In vivo mechanical study of helical cardiac pacing electrode interacting with canine myocardium

Cardiac pacing is a medical device to help human to overcome arrhythmia and to recover the regular beats of heart. A helical configuration of electrode tip is a new type of cardiac pacing lead distal tip. The helical electrode attaches itself to the desired site of heart by screwing its helical tip into the myocardium. In vivo experiments on anesthetized dogs were carried out to measure the acute interactions between helical electrode and myocardium during screw-in and pull-out processes. These data would be helpful for electrode tip design and electrode/myocardium adherence safety evaluation. They also provide reliability data for clinical site choice of human heart to implant and to fix the pacing lead. A special design of the helical tip using strain gauges is instrumented for the measurement of the screw-in and pull-out forces. We obtained the data of screw-in torques and pull-out forces for five different types of helical electrodes at nine designed sites on ten canine hearts. The results indicate that the screw-in torques increased steplike while the torque-time curves presente saw-tooth fashion. The maximum torque has a range of 0.3-1.9 Nmm. Obvious differences are observed for different types of helical tips and for different test sites. Large pull-out forces are frequently obtained at epicardium of left ventricle and right ventricle lateral wall, and the forces obtained at right ventricle apex and outflow tract of right ventricle are normally small. The differences in pull-out forces are dictated by the geometrical configuration of helix and regional structures of heart muscle.

Effects of right atrial and ventricular DDD pacing on cardiac function and ventricular contraction synchrony

Background Right ventricular apical pacing has been reported to reduce cardiac performance. But there are few reports on the effects of dual chamber (DDD) pacing on cardiac function compared to sinus rhythm. In this study, we evaluated the effects of right atrial and ventricular DDD pacing on cardiac function and ventricular contraction synchrony using equilibrium radionuclide angiography. Methods Ten patients implanted with a right atrial and ventricular DDD pacemaker underwent equilibrium radionuclide angiography. The scintigraphic data were obtained during sinus rhythm and pacing rhythm. Cardiac function parameters were obtained semimanually. Phase analysis was used to study the ventricular activation sequence and ventricular synchrony. Results The left ventricular 1/3 ejection fraction decreased significantly during pacing compared with that during sinus rhythm[ (23.4 +/- 6.1)% vs (27.7 +/- 4.5) %, P = 0.01]. Regional ejection fraction also decreased during pacing, although the difference was not statistically significant. Phase analysis showed that the right ventricle was activated earlier than the left ventricle during pacing, and that the phase shift was significantly greater during pacing than that during sinus rhythm[ 64.13degrees +/- 16.80degrees vs 52.88degrees +/- 9.26degrees, P = 0. 007 ]. The activation of both ventricles occurred simultaneously during sinus rhythm, with the activation sequence from proximal septum or base of left ventricle to apex. The earliest activation during pacing occurred at the right ventricular apex, and subsequently spread to the base and left ventricle. Conclusion Right atrial and ventricular DDD pacing impairs left ventricular systolic function and ventricular synchrony.

Epicardial Versus Endocardial Pacemakers in the Pediatric Population:A Comparative Inquiry

Background:Most children in need of cardiac pacemakers remain dependent on the function of the permanent from childhood to adulthood.We sought to evaluate and compare the function between epicardial and endocardial pacemakers in pediatric groups with different conditions.Methods:Between 2012 and 2018,this single-canter study evaluated 44 pediatric patients with indications for epicardial or endocardial pacemakers.Results:The 2 groups,at a median age of 5(0.1–16)years,were compared concerning the characteristics of the leads used(n=80:bipolar,unipolar,steroid-eluting,and non–steroid-eluting),survival data,and complications.The reason for pacemaker implantation was congenital complete heart block in 11(25%)cases and postoperative heart block in 33(75%)cases.The commonest congenital heart disease accompanied by postoperative block was the ventricular septal defect.In the endocardial lead group,the mean ventricular pacing threshold immediately after the implantation and during the follow-up was less than that in the epicardial lead group(0.75 vs.0.81 V;P=0.01 and 0.8 vs.2.4 V;P=0.001).During the follow-up,the mean battery longevity was better in the endocardial group(last visit:6.7 endocardial vs.3.3 years epicardial).Lead failure was commoner in the epicardial pacemaker,and chronic high-pacing threshold pattern was seen in 14 patients in this group.After 3 years,freedom from lead failure was 94%and 63%in the endocardial and epicardial leads.Conclusions:Pacemakers with endocardial bipolar steroid-eluting leads showed better lead characteristics regarding survival and battery longevity than epicardial pacemakers without these lead characteristics.An appropriate pacemaker type should be selected based on the patient’s condition.

Brain Rattled, Heart Shackled: Ictal Asystole in a Patient without Prior History of Epilepsy or Arrhythmia

We present a case of ictal asystole in an 81-year-old female, with no prior history of epileptic activity, or cardiac history suggestive of arrhythmia, who suffered several seemingly unrelated epileptic and asystolic episodes prior to finally having a witnessed seizure followed by an asystolic event. Following this event, all atrioventricular (AV) nodal blockers, and medications with potential seizure threshold lowering activity were stopped, and anti-epileptic medication was optimized. Due to the wishes of the patient’s family, no invasive interventions were pursued.However, the patient continued to be medically treated with anti-epileptic therapy and had no further asystolic events. Unfortunately, the patient’s overall clinical status deteriorated, and she subsequently passed during her hospital stay after being made do not resuscitate and do not intubate (DNR/DNI) by the family and then subsequently comfort care. Prior to her passing, however, she had remained free of epileptic events for 10 days and free of asystolic events for 21 days.

Influence of anxiety/depression on health related quality of life of patients with various pacing modes

Background The thesis is to study the influence of anxiety/depression on health related quality of life （HRQoL） of patients with various pacing modes a month after they have had a pacemaker implanted. Methods HRQoL was assessed consecutively in patients （50 men, 48 women, mean age 52.7±14.1 years） with implanted pacemaker （PM） from June to December 2009 in our hospital （22 patients received VVI pacemaker, 26 received VVIR pacemaker, 26 received DDD pacemaker, 24 received DDDR pacemaker）. HRQoL was measured by the SF-36 and Aquarel questionnaires, anxiety by Zung anxiety scale （SAS） and depression by Zung depression scale （SDS）. Results Patients with rate-adaptive pacing had higher scores in SF-36 scales （health perception, vitality, social functioning and mental health） and Aquarel （chest pain, dyspnea and arrhytmia）; they also presented lower degree of anxiety and depression compared with those with non-rate-adaptive pacing. Differences were shown only in the group with dual chamber pacemakers, but not in the group with single chamber pacemakers. Significant differences were observed between patients with single chamber and dual chamber PM in rate-adaptive pacing. There was a strong correlation between the degree of anxiety and depression and the HRQoL for pacemaker patients. Conclusion Dual chamber rate-adaptive pacing offers better HRQoL and psychological profile than dual chamber non-rate-adaptive pacing. Significant improvement in five SF-36 subscales was observed with DDDR pacing compared with VVIR pacing. Anxiety and depression are important factors in the HRQoL of patients with implanted pacemakers. Early detection and intervention in patients with psychological problems are imperative.

Relevance of Depression/Anxiety and Health-related Quality of Life in Paced Patients

Depression/anxiety is commonly present in paced patients and is associated with increased cardiovascular morbidity and mortality. The high prevalence of depression/anxiety in paced patients supports a strategy of increased awareness and treatment for depression/anxiety in paced patients. Health-related quality of life （HRQoL） is being increasingly considered as an expected out-come of therapeutic interventions and rehabilitation programs in clinical cardi- ology including patients before and after pacemaker（PM） implantation. This multispeciahy consensus document reviews the evidence linking depression/anxiety with arrhythmia and cardiac pacing; HRQoL and cardiac pacing, at the same time, provides recommendations for healthcare providers for the treatment of depression/anxiety. （S Chin J Cardiol 2009; 10（4） ： 190 -195）