Hayes, David L.

AbstractBackgroundTransthoracic impedance measurements (TIM) is primarily used for minute ventilation rate adaptive sensors in pacemakers. With elevated impedance, the TIM electrical signal itself is oversensed, causing device malfunction.ObjectiveWe report an increased incidence of TIM oversensing.MethodRetrospective chart review. We review existing records of 18 patients who have demonstrated device malfunction with TIM oversensing.ResultsWe have found a 1.8% incidence of TIM‐related oversensing in our patient population of 959 patients with contemporary Boston Scientific (Marlborough, MA, USA) pacemakers and cardiac resynchronization therapy pacemakers. One patient experienced a syncopal episode.ConclusionOversensing with pacing inhibition is apparent with the potential of adverse effects to patients.

ICD Characteristics and Survival in Young PatientsIntroductionIndications for implantable cardioverter defibrillators (ICDs) in young patients have expanded and differ from those in older adults. We sought to provide descriptive characteristics and data regarding ICD therapy and outcomes among younger and older ICD recipients.Methods and ResultsDemographics, device type and programming, remotely transmitted data, shock events, and survival were compared among younger (≤30 years) and older (>30 years) cohorts with ICDs from a single manufacturer followed on a remote network. The younger cohort included 904 patients (1.6% of all implants). This group had more females (46% vs. 25%; P < 0.01), single‐coil leads (21% vs. 4%; P < 0.01), and single‐chamber devices (46% vs. 34%; P < 0.01). Shock incidence was higher (40% younger vs. 32% older at 4 years; P < 0.01) and survival was better over comparable follow‐up (88% vs. 72%; P < 0.01). Remote monitoring was associated with improved survival in both groups (93% vs. 86% ≤ 30 years, P < 0.01; 73% vs. 66% > 30 years, P < 0.01). Shock for polymorphic ventricular tachycardia/fibrillation (VT/VF) was more frequent in younger patients (12% vs. 5%; P < 0.01); 39% of all shocks were inappropriate. A 10‐fold increased risk of mortality was seen among young patients with shocks for atrial fibrillation/flutter (AF/AFL).ConclusionsDifferences in survival, shock incidence, and prognostic significance of VT/VF and AF/AFL exist between younger and older ICD recipients. These suggest distinct differences in myocardial substrates and diseases that ultimately impact ICD management.

Background Physical activity data are collected automatically by implantable cardioverter‐defibrillators ( ICD s). Though these data potentially provide a quantifiable and easily accessible measure of functional status, its relationship with survival has not been well studied. Methods and Results Patients enrolled in the Boston Scientific LATITUDE remote monitoring system from 2008 to 2012 with ICD s were eligible. Remote monitoring data were used to calculate mean daily activity at baseline (30 to 60 days after implantation), and longitudinally. Cox regression was used to examine the association between survival and increments of 30 minutes/day in both (1) mean baseline activity and (2) time‐varying activity, with both adjusted for demographic and device characteristics. A total of 98 437 patients were followed for a median of 2.2 years (mean age of 67.7±13.1 years; 71.7% male). Mean baseline daily activity was 107.5±66.2 minutes/day. The proportion of patients surviving after 4 years was significantly higher among those in the most versus least active quintile of mean baseline activity (90.5% vs. 50.0%; log‐rank P value, <0.001). Lower mean baseline activity (i.e., incremental difference of 30‐minutes/day) was independently associated with a higher risk of death (adjusted hazard ratio [ AHR ], 1.44; 95% confidence interval [ CI ], 1.427 to 1.462). Time‐varying activity was similarly associated with a higher risk of death ( AHR , 1.48; 95% CI , 1.451 to 1.508), indicating that a patient having 30 minutes per day less activity in a given month has a 48% increased hazard for death when compared to a similar patient in the same month. Conclusions Patient activity measured by ICD s strongly correlates with survival following ICD implantation.

SummaryThe cardiac effects of hypercalcaemia are usually manifest as a shortening of the QT-interval. Hypercalcaemia is infrequently associated with a clinically manifest arrhythmia. However, concomitant therapy with digoxin or underlying cardiac disease can potentiate the arrhythmogenic effects of hypercalcaemia, leading to a symptomatic rhythm disorder. We describe a symptomatic arrhythmia, which developed in a patient with hypercalcaemia secondary to squamous cell carcinoma of the bronchus. The patient was on digoxin therapy at the time. The arrhythmia did not recur after discontinuation of digoxin therapy and correction of the hypercalcaemia. Because of its effect on cardiac conduction, hypercalcaemia should be considered in the evaluation of any patient with an unexplained bradyarrhythmia. Conversely, patients with hypercalcaemia should discontinue digoxin therapy and be evaluated for the presence of rhythm disorders while receiving appropriate treatment for hypercalcaemia.

Background— Prompt recognition of underlying cardiovascular implantable electronic device (CIED) infection in patients presenting with Staphylococcus aureus bacteremia (SAB) is critical for optimal management of these cases. The goal of this study was to identify clinical predictors of CIED infection in patients presenting with SAB and no signs of pocket infection. Methods and Results— All cases of SAB in CIED recipients at Mayo Clinic from 2001 to 2011 were retrospectively reviewed. We identified 131 patients with CIED who presented with SAB and had no clinical signs of device pocket infection. Forty-five (34%) of these patients had underlying CIED infection based on clinical or echocardiographic criteria. The presence of a permanent pacemaker rather than an implantable cardioverter-defibrillator (odds ratio, 3.90; 95% confidence interval, 1.65–9.23; P =0.002), >1 device-related procedure (odds ratio, 3.30; 95% confidence interval, 1.23–8.86; P =0.018), and duration of SAB ≥4 days (odds ratio, 5.54; 95% confidence interval, 3.32–13.23; P <0.001) were independently associated with an increased risk of CIED infection in a multivariable model. The area under the receiver operating characteristics curve for the multivariable model was 0.79, indicating a good discriminatory capacity to distinguish SAB patients with and without CIED infection. Conclusions— Among patients presenting with SAB and no signs of pocket infection, the risk of underlying CIED infection can be calculated based on the type of device, number of device-related procedures, and duration of SAB. We propose that patients without any of these high-risk features have a low risk of underlying CIED infection and may be monitored closely without immediate device extraction. Prospective studies are needed to validate this risk prediction model.

Femoral ExtractionLaser and radiofrequency energy–assisted lead extraction has greatly facilitated this complex procedure. Although success rates are high, in some instances alternate methods of extraction are required. In this review, we discuss techniques for femoral extraction of implanted leads and retained fragments. The major tools available, including commonly used snares and delivery tools, are discussed. We briefly describe combined internal jugular and femoral venous extraction approaches, as well as complimentary utilization of more than one technique via the femoral vein. Animated and procedural sequences are included to help the reader visualize the key components of these techniques.

Abstract Aims Prognostic benefit from CRT compared with controls is well established. Symptomatic response rates, however, are controversial and have never been systematically evaluated with standard subtraction of control rates to establish the incremental symptomatic response effect of CRT pacing. Methods and results First, we identified 150 consecutive CRT papers and assessed researchers’ perceptions of the symptomatic response to CRT. The mean quoted response rate was 66%. Only 26 studies acknowledged the existence of response without the device. Secondly, we examined actual symptomatic response rates in the randomized trials (CARE-HF, COMPANION, CONTAK-CD, MIRACLE, MIRACLE-ICD, MIRACLE-ICD II, MUSTIC, and REVERSE) totalling 3904 patients. The NYHA status improved in 51% of those randomized to CRT vs. 35% of controls (incremental effect 16%). This incremental improvement was significantly greater in open studies (with no device for controls) than in blinded studies (control arm receiving a device but no CRT, such as a defibrillator or a CRT programmed off), 20% vs. 13%, P &lt; 0.001. Conclusions Quoting CRT responder rates in isolation without recognizing spontaneous ‘response’ is common but unwise. The incremental symptomatic response rate from CRT pacing is ∼16%, much lower than widely reported. This value is similar to that for drugs in heart failure and should not be considered disappointing: they both exert powerful prognostic benefits. For scientific purposes, e.g. to explore potential improvements, symptomatic benefit from CRT should be quantified, like all other effects, by comparison with a control.