianulli.

5 recordsLinked to original sources

PubMed1994

Multiple-sensor systems for physiologic cardiac pacing.

PURPOSE: To review the status of artificial sensors in cardiac pacemakers and the rationale for developing pacing systems that use multiple sensors. DATA SOURCES: Journal articles published between 1982 and 1993 indexed in MEDLINE using the keywords pacemakers, sensors, and rate-adaptive, as well as abstracts and articles in the authors' personal files. STUDY SELECTION: Articles describing clinical experience with or clinical evaluation of cardiac pacing systems using multiple artificial sensors. DATA SYNTHESIS: Artificial sensors were created to adjust pacing rate reliably in response to changes in levels of physical exertion for patients with sinoatrial disease in whom exercise heart rate response is inadequate (for example, chronotropic incompetence in sinoatrial disease). To achieve this, various artificial sensors were developed and many reports confirm improved exertional tolerance. More recently, sensors have assumed a greater role in cardiac pacemakers. For example, sensors are used to permit automatic adjustment of certain programmable pacemaker settings, such as the atrioventricular interval. In the future, they may also be used to maximize pacemaker longevity by automatically optimizing energy output (voltage, pulse width). No single sensor is ideal for all potential applications, and investigators have advocated using two or more sensors. Several pacemakers that use multiple sensors with different but complementary operating characteristics are already commercially available outside the United States. Although preliminary findings are encouraging, additional clinical experience with these pacemakers is needed to determine their ultimate role in clinical practice. CONCLUSION: Simultaneous use of multiple complementary artificial sensors may permit development of cardiac pacemakers that operate more physiologically yet require less specialized medical follow-up.

Clinical Trials as Topic↗

PubMed1989

An office-based exercise protocol for predicting chronotropic response of activity-triggered, rate-variable pacemakers.

Activity-triggered, rate-variable pacing systems offer a wide range of pacemaker patients the benefits of an appropriate paced chronotropic response. However, optimizing settings for these devices often entails treadmill exercise testing. To assess simpler procedures for predicting appropriate settings, pacing rates of "strapped-on" and implanted Activitrax pacemakers were evaluated during arm exercise, walk-in-place exercise and treadmill exercise (0% slope at 1.5, 2.0 and 3.0 mph). For exercise of similar duration, steady-state pacing rates of implanted devices during arm and walk-in-place exercise were lower than those achieved during treadmill exercise. Linear regression analysis resulted in the slope of these relations most closely approaching 1.0 for arm exercise at "low" activity threshold, while walk-in-place tended to result in slopes approaching 1.0 at all activity thresholds. Similarly, although strapped-on devices underestimated rates obtained with implanted devices, differences fell within a narrow range (-6 to -14%). Thus, in patients with implanted or strapped-on Activitrax pacemakers, relatively simple exercise procedures suitable for office or clinic environment may be useful to provide an estimate of pacing rates during physical activity, and may thereby facilitate selection of appropriate programmable settings.

Adult↗

PubMed1988

Usefulness of transcutaneous triggering of conventional implanted pulse generators by an activity-sensing pacemaker for predicting effectiveness of rate response pacing.

A noninvasive procedure has been developed to assess effectiveness of activity-sensing rate response ventricular (VVIR) pacing systems in patients with implanted conventional fixed-rate ventricular (VVI) pacemakers capable of triggered mode operation (VVT). A VVIR pacemaker (activity threshold medium or low, rate response 6 to 10, upper rate 125 or 150 beats/min) was strapped to the chest wall (prepectoral area) of patients with previously implanted fixed-rate VVI pacemakers. In 17 of the 18 patients included in the study, the implanted pacemaker was capable of triggered mode operation (VVT). Triggering of the conventional pacemaker was achieved by reprogramming it to the VVT mode (high sensitivity, short refractory) and connecting the output of the "strapped-on" VVIR pacemaker (5 volts, 1.5-ms pulse width) to 2 standard cutaneous electrodes positioned so as to be in proximity to the implanted intracardiac electrode system. Patients underwent symptom-limited treadmill exercise tests during both VVI and VVIR pacing. Triggering conventional VVI pulse generators by a "strapped-on" VVIR pacing system proved feasible in 16 of 17 cases and improved overall heart rate response (fixed rate 86 +/- 22 vs VVIR 118 +/- 7 beats/min) and exercise duration (fixed rate 6.6 +/- 4.9 vs VVIR 10.1 +/- 4.8 minutes) (mean values for all patients studied during exercise testing). Triggering of a previously implanted permanent pacemaker by a strapped-on activity-triggered device may be useful to assess rate response pacing before implantation of a VVIR device in patients in whom elective pulse generator replacement is planned.

Adolescent↗

PubMed1987

Single-chamber cardiac pacing with activity-initiated chronotropic response: evaluation by cardiopulmonary exercise testing.

In this study, sequential cardiopulmonary exercise testing was used to assess the physiologic benefits of a single-chamber ventricular pacing system that utilizes a piezoceramic sensor to adjust heart rate by detecting "physical activity." An initial exercise test was conducted with the pacemaker programmed (based on a randomization table) to either the fixed rate (VVI, 70 beats/min) or rate-variable (VVI-Act) mode, and the results were compared with those obtained during a second exercise test in which the pacemaker was programmed to the alternate pacing mode. A 1.5 to 2 hr rest period was permitted between exercise tests, each of which consisted of a symptom-limited constant speed (3.0 mph) Balke protocol with 2 min stages commencing at 0.0% grade with increments of 2.5% at end of each stage. Compared with findings during fixed-rate VVI pacing, VVI-Act pacing was associated with greater exercise-induced positive chronotropic response (mean maximum heart rate VVI-Act 128 +/- 15.3 beats/min vs VVI 90 +/- 28.4 beats/min; p less than .01), prolongation of exercise duration (VVI-Act 10.2 +/- 3.8 min vs VVI 7.7 +/- 2.5 min; p less than .01), increased peak oxygen consumption (VVI-Act 1617 +/- 656 ml O2/min vs VVI 1325 +/- 451 ml O2/min; p less than .01), and onset of anaerobic threshold at a higher oxygen consumption (VVI-Act 1208 +/- 343 ml O2/min vs VVI 1064 +/- 377 ml O2/min: p less than .01). Additionally, of 44 comparable exercise stages tested in the two pacing modes, perceived exertion (assessed by a numerical grading system) was lower in 38 of 44 instances during VVI-Act compared with VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1987

Sensor-triggered, rate-variable cardiac pacing. Current technologies and clinical implications.

Conventional implantable dual-chamber cardiac pacemakers adjust heart rate and maintain normal atrial and ventricular contraction by tracking "native" atrial electrical activity and pacing the ventricles after a predetermined programmable atrioventricular delay. However, in patients with symptomatic bradyarrhythmias, optimal function of "atrial-tracking" devices may be limited by concomitant sinoatrial disease. Provision of chronotropic response during physical exertion or emotional stress may be achieved by using physiologic sensors to alter pacing rate independently of atrial activity. Additional systems using sensor technologies are being developed. Future pacing systems will have dual-chamber pacing capability and may use several sensors coupled synergistically in order to take advantage of particular strengths of each. Physiologic sensor technology may be of diagnostic value in both antitachycardia devices and implantable cardioverter and defibrillator systems.

Bradycardia↗