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Biomedical subjects

Soo G Kim

Publications and source records attributed to Soo G Kim.

13 recordsLinked to original sources
PubMed2006

Effects of cardioactive medications on retrograde conduction: continuing relevance for current devices.

INTRODUCTION: Retroconduction (ventriculo-atrial conduction) remains a problem for patients with implanted cardiac rhythm devices. Pacemaker algorithms can detect and terminate endless loop tachycardia (ELT), but actual prevention of ELT may require anti-arrhythmic drugs (AADs). Similarly, AADs can affect ICD rhythm discrimination algorithms that depend on atrio-ventricular ratios. There is concern whether these drugs remain effective during stress situations. METHODS: Electrophysiologic studies that included retroconduction testing using slow ramp pacing were done in 1332 patients. The presence or absence of retroconduction at baseline and with drug was recorded, as was the rate at block. As a stress surrogate, isoproterenol was used to test retroconduction and reversal of drug-induced block. RESULTS: Procainamide, mexiletine, phenytoin, disopyramide, quinidine, beta-blockers, encainide, and amiodarone caused complete retrograde block or decreased the rate at which block occurred (mean 76% of patients, p < 0.008), whereas digoxin, lidocaine, diltiazem, and verapamil did not. Isoproterenol (in the absence of AADs) increased the rate at block in 82% of 404 patients with retroconduction at baseline (p < 0.005). Of 319 patients without retroconduction at baseline, 134 (42%) developed retroconduction after isoproterenol. Isoproterenol reversed retrograde block in 39% of patients with block on an AAD. Amiodarone, digoxin, and the combination of digoxin plus a beta-blocker were most effective at resisting this reversal of ventriculo-atrial block (80%, 68%, and 75% respectively). CONCLUSION: Most of the AADs reviewed increase the cycle length at block or abolish retroconduction, while isoproterenol has the opposite effect. Anti-arrhythmic medications, particularly amiodarone, digoxin, and the combination of digoxin plus a beta-blocker may be considered for a patient with multiple ELT episodes or certain ICD detection problems.

Adrenergic beta-Agonists↗
PubMed2005

Functional status in rate- versus rhythm-control strategies for atrial fibrillation: results of the Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) Functional Status Substudy.

OBJECTIVES: The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) functional status substudy aimed to test the hypothesis that functional status is similar in rate-control and rhythm-control strategies. BACKGROUND: Randomized studies, including the AFFIRM study, have failed to demonstrate survival benefits between rate-control and rhythm-control strategies for atrial fibrillation (AF). However, AF may cause functional capacity or cognitive impairment that might justify maintenance of sinus rhythm. METHODS: Investigators of the AFFIRM study enrolled 4,060 patients with AF who required long-term therapy and who were 65 years of age or older or who had another risk factor for stroke or death. New York Heart Association functional class (NYHA-FC) and Canadian Cardiovascular Society Angina Classification were assessed at initial and each follow-up visit. From 22 randomly chosen functional status substudy sites, 245 participants underwent 6-min walk tests and Mini-Mental State Examination (MMSE) at initial, two-month, and yearly visits. Patients were assigned randomly to rate-controlling drugs, allowing AF to persist, or rhythm-controlling antiarrhythmic drugs, to maintain sinus rhythm. RESULTS: The NYHA-FC worsened with time in both rate-control and rhythm-control groups, with no differences between groups. Presence of AF was associated with worse NYHA-FC (p < 0.0001). No differences were observed in Canadian Cardiovascular Society Angina Classification or MMSE scores. Six-minute walk distance improved over time in both study arms. On average, walk distance was 94 feet greater in the rhythm-control group (adjusted p = 0.049). CONCLUSIONS: Modest improvement in 6-min walk distance was noted in the rhythm-control arm. Presence of AF was associated with worse NYHA-FC. No difference in cognitive function was detected.

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PubMed2005

Occurrence and characteristics of stroke events in the Atrial Fibrillation Follow-up Investigation of Sinus Rhythm Management (AFFIRM) study.

BACKGROUND: Atrial fibrillation (AF) is a risk factor for stroke, especially when accompanied by other high-risk cardiovascular predictors. The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) Study was a multicenter comparison of high-risk patients with AF who were randomized to either a sinus rhythm control or a rate control strategy. METHODS: Physicians were encouraged to continue anticoagulation therapy for their patients. Patients in the sinus rhythm control group could stop warfarin sodium therapy after 4 (preferably a minimum of 12) weeks if they maintained sinus rhythm while receiving an antiarrhythmic drug. RESULTS: The AFFIRM Study enrolled 4060 patients. Mortality was the same in both groups. Two hundred eleven patients (8.2%) had a stroke event. Ischemic stroke occurred in 157 patients (6.3%), primary intraparenchymal hemorrhage in 34 (1.2%), and subdural or subarachnoid hemorrhage in 24 (0.8%). The most frequently determined ischemic stroke mechanism was cardioembolic (35/71 [49%]). Treatment assignment had no significant effect on the occurrence of ischemic stroke. Patients in AF at the time of the stroke event had a 60% greater chance of having an ischemic stroke, and those taking warfarin at the time of follow-up had a 69% decrease in the risk of having an ischemic stroke. CONCLUSIONS: In the AFFIRM Study, stroke rates were not significantly different in the rate control and sinus rhythm control arms. However, several clinical and therapeutic variables were associated with stroke risk. In patients with a history of AF at high risk for stroke or death, the presence of AF increases the risk of having a stroke, and warfarin therapy reduces the risk of having a stroke. The beneficial effect of warfarin therapy is seen not only in patients in AF but also in patients with a history of AF but who presumably remain in sinus rhythm.

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PubMed2005

Value of pre-hospital discharge defibrillation testing in recipients of implanted cardioverter defibrillators.

Opinions vary regarding the need to perform defibrillation testing prior to hospital discharge in recipients of state-of-the-art cardioverter defibrillators (ICDs). Our protocol is to perform predischarge ICD testing 1 day after implant. This report includes 682 consecutive implants. Adverse observations at testing were grouped into (1) risk of defibrillation failure, (2) surgical complications, (3) sensing/pacing issues or narrow defibrillation margin warranting closer follow-up, or (4) findings correctable by device reprogramming. Among the 682 patients, 63% had single-chamber and 37% dual-chamber or biventricular ICDs. In 48 patients (7%) there were 69 concerns and/or interventions, with overlaps among the four categories, including one failure to defibrillate (0.15%), and six other patients at risk. Surgical complications included 11 hematomas (1.6%), and six lead dysfunctions. Closer follow-up was indicated in 19 patients (2.7%), for high pacing thresholds in seven, sensing issues in seven, and <10 J defibrillation margin in five. Device reprogramming was needed in 31 patients (4.5%), for tachycardia detection and therapy settings in 12, and for pacing/sensing functions in 22 patients. In eight patients ventricular fibrillation could not be induced. There was no morbidity or mortality due to testing. The state-of-the-art ICDs delivering biphasic shocks are remarkably reliable. The routine pre-hospital discharge defibrillation testing of such ICDs may be optional and left to the physicians' discretion.

Defibrillators, Implantable↗
PubMed2004

Comparison of rectilinear biphasic waveform energy versus truncated exponential biphasic waveform energy for transthoracic cardioversion of atrial fibrillation.

Success rates of cardioversion with a defibrillator using the truncated exponential biphasic waveform (with a maximum energy of 360 J) and a defibrillator using the rectilinear biphasic waveform (with a maximum energy of 200 J) were randomly compared in 145 patients. Success rates at 50, 100, 150, and 200 J were not significantly different, but 2 patients who did not achieve cardioversion after a 200-J maximum energy shock by the rectilinear device underwent successful cardioversion with a 360-J shock by the truncated exponential device after crossover.

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PubMed2004

Easy surgical approach for completion of biventricular pacing.

Placement of a pacing lead into a branch of the coronary sinus for biventricular pacing sometimes is difficult or impossible. Surgical completion typically has included immediate or subsequent thoracotomy lead placement with hookup to the device at the time of chest surgery. We describe an alternative procedure of complete device-lead hookup and permanent pocket closure in the electrophysiology laboratory. The left ventricular lead is an epicardial type. The lead is tunneled to a position where the surgeon subsequently can recover it using the thoracotomy incision and implant the lead on the epicardium using device-based testing.

Aged↗
PubMed2004

Lead stuck (frozen) in header: salvage by bone cutter versus other techniques. jfisher@montefiore.org.

It is occasionally difficult to disconnect leads from headers at the time of pulse generator replacement without injuring the fragile leads. Over a 2.5-year period we encountered this problem in six cases (1.7% of pulse generator replacements). The posterior portion of the header was clipped off using an orthopedic bone cutter in four cases. The cut was aligned with the deep end of the lead socket in the header. A metal rod was then used to push the lead out of the socket. Bench testing of alternative methods was done on previously explanted pulse generators that were firmly held in a vice. Motorized microtools were used to drill holes from the end of the header to the deep end of the socket; or with a rotary saw attachment to slice off the back of the header, allowing a retained lead to be pushed out. The latter was also done with a hand held razor saw, and attempts were made with a scalpel. Lead removal in the clinical cases was accomplished quickly in the four cases using the bone-cutter, without trauma to the lead. Bench testing results varied. The bone cutter was the most efficient method for most brands, but was ineffective on one. The motorized tool was difficult to position, produced sprays of plastic particles, and would have been risky in a clinical setting. The razor saw was difficult to use safely, or efficiently, except in some headers that resisted the bone cutter. The scalpel failed except in one "soft header" pacemaker. An orthopedic bone cutter is a useful tool for removing a retained lead from a pulse generator header. Different header designs and materials necessitate knowledge of several lead detachment methods.

Device Removal↗
PubMed2004

Pacemakers and implantable cardioverter defibrillators: device longevity is more important than smaller size: the patient's viewpoint.

The size of pacemakers and implantable cardioverter defibrillators (ICDs) has been diminishing progressively. If two devices are otherwise identical in components, features and technology, the one with a larger battery should have a longer service life. Therefore, patients who receive smaller devices may require more frequent surgery to replace the devices. It is uncertain whether this tradeoff for smaller size is desired by patients. We surveyed 156 patients to determine whether patients prefer a larger, longer-lasting device, or a smaller device that is less noticeable but requires more frequent surgery. The effects of subgroups were evaluated; these included body habitus, age, gender, and patients seen at time of pulse generator replacement (PGR), initial implant, or follow-up. Among 156 patients surveyed, 151 expressed a preference. Of these, 90.1% preferred the larger device and 9.9% the smaller device (P <0.0001). Among thin patients, 79.5% preferred a larger device. Ninety percent of males and 89.2% of females selected the larger device. Among younger patients (< or =72 years), 89.6% preferred the larger device, as did 90.5% of older patients (>72 years). Of patients undergoing PGR or initial implants, 95% favored the larger device, as did 86% of patients presenting for follow-up. The vast majority of patients prefer a larger device to reduce the number of potential replacement operations. This preference crosses the spectrum of those with a previously implanted device, those undergoing initial implants, those returning for routine follow-up, and patients of various ages, gender, and habitus.

Adult↗
PubMed2003

Simplified tilt table test protocol with continuous upright position during medication administration and no hydration.

Recommendations for head-up tilt testing (HUT) often include the prolonged abstaining from food and water consumption (nothing by mouth [NPO]) and intravenous fluids administration before HUT. After the baseline test, supine equilibration periods are recommended before and between each dose of medication. The aim of this study was to determine if similar results are obtainable with a simpler protocol. After 2-3 hours NPO, 1,540 HUTs were performed at 70 degrees for 30 minutes unless predetermined endpoints were reached. Then, with the patient remaining in the tilted position, isoproterenol (ISO) (1 microgram/min), titrated every 3 minutes to a maximum of 5 micrograms/min (n = 803 patients), sublingual nitroglycerin (NTG) (300-400 micrograms) (n = 143 patients), or edrophonium (EDP) (5 mg) repeated once after 3 minutes (n = 46 patients) were administered. No aspiration or other adverse effects attributable to the abbreviated fasting period were observed. ISO was well tolerated as doses were increased. Vasovagal manifestations developed in 31% of ISO tests, in 11% with EDP, and in 50% with NTG (P < 0.001). Time consumed with rehydration before and postural changes during HUTs may be avoided when ISO is administered. With NTG the response may be excessive.

Edrophonium↗
PubMed2003

Broad applicability of ultrarapid train stimulation as an efficient alternative to conventional programmed electrical stimulation.

BACKGROUND AND STUDY OBJECTIVE: Conventional programmed electrical stimulation (PES) is useful for establishing inducibility or noninducibility of clinical ventricular arrhythmias (VA), but is complex and time-consuming. This study compared a standard PES protocol with ultrarapid train stimulation (UTS) in a broad range of patients with and without a history of ventricular arrhythmias or structural heart disease. METHODS: Patients prospectively underwent electrophysiologic testing with both UTS and conventional PES protocols in a randomized, crossover design. RESULTS: The results were concordant in 79% of 150 matched pairs of comparisons in 104 patients (NS). There were no differences related to underlying heart disease or arrhythmia, or antiarrhythmic treatment. Induction of nonclinical arrhythmias with the two methods was similar (P = 0.524). Inhibition phenomena were minor except in some patients receiving amiodarone. Fewer drive-extrastimuli sequences and less time were needed to complete the trains protocol (P < 0.0001). CONCLUSIONS: In cases where the main intent is to induce ventricular arrhythmias, UTS yields results that are similar to those of conventional PES protocols in a shorter length of time.

Anti-Arrhythmia Agents↗
PubMed2002

Runaway pulse generator malfunction resulting from undetected battery depletion.

Runaway pacemaker is an uncommon, potentially lethal circuit malfunction characterized by sudden onset of erratic pacing at rapid nonphysiological rates. Two patients with a single chamber pacemaker (Medtronic ST 8331 and 8419) presented with episodic dizziness. ECG revealed recurrent decrescendo amplitude episodes of runaway stimuli at 2,400 and 2,600 ppm, approximately 3 seconds in duration, separated by pacing at 62.5 and 65 ppm, respectively. Fortunately the runaway stimuli were subthreshold and did not result in capture of the ventricle. Emergency pulse generator replacement was uneventful. Both leads were normal and both pulse generators had low battery voltages at 1.488 and 1.78 V, respectively.

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