Reduction of right ventricular pacing in patients with dual-chamber ICDs

BACKGROUND: Unnecessary right ventricular (RV) pacing in patients with implantable cardioverter defibrillators (ICD) may adversely affect heart failure morbidity and total mortality. Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) is a prospective, multicenter, randomized trial evaluating outcomes in ICD recipients programmed to single-chamber pacing (VVI) versus dual-chamber (DDDR) pacing with AV search hysteresis (AVSH). METHODS: Patients underwent ICD implant (for standard indications). The ICD was programmed to DDDR with AVSH regardless of any need for pacing. Rate-adaptive pacing was set at 60-130 ppm with dynamic AV delay from 200 to 90 ms. AVSH was programmed to search every 32 intervals and extend the AV delay by 50%. One week post-implant patients with ICDs were interrogated to assess the percentage of RV pacing with the expectation that most would have <20% RV pacing and would be randomized into INTRINSIC RV. Early analysis showed that targets for randomization were not met. AVSH parameters were modified under a protocol amendment to increase AV delay extension to 100%. We report findings related to this programming change based upon analyses of (nonrandomized) data pre- and post-amendment. RESULTS: Twenty-one percent of patients (n = 314) were enrolled pre-amendment and 79% (n = 1,216) were enrolled post-amendment. The mean percentage of RV pacing at the 1-week visit was 41.4 +/- 29.6% pre-amendment and 14.7 +/- 22.6% post-amendment (P < 0.0001). The proportion of patients eligible for randomization (RV pacing <20% at the 1-week visit) was 31.2% pre-amendment and 76.8% post-amendment (P < 0.0001). CONCLUSION: AVSH can dramatically reduce the percentage of RV pacing among ICD recipients.     

Multicenter experience with implantable defibrillators subject to recall

Background: The management of implantable cardioverter defibrillators (ICDs) affected by advisories, which often include generator replacement, is complex and the risk of device failure needs to be carefully assessed for each patient. Methods: We analyzed the response to the advisory communication in the Italian centers involved in the recall for the Prizm 1861 and Renewal (Boston Scientific–formerly Guidant—St. Paul, MN, USA) communication. Results: One hundred and thirty‐nine of 843 Prizm (16.5%) and 458 of 2,342 Renewal devices (19.6%) were explanted. The total incidence over a 4‐year time frame of the failure event was equal to zero of 710 (0%) for Prizm ICDs and eight of 2,342 (0.34%) for Renewal ICDs. A limited percentage of devices affected by recall were definitely explanted following the indications stated by the advisory. The failure rates that resulted from analysis of our data (0% for Prizm and 0.34% for Renewal) were inferior to those already found or projected along the device lifetime globally, as reported in the most recent Company Product Performance Report (0.72% for Prizm and 1.83% for Renewal). Conclusions: In absence of underestimation of the events, a lower incidence than expected could resize the dimension of the problem, justifying the concept of a more frequent follow‐up of patient with respect to the choice of an immediate device explant. (PACE 2011; 34:998–1002)     

应用直接节段多频生物电阻抗分析方法评价血液透析患者全身容量负荷变化的准确性

目的探讨运用直接节段多频生物电阻抗分析方法(direct segmental multi-frequency bioimpedance analysis:DSM-BIA)评估维持性血液透析患者全身容量负荷变化的准确性。方法应用DSM-BIA测量患者单次血液透析前全身总水量(Total body water by DSM-BIA before hemodialysis:TBWDSM-pre)及透析后全身总水量(Total body water by DSM-BIA after hemodialysis:⊿TBWDSM-post);同时应用以整体踝腕法为基础的人体构成频谱方程(body composition spectroscopy equations:BCSE)来计算透析前TBW(⊿TBWBCSE-pre)、透析后TBW(⊿TBWBCSE-post);将透析前后实际体质量的变化值当做实际脱水量(actualul trafiltration volume:AUV);分别将DSM-BIA、BCSE2种方法所得透析前后TBW的差值与AUV比较。结果由DSM-BIA测量透析前后体质量的变化与AUV有统计学差异(2.32±1.1与2.65±1.04L,t=2.962,P<0.01)。DSM-BIA测得透析前后TBW的差值与AUV有较好的一致性,虽然会低估AUV(-0.3±1.4L),不过相较于BCSE(-0.65±1.65L),DSM-BIA对AUV的评估更加准确。结论与BCSE方法相比,DSM-BIA可以更准确反应维持性血液透析患者的全身容量负荷的变化。     

ICD implantation and arrhythmia-free survival in patients with depressed LV function following surgery for valvular heart disease

Background: Although prophylactic implantable cardioverter‐defibrillator (ICD) implantation is beneficial in patients with severe ischemic cardiomyopathy, it is unclear whether patients with cardiomyopathy due to valvular heart disease have a similar benefit. Methods: We followed 17 patients (14 men/three women, age 62 ± 13 years, left ventricular ejection fraction [LVEF] 29 ± 10%) who had nonischemic valvular cardiomyopathy, underwent valvular heart surgery (aortic valve replacement, mitral valve replacement, and/or mitral valve repair), and subsequently had an electrophysiology study (EPS), for a median of 2.8 years. These patients were compared with 34 patients with prior myocardial infarction and no significant valvular heart disease, who were matched (1:2) for age, gender, LVEF, EPS result, T‐wave alternans result, and ICD placement. Occurrence of arrhythmias was ascertained from ICD device clinic follow‐up and vital status was determined using the National Death Index. Results: There were no differences between the groups in overall survival (P = 0.24) or arrhythmia‐free survival (P = 0.38), and the 2‐year arrhythmia‐free survival was 82% for the valvular patients versus 73% for the ischemic patients. Among patients with ICDs, there was no difference between the groups in overall survival (P = 0.34), time to first appropriate ICD therapy (P = 0.54), and arrhythmia‐free survival (P = 0.51). Conclusion: Patients with valvular cardiomyopathy and residual left ventricular dysfunction following valvular surgery who underwent a tailored approach to ICD implantation had similar overall and arrhythmia‐free survival as patients with ischemic cardiomyopathy.     

Cardiac resynchronisation therapy for heart failure

Cardiac resynchronisation therapy (CRT) reduces symptoms and improves left ventricular function in chronic heart failure (CHF) patients with left ventricular systolic dysfunction and prolonged QRS duration. Recent studies have demonstrated a reduction in mortality associated with CRT. When combined with an implantable cardioverter defibrillator (ICD) reduction in mortality is likely to reduce further. Cardiac resynchronisation therapy is well tolerated and free from compliance issues and therefore should be considered for all suitable patients. Identifying patients who will derive maximum benefit requires further study and has health economic implications. We review here the CRT trial evidence as well as the implantation technique and complications. We also describe a case report where an intra-aortic balloon pump was used successfully as a bridge to CRT to treat a patient with end-stage heart failure.     

An impaired renal function: a predictor of ventricular arrhythmias and mortality in patients with nonischemic cardiomyopathy and heart failure

Background: This study investigated the overall mortality and the incidence of ventricular tachyarrhythmia (VT) in 99 patients with nonischemic cardiomyopathy (NICM) and with an implantable cardioverter defibrillator (ICD) suffering from heart failure. Methods: We performed a stepwise regression model to identify independent risk factors for the occurrence of ventricular arrhythmias. Using a Cox regression model, independent risk factors for total mortality were evaluated and, subsequently, a Kaplan‐Meier analysis was applied. The primary endpoint of this study was the identification of independent predictors of overall mortality and the incidence of malignant arrhythmias. Results: One hundred twenty‐five VT (≥310 ms), 51 fast VT (between 310 ms and 240 ms), and 48 episodes of ventricular fibrillation (≤240 ms) were documented in 32 patients. Independent predictors of arrhythmias detected and treated by the ICD included female gender (odds ratio [OR] 3.4), lack of statin therapy (OR 3.5), and increased serum creatinine (OR 3.7). The Kaplan‐Meier analysis showed no difference in survival between participants with or without VT. Total mortality was predicted by increased age (OR 2.3) and an impaired renal function (OR 1.9), independently. Conclusions: In this cohort of NICM patients with heart failure, female gender, lack of statin therapy, and increased creatinine represented independent risk factors for the incidence of malignant arrhythmias. Furthermore, renal insufficiency and age favored total mortality. Considering these results, impaired renal function might represent a valuable noninvasive tool to identify NICM patients who, despite ICD implantation, have the highest risk of mortality and therefore require a particularly thorough follow‐up. (PACE 2011; 34:894–899)     

Temporal and geographical trends in indications for implantation of cardiac defibrillators in Europe 1993-1998. Medtronic ICD System Investigators

Despite the demonstrated efficacy of implantable cardioverter defibrillators (ICDs) in reducing sudden and total mortality in selected populations, their implantation rates vary greatly between countries. The aim of our study was to analyze temporal and geographical trends in ICD implantations in countries with similar health related expenditure in Western Europe. A total of 2,257 patients from ten European evaluation studies of Medtronic defibrillators and defibrillation electrodes, conducted between 1993 and 1998, representing 12 countries, was included in this analysis. Rates of implantation and clinical characteristics were compared between countries and years of implantation. Rates of implantation differed greatly between Western European countries and did not correlate with indices of health related expenditure (i.e., number of patients per physician and number of patients per hospital bed). However, there was a strong and statistically significant negative correlation between the use of amiodarone and the rates of implantation (r = -0.66, P = 0.02). Temporal trends showed a significant increase in the age of the patients receiving an ICD between 1993 and 1998 (57 +/- 14 vs 61 +/- 12 years, mean +/- SD, P < 0.001). There was also a temporal trend towards an increased incidence of coronary artery disease and a significant decrease in the incidence of cardiomyopathy. There was a temporal increase in implantations in patients with a history of ventricular tachycardia. Despite a general scientific agreement that ICDs are a first line treatment for patients at high risk of sudden cardiac death, their acceptance remains low in several developed countries. This low acceptance may not be entirely related to budget constraint but may also be related to their perceived efficacy by physicians and health authorities.     

Unrecognized failure of a narrow caliber defibrillation lead: the role of defibrillation threshold testing in identifying an unprotected individual

In this case report we describe a short circuit in the Riata 1570 defibrillator lead (Riata 1570, St. Jude Medical, St. Paul, MN, USA) that was unsuspected owing to normal lead parameters until defibrillator threshold testing at the time of elective generator change. On this occasion, the short circuit manifested as unsuccessful defibrillation of ventricular fibrillation with immediate battery depletion. This report adds weight to existing concerns over narrow caliber leads, it draws attention to the possibility of lead malfunction despite unremarkable interrogation, and lastly it highlights the potential role of routine defibrillator threshold testing, particularly at elective generator change (an issue that remains sparingly addressed in the existing literature).     

Predictors of Fracture Risk of a Small Caliber Implantable Cardioverter Defibrillator Lead

Introduction: The Sprint Fidelis 6949 implantable cardioverter defibrillator (ICD; Medtronic Inc., Minneapolis, MN, USA) lead has a high rate of fracture. Identification of predictors of subsequent fracture is useful in decision making about lead replacement and for future lead design. We sought to determine if there are clinical, procedural, or radiological features associated with a greater risk of subsequent lead fracture. Methods: Patients with Sprint Fidelis 6949 lead fractures (Fracture group) were identified from our institutional database. Each patient in the Fracture group was matched to two controls, immediately preceeding and succeeding Sprint Fidelis 6949 implant. Clinical and procedural characteristics were compared. Chest radiographs performed 2 weeks after ICD implant were reviewed by an observer blinded to outcomes. The following features were assessed: ICD tip location, lead slack, kinking of the lead body (≥90°), and presence of lead “crimping” within the anchoring sleeve. Results: Twenty‐six patients with Sprint Fidelis 6949 lead fractures were identified and were matched to 52 control patients. On univariate analysis, a higher left ventricular ejection fraction (LVEF), prior ipsilateral device implant, history of prior ICD lead fracture, and noncephalic venous access were associated with risk of lead fracture. On multivariate analysis, a higher LVEF was the only independent predictor of lead fracture (P = 0.006). Radiological features were similar between the two groups. Conclusions: In this study, a higher LVEF was associated with a greater risk of lead fracture in patients with Sprint Fidelis 6949 ICD leads. Radiographic features did not predict subsequent risk of lead fracture in our population. (PACE 2010; 437–443)     

Alleviation of central sleep apnea by ventricular pacing in a patient with an implanted cardioverter defibrillator

A 75-year-old man with a single chamber cardioverter defibrillator implanted for the management of sustained ventricular tachycardia developing after a healed myocardial infarction was admitted for evaluation of a sleep disorder. Polysomnography confirmed the presence of severe predominant central sleep apnea syndrome. The apnea-hypopnea index score decreased from 43.3 during spontaneous cardiac rhythm to 24.6 during VVI pacing at a rate of 70 beats/min. Ventricular pacing reduced the number of episodes of central sleep apnea/hypopnea without reducing the total sleep time, though it had no effect on episodes of obstructive sleep apnea/hypopnea.     

Effect of depression on mortality in implantable cardioverter defibrillator recipients--findings from the prospective LICAD study

Introduction: Depression predicts mortality in patients with coronary artery disease and heart failure. However, its effect on patient outcome in the presence of an implantable cardioverter defibrillator (ICD) has not been investigated. Methods: A total of 236 ICD patients (76 females, 58.6 ± 14.0 years) were screened for depressive symptoms using the Hospital Anxiety and Depression Scale (HADS). The outcome measure was all‐cause mortality and the prognostic effect of depression was evaluated with Cox proportional hazards regression analysis. Results: Fifty (21%) patients reported depressive symptoms (HADS score ≥ 8). Renal failure (odds ratio [OR]= 4.0, 95% confidence intervals [CI]= 1.47–10.87, P = 0.007), prior angina (OR = 2.1, 95% CI = 1.07–4.12, P = 0.03), but not the experience of ICD shocks were associated with baseline depressive symptoms. In a mean follow‐up period of 6.1 ± 2.5 years, 74 patients (31%) died. Mortality significantly increased from 45.1 deaths per 1,000 person‐years among patients without depression to 80.3 deaths per 1,000 person‐years in patients with depressive symptoms (P = 0.039). In the univariate model, depression (HADS score ≥8) was a significant predictor of mortality (OR = 1.81, 95% CI = 1.1–3.0, P = 0.02). However, in the multivariate model, depression lost its prognostic significance. Conclusions: In our prospective patient cohort, one‐fifth of ICD recipients reported depressive symptoms. Depression increased the absolute mortality risk but was not an independent predictor of mortality. (PACE 2011; 34:991–997)     

Remote Monitoring of Implantable Cardioverter Defibrillators:

A prospective study evaluating the functionality and ease of use of the Medtronic CareLink^® Network, "CareLink," was conducted at ten investigational sites. This internet-based remote monitoring service allows clinicians to remotely manage their patients' implantable cardioverter defibrillators (ICDs) and chronic diseases. The network is comprised of a patient monitor, a secure server, and clinician and patient websites. Under clinician direction, patients interrogated their ICDs at home, and transmitted data to secure servers via a standard telephone line. Comprehensive device data and a 10-second presenting rhythm electrogram were captured by the monitor and available for access and review on the clinician website. The information could also be printed using a standard desktop computer with internet access. During this study, patients were asked to transmit device data twice, at least 7 days apart, as scheduled by the clinic. Monitor functionality was assessed, and ease of using the system components was evaluated via questionnaires completed by patients and clinicians following each data transmission and review. Fifty-nine patients (64 ± 14 years, range 22-85 years) completed 119 transmissions with only 14 calls to the study support center. Clinician review of data transmissions revealed several clinically significant findings, including silent AF discovery, assessment of antiarrhythmic drug efficacy in a previously diagnosed AF patient, previously unobserved atrial undersensing, and ventricular tachycardia. ICD patients found the monitor easy to use. Clinicians were pleased with the performance of the network and the quality of the web-accessed data, and found it comparable to an in-office device interrogation. CareLink is a practical tool for routine device management and may allow timely identification of clinically important issues. (PACE 2004; 27[Pt. I]:757–763)     

Outcomes of Elderly Recipients of Implantable Cardioverter Defibrillators

Aims of the Study: To examine the patterns of use, complication rates, and survival in elderly recipients of implantable cardioverter defibrillators (ICD).
Methods and Results: We followed 500 consecutive patients included in the Marburg Defibrillator database for 48 ± 39 months. There were 40 patients (8%) ≥75 and 460 (92%) <75 years of age at the time of implant. The 5-year Kaplan-Meier estimate for appropriate treatment of VT or VF by ICD was 49% among patients <75- versus 57% among patients ≥75-years-old (P = 0.17). The 5-year sudden death rate was similarly low in both groups of patients (2% versus 3%). The 5-year overall mortality rate was significantly higher in patients ≥75 than in patients <75 years of age (55% versus 21%, P = 0.001), due to a higher mortality from heart failure (HF). All procedure-related, lead-related, and pulse generator-related complications were similar in both patient groups (23% versus 25%).
Conclusions: ICD therapy was equally effective in patients ≥75 and patients <75 years of age in the prevention of sudden cardiac death. While the complication rates were similar in both age groups, the long-term mortality was considerably higher in elderly patients, due to a higher mortality from HF. The current ICD therapy guidelines appear applicable to elderly patients who are otherwise medically stable and without advanced HF.     

Response to Cardiac Resynchronization Therapy in Patients with Heart Failure and Renal Insufficiency

Background: Renal insufficiency (RI) adversely impacts prognosis in heart failure (HF) patients, partly because renal and cardiac dysfunction are intertwined, yet few cardiac resynchronization therapy (CRT) studies have examined patients with moderate‐to‐severe RI. Methods: We analyzed 787 CRT‐defibrillator (CRT‐D) recipients with a glomerular filtration rate (GFR) measured prior to implant. Patients were grouped by GFR (in mL/min/1.73 m²): ≥60 (n = 376), 30–59 (n = 347), and <30 (n = 64). Overall survival, changes in left ventricular (LV) ejection fraction and LV end‐systolic diameter, and GFR change at 3–6 months were compared among CRT‐D groups and with a control cohort (n = 88), also stratified by GFR, in whom LV lead implant was unsuccessful and a standard defibrillator (SD) was placed. All patients met clinical criteria for CRT‐D. Results: Among CRT‐D recipients, overall survival improved incrementally with higher baseline GFR (for each 10 mL/min/1.73 m² increase, corrected hazard ratio [HR] 1.21, 95% confidence interval [CI] 1.13–1.30, P < 0.0001). Survival among SD and CRT‐D patients within GFR < 30 and GFR ≥ 60 groups was similar, whereas CRT‐D recipients with GFR 30–59 had significantly better survival compared to SD counterparts (HR 2.23, 95% CI 1.34–3.70; P = 0.002). This survival benefit was associated with improved renal and cardiac function. CRT recipients with GFR ≥ 60 derived significant echocardiographic benefit but experienced a GFR decline, whereas those with GFR < 30 had no echocardiographic benefit but did improve GFR. Conclusions: CRT may provide the largest survival benefit in HF patients with moderate RI, perhaps by improving GFR and LV function. Severe baseline RI predicts poor survival and limited echocardiographic improvement despite a modest GFR increase, such that CRT may not benefit those with GFR < 30 mL/min/1.73 m². CRT recipients with normal renal function derive echocardiographic benefit but no overall survival advantage. (PACE 2010; 850–859)