Pacemaker malfunction due to subcutaneous emphysema--a case report

The authors describe a cas of pacemaker malfunction due to a critical increase of impedance resulting from air entrapment in the pacemaker pocket.

Fourier analysis in patients with different pacing modes

The purpose of this study was to evaluate the usefulness of phase analysis in detecting the altered activation sequence induced by different pacing modes. Radionuclide ventriculography and planar gated blood pool scintigraphy were performed at rest in 56 patients with different pacemakers. This method permitted us to localize the pacemaker impulse site in the right ventricle and its diffusion in the heart. In patients with VVI pacemaker, this technique showed an evident asynchronism of contraction and relaxation of each ventricle and the standard deviation of phase angle (sigma), calculated by computer, is greater during pacing than sinus rhythm for left (LV) and right (RV) ventricles (LV sigma: 17 degrees +/- 4 vs 11 degrees +/- 3, less than 0.001; RV sigma: 31 degrees +/- 7 vs 14 degrees +/- 4, P less than 0.001). In the patients with VVI rate responsive pacemakers, the LV sigma changed from 18.5 +/- 3 under pacing to 11 degrees +/- 3 in sinus rhythm, P less than 0.001, while the RV sigma changed from 30 degrees +/- 8 to 14 degrees +/- 4, P less than 0.001. Instead in the patients with DDD pacemakers, the LV sigma changed from 15.5 degrees +/- 2 under pacing to 11 degrees +/- 3 in sinus rhythm, P less than 0.05, while the RV sigma changed from 29.1 degrees +/- 6 to 14 degrees +/- 4, P less than 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)

Follow-up of a respiratory rate modulated pacemaker

The efficacy of 27 respiration sensitive rate modulated pacemakers (Biorate RDP-3 Biotec) implanted in the left pectoral area was evaluated every 3 months during a mean follow-up period of 29 months (range 10-50 months). Rate modulation function was unchanged other than for three patients in whom the auxiliary leads became displaced. Two implants lost ventricular sensing in this nonprogrammable model. In all but the three patients, Holter monitoring demonstrated pacing rate variation corresponding to daily activity. Stress test duration increased from 8.2 +/- 1.5 minutes (in fixed rate VVI rate) to 12.83 +/- 2.0 minutes (in the VVIR mode) (P less than 0.05). Right arm movement increased the pacing rate by 5 +/- 3 beats/min (NS), while the left arm movement increase was 30 +/- 5 beats/min (P less than 0.05). Mental, arithmetic, and nifedipine tests did not change the rate modulated pacing rate. The system responded to a change in respiratory rate by an increase in stimulation rate. A satisfactory response in sensitivity and velocity was present only with medium-high workloads. Interference with rate modulation occurred with movement of the arm ipsilateral to the implanted pulse generator.

Efficacy of automatic mode switching in DDDR mode pacemakers: the most 2 study

BACKGROUND

Effective automatic mode switching (AMS) algorithms capable of detecting a range of supraventricular tachyarrhythmias is important given evidence of atrial fibrillation (AF), atrial flutter (AFL), and atrial tachycardia (AT) post-implantation of pacemakers.

OBJECTIVES

The aim of the study was to assess the efficacy, defined as ability to detect a specific atrial rate and activate AMS, of five different AMS mechanisms during simulation of AF, AFL, and AT.

MATERIALS AND METHODS

A total of 48 subjects (35 men, 13 women; mean age: 69 +/- 8 years) implanted with DDDR pacemakers utilizing five different AMS mechanisms (mean atrial rate, rate cut-off, complex 'fallback' algorithm, retriggerable atrial refractory period, and physiological band 'beat-to-beat') were tested using an external electronic device that simulated the occurrence of supraventricular tachyarrhythmias. AF, AFL, and AT were simulated by delivering low voltage pulse trains at 350, 250 and 160 beats/min, respectively.

RESULTS

Mean efficacy for all AMS mechanisms was 81% [range: 57% to 100%] at 350 beats/min, 81% [range: 57-100%] at 250 beats/min, and 79% [range: 57-100%] at 160 beats/min. The AMS mechanisms that yielded 100% efficacy were the rate cut-off and physiological band 'beat-to-beat.'

CONCLUSION

Not all AMS algorithms are equally efficacious at detecting atrial arrhythmias and subsequently activating AMS. Our results suggest that the most efficacious AMS algorithms are those that use rate cut-off and physiological band 'beat-to-beat' to detect supraventricular tachyarrhythmias.

Role of semiautomatic defibrillators in a general hospital: "Naples Heart Project"

In Italian hospitals, 85% of patients hospitalized in general medical wards who experience cardiac arrest die, while the incidence is much lower in patients in intensive care units. Defibrillation, in Italian hospitals, often occurs very late, either due to a lack of defibrillators, or due to architectural and structural barriers. The object of an in-hospital emergency service is to prevent and treat cardiac arrest without subsequent complications, such as brain damage, renal failure etc. The Naples Heart Project was based on a feasibility study of the in-hospital emergency service to evaluate and analyze problems associated with type of structure, departmental and institutional dislocation, internal practicability (architectural features and preferential ways), staff numbers and distribution, the calling system for emergency, and the equipment available. The Naples Heart Project began in July 2001, since then it has already created 835 BLSD first responders among the hospital staff; 440 were physicians and physicians still in training, 310 were nurses and 85 were administrative staff.

Pacemaker Malfunction Due to Subcutaneous Emphysema

The authors describe a case of pacemaker malfunction due to a critical increase of impedance resulting from air entrapment in the pacemaker pocket.

Left ventricular pacing in patients with heart failure: evaluation study with Fourier analysis of radionuclide ventriculography

BACKGROUND

In order to correct the activation, contraction, and relaxation asynchronism, multisite biventricular stimulation has been proposed as a non-pharmacological alternative for the treatment of patients with congestive heart failure (CHF) NYHA class II-III-IV, resistant to maximal drug therapy and with a QRS duration > 120 ms. Fourier analysis appears a feasible technique for the quantitative and non-invasive evaluation of the inter- and intraventricular conduction delays. The aim of our study was to evaluate the usefulness of Fourier analysis when estimating the electromechanical resynchronization in CHF biventricular paced patients and to follow up these patients.

METHODS

Forty-five male patients (mean age 64 +/- 5 years) with severe drug-refractory CHF, were submitted to radionuclide ventriculography 14 +/- 7 days, 24 and 36 months after the implantation of a biventricular pacemaker, in order to assess left ventricular ejection fraction using Fourier analysis of the right and left ventricular phase images. Each patient was examined during spontaneous sinus rhythm, P-synchronous right ventricle and P-synchronous biventricular pacing.

RESULTS

Fourteen days after biventricular pacemaker implantation, QRS duration decreased from 170 +/- 25 to 147 +/- 25 ms (p < 0.01), left ventricular ejection fraction increased from 24 +/- 6 to 31 +/- 9% (p < 0.005), while standard deviation of the left ventricular phase decreased from 53 +/- 6 to 35 +/- 9 degrees (p < 0.0005). Similar results were obtained at 24 and 36 months.

CONCLUSIONS

Biventricular pacing appears to be associated with shortening of QRS duration and an improvement in NYHA class and left ventricular ejection fraction in CHF patients with inter- and intraventricular conduction delays as assessed at Fourier analysis radionuclide ventriculography.

[Transthoracic cardioversion in patients with atrial fibrillation: comparison of three different waveforms]

BACKGROUND

Transthoracic electrical cardioversion represents the most effective therapy in converting atrial fibrillation (AF) to sinus rhythm. External cardioverter-defibrillators discharge a current with monophasic and most recently biphasic waveforms. Lately, many articles support the superiority of the biphasic waveform over the monophasic one. Moreover, we have the opportunity to use different biphasic waveforms. The aim of this study was to compare the efficacy (success rate and energy delivered) of a monophasic wave and two different biphasic waves, in patients with persistent AF undergoing external electrical cardioversion. The monophasic wave was delivered by a Zoll M series NM PDMA-9, while the so-called "rectilinear" biphasic waveform was used by a Zoll M series PDM-7S and the biphasic truncated exponential wave by a Laerdal Heartstart 4000.

METHODS

Sixty-four patients with clinical indications to undergo external electrical cardioversion were randomized into three groups. All the groups were homogeneous for almost all characteristics, particularly atrial dimensions, body surface area, and duration of AF and therapy. Eighteen patients underwent external cardioversion with monophasic waveform (group 1), 22 patients were treated with rectilinear biphasic waveform (group II), and 24 patients with biphasic truncated waveform (group III). A cardioversion protocol, providing up to 5 shocks, with incremental energy levels was used. A blood sample was obtained 6 hours later to evaluate myocardial damage due to shock therapy for each patient.

RESULTS

Both biphasic devices demonstrated to be more effective than the monophasic one (group I 78%, group II 95%, group III 100%). Moreover, none of them caused any significant myocardial damage, evaluated in terms of cardiac enzyme release. Nonetheless, the biphasic truncated exponential wave demonstrated an efficiency of 10 0% compared to 95 % of the rectilinear one and 78% of the monophasic one, using less energy/patient (873 +/- 101 J group I, 390 +/- 48 J group II, and 280 +/- 42 J group III), at almost the same shock attempts.

CONCLUSIONS

Biphasic truncated exponential wave seems to be more effective at a lower energy level.

[Public access defibrillation in the Sorrento Peninsula]

Early cardiac defibrillation is the only effective therapy to stop ventricular fibrillation or pulseless ventricular tachycardia. It is still considered the gold standard for the treatment of ventricular tachycardia/fibrillation, and is the only intervention capable of improving survival in cardiac arrest survivors. Timing of intervention, however, is crucial because after only 10 min success rates are very low (0-2%). Unfortunately, adequate relief cannot always be provided within the necessary time. The purpose of the public access defibrillation project in Sorrento was to create fixed and mobile first aid with automated external defibrillators in combination with the local 118 emergency system. With the involvement of pharmacies, bathing establishments and schools, 31 equally distant sites for public access defibrillation were made available. This organization was supplemented by mobile units on the cars of the Municipal Police and Civil Protection, and on patrol boats in the harbor.

[Recommendations for protection against electromagnetic interference risk caused by pacemakers and implantable defibrillators in hospitals]

Electromagnetic interference and compatibility are problems that claim an increasing attention of biomedical industries, all over the world. For electromagnetic interference we intend a phenomenon that can occur when an electronic device undergoes the influence of an electromagnetic field, which may cause temporary or definitive malfunctioning of the device itself. Indeed, electromagnetic compatibility is the capacity of an electric device either to operate normally, without generating electromagnetic disturbances that may interfere with other devices or to operate without being influenced by electromagnetic field generated by other electric devices. Pacemaker (PM) and implantable-cardioverter defibrillator (ICD) functioning can be significantly compromised by electromagnetic fields, even though their circuits, nowadays, are well protected from most of electromagnetic wave sources. The basis for electromagnetic interference on PM and ICD lays on different factors even physical such as the power of external signal, the distance between the signal and the PM and ICD, the frequency range, modulation type and immunity level of the PM and ICD. The electromagnetic interference on PM and ICD may result into a temporary or permanent malfunctioning, like pacing inhibition, asynchronous pacing, or the switching of the pacing mode. The purpose of this work is to give useful indications for a correct in-hospital management of patients with PM or ICD, in order to avoid dangerous electromagnetic interference.

[Management of electrical storm in implantable cardioverter-defibrillator recipients]

The term "electrical storm" (ES) indicates a state of cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias (VTs) within a short time. In patients with an implantable cardioverter-defibrillator (ICD), ES is best defined as three appropriate VT detections in 24h, treated by antitachycardia pacing, shock or eventually untreated but sustained in a VT monitoring zone. ES seems to have a low immediate mortality (1%) but frequently (50-80%) leads to hospitalization. Antiarrhythmic drugs have been shown to be very effective in treating ES in patients without ICD, whereas in ICD recipients, device programming is probably a key issue to prevent ES. Since sympathetic overreactivity is an important trigger, the risk of shock delivery should be minimized. Antitachycardia pacing can successfully terminate a significant percentage of fast VTs. Important parameters such as the number of VT cycles needed for VT detection can be increased from nominal values to allow spontaneous termination, and safety features that deliver a shock after a programmable time window independent of programming of antitachycardia pacing (sustained rate duration) should be prolonged or disabled. In some cases it may be advisable to turn off the ICD tachy mode to avoid multiple ineffective shocks. Substrate mapping and VT ablation may be useful for the treatment and prevention of ES.

[Evaluation of BLS-D training in lay people]

BACKGROUND

The possibility of saving persons with sudden cardiac arrest (SCA) lowers of 10% every minute since the beginning of the event. The early defibrillation (within 4 min) of a person with SCA performed by first responders suitably trained increases the survival rate up to 50%. The basic aim is that early defibrillation is performed as soon as possible by the first responder.

METHODS

Within the Public Access Defibrillation (PAD) "Napoli Cuore" Project, 220 highway patrol agents of the Campania Region district were trained through theoretical and practical courses to acquire suitable psychomotor skills to perform the first aid. The learning evaluation was performed with a written exam and a practical test to assess how much every agent had learned about basic life support-defibrillation (BLS-D) schemes.

RESULTS

98.5% of the participants passed the exams and obtained the BLS-D rescuer license, and 15.5% of them obtained the highest score. The analysis of the report cards showed that most of the participants expressed an excellent opinion about this experience.

CONCLUSIONS

To implement a PAD project it is necessary to awaken all the structures involved in the campaign against SCA. Hence, it is important that all emergency specialists, public institutions and police departments work all together to make everyone feels safe.

[Anaerobic threshold in the evaluation of heart function in patients with rate-responsive pacemaker]

It is very difficult to evaluate the ability of carrying out physical exercise in patients with rate responsive (RR) pacemaker (PM). However, the anaerobic threshold (AT) proved to be a useful parameter in the evaluation of cardiac function. The AT can be easily reproduced and not influenced from emotional aspects of both the patient and the physician, moreover being under maximum and then easy to achieve. Aims of our study were: to evaluate if the cardiopulmonary stress test can represent a method to be used for a more correct rate responsive pacemaker programming; to compare the data obtained of 3 rate responsive pacemakers steered by different sensors. We have studied 24 patients, of whom 10 with Activitrax (A), 8 with Meta (M), and 6 with Phymos MPT (P) pacemakers. Patients were submitted to symptoms limited cycloergometer stress test at 2 different settings: fixed rate at 70 b/min; increasing rate at until 85% of maximum heart rate for each patient, with range 0 + 10 W/min. Gas exchange data were continuously collected using an automated system (Medical Graphic System 2001) based on Whipp and Wasserman's method.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of coronary artery disease with Tc 99m-methoxy isobutyl isonitrile and transesophageal pacing

Recently the use of a new radioactive agent with physical and biological properties more favorable than those of thallium 201, methoxy-isobutyl-isonitrile (MIBI) labeled with technetium 99m (Tc 99m), has permitted simultaneous performance of perfusion and function studies in ischemic cardiopathy. Transesophageal atrial pacing (TAP) technique has evolved as an alternative provocative test of ischemia. The authors compared the capability of Tc 99m-MIBI myocardial scintigraphy, combined with TAP, with that of Tc 99m-MIBI, combined with maximal stress test, in the diagnosis of ischemic cardiopathy. They studied 11 patients with a clinical history of angina pectoris. Myocardial scintigraphy was performed at rest, after stress test, and after TAP. Finally, all the patients underwent coronary angiography. The analysis of myocardial perfusion images on both Tc 99m-MIBI associated with TAP and with stress demonstrated, in 165 myocardial segments examined: 143 normal, 20 reversible defects, 2 irreversible defects. The concordance of localization between coronarographic data and scintigraphic reversible and irreversible defects was 85%. In conclusion TAP proves to be a valid and sensitive provocative test of ischemia when combined with myocardial scintigraphy and with Tc 99m-MIBI.

[Computerized follow-up cards for ambulatory patients with implanted pacemaker or defibrillator]

The follow up of pacemaker and defibrillator dependent patients has a significant role for both the evaluation of pacing effectiveness and check of hemodynamic advantages about patient's quality of life. The bulky paper archives are often inaccurate, hampering the consultation. At present the paper card is the only document which can be utilized to record some data concerning the implant and patient clinical story. Therefore, there is the necessity for a card that can include all patient's data, and the implant and programming pacemaker/defibrillator data during follow up. This new pacemaker card has portable file or data-base including shared data with safety mechanism, which can be utilized in several controls by different users (physicians, hospital ward, primary care units, insurance companies). The pacemaker card includes a chip that permits to store a considerable amount of data; it can be update in every further medical control, in observance of laws. The card Chip Operating System (C.O.S.) consists of a microchip with a memory completely managed by the operating system inside the chip itself. The card can be read by means of a GCR-200 modem linked with a PC IBM-compatible computer and the data can be updated during the follow up. The pacemaker-defibrillator card will appear immediately on screen, and it can be printed, updated and/or modified by a Microsoft Windows operating programme. With this pacemaker card we are able to ensure serviceable medical work, particularly in terms of cost/benefit ratio giving to patient more and more reasoning and safe service.