Technologies for Prolonging Cardiac Implantable Electronic Device Longevity

Prolonged longevity of cardiac implantable electronic devices (CIEDs) is needed not only as a passive response to match the prolonging life expectancy of patient recipients, but will also actively prolong their life expectancy by avoiding/deferring the risks (and costs) associated with device replacement. CIEDs are still exclusively powered by nonrechargeable primary batteries, and energy exhaustion is the dominant and an inevitable cause of device replacement. The longevity of a CIED is thus determined by the attrition rate of its finite energy reserve. The energy available from a battery depends on its capacity (total amount of electric charge), chemistry (anode, cathode, and electrolyte), and internal architecture (stacked plate, folded plate, and spiral wound). The energy uses of a CIED vary and include a background current for running electronic circuitry, periodic radiofrequency telemetry, high‐voltage capacitor reformation, constant ventricular pacing, and sporadic shocks for the cardiac resynchronization therapy defibrillators. The energy use by a CIED is primarily determined by the patient recipient's clinical needs, but the energy stored in the device battery is entirely under the manufacturer's control. A larger battery capacity generally results in a longer‐lasting device, but improved battery chemistry and architecture may allow more space‐efficient designs. Armed with the necessary technical knowledge, healthcare professionals and purchasers will be empowered to make judicious selection on device models and maximize the utilization of all their energy‐saving features, to prolong device longevity for the benefits of their patients and healthcare systems.     

The Development of General Practice in China

The concepts and principles of general practice are consistentwith Chinese cultural values; the leading authorities at theGeneral Practice Training Centre are extremely enthusiasticabout the general practice movement; the Ministry of PublicHealth is totally supportive of the general practice training;the medical/allied health professionals are eager to participatein general practice activities; and general practice certainlyis responsive to public expectations. General practice willbe flourishing and prosperous in China; however, there may betimes when the specialty of general practice in China experiencesgrowing pains with obstacles. The experiences gained from thedevelopment of general practice training programmes in Taiwanand other countries to handle the obstacles are of tremendousvalue to the development of general practice in China. It isexpected that communication and exchange between the generalpractice educators of Taiwan and China will play an importantrole in the further development of general practice in China.     

Autocannibalism: The Etiology of Nerve-Resection Anemia

1. The finding of Hollán that severe anemia follows nerve resection in ratshas been confirmed.

2. By the use of total-body labeling with radioiron, it has been demonstratedthat this anemia is due to blood loss.

3. The blood lost by the nerve-sectioned rat is found in the stools, but autopsy reveals no source of gastrointestinal bleeding.

4. Anemia occurs only in animals with excoriation of the denervated foot.Anemia may be precipitated by withdrawing food for 48 hours. Hollán hasfound that amputation of the denervated limb prevents onset of the anemia.

5. It is concluded that nerve-resection anemia in the rat is due to autocannibalism of the denervated foot.

Submitted on June 1, 1959 Accepted on August 19, 1959     

Neurocardiac Responses to Vagoafferent Electrostimulation in Humans

To determine if cardiac vagal tone is enhanced by vagal electrostimulation (VES), we examined the heart rate autospectrum (HRA) in eight patients with implanted stimulators for complex partial seizures. In four patients the VES was activated at 30 Hz and 500-msec pulse (HiStim group) compared to 2 Hz and 130-msec pulse for the LoStim group (n = 4). Continuous ECG and respiratory waveforms were recorded for 45 minutes every 8 hours (7–8 AM; 3–4 PM 11–12 PM) during resting supine wakeful epochs both before and 15 days after surgical implantation. From the HRA cardiac sympathovagal balance was expressed as the ratio of the low frequency (LF) power to the high frequency (HF) power. RESULTS: There were no presurgical differences between the groups in heart rate, its variance, or the energies contained in any autospectral band. The LoStim group showed no significant change in heart rate (HR), HF peak power, or LF:HF ratios during 2 weeks of VES. Conversely, in the HiStim group, the LF:HF peak power ratio fan expression of sympathetic dominance) decreased from 2.5 ± 1.5 preimplant to 1.5 ± 0.49 (P < 0.02) with VES. During VES there was a significantly higher HF power in the HiStim compared to LoStim group. No diurnal variations in HRA values were seen for either group. CONCLUSIONS: (1) A relationship exists between selective vagal nerve electrostimulation and the HRA; and (2) high stimulation frequency of the vagus nerve in man is associated with sustained augmentation of cardiac vagal tone throughout a 24-hour cycle.     

Short-Term and Long-Term Changes of Left Ventricular Volumes During Rate-Adaptive and Single-Rate Pacing

To evaluate the adaptation of the heart to exercise during pacing, 15 patients with permanent endocardial pacemakers were studied; nine patients had atrioventricular universal (DDD) pacemakers (Symbios 7005) and six patients had activity detecting rate-responsive ventricular (VVIR) pacemakers (Activitrax 8403). Left ventricular function in each patient during rate variable pacing was compared to ventricular function during VVI single-rate pacing. End-systolic and end-diastolic volume changes during exercise were measured by radionuclide angiography and the amount of volume change was used to assess left ventricular function. Both short-term (within 4 hours) and long-term measurements (after at least 4 weeks) were made at rest and at 50% of the maximal exercise capacity in DDD or VVIR mode and were compared with VVI single-rate pacing. All patients, when changed from DDD or VVIR mode to VVI single-rate pacing showed a significant increase of the end-diastolic volume during exercise, which increased even more after long-term VVI pacing. During long-term rate variable pacing, there was no increase of the end-diastolic volume during exercise. DDD or VVIR pacing initially showed a substantial increase of the end-systolic volume during exercise combined with a decrease of left ventricular ejection fraction, suggesting a decrease of the left ventricular contractility. After 4 weeks, contractility improved both with DDD and VVIR pacing. We conclude that short-term DDD and VVIR pacing induces a temporary impairment of left ventricular function that improves after 4 weeks, whereas long-term VVI pacing is associated with left ventricular dilatation even at moderate levels of exercise.     

AGRANULOCYTIC ANGINA (SCHULTZ) AND F-UNCTIONAL GRANULOCYTOPENIA

Schultz (1) in 1922 dcscribed what appeared to be a new syndro me characterized by an ulcerative angina, extre-me leukopenia with complete or almost cornplcte disappearance of the polymorphonuclear cells, its occurrence in middle-aged women, with marked prostration, a rapidly fatal outcome, and unknown etiology. This symptom-com- plex was given the name of agranulocytosis, later described as agranu. locytic angina and believed to be a new clinical entity. Since then some 150 cases have been reported chiefiyin Germany, Austria, and the United States. Many of the cascs conform to the originaldes- cription and others do not. It was soon discovered that the disease is not peculiar to women nor always fatal. Kastlin {2) reviewing the literature in 1927 found 43 cascs of which t4 were in women. Includ- ing his two cases there were in the series 42 deaths and 3 recoveries. In the same year Haken (3) reported 3 cases occurring in children aged 4, 6, and 8 years respectiveIy and.Weiss (3) reported the occur- rence of agranulocytosis in a child 6 years old. Potts (3) in the latter part of 1928 reviewed 38 additional cases including the 4 juvenile patients already mentioned. Of these 38 patients, 33 died. Women were attacked about three and a balf times as frcqucntly as men and children combined.