VOO Mode Research Articles

Yes Is No

Yes Is No

Current Status and Issues Concerning Magnetic Resonance Imaging in Patients with a Magnetic Resonance Conditional Cardiac Implantable Electrical Device: A Single-center Study.

Objective Following the introduction of magnetic resonance (MR)-conditional cardiac implantable electrical devices (CIEDs), patients with CIEDs have undergone MRI scanning more frequently. As the required settings of MRI equipment for scanning patients with a CIED vary by device, a number of precautions should be taken to allow safe examinations, including the confirmation of conditions and selection of MRI modes appropriate for pacing status in individual patients. In this study, we examined the current status and issues concerning the performance of MRI examinations in patients with an MRI-conditional CIED. Method and Results We reviewed a total of 262 MRI scans. The most common site of MRI scanning was the head, followed by the spine, abdomen, and heart in order. Regarding the MRI mode, DOO was most often used, followed by OFF, AOO, and finally VOO mode, to maintain atrioventricular synchrony. Although no obvious adverse events were observed related to MRI scanning, there were several cases encountered that might have been predisposed to a significant incident or in which the patient's intrinsic pulse rates or subjective symptoms changed before and during scanning. Conclusion As MRI is a very useful diagnostic tool for cerebrovascular diseases and orthopedic disorders, the demand for MRI scanning is high when treating these areas. Although MRI scanning in patients with MR-conditional devices was performed without any adverse events, there were incidents that could have potentially led to major harm. This highlights the importance of confirming the appropriate MRI mode is being used before scanning and monitoring patients during scanning.

The radiofrequency interference on CRT-D functioning during AV node ablation: An educational case.

We have described some unusual findings of radiofrequency interference with ICD functioning during AV nodal ablation, guiding the reader to the possible explanation of the phenomena.

Anesthetic consideration for patients with micra leadless pacemaker

MICRA, miniaturized leadless single chamber pacemaker, is inserted directly into the right ventricular myocardium via transcatheter approach. We present a case of a 66-year-old patient with a Micra pacemaker scheduled for kidney-pancreas transplant. The patient is pacemaker dependent. The preoperative cardiology consult did not comment on the need of reprogramming. One hour prior to the surgery, the anesthesia team was unable to locate the pacemaker on the chest wall. The Medtronic hotline was called, and the caregivers learned that the particular pacemaker is buried within the ventricular wall and is not responsive to an external magnet. Thus, the case was delayed and a cardiac electrophysiology team was contacted to reprogram the pacemaker to VOO (fixed ventricular pacing) mode. We suggest that the pacemaker can pose perioperative challenges due to its novelty, paucity of report, and guidelines.

Inadvertent left ventricular pacing through a patent foramen ovale diagnosed by trans-thoracic echocardiography.

A trans-thoracic echocardiogram was performed to monitor the progression of aortic stenosis in an 87-year-old lady who had undergone permanent pacemaker insertion 4 months previously for symptomatic sinus bradycardia. The apical four-chamber view (Fig. 1, supplementary video) revealed that the ventricular lead (v-lead) had passed through a patent foramen ovale (PFO) and was fixed to the lateral left ventricular wall. A pacemaker check confirmed right bundle branch block (RBBB) morphology during VOO mode pacing (Fig. 2). The patient was advised to consider anticoagulation in the short term and repositioning of the v-lead at the time of aortic valve surgery as definitive therapy. However, she declined surgical intervention and is currently on long-term anticoagulation. Inadvertent left ventricular pacing may arise from the v-lead traversing a previously undetected PFO or perforation of the ventricular septum during implantation [1]. The major complication of LV pacing is systemic thromboembolism within days or years later [2] which prompts the standard recommendation of lead extraction and repositioning in such patients. However, a case series of patients who have undergone intentional endocardial LV pacing suggests that anticoagulation [international normalized ratio (INR) 2.5–3.5] provides adequate protection from thrombo-embolic events [3].

Design Overview Of Processor Based Implantable Pacemaker

Implantable pacemaker is a battery operated real time embedded system, which includes software/hardware codesign strategy. As it is placed within the heart by surgery, battery life is an important constraint to extend device lifetime. In this paper, pacemaker’s functionalities like basic pacing, pulse width, refractory period in VOO mode has been realized using ultralow power processor MSP 430F1611 and IAR workbench. Software related instruction level instantaneous current is measured and Current/Energy performance, battery longevity is tested. It is verified that, change in pure cost and interinstruction cost (current/Energy) varies from 2.0 to 3.0 %. This methodology seems to be an innovative concept in software related energy estimation of such power critical real time system.

Supraventricular arrhythmias in children with permanent pacemakers during long follow-up

Purpose of study was to evaluate the frequency of supraventricular arrhythmias in children with permanent pacemakers during long follow-up. Methods used Pacemakers were implanted in 81 children 43 males (53%) at the age of 3 to 192 month (mean age 110.9±53.6 month). 35 (43.2%) children underwent the VVI or VOO pacemaker implantation and 46 (56,8%) patients were paced in physiological pacing modes (AAI, VDD, VDDR, DDD, DDDR). Followup was performed for 12 to 360 month (mean follow-up – 119,1±87,9 month). Results Supraventricular arrhythmias were found in 11 patients (13, 6%) – group 1. In 6 (54.5%) patients of this group it was permanent atrial fibrillation and in 4(36.4%) patients – paroxysmal atrial fibrillation. In 1 (9.1%) patient permanent atrial flutter was detected. Two distinctive features were found in this group of patients: first – they were paced for a long period, second it was no physiological pacing. 2 of them were paced in VOO mode and 9 patients in VVI mode. Mean follow-up was 230,7±62,8 month. In contrast the mean follow-up of the second group consist of 24 patients without any supraventricular arrhythmias and who were also paced in VVI mode was 105,2±62,7 month (p=0,000024). We have seen statistical differences in hemodynamic parameters in these two groups of patients. Conclusion Supraventricular arrhythmias are more frequent in patients who have nonphysiological pacing (VOO, VVI) for a long time (more than 10 years)

Anesthetic management of a patient with severe dilated cardiomyopathy and an automatic implantable cardioverter-defibrillator (AICD) during total gastrectomy

We report a case of severe dilated cardiomyopathy with an automatic implantable cardioverter-defibrillator (ICD) undergoing total gastrectomy. During the operation, the defibrillation function of the ICD was suspended and its pacing function was used solely in VOO mode. Electrodes of an external defibrillator were attached on the chest wall, and a pulmonary arterial (PA) catheter with a ventricle pacing port was inserted into the pulmonary artery. Proper perioperative management, including measures that the patient underwent the surgery uneventfully and could attain a rapid and successful discharge from the intensive care unit.

Radiofrequency Treatment of Hepatic Neoplasms in Patients With Permanent Pacemakers

Radiofrequency Treatment of Hepatic Neoplasms in Patients With Permanent Pacemakers

912-39 Interactions Between Handy Phones and Pacemaker Function in Patients with Permanent Pacemakers

To date, it is unclear whether handy phones (C-net or D-net) can be used safely by patients with permanent pacemakers. Possible interactions between handy phones and pacemaker function include: 1) inhibition of the pacemaker, 2) change of temporary or permanent pacemaker programming, and 3) switch to VOO mode. Thirty pts (14 f, age: 48–87 years) with single chamber (13 pts) or dual chamber pacemakers (17 pts) were studied during routine follow-up in our outpatient department. Pacemaker sensing was unipolar in 17 pts, and bipolar in 13 pts. After completion of the routine pacemaker check, each pt was asked to make several phone calls with a handy phone (Ericsson R ; D-net; 2.5 watts). A surface ECG (Mingograph) was recorded continuously during each phone call in order to detect possible interactions between pacemaker function and handy phone use. Phone calls were repeated after pacemaker programming to 1) minimum ventricular rate of 90 bpm and previous sensitivity, and 2) minimum rate of 90 bpm and maximum sensitivity without T-wave oversensing. A change of the pacemaker programming or a switch to VOO pacing due to handy phone calls was not observed in any pt. Two of 30 pts (3%) reproducibly showed intermittent pacemaker inhibition during handy phone calls. Both pacemakers had unipolar sensing. Both pts remained asymptomatic during pacemaker inhibition since they were not completely pacemaker dependent. Although interactions between handy phone use and pacemaker function appear to be rare, pacemaker inhibition during phone calls may occasionaly occur, particularly if unipolar sensing is used. Therefore, pacemaker dependent patients should currently avoid the use of handy phones.

Revised Implantation Procedure for Programmable Automatic Implantable Cardioverter Defibrillator: Don't Discard the Magnet

The newest implantable defibrillator (Ventak 1550 AICD) introduces radiofrequency telemetric communication that obviates the need for activation and deactivation of the device by a magnet during implantation. We present three of our first ten cases of implantation in which difficulties in intraoperative sensing would have been undetected without use of the magnet for audible evaluation of sensing. Based on this experience, we recommend a revised implantation protocol in which audible confirmation of sensing for 30 to 60 seconds by means of a sterile magnet is performed twice (with a pacemaker, if present in DOO or VOO mode): at the time of system test before induction of arrhythmia with testing cables connected to permit recording of rate, morphology, and ECG interpretation channel signals; and after final connection of the leads to the AICD. This simple additional maneuver is a powerful troubleshooting tool during implantation that permits prompt identification of sensing problems.

Ventricular Fibrillation Following Elective Cardioversion in a Patient with Permanent Pacemaker

Elective cardioversion was undertaken in a patient with a VVI pacemaker and atrial tachyarrhythmia after converting the pacemaker to a VOO mode of function. The cardioverter output energy was unwittingly synchronized to the pacemaker output pulses that were falling randomly in various portions of the cardiac cycle. This resulted in the cardioverter DC shock being discharged in the ST segment of the native QRS with consequent ventricular fibrillation.

The Effect of Radiofrequency Catheter Ablation on Permanent Pacemakers: An Experimental Study

Radiofrequency current is being investigated as an alternative to direct current shock for transcatheter ablation of cardiac arrhythmias. Permanent pacemakers are known to be susceptible to high frequency electromagnetic interference. This study was performed to examine the effects of transcatheter radiofrequency ablation on permanent pacemakers in a worst-case scenario. Nineteen pulse generators representing 16 models from seven manufacturers were acutely implanted in 12 dogs to assess their function during and after ablation. Pulse generators were implanted subcutaneously in the neck and connected to a transvenous permanent pacing lead positioned in the right ventricular apex. A 6F quadripolar electrode catheter was positioned approximately 1 cm from the tip of the permanent pacing lead. Radiofrequency current from an electrosurgical unit was applied between the distal electrode of the catheter and a large diameter skin electrode placed below the left scapula. Three additional ablation sessions were performed with the catheter situated 4-5 cm from the permanent pacing lead. Each ablation consisted of 15 W of radiofrequency power, delivered for up to 30 seconds. Twelve pulse generators were falsely inhibited during radiofrequency ablation while programmed to the VVI or DDD mode, nine of which continued to be inhibited while programmed to the VOO or DOO mode. Five pulse generators paced at abnormal rates, including three examples of one pulse generator model that displayed pacemaker runaway. Runaway was observed during eight ablations, resulting in two episodes of ventricular fibrillation. Eleven pulse generators reverted to noise mode behavior during ablation. Only three pulse generators were unaffected during ablation. No reprogramming or pacing system malfunctions were observed after cessation of radiofrequency current application or during ablations greater than 4 cm from the permanent lead.(ABSTRACT TRUNCATED AT 250 WORDS)

Resetting of DDD Pacemakers Due to EMI

Multiprogrammable pacemakers have long been subject to inappropriate reprogramming and electromagnetic interference (EMI). A limited clinical experience with DDD pacing systems precludes the significance of such phenomena in these units. Since August 1981, in a series of 140 DDD systems, certain units demonstrated consistent and reproducible resetting to the back-up modes caused by electrocautery. One unit was permanently reset to the VOO mode. These observations suggest the need for renewed caution at the time of surgery; they also underscore the importance of a thorough understanding of any DDD system and careful follow-up so that such phenomena will not be misinterpreted as pacemaker failure, resulting in erroneous pacemaker removal.