[Show abstract][Hide abstract] ABSTRACT: We hypothesized that amiodarone (AM), unlike d-sotalol (DS) (a 'pure' Class III agent), not only prolongs the action potential duration (APD) but also causes post-repolarization refractoriness (PRR), thereby preventing premature excitation and providing superior antiarrhythmic efficacy.
[Show abstract][Hide abstract] ABSTRACT: Despite remarkable advances in design, implantable cardioverter-defibrillator (ICD) leads remain the component most susceptible to failure, which often leads to substantial adverse clinical outcomes. This article focuses on management strategies when ICD lead systems fail. Two cases involving management decisions for ICD lead failures are presented and discussed. One involves a common mode of presentation, inappropriate shocks. The second involves an alert in a patient with a complex system and multiple comorbidities. Although a systematic approach is outlined, management decisions must be balanced by a risk-and-benefit assessment of the individual patient.
No preview · Article · Jun 2012 · Cardiac electrophysiology clinics
[Show abstract][Hide abstract] ABSTRACT: Epidemiological findings, based largely on middle-aged populations, support an inverse and independent association between exercise capacity and mortality risk. The information available in older individuals is limited.
Between 1986 and 2008, we assessed the association between exercise capacity and all-cause mortality in 5314 male veterans aged 65 to 92 years (mean+/-SD, 71.4+/-5.0 years) who completed an exercise test at the Veterans Affairs Medical Centers in Washington, DC, and Palo Alto, Calif. We established fitness categories based on peak metabolic equivalents (METs) achieved. During a median 8.1 years of follow-up (range, 0.1 to 25.3), there were 2137 deaths. Baseline exercise capacity was 6.3+/-2.4 METs among survivors and 5.3+/-2.0 METs in those who died (P<0.001) and emerged as a strong predictor of mortality. For each 1-MET increase in exercise capacity, the adjusted hazard for death was 12% lower (hazard ratio=0.88; confidence interval, 0.86 to 0.90). Compared with the least fit individuals (< or =4 METs), the mortality risk was 38% lower for those who achieved 5.1 to 6.0 METs (hazard ratio=0.62; confidence interval, 0.54 to 0.71) and progressively declined to 61% (hazard ratio=0.39; confidence interval, 0.32 to 0.49) for those who achieved >9 METs, regardless of age. Unfit individuals who improved their fitness status with serial testing had a 35% lower mortality risk (hazard ratio=0.65; confidence interval, 0.46 to 0.93) compared with those who remained unfit.
Exercise capacity is an independent predictor of all-cause mortality in older men. The relationship is inverse and graded, with most survival benefits achieved in those with an exercise capacity >5 METs. Survival improved significantly when unfit individuals became fit.
[Show abstract][Hide abstract] ABSTRACT: Background. Right ventricular pacing (RVP) has been associated with adverse outcomes, including heart failure and death. Minimizing RVP has been proposed as a therapeutic goal for a variety of pacing devices and indications.
Objective. Quantify survival according to frequency of RVP in veterans with pacemakers. Methods. We analyzed electrograms from transtelephonic monitoring of veterans implanted with pacemakers between 1995 and 2005 followed by the Eastern Pacemaker Surveillance Center. We compared all cause mortality and time to death between patients with less than 20% and more than 80% RVP. Results. Analysis was limited to the 7198 patients with at least six trans-telephonic monitoring records (mean = 21). Average follow-up was 5.3 years. Average age at pacemaker implant was significantly lower among veterans with <20% RVP (67 years versus 72 years; P < .0001). An equal proportion of deaths during follow-up were noted for each group: 126/565 patients (22%) with <20% RVP and 1113/4968 patients (22%) with >80% RVP. However, average post-implant survival was 4.3 years with <20% RVP versus 4.7 years with >80% RVP (P < .0001). Conclusions. Greater frequency (>80%) of RVP was not associated with higher mortality in this population of veterans. Those veterans utilizing <20% RVP had a shortened adjusted survival rate (P = .0016).
Full-text · Article · May 2010 · Cardiology Research and Practice
[Show abstract][Hide abstract] ABSTRACT: Heart failure is associated with ventricular tachyarrhythmias (VT/VF). Fluid accumulation during worsened heart failure may trigger VT/VF. Increased intrathoracic impedance has been correlated with fluid accumulation during heart failure. Implanted defibrillators capable of daily measures of intrathoracic impedance allow correlation of impedance with occurrence of VT/VF. We hypothesized that VT/VF episodes are preceded by decreases in intrathoracic impedance. The goal was to identify the relationship of intrathoracic impedance measured by implanted cardioverter defibrillators to the occurrence of VT/VF.
Implanted defibrillator follow-up data were obtained retrospectively. Those with Medtronic OptiVol (Medtronic Inc., Minneapolis, MN, USA), storing averaged daily and reference impedance values, were reviewed for VT/VF episodes. Impedance changes in the week leading up to VT/VF were analyzed.
A total of 317 VT/VF episodes in a cohort of 121 patients' follow-up data were evaluated. Averaged daily intrathoracic impedance declined preceding 64% of VT/VF episodes, with an average decline of 0.46 +/- 0.35 Ohms from the day before the VT/VF episodes. However, the mean values of the averaged daily and reference impedance did not change significantly. A novel measure, DeltaTI, the sum of the daily differences between the averaged daily and reference impedance, was negative preceding 66% of VT/VF episodes (P < 0.001). The mean DeltaTI was -4.0 +/- 1.3 Ohms, which was significantly lower than the theoretically expected value of zero Ohms (P < 0.01).
(1) Averaged daily impedance declined preceding 64% of VT/VF episodes, but the overall decline was of small magnitude; (2) a novel measure, DeltaTI, was negative preceding 66% of VT/VF episodes, and significantly below zero.
No preview · Article · Mar 2010 · Pacing and Clinical Electrophysiology
[Show abstract][Hide abstract] ABSTRACT: Defibrillator implanters have adopted different approaches to managing failures of multicomponent implanted cardioverter defibrillator (ICD) leads. Although recent publications identified single-component failures as common mechanisms of failure, there are no published data regarding how best to manage these failures.
An internet-based survey was conducted to identify current management strategies. Questions were asked regarding isolated failure of a high-voltage coil or of a pace/sense electrode, in order to identify the frequency of various techniques to correct these failures.
A worldwide query collected strategies from 376 physicians identifying themselves as ICD-implanting physicians. Replies came from 28 countries, with the USA accounting for 83.2%. The survey was completed by 85.6% of respondents. Implant experience was >10 years for 61.1%, 3-10 years for 29.1%, and <3 years for 10.4%. When the right ventricular coil failed, 52% abandoned and 48% explanted the failed lead. In superior vena cava coil failure, 61.2% chose to simply exclude this coil, using the other intact lead components. For pace/sense defects, 53.1% chose to implant a new pace/sense lead or switch sensing electrodes, using the intact lead components. Medical literature (76.1%), personal experience (67.6%), and professional guidelines (63.7%) were strong decision-making influences.
(1) Management decisions for single-component failures of ICD leads are complex; (2) Significant differences in management strategy exist among physicians; (3) Medical literature and professional guidelines are strong influences for these decisions; (4) A lead failure registry could help identify reasons for such differences and help guide management.
No preview · Article · Sep 2009 · Pacing and Clinical Electrophysiology
[Show abstract][Hide abstract] ABSTRACT: Increased QT Variability (QTVI) is predictive of life threatening arrhythmias in vulnerable patients. The predictive value of QTVI is based on resting ECGs, and little is known about the effect of acute exercise on QTVI. The relation between QTVI and arrhythmic vulnerability markers such as T-wave alternans (TWA) has also not been studied. This study examined the effects of exercise on QTVI and TWA in patients with arrhythmic vulnerability.
Digitized ECGs were obtained from 47 ICD patients (43 males; age 60.9 +/- 10.1) and 23 healthy controls (18 males; age 59.7 +/- 9.5) during rest and bicycle exercise. QTVI was assessed using a previously validated algorithm and TWA was measured as both a continuous and a categorical variable based on a priori diagnostic criteria.
QTVI increased with exercise in ICD patients (-0.79 +/- 0.11 to 0.36 +/- 0.08, P < 0.001) and controls (-1.50 +/- 0.07 to -0.19 +/- 0.12, P < 0.001), and QTVI levels were consistently higher in ICD patients than controls during rest and exercise (P < 0.001). The magnitude of QTVI increase from baseline levels was not larger among ICD patients versus controls (P > 0.20). Among ICD patients, elevated exercise QTVI was related to lower LV ejection fraction and inducibility of ischemia (P < 0.05). QTVI at rest correlated with exercise TWA (r = 0.54, P = 0.0004).
QT variability increases significantly with exercise, and exercise QTVI is related to other well-documented markers of arrhythmic vulnerability, including low ejection fraction, inducible ischemia, and TWA. Resting QTVI may be useful in the risk stratification of individuals incapable of performing standard exercise protocols.
No preview · Article · Jan 2009 · Annals of Noninvasive Electrocardiology
[Show abstract][Hide abstract] ABSTRACT: This is the case of a 77-year-old man with hypertension, diabetes, ischemic cardiomyopathy, heart failure, and an extensive device history. In May 2005, he underwent implantation of a right-sided biventricular implantable cardioverter defibrillator (ICD) system (Medtronic Insync Maximo 7303), Capsure Fix Novus 4076 atrial lead (Medtronic), Sprint Fidelis 6949 right ventricular (RV) dual coil ICD lead (Medtronic), and Attain OTW Bipolar 4194 left ventricular (LV) lead (Medtronic). In September 2007, he was using his right arm to dig a ditch and lay bricks. The next day while holding up a newspaper to read, he received multiple shocks. He was taken to a local emergency room where his ICD was reprogrammed to prevent shocks, and he was transferred to our facility for management.
No preview · Article · Aug 2008 · Pacing and Clinical Electrophysiology
[Show abstract][Hide abstract] ABSTRACT: Exercise capacity is inversely related to mortality risk in healthy individuals and those with cardiovascular diseases. This evidence is based largely on white populations, with little information available for blacks.
We assessed the association between exercise capacity and mortality in black (n=6749; age, 58+/-11 years) and white (n=8911; age, 60+/-11 years) male veterans with and without cardiovascular disease who successfully completed a treadmill exercise test at the Veterans Affairs Medical Centers in Washington, DC, and Palo Alto, Calif. Fitness categories were based on peak metabolic equivalents (METs) achieved. Subjects were followed up for all-cause mortality for 7.5+/-5.3 years. Among clinical and exercise test variables, exercise capacity was the strongest predictor of risk for mortality. The adjusted risk was reduced by 13% for every 1-MET increase in exercise capacity (hazard ratio, 0.87; 95% confidence interval, 0.86 to 0.88; P<0.001). Compared with those who achieved <5 METs, the mortality risk was approximately 50% lower for those with an exercise capacity of 7.1 to 10 METs (hazard ratio, 0.51; 95% confidence interval, 0.47 to 0.56; P<0.001) and 70% lower for those achieving >10 METs (hazard ratio, 0.31; 95% confidence interval, 0.26 to 0.36; P<0.001). The findings were similar for those with and without cardiovascular disease and for both races.
Exercise capacity is a strong predictor of all-cause mortality in blacks and whites. The relationship was inverse and graded, with a similar impact on mortality outcomes for both blacks and whites.
[Show abstract][Hide abstract] ABSTRACT: To assess if mental stress hemodynamic responses are impaired and related to mental stress (MS) ischemia in patients with left ventricular (LV) dysfunction.
Impaired LV function is an important coronary artery disease (CAD) risk factor and hemodynamic characteristics play an important role in clinical outcomes. Patients with severe LV dysfunction (SLVD) are frequently excluded from prior studies and the effects of LV dysfunction on MS hemodynamic responses are not known.
Fifty-eight patients with CAD, consisting of 22 patients with normal LV function (ejection fraction (EF) > or =50%), 16 patients with mild-to-moderate LV dysfunction (30% < EF < 50%), and 20 patients with severe LV dysfunction (EF < or =30) underwent bicycle exercise (EX) and MS testing with 12-lead electrocardiogram and monitoring of vital signs on consecutive days in random order. Blood pressure and heart rate (HR) measurements were obtained. Ischemia was measured using single photon emission computed tomography.
Both MS and EX produced significant increases in all hemodynamic measurements. HR levels were higher both at rest and during MS in SLVD patients. LV groups increased similarly from rest to stress (both MS and EX) for all measurements except HR during MS, which increased more in patients with SLVD than patients with normal LV function. Hemodynamic responses to MS were not related to myocardial ischemia or heart failure symptoms.
HR response during MS is increased in patients with SLVD, whereas blood pressure responses are similar to those in patients with preserved LV function. Hemodynamic reactivity is unrelated to MS-induced ischemia.
Full-text · Article · Jul 2007 · Psychosomatic Medicine
[Show abstract][Hide abstract] ABSTRACT: Heart failure complicated by atrial fibrillation (AF) is associated with excessive mortality and morbidity. The aim of the study was to determine the role of amiodarone or implantable cardioverter/defibrillator (ICD) in patients with AF and heart failure.
Patients were determined to be in sinus rhythm (SR) or AF on the baseline electrocardiogram. Mortality, ICD discharge, or change in rhythm was assessed.
Of the 2521 patients at baseline, 2328 were in SR and 173 were in AF. Overall, after adjusting for differences in baseline variables, there was no difference in mortality between patients with SR and patients with AF (P = .98), nor within assigned groups: placebo (P) (P = .82), amiodarone (A) (P = .68), and ICD (P = .40). For patients with SR, ICD decreased mortality (P vs ICD, P = .004; A vs ICD, P = .004; P vs A, P = .75). For patients with AF, there were no differences in mortality among groups (P vs ICD, P = .99; A vs ICD, P = .88; P vs A, P = .88). Of patients with SR at baseline, 11% (264) developed AF by any electrocardiogram during follow-up (P 12%, A 8%, ICD 15%; A vs P, P = .019; A vs ICD, P = .001; P vs ICD, P = .044). Of patients with AF, 70% (121) developed SR during follow-up (P 66%, A 67%, ICD 75%, all P = not significant against each other). Any ICD shock was seen in 52% (34) of patients with AF vs 30% (222) of patients with SR (P = .001). Inappropriate shocks were seen in 37% (24) of patients with AF vs 14% (107) of patients with SR (P = .001). Appropriate shocks were more often seen in AF vs SR (P = .03).
After adjustments for baseline differences, patients with AF and patients with SR have similar overall mortality rates. Compared to P or A, ICD improves survival in patients with SR, but may not in patients with AF. Amiodarone is effective in reducing new AF, but not in converting AF to SR. Implantable cardioverter/defibrillator, inappropriate, and appropriate shocks were more often seen in AF than in SR.
No preview · Article · Dec 2006 · American heart journal
[Show abstract][Hide abstract] ABSTRACT: Implantable pacemaker cardioverter defibrillators are now available with biphasic waveforms, which have been shown to markedly improve defibrillation thresholds (DFTs). However, in a number of patients the DFT remains high. Also, DFT may increase after implantation, especially if antiarrhythmic drugs are added. We report on the use of a subcutaneous patch in the pectoral position in 15 patients receiving a transvenous defibrillator as a method of easily reducing the DFT. A 660-mm2 patch electrode was placed beneath the generator in a pocket created on the pectoral fascia. The energy required for defibrillation was lowered by 56% on average, and the system impedance was lowered by a mean of 25%. This maneuver allowed all patients to undergo a successful implant with adequate safety margin.
No preview · Article · Jun 2006 · Pacing and Clinical Electrophysiology